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Showing 1 - 200 of 3030 Journals sorted alphabetically
AASRI Procedia     Open Access   (Followers: 15)
Academic Pediatrics     Hybrid Journal   (Followers: 20, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 16, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 79, SJR: 1.109, h-index: 94)
Accounting Forum     Hybrid Journal   (Followers: 22, SJR: 0.612, h-index: 27)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 27, SJR: 2.515, h-index: 90)
Achievements in the Life Sciences     Open Access   (Followers: 4)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 5, SJR: 0.338, h-index: 19)
Acta Astronautica     Hybrid Journal   (Followers: 303, SJR: 0.726, h-index: 43)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 3)
Acta Biomaterialia     Hybrid Journal   (Followers: 25, SJR: 2.02, h-index: 104)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription  
Acta de Investigación Psicológica     Open Access   (Followers: 2)
Acta Ecologica Sinica     Open Access   (Followers: 8, SJR: 0.172, h-index: 29)
Acta Haematologica Polonica     Free   (SJR: 0.123, h-index: 8)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.604, h-index: 38)
Acta Materialia     Hybrid Journal   (Followers: 196, SJR: 3.683, h-index: 202)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.615, h-index: 21)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.442, h-index: 21)
Acta Oecologica     Hybrid Journal   (Followers: 9, SJR: 0.915, h-index: 53)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription   (Followers: 1)
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 3, SJR: 0.311, h-index: 16)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 2)
Acta Poética     Open Access   (Followers: 4)
Acta Psychologica     Hybrid Journal   (Followers: 21, SJR: 1.365, h-index: 73)
Acta Sociológica     Open Access  
Acta Tropica     Hybrid Journal   (Followers: 5, SJR: 1.059, h-index: 77)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 4)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 3)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 3, SJR: 0.383, h-index: 19)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 2)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 5, SJR: 0.141, h-index: 3)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 4, SJR: 0.112, h-index: 2)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 4)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.967, h-index: 57)
Addictive Behaviors     Hybrid Journal   (Followers: 15, SJR: 1.514, h-index: 92)
Addictive Behaviors Reports     Open Access   (Followers: 5)
Additive Manufacturing     Hybrid Journal   (Followers: 7, SJR: 1.039, h-index: 5)
Additives for Polymers     Full-text available via subscription   (Followers: 20)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 120, SJR: 5.2, h-index: 222)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 11, SJR: 1.265, h-index: 53)
Advanced Powder Technology     Hybrid Journal   (Followers: 16, SJR: 0.739, h-index: 33)
Advances in Accounting     Hybrid Journal   (Followers: 8, SJR: 0.299, h-index: 15)
Advances in Agronomy     Full-text available via subscription   (Followers: 15, SJR: 2.071, h-index: 82)
Advances in Anesthesia     Full-text available via subscription   (Followers: 24, SJR: 0.169, h-index: 4)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 3)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 6, SJR: 1.054, h-index: 35)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 10, SJR: 0.801, h-index: 26)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 21, SJR: 1.286, h-index: 49)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 16, SJR: 3.31, h-index: 42)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.277, h-index: 43)
Advances in Botanical Research     Full-text available via subscription   (Followers: 3, SJR: 0.619, h-index: 48)
Advances in Cancer Research     Full-text available via subscription   (Followers: 26, SJR: 2.215, h-index: 78)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9, SJR: 0.9, h-index: 30)
Advances in Catalysis     Full-text available via subscription   (Followers: 5, SJR: 2.139, h-index: 42)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 12)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 24, SJR: 0.183, h-index: 23)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 10, SJR: 0.665, h-index: 29)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 8, SJR: 1.268, h-index: 45)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 28, SJR: 0.938, h-index: 33)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18, SJR: 2.314, h-index: 130)
Advances in Computers     Full-text available via subscription   (Followers: 16, SJR: 0.223, h-index: 22)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 11)
Advances in Digestive Medicine     Open Access   (Followers: 4)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 5)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Ecological Research     Full-text available via subscription   (Followers: 39, SJR: 3.25, h-index: 43)
Advances in Engineering Software     Hybrid Journal   (Followers: 25, SJR: 0.486, h-index: 10)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 7)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 38, SJR: 5.465, h-index: 64)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 3)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 41, SJR: 0.674, h-index: 38)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 14)
Advances in Genetics     Full-text available via subscription   (Followers: 15, SJR: 2.558, h-index: 54)
Advances in Genome Biology     Full-text available via subscription   (Followers: 11)
Advances in Geophysics     Full-text available via subscription   (Followers: 6, SJR: 2.325, h-index: 20)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 18, SJR: 0.906, h-index: 24)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 0.497, h-index: 31)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 22)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 2, SJR: 0.396, h-index: 27)
Advances in Immunology     Full-text available via subscription   (Followers: 33, SJR: 4.152, h-index: 85)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 1.132, h-index: 42)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 3, SJR: 1.274, h-index: 27)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 4)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 4)
Advances in Life Course Research     Hybrid Journal   (Followers: 7, SJR: 0.764, h-index: 15)
Advances in Lipobiology     Full-text available via subscription   (Followers: 1)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 8)
Advances in Marine Biology     Full-text available via subscription   (Followers: 16, SJR: 1.645, h-index: 45)
Advances in Mathematics     Full-text available via subscription   (Followers: 10, SJR: 3.261, h-index: 65)
Advances in Medical Sciences     Hybrid Journal   (Followers: 5, SJR: 0.489, h-index: 25)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 4, SJR: 1.44, h-index: 51)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 21)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 10)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 6, SJR: 0.324, h-index: 8)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 3)
Advances in Oncobiology     Full-text available via subscription   (Followers: 3)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15, SJR: 2.885, h-index: 45)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7, SJR: 0.148, h-index: 11)
Advances in Parasitology     Full-text available via subscription   (Followers: 7, SJR: 2.37, h-index: 73)
Advances in Pediatrics     Full-text available via subscription   (Followers: 20, SJR: 0.4, h-index: 28)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 14)
Advances in Pharmacology     Full-text available via subscription   (Followers: 13, SJR: 1.718, h-index: 58)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 7, SJR: 0.384, h-index: 26)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.248, h-index: 11)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 8)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 5)
Advances in Porous Media     Full-text available via subscription   (Followers: 4)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 17, SJR: 1.5, h-index: 62)
Advances in Psychology     Full-text available via subscription   (Followers: 56)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5, SJR: 0.478, h-index: 32)
Advances in Radiation Oncology     Open Access  
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 1, SJR: 0.1, h-index: 2)
Advances in Space Research     Full-text available via subscription   (Followers: 332, SJR: 0.606, h-index: 65)
Advances in Structural Biology     Full-text available via subscription   (Followers: 7)
Advances in Surgery     Full-text available via subscription   (Followers: 6, SJR: 0.823, h-index: 27)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 28, SJR: 1.321, h-index: 56)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 14)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 12)
Advances in Virus Research     Full-text available via subscription   (Followers: 5, SJR: 1.878, h-index: 68)
Advances in Water Resources     Hybrid Journal   (Followers: 42, SJR: 2.408, h-index: 94)
Aeolian Research     Hybrid Journal   (Followers: 5, SJR: 0.973, h-index: 22)
Aerospace Science and Technology     Hybrid Journal   (Followers: 304, SJR: 0.816, h-index: 49)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.318, h-index: 36)
African J. of Emergency Medicine     Open Access   (Followers: 4, SJR: 0.344, h-index: 6)
Ageing Research Reviews     Hybrid Journal   (Followers: 7, SJR: 3.289, h-index: 78)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 390, SJR: 1.385, h-index: 72)
Agri Gene     Hybrid Journal  
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 15, SJR: 2.18, h-index: 116)
Agricultural Systems     Hybrid Journal   (Followers: 29, SJR: 1.275, h-index: 74)
Agricultural Water Management     Hybrid Journal   (Followers: 36, SJR: 1.546, h-index: 79)
Agriculture and Agricultural Science Procedia     Open Access  
Agriculture and Natural Resources     Open Access   (Followers: 1)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 48, SJR: 1.879, h-index: 120)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.434, h-index: 14)
Air Medical J.     Hybrid Journal   (Followers: 3, SJR: 0.234, h-index: 18)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.285, h-index: 3)
Alcohol     Hybrid Journal   (Followers: 9, SJR: 0.922, h-index: 66)
Alcoholism and Drug Addiction     Open Access   (Followers: 5)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 1, SJR: 0.436, h-index: 12)
Alexandria J. of Medicine     Open Access  
Algal Research     Partially Free   (Followers: 7, SJR: 2.05, h-index: 20)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.46, h-index: 29)
Allergology Intl.     Open Access   (Followers: 5, SJR: 0.776, h-index: 35)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 6, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 45, SJR: 4.289, h-index: 64)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 5)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 3)
American Heart J.     Hybrid Journal   (Followers: 45, SJR: 3.157, h-index: 153)
American J. of Cardiology     Hybrid Journal   (Followers: 47, SJR: 2.063, h-index: 186)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 34, SJR: 0.574, h-index: 65)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 6, SJR: 1.091, h-index: 45)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 14, SJR: 1.653, h-index: 93)
American J. of Human Genetics     Hybrid Journal   (Followers: 32, SJR: 8.769, h-index: 256)
American J. of Infection Control     Hybrid Journal   (Followers: 25, SJR: 1.259, h-index: 81)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 31, SJR: 2.313, h-index: 172)
American J. of Medicine     Hybrid Journal   (Followers: 48, SJR: 2.023, h-index: 189)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 174, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 51, SJR: 2.803, h-index: 148)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 2)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.249, h-index: 88)
American J. of Otolaryngology     Hybrid Journal   (Followers: 22, SJR: 0.59, h-index: 45)
American J. of Pathology     Hybrid Journal   (Followers: 23, SJR: 2.653, h-index: 228)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 21, SJR: 2.764, h-index: 154)
American J. of Surgery     Hybrid Journal   (Followers: 32, SJR: 1.286, h-index: 125)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 13, SJR: 0.653, h-index: 70)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 5)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.066, h-index: 51)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 52, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 3)
Anales de Cirugia Vascular     Full-text available via subscription  
Anales de Pediatría     Full-text available via subscription   (Followers: 2, SJR: 0.209, h-index: 27)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription   (SJR: 0.104, h-index: 3)
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 2, SJR: 2.577, h-index: 7)
Analytica Chimica Acta     Hybrid Journal   (Followers: 38, SJR: 1.548, h-index: 152)
Analytical Biochemistry     Hybrid Journal   (Followers: 154, SJR: 0.725, h-index: 154)
Analytical Chemistry Research     Open Access   (Followers: 7, SJR: 0.18, h-index: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 10)
Anesthésie & Réanimation     Full-text available via subscription  
Anesthesiology Clinics     Full-text available via subscription   (Followers: 21, SJR: 0.421, h-index: 40)
Angiología     Full-text available via subscription   (SJR: 0.124, h-index: 9)
Angiologia e Cirurgia Vascular     Open Access  
Animal Behaviour     Hybrid Journal   (Followers: 143, SJR: 1.907, h-index: 126)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 5, SJR: 1.151, h-index: 83)
Animal Reproduction Science     Hybrid Journal   (Followers: 5, SJR: 0.711, h-index: 78)
Annales d'Endocrinologie     Full-text available via subscription   (SJR: 0.394, h-index: 30)
Annales d'Urologie     Full-text available via subscription  
Annales de Cardiologie et d'Angéiologie     Full-text available via subscription   (SJR: 0.177, h-index: 13)
Annales de Chirurgie de la Main et du Membre Supérieur     Full-text available via subscription  
Annales de Chirurgie Plastique Esthétique     Full-text available via subscription   (Followers: 2, SJR: 0.354, h-index: 22)
Annales de Chirurgie Vasculaire     Full-text available via subscription   (Followers: 1)

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Journal Cover Aerospace Science and Technology
  [SJR: 0.816]   [H-I: 49]   [304 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1270-9638
   Published by Elsevier Homepage  [3030 journals]
  • Dynamic stability of rolling missile with proportional navigation & PI
           autopilot considering parasitic radome loop
    • Authors: Duo Zheng; Defu Lin; Xinghua Xu; Song Tian
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Duo Zheng, Defu Lin, Xinghua Xu, Song Tian
      The dynamic stability of coning motion for a radar homing rolling missile is studied in this paper, and the parasitic radome loop is considered and introduced into the guidance system of the radar homing rolling missile. A mathematical model with complex summation considering the parasitic radome loop is proposed, and the sufficient and necessary conditions for the dynamic stability of the coning motion for the rolling missile are analytically derived by using the stability criterion of third-order characteristic equation with complex coefficients. Numerical simulations with different parameters are conducted to demonstrate the effectiveness of the proposed stability condition. The stability condition proposed in this paper can be used in the guidance and control system design of a radar homing rolling missile while considering the parasitic radome loop.

      PubDate: 2017-04-16T05:18:38Z
      DOI: 10.1016/j.ast.2017.03.036
      Issue No: Vol. 67 (2017)
  • Target threat level assessment based on cloud model under fuzzy and
           uncertain conditions in air combat simulation
    • Authors: Shidong Ma; Hongzhi Zhang; Guoqing Yang
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Shidong Ma, Hongzhi Zhang, Guoqing Yang
      The good real-time performance and the accuracy of the target threat level assessment are very important in air combat simulation. In order to solve the problem of target threat level assessment caused by the fuzziness and uncertainty of battlefield information collection, the target threat assessment technology based on cloud model is proposed. Using fuzzy description, battlefield situation is expressed in many qualitative concepts, and then these qualitative concepts are expressed and processed using cloud model related theory, and through Bayes revision on the membership clouds obtained depending on experts' experience which evaluated qualitative concepts, the staff gauges clouds were obtained. Finally the cloud diagram of target threat assessment was obtained through battlefield situation information matching the staff gauges clouds, and threat level assessment was realized. The description of battlefield situation with qualitative concept and membership clouds achieve a good integration in fuzziness and uncertainty, which reflect fuzziness and uncertainty when obtain information in air combat. Qualitative and quantitative concepts descriptions do not need precision battlefield situation data in target threat level assessment using cloud model. An example was given to validate the target threat level assessment technology based on cloud model, and the results indicate that threat level assessment can be realized availably by this technology.

      PubDate: 2017-04-16T05:18:38Z
      DOI: 10.1016/j.ast.2017.03.033
      Issue No: Vol. 67 (2017)
  • An experimental study on the low velocity impact resistance of fibre metal
           laminates under successive impacts with reduced energies
    • Authors: M. Sadighi; M. Yarmohammad Tooski; R.C. Alderliesten
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): M. Sadighi, M. Yarmohammad Tooski, R.C. Alderliesten
      The response of Glare 3 and Glare 5 to repeated impacts and dropped tools was experimentally investigated using drop weight equipment. Two repetition sequences were tested. The first sequence consisted of successive impacts with the same impact energy, but lower than the first impact. In the second sequence the rebound energy of one impact was taken as the impact energy for the subsequent impact. This sequence represents the drop weight impact. The damage was evaluated using visual inspection and ultrasonic C-scan. Three categories of impact damage were observed: visible deformation without internal or external damage, visible internal damage (C-scan) without external damage, and visible internal and external damages. The “threshold energy” defined as the magnitude of maximum impact energy in successive impacts that caused no further damage after the first impact. For the successive impacts with energy between the threshold energy and the first impact, repeated impacts were observed to cause damage propagation. Successive impacts with impact energy less than the threshold did not reveal any effect on the structural integrity. The dropped tool sequence revealed that the rebound energies do not have a considerable effect; the force–time and force–displacement curves for Glare laminates did not change with successive rebound impacts. Therefore, it can be concluded that damage propagation due to rebound energies is negligible.

      PubDate: 2017-04-16T05:18:38Z
      DOI: 10.1016/j.ast.2017.03.042
      Issue No: Vol. 67 (2017)
  • Adaptive backstepping sliding mode control for 3-DOF permanent magnet
           spherical actuator
    • Authors: Jingmeng Liu; Huiyang Deng; Cungang Hu; Zhiquan Hua; Weihai Chen
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Jingmeng Liu, Huiyang Deng, Cungang Hu, Zhiquan Hua, Weihai Chen
      In this paper, a robust adaptive control system combining backstepping and sliding mode control method has been implemented for the 3-DOF permanent magnet (PM) spherical actuator in order to improve its trajectory tracking performance. Due to the complexity of both mechanical structure and electromagnetic field, the dynamic model of a PM spherical actuator inevitably contains uncertainties, such as disturbances and model errors, which will gravely influence the performance of conventional control system. Therefore, a backstepping sliding mode approach is firstly applied, where the backstepping design is to synthesize the controller and the sliding mode term is to compensate disturbances. Then, an adaptive law is presented to estimate the model errors during the control process, where the parameters of the model are initially assumed to be accuracy. Correspondingly, the stability can be guaranteed by choosing the appropriate Lyapunov function. Both simulations and experiments are designed to demonstrate the effectiveness of the proposed control scheme.

      PubDate: 2017-04-16T05:18:38Z
      DOI: 10.1016/j.ast.2017.03.032
      Issue No: Vol. 67 (2017)
  • Space robot active collision avoidance maneuver under thruster failure
    • Authors: Yongqiang Qi; Di Tang; Jian Wang
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Yongqiang Qi, Di Tang, Jian Wang
      The problem of robust control for space robot collision avoidance maneuver under constant thrust is studied in this paper. Firstly, based on the Clohessy–Wiltshire (C–W) equations and by considering uncertainties and thruster failure in radial direction, the dynamic model for space robot is proposed. Then, based on the established model, a parametric design method of robust controller is given by using the eigenstructure assignment theory and the model reference theory. Next, a new constant thrust switching algorithm is proposed by using the impulse compensation method. Finally, simulation results and performance analysis validate the effectiveness of the proposed approach.

      PubDate: 2017-04-16T05:18:38Z
      DOI: 10.1016/j.ast.2017.03.037
      Issue No: Vol. 67 (2017)
  • The spray characteristics of an open-end swirl injector at ambient
    • Authors: Chen Chen; Yang Yang; Shun-hua Yang; Hong-li Gao
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Chen Chen, Yang Yang, Shun-hua Yang, Hong-li Gao
      To study the spray characteristics of an open-end swirl injector under ambient pressure, cold flow tests were conducted using a high-speed shadowgraph system. The effects of geometrical parameters (including tangential inlet diameter and injector length) and operating parameters (including injection pressure drop) under high ambient pressure were systematically investigated. The experimental results indicate that spray is suppressed by ambient pressure. With increased ambient pressure, the discharge coefficient increased while the spray cone angle, spray width and breakup length decreased. Under a low injection pressure drop of 0.1 MPa, the maximum deviations of the discharge coefficient and spray cone angle under 5 ambient pressure conditions were 22.6% and 31.2%, respectively. Under a high injection pressure drop of 0.7 MPa, the maximum deviations under 5 ambient pressure conditions were 1% and 18.1%, respectively. A critical pressure value was found at which the spray structure converts from a wide hollow cone to a narrow contracting bell. Increasing the tangential inlet diameter ( D p ) or the ratio of the injector length to the injector orifice diameter ( L / D ) would eventually decrease the swirling intensity. Therefore, the discharge coefficient increases while the spray cone angle decreases. Comprehensively considering the effects of geometrical and operating parameters, empirical formulas for the discharge coefficient and spray cone angle are proposed for engineering applications.

      PubDate: 2017-04-16T05:18:38Z
      DOI: 10.1016/j.ast.2017.03.035
      Issue No: Vol. 67 (2017)
  • Trajectory optimization for a ramjet-powered vehicle in ascent phase via
           the Gauss pseudospectral method
    • Authors: Shengbo Yang; Tao Cui; Xinyue Hao; Daren Yu
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Shengbo Yang, Tao Cui, Xinyue Hao, Daren Yu
      To determine the optimal trajectory for the ascent phase of a general supersonic vehicle propelled by a hydrocarbon-fueled ramjet, a strategy is developed based on the coupling characteristics of a flight-propulsion system. With two different cost functions and a series of necessary constraints, minimum-fuel and minimum-time trajectory problems are formulated. Both problems are transformed into typical continuous Bolza problems, which can be solved via the Gauss pseudospectral method. The results show that along the two optimal trajectories, the vehicle accelerates horizontally at the onset of the ascent process until the dynamic pressure can provide sufficient lift. Efficiency analysis is conducted to reveal the coordination between engine performance and atmosphere characteristics. It is found that the take-off weight influences the optimized results. The difference between the two optimal trajectories narrows as the take-off weight increases.

      PubDate: 2017-04-16T05:18:38Z
      DOI: 10.1016/j.ast.2017.04.001
      Issue No: Vol. 67 (2017)
  • Performance based multidisciplinary design optimization of morphing
    • Authors: Frederico Afonso; José Vale; Fernando Lau; Afzal Suleman
      Pages: 1 - 12
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Frederico Afonso, José Vale, Fernando Lau, Afzal Suleman
      The aeronautical industry is currently facing contradictory aircraft design requirements. There is a need to increase speed and capacity while minimizing the environmental impact. Novel configurations and morphing solutions are being proposed to address these requirements. In order to achieve the optimal aircraft configuration or the best morphing solution for a given mission, it is necessary to explore Multidisciplinary Design Optimization (MDO) solutions during the conceptual design phase. To this end, a MDO framework is proposed for conceptual design and analysis of new aircraft configurations, including the capability to analyze and quantify the effect of morphing wing solutions on aircraft performance. To illustrate the versatility and capabilities of the MDO tool, the design of a morphing wingtip on a conventional aircraft for two different flight conditions is assessed based on a reference model transport aircraft. Also, the performance of a morphing bending and twist control applied to a reference joined-wing configuration to improve lateral-directional stability is quantified. The results obtained show a significant reduction in fuel consumption when introducing a wingtip, although an incremental and negligible reduction was verified when enabling the wingtip with morphing capabilities. A considerable increase in yaw authority was achieved for the joined-wing model with the bending-twist morphing wingtip, however this morphing concept was not able to reach the same roll authority as conventional ailerons.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.029
      Issue No: Vol. 67 (2017)
  • CFD-based aeroelastic reduced-order modeling robust to structural
           parameter variations
    • Authors: Maximilian Winter; Florian M. Heckmeier; Christian Breitsamter
      Pages: 13 - 30
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Maximilian Winter, Florian M. Heckmeier, Christian Breitsamter
      This article deals with the development of two efficient computational-fluid-dynamics (CFD) based models for the computation of unsteady aerodynamic motion-induced forces. In contrast to established reduced-order modeling (ROM) approaches, which are generally fixed to a given set of structural eigenmodes, the proposed methods can be applied for variable mode shapes. Hence, the generated aerodynamic models remain valid to some extent even if mass and stiffness variations within the underlying finite-element (FE) model are considered. In this way, additional computationally demanding CFD computations are avoided once the model has been obtained. Under this premise, two modeling frameworks robust to structural parameter variations are developed, while so-called basis modes are employed to approximate arbitrary mode shapes. Firstly, a time-domain ROM originating from linear system identification principles (SI-ROM) is presented and, secondly, a frequency-domain approach based on a small disturbance CFD solver (SD-ROM) is proposed. Moreover, two different strategies for the basis mode generation are evaluated. The first method is based on a local approximation using radial basis functions, whereas the second method uses two-dimensional Chebyshev polynomials in order to yield a global approximation of the structural grid deformations. Both novel ROM approaches combined with the two basis mode construction techniques are demonstrated and assessed regarding their efficiency and accuracy. The results in terms of the well-known AGARD 445.6 wing configuration demonstrate that the proposed methods can reproduce the unsteady aerodynamic forces accurately, while the computational effort is significantly reduced. Moreover, generic modifications with respect to the FE model are considered to indicate the potential of the new methods regarding aircraft aeroelastic design and optimization.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.030
      Issue No: Vol. 67 (2017)
  • Experimental and numerical investigation on hysteresis characteristics and
           formation mechanism for a variable geometry dual-mode combustor
    • Authors: Shuo Feng; Juntao Chang; Chenlin Zhang; Youyin Wang; Jicheng Ma; Wen Bao
      Pages: 96 - 104
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Shuo Feng, Juntao Chang, Chenlin Zhang, Youyin Wang, Jicheng Ma, Wen Bao
      As part of our efforts to study the hysteresis characteristic and formation mechanism for a variable geometry dual mode combustor, a series of geometry path continuous adjustment experiments and numerical simulation were conducted in the variable geometry dual mode combustor with a Mach number of 3, a divergent ratio ranging from 1.6 to 2.54 and a fuel equivalence ratio ranging from 0.6 to 1.0. Experimental results indicated that the wall static pressure of feature points had an obvious hysteresis phenomenon with the geometry path continuous variation. For given feature points, the hysteresis becomes much smaller with the increasing of the divergent ratio. The interaction between the oblique shock train motion and combustion heat release distribution was adequately considered to explicate the mechanism of the hysteresis formation. It was found that the hysteresis phenomenon was produced from the unstable positive feedback effect of the oblique shock train motion in the isolator. Moreover, the effect of the hysteresis on the total pressure loss, irreversible entropy loss and combustion performance were investigated numerically and experimentally. It was therefore strongly believed that the study of the hysteresis characteristic and formation mechanism on the combustion performance could be very significant to improve combustion performance for the variable geometry dual mode combustor, especially for a wide range of flight Mach numbers.

      PubDate: 2017-04-23T05:32:08Z
      DOI: 10.1016/j.ast.2017.03.040
      Issue No: Vol. 67 (2017)
  • Fault severity recognition of aviation piston pump based on feature
           extraction of EEMD paving and optimized support vector regression model
    • Authors: Chuanqi Lu; Shaoping Wang; Viliam Makis
      Pages: 105 - 117
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Chuanqi Lu, Shaoping Wang, Viliam Makis
      Recognizing an early fault for aviation hydraulic pump and evaluating its size is essential in this industrial application. This paper proposes a new method which combines ensemble empirical mode decomposition (EEMD) paving and optimized support vector regression (SVR) model to detect faults and estimate the fault sizes of a piston pump. Different from other feature extraction methods in which the information of intrinsic mode functions (IMFs) is not being fully utilized, the collected pressure signals are first decomposed by EEMD, and then some useful IMFs are selected by calculating the correlation coefficients between the signals reconstructed by the chosen IMFs and the original signals. These selected IMFs are referred to as EEMD paving. Subsequently, some new fault features considering time domain, frequency domain, and time–frequency domain are extracted from the paving of EEMD. To acquire the most sensitive fault features, principal component analysis (PCA) is then employed to reduce the dimensionality of the original feature vectors. Finally, SVR model is constructed to identify different fault sizes of aviation pump. To achieve higher recognition accuracy, a new method combining genetic algorithm (GA) with grid search is adopted to optimize the parameters of the SVR model. The effectiveness of the proposed method is verified by two datasets collected from a test rig under different conditions. The results demonstrate that the fault features based on the proposed method can be used to characterize the pump fault severity more accurately, and the constructed SVR model has higher recognition accuracy and better prediction ability when compared with previously published methods. The proposed method can also be readily used in other industrial applications.

      PubDate: 2017-04-23T05:32:08Z
      DOI: 10.1016/j.ast.2017.03.039
      Issue No: Vol. 67 (2017)
  • Formation flying on quasi-halo orbits in restricted Sun–Earth/Moon
    • Authors: Ming Xu; Yuying Liang; Xiaoyu Fu
      Pages: 118 - 125
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Ming Xu, Yuying Liang, Xiaoyu Fu
      Due to the strong nonlinear perturbations near the libration points, the continuous low-thrust technique has many potential applications in stationkeeping relative motions. The Hamiltonian structure-preserving (HSP) control is employed in this paper to stabilize formation flying on quasi-periodic orbits near L L 1 of the restricted Sun–Earth–Moon–spacecraft system. In the bi-circular model (BCM), a multiple shooting corrector is developed to refine quasi-periodic orbits as the chief spacecraft's reference trajectories. The linearized variation equation in BCM is used to design the stationkeeping control. A HSP controller is constructed to change the topology of the equilibrium from hyperbolic to elliptic using only relative position feedbacks consisting of stable, unstable and center manifolds. The critical control gains for transient and long-term stabilities are presented to guide the selection of control gains.

      PubDate: 2017-04-23T05:32:08Z
      DOI: 10.1016/j.ast.2017.03.038
      Issue No: Vol. 67 (2017)
  • On the accuracy of RANS, DES and LES turbulence models for predicting drag
           reduction with Base Bleed technology
    • Authors: F. Nicolás-Pérez; F.J.S. Velasco; J.R. García-Cascales; R.A. Otón-Martínez; A. López-Belchí; D. Moratilla; F. Rey; A. Laso
      Pages: 126 - 140
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): F. Nicolás-Pérez, F.J.S. Velasco, J.R. García-Cascales, R.A. Otón-Martínez, A. López-Belchí, D. Moratilla, F. Rey, A. Laso
      Base bleed technology is a common strategy used for body drag reduction. This work assessed the capacity of different RANS, DES and LES models to estimate the drag coefficient of slender bodies with spin and Base Bleed technology under transonic and supersonic (Mach number 0.99–1.5) quasi-steady conditions. 2-dimensional and 3-dimensional numerical models based on RANS and DES with k – ε RNG, k – ω Standard and k – ω SST, as well as LES Smagorinsky–Lilly, Wall Adapting Local Eddy (WALE) and Dynamic sub-grid Kinetic Energy Equation models were presented and benchmarked against ad-hoc experimental flight measurements performed with both active and inactive Base Bleed units. Results showed that RANS and DES models had very limited accuracy in drag prediction when facing a problem involving a high temperature jet mixing layer with a transonic wake as in the case of active Base Bleed. Notwithstanding, a reasonable agreement was found between numerical predictions of drag reduction and experimental data for the case of LES WALE.

      PubDate: 2017-04-23T05:32:08Z
      DOI: 10.1016/j.ast.2017.03.031
      Issue No: Vol. 67 (2017)
  • Correlated optimum lift coefficient and thrust-vector angle for
           longitudinal performance
    • Authors: Laurent Bovet
      Pages: 141 - 143
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Laurent Bovet
      This note explores the optimization of thrust-vector angle for the cruise and initial climb phases of an airliner. For each performance, the lift coefficient and thrust-vector angle have been optimized simultaneously leading to a global optimum. However, the gain offered on the longitudinal performance by an ad-hoc inclination is limited. Finally, analytical expressions of the optimum thrust-vector angle have been derived for each performance, in complement to the expressions already provided by former studies on this subject.

      PubDate: 2017-04-23T05:32:08Z
      DOI: 10.1016/j.ast.2017.04.003
      Issue No: Vol. 67 (2017)
  • State dependent multiple model-based particle filtering for ballistic
           missile tracking in a low-observable environment
    • Authors: Miao Yu; Wen-Hua Chen; Jonathon Chambers
      Pages: 144 - 154
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Miao Yu, Wen-Hua Chen, Jonathon Chambers
      This paper proposes a new method for tracking the whole trajectory of a ballistic missile (BM), in a low-observable environment with ‘imperfect’ sensor measurement incorporating both miss detection and false alarms. A hybrid system with state dependent transition probabilities is proposed where multiple state models represent the ballistic missile movement during different phases; and domain knowledge is exploited to model the transition probabilities between different flight phases in a state-dependent way. The random finite set (RFS) is adopted to model radar sensor measurements which include both miss detection and false alarms. Based on the proposed hybrid modeling system and the RFS represented sensor measurements, a state dependent interacting multiple model particle filtering method integrated with a generalized measurement likelihood function is developed for the BM tracking. Comprehensive simulation studies show that the proposed method outperforms the traditional ones for the BM tracking, with more accurate estimations of flight mode probabilities, positions and velocities.

      PubDate: 2017-04-23T05:32:08Z
      DOI: 10.1016/j.ast.2017.03.028
      Issue No: Vol. 67 (2017)
  • Linear adaptive actuator failure compensation for wing rock motion control
    • Authors: Sabri Boulouma; Salim Labiod; Hamid Boubertakh
      Pages: 155 - 168
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Sabri Boulouma, Salim Labiod, Hamid Boubertakh
      In this paper, a novel adaptive actuator failure compensation control strategy is developed for wing rock motion control in the presence of both system and actuator failure uncertainties. The proposed strategy can compensate for both total and partial loss of effectiveness. A proportional actuation scheme of redundant aileron segments is used. This allows bringing the faulty multi-input single-output nonlinear system into an equivalent perturbed single-input single-output system. Afterward, an adaptive actuator failure compensation control scheme is developed around a linear approximation of an ideal feedback linearization controller. A failure estimation and compensation term is appended to this controller to account for possible actuator failures. Closed-loop stability and tracking performance are proved based on Lyapunov theory and a piecewise analysis is also introduced to show that stability properties hold despite the presence of parameter jumps caused by abrupt actuator failures. Simulation results on a small scale wind tunnel based wing rock model with redundant actuators show the effectiveness of the proposed adaptive control strategy.

      PubDate: 2017-04-23T05:32:08Z
      DOI: 10.1016/j.ast.2017.03.025
      Issue No: Vol. 67 (2017)
  • Experimental validation of quadrotor simulation tool for flight within
           building wakes
    • Authors: Syed Ali Raza; M. Sutherland; J. Etele; Giovanni Fusina
      Pages: 169 - 180
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Syed Ali Raza, M. Sutherland, J. Etele, Giovanni Fusina
      Experimental test flights are conducted to validate a novel simulation tool capable of predicting the effects of building generated turbulent winds on the flight performance of autonomous quadrotors. Wind conditions are modeled using time accurate Large Eddy Simulations where five representative points within the building wake are used to predict an average position hold deviation. Three control methods for autonomous position control tuned under no wind conditions are evaluated (Proportional Derivative (PD), Integral Backstepping, and Fuzzy Logic). Flight tests using a small (≈2 kg) quadrotor UAV within a building wake show that the simulation tool is able to predict average position deviation to within a single body length (0.55 m) in the horizontal plane for observed freestream wind speeds between 1 and 2 m/s (with predicted gusts of up to ±6 m/s). The simulation tool is also shown to be able to predict relative differences between control methods both overall and specifically along each co-ordinate axis. A PD controller is predicted to hold position more accurately with a building wake in the direction perpendicular to the freestream wind by ≈± half a body length while a Fuzzy controller achieves the same result in the direction parallel to the freestream wind. These results are validated by flight test data where both the most effective control strategy, and the magnitude of the position control difference, are shown to match the simulation results.

      PubDate: 2017-04-23T05:32:08Z
      DOI: 10.1016/j.ast.2017.03.043
      Issue No: Vol. 67 (2017)
  • Shape effects of single axisymmetric cavity in a circular duct on flow
           induced acoustic oscillations
    • Authors: M. Thirumoorthy; S.R. Chakravarthy; P.V.G. Brahmanandam
      Pages: 181 - 192
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): M. Thirumoorthy, S.R. Chakravarthy, P.V.G. Brahmanandam
      The acoustic oscillations excited by flow past an axisymmetric cavity in a circular duct are experimentally investigated. The focus of the work is on the effects of different dimensions and shapes of the cavity, namely, rectangular, V, and U shapes. A large number of transducers are used to simultaneously record the variation of acoustic pressure axially and azimuthally in the duct. The trapped acoustic modes excited in the duct are confirmed by the observation of axial decay of the acoustic pressure amplitude away from the cavity. Shifts are observed between tangential natural acoustic modes of the duct, corresponding to which the amplitudes rise and fall. The subdominant mode amplitude increases simultaneously as the dominant mode decreases during a mode shift. The experimentally observed azimuthal variation of amplitude and phase indicate the prevalence of mixed standing and spinning wave modes, which are separated so as to evaluate the spin ratio, defined as the ratio of the amplitude of the spinning part to the total amplitude comprising both the spinning and standing modes. It is found that the spin ratio reaches low values corresponding to when the mode shifts occur. Accordingly, the ratio of the dominant to subdominant amplitudes registers a spike. The results suggest that, when a dominant mode prevails over a velocity range, the acoustic energy is substantially contributed towards the spinning mode, whereas during conditions of mode shifts, the amplitudes of the competing modes decrease, leaving only their standing wave patterns to prevail mostly. The depth of the cavity affects the natural frequency excited, whereas the length influences the amplitude. The U- and V-shaped cavities offer lesser effective geometric depths to the acoustic modes. The shape of the cavity influences the amplitude excited, with the U-shaped cavity registering the lowest levels. It is expected that the dynamics in the shear layers between the central large-scale vortex and the corner vortices accommodated by the cavity shape contributes to the acoustic oscillations excited.

      PubDate: 2017-04-23T05:32:08Z
      DOI: 10.1016/j.ast.2017.03.021
      Issue No: Vol. 67 (2017)
  • Three-dimensional cooperative guidance law for multiple missiles with
           finite-time convergence
    • Authors: Junhong Song; Shenmin Song; Shengli Xu
      Pages: 193 - 205
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Junhong Song, Shenmin Song, Shengli Xu
      For the three-dimensional terminal guidance problem of multiple missiles cooperatively intercepting a maneuvering target, a novel finite-time cooperative guidance law with impact angle constraints is proposed. It is continuous and requires no information on target maneuvers. Firstly, the multiple missiles cooperative guidance model with impact angle constraints is constructed. We subsequently divide the process of cooperative guidance law design into two stages. In the first stage, based on the adaptive super-twisting algorithm and integral sliding mode, a new finite-time consensus protocol, i.e., the acceleration command on the line-of-sight direction, is designed to guarantee that all missiles reach the maneuvering target simultaneously. In the second stage, a new adaptive nonsingular fast terminal sliding mode control law, i.e., the acceleration command on the normal direction of the line-of-sight, is developed to ensure the finite-time convergence of the line-of-sight angular rate and line-of-sight angle between individual missile and the target. Furthermore, the detailed finite-time stability analysis is given based on the Lyapunov theory. Finally, numerical simulations demonstrate the effectiveness of the proposed cooperative guidance law.

      PubDate: 2017-04-23T05:32:08Z
      DOI: 10.1016/j.ast.2017.04.007
      Issue No: Vol. 67 (2017)
  • LPI optimization framework for search radar network based on information
    • Authors: Seyed Mehdi Hosseini Andargoli; Javad Malekzadeh
      Pages: 206 - 214
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Seyed Mehdi Hosseini Andargoli, Javad Malekzadeh
      This paper addresses the problem of joint power management and radar assignment to detect multiple targets in surveillance region for a distributed mono-static radar network while a low probability of interception (LPI) has been attained. Based on detection probabilities and target location estimates, the targeted problem is formulated as a combinatorial non-convex optimization problem which needs exhaustive search through all assignment schemes to reach optimal solution. Due to NP-hardness and non-convexity of the problem, some relaxations are proposed to transform the problem to a more tractable form. The main problem can be considered from two viewpoints, without information fusion and with information fusion. As another relaxation, we separated power allocation from radar assignments through two sub-problems in which first, the optimum power allocation is obtained for each assignment scheme and second, the target assignment schemes are selected based on the allocated powers. Simulation results show that our proposed algorithms not only guarantee detection performances but also considerably improve LPI specification in comparison with benchmark algorithms.

      PubDate: 2017-04-23T05:32:08Z
      DOI: 10.1016/j.ast.2017.04.004
      Issue No: Vol. 67 (2017)
  • Aircraft vulnerability assessment against fragmentation warhead
    • Authors: Hüseyin Emrah Konokman; Altan Kayran; Mustafa Kaya
      Pages: 215 - 227
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Hüseyin Emrah Konokman, Altan Kayran, Mustafa Kaya
      This article presents the detailed methodology developed for the vulnerability assessment of the military aircraft against fragmentation warhead. Vulnerability assessment methodology consists of calculation of the dispersion of the fragments, determination of the hit locations, penetration calculations and probability of kill calculations for the aircraft utilizing the fault tree established for the particular aircraft studied. Based on the developed methodology, vulnerability assessment and survivability analysis of a generic aircraft is performed for different predefined approach angles of the missile threat. For the measure of the vulnerability, mean volume of effectiveness of the warhead is proposed as the metric which is defined as the volume integral of the probability of kill distribution around the aircraft for different intercept directions of the missile. Through the case study, it is shown that mean volume of effectiveness can be used as the single measure of the overall vulnerability assessment of the aircraft.

      PubDate: 2017-04-23T05:32:08Z
      DOI: 10.1016/j.ast.2017.04.005
      Issue No: Vol. 67 (2017)
  • Precise real-time navigation of LEO satellites using a single-frequency
           GPS receiver and ultra-rapid ephemerides
    • Authors: Xiucong Sun; Chao Han; Pei Chen
      Pages: 228 - 236
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Xiucong Sun, Chao Han, Pei Chen
      Precise (sub-meter level) real-time navigation using a space-capable single-frequency global positioning system (GPS) receiver and ultra-rapid (real-time) ephemerides from the international global navigation satellite systems service is proposed for low-Earth-orbiting (LEO) satellites. The C/A code and L1 carrier phase measurements are combined and single-differenced to eliminate first-order ionospheric effects and receiver clock offsets. A random-walk process is employed to model the phase ambiguities in order to absorb the time-varying and satellite-specific higher-order measurement errors as well as the GPS clock correction errors. A sequential Kalman filter which incorporates the known orbital dynamic model is developed to estimate orbital states and phase ambiguities without matrix inversion. Real flight data from the single-frequency GPS receiver onboard China's SJ-9A small satellite are processed to evaluate the orbit determination accuracy. Statistics from internal orbit assessments indicate that three-dimensional accuracies better than 0.50 m and 0.55 mm/s are achieved for position and velocity, respectively.

      PubDate: 2017-04-23T05:32:08Z
      DOI: 10.1016/j.ast.2017.04.006
      Issue No: Vol. 67 (2017)
  • Aeroservoelastic modelling and control of a slender anti-air missile for
           active damping of longitudinal bending vibrations
    • Authors: Anatole Verhaegen; Rafał Żbikowski
      Pages: 20 - 27
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Anatole Verhaegen, Rafał Żbikowski
      Slender anti-air missiles experience longitudinal bending in supersonic flight and yet their autopilots are designed under the rigid-body assumption. Such autopilot design employs notch filters to remove the modal frequencies of the elastic airframe but this approach limits the autopilot bandwidth. In this paper, aeroservoelastic modelling and control of the ASTER 30 missile is proposed to enable autopilot design with extended bandwidth. The aeroservoelastic model combines missile flight dynamics, actuator dynamics and airframe elasticity, the latter focusing on longitudinal bending treated as a continuous Euler–Bernoulli beam problem. The beam is discretised leading to a nodal model and the modal analysis is then performed. The modal model is expressed in the state-space form and its order is reduced to enable optimal sensor placement and active damping control. The aeroservoelastic model of the ASTER 30 missile is further refined for control purposes by optimally choosing actuator inputs together with the number and position of sensors to be mounted on the missile airframe. Once these choices are made, several variants of active vibration damping control are proposed and analysed in order to enable an extended bandwidth for the autopilot by countering the airframe deformation measured by these sensors.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.001
      Issue No: Vol. 66 (2017)
  • Development of a smoothed particle hydrodynamics method and its
           application to aircraft ditching simulations
    • Authors: Tianhang Xiao; Ning Qin; Zhaoyan Lu; Xuan Sun; Mingbo Tong; Zhengzhong Wang
      Pages: 28 - 43
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Tianhang Xiao, Ning Qin, Zhaoyan Lu, Xuan Sun, Mingbo Tong, Zhengzhong Wang
      The present study addresses the development and validation of a smoothed particle hydrodynamics (SPH) method, particularly to examine its feasibility and capability in hydrodynamics and dynamics of aircraft during ditching. The developed method solves the weakly compressible Navier–Stokes equations coupled with six-degree of freedom dynamics to achieve an accurate prediction of the interaction between the aircraft and the fluid. In this SPH method, a dummy particle wall-boundary condition is automatically implemented to meet the requirement of application on geometrically complex engineering problems. An efficient particle search strategy merging the ideal of Cell-linked list with Vertlet list is proposed to speed up the neighbor particles search process. The present SPH method uses an OpenMP memory-shared parallelization in conjunction with Z-curve reordering to accelerate the computation. Validations have been performed on several classic hydrodynamic problems, where good agreements were achieved via comparing with documented experimental results. The developed SPH method is applied to predict the ditching event of a complex helicopter model. Results demonstrate the ditching process, indicating that the method can be potentially used in aircraft ditching applications.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.02.022
      Issue No: Vol. 66 (2017)
  • Design of shape morphing hypersonic inward-turning inlet using multistage
    • Authors: Jifei Wang; Jinsheng Cai; Yanhui Duan; Yuan Tian
      Pages: 44 - 58
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Jifei Wang, Jinsheng Cai, Yanhui Duan, Yuan Tian
      To make a compromise between compression efficiency and aerodynamic performance, a novel multistage optimization approach is proposed to improve the design of the shape morphing hypersonic inward-turning inlet. In the first stage, a parent flow inside an internal cone shaped from a special dual-inflection-point generatrix is optimized for the improvements of total pressure recovery and flow uniformity. The second stage is established to design the inlet lip shape via a single-objective optimization aiming to minimize the inviscid drag of the inlet. For rapidly predicting the inlet inviscid drag, we propose a streamline integral method characterized by high levels of computational efficiency and accuracy. The last stage is auxiliary to improve the practicability, mainly including an algebraic shape transition to regulate the inlet exit shape. Numerical results demonstrate that both the flow non-uniformity and the total pressure loss of the optimized parent flow are decreased significantly compared with the baseline parent flow. With the optimized lip shape, the inlet inviscid drag per unit mass flow rate is decreased as well. A simple quadratic function is the best choice to achieve the shape transition, which is beneficial to improve the inlet practicability with a less performance loss. With the multistage optimization framework, the improvements of the compression efficiency and the aerodynamic performance are both achieved and the balance between them is carefully manipulated as well. All the above demonstrates that the proposed optimization approach for the design of the shape morphing hypersonic inward-turning inlet is practical and efficient.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.02.018
      Issue No: Vol. 66 (2017)
  • Time domain raised cosine-binary coded symbol modulation for satellite
    • Authors: Yanbo Sun; Rui Xue; Danfeng Zhao
      Pages: 59 - 69
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Yanbo Sun, Rui Xue, Danfeng Zhao
      The number of satellite navigation signals in space grows dramatically as the number of global and regional navigation satellites constant increases. This phenomenon further aggravates an already crowded radio spectrum in-band and increases out-of-band (OOB) emissions. One feasible solution to the issue of signal compatibility is to design a spectrum-efficient modulation signal that has better navigation performance and backward compatibility with adjacent signals and services in operation. In this study, a time domain raised cosine (TDRC) pulse is introduced as an alternative waveform. A binary coded symbol (BCS) modulation family based on TDRC pulse called TDRC-BCS is also proposed as a candidate for future global navigation satellite system (GNSS). An extensive study on the multipath model analysis approach is also provided. The proposed modulation and existing modulations are then comprehensively evaluated. Theoretical analysis and simulation results show that TDRC-BCS signals offer superior navigation performance compared with existing modulations in terms of code tracking accuracy, multipath mitigation capacity, while maintaining comparable or better anti-jamming performance. These signals can also attain higher spectral efficiency and better backward compatibility with the existing GNSS signals. The proposed modulation scheme provides additional degrees of freedom for GNSS signal design.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.002
      Issue No: Vol. 66 (2017)
  • Investigation of corner separation and suction control in constant area
    • Authors: Yubao He; Hongyan Huang; Daren Yu
      Pages: 70 - 82
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Yubao He, Hongyan Huang, Daren Yu
      To control shock-wave/boundary-layer interaction with suction, numerical simulations in a constant-area rectangular isolator with asymmetry nozzle are conducted to understand the complex flow phenomena. Results show that three-dimensional effect significantly weakens isolator resistance to backpressure, which indirectly emphasizes enormous role of viscous effect and geometry to the dynamic behavior of shock train or pseudo-shock wave. The large-scale separated flow only locates at the corner of the upper wall. The mechanism analysis indicates that the flow is accelerated more rapidly along the bottom wall, thereby providing more momentum at the nozzle exit. The displacement and momentum thicknesses and their increasing rate on the upper wall are all greater than that of the bottom wall, which means that upper corner flow is subjected easily to separation. The vortex structure of different cross sections in the pseudo-shock region is formed in different ways and the large-scale vortex still exists after the airflow mixing, which contributes to the deceleration and pressurization. Through the control effect analysis of suction slot, the suction slot in spanwise direction on the side wall can shorten effectively the length of shock train, which indicates that removing the low-momentum fluid near the corners can control significantly the shock-wave/boundary-layer interactions.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.01.029
      Issue No: Vol. 66 (2017)
  • Free vibration of functionally graded porous cylindrical shell using a
           sinusoidal shear deformation theory
    • Authors: Yuewu Wang; Dafang Wu
      Pages: 83 - 91
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Yuewu Wang, Dafang Wu
      The present study focuses on performing a free vibration analysis of a functionally graded (FG) porous cylindrical shell subject to different sets of immovable boundary conditions. It is assumed that the modulus of elasticity of the porous composite is graded in the thickness direction. The open-cell metal foam provides a typical mechanical feature to determine the relationship between coefficients of density and porosity. A sinusoidal shear deformation theory (SSDT) in conjunction with the Rayleigh–Ritz method is employed to derive the governing equations associated with the free vibration of the circular cylindrical shell. Two types of graded porosity distributions in the thickness direction are considered. The study investigates the effects of FG porosity, boundary conditions, and geometrical parameters on free vibration characteristics of the FG porous cylindrical shell.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.003
      Issue No: Vol. 66 (2017)
  • LPV modeling of a flexible wing aircraft using modal alignment and
           adaptive gridding methods
    • Authors: Ali Khudhair Al-Jiboory; Guoming Zhu; Sean Shan-Min Swei; Weihua Su; Nhan T. Nguyen
      Pages: 92 - 102
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Ali Khudhair Al-Jiboory, Guoming Zhu, Sean Shan-Min Swei, Weihua Su, Nhan T. Nguyen
      One of the earliest approaches in gain-scheduling control is the gridding based approach, in which a set of local linear time-invariant models are obtained at various gridded points corresponding to the varying parameters within the flight envelop. In order to ensure smooth and effective Linear Parameter-Varying control, aligning all the flexible modes within each local model and maintaining small number of representative local models over the gridded parameter space are crucial. In addition, since the flexible structural models tend to have large dimensions, a tractable model reduction process is necessary. In this paper, the notion of σ-shifted H 2 - and H ∞ -norm are introduced and used as a metric to measure the model mismatch. A new modal alignment algorithm is developed which utilizes the defined metric for aligning all the local models over the entire gridded parameter space. Furthermore, an Adaptive Grid Step Size Determination algorithm is developed to minimize the number of local models required to represent the gridded parameter space. For model reduction, we propose to utilize the concept of Composite Modal Cost Analysis, through which the collective contribution of each flexible mode is computed and ranked. Therefore, a reduced-order model is constructed by retaining only those modes with significant contribution. The NASA Generic Transport Model operating at various flight speeds is studied for verification purpose, and the analysis and simulation results demonstrate the effectiveness of the proposed modeling approach.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.009
      Issue No: Vol. 66 (2017)
  • A robust predictor–corrector entry guidance
    • Authors: Tao Wang; Hongbo Zhang; Liang Zeng; Guojian Tang
      Pages: 103 - 111
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Tao Wang, Hongbo Zhang, Liang Zeng, Guojian Tang
      With the development of aerospace industry, the guidance system of an entry vehicle becomes more robust, reliable and autonomous. Based on fuzzy logic, a predictor–corrector guidance law is proposed in this paper, where the trajectory prediction is realized by numerical integration. The correction system consists of two fuzzy controllers, which correct longitudinal motion and lateral motion synergistically. A drag acceleration profile is designed through interpolating between upper drag boundary and lower drag boundary, which is corrected continually to eliminate the range error. Attack angle, a secondary control variable in the paper, is used to eliminate the altitude error. In addition, the lateral error is removed by regulating the reversal time of bank angle. Compared with the traditional guidance laws, the method in this paper not only can correct synergistically the longitudinal motion and lateral motion of the vehicle, but also can easily cope with the flight constraints using interpolated drag acceleration profile. Moreover, in a correction cycle, the method designed in this paper only needs a single trajectory prediction, which reduces the on-board computation. The guidance law demonstrates a high precision and robustness in the simulation scenario.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.010
      Issue No: Vol. 66 (2017)
  • Parametric study of injector radial penetration on stalling
           characteristics of a transonic fan
    • Authors: Hossein Khaleghi
      Pages: 112 - 118
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Hossein Khaleghi
      This paper reports on a numerical investigation of the radial penetration of injectors in a high-speed axial fan. Four annular injectors with different radial heights were placed over the casing and choke to stall unsteady computations were performed for each case. Results reveal that as long as the blade is “wall–stall” (i.e., stall is initiated from the tip), range extension is mostly due to injecting into the tip of the blade. If the injector is located close enough to the blade, however, increasing the radial penetration of the injector can provide considerable range extension by changing the rotor stalling mode from “wall–stall” to “blade–stall”. The rotor with zero tip clearance has been also studied in the current work. Results show that endwall injection can desensitize the compressor to the detrimental effects of the tip clearance.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.02.020
      Issue No: Vol. 66 (2017)
  • Insights into flow and heat transfer aspects of hypersonic rarefied flow
           over a blunt body with aerospike using direct simulation Monte-Carlo
    • Authors: Arun Kumar Chinnappan; G. Malaikannan; Rakesh Kumar
      Pages: 119 - 128
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Arun Kumar Chinnappan, G. Malaikannan, Rakesh Kumar
      Hypersonic aero-thermodynamic study of a blunt body with different aerospike configurations is carried out in the Direct Simulation Monte Carlo framework. Influence of aerospike geometry variation on the surface properties such as drag coefficient and convective heat transfer rate are analyzed for a freestream Mach number of 5.75 at 70 km altitude. Numerical investigations are done by varying the diameter of an aerodisk/front body and aerospike length. The simulation results show that an aerodisk of appropriate length and diameter reduces drag coefficient significantly with a moderate value of heat flux. The aerospike length significantly changes the flow behavior and results in some interesting flow features that alter drag and heat flux variation on the surface.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.02.024
      Issue No: Vol. 66 (2017)
  • A new design method of single expansion ramp nozzles under geometric
           constraints for scramjets
    • Authors: Zheng Lv; Jinglei Xu; Yang Yu; Jianwei Mo
      Pages: 129 - 139
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Zheng Lv, Jinglei Xu, Yang Yu, Jianwei Mo
      A new method based on maximum thrust theory to design a two-dimensional single expansion ramp nozzle with geometric constraints directly is presented in this paper. To generate the contour of the nozzle, the inviscid flowfield is calculated by using the method of characteristics and the reference temperature method is applied to correct the boundary layer thickness. The computational fluid dynamics approach is employed to obtain the aerodynamic performance of the nozzles. The results show that the initial arc radius slightly influences the axial thrust coefficient and that the variations in the length and initial expansion angle of the cowl significantly affect the axial thrust coefficient. The nozzle designed by truncating ideal nozzle is also investigated for comparison to verify the superiority of this new method. The nozzle designed by this proposed method shows increases in the axial thrust coefficient, lift, and pitching moment of 5.5%, 1098.2% and 20.3%, respectively, at the design point. Moreover, the proposed nozzle provided the positive lift with considerable increments in the axial thrust coefficient and in the pitching moment at off-design operations.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.013
      Issue No: Vol. 66 (2017)
  • Efficient ascent trajectory optimization using convex models based on the
           Newton–Kantorovich/Pseudospectral approach
    • Authors: Xiaoming Cheng; Huifeng Li; Ran Zhang
      Pages: 140 - 151
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Xiaoming Cheng, Huifeng Li, Ran Zhang
      This paper presents an iterative convex programming algorithm for the complex ascent trajectory planning problem. Due to the nonlinear dynamics and constraints, ascent trajectory planning problems are always difficult to be solved rapidly. With deterministic convergence, convex programming is becoming increasingly attractive to such problems. In this paper, first, path constraints (dynamic pressure, load and bending moment) are convexified by a change of variables and a reasonable approximation. Then, based on the Newton–Kantorovich/Pseudospectral (N–K/PS) approach, the dynamic equations are transcribed into linearized algebraic equality constraints with a given initial guess, and the ascent trajectory planning problem is formulated as a convex programming problem. At last, by iteratively solving the convex programming problem with readily available convex optimization methods and successively updating the initial guess with the Newton–Kantorovich iteration, the trajectory planning problem can be solved accurately and rapidly. The convergence of the proposed iterative convex programming method is proved theoretically, and numerical simulations show that the method proposed can potentially be implemented onboard a launch vehicle for real-time applications.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.02.023
      Issue No: Vol. 66 (2017)
  • Robust model reference adaptive control based on linear matrix inequality
    • Authors: Zhongjiao Shi; Liangyu Zhao
      Pages: 152 - 159
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Zhongjiao Shi, Liangyu Zhao
      Model reference adaptive control (MRAC) has been used in numerous applications to improve system performance in the presence of system uncertainties. To achieve stringent tracking performance specifications, fast adaptation is required in the MRAC framework. However, fast adaptation with high gain adaptive rates could cause high frequency oscillation in the control response, resulting in system instability. In this paper, a novel method is proposed to improve the transient performance, and to restrain high frequency oscillation of the control signal, without modifying the selected reference model. An error feedback compensator is introduced into the control signal in this method, to restrict the control signal oscillation, caused by the estimate error of unknown parameter. Based on the augmented error dynamics, the compensator is designed as a robust controller. Moreover, the error feedback matrix can be obtained by solving a set of linear matrix inequalities. The control method is applied to a controlled wing rock aircraft dynamics model to verify the effectiveness. Simulation results show that the proposed method allows for fast adaptation with high gain adaptive rates, while eliminating high frequency oscillation and guaranteeing transient performance.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.017
      Issue No: Vol. 66 (2017)
  • Characteristics of cylindrical cavities in a compressible turbulent flow
    • Authors: Kung-Ming Chung; Kuan-Huang Lee; Keh-Chin Chang
      Pages: 160 - 164
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Kung-Ming Chung, Kuan-Huang Lee, Keh-Chin Chang
      The characteristics of flow over rectangular cavities have been well documented. However, few studies have considered cylindrical cavity flows. For compressible cylindrical cavity flows, the type of cavity flowfield is dependent on the diameter-to-depth ratio ( D / H ), which is similar to the length-to-depth ratio for a rectangular cavity flow. For an open-type cavity flow ( D / H ≤ 6.14 ), there is a slight upstream influence and uniform static pressure distributions are observed inside the cavity; a small adverse pressure gradient ahead of the rear face and a downstream expansion. The leading- and rear-edge expansions are more significant for transitional- ( D / H = 8.60 – 21.00 ) and closed-type ( D / H = 43.00 ) cavities. The amplitude of surface pressure fluctuations increases toward the rear face, for all of the test cases, whereas an additional peak near the middle of cavity floor is observed for a closed-type cavity. Notably, the effect of freestream Mach number is pronounced only on the amplitude of peak pressure fluctuations near the rear wall. Similarities between a cylindrical cavity and a rectangular cavity for a compressible flow are also highlighted in this study.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.022
      Issue No: Vol. 66 (2017)
  • Low velocity impact response of sandwich beams with soft cores and carbon
           nanotube reinforced face sheets based on Extended High Order Sandwich
           Panel Theory
    • Authors: S. Jedari Salami
      Pages: 165 - 176
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): S. Jedari Salami
      Response of sandwich beam with carbon nanotube reinforced composite (CNTRC) face sheets and soft core subjected to the action of an impacting mass based on the Extended High Order Sandwich Panel Theory (EHSAPT) is first analyzed. Distribution of fibers through the thickness of the face sheets could be uniform or functionally graded (FG). Contact force between the impactor and the beam is obtained using the conventional Hertz law. The field equations are derived via the Ritz based applied to the total energy of the system. The solution is obtained in the time domain by implementing the well-known Runge–Kutta method. After examining the validity of the present solution, the effects of distribution of Carbon Nanotubes (CNTs), nanotube volume fraction, core-to-face sheet thickness ratio, initial velocity of the impactor and the impactor mass are studied in detail. Finally, it is concluded that, the highest peak contact force and the lowest indentation of the top face sheet belong to the sandwich beam with V distribution figure of face sheet, followed by the UD and Λ-ones, respectively. Also, numerical results reveal that employing FG-CNTs in face sheets has a prominent role on impact response of the sandwich panel with soft core.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.007
      Issue No: Vol. 66 (2017)
  • Thermodynamic properties of carbon–phenolic gas mixtures
    • Authors: James B. Scoggins; Jason Rabinovitch; Benjamin Barros-Fernandez; Alexandre Martin; Jean Lachaud; Richard L. Jaffe; Nagi N. Mansour; Guillaume Blanquart; Thierry E. Magin
      Pages: 177 - 192
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): James B. Scoggins, Jason Rabinovitch, Benjamin Barros-Fernandez, Alexandre Martin, Jean Lachaud, Richard L. Jaffe, Nagi N. Mansour, Guillaume Blanquart, Thierry E. Magin
      Accurate thermodynamic properties for species found in carbon–phenolic gas mixtures are essential in predicting material response and heating of carbon–phenolic heat shields of planetary entry vehicles. A review of available thermodynamic data for species found in mixtures of carbon–phenolic pyrolysis and ablation gases and atmospheres rich with C, H, O, and N such as those of Earth, Mars, Titan, and Venus, is performed. Over 1200 unique chemical species are identified from four widely used thermodynamic databases and a systematic procedure is described for combining these data into a comprehensive model. The detailed dataset is then compared with the Chemical Equilibrium with Applications thermodynamic database developed by NASA in order to quantify the differences in equilibrium thermodynamic properties obtained with the two databases. In addition, a consistent reduction methodology using the mixture thermodynamic properties as an objective function is developed to generate reduced species sets for a variety of temperature, pressure, and elemental composition spaces. It is found that 32 and 23 species are required to model carbon–phenolic pyrolysis gases mixed with air and CO2, respectively, to maintain a maximum error in thermodynamic quantities below 10%.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.02.025
      Issue No: Vol. 66 (2017)
  • Adaptive non-affine control for the short-period model of a generic
           hypersonic flight vehicle
    • Authors: Yuhui Wang; Qingxian Wu
      Pages: 193 - 202
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Yuhui Wang, Qingxian Wu
      This paper presents an adaptive non-affine control scheme for the longitudinal short-period model of a generic hypersonic flight vehicle (HFV). Firstly, the non-affine nonlinear characteristics of the aerodynamic coefficients are analyzed, which have great influence on the flight dynamical behaviors. Secondly, without ignoring the non-affine nonlinear aerodynamics, a fuzzy sliding mode adaptive non-affine controller is designed. Under the existence of external disturbances and unmodeled dynamics, the controller can still ensure that the angle of attack tracks the desired signal robustly and asymptotically. Furthermore, the proposed controller does not require the exact bound values of the external disturbances and unmodeled dynamics, which is very important for hypersonic vehicles because the values usually cannot be obtained at hypersonic flight conditions. Finally, the simulation results are provided to illustrate the feasibility and effectiveness of the proposed scheme.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.005
      Issue No: Vol. 66 (2017)
  • Vibro-acoustic analysis under stationary and non-stationary random
           excitations with KLE/FEM/BEM
    • Authors: Yanbin Li; Sameer B. Mulani; Qingguo Fei; Shaoqing Wu; Peng Zhang
      Pages: 203 - 215
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Yanbin Li, Sameer B. Mulani, Qingguo Fei, Shaoqing Wu, Peng Zhang
      An algorithm that integrates Karhunen–Loeve expansion (KLE), finite element method (FEM), and boundary element method (BEM) is proposed to carry out a vibro-acoustic analysis under stationary and non-stationary random excitations which are uncorrelated or correlated. In the KLE, a set of orthogonal basis functions is employed to discretize the auto-covariance function of the excitations and obtain the eigenvalues and eigenfunctions of the auto-covariances. The KLE for correlated random excitation relies on the expansions of correlated random variables. During the response calculation, the FEM and BEM are employed to obtain structural and acoustic responses. A circular piston in an infinite baffle and a stiffened panel excited by stationary or non-stationary random processes are used to illustrate the proposed algorithm's accuracy. Results show that the statistics of vibro-acoustic response are accurately obtained with the proposed method and this method is also applicable for the vibro-acoustic analysis of more complex structures under various types of random excitations.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.011
      Issue No: Vol. 66 (2017)
  • Progress in frequency selective surface-based smart electromagnetic
           structures: A critical review
    • Authors: Ravi Panwar; Jung Ryul Lee
      Pages: 216 - 234
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Ravi Panwar, Jung Ryul Lee
      This article analyzes a review of recent developments in the field of frequency selective surface (FSS)-based advanced electromagnetic (EM) structures. FSSs have been the subject of intensive investigation for distinct EM applications for more than four decades. An FSS is a type of filter consisting of an array of periodic metallic patches or apertures on a dielectric substrate. The high-pass (inductive FSS) and low-pass (capacitive FSS) filtering operation of FSS results in the exhibition of total transmission and reflection near the resonance wavelength. This paper deals with an overview of different FSS geometries, namely, traditional, active, fractal, three-dimensional and multilayered FSSs. A number of recent practical EM applications of FSS structures like microwave absorbers, radomes, textiles and antennas are discussed. In addition, different types of optimization and fabrication techniques for FSS-based EM structures are incorporated. The FSS-based research directions described in this study may be of interest to the scientific community working in this particular field.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.006
      Issue No: Vol. 66 (2017)
  • A comparative study on the bending, vibration and buckling of viscoelastic
           sandwich nano-plates based on different nonlocal theories using DC, HDQ
           and DQ methods
    • Authors: Reza Kolahchi
      Pages: 235 - 248
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Reza Kolahchi
      In this paper, bending, buckling and buckling of embedded nano-sandwich plates are investigated based on refined zigzag theory (RZT), sinusoidal shear deformation theory (SSDT), first order shear deformation theory (FSDT) and classical plate theory (CPT). In order to present a realistic model, the material properties of system are assumed viscoelastic using Kelvin–Voigt model. The elastic medium is simulated by orthotropic visco-Pasternak medium. Based on energy method and D'Alembert's principle, the derivation of the nonlinear equations of motion is presented. A novel numerical method namely as differential cubature (DC) method is applied for obtaining the static response, the natural frequencies and the buckling loads of nano-sandwich plates. The effects of different parameters such as nonlocal parameter, structural damping, viscoelastic foundation, geometrical parameters, stiffness of core and boundary conditions are shown on the bending, buckling and vibration behaviors of nanostructure. The accuracy of the proposed method is verified by comparing its numerical predictions with other published works as well as solution of system with differential quadrature (DQ) and harmonic differential quadrature (HDQ) methods. The numerical investigation shows that RZT is highly accurate in predicting the deflection, frequency and buckling load of nano-sandwich plates without requiring any shear correction factors.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.016
      Issue No: Vol. 66 (2017)
  • Robust extended Kalman filtering for nonlinear stochastic systems with
           random sensor delays, packet dropouts and correlated noises
    • Authors: Huaming Qian; Zhenbing Qiu; Yonghui Wu
      Pages: 249 - 261
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Huaming Qian, Zhenbing Qiu, Yonghui Wu
      In this paper, the robust filtering problem is investigated for nonlinear stochastic systems with random sensor delays, packet dropouts and correlated noises. The stochastic multiplicative noises which enter into both state equation and measurement equation are modeled as random variables with bounded variance, and a Bernoulli distributed random sequence is introduced to describe the random delays and packet dropouts. Then, the system is converted to the stochastic parameterized one through introducing a group of new variables. Moreover, the two-step prediction framework is employed to achieve the goal of noise decoupling. The objective of the addressed estimation problem is to design a filter, such that in the presence of random delays, packet dropouts, multiplicative noises and correlated noises, the upper bounds for the prediction error and estimation error covariance can be guaranteed. Subsequently, the upper bounds are minimized by designing the optimal prediction gain and filter gain. Finally, the attitude estimation example is used to demonstrate the effectiveness of the proposed robust extended Kalman filter.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.020
      Issue No: Vol. 66 (2017)
  • Traffic system operation optimization incorporating buffer size
    • Authors: Yun-xiang Han; Xiao-qiong Huang; Yan Zhang
      Pages: 262 - 273
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Yun-xiang Han, Xiao-qiong Huang, Yan Zhang
      This paper presents a general framework for resolving resource utilizations conflicts of air traffic system, expressed in the form of a max-plus linear model. The general air traffic system optimization model is presented taking into account buffer size in view of different purposes. The proposed air traffic system model is very flexible and it is extensible focusing on distinct circumstances. The dynamics of air traffic systems is characterized through the occurrence of discrete events such as aircrafts entering or leaving sub-segments. We focus on input control of air traffic system modeled by max-plus algebra by controlling the inflow of aircraft into the system. The constraints between input variables, state variables and output variables were obtained. The proposed method aims to minimize system total delay to meet demand specifications, allowing the air traffic controller to obtain the best control policy, which delays the occurrence of input events or varying input rate of system resources. Through simulations we verify the performance of the proposed max-plus linear model control scheme.

      PubDate: 2017-04-09T17:08:29Z
      DOI: 10.1016/j.ast.2017.03.012
      Issue No: Vol. 66 (2017)
  • Stochastic buckling behaviour of laminated composite structures with
           uncertain material properties
    • Authors: Hoang X. Nguyen; Ta Duy Hien; Jaehong Lee; H. Nguyen-Xuan
      Pages: 274 - 283
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Hoang X. Nguyen, Ta Duy Hien, Jaehong Lee, H. Nguyen-Xuan
      In this study, the effects of uncertain material properties on the buckling response of laminated composite structures based on the isogeometric analysis will be presented. The target modulus of elasticity fields are assumed to be a stochastic field and case studies are considered for laminated composite structures including beams and plates. The spectral representation is employed as the crucial method of generating samples. Numerical results show a successful establishment of spectral representation method based on Monte Carlo simulation and isogeometric analysis for evaluating accurately the effects of uncertain material property on the buckling responses. It is demonstrated that linear-like relations between the standard deviation of modulus of elasticity and the standard deviation of critical buckling load of composite beams and plates are accomplished. In addition, isogeometric analysis, which is employed as a solver for the analysis of composite plate based on C1 four-unknown refined plate theory, remarkably outweighs the finite element analysis approach in terms of computational cost of the simulations.

      PubDate: 2017-04-02T02:48:40Z
      DOI: 10.1016/j.ast.2017.01.028
      Issue No: Vol. 66 (2017)
  • A new theoretical model of aircraft arresting system based on polymeric
           foam material
    • Authors: Xianfeng Yang; Zhiqiang Zhang; Yun Xing; Jialing Yang; Yuxin Sun
      Pages: 284 - 293
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Xianfeng Yang, Zhiqiang Zhang, Yun Xing, Jialing Yang, Yuxin Sun
      The engineering material arresting system (EMAS) has been widely employed in airports around the world for purpose of stopping the overrun airplanes from damage. However, the foamed concrete, which is used as the EMAS core at present, has drawn increasing criticism from the public opinion for environmental issue and aging problem. In this paper, a new arresting system made of polyurethane foam with high energy absorption capacity was proposed to overcome the above problems. An analytical model based on the Avalle empirical model, which takes into account the coupling effect between the aircraft wheel and the foam material, was presented to estimate the horizontal resistances exerted on the aircraft wheel, including the crushing drag, the tearing drag, the adhesive drag and the friction drag. In addition, the stopping distance required to arrest the overrun aircraft was predicted. Furthermore, the accuracy of the theoretical results was validated through comparison with the results of FAA full-scale arresting tests. Besides, the influences of the arrestor height, material strength, aircraft weight and the radius of aircraft wheel on the arresting performance of polyurethane foam material were performed, indicating that a reasonable parametric selection is extremely crucial to obtain the optimal design for the aircraft arresting system.

      PubDate: 2017-04-02T02:48:40Z
      DOI: 10.1016/j.ast.2017.03.019
      Issue No: Vol. 66 (2017)
  • Analytical deployment control law for a flexible tethered satellite system
    • Authors: B.S. Yu; D.P. Jin; H. Wen
      Pages: 294 - 303
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): B.S. Yu, D.P. Jin, H. Wen
      The deployment process of a tethered satellite system in a space environment is by nature unstable due to the negative-damping effect in the system. Hence, this paper addresses the deployment stability in controlling a space flexible tethered satellite in which the perturbations from a space environment, such as the J 2 perturbation, air drag force, and solar pressure, are considered. An analytical tether length rate control law for the deployment is presented by using a simplified elastic rod model of the flexible tethered satellite. Then, the stability of the controlled time-varying system during deployment is analyzed via the Floquet theory. The parameter regions for stable deployment are obtained to maintain a tensile state of the tether during the deployment phase. The numerical simulations show that the proposed analytical control law is capable of suppressing the in-plane oscillation of the flexible tethered satellite during deployment while maintaining deployment stability.

      PubDate: 2017-04-02T02:48:40Z
      DOI: 10.1016/j.ast.2017.02.026
      Issue No: Vol. 66 (2017)
  • Stochastic analysis of fuel consumption in aircraft cruise subject to
           along-track wind uncertainty
    • Authors: Rafael Vazquez; Damián Rivas; Antonio Franco
      Pages: 304 - 314
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Rafael Vazquez, Damián Rivas, Antonio Franco
      The effects of along-track wind uncertainty on aircraft fuel consumption are analyzed. The case of cruise flight subject to an average constant wind is considered. The average wind is modeled as a random variable, which in this paper is assumed to follow either a uniform or a beta distribution. The probability density function (pdf) of the fuel consumption is obtained using a numerical approach that is based on the Probability Transformation Method (a method that evolves the wind pdf). The dynamics of aircraft mass evolution in cruise flight is defined by a simple nonlinear equation that can be solved analytically; this exact solution is used to assess the accuracy of the method. A general analysis is performed for arbitrary along-track winds. Comparison of the numerical results with the exact analytical solution shows an excellent agreement in all cases. A linear approximation is analyzed as well, which turns out to be very accurate for this problem. The results show that the standard deviation of the fuel mass distribution varies almost linearly with the standard deviation of the wind, whereas the mean of the fuel mass is practically independent of the wind uncertainty. They also show that, for the same along-track wind uncertainty, the uncertainty in the fuel consumption is larger in the case of headwinds than in the case of tailwinds.

      PubDate: 2017-04-02T02:48:40Z
      DOI: 10.1016/j.ast.2017.03.027
      Issue No: Vol. 66 (2017)
  • Analytical entry guidance based on pseudo-aerodynamic profiles
    • Authors: Wenbin Yu; Wanchun Chen; Zhiguo Jiang; Hao Zhou; Xiaoming Liu; Ming Liu
      Pages: 315 - 331
      Abstract: Publication date: July 2017
      Source:Aerospace Science and Technology, Volume 66
      Author(s): Wenbin Yu, Wanchun Chen, Zhiguo Jiang, Hao Zhou, Xiaoming Liu, Ming Liu
      An autonomous entry guidance is developed for a hypersonic glide vehicle with high Lift-to-Drag ratio (L/D) based on 3-D analytical glide formulas. To compensate the effects of the Earth's rotation, the pseudo-aerodynamic forces are introduced as the fusions of the aerodynamic forces and inertial forces due to the Earth's rotation. To avoid drastic changes in Angle of Attack (AOA) and bank angle, we carefully forecast the change trends of the inertial forces and then design the pseudo-aerodynamic profiles as inversely proportional functions. Here a complex but useful identity is found and proved theoretically, which helps to simplify the pseudo-aerodynamic profiles without losing accuracy significantly. Subsequently, new 3-D analytical glide formulas are derived for these inversely-proportional profiles and then used to determine the profile parameters and bank reversals. Due to the careful design, the guidance is capable of steering the high-L/D vehicle to any place on the Earth accurately while achieving almost constant commands during the steady glide phase, a major phase of flight. The superior performance of the guidance is verified by the Monte Carlo simulations with challenging disturbances including initial state dispersions, aerodynamic uncertainties, and atmospheric perturbations.

      PubDate: 2017-04-02T02:48:40Z
      DOI: 10.1016/j.ast.2017.03.018
      Issue No: Vol. 66 (2017)
  • A comparison of PIV and interferometric Rayleigh scattering measurements
           in the near field of underexpanded sonic jets
    • Authors: Kemal
      Abstract: Publication date: August 2017
      Source:Aerospace Science and Technology, Volume 67
      Author(s): Kemal Bülent Yüceil
      Velocity measurements were made in the near field of underexpanded sonic air jets using particle image velocimetry (PIV), interferometric Rayleigh scattering and total pressure tubes. Shadowgraph technique was also used to visualize the shock waves generated due to underexpansion in the near field of the jets. The two main objectives were to study the effect of underexpansion ratio on the flow structure and to determine the suitability of the PIV technique in high-speed flows with shock waves. The jets were produced by a convergent nozzle connected to a settling chamber. Different underexpansion conditions were obtained by changing the chamber (jet total) pressure against the atmospheric ambient. Jet exit-to-ambient pressure ratios ranged between 1 and 20.32 corresponding to fully-expanded jet Mach numbers between 1 and 3.03, respectively. The PIV measurements of the streamwise and transverse velocities in the near field up to ten nozzle diameters were made, from which distributions of mean velocities, turbulence intensities and turbulent shear stress were obtained. In order to check the accuracy of the PIV measurements (particularly, the particle lag effects) an interferometric Rayleigh scattering technique was also used to obtain the streamwise velocity for certain jet conditions. Additionally, some pressure measurements were made using a total pressure tube to provide a comparison with the two optical techniques. In general, the PIV method provided good velocity data in the jet near field and allowed the identification of flow structures and their respective locations such as shock waves, expansion regions, slip lines and shear layers. However, when compared to the Rayleigh scattering data, the effect of particle inertia was evident in certain locations in the jets. This effect was most dramatic just downstream of the Mach disk (barrel shock) in the case of highly underexpanded jets.

      PubDate: 2017-04-09T17:08:29Z
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