Subjects -> ASTRONOMY (Total: 94 journals)
Showing 1 - 46 of 46 Journals sorted alphabetically
Advances in Astronomy     Open Access   (Followers: 49)
Annual Review of Astronomy and Astrophysics     Full-text available via subscription   (Followers: 50)
Annual Review of Earth and Planetary Sciences     Full-text available via subscription   (Followers: 67)
Artificial Satellites     Open Access   (Followers: 21)
Astrobiology     Hybrid Journal   (Followers: 11)
Astronomical & Astrophysical Transactions: The Journal of the Eurasian Astronomical Society     Hybrid Journal   (Followers: 7)
Astronomical Review     Open Access   (Followers: 5)
Astronomische Nachrichten     Hybrid Journal   (Followers: 4)
Astronomy & Geophysics     Hybrid Journal   (Followers: 49)
Astronomy and Astrophysics     Full-text available via subscription   (Followers: 67)
Astronomy and Computing     Hybrid Journal   (Followers: 6)
Astronomy Letters     Hybrid Journal   (Followers: 22)
Astronomy Reports     Hybrid Journal   (Followers: 22)
Astronomy Studies Development     Open Access   (Followers: 15)
Astroparticle Physics     Hybrid Journal   (Followers: 10)
Astrophysical Bulletin     Hybrid Journal   (Followers: 4)
Astrophysics     Hybrid Journal   (Followers: 35)
Astrophysics and Space Science     Hybrid Journal   (Followers: 49)
Astrophysics and Space Sciences Transactions (ASTRA)     Open Access   (Followers: 60)
Astropolitics: The International Journal of Space Politics & Policy     Hybrid Journal   (Followers: 13)
Celestial Mechanics and Dynamical Astronomy     Hybrid Journal   (Followers: 15)
Chinese Astronomy and Astrophysics     Full-text available via subscription   (Followers: 25)
Colloid Journal     Hybrid Journal   (Followers: 2)
Comptes Rendus : Physique     Open Access   (Followers: 2)
Computational Astrophysics and Cosmology     Open Access   (Followers: 6)
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 143)
Earth, Moon, and Planets     Hybrid Journal   (Followers: 47)
Earth, Planets and Space     Open Access   (Followers: 77)
EAS Publications Series     Full-text available via subscription   (Followers: 8)
EPL Europhysics Letters     Partially Free   (Followers: 8)
Experimental Astronomy     Hybrid Journal   (Followers: 38)
Expert Opinion on Astronomy and Astrophysics     Open Access   (Followers: 8)
Extreme Life, Biospeology & Astrobiology - International Journal of the Bioflux Society     Full-text available via subscription   (Followers: 4)
Few-Body Systems     Hybrid Journal   (Followers: 1)
Foundations of Physics     Hybrid Journal   (Followers: 40)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 15)
Galaxies     Open Access   (Followers: 6)
Globe, The     Full-text available via subscription   (Followers: 3)
Gravitation and Cosmology     Hybrid Journal   (Followers: 6)
Icarus     Hybrid Journal   (Followers: 71)
International Journal of Advanced Astronomy     Open Access   (Followers: 21)
International Journal of Astrobiology     Hybrid Journal   (Followers: 4)
International Journal of Astronomy     Open Access   (Followers: 22)
International Journal of Astronomy and Astrophysics     Open Access   (Followers: 36)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 15)
International Letters of Chemistry, Physics and Astronomy     Open Access   (Followers: 8)
ISRN Astronomy and Astrophysics     Open Access   (Followers: 14)
Journal for the History of Astronomy     Full-text available via subscription   (Followers: 20)
Journal of Astrobiology & Outreach     Open Access   (Followers: 5)
Journal of Astronomical Instrumentation     Open Access   (Followers: 3)
Journal of Astrophysics     Open Access   (Followers: 33)
Journal of Astrophysics and Astronomy     Open Access   (Followers: 58)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 133)
Journal of Geophysical Research : Planets     Full-text available via subscription   (Followers: 116)
Journal of Geophysical Research : Space Physics     Full-text available via subscription   (Followers: 136)
Journal of High Energy Astrophysics     Full-text available via subscription   (Followers: 25)
Kinematics and Physics of Celestial Bodies     Hybrid Journal   (Followers: 11)
KronoScope     Hybrid Journal   (Followers: 1)
Macalester Journal of Physics and Astronomy     Open Access   (Followers: 5)
Monthly Notices of the Royal Astronomical Society     Hybrid Journal   (Followers: 13)
Monthly Notices of the Royal Astronomical Society : Letters     Hybrid Journal   (Followers: 2)
Nature Astronomy     Hybrid Journal   (Followers: 14)
New Astronomy     Hybrid Journal   (Followers: 26)
New Astronomy Reviews     Full-text available via subscription   (Followers: 19)
Nonlinear Dynamics     Hybrid Journal   (Followers: 19)
NRIAG Journal of Astronomy and Geophysics     Open Access   (Followers: 4)
Physics of the Dark Universe     Open Access   (Followers: 4)
Planetary and Space Science     Hybrid Journal   (Followers: 106)
Planetary Science     Open Access   (Followers: 52)
Proceedings of the International Astronomical Union     Full-text available via subscription   (Followers: 2)
Publications of the Astronomical Society of Australia     Hybrid Journal   (Followers: 3)
Publications of the Astronomical Society of Japan     Hybrid Journal   (Followers: 4)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 20)
Research in Astronomy and Astrophysics     Full-text available via subscription   (Followers: 38)
Revista Mexicana de Astronomía y Astrofísica     Open Access   (Followers: 3)
Science China : Physics, Mechanics & Astronomy     Full-text available via subscription   (Followers: 4)
Science China Physics, Mechanics & Astronomy     Hybrid Journal   (Followers: 4)
Solar Physics     Hybrid Journal   (Followers: 29)
Solar System Research     Hybrid Journal   (Followers: 15)
Space Science International     Open Access   (Followers: 118)
Space Science Reviews     Hybrid Journal   (Followers: 92)
Space Weather     Full-text available via subscription   (Followers: 27)
Transport and Aerospace Engineering     Open Access   (Followers: 13)
Universe     Open Access   (Followers: 6)
Similar Journals
Journal Cover
Science China : Physics, Mechanics & Astronomy
Journal Prestige (SJR): 0.116
Number of Followers: 4  
 
  Full-text available via subscription Subscription journal
ISSN (Print) 1674-7275 - ISSN (Online) 1862-2844
Published by Science in China Press Homepage  [1 journal]
  • An Adaptive Voltage Control Using Local Voltage Profile Mode and
           Similarity Ranking

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      Authors: Haomin Ma, Genping Wang, Xiang Gao, Zhouyiao Zou, Yanfei Dong
      Abstract: Emergency voltage control provides a real-time online response to maintain the long-term voltage stability of a power system. Searching for an optimal emergency control solution is a hard combinatorial optimization problem because of the highly dynamic and nonlinear characteristics of power systems with discrete control variables. Additionally, real-time response is required. A new mode-matching–based adaptive voltage control is proposed in this article to achieve a fast response by exploring local voltage profile modes and the technique of similarity ranking. First, some typical emergencies are studied in advance, and their control knowledge is collected for preparation. The set of local voltage profile modes and their corresponding optimal control solutions are stored as knowledge for each emergency. Second, fast online control is realized and the control solution is configured according to a similarity ranking among local voltage profile modes. Furthermore, a learning process is applied to accumulate knowledge in case of unprepared situations. Thus, improved control performances in the future are ensured. This article depends on a new concept of local voltage profile mode with which knowledge preparation, emergency identification, configuration of control, and knowledge accumulation work together to perform an effective response. Simulations of the IEEE 39-bus system verify the outcomes of this voltage control scheme.
      PubDate: 2022-05-19T00:00:00Z
       
  • Dual Set-Membership State Estimation for Power Distribution Networks Under
           Event-Triggered Mechanism

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      Authors: Xingzhen Bai, Guhui Li, Mingyu Ding, Xingquan Ji, Jing Li, Xinlei Zheng
      Abstract: This article is concerned with the set-membership state estimation problem for power distribution networks (PDNs) over a resource-constrained communication network under the influence of unknown but bounded (UBB) noises. Firstly, in order to alleviate the pressure of information communication network (ICN) while meeting the state estimation requirements, the event-triggered mechanism is adopted to send data containing more valid information to estimation center, reasonably reducing the signal transmission frequency. Secondly, an event-triggered dual set-membership filter (ET-DSMF) is designed to improve the performance of state estimation. The proposed filter performs a discrete approximation for a semi-infinite programming problem by the random sampling technique, and a compact linearization error bounding ellipsoid is obtained by solving the dual problem of the nonlinear programming. Subsequently, a sufficient condition for the existence of the estimated ellipsoid is derived depending on the mathematical induction method. The key time-varying filter gain matrix and optimal estimated ellipsoid are determined recursively by solving a convex optimization problem, according to the minimum trace criterion. Finally, the effectiveness of the proposed filtering algorithm is demonstrated by performing simulation experiments on the IEEE 13 distribution test system.
      PubDate: 2022-05-19T00:00:00Z
       
  • Assisting Smart Construction With Reliable Edge Computing Technology

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      Authors: Qiang Yue, Song Mu, Longguan Zhang, Zhun Wang, Zhonghua Zhang, Xing Zhang, Yongge Wang, Zhuang Miao
      Abstract: Although smart construction tools are already assisting the construction sector, still major reforms are considerably seen in the coming years with Artificial Intelligence of Things (AIoT). The purpose of this work was to develop a down-to-earth reliable edge-computing design and plan, which can be utilized to bolster savvy development situations with high quality of service. The number of devices connected to industrial processes is growing in tandem with the advancement of sophisticated technologies and the use of the AIoT. Big data are created as gadgets grow more integrated and need more computing power. However, as the amount of big data generated grows, processing and analytical issues arise. Cloud computing technologies are now being used to solve processing and analytical challenges. However, by using edge computing technologies, greater emphasis is placed on executing calculations as near to the device as feasible. As a result of these facts, this article suggests the arrangement plan, which depends on the most recent cloud and computer program designing approaches and advances, and gives flexibility, interoperability, and adjustment to construction companies' particular needs.
      PubDate: 2022-05-19T00:00:00Z
       
  • Simultaneous Impact of Hollow Droplet and Continuous Dense Droplet on
           Liquid Film

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      Authors: Dashu Li, Gangtao Liang, Dan Hua
      Abstract: The Simultaneous impact of a hollow droplet and a continuous dense droplet on a liquid film was investigated using the coupled level set and volume of fluid (CLSVOF) method. Analyses included fluid dynamics and heat transfer characteristics in impact. Results showed that the interfacial phenomena after impact incorporates spreading, central jet between droplets, edge liquid sheet, and counter jet inside the hollow droplet. The pressure gradient is the major cause for the above phenomena. The significant parameter of impact velocity is closely related to the dynamics and heat transfer for droplets impacting on a liquid film. Droplets with higher impact velocity exhibit a greater spreading factor, central jet height, edge jet height, and counter jet height. Besides, wall heat flux increases more notably for droplets with a higher impact velocity. Compared with the continuous droplet, the hollow droplet shows a smaller spreading factor and edge jet height, a higher wall heat flux, but a narrow thermally affected region. This study provides a fundamental understanding for the application of high-pressure spray combustion.
      PubDate: 2022-05-19T00:00:00Z
       
  • Artificial Intelligence Early Warnings of Agricultural Energy Internet

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      Authors: Xueqian Fu, Feifei Yang
      PubDate: 2022-05-19T00:00:00Z
       
  • An Optimal Scheduling Strategy for Integrated Energy Systems Using Demand
           Response

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      Authors: Shunfu Lin, Mengchen Lin, Yunwei Shen, Dongdong Li
      Abstract: With the development of power-to-gas (P2G) technology and demand-response (DR) technology, new ideas have been proposed for research into the scheduling strategy for integrated energy systems (IER). Focusing on wind power consumption, this paper proposes a day-ahead scheduling strategy for IER with P2G equipment, taking into consideration DR. On the energy consumption side, a demand elasticity matrix is introduced to describe the user’s participation in DR. On the energy supply side, P2G equipment is introduced to improve the coupling of electricity and natural gas, and scenario generation and reduction techniques are introduced to describe the uncertainty of renewable energy output. The maximum net income of the IER is set as the objective function. The optimal scheduling scheme of the system was obtained by solving the scheduling model. The results indicate that the proposed strategy outperforms the traditional operation and can achieve peak cutting and valley filling, maximize the net income of the IER operators, promote the consumption of renewable energy and improve the energy utilization rate of the system.
      PubDate: 2022-05-19T00:00:00Z
       
  • Bioinspired Fiber for Directional Droplet Self-Transportation and Its
           Potential for Enhanced Condensation

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      Authors: Qianchen Rui, Wei Yu
      PubDate: 2022-05-19T00:00:00Z
       
  • The Economic Impact of a Renewable Biofuels/Energy Industry Supply Chain
           Using the Renewable Energy Economic Analysis Layers Modeling System

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      Authors: Burton C. English, R. Jamey Menard, Bradly Wilson
      Abstract: The University of Tennessee’s (UT) Department of Agricultural and Resource Economics models supply chains for both liquid and electricity generating technologies currently in use and/or forthcoming for the bio/renewable energy industry using the input–output model IMPLAN®. The approach for ethanol, biodiesel, and other liquid fuels includes the establishment and production of the feedstock, transportation of the feedstock to the plant gate, and the one-time investment as well as annual operating of the facility that converts the feedstock to a biofuel. This modeling approach may also include the preprocessing and storage of feedstocks at depots. Labor/salary requirements and renewable identification number (RIN) values and credits attributable to the conversion facility, along with land-use changes for growing the feedstock are also included in the supply chain analyses. The investment and annual operating of renewable energy technologies for electricity generation for wind, solar, and digesters are modeled as well. Recent modeling emphasis has centered on the supply chain for liquid fuels using the Bureau of Economic Analysis’s 179 economic trading areas as modeling regions. These various data layers necessary to estimate the economic impact are contained in UT’s renewable energy economic analysis layers (REEAL) modeling system. This analysis provides an example scenario to demonstrate REEAL’s modeling capabilities. The conversion technology modeled is a gasification Fischer–Tropsch biorefinery with feedstock input of 495,000 metric tons per year of forest residue transported to a logging road that is less than one mile in distance. The biorefinery is expected to produce sustainable aviation fuel (SAF), diesel, and naphtha. An estimated one million tons of forest residue are required at fifty percent moisture content. Based on a technical economic assessment (TEA) developed by the Aviation Sustainability Center (ASCENT) and the quantity of hardwood residues available in the Central Appalachian region, three biorefineries could be sited each utilizing 495,000 dry metric tons per year. Each biorefinery could produce 47.5 million liters of SAF, 40.3 million liters of diesel, and 23.6 million liters of naphtha. Annual gross revenues for fuel required for the biorefineries to break even are estimated at $193.7 million per biorefinery. Break-even plant gate fuel prices when assuming RINs and 12.2 percent return on investment are $1.12 per liter for SAF, $1.15 per liter for diesel, and $0.97 per liter for naphtha. Based on IMPLAN, an input–output model, and an investment of $1.7 billion, the estimated economic annual impact to the Central Appalachian region if the three biorefineries are sited is over a half a billion dollars. Leakages occur as investment dollars leaving the region based on the regions local purchase coefficients (i.e., LPPs), which totals $500 million. This results in an estimated $2.67 billion in economic activity with a multiplier of 1.7, or for every million dollars spent, an additional $0.7 million in economic activity is generated in the regional economy. Gross regional product is estimated at $1.28 billion and employment of nearly 1,200 jobs are created during the construction period of the biorefineries, which results in $700 million in labor income with multiplier effects. Economic activity for the feedstock operations (harvesting and chipping) is estimated at slightly more than $16.8 million resulting in an additional $30 million in the economic impact. The stumpage and additional profit occurring from the harvest of the forest residues result in $40 million directly into the pockets of the resource and logging operation owners. Their subsequent expenditures resulted in a total economic activity increase of $71.4 million. These operations result in creating an estimated 103 direct jobs for a total of 195 with multiplier effects. Direct feedstock transportation expenditures of more than $36.7 million provide an estimated increase in economic activity of almost $68 million accounting for the multiplier effects.
      PubDate: 2022-05-18T00:00:00Z
       
  • Optimal Scheduling of Demand Side Load Management of Smart Grid
           Considering Energy Efficiency

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      Authors: Shoaib Balouch, Muhammad Abrar, Hafiz Abdul Muqeet, Muhammad Shahzad, Harun Jamil, Monia Hamdi, Abdul Sattar Malik, Habib Hamam
      Abstract: The purpose of this research is to provide power grid energy efficiency solutions. In this paper, a comprehensive review and its optimal solution is proposed considering the various challenges of smart grid demand-side management. The main technique is based on a novel idea in the Smart Grid—demand response optimization which enables autonomous energy management on the demand side for a wide variety of customers. The first section of this research examines the smart grid issue and evaluates the state-of-the-art load management techniques in terms of the work’s scope. The demand-side load management architecture consists of three primary levels, two of them in line planning and low-cost scheduling, while the third layer, demand response which is a significant expansion of this domain. The implementation of the proposed architecture in MATLAB/Simulink, with test results. demonstrating the significance of the proposed solution
      PubDate: 2022-05-18T00:00:00Z
       
  • Experimental Study on Gas Flow in a Rough Microchannel

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      Authors: Deming Li, Ruixue Yang, Hui Cao, Feng Yao, Chaoqun Shen, Chengbin Zhang, Suchen Wu
      Abstract: The shape and relative roughness of a rough surface have an important influence on microscale flow and heat transfer. In this study, a rectangular silicon microchannel (0.8 mm width and 11.9 μm height) with a large width-depth ratio is fabricated by the MEMS micromachining process. The silicon surface of the microchannel and the two-dimensional rough contours of the glass surface are measured, and the fractal dimensions taken as the only quantitative parameter of the surface morphology are calculated. The three-dimensional morphology of the silicon surface is measured by a confocal laser microscope and atomic force microscope. On this basis, a microscale gas flow performance test system is designed and built, and the flow characteristics of nitrogen and helium in rough silicon microchannel are experimentally studied. The experimental results show that the rough profiles of the silicon surface and the glass surface have possessed self-affine characteristics. Both nitrogen and helium show a certain degree of boundary slip when they flow in a microchannel. The degree of slip of helium flow is larger than that of nitrogen flow, which verifies the rarefied effect of microscale gas flow.
      PubDate: 2022-05-18T00:00:00Z
       
  • Experimental Investigation of the Pressure Dependence of Iso-Octane
           Combustion

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      Authors: S. Shaqiri, D. Kaczmarek, F. vom Lehn, J. Beeckmann, H. Pitsch, T. Kasper
      Abstract: Iso-octane is frequently used as a surrogate fuel or as a component in primary reference fuel blends when low-temperature combustion strategies in engines are investigated. To develop control strategies for these engines, the reaction kinetics of iso-octane must be known starting from the low temperatures and intermediate pressures before ignition to the high temperatures and pressures of combustion. This work adds new experimental data sets to the validation data for reaction mechanism development by investigating the oxidation of iso-octane in stoichiometric mixtures in a flow reactor at pressures of p = 1, 10, and 20 bar and 473K ≤ T ≤ 973 K. The experimental data are compared to simulations with recent reaction mechanisms [Atef et al., Combustion and Flame 178, (2017), Bagheri et al., Combustion and Flame 212, (2020), Cai et al., Proceedings of the Combustion Institute 37, (2018), Fang et al., Combustion and Flame 214, (2020)]. The comparison between experimental and simulated mole fractions as function of temperature show reasonable agreement for all investigated pressures. In particular, the experimentally observed onset of low-temperature reactivity above a certain pressure, the shift of the negative temperature coefficient (NTC) regime with increasing pressure to higher temperatures, and the acceleration of the high-temperature chemistry are captured well in the simulations. Deviations between experimental and simulated results are discussed in detail for the reactivity of iso-octane and some key intermediates such as 2,2,4,4-tetramethyl-tetrahydrofuran, iso-butene and acetone at low temperatures.
      PubDate: 2022-05-18T00:00:00Z
       
  • Research on Countercurrent Flow Limitation in Reactor Hot Leg at the Loss
           of Coolant Accident-Thermohydraulic Calculation With System Code RELAP5

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      Authors: Xiang Li, Lingyuan Gao, Caihong Xu, Ting Wang, Wan Sun, Wen Zhu, Luteng Zhang, Zaiyong Ma, Longxiang Zhu, Liangming Pan
      Abstract: Since the counter current flow limitation (CCFL) of the two-phase flow has an important influence on the safety analysis of the reactor, it is also of great significance to study some characteristics and flow pattern transitions of the two-phase flow. In order to explore the characteristics and influencing factors of two-phase counter current flow in the hot leg under the condition of the Loss of Coolant Accident, this research, using RELAP5 simulation calculation, analyzed the effect of the lengths of the flow path of the hot leg, the shapes of the upper outlet of the inclined pipe, and the shapes of the elbow connecting the horizontal pipe and the inclined pipe on the characteristics of the CCFL. This research also evaluated the limitation of the model. The simulation founded that under the same liquid flow rate, the longer the horizontal pipe, the lower the gas flow rate at the beginning of the counter current flow; the effect of the elbow on the CCFL was not great; compared with the sharp outlet shape, the Jf of the gentle circle was slightly larger. The method established in this study is suitable for the prediction of CCFL in the hot leg during Loss of Coolant Accident.
      PubDate: 2022-05-18T00:00:00Z
       
  • Estimating the Permeability of the Ceramic Coating on Lithium-Ion Battery
           Separators via the Ideal Laminate Theory

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      Authors: Sung Cik Mun, Jong Ho Won
      Abstract: In this study, a simple method for quantifying the porous nature based on the permeability of the thin ceramic coating on microporous polyolefin flims used as separators in lithium-ion batteries is demonstrated. The air permeability of the ceramic coating was determined via the ideal laminate theory (ILT), which is widely accepted for multilayered films or well-defined laminates. This study mainly aims at introducing an ILT-based resistors-in-series model with the Gurley method and its potential applications in battery separators. We investigated a few previously reported examples of ceramic-coated separators to compare the air permeability of various ceramic coatings along with their base polyolefin films.
      PubDate: 2022-05-18T00:00:00Z
       
  • Nanogenerator-Based Sensors for Energy Harvesting From Cardiac Contraction

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      Authors: Ebtesam Abdullah Al-Suhaimi, Meneerah Abdulrahman Aljafary, Tahani M. Alfareed, Hussah Abdullah Alshuyeh, Galyah Mohammed Alhamid, Bayan Sonbol, Atheel Almofleh, Fadwa Mohammed Alkulaifi, Reham Khalid Altwayan, Jamilah Naif Alharbi, Noha Mubarak Binmahfooz, Eman Saleh Alhasani, Huseyin Tombuloglu, Alia Saeed Rasdan, Amer A. lardhi, Abdulhadi Baykal, A. M. Homeida
      Abstract: Biomedical electric devices provide great assistance for health and life quality. However, their maintainable need remains a serious issue for the restricted duration of energy storage. Therefore, scientists are investigating alternative technologies such as nanogenerators that could harvest the mechanical energy of the human heart to act as the main source of energy for the pacemaker. Cardiac contraction is not a source for circulation; it utilizes body energy as an alternative energy source to recharge pacemaker devices. This is a key biomedical innovation to protect patients’ lives from possible risks resulting from repeated surgery. A batteryless pacemaker is possible via an implantable energy collecting tool, exchanging the restriction of the current batteries for a sustainable self-energy resource technique. In this context, the physiology of heart energy in the preservation of blood distribution pulse generation and the effects of cardiac hormones on the heart’s pacemaker shall be outlined. In this review, we summarized different technologies for the implantable energy harvesters and self-powered implantable medical devices with emphasis on nanogenerator-based sensors for energy harvesting from cardiac contraction. It could conclude that recent hybrid bio-nanogenerator systems of both piezoelectric and triboelectric devices based on biocompatible biomaterials and clean energy are promising biomedical devices for harvesting energy from cardiac and body movement. These implantable and wearable nanogenerators become self-powered biomedical tools with high efficacy, durability, thinness, flexibility, and low cost. Although many studies have proven their safety, there is a need for their long-term biosafety and biocompatibility. A further note on the biocompatibility of bio-generator sensors shall be addressed.
      PubDate: 2022-05-17T00:00:00Z
       
  • Blue Energy Spearheading the Energy Transition: The Case of Crete

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      Authors: Hrvoje Stančin, Antun Pfeifer, Christoforos Perakis, Nikolaos Stefanatos, Marko Damasiotis, Stefano Magaudda, Federica Di Pietrantonio, Hrvoje Mikulčić
      Abstract: Decarbonization of remote or isolated island communities represents a significant challenge nowadays. Nevertheless, the environmental, economic, and social benefits seek more attention. Lately, blue energy sources, particularly offshore wind power, are gaining momentum to take the lead in the energy transition process, simultaneously offering numerous benefits for local communities and potential investors. In this research, offshore wind power is considered the main driver of the energy transition for the case of the island of Crete. The energy systems’ development scenarios are developed using an energy planning model EnergyPLAN, starting from a reference model developed for the year 2017. Since the island was recently isolated without connections to the mainland grid, integrating renewable energy sources was a challenging task that led to poor energy potential exploitation. The decarbonization of the power generation sector by offshore and onshore wind and photovoltaics can only partially reduce the import dependence on fossil fuels. At the same time, more significant efforts are expected in the transport and industry sectors. With the operational interconnections, 300 MW of offshore wind capacities can be deployed, averaging annual electricity production of 1.17 TWh, satisfying around 70% of total electricity demand.
      PubDate: 2022-05-17T00:00:00Z
       
  • Impact of Electrical Connection Distance on the Open Loop Modal Resonance
           of Grid Connected Photovoltaic Farms

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      Authors: Bo Zhou, Peng Shi, Yunyang Xu, Zhuolin Zeng
      Abstract: The grid connection of photovoltaic (PV) farms may cause power system oscillations under the condition of open-loop modal resonance (OLMR). This study elucidated the origin of the induced low-frequency oscillations and examined the impact of the electrical distance between grid-connected PV farms on OLMR intensity by using a simplified real power network. A linearized state-space model of the real power system comprising grid-connected PV farms was derived. Based on this, an OLMR analysis was performed to examine the impact of the electrical distance between the grid-connected PV farms as well as between each grid-connected PV farm and the main grid. The OLMR analysis results indicate that the strength of the OLMR increases with the electrical distance between the PV farms, thereby leading to growing power oscillations. Moreover, the increase of electrical distance between each of the grid-connected PV farms and the main grid has a greater effect on OLMR intensity. Additionally, the non-linear simulations were performed to confirm the correctness of the OLMR analysis. Finally, by re-tuning the parameters of the control system of the grid-connected PV farms to reduce the phase-locked loop bandwidth, the OLMR can be effectively eliminated to avoid power oscillations.
      PubDate: 2022-05-17T00:00:00Z
       
  • Experimental and Numerical Studies of Ignition Delay Time and Laminar
           Flame Speed of JP-10 at Elevated Temperature Conditions

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      Authors: Junsen Yang, Yi Wu, Zhenpeng Zhang, Yanlei Shang, Lun Pan
      Abstract: In this work, the laminar flame speeds of JP-10/air mixtures and ignition delay time of JP-10/O2/Ar mixtures have been studied over a wide range of experimental conditions using a premixed Bunsen flame and a shock tube. Laminar flame speed measurements of the JP-10/air mixture were measured at T = 360–453 K, φ = 0.7–1.3 and p = 1 atm. The ignition delay times of JP-10 with fuel mole fraction of 0.2% JP-10/2.8% O2/97% Ar were measured with a heated shock tube behind the reflected shock wave at 1183–1478 K and pressure of 3.4 atm. Numerical calculation and sensitivity analysis of the laminar flame speed and ignition delay time of JP-10 were performed by using published detailed and skeletal kinetic mechanisms. The comparison of experimental and numerical results showed that all models tend to overestimate the laminar flame speed under the studied conditions, especially under lower temperature conditions (360–423 K). A temperature dependency empirical correlation of laminar flame speed was then proposed by power law theory. The sensitivity analysis identified three important reactions [H+O2 = O+OH, C5H5+H (+M) = C5H6(+M), C3H3+C2H2 = C5H5] that determined the laminar flame speed and ignition delay time.
      PubDate: 2022-05-16T00:00:00Z
       
  • Investigation of Fluid Excitation Forces Induced by Cylindrical and
           Conical Whirls in a Long Annular Seal Using Transient CFD Methods

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      Authors: Fengqin Li, Lulu Zhai, Baoling Cui, Zuchao Zhu, Jia Guo
      Abstract: Annular seals can induce fluid excitation forces that severely affect the stability of the pump rotor systems. In this paper, a transient computational fluid dynamic method with a mesh deformation technique is used to study the fluid excitation forces generated on the long annular seal caused by cylindrical whirls and conical whirls. The reliability of the method is verified by comparing the simulation results with the experimental results. The whirl motion, composed of cylindrical and conical whirls, is realized by the phase difference between the whirl movements at the annular seal inlet and outlet, and the effects of the phase difference and inlet preswirl on the fluid excitation forces are studied numerically. The results show that the fluid excitation forces significantly depend on the phase difference of the rotor whirl movement, and tangential force acts as a stabilizing force only when the phase difference approaches 45°. The tangential forces of the cylindrical whirl, the conical whirl and the form of cylindrical and conical combined whirl are sensitive to inlet preswirl, while the effect of inlet preswirl on the radial forces becomes obvious only when the rotor whirls in the form of combined whirls.
      PubDate: 2022-05-16T00:00:00Z
       
  • Correlations Between Wake Phenomena and Fatigue Loads Within Large Wind
           Farms: A Large-Eddy Simulation Study

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      Authors: Maud Moens , Philippe Chatelain
      Abstract: This work proposes a methodology aiming at simulating the whole wind farm behavior, from the wake phenomena to the wind turbine fatigue loads, in a both accurate and efficient way and for a large range of operating conditions. This approach is based on Large Eddy Simulation (LES), coupled to an Actuator Disk (AD) approach. In order to recover pertinent fatigue loads with that wind turbine model, the blade trajectories are replicated through the disk and the AD aerodynamic forces are interpolated onto these “virtual blades” at each time step. The wake centerline is also tracked in the whole wind farm, in order to highlight the correlations between the wake phenomena and the wind turbine fatigue damage. The described methodology is deployed in simulations of the Horns Rev wind farm for several wind directions. The time-averaged power production is first compared to measurements and other LES results, with a very good agreement for large wind sectors. We then investigate the fatigue loads for several machines inside the wind farm and wind directions. We clearly show the link between the upstream wake movement and the resulting high and low frequency oscillations of the root bending moments and of the yaw and tilt moments, and therefore on the resulting fatigue equivalent loads. This study demonstrates the capacity of the numerical tool to accurately capture the wind farm flow and the rotor behaviors, as well as the correlations between the wake phenomena and the resulting fatigue loads.
      PubDate: 2022-05-13T00:00:00Z
       
  • Study on Trajectory Optimization of Hypersonic Vehicle Based on Neural
           Network

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      Authors: Feichao Cai, Xing Huang
      Abstract: For the horizontal take-off hypersonic cruise aircraft, research on the combined design method of multi-section was carried out, the main design parameters of different sections were analyzed, the parametric design model of the flight path was established, and the characteristics of the typical flight path were studied. On this basis, the calculation of sample points was carried out, and a prediction model of aircraft range and flight time based on the design parameters of the four main flight sections was established based on the neural network method. The genetic algorithm is used to optimize the flight path of the prediction model with the range as the objective function. The research results show that the neural network prediction model based on the parametric design of the trajectory can predict random sample points better than the trajectory model For the prediction of random sample points, compared with the calculation results of the trajectory model, the maximum errors of the flight range and flight time are within 0.82% and 0.45%. The prediction model is optimized with the flight range as the objective function, and the relative error between the optimal range and the trajectory model under the corresponding section parameters is less than 0.2%, which shows that the model established in this paper can better predict the range and flight time according to the section design parameters. Parametric modeling and neural network optimization are feasible methods for aircraft trajectory design and section parameter optimization.
      PubDate: 2022-05-13T00:00:00Z
       
 
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