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  Subjects -> SCIENCES: COMPREHENSIVE WORKS (Total: 374 journals)
Showing 201 - 265 of 265 Journals sorted alphabetically
Jurnal Udayana Mengabdi     Open Access  
Karaelmas Science and Engineering Journal     Open Access  
Karbala International Journal of Modern Science     Open Access  
Kennedy Institute of Ethics Journal     Full-text available via subscription   (Followers: 10)
LOGIKA Jurnal Ilmiah Lemlit Unswagati Cirebon     Open Access  
Makara Journal of Science     Open Access  
Malawi Journal of Science and Technology     Open Access   (Followers: 6)
Maskana     Open Access  
MethodsX     Open Access   (Followers: 1)
Metode & Forskningsdesign     Open Access  
Mètode Science Studies Journal : Annual Review     Open Access  
Middle East Journal of Science     Open Access  
Middle European Scientific Bulletin     Open Access  
Modern Applied Science     Open Access   (Followers: 1)
Momona Ethiopian Journal of Science     Open Access   (Followers: 5)
MUST : Journal of Mathematics Education, Science and Technology     Open Access   (Followers: 4)
Mutis     Open Access  
National Academy Science Letters     Hybrid Journal   (Followers: 3)
National Science Review     Hybrid Journal   (Followers: 1)
Natural Sciences     Open Access  
Natural Sciences Education     Hybrid Journal  
Naturen     Full-text available via subscription  
Nepal Journal of Science and Technology     Open Access  
Network Science     Hybrid Journal   (Followers: 4)
New Directions in the Teaching of Physical Sciences     Open Access   (Followers: 2)
Nordic Journal of Science and Technology     Open Access   (Followers: 2)
Nordic Studies in Science Education     Open Access   (Followers: 3)
Nova     Open Access  
Nuncius     Hybrid Journal   (Followers: 2)
OmniScience : A Multi-disciplinary Journal     Full-text available via subscription  
Open Conference Proceedings Journal     Open Access  
Open Journal of Applied Sciences     Open Access  
Orbis Cógnita : Revista Científica     Open Access   (Followers: 3)
Patterns     Open Access  
PENDIPA : Journal of Science Education     Open Access  
People and Nature     Open Access   (Followers: 3)
Población y Desarrollo - Argonautas y caminantes     Open Access  
Politique et Sociétés     Full-text available via subscription   (Followers: 1)
Portal de la Ciencia     Open Access  
Proceedings of the Indian National Science Academy     Full-text available via subscription  
Proceedings of the Linnean Society of New South Wales     Full-text available via subscription   (Followers: 2)
Proceedings of the Royal Society of Queensland, The     Full-text available via subscription  
QScience Connect     Open Access  
RAC: Revista Angolana de Ciências     Open Access  
Rafidain Journal of Science     Open Access  
Rehabilitation Research, Policy, and Education     Hybrid Journal   (Followers: 2)
Rekayasa     Open Access  
Reportes Científicos de la FaCEN     Open Access  
Reports in Advances of Physical Sciences     Open Access  
Research     Open Access   (Followers: 1)
Research Ideas and Outcomes     Open Access  
Research Integrity and Peer Review     Open Access  
Research Policy : X     Open Access   (Followers: 2)
Respuestas     Open Access  
Reviews in Theoretical Science     Full-text available via subscription  
Revista Bases de la Ciencia     Open Access  
Revista Binacional Brasil - Argentina: Diálogo entre as ciências     Open Access  
Revista Brasileira de Iniciação Científica     Open Access  
Revista Catarinense da Ciência Contábil     Open Access  
Revista Ciencia y Tecnología     Open Access  
Revista Ciência, Tecnologia & Ambiente     Open Access  
Revista Científica de la FAREM     Open Access  
Revista Científica de la Universidad Nacional del Este     Open Access   (Followers: 1)
Revista Cientifica Guillermo de Ockham     Open Access  
Revista Científica y Tecnológica UPSE     Open Access  
Revista Conhecimento Online     Open Access  
Revista Crítica de Ciências Sociais     Open Access  
Revista de Ciencia y Tecnología     Open Access  
Revista de Información Científica     Open Access  
Revista de la Academia Colombiana de Ciencias Exactas, Físicas y Naturales     Open Access  
Revista de la Sociedad Científica del Paraguay     Open Access  
Revista de la Universidad del Zulia     Open Access  
Revista Eletrônica Ludus Scientiae     Open Access  
Revista Logos Ciencia & Tecnología     Open Access  
Revista MundoFesc     Open Access  
Revista Politécnica     Open Access  
Revista Saber Digital     Open Access  
Revista Sociedad y Economía     Open Access  
Revista Tecnológica     Open Access  
Revista Theoria     Open Access   (Followers: 1)
Revista UNIMAR     Open Access  
Revista UniVap     Open Access  
Revista Vivências em Ensino de Ciências     Open Access   (Followers: 1)
Rihan Journal for Scientific Publishing     Open Access  
Royal Society Open Science     Open Access   (Followers: 7)
Ruhuna Journal of Science     Open Access  
Sainstek : Jurnal Sains dan Teknologi     Open Access  
SAINSTIS     Open Access  
Sainteknol : Jurnal Sains dan Teknologi     Open Access  
Sakarya Üniversitesi Fen Bilimleri Enstitüsü Dergisi     Open Access  
Scholedge International Journal of Multidisciplinary & Allied Studies     Open Access  
Sci     Open Access  
Science     Full-text available via subscription   (Followers: 4354)
Science & Diplomacy     Free   (Followers: 3)
Science & Technology Studies     Open Access   (Followers: 3)
Science Advances     Free   (Followers: 27)
Science and Technology     Open Access   (Followers: 2)
Science Diliman     Open Access  
Science Heritage Journal     Open Access  
Science World Journal     Open Access  
Science, Technology and Arts Research Journal     Open Access   (Followers: 1)
ScienceRise     Open Access  
Sciences du jeu     Open Access  
Sciential     Open Access  
Scientific African     Open Access  
Scientific American     Full-text available via subscription   (Followers: 446)
Scientific American Mind     Full-text available via subscription   (Followers: 10)
Scientific Bulletin     Open Access  
Scientific Data     Open Access   (Followers: 5)
Scientific Journal of Mehmet Akif Ersoy University     Open Access  
Scientific Journal of Pure and Applied Sciences     Open Access   (Followers: 1)
Scientific Reports     Open Access   (Followers: 85)
Scientific World     Open Access  
Scientonomy : Journal for the Science of Science     Open Access   (Followers: 1)
Scienze Regionali : Italian Journal of Regional Science     Full-text available via subscription   (Followers: 18)
Selforganizology     Open Access  
Seminário de Iniciação Científica e Seminário Integrado de Ensino, Pesquisa e Extensão     Open Access  
Simbiótica     Open Access  
SINET : Ethiopian Journal of Science     Open Access   (Followers: 5)
Smart Science     Open Access  
South African Journal of Science     Open Access   (Followers: 3)
South American Sciences     Open Access  
South East European University Review (SEEU Review)     Open Access   (Followers: 2)
Springer Science Reviews     Hybrid Journal   (Followers: 2)
Studies in Science Education     Hybrid Journal   (Followers: 18)
Sultan Qaboos University Journal for Science     Open Access  
Tanzania Journal of Science     Open Access   (Followers: 4)
TD : The Journal for Transdisciplinary Research in Southern Africa     Open Access  
Technologies     Open Access   (Followers: 1)
TECNOSCIENZA: Italian Journal of Science & Technology Studies     Open Access   (Followers: 1)
Temas y Debates     Open Access  
The Innovation     Open Access  
The Scientific World Journal     Open Access  
The Social Studies     Hybrid Journal   (Followers: 3)
The Winnower     Open Access  
Theoria     Open Access   (Followers: 3)
THEORIA : An International Journal for Theory, History and Foundations of Science     Full-text available via subscription   (Followers: 1)
Transactions of Tianjin University     Full-text available via subscription  
Trilogía     Open Access  
TÜBAV Bilim Dergisi     Open Access  
Türk Bilim ve Mühendislik Dergisi     Open Access  
Tydskrif vir Geesteswetenskappe     Open Access  
Uluslararası Bilimsel Araştırmalar Dergisi (IBAD)     Open Access   (Followers: 1)
UNED Research Journal / Cuadernos de Investigación UNED     Open Access  
Uni-pluriversidad     Open Access  
Uniciencia     Open Access  
Universidad, Ciencia y Tecnología     Open Access  
Universitas (León)     Open Access  
Universitas Scientiarum     Open Access  
Unnes Science Education Journal     Open Access  
Vilnius University Proceedings     Open Access  
Walailak Journal of Science and Technology     Open Access  
WikiJournal of Science     Open Access  
World Scientific Research     Open Access  
Zeitschrift für Didaktik der Naturwissenschaften     Hybrid Journal  
Образование и наука     Open Access   (Followers: 1)
Східно-Європейський журнал передових технологій : Eastern-European Journal of Enterprise Technologies     Open Access   (Followers: 2)

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Sakarya Üniversitesi Fen Bilimleri Enstitüsü Dergisi
Number of Followers: 0  

  This is an Open Access Journal Open Access journal
ISSN (Print) 1301-4048 - ISSN (Online) 2147-835X
Published by Sakarya Üniversitesi Homepage  [3 journals]
  • Site Calibration of a Temperature-based Model for Estimating the Global
           Solar Radiation

    • Authors: Ceyda AKSOY TIRMIKÇI
      Abstract: In this paper, a commonly used global solar radiation (GSR) model is locally calibrated and tested for Kartepe, Kocaeli station. The coefficients of the model are calibrated for monthly and yearly by performing a regression analysis using the measured temperatures. Regression analysis results for both models provide that correlating the clearness index with the second degree of maximum temperature divided by minimum temperature gives the best accuracy for the selected location. Besides, the estimation results for each month indicate that the monthly calibrated coefficients provide very accurate results in terms of statistical errors. Moreover, yearly calibration of the model gives less accurate predictions. The simple and accurate results by monthly calibrated models using this approach can be used in designing and evaluating solar energy applications in the absence of accurate sunshine data.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • Early-breeding Season Movements of the Yelkouan Shearwater (Puffinus
           yelkouan, Acerbi, 1827) at the Dardanelles Strait

    • Authors: İbrahim UYSAL; Lider SİNAV, Yakut Can AŞIKOĞLU, Şafak ARSLAN
      Abstract: We aimed to make censuses of Puffinus yelkouan at the Dardanelles and to evaluate the movements at the Aegean and the Marmara Sea during the early breeding period. Field studies were carried out in the morning and afternoon for 40 days between 6 February and 22 March 2019. In the censuses, the highest number of birds, passing in both directions in a day was 78145 individuals; 56451 of them were counted in the direction of the Aegean Sea on 17 February, which is the highest number counted in one direction in a day. As a result, the number of birds crossing to the Aegean Sea through the Dardanelles in the afternoon is significantly higher than the number of birds crossing to the Aegean Sea in the morning. In the afternoon, the number of birds flying towards the Aegean Sea is significantly higher than the number of birds flying towards the Marmara Sea. Considering that the species visits the breeding colonies at night, this movement pattern could be related to the fact that the shearwater breeding population is predominantly found in the Aegean or in the Mediterranean Sea. In addition, some issues, such as how long the birds stay in these sea regions after flying to the Aegean Sea or the Marmara Sea, which route they follow or how the flocks mix require further investigation.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • Metabolism Determination By Soft Computing Methods From Breath Molecules

    • Authors: Sedat METLEK; Hatice AKMAN, Ismail BAYRAKLI
      Abstract: The breath analysis is a non-invasive risk-free and painless method used to diagnose specific diseases. Since the breath analysis method is a new study field than the other methods, there are many unsettled standards and unknown parameters. Numerous complex metabolisms are constantly working in the human body. Therefore, there are numerous unknown molecular relationships. ANN can produce solutions in these unexplained situations.In our pilot study, breath of 19 healthy people has been analyzed. The TD / GC-MS method, which is an analytical method of breath analysis, has been used to detect molecules in the breaths. Using soft computing methods to the results of the 19 breath samples, the relation between fermentation and carbon hydrate metabolism has been associated with breath analysis technique. The results indicated that, there can be a relationship between these metabolisms. There must be done more studies for the exact results.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • The Variation of the Linewidths and Amplitudes of Sub-Doppler Resonances
           of 87Rb D2 Line with Laser Beam Intensity

    • Authors: Ersoy ŞAHİN
      Abstract: The sub-Doppler resonances linewidths and amplitudes depend on the laser beam intensity. The effect of laser beam intensity on the resonance linewidths and amplitudes obtained from different energy transitions of atoms varies from resonance to resonance. The effect of laser beam intensity on resonance linewidths and amplitudes is of great importance for diode laser frequency stability applications. It needs to be determined by measuring. The effect of the laser beam intensity on the linewidths and amplitudes of sub-Doppler resonances were measured by laser heterodyne spectroscopy using the linearly polarized frequency stabilized extended cavity diode lasers. The measurements are compatible with the theory and the uncertainty of the measurements are fewer than 1.6 MHz and 0.3 mV for linewidths and amplitudes, respectively.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • Performance of Gas-Phase Toluene by Adsorption onto Activated Carbon
           Prepared from Robinia Pseudoacacia L. as Lignocellulosic Material

    • Authors: Kaan IŞINKARALAR
      Abstract: The main target of this study was to eliminate gas-phase toluene with activated carbon from indoor air. The activated carbons were prepared from Robinia pseudoacacia L. biomass under different conditions. The change in surface functional groups of the produced activated carbon biomass raw material and produced by pyrolysis in the absence of oxygen at 500–900 °C, and activation by potassium hydroxide (KOH). The highest surface area of 1271.3 m2/g which gives reason for its external porous surface. The surface porosity and the graphite properties of the prepared KNxACs were detected by scanning electron microscope (SEM). The amount of adsorbed toluene (C7H8) was determined using a gas chromatograph-mass spectrometry with a thermal desorber system (TD–GC–MS) on the KNxAC surface. The adsorption capacity of toluene was reached 111 mg/g at 25 °C and for 1000 ppm. As a result, the study revealed that the prepared KN24AC from the Robinia pseudoacacia L. biomass has the best adsorption capacity of gas-phase toluene from indoor air.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • Numerical Investigation of The Effect of Impeller Blade Angle for Stirred
           Tank

    • Authors: Dogan Engin ALNAK; Ferhat KOCA, Yeliz ALNAK
      Abstract: In this study, the most widely used Rushton turbine in the industry was discussed, and the effect of different blade angles on the mixture was investigated numerically. As a standard model, 6 bladed propellers were used and 4 baffles were placed in the stirred tank. The selected tank model is in the form of a flat bottom cylindrical container. Flow characteristics were obtained by giving angles (10°, 20°, 30°, 40°, 50°, 60°) to the propeller blades used in the straight model. The obtained results were compared with each other. In addition, analyzes were repeated at different rotation speeds (600 rpm, 750 rpm, 1000 rpm) for each model at each angle. ANSYS Fluent 18 commercial software, which is the most preferred CFD program in the literature, was used for this numerical study. The analyzes were provided in the standard k-epsilon (ε) turbulence model. The Multiple Reference Frame (MRF) approach was used to simulate impeller rotation. The velocity profiles obtained from the simulations have been shown to be in consistent with the experimental estimates and the results of previous studies. As a result, it has been revealed that the best mixing balance is provided by the impeller blade at 40 and 50 degrees.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • Quantum Reservoir Parameter Estimation via Fisher Information

    • Authors: Ufuk KORKMAZ; Deniz TÜRKPENÇE
      Abstract: In this study, we show that as a result of weak interaction of different information environments structured with a single probe qubit, these environments can perform binary classification of the information they contain. In this way, we refer to these environments as quantum information baths because they consist of sequences of identical qubits in certain pure quantum states. A micro-maser like master equation has been developed to clearly describe the system dynamics analytically and the quantum states of different information reservoirs. The model can also be treated as a quantum neuron, due to the single-qubit probe that makes a binary decision depending on the reservoir parameters in its steady state. The numerical results of the repeated interaction process based on the divisibility and additivity of the quantum dynamic maps are compared with the analytical results. Besides being a single quantum classifier, the model we present can also serve as a basic unit of a quantum neural network within the framework of the dissipative model of quantum computing.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • Aeroacoustic Simulation of an Owl Wing Cross-section Using Computational
           Fluid Dynamics

    • Authors: Ferit YILDIZ; Sedat TOKGOZ
      Abstract: In this study, we aim to investigate the low noise flights of owls in terms of aerodynamics. The flow around cross-section of an owl wing, which is known for its nearly silent flight, is numerically analyzed using Computational Fluid Dynamics (CFD). The analysis are based on the parameters of angle of attack and the flight speed. The aerodynamic effects on the acoustic is compared in terms of vorticity and sound pressure level, where the frequency interval for the acoustic data is set to 0-7500Hz. It was seen that the vortical organisations around the airfoils are closely related to the acoustic results. The results show that the increase in both velocity and angle of attack affect the vorticity, thus lead to a rise in sound pressure level. It can be stated that the owl airfoil shape ensures a relatively silent flight.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • GC-MS Analysis and Potential Apoptotic Effect of Paliurus spina-christi
           Mill. Leaf and Flower Extracts against Breast Cancer Cells

    • Authors: Ferdi OGUZ; Çisil ÇAMLI PULAT, Süleyman İLHAN, Harika ATMACA
      Abstract: In recent years, herbal medicines have become a significant novel source of treatment for various types of cancer, including breast cancer. Various investigations have declared that Paliurus spina-christi Mill. (PSC) shows antioxidant, antifungal, antimicrobial, and antibacterial properties, but its effect on cancer cells is unknown. This study purposed to evaluate the possible anti-cancer effects of the ethanolic extract of the PSC in human MCF-7 and MDA-MB-231 breast cancer cells. The leaf and flower extracts of PSC were prepared in ethanol and volatile compounds were determined by GC-MS analysis. The possible cytotoxic effects of extracts were evaluated via MTT assay. Apoptotic effect was examined using the PI Annexin V Apoptosis Detection Kit. Significant cytotoxic effects were detected after 72 h treatment of ethanolic leaf and flower extracts in MCF-7 cells but not in MDA-MB-231 cells. Both leaf and flower extracts of PSC induced apoptotic cell death in MCF-7 cells. On phytochemical screening, it was shown that the leaf extract of PSC contains pyrrolidine, 2-decenal, 2-undecanal, phytol, oleic acid, oleamide, squalane, vitamin E, and gamma-sitosterol and the flower extract contains pyrrolidine, 2-decenal, 2-undecenal, oleic acid, lupeol, and gamma-sitosterol. These data report that PSC leaf and flower extracts have cytotoxic and apoptotic effects in MCF-7 breast cancer cells. Moreover, this study can be considered an in vitro background for further in vivo cancer experiments.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • Seismic Performance Evaluation and Retrofit of Liquid Storage Tanks- Case
           Study

    • Authors: Bülent ERKMEN
      Abstract: Seismic performance of existing liquid pentane storage tanks located in a tank farm in Turkey Kocaeli region, which is a high seismic region, is studied. The tanks are free-to-slide on their existing reinforced concrete foundation. The tanks seismic performance is evaluated based on the 2018-Turkish Building Seismic Code and API 650 provisions using three-dimensional (3D) finite element methods with nonlinear time-history analysis. The developed FE model for seismic performance assessment of the existing tanks includes tank-foundation dynamic interaction, tank supports uplifting, and sliding over the foundation. The study revealed poor and inadequate seismic performance for the existing tanks due to lack of tank foundation-anchorage. A practical seismic retrofit strategy is developed to anchor the tanks to the existing reinforced concrete foundation. Prefabricated and field-welding free steel split sleeves are developed for the tank anchorage. The retrofitted tank seismic performance is evaluated to verify the proposed retrofit strategy and its effects on tank seismic behavior. The base shear and uplift reactions for the retrofitted tank are monitored for the anchorage design. Tank top drift, which is an important seismic performance parameter for tank piping, and tank steel material yielding are also checked to verify adequacy of the proposed retrofit strategy.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • CFD Analysis of Convection Heat Transfer in Corrugated Channels for
           Different Inclination Angle

    • Authors: Haydar KEPEKÇİ; Erman ASLAN
      Abstract: Three different geometries have been used in this study, which investigated the effect of inclination angle on convective heat transfer in corrugated channels. The corrugated channel geometries used have inclination angles of 30°, 45°, and 60°. The finite volume method has been used in the study with numerical methods. k-ω, SST, and transition SST have been used as turbulence models. The mesh file used in the analysis consists of 192000 cells. The results obtained from the calculations using a corrugated channel with a 30° inclination angle have been compared with the experimental data. As a result of this comparison, the turbulence model to be used for this study has been determined as SST. SST turbulence model has been used in the analyzes made using a corrugated channel with 45° and 60° inclination angles and the results have been compared with each other. The Reynolds number ranges from 2225 to 7380. The Nusselt number and friction factor have been calculated using the data obtained as a result of the analysis. Based on the calculated values, it has been determined that the heat transfer increases as the angle of inclination increases in the corrugated channels. It has been also observed that the Nusselt number increased as the Reynolds number increased. It has been also seen that the analyzes for high Reynolds number gave results closer to the experimental data.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • Real-Time Encrypted Traffic Classification with Deep Learning

    • Authors: Deniz Tuana ERGÖNÜL; Onur DEMİR
      Abstract: Confidentiality requirements of individuals and companies led to the dominance of encrypted payloads in the overall Internet traffic. Hence, traffic classification on a network became increasingly difficult as it must rely on only the packet headers. Many vital tasks such as differential pricing, providing a safe Internet for children, and eliminating malicious connections require traffic classification, even if the payload contents are encrypted. Encrypted traffic is harder to classify as packet content becomes unreadable. In this work, we aim to provide an insight into traffic classification using encrypted packets in terms of both accuracy and packet processing time. LSTM (Long Short-Term Memory) architecture is a good candidate for this problem as it can handle sequences. Each flow can be modeled as a sequence and patterns of the sequences can provide valuable information. We compare the performance of LSTM with other methods in both real-time and offline experiments. Compared to a machine learning method both online and offline LSTM excelled with precision and recall differences up to 50%. Average accuracy with LSTM was measured as 97.77% offline and 91.7% in real-time. Average packet processing time in real-time was recorded as 0.593 msec which is 5 times faster than a recent work that uses LSTM method.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • Changes in Food Supply and Consumption Practices of People in Turkey
           During the COVID-19 Pandemic

    • Authors: Hatice SIÇRAMAZ; Güliz HASKARACA, Yusuf ARSLAN
      Abstract: The COVID-19 pandemic has had social and economic impacts on every country in the world and has caused significant changes in human nutrition. In this study, changes in the food supply chain and consumption practices before and after the controlled normalization of people living in Turkey were examined, with a survey of 1087 people. The results revealed that people focused on a healthier diet during the pandemic. The increase in dietary supplement consumption has not been too high, only 11% of people started to take dietary supplements, but fast food consumption had a sharp fall. The packaging has become more critical. People continued to use take-out services from supermarkets and fast-food restaurants. Although normalization has begun, most of them (90%) reduced or did not think about eating out until COVID-19 will over. This study revealed the effects of the pandemic on human nutrition and showed which direction the food supply should go.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • Reliability Analysis of Sakarya Area Electricity Distribution System

    • Authors: Adem TAŞIN; Türker Fedai ÇAVUŞ
      Abstract: Power system reliability is an important issue for providing minimal loss of service to each user. It is accepted that almost 90% of power outages are caused by failures in the Electricity Distribution System. In this study, the reliability analysis of the Alancuma feeder belonging to the Sakarya distribution system was aimed. The reliability assessment of the feeder was made using the analytical approach, Monte Carlo simulation (MCS) technique and ETAP (Electrical Transient and Analysis Program) software, and the results were observed to be close to each other. The most commonly used SAIFI and SAIDI system indices were evaluated according to the Turkey average and the reasons for the interruption for the feeder were investigated.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • Theoretical Investigation of W(CO)6 and CO Selenization Process

    • Authors: Nadire NAYİR
      Abstract: Detailed atomic-level insight into the mechanism of W(CO)6 and CO selenization is essential for the fabrication of cheap and environmentally benign transition metal chalcogenides such as MoS2 and WSe2. Earlier discussions in literature have focused mainly on the CO methanation by sulfur and its derivatives but H2Se mediated CO methanation at the atomic level is yet to be explored. First-principles calculations and ReaxFF-based molecular dynamics simulations are conducted here to explore the relative stabilities of intermediates formed during the gas-phase interactions of W(CO)6 and H2Se, determined associated reaction energies and kinetic barriers. The methanation of CO, which is released from the organometal, by H2Se is further investigated. The results indicate that the chain reactions of W(CO)6 and H2Se lead to the formation of a thermodynamically stable end product of W(SeH)2Se2. Depending on the temperature, W(HSe)2Se2 is expected to go through a last uphill reaction by releasing H2Se into the environment and evolving into a WSe3 molecule. Additionally, the dehydrogenation of organometallic molecules is thermodynamically feasible but kinetically controlled, requiring a significant activation energy. When all CO groups are released from the W atom, the H2 release from W-compund becomes nearly barrierless. Since CO radical groups are dominant byproducts formed during the MOCVD chain reactions but in a chalcogen rich environment, this work also shed light into the CO selenization during the growth of transition metal diselenides (e.g., WSe2, MoSe2, CrSe2) and discusses the formation of potential products such as CSe2, CH4, H2Se, CO, H2O, Se2.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • Identification of Lactic Acid Bacteria in Fermented Cornichon Pickles
           Produced with Acid Whey and Vinegar

    • Authors: Semanur CEBECİ AVUNCA; Özlem ÖZTÜRK ÇETİN, Arzu ÇAĞRI MEHMETOĞLU, Mustafa ÖZTÜRK
      Abstract: The purpose of this study is to isolate, identify and compare lactic acid bacteria responsible for fermentation from pickles produced with vinegar and acid whey (AW). For this reason, fermented cornichon pickles were produced by using AW and vinegar as brine media. Colonies with different morphologies were selected and isolated at the 0, 7, 14, 21, 35, 49, 77 and 105th days of fermentation. A total of 139 isolates were obtained. Salt, acidity and pH values of brine and cornichon were followed on each analysis day. Growth and gas formation from glucose of isolates at different temperatures (10, 45, and 50 oC), salt concentrations (2, 4.5, and 10% (w/w)), different pH values (3, 4.5, and 9.6), were analyzed. Eight isolates were determined as heterofermentative according to their ability to produce CO2 from glucose. The isolates were observed to show the highest growth at 10 oC, and a very few isolates developed at 45 oC and 50 oC. No isolates were able to grow at pH 9.6, 25 of the isolates were able to grow at pH 4, and only 4 isolates were able to grow at pH 3. Only one isolate was able to show resistance to 10% salt concentration. Almost all isolates grew at 2% and 6.5% salt concentrations. 48 selected isolates were identified with API 50 CHL. 19 isolates were determined as Lactobacillus pentosus (8 vinegar, 11 AW) and 29 isolates as Lactobacillus plantarum (16 vinegar, 13 AW). As a result, L. plantarum and L. pentosus species were the dominant bacteria for cornichon pickles produced with AW and vinegar. Microbial flora in the pickles produced with two different brines were similar. The results show that AW can be successfully used for pickle production.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • Quasi-Resonant Half-Wave Buck Converter with Non-Isolated High Side
           Switching Techniques

    • Authors: Burak GÖRDÜK; Elif TOPUZ, Deniz YILDIRIM
      Abstract: Power density of the power converters became one of the most important parameters in many applications. Power density is increased by reducing the losses through use of better performing components and circuit topologies. It can be increased further by reducing the size of filter components through increasing the switching frequency. In hard-switching converters however, losses due to switching will eventually render this method not applicable. Instead, resonant converters are utilized in many high-frequency switched power supplies. Soft-switching feature of these converters provide increased efficiency due to decreased switching losses. Such converters exploit the resonance of the specific inductors and capacitors in the circuit called as resonant tank elements. Resonance behavior is used in order to eliminate turn-on or turn-off losses. Existing power converter topologies can be modified to create the resonance during switching period. Such converters are called as quasi-resonant converters. This paper presents analysis and design of Zero Current Switching (ZCS) half-wave quasi-resonant buck converters. In this topology, high-side switching is required. Two different non-isolated high-side switching techniques are utilized. Experimental results are obtained for light load to full load operation. Both techniques are compared in detail.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • A Numerical Investigation for the Effect of Environmental Conditions on
           the Bending Behaviour of Laminated Composites

    • Authors: Rabi Ezgi BOZKURT; Fatih DARICIK
      Abstract: In this study, the bending behavior of fiber-reinforced laminated composites (FRCs) with a balanced and symmetric stacking sequence was investigated numerically under different environmental conditions. The numerical models of carbon/ bismaleimide, carbon/epoxy, and S-glass/epoxy laminated composites were designed and analyzed using ESAComp software. Deformation of the FRCs models was simulated with three-point bending conditions and the effects of material properties varying with environmental conditions on the flexural analysis were investigated according to the Tsai-Wu criterion and the Puck criterion. The Tsai-Wu criterion detects the failure of FRCs earlier and behaves more conservative than the Puck criterion for all environmental conditions. The flexural strength and failure mode of the laminates vary with the variation of environmental conditions. The order of the first damaged ply varied depending on the type of reinforcing fiber. Especially the presence of moisture and high temperature significantly influences the flexural strength of the laminated composites.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • An Existing Problem for Symmetric Design: Bruck Ryser Chowla Theorem

    • Authors: Emek DEMİRCİ AKARSU; Safiye ÖZTÜRK
      Abstract: Symetric designs are interesting objects of combinatorics, and have some relations with coding theory, difference sets, geometry and finite group theory. They have applications on statistics and design experiments. In the present paper we study an existing problem for symmetric design due to Bruck, Ryser and Chowla and write an algorithm by using their theorem called BRC Theorem.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
  • Electrochemical Reduction of Lead Sulphide in NaCl-KCl and NaCl-KCl-%2Na2S

    • Authors: Levent KARTAL
      Abstract: In this study, the lead production from lead sulfide (PbS) by molten salt electrolysis was investigated under potentiostatic and galvanostatic conditions using NaCl-KCl and NaCl-KCl-2%Na2S electrolytes. Stable cell voltage and current were aimed with the addition of Na2S to the NaCl-KCl electrolyte. Reduction experiments were carried out at constant 700 °C temperature and for 15 min. duration. The current density was set to 250 mA/cm2 for the galvanostatic reduction experiments. It was observed that there was an increase in cell voltage in both electrolytes due to the decrease in the amount of PbS in galvanostatic experiments. In these experiments, it was determined that the reduction occurred at higher cell voltages in the NaCl-KCl electrolyte compared to the NaCl-KCl-2%Na2S electrolyte. Although the cell voltage was aimed to remain constant with the Na2S addition, the cell voltage decreased slightly compared to the NaCl-KCl electrolyte, but increased with the experiment duration as in the NaCl-KCl electrolyte. Potentiostatic reduction experiments carried out at a constant cell voltage of 3.0 V under the electrolyte decomposition voltage. The morphology of the cathode products was examined by SEM-EDS analysis and, the phases were examined by X-ray diffractometry. Higher current values were obtained in the NaCl-KCl-%2Na2S electrolyte compared to the NaCl-KCl electrolyte. Current variation with electrolysis duration showed similar trends in both electrolytes. According to structural characterization, it was determined that the metallic lead mass did not contain any impurities.
      PubDate: Sat, 30 Apr 2022 00:00:00 +030
       
 
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