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H2 Evolution Reaction Pathway of a Cobalt Bis-bipyridyl Planar Catalyst Revealed by Ab Initio Simulations
No full textLigand type and ligand coordination around cobalt photocatalysts influence the reaction mechanism of H2 production via water splitting. We investigated the H2 production mechanisms of a cobalt bis-bipyridyl planar water reduction catalyst in an aqueous solution using ab initio molecular dynamics, metadynamics, density functional theory, and free energy perturbation theory. Modeling each intermediate step of the reaction mechanism reveals that the cobalt-based planar catalyst exhibits a preference for a pathway involving two successive reductions, followed by two protonation steps. The reason for this preference is the presence of an energy barrier for the conformational change of water molecules in the first solvation shell following the first reduction. This barrier prevents direct coordination of cobalt with protons, which is necessary for the initial protonation step in the sequential electron- and proton-transfer mechanisms. In the mechanism involving two successive reductions followed by two protonations, however, the second reduction step facilitates direct interaction between cobalt and protons, enabling the initial protonation. Following the second protonation of this mechanism, H2 is produced and released into the solvent. Reduction free energy calculations reveal that, following the first reduction, the singlet spin state of the system is more favorable than the triplet spin state. The reduction free energy of the second electron transfer is 0.19 eV less energetic than that of the first reduction reaction.T?rkiye Bilimsel ve Teknolojik Arastirma Kurumu; Scientific and Technological Research Council of Turkiye (TUBITAK) [120Z240]; TUBITAKY.G. acknowledges the Scientific and Technological Research Council of Turkiye (TUBITAK). This study has received funding from the TUBITAK under the 3501 Career Development Program (grant agreement No. 120Z240). The calculations reported in this paper were performed at the TUBITAK ULAKBIM, High Performance and Grid Computing Center (TRUBA), based in Turkiye
Electromagnetic wave absorption in polyaniline coated Y3Fe5O12/Carbon-Black hybrid composites
No full textY3Fe5O12(YIG)(1-x)/Carbon-Black(CB)(x) (0.00 <= x <= 1.00; 0.25 steps) coated with polyaniline (PANI), forming a core-shell structure, were synthesized by in-situ polymerization following sol-gel and solid-state reactions. The crystalline, surface morphology and magnetic properties of YIG(1-x)/CBx and PANI@YIG(1-x)/CBx hybrid composites were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM), respectively. Electromagnetic wave (EMW) absorbing properties were investigated by measuring dielectric parameters in the 2-18 GHz frequency range. The reflection loss (RL), impedance matching, and loss tangent were studied in detail. The electromagnetic wave absorbing mechanisms were discussed by considering dielectric and magnetic losses, as well as microstructural properties of the samples. The EMW absorbing performance of the YIG(1-x)/CBx composites showed a broadband absorption property (7.0 GHz bandwidth at -10 dB reflection loss value) in YIG(0.75)/CB0.25 composite. When the composites are covered with conductive PANI, the EMW absorbing performance is enhanced in terms of RL (minimum -36.5 dB) and effective absorption bandwidth (EAB) (maximum 10.2 GHz at -10 dB) values due to increasing scattering probability, interfacial polarization and conduction loss of the penetrated EMW. The results showed that a wider absorption frequency range could be obtained by coating PANI on YIG/CB composite.Koluman Automotive Industry [RD57]; Adana Alparslan Turkes Science and Technology University Scientific Research Council [22303007]This work was supported by Koluman Automotive Industry with project number RD57. This work was partially supported by Adana Alparslan Turkes Science and Technology University Scientific Research Council under Project No: 22303007
The energy rebound effect within the framework of environmental sustainability
No full textThe energy rebound effect, characterized by increasing energy use despite enhanced efficiency, has emerged as a complex interdisciplinary topic in the literature, reflecting its significance in both production and consumption sustainability. Recognizing the pivotal role of academic research in shaping energy management strategies and policies, this study conducted a comprehensive bibliometric review, accessing 530 articles from major citation indexes. This analysis provides insights into the evolution of the energy rebound field and potential future directions. Understanding the existing literature on the rebound effect serves as a valuable foundation for forthcoming research endeavors, addressing the intricate challenge of reconciling energy efficiency with sustainable energy consumption and production. The review explores the extensive literature on the energy rebound effect, highlighting a predominant focus on residential (e.g., cooling, heating, lighting, transportation) and industrial energy consumption in the majority of studies. Empirical applications primarily emphasize the measurement of the energy rebound effect, with a notable trend of increasing research concentration in China in recent years. Additionally, there is a growing body of economy-wide analyses in this field. However, the literature exhibits complexity in both the analyses conducted and the methods employed for measuring the rebound effect. Research gaps are apparent, numerous studies tend to concentrate solely on the rebound effect at the overall energy consumption level, neglecting variations in energy types and the behavioral patterns of economic actors. Furthermore, despite consistent findings of a higher rebound effect in developing nations, there is a noticeable lack of scholarly literature addressing this issue about these countries. This article is categorized under: Sustainable Energy > Energy Efficiency Human and Social Dimensions > Behavioral Science Policy and Economics > Governance and Regulatio
Design of spectrally selective multilayer stacks with optimized properties for mid-temperature concentrating solar applications
No full textThis study presents an original method to optimally design the multi-layer stacks at varying layer counts, depths, and orders using 20 widely used candidate materials on copper (Cu) and stainless steel (SS) substrates. The water cycle algorithm (WCA) for the constrained design problem using genetic operators was adapted as an optimization algorithm. The study aims to design stacks for two different substrates, with high absorptivity (>0.95) in the solar spectrum and low emissivity (<0.1) in the infrared region for concentrating solar applications operating between 673 and 973 K. Two fitness functions, F-1 and F-2, are proposed and benchmarked at specified design conditions to analyze their efficacies. Results show that the increase in the coating efficiency (eta(c)) is less than 0.94 % in the case of adding more than 5 layers on the substrates. The difference between the coating efficiencies of the proposed stacks using SS and Cu substrates is less than 0.26 %. It is believed that the advanced optimization algorithm given in the paper will pave the way for more efficient solar selective absorber designs
The physicochemical properties and molecular docking study of plasticized amphotericin B loaded sodium alginate, carboxymethyl cellulose, and gelatin-based films
No full textPlasticizers are employed to stabilize films by safeguarding their physical stability and avoiding the degradation of the loaded therapeutic drug during processing and storage. In the present study, the plasticizer effect (glycerol) was studied on bioadhesive films based on sodium alginate (SA), carboxymethyl cellulose (CMC) and gelatin (GE) polymers loaded with amphotericin B (AmB). The main objective of the current study was to assess the morphological, mechanical, thermal, optical, and barrier properties of the films as a function of glycerol (Gly) concentration (0.5-1.5 %) using different techniques such as Scanning Electron Microscope (SEM), Texture analyzer (TA), Differential Scanning Calorimeter (DSC), X -Ray Diffraction (XRD), and Fourier Transforms Infrared Spectroscopy (FTIR). The concentration increase of glycerol resulted in an increase in Water Vapor Permeability (WVP) (0.187-0.334), elongation at break (EAB) (0.88-35.48 %), thickness (0.032-0.065 mm) and moisture level (17.5-41.76 %) whereas opacity, tensile strength (TS) (16.81-0.86 MPa), and young's modulus (YM) (0.194-0.002 MPa) values decreased. Glycerol incorporation in the film -Forming solution decreased the brittleness and fragility of the films. Fourier Transform Infrared (FTIR) spectra showed that intermolecular hydrogen bonding occurred between glycerol and polymers in plasticized films compared to control films. Furthermore, molecular docking was applied to predict the binding interactions betweem AmB, CMC, gelatin, SA and glycerol, which further endorsed the stabilizing effects of glycerol in the complex formation between AmB, CMC, SA, and gelatin. The Findings of the current study demonstrated that this polymeric blend could be used to successfully prepare bioadhesive films with glycerol as a plasticizer.Research Council, Oman [BFP/URG/HSS/22/127, BFP/RGP/HSS/22/007]The study was supported by The Research Council, Oman grant number BFP/URG/HSS/22/127 and BFP/RGP/HSS/22/007
Impregnation of Pectin-Sodium Caseinate Films with Lemongrass Essential Oil: Physical-Chemical, Antimicrobial, and Antioxidant Assessment
No full textBiopolymers derived from natural resources have gained much interest in the past few decades to replace conventional nonbiodegradable petroleum-based packaging. Essential oils and plant extracts are frequently utilized for their antimicrobial and antioxidant properties in the development of edible films and coatings serving as bioactive compounds. The current study investigated the impact of various concentrations of lemongrass essential oil (LEO) on the physical and chemical characteristics as well as the antioxidant capabilities of films made from sodium caseinate and pectin. The addition of LEO led to a decrease in mechanical parameters of film samples like elongation at break (EAB) decreased from 19.73 +/- 0.81 to 4.06 +/- 0.20 and tensile strength (TS) decreased from 11.16 +/- 0.81 to 2.43 +/- 0.08 but a rise in opacity (4.39 +/- 0.14 to 5.60 +/- 0.13), thickness (0.044 +/- 0.005 to 0.078 +/- 0.005), and water vapor permeability (WVP) (0.391 +/- 0.013 to 0.760 +/- 0.035) was observed. The gloss value of the film samples increased from 11.9 +/- 0.1 to 13.1 +/- 0.1, and haziness increased from 45.85 +/- 1.05 to 71.69 +/- 0.25 as the concentration of LEO increased, reducing their transparency (89.22 +/- 0.27-88.24 +/- 0.19). Scanning electron microscopy (SEM) revealed additional microstructural alterations in the films as a result of the addition of LEO. Furthermore, antimicrobial activity was detected in the PSC4 film sample against E. coli. The oil-loaded films showed significantly higher antioxidant activity of 40.41% compared to the control film sample, having 16.57% antioxidant activity. Contact angle measurements demonstrated that the film samples became more hydrophobic with the addition of LEO (55.52 degrees in the maximum LEO concentrated film). This study introduces a promising method for creating active food packaging materials for packaging applications.Natural and Medical Sciences Research Center, University of Nizwa, OmanThe authors are thankful to the Natural and Medical Sciences Research Center, University of Nizwa, Oman, for providing research facilities to conduct the current study
Modeling and control of a new multi-port converter for hybrid energy system integration
No full textThis research introduces a new topology called the quasi-Z-source integrated isolated multiport bidirectional resonant DC-DC converter. The aim is to achieve cost-effective and efficient multi-directional power flow between photovoltaic (PV), battery/supercapacitor, and DC loads. The proposed topology ensures uninterrupted power supply to the loads and supports reverse power transfer through its bidirectional power flow capability. By combining quasi z-source and H-bridge resonant converters with an existing switch, a four-port converter is achieved without the need for separate converters or additional switches. The high-gain quasi z-source converter reduces the required voltage ratings of the battery and supercapacitor packs while enabling the utilization of a high-frequency transformer (HFT) with a low turns ratio. Isolation between the ports is achieved using a secondary center-tapped HFT equipped with a controlled full-wave rectifier on the secondary side, allowing bidirectional power flow. A power flow management system and corresponding control scheme are proposed to optimize the system's performance. The proposed system's performance is evaluated under various operating conditions, demonstrating its effectiveness in power flow management and overall efficiency. The results confirm the feasibility and effectiveness of the proposed system.Scientific Project Unit of Adana Alparslan Turkes Science and Technology University [21103002]The authors also would like to acknowledge the Scientific Project Unit of Adana Alparslan Turkes Science and Technology University (Project Number: 21103002) for full financial support
Saldırı tespiti için sürü zekası özellik seçimi ile birleştirilmiş ağaç tabanlı makine öğrenimi yöntemleri
No full text19.09.2026 tarihine kadar kullanımı yazar tarafından kısıtlanmıştır.Lisansüstü Eğitim Enstitüsü, Bilişim Teknolojileri Ana Bilim DalıGelişen teknoloji iletişim ve bilgi taşıma sürecini nesnel dünyadan dijital ortama taşımıştır. Bu değişim özellikle ağ trafiğinde atışa neden olmuştur. Bunun yanı sıra nesnel dünyada gerçekleştirilen bir çok iş ve işlem de dijital dünyaya aktarılmıştır. Banka bilgileri, ticari sır niteliğindeki bilgiler, kişisel veriler gibi hassas veriler de dijital ortama aktarıldığı için bu verilere ulaşıp çıkar elde etmeyi isteyen kötü amaçlı insanlar, geliştirdikleri yazılımlarla veri güvenliğini tehdit etmektedir. Bunun yanı sıra yoğun veri trafiği, kullanıcı sayısının çokluğu veri güvenliği sistemlerinin kapasitelerini zorlamaktadır. Veri trafiği datalarının toplanması ve veri trafiğinin normal olanla anormal olanın ayıklanması süreci yukarıda açıklanan nedenlerden ötürü zorlu bir süreçtir. Veri güvenliği sürecinin bir parçası olarak saldırı tespit sistemleri (IDS) bu süreçte görev alan yapılardan biridir. Bu sistemden beklenen, normal veri trafiği ile anormal veri trafiğini birbirinden ayırması ve bu işlemi yüksek doğruluk oranı ve olabildiğince düşük işlem süresinde yerine getirebilmesidir. Bilim dünyasında saldırıların tespiti süreci çeşitli yöntemlerle ele alınmıştır. Bazı tespit yöntemleri, daha önce anormal veri trafiği olarak işaretlenmiş verilerin izini yani imzasını ararken, bazı tespit sistemleri veri trafiğindeki anormalliği tespit etmeyi hedeflemiştir. Bu çalışmada anomali tespit yöntemi baz alınmıştır. Makine öğrenmesi otonom olması ve yüksek veri boyutlarıyla başa çıkabilmesi özellikleri nedeniyle bu yöntemde sıklıkla kullanılmıştır. Bu araştırma çalışmasında makine öğrenmesi modellerinde kullanılacak veri setini en iyi temsil eden öz nitelikleri belirlemek amacıyla sürü zekası algoritmaları kullanılmış, elde edilen özet veri seti makine öğrenmesi modelleri ile sınıflandırma işlemine tabi tutulmuştur. Önceki çalışmalarda elde edilen sonuçlarla kıyas yapabilmek için yaygın kullanılan 3 veri seti seçilmiştir. Çalışmada elde edilen sonuçlara göre, sürü zekası algoritmaları ile özetlenen veriyi kullanan makine öğrenmesi modelleri yüksek doğruluk oranına ulaşmış ve sürü zekası algoritmaları bu sürece işlem süresini kısaltma anlamında katkı sağlamıştır.With advancing technology, communication and information transfer have shifted from the physical world to the digital realm. This change has led to an increase in network traffic. At the same time, many tasks and transactions carried out in the physical world have been transferred to the digital environment. Sensitive information such as bank details, trade secrets, and personal data are moved to digital platforms, and malicious individuals aiming to access this information for profit are threatening data security with their developed software. In addition, the high volume of data traffic and the large number of users strain the capacity of data security systems. Collecting data traffic information and distinguishing between normal and abnormal data is challenging due to the reasons mentioned above. Intrusion detection systems (IDS) are key components of data security. These systems are expected to distinguish between normal and abnormal data traffic with high accuracy and in the shortest possible processing time. The scientific community has addressed the process of detecting attacks through various methods. Some detection methods search for data signatures previously marked as abnormal, while others aim to identify anomalies in data traffic. In this study, the anomaly detection method has been adopted. Machine learning is frequently used in this method due to its autonomous nature and ability to handle large data volumes. In this research, swarm intelligence algorithms were employed to determine the features that best represent the dataset used in machine learning models. The resulting summarized dataset was classified with machine learning models. Three commonly used datasets were selected to compare with results from previous studies. According to the study's results, machine learning models using data summarized by swarm intelligence algorithms achieved high accuracy rates, and swarm intelligence algorithms contributed to the process by reducing processing time
Low-cost saw/sinus-tooth-shaped circular microstrip patch antenna for in-space and satellite applications
No full textAntennas operating in S and C bands are crucial in space satellite applications due to their high bandwidth, which facilitates the swift transmission of large data volumes from space vehicles to Earth. These bands are less affected by atmospheric disturbances and exhibit lower noise levels, ensuring uninterrupted and reliable communication between spacecraft and Earth centers. They are essential for satellite-based remote sensing, analyzing surface properties, transmitting high-resolution images, scientific data, and other information. Additionally, they are used for spacecraft control and navigation, enabling precise mission operations. This study emphasizes user-friendly production antennas with different geometries and distinct feeding techniques, demonstrating various design implementations using CST Microwave Studio software. Innovative manufacturing methods such as 3D printing PLA substrates and using copper tape for antenna elements were explored to optimize costs and production processes. Precise cutting of antenna radiation geometries was achieved using the Cricut machine. Experimental validation through reflection coefficient (S11) measurements with a handheld vector network analyzer confirmed the practical application of theoretical foundations. The study's novelty lies in examining unconventional materials like PLA filament for antenna substrates, exploring fractalization theory for enhancing bandwidth, and discussing advancements in material science with flexible filaments like TPU. These contributions offer insights into user-friendly antenna production, innovative manufacturing techniques, and theoretical explorations in antenna design, enhancing the efficiency and effectiveness of space satellite communication systems.Adana Alparslan Tuerkes University Scientific Research Projects Unit [22119001]The Adana Alparslan Tuerkes University Scientific Research Projects Unit, Project Number 22119001, supports this study
Gain and bandwidth enhancement using superstrate loaded 2x2 circular-array antenna for X-Band and RADAR applications
No full textThis article demonstrates the fabrication, and measurements of a corporate offset-fed 2 x 2 array electromagnetically coupled patch (EMCP) circular-antenna based on the Fabry-Perot cavity principle. Single element antenna has a low gain of 6.28 dBi and is enhanced to 13.45dBi by loading the array with a superstrate. The antenna parameters -10 dB fractional bandwidth (FBW) and gain are improved by an air gap with 4-stacked circular patches and 4 stubs in the proposed design. The peak gain of the 2 x 2 array without superstrate was 8.88 dBi at 8.19 GHz, which is enhanced to 13.82 dBi at 9.55 GHz by parasitic loading and superstrate. The FBW of the proposed array antenna was enhanced by arranging four stubs between the 4-circles in the superstrate structure. The -10 dB FBW without stubs was 24.82% (7.62-9.73 GHz) and with stubs it became 38.47% (7.73-11.0 GHz). Adjustment of the height of the superstrate at 2.0 mm not only enhanced the gain and bandwidth but also advancement in the unidirectional radiation patterns. The array is prototyped is measured to validate the reflection coefficients and radiation characteristics and they found an excellent match with simulated results. The suggested array is most suitable for energy launchers in transitions, RADAR, military, satellite, X-band communications, and microwave laboratory applications