Okan University GCRIS Standard Database
Not a member yet
7992 research outputs found
Sort by
Heat Transfer Enhancement of Phase Change Materials Using Tree Shaped Fins: a Comprehensive Review
No full textKadhim, Saif Ali/0000-0003-0359-5022The efficiency of thermal energy storage is essential in phase change material (PCM) systems. Many traditional configurations of fins, such as radial, rectangular, and pin fins, have yet to be found lacking in how they facilitate heat transfer at charging and discharging processes, causing more extended phase change periods and decreasing the entire system's efficiency. This review seeks to fill the gap in thermal performance improvement and categorizes the existing literature related to melting, solidification, and a combination of both melting and solidification processes. Scientific research carried out in the melting section shows that tree-shaped fins have the potential to cut down melting time by 60 % compared to conventional fins and thereby significantly improve the ability to store energy. The solidification section highlights that such revolutionary fin configurations can reduce solidification time by 30 to 50 %, thus improving the system's performance. Additionally, the synchronized analysis of the trees proves that while the tree fins enhance the distribution of heat all over the trees, they also enhance the natural convection, improving the uniformity of temperatures and the effectiveness of phase change. The outcomes reveal that even though tree-shaped fins are capital-intensive, their low operating costs and higher efficiency leverage initial costs. Incorporating tree-shaped fins in the PCM system is a novel step in enhancing thermal energy storage systems with significant enhancement of solidification and melting in thermal management applications, which are crucial challenges to energy efficiency and sustainability.Science Citation Index Expande
The Relationship Between Accounting Information and Stock Price in the Lights of National Economic Performance: the Case of Borsa İstanbul
No full textHisse senedi fiyatını etkileyen çok sayıda faktör olmasına rağmen, finansal tabloların muhasebe rakamlarıyla temsil edilen finansal bilgiler, hisse senedi fiyatının belirlenmesinde en önemli rolü oynamaktadır. Bu çalışma, ulusal ekonomik performanstaki değişiklikleri göz önünde bulundurarak muhasebe bilgileri ile hisse senedi fiyatı arasındaki ilişkiyi araştırmaktadır. Ohlson modelinin genişletilmiş versiyonu, hisse senedi fiyatı üzerindeki defter değeri, hisse başına kazanç ve hisse başına temettünün etkisini incelemek için GSYİH büyüme oranını düzenleyici değişken olarak kullanarak uygulanmıştır. Trend giderme ve duygusal analiz teknikleri kullanılarak Ohlson modelinin genişletilmiş versiyonu, Borsa İstanbul'da BIST 100'de listelenen ve farklı sektörlerde faaliyet gösteren 91 şirketi içeren bir panel veri örneğine ve 2000-2022 dönemine uygulanmıştır. Çalışma sonuçları, test edilen modelin yüksek açıklayıcı gücüne ve muhasebe bilgileri ile hisse senedi fiyatı arasında anlamlı bir ilişkiye sahip olduğunu göstermiştir. Sonuçlar ayrıca, ulusal ekonomik performanstaki değişikliklerin Borsa İstanbul'da muhasebe bilgileri ile hisse senedi fiyatı arasındaki ilişki üzerinde anlamlı bir etkisi olduğunu göstermiştir. Ayrıca, sonuçlar hisse başına temettü ve hisse başına kazancın hisse senedi fiyatı üzerindeki bireysel etkisinin hisse başına defter değerinin bireysel etkisine kıyasla daha anlamlı olduğunu gösterdi. Sektör perspektifinden, sonuçlar test edilen modelin açıklayıcı gücünün diğer sektörlere kıyasla imalat ve konglomera sektörleri için belirgin şekilde daha yüksek olduğunu gösterdi. Anahtar kelimeler: Ohlson modeli, hisse başına defter değeri, hisse başına kazanç, hisse başına temettü, hisse senedi fiyatı, gayri safi yurtiçi hasılaDespite the numerous factors that affect the stock price, financial information represented by the financial statements' accounting figures play the most significant role in determining the stock price. This study investigates the relationship between accounting information and stock price considering the changes in the national economic performance. Extended version of Ohlson model is applied to study the impact of book value per share, earnings per share, and dividends per share on the stock price using GDP growth rate as a moderating variable. Using detrend and sentimal analysis techniques, extended version of Ohlson model is applied on a sample of panel data that includes 91 companies listed in BIST 100 in Borsa Istanbul and operating in different sectors and during 2000-2022 period. The study results showed high explanatory power of the model tested and significant relationship between the accounting information and stock price. The results also showed significant influence of the changes in the national economic performance on the relationship between accounting information and stock price in Borsa Istanbul. Besides, the results showed that the individual influence of dividends per share and earnings per share on the stock price is more significant comparing to the individual influence of book value per share. From sector perspective, the results showed that the explanatory power of the model tested is notably higher for manufacturing and conglomerate sectors comparing to other sectors. Key words: Ohlson model, book value per share, earnings per share, dividends per share, stock price, gross domestic produc
Investigating the Nexus Between Radiolysis Using Spent Nuclear Fuel and Hydrogen Production, With Environmental Safety Considerations - a Literature Review
No full textChowdhury, Prangon/0009-0004-1394-2993Given the detrimental consequences of climate change on the environment, hydrogen appears to be one of the solutions to possible decarbonization. Although it is a potential option, the subject of hydrogen production utilizing nuclear spent fuel (SNF) through water radiolysis has not received much attention to explore its potential use for large-scale hydrogen production. This review, therefore, presents an overview of research work on the use of SNF's ionizing radiation for the production of hydrogen and its potential impact on environmental safety. This paper investigates the advantages and difficulties of hydrogen generation in SNF storage system by utilizing a bibliometric and systematic review technique to analyse previous research works. The research themes were classified into motor, niche, emerging/declining, and basic themes. Some important themes that were found to be central to the topic included radiation shielding, hydrogen production, and environmental sustainability; life cycle assessment; renewable energy integration; nuclear waste management; hydrogen storage; and modular reactors. The study identified some potential research gaps and provided some recommendations for future research. This includes the improvement in the hydrogen detection systems, hydrogen collection and ventilation, containment of radioactive isotopes, understanding radiolysis impacts, and the development of purification and storage methods for hydrogen from spent nuclear fuel. The outcome of this study is expected to shape future research on the subject matter and serve as the foundation for deeper understanding of radiolysis for commercial-scale hydrogen production.Ministry of Science and Higher Education of the Russian Federation [N 975.42]; Young Scientist laboratory [347/23, FEUZ-2022-0031]The research funding was from the Ministry of Science and Higher Education of the Russian Federation (Ural Federal University Program of Development within the Priority-2030 Program) and (Tolerant Efficient Energy Based on Renewable Energy Sources) grant number: N 975.42. Young Scientist laboratory 347/23. Grant Number FEUZ-2022-0031.Science Citation Index Expande
The History of Micromobility
No full textAlthough it has been a part of our lives for a long time, it is difficult to pinpoint when micromobility, as a concept, actually began. This is because, up until almost two centuries ago, the speeds provided by micromobility vehicles were considered high within the transportation system. Therefore, it is quite challenging to define wheremicromobility diverges from general mobility. For this reason, in this chapter, the history of the transportation system is briefly examined first. The development of roads in the context of the need for transportation is discussed, linking it to human history, followed by a focus on the emergence of different types of transportation. After discussing the current situation, new and innovative transportation systems are briefly mentioned, and some insights are provided on what can be expected in the future. Then, the historical development of the bicycle, along with its different types and models, is discussed with support of figures. Lastly, the development of scooters, with a particular focus on shared e-scooter systems, is briefly summarized by examining some historical examples.Book Citation Index – Social Sciences & Humanities - Book Citation Index – Scienc
Molecular Dynamics Simulation of Reinforced Silica Aerogel With a Phase Change Material at Different Initial Pressures
No full textAerogel, the lightest known solid, has distinctive features that make it advantageous for aerospace and advanced materials applications. This study investigates the mechanical properties of silica aerogel supplemented with paraffin as a phase transition material, evaluating the effect of initial pressures ranging from 1 to 10 bar. Molecular dynamics simulations are utilized to explore changes in stress-strain behavior, ultimate strength, and Young's modulus to assess structural responses in a variety of conditions. The equilibration procedure resulted in temperature stabilization at 300 K and potential energy convergence at -1500.789 eV, hence demonstrating system stability. As the initial pressure escalated from 1 to 5 bar, both ultimate strength and Young's modulus diminished from 620.32 MPa and 1777.53 MPa to 538.31 MPa and 1188.13 MPa, respectively. This reduction was ascribed to diminished atomic cohesion and heightened particle oscillation. Nonetheless, elevating the pressure from 5 to 10 bar altered this tendency, resulting in ultimate strength and Young's modulus increasing to 563.23 MPa and 1316.39 MPa, respectively, indicating enhanced mechanical stability. The results indicate that adjusting the initial pressure served as a method to regulate the mechanical strength of aerogel, presenting significant advantages for industries necessitating lightweight, robust materials. The work enhanced existing knowledge by clarifying the intricate function of initial pressure in maximizing the structural integrity of reinforced aerogels, surpassing earlier static reinforcing techniques.Science and Technology Plan Project of Luzhou City [2024XDY202]Funding This work was supported by Science and Technology Plan Project of Luzhou City (2024XDY202) .Science Citation Index Expande
Exploring the Role of Filaments in Channel Flow Modification Using the Immersed Boundary Lattice Boltzmann Method
No full textManipulating flow at the miniature is a challenging task. This study explores the potential application of elastic filaments to manipulate the flow field in a channel using the immersed boundary-lattice Boltzmann (IB-LBM) method. The channel width and the initial elastic filament length were 4 cm and 1.3 cm, respectively. The presence of the filaments on the channel's center and walls is investigated separately. For the case with two inclined elastic filaments in the middle of the channel, the results showed that the elastic filament deviates from its original state under the influence of the fluid momentum and tends to move in the direction of the flow. The filaments stretch and reach their final position, then start to oscillate under the influence of elasticity and vortexes formed behind them. For the case with 10 filaments distributed over the top and bottom walls with a constant distance between them, the results show that initially the filaments near the entrance cause a disturbance in the flow and induce large vortexes at the end of the channel. However, over time, as the flow reaches a steady state, small vortexes form behind the filaments and, the filaments start to oscillate and the main flow inside the channel remains pretty uniform without obvious vortexes.Science Citation Index Expande
The Impact of Channel Edge Type on the Particle Diffusion and Permeability of Carbon Nanotubes as a Membrane in Reverse Electrodialysis Process Using Molecular Dynamics Simulation
No full textThermal energy storage with phase change materials offers effective solutions for energy management by absorbing and releasing thermal energy during phase transitions. Integrating nanoparticles, like gold, enhances thermal conductivity, modifies phase change characteristics, and boosts energy storage capacity. These advancements are valuable in renewable energy, precise thermal management, and high-efficiency energy storage, fostering innovation and sustainability in thermal science. This study investigates the effects of adding gold nanoparticles to paraffin-based phase change material, analyzing thermal property changes through molecular dynamics simulations to assess improvements in heat storage and energy efficiency. The results show that the carbon nanotube structure with the armchair edge was used to achieve the maximum electric current in the sample. Due to the strong interactions among carbon atoms in the armchair-edged carbon nanotube structure, the interaction between the fluid and the AC decreased. Also, the interaction between the base fluid and the channel wall varied with the edge type of carbon nanotubes. Based on the results, maximum electric current was achieved with a carbon nanotube featuring an armchair edge. © 2025 Elsevier Lt
Unveiling the Bioactive Potential of Scabiosa Rotata M. Bieb Fruits: a Landmark Study on Cytotoxic, Antioxidant, and Antibacterial Activities Through Liquid Chromatography-Mass Spectrometry Profiling and Molecular Docking
No full textThe aim of this study was to investigate the antioxidant, cytotoxic, and antibacterial activities of ethanol extract (SRE) and its hexane (SRH), chloroform (SRC), ethyl acetate (SREA), and aqueous ethanol (SRAE) sub-extracts obtained from the fruits of Scabiosa rotata M. Bieb. Molecular docking studies were also performed to evaluate the interactions of the most active sub-extract with the human mitochondrial ABC transporter (ABCB10) protein, plays an important role in cellular oxidative stress regulation and mitochondrial function. Total phenolic (TPC) and flavonoid (TFC) contents and antioxidant radical scavenging activities (1, 1-diphenyl-2-picryl hydrazyl [DPPH] and 3-ethylbenzothiazoline-6 sulfonic acid [ABTS]) of all extracts were determined. Cytotoxic activity was evaluated on different cell lines, such as HepG2 (liver cancer), MCF-7 (breast cancer), and HeLa (cervical cancer) cells. Antibacterial activity was tested against Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, and Staphylococcus aureus. SREA showed the best antioxidant activity with IC50 values of 54.20 mu g/ml and 48.56 mu g/ml for DPPH and ABTS, respectively, and also had high TPC (499.06 mg GA/g) and TFC (327.45 mg QE/g). Furthermore, SREA showed significant cytotoxicity comparable to cisplatin with IC50 values of 51.29, 51.41, and 52.89 mu g/ml for HepG2, MCF-7, and HeLa cells, respectively. However, none of the extracts showed antibacterial activity. The analysis using liquid chromatography-mass spectrometry (LC/MS-MS) on SREA found that the main phenolic compounds are chlorogenic acid, hesperidin, quinic acid, and isoorientin. Molecular docking of the major compounds showed that chlorogenic acid (2.21 mM) exhibited the strongest binding affinity, followed by hesperidin (5.83 mM), quinic acid (8.86 mM), and isoorientin (13 mM). These findings indicate the potential of SREA to be used as a natural antioxidant and anticancer agent.Science Citation Index Expande
Towards the Development of Gaussian Clustering Algorithm Technology To Extend the Lifetime of Manets
No full textMobile Ad hoc Networks (MANETs) are infrastructure-independent wireless networks where nodes communicate directly or through relays without a central base station. Routing protocols employed in MANETs face numerous challenges due to their limited resources. Cross-layer optimization is fundamental to conserving energy and achieving quality of service parameters. However, reducing end-to-end diversity conflicts with power consumption, creating a problem when trying to improve network lifetime. In this work, a Lifetime Enhancement Routing (LER) protocol, which selects the most efficient path to the destination using residual energy and cost exchange metrics, is proposed. LER primarily reduces node overutilization and load to prolong the network lifetime. The proposed MANET performance optimization technique is Gaussian clustering algorithm with one of the deep learning (RNN) techniques as a combined technique. The simulation results show that the proposed protocol significantly reduced energy consumption and augmented the ability to send data through the best path available in the network with a high efficiency of up to 92%. © by the authors
A Novel Analysis of the Fractional Cauchy Reaction-Diffusion Equations
No full textThis article considers the Cauchy reaction-diffusion equations and derives the numerical solutions using the fractional natural decomposition method (FNDM). The projected solution approach works without conversion or perturbation. The examples confirm the method’s accuracy and reliability, allowing for fractional order studies in real-world problems. Plots and tables validate the accuracy of the proposed scheme. This research reveals the influences of temporal history in the fractional Cauchy reaction-diffusion equations, which is the novelty of this work. © Indian Association for the Cultivation of Science 2024.Science Citation Index Expande