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Article Citation - WoS: 1Citation - Scopus: 2Parametric Sensitivity Analysis and Performance Evaluation of High-Temperature Macro-Encapsulated Packed-Bed Latent Heat Storage System Operating With Transient Inlet Boundary Conditions(Mdpi, 2022) Mehrtash, Mehdi; Tari, IlkerThis paper presents the results of comprehensive numerical analyses in the performance of a packed-bed latent heat storage (PBLHS) system in terms of key performance indicators, namely charging time, charging rate, charging capacity, and charging efficiency. Numerical simulations are performed for the packed bed region using a transient two-dimensional axisymmetric model based on the local thermal non-equilibrium (LTNE) approach. The model considers the variation in the inlet temperature of the system as these storage systems are typically integrated with solar collectors that operate with intermittent solar radiation intensity. The model results are validated using the experimental data for temperature distribution throughout the bed. The simulations are carried out while changing the operating parameters such as the capsule diameter, bed porosity, inlet velocity, and the height-to-diameter aspect ratio to investigate their impact on the performance indicators. Observations indicate that low porosity, large-sized capsules, low inlet velocity, and a low height-to-diameter aspect ratio increase the charging time. In terms of achieving a high charging rate, a bed with low porosity, small-sized capsules, a high inflow velocity, and a high height-to-diameter aspect ratio is deemed advantageous. It is shown that raising the flow velocity and the height-to-diameter aspect ratio can improve the charging efficiency. These findings provide recommendations for optimizing the design and operating conditions of the system within the practical constraints.Article Citation - WoS: 2Citation - Scopus: 1Comparison of the Performance of Structural Break Tests in Stationary and Nonstationary Series: a New Bootstrap Algorithm(Springer, 2024) Camalan, Ozge; Hasdemir, Esra; Omay, Tolga; Kucuker, Mustafa CanStructural breaks are considered as permanent changes in the series mainly because of shocks, policy changes, and global crises. Hence, making estimations by ignoring the presence of structural breaks may cause the biased parameter value. In this context, it is vital to identify the presence of the structural breaks and the break dates in the series to prevent misleading results. Accordingly, the first aim of this study is to compare the performance of unit root with structural break tests allowing a single break and multiple structural breaks. For this purpose, firstly, a Monte Carlo simulation study has been conducted through using a generated homoscedastic and stationary series in different sample sizes to evaluate the performances of these tests. As a result of the simulation study, Zivot and Andrews (J Bus Econ Stat 20(1):25-44, 1992) are the best-performing tests in capturing a single break. The most powerful tests for the multiple break setting are those developed by Kapetanios (J Time Ser Anal 26(1):123-133, 2005) and Perron (Palgrave Handb Econom 1:278-352, 2006). A new Bootstrap algorithm has been proposed along with the study's primary aim. This newly proposed Bootstrap algorithm calculates the optimal number of statistically significant structural breaks under more general assumptions. Therefore, it guarantees finding an accurate number of optimal breaks in real-world data. In the empirical part, structural breaks in the real interest rate data of the US and Australia resulting from policy changes have been examined. The results concluded that the bootstrap sequential break test is the best-performing approach due to the general assumption made to cover real-world data.Article Citation - WoS: 14Citation - Scopus: 25On Coupled Fixed Point Theorems on Partially Ordered g-metric Spaces(Springeropen, 2012) Karapinar, Erdal; Kaymakcalan, Billur; Tas, KenanIn this manuscript, we extend, generalize and enrich some recent coupled fixed point theorems in the framework of partially ordered G-metric spaces in a way that is essentially more natural.Article Citation - WoS: 5Citation - Scopus: 6A Novel Deep Learning-Based Framework With Particle Swarm Optimisation for Intrusion Detection in Computer Networks(Public Library Science, 2025) Yilmaz, Abdullah AsimIntrusion detection plays a significant role in the provision of information security. The most critical element is the ability to precisely identify different types of intrusions into the network. However, the detection of intrusions poses a important challenge, as many new types of intrusion are now generated by cyber-attackers every day. A robust system is still elusive, despite the various strategies that have been proposed in recent years. Hence, a novel deep-learning-based architecture for detecting intrusions into a computer network is proposed in this paper. The aim is to construct a hybrid system that enhances the efficiency and accuracy of intrusion detection. The main contribution of our work is a novel deep learning-based hybrid architecture in which PSO is used for hyperparameter optimisation and three well-known pre-trained network models are combined in an optimised way. The suggested method involves six key stages: data gathering, pre-processing, deep neural network (DNN) architecture design, optimisation of hyperparameters, training, and evaluation of the trained DNN. To verify the superiority of the suggested method over alternative state-of-the-art schemes, it was evaluated on the KDDCUP'99, NSL-KDD and UNSW-NB15 datasets. Our empirical findings show that the proposed model successfully and correctly classifies different types of attacks with 82.44%, 90.42% and 93.55% accuracy values obtained on UNSW-B15, NSL-KDD and KDDCUP'99 datasets, respectively, and outperforms alternative schemes in the literature.Article Citation - WoS: 19Citation - Scopus: 17Further Discussion on Modified Multivalued Α*-ψ-contractive Type Mapping(Univ Nis, Fac Sci Math, 2015) Ali, Muhammad Usman; Kamran, Tayyab; Karapinar, ErdalIn this paper, we investigate the existence of a fixed point for modified multivalued alpha(*)-psi-contractive type mapping in the context of complete metric space. We also construct some examples to illustrate the main result. Our results extend, improve and generalize the results on the topic in the literature.Article Citation - WoS: 58Two-Dimensional Fluorinated Boron Sheets: Mechanical, Electronic, and Thermal Properties(Amer Chemical Soc, 2018) Pekoz, Rengin; Konuk, Mine; Kilic, M. Emin; Durgun, EnginThe synthesis of atomically thin boron sheets on a silver substrate opened a new area in the field of two-dimensional systems. Similar to hydrogenated and halogenated graphene, the uniform coating of borophene with fluorine atoms can lead to new derivatives of borophene with novel properties. In this respect, we explore the possible structures of fluorinated borophene for varying levels of coverage (BnF) by using first-principles methods. Following the structural optimizations, phonon spectrum analysis and ab initio molecular dynamics simulations are performed to reveal the stability of the obtained structures. Our results indicate that while fully fluorinated borophene (BF) cannot be obtained, stable configurations with lower coverage levels (B4F and B2F) can be attained. Unveiling the stable structures, we explore the mechanical, electronic, and thermal properties of (BnF). Fluorination significantly alters the mechanical properties of the system, and remarkable results, including direction-dependent variation of Young's modulus and a switch from a negative to positive Poisson's ratio, are obtained. However, the metallic character is preserved for low coverage levels, and metal to semiconductor transition is obtained for B2F. The heat capacity at a low temperature increases with an increasing F atom amount but converges to the same limiting value at high temperatures. The enhanced stability and unique properties of fluorinated borophene make it a promising material for various high-technology applications in reduced dimensions.Article Citation - WoS: 13Citation - Scopus: 13Investigating Space Utilization in Skyscrapers Designed with Prismatic Form(Mdpi, 2024) Ilgin, Hueseyin Emre; Aslantamer, Ozlem NurThe enduring appeal of prismatic shapes, historically prevalent in office building designs, persists in contemporary skyscraper architecture, which is attributed particularly to their advantageous aspects concerning cost-efficiency and optimal space utilization. Space efficiency is a crucial factor in prismatic skyscraper design, carrying substantial implications for sustainability. However, the current academic literature lacks a complete exploration of space efficiency in supertall towers with prismatic forms, despite their widespread use. This paper seeks to address this significant gap by conducting a comprehensive analysis of data gathered from a carefully selected set of 35 case studies. The primary discoveries presented in this paper are outlined as follows: (i) average space efficiency stood at approximately 72%, covering a range that extended from 56% to 84%; (ii) average core to gross floor area ratio averaged around 24%, spanning a spectrum that ranged from 12% to 36%; (iii) the majority of prismatic skyscrapers utilized a central core approach, mainly customized for residential use; (iv) the dominant structural system observed in the analyzed cases was the outriggered frame system, with concrete being the commonly utilized material for the structural components; and (v) the impact of diverse structural systems on space efficiency showed no significant deviation, although differences in function led to variations in average space efficiency. The authors expect that these findings will provide valuable guidance, especially for architects, as they strive to enhance the sustainable planning of prismatic towers.Article Citation - WoS: 9Citation - Scopus: 15Therapeutic Efficacy of Boric Acid Treatment on Brain Tissue and Cognitive Functions in Rats With Experimental Alzheimer's Disease(Dove Medical Press Ltd, 2023) Ozdemir, Cagri; Arslan, Mustafa; Kucuk, Aysegul; Yigman, Zeynep; Dursun, Ali DoganIntroduction: Oxidative stress has an important role in the pathophysiology of Alzheimer's disease (AD), the most common type of dementia. Boric acid (BA) contributes significantly to the protection of the brain by reducing lipid peroxidation and supporting antioxidant defense. We aimed to evaluate the therapeutic potential of BA treatment in AD rats. Materials and Methods: Four groups were formed as Control (C), Alzheimer's (A), Alzheimer's + Boric acid (ABA), Boric acid (BA). Intracerebroventricular injection of Streptozotocin (STZ) was preferred to create an AD. After 4 weeks, BA was applied 3 times every other day. The Radial Arm Maze Test (RAMT) was used to evaluate memory and learning abilities. Biochemical and histopathological evaluations were made in the hippocampus. Results: Initial RAMT inlet/outlet (I/O) numbers were similar. Two weeks after STZ injection, I/O numbers decreased in group A and ABA compared to group C and BA (p<0.05). After the second BA application, I/O numbers increased in the ABA group compared to the A group (p<0.05). In group A, PON-1, TOS and OSI levels were higher and TAS levels were lower than in groups BA and C. After BA treatment, PON-1 and OSI levels were lower in the ABA group than in the A group (p<0.05). Although there was an increase in TAS value and a decrease in TOS, this did not make a statistical difference. The thickness of the pyramidal cell in CA1 and the granular cell layers in the dentate gyrus, and the number of intact and degenerated neurons in the pyramidal cell layer were similar between the groups. Discussion: Significant improvement in learning and memory abilities after BA application is promising for AD. Conclusion: These results show that BA application positively affects learning and memory abilities, and reduces oxidative stress. More extensive studies are required to evaluate histopathological efficacy.Article Citation - WoS: 24Citation - Scopus: 39Network Intrusion Detection With a Hashing Based Apriori Algorithm Using Hadoop Mapreduce(Mdpi, 2019) Azeez, Nureni Ayofe; Ayemobola, Tolulope Jide; Misra, Sanjay; Maskeliunas, Rytis; Damasevicius, RobertasUbiquitous nature of Internet services across the globe has undoubtedly expanded the strategies and operational mode being used by cybercriminals to perpetrate their unlawful activities through intrusion on various networks. Network intrusion has led to many global financial loses and privacy problems for Internet users across the globe. In order to safeguard the network and to prevent Internet users from being the regular victims of cyber-criminal activities, new solutions are needed. This research proposes solution for intrusion detection by using the improved hashing-based Apriori algorithm implemented on Hadoop MapReduce framework; capable of using association rules in mining algorithm for identifying and detecting network intrusions. We used the KDD dataset to evaluate the effectiveness and reliability of the solution. Our results obtained show that this approach provides a reliable and effective means of detecting network intrusion.Article Citation - WoS: 3Citation - Scopus: 4High Persistence and Nonlinear Behavior in Financial Variables: a More Powerful Unit Root Testing in the Estar Framework(Mdpi, 2021) Omay, Tolga; Corakci, Aysegul; Hasdemir, EsraIn this study, we consider the hybrid nonlinear features of the Exponential Smooth Transition Autoregressive-Fractional Fourier Function (ESTAR-FFF) form unit root test. As is well known, when developing a unit root test for the ESTAR model, linearization is performed by the Taylor approximation, and thereby the nuisance parameter problem is eliminated. Although this linearization process leads to a certain amount of information loss in the unit root testing equation, it also causes the resulting test to be more accessible and consistent. The method that we propose here contributes to the literature in three important ways. First, it reduces the information loss that arises due to the Taylor expansion. Second, the research to date has tended to misinterpret the Fourier function used with the Kapetanios, Shin and Snell (2003) (KSS) unit root test and considers it to capture multiple smooth transition structural breaks. The simulation studies that we carry out in this study clearly show that the Fourier function only restores the Taylor residuals of the ESTAR type function rather than accounting forthe smooth structural break. Third, the new nonlinear unit root test developed in this paper has very strong power in the highly persistent near unit root environment that the financial data exhibit. The application of the Kapetanios Shin Snell- Fractional Fourier (KSS-FF) test to ex-post real interest rates data of 11 OECD countries for country-specific sample periods shows that the new test catches nonlinear stationarity in many more countries than the KSS test itself.
