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Article Citation - WoS: 1Citation - Scopus: 2Existence of Solutions for Odd-Order Multi-Point Impulsive Boundary Value Problems on Time Scales(Walter de Gruyter Gmbh, 2022) Georgiev, Svetlin G.; Akgol, Sibel Dogru; Kus, Murat EymenUsing a fixed point theorem due to Schaefer, the existence of solutions for an odd-order m-point impulsive boundary value problem on time scales is obtained. The problem considered is of general form, where both the differential equation and the impulse effects are nonlinear. Illustrative examples are provided.Article Citation - WoS: 144Citation - Scopus: 148Uniqueness of Solution for Higher-Order Nonlinear Fractional Differential Equations With Multi-Point and Integral Boundary Conditions(Springer-verlag Italia Srl, 2021) Sevinik-Adiguzel, Rezan; Aksoy, Umit; Karapinar, Erdal; Erhan, Inci M.This study is devoted to the development of alternative conditions for existence and uniqueness of nonlinear fractional differential equations of higher-order with integral and multi-point boundary conditions. It uses a novel approach of employing a fixed point theorem based on contractive iterates of the integral operator for the corresponding fixed point problem. We start with developing an existence-uniqueness theorem for self-mappings with contractive iterate in a b-metric-like space. Then, we obtain the unique solvability of the problem under suitable conditions by utilizing an appropriate b-metric-like space.Article Citation - WoS: 4Citation - Scopus: 4Fixed Point Theorems for Generalized Weak Contractions Satisfying Rational Expression on a Ordered Partial Metric Space(Maik Nauka/interperiodica/springer, 2013) Karapinar, Erdal; Marudai, M.; Pragadeeswarar, V.The purpose of this manuscript is to present a fixed point theorem using a generalized weak contraction condition of rational type in the context of partial metric spaces.Article Citation - WoS: 39Citation - Scopus: 49Focus Variation Measurement and Prediction of Surface Texture Parameters Using Machine Learning in Laser Powder Bed Fusion(Asme, 2020) Ozel, Tugrul; Altay, Ayca; Kaftanoglu, Bilgin; Leach, Richard; Senin, Nicola; Donmez, AlkanThe powder bed fusion-based additive manufacturing process uses a laser to melt and fuse powder metal material together and creates parts with intricate surface topography that are often influenced by laser path, layer-to-layer scanning strategies, and energy density. Surface topography investigations of as-built, nickel alloy (625) surfaces were performed by obtaining areal height maps using focus variation microscopy for samples produced at various energy density settings and two different scan strategies. Surface areal height maps and measured surface texture parameters revealed the highly irregular nature of surface topography created by laser powder bed fusion (LPBF). Effects of process parameters and energy density on the areal surface texture have been identified. Machine learning methods were applied to measured data to establish input and output relationships between process parameters and measured surface texture parameters with predictive capabilities. The advantages of utilizing such predictive models for process planning purposes are highlighted.Article Citation - WoS: 9Citation - Scopus: 8Existence and Uniqueness of Best Proximity Points Under Rational Contractivity Conditions(Walter de Gruyter Gmbh, 2016) Karapinar, Erdal; Roldan-Lopez-de-Hierro, Antonio-Francisco; Sadarangani, KishinThe main aim of this paper is to present some theorems in order to guarantee existence and uniqueness of best proximity points under rational contractivity conditions using very general test functions. To illustrate the variety of possible test functions, we include some examples of pairs of functions which are included in innovative papers published in the last years. As a consequence, we prove that our results unify and extend some recent results in this field.Article Citation - WoS: 11Citation - Scopus: 20Reinforcement Learning Using Fully Connected, Attention, and Transformer Models in Knapsack Problem Solving(Wiley, 2022) Yildiz, Beytullah; Yıldız, Beytullah; Yıldız, BeytullahKnapsack is a combinatorial optimization problem that involves a variety of resource allocation challenges. It is defined as non-deterministic polynomial time (NP) hard and has a wide range of applications. Knapsack problem (KP) has been studied in applied mathematics and computer science for decades. Many algorithms that can be classified as exact or approximate solutions have been proposed. Under the category of exact solutions, algorithms such as branch-and-bound and dynamic programming and the approaches obtained by combining these algorithms can be classified. Due to the fact that exact solutions require a long processing time, many approximate methods have been introduced for knapsack solution. In this research, deep Q-learning using models containing fully connected layers, attention, and transformer as function estimators were used to provide the solution for KP. We observed that deep Q-networks, which continued their training by observing the reward signals provided by the knapsack environment we developed, optimized the total reward gained over time. The results showed that our approaches give near-optimum solutions and work about 40 times faster than an exact algorithm using dynamic programming.Article Citation - WoS: 22Citation - Scopus: 23On Residual Lifetime of Coherent Systems After the rth Failure(Springer, 2013) Eryilmaz, SerkanIn this article we study the residual lifetime of a coherent system after the rth failure, i.e. the time elapsed from the rth failure until the system failure given that the system operates at the time of the rth failure. We provide a mixture representation for the corresponding residual lifetime distribution in terms of signature. We also obtain some stochastic ordering results for the residual lifetimes.Article Citation - WoS: 37Citation - Scopus: 45Study on the Cytocompatibility, Mechanical and Antimicrobial Properties of 3d Printed Composite Scaffolds Based on Pva/ Gold Nanoparticles (aunp)/ Ampicillin (amp) for Bone Tissue Engineering(Elsevier, 2021) Topsakal, Aysenur; Midha, Swati; Yuca, Esra; Tukay, Ari; Sasmazel, Hilal Turkoglu; Kalaskar, Deepak M.; Gunduz, OguzhanOver the years, gold nanoparticles (AuNP) have been widely used in several biomedical applications related to the diagnosis, drug delivery, bio-imaging, photo-thermal therapy and regenerative medicine, owing to their unique features such as surface plasmon resonance, fluorescence and easy surface functionality. Recent studies showed that gold nanoparticles display positive effect on osteogenic differentiation. In line with this effect, 3-Dimesional (3D) scaffolds that can be used in bone tissue were produced by exploiting the properties of gold nanoparticles that increase biocompatibility and support bone tissue development. In addition, ampicillin was added to the scaffolds containing gold nanoparticles as a model drug to improve its antimicrobial properties. The scaffolds were produced as composites of polyvinyl alcohol (PVA) main matrix as PVA, PVA/AuNP, PVA/Ampicillin (AMP) and PVA/AuNP/AMP. Scanning Electron Microscopy (SEM) Fourier Transform Infrared Spectroscopy (FTIR), tensile measurement tests, and in vitro applications of 3D scaffolds were performed. As depicted by SEM, scaffolds were produced at pore sizes appropriate for bone tissue regeneration. According to FTIR results, there was no modification observed in the AMP, PVA and gold nanoparticles due to mixing in the resultant scaffolds. In vitro results show that 3D printed composite scaffold based on PVA/AuNP/AMP are biocompatible, osteo-inductive and exhibit antimicrobial properties, compared to PVA scaffolds. This study has implications for addressing infections during orthopedic surgeries. The PVA-based gold nanoparticle 3D tissue scaffold study containing ampicillin covers a new study compared to other articles based on gold nanoparticles.Article Citation - WoS: 29Citation - Scopus: 36Massive Mimo Systems for 5g: a Systematic Mapping Study on Antenna Design Challenges and Channel Estimation Open Issues(inst Engineering Technology-iet, 2021) Benzaghta, Mohamed; Rabie, Khaled M.The next generation of mobile networks (5G) is expected to achieve high data rates, reduce latency, as well as improve the spectral and energy efficiency of wireless communication systems. Several technologies are being explored to be used in 5G systems. One of the main promising technologies that is seen to be the enabler of 5G is massive multiple-input multiple-output (mMIMO) systems. Numerous studies have indicated the utility of mMIMO in upcoming wireless networks. However, there are several challenges that needs to be unravelled. In this paper, the latest progress of research on challenges in mMIMO systems is tracked, in the context of mutual coupling, antenna selection, pilot contamination and feedback overhead. The results of a systematic mapping study performed on 63 selected primary studies, published between the year 2017 till the second quarter of 2020, are presented. The main objective of this secondary study is to identify the challenges regarding antenna design and channel estimation, give an overview on the state-of-the-art solutions proposed in the literature, and finally, discuss emerging open research issues that need to be considered before the implementation of mMIMO systems in 5G networks.Article Citation - WoS: 1Citation - Scopus: 1Synthesis and Characterization of New Dithienosilole Based Copolymers(Electrochemical Soc inc, 2016) Karabay, Lutfiye Canan; Al-Jumaili, Mohammed; Cihaner, Atilla2-Ethylhexyl substituted dithienosilole based soluble polymers including thiophene (1) and bithiophene (2) units were synthesized via Stille coupling reaction. The presence of 2-ethylhexyl substituents on the silole ring gave solubility property to the polymers in common solvents. According to gel permeation chromatography measurements, the weight average molecular weights of the polymers 1 and 2 were found to be as 70,977 with a polydispersity index of 2.30 and 110,439 with a PDI of 1.42, respectively. Fluorescent polymers in toluene solution have maximum emisssion bands at 634 nm for the polymer 1 and 613 nm for the polymer 2. Chemical and electrochemical doping of the polymers in the solution and in the film forms were monitored by using ultraviolet-visible spectroscopic technique. The polymers exhibited chromic (chemochromic and electrochromic) properties. While the colors of the neutral polymer films are purple for the polymer 1 and reddish brown for the polymer 2, both polymers are transparent sky blue at their oxidized states. The bandgaps of polymers in film forms were calculated as 1.81 eV for the polymer 1 and 1.92 eV for the polymer 2. Also, electrochromic device applications of the polymers were done. Electrochemical and optical behaviors of the polymers demonstrated that they can be good candidates for optoelectronic applications. (C) 2016 The Electrochemical Society. All rights reserved.
