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Permanent URI for this collectionhttps://ada.atilim.edu.tr/handle/123456789/19

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Citation Count: 5
3-D Dynamic UAV Base Station Location Problem
(informs, 2021) Cicek, Cihan Tugrul; Shen, Zuo-Jun Max; Gultekin, Hakan; Tavli, Bulent; Industrial Engineering
We address a dynamic covering location problem of an unmanned aerial vehicle base station (UAV-BS), in which the location sequence of a single UAV-BS in a wireless communication network is determined to satisfy data demand arising from ground users. This problem is especially relevant in the context of smart grid and disaster relief. The vertical movement ability of the UAV-BS and nonconvex covering functions in wireless communication restrict utilizing classical planar covering location approaches. Therefore, we develop new formulations to this emerging problem for a finite time horizon to maximize the total coverage. In particular, we develop a mixed-integer nonlinear programming formulation that is nonconvex in nature and propose a Lagrangean decomposition algorithm (LDA) to solve this formulation. Because of the high complexity of the problem, the LDA is still unable to find good local solutions to large-scale problems. Therefore, we develop a continuum approximation (CA) model and show that CA would be a promising approach in terms of both computational time and solution accuracy. Our numerical study also shows that the CA model can be a remedy to build efficient initial solutions for exact solution algorithms. Summary of Contribution: This paper addresses a facet of mixed integer nonlinear programming formulations. Dynamic facility location problems (DFLPs) arise in a wide range of applications. However, classical DFLPs typically focus on the two-dimensional spaces. Emerging technologies in wireless communication and some other promising application areas, such as smart grids, have brought new location problems that cannot be solved with classical approaches. For practical reasons, many research attempts to solve this new problem, especially by researchers whose primary research area is not OR, have seemed far from analyzing the characteristics of the formulations. Rather, solution-oriented greedy heuristics have been proposed. This paper has two main objectives: (i) to close the gap between practical and theoretical sides of this new problem with the help of current knowledge that OR possesses to solve facility location problems and (ii) to support the findings with an exhaustive computational study to show how these findings can be applied to practice.
Citation Count: 2
Ab initio study of structural and electronic properties of single crystal and core/shell II-VI semiconductor nanowires
(Elsevier, 2016) Pekoz, R.; Department of Electrical & Electronics Engineering
Structural and electronic properties of pristine and H-passivated wurtzite type ZnSe, ZnTe nanowires and ZnX/ZnY (X = Se(Te) and Y = Te(Se)) core/shell nanowires oriented along the [0001] direction have been investigated using first-principles calculations. The changes in the electronic structure of the nanowires due to the quantum confinement and morphology have been searched. Quantum confinement increases the band gap energy as the diameters of ZnSe and ZnTe nanowires decrease. Both homostructured and heterostructured nanowires are found to show a semiconducting character with direct band gaps at Gamma-point. Changing the morphology from homostructured nanowires to heterostructured core/shell nanowires has an important impact on the electronic structure. For instance, the charge separation of electrons and holes along the infinite direction of core/shell nanowires shows a strong preference for electron(hole) states localized inside ZnSe(ZnTe) regions. (C) 2016 Elsevier B.V. All rights reserved.
Citation Count: 28
Accessibility evaluation of top university websites: a comparative study of Kyrgyzstan, Azerbaijan, Kazakhstan and Turkey
(Springer Heidelberg, 2018) Ismailova, Rita; Inal, Yavuz; Information Systems Engineering
It is important that university websites and services offered through their sites are used effectively, efficiently and satisfactorily by the whole target group of the university, including disabled users. However, universities in many countries are still unable to meet the criteria for web accessibility. This study aimed to test the websites of the top universities in Kyrgyzstan, Kazakhstan, Azerbaijan and Turkey using automated assessment tools. The results showed that university websites are more popular in Turkey, and in Turkish universities developers pay more attention to the performance of websites, followed by websites of Azerbaijani, Kyrgyz and Kazakh universities. The majority of the university websites in the study did not meet the WCAG 2.0 accessibility criteria. Only two Kyrgyz and two Kazakh university websites attained conformance level A, and only three, one Kyrgyz and two Kazakh, achieved accessibility conformance level AAA. Based on the results, it was determined that universities included in the present study need to devote more effort to making their websites more accessible for their users.
Citation Count: 0
Adaptive neuro-fuzzy inference technique for estimation of light penetration in reservoirs
(Springer Japan Kk, 2007) Soyupak, Selcuk; Karaer, Feza; Senturk, Engin; Hekim, Huseyin
An adaptive neuro-fuzzy inference technique has been adopted to estimate light levels in a reservoir. The data were collected randomly from Doganci Dam Reservoir over a number of years. The input data set is a matrix with vectors of time, depth, sampling location, and incident solar radiation. The output data set is a vector representing light measured at various depths. Randomization and logarithmic transformations have been applied as preprocessing. One-half of the data have been utilized for training; testing and validation steps utilized one-fourth each. An adaptive neuro-fuzzy inference system (ANFIS) has been built as a prediction model for light penetration. Very high correlation values between predictions and real values on light measurements with relatively low root mean square error values have been obtained for training, test, and validation data sets. Elimination of the overtraining problem was ensured by satisfying close root mean square error values for all sets.
Citation Count: 1
Air refueling optimisation for more agile and efficient military deployment operations
(Cambridge Univ Press, 2022) Toydas, M.; Malyemez, C.
Strategic airlift is a crucial capability for any country that wants to protect its global interests around the world. Air refueling may offer more agile and efficient airlift capabilities by increasing cargo aircraft payload and shortening airlift time. We investigated whether air refueling can shorten the total time of an airlift operation and decrease the number of cargo aircraft sorties required in a deployment scenario, especially where the distance between origin and destination is within the range of cargo aircraft. We introduced two mathematical models to compare the total airlift time and number of cargo aircraft required for given origin-destination and tanker base locations and total freight to be moved. We optimised initial cargo and fuel amount for cargo aircraft along with rendezvous point coordinates to minimise total airlift time. We used a numerical example to show that substantial airlift time and cargo aircraft sortie savings are possible through air refueling.
Citation Count: 20
Analysis of cultural and gender influences on teamwork performance for software requirements analysis in multinational environments
(Wiley, 2012) Fernandez-Sanz, L.; Misra, Sanjay; Computer Engineering
Software development is mainly a social activity where teams of developers should work as a coordinated unit to fulfill the needs of customers. Studies have shown the importance of teamwork ability as the main skill for software professionals both in local settings and in global software development. Teamwork performance can be evaluated according to different approaches but we need deeper analysis within software teams of differences in individuals' performance related to culture, nationality or even gender. We applied a simple evaluation experience named teamwork benefits awareness (TBA) to groups of last-year students of computing degrees with experience as junior IT professionals during intensive multinational workshops based on international software projects. TBA allowed to measure individual and team performance during a requirements analysis session based on a real project. Results segmented by nationality and gender are presented and analysed in comparison with the data collected from computing professionals in local settings. In general, no significant differences have been found out although interesting relations are suggested with two Hofstede's country indicators. TBA is also perceived as a good technique for highlighting both teamwork benefits as well as the nature of real situations of software requirements analysis and orientation to customer needs.
Citation Count: 6
Analysis of Double Gaussian Distribution on Barrier Inhomogeneity in a Au/n-4H SiC Schottky Diode
(Springer, 2021) Gullu, H. H.; Sirin, D. Seme; Yildiz, D. E.; Department of Electrical & Electronics Engineering
A n-4H SiC based diode is fabricated by an Au front metal contact to provide rectification at the metal-semiconductor (MS) junction, and a back ohmic contact is also obtained using Au metal with post-thermal heating. MS diode characteristics are investigated by current-voltage (I - V) measurements with a wide range of temperature from 80 K to 300 K. At each temperature, rectifying behavior is achieved and it is improved with an increase in temperature. Barrier height and ideality factor are calculated according to the thermionic emission (TE) model from linearity in the forward bias region of the ln(I) versus V plot. The experimental zero-bias barrier height (Phi(b0)) values are in a good agreement with literature, and at around room temperature the ideality factor (n) reaches unity. At saturation regions in I - V curves, parasitic resistance values are derived by Ohm's law and the series resistance values are also reevaluated by Cheung's relation. Detailed I - V analysis is performed by modifying the TE model with an approximation of low barrier patches embedded in the main barrier height. Two linear relations in the characteristic plots of Phi(b0) and n indicate that double Gaussian distribution is a suitable current conduction model via localized barrier patches at low temperatures. Additionally, reverse bias current flow is analyzed under the dominant effect of Poole-Frenkel emission associated with the interfacial traps. According to the characteristic electric field-dependent current density plot, emission barrier height and relative dielectric constant for n-4H SiC are calculated.
Citation Count: 6
Analysis of the Hall effect in TlGaTe₂ single crystals
(Iop Publishing Ltd, 2009) Qasrawi, A. F.; Gasanly, N. M.; Department of Electrical & Electronics Engineering
The electrical resistivity and Hall coefficient of p-type TlGaTe2 crystals were measured in the temperature range of 110-320 K. The electrical resistivity, charge carrier density and Hall mobility data for the crystals have been analyzed by means of existing theories and models to determine the extrinsic energy levels, the carrier effective mass, the donor and acceptor concentrations and the dominant scattering mechanism in the crystal as well. The analysis of the temperature-dependent electrical resistivity recorded parallel and perpendicular to the crystal's axis ( c-axis) reflected the existence of energy levels located at 0.26 and at 0.20 eV, respectively. The difference of these two energy levels is due to crystal anisotropy. The energy level at 0.26 eV was found to represent an acceptor level, as confirmed from Hall data analysis. The temperature dependence of the carrier density was analyzed by using the single-donor-single-acceptor model. The latter analysis revealed the carrier effective mass and the acceptor and donor concentrations as 0.73m(0), 4.10 x 10(17) cm(-3) and 1.20 x 10(17) cm(-3), respectively. The Hall mobility of TlGaTe2 is found to be limited by the scattering of hole-acoustic phonon interactions. The calculated theoretical mobility fits to the experimental one under the condition that the acoustic deformation potential is 11.0 eV, which is the energy position of the top of valence band maximum that is formed by the Te 5s states.
Citation Count: 39
Analyzing Human Resource Management Practices Within the GSD Context
(Taylor & Francis inc, 2012) Colomo-Palacios, Ricardo; Casado-Lumbreras, Cristina; Soto-Acosta, Pedro; Misra, Sanjay; Garcia-Penalvo, Francisco Jose; Computer Engineering
The development of software across different countries (and time zones) differs substantially from software development in one single country or region. The management of processes and people, who work in globally distributed teams, requires a high level of coordination and collaboration which needs to be based on established human resource management practices. The People Capability Maturity Model (People-CMM) provides a complete framework that enables quality in human resource management to be improved. However, today, the adoption of the People-CMM within organizations using Global Software Development (GSD) is not an easy task. This paper uses an empirical study to analyze the implementation of the People-CMM within the GSD context. Results confirm that cultural and communication problems are the main challenges in the implementation of the People-CMM adoption within GSD scenarios.
Citation Count: 1
Analyzing two decades of intimate partner femicide-suicides in T?rkiye*
(Elsevier Sci Ltd, 2023) Cavlak, Mehmet; Odabasi, Aysun Balseven; Mutlu, Niluefer Dilara Ar; Erbaydar, Nueket Paksoy
Intimate partner femicide-suicide (IPF-S) is an understudied subgroup of homicide-suicide deaths. Limited research has been conducted on IPF-Ss in the Eastern Mediterranean region. This study thus aimed to evaluate the characteristics of IPF-Ss that occurred in Turkiye between 2000 and 2019. IPF-Ss (n = 226) were extracted from electronic news stories. Data on victims, perpetrators, their relationships, and incidents of murder and suicide were collected. Descriptive statistics were calculated, and logistic regression analysis, mortality rates, and proportion of IPF-S in femicide calculations were conducted, showing that 13.3% of the femicides (n = 1699) were IPF-Ss. The IPF-Ss increased in 5-year intervals and were the highest during the 2015-2019 period (62.5%). Victims were married in 48.2% of the cases and 56% were aged <35 years, while 51.3% of the perpetrators were married and 52.6% were aged >40 years. In 42.0% of the cases, the perpetrator lived with the victim. Most (79.2%) of the cases took place in urban settlements, and the perpetrators used firearms in 84.1% of femicide cases. Firearm use was the most common method in cases where IPF-S was planned (OR = 2.98), when the IPF-S method was the same (OR = 29.6), and when the perpetrator committed suicide (OR = 7.82). In addition, it was found that firearm ownership is an important risk factor for IPF-S in Turkiye. Therefore, we recommend legislation to restrict firearms, as well as new measures to prevent illegal access to weapons.
Citation Count: 2
Anisotropic electrical and dispersive optical parameters in InS layered crystals
(Pergamon-elsevier Science Ltd, 2010) Qasrawi, A. F.; Gasanly, N. M.; Department of Electrical & Electronics Engineering
The anisotropy effect on the current transport mechanism and on the dispersive optical parameters of indium monosulfide crystals has been studied by means of electrical conductivity and polarized reflectance measurements along the a-axis and the b-axis, respectively. The temperature-dependent electrical conductivity analysis in the range 10-350 K for the a-axis and in the range 30-350 K for the b-axis revealed the domination of the thermionic emission of charge carriers and the domination of variable range hopping above and below 100 K, respectively. At high temperatures (T > 100 K) the conductivity anisotropy, s, decreased sharply with decreasing temperature following the law s proportional to exp(-E(s)/kT). The anisotropy activation energy, E(s), was found to be 330 and 17 meV above and below 220 K, respectively. Below 100 K, the conductivity anisotropy is invariant with temperature. in that region, the calculated hopping parameters are altered significantly by the conductivity anisotropy. The optical reflectivity analysis in the wavelength range 250-650 nm revealed a clear anisotropy effect on the dispersive optical parameters. In particular, the static refractive index, static dielectric constant, lattice dielectric constant, dispersion energy and oscillator energy exhibited values of 2.89, 8.39, 19.7, 30.02 eV and 4.06 eV, and values of 2.76, 7.64, 25.9, 22.26 eV and 3.35 eV for light polarized along the a-axis and the b-axis, respectively. (C) 2009 Elsevier Ltd. All rights reserved.
Citation Count: 22
Anomaly detection using fuzzy Q-learning algorithm
(Budapest Tech Polytechnical Institution, 2014) Shamshirband,S.; Anuar,N.B.; Kiah,M.L.M.; Misra,S.; Computer Engineering
Wireless networks are increasingly overwhelmed by Distributed Denial of Service (DDoS) attacks by generating flooding packets that exhaust critical computing and communication resources of a victim's mobile device within a very short period of time. This must be protected. Effective detection of DDoS attacks requires an adaptive learning classifier, with less computational complexity, and an accurate decision making to stunt such attacks. In this paper, we propose an intrusion detection system called Fuzzy Q-learning (FQL) algorithm to protect wireless nodes within the network and target nodes from DDoS attacks to identify the attack patterns and take appropriate countermeasures. The FQL algorithm was trained and tested to establish its performance by generating attacks from the NSL-KDD and CAIDA DDoS Attack datasets during the simulation experiments. Experimental results show that the proposed FQL IDS has higher accuracy of detection rate than Fuzzy Logic Controller and Q-learning algorithm alone. © 2014 Instituto de Pesquisas Economicas da FEA-USP. All rights reserved.
Citation Count: 0
Anticipatory effect of execution on observation: an approach using ExoPinch finger robot
(Tubitak Scientific & Technological Research Council Turkey, 2019) Arıkan, Kutluk Bilge; Zadeh, Hassan Gol Mohammad; Turgut, Ali Emre; Zinnuroğlu, Murat; Bayer, Gözde; Günendi, Zafer; Cengiz, Bülent; Department of Mechatronics Engineering
Background/aim: This study aims to explore the mirror neuron system (MNS) involvement using mu (8–12 Hz)/beta (15–25 Hz) bandsuppression in an action observation-execution paradigm.Materials and methods: Electrophysiological (EEG) data from 16 electrodes were recorded while 8 participants observed video clips ofa hand squeezing a spring. Specifically, the effect of anticipated execution on observation was studied. For this purpose, a fully actuatedfinger exoskeleton robot was utilized to synchronize observation and execution and to control the execution condition for the participants. Anticipatory effect was created with a randomized robot accompany session.Results: The results showed that the observational condition (with or without anticipation) interacted with hemisphere at central channels near somatosensory cortex. Additionally, we explored the response of MNS on the kinetics features of visual stimuli (hard or softspring).Conclusion: The results showed an interaction effect of kinetics features and hemisphere at frontal channels corresponding nearly tothe ventral premotor cortex area of the brain. The activation of mirror neurons in this area plays a crucial role in observational learning.Based on our results, we propose that specific type of visual stimuli can be combined with the functional abilities of the MNS in the action observation based treatment of hand motor dysfunction of stroke patients to have a positive additional impact.
Citation Count: 0
Antiproliferative activity of platinum(II) and copper(II) complexes containing novel biquinoxaline ligands
(Oxford Univ Press, 2024) El-Beshti, Hager Sadek; Gercek, Zuhal; Kayi, Hakan; Yildizhan, Yasemin; Cetin, Yuksel; Adiguzel, Zelal; Ozalp-Yaman, Seniz; Chemical Engineering
Nowadays, cancer represents one of the major causes of death in humans worldwide, which renders the quest for new and improved antineoplastic agents to become an urgent issue in the field of biomedicine and human health. The present research focuses on the synthesis of 2,3,2MODIFIER LETTER PRIME,3MODIFIER LETTER PRIME-tetra(pyridin-2-yl)-6,6MODIFIER LETTER PRIME-biquinoxaline) and (2,3,2MODIFIER LETTER PRIME,3MODIFIER LETTER PRIME-tetra(thiophen-2-yl)-6,6MODIFIER LETTER PRIME-biquinoxaline) containing copper(II) and platinum(II) compounds as prodrug candidates. The binding interaction of these compounds with calf thymus DNA (CT-DNA) and human serum albumin were assessed with UV titration, thermal decomposition, viscometric, and fluorometric methods. The thermodynamical parameters and the temperature-dependent binding constant (KMODIFIER LETTER PRIMEb) values point out to spontaneous interactions between the complexes and CT-DNA via the van der Waals interactions and/or hydrogen bonding, except Cu(ttbq)Cl2 for which electrostatic interaction was proposed. The antitumor activity of the complexes against several human glioblastomata, lung, breast, cervix, and prostate cell lines were investigated by examining cell viability, oxidative stress, apoptosis-terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, in vitro migration and invasion, in vitro-comet DNA damage, and plasmid DNA interaction assays. The U87 and HeLa cells were investigated as the cancer cells most sensitive to our complexes. The exerted cytotoxic effect of complexes was attributed to the formation of the reactive oxygen species in vitro. It is clearly demonstrated that Cu(ttbq)Cl2, Pt(ttbq)Cl2, and Pt(tpbq)Cl2 have the highest DNA degradation potential and anticancer effect among the tested complexes by leading apoptosis. The wound healing and invasion analysis results also supported the higher anticancer activity of these two compounds. Graphical Abstract Antitumor activity of biqunoxaline complexes.
Citation Count: 55
Applications of the extended fractional Euler-Lagrange equations model to freely oscillating dynamical systems
(Publishing House of the Romanian Academy, 2016) Agila,A.; Baleanu,D.; Eid,R.; Irfanoglu,B.; Department of Mechatronics Engineering; Mathematics
The fractional calculus and the calculus of variations are utilized to model and control complex dynamical systems. Those systems are presented more accurately by means of fractional models. In this study, an extended version of the fractional Euler-Lagrange equations is introduced. In these equations the damping force term is extended to be proportional to the fractional derivative of the displacement with variable fractional order. The finite difference methods and the Coimbra fractional derivative are used to approximate the solution of the introduced fractional Euler-Lagrange equations model. The free oscillating single pendulum system is investigated. © 2016, Editura Academiei Romane. All rights reserved.
Citation Count: 5
Applying model-driven paradigm for the improvement of web requirement validation
(2012) Aragon,G.; Escalona,M.J.; Hilera,J.R.; Fernandez-Sanz,L.; Misra,S.; Computer Engineering
This paper proposes an approach for Web requirements validation by applying the model-driven paradigm in classical requirements validation techniques. In particular, we present how the Navigational Development Techniques (NDT) approach exploits the model-driven paradigm to improve its requirements validation task by exploring tool cases that systematize or even automate the application of requirements validation techniques. Our solution is validated by applying it in a real industrial environment. The results and the learned lessons are presented accordingly.
Citation Count: 11
An approach for e-Commerce on-demand service-oriented product line development
(Budapest Tech Polytechnical Institution, 2013) Ezenwoke,A.; Misra,S.; Adigun,M.; Computer Engineering
The growth of Small, Medium and Micro Enterprises (SMMEs) is important to the economic development of Africa. This growth can be greatly enhanced by leveraging IT in business activities since e-commerce is a vital tool to allow participation in globalization. Many SMMEs cannot afford to own e-commerce facilities and to reduce cost. An SMME can pay for just the e-commerce facility they use without owning the services or infrastructure. Due to the dynamic nature of the business domain, delivering such on-demand functionalities involves high flexibility in adapting to new client requirements; therefore, a systematic approach to software component reuse must be adopted to reduce cost and the time to market for new products. This work explores the reuse capabilities of a hybridization of Service Oriented Architecture (SOA) and Software Product Line (SPL).
Citation Count: 15
An approach for the empirical validation of software complexity measures
(2011) Misra,S.; Computer Engineering
Software metrics are widely accepted tools to control and assure software quality. A large number of software metrics with a variety of content can be found in the literature; however most of them are not adopted in industry as they are seen as irrelevant to needs, as they are unsupported, and the major reason behind this is due to improper empirical validation. This paper tries to identify possible root causes for the improper empirical validation of the software metrics. A practical model for the empirical validation of software metrics is proposed along with root causes. The model is validated by applying it to recently proposed and well known metrics.
Citation Count: 17
The approximation by q-Bernstein polynomials in the case q ↓ 1
(Springer Basel Ag, 2006) Ostrovska, S; Mathematics
Let B-n (f, q; x), n = 1, 2, ... , 0 < q < infinity, be the q-Bernstein polynomials of a function f, B-n (f, 1; x) being the classical Bernstein polynomials. It is proved that, in general, {B-n (f, q(n); x)} with q(n) down arrow 1 is not an approximating sequence for f is an element of C[0, 1], in contrast to the standard case q(n) up arrow 1. At the same time, there exists a sequence 0 < delta(n) down arrow 0 such that the condition 1 <= q(n) <= delta(n) implies the approximation of f by {B-n(f, qn; x)} for all f is an element of C[0, 1].
Citation Count: 2
Are CO₂ Emissions Stationary After All? New Evidence from Nonlinear Unit Root Tests
(Springer, 2022) Romero-Avila, Diego; Omay, Tolga; Economics
This study applies a large battery of state-of-the-art nonlinear unit root tests to examine the stationarity properties of carbon dioxide emission series for 28 industrialized countries, five BRICS and seven transition economies over a very long horizon, in some cases over more than two and a half centuries. The application of time-dependent and state-dependent nonlinear unit root tests separately provides mixed evidence regarding the time-series properties of CO2 emissions and a high degree of variability across the different tests. However, the use of hybrid nonlinear unit root tests, combining the presence of structural breaks with symmetric or asymmetric ESTAR adjustment, leads to the rejection of the unit root hypothesis in each of the countries under study with at least one of the hybrid tests. This has important climate policy implications.

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