WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8653
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Article Citation - WoS: 2Routines and the Environment: Bridging the Gaps(Elsevier Science inc, 2008) Gossart, CedricThe paper examines the hypothesis that the mechanisms used by firms to improve their environmental performance are organisational routines. The concept of routines has been developed by evolutionary economists to investigate firms' innovative behaviour, but it has not been used to study how firms address environmental issues. Based on an applicable definition of routines, a methodology is designed to identify environmental routines in a case study of 13 oil refineries located in four different countries. Results confirm the hypothesis for firms operating under strict environmental regulations (France, UK). A comparative analysis of the degrees of routineness of the environmental mechanisms used by case study firms reveals and explains important gaps between European and North African refineries. Solutions to reduce them are proposed. (c) 2007 Elsevier Inc. All rights reserved.Article Citation - WoS: 5Citation - Scopus: 6The Use of Discrete Element Models for the Seismic Assessment of Concrete Gravity Dams(Elsevier Science inc, 2024) Soysal, Berat Feyza; Arici, YalinThe assessment of the seismic performance of gravity dams is a difficult engineering problem requiring consideration of the cracking in a brittle medium as well as the interaction of the reservoir and the massive concrete structure. The problem is challenging from a practical point of view as well; a clear-cut damage indicator for assessing the performance of these systems is not present. The generally used finite element method (FEM)/rotating crack combination led to the utilization of indirect global demand parameters like crest displacements or damaged area ratios as damage indicators. While very robust in terms of the solution, the aforementioned combination leads to highly diffused crack patterns for large shaking, limiting the interpretation of the results for these systems on which discrete cracks' extent and widths are the primary damage measures. This limitation can be overcome by utilizing methods that simulate the discrete fracture phenomenon; in this study, the nonlinear seismic behavior of a concrete gravity dam-reservoir system was investigated using the developed discrete element framework, the modified applied element method (MAEM). Using incremental dynamic analysis, the cracking on the dam body was compared with those of the FEM qualitatively first, followed by a quantitative comparison focused on the propagation of the cracking using fragility curves. Then, the use of crack widths as a damage indicator was utilized, and model outcomes were compared. The utilized model reduced the diffusion of cracking commonly observed in FEM models using total strain smeared crack formulation and predicted more adverse behavior in terms of total crack widths and crack propagation.Article Citation - WoS: 19Citation - Scopus: 27Software Professionals During the Covid-19 Pandemic in Turkey: Factors Affecting Their Mental Well-Being and Work Engagement in the Home-Based Work Setting(Elsevier Science inc, 2022) Tokdemir, GulWith the COVID-19 pandemic, strict measures have been taken to slow down the spread of the virus, and consequently, software professionals have been forced to work from home. However, home based working entails many challenges, as the home environment is shared by the whole family simultaneously under pandemic conditions. The aim of this study is to explore software professionals' mental well-being and work engagement and the relationships of these variables with job strain and resource-related factors in the forced home-based work setting during the COVID-19 pandemic. An online cross-sectional survey based on primarily well-known, validated scales was conducted with software professionals in Turkey. The analysis of the results was performed through hierarchical multivariate regression. The results suggest that despite the negative effect of job strain, the resource related protective factors, namely, sleep quality, decision latitude, work-life balance, exercise predict mental well-being. Additionally, work engagement is predicted by job strain, sleep quality, and decision latitude. The results of the study will provide valuable insights to management of the software companies and professionals about the precautions that can be taken to have a better home-based working experience such as allowing greater autonomy and enhancing the quality of sleep and hence mitigating the negative effects of pandemic emergency situations on software professionals' mental well-being and work engagement. (C)& nbsp;2022 Elsevier Inc. All rights reserved.Article Citation - WoS: 5Citation - Scopus: 9Strategy Creation, Decomposition and Distribution in Particle Navigation(Elsevier Science inc, 2007) Leblebicioglu, Kemal; Beldek, UlasStrategy planning is crucial to control a group to achieve a number of tasks in a closed area full of obstacles. In this study, genetic programming has been used to evolve rule-based hierarchical structures to move the particles in a grid region to accomplish navigation tasks. Communications operations such as receiving and sending commands between particles are also provided to develop improved strategies. In order to produce more capable strategies, a task decomposition procedure is proposed. In addition, a conflict module is constructed to handle the challenging situations and conflicts such as blockage of a particle's pathway to destination by other particles. (C) 2006 Elsevier Inc. All rights reserved.Article Citation - WoS: 25Citation - Scopus: 27Microstructural and Texture Evolution During Thermo-Hydrogen Processing of Ti6al4v Alloys Produced by Electron Beam Melting(Elsevier Science inc, 2020) Esen, Ziya; Davut, Kemal; Tan, Evren; Gumus, Berkay; Dericioglu, Arcan F.; Dogu, Merve NurThe present study was conducted to reveal the effects of building angles and post heat-treatments (2-step Thermo-Hydrogen Processing (THP) and conventional annealing treatment) on the density, microstructure and texture of Ti6Al4V alloy parts produced by Electron Beam Melting (EBM). The results showed that regardless of the building angle; the density, microstructure and crystallographic texture (defined with respect to building angle) of the as-produced samples were identical; having Widmanstatten a structure and columnar beta-grains which are parallel to building direction. The main texture component for the alpha phase was (10 (1) over bar0)//building direction, and for beta phase (001)//building or heat flow direction. The first step of THP, namely, the hydrogenation step, produced a needle-like microstructure and increased the local misorientations due to lattice distortion. On the other hand, after application of the second step of THP, dehydrogenation step, microstructure was refined, particularly alpha-grains that were larger than 10 mu m and located at grain boundaries. Moreover, THP randomized the crystallographic texture since it involves beta to alpha phase transformation, at which one beta-grain can produce 12 distinct alpha-variants. The grain boundary misorientation distributions also changed in accordance with the microstructural changes during the 2-step THP. On the other hand, annealing coarsened the grain boundary and Widmanstatten alpha phases; moreover, it changed the texture so that the basal planes (0001) rotated 30 degrees around the building direction.Article Citation - WoS: 22Citation - Scopus: 21Experimental Investigation of Damaged Square Short Rc Columns With Low Slenderness Retrofitted by Cfrp Strips Under Axial Load(Elsevier Science inc, 2020) Ghoroubi, Rahim; Mercimek, Omer; Ozdemir, Anil; Anil, OzgurThe aim of this study is to develop the retrofitting details, which will increase axial ultimate load capacity, stiffness, displacement ductility ratios, and energy dissipation capacities of short reinforced concrete (RC) low slenderness columns to avoid adverse effects on earthquake performance. The main variables examined in the experimental study are the Carbon Reinforced Fiber Polymer (CFRP) strip width used for retrofitting, the distance between CFRP strips, the use of the anchor at the overlap zone in the CFRP strips, and the placement of the CFRP strips horizontally or vertically to the column axis. For these purposes, eleven square short RC columns with a dimension of 150x150x500 mm (with low slenderness ratio: lambda = 11.5) were produced. The columns were damaged up to 50% of their axial load carrying capacity, then retrofitted with CFRP strips in different ways. The short RC columns with low slenderness ratio were tested under monotonic axial loading until they failure. By obtaining the axial load-displacement graphs of the test specimens, the ultimate axial load capacity, initial stiffness value, displacement-ductility ratios, and energy dissipation capacities are calculated and interpreted. It has been found that the most successful retrofitting detail is obtained when CFRP strips are placed perpendicular to the column axis, and CFRP fan-type anchors are used in the strip overlap region.Article Citation - WoS: 9Citation - Scopus: 7The Effects of Federal Regulations on Corruption in Us States(Elsevier Science inc, 2020) Gunalp, Burak; Dincer, OguzhanUsing the newly constructed Federal Regulation and State Enterprise Index (FRASE Index) to measure the federal regulations and the existing Corruption Convictions Index (CCI), we investigate the effects of federal regulations on corruption in U.S. states. Controlling for several demographic and economic variables including the Fraser Institute's Economic Freedom Index (EFI), which measures the size and scope of government in U.S. states, we find a positive and statistically significant relationship between federal regulations and corruption. Our findings have important policy implications. A 1 standard deviation increase in FRASE Index causes CCI to increase by approximately 0.5 standard deviations. Standardized coefficient of EFI is also approximately equal to 0.5. In other words, it is possible to mitigate the effects of regulations at the federal level by reducing the size and the scope of the government at the state level.Article Citation - WoS: 22Citation - Scopus: 37Performing and Analyzing Non-Formal Inspections of Entity Relationship Diagram (Erd)(Elsevier Science inc, 2013) Tokdemir, Gul; Kilic, Ozkan; Topalli, Damla; Cagiltay, Nergiz ErcilDesigning and understanding of diagrammatic representations is a critical issue for the success of software projects because diagrams in this field provide a collection of related information with various perceptual signs and they help software engineers to understand operational systems at different levels of information system development process. Entity relationship diagram (ERD) is one of the main diagrammatic representations of a conceptual data model that reflects users' data requirements in a database system. In today's business environment, the business model is in a constant change which creates highly dynamic data requirements which also requires additional processes like modifications of ERD. However, in the literature there are not many measures to better understand the behaviors of software engineers during designing and understanding these representations. Hence, the main motivation of this study is to develop measures to better understand performance of software engineers during their understanding process of ERD. Accordingly, this study proposes two measures for ERD defect detection process. The defect detection difficulty level (DF) measures how difficult a defect to be detected according to the other defects for a group of software engineers. Defect detection performance (PP) measure is also proposed to understand the performance of a software engineer during the defect detection process. The results of this study are validated through the eye tracker data collected during the defect detection process of participants. Additionally, a relationship between the defect detection performance (PP) of a software engineer and his/her search patterns within an ERD is analyzed. Second experiment with five participants is also conducted to show the correlation between the proposed metric results and eye tracker data. The results of experiment-2 also found to be similar for DF and PP values. The results of this study are expected to provide insights to the researchers, software companies, and to the educators to improve ERD reasoning process. Through these measures several design guidelines can be developed for better graphical representations and modeling of the information which would improve quality of these diagrams. Moreover, some reviewing instructions can be developed for the software engineers to improve their reviewing process in ERD. These guidelines in turn will provide some tools for the educators to improve design and review skills of future software engineers. (c) 2013 Elsevier Inc. All rights reserved.Article Citation - WoS: 39Citation - Scopus: 42A Second Order Accurate Approximation for Fractional Derivatives With Singular and Non-Singular Kernel Applied To a Hiv Model(Elsevier Science inc, 2020) Baleanu, Dumitru; Arshad, Sadia; Defterli, OzlemIn this manuscript we examine the CD4(+) T cells model of HIV infection under the consideration of two different fractional differentiation operators namely Caputo and Caputo-Fabrizio (CF). Moreover, the generalized HIV model is investigated by considering Reverse Transcriptase (RT) inhibitors as a drug treatment for HIV. The threshold values for the stability of the equilibrium point belonging to non-infected case are calculated for both models with and without treatment. For the numerical solutions of the studied model, we construct trapezoidal approximation schemes having second order accuracy for the approximation of fractional operators with singular and non-singular kernel. The stability and convergence of the proposed schemes are analyzed analytically. To illustrate the dynamics given by these two fractional operators, we perform numerical simulations of the HIV model for different biological scenarios with and without drug concentration. The studied biological cases are identified by considering different values of the parameters such as infection rate, growth rate of CD4(+) T cells, clearance rate of virus particles and also the order of the fractional derivative. (C) 2020 Elsevier Inc. All rights reserved.Article Citation - WoS: 18Citation - Scopus: 21A Spectral Collocation Method With Piecewise Trigonometric Basis Functions for Nonlinear Volterra-Fredholm Integral Equations(Elsevier Science inc, 2020) Hajipour, Mojtaba; Baleanu, Dumitru; Amiri, SadeghThe aim of this paper is to investigate an efficient numerical method based on a novel shifted piecewise cosine basis for solving Volterra-Fredholm integral equations of the second kind. Using operational matrices of integration for the proposed basis functions, this integral equation is transformed into a system of nonlinear algebraic equations. The convergence and error analysis of the proposed method are studied. Some comparative results are provided to verify the efficiency of the presented method. (C) 2019 Elsevier Inc. All rights reserved.