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Article Citation - WoS: 44Citation - Scopus: 51On the lifetime behavior of a discrete time shock model(Elsevier, 2013) Eryilmaz, SerkanIn this article, we study a shock model in which the shocks occur according to a binomial process, i.e. the interarrival times between successive shocks follow a geometric distribution with mean 1/p. According to the model, the system fails when the time between two consecutive shocks is less than a prespecified level. This is the discrete time version of the so-called delta-shock model which has been previously studied for the continuous case. We obtain the probability mass function and probability generating function of the system's lifetime. We also present an extension of the results to the case where the shock occurrences are dependent in a Markovian fashion. (C) 2012 Elsevier B.V. All rights reserved.Article Citation - WoS: 43Citation - Scopus: 60Impact of Physical Ambiance on Communication, Collaboration and Coordination in Agile Software Development: an Empirical Evaluation(Elsevier, 2012) Mishra, Deepti; Mishra, Alok; Ostrovska, SofiyaContext: Communication, collaboration and coordination are key enablers of software development and even more so in agile methods. The physical environment of the workspace plays a significant role in effective communication, collaboration, and coordination among people while developing software. Objective: In this paper, we have studied and further evaluated empirically the effect of different constituents of physical environment on communication, coordination, and collaboration, respectively. The study aims to provide a guideline for prospective agile software developers. Method: A survey was conducted among software developers at a software development organization. To collect data, a survey was carried out along with observations, and interviews. Results: It has been found that half cubicles are 'very effective' for the frequency of communication. Further, half cubicles were discovered 'effective' but not 'very effective' for the quality/effectiveness of communication. It is found that half-height cubicles and status boards are 'very effective' for the coordination among team members according to the survey. Communal/discussion space is found to be 'effective' but not 'very effective' for coordination among team members. Our analysis also reveals that half-height glass barriers are 'very effective' during the individuals problem-solving activities while working together as a team. Infact, such a physically open environment appears to improve communication, coordination, and collaboration. Conclusion: According to this study, an open working environment with only half-height glass barriers and communal space plays a major role in communication among team members. The presence of status boards significantly help in reducing unnecessary communication by providing the required information to individuals and therefore, in turn reduce distractions a team member may confront in their absence. As communication plays a significant role in improving coordination and collaboration, it is not surprising to find the effect of open working environment and status boards in improving coordination and collaboration. An open working environment increases the awareness among software developers e.g. who is doing what, what is on the agenda, what is taking place, etc. That in turn, improves coordination among them. A communal/discussion space helps in collaboration immensely. (C) 2012 Elsevier B.V. All rights reserved.Article Citation - WoS: 2Geoengineering Properties of the Ertugrul (cayirkoy) District, Nilufer Province, Bursa-Turkey, by Using Geophysical Methods and Borehole Data(Elsevier, 2020) Cetin, Fatma; Kutluk, Hatice; Aydemir, AttilaIn this study, soil classification experiments and geophysical studies are carried out for the evaluation of local ground soil conditions by using the data and samples from the boreholes in the Quaternary sediments in the Ertugrul district of Nilufer, Bursa, then the engineering parameters and index classifications are also investigated with the soil mechanics experiments using the disturbed samples from the drill holes. The grade of swelling (bulking) potential in the ground soil is found medium, high and very high in different parts of the study area. The basement units for the constructions bear very low liquefaction risk. The plasticity index varies between 9 and 25, but active mass movements are not expected. However, engineering problems such as swelling (bulking), soil settlements, bearing capacity reduction may be expected under the seismic forces because of the alluvial composition, 0-5 degree soil inclinations and being located in the 1st degree earthquake hazard risk zone. Therefore, the study area may be classified in the 'precautionary zone' in the urbanization category in terms of engineering problems. (C) 2020 Elsevier B.V. All rights reserved.Article Citation - WoS: 10Citation - Scopus: 15Bifunctional Praseodymium-Doped Sns2 Thin Films for Photocatalytic and Antibacterial Applications(Elsevier, 2024) Ech-Chergui, Abdelkader Nebatti; Bennabi, Farid; Isik, Mehmet; Khane, Yasmina; Garcia, Francisco Jose Garcia; Kadari, Ali Sadek; Amrani, BouhalouaneThis paper introduces a novel application of bifunctional Pr-doped SnS2 thin films, demonstrating their efficacy in both photocatalytic degradation of dye and antibacterial activities. The thin films were fabricated using an eco-friendly spray-coated method, encompassing undoped and Pr-doped SnS2 variations. The study comprehensively examines the structural, morphological, chemical, photocatalytic, and antibacterial characteristics of these films. The crystal structure of both undoped and Pr-doped SnS2 thin films exhibited hexagonal patterns, prominently favouring the growth in (1 0 1) orientation. Notably, an increase in crystallite size was observed with higher levels of Pr-doping. Raman spectroscopy analysis highlighted a distinct peak at 315 cm -1, corresponding to the A1 g vibrational mode associated with Sn-S bonds along the c-axis of the structure. Employing X ray Photoelectron Spectroscopy (XPS), the presence of essential components - Sn, S, and Pr - within the fabricated thin films was confirmed, consistent with experimental values of undoped and Pr -doped SnS2-x compositions. Importantly, the XPS analysis confirmed the integration of the Pr3+ oxidation state within Pr -doped SnS2 films. The photocatalytic degradation and antibacterial activities of the films were investigated. Notably, the photocatalytic potential of the synthesized materials against Congo Red exhibited a direct correlation with the Pr3+ doping percentage, indicating enhanced pollutant degradation with increasing doping levels. Similarly, the antibacterial performance against Escherichia coli displayed improvement with increasing Pr -doping content, highlighting the promising antimicrobial capabilities of the films. This study presents an innovative avenue to address both organic pollutant degradation and microbial control. By harnessing the attributes of Pr -doped SnS2 thin films, this research introduces a promising strategy for sustainable material applications in environmental purification and improvement in public health.Article Citation - WoS: 4Citation - Scopus: 6An Automata Networks Based Preprocessing Technique for Artificial Neural Network Modelling of Primary Production Levels in Reservoirs(Elsevier, 2007) Kilic, Hurevren; Soyupak, Selcuk; Tuzun, Ilhami; Ince, Ozlem; Basaran, GokbenPrimary production in lakes and reservoirs develops as a result of complex reactions and interactions. Artificial neural networks (ANN) emerges as an approach in quantification of primary productivity in reservoirs. Almost all of the past ANN applications employed input data matrices whose vectors represent either water quality parameters or environmental characteristics. Most of the time, the components of input matrices are determined using expert opinion that implies possible factors that affect output vector. Major disadvantage of this approach is the possibility of ending-up with an input matrix that may have high correlations between some of its components. In this paper, an automata networks (AN) based preprocessing technique was developed to select suitable and appropriate constituents of input matrix to eliminate redundancy and to enhance calculation efficiency. The proposed technique specifically provides an apriori rough behavioral modeling through identification of minimal AN interaction topology. Predictive ANN models of primary production levels were developed for a reservoir following AN based pre-modeling step. The achieved levels of model precisions and performances were acceptable: the calculated root mean square error values (RMSE) were low; a correlation coefficient (R) as high as 0.83 was achieved with an ANN model of a specific structure. (c) 2006 Elsevier B.V. All rights reserved.Review Citation - WoS: 67Citation - Scopus: 81Software Test Maturity Assessment and Test Process Improvement: a Multivocal Literature Review(Elsevier, 2017) Garousi, Vahid; Felderer, Michael; Hacaloglu, TunaContext: Software testing practices and processes in many companies are far from being mature and are usually conducted in ad-hoc fashions. Such immature practices lead to various negative outcomes, e.g., ineffectiveness of testing practices in detecting all the defects, and cost and schedule overruns of testing activities. To conduct test maturity assessment (TMA) and test process improvement (TPI) in a systematic manner, various TMA/TPI models and approaches have been proposed. Objective: It is important to identify the state-of-the-art and the-practice in this area to consolidate the list of all various test maturity models proposed by practitioners and researchers, the drivers of TMA/TPI, the associated challenges and the benefits and results of TMA/TPI. Our article aims to benefit the readers (both practitioners and researchers) by providing the most comprehensive survey of the area, to this date, in assessing and improving the maturity of test processes. Method: To achieve the above objective, we have performed a Multivocal Literature Review (MLR) study to find out what we know about TMA/TPI. A MLR is a form of a Systematic Literature Review (SLR) which includes the grey literature (e.g., blog posts and white papers) in addition to the published (formal) literature (e.g., journal and conference papers). We searched the academic literature using the Google Scholar and the grey literature using the regular Google search engine. Results: Our MLR and its results are based on 181 sources, 51 (29%) of which were grey literature and 130 (71%) were formally published sources. By summarizing what we know about TMA/TPI, our review identified 58 different test maturity models and a large number of sources with varying degrees of empirical evidence on this topic. We also conducted qualitative analysis (coding) to synthesize the drivers, challenges and benefits of TMA/TPI from the primary sources. Conclusion: We show that current maturity models and techniques in TMA/TPI provides reasonable advice for industry and the research community. We suggest directions for follow-up work, e.g., using the findings of this MLR in industry-academia collaborative projects and empirical evaluation of models and techniques in the area of TMA/TPI as reported in this article. (C) 2017 Elsevier B.V. All rights reserved.Article Citation - WoS: 25Citation - Scopus: 34Modelling and Controlling of Drill String Stick Slip Vibrations in an Oil Well Drilling Rig(Elsevier, 2022) Sadeghi, Amir Noabahar; Arikan, Kutluk Bilge; Ozbek, Mehmet EfeMitigating of drill string vibrations, plays a distinctive role in increase of rate of penetration and consequently decrease of the operation costs, prevent of severe damages to drill string and bit, increase of drilling operation quality and safety, and enhance the performances of the controllers. This study deals with modelling and controlling of drill string vibrations with focus on stick slip vibrations in vertical wells. The approach taken to subdivide the drill string into smaller torsional sections and model the complete system dynamically and employ the extracted torsional model to model the stick slip vibrations mathematically. To mitigate and or active control of stick slip vibrations, three architectures are developed and proposed, manipulation of the rotational speed, manipulation of the weight on bit, and increasing of the damping in the bottom of the drill string. The performance of each strategy is analysed individually as well as relative to each other, using a mathematical measure when the drill string length is divided into smaller torsional sections. By the aid of the simulations and mathematical measures, it is shown that manipulation of rotational speeds at the surface may not be an effective solution to reduce the stick slip vibrations, however manipulation of weight on bit and increasing of damping at the bottom of string can be two effective solutions to mitigate these kinds of vibrations. As a general conclusion, it is proved that the manipulation of bottom side drilling parameters is more effective than the manipulation of surface drilling parameters.Article Citation - WoS: 47Citation - Scopus: 44Investigation of Structural, Electronic, Magnetic and Lattice Dynamical Properties for Xcobi (x: Ti, Zr, Hf) Half-Heusler Compounds(Elsevier, 2020) Surucu, Gokhan; Isik, Mehmet; Candan, Abdullah; Wang, Xiaotian; Gullu, Hasan HuseyinStructural, electronic, magnetic, mechanical and lattice dynamical properties of XCoBi (X: Ti, Zr, Hf) Half-Heusler compounds have been investigated according to density functional theory and generalized gradient approximation. Among alpha, beta and gamma structural phases, gamma-phase structure has been found as the most stability characteristics depending on the calculated formation enthalpies, energy-volume dependencies and Cauchy pressures. Energy-volume plots of possible magnetic orders of gamma-phase XCoBi compounds have been analyzed and the most stable order has been found as paramagnetic nature. The theoretical studies on gamma-phase structures resulted in band gap energies of 0.96, 0.99 and 0.98 eV for TiCoBi, ZrCoBi and HfCoBi semiconducting compounds, respectively. Born-Huang criteria applied on elastic constants of interest compounds has indicated that gamma-phase is also mechanically stable for all studied compounds. In addition, various mechanical, lattice dynamical and thermodynamical parameters of XCoBi compounds have been calculated in the present study.Article Citation - WoS: 44Citation - Scopus: 54Towards a Circular Economy: Investigating the Critical Success Factors for a Blockchain-Based Solar Photovoltaic Energy Ecosystem in Turkey(Elsevier, 2021) Erol, Ismail; Peker, Iskender; Ar, Ilker Murat; Turan, Ismet; Searcy, CoryNovel business models can be implemented through digital platforms to enable better circular economy (CE) performance in the renewable energy industry. For example, blockchain can assist in developing innovative business models throughout the solar photovoltaic energy ecosystem (SPVEE) to improve CE. Ranked fifth in total installed photovoltaic (PV) capacity, Turkey, as a developing country, should take the necessary steps and make progress towards achieving CE in the SPVEE. The solar PV industry requires further innovation to address the negative environmental impact of existing linear business models. To ensure favorable results, identifying and evaluating critical success factors (CSFs) are necessary. However, no study has investigated CSFs for SPVEE or any other renewable energy source to achieve a blockchain-based infrastructure towards increased CE performance. Therefore, the goal of this study is to identify and examine the CSFs to improve the performance of a blockchain-based SPVEE towards CE in Turkey. To this end, first, the CSFs for blockchain-based SPVEE were identified through both a literature review and the Nominal Group Technique (NGT). Then, Intuitionistic Fuzzy (IF)DEMATEL was used to explore their interrelationships based on the expert data. Finally, IF-DELPHI was employed to validate the results. Our findings suggested that effective government incentive programs and regulations are significant for blockchain-based SPVEE towards CE in Turkey. The findings of this study assist macro and micro decision-making in the potential implementation of blockchain in Turkish SPVEE to improve CE. They are also invaluable for other countries and can be used as a reference point. (c) 2021 International Energy Initiative. Published by Elsevier Inc. All rights reserved.Article Citation - WoS: 27Citation - Scopus: 29Assessing Dependency of Part Properties on the Printing Location in Laser-Powder Bed Fusion Metal Additive Manufacturing(Elsevier, 2022) Mussatto, Andre; Groarke, Robert; Vijayaraghavan, Rajani K.; Hughes, Cian; Obeidi, Muhannad Ahmed; Dogu, Merve Nur; Brabazon, DermotDespite the accelerated growth of laser-powder bed fusion in recent years, there are still major obstacles to be overcome before the technology enjoys truly widespread adoption. These include inconsistent part quality and repeatability issues linked to variability in the properties of printed parts. Commonly, the print location across the build platform is overlooked and assumed to have little or no effect on the overall part properties. There is a lack of previous systematic studies and a lack of knowledge of the influences of the location parameter on the final part properties. Therefore, to address the existing problem, the current study completely isolated the location parameter to accurately assess any effect of this variable on the microstructure and mechanical properties of laser-powder bed fusion manufactured parts. The results revealed the importance of the build location and showed that there is correlation between the location parameter and part properties as qualitative and quantitative properties of printed parts varied between the selected extremity locations. The findings highlight the importance of considering the location of the part being printed on the build platform and how the location may need to be fixed for multiple builds in order to achieve acceptable repeatability.
