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Yayın Generic BER analysis of VLC channels impaired by 3D user-mobility and imperfect CSI(Institute of Electrical and Electronics Engineers Inc., 2021-07) Reddy Sekhar, K.; Miramirkhani, Farshad; Mitra, Rangeet; Turlapaty, Anish ChandVisible light communications (VLC) has emerged as a high-speed, low-cost, and green supplement for the existing radio frequency (RF) based infrastructures. However, the performance of VLC based systems is found to degrade significantly due to detrimental outages caused by non-negligible variations in the VLC channel-gain, that are jointly induced by radial user-mobility and random photodetector-orientation (together designated as 3D mobility in this letter). In addition to the 3D user-mobility mentioned above, the performance of VLC based systems is further limited by imperfect channel-state information (CSI). Such degradations in the VLC-link caused by the aforementioned factors necessitate the quantification of performance-metrics for further benchmarking/receiver-design. In this work, an analytical expression for bit-error rate (BER) is derived for a single LED indoor VLC system considering the radial user-mobility, random receiver orientation, and imperfect CSI altogether. Further, the derived BER expressions are validated using computer-simulations using typical VLC channel models from the literature. A close agreement between the analytical and the simulated BER is observed, which verifies the accuracy of the presented analysis.Yayın Improvement of seismic performance of precast frames with cladding panels fastened by energy dissipative steel cushions(Springer, 2021-09) Özkaynak, Hasan; Khajehdehi, Arastoo; Yüksel, Ercan; Karadoğan, Hüseyin FarukPrecast reinforced concrete panels are commonly used as wall claddings in precast buildings. The cladding panels are generally evaluated as non-structural members and are joined to structural systems via mechanical, welding, and bolted dry connections. Several failures were observed in the last seismic events in Southern Europe, which demonstrate the deficiencies of the cladding connections in terms of strength and ductility. A comprehensive research activity named SAFECLADDING was conducted in Europe to provide knowledge for proper seismic design of precast structures with cladding panels. In this context, energy dissipative steel cushions were developed and evaluated through the extensive experimental and numerical studies. Steel cushions can provide robust interaction of the structural system with the cladding panels. This paper numerically evaluates the effects of cladding panels with steel cushions on the global seismic behaviour of the buildings. An existing representative industrial building is selected to perform intensive nonlinear dynamic analyses. Analyses performed on the bare and hybrid systems showed that the hybrid system has high performance in terms of story drifts, internal forces, and deformations with respect to the bare system. The overall drifts in longitudinal and transversal directions of the building are reduced by about 78 and 54%, respectively. Average residual drifts of cladding panels and steel cushions indicated that the applied steel cushion placement scheme has a promising re-centring capability during seismic action.Yayın Sustainability via extended warranty contracts: design for a consumer electronics retailer(MDPI, 2024-01) Aksezer, Sezgin ÇağlarWarranty is one of the most important attributes of any product, from both manufacturer and consumer points of view. Although the retailers connect manufacturers to customers by selling goods, traditionally, they have isolated themselves from warranty-related matters such as customer complaints and maintenance costs. However, recent trends in consumer behavior toward extended warranty contracts have changed this approach. While retailers have started to generate considerable revenue from the sale of these contracts, sustainability is also achieved by longer product life cycles. This study analyzed the failure behavior of different classes of cell phone products and their related costs through a chain of consumer electronics retailer operating in Türkiye. To compete on pricing and customer service, a novel policy was designed for the retailer to honor the contracts in house rather than underwriting to a third party insurer as the industry standard. The maintenance records of 328 previous failures were analyzed to plot a failure model. Failure mode and effects analysis was carried out to identify failure classes and the respective costs for extended warranty design for cell phones. The expected warranty costs for coverage of the third, fourth, and fifth years of operation were determined. The results show that the retailer may achieve the same level of profit by increasing customer satisfaction along with the sustainability of the product through repair actions.Yayın Assessment of speech intelligibility during different teaching activities in classrooms with and without acoustic treatment(Elsevier Ltd, 2023-05) Şaher, Konca; Bulunuz, Mızrap; Kelmendi, Jonida; Nas, SezinThere is limited data for assessing speech intelligibility in real classrooms with realistic occupied noise levels and teacher's and students’ speech levels for different teaching activities in Turkish secondary school classrooms. This study investigates the effect of reverberation time (RT), occupied noise levels and signal-to-noise ratio (SNR) on speech transmission index (STI) in real classrooms for instruction and group work. Noise levels were measured and STI values were calculated in two secondary school classrooms with RT of 0.88 s and 2.73 s. During instruction situation, calculated mean STI values were 0.63 (classroom with acoustic treatment) and 0.29 (classroom without acoustic treatment) for normal voice effort and 0.65 (classroom with acoustic treatment) and 0.39 (classroom without acoustic treatment) for raised voice effort. During group work, STI values ranged from 0.50 to 0.74 in classroom with acoustic treatment and from 0.01 to 0.34 in classroom without any acoustic treatment. SNR of 15 dBA is only approached in classroom with acoustic treatment during instruction situation. The effect of increasing SNR on STI is prominent in the classroom without acoustic treatment which already has low SNR values. The present results show that the classroom with acoustic treatment will have good speech intelligibility for instruction with normal vocal effort and for group work with raised vocal effort at 3 m distance. However, the classroom with no acoustic treatment will have STI values in the range of bad and poor intelligibility. The present results confirm the impact of SNR and RT on speech intelligibility and shows that RT value of minimum 0.8 s is optimal to have good speech intelligibility in a secondary school classroom of approximately 250 m3 with a capacity of 18 students.Yayın How do local actors interpret, enact and contest policy? An analysis of local government responses to meeting the needs of Syrian refugees in Turkey(Routledge, 2022-05-04) Lowndes, Vivien; Karakaya Polat, RabiaAlthough 98% of Turkey’s 3.6 million Syrian refugees live outside camps, municipalities lack formal authority to initiate policies, while receiving no government funding for refugees. Drawing on interpretive policy analysis (IPA), the article unpacks the empirical puzzle of how formally weak local governments respond to refugee needs. IPA expects policy to be constituted through diverse sets of local meanings. Case studies in three districts in Istanbul revealed distinctive local narratives, some of which consolidated the national agenda of ‘hospitality’ while others focused on equal rights and integration. Municipal narratives reflected particular local contexts, selectively mobilizing deeper governing traditions. Local interpretations were enacted in specific approaches to refugee service delivery. Working with local NGOs, municipalities accessed international funds, despite national government’s vociferous critique of EU refugee policy. Even in an increasingly authoritarian setting, refugee policy was being constituted through multiple and contingent processes of local government interpretation.Yayın Cost-effective fault diagnosis of a multi-component dynamic system under corrective maintenance(Elsevier Ltd, 2021-04) Özgür Ünlüakın, Demet; Türkali, Busenur; Aksezer, Sezgin ÇağlarMaintenance planning and execution are challenging tasks for every system with complex structure. Interdependent nature of the components that builds up the system may have significant effect on system integrity. While preventive maintenance actions can be carried out in a more planned fashion, corrective actions are more time sensitive as they directly affect the availability of the system. This study proposes a cost-effective dynamic Bayesian network modeling scheme to be used in the planning of corrective maintenance actions on systems having hidden components which have stochastic and structural dependencies. In such context, the regenerative air heater system which is a key element of a power plant is taken into consideration. The proposed maintenance framework offers several methods, each aiming to balance the cost with the probability effect using a normalization procedure. The methodologies are extensively simulated for sensitivity analysis under various downtime cost values. Fault effect methods with worst state probability efficiency measures give the least total cost for all downtime cost values and their distinction becomes significant as this value increases. Further statistical analysis concludes that considerable gains on maintenance costs can be achieved by the proposed approach.Yayın Maintenance policy analysis of the regenerative air heater system using factored POMDPs(Elsevier Ltd, 2022-03) Kıvanç, İpek; Özgür Ünlüakın, Demet; Bilgiç, TanerMaintenance optimization of multi-component systems is a difficult problem. Partially Observable Markov Decision Processes (POMDPs) are powerful tools for such problems under uncertainty in stochastic environments. In this study, the main POMDP solution approaches and solvers are surveyed. Then, based on experimental models with different complexities in the size of the system space, selected POMDP solvers using different representation patterns for modeling and different procedures for updating the value function while solving are compared. Furthermore, to show that factored representations are advantageous in modeling and solving the maintenance problem of multi-component systems where there exist also stochastic dependencies among the components, the maintenance problem of the one-line regenerative air heater system available in thermal power plants is modeled and solved with factored POMDPs. In-depth sensitivity analyses are performed on the obtained policy. The results show that factored POMDPs enable compact modeling, efficient policy generation and practical policy analysis for the tackled problem. Furthermore, they also motivate the use of factored POMDPs in the generation and analysis of maintenance policies for similar multi-component systems.Yayın Inductor saturation compensation in three-phase three-wire voltage-source converters via inverse system dynamics(Institute of Electrical and Electronics Engineers Inc., 2022-05-01) Özkan, Ziya; Hava, Ahmet MasumIn three-phase three-wire (3P3W) voltage-source converter (VSC) systems, utilization of filter inductors with deep saturation characteristics is often advantageous due to the improved size, cost, and efficiency. However, with the use of conventional synchronous frame current control methods, the inductor saturation results in significant dynamic performance loss and poor steady-state current waveform quality. This article proposes an inverse dynamic model-based compensation (IDMBC) method to overcome these performance issues. For this purpose, two-phase exact modeling of the 3P3W VSC control system is obtained. Based on the modeling, the inverse system dynamic model of the nonlinear system is obtained and employed such that the nonlinear plant is converted to a virtual linear inductor system for linear current regulators to perform satisfactorily. Further, to control phase currents in the synchronous frame, a two-phase coordinate transformation is proposed. The IDMBC method is tested via dynamic command response and waveform quality simulations and experiments that employ saturable inductors reaching down from full inductance at zero current to 1/9th inductance at full current. The results obtained demonstrate the suitability of the method for 3P3W VSCs employing saturable inductors.Yayın People respond with different moral emotions to violations in different relational models: a cross-cultural comparison(American Psychological Association, 2021-06) Sunar, Diane; Cesur, Sevim; Piyale, Zeynep Ecem; Tepe, Beyza; Biten, Ali Furkan; Hill, Charles T.; Koç, YasinConsonant with a functional view of moral emotions, we argue that morality is best analyzed within relationships rather than in individuals, and use Fiske's (1992) theory of relational models (RMs: communal sharing [CS], authority ranking [AR]. equality matching [EM], and market pricing [MP]) to predict that violations in different RMs will arouse different intensities of other-blaming emotions (anger, contempt and disgust) in both observers and victims, together with different intensities of self-blaming emotions (shame and guilt) in perpetrators, and to predict that these patterns of emotion will show similarity across both individuals and cultures. Three studies, using vignettes portraying moral violations in all RMs in different experimental designs. supported these expectations. while also producing some unexpected results. The intensity of shame and guilt varied markedly across RMs, but with little difference between the two emotions. The intensity of all 3 other-blaming emotions also varied across RMs. Anger was the most intense emotional response to violation in all RMs, whereas disgust and contempt were stronger in CS than in other RMs. Disgust and shame were linked more strongly in CS than in other RMs, and anger and guilt were more strongly linked than other emotion pairs in EM. Moral emotions in RMs involving hierarchy (AR and MP) differed widely depending on the perpetrator's dominant or subordinate status. Both Turkish (TR) and English-speaking (EN) samples showed similar patterns of all moral emotions across RMs. Understanding the functions of moral emotions in relationships using relational models can help to clarify multiple aspects of moral psychology.Yayın Image recovery of inaccessible rough surfaces profiles having impedance boundary condition(IEEE, 2022) Sefer, Ahmet; Yapar, AliThis letter addresses a reconstruction algorithm of locally rough inaccessible surface profiles via the knowledge of the scattered field data under the consideration of the impedance boundary condition (IBC). To this aim, first, the synthetic scattered field data are obtained through the solution of the conventional surface integral equation (SIE) written on the rough surface. Then, the same SIE together with the data equation is solved iteratively via Newton's method to obtain the image of the rough surface profile. In the numerical implementation, the nonlinear ill-posed inverse problem is linearized in an iterative fashion via the Newton method and regularized by Tikhonov in the least-squares sense. The feasibility of the algorithm is provided via numerical examples, which shows that the method is effective and promising.
