Browsing by Subject "Safety"
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Item Open Access The analysis and design of urban near-home environments according to psycho-social needs and behavior of human beings(1996) Serpil, BurçakIn this study, the design of urban near-home environments is examined considering the social and psychological needs of human beings as well as human spatial behavior. After an introduction to the concepts such as environment, near-home environments, human-environment interaction, human basic needs and human spatial behavior; the basic psycho-social needs of human beings are classified as safety, identity, social contact and privacy. These needs are analysed in relation to the design of urban near-home environments. Within this framework, behavioral concepts like territorility, personalisation, crowding are also considered. Furthermore, a research is conducted in Ankara, in two middle-density apartments with near-home environment of different design features. This research explores and compares the influences of these environments--which differ within themselves in terms of design characteristics--on the satisfaction of residents' psycho-social needs. Design suggestions are proposed at the end of the analysis of the findings of the research.Item Open Access Analysis of design parameters in safety-critical computers(IEEE Computer Society, 2018) Ahangari, H.; Atik, F.; Ozkok, Y. I.; Yildirim, A.; Ata, S. O.; Ozturk, O.Nowadays, safety-critical computers are extensively used in many civil domains like transportation including railways, avionics, and automotive. In evaluating these safety critical systems, previous studies considered different metrics, but some of safety design parameters like failure diagnostic coverage (C) or common cause failure (CCF) ratio have not been seriously taken into account. Moreover, in some cases safety has not been compared with standard safety integrity levels (IEC-61508: SIL1-SIL4) or even have not met them. Most often, it is not very clear that which part of the system is the Achilles heel and how design can be improved to reach standard safety levels. Motivated by such design ambiguities, we aim to study the effect of various design parameters on safety in some prevalent safety configurations, namely, 1oo2 and 2oo3, where 1oo1 is also used as a reference. By employing Markov modeling, we analyzed the sensitivity of safety to important parameters including: failure rate of processor, failure diagnostic coverage, CCF ratio, test and repair rates. This study aims to provide a deeper understanding on the influence of variation in design parameters over safety. Consequently, to meet appropriate safety integrity level, instead of improving some parts of a system blindly, it will be possible to make an informed decision on more relevant parameters. IEEEItem Open Access Analysis of design parameters in SIL-4 safety-critical computer(IEEE, 2017-01) Ahangari, Hamzeh; Özkök, Y. I.; Yıldırım, A.; Say, F.; Atik, Funda; Öztürk, ÖzcanNowadays, Safety-critical computers are extensively used in may civil domains like transportation including railways, avionics and automotive. We noticed that in design of some previous works, some critical safety design parameters like failure diagnostic coverage (DC) or common cause failure (CCF) ratio have not been seriously taken into account. Moreover, in some cases safety has not been compared with standard safety levels (IEC-61508 SIL1-SIL4) or even have not met them. Most often, it is not very clear that which part of the system is the Achilles' heel and how design can be improved to reach standard safety levels. Motivated by such design ambiguities, we aim to study the effect of various design parameters on safety in some prevalent safety configurations: 1oo2 and 2oo3. 1oo1 is also used as a reference. By employing Markov modeling, sensitivity of safety to each of the following critical design parameters is analyzed: failure rate of processing element, failure diagnostics coverage, common cause failures and repair rates. This study gives a deeper sense regarding influence of variation in design parameters over safety. Consequently, to meet appropriate safety integrity level, instead of improving some system parts blindly, it will be possible to make an informed decision on more relevant parameters. © 2017 IEEE.Item Embargo Architecture for safety–critical transportation systems(Elsevier B.V., 2023-03-15) Ahangari, Hamzeh; Özkök, Yusuf İbrahim; Yıldırım, Asil; Say, Fatih; Atık, Funda; Ozturk, OzcanIn many industrial systems, including transportation, fault tolerance is a key requirement. Usually, faulttolerance is achieved by redundancy, where replication of critical components is used. In the case oftransportation computing systems, this redundancy starts with the processing element. In this paper, we useMarkov models to assess the level of safety with different redundancy techniques used in the literature. Morespecifically, we give implementation details for various architecture options and evaluate one out of two (1oo2)and two out of three (2oo3) implementations. We observe that both 1oo2 and 2oo3 can reduce the averageprobability of failure per hour (PFH) down to 10−7 which provides Level-3 (SIL3) safety according to thestandards.Item Open Access Assessment of hazardous material risks for rail yard safety(Elsevier, 2007) Glickman, T. S.; Erkut, E.This paper illustrates the application of quantitative risk assessment in a rail yard where tank cars of hazardous materials are received and stored. The assessment was conducted in response to community concerns about the safety of a proposed yard expansion. Six different chemicals are involved. For each one, the average monthly volume and the hazard of most concern are specified. We use an event tree populated with empirical data to compute the probability of a major spill in each case and we estimate the corresponding critical impact distances using available modeling tools. We find that for some of the chemicals, the relative increases in risk are appreciable, but that in all cases, the absolute levels of risk remain low. Then we identify some ways in which such an analysis can be extended and discuss the potential difficulties associated with these extensions.Item Open Access Aviation risk perception: a comparison between experts and novices(Wiley-Blackwell Publishing, 2004) Thomson, M. E.; Önkal D.; Avcioǧlu, A.; Goodwin, P.This article describes an exploratory investigation of the risk perceptions of experts and novices in relation to helicopter operations, under conditions where the participants are matched on various characteristics previously found to affect perceptions, such as demographic, gender, and background factors. The study reports considerable evidence of perceptual differences between the two participant groups (i.e., expert pilots and candidate pilots). We find that the experts' perceptions of relative risks are more veridical, in terms of their higher correlation with the true relative frequencies. A significant positive correlation between the flight hours and the contextual risk-taking tendency is also shown, leading the experienced pilots' choices toward risky alternatives in scenarios - a potential result of their overconfidence based on superior task performance. Possible explanations are offered for the findings and potential avenues for future research are identified.Item Open Access Computer vision based forest fire detection(IEEE, 2008) Töreyin, B. Uğur; Çetin, A. EnisLookout posts are commonly installed in the forests all around Turkey and the world. Most of these posts have electricity. Surveillance cameras can be placed on to these surveillance towers to detect possible forest fires. Currently, average fire detection time is 5 minutes in manned lookout towers. The aim ofthe proposed computer vision based method is to reduce the average fire detection rate. The detection method is based on the wavelet based analysis of the background images at various update rates.Item Open Access Extending the importance–performance analysis (IPA) approach to Turkish elderly people’s self-rated home accessibility(Springer, 2019) Afacan, YaseminDesigners are still struggling to make good and fair home designs for elderly people. Although there are a lot of studies on accessibility in homes, there are few methodologies to rate the importance of accessible home attributes, or address the relationships between the most important and most satisfactory attributes (in terms of creating a good fit between the elderly and their homes). This study suggests using the importance–performance analysis (IPA) approach to set accessibility priorities and identify the critical performance factors that determine the elderly’s satisfaction with accessible homes. A self-assessment questionnaire instrument was developed based on housing accessibility literature and conducted with 342 Turkish elderly people chosen through stratified sampling among neighborhood clusters in Ankara, Turkey. The descriptive results and factor analysis of the study are significant in that they indicate significant differences among dwelling types. There were differences in importance and performance priority levels of home accessibility factors associated with each dwelling type. Moreover, the study found that safety and ease of use are the key indicators of home accessibility. According to the results, the IPA could be an effective tool to overcome the messy character of evaluating home accessibility for the elderly. By extending the accessibility attributes with the IPA analysis, it is possible to identify specific accessibility attributes, establish highest and lower priorities for intervention and decide which attributes should be maintained and/or ignored. Thus, this study contributes to the literature on aging by being the first study to explore the applicability of the IPA technique while eliciting elderly people’s accessibility requirements for healthy aging.Item Open Access Hierarchical reasoning game theory based approach for evaluation and testing of autonomous vehicle control systems(IEEE, 2016) Li, N.; Oyler, D.; Zhang, M.; Yıldız, Yıldıray; Girard, A.; Kolmanovsky, İ.A hierarchical game theoretic decision making framework is exploited to model driver decisions and interactions in traffic. In this paper, we apply this framework to develop a simulator to evaluate various existing autonomous driving algorithms. Specifically, two algorithms, based on Stackelberg policies and decision trees, are quantitatively compared in a traffic scenario where all the human-driven vehicles are modeled using the presented game theoretic approach.Item Open Access Modeling of electrodes and implantable pulse generator cases for the analysis of implant tip heating under MR imaging(Wiley-Blackwell Publishing, Inc., 2015) Acikel, V.; Uslubas, A.; Atalar, ErginPurpose: The authors purpose is to model the case of an implantable pulse generator (IPG) and the electrode of an active implantable medical device using lumped circuit elements in order to analyze their effect on radio frequency induced tissue heating problem during a magnetic resonance imaging (MRI) examination. Methods: In this study, IPG case and electrode are modeled with a voltage source and impedance. Values of these parameters are found using the modified transmission line method (MoTLiM) and the method of moments (MoM) simulations. Once the parameter values of an electrode/IPG case model are determined, they can be connected to any lead, and tip heating can be analyzed. To validate these models, both MoM simulations and MR experiments were used. The induced currents on the leads with the IPG case or electrode connections were solved using the proposed models and the MoTLiM. These results were compared with the MoM simulations. In addition, an electrode was connected to a lead via an inductor. The dissipated power on the electrode was calculated using the MoTLiM by changing the inductance and the results were compared with the specific absorption rate results that were obtained using MoM. Then, MRI experiments were conducted to test the IPG case and the electrode models. To test the IPG case, a bare lead was connected to the case and placed inside a uniform phantom. During a MRI scan, the temperature rise at the lead was measured by changing the lead length. The power at the lead tip for the same scenario was also calculated using the IPG case model and MoTLiM. Then, an electrode was connected to a lead via an inductor and placed inside a uniform phantom. During a MRI scan, the temperature rise at the electrode was measured by changing the inductance and compared with the dissipated power on the electrode resistance. Results: The induced currents on leads with the IPG case or electrode connection were solved for using the combination of the MoTLiM and the proposed lumped circuit models. These results were compared with those from the MoM simulations. The mean square error was less than 9%. During the MRI experiments, when the IPG case was introduced, the resonance lengths were calculated to have an error less than 13%. Also the change in tip temperature rise at resonance lengths was predicted with less than 4% error. For the electrode experiments, the value of the matching impedance was predicted with an error less than 1%. Conclusions: Electrical models for the IPG case and electrode are suggested, and the method is proposed to determine the parameter values. The concept of matching of the electrode to the lead is clarified using the defined electrode impedance and the lead Thevenin impedance. The effect of the IPG case and electrode on tip heating can be predicted using the proposed theory. With these models, understanding the tissue heating due to the implants becomes easier. Also, these models are beneficial for implant safety testers and designers. Using these models, worst case conditions can be determined and the corresponding implant test experiments can be planned.Item Open Access Moral mechanisms(Kluwer Academic Publishers, 2014) Davenport, D.As highly intelligent autonomous robots are gradually introduced into the home and workplace, ensuring public safety becomes extremely important. Given that such machines will learn from interactions with their environment, standard safety engineering methodologies may not be applicable. Instead, we need to ensure that the machines themselves know right from wrong; we need moral mechanisms. Morality, however, has traditionally been considered a defining characteristic, indeed the sole realm of human beings; that which separates us from animals. But if only humans can be moral, can we build safe robots? If computationalism - roughly the thesis that cognition, including human cognition, is fundamentally computational - is correct, then morality cannot be restricted to human beings (since equivalent cognitive systems can be implemented in any medium). On the other hand, perhaps there is something special about our biological makeup that gives rise to morality, and so computationalism is effectively falsified. This paper examines these issues by looking at the nature of morals and the influence of biology. It concludes that moral behaviour is concerned solely with social well-being, independent of the nature of the individual agents that comprise the group. While our biological makeup is the root of our concept of morals and clearly affects human moral reasoning, there is no basis for believing that it will restrict the development of artificial moral agents. The consequences of such sophisticated artificial mechanisms living alongside natural human ones are also explored.Item Open Access Patient’s body composition can significantly affect RF power deposition in the tissue around DBS implants: ramifications for lead management strategies and MRI field-shaping techniques(Institute of Physics Publishing Ltd., 2021-01-13) Bhusal, B.; Keil, B.; Rosenow, J.; Kazemivalipour, Ehsan; Golestanirad, L.Patients with active implants such as deep brain stimulation (DBS) devices have limited access to magnetic resonance imaging (MRI) due to risks associated with RF heating of implants in MRI environment. With an aging population and increased prevalence of neurodegenerative disease, the indication for MRI exams in patients with such implants increases as well. In response to this growing need, many groups have investigated strategies to mitigate RF heating of DBS implants during MRI. These efforts fall into two main categories: MRI field-shaping methods, where the electric field of the MRI RF coil is modified to reduce the interaction with implanted leads, and lead management techniques where surgical modifications in the trajectory reduces the coupling with RF fields. Studies that characterize these techniques, however, have relied either on simulations with homogenous body models, or experiments with box-shaped single-material phantoms. It is well established, however, that the shape and heterogeneity of human body affects the distribution of RF electric fields, which by proxy, alters the heating of an implant inside the body. In this contribution, we applied numerical simulations and phantom experiments to examine the degree to which variations in patient's body composition affects RF power deposition. We then assessed effectiveness of RF-heating mitigation strategies under variant patient body compositions. Our results demonstrated that patient's body composition substantially alters RF power deposition in the tissue around implanted leads. However, both techniques based on MRI field-shaping and DBS lead management performed well under variant body types.Item Open Access Universal product design involving elderly users: a participatory design model(Elsevier, 2004-07) Demirbilek, O.; Demirkan, H.Recent studies have shown that people prefer to age in their familiar environments, thus guiding designers to provide a safe and functionally appropriate environment for ageing people, regardless of their physical conditions or limitations. Therefore, a participatory design model is proposed where human beings can improve their quality of life by promoting independence, as well as safety, useability and attractiveness of the residence. Brainstorming, scenario building, unstructured interviews, sketching and videotaping are used as techniques in the participatory design sessions. Quality deployment matrices are employed to find the relationships between the elderly user's requirements and design specifications. A case study was devised to apply and test the conceptual model phase of the proposed model.