فهرس المقالات Reliability analysis

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  1 - Time-Dependent Reliability Analysis of Mechanical Structures using an Analytical Approach
  Mohammad Reza Moarefzadeh
  Time-dependent reliability analysis of mechanical structures is concerned by the use of an outcrossing approach. In this approach the so-called outcrossing rate plays a critical role and thus it is important to estimate it as straight ward as possible. Despite the avail أکثر

  Time-dependent reliability analysis of mechanical structures is concerned by the use of an outcrossing approach. In this approach the so-called outcrossing rate plays a critical role and thus it is important to estimate it as straight ward as possible. Despite the availability of a variety of methods to estimate this rate in the literature, still more general and at the same time less sophisticated approaches are desired. In this paper, an analytical method is proposed to evaluate the required outcrossing rate in which the basics of "Parallel System Reliability Formulation" in the framework of directional simulation are used. To indicate the accuracy and efficiency of the method, it is applied to carry out the reliability analysis of a hydrokinetic turbine blade. Since the random variables/processes involved in this analysis possess a set of extremely different variances (and thus make a so-called "non-proportional space); it is shown that the proposed method is also capable to satisfactorily employ a technique of directional importance sampling in order to prohibit massive computations, normally required in such spaces. The results of the analysis show that the proposed method could be successfully applied for the circumstances whose involving processes may be non-stationary and whose space of random variables/processes is extremely non-proportional. تفاصيل المقالة
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  2 - تحلیل حساسیت مبتنی بر قابلیت اطمینان سازه‌ها‌ی قاب خمشی فولادی تحت اثر برخورد وسیله‌ی نقلیه‌ی سنگین
  عباسعلی صادقی حمید کاظمی میثم ٌصمدی
  در چند دهه ی اخیر، با گسترش حوادث غیرطبیعی مانند آتش سوزی، انفجار و برخورد وسایل نقلیه، مطالعه ی رفتار سازه ها تحت اثر بارگذاری‌های نامتعارف مورد توجه پژوهشگران و مهندسین سازه قرار گرفته است. در این تحقیق، سازه ها ی قاب خمشی فولادی 2 و 5 طبقه تحت اثر ضربه ی ناشی از بر أکثر

  در چند دهه ی اخیر، با گسترش حوادث غیرطبیعی مانند آتش سوزی، انفجار و برخورد وسایل نقلیه، مطالعه ی رفتار سازه ها تحت اثر بارگذاری‌های نامتعارف مورد توجه پژوهشگران و مهندسین سازه قرار گرفته است. در این تحقیق، سازه ها ی قاب خمشی فولادی 2 و 5 طبقه تحت اثر ضربه ی ناشی از برخورد وسیله ی نقلیه ی سنگین، با در نظر گرفتن عدم قطعیت‌ در مصالح و بارهای اعمالی، به کمک نرم افزارOpenSees مدل‌سازی گردیده و تحلیل حساسیت مبتنی بر قابلیت اطمینان متغیرهای تصادفی مورد مطالعه در نرم افزارMATLAB انجام ‌شده است. سپس تأثیرهرکدام از متغیرها با استفاده از روش‌های شبیه سازی براساس توابع شرایط حدی مبتنی بر حداکثر دوران مجاز تیر دهانه ی آسیب دیده ی قاب ها بررسی گردیده است. نتایج این مطالعه نشان می دهد که در سازه های موردنظر، متغیرهای تصادفی جرم و سرعت وسیله ی نقلیه و مقاومت تسلیم مصالح، تأثیرگذارترین متغیرها در محاسبه ی احتمال خرابی بوده اند و روش شبیه‌سازی زیرمجموعه ای بر مبنای تکنیک متغیر کنترل (CSS) نسبت به روش مونت‌کارلو (MCS)، با تعداد نمونه ی کمتر و زمان اجرای کوتاه تر، احتمال خرابی را با خطای قابل قبولی تخمین زده است. همچنین نتایج این تحقیق نشان می دهد که با افزایش تعداد طبقات ساختمان، احتمال خرابی آن در اثر برخورد وسیله ی نقلیه افزایش می‌یابد به طوری که براساس نتایج این مطالعه، مقدار پارامتر دوران تیر دهانه ی آسیب دیده ی قاب 5 طبقه نسبت به 2 طبقه تحت توابع LSF1، LSF2 و LSF3 به ترتیب معادل 55، 18 و 33 درصد افزایش یافته است. تفاصيل المقالة
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  3 - Reliability analysis of repairable systems using system dynamics modeling and simulation
  M. Srinivasa Rao V. N. A. Naikan
  Repairable standby system’s study and analysis is an important topic in reliability. Analytical techniques become very complicated and unrealistic especially for modern complex systems. There have been attempts in the literature to evolve more realistic techni أکثر

  Repairable standby system’s study and analysis is an important topic in reliability. Analytical techniques become very complicated and unrealistic especially for modern complex systems. There have been attempts in the literature to evolve more realistic techniques using simulation approach for reliability analysis of systems. This paper proposes a hybrid approach called as Markov system dynamics (MSD) approach which combines the Markov approach with system dynamics simulation approach for reliability analysis and to study the dynamic behavior of systems. This approach will have the advantages of both Markov as well as system dynamics methodologies. The proposed framework is illustrated for a standby system with repair. The results of the simulation when compared with that obtained by traditional Markov analysis clearly validate the MSD approach as an alternative approach for reliability analysis. تفاصيل المقالة
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  4 - Reliability analysis of a robotic system using hybridized technique
  Naveen Kumar Komal Komal J. S. Lather
  In this manuscript, the reliability of a robotic system has been analyzed using the available data (containing vagueness, uncertainty, etc). Quantification of involved uncertainties is done through data fuzzification using triangular fuzzy numbers with known spreads as أکثر

  In this manuscript, the reliability of a robotic system has been analyzed using the available data (containing vagueness, uncertainty, etc). Quantification of involved uncertainties is done through data fuzzification using triangular fuzzy numbers with known spreads as suggested by system experts. With fuzzified data, if the existing fuzzy lambda–tau (FLT) technique is employed, then the computed reliability parameters have wide range of predictions. Therefore, decision-maker cannot suggest any specific and influential managerial strategy to prevent unexpected failures and consequently to improve complex system performance. To overcome this problem, the present study utilizes a hybridized technique. With this technique, fuzzy set theory is utilized to quantify uncertainties, fault tree is utilized for the system modeling, lambda–tau method is utilized to formulate mathematical expressions for failure/repair rates of the system, and genetic algorithm is utilized to solve established nonlinear programming problem. Different reliability parameters of a robotic system are computed and the results are compared with the existing technique. The components of the robotic system follow exponential distribution, i.e., constant. Sensitivity analysis is also performed and impact on system mean time between failures (MTBF) is addressed by varying other reliability parameters. Based on analysis some influential suggestions are given to improve the system performance. تفاصيل المقالة
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  5 - The Role of EFL Teachers’ Socio-affective Strategies in Learners’ Willingness to Communicate: Learners’ Perceptions
  Nahid Zarei مهناز سعیدی سعبده آهنگری
  10.30495/ttlt.2023.707371
  The present study set out to develop a willingness to communicate (WTC) questionnaire addressingteachers’ socio-affective strategies. It also aimed at exploring learners’ perceptions toward thesestrategies affecting their WTC. Participants of the study, who أکثر

  The present study set out to develop a willingness to communicate (WTC) questionnaire addressingteachers’ socio-affective strategies. It also aimed at exploring learners’ perceptions toward thesestrategies affecting their WTC. Participants of the study, who were selected by a non-probabilityconvenience sampling method, were 153 English as a foreign language learner in three popular EnglishInstitutes in Iran. A questionnaire including 45 items was designed by referring to a previouslyconducted focus group interview of Iranian EFL teachers and the review of the literature. Afterthe questionnaire was administered to and completed by the learners, an exploratory factor analysis(EFA) was performed. The analysis yielded 37 items and six factors: (a) creating a positive interaction(8 items), (b) teachers’ enthusiasm (6 items), (c) teachers’ fairness (5 items), (d) teachers’ presence (6items), (e) teachers’ immediacy (6 items), and (f) teaching skills and participation in group activities(6 items). The reliability measures were also examined and the results were satisfactory. The sixfactors were compared against each other and teachers’ enthusiasm and fairness were found to be themost important factor in promoting learners’ WTC. Implications for teacher trainers and teachers arediscussed and suggestions for further research are offered. تفاصيل المقالة