Loading...
Search for:
reliability-analysis
0.008 seconds
Total 193 records
Component damage models for detailed seismic risk analysis using structural reliability methods
, Article Structural Safety ; Volume 76 , 2019 , Pages 108-122 ; 01674730 (ISSN) ; Mahsuli, M ; Sharif University of Technology
Elsevier B.V
2019
Abstract
A probabilistic approach to modeling the seismic damage incurred by structural and nonstructural components is developed in this study. The resulting models are intended for use in detailed risk analysis of structures through structural reliability methods. The proposed modeling approach employs Bayesian linear regression to characterize the epistemic uncertainty in the model. In this approach, regressors are selected and constructed based on the mechanics of damage. In turn, the probability distributions of the model parameters and the model error are quantified by Bayesian linear regression using real-life data from laboratory experiments and/or post-earthquake inspections of damaged...
Simultaneous management of peak-power and reliability in heterogeneous multicore embedded systems
, Article IEEE Transactions on Parallel and Distributed Systems ; Volume 31, Issue 3 , 2020 , Pages 623-633 ; Saber Latibari, J ; Pasandideh, M ; Ejlali, A ; Sharif University of Technology
IEEE Computer Society
2020
Abstract
Analysis of reliability, power, and performance at hardware and software levels due to heterogeneity is a crucial requirement for heterogeneous multicore embedded systems. Escalating power densities have led to thermal issues for heterogeneous multicore embedded systems. This paper proposes a peak-power-aware reliability management scheme to meet power constraints through distributing power density on the whole chip such that reliability targets are satisfied. In this paper, we consider peak power consumption as a system-level power constraint to prevent system failure. To balance the power consumption, we also employ a Dynamic Frequency Scaling (DFS) method to further reduce peak power...
Extended reliability model of a unified power flow controller
, Article IET Generation, Transmission and Distribution ; Volume 1, Issue 6 , 2007 , Pages 896-903 ; 17518687 (ISSN) ; Fotuhi Firuzabad, M ; Billinton, R ; Sharif University of Technology
2007
Abstract
One of the most important aspects in evaluating system reliability is to have a complete understanding of the engineering implications of the system and its associated components. The next step involved in reliability assessment is to appropriately model the system components to represent their characteristics and functions in the overall system. The unified power flow controller (UPFC) is an important flexible AC transmission system controller that can be used to enhance power system reliability. A complete reliability model of a UPFC is developed. A UPFC consists of three subsystems, and a reliability model associated with each subsystem is developed. The individual equivalent models are...
An adaptive secure channel coding scheme for data transmission over LEO satellite channels
, Article Scientia Iranica ; Volume 13, Issue 4 , 2006 , Pages 373-378 ; 10263098 (ISSN) ; Ahmadian, M ; Aref, M. R ; Sharif University of Technology
Sharif University of Technology
2006
Abstract
Both secure and error control coding are very extensive subjects, each with a variety of subdisciplines. A secure channel coding (joint encryption-channel coding) scheme provides both data secrecy and data reliability in one process to combat problems in an insecure and unreliable channel. In this paper, a joint encryption-channel coding scheme is developed, based on concatenated turbo codes for more efficient and secure transmission of LEO satellite data. Reliability and security are achieved by adapting the pseudo-random puncturing strategy with a change of distance between satellites and ground stations in the communication séance, an issue further burdened by reducing energy consumption...
Seismic reliability assessment of steel moment-resisting frames using Bayes estimators
, Article Proceedings of the Institution of Civil Engineers: Structures and Buildings ; 2021 ; 09650911 (ISSN) ; Hajirasouliha, I ; Filizadeh, R ; Sharif University of Technology
ICE Publishing
2021
Abstract
The aim of this study was to develop an efficient probability-based seismic fragility assessment method for steel moment-resisting frames (MRFs). In this method, Bayes estimators are used to improve the accuracy of the results based on new analyses or experimental observations. The efficiency of Bayes estimators in the updating process of fragility curves is demonstrated based on the results of incremental dynamic analysis of three-, five- and seven-storey steel MRFs under a set of 40 spectrum-compatible earthquake ground motions. The results indicate that the constant-hazard-level (engineering demand parameter based) fragility analysis approach leads to less than 6% error in the prediction...
Tolerating permanent faults with low-energy overhead in multicore mixed-criticality systems
, Article IEEE Transactions on Emerging Topics in Computing ; 2021 ; 21686750 (ISSN) ; Safari, S ; Hessabi, S ; Sharif University of Technology
IEEE Computer Society
2021
Abstract
Due to the battery-operated nature of embedded Mixed-Criticality Systems, simultaneous energy and reliability management is a cru-cial issue in designing these systems. We propose two comprehensive schemes, MC-2S and MC-4S, which tolerate permanent faults through exploiting the inherent redundancy of multicore systems for applying standby-sparing technique and maintaining the system re-liability against transient faults with low energy overhead. In these schemes, two copies of each high-criticality task are scheduled on different cores to guarantee their timeliness in case of permanent fault occurrence. In order to guarantee the quality of service of low-criticality tasks, in the MC-2S...
Reliability assessment of distribution system with the integration of photovoltaic and energy storage systems
, Article Sustainable Energy, Grids and Networks ; Volume 28 , 2021 ; 23524677 (ISSN) ; Esmaeili Nezhad, A ; Moeini Aghtaie, M ; Fotuhi Firuzabad, M ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
With the current focus on energy and the environment, efficient integration of renewable energies, especially solar energy into power systems, is becoming indispensable. Moreover, to fully capture solar potentials and to recognize the unique characteristics associated with solar energy in power systems reliability assessment, a profound investigation is needed. Accordingly, this paper attempts to establish a comprehensive analytical approach for modeling the reliability of a hybrid system (Photovoltaic (PV) system with Energy Storage System (ESS)). To this end, the output of the PV system is modeled by a multi-state model, and the ESS system is modeled as a two-state Markov model. Moreover,...
Introduction and evaluation of attachability for mobile IoT routing protocols with markov chain analysis
, Article IEEE Transactions on Network and Service Management ; Volume 19, Issue 3 , 2022 , Pages 3220-3238 ; 19324537 (ISSN) ; Taghizade, H ; Hosseini Monazzah, A. M ; Talaei Khoosani, K ; Sadeghi, P ; Mohammadsalehi, A ; Henkel, J ; Ejlali, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
Reliability of routing mechanisms in wireless networks is typically measured with Packet Delivery Ratio (PDR). Basically, PDR is reported with an optimistic assumption that the topology is fully constructed, and the nodes have started their packet transmission. This is despite the fact that prior to being able to transmit packets, nodes must first join the network, and then try to keep connected as much as possible. This is a key factor in the overall reliability provided by the routing protocols, especially in mobile IoT applications, where disconnections occur frequently. Nevertheless, there is a lack of appropriate metrics, which could evaluate the routing mechanisms from this...
Reliability assessment of the standby system with dependent components by bivariate exponential distributions
, Article Proceedings of the Institution of Mechanical Engineers, Part O: Journal of Risk and Reliability ; Volume 236, Issue 5 , 2022 , Pages 761-769 ; 1748006X (ISSN) ; Gholami, P ; Sharif University of Technology
SAGE Publications Ltd
2022
Abstract
In the reliability analysis of systems, all system components are often assumed independent and failure of any component does not depend on any other component. One of the reasons for doing so is that considerations of calculation and elegance typically pull in simplicity. But in real-world applications, there are very complex systems with lots of subsystems and a choice of multiple components that may interact with each other. Therefore, components of the system can be affected by the occurrence of a failure in any of the components. The purpose of this paper is to give an explicit formula for the computation of the reliability of a system with two parallel active components and one spare...
Reliability framework for characterizing heat wave and cold spell events
, Article Natural Hazards ; Volume 112, Issue 2 , 2022 , Pages 1503-1525 ; 0921030X (ISSN) ; Jahangir, M. S ; Sharif University of Technology
Springer Science and Business Media B.V
2022
Abstract
Extreme weather events such as heat waves and cold spells affect people’s lives. This study develops a probabilistic framework to evaluate heat waves and cold spells. As case studies, average daily temperatures of meteorological stations of the two cities (Tehran and Vancouver) from 1995 to 2016 are used to identify four main indicators including intensity, average intensity, duration, and the rate of the occurrence. In addition, probabilistic spatial analysis of the events is obtained through MODIS’s land surface temperature product. To include possible uncertainties, the predictive probability distributions of the intensity and duration are derived using a Bayesian scheme and Monte Carlo...
Evaluating the impact of operation scheduling methods on microgrid reliability using monte carlo simulation
, Article 30th International Conference on Electrical Engineering, ICEE 2022, 17 May 2022 through 19 May 2022 ; 2022 , Pages 670-675 ; 9781665480871 (ISBN) ; Jooshaki, M ; Abbaspour, A ; Fotuhi Firuzabad, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
This paper provides a general methodology for evaluating the reliability of microgrids embedding conventional and renewable energy sources (RESs), as well as energy storage systems (ESSs). The developed reliability assessment model is then leveraged to investigate the impact of different resource scheduling methods on the reliability. The technique applied in this article to assess microgrid reliability is based on the sequential Monte Carlo simulation. In this approach, the coincidence of faults is considered, aside from the annual generation pattern of RESs, i.e., wind and photovoltaic, and the network load profiles. For the sake of considering priority of the microgrid loads, two...
Service life prediction of worn contact wires under multiple failure modes
, Article Structure and Infrastructure Engineering ; 2022 ; 15732479 (ISSN) ; Mahmoodian, M ; Khaloo, A ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
Contact wires are critical components of railway overhead infrastructure which provide power for trains. This paper proposes an innovative method to determine the service life of worn contact wires under three failure modes: tension, fatigue, and attrition. The tensile stress, fatigue damage, and cross-section loss of contact wire have been modelled as stochastic processes following lognormal distribution. The first-passage probability method is then used to determine the time-dependent failure probability for contact wires under each failure mode. The service life of the contact wire is determined through system reliability analysis. This method has then been applied to a case study to...
Probabilistic safety assessment of a UF 6 production process
, Article Advances in Safety, Reliability and Risk Management - Proceedings of the European Safety and Reliability Conference, ESREL 2011 ; 2012 , Pages 1384-1389 ; 9780415683791 (ISBN) ; Sharif University of Technology
2012
Abstract
Application of Probabilistic Safety Assessment (PSA) to a Uranium hexafluoride (UF 6) production process is presented in this paper. The process is constituted from three main units: UF 4 conversion to UF 6, condensation of produced UF 6 gas and tail gas treatment. Radioactive gas is present in all parts of the process and occurrence of high pressure or high temperature in the process equipments may lead to radioactive release to workplace and environment. The work is mainly based on PSA experience in nuclear power plants. Accordingly for the process, eight group of Initiating Events (IE) that lead to UF 6 gas release have been identified using HAZOP study. For each IE, based on related...
A new stochastic oil spill risk assessment model for Persian Gulf: Development, application and evaluation
, Article Marine Pollution Bulletin ; Volume 145 , 2019 , Pages 357-369 ; 0025326X (ISSN) ; Raie, M ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Persian Gulf is a semi-enclosed highly saline reverse estuary that is exposed to the risk of oil spills in offshore oil and gas activities. In the early 2000s, a specific version of NOAA's Trajectory Analysis Planner (TAP II) was developed for Persian Gulf to assist regional organizations in preparing oil spill contingency plans. In this research, a new stochastic model is developed to cover the limitations of TAP II. The new model is based on an advanced trajectory model, which is now linked with high resolution spatiotemporal data of the wind and sea current. In a case study, the developed model is compared with TAP II, and evaluated by multiple tests designed for analysis of uncertainty,...
Application of Endurance Time Method in Optimum Seismic Design of Structures Based on Life Cycle Cost
, Ph.D. Dissertation Sharif University of Technology ; Esmaeil Pourestekanchi, Homayun (Supervisor)
Abstract
In recent decades, large economic losses and social impacts following earthquakes and hurricanes have revealed the need for improved design criteria intended to reduce consequences including economic impacts to an acceptable level along with life protection. So, it is tried to express the expected performance of structures as financial and social criteria. Any assessment on earthquake consequences requires estimations of structural responses to seismic excitations. Endurance Time (ET) method as a dynamic procedure requiring reasonably reduced computational effort compared to other common time-history based procedures, is used to estimate the response of the structure in all levels of hazard...
Seismic Reliability and Global Sensitivity Analysis of Concrete Gravity Dams
, M.Sc. Thesis Sharif University of Technology ; Ghaemian, Mohsen (Supervisor) ; Toufigh, Vahab (Supervisor)
Abstract
This research investigated the seismic performance of gravity dam in the reliability and sensitivity analysis framework under earthquake loading. The performance criteria were defined using crest displacement and tensile stress. The uncertainty due to the material properties of the dam was considered for the reliability approach, in addition to the different ground motion intensity levels for parametric analysis. The exceedance probability of the limit-state functions was computed for varying threshold values through Mean-Value Second-Moment, First-Order Reliability Method and improved Latin Hypercube sampling. Approximation methods were applied along with the sampling method for considering...
Design of Fillet Welds in Plastic State
, M.Sc. Thesis Sharif University of Technology ; Maleki, Shervin (Supervisor)
Abstract
Fillet welds are widely used in steel construction due to their high strength and economy. In the joints used in construction, eccentricity loads in complex weld stress. The current research involves 72 bending specimens and 16 torsion specimens being modeled to study different design code relationships regarding the plastic properties of welds. In line with an even comprehensive study, the previous experimental programs in this field have been added to the modeling results.Reliability analysis has been applied to examine code relationships more precisely. The analysis involved examination of various uncertainties which showed that applying elastic methods proves more conservative than other...
The Durability of Geopolymer Concrete Confined with Fiber Reinforced Polymer Materials
, M.Sc. Thesis Sharif University of Technology ; Toufigh, Vahab (Supervisor)
Abstract
Material durability is quite critical in corrosive environments. In this study, two hundred and seventy geopolymer concrete specimens with different mix designs were prepared and then wrapped with two different fiber reinforced polymer (FRP) materials. For 12960 hrs (eighteen months), the specimens were exposed to four different pHs (2.5, 7, 7.25, 12.5). The reliability and SEM analysis were performed after modeling the compressive strength over time. Based on the results, the reduction of the compressive strength was up to 22% in an acidic environment. The compressive strength of the specimens was increased up to 11 percent after alkaline solution exposure. The ductility of all specimens...
Reliability-Based Multidisciplinary Design Optimization Under Uncertainty for Reusable Flexible Launch Vehicle Using Genetic Algorithm
, M.Sc. Thesis Sharif University of Technology ; Fathi Jegarkandi, Mohsen (Supervisor)
Abstract
In this research, a Reusable Flexible Launch Vehicle (RFLV) design problem is presented by Multi-Disciplinary Design Optimization (MDO) approach in primary design phase. Trajectory, structure, aerodynamic, aeroelasticity and thermal protection system are considered as involved disciplines in design problem. The study purpose will be to obtain an optimal trajectory which meets all the control and structure limitation while the estimating body skin and thermal protection thicknesses base on structural evaluating in re-entry trajectory is in process. The flexible launch vehicle body is considered as a free-free Bernoulli-Euler beam and D’alembert’s principle addresses inertia force in static...
Impact of WAMS malfunction on power system reliability assessment
, Article IEEE Transactions on Smart Grid ; Vol. 3, issue. 3 , 2012 , p. 1302-1309 ; ISSN: 19493053 ; Fotuhi-Firuzabad, M ; Shahidehpour, M ; Safdarian, A ; Sharif University of Technology
Abstract
Monitoring/control infrastructures are often assumed to be fully reliable in power system reliability studies. However, recent investigations on blackouts have revealed the crucial impacts of monitoring/control system malfunctions. This paper addresses the impact of situational awareness and controllability on power system reliability assessment. A methodology is proposed to simulate a situation in which a limitation of either or both monitoring and control functions could spread the consequence of power system events throughout the grid. It is assumed that the monitoring/control infrastructure is based on a wide-area measurement system (WAMS). While the proposed methodology is applicable to...