Sharif Digital Repository

Evaluation of the wind energy potential in different climates includes high level of uncertainties. To address the uncertainties, this study performs reliability analysis by defining a limit state function for the wind power density (WPD) to determine failure or success of the system in the probabilistic framework. The probability distributions of the variables including wind speed and air density simulated by the Weather Research and Forecasting (WRF) model with 2 km resolution are used in the limit state function to form a nondeterministic model in southwest of Iran. Given significant correlation between air density and wind speed in most of the pixels, Nataf transformation is applied to... 

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... 

The eccentric bracing system equipped with vertical links is capable of providing high levels of stiffness, strength and ductility, and therefore, can be efficiently used for seismic retrofit of existing structures. This study aims to investigate the seismic reliability of steel moment-resisting frames retrofitted by this system using a novel combined series–parallel system approach. The seismic response of 4, 8 and 12-storey steel moment-resisting frames (MRFs) are evaluated under a set of design basis earthquakes (DBE) before and after retrofitting intervention. Adopting an engineering demand parameter approach (EDP-Based) for reliability assessment and development of analytical models for... 

Extensive recent researches have been underway to model the fracture mechanics degradation based on continuum damage mechanics (CDM) technique. CDM theory is a powerful tool for solving problems such as large plastic deformations that the fracture mechanics is unable to solve. This model is derived by means of the thermodynamics internal variable theory and based on the experimental results on material properties. In this paper, the reliability of rectangular plates containing a central circular hole under static tensile load using the CDM approach for ductile fracture has been studied. To investigate the initiation and evolution of damages, anisotropic damage expressed by second order... 

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... 

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,... 

This paper presents a review of the existing models for the estimation of explosion-induced crushed and cracked zones. The control of these zones is of utmost importance in the rock explosion design, since it aims at optimizing the fragmentation and, as a result, minimizing the fine grain production and recovery cycle. Moreover, this optimization can reduce the damage beyond the set border and align the excavation plan with the geometric design. The models are categorized into three groups based on the approach, i.e., analytical, numerical, and experimental approaches, and for each group, the relevant studies are classified and presented in a comprehensive manner. More specifically, in the... 

The purpose of maintenance is to ensure the maximum efficiency and availability of production assets at optimal cost considering quality, safety, and environmental aspects. Assets criticality analysis is one of the main steps in many maintenance methodologies, including Reliability Centered Maintenance. The present study seeks to provide a solution for determining critical assets for more efficient maintenance management. In this regard, an integrated approach of the analytical hierarchy process and fuzzy inference system was proposed based on the concept of the risk matrix. According to the concept of the risk matrix, two main criteria of failure consequences and probability were employed... 

Reliability evaluations play a significant role in engineering applications to ensure the serviceability and safety of advanced structures such as those made of composites. Here, a dynamic reliability evaluation analysis based on the probability density evolution Method (PDEM) has been adapted to assess the reliability of composite structures under uncertainties within the material properties and the external loadings. A Back-Propagation Neural Network approach is employed to identify the system's nonlinear structural response, which is often the case under large deformations. To exemplify, a split Hopkinson pressure bar system was employed to mimic the mechanical behavior of a... 

I/O caching techniques are widely employed in enterprise storage systems in order to enhance performance of I/O intensive applications in large-scale data centers. Due to higher performance compared to Hard Disk Drives (HDDs) and lower price and non-volatility compared to Dynamic Random-Access Memories (DRAM), Flash-based Solid-State Drives (SSDs) are used as a main media in the caching layer of storage systems. Although SSDs are known as non-volatile devices but recent studies have reported large number of data failures due to power outage in SSDs. To overcome the reliability implications of SSD-based I/O caching schemes, RAID-1 (mirrored) configuration is commonly used to avoid data loss... 

Reliability evaluations play a significant role in engineering applications to ensure the serviceability and safety of advanced structures such as those made of composites. Here, a dynamic reliability evaluation analysis based on the probability density evolution Method (PDEM) has been adapted to assess the reliability of composite structures under uncertainties within the material properties and the external loadings. A Back-Propagation Neural Network approach is employed to identify the system's nonlinear structural response, which is often the case under large deformations. To exemplify, a split Hopkinson pressure bar system was employed to mimic the mechanical behavior of a... 

I/O caching techniques are widely employed in enterprise storage systems in order to enhance performance of I/O intensive applications in large-scale data centers. Due to higher performance compared to Hard Disk Drives (HDDs) and lower price and non-volatility compared to Dynamic Random-Access Memories (DRAM), Flash-based Solid-State Drives (SSDs) are used as a main media in the caching layer of storage systems. Although SSDs are known as non-volatile devices but recent studies have reported large number of data failures due to power outage in SSDs. To overcome the reliability implications of SSD-based I/O caching schemes, RAID-1 (mirrored) configuration is commonly used to avoid data loss... 

Low power consumption, real-time computing, and high reliability are three key requirements/design objectives of real-time embedded systems. The standby-sparing technique can improve system reliability while it might increase the temperature of the system beyond safe limits. In this paper, we propose a thermal-aware standby-sparing (TASS) technique that aims at maximizing the Quality of Service (QoS) of soft real-time tasks, which is defined as a function of the finishing time of running tasks. The proposed technique tolerates permanent and transient faults for multicore real-time embedded systems while meeting the Thermal Safe Power (TSP) as the core-level power constraint, which avoids... 

Reliability evaluations play a significant role in engineering applications to ensure the serviceability and safety of advanced structures such as those made of composites. Here, a dynamic reliability evaluation analysis based on the probability density evolution Method (PDEM) has been adapted to assess the reliability of composite structures under uncertainties within the material properties and the external loadings. A Back-Propagation Neural Network approach is employed to identify the system's nonlinear structural response, which is often the case under large deformations. To exemplify, a split Hopkinson pressure bar system was employed to mimic the mechanical behavior of a... 

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... 

Due to the system-level power constraints, it is encountered that not all cores in a multicore chip can be simultaneously powered-on at the highest voltage/frequency levels. Also, in the future technology nodes, reliability issues due to the susceptibility of systems to transient faults should be considered in multicore platforms. Therefore, two major objectives in designing multicore embedded systems are low energy/power consumption and high reliability. This letter presents an energy management system that optimizes the energy consumption such that it satisfies reliability target and meets timing, thermal design power (TDP) and thermal safe power (TSP) constraints. Toward the... 

The eccentric bracing system equipped with vertical links is capable of providing high levels of stiffness, strength and ductility, and therefore, can be efficiently used for seismic retrofit of existing structures. This study aims to investigate the seismic reliability of steel moment-resisting frames retrofitted by this system using a novel combined series–parallel system approach. The seismic response of 4, 8 and 12-storey steel moment-resisting frames (MRFs) are evaluated under a set of design basis earthquakes (DBE) before and after retrofitting intervention. Adopting an engineering demand parameter approach (EDP-Based) for reliability assessment and development of analytical models for... 

Continuity of supply plays a significant role in modern distribution system planning and operational studies. Accordingly, various techniques have been developed for reliability assessment of distribution networks. However, owing to the complexities and restrictions of these methods, many researchers have resorted to several heuristic optimization algorithms for solving reliability-constrained optimization problems. Therefore, solution quality and convergence to global optimality cannot be guaranteed. Aiming to address this issue, two salient mathematical models are introduced in this paper for topology-variable-based reliability evaluation of both radial and radially-operated meshed... 

Emergence of Solid-State Drives (SSDs) have evolved the data storage industry where they are rapidly replacing Hard Disk Drives (HDDs) due to their superiority in performance and power. Meanwhile, SSDs have reliability issues due to bit errors, bad blocks, and bad chips. To help reliability, Redundant Array of Independent Disks (RAID) configurations, originally proposed to increase both performance and reliability of HDDs, are also applied to SSD arrays. However, the conventional reliability models of HDD RAID cannot be intactly applied to SSD arrays, as the nature of failures in SSDs are totally different from HDDs. Previous studies on the reliability of SSD arrays are based on the... 

A framework for optimal seismic design of structures, considering maximum value as the design objective, is introduced. In this framework, the value parameter incorporates a comprehensive set of performance indicators. Decision indicators are mapped into equivalent economic values and are directly involved in the design process. This approach leads to optimal assignment of the available resources to meet infrastructure requirements. The construction cost and the risk of seismic consequences are considered as the value components. FEMA-P58 methodology is utilized in estimation of the seismic consequences including the repair cost, repair time, injuries and casualties. Endurance Time method is...