Sharif Digital Repository

The applications of available transfer capability (ATC) have received considerable attention in restructured power systems. System operators calculate and post ATC values for different time intervals considering power system operation issues, including security issues. On the other hand, competitive electricity market has added economic issues to transmission services such that they could have different price, type (recallable/non-recallable) and curtailment cost. The inclusion of economic issues in ATC calculation to obtain NATC and RATC has not been sufficiently addressed yet. This paper presents a method to calculate ATC on a weekly base in restructured power systems which incorporates... 

Update of software usually equates disruption to a program's execution. However, such disruptions in the execution of applications that provide round-the-clock services is not desirable. Examples of such applications include multi-tier enterprise systems with which users may interact via distinct presentation tiers at the same time. Existing software updating systems do not operate in the enterprise applications, or they need most of the redeployment tasks to be performed manually. In this paper, we present a framework capable of Automatically Redeploying Enterprise Software Applications (ARESA). This system combines the idea of incremental and integral updates to preserve the consistency of... 

Anthropogenic activities have added a large amount of heavy metals to the environment. Heavy metal contaminants affect the physiological and biological properties of soil and plant health. Zinc (Zn) is an essential micronutrient and it promotes plant growth and development but a higher concentration of the metal causes reduction in plant growth. The present study was aimed to evaluate the response of Bacillus cereus on maize plants at different concentrations of ZnSO4 (20, 40 and 60 mg kg–1) amended in the soil under pot experiment conditions. The experiment was conducted by using complete randomized design (CRD) with three replications. Higher doses of ZnSO4 inhibited maize growth and... 

Under new reregulation environment an open access to transmission system is desired. Transmission system operators (TSOs) are encouraged to use the existing facilities more efficiently. This paper focuses on the evaluation of the impact of FACTS devices on Available Transfer Capability (ATC) and its enhancement. Genetic algorithm is used for optimisation process of the best location of SVC as a FACTS device. Improvement of voltage profile as well as TTC enhancement is achieved by applying a proposed methodology through some case studies  

In this paper we discuss an improved method for the calculation of Available Transfer Capability (ATC) in a restructured power system. The ATC calculation is performed through an optimal power flow approach. The objective function is to maximize the sum of the receiving-end load in a specified area as well as to send generation to other control areas while a minimum cost of generation is continuously achieved. The constraints are ac power flow equations and system operation limits. It is assumed that the generation cost curve of each generator is available. A genetic algorithm is used for the optimization process. An IEEE 30 bus test system is used for testing the proposed algorithm and the... 

Availability of the service delivered by cloud providers is one of the most important QoS factors of the service level agreements between providers and customers. Since current Infrastructure-as-a-Service providers use virtualization technology to manage data centers, virtual data centers (VDCs) have become a popular infrastructure for cloud computing. In order to study the service availability, a stochastic activity network (SAN) model is presented in this paper. The proposed SAN model can be appropriately used to investigate the impact of different characteristics and policies on service availability of VDCs  

Purpose: The purpose of this paper is to derive a closed-form expression for the steady-state availability of a cold standby repairable k-out-of-n system. This makes the availability calculation much easier and accurate. Design/methodology/approach: Assuming exponential distributions for system failure and repair, the Markov method is employed to derive the formula. Findings: The proposed formula establishes an easier and faster venue and provides accurate steady-state availability. Research limitations/implications: The formula is valid for the case when the probability density function of the component failure and the repair is exponential. Originality/value: The Markov method has never... 

High availability of software systems is an essential requirement for pervasive computing environments. In such systems self-adaptation, using dynamic reconfiguration is also a key feature. However, dynamic reconfiguration potentially decreases the system availability by making parts of the system temporary frozen, especially during incomplete or faulty execution of the reconfiguration process. In this paper, we propose Assured Dynamic Reconfiguration Framework (ADRF), consisting of run-time analysis phases, assuring the desired correctness and completeness of dynamic reconfiguration process. We also specify factors that affect availability of reconfigurable software in pervasive computing... 

In this paper we present a method for transient analysis of availability and survivability of a system with the identical components and identical repairmen. The considered system is supposed to consist of series of k-out-of-n or parallel components. We employed the Markov models, eigen vectors and eigenvalues for analyzing the transient availability and survivability of the system. The method is implemented through an algorithm which is tested in MATLAB programming environment. The new method enjoys a stronger mathematical foundation and more flexibility for analyzing the transient availability and survivability of the system. © 2006 Elsevier Inc. All rights reserved  

A new method for the shape reconstruction of conducting cylinders from the measured data based on the cubic uniform B-splines was discussed. B-Spline was defined by an ordered set of control points which determined the shape of the curve. A direct problem was formulated using standard integral equations that were solved using method of moments. Principal polarization were treated separately. The method was found less sensitive to noise than those using Fourier expansions  

Redundancy technique is considered as a way to enhance the reliability and availability of a system. This paper models availability of a repairable system with multiple subsystems in which the involved components follow the load sharing strategy. In redundancy allocation problems, the redundancy level is just considered, whereas, in this paper, the number of repair facility (repairman) is added to the decision variables. The goal is to find the optimal number of repairmen and redundant components in each subsystem for optimization of availability subject to weight, cost and volume constraints. The main contribution of this study is to present a straightforward model for availability... 

Despite widespread use of SRAM-based reconfigurable devices (SRDs) in mainstream applications, their usage has been very limited in enterprise and safety-critical applications due to SRAM susceptibility to soft errors. Previous mitigation techniques to protect SRDs impose significant area and power overheads. Additionally, they suffer from susceptibility of configuration bits to multiple bit upsets (MBUs). In this paper, we present a highly available fault-tolerant architecture to protect SRD-based designs against MBUs in both configuration and user bits. In the proposed architecture, the entire design is duplicated with respect to the relative locations of logic blocks within the SRD and... 

Security techniques have been designed to obtain certain objectives. One of the most important objectives all security mechanisms try to achieve is the availability, which insures that network services are available to various entities in the network when required. But there has not been any certain parameter to measure this objective in network. In this paper we consider availability as a security parameter in ad-hoc networks. However this parameter can be used in other networks as well. We also present the connectivity coefficient of nodes in a network which shows how important is a node in a network and how much damage is caused if a certain node is compromised  

When there are transmission service requests for a specific sink/source pair in a transmission system, the ISO must allocate the ATC of that pair to the requests. Since the requests could have different types, tariffs and time frame, the allocation must be accomplished in a sound and fair manner that considers various aspects of the requests. This paper proposes an approach to allocate the ATC to transmission service requests in both operating and planning horizons. The proposed method considers types and tariffs of requests in a nonlinear optimization which maximizes the expected net revenue of ATC allocation. The solution to the optimization problem gives the amount of accepted requests.... 

Fault tree analysis is one of the key approaches used to analyze the reliability of critical systems. Fault trees are usually analyzed using mathematical approaches or Monte Carlo simulation (MCS). This paper presents a Fuzzy-Monte Carlo simulation (FMCS) approach in which the uncertain data is generated by the MCS approach. The FMCS approach is applied to the Weibull probability distribution which is widely been used in the analysis of reliability, availability, maintainability and safety (RAMS). Using the fuzzy arithmetic, times to failure (TTF) of the components are generated. These results are processed by a kind of fault tree (e.g. time-to-failure tree) to produce the TTF of the whole...