Sharif Digital Repository

This paper presents a robust control scheme for an islanded microgrid in the presence of structured uncertainties. The microgrid consists of parallel connection of two Distributed Generation (DG) units and a passive load. The DG units are connected to the passive load by using the power electronics converters. The microgrid model is structurally uncertain due to the large perturbations in the load parameters. To deal with the uncertainties, a Linear Fractional Representation (LFR) of the parametrically uncertain system is obtained. To achieve robust performance, the μ-synthesis approach is applied to the derived LFR model to design a μ controller. The resultant controller is structurally... 

Vulnerabilities are now part of all software systems. To handle vulnerabilities, many approaches have been proposed till now. Many of these approaches try to analyze vulnerabilities based on model checking techniques. However, the models used in these approaches handle authorized and unauthorized rules separately. This basically cause in weaker modeling abilities and consequently weaker vulnerability analysis. From authorized and unauthorized rules, we mean those emanated from access control model and those originated from vulnerabilities respectively. Currently, a new general graph-based protection system concentrating on vulnerabilities called VGBPS is proposed to overcome the mentioned... 

A large number of people are exposed to whole body vibration in their occupational life. Measuring vibration is an important tool in rehabilitation and biomechanical fields of research. We have proposed image processing as a new method to record and determine the frequency response of human body. The arranged set up for forced vibration consisted of an AC motor, a variable speed drive unit and a shaking table for producing one directional sinusoidal vibration. Volunteers were asked to stand on the shaking table at a relaxed posture. Two digital camcorders were used to capture the motion of colored pencil-dot markers on the skin of human body (forehead) and on the edge of the shaking table.... 

In this study, a periodic beam-like structure consisting of the horizontal and inclined beam elements is proposed. Three models with three different angles of inclination are considered. The generalized differential quadrature (GDQ) and generalized differential quadrature rule (GDQR) methods are used to solve the differential equations of longitudinal and transverse vibrations, respectively. The effects of two geometrical parameters on the first three band gaps of each model are investigated, comprehensively. Results show that this periodic structure has wide band gaps at low frequency ranges. Furthermore, the band gaps can get close to each other by changing the geometrical parameters.... 

In this study, a periodic beam-like structure consisting of the horizontal and inclined beam elements is proposed. Three models with three different angles of inclination are considered. The generalized differential quadrature (GDQ) and generalized differential quadrature rule (GDQR) methods are used to solve the differential equations of longitudinal and transverse vibrations, respectively. The effects of two geometrical parameters on the first three band gaps of each model are investigated, comprehensively. Results show that this periodic structure has wide band gaps at low frequency ranges. Furthermore, the band gaps can get close to each other by changing the geometrical parameters.... 

In this study, a periodic beam-like structure consisting of the horizontal and inclined beam elements is proposed. Three models with three different angles of inclination are considered. The generalized differential quadrature (GDQ) and generalized differential quadrature rule (GDQR) methods are used to solve the differential equations of longitudinal and transverse vibrations, respectively. The effects of two geometrical parameters on the first three band gaps of each model are investigated, comprehensively. Results show that this periodic structure has wide band gaps at low frequency ranges. Furthermore, the band gaps can get close to each other by changing the geometrical parameters.... 

In recent years Open Source Software programs have caused great changes in software world. Open Source software development is something beyond a method of software development or technology. As a result, using open source software development has diverse aspects. In this article the open source software development has been studied and investigated through reviewing some of the carried out works. © 2008 IEEE  

Wet cooling towers are one of the most water-intensive technologies, which are widely used in air conditioning applications, especially in dry regions. Considering the current water crisis around the world, it is essential to improve the design of these cooling towers to reduce their water consumption, while maintaining their cooling performance. Makeup water of cooling tower is usually a constant-temperature water which is cold enough to condensate the moisture content of the cooling tower exhaust air. Therefore, it has great potential to recycle water evaporation of cooling towers, which is not considered so far. This paper investigates a novel design for cooling towers utilising the... 

Reusing the programs which have already been developed can shorten the production time and reduce costs and expenses. One of the important issues in software reuse is finding a program or a program component in a program library which has been already developed and using it in the new program. In view of precision and automation that formal methods can provide, we can use formal methods in retrieval appropriate components from the software libraries. In this paper, some of the works done in the field of retrieval of the components from the libraries by the help of formal methods have been surveyed and reviewed  

Many software development methodologies are based on modeling the real world. In some of these methodologies, real-world models are gradually transformed into software models, while in others, the real world is only considered as a preliminary source of insight into the physical business domain. Real-world modeling was pushed to the sidelines due to anomalies in real-world modeling approaches; however, with the advent of the Model-Driven Architecture (MDA), real-world conceptual modeling is likely to regain its importance. We propose a method for using Design Patterns in the context of model transformation, where real-world models are refactored through application of these patterns.... 

Object-oriented frameworks are widely used to develop new applications. They provide reusable concepts that are instantiated in application code through potentially complex implementation steps such as subclassing, implementing interfaces, and calling framework operations. Unfortunately, many modern frameworks are difficult to use because of their large and complex APIs and frequently incomplete user documentation. To cope with these problems, developers often use existing framework applications as a guide. However, locating concept implementations in those sample applications is typically challenging due to code tangling and scattering. To address this challenge, we introduce the notion of... 

In this research, the effect of alternative fuels and the inlet charged air temperature is numerically investigated on the performance of a turbocharged spark-ignition engine. For this purpose, a one-dimensional engine and turbocharger model is created in an engine simulation and performance analysis software and validated with former experimental results. Then, the model is run with four fuel types, including two gasoline types with different octane numbers and two ethanol–gasoline blend fuels—E25 and E85. In each case, the inlet charged air temperature is changed from cold to hot condition and performance characteristics such as the spark advance timing, brake torque, brake-specific fuel... 

This paper presents a software-based error detection scheme called enhanced committed instructions counting (ECIC) for embedded and real-time systems using commercial off-the-shelf (COTS) processors. The scheme uses the internal performance monitoring features of a processor, which provides the ability to count the number of committed instructions in a program. To evaluate the ECIC scheme, 6000 software induced faults are injected into a 32-bit Pentium® processor. The results show that the error detection coverage varies between 90.52% and 98.18%, for different workloads. © 2004 Elsevier Ltd. All rights reserved  

Selecting a suitable Requirements Engineering (RE) process is usually based on personal preferences or existing company practices rather than on the characteristics of the project at hand (project situation). Feature-oriented software development is the overall process of developing software systems in terms of their features. The Software Product Line (SPL) approach is a paradigm for systematic reuse of software products, and a Software Factory is a SPL aimed at the industrialization of software development. Based on the notion that a software/RE process can be developed via an engineering process, this research aims to provide a feature-based RE process factory to develop RE processes... 

Due to the extreme use of method engineering and increasing attention to construct methods customized for a specific project, domain, organization or a generic method compatible with the team characteristics and needs, existence of suitable and formalized frameworks and guidelines is one of the challenges method engineers are encountered. In this area, considering method construction as the goal of method engineering brings to the mind the software development process in which the product is a method adapting the method users' needs. This paper, with a new approach of applying software architecture in method engineering and making use of architecture styles, tries to take advantage of... 

Nowadays, knowledge is the key to success in all software engineering processes. This valuable knowledge, obtained through analysis, design, development, and maintenance processes of the system, should be saved and reused in designing and developing current and similar systems. Using pre-existing knowledge is a practical approach which reduces design complexity, improves software architecture design and manages software quality. In this paper, we describe an approach to create architecture design knowledge using a hierarchical structure of architectural styles based on quality attributes. Knowledge is most importance asset of our approach that reuses similar domains, correlates architectures... 

Situational Method Engineering (SME)1approaches help construct bespoke software development processes according to the specifications of the project at hand, but they are time-consuming and costly. A Software Process Line (SPrL) tackles this problem by allowing software processes to be constructed for specific project situations through reusing core process assets. Model-Driven Development (MDD) has been used for automating SPrL Engineering (SPrLE); however, existing model-driven SPrLE methods are deficient as to their coverage of key MDD features. We propose a novel model-driven SPrLE approach that aims to address these shortcomings; it can be regarded as a framework that specifies the... 

It has become essential to scrutinize and evaluate software development methodologies, mainly because of their increasing number and variety. Evaluation is required to gain a better understanding of the features, strengths, and weaknesses of the methodologies. The results of such evaluations can be leveraged to identify the methodology most appropriate for a specific context. Moreover, methodology improvement and evolution can be accelerated using these results. However, despite extensive research, there is still a need for a feature/criterion set that is general enough to allow methodologies to be evaluated regardless of their types. We propose a general evaluation framework which addresses... 

Nowadays, product line, as an important topic in software development domain, has been paid attention by software engineering practitioners. Finding suitable components to construct an efficient and comprehensive product line with low costs is one of the critical problems in this domain which demands to be satisfied. In this paper a method is presented which can manage and control complexities of component selection problem, an NP problem, and result in creation of declared product line. By making use of this method, a product line will be constructed with suitably-adopted components to cover up requirements based on architecture; that's why software product line development process will... 

Evaluating architectures and choosing the correct one is a critical issue in software engineering domain, in accordance with extremely extension of architecturedriven designs. In the first years of defining architecture styles, some special quality attributes were introduced as their basic attributes. After a moment, by utilizing them in practice, some results were obtained confirming some of attributes; some others meanwhile were not witnessed. As software architecture construction process is dependent on and addressed by both usage conditions and quality attributes, in this paper a framework has been proposed to provide an environment and a platform that can cover evaluation of...