Sharif Digital Repository

Facility layout problem (FLP) is one of the classical and important problems in real-world problems in the field of industrial engineering where efficiency and effectiveness are very important factors. To have an effective and practical layout, the deterministic assumptions of data should be changed. In this study, it is assumed that we have dynamic and uncertain values for departments’ dimensions. Accordingly, each dimension changes in a predetermined interval. Due to this assumption, two new parameters are introduced which are called length and width deviation coefficients. According to these parameters, a definition for layout in uncertain environment is presented and a mixed integer... 

This paper presents a simulation-based environment to study fault effects in message missing failures in CAN-based systems. A CAN controller is modeled by VHDL at behavioral level and is exploited to set up a network composed of several nodes. A total of 27,000 transient faults of seven types are injected into five critical portions of the system including the bus and four portions of the CAN controller. The experimental results show that the faults affect the message sending in which more than 20% of faults cause the failure. Besides, with a heavy workload, faults that are occurred into the CAN controller and on the bus cause about 90% and 10% of all failures, respectively  

This paper presents a comprehensive comparison between job-level dynamic scheduling algorithms on real-time multiprocessor environments using simulation. Earliest Deadline First (EDF) and Least Laxity First (LLF) are two well-known and extensively applied dynamic scheduling algorithms which have been proved to be optimal on uniprocessor systems. However, neither is shown to be optimal on multiprocessors. Many researches have already been done on aforementioned algorithms, but to the best of our knowledge, none of which has compared the efficiency of the two algorithms under similar conditions. Perhaps the main reason is that LLF algorithm is fully dynamic and impractical to implement. In... 

The Facility Layout Problem (FLP) is the problem of locating each department in a long plant floor without any overlap between departments in order to minimize the material handling cost. The main purpose of this study is to show the effectiveness of a robust approach to solve FLP. In this study, it is assumed that the departments’ length and width are not predetermined. For modeling this kind of uncertainty, the size of each department is considered as a bounded variable and two new parameters are also introduced to implement a robust approach. Moreover, a new adaptive algorithm is designed to determine the robust layout with respect to the decision makers’ requirements. Furthermore, the... 

Considering that about 90% of international trade is transported via sea and ship ventilation systems consume between 3.5% and 5.5% of the ship’s rated power, ship energy consumption is of particular interest and modelling and enhancing ventilation systems are vital to reducing and optimising energy consumption. Using Computational Fluid Dynamics (CFD) simulation, modelling heat transfer and airflow patterns helped us improve the ventilation system and temperature distribution, provide thermal comfort for staff and equipment, and increase energy efficiency. We discussed the radiation effect in CFD analysis; it affected wall temperatures significantly and temperature contours to some extent;... 

In general, reliability is the ability of a system to perform and maintain its functions in routine, as well as hostile or unexpected, circumstances. The Redundancy Allocation Problem (RAP) is a combinatorial problem which maximizes system reliability by discrete simultaneous selection from available components. The main purpose of this study is to develop an effective approach to solve RAP, expeditiously. In this study, the basic assumption is considering Erlang distribution density for component failure rates. Another assumption is that each subsystem can have one of cold-standby or active redundancy strategies. The RAP is a NP-Hard problem which cannot be solved in reasonable time using... 

Water quality is one of the most important factors contributing to a healthy life. From the water quality management point of view, TDS (total dissolved solids) is the most important factor and many water developing plans have been implemented in recognition of this factor. However, these plans have not been perfect and very successful in overcoming the poor water quality problem, so there are a good volume of related studies in the literature. We study TDS and the water flow of the Karoun river in southwest Iran. We collected the necessary time series data from the Harmaleh station located in the river. We present two Univariate Seasonal Autoregressive Integrated Movement Average (ARIMA)... 

Hardware/Software (HW/SW) partitioning plays one of the most important roles in Co-design of embedded systems that is due to made at the beginning of the cycle of the design. The ultimate designed system's performance strongly depends on partitioning. Therefore, achieving the optimum solutions can reduced the systems cost and delay. On the other hand, Genetic algorithms (GAs) are powerful function optimizers that are used successfully to solve problems in many different disciplines. Parallel GAs (PGAs) are particularly easy to implement and promise substantial gains in performance and results. In this paper, we present a PGA-based approach to achieve near optimal solutions for HW/SW... 

During the past years, the development of piezoelectric energy harvesters is extensively increased for providing the required energy of sensor nodes. It has been proven that changing the beam’s cross-section along its length direction may lead to extract more power with less mass. In this article, a hybrid metaheuristic algorithm called tabu continuous ant colony system is employed to optimize the tapered piezoelectric energy harvester in a fast and course manner. The exponential and fourth-order polynomial functions are considered as shaping functions for tapering the beam’s width along its length direction. An experiment is also set up to evaluate the performance of the optimization... 

It has been proven that tapering the piezoelectric beam through its length optimizes the power extracted from vibration based energy harvesting. This phenomenon has been investigated by some researchers using semianalytical, finite element and experimental methods. In this paper, an exact analytical solution is presented to calculate the power generated from vibration of exponentially tapered unimorph and bimorph with series and parallel connections. The mass normalized mode shapes of the exponentially tapered piezoelectric beam with tip mass are implemented to transfer the proposed electromechanical coupled equations into modal coordinates. The steady states harmonic solution results are... 

Cooperative systems have been extensively investigated in literature. Herein the criteria and implementation for finding the optimal configuration of the Dual-Arm Cam-Lock (DACL) robot manipulators at a specific point with the objective to optimize the applicable task-space force in a desired direction are addressed. The DACL robot manipulators are reconfigurable arms formed by two parallel cooperative manipulators. Some of their joints may lock into each other. Therefore, the arms normally operate redundantly. However, when higher structural stiffness is needed these two arms can lock into each other in specific joints and loose some degrees of freedom. The dynamics of the DACL robot is... 

This paper scrutinizes faults in a CAN controller that may result in masquerade failures, and suggests an even parity mechanism to detect them with minimum hardware overhead. To do this, a CAN controller is modeled by VHDL at behavioral level and is exploited to setup a CAN-based network composed of two nodes. A total of 5,500 faults are injected into essential parts of one of the controllers. The results show that about 3.44% of faults terminate in masquerade failures. The results, also, show that Register bank in the CAN controller are the most sensitive portions in which 92.10% of faults occurring in the Register bank result in masquerade failures. The even parity mechanism detects about... 

Recently, there has been great interest in Bio informatics among researches from various disciplines such as computer science, mathematics, statistics and artificial intelligence. Bioinformatics mainly deals with solving biological problems at molecular levels. One of the classic problems of bioinformatics which has gain a lot attention lately is Haplotyping, the goal of which is categorizing SNP-fragments into two clusters and deducing a haplotype for each. Since the problem is proved to be NP-hard, several computational and heuristic methods have addressed the problem seeking feasible answers. In this work it is shown that using PCM to solve Haplotyping problem in DALY dataset yields... 

Purpose: The purpose of this paper is to study brain drain as a social problem and elaborate a five-dimensional social justice model as the main cause of brain drain. The paper explores the effects of distributional justice, emotional justice, procedural justice, transactional justice, and informational justice on brain drain intention. Design/methodology/approach: The method of research is survey method. This research is functional in terms of target and is descriptive. Moreover, the research is a field study from the information gathering perspective; and from the aspect of relationship between variables, it has casual type. Findings: The results of this study demonstrate that justice is a... 

In this paper, the V-shape development model approach for designing an automotive floor panel made by laminated structure is investigated to attain the best trade-off between the system and subsystem level requirements while improving the local and global performance of the vehicle. For this purpose, the bending and torsional stiffness of the body structure, as well as mass, strength, and vibration attenuation of the floor panel, are considered as design objectives at the system and subsystem levels. A multi-objective discrete optimization of a laminated configuration is performed using the Taguchi-based grey relational analysis. Material grades and thicknesses of the sandwich panel face...