Sharif Digital Repository

The aim of this research is to study performance of Rao Score Test control chart in phase II monitoring of generalized linear profiles for drift and multiple changes which can be isotonic or antitonic. Moreover, the performance of the method is compared with two common methods in the generalized linear profile literature: Hotelling T2 and multivariate exponential weighted moving average. Afterward multivariate cumulative sum chart is proposed to be used in monitoring antitonic multiple change in the parameter of Poisson profiles. Finally, a real world example is presented in which Rao Score Test method is applied to real data and the performance of this method is compared with other methods.... 

The traveling salesman problem consists of a salesman and a set of cities in which the salesman has to visit each one of the cities only once, starting from an arbitrary city and returning to the same city. The challenge of the problem is that to find a trip to minimize the total length of the tour.The Travelling Salesman problem is a well-known and important combinatorial optimization problem. Despite this simple problem statement, solving the TSP is difficult since it belongs to the class of NP-complete problems. Due to its computational complexity, recent researches suggest that meta-heuristic approaches can be the best solution approach for the general form of this problem.This thesis... 

The limitation of energy resources and the increasing energy consumption has led researchers to look more closely at industrial processes such as condensation to improve these processes and prevent energy wastage. Increasing the efficiency of the condensation process will improve the performance of energy systems, save energy and protect the environment. In this research, various surfaces are fabricated, each of which in some way makes it possible to improve the condensation process. To perform the condensation test, the condensation surface, which is placed in the condensation test chamber, is cooled with a heat exchanger. Due to the high temperature of water vapor, many of the surfaces... 

This is the first attempt at process modeling in terms of predictive control using a hierachical method based on regression analysis and artificial neural networks(ANNs).This hierachical use leads to the reliability improvement of neural model of process in prediction (extrapolation and interpolation) of process output. such an outlook makes it possible to predict the proper input settings which achieved a desired process output by designing various senarios for process set up. This approach was applied in Tile industry for spray dring process and in order to indicate the achieved improvement,three models:(i) regression model of process using multiple linear regression,(ii)Neural model of... 

One technique to reduce variance of output in comparing two or more systems via simulation is random number synchronization. the primary technique for achieving synchronization is to assign an independent seed to each random process and then use the same collection of seeds across all systems . Another way of synchronization in systems with limited customer population is to assign different seed to each customer (transaction) and then use the same collection of seeds across all systems. The main Question to be considered here is which of these methods of synchronization can better reduce variance of output in a queue with finite customer population  

Many simulation optimization problems are defined in random settings and their inputs have uncertainty. Therefore, in defining an optimal solution for these problems, uncertainties should be taken into account. The primary way of dealing with this , is Robust Optimization which finds solution immune to these changing settings. Aiming at finding a new approach for simulation optimization problems, this study investigates these uncertainties and robust methods. In the optimization problem, the goal and constraints are considered with separate risk measures and a related problem is defined as follows: Minimizing the weighted sum of all risks subject to the problem constraints. To solve the... 

Control charts are the most popular Statistical Process Control tools used to monitor process changes. However, they are not capable of identifying the real time of a process change, which is essential for diagnosing assignable causes of the change. Therefore, a number of methods of change-point estimation have been developed. In the literature, relatively little study has been done on multiple changes. In this research, a new method based on Maximum Likelihood Estimator (MLE) is introduced to identify linear drifts and step changes in multivariate multiple linear profiles. Due to the massive increase in the amount and time of the calculations along with the growth of the number of the... 

Due to environmental concerns and continuous decrease in the price, photovoltaic (PV) generations have been increasing in the recent years. PV units can operate in grid-connected or islanded modes. In grid-connected mode, the PV unit delivers its generated power to the grid; on the other hand, in islanded mode, it supplies the local loads. In this research, a new decentralized power management and load sharing method for a photovoltaic based islanded microgrid consisting of various PV units, battery units and hybrid PV/battery units is proposed. Unlike the previous methods in the literature, there is no need to communication among the units and the proposed method is not limited to the... 

Before a construction project gets under way an attempt is made to examine different ways and scenarios for its implementation. Through such a process the more appropriate scenarios should be selected based on several criteria that are not necessarily at the same level in terms of importance. The purpose of this study is to examine different scenarios for implementing operations in the pre-construction phase of a project, based on several competing criteria with different importance levels in order to achieve a more efficient execution plan. This paper presents a new framework that integrates discrete event simulation (DES) and data envelopment analysis (DEA) to rank different scenarios for... 

In this dissertation, two parts of research has been conducted. First, with the aim of minizing the fluctuations of power output of wind farms and the need for energy storage system, optimization of wind farm (WF) layout has been studied. Deployment of battery energy storage system (BESS) is a viable option to alleviate the inherent power fluctuation of wind farms. In this thesis and based on the power spectrum density (PSD) theorem, it is hown that the WF layout affects not only the total harvested energy but also the level of power fluctuation, which in turn influences required capacity of battery energy storage system (BESS) needed to mitigate the inherent power fluctuation of the wind... 

In this thesis we will provide a comprehensive study of process capability indices, and we use multivariate g-and-h Tukey distribution for calculating process capability indices of multivariate non-normal processes. Univariate process capability indices have been used commonly in literature for measuring the capability of a process. However, there are several processes with more than one quality characteristic. When these characteristics are independent, we can use univariate process capability indices, but when the characteristics are dependent we should use multivariate methods for measuring process capability. There have been several studies about multivariate process capability indices,... 

In some statistical process control applications, quality of a process or product 1s characterized by a relationship between a response variable and one or more explanatory variables which is referred to as profile by researchers. In some applications such as calibration, this relationship is characterized by a simple linear regression. However, in some situations, more complicated models are needed. It seems that there is a little attention to monitoring of profiles with binary response variables. Furthermore, the extensive applications of binary response variables in real industrial worlds make it necessary to concentrate on this kind of profiles. In this ... 

In this work, we propose a metamodel-based simulation optimization algorithm using a novel hybrid sequential experimental design. The algorithm starts with a metamodel construction phase in which at each stage, a sequential experimental design is used to select a new sample point from the search space using a hybrid exploration-exploitation search strategy. Based on the available design points at each stage, a metamodel is constructed using Artificial Neural Network (ANN) and Kriging interpolation techniques. The resulting metamodel is then used in the optimization process to evaluate new solutions. We use Imperialist Competitive Algorithm (ICA) which is a powerful population-based... 

Sampling is so deep-rooted in our habits that it usually takes place unconsciously. A large number of books and articles have been published in this field. The connection between sampling and quality control is the reason that many industries have focused their attention on sampling; however, only a few numbersare familiar with bulk material sampling related issues. Describing this theory along with its seven errors is the main object of this research. Using this theory, characteristics of the lot of interest was analyzed. Creating necessary conditions for assuring sampling correctness is very critical and if these conditions cannot be provided, implementing some part of the theory issues... 

This thesis presents a method to solve a redundancy allocation problem for the series-parallel system. The modeling formulation deals with the choice of the best redundancy strategy, component and redundancy level for each subsystem in order to maximize the system reliability under system-level constraints. Majority of the solution methods for the general redundancy allocation problems assume that the failure rate of components is determined. However, in practice variable failure rate may be used. The complexity of this problem is known as NP-hard and therefore the optimal solution is not accessible in the normal course of events. It is demonstrated in this thesis that genetic algorithm is... 

This work attempt to analyze the impact of changes in nurse scheduling on quality of services at emergency department of Emam Khomeini Hospital Complex. In nurse scheduling some constraints such as maximum working hours per week and unacceptable working sequences must be considered. A simulation model is developed to cover the complete flow for the patient through the emergency department. Emergency department of Emam Khomeini is simulated in order to obtain the patient average waiting time for each nurse roster. Then a genetic algorithm is integrated with the simulation model. In each iteration genetic algorithm produces many nurse rosters . For each roster the patient average waiting time... 

Nowadays, electrical energy is one of the crucial requirements in human beings’ lives. Since the majority of the world’s energy is met by fossil fuel, the problems such as global warming, the reduction of fossil fuel resources, and unpredictable oscillation of the prices of such fuels have led to a serious crisis for the people of the world. Furthermore, due to the increasing energy demand, the economic development of most countries has a strong correlation with fossil fuel prices. The abovementioned problems have made a lot of countries take alternative policies in terms of generating energy, one of which is using renewable energy resources. This approach is reported to be clean and... 

In many cases even high-quality products cannot satisfy the customer needs and this leads to having a lower share of the market. To achieve this purpose, customer satisfaction and robust design are regarded simultaneously to achieve a better quality. Balance Score Card (BSC) is proposed as a technique that could potentially has a great improvement effect on customer satisfaction. Moreover, with a non-linear programming (NLP), a novel method for integrating RSM and BSC have been proposed to accede robustness in design. The opinions of the customers are regarded in every system design, parameter design and tolerance design. To validate the applicability of the proposed approach, the approach...