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mokhtari-garekani--rasoul
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Preparation and Characterization of Asymmetric and Thin Film Composite Nanofiltration Membranes for Water Softening
, M.Sc. Thesis Sharif University of Technology ; Mousavi, Abbas (Supervisor) ; Roosta Azad, Reza (Supervisor)
Abstract
In this study three type of nanofiltration membranes were prepared from PVC for water softening; (i) asymmetric PVC nanofiltration membrane, and two different thin film composite (TFC) membranes: (ii) polyamide (PA)/PVC composite membrane (iii) poly vinyl alcohol (PVA)/PVC composite membrane. Asymmetric nanofiltration membranes were prepared by phase inversion. The effect of PVC concentration, solvent (THF) and additive (PVP) on morphology and performance were studied by scanning electron microscopy (SEM) and measuring pure water flux and salt rejection. Increasing PVC concentration decreased pure water flux and increased salt rejection. Adding tetrahydrofuran(THF) decreased the pure water...
Block shear failure in welded gusset plates under combined loading
, Article Journal of Constructional Steel Research ; Volume 170 , July , 2020 ; Ghaderi Garekani, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Block shear failure in the base metal of welded steel connections is a potential failure mode affecting many steel structures. However, there are only a few studies on the block shear failure of welded connections under combined shear and axial loading. Combined loading is defined as a simultaneous loading parallel and perpendicular to the weld lines (or an inclined loading) in the plane of the connecting plate. In this research, a nonlinear finite element model is used to study the effect of connection geometry and weld group configuration on the block shear strength of welded connections under combined loading. In current design standards, the block shear failure planes are assumed to...
An investigation of shear failure in welded channel and angle brace members
, Article Structures ; Volume 45 , 2022 , Pages 1287-1306 ; 23520124 (ISSN) ; Maleki, S ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Shear yielding (SY) and shear rupture (SR) are base metal failure modes in welded connections of brace members to gusset plates. Although gusset plated connections have been extensively investigated in the past nonetheless, the shear failure limit states of welded brace members have not received significant attention. This paper aims to shed some light on the shear failure mechanism and strength of welded brace members consisting of single and double channels and angles. For this purpose, a nonlinear finite element (FE) model with ductile damage simulation is developed and validated against the authors’ experiments and other available test results. Then an extensive parametric study using...
Experimental and Numerical Investigations of Base Metal Strength in Welded Bracing Connections
, Ph.D. Dissertation Sharif University of Technology ; Maleki, Shervin (Supervisor)
Abstract
The strength of welded joints is determined by the lower value of the weld metal and base metal strength. In welded bracing connections, the latter includes the connecting element (i.e., the gusset plate) and the bracing member. According to the American steel design standard AISC 360, the base metal strength is determined based on the limit states of tensile rupture, shear yielding, shear rupture, and block shear. While extensive research has been conducted on the limit state of tensile rupture, limited attention has been given to the limit states of shear yielding, shear rupture, and block shear in welded bracing connections. Furthermore, the design strength equations adopted by AISC 360...
Performance evaluation of thyristor-based static transfer switch with respect to cross current
, Article IEEE/PES Transmission and Distribution Conference and Exhibition 2002 : Asia Pacific, Yokahama, 6 October 2002 through 10 October 2002 ; Volume 2, Issue ASIA PACIFIC , 2002 , Pages 1326-1331 ; Sharif University of Technology
2002
Abstract
Providing clean, continuous and reliable power to many industrial customers has become a necessity. Where possible, sensitive customers are supplied by two medium-voltage utility feeders one of which is used as back up. Thyristor-based Static Transfer Switches (STSs) are able to provide the loads with a fast transfer to the back up feeder when the main one fails. In addition to being fast, the transfer must be performed with no source paralleling which creates a cross current flowing between the main feeder and the back up one. Due to practical limitations, however, in some cases, cross current cannot be avoided. This paper investigates the performance of thyristor-based STSs with respect to...
Establishment of ISO/TS 16949:2002 Standard and Combining with Sapco 86 and AR/8601 Saipa Sazeh Gostar Requirements in Auto Parts Manufacturing Company
, M.Sc. Thesis Sharif University of Technology ; Hajji, Rasoul (Supervisor)
Abstract
The quality is the last word of customer satisfaction concept. The structure and the main goal of many of large and small companies have been formed with systems aggregate related to process and product quality. Whereas quality is not achieved only under the protection of inspecting and controlling, then the quality management standards have been designed and produced to control all the activities and organization effective processes. Quality management standards in auto industries have been developed with increasing of customer desire and their severity simultaneously. Which the set of some standards such as ISO 9000, QS 9000, VDA, … and the most ISO TS 16949 requirements have been used....
Economic Batch Quantity (EBQ) for a Single-Stage Production System with Rework and Scrapping
, M.Sc. Thesis Sharif University of Technology ; Haji, Rasoul (Supervisor)
Abstract
The classical economic batch quantity (EBQ) model assumes that all produced items have a perfect quality. But in real-life production systems, generation of defective items is inevitable. A portion of these defective items is considered to be scrap , while the other is assumed to be reworkable and reworking them can reduce costs and increase productivity. In this thesis we have studied the economic batch quantity for a single stage production system with rework and scrapping . We want to satisfy the customer demand and minimize total costs of the system like set up costs , production costs , rework costs , holding costs , shortage costs and scrapping costs . In the first chapter of this...
Systematic Planned (Preventive) Maintenance in Hospitals And Medical Centers of Iran
,
M.Sc. Thesis
Sharif University of Technology
;
Haji, Rasoul
(Supervisor)
Abstract
Based on the latest statistical figures, more than 50 billion Rials worth of medical equipment exists in Iran’s medical centers. In spite of this, Breakdown maintenance is used in all hospitals, which means that the equipment is utilized as long as it is not out of order and only in such a situation, i.e. a breakdown, the necessary repair operation is conducted on the equipment. In fact, no maintenance is carried out to prevent a breakdown, while the “prevention from breakdown” concept has long been introduced in the majority of industries in many countries including Iran and its positive impacts are undisputable. This thesis aims at proposing a solution for the implementation of a “planned...
A Semantic-Aware Authorization Model Based on Deontic Logic
, Ph.D. Dissertation Sharif University of Technology ; Jalili, Rasoul (Supervisor)
Abstract
Semantic technology provides an abstraction layer above existing computational environments, especially the Web, to give information a well-defined meaning. Moving toward semantic-aware environments imposes new security requirements. One of the most important requirement is the authorization and security policy inference based on the existing semantic relationships in the abstract (conceptual) layer. Most of the authorization models proposed for these environments so far are incomplete and their inference rules are not guaranteed to be consistent, sound, and complete. To have a sound and complete system for policy specification and inference, in this thesis, a family of modal logics, called...
Formal Verification of Privacy Property Using Applied Pi Calculus and Epistemic Logic
, M.Sc. Thesis Sharif University of Technology ; Ramezanian, Rasoul (Supervisor)
Abstract
Applied pi calculus is a variant of the pi calculus with extensions for modeling cryptographic protocols. In such a calculus, the security guarantees are usually stated as equivalences. While process calculi provide a natural means to describe the protocols themselves, epistemic logics are often better suited for expressing certain security properties such as secrecy and anonymity. These methods studied in this work to investigation the verification of privacy properties in security protocols. And finally, a new approach is introduced to bridge the gap between these two approaches: using the set of traces generated by a process as models. In this method an epistemic logic has constructs for...
Query Correctness Assurance for Outsourced Databases
, M.Sc. Thesis Sharif University of Technology ; Jalili, Rasoul (Supervisor)
Abstract
In the secure data outsourcing scenario, verification of the reply of an unreliable server includes assessing the authenticity, completeness and it’s integrity. In this thesis, an efficient method, with emphasis on freshness, has been introduced to evaluate the correctness of the replies from a server. It takes in hand different application needs, inherent differences in the data, and different update mechanisms. This method evaluates freshness by using timestamps alongside the data being out sourced. Due to the requirement of verifying not only the freshness of the response, but the correctness of the timestamps as well, two general methods for evaluating and verifying the responses were...
Access Control in Semantic Social Network
, M.Sc. Thesis Sharif University of Technology ; Jalili, Rasoul (Supervisor)
Abstract
Growth of tools that ease sharing information and resources in social networks can cause privacy issues for the users. Protecting user’s personal information against unauthorized access is a crucial task, and it is considered as a first step for preserving user’s privacy in such networks. Policies, access control rules, and the way rules are applied to online social networks are issues that are less investigated and most existing frameworks have used simple models. Growth of users joining social networks and significant volume of resources shared in these networks make such environments suitable for using semantic technology. Semantic technology is used for modeling various resources, users,...
“Determination of Economic Order and Production Quantity in Inventory System Regarding the Quality of Items”
, M.Sc. Thesis Sharif University of Technology ; Haji, Rasoul (Supervisor)
Abstract
EOQ and EPQ models have been among the most important and commonly used techniques for about 100 and 60 years respectively .But, they are involved in some assumptions that sometimes prevent them from being implemented in real situation of industry and production. One of these unrealistic assumptions is that all of items received or produced are of perfect quality. In order to overcome this constraint and make the mentioned models closer to the real environmentsome researches have been done. To this end,following the previous attemptsin this project we assumed to have destructive inspections and existence of imperfect and rejected items after rework. In our models, considering 3 circumstances...
Analysis of Non-monotonicity Property in Access Control for Pervasive Computing Environment
, M.Sc. Thesis Sharif University of Technology ; Jalili, Rasoul (Supervisor)
Abstract
Access control, which is the process of mediating every request to resources and data maintained by a system and determining whether the request should be granted or denied, plays an important role in the system security. The existing of non-monotonicity property in a deduction and decision making process means that some of the previous deductions or decisions may be retracted by adding new information and premises. Based on the definition, in a non-monotonic access control system, adding new information or access control rules may invalidate some of the previous conclusions (permissions/prohibitions). The requirements such as decision making based on the imperfect information, supporting...
Selecting and Optimizing Portfolio Using Methaheuristic Methods
, M.Sc. Thesis Sharif University of Technology ; Rmezanian, Rasoul (Supervisor)
Abstract
Portfolio is a collection of different stocks for investment. The investors' objectives in portfolio formation are to get the highest return against exposure to the lowest risk. Portfolio Optimization Problem is one of the most complicated problems in investment and finance. It may be simply explained as follows: Let's imagine a set of N stocks for selection. We would like to see what percentage of the total amount of investment should be dedicated to each stock to maximize portfolio's total return and minimize its total risk.
Portfolio Optimization Problem is a NP-Hard problem and generally there exists no polynomial-time deterministic algorithm to find a precise solution to such a...
Portfolio Optimization Problem is a NP-Hard problem and generally there exists no polynomial-time deterministic algorithm to find a precise solution to such a...
Transportation Problem of Hub Network with Direct Links
, M.Sc. Thesis Sharif University of Technology ; Haji, Rasoul (Supervisor)
Abstract
Hub and Spoke networks come into play when considering direct link between all origins and destinations is either impossible or expensive in a transportation system. In this kind of problems, some nodes are chosen as hub from all origin and destination nodes to collect flows and then distribute them. Implementing hub network leads to minimizing transportation cost, sorting flows and conveying them in economies of scale. Otherwise, shipping flows directly may cause decreasing the travelling distance and the delivery time consequently. In this dissertation, combination of hub network and direct shipment is investigated. To obtain the optimal hub locations and direct links between non-hub nodes...
Punishment Normative Systems
, M.Sc. Thesis Sharif University of Technology ; Ramezanian, Rasoul (Supervisor)
Abstract
In real life, we can not always expect agents and authorities to have the same desires. Also when it comes to conflicts, agents always tend to break the authorities’ norms to follow their own strategies. Hence we can not expect strict norms to model an actual real life situation.In this article we introduce punishment normative systems, based on multi-agent Marokov chain processes (MMDPs). We try to extend the punishment idea to be also applicable on long-run and infinite strategies. We consider a version of the multi-agent model that is widely used in different situations and then provide an algorithm to find a fair normative system that distributes obligations equally on the agents, while...
Developing Inventory Control Policies with No Ordering Costs in Two-Echelon Supply Chains
, Ph.D. Dissertation Sharif University of Technology ; Haji, Rasoul (Supervisor)
Abstract
This dissertation attempts to develop four inventory control models for two-echelon supply chains. For the all models, the retailers face Poisson demand and lost sales during a stockout. There is also a time-dependent holding cost and a cost per unit of lost sales. However, there is no (or negligible) cost associated with placing an order.
For the first model, we consider a two-echelon inventory system with one central warehouse and a number of retailers. The central warehouse applies (R, Q) policy and retailers apply base stock policy. In this model, we approximate the arrival process of the central warehouse and obtain the total cost of the system, as well as the optimal solution....
For the first model, we consider a two-echelon inventory system with one central warehouse and a number of retailers. The central warehouse applies (R, Q) policy and retailers apply base stock policy. In this model, we approximate the arrival process of the central warehouse and obtain the total cost of the system, as well as the optimal solution....
Multi-Objective Production Planning and Job Shop Scheduling
, M.Sc. Thesis Sharif University of Technology ; Haji, Rasoul (Supervisor)
Abstract
Production scheduling is such a key issue that directly influences on the performance of the machines and efficiency of production line. This category of problems is to find simultaneously the lot sizes and their sequence over a finite set of planning periods.
In this Thesis a multi objective production planning and job shop scheduling problem is investigated. The objectives are minimization of the production cost and minimization of production time smoothness in consecutive periods. As the problem is shown to be NP-hard, two multi-objectives genetic algorithms with two approaches in selection of parents and crowding distance index are proposed to solve this problem. In these two meta...
In this Thesis a multi objective production planning and job shop scheduling problem is investigated. The objectives are minimization of the production cost and minimization of production time smoothness in consecutive periods. As the problem is shown to be NP-hard, two multi-objectives genetic algorithms with two approaches in selection of parents and crowding distance index are proposed to solve this problem. In these two meta...
A Hybrid Approach of Similarity-based and Scenario-based Algorithms in Alert Correlation
, M.Sc. Thesis Sharif University of Technology ; Jalili, Rasoul (Supervisor)
Abstract
The rapid growth and increase in complexity of modern network and communication systems have made a demand for protecting organizations’ sensitive data and resources from malicious intrusions. Attackers and intruders perform malicious attacks by exploiting vulnerabilities, weaknesses, and flaws in computer systems using novel and advanced techniques. Traditional security mechanisms, such as authentication, access control, and firewall cannot prevent these attacks. Therefore, Intrusion detection systems (IDSs) are employed to detect abnormal activities and monitor network traffic and hosts’ events. These systems suffer from several limitations, including generating a huge amount of alerts and...