Dynamics of null hypersurfaces in general relativity

, Article General Relativity and Gravitation ; Volume 34, Issue 2 , 2002 , Pages 243-253 ; 00017701 (ISSN) Nozari, K ; Mansouri, R ; Sharif University of Technology

2002

Abstract

This paper shows how the structure and dynamics of a lightlike thin shell in general relativity can be obtained from a distributional approach

The methods of gluing manifolds in general relativity

, Article Journal of Mathematical Physics ; Volume 43, Issue 3 , 2002 , Pages 1519-1535 ; 00222488 (ISSN) Nozari, K ; Mansouri, R ; Sharif University of Technology

2002

Abstract

Some areas of modern theoretical physics such as modern cosmology contain different manifolds which must be glued together along a common boundary. These boundaries can be spacelike, timelike, or lightlike hypersurfaces. This paper shows how this gluing for different hypersurfaces is possible. Two different approaches are considered and the extent to which these approaches are equivalent are discussed. In particular, we will construct a distributional approach for dynamics of lightlike hypersurfaces in general relativity. Since Einstein's equations are nonlinear PDEs, for discontinuous metrics such as signature changing metrics, product of distributions are unavoidable. To glue two different...

Experimental Study on Erosion Control at Channel Junctions with Submerged Vanes

, M.Sc. Thesis Sharif University of Technology Nozari, Soheil (Author) ; Jamali, Mirmosaddegh (Supervisor)

Abstract

In this study, the effect of submerged vanes on the bed erosion pattern at a 90° open-channel junction has been evaluated experimentally. In this study, 41 tests have been conducted in four different steps. In each test, the bed surface level has been measured at the end of 1st, 2nd and 24th hour. In the first step, the preliminary tests have been conducted. In this step, six different formations of submerged vanes have been selected and their performance has been evaluated and the most efficient formation, in the field of maximum scour depth reduction, has been selected. In the second step, six different formations of submerged vanes have been selected and their performance has been...

Experimental Study of Flame Stability on a Reheat System

, M.Sc. Thesis Sharif University of Technology Nozari, Hadi (Author) ; Farshchi, Mohammad (Supervisor)

Abstract

In conventional afterburning systems, the burnt products of the primary combustion enter the afterburning zone, where the fuel is injected and the mixture is ignited to form a flame which is stabilized by a flameholder.
The present experimental study focuses on concepts of afterburning and flame stability in a reheat system. For this purpose an afterburner setup is designed and manufactured. The setup comprises of two main regions; the preheating region and the reheat zone. Fuel used in preheater is LPG while jet fuel is injected in reheat zone. Through the tests the key parameters which are adjusted to be in similar ranges as the conventional afterburners are the oxygen amount of the...

Stake Size Effect on Guilt Aversion in Psychological Games Master Thesis

, M.Sc. Thesis Sharif University of Technology Nozari, Salar (Author) ; Talebian, Masoud (Supervisor)

Abstract

Guilt aversion, the process of avoiding guilt, when guilt indicates the human sense which is present when they let down other's expectations. As the definition suggests, guilt is related to what one thinks of the others’ thoughts; i.e. the second-order beliefs. Incomplete information models of guilt aversion are the most reliable ones in the literature due to economic experiments. Based on these models, the dictator game and the trust game are applied to measure the degree of guilt aversion. In both the above psychological games, there are two players where Player A has the power to decide about the split of the money. We use the amount of transferred money to Player B is as a sign of guilt...

Optimization of Xylitol Production

, M.Sc. Thesis Sharif University of Technology Nozari, Nafise (Author) ; Alemzade, Iran (Supervisor)

Abstract

Xylitol is a sugar alcohol or polyol that has been used as a food additive and sweetening agent due to Its high sweetening power, anti-cariogenic properties and possibilities for use in diabetic food products, makes xylitol an attractive sucrose substitute in a wide variety of foods and beverages. Xylitol is a five carbon polyol or pentitol obtained by the hydrogenation of xylose. xylitol could be produced from xylose in rice seed coats medium by Saccharomyces cerevisiae. For xylitol production, S.cerevisiae was grown in preculture medium at 30°C and agitated at 120 rpm on a rotary platform shaker. The cells were harvested after 20hr, were centrifuged and transferred to the production...

Kinetic Study of Selective Catalytic Reduction of over a Cu/Zeolite Catalyst for Emission Control from Diesel Engines

, M.Sc. Thesis Sharif University of Technology Nozari, Sara (Author) ; Hamzehlouyan, Tayebeh (Supervisor)

Abstract

Urban air pollution has become a significant environmental concern in recent times. NOx recognized as a criterion pollutant, is especially problematic. In 2021, the Tehran Air Quality Control Company reported that the ambient concentration of NOx in Tehran was around 50 ppb, which surpasses both the initial and final targets recently established by the World Health Organization (40 ppb and 10 ppb, respectively). To control and predict NOx emissions from diesel engines, A detailed selective catalytic reduction (SCR) model has been developed to describe the global kinetic reactions within the catalyst. This model incorporates two types of sites for high- and low-temperature NH3...

Collision-free path planning of a novel reconfigurable mobile parallel mechanism

, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 231, Issue 20 , 2017 , Pages 3728-3742 ; 09544062 (ISSN) Nozari Porshokouhi, P ; Tale Masouleh, M ; Kazemi, H ; Sharif University of Technology

2017

Abstract

This paper initially deals with the design of a new customized reconfigurable mobile parallel mechanism. This mechanism is called the 'Taar Reconfigurable ParaMobile' (TRPM), consisting of three mobile robots as the main actuators. Then, the kinematics and path planning for this mechanism are presented. The newly proposed mechanism is expected to circumvent some shortcomings of inspection operation in unknown environments with unexpected changes in their workspace, for example, in a water pipe with a non-uniform cross-sectional area. In this paper, 'Artificial Potential Field' (APF) has been assumed to be the path planning algorithm and its resulting attractive and repulsive forces are only...

Study of the Effect of Presence of Nano- Particles on the Mass Transfer and Hydrodynamics of Drops

, M.Sc. Thesis Sharif University of Technology Nozari, Ali (Author) ; Bastani, Daruoosh (Supervisor) ; Goodarznia, Iraj (Supervisor)

Abstract

Regarding to the effect of nanoparticles on mass transfer and hydrodynamics characteristics, limited number of studiesavailableinthe literature.In this work, mass transfer performanceand hydrodynamic characteristics nanoﬂuidshavebeeninvestigated in the liquid−liquid extraction process. The chemical system of toluene-acetic acid-water was used, and two Extraction columnswith diameter of 10cm and height of 55cm and 6 cm were designed. The drops were organic nanofluids containing silica nano-particles and carbon nano-tubes.Synthesized silica nanoparticles by sol-gel methods, were modified with Triethoxyoctylsilane and Polydimethylsiloxane as well as Carbon nano-tubes were modified with dodecyl...

Introduction and Analysis of Energy Index to Evaluate Arm Motion Quality in Neuromuscular Patients

, M.Sc. Thesis Sharif University of Technology Nozari Porshokouhi, Pouria (Author) ; Behzadipour, Saeed (Supervisor) ; Hoviattalab, Maryam (Supervisor)

Abstract

Quantitative motion quality evaluation has been always of much significance for CVA patients, especially the HCP ones. The purpose of the present study is to introduce and analyze the efficiency of a novel index, namely “Consumed Energy Index”, for evaluating the quality of the motions performed by HCP patients. For this purpose, Firstly, a Musculo-Skeletal model of the human arm was provided on Matlab and OpenSim softwares, with four DoFs: three DoFs at shoulder and one DoF at elbow joint as well as eight muscles. The muscles are in pairs of flexor-extensor at each DoF. The model is capable of receiving Cartesian trajectories for joints and solving inverse kinematics and dynamics to obtain...

Aeroelastic Analysis of Horizontal Axis Wind Turbine Based on Actuator Disk Method

, M.Sc. Thesis Sharif University of Technology Nozari, Mostafa (Author) ; Ebrahimi, Abbas (Supervisor) ; Rezaei, Mohammad Mahdi (Co-Advisor)

Abstract

The issue of solid and fluid interaction in horizontal axis wind turbines with diameter of more than 120 meters is one of the most important researching subjects of this type of turbines. This issues needs quick and exact solutions because of the high computational cost of fluid and structural domains.In this research a quick method with acceptable accuracy has been suggested which is based on computational fluid dynamic to examine the aeroelastic behavior of rotor and wind turbine tower. The actuator disc method in two domains of axisymmetric and three-dimensional has been used to compute aerodynamic forces. For this purpose a code has been written in C++ to set down virtual momentum on...

Collision-free path planning of a novel reconfigurable mobile parallel mechanism

, Article International Conference on Robotics and Mechatronics, ICROM 2015, 7 October 2015 through 9 October 2015 ; 2015 , Pages 389-394 ; 9781467372343 (ISBN) Nozari Porshokouhi, P ; Kazemi, H ; Masouleh, M. T ; Novin, R. S ; Sharif University of Technology

Institute of Electrical and Electronics Engineers Inc 2015

Abstract

This paper initially deals with the design of a new customized reconfigurable mobile parallel mechanism. This mechanism is called "Taar Reconfigurable ParaMobile (TRPM)", consisting of three mobile robots as the main actuators. Then, the kinematics and path planning for this mechanism are represented. The newly proposed mechanism is expected to circumvent some shortcomings of inspection operation in unknown environments with unexpected changes in their workspace, e.g., in a water pipe with non-uniform section area. In this paper, "Artificial Potential Field (APF)" has been assumed to be the path planning algorithm and its resulting attractive and repulsive forces are only applied to the...

Periodic solutions for a semi-ratio-dependent predator-prey dynamical system with a class of functional responses on time scales

, Article Discrete and Continuous Dynamical Systems - Series B ; Volume 9, Issue 2 , 2008 , Pages 267-279 ; 15313492 (ISSN) Mostafa, F ; Hesaaraki, M ; Sharif University of Technology

2008

Abstract

In this paper we explore the existence of periodic solutions of a nonautonomous semi-ratio-dependent predator-prey dynamical system with functional responses on time scales. To illustrate the utility of this work, we should mention that, in our results this system with a large class of monotone functional responses, always has at least one periodic solution. For instance, this system with some celebrated functional responses such as Holling type-II (or Michaelis-Menten), Holling type-III, Ivlev, mx (Holling type I), sigmoidal [e.g., Real and mx2/((A + x)(B +x))] and some other monotone functions, has always at least one ω-periodic solution. Besides, for some well-known functional responses...

Modified Load Scheduling Using Smart Meters

, M.Sc. Thesis Sharif University of Technology Bahrami, Shahab (Author) ; Parniani, Mostafa (Supervisor)

Abstract

Implementation of various incentive-based demand response strategies has great potential to decrease peak load growth and customer electricity bill cost. Using advanced metering and automatic demand management makes it possible to optimize energy consumption, to reduce grid loss, and to release generation capacities for the sake of providing sustainable electricity supply, and reducing electricity bills for the customers. With these objectives, this thesis examines the previously suggested load scheduling programs in both residential and industrial sectors, and proposes new practical strategies for load management. This thesis has mainly focuses on three subdivisions of load management...

The Analysis of Total Productive Maintenance Based on Computerized Maintenance Management System

, M.Sc. Thesis Sharif University of Technology Behshad, Amir (Author) ; mostafavi, mostafa (Supervisor)

Abstract

The main purpose of this thesis is to analyze the total productive maintenance based on computerized maintenance management system. At first, a detailed study on total productive maintenance is performed and then the requirements of this maintenance strategy are specified. Also, a computerized maintenance management system is defined which can help total productive maintenance to reach to its requirements. Finally, a conceptual model and entity-relationship model for computerized maintenance management system data base has been created

Study of HVDC Transmission for Offshore Wind Farms Based on Voltage Source Converters

, M.Sc. Thesis Sharif University of Technology Safaeian, Reza (Author) ; Parniani, Mostafa (Supervisor)

Abstract

In this thesis, DC transmission of offshore wind farms is studied thoroughly. Various system configurations that are introduced in the literatures are discussed and their control scheme for normal conditions and grid faults are studied. Then, the HVDC transmission based on voltage source converter, located between a local offshore ac grid and the onshore ac system is investigated as the most practical choice. The HVDC linke circuit elements are calculated and the control strategies of the offshore and onshore converters are introduced. DFIGs are considered to be the best choice for the offshore wind turbine generators. Then, the system is simulated and the frequency of the offshore grid is...

Feasibility Study of Producing Active Pharmaceutical Ingredient from Conceptual Process to Mass Production-Case Study

, M.Sc. Thesis Sharif University of Technology Tavakoli, Meysam (Author) ; Mostafavi, Mostafa (Supervisor)

Abstract

The main aim of this thesis is to develop the technical knowledge of designing and making active ingredients of domestically produced drugs, decreasing the costs, independency in producing these products, and checking outflow of currency. It also aims to reduce the financial challenges of patients who have to pay huge amounts for such drugs. Conducting research in the field of reverse engineering and using its definition, and attempt in made to get knowledge into the stages of product development process, to determine the technical standards associated with each stage, to recognize how knowledge is shared during this process, and to present some methods of establishing the infrastructure...

Performance Improvement of Maximum Power Point Tracker in Grid-Connected Photovoltaic Systems

, M.Sc. Thesis Sharif University of Technology Mohammadian, Hossein (Author) ; Parniani, Mostafa (Supervisor)

Abstract

Increase in growing concerns over environmental pollution and depletion of fossil fuel resources motivate the need for cleaner energy technologies and stimulate research in facilitating renewable energy systems. In recent years, photovoltaic systems have attracted great attention since they remove the need for energy storage systems and intermediate processess for energy conversion. However, high capital cost, low efficiency and low energy density per area of these systems, as compared with other technologies hinder its industrial use. To surmount these bottlenecks and improve technical performance of PV systems, it is crucial to optimize configuration of convertor connection and to improve...

Coordinated Voltage Control of Power Systems in Normal and Emergency Operation States

, Ph.D. Dissertation Sharif University of Technology Rabiee, Abbas (Author) ; Parniani, Mostafa (Supervisor)

Abstract

One of the main objectives in operating a power system is to maintain the system voltage properly to avoid equipment damage and transfer power efficiently. Automatic control of transmission network voltage provides significant improvements in security, quality and efficiency of power system operation. This thesis investigates coordinated voltage control of power systems in normal, alert and emergency states. The aim is to propose a comprehensive framework for real-time operation of practical power systems, ensuring secure operation of the system in the normal state and after occurrence of sever contingencies.
At the first, a new coordinated voltage control scheme is proposed to ensure...

The Analysis of Knowledge Management, Dimensions and Implementation Methods-Case study: Sardsaz Khodro Ind. Co

, M.Sc. Thesis Sharif University of Technology Saghafian, Hamideh (Author) ; Mostafavi, Mostafa (Supervisor)

Abstract

Today, organizations are surrounded by basic and continuous changes such as declining organizational resources, reduction of the production cycles, and the need for rapid adaption. Those organizations remain competitive while maintaining their productivity, that have following characteristics: accurately plan and assess their knowledge resources, create and absorb beneficial knowledge, store and organize their knowledge, disseminate knowledge to needed areas, and use knowledge in practice and decision making, to improve their products/services as well as their performance. Therefore, the human capital has been considered as knowledge owners and the most important organizational resource, on...