Sharif Digital Repository

In this thesis a 2-3PRS hybrid mechanism is presented. This manipulator is consisted of two serially connected parallel 3PRS mechanisms, each mechanism has three degrees of freedom, so that the overall degrees of freedom of the manipulator are six. The relations for position, velocity and acceleration of the mechanism in both forward and inverese kinematics are derived and then singular points are determined. After that, the inverse dynamic equations for one of the 3PRS mechanisms are derived through the Newton-Euler and aslo Lagrange approach and the results are verified. Then the derived Newton-Euler equations are implemented for inverse and forward dynamics of the hybrid manipulator. The... 

Creating synchronous conditions of precision and speed in rotating systems is a requirement for the design of these systems. The requirement to create these conditions is essential in various applications, such as machine tools and computer equipment. One of the main sources of error in the motion of the high speed spindles is the occurrence of non-repetitive runouts. The presence of non-repetitive runouts at high speeds greatly affects the accuracy of the rotating motion of rotating systems and reducing its effects is always considered in the design of high speed rotary systems. Usually, one of the most important factors in the occurrence of non-repetitive runouts is related to spindle... 

Heat losses and pump electrical energy consumption are inevitable during the operation of a district heating(DH) network. Therefore, the appropriate design and operating strategy of a DH network is required in order to reduce the heat losses and pump energy consumption. This study is aimed at optimizing pipe diameters and mass flow rate in a DH network according to heat demand of the building in order to minimizing operating cost of the network.For this purpose first drawings of the building is modeled in Auto Cad software. Then according to the position of building to the sun, the building is modeled in Desighn Builder software. In this software the buildings charactersitics like materials... 

In the present thesis, A Computer software has been developed to evaluate technical and economic aspects of photovoltaic systems, off-grid and on-grid configuration, in urban areas where the electricity grid is accessible. As a case study the building of Energy Engineering faculty with annual demand of electricity in lighting section equals to 80048 kWh was considered. Regarding incident radiation and PV system characteristics with the aid of utilizability concept, a technical evaluation has been performed then life-cycle saving index was considered as a criterion for choosing an optimum nominal size of the system. Results show that for current electricity tariff of educational buildings ... 

Rehabilitation science has been proved that, in most cases, manipulation of injured body part, repeatedly, can help in returning the performance of that part. So robots can be useful for rehabilitation applications. Rehabilitation robots can record physical parameters such as position, velocity and force, so can play important role in developmentof making decisions on exercise types. Among the existing robots, cable-driven robots have specifications such as vast workspace, low cost, flexibility and light weight which make them suitable for rehabilitation applications.
The purpose of this research is kinematic design of a multi-link cable-driven robot for arm rehabilitation.In the most of... 

The optimal design of a ground-coupled heat pump (GCHP) system with vertical ground heat exchanger (VGHX) includes thermal modeling of the system and selection of optimal design parameters is presented in this research. Then, by applying Nelder-Mead optimization algorithm, an objective function (Total Annual Cost which is the sum of annual investment and operating costs of the system) is defined and minimized, exposed to specified design constraints. Also, Genetic Algorithm is used to verify the optimal design process. In order to evaluate the accuracy of a presented model, the optimum values of a heat pump design parameters includes saturated temperature/pressure of a condenser and... 

In this thesis, we determine the optimal capacity of the power plants considering site specifications and Flow Duration Curve and evaluating economic parameters. Finally a design with more sufficient economical and hydrualical performance would be selected. The optimization algorithm used in this thesis is called "Charged System search" that is one of the newest meta-heuristic algorithms. This algorithm is inspired by the coulomb and gauss's laws of electrostatics in physics and utilizes a number of charged particles which influence each other based on their fitness values and their separation distances considering the governing law of coulomb.The proposed method in this thesis can be... 

A gating system is network of canals which leads molten metal to mold cavity. Fluid flow during mold filling is highly complex, involving transients, combined and divided flows at junctions, simultaneous heat transfer during fluid flow, turbulence, momentum exchange and energy loss. In case of non-uniform fluid flow at ingates, it causes week mechanical properties, and non-directional solidification. Accordingly, it cause riser insufficiency . In this Work by solving Bernoulli equations, fluid flow at each ingate was obtained and Genetic Algorithm was utilized for fluid flow optimization. Using this optimization method leads to reach to ideal design, simultaneously SUTCAST software was used... 

Hydro power is a clean energy resource which has numerous advantages over other renewable energy systems including competitiveness with fossil fuel systems, high reliability, considerable potential, and availability of technology. These advantages have drawn attention to hydropower systems. Small Hydro Power (SHP) systems can be used for supplying the demand of rural and remote areas where electricity network rarely exists. SHP may also provide an investment opportunity. Comprehensive analysis of design features and operation of SHP and management of risks involved requires development and application of reliable analytical tools. The present research aims at developing a model for optimal... 

Powder metallurgy is one of the most important and most usable methods in industries. Nowadays, many of the specimens are made this way. In this method, after powder compaction stage, because of sintering in high temperature, crystallographical structure of the material changes. This change results in poorer strength than initial powde. In order to avoid change and decrease in powder strength, shock consolidation is used. In this research, because of complication of this phenomenon and final quality of the specimen, shock consolidation of metal powders is investigated and analysed. This phenomenon is modeled, simulated, analysed and optimized mathematically.Various methods are used to create... 

Several diseases and injuries may cause disability in locomotion (especially walking). Spinal cord injuries, brain stroke and disease like Parkinson are the most major causes. In the past, some efforts has been made to reduce the effect of organ’s disabilities, but today, there is the chance of healing the spinal cord injury By using new (Schwann Cell) method. Due to long time stillness and severe muscles weakness; condensed physiotherapy exercise is essential to recover locomotion abilities, particularly in walking. In this way, if the practices matches with the normal walking (especially weight bearing); it has more physiological and psychological effect. In order to achieve this goal, a... 

In this investigation, the behavior of pin loaded composite plates is studied numerically. A failure prediction model is used to predict the ultimate strength considering three different mechanisms of failure: bearing, shearout and net tension. The model consists of two major parts: stress analysis and failure analysis. The main difference between this investigation and others is considering more realistic assumptions in modeling of the problem. As an example, we consider nonlinear behavior in the shear stress/ shear strain relationship of each unidirectional ply and use this model in optimization problem to reach maximum strength. The results are compared with experimental results available... 

Recently, parametric excitation has been proposed and experimentally proven to provide micro gyroscopes with robustness to parameter variations and enhancement of sensitivity. harmonic excitation gyroscopes are very sensitive to response of a resonance at the resonant frequency; therefore it has to be created accurately. However, parametric excitation gyroscopes are not sensitive as a result of wide bound of frequency at drive mode, accordingly it is not necessary to be formed accurately in the same way as harmonic excitation gyroscope.
The produced stress at combs have a significance effect on robustness, sensitivity and calibration curves of parametric excitation gyroscope, as a... 

Nowadays, microgrids which comprise decentralized generation (DG) have attracted considerable attention. Establishment of DG-based microgrids that are normally connected to the main grid, is a practical method to reduce the costs of power outage and to increase the electricity supply reliability. The aim of this thesis is optimum planning of a microgrid containing wind turbines, photovoltaic systems and diesel generators, considering both the grid-connected and isolated modes of operation.
In the areas with considerable solar radiation and wind potential valuable opportunities exist in utilizing these resources. In addition to these renewable resources, the use of controllable resources...