Sharif Digital Repository

The tolerance stack-up in mechanical assemblies is closely related to the quality of finished products and to the costs of production. In practice, choosing a large tolerance range will result in performance reduction. On the other hand, with small tolerances considered, production costs will increase. Tolerance allocation is a useful tool to control the dimensional and geometric variables of the product, so design engineers can control the final product quality level, production cost, and other variables. The proposed method for tolerance design considers the effects of degradation and quality loss over time and allocates tolerances so that, the functional key characteristic satisfies, as... 

Vortex engine has shown to be a credible substitute in thermal power and aerospace industries mainly due to their advantages such as better mixing, improved combustion, and considerable cooled walls of combustion chamber. The engine geometry and tangential inlet oxidizer create inner and outer vortices rotating in the same angular direction. The inner vortex moves from head to the end of engine in the axial direction and outer vortex moves in the opposite direction. In the vortex engine, vortices affect spray droplets and force them to have a spiral path and apply a centrifugal force on the droplets to push them towards sidewall. Also axial relative velocity of droplets and flow filed act as... 

Dealing with complicated organizational situations in the current competitive and uncertain market requires making the best management decisions at the earliest time possible. As making the best decisions requires the possession of adequate and accurate knowledge, knowledge has become the most valuable asset of organizations. Knowledge Management (KM) spans managing the identification, capture, storage, sharing, usage and creation of knowledge. Using an appropriate Knowledge Management System (KMS) can ensure the provision of essential knowledge for decision making, and can manage the complexity of the competitive market by maintaining and managing the relevant organizational knowledge.... 

Destruction of green lands, especially forests, is one of the most common forms of environmental degradation. Meanwhile, political institutions can play an important role in protecting or destroying the environment, especially forests. The creation of town and village councils as a change in political institutions and decentralization can have an impact on the environment. Land use change, implementation of development projects and the task of overseeing the implementation of environmental protection laws are among the duties and powers of councils that affect the coverage of various areas. At different eras, town and village councils’ elections have been annulled or dissolved in a... 

Design and parametric study of a coupled thermoacoustic refrigerator system has been carried out based on thermoacoustic theories. The purpose of coupled thermoacoustic refrigerator design is to cool a container with small dimensions for use in cold storage above zero. The application of this refrigerator is where the waste heat of piston engines of distributed generation (DG) plants can be used as energy input. The design is based on the simplicity and low cost of the refrigerator. Therefore, the engine and refrigerator part of the coupled thermoacoustic refrigerator is enclosed in a resonator with a fixed diameter, which is closed on both sides of the resonator. Two standing-wave... 

People's lives have been affected by the spread of the Covid-19 virus. Due to the high infectivity, governments have screened people, imposed curfews, mandated the use of masks, and so on to reduce the rate of transmission of the disease among people. Meanwhile, infected people are getting treatments: people who are slightly affected are quarantined at home, and those who are heavily affected are treated in hospitals. Hence there is an excessive increase in the hospital workload. On the one hand, this increased workload leads to physical fatigue and, on the other hand, to psychological problems, stress, etc. for the healthcare professionals. Therefore, it is very important to take care of... 

In today’s methodical corporate world, processes have been recognized as valuable organizational knowledge assets. Situational Method Engineering (SME) processes are considered particularly valuable because of their effectiveness in building context-specific software processes for developing efficient software systems; thus, they indirectly affect all software-dependent organizational knowledge assets, including organizational processes. It is therefore logical to deduce that managing SME knowledge would improve the efficiency of both SME and organizational processes. Unfortunately, existing SME processes suffer from weaknesses that are rooted in loss of knowledge within method engineering... 

The exploration of bipedal robot locomotion is primarily motivated by a variety of sociological and commercial imperatives, such as the aspiration to substitute humans in hazardous occupations (e.g., mining, nuclear power plant inspections, military operations) and advancements in dynamic control for purposes like rehabilitation with robotic assistance and nerve stimulation. The complexity arising from a high number of degrees of freedom, intricate nonlinear dynamics, and persistent challenges in modeling ground interactions pose significant obstacles in the development of control strategies for bipedal systems. With the increasing integration of robots into diverse sectors like education... 

Robust model predictive control(RMPC) is a control strategy that has been widely adopted in industry and academic researches.In this project we have modified robust nonlinear model predictive control using SOS and dynamic feedback. In this control strategy we will linearize the nonlinear model of the system about it’s operating point. We will consider the error of linearization as an uncertainty and find an upper bound for uncertainty. Then we will change control objective to minimizing this upper bound. The most advantage of changing the control objective is that nonlinear system results a non-convex optimization problem but this strategy terminates a convex optimization problem. To find...