Sharif Digital Repository

With intensified concerns of rising fuel vehicles that reduce fossil fuel globally and also prescript strict rules by standard institutes, vehicle manufacturers try to find a way for reducing the fuel of their products. One these methods use a continuously variable transmission (CVT) instead of manual and automatic gearboxes. Various CVT’s have been proposed in recent year.
One of the proposed systems is traction infinitely variable transmission (TIVT) that is type of traction drive continuously variable transmission and has been presented in 2007. Research on this system showed that average efficiency is about 96% that is high efficiency. Completed research in 2011 showed that despite... 

The investigations on hydrophobic surfaces have attracted lots of intrests in science and technology. Silica sols have been used extensively in the area of producing hydrophobic coatings. On the other hand, carbon-based materials have attracted of a great deal of scientific interest in recent years. The purpose of this research is synthesis and investigation on the properties of Silica- Graphene Oxide nanocomposite coating.Graphene Oxide synthesized by using Hummer’s method. Silica nanoparticles were prepared using sol-gel process and tetraethylorthosilicate (TEOS) as precursor. The surface hydroxyl groups of silica nanoparticles are replaced with Methyl groups by treatment with... 

Hyderogels are hydrophilic polymers with three dimensional network structure, due to their high water absoption, their application to life and industry is increasing from day to day, such as tissue engineering, actuators and sensors, drug delivery and therapeutic treatment. In this project, it has been attempted to produce polyacrylamide/alginate double network hydrogels with the use of graphene oxide nanosheets to indicate that it is possible to combine toughness and self-healing in a hydrogel with the opposite nature of each other. To evaluate mechanical properties, uniaxial tensile test and loading-unloading test were used. The results indicate that increase the weight ratio of acrylamide... 

In recent decades, many building projects have been implemented in the form of partnership agreements between the land owners and the private contractors, investing in the buildings’ construction. The growing trend of implementing such projects is due to the increased price of land and the constructors’ inability to separately buy a piece of land and implement their individual building projects. On the other hand, many owners cannot afford the construction cost of building projects. At present, this form of building partnership agreement arranged and concluded between the landowner and the contractor is not normally signed through balanced and thoroughly thought contract documents. This... 

In accomplishment of knowledge management in real world, organization can be in different processes of awareness about importance of knowledge management and its achievements. Recognition of strength and weakness points of organization helps to logical planning and success in performance of knowledge management. For avoiding from failing in knowledge management projects, it is necessary that before stating for project performance, evaluate development level of organization from viewpoint of knowledge management, and determine some approaches for control of general problems of knowledge management, like abundance of information, work complexities, knowledge Storage.
In literature of... 

In modern society, engineers, technical managers are responsible for planning, design, construction, exploitation of simplest to most complex systems. Crashes cause disruption of systems at different levels and can be considered as a serious threat to society and the environment, thus consumers and people expect reliable products and systems. There are different methods for increasing the reliability of systems, one of them is related to their quality and another way is related to use of standby systems. Also maintenance and repairing have major role for keeping up reliability or availability of systems. In the first part of project, optimization the reliability of system by standby... 

Aluminum alloys have many applications in various industries such as automotive and aerospace due to their high strength to weight ratio. Today, much research is being done on the strength of metals and alloys after severe plastic deformation. Among these studies, limited work has been done on the hot deformation behavior of alloys that have undergone a severe plastic deformation process. In this research, aluminum alloy 2024-O is subjected to various passes under a type of severe plastic deformation process called multi-directional forging. Samples were divided into zero passes (annealed), one pass, three passes and five passes. After preparing pressure samples from them, hot pressure with... 

This research considers the permutation flowshop scheduling problem with sequence‐dependent set‐up times .In this model, every job has a distinct due date and a tardy penalty rate. A mathematical model is developed for the proposed problem. As it has been proved to be strongly NP‐hard, only small‐size problems can be solved with the mathematical approaches. Thus, a meta heuristic algorithm based on the Particles Swarm Optimization (PSO) algorithm is developed to solve the real size problems. Particle swarm optimization (PSO) has been developing rapidly and has been applied, as it is easily understood and realized. Since the PSO algorithm has been introduced for the continuous solution space,... 

The “hypothalamus-pituitary-adrenal” axis is one of the most important axes of the human body, and cortisol is one of its key products, which plays an essential role in the immune system, stress management, and many diseases. Appropriate modeling and simulation of this axis can help us to understand how the body reacts to stress and inflammation, to examine relevant diseases, and how drugs affect the body. In this study, by combining an axial model of the hypothalamic-pituitary-adrenal axis with a model of adrenal cells, a bi-level model including several time delays has been developed that can predict the effect of stress on this axis. Some parameters of the model have been modified through...