Sharif Digital Repository

The question of the time is one of the obscure and challenging subjects which has been discussed as a mysterious problem in various civilizations. In ancient Greece, the question has been debated among the supporters of existence and eternity. We observe the words of Plato, on the existence of the absolute essence of eternity against the change and transition time instantiated as a conducted river in the Heraclitus view. Other discussions focused on the relationship between the change and displacement, or the the spatial relations to which Aristotle paid attention. With the passing of time from the ancient and medieval eras to the Renaissance period, along with the growth of the science in... 

In recent decades, due to economic, political and environmental issues, tend to use of the CHP systems (combined heating and power) have increased. CHP systems not only increase energy efficiency, but also decrease fuel consumption and emission levels of systems. The use of CHP technology in the industry has a long history, but the use of these systems in the commercial and residential sector, is considered, recently. As to the residential buildings, both electricity and thermal energy demands fluctuate seasonally and hourly, so it is necessary to take account of the plant’s annual operational strategies for the variations of load demands. In this paper, a nonlinear programming model is... 

With the popular choice of using underground structures and tunnel in big cities and with significant damage in recent large earthquake; therefore more attention is given to the behavior of the underground structure in seismic area. The purpose of this thesis is to present the Soil-Tunnel-Structure Interaction analysis performed for different dynamic load condition. Therefore we modeled a 3D intersection part of two different tunnels in homogeneous soil by ABAQUS software. The soil and concrete structure of tunnel is modeled by three dimensional solid finite elements and the boundary of soil is modeled by three dimensional infinite elements with 8 nodes. The results demonstrate the geostatic... 

A brief overview of the proposed research, its aims, engineering relevance and applications Underground space has long been exploited through the history to fulfill different human necessities. Underground facilities built in areas subject to earthquake activity must withstand both seismic and static loads. Some underground structures have experienced significant damage in recent large earthquakes. Tehran is located in seismic zone and investigation and research on the subject has significant role in design and construction of underground spaces for earthquake loads. Underground structures are complex structures which consist of different parts Such as passage way and platform space. Passage... 

Cable-driven robots are referred to as parallel robots actuated with cables. In fact,in such robots rigid links are replaced by cables, which may be extended to desired lengths without making mechanism much heavy. This robot possesses a number of unique properties that makes it suitable for many industrial applications. The main factor which makes cable robots analysis different from other parallel robots is the incapability of cables to push objects. Hence, obtaining the workspace of a cable robot is one of the most important subjects associated with this type of robot.The goal of this thesis is to design a spatial translational cable driven robot, which may be used for object handling. For... 

Uncertain fuel prices and also global climate changes are accompanied by some state initiatives such as renewable portfolio standards (RPS). This has caused a fast growth in the amount of renewable energy installed worldwide especially wind energy over last decades. However, the intrinsic characteristics of wind farms output power, i.e. intermittency and volatility of wind speed along with being non-dispatchable in output generation of wind turbine raises many new technical and financial challenges for power system operators and planners. Up to these issues, large level of wind power penetration causes a growing concern in wind energy curtailment issue which the wind farm’s operator may be...