Sharif Digital Repository

The phenomenon of soil liquefaction has caused significant damage to deep foundations of engineering structures such as bridges and buildings in past earthquakes. In recent years, many researchers have studied the effects of soil liquefaction on the pile response, but there are still many unknowns that require further research and study. The present study is part of a comprehensive research that involves several Ph.D. and master students at Sharif University of Technology (SUT). In this study, the effects of soil liquefaction on two pile 2×2 groups (one with a lumped mass and another without) in a level ground with a sloping bed were investigated. A surface non-liquefied layer was also... 

The parameters within the reactor core can be categorized into two distinct groups of measurable parameters and unmeasurable parameters. The determination of unmeasurable parameters, such as void fraction and critical heat flux, plays a pivotal and fundamental role in predicting the occurrence of accidents and emergency situations within the reactor. The utilization of deep neural networks represents one of the methods for accurately and reliably estimating these parameters within future temporal intervals. Such estimations facilitate the implementation of necessary measures to prevent accidents or mitigate their consequences. In this study, we employ three deep neural network models namely... 

Concrete dams are one of the most important infrastructures in any country. In recent years new safety standards, such as the analysis of concrete dams in various modes of potential failure or performance-based design are proposed. Many of existing dams may fail to meet revised safety criteria. For this reason it is necessary to control built dams with this new standards. In this reseach, fragility assessment is used for rational safety evalution and decision-making. fragility curves are defined by the probability of a structural limit. We examined the fragility curves for the nonlinear behavior and safety of the dam under earthquakes. fragility curves based on the cracking area are more... 

In finance literature there are different views of individual and institutional investors for variety of reasons. Despite having consensus on the difference of individual and institutional investors due to complexity and size, it seems there are much disagreement on how they affect the key process of market like return and liquidity. In this paper we consider the effect of individual and institutional trading on the short-term return of stocks. Specifically, first we define some factors to measure the trading activity of individual and institutional investors. Then we use these factors to sort each stock in the cross section to create decile portfolios and we compare the short-term return... 

In recent years, machine learning techniques have been available to predict and interpret the structural behavior of dams. The main goal of this research is to predict structural behavior through modeling with data read by accurate instruments of dams. This requires the selection of several machine learning methods such as Random Forests (RF), Boosted Regression Trees (BRT), Artificial Neural Networks (ANN), Support Vector Regression (SVR), and Decision Tree Regression (DTR) algorithms. In this research, considering the 24 target variables defined from the detailed instrumentations studied, the behavior of the dam is modeled using selected machine learning models. These precision instruments... 

In present thesis, the effect of cosmological constant, Λ, in bending of light by spherical symmetric mass has been studied. At first we obtain the Schwarzschild-de Sitter solution as spherical symmetric solution of General relativity field equations with cosmological constant, without we suppose the solution is static. Then we obtain gravitational lens equation by considering the space geometry and we benefited from several approach to specify the contribution of cosmological constant to the deflection angle. Furthermore we put new upper bounds on the value of the lambda independently of cosmological constraints. Finally for study the contribution of lambda in gravitational lensing... 

Planning safe rendezvous and docking trajectories between two spacecrafts has a high importance in the space applications. In order to make two spacecrafts moving in different orbits closer, two stages must be completed simultaneously: First the implementation of rendezvous maneuver which deals with the generation of control/guidance commands leading to trajectories that lead the chaser towards the target. Second the docking maneuver incorporation which makes the two spacecrafts closer with the relative zero attitude. Various approaches have been dealt with till now using the analytical and numerical approaches generally considering rendezvous, not the docking maneuver. These approaches... 

Today, the global environmental restrictions as well as; energy problems have directed researchers toward developing ideas of producing a clean liquid fuel from coal or natural gas as a major research topic. In this regard, a special attention is paid to the dimethyl ether (DME) as a clean material containing 34.8% oxygen possessing enough positive potential to replace the diesel and LPG fuels. One of the most economic routes for producing the DME is known to be the direct conversion of the synthesis gases and carbon dioxide first to the methanol and then its dehydration to the DME. Moreover, the DME is not limited to a particular country or resource area since small reservoirs of natural... 

In recent years, ability of computers to recognize human actions, because of numerousapplications, has attracted scientists. Surveillancesystems in house, work and public places, human computer interaction, study of human movement problems, remote supervision of ill or old people and sport training are only some of the applications. In this thesis 10 actions are considered. These actions are Walking, Running, Galloping side, Bending, Jump jacking, Jumping, Jumping in place, Skipping, Waving one hand and Waving two hands. All actions exist in Weisemann dataset so this dataset is used as training and testing dataset. Here important objectives are recognising human action so that it is... 

We have tried this for the first time to reperesent a comprehensive description of the evolution of a perfect fluid in inhomogeneous relativistic models.We solve Einstein equations using numerical methods.In this procedure we can evaluate the effect of pressure in perfect fluid evolution.Also we look at the behavior of the various horizons, and in the end we will present a cosmological model to a black hole  

Knowledge about travel demand patterns is an important requirement for strategic planning and management of urban transportation networks. Use of theoretical trip distribution models such as growth, gravity or intervening opportunities, estimation with the help of questionnaire surveys and development of volume- based O-D estimation methods have been major fields of scientific efforts in recent years.Rapid changes in land use and transportation networks especially in developing countries has raised the importance level of knowledge about changes in travel demand.Traditional approaches are costly, time consuming and suffer from inaccuracies, so,... 

The running time of almost every algorithm in the graph theory depend on the number of edges. Thus, these algorithms are often too slow when the input graphs are dense. Therefore, it is useful to reduce the number of edges by sparsification. In fact, sparsification is the task of approximating a graph G = (V;E) by another graph ~G = (V; ~E) so that ~E E (j~Ej jEj) and ~G maintain a main prefixed property of G. Depending on these properties several notions of graph sparsification have been proposed. In this thesis we study a notion of sparsification that is called spectral sparsification which is based on the contributions of Daniel A. Spielman et.al..In this notion of sparsification...