Sharif Digital Repository

In general, Constrain Satisfaction Problems (CSP’s) are NP-complete, however, this is not the case, if we impose some restrictions on the constraints. Due to importance and applications of CSP’s in different areas of engineering and science including artificial intelligence, relational databases and logic, investigating the computational complexity of CSP’s is an important issue. Computational complexity of CSP’s has been investigated from a variety of aspects, including the Universal Algebraic approach that has given rise to a solution of dichotomy conjecture recently. In this thesis based on contributions of Bulatov, Krokhin and Jeavons, we try to explain this universal algebraic approach... 

One of the most practical deformation processes has been used to produce profiles with a diversity of shapes is forward extrusion. Minimizing the extrusion pressure along with reducing the curvature of the final product have always been the main concerns of the researchers in this area. To achieve the former, researchers have designed nonlinear dies and proposed various equations to determine proper die profile. To accomplish the latter, they have used bearing at the exit section of the extrusion die. The primary object of the current study is to design a proper bearing in order to eliminate the curvature of the final product in extrusion process. The effects of both bearing and die profile... 

Undoubtedly, machine learning and its practical applications have become essential topics in research and industry. Among these, representation learning holds special importance. The goal in this field is to find low-dimensional and meaningful representations of high-dimensional data that encapsulate essential information. Most existing methods focus only on the statistical correlations in data, which do not necessarily indicate real relationships between variables and can affect learning performance. This becomes even more problematic when the distribution of test data differs from the training data, as it makes the learned representations less generalizable. To tackle this problem, causal... 

In this thesis, hemodynamic parameters of flow and deposition of low density lipoproteins (LDL) on wall of coronary arteries with taking into account their curvature on the heart are studied. At first, numerical solution of the blood flow by assumption of blood as incompressible and Newtonian fluid for steady and pulsatile inlet is done. Then by assuming LDL particles as dilute solute in the blood, LDL transport from artery lumen into arterial wall is studied. LDL accumulation and penetration into the vessel wall cause thickening of the walls and eventually eclipse it and its known as the first stage of atherosclerosis disease. The results show that low shear region occurs on inner wall... 

The constant and proper functioning of data center infrastructures is considered a vital element in the modern processing of data and information. Failure in the electricity supply system is the key reason for workload processing stalls in data centers. Energy supply systems, therefore, need to be highly reliable in terms of adequacy and security. Nonetheless, data centers tend to become volatile and, to some degree, unresponsive in the face of a multitude of such errors occurring simultaneously which in turn could lead to higher rates of processing interruptions. Recent years have witnessed an increase in the number of natural occurrences with high impact and low probability (a.k.a., HILP... 

One of the most important problem in oil and gas well drilling is well cleaning and pipe sticking. This problem more sensitive when depth is increase. When a well is drilled, cuttings must be transported to the surface. For this reasen use drilling mud to circulate in well and transport the cuttings. Drilling mud exit from bit nozzle, wash and clean the well. Well cleaning depends on this parameter: fluid viscosity, annulas flowrate, well inclination, cutting size and shape, cutting density and mud density.The aim of this thesis is study and simulate of cutting transport phenoimena while drilling is running with comertial software like Fluent and Comsol. We study forces acts on cutting...