Sharif Digital Repository

In today’s competitive world, productivity is one of the main components that guarantee the success and profitability of an industry or a project. This research has studied productivity of dam construction projects in Iran that are usually classified as mega projects. First, the major factors influencing productivity of dam construction projects in Iran were identified and evaluated. Three main sources of information namely; literature review, records and lesson learned from previous projects and experts’ opinions were used to identify these factors. Then, 41 main factors influencing productivity were selected and the effect of each factor was measured based on the results obtained from... 

We show that the equations of reinforcement learning and light transport simulation (rendering equation) are related integral equations. Based on this correspondence, a scheme to learn importance while sampling path space is derived. The new approach is demonstrated in a consistent ray tracing algorithm that uses reinforcement learning to progressively learn where light comes from. As using this information for importance sampling includes information about visibility, too, the number of light transport paths with non-zero contribution is dramatically increased, resulting in much less noisy images within a fixed time budget  

Recently, cooperative communications have gained much interest due to its ability to mitigate fading in wireless networks through achieving spatial diversity while resolving the difficulties of installing multiple antennas on small communication terminals. There have been considerable research efforts on the performance analysis of cooperative diversity. This is while most of the current works assume that perfect knowledge of the channel information is available at the destination and/or relay terminals. However, in many practical scenarios, due to the errors caused by Doppler shift or noise on the pilot signals the perfect estimation of channel coefficients is not possible. In this thesis,... 

In the present study liquid thermophysical properties in electrospray has been studied. Other parameters such as electrical configuration do not change during this study. For this purpose Alcoholic fuels have been chosen because of their high energy density and their polarity that make them suitable for electrospraying. Electrical conductivity, surface tension, viscosity, density and permittivity are the most effective liquid properties in the electrospraying. The visualization method used for this study is shadowgraphy and light scattering method. In this study the range of flow rate and voltage is acquired for each operational mode and Q-V diagram has been obtained for all liquids... 

Laser-assisted machining is nowadays considered as an alternative to conventional machining processes including ceramics grinding, which has provided the basis for extensive experimental and numerical studies in this field. Since the main difference between laser-assisted machining and conventional machining is in the presence of lasers, the main purpose of this study was to investigate the effects of laser on the laser assisted machining process. In this regard, in the first step the process of laser heating to the ceramic workpiece has been studied experimentally and numerically by finite element method. The material used in this research is a slip cast fused silica ceramic. The... 

Biosorption capacity of zinc (II) by biomasses produced from four species of microorganism including two kinds of bacteria (Pseudomonas putida and Streptomyces rimosus) and two kinds of fungi ( Aspergillus niger and Phanerochate chrysosporium) in batch case were investigated and compared. In all cases dried original bio mass and dried pretreated bio mass with NaOH were used. In all cases biosorption capacity of pretreated biomasses were much higher than non-treated biuomasses to the ratio of 3.8 – 1.4 times. Freundlich and Langmuir equilibrium isotherms were used to match with experimental results of this research. Except S.rimosus, all others were completely matched with Langmuir... 

This thesis seeks to identify the critical barriers to strategy implementation in an Iranian firm, and also concentrates on the readiness for strategy implementation phase. Previous studies show that many of strategic plans fail in implementation phase. Therefore, implementation and readiness for implementation phases are both important phases. The very few studies in this topic in Iranian industrial context illustrate the same issue in local context; however, these barriers may vary from one context to another. Different approaches and frameworks in the literature have been reviewed in order to build a theoretical frame work to seek the barriers to implementing a strategic plan in an... 

Despite the profound impact of formal strategic planning on the performance of companies, there have been a few researches on the factors that influence the starting phase of strategic planning process. This research tries to identify these factors and clarify the decision process of conducting strategic planning. In other words, the main purpose of this study is to identify the rationales of companies for initiation of strategic planning. Regarding limited previous studies on this topic, especially about the decision process about conducting strategic planning in Iranian companies, the case study methodology is used. The study is conducted in two phases. In the first phase, five companies... 

Understanding the behavioral processes of boards has been a new line of inquiry in the board literature. This study has focused on the leadership roles of heads of boards of subsidiary companies in a corporation. This subject is widely practical in most industries but rarely explored. An embedded multiple case study design was used to compare the leadership roles of heads of boards of two groups of boards with high and low effectiveness in a corporation assessed by a multi-source appraisal method. Based on several interviews with different stakeholders of the corporation within subsidiary boards of these two groups and the staff managers of the parent company, we compared the mechanisms that... 

Although technology acceptance and continuance intention have been studied for years, certain ambiguities remain unexplored. Researchers have consistently sought to identify the factors influencing individuals' decision-making processes regarding technology adoption, on one hand, and the determinants of their continuance intention, on the other. While extrinsic and intrinsic motivations have been examined as influential factors at the acceptance stage, the dynamics within motivational mechanisms and their differential impacts at the acceptance stage versus the initial usage phase have been overlooked. This study investigates (1) the relationship between users' motivational mechanisms in the... 

For neurodegenerative diseases like Multiple Sclerosis, Alzheimer’s, or Parkinson’s disease early detection is required to slow progression and prevent disease onset. To do so, identifying early signs and symptoms of the disease as well as modifying lifestyle can play a crucial role. Nowadays, the increasing use of smart gadgets and sensors has paved the way for collecting behavioral data and therefore analyzing and extracting meaningful patterns. In this study, lifestyle and cognitive performance data have been collected via a platform called OptiMind. Previous studies have shown that the Integrated Cognitive Assessment (ICA) can identify patients with neurodegenerative disorders (such as... 

Labneh is a semisolid product that is produced by concentrating milk to approximately 23% total solids (wt/vol) by the traditional cloth bag method, ultrafiltration and direct reconstitution. For ultrafiltration membrane processing is carried out either before or immediately after fermentation. The effect of storage time on the flow properties of concentrated yogurt (labneh) was investigated using a rotational viscometer. Experiments were performed at after 0, 2, 5 and 14 days after production. The apparent viscosity of fresh sample was then measured as a function of shear rate. For a given shear rate, the apparent viscosity was measured as a function of shearing time. The increase in the... 

Laser cladding is a processing technique of layer-by-layer material deposition which is widely used to repair important components. However, tensile residual stresses generated in this process may result in detrimental effects such as crack, undesirable deformation and reduced fatigue life. A thermo-mechanical finite element model is developed to accurately predict residual stresses of the multiple beads laser cladding process with incorporating the cyclic plasticity into the analysis by utilizing the nonlinear kinematic hardening behavior. FE results are presented for Inconel 718, a material for which the laser cladding process is widely used. The FE results are compared with those of... 

Multi-participant virtual environments are network applications that simulate the experience of real-time interaction among multiple usersdistributed all over the internet In order to share the common sense of time and place, multiple entities interacting in the shared virtual environment should become aware of the modification to the shared environment, or the result of on the other objects interactions shortly after such events occur. This is achieved through the distribution of update messages. As the number of users and entities increases, there is a considerable increase in the amount of update messages exchanged among the users and entities. This is considered as one of the most... 

The purpose of this study was to identify the dimensions of readiness for change in senior managers in the academic environment. In the literature, the emotional component of readiness for change requires more empirical research. The main question of this research is to identify cognitive and affective dimensions of readiness for change. This research has an exploratory approach, and a qualitative research method has been used to reach the research goals. In order to answer the questions of this research, a case study of Strategic Budgeting Implementation Plan at Sharif University of Technology has been studied. Interviews were conducted with the heads of the depatments of Sharif University... 

In the Ion Implanter system a controled current through a tungesten filament, supplies the heat which causes the thermoionic emmition to ionize the gas molecules. Then the negativly charged electrones that are boiled off the filament, and also the ones that are removed from the outer ring of the gas molecules during the ionization process, are attracted by an adjustable voltage source. In this thesis, two resonant converter topologies are proposed to designe and to implement the adjustable current and voltage sources for ion implantation system. Unlike the PWM converters soft switching techniques, used auxiliary circuits to reduce the switching losses and EMI noises, in the proposed resonant...