Sharif Digital Repository

The topic of knowledge creation and knowledge management is one of the most leading issues in management studies in today’s world’s organizations.Knowledge creation is known as the first and the most basic step in knowledge management and it can provide the prefaces of developing a management work frame in an organization.In this thesis after reviewing the goals and purpose of the project under consideration, the literature of knowledge management is reviewed and the most important models of knowledge management are selected and analyzed.Also, the organization selected as a case study is fully studied and the necessary information is gathered on the basis of proposed indexes at two public... 

The most important task of a power system is generating and transmitting electricity for consumers, according to electricity quality standards. One of these quality criteria is preservation of grid frequency close to nominal value with continuity of energy delivery to consumers. Electricity is a specific commodity that its generation and consumption should be equal continually; otherwise the network frequency will change and may become unstable, causing severe damage to the network equipment. There for different control and protective actions are deployed to maintain balance between generation and consumption, and thus to keep grid frequency close to nominal value. Characteristics of... 

Poorly damped Low Frequency electromechanical Oscillations (LFOs) confine the capability of power system transmission lines. This phenomenon, which is the result of dynamic interactions among generator groups, may make the system prone to small- signal instability in some cases. Due to the use of some system controllers such as AVRs, these oscillations are inevitable.
Hence, electromechanical modes detection and assessing stability margin are important requirement in power system planning and operation, and can provide significant help to power system operators by preventing stability problems.
From the distant past, in order to monitor small-signal stability, power system operators... 

Global growth of electrical energy consumption and various limitations on the use of fossil fuels, such as environmental problems, rising prices and their limited available resources, have resulted in growing interest and investment in the usage of renewable energy generation, especially photovoltaic (PV) systems. Although the off-grid operation of PV systems was its dominant operation form in the past, proliferation of these systems has made the grid-connected operating mode widespread in recent years. However, their grid connection causes technical problems which need to be resolved. This thesis studies and analyses the steady state and dynamic operation of PV systems in grid-connected... 

This thesis aims at developing control system of a full converter wind turbine with modular and parallel back-to-back converters. Modular structures and paralleling of power electronic converters are the state-of-the-art methods for increasing their transferable power to the grid. Technological advances in high power wind turbines, especially for the offshore installations, which contain permanent magnet synchronous generators with back-to-back full converters, promote the use of modular structures.
In addition to developing the regular control systems of wind turbines for modular structures, selection of appropriate structures, power sharing between parallel converters and mitigation of... 

According to authorities and statistical figures, Iran is seriously facing insufficient housing crisis. Studies show that through an increase of 1.5 million units in annual housing construction capacity, this crisis will be overcome in 5 years. Although successful execution of such a big project is not unprecedented in the world, housing experts believe fulfillment of this plan through traditional method of construction in the country is impossible. The country's capacity of industrialized construction which is known as the remedy, is only limited to 2-3% of total construction. Thus development of this approach through financial, legal, ... supports of investment in prefabrication... 

Due to daily decrease of fossil energy resources, increase of environmental pollution which is included of toxic and greenhouse gases, and extensive growing rate of demands in transportation industry, especially vehicle industry, developing solutions in using fuel cells are vital for this industry in our country. Fuel cells are green, efficient and also powerful energy generators. According to potential advantages of fuel cells, structure, performance, benefits and also types of fuel cells are introduced as a desired energy resource. Indentifying existing choices of energy generators and ranking them using MCDM (Multi-Criteria Decision Making) technique was the first step to perform a... 

Although voltage control and stability issues are not new to the electricity industry, but nowadays, in most modern power systems, special attention has been paid to this issue. Once, only weak systems with long lines were involved in voltage instability, while today due to heavy loading, voltage stability is a serious concern even in developed networks. Over tim, with increasing demand for electricity and emergence of electricity market and economic constraints, power systems are more exposed to voltage instability and even voltage collapse. Therefore, reliable operation of the system in such circumstances requires evaluating voltage stability of the network at both stages of planning and... 

Global trends of electrical energy production indicate high penetration of renewable wind energy resources in power grids around the world.Although high penetration of these resources benefits the grid operators and end-users in various aspects, several new challenges should be addressed. These challenges can be focused on in various studies with different time intervals and different technical and economic issues. One of the most important issues relates to the system frequency regulation and control aspects in high wind and photovoltaic (PV) penetrated grids. This is due to the fact that wind turbine generators (WTGs) as well as PV systems do not provide inertial response for the system... 

Nowadays, concerns about the reduction of fossil fuels and environmental issues, have made renewable resources more important. Among these resources, photovoltaic (PV) systems are more popular than others, due to their environmental compatibility and unlimited availability of sunlight. Increasing the penetration level of PV systems in electricity networks presents various technical and control challenges such as voltage and frequency variations; and protection and harmonics issues. In this thesis, voltage rise problem due to reverse power flow in distribution feeders is discussed. This is one of the main obstacles to the expansion of these resources in distribution networks.Various solutions... 

Cancer invasion of tissue is a key aspect of the growth and spread of cancer and is crucial in the process of metastatic spread i.e. the growth of secondary cancers. Invasion consists in cancer cells secreting various matrix degrading enzymes (MDEs) which destroy the surronding tissue or extracellular matrix (ECM). Through a combination of proliferation and migration, the cancer cells then actively spread locally into the surrounding tissue. Thus processes occuring at the level of individual cells eventually give rise to processes occuring at the tissue level. In this thesis we introduce a new type of multiscale model describing the process of cancer invasion of tissue.Our multiscale model... 

This research represents findings about obstacles in using value engineering in construction projects of khorasan razavi province via collection of information and views of experts of value engineering.The research shows that the value engineering in the majority of the projects is not practiced and majority of the projects are not benefited from this technique. Many experts believe that lack of required culture and motivation to save up and lack of organisational position for this technique are the main factors for non-progressive use of assessment engineering.The absence of proper understanding of the objectives and place of the value engineering is also an effective factor of on its... 

Hyperbolic branching Brownian motion is a branching diffusion process in which individual particles follow independent Brownian paths in the hyperbolic plane H2, and undergo binary fission(s) at rate λ > 0. It is shown that there is a phase transition in λ : For λ ≤ 1/8 the number
of particles in any compact region of H2 is eventually 0, w.p.1, but for λ > 1/8 the number of particles in any open set grows to ∞ w.p.1. In the subcritical case (λ ≤ 1/8) the set Λ of all limit points in ∂H2 (the boundary circle at ∞) of particle trails is a Cantor set, while in the supercritical case (λ > 1/8) the set Λ has full Lebesgue measure. For λ ≤ 1/8 it is shown that w.p.1 the Hausdorff dimension of Λ... 

In this thesis, we propose a first-order interior-point method for linearly constrained smooth optimization which was recently proposed in the literatuare that unifies and extends first-order affine-scaling method and replicator dynamics method for standard quadratic programming. Global convergence and, in the case of quadratic program, the (sub)linear convergence rate and iterate convergence results are derived.The method is implemented and numerical experiments on simplex onstrained problems with 1000 variables is reported  

In this thesis, unconstrained convex quadratic optimization problems subject to parameter perturbations are considered. A robustification approach is proposed and analyzed which reduces the sensitivity of the optimal function value with respect to the parameter. Since reducing the sensitivity and maintaining a small objective value are competing goals, strategies for balancing these two objectives are discussed. Numerical examples illustrate the approach  

In this thesis, the aim is to stating some of the noncommutative geometry(NCG) applications in formulating and describing the gravity. So, in the first chapter, we will work on some of metric aspects of NCG. In this chapter, we will review elements of the spin geometry, specifically we will define the Dirac operator which is the most important object in this thesis. Then, we will try to find counterparts of some of Riemannian geometric notions like integral and distance in the NCG framework. We will define some notions such as noncommutative infinitesimals, Dixmier trace, Wodzicki residue, noncommutative integral and spectral triples. Then, in the second chapter, we will work on some of the...