Sharif Digital Repository

Bone scaffolds are combinations of several materials, for achieving suitable properties and usage for replacing with defected bone. In this study, TCP/Agarose scaffolds are fabricated by two different approaches. The first one is using polymer sponge and gel casting technique and the other one is using foaming agent in order to obtain scaffolds with same porosity. The results show that in spite of same structure and porosity, scaffolds have different mechanical properties due to their different morphologies. Compressive strength of the scaffolds which were fabricated using polymer sponge method is 2.25MPa and elastic modulus is 56.8MPa. After coating with Agarose, compressive strength... 

The Brushless Doubly-Fed Machine (BDFM) is a machine which incorporates the robustness of the squirrel cage induction machine and the speed and power factor control of a synchronous machine. All of these advantages are obtainable from a relatively low rating power electronic converter (e.g. 30% of the machine’s rating). The stator of a BDFM is furnished with two balanced three phase windings of conventional design (power and control winding). These windings differ in pole number and are often excited at different frequencies. Hence, there is no direct magnetic coupling between them. The power winding is connected to a constant-voltage, constant-frequency source and the control winding is... 

In recent decades, electricity generation using renewable energy sources especially wind has gained considerable attention worldwide. Various generating systems have been proposed for wind turbines to convert wind mechanical power into electrical power. Up to 70% of the installed wind turbines incorporate Doubly-Fed Induction Generator (DFIG) and a fractionally rated power converter. Other schemes still have technological and economic penalties such as high cost of active materials, complexity of machine manufacturing and control systems and large and expensive converter, which limit their spread in wind power plants. Among these, Brushless Doubly-Fed Induction Generator (BDFIG) has... 

Occurrence of natural disasters such as earthquake could seriously damage most buildings especially those with insufficient resistance located in urban worn-out textures. In order to reduce unpleasant consequences of an earthquake, appropriate policies need to be considered to persuade the beneficiaries to follow retrofitting standards in the process of planning, designing, and construction of buildings. These policies shall be implemented through institutions in arbitrary or obligatory forms, by encouragement or penalty mechanisms. In order to consider these policies, first of all we need to identify the beneficiaries and their particulars. By studying and considering subjects discussed in... 

Chemotherapy is a proven and effective systematic approach to treat various types of cancers. Despite its advantages, chemotherapy would kill healthy as well as cancer cells. To overcome this problem, different controlling strategies are implemented. This study aims to provide a medicine drug delivery schedule for chemotherapy (by designing a proper controlling system) based on the verifiable mathematical models. First, the dynamic model is analysed and stability points are reviewed. The selected model has five state variables and two inputs. In this study, the focus is on dynamic model analysis and obtaining an effective and appropriate treatment pattern by designing a proper controller. To... 

Natural disasters can damage the infrastructure of society. Damages to the infrastructure components of society can disrupt their service delivery. Disruption in providing services to society's infrastructure can disrupt social and economic activities and impose various significant costs on society. The cost of repairing the damaged infrastructure and reducing the income of households are among the economic damages of accidents. The decline in the quality of life, as well as the death and injury of people due to the breakdown of the infrastructure or the disruption in their services, are among the social damages caused by accidents. In the same way, natural disasters are considered a... 

Due to the vulnerability of urban fabric and residential buildings to earthquakes and considering its destructive social and economic effects on society, the need to adopt appropriate policies to prevent and reduce vulnerability, has been increasingly considered by policy makers. Despite the laws, regulations, incentives and penalties that policymakers have envisioned to prevent unprincipled and unsafe construction, evidence shows that a significant number of new buildings being built in the country are not earthquake resistant and there are many violations in design, implementation and supervision that is done by the stakeholders. To solve this problem, research has been done on the... 

Soil and water pollution is one of the most common types of pollution in terrestrial and aquatic ecosystems. The development of mines and the oil and petrochemical industry on one hand and the non-compliance with environmental requirements on the other hand have caused large amounts of hydrocarbon pollutants and heavy metals to enter the environment in recent decades. Petroleum materials and heavy metals leak into the surrounding environment during drilling and extraction in oil sites and mines or during land and sea transportation, despite the measures taken to control their pollution. The conducted studies show that human industrial activities are the only cause of environmental pollution... 

The power control of horizontal axis wind turbines can affect significantly the vibration loads and fatigue life of the tower and the blades. In this thesis, we are going to consider both the power control and vibration load mitigation of the tower fore-aft vibration. For this purpose, at first, we developed a fully coupled model of the NREL 5MW turbine. This model considers the full aeroelastic behavior of the blades and tower and is validated by experiment results, comparing the time history data with the FAST (Fatigue, Aerodynamics, Structures, and Turbulence ) code which is developed by NREL (National Renewable Energy Lab in the United States). In the next, to estimate EWV, a novel... 

Laboratory studies to investigate the effects of different saline concentrations (such as sodium chloride or calcium chloride) on the soil water retention behavior of clayey soils and their volumetric changes have received much attention recently. However, many previous studies have investigated these effects in only one path of the SWRC (wetting or drying path) and the effects of saline concentration on hydraulic hysteresis have not been considered. In addition, researchers have frequently studied these effects on SWRC on clay samples, and little research has been done on collapsible soils. Therefore, the most important purpose of this study is to investigate the effects of increasing... 

Nowadays electricity power has a key role in developing various aspects of the world. The great importance of fossil fuel power plants come from their large contribution in electricity power generation. Among the different fossil fuel power generation technologies, supercritical power plants have great advantages. They are an advanced power generation technology with high plant efficiency, high coal utilization and low emission. Their complexity and existing many unavoidable uncertainty sources in their dynamic such as changes of ambient temperature, climate condition and wear of components make their control challenging. To overcome mentioned problems and achieving a good performance, a...