Sharif Digital Repository

Nerve repair plays a very prominent and significant role among the efforts that have been made to integrate the concepts of tissue engineering in strategies to repair almost all parts of the body. This is partly due to the complexity of the nervous anatomy system and its function as well as the inefficiency of conventional repair methods that are based on a component of biomaterials or cells alone. Studies show that electrical stimulation can enhance the nerve regeneration process; so the use of conducting polymers has attracted much attention for the construction of neural tissue engineering scaffolds. In this study, the electrical properties of neurons and the effects of electrical... 

Software Product Line Engineering (PLE) and Agile Software Development are two leading approaches in the software industry. Despite the inherent differences between the two approaches, they are intended to fulfill common goals, such as: Reducing time to market, increasing customer satisfaction, promoting product quality, managing changes in requirements, and lowering the costs of development. In addition, each of them has certain positive features which address the other’s weaknesses. As a result, it seems reasonable to integrate the two approaches in order to produce a combined method which fulfills the common goals while addressing the weaknesses. Agile Product Line Engineering (APLE) is a... 

In general, repair and regeneration of damaged tissues or lost organ is base definition of a technology named tissue engineering. Tissue engineering technology provides innovative path to achieve better medical treatment, including different methods which manipulate natural or synthetic biomaterials mimicking stem cells environmental condition inside the body, in order to facilitate desired cell expansion and differentiation. Recently, application of cell carriers in form of microcarriers which are injectable, biodegradable and biocompatible have attracted significant attention. Due to increasing effectiveness in animal cell culture.
The aim of this work was fabrication of... 

One strategy for increasing efficiency and decreasing brake specific fuel consumption in spark ignition engines is using variable valve timing mechanism which is proportional to engine speed and load. Variable timing refers to the opening and closing time of inlet and outlet valves and their duration and overlap. In conventional SI engines the performance of valves is designed on a fixed point at special engine load and speed. While investigations show that if performance time of valves is changed according to engine load and speed, performance parameters of engine will improve.
In reviewing articles related to variable valve timing, their effect was considered on volumetric efficiency.... 

In the process of industrial and economic development and in the competitive environment in the world, reducing the cost of industrial products is an important factor for more customers' satisfaction, more revenue acquisition, and stability and success in the business. Cost engineering is the area of engineering practice concerned with the application of scientific principles and techniques to problems of cost estimating, cost control, business planning, management science, profitability analysis, project management, planning and scheduling. In this research through the studying the structures and models of cost engineering, in addition to consider this dimensions of cost engineering, the... 

As the increased use of workflow engine based systems in various domains, quality assurance and testing them has become critical. The majority of these systems are designed and implemented by a workflow language, so testing these systems is highly dependent of workflow language. In this thesis the common domain of business processes is chosen. In this area, little researches have examined the implemened processes with the second version of BPMN modeling language, and most methods, examined another language called BPEL. For this reason and due to the increased use of BPMN language because of its unique characteristics, this study focuses on testing of systems implemented with this language.... 

Due to high strength, hardness and high resistance to abrasion, ceramics are difficult for machining. Also as the conductivity coefficient of these materials is low, major amount of produced heat during machining process will be absorbed in the cutting tool which causes intensive wear in cutting tool edge. As a result employing traditional machining for these materials because of low machining speed, tool wear, high roughness and large cutting force, has little efficiency in practice. Therefore non-traditional machining method may improve efficacy. In this thesis effect of utilizing ultrasonic vibration in machining process of fused cast silica ceramic has been studied. Aim of this study at... 

In the current decade there has been research works around adopting agile methodologies for software product line engineering. However, the emphasis has been on the process part of the methodology and the main product which is the source code has been neglected.The prevalent modeling and implementation method of software product line is the featureoriented method. The concept of ”Feature-to-code mapping” is introduced in the implementation phase which recently novel approaches have been proposed to realize it.Despite superiority of the novel approaches in this field, prevalent industrial product lines still use C language and map features to code by leveraging traditional preprocessors of C... 

Fuel system is one of the most important parts of pulse detonation engine which has the responsibility of fuel, oxidizer and also purge gas in the different operational frequencies of engine. Although pulse detonation engines are sort of air breathing engines and purge gas and oxidizer one in the same unit in their structure, due to existence idea in the pulse detonation rocket engines coverage of functional condition, fuel, oxidizer and purge gas, will study it in three different structures.
In this study purpose is improvement of the pulse detonation engine of Sharif University which will provide as the possibility of safe functional condition and high operational frequency in... 

The heart stoke which happens due to an obstruction in the coronary artery can result in the presence of a dead part on the heart muscle called Myocardial Infarction (MI). MI can lead to next heart strokes and even the death of the patient. So far, a great number of biomaterials consisting of natural and synthetic polymers and Extra Cellular Matrix (ECM) of human body have been recommended for being used in tissue engineering approaches aiming to rehabilitate the infarcted site. The use of ECM is recommended for mimicking the microenvironment of the body as much as possible which can be very helpful in proliferation of the cultured cells. In this project, we fabricated a composite... 

Chronic wounds are among the serious injuries which have called the attention of scientists to invest in an effort to fabricate temporary skin grafts and wound dressing materials. One of the widely acceptable solutions to this obstacle is to design a bioactive scaffold capable of regenerating tissue as well as delivering active agents to the site specific area. To this end, natural biopolymers are considered as suitable candidates to be employed in regenerative medicine due to their excellent biocompatibility. In addition, nanoparticles possess special properties such as the ability in sequestering the drug release which make them promising candidates in the fabrication of the... 

Once damaged, articular cartilage has very little capacity for spontaneous healing because of the avascular nature of the tissue. Although many repair techniques have been proposed over the past decades, none has successfully regenerated long-lasting tissue to replace damaged cartilage. Tissue engineering have recently demonstrated tremendous approaches for regeneration of cartilage tissue lesions. Tissue engineering is based on three principles: cells, scaffolds for cell adhesion and growth factors. Three-dimensional biodegradable scaffolds play an important role in tissue engineering. In this study, novel cross-linked hybrid chitosan/ECM scaffolds were prepared for articular cartilage... 

Cartilage is an avascular tissue, having limited ability to repair itself. Since the methods for treatment of cartilage defects have been not effective, in recent years, new therapies based on tissue engineering are considered.This paper reports on the development of porous microcarriers composed of acellular matrix of cartilage and natural polymer chitosan. Microcarriers were prepared by electrospray method. Results of mechanical tests, SEM imaging, water uptake behaviour, biodegradation test, and MTT assay demonstrated that the microcarriers composed of 2% (wt) chitosan and 1% (wt) ECM has the best potential for growth and proliferation of primary chondrocyte cells. These results... 

In present work, hydroxyapatite nano-rods are synthesized using a simple sol-gel method with calcium nitrate and potassium dihydrogenphosphate as calcium and phosphorus precursors respectively and ammonia was used for adjusting the pH=9. To obtain rod shape hydroxyapaite powder, multi wall carbon nanotubes were added to the solution, nHA powder was calcinated at 60 and 450 ℃. In second step, chitosan-gelatin/nanoHA solution were prepared by blending chitosan and gelatin in different concentrations with nanoHA powder, then the solution was freeze dried to maintain a composite scaffold. The prepared HA powder and bio-composite scaffold were characterized by X-ray diffraction (XRD), field... 

Following heart coronary artery occlusion, heart stroke (HS) happens which leads to the creation of a dead zone on heart tissue named Myocardial Infarction (MI), the presence of which on a patient’s heart will result in succeeding HSs and the death of the patient. In this study, porous microcarriers capable of being utilized in cardiovascular tissue engineering is fabricated using a mixture of myocardium ectracellular matrix (ECM) and Chitosan (Cs). Results of Elasticity tests, SEM images, swelling behavior, biodegradability test, and cell proliferation assay showed that the scaffold consisting of 3.5% (w/w) Chitosan and 0.66% (w/w) ECM has the best potential in providing cardiovascular... 

Microcarriers (MCs) are an attractive technology with various applications in tissue engineering. In this study, chitosan/gelatin MCs were fabricated with blends of different ratio of chitosan/gelatin, by using a setup containing high voltage electrostatic field and syringe pump. Optimization of blend ratio, voltage and syringe pump flow carried out by the “Design expert” software leads to fabrication of MCs with constant diameter while having various elasticity. Mechanical strength and elasticity of MCs were determined. Human umbilical cord mesenchymal stem cells (hUCMSCs) were cultured on MCs dynamically by using mini-rocher in an incubator. Cells adhesion on MCs were successfully shown by... 

By new advancements in vehicle manufacturing; vehicle quality evaluation and assurance has become a more critical issue. Today noise and vibration generated inside and outside a vehicle are more important factors than before. In present work, the vibration transfer path analysis and vibration path ranking of a car interior has been performed. The method is similar to classical multilevel TPA methods but has distinct differences. The method is named VIVS which stands for Vehicle Interior Vibration Simulation. Performance of some tests like chassis dyno test, virtual mass function test and body transfer function test are required in this approach. The accelerations on both sides of the engine... 

The main goal of this project is to fabricate the scaffolds including Polycaprolactone and Polyvinyle alcohol nanofibers in order to use as artificial skin. For this purpose, electrospinning parameters have been optimized for various injection rates and the scaffolds containing different percent of PCL and PVA have been made. By investigating the cell growth on these scaffolds, the one made up PVA/PCL (30% ) has been introduced as the best scaffold. To improve biological properties of chosen scaffold, a layer of collagen was coated. The angiogenesis capacity has been improved by adding Heparin to PVA nanofibers. Based on assay of heparin release, it was shown that Heparin is released within... 

Ultrasonic assisted grinding is a novel method for improving the grinding process of difficult-to-cut materials. In the present research a novel set-up has been designed and manufactured for utilizing ultrasonic vibrations in cylindrical grinding. The designed ultrasonic head vibrates a rotating workpiece in axial direction. An alumina-zirconia ceramic (AZ90) has been selected as the workpiece material. Energy aspects and workpiece surface characteristics of ultrasonic assisted cylindrical grinding (UACG) and conventional cylindrical grinding (CG) processes have been analytically modeled and corresponding grinding experiments have been performed. The combined kinematics of the cylindrical... 

In this thesis to simulate the behavior of liquid engine Thrust chamber of hot gas from a quasi one dimensional code used when the effects of the heat transfer and friction in those terma. As well as during the regenerative channel is simulated by considering the equation’s of continuity, momentum and energy for one dimensional, effects of increase temperature, pressure drop, change the density of coolant flow resulting from the warming which is visible along the way to increase the accuracy of calculation of the thermal flux output of the engine, use a suitable model for unclear boiling in consideration of heat transfer coefficient used coolant flow it has been. As well as coupling of heat...