Sharif Digital Repository

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 recent years, many efforts have been made in tissue engineering and new methods for the treatment of cartilage damage, with an emphasis on their non-invasive and less aggressive nature. Meanwhile, injectable and in situ forming hydrogels have been considered as a less invasive nature. On the other hand, lack of enough mechanical properties in these hydrogels is one of their main problem. In this study, gelatin and alginate was used to fabricate hydrogel as interpenetrating network (IPN) hydrogel and silica nano particles were also used to increase mechanical properties in the fabricating of hydrogels. Gelatin is also combined with dopamine in order to induce bio adhesive properties of... 

Large-size buried pipelines are an efficient way of transporting of water, waste water, sewage, gas, and oil resources in across the world. Since the buried pipe lines are exposed to many unexpected conditions, such as landslides, corrosion, fatigue, unexpected loading, earthquakes, material flaws or even intentional damaging, so the inspection requirements lead to adoption of new method of maintenance, protection and conserving of pipelines. This proposed project aims to improve the trustworthiness, reliable, yet economical technologies for monitoring of behavior of buried pipe lines during operation and assessing the risk of pipe lines failure. Piezoelectric sensor is bonded on the surface... 

Structures that change shapes are often called morphing structures. Smart morphing composites refer to the morphing structures that can detect the change in conditions and, through a control mechanism, command the actuators to maintain the stability and/or perform a new task. The present report provides a framework on the eld of smart morphing composite structures. The emphasis on this work is on, particularly, multi-stable composite structures with capability to detect the new conditions and adapt themselves to properly respond to them. Due to cycling nature of applied load on morphing, these structures are vulnerable to failure due to fatigue. A failure control mechanism utilizing a... 

Vibration is one of the major problems in gas and oil pipelines. Vibrations can cause damage to the pipes, supports, valves and other equipment installed in the system. These vibrations can be caused by equipment installed on pipelines like compressors and pumps or by fluid flow in pipes and fixed equipment like connections and valves. This research investigates the dynamic behavior of fluid flow in pipelines in Karanj and Parsi oil fields located in the southern part of Iran. The pipeline is responsible for injecting gas into the field. Excessive vibrations in the system cause repeatable damage which in turn increases the operating and maintenance cost. First, the vibration of pipelines has... 

During the past two decades, laminated composite structures have been used for many engineering applications, including aerospace, automotive, sport equipment and pressure vessels.
In spite of the excellent properties of strength to weight ratio, composite structures are vulnerable to failure when subjected to impact and vibration. It is well known that impact damage may severely degrade the strength and stability of laminated composite structures. For this reason the effect of impact on composites has been a subject of extensive research.
There are several ways of decreasing the vibration energy of structures, such as diminishing the source energy, designing structures... 

Minimally Invasive Surgery (MIS) is a modern surgical technique in which the operation is performed through small incisions in the body. Therefore, the surgeon looses his/her sense of touch which is of high importance in any medical operation. In the present work, a novel smart grasper is presented in which the surgeon can virtually acquire a feeling of force/momentum experienced by the organ/tissue. The smart grasper uses piezoelectric sensors bonded at desired locations to detect the applied force/momentum applied by surgeon and to measure the transmitted force/momentum to the tissue/organ. First, an accurate electro-mechanical model of the smart grasper is developed and the relations... 

Marine offshore structures are huge structures constructed in very harsh environments, like oceans and seas. These structures are highly exposed vibration due to ocean’s waves, wind, helicopter landing, etc. Preventing the damage to these structures due unpredicted vibration using a semi active vibration control is being considered. Magnetrorehological (MR) dampers have been used as active element to control the vibration and to provide the structural integrity of the structure. Providing high dynamic range, lower power requirements, large force capacity, robustness, and safe manner operation in case of fail made the MR dampers attractive devices to passive, semi-active and active control... 

Image segmentation is middle and an important task in image analysis and machine vision applications. The output images of imaging systems are often fuzzy because of noise, limitation in spatial and temporal resolution, blurring and intensity inhomogeneity in the objects. The goal of this thesis is exploring the fuzzy methods in multispectral image segmentation and proposing a new one to solve some of the recent difficulties and problems. The difficulties and problems such as simultaneous utilization of spatial and spectral information, necessity for dimension reduction, spatial and spectral and intra-cluster image information redundancy, existence of regions with widely varying size,...