Sharif Digital Repository

It is not possible to compute a linear classifier to classify real world images, which are the focus of this thesis. Therefore, the space of such images is considered as a complex. In such cases, kernel trick in which data samples are implicitly mapped to a higher dimension space, leads to a more accurate classifier in such spaces. In kernel learning methods, the best kernel is trained for the classification problem in hand. Multiple Kernel Learning is a framework which uses weighted sum of multiple kernels. This framework achieves good accuracy in image classification since it allows describing images via various features. In the image input space which is composed of different extracted... 

Railroads should be well maintained for safe and efficient operation. The most important reason for the failure of railways is overload and asymmetric load on them. Also, the proper interval for repairs should be adjusted to fit the load crossed over. In order to carry out all these tasks, a constant observation of the weight on the rails must take place. Current dynamic weighing systems are costly. In addition, the installation of these systems is time-consuming and causes permanent damage to the rails. On the other hand, some of the cheaper models of weighing systems require full stop and static weighing, which practically does not work at all, especially on busy rails due to delays. The... 

The main object of the presented thesis is manufacturing ultra high molecular weight polyethylene(UHMWPE)/Graphene nanocomposites by insitu polymerization using Ziegler Natta catalysts. In this study, three types of Ziegler Natta Catalysts such as Magnesium ethoxide supported, single-supported and bi-supported have been studied. Experimental conditions are optimized (from point of productivity and molecular weight) by Design expert software with response surface methodology (Box-Behnken design). Effect of process parameters like temperature, pressure and [Al]/[Ti] molar ratio on productivity and Molecular weight are investigated. Also, the effect of hydrogen presence and type of cocatalyst... 

Ultra high molecular weight polyethylene has attracted the attention of numerous researchers and industries. This polymer due to its strong properties can be used in advanced military industries, medical engineering and cases in which high strength and high abrasion resistance is required. Present study aims to fabricate UHMWPE/Molybdenum disulfide composites, using in-situ polymerization. Before carrying out the polymerization process, nanoparticles of molybdenum disulfide underwent various processes such as oxidation, pickling, ultrasonic and thermal shock, in order to increase the interlayer distance and creating functional groups on the surface, then various analyzes, such as XRD, FESEM,... 

Today polyolefin definitely is one of the most applicable polymers in the world. One of these polymers is ultra-high molecular weight polyethylene. Being applicable in a number of high-tech industries such as military service, battery separators, and other areas, expands the usage of these polymers. Electrospinning is one of the molding methods in order to synthesize fiber polymers. Using this method, a great deal of polymer fibers have been prepared. It is worth noting that the device used for olefins should have temperature control and temperature increase ability. The electrospinning device with the temperature control has not been built in the country; therefore, this device has been... 

Medical engineering advances in total joint replacements and society’s rising demand for long lasting materials, have proven it essential to manufacture materials that are more similar to the original tissue in the fields of mechanical, tribological and biological properties. Ultra High Molecular Weight Polyethylene(UHMWPE), is a polymer widely used in arthroplasty applications due to its biocompatibility, chemical stability and proper mechanical properties. In this study, UHMWPE-HAp nanocomposites reinforced with Zirconia and Graphene were manufactured aiming to reach a structure that is more compatible with bone tissue and also to improve overall properties. First, using ultrasonication... 

The increasing growth of marine tourism has strengthened the activities related to this industry. One of the most profitable of these activities is recreational submarines. A traction recreational submarine is an idea in this field, in order to reduce costs, the propulsion force is removed and the submarine is towed by the mother ship. The most important reason for using the traction system and removing the independent drive is to prevent vibration and noise caused by the rotation of the propeller to prevent the escape of aquatic animals and to create a beautiful view from under the sea to watch underwater wonders. Searching for safety and saving people's lives in emergency situations is an...