Sharif Digital Repository

From the past, the damask rose has an important place in various pharmaceutical, food, health and cosmetic industries. This product has the largest cultivated area in Iran, which is about 24,000 hectares, equal to 60% of its total cultivation in the world. Considering the conditions required for the cultivation of this plant, including the low water requirement, the expansion of its cultivation has been considered. One of the important obstacles to not expanding cultivation is manual harvesting, which strongly affects the quality and mass of essential oil and rose water. The efforts that have been made so far in the field of designing and producing the rose harvesting machine have not had... 

Additive manufacturing enables fabricating lattice structures with tailored mechanical responses based on lattice materials. Full exploitation of such a possibility requires reliable and efficient mechanical analysis tools to be explored by topology optimization algorithms for designing the interior architecture of the structures to meet the desired mechanical behavior. However, detailed mechanical analysis of lattice-based structures using the conventional finite element approach is prohibitively expensive due to lattices’ complex and fine features that demand adopting very fine space discretization. As an alternative, equivalent models based on the homogenization principle have widely been... 

Corneal keratoconus is one of the common eye diseases that usually occurs in the teenage years or the beginning of the third decade of life. In this disease, the cornea thins and loses its original shape and becomes conical. To treat this disease, ophthalmologists use different methods such as using glasses, contact lenses (hard and soft), corneal transplantation, and also corneal cross-linking, each of these methods has limitations, on the other hand, considering that The disease progresses and its severity increases, Ophthalmologists use corneal rings to treat this disease in more advanced stages, implanting a suitable ring in the patient's cornea both increases the strength of the... 

Cardiovascular diseases are one of the leading causes of death in the world. Identifying the mechanical behavior of arteries and their growth and remodeling under applied loadings can help to better understand the progression of the disease and provide more effective clinical interventions. Therefore, many researchers in recent decades have turned their attention to modeling the process of stress-mediated growth and remodeling in soft tissues. Among the most important models proposed to study this process are the constrained mixture model proposed by Humphrey et al. and the volumetric growth model proposed by Hoger et al.. The constrained mixture model is based on the continuous turnover of... 

Nowadays, with progresses made in manufacturing technologies, it is possible to produce micro-scale products such as micro-electromechanical systems. Micro-motors are one type of these systems that can be used in such applications as power supply of electronic devices. To achieve a better performance, these systems must rotate at high rotational speeds (about one million revolutions per minute). At such a high rotational speed, vibrational analysis is highly crucial. The results of recent studies indicate the inability of classical theories of continuum mechanics to analyze the behavior of these micro systems. Therefore, in this research, the rotor of micro-motors are modeled using the... 

Research in the field of medical science goes back decades and significant progress has been made in understanding the behavior of organs and living tissues. Consequently, scientists need to work towards identifying how to mathematically model the mechanical behavior of these living organisms. If we consider any living entity, we can see that they are a product of atoms, molecules, cells, tissues, and/or organs. Differential geometry and continuum mechanics indicate that during the growth process these organisms are influenced by the phenomena of aging, remodeling and morphogenesis. The majority of research in this area, i.e. the study of these important phenomena in living tissues, has... 

Keratoconus is one of the most common optical (visual, eye) diseases that usually occurs in youth or early third decade of life. In this disease, cornea gets thin and loses it initial shape and becomes conical. Doctors use different methods for its treatment including use of glasses, contact lenses (hard or soft), cornea transplantation and also cross linking of cornea. Each of these methods have their limitations, on the other hand, considering that this disease progresses and intensifies, ophthalmologists use corneal ring implant surgery for the treatment of this disease in its advanced levels. A good ring implant in corneal causes increased strength and also cause corneal to get back to... 

Experimental observations on multilayer graphene structures show that interlayer interactions including compressive and shear effects between layers are very important in their mechanical behavior. Existing analytical investigations have generally addressed the issue of pressure interactions between layers using interatomic potentials, while the models which consider the interlayer shear effect are rarely found in the literature. To address this shortcoming, this thesis presents a new formulation for multilayer graphene structures with desired shapes and boundaries, taking into account the interlayer shear effect according to the classical continuum mechanics theory. Next, size-dependent... 

Heart failure is one of the leading causes of death around the world and diastolic dysfunction is the main culprit behind about 30 percent of them. End-diastolic pressure-volume relationship is one of the most important indices of ventricles diastolic function, however invasive nature of assessment, has hindered its use in clinical applications. Despite the advances in computational modeling and bio-mechanical simulations, computational cost of these procedures often renders the computational methods unsuitable for clinical implications. Machine learning methods are usually the proper substitute in such cases. However, this method requires a large set of pre-calculated data for training,... 

Pumps are widely used in oil and gas industry. Therefore condition monitoring for this type of equipment is very important. The motor current signature analysis (MCSA) technique as one of the condition monitoring techniques is very effective in the industry, but it is less used in industry. All conventional methods require additional sensors to be installed in the system; current signature analysis as a sensorless method can reduce the cost of condition monitoring. In this study, motor current signature analysis technique was used to diagnosis a centrifugal pump with a capacity of 187 kW from the refinery industry. The impeller wearing ring clearance problem has been investigated. This... 

Keratoconus is a progressive disease in which the cornea becomes thin and due to the presence of internal pressure in the eye and its application to the cornea, the cornea becomes bulging and conical. In recent years, due to the relatively large number of patients with keratoconus and also the ability of this disease to progress over time, the need to study and research on the treatment of this disease is noticeable. Early and non-surgical methods for the treatment of keratocous are use glass and contact lenses, but since the disease is progressive and usually appears more severely over time, ophthalmologists use the method of corneal ring implant for treatment.In this study, 9 types of... 

owning to the side effects and disadvantages of conventional methods of cancers treatments such as chemotherapy, currently, scientists are attempting to find new methods to replace them. Furthermore, many human diseases like SCID and Hemophilia are due to genetic disorders and scientists are also seeking to find permanent treatments instead of available temporary ones for them. in recent years, regarding the obtained achievement, Gene Therapy is being considered as a promising method for both cancers and genetic disorders treatment. But due to low efficiency of this method at this stage, there is an endevour among researchers for a more profound comprehension of the basics of gene therapy to... 

Circular cylindrical shells have been widely used in many engineering structures such as spacecraft, submarines, offshores, and storage tanks. Their high stiffness-to-weight ratio and load-carrying capability make them well suited for use in civil and aerospace structures. The consecutive development of material engineering along with the increasing demands for lightweight, heat-resistant, and high strength structures have led to the usage of advanced materials namely functionally graded (FG) materials in designing such structures. In this thesis, the nonlinear static analysis of thin FG cylindrical shells is carried out using the Donnell’s shell theory with first-order approximation and the... 

In this study pollution generated by a electronic cigarette in a bus is observed. Resultant smoke from these products consist of different components which may endanger health and one should make sure them amount in general transport vehicles like bus are in permissible limit. These components are initially in liquid shape and evaporate. Tracking liquid particles are done with the aim of Lagrangian approach. For this the geometry is generated at first. Then structured mesh was generated with ICEM CFD which is a powerful mesher. Different conditions of smoking source and bus doors were studies and results were compared.Change of pollutant concentrations is strictly depend on position of... 

Due to the features like small dimensions, low manufacturing cost and low power consumption, micro-electromechanical systems (MEMS) are widely utilized in engineering applications. Many experimental investigations have indicated that the mechanical behavior of constructive microelements of these systems isn’t predictable by classical continuum theory. Therefore, to analyze the behavior of microelements, the non-classical continuum theories which can capture size effects should be utilized. On the other hand, various experimental observations have confirmed that thermoelastic damping (TED) is a dominant source of energy dissipation in microelements, in contrast to the non-small parts and... 

The analysis of nonlinear forced vibration of micro-rotors (rotating micro-shafts with disks) is carried out under loads of mass eccentricity distribution and in the presence of internal damping. For the analysis, the non-classical continuum theories of couple stress and strain gradient are employed. Vibrational behavior of micro-rotors is extremely sensitive due to the very high rotational speed, which is at the order of several millions per minute speed. The considered nonlinearity is of geometrical type due to the mid-plane stretching. First, the governing equations of motion of micro-rotors are derived by utilizing the Hamilton principle. In the next step, the Galerkin and multiple scale... 

Todays, advances in manufacturing technologies have led to design and production of micro-scale elements, including the elements employed in micro-electro-mechanical systems (MEMS). Micro-rotating systems like the micro-turbines are that kind of systems at which the high rotational speeds and the complexity of design and analysis have led to a special attention in modeling and investigating of their dynamic-vibrational behavior. In addition, in small scales, using the non-classical continuum mechanics theories such as the couple stress theory and the strain gradient theory is required to obtain the high precise results. On the other hand, attention to the torsional deformation of rotors... 

Incapability of the classical continuum mechanics theory to justify the experimental observations of the mechanical response of the small-scale structures and parts motivated the researchers to pursue the introduction and utilization of the non-classical continuum theories for analysis and design of such structures and parts. In this paper, utilizing the modified couple stress theory and the strain gradient theory as well-known and powerful non-classical continuum theories, the mechanical response, including the displacement and stress fields, for micro-rotating disks with angular acceleration is investigated. The governing differential equations of motion and the corresponding boundary... 

Polymeric microspheres which can load biomolecules, proteins and growth factors play an important role in tissue engineering and drug delivery systems. The size of the microspheres and encapsulation efficiency exert a considerable impact on the usability of them. In this study double emulsion method is used for fabrication of microspheres. Effect of different parameters namely the speed of homogenization, time of homogenization, the amount of polymer in oil phase, the surfactant concentration in different phases on the size and surface morphology of the microspheres are investigated. Moreover, a release test for BSA loaded microspheres is conducted. Results indicate that by increasing the... 

In recent years, the world has seen a great progress in micro electro-mechanical systems (MEMS). Small size, low weight, high accuracy and low energy consumption have made these devices applicable in a variety of usages. In MEMS devices, mechanical components are used for specific purposes among which one of the most widely used are micro plates. Microplates are used in the structure of many devices such as microswitchs and atomic force microscopes. Therefore, studying of static and dynamic behavior of microplates is important. As the object gets smaller (to the scale of micro and nano meters), the classic theory of mechanics of continuous media cannot predict the behavior due to its...