Sharif Digital Repository

In this research, the effect of organizational Bureaucracy on the integration of technical knowledge and market knowledge in the process of developing new products, along with other factors mentioned in previous literature, has been studied. To this purpose, a questionnaire was prepared which measured both the degree of integrity and the effect of bureaucracy on integrity. This questionnaire was completed by marketing and research and development managers of 39 innovative companies in the field of information and communication technology (ICT). Regression analysis was used for data analysis. The results of this research show that bureaucracy as an organizational factor, along with other... 

The inlet duct is one of the most important components of the waterjet propulsion system, whose hydrodynamic performance is directly related to the capabilities and efficiency of the waterjet propulsion system. In this study, a procedure was proposed to improve the hydrodynamic performance of an inlet duct. According to this proposed procedure, first the basic intake duct geometry of the waterjet propulsion system was prepared using visual programming to simplify the repetition of the design in Rhino design software, and then the numerical analysis of the designed geometry in Star CCM+ commercial software was performed. The simulation results were validated with the results of an... 

The concept of symmetry has long been the focus of numerous debates in different fields; some have come up with an artistic approach looking for a beautiful notion germane to the concept of symmetry. Others have examined this issue from a philosophical viewpoint and studied the ontology of symmetry and philosophers like Kant moved beyond the limits and have given their symmetry a transcendental position. On the other hand, in an anti-realist position relying on the fact that the goal of science is not truth but merely it’s an empirical adequacy, Van Fraassen argued that “science was rapidly gaining autonomy not only from theology but from all of philosophy, and was exploiting concepts and... 

In this thesis, first we study superconductivity and its mechanisms then classify different types of that based on symmetry of gap function. After that, we shall discuss metallic systems that have impurities in them and propose two successful model describing this phenomenon, Anderson’s model and Kondo’s model. In the next step, by introducing Kondo lattice model which is an ordered array of impurities in system, try to solve it by mean-field approximation and will be seen a phase transition in a characteristic temperature known as Kondo’s temperature. Then generalize these models to situation when background system is a superconductor and study it’s behavior and quantum phases. Although... 

In this thesis, a novel graphene oxide (GO)/sodium alginate (SA)/polyacrylamide (PAM) ternary nanocomposite hydrogel with excellent mechanical performance has been fabricated through freeradical polymerization of acrylamide (AAm) and SA in the presence of GO in an aqueous system followed with ionically crosslinking of calcium ions. Physical and chemical characteristics of the composite were investigated by Fourier transform infrared spectroscopy and scanning electron microscopy. The swelling behaviors of the composite hydrogels were investigated under varying conditions of time and pH. The optimized swelling capacity in standard conditions was found to be 1711% per gram of the hydrogel. The... 

Low salinity/smart waterflooding is simple to apply and a promising enhanced oil recovery method in which ion-tuned saltwater is injected into subsurface oil reservoirs. Many aspects of this operation, in particular those pertaining to nano-scale, are not yet fully understood. The present dissertation is an attempt to shed light on the microscopic properties and behavior of rock/brine/oil interfaces throughout low salinity/smart waterflooding. Several simulations were carried out for oil/brine and calcite/brine categories each containing various ions and hydrocarbons compounds. The surface contribution of non-functional oil compounds (aromatics and aliphatics) near brine medium was... 

The analysis of electrical energy consumption parameters such as rate and amount of consumption, plays an important role in the planning of power systems. Because the dynamic analysis and evaluation of these parameters provides a detailed forecast of consumption and power system load. these forecasts is given to planners and engineers as the input of power system planning .Given that the electrical energy consumption system can be thought as a dynamic system, System Dynamics (SD) method would be very appropriate for modeling and analyzing its behavior. In this thesis, based on the SD and by means of dynamic loops, a comprehensive dynamic system for electrical energy is introduced. So the... 

In recent years, due to restructuring in the electric power industry, distributed generation has become one of the most important subjects and DGs and renewable energy sources have been increasingly expected as a supplement and an alternative to a conventional large scale central power system. their success depends not only on the distribution of the available renewable energy sources in a region but also on the power grids connectable capacity in the area. Photovoltaic system is one of the best RESs for residential electricity supply because it is noiseless and solar power is widely available and households can use it via photovoltaic cells in their homes. There are two major problems... 

The outpatient clinics have some features that make them different from other types of the clinic. Something that must be paid attention is adherence to appointments by outpatients, which have an undeniable effect on the productivity of the Outpatient Appointment System. In most of the outpatient clinics, outpatients are supposed to schedule their appointment in advance. As a result, if patients do not come to the health center based on their scheduled appointment, and they do not inform the health center about their absence, not only will the clinic become deprived of the opportunity to utilize its resources efficiently, but also healthcare access for other patients will reduce. The rate of... 

Microfluidic technology is a field of science that deals with the design, fabrication, and experimental tests of small-scale fluid systems and has made great strides over the past decade. As an interdisciplinary field, this growing field of technology has many applications in medicine, diagnostics, chemical analysis, electronics industry, etc. One of the primary applications of the microfluidic devices is the development of " laboratory on-chip (LOC)" tools as point-of-care (POC) diagnostic tools, such as, rapid detection during surgery. A LOC device includes various application modules, sample transfer and preparation modules, separation modules, and detection and analysis modules. The... 

Microfluidics is the science of fabricating systems interfacing fluids of small volume and size ranging from microliters (10-6) to picolitres (10-12). Due to its remarkable features, such as low sample and reagent consumption, high sensitivity, low cost, automated devices, and short experimental time, microfluidic chips have been widely used as laboratory assays. As a term often used and described in “lab on a chip” and “organ on a chip” technologies, microfluidic chips have been used in the fast and frugal diagnosis of infectious diseases such as HIV, microscale surgery on single cells and tiny organisms and cell culture.The design, simulation, optimization, and fabrication of an... 

Microfluidic technology is a field of science that deals with the design, implementation, optimization, and testing of fluid systems in small dimensions. This technology has made significant progress in various fields in the last decade, especially in medical engineering. As an interdisciplinary scientific field, this growing technology has many applications in medicine, pharmaceuticals, chemistry, and electronic industries. One of the primary applications of microfluidic devices is the development of "lab-on-a-chip" systems as point-of-care diagnostic tools, such as rapid diagnosis during surgery. A microfluidic system includes various functional modules: sample preparation and fluid... 

High speed and high accuracy are two of the major trends for many systems in the 21st century, such as machine tools and semiconductor equipment. For the purpose of high speed, it is well known that active magnetic bearing (AMB) is an inevitable substitute for conventional bearings. The noncontact nature of AMB brings up many advantages over the conventional bearing, including energy efficiency, low wearing, long life span, and absence of lubrication. Hence, AMBs are especially essential for high-speed rotating devices nowadays.
While the 3-pole AMB has been proposed for many years, it received little attention due to the magnetic coupling between poles that makes the 3-pole AMB system... 

Magnetic bearings have been used in industry to achieve an acceptable performance, high precision and vibration suppression of rotating machinery in recent decades.The absence of physical contact between the bearing and rotating components provides access to high rotational speeds which is a problem in conventional bearings.In addition, capabilities such as stiffness and damping adjustment can be used to reduce the harmonic vibrations caused by mass unbalance. The unbalance compensation is one of the main topicswhich has attracted the attention of many researchers in the field of rotordynamics. The aim of this thesis is to design and fabricatea three-pole active magnetic bearing test rig and... 

Disturbances due to sensor runout and mass unbalance are the main sources of harmonic disturbances in active magnetic bearing systems. Existence of this type of the disturbance not only causes harmonic vibrations in the system but also changes the steady-state position of the axis of rotation from the geometric center of the AMB. In this research, an observer-based control method used to estimate and reject this disturbance. Proposed integral observer estimates dc and harmonic content of the sensor runout and also estimates the states of the system at the same time with good precision. Lyapunov method is used to prove asymptotic stability of the proposed observer and demonstrated that sensor... 

The ability to predict the remaining life of bearings is one of main aspects for improvement of reliability of bearings. However, techniques to predict the lifetime of a bearing under the practical operating conditions have not been well developed. In this thesis, prognostic model for bearing systems based on vibration response analysis is considered as a single-degree-of-freedom vibratory system. As the bearing system is considered as a single-degree-of-freedom vibratory system, its acceleration amplitude at the natural frequency can be related to the system stiffness. Moreover, the relationship between failure lifetime, running time and stiffness variation can be established from the... 

Rolling element bearings are the most widely used components in rotating machinery and so, estimation of their remaining useful lifetime in order to increase the reliability and availability of them is a critical issue in the field of condition monitoring of these machinery. Despite numerous researches which have tried to develop a model for precise prediction of rolling element bearings’ lifetime, there is no method which can predict their remaining lifetime exactly. The failure criterion in these components is the area of defect in their races and rolling elements. Consequently, an approach which can predict the defect area of these components is susceptible to prediction of their... 

Rolling bearings are important parts in rotating machinery. Unsuitable practice of this bearing causes unsuitable output in this collection. In some machines like helicopters, sudden faults of this rolling bearing cause body dangers. According to this point, diagnose of bearing fault is an important case in condition monitoring domain. There are many ways for diagnose of fault in bearing which most of them are important subject in signal processing. In this project first of all, the most important and applicable signal processing methods, which are useful in diagnose of fault in bearings are introduced then three of these methods are chosen and applied on time signals of experimental... 

Diagnostic and prognostic of spall defect in the rolling element bearings is investigated in this thesis. A new numerical model is proposed which considers defect size, defect clearance and defect roughness. The results of this model based on surface roughness show superior similarity to experimental data than classic model. To improve diagnostic ability in the rolling element bearings, four new methods are proposed in this thesis. These methods are short-time statistical features, local curve roughness, level crossing and wavelet packet decomposition. These methods are applied in outer ring, inner ring and ball defects and it is showed that these methods have better detection ability... 

In this project, the effect of improper lubrication on vibrational behavior of rolling element bearings is investigated. Different lubrication conditions were deliberately produced using three oils with different viscosity grades on a bearing at different loads and speeds. The acceleration of bearing vibrations were measured, then analyzed by means of squared envelope analysis, a special case of cyclostationary analysis. The results and their comparison showed that decrease in lubricant’s viscosity grade can lead to an increase in magnitude of cyclic frequencies equal to cage frequency and its harmonics. This observation can be helpful in detection of lubricant degradation and in...