Sharif Digital Repository

In the domain of manufacturing, computer numerically controllers (CNC) technology is a major contributor to the production capacity of the enterprises. The advances in CNC technology coupled with enhancements in computing systems have provided the basis to re-examine the way in which computer-aided systems (CAx) can be used to enable global manufacturing. Interoperability of the various components of the CAx chain is therefore a major prerequisite for manufacturing enterprises for becoming strategically agile and consequently globally competitive. Being interoperable, resources can be utilized interchangeably in a plug-and-produce manner. Over the last 8years the eminence of a STEP... 

Fair exchange of digital items through computer network is an important research topic of modern cryptography. Generallty, a fair exchange protocol is a way which helps two parties to exchange their digital items fairly, so that at the end of the protocol execution, both parties recieve their desirable items or none of them recieves anything. In a practical applications, fair exchange protocol is widely used in different but related fields like contract signing protocols,non-repudiation protocols,e-ayment system and certified e-mails. In a fair exchange protocol, a trusted third party (TTP) acts as an arbitrator between two parties. To reduce the traffic load of the arbitrator, the concept... 

In this thesis, we consider a neutral predator–prey model with the Beddington–DeAngelis functional response and impulsive effect. Sufficient conditions are obtained for the existence of positive periodic solutions by a systematic qualitative analysis. Some known results in the literature are generalized  

In this thesis, we consider a system containing fluid equations, structure equations, and equations of these two materials’ common interface in three dimensions and on the regular domains. We suppose that the solid which is described by the Lamé system of linear elasticity, moves inside an incompressible viscous fluid in three dimensions, and the fluid obeys the incompressible Navier-Stokes equations in a time-dependent domain. At the fluid–solid interface, natural conditions are imposed, continuity of the velocities and of the Cauchy stress forces. The fluid and the solid are coupled through these conditions. By this interaction, the fluid deforms the boundary of the solid which in turn... 

Cement as a major industrial product plays an important role in the growth and development of countries. However, the economic condition in Iran has led to a decline of the production of this strategic product in recent years. At the moment, most of cement factories are faced with overproduction and inefficiency due to high production cost, broken financial situations, high energy cost, wages and overhead cost that have led to a serious crisis in cement industry. Scientific research must be carried out to find solutions to the present critical situation in the cement industry. The application of Lean Management System leads to a sustainable development of cement industry.In this study, a... 

Third order differential equations which describe pseudospherical surfaces are considered. The complete classification of a class of such equations is given. A linear problem with one or more parameters, also known as zero curvature representation, for which the equation is the integrability condition, is explicitly given. The classification provides five large families of differential equations. Third order nonlinear dispersive wave equations, such as the Camassa–Holm equation and Degasperis–Procesi equation are examples contained in the classification. Many other explicit examples are included  

We consider a system of nonlinear partial differential equations corresponding to a generalization of a mathematical model for geographical spreading of dengue disease. the mosquito population is divided into subpopulations: winged form (mature female mosquitoes) and aquatic form (comprising eggs, larvae and pupae); the human population is divided into the subpopulations:susceptible, infected and removed (or immune). On the other hand we allow higher spatial dimensions and also parameters depending on space and time. is last generalization is done to cope with possible abiotic effects as variations in temperature, humidity, wind velocity, carrier capacities, and so on; thus, the results... 

An understanding of the effect of degree of cementation on static behavior of cemented soils in becoming increasingly important in design and analysis of geotechnical engineering problems. Naturally cemented coarse-grained soils are widely present in many parts of the world. Misunderstanding of the behavior of such soils could lead to under or overestimate of the soil parameters. Previous studies conducted by Prof. Haeri and his co-workers show that most of the alluvial deposit of Tehran, the capital city of Iran. The amount and characteristics of the cementation of the deposit varies in different parts from highly cemented in the north to non-cemented in the south. This deposit consists of... 

Optimization always has been a major industrial field of study. Optimization is the process of finding the best result based on some events. In design, construction and maintenance of any kind of engineering system ,engineers must take a lot of decisions in the case of management or engineering at different levels in order to minimize the attempts to reach the optimum conditions and obtain the maximum profit on the other side. high speed of processing and litle time for calculations by using computers is very common nowadays which is caused in many improvements in optimization approaches. In this thesis some different classical optimization methods have been applied on Williams-Otto reactor... 

Artificial immune systems (AIS) constitute a novel area of bio-inspired computing. Biological models of the natural immune system, in particular the theories of clonal selection, immune networks and negative selection, have provided the inspiration for AIS algorithms. Moreover, such algorithms have been successfully employed in a wide variety of different areas, but have not been applied for chemical processes yet. One important part of the immune systems is lymphatic system. Clonal selection is one of the few algorithms that belong to the family of AIS techniques. Clonal selection algorithm is the computational implementation of the clonal selection principle. In this project, we have... 

Fatigue life and crack growth retardation due to periodic tensile overload that superposed on constant amplitude cycles has been investigated. The tests were performed using C(T) specimens made of 7075 aluminium. All periodic overload tests were carried out at the same spacing between overloads and the effect of overload ratio on fatigue life has been investigated. Results of experiments revealed that the at low and high overload ratios, crack growth rate is relatively high and there is an optimum OLR that maximize interaction and thus minimize FCGR. Whit OCR-1=50, overload ratio of 1.85 led to maximum interaction and resulted in 219% increase in specimen's life relative to CA loading. Also... 

Diabete is disability in the body to produce insulin or use it. Body insulin hormone needed to convert starch, sugar and other foods to energy and thus the body is functioning properly. Considering this incurable disease and its complications, many doctors and researchers trying to control the disease, reduce complications and to create favorable conditions and appropriate solutions for preventing its expanding and also strengthening patients mentally. Be destroyed in digestive system, insulin can not through tablets or similar cases received. The best way known to enter insulin to the body, is injection. This project is about a device to reduce the level of blood glucose in patients with... 

Telecommunication Company of Iran (TCI), as a government owned company that provides fixed, mobile and Internet services. It is in the process of privatization. In order to be survived in competitive environment, it is required to be an agile and dynamic organization. Also it should be seriously sensitive in profit margin. To be a dynamic company, the management of the company is expecting to introduce a new and modern service named Advanced Communication Services (ACS). This service consists of Video on Demand (VOD), live and archive television programs, tell-learning and e- shopping. For TCI, it's crucial to find a right and precise answer to the challenging question "Will ACS be a... 

Integrated design includes CAD, process planning and CNC code generation based on an integrated data structure. To enable different CAD/CAM software solutions to be interoperable, it is required to support data exchange in manufacturing enterprises. To realize interoperability there are two basic approaches: i. to focus on STEP standard to support data exchange between CAD systems as well as CAPP/CAM and CNC machining systems; the use of STEP standard ensures the data integration based on STEP standard. ii. utilizing a platform consists of structures and procedures to enable exchange of data between different CAD/CAM/CAPP software applications seamlessly. In this article, the important... 

Lean manufacturing, was published as a research work named “the machine that changed the world” by James Womack and his assistants in MIT in 1990. Lean thinking can be presented in five principles: specifying what creates value, identifying value stream, creating value flow, make only what is pulled by the customer, and strive for perfection. In contrast with what is generally believed that lean manufacturing can only be used in production systems, lean tools and methods can be used in administrative departments of a factory or in a service firm. In such processes, not only hardware, but also service added values should be considered using information and the software service tools. In this... 

In batch cooling crystallization, the crucial control problem is to design a temperature trajectory which produces a desired crystal size distribution. Here, a completely different solution is presented. Designing model-based controller for crystallizer has two steps; first step is determining optimal temperature trajectory which is some kind of feedforward control, second step is adding feedback controller (with manipulated variable of jacket temperature or cooling flow) to track the set-point (determined in first step) and rejecting possible disturbances. Traditionally, determining optimal temperature of crystallizer is done by using calculus of variations of distributed system. In this... 

Based on the air entrainment, the water conveyance tunnels can be categorized as pressurized, two-phase flow. When the flow is controlled by gates, sudden closure of gates would produce unsteady two-phase flow. The most important effect of such an event is the sudden change in the pressure which can be a function of channel slope, air and water inflow and their ratio. In this thesis the pressure change in unsteady two-phase in an experimental set up using rectangular tunnel is studied. About 100 tests were carried out for single and two-phase flow with various water and air discharges causing unsteady flow with different slopes. It was observed that in a defined slope the ratio of the... 

The goal of using speed humps is to reduce the velocity of cars to allowable value. Reducing the speed more than necessary before arriving at the hump, causes losing kinetic energy whose compensation needs consuming more fuel. In fact, the total fuel consumption of vehicles is noticeable and it expresses the need for allowable speed definition to prevent wasting fuel. In this project, using different methods in engineering design and by defining allowable speed, an intelligent speed hump is designed and selected from different patterns which may remain protuberant or become like the road surface in level. The parts considered for this hump are selected simple to lower the cost of... 

Moving of living organisms appears in many interesting problems, e.g. the growth of bacteria colonies, tumor growth, wound healing, color patterns of animals and etc. There are many ways to model such problems and PDE theory is widely used to investigate these problems. In this thesis, we study two well-known classic models. First, macroscopic “Keller–Segel” model and then kinetic “Othmer–Dunbar–Alt” System. Since these models have a nice behavior in two dimensions that they don’t have in other dimensions, we propose a way to alter them such that they behave in this way in all dimensions. Also none of the known models have the suitable dynamics in one dimension, so our model has the property... 

Fluid transient in a conduit is an unsteady flow, which is followed by the change in the flow rate condition. Pressure transients in pipeline systems are caused by fluid flow interruption from operational changes such as starting/stopping of pumps, sudden changes to valve setting, etc. Fluid transient analysis is commonly based on the assumption of no air in the liquid. However, air entrainment, trapped air pockets, free gas, and dissolved gases frequently are present in the pipeline. In fact, Air changes flow properties and transient pressure peaks in comparison with single-phase flow. Experimental study has been carried out to verify characteristics of transient pressure inside a...