Sharif Digital Repository

We consider a system of two coupled integro-differential equations modelling populations of healthy and cancer cells under chemotherapy. Both populations are structured by a phenotypic variables, representing their level of resistance to the treatment. we analyse the asymptotic behaviour of the model under constant infusion of drugs. By designing an appropriate Lyapunov function, we prove that both cell densities converge to Dirac masses. We then define an optimal control problem, by considering all possible infusion protocols and minimising the number of cancer cells over a prescribed time frame. We provide a quasi-optimal strategy and prove that it solves this problem for large final... 

One of the novel methods of stabilization of nuclear waste is the use of vitrification technology. In order to stabilize high level wastes (HLLW) in glass, it is required that the elements are in their oxide form. Therefore, it is necessary to evaporate the waste and turn it into a solid form so that the elements can be converted into oxide form in the calcination furnace. Hence, one of the challenges of stabilization is the optimization of evaporation and calcination conditions. In this research, the parameters affecting evaporation were first investigated. Using laboratory measurements of application: temperature (110 to 180 °C), presence of nitric acid (0.5 to 4 mol/L), ratio of zirconium... 

One of the most common spinal surgeries involves spinal fusion or vertebral fixation, which is used to treat various conditions such as intervertebral disc disease, scoliosis (lateral deviation of the spinal column), fractures, infections, or the presence of tumors in the spinal column. In this surgical procedure, the use of pedicle screws and titanium rods prevents motion and friction between two vertebrae. Screws may enter the vertebrae in the wrong position and angle, causing bone weakening, rupture of nerve roots or blood vessels, weakness or lack of sensation in some parts of the body, spinal cord injury, and in severe cases, paralysis of the patient. For this reason, fusion surgery is... 

In this research, the physical structure of road transportation networks in Asia, Europe and Africa has been analyzed. With the analyses done in this research, we will recognize these networks and different combinations related to them. Paying more attention to existing transportation situations in mentioned geographical boundary will smooth the way to analyze and evaluate the development of business and carrying goods between the countries of these continents. In this research networks called Asia-Europe-Africa, AEA, are made which are recognized as road AEA networks and rail AEA networks according to basis transportation way available in them. These networks are made of three continental... 

The robots that can move on rough terrains are very important especially in rescue operation, exploration of mine and etc. Since contact surfaces between the robot and the ground are unpredictable, the structure of the robot is usually unintelligible and its motion analysis is difficult. In this research, a ring-like shape robot with flexible body is proposed for motion in rough terrain, gradient paths and passing bars. The ring shape has more usages than other shapes for example as a wheel in a larger robot. Also its flexibility helps the motion particularly on rough terrains. This robot consists of a central section for setting equipments and arms around that. Being radially and... 

Today safety is one of the major competition factors in automotive industries . The vehicles of today are more and more dependent on electronic systems , for driving safety and ease on control for the driver . Some systems are more or less standard in vehicles on the market , examples of such systems are ABS , ABC , etc. Despite of the effect of these systems on vehicle dynamics ,because they only control longitudinal dynamics and don't receive any feedback from vehicle lateral behavior , now control systems ,named VDC , have been developed and implemented in advanced vehicles. The operation of such systems is as this that in any time instance they evaluate vehicle dynamical behavior.... 

In this thesis a hybrid guidance law has been designed for a ground-based system to intercept an exoatmospheric target. In this regard a three stage interceptor with a kinetic kill vehicle has been proposed, the design parameters of which are determined according to a conceptual design procedure. The guidance law consists three phases namely boost, midcourse and terminal phases. In boost phase, a ballistic guidance law steers the first and the second stages of the interceptor ahead of the predeicted intercept point. In the midcourse phase, the third stage of the interceptor corrects the engagement plane while it also provides the head on interception condition for the kinetic kill vehicle....