Sharif Digital Repository

Combination of three-dimensional (3D) IC technology and network on chip (NoC) is an effective solution to increase system scalability and also alleviate the interconnect problem in large-scale integrated circuits. However, because of the increased power density in 3D NoC systems and the destructive effect of high temperatures on chip reliability, applying thermal management solutions becomes crucial in such circuits. In this study, the authors propose a runtime distributed migration algorithm based on game theory to balance the heat dissipation among processing elements (PEs) in a 3D NoC chip multiprocessor. The objective of this algorithm is to minimise the 3D NoC system's peak temperature,... 

Thermal management of electronic devices is presently a serious concern. This article investigates the thermal performance of a five-turn open-loop pulsating heat pipe in both start-up and steady thermal conditions. The effects of working fluid, namely water and ferrofluid, heat input, charging ratio, ferrofluid concentration, orientation, as well as application of magnetic field, are explored. Experimental results show that using ferrofluid enhances the thermal performance in comparison with the case of distilled water under certain conditions. In addition, applying a magnetic field on the open-loop pulsating heat pipe charged with ferrofluid improves its thermal performance. Charging... 

Functionally graded materials (FGMs) have been introduced to significantly reduce the temperature and thermal stresses on structures at severe thermal loading. Design and development of FGMs as the heat treatable and energy-absorbing materials for high-temperature and thermal protection systems requires understanding of exact temperature and thermal stress distribution, in order to optimize their resistance to failure. In this study, transient temperature and associated thermal stresses in a functionally graded slab symmetrically heated on both sides are determined by separation of the variables scheme. This method is applied to the heat conduction equation in terms of heat flux for... 

Combination of three-dimensional (3D) IC technology and network on chip (NoC) is an effective solution to increase system scalability and also alleviate the interconnect problem in large-scale integrated circuits. However, because of the increased power density in 3D NoC systems and the destructive effect of high temperatures on chip reliability, applying thermal management solutions becomes crucial in such circuits. In this study, the authors propose a runtime distributed migration algorithm based on game theory to balance the heat dissipation among processing elements (PEs) in a 3D NoC chip multiprocessor. The objective of this algorithm is to minimise the 3D NoC system's peak temperature,... 

Currently, the thermal management of microelectromechanical systems (MEMS) has become a challenge. In the present research, a micro pulsating heat pipe (MPHP) with a hydraulic diameter of 508 lm, is experimented. The thermal performance of the MPHP in both the transient and steady conditions, the effects of the working fluid (water, silver nanofluid, and ferrofluid), heating power (4, 8, 12, 16, 20, 24, and 28 W), charging ratio (20, 40, 60, and 80%), inclination angle (0 deg, 25 deg, 45 deg, 75 deg, and 90 deg relative to horizontal axis), and the application of magnetic field, are investigated and thoroughly discussed. The experimental results show that the optimum charging ratio for water... 

There has been great demand for shape memory alloy (SMA) wires as actuators for shape control of flexible structures. The experimental setup of this study consists of a flexible beam actuated by two active SMA actuators. The input applied to the SMA actuator in this setup is electrical current while the output is the strain or position. To control strain of the actuator, the SMA wire is heated resistively in order to reach the desired temperature calculated by inverse of the phenomenological model. In heating the SMA wire resistively, the controllable quantity is the heat input to the wire via an applied current. In controller design, changes of physical properties of SMA wires and the... 

In this investigation, a reactor model for prediction of the deactivation behavior of MTO's porous catalyst in a fixed bed reactor is developed. Effect of coking on molecular transport in the porous structure of SAPO-34 has been simulated using the percolation theory. Thermal effects of the reaction were considered in the model and the temperature profile of the gas stream in the reactor was predicted. The predicted loss in catalyst activity with time-on-stream was in very good agreement with the experimental data. The resulting coke deposition and gas temperature profiles along the length of reactor suggested a reaction front moving toward the outlet of the fixed bed reactor at the... 

In this paper, a new structure for the rotor of the Brushless Doubly-Fed Machine (BDFM) is introduced to reduce the machine's torque ripple. The ripple has a considerable effect on the machine start up. At the first section of the paper, analytical expressions for the air gap permeance distribution, the air gap MMF distribution, cogging torque and back EMF are presented. Then, the effects of skewing the rotor loops are analyzed. Finally, the relation between non-skewed quantities and their values in skewed coordinate are introduced  

In this paper, the fractionalized differentiating method is implemented to reduce commensurate fractional order models complexity. The prominent properties of this method are its simplicity and guarantee of preserving the stability of a specific class of fractional order models in their reduced counterparts. The presented reduction method is employed in simplifying complicated fractional order controllers to a fractional order PID (FOPID) controller and proposing tuning rules for its parameters adjustment. Finally, the efficiency of the FOPID tuning rule obtained based on the proposed reduction method is shown in the temperature control of a cutting process  

Abstract A desired circulatory flow in flat-plate closed-loop pulsating heat pipes (FP-CLPHPs), which may ameliorate electronic thermal management, was achieved by using the new idea of interconnecting channels (ICs) to decrease flow resistance in one direction and increase the total heat transfer of fluid. In order to experimentally investigate the effects of the IC, two aluminum flat-plate thermal spreaders - one with ICs (IC-FP-CLPHP) and one without them - were fabricated. The FP-CLPHPs were charged with ethanol as working fluid with filling ratios of 35%, 50%, 65%, and 80% by volume. Performance of interconnecting channels in different heat inputs was explored, and the results... 

A distributed embedded system consists of different processing elements (PEs) communicating via communication links. PEs have various power characteristics and in turn, have different thermal profiles. With new technologies, processor power density is dramatically increased which results in high temperature. This alarming trend underscores the importance of temperature management methods in system design. The majority of proposed techniques to address thermal issues, impose severe penalties on performance and reliability. We present Schedule Swapping, a technique for reducing peak temperature in distributed embedded systems while satisfying real-time constraints. Contrary to many other... 

The design of controlled rolling process of microalloyed steel sheets is affected by several factors. In this investigation, effect of the reheating, finishing and coiling temperatures of rolling, which are considered as the most effective parameters on microstructure of hot rolled products has been studied. For this purpose, seven different reheating temperatures between 1000 to 1300°C with 50°C increments, three different finishing temperatures of 950, 900 and 850°C below the non-recrystallization temperature and one temperature of 800°C in the inter critical range and four different coiling temperatures of 550, 600, 650 and 700°C were chosen. By soaking the specimens in furnace, the grain... 

This paper will first describe the Linear Quadratic Regulator (LQR) and Fuzzy logic controller when the Proportional-Integral-Derivative (PID) controllers are inactive for procedures that have large delay time (LDT) in transfer stage. Therefore in those states, LQR and Fuzzy controllers perform better than the PID controllers. The constrained LQR is optimal and stabilizing. The solution algorithm is guaranteed to terminate in finite time with a computational cost that has a reasonable upper bound compared to the minimal cost for computing the optimal solution. The system determines the amount of fuel required from a fuzzy algorithm to arrive at the desired temperature. The parameters of the... 

In this paper an enhanced ETSI-Hata propagation model tuning is presented. The three-dimensional (3D) digital terrain map (DTM) was included in the simulation process. For the enhancement of the model tuning process and precision verification of ETSI-Hata model, the real 3D map of the buildings of the simulated area was incorporated over the DTM. Multiple knife edge diffraction method and the antenna effective height method were used to calculate the diffraction loss. This method was applied for a real urban scenario. For every sector in the coverage area, a tuned model was exploited. Using a genetic algorithm, frequency planning for the entire urban area was performed, which resulted in an... 

In this paper an analytical method and a PDE-based solution to control temperature distribution in FGM plates is introduced. For the rectangular FGM plate under consideration, it is assumed that the material properties such as thermal conductivity, density, and specific heat capacity, vary in the width direction (y); and the governing heat conduction equation of the plate is a second-order partial differential equation. Since there has been little control synthesis work for PDE-based systems as compared to the abundance of control design techniques available for ordinary differential equations (ODEs), most of the proposed control approaches for continuous domain rely on discretizing the PDE...