Sharif Digital Repository

In this paper, we show that the stability can not be achieved with current stabilizing MPC methods for some unstable processes. Hence we present a new method for stabilizing these processes. The main idea is to use a new time varying weighted cost function for traditional GPC. This stabilizes the closed loop system without adding soft or hard constraint in optimization problem. By studying different examples it is shown that using the proposed method, the closed-loop stability of unstable nonminimum phase process is achieved. COPYRIGHT © ENFORMATIKA  

An analytic method to predict the oscillation amplitude and supply current values of a differential CMOS oscillator is presented. A simplified model to predict the phase noise performance for this type of oscillator is developed. Using this method, it becomes possible to design an optimised oscillator in terms of a minimum phase noise and low power consumption. The validity of the method has been verified by designing a LC CMOS oscillator using 0.25 μm CMOS technology. The predictions are in good agreement with simulation results over a wide range of the supply voltage  

In this paper, the application of an actuator wire made of shape memory alloy (SMA) and externally attached to a cantilever beam is analyzed. To this end, an integrated model that includes the constitutive equations of the SMA, the phase transformation equations from martensite to austenite and vice versa, the heat transfer equation for the SMA that also includes the input energy from an electric source, and the equations of the elastic deformation of the cantilever beam as well as the SMA wire, is presented. The simultaneous solution of the mentioned set of equations can result in the evaluation of the system response to an electrical activation of SMA  

The main purpose of the present research is to investigate the shunting phenomenon in a three-sheet RSW joint usingfinite element simulation. To this end, a three-sheet resistance spot weldingjoint was simulatedas an electrical-thermal-mechanical couplingproblem.Tovalidate the presentedsimulation, the finite element results were compared with the experimental results, including nugget size and geometric shapein theresistance spot weldingjoint.Afterwards, the multi-spot welds of three-sheet low carbon steels with the same thicknesses were analyzed considering the sequential distance of 45 mm. Various techniques, includingnewspot-welddiametermeasurement, electrical current density, electrical... 

In this paper, an algorithm for fault diagnosis of permanent magnet DC electromotors.has been investigated, based on vibration and electrical current monitoring. Several permanent magnet DC electromotors.with previously determined faults have been prepared and the vibration, current and speed data have been measured. The relationship between certain related measured data and faults has been determined. A fault diagnosis algorithm has been developed in this research based on these relationships. This algorithm can be used in mass production lines for quality control  

In this paper, for the first time, current distribution inside multiwall carbon nanotube (MWCNT) bundles is studied in the high frequency range in which resistance becomes saturated. It is shown that current distribution of MWCNT bundles in this range is not strictly decreasing vs. distance from surface as in Cu wires  

this paper presents a new class AB circuit for current-mode signal processing. The proposed circuit provides high-dynamic range, low distortion and accurate definition of quiescent current and it is well suited for high-speed applications. A third-order low-pass filter with a cutoff frequency of 200MHz and 51dB dynamic range is also presented. The Alter consumes 2.7mW from 1.8V supply. © 2007 IEEE  

Paralleling power modules is designed to share system loads (stresses) equally to improve system reliability. Due to variations in the parameters in the power converter system, temperature mismatches may occur. These mismatches may lead to unequal life expectancy of individual converters in the total system. It is believed that equalizing the operating temperature of the semiconductor devices may improve total system reliability. In this paper a new thermal-based load-sharing scheme for parallel converters is proposed. In this scheme, the load current is redistributed among parallel converters based on the temperature of the converters. The main goal is to minimize the relative temperature... 

A high speed, high resolution switched-current sample and hold (SI S/H) based on a new class AB transconductance stage is presented. Simulations performed on the SI S/H in standard 0.18um CMOS technology with 1.5v supply voltage indicate low power dissipation, high sampling speed and high SNR. © 2006 IEEE  

Partial discharges (PD) are recognized as the main cause of the inner insulation deterioration process in power transformers. Therefore, the optimum inner insulation design is one of the challenges a transformer designer is faced with. Transformer strength, especially during transient conditions, is a criterion for transformer insulation designers. This challenge has made designers initiate and employ other types of winding, for example, rather than ordinary layer and disc windings employ the multiple-α windings. Multiple-α windings have a more complicated structure and are comprised of various parts with different physical structures and electrical characteristics. Typical partial discharge... 

Lost sensory or motor functions can be restored using electrical neural prostheses (NP), which include surface NPs, implanted or subcutaneous NPs and the more recent Stimulus Router System (SRS). The latter type of NP outperforms the other types in its selective excitation and least invasiveness. In each case, the achieved performance depends on a multitude of design factors among which the electrical excitation waveform shape, frequency, duration of pulses, configuration of electrodes, number of intervals, thermal conditions and electrode material. To investigate the effects of these parameters on the distribution of electric current inside biological tissues, numerical modeling can be... 

Net fluid flow of soap films induced by (ac or dc) electric fields in asymmetric frames is presented. Previous experiments of controllable soap film flow required the simultaneous use of an electrical current passing through the film and an external electric field or the use of nonuniform ac electric fields. Here a single voltage difference generates both the electrical current going through the film and the electric field that actuates on the charge induced on the film. The film is set into global motion due to the broken symmetry that appears by the use of asymmetric frames. If symmetric frames are used, the film flow is not steady but time dependent and irregular. Finally, we study... 

In this paper, a high speed and low cost error correction technique is proposed for the Carry Select Adder (CSA) which can correct both transient and permanent errors and is applicable on all partitioning types of the basic CSA circuit. The proposed error correction technique is compatible with all existing error detection techniques which are proposed for the CSA adder. The synthesized results show that applying this novel error correction technique to a CSA with error detection technique results in up to 18.4%, 3.1% and 14.9%, increase in power consumption, delay and area respectively. © 2009 IEEE  

Density currents are continuous currents which move down-slope due to the fact that their density is greater than that of ambient water. The density difference is caused by temperature differences, chemical elements, dissolved materials, or suspended sediment. Many researchers have studied the density current structures, their complexities and uncertainties. However, there is not a detailed 3-D turbulent density current data set perfectly. In this work, the structure of 3-dimensional salt solution density currents is investigated. A laboratory channel was used to study the flow resulting from the release of salt solution into freshwater over an inclined bed. The experiments were conducted... 

In this paper a theoretical comparison between the performance of switched-capacitor (SC) and switched-current (SI) pipeline analog-to-digital converters (ADCs) is presented. Power dissipation and die area of SC and SI implementations are compared based on linearity and noise constraints. It is shown that if nonlinearity errors of the class AB SI ADCs are removed by calibration, their performance prevails that of the SC ADCs. Also it is shown that class AB SI ADCs occupy less die area than SC ADCs for a given resolution. © 2007 IEEE  

This paper deals with the definition of power factor and reactive current component in a three-phase system. For a single-phase system, power factor and reactive current component are defined based on the phase-angle displacement between the measured voltage and current waveforms. This definition can be directly extended to balanced three-phase systems. However, this extension is not suitable when the three-phase system (voltages or currents) is unbalanced. Reason is that the conventional definition of phase-angle does not directly apply to an unbalanced three-phase system and needs further refinements. This paper defines the concept of symmetrical power factors and symmetrical reactive... 

Power transformers are in service in different environmental, electrical and mechanical conditions. Many experiences have proved that the inner insulation system degradation may pose the transformer to fail while in service. On the other hand, partial discharges (PD) are recognized as the main cause of insulation deterioration process. Therefore, reaching the optimum inner insulation system is one of the challenges a transformer designer is faced with. The solution lies in the correct and accurate modelling of different types of transformer windings. Transformer strength especially during transient conditions is a criterion for transformer insulation designers. This challenge has made... 

This paper presents a zero-voltage switching current mode sample and hold(S/H) circuit. The proposed S/H has 12 bit linearity at 180MHz sampling rate for 1.5v supply voltage. The S/H circuit is designed for 0.18μm CMOS technology  

A high-speed current-mode sample-and-hold circuit is presented. This circuit allows for high sampling speed together with high linearity and precision. The sample-and-hold circuit has been designed and simulated in standard 0.18μm CMOS technology with 1.5V supply voltage. It is capable of operation with sampling frequency of 150MHz (300MHz using double sampling technique) for 12-bit accuracy using 3.7mW power