Sharif Digital Repository

Pricing for an insurance policy can be described as the process of calculation of expected compensation to be paid to property losers as well as associated costs of potential risks. Loss forecast is accurate if the risks will be identified appropriately in order to calculate the frequency and expected severity of losses.This is particularly important about environmental risks since most of them appear in the long run. Environmental risk assessment model is both able to estimate the environmental liability premium for environmental pollution and degradation, and it can play a valuable role in promoting this industry. ELIS (Environmental Liability Insurance) software calculates the... 

The presence of bias in measurement of rate gyros is a performance limiting factor for satellite attitude determination systems. Gyro bias is usually handled by Kalman filtering methods which are mostly based on linearization approaches and lack global convergence properties. On the other hand, the existing asymptotically convergent nonlinear observers take into account the gyro bias only when multiple vector measurements are available. We present an asymptotically convergent attitude estimator which uses only one vector measurement and a rate gyro whose output is contaminated with an unknown and constant bias. The effect of unknown bias is compensated by means of a parameter adaptation law.... 

In this paper, a small signal model is proposed for four-switch rectifier with input power factor correction. The required transfer functions are determined and calculated for a typical rectifier. This model is used to design an appropriate controller with defined characteristic to improve the rectifier performance. Another controller is used to compensate capacitors dc voltage difference. The system is simulated in Simulink and the results are provided. These results confirm the accuracy of the developed model, and also the effectiveness of the proposed controllers  

Neglecting actuator dynamics in control of rigid manipulators can degrade performance and stability of the system. However, consideration of actuator dynamics usually requires measurement of joint torque or armature currents. In this paper, we present an adaptive controller for motion tracking of an n-DOF manipulator without using joint torque measurement. Semi-global convergence of motion and torque tracking errors to zero is proven. We show that the use of non-minimal representation of manipulator dynamics significantly simplifies its linear parametrization. Simulation example shows that avoiding joint torque measurement reduces system sensitivity to sensor failure and noise  

This brief presents an algorithm for decoupling multivariable systems based on quadratic programming (QP). A single framework is presented which can be used to design centralized, decentralized, and sparse structures of arbitrary dynamical order. A worked example and a case study are presented to demonstrate the usage and performance. It is shown that only previous methods based on Evolutionary Algorithms are able to achieve slightly higher performance than the proposed algorithm. However, these minor improvements are outweighed by the huge increase in time and costs associated with evolutionary optimizations  

This paper is aimed at investigating some computational aspects of different isoperimetric problems on weighted trees. In this regard, we consider different connectivity parameters called minimum normalized cuts/isoperimetric numbers defined through taking the minimum of the maximum or the mean of the normalized outgoing flows from a set of subdomains of vertices, where these subdomains constitute a partition/subpartition. We show that the decision problem for the case of taking k-partitions and the maximum (called the max normalized cut problem NCPM), and the other two decision problems for the mean version (referred to as IPPm and NCPm) are NP-complete problems for weighted trees. On the... 

The purposes of this paper are determination of the current density and safety factor profiles, J(r) and q(r), in IR-T1 tokamak. For these purposes, a diamagnetic loop with its compensation coil, and also an array of magnetic probes were designed, constructed, and installed on outer surface of the IR-T1 tokamak chamber, and then the poloidal beta and poloidal and radial magnetic fields measured. Moreover, a few approximate values of the internal inductance for the different possible profiles of the plasma current density are also calculated. From the results, current density and q-profiles obtained  

A new nonlinear Time to Digital Converter (TDC) based on time difference amplification is the proposed. A new gain compensation method is presented to expand the DR of conventional × 2 Time Amplifiers (TAs). Instead of conventional gain compensation approach based on changing strength of current sources, the proposed technique uses current difference which results more stable gain over wider DR. In order to avoid two different paths of the stages, a sign bit detection part is the proposed at the front of the TDC to allow using one path of stages for both positive and negative input time differences. As a result, the most advantages of the proposed TDC are its high resolution, wide DR, and... 

Micro motion stages are one of the essential components in field of micro robotics and ultra fine positioning systems. This research presents the optimum design of a 3-DOF micro motion stage and its position control using FEM simulation. This stage to be studied uses a 3 RRR flexure hinge base compliant mechanism driven by three piezoelectric stack actuators to provide micro scale planar motion. First of all parametric modeling of the stage will be fulfilled in ANSYS environment utilizing a commercial piezostack and different types of flexure hinges. Hence the Jacobian matrix will be achieved for each case. The optimum selection of the hinge form will be achieved upon results of the previous... 

The impact of an interline power-flow controller (IPFC) on composite system delivery point and overall system reliability indices is examined in this paper. In this application, the IPFC with dc transmission lines is employed in a system for coordinated control of line impedances of two, distance away, transmission lines with the objective of managing power flows on the two lines. It is also used to balance the real power being transferred between the compensated lines. For this purpose, the reliability model associated with a converter station has been developed and incorporated in an IPFC reliability model. A number of reliability indices are calculated at both the loadpoint and system... 

This paper presents modeling of Distribution STATCOM (D-STATCOM) in load flow calculations for the steady-state voltage compensation. An accurate model for D-STATCOM is derived to use in load flow calculations. The rating of this device as well as the direction of required reactive power injection for voltage compensation in the desired value (1 p.u.) is derived and discussed analytically and mathematically by the phasor diagram method. Furthermore, an efficient method for node and line identification used in load flow calculations is presented. The validity of the proposed model is examined by using two standard distribution systems consisting of 33 and 69 nodes, respectively. The best... 

Mobile manipulators are developed in order to execute separately in various regions where there is not possibility for human to appear there. Recently, the size of mobile manipulators has been decreased according to their given tasks. For such systems, the stability issue is very important. The robot system should be able to keep itself in an optimal situation. For reaching to this goal, one can use a redundant degree of freedom for the mobile manipulator such that this redundancy makes it possible to recover the system's stability by dynamic compensatory motion of manipulator when the system is unstable. In this paper, we present an algorithm which is fast enough to stabilize the mobile... 

The paper presents the application of a rule- based control scheme for an Advanced Static Var Compensator (ASVC) to improve power system transient stability. The proposed method uses a current reference, based on the Transient Energy Function (TEF) approach. The proposed scheme provides, also, a continuous control of the reactive power flow. The performance of the proposed approach is compared with that of a system using a conventional control method and of a system without ASVC. A single-machine system and an IEEE three machine system are used to verify the performance of the proposed method. © Sharif University of Technology  

Video transcoding comprises the necessary operations for the conversion of a compressed video stream from one syntax to another one for inter-network communications, without the need of any further decoding and re-encoding process. The two most recent and popular standard video coders are H.263 and H.264. In this paper, we present tools to enable low complexity intra transcoding from H.263 to H.264 using a novel fast intra prediction mode decision algorithm that does not require extra computation. It is shown that due to basic similarities of H.263 and H.264 it is possible to reuse predictor side information, so this side information is used to simplify the mode and direction decision for... 

In this paper, a Static Synchronous Series Compensator (SSSC) is used to avoid torsional mode instability in a series compensated transmission system. The power system used in this study is the IEEE first benchmark model for Sub-Synchronous Resonance (SSR) analysis. Simulation results in time domain using PSCAD/EMTDC presented and discussed. ©2006 IEEE  

This paper describes a new compensating system for the flicker and harmonics generated by a highly-varying load, e.g. a welding machine, connected between two phases of a three-phase system. The proposed system is an active filter with two-phase structure employed in a three-phase system. The system also employs simple and effective control strategies for dc-bus regulation and current control. The proposed system is a package with less switches compared to the conventional three-phase systems. It results in no increase in switch ratings, thus giving a more economic compensator. © 2006 IEEE  

In United States (U.S.), government-funded organizations, such as NLDAC, reimburse travel and subsistence expenses incurred during living-organ donation process. However, in Iran, there is a non-governmental organization called Iranian Kidney Foundation (IKF) that funds the direct and indirect costs of donors through charitable donations and contributions from participants in the exchange program. In this article, for countries outside the U.S. that currently use an equality approach, we propose a potential new compensation-apportionment approach (equitable approach) for kidney-exchange chains and compare it with the currently available system (equality approach) in terms of the...