Abstract: In this paper the behavior of fixed series compensated
extra high voltage transmission lines during faults is simulated. Many
over-voltage protection schemes for series capacitors are limited in
terms of size and performance, and are easily affected by
environmental conditions. While the need for more compact and
environmentally robust equipment is required. use of series
capacitors for compensating part of the inductive reactance of long
transmission lines increases the power transmission capacity.
Emphasis is given on the impact of modern capacitor protection
techniques (MOV protection). The simulation study is performed
using MATLAB/SIMULINK®and results are given for a three phase
and a single phase to ground fault.
Abstract: This work is an attempt to use the standard Smoothed
Particle Hydrodynamics methodology for the simulation of the
complex unsteady, free-surface flow in a rotating Turgo impulse
water turbine. A comparison of two different geometries was
conducted. The SPH method due to its mesh-less nature is capable of
capturing the flow features appearing in the turbine, without
diffusion at the water/air interface. Furthermore results are compared
with a commercial CFD package (Fluent®) and the SPH algorithm
proves to be capable of providing similar results, in much less time
than the mesh based CFD program. A parametric study was also
performed regarding the turbine inlet angle.
Abstract: Due to the complex network architecture, the mobile
adhoc network-s multihop feature gives additional problems to the
users. When the traffic load at each node gets increased, the
additional contention due its traffic pattern might cause the nodes
which are close to destination to starve the nodes more away from the
destination and also the capacity of network is unable to satisfy the
total user-s demand which results in an unfairness problem. In this
paper, we propose to create an algorithm to compute the optimal
MAC-layer bandwidth assigned to each flow in the network. The
bottleneck links contention area determines the fair time share which
is necessary to calculate the maximum allowed transmission rate used
by each flow. To completely utilize the network resources, we
compute two optimal rates namely, the maximum fair share and
minimum fair share. We use the maximum fair share achieved in
order to limit the input rate of those flows which crosses the
bottleneck links contention area when the flows that are not allocated
to the optimal transmission rate and calculate the following highest
fair share. Through simulation results, we show that the proposed
protocol achieves improved fair share and throughput with reduced
delay.
Abstract: This research deals with techno economic analysis to select the most economic desalination method for Asalouyeh combined cycle power plant . Due to lack of fresh water, desalination of sea water is necessary to provide required DM water of Power Plant. The most common desalination methods are RO, MSF, MED, and MED–TVC. In this research, methods of RO, MED, and MED– TVC have been compared. Simulation results show that recovery of heat of exhaust gas of main stack is optimum case for providing DM water required for injected steam of MED desalination. This subject is very important because of improving thermal efficiency of power plant using extra heat recovery. Also, it has been shown that by adding 3 rows of finned tube to de-aerator evaporator, which is very simple and low cost, required steam for generating 5200 m3/day of desalinated water is obtainable.
Abstract: A zero-field ferromagnetic Ising model is utilized to
simulate the propagation of infection in a population that assumes a
square lattice structure. The rate of infection increases with
temperature. The disease spreads faster among individuals with low J
values. Such effect, however, diminishes at higher temperatures.
Abstract: Transient simulation of power electronic circuits is of
considerable interest to the designer. The switching nature of the
devices used permits development of specialized algorithms which
allow a considerable reduction in simulation time compared to
general purpose simulation algorithms. This paper describes a
method used to simulate a power electronic circuits using the
SIMULINK toolbox within MATLAB software. Theoretical results
are presented provides the basis of transient analysis of a power
electronic circuits.
Abstract: Sedimentation is a hydraulic phenomenon that is
emerging as a serious challenge in river engineering. When the flow
reaches a certain state that gather potential energy, it shifts the
sediment load along channel bed. The transport of such materials can
be in the form of suspended and bed loads. The movement of these
along the river course and channels and the ways in which this could
influence the water intakes is considered as the major challenges for
sustainable O&M of hydraulic structures. This could be very serious
in arid and semi-arid regions like Iran, where inappropriate watershed
management could lead to shifting a great deal of sediments into the
reservoirs and irrigation systems. This paper aims to investigate
sedimentation in the Western Canal of Dez Diversion Weir in Iran,
identifying factors which influence the process and provide ways in
which to mitigate its detrimental effects by using the SHARC
Software.
For the purpose of this paper, data from the Dezful water authority
and Dezful Hydrometric Station pertinent to a river course of about 6
Km were used.
Results estimated sand and silt bed loads concentrations to be 193
ppm and 827ppm respectively. Given the available data on average
annual bed loads and average suspended sediment loads of 165ppm
and 837ppm, there was a significant statistical difference (16%)
between the sand grains, whereas no significant difference (1.2%)
was find in the silt grain sizes. One explanation for such finding
being that along the 6 Km river course there was considerable
meandering effects which explains recent shift in the hydraulic
behavior along the stream course under investigation. The sand
concentration in downstream relative to present state of the canal
showed a steep descending curve. Sediment trapping on the other
hand indicated a steep ascending curve. These occurred because the
diversion weir was not considered in the simulation model.
Abstract: The purpose of this work is fast design optimization of
the seal chamber. The study includes the mass transfer between lower
and upper chamber on seal chamber for hot water application pumps.
The use of Fluent 12.1 commercial code made it possible to capture
complex flow with heat-mass transfer, radiation, Tailor instability,
and buoyancy effect. Realizable k-epsilon model was used for
turbulence modeling. Radiation heat losses were taken into account.
The temperature distribution at seal region is predicted with respect
to heat addition.
Results show the possibilities of the model simplifications by
excluding the water domain in low chamber from calculations. CFD
simulations permit to improve seal chamber design to meet target
water temperature around the seal. This study can be used for the
analysis of different seal chamber configurations.
Abstract: This paper introduces an adiabatic register file based
on two-phase CPAL (Complementary Pass-Transistor Adiabatic
Logic circuits) with power-gating scheme, which can operate on a
single-phase power clock. A 32×32 single-phase adiabatic register file
with power-gating scheme has been implemented with TSMC 0.18μm
CMOS technology. All the circuits except for the storage cells employ
two-phase CPAL circuits, and the storage cell is based on the
conventional memory one. The two-phase non-overlap power-clock
generator with power-gating scheme is used to supply the proposed
adiabatic register file. Full-custom layouts are drawn. The energy and
functional simulations have been performed using the net-list
extracted from their layouts. Compared with the traditional static
CMOS register file, HSPICE simulations show that the proposed
adiabatic register file can work very well, and it attains about 73%
energy savings at 100 MHz.
Abstract: As originally designed for wired networks, TCP (transmission control protocol) congestion control mechanism is triggered into action when packet loss is detected. This implicit assumption for packet loss mostly due to network congestion does not work well in Mobile Ad Hoc Network, where there is a comparatively high likelihood of packet loss due to channel errors and node mobility etc. Such non-congestion packet loss, when dealt with by congestion control mechanism, causes poor TCP performance in MANET. In this study, we continue to investigate the impact of the interaction between transport protocols and on-demand routing protocols on the performance and stability of 802.11 multihop networks. We evaluate the important wireless networking events caused routing change, and propose a cross layer method to delay the unnecessary routing changes, only need to add a sensitivity parameter α , which represents the on-demand routing-s reaction to link failure of MAC layer. Our proposal is applicable to the plain 802.11 networking environment, the simulation results that this method can remarkably improve the stability and performance of TCP without any modification on TCP and MAC protocol.
Abstract: In this paper, Lattice Boltzmann Method (LBM) is used to study laminar flow with mixed convection heat transfer inside a two-dimensional inclined lid-driven rectangular cavity with aspect ratio AR = 3. Bottom wall of the cavity is maintained at lower temperature than the top lid, and its vertical walls are assumed insulated. Top lid motion results in fluid motion inside the cavity. Inclination of the cavity causes horizontal and vertical components of velocity to be affected by buoyancy force. To include this effect, calculation procedure of macroscopic properties by LBM is changed and collision term of Boltzmann equation is modified. A computer program is developed to simulate this problem using BGK model of lattice Boltzmann method. The effects of the variations of Richardson number and inclination angle on the thermal and flow behavior of the fluid inside the cavity are investigated. The results are presented as velocity and temperature profiles, stream function contours and isotherms. It is concluded that LBM has good potential to simulate mixed convection heat transfer problems.
Abstract: In this paper, we investigate the study of techniques
for scheduling users for resource allocation in the case of multiple
input and multiple output (MIMO) packet transmission systems. In
these systems, transmit antennas are assigned to one user or
dynamically to different users using spatial multiplexing. The
allocation of all transmit antennas to one user cannot take full
advantages of multi-user diversity. Therefore, we developed the case
when resources are allocated dynamically. At each time slot users
have to feed back their channel information on an uplink feedback
channel. Channel information considered available in the schedulers
is the zero forcing (ZF) post detection signal to interference plus
noise ratio. Our analysis study concerns the round robin and the
opportunistic schemes.
In this paper, we present an overview and a complete capacity
analysis of these schemes. The main results in our study are to give
an analytical form of system capacity using the ZF receiver at the
user terminal. Simulations have been carried out to validate all
proposed analytical solutions and to compare the performance of
these schemes.
Abstract: We present a new approach to evaluation of Cyber Security in Power Systems using the method of modeling the power systems Infrastructure using software agents. Interfaces between module and the home smart meter are recognized as the primary points of intrusion.
Abstract: The hydraulic actuated excavator, being a non-linear
mobile machine, encounters many uncertainties. There are
uncertainties in the hydraulic system in addition to the uncertain
nature of the load. The simulation results obtained in this study show
that there is a need for intelligent control of such machines and in
particular interval type-2 fuzzy controller is most suitable for
minimizing the position error of a typical excavator-s bucket under
load variations. We consider the model parameter uncertainties such
as hydraulic fluid leakage and friction. These are uncertainties which
also depend up on the temperature and alter bulk modulus and
viscosity of the hydraulic fluid. Such uncertainties together with the
load variations cause chattering of the bucket position. The interval
type-2 fuzzy controller effectively eliminates the chattering and
manages to control the end-effecter (bucket) position with positional
error in the order of few millimeters.
Abstract: In this paper a three dimensional thermal model of
high breaking capacity fuse with unequal fuse links is proposed for
both steady-state or transient conditions. The influence of ambient
temperature and electric current on the temperature distribution
inside the fuse, has been investigated. A thermal analysis of the
unbalanced distribution of the electric current through the fuse
elements and their influence on fuse link temperature rise, has been
performed. To validate the three dimensional thermal model, some
experimental tests have been done. There is a good correlation
between experimental and simulation results.
Abstract: The presented article deals with the description of a
numerical model of a corridor at a Central Interim Spent Fuel Storage
Facility (hereinafter CISFSF). The model takes into account the
effect of air flows on the temperature of stored waste. The
computational model was implemented in the ANSYS/CFX
programming environment in the form of a CFD task solution, which
was compared with an approximate analytical calculation. The article
includes a categorization of the individual alternatives for the
ventilation of such underground systems. The aim was to evaluate a
ventilation system for a CISFSF with regard to its stability and
capacity to provide sufficient ventilation for the removal of heat
produced by stored casks with spent nuclear fuel.
Abstract: The purpose of this paper is to elucidate the flow unsteady behavior for moving plug in convergent-divergent variable thrust nozzle. Compressible axisymmetric Navier-Stokes equations are used to study this physical phenomenon. Different velocities are set for plug to investigate the effect of plug movement on flow unsteadiness. Variation of mass flow rate and thrust are compared under two conditions: First, the plug is placed at different positions and flow is simulated to reach the steady state (quasi steady simulation) and second, the plug is moved with assigned velocity and flow simulation is coupled with plug movement (unsteady simulation). If plug speed is high enough and its movement time scale is at the same order of the flow time scale, variation of the mass flow rate and thrust level versus plug position demonstrate a vital discrepancy under the quasi steady and unsteady conditions. This phenomenon should be considered especially from response time viewpoints in thrusters design.
Abstract: Series compensators have been used for many years,
to increase the stability and load ability of transmission line. They
compensate retarded or advanced volt drop of transmission lines
by placing advanced or retarded voltage in series with them to
compensate the effective reactance, which cause to increase load
ability of transmission lines. In this paper, two method of fuzzy
controller, based on power reference tracking and impedance
reference tracking have been developed on TCSC controller in
order to increase load ability and improving power oscillation
damping of system. In these methods, fire angle of thyristors are
determined directly through the special Rule-bases with the error
and change of error as the inputs. The simulation results of two
area four- machines power system show the good performance of
power oscillation damping in system. Comparison of this method
with classical PI controller shows the increasing speed of system
response in power oscillation damping.
Abstract: Component handling system is one of the important sub systems of Prototype Fast Breeder Reactor (PFBR) used for fuel handling. Core handling system is again a sub system of component handling system. Core handling system consists of in-vessel and ex-vessel subassembly handling. In-vessel core handling involves transfer arm, large rotatable plug and small rotatable plug operations. Modeling and simulation of in-vessel core handling is a part of development of Prototype Fast Breeder Reactor Operator Training Simulator. This paper deals with simulation and modeling of operations of transfer arm, large rotatable plug and small rotatable plug needed for in-vessel core handling. Process modeling was developed in house using platform independent Cµ code with OpenGL (Open Graphics Library). The control logic models and virtual panel were modeled using simulation tool.
Abstract: The Eulerian numerical method is proposed to analyze
the explosion in tunnel. Based on this method, an original software
M-MMIC2D is developed by Cµ program language. With this
software, the explosion problem in the tunnel with three
expansion-chambers is numerically simulated, and the results are
found to be in full agreement with the observed experimental data.