Abstract: The paper presents the applications of artificial
intelligence technique called adaptive tabu search to design the
controller of a buck converter. The averaging model derived from the
DQ and generalized state-space averaging methods is applied to
simulate the system during a searching process. The simulations
using such averaging model require the faster computational time
compared with that of the full topology model from the software
packages. The reported model is suitable for the work in the paper in
which the repeating calculation is needed for searching the best
solution. The results will show that the proposed design technique
can provide the better output waveforms compared with those
designed from the classical method.
Abstract: Complex statistical analysis of stresses in concrete
slab of the real type of rigid pavement is performed. The
computational model of the pavement is designed as a spatial (3D) model, is based on a nonlinear variant of the finite element method
that respects the structural nonlinearity, enables to model different arrangement of joints, and the entire model can be loaded by the
thermal load. Interaction of adjacent slabs in joints and contact of the slab and the subsequent layer are modeled with help of special
contact elements. Four concrete slabs separated by transverse and
longitudinal joints and the additional subgrade layers and soil to the depth of about 3m are modeled. The thickness of individual layers,
physical and mechanical properties of materials, characteristics of
joints, and the temperature of the upper and lower surface of slabs are supposed to be random variables. The modern simulation technique
Updated Latin Hypercube Sampling with 20 simulations is used for statistical analysis. As results, the estimates of basic statistics of the
principal stresses s1 and s3 in 53 points on the upper and lower surface of the slabs are obtained.
Abstract: A multi-block algorithm and its implementation in two-dimensional finite element numerical model CCHE2D are presented. In addition to a conventional Lagrangian Interpolation Method (LIM), a novel interpolation method, called Consistent Interpolation Method (CIM), is proposed for more accurate information transfer across the interfaces. The consistent interpolation solves the governing equations over the auxiliary elements constructed around the interpolation nodes using the same numerical scheme used for the internal computational nodes. With the CIM, the momentum conservation can be maintained as well as the mass conservation. An imbalance correction scheme is used to enforce the conservation laws (mass and momentum) across the interfaces. Comparisons of the LIM and the CIM are made using several flow simulation examples. It is shown that the proposed CIM is physically more accurate and produces satisfactory results efficiently.
Abstract: As one result of the project “Reactive Construction
Project Scheduling using Real Time Construction Logistic Data and
Simulation”, a procedure for using data about uncertain resource
availability assumptions in reactive scheduling processes has been
developed. Prediction data about resource availability is generated in
a formalized way using real-time monitoring data e.g. from auto-ID
systems on the construction site and in the supply chains. The paper
focusses on the formalization of the procedure for monitoring
construction logistic processes, for the detection of disturbance and
for generating of new and uncertain scheduling assumptions for the
reactive resource constrained simulation procedure that is and will be
further described in other papers.
Abstract: The temperature distribution and the heat transfer
rates through a multi-layer door of a furnace were investigated. The
inside of the door was in contact with hot air and the other side of the
door was in contact with room air. Radiation heat transfer from the
walls of the furnace to the door and the door to the surrounding area
was included in the problem. This work is a two dimensional steady
state problem. The Churchill and Chu correlation was used to find
local convection heat transfer coefficients at the surfaces of the
furnace door. The thermophysical properties of air were the functions
of the temperatures. Polynomial curve fitting for the fluid properties
were carried out. Finite difference method was used to discretize for
conduction heat transfer within the furnace door. The Gauss-Seidel
Iteration was employed to compute the temperature distribution in
the door.
The temperature distribution in the horizontal mid plane of the
furnace door in a two dimensional problem agrees with the one
dimensional problem. The local convection heat transfer coefficients
at the inside and outside surfaces of the furnace door are exhibited.
Abstract: In this paper, stability and Hopf bifurcation analysis of
a novel hyperchaotic system are investigated. Four feedback control
strategies, the linear feedback control method, enhancing feedback
control method, speed feedback control method and delayed feedback
control method, are used to control the hyperchaotic attractor to
unstable equilibrium. Moreover numerical simulations are given to
verify the theoretical results.
Abstract: Social, mobility and information aggregation inside
business environment need to converge to reach the next step of
collaboration to enhance interaction and innovation. The following
article is based on the “Assemblage" concept seen as a framework to
formalize new user interfaces and applications. The area of research
is the Energy Social Business Environment, especially the Energy
Smart Grids, which are considered as functional and technical
foundations of the revolution of the Energy Sector of tomorrow. The
assemblages are modelized by means of mereology and simplicial
complexes. Its objective is to offer new central attention and
decision-making tools to end-users.
Abstract: Study fluid flow and heat transfer characteristics of
microchannel in a primary Cross-corrugated(CC) surface recuperators
with corrugations and without corrugations, using CFD method. The
pitch-over-height ratios P/H of Cross-corrugated (CC) surface is from
1.5 to 4.0, included angles β=75º. The study was performed using CFD
software FLUENT to create unit model and simulate fluid
temperature, velocity, heat transfer coefficient and other parameters.
The results from these simulations were compared to experimental
data. It is concluded that, when the Reynolds number is constant, if
increase P/H, j/f will decrease, also the decreasing trend will become
weak. Under the condition of P/H=2.2, if increase the inlet velocity j/f
will decrease; in addition, the heat transfer performance in surface
with corrugation will increase 10% compared to that without
corrugation. The study results can provide the basis to optimize the
design, select the type of heat transfer surface, the scale structure, and
heat-transfer surface arrangement for recuperators.
Abstract: The study concerns an experimental investigation in
the laboratory of the water erosion using a rainfall simulator. We
have focused our attention on the influence of rainfall intensity on
some hydraulic characteristics. The results obtained allow us to
conclude that there is a significant correlation between rainfall
intensity and hydraulic characteristics of runoff (Reynolds number,
Froude number) and sediment concentration.
Abstract: In this paper; we are interested in dynamic modelling of quadrotor while taking into account the high-order nonholonomic constraints as well as the various physical phenomena, which can influence the dynamics of a flying structure. These permit us to introduce a new state-space representation and new control scheme. We present after the development and the synthesis of a stabilizing control laws design based on sliding mode in order to perform best tracking results. It ensures locally asymptotic stability and desired tracking trajectories. Nonlinear observer is then synthesized in order to estimate the unmeasured states and the effects of the external disturbances such as wind and noise. Finally simulation results are also provided in order to illustrate the performances of the proposed controllers.
Abstract: In this paper, an attempt has been made to obtain nonsensitive
solutions in the multi-objective optimization of a
photovoltaic/thermal (PV/T) air collector. The selected objective
functions are overall energy efficiency and exergy efficiency.
Improved thermal, electrical and exergy models are used to calculate
the thermal and electrical parameters, overall energy efficiency,
exergy components and exergy efficiency of a typical PV/T air
collector. A computer simulation program is also developed. The
results of numerical simulation are in good agreement with the
experimental measurements noted in the previous literature. Finally,
multi-objective optimization has been carried out under given
climatic, operating and design parameters. The optimized ranges of
inlet air velocity, duct depth and the objective functions in optimal
Pareto front have been obtained. Furthermore, non-sensitive solutions
from energy or exergy point of view in the results of multi-objective
optimization have been shown.
Abstract: Hot tear cracking and residual stress are two different consequences of thermal stress both of which can be considered as casting problem. The purpose of the present study is simulation of the effect of casting shape characteristic on hot tearing and residual stress. This study shows that the temperature range for simulation of hot tearing and residual stress are different. In this study, in order to study the development of thermal stress and to predict the hot tearing and residual stress of shaped casting, MAGMASOFT simulation program was used. The strategy of this research was the prediction of hot tear location using pinpointing hot spot and thermal stress concentration zones. The results shows that existing of stress concentration zone increases the hot tearing probability and consequently reduces the amount of remaining residual stress in casting parts.
Abstract: The main idea behind in network aggregation is that,
rather than sending individual data items from sensors to sinks,
multiple data items are aggregated as they are forwarded by the
sensor network. Existing sensor network data aggregation techniques
assume that the nodes are preprogrammed and send data to a central
sink for offline querying and analysis. This approach faces two major
drawbacks. First, the system behavior is preprogrammed and cannot
be modified on the fly. Second, the increased energy wastage due to
the communication overhead will result in decreasing the overall
system lifetime. Thus, energy conservation is of prime consideration
in sensor network protocols in order to maximize the network-s
operational lifetime. In this paper, we give an energy efficient
approach to query processing by implementing new optimization
techniques applied to in-network aggregation. We first discuss earlier
approaches in sensors data management and highlight their
disadvantages. We then present our approach “Energy Efficient
Indexed Aggregation" (EEIA) and evaluate it through several
simulations to prove its efficiency, competence and effectiveness.
Abstract: The current practice of determination of moisture diffusivity of building materials under laboratory conditions is predominantly aimed at the absorption phase. The main reason is the simplicity of the inverse analysis of measured moisture profiles. However, the liquid moisture transport may exhibit significant hysteresis. Thus, the moisture diffusivity should be different in the absorption (wetting) and desorption (drying) phase. In order to bring computer simulations of hygrothermal performance of building materials closer to the reality, it is then necessary to find new methods for inverse analysis which could be used in the desorption phase as well. In this paper we present genetic algorithm as a possible method of solution of the inverse problem of moisture transport in desorption phase. Its application is demonstrated for AAC as a typical building material.
Abstract: Simulations of magnetic microstructure in elliptical
Permalloy elements used for controlled motion of magnetic particles
are discussed. The saturating field of the elliptical elements was
studied with respect to lateral dimensions for one-vortex, cross-tie,
diamond and double-diamond states as initial zero-field domain
configurations. With aspect ratio of 1:3 the short axis was varied
from 125 nm to 1000 nm, whereas the thickness was kept constant at
50 nm.
Abstract: Optimal selection of electrical insulations in electrical
machinery insures reliability during operation. From the insulation
studies of view for electrical machines, stator is the most important
part. This fact reveals the requirement for inspection of the electrical
machine insulation along with the electro-thermal stresses. In the
first step of the study, a part of the whole structure of machine in
which covers the general characteristics of the machine is chosen,
then based on the electromagnetic analysis (finite element method),
the machine operation is simulated. In the simulation results, the
temperature distribution of the total structure is presented
simultaneously by using electro-thermal analysis. The results of
electro-thermal analysis can be used for designing an optimal cooling
system. In order to design, review and comparing the cooling
systems, four wiring structures in the slots of Stator are presented.
The structures are compared to each other in terms of electrical,
thermal distribution and remaining life of insulation by using Finite
Element analysis. According to the steps of the study, an optimization
algorithm has been presented for selection of appropriate structure.
Abstract: In this paper the authors propose a flexible electronic solution, to improve the energetic efficiency of a thermo plant. This is achieved by replacing the mechanical gear box, placed traditionally between a gas turbine and a synchronous generator; by a power electronic converter. After reminding problematic of gear boxes and interest of a proposed electronic solution in high power plants, the authors describe a new control strategy for an indirect frequency converter, which is characterized by its high efficiency due to the use of SWM: Square Wave Modulation. The main advantage of this mode is the quasi absence of switching losses. A control method is also proposed to resolve some problems incurred by using square wave modulation, in particular to reduce the harmonics distortion of the output inverter voltage and current. Simulation examples as well as experimental results are included.
Abstract: This paper attempts to model and design a simple
fuzzy logic controller with Variable Reference. The Variable
Reference (VR) is featured as an adaptability element which is
obtained from two known variables – desired system-input and actual
system-output. A simple fuzzy rule-based technique is simulated to
show how the actual system-input is gradually tuned in to a value
that closely matches the desired input. The designed controller is
implemented and verified on a simple heater which is controlled by
PIC Microcontroller harnessed by a code developed in embedded C.
The output response of the PIC-controlled heater is analyzed and
compared to the performances by conventional fuzzy logic
controllers. The novelty of this work lies in the fact that it gives
better performance by using less number of rules compared to
conventional fuzzy logic controllers.
Abstract: We created the tool, which combines the powerful
GENESIS (GEneral NEural SImulation System) simulation language
with the up-to-date visualisation and internet techniques. Our
solution resides in the connection between the simulation output from
GENESIS, which is converted to the data-structure suitable for
WWW browsers and VRML (Virtual Reality Modelling Language)
viewers. The selected GENESIS simulations are once exported into
the VRML code, and stored in our neurovisualisation portal
(webserver). There, the loaded models, demonstrating mainly the
spread of electrical signal (action potentials, postsynaptic potentials)
along the neuronal membrane (axon, dendritic tree, neuron) could be
displayed in the client-s VRML viewer, without interacting with
original GENESIS environment. This enables the visualisation of
basic neurophysiological phenomena designed for GENESIS
simulator on the independent OS (operation system).
Abstract: Silicon nanowire (SiNW) based thermoelectric device (TED) has potential applications in areas such as chip level cooling/ energy harvesting. It is a great challenge however, to assemble an efficient device with these SiNW. The presence of parasitic in the form of interfacial electrical resistance will have a significant impact on the performance of the TED. In this work, we explore the effect of the electrical contact resistance on the performance of a TED. Numerical simulations are performed on SiNW to investigate such effects on its cooling performance. Intrinsically, SiNW individually without the unwanted parasitic effect has excellent cooling power density. However, the cooling effect is undermined with the contribution of the electrical contact resistance.