Abstract: Avoidable unscheduled maintenance events and unnecessary
spare parts deliveries are mostly caused by an incorrect choice
of the underlying maintenance strategy. For a faster and more efficient
supply of spare parts for aircrafts of an airline we examine options for
improving the underlying logistics network integrated in an existing
aviation industry network. This paper presents a dynamic prediction
model as decision support for maintenance method selection considering
requirements of an entire flight network. The objective is
to guarantee a high supply of spare parts by an optimal interaction
of various network levels and thus to reduce unscheduled maintenance
events and minimize total costs. By using a prognostics-based
preventive maintenance strategy unscheduled component failures are
avoided for an increase in availability and reliability of the entire
system. The model is intended for use in an aviation company that
utilizes a structured planning process based on collected failures data
of components.
Abstract: In a handwriting recognition problem, characters can
be represented using chain codes. The main problem in representing
characters using chain code is optimizing the length of the chain
code. This paper proposes to use randomized algorithm to minimize
the length of Freeman Chain Codes (FCC) generated from isolated
handwritten characters. Feedforward neural network is used in the
classification stage to recognize the image characters. Our test results
show that by applying the proposed model, we reached a relatively
high accuracy for the problem of isolated handwritten when tested on
NIST database.
Abstract: The iron loss is a source of detuning in vector controlled
induction motor drives if the classical rotor vector controller is used for
decoupling. In fact, the field orientation will not be satisfied and the
output torque will not truck the reference torque mostly used by Loss
Model Controllers (LMCs). In addition, this component of loss, among
others, may be excessive if the vector controlled induction motor is
driving light loads. In this paper, the series iron loss model is used to
develop a vector controller immune to iron loss effect and then an LMC
to minimize the total power loss using the torque generated by the speed
controller.
Abstract: The two-dimensional gel electrophoresis method
(2-DE) is widely used in Proteomics to separate thousands of proteins
in a sample. By comparing the protein expression levels of proteins in
a normal sample with those in a diseased one, it is possible to identify
a meaningful set of marker proteins for the targeted disease. The major
shortcomings of this approach involve inherent noises and irregular
geometric distortions of spots observed in 2-DE images. Various
experimental conditions can be the major causes of these problems. In
the protein analysis of samples, these problems eventually lead to
incorrect conclusions. In order to minimize the influence of these
problems, this paper proposes a partition based pair extension method
that performs spot-matching on a set of gel images multiple times and
segregates more reliable mapping results which can improve the
accuracy of gel image analysis. The improved accuracy of the
proposed method is analyzed through various experiments on real
2-DE images of human liver tissues.
Abstract: Power consumption of nodes in ad hoc networks is a
critical issue as they predominantly operate on batteries. In order to
improve the lifetime of an ad hoc network, all the nodes must be
utilized evenly and the power required for connections must be
minimized. In this project a link layer algorithm known as Power
Aware medium Access Control (PAMAC) protocol is proposed
which enables the network layer to select a route with minimum total
power requirement among the possible routes between a source and a
destination provided all nodes in the routes have battery capacity
above a threshold. When the battery capacity goes below a
predefined threshold, routes going through these nodes will be
avoided and these nodes will act only as source and destination.
Further, the first few nodes whose battery power drained to the set
threshold value are pushed to the exterior part of the network and the
nodes in the exterior are brought to the interior. Since less total
power is required to forward packets for each connection. The
network layer protocol AOMDV is basically an extension to the
AODV routing protocol. AOMDV is designed to form multiple
routes to the destination and it also avoid the loop formation so that it
reduces the unnecessary congestion to the channel. In this project, the
performance of AOMDV is evaluated using PAMAC as a MAC layer
protocol and the average power consumption, throughput and
average end to end delay of the network are calculated and the results
are compared with that of the other network layer protocol AODV.
Abstract: In rail vehicles, air springs are very important isolating component, which guarantee good ride comfort for passengers during their trip. In the most new rail–vehicle models, developed by researchers, the thermo–dynamical effects of air springs are ignored and secondary suspension is modeled by simple springs and dampers. As the performance of suspension components have significant effects on rail–vehicle dynamics and ride comfort of passengers, a complete nonlinear thermo–dynamical air spring model, which is a combination of two different models, is introduced. Result from field test shows remarkable agreement between proposed model and experimental data. Effects of air suspension parameters on the system performances are investigated here and then these parameters are tuned to minimize Sperling ride comfort index during the trip. Results showed that by modification of air suspension parameters, passengers comfort is improved and ride comfort index is reduced about 10%.
Abstract: The present work analyses different parameters of pressure die casting to minimize the casting defects. Pressure diecasting is usually applied for casting of aluminium alloys. Good surface finish with required tolerances and dimensional accuracy can be achieved by optimization of controllable process parameters such as solidification time, molten temperature, filling time, injection pressure and plunger velocity. Moreover, by selection of optimum process parameters the pressure die casting defects such as porosity, insufficient spread of molten material, flash etc. are also minimized. Therefore, a pressure die casting component, carburetor housing of aluminium alloy (Al2Si2O5) has been considered. The effects of selected process parameters on casting defects and subsequent setting of parameters with the levels have been accomplished by Taguchi-s parameter design approach. The experiments have been performed as per the combination of levels of different process parameters suggested by L18 orthogonal array. Analyses of variance have been performed for mean and signal-to-noise ratio to estimate the percent contribution of different process parameters. Confidence interval has also been estimated for 95% consistency level and three conformational experiments have been performed to validate the optimum level of different parameters. Overall 2.352% reduction in defects has been observed with the help of suggested optimum process parameters.
Abstract: To minimize power losses, it is important to
determine the location and size of local generators to be placed in
unbalanced power distribution systems. On account of some inherent
features of unbalanced distribution systems, such as radial structure,
large number of nodes, a wide range of X/R ratios, the conventional
techniques developed for the transmission systems generally fail on
the determination of optimum size and location of distributed
generators (DGs). This paper presents a simple method for
investigating the problem of contemporaneously choosing best
location and size of DG in three-phase unbalanced radial distribution
system (URDS) for power loss minimization and to improve the
voltage profile of the system. Best location of the DG is determined
by using voltage index analysis and size of DG is computed by
variational technique algorithm according to available standard size
of DGs. This paper presents the results of simulations for 25-bus and
IEEE 37- bus Unbalanced Radial Distribution system.
Abstract: In the literature of information theory, there is
necessity for comparing the different measures of fuzzy entropy and
this consequently, gives rise to the need for normalizing measures of
fuzzy entropy. In this paper, we have discussed this need and hence
developed some normalized measures of fuzzy entropy. It is also
desirable to maximize entropy and to minimize directed divergence
or distance. Keeping in mind this idea, we have explained the method
of optimizing different measures of fuzzy entropy.
Abstract: Majority of researches conducted on Iranian urban
development plans indicate that they have been almost unsuccessful
in terms of draft, execution and goal achievement. Lack or shortage
of essential statistics and information can be listed as an important
reason of the failure of these plans. Lack of figures and information
has turned into an obvious part of the country-s statistics officials.
This problem has made urban planner themselves to embark on
physical surveys including real estate and land pricing, population
and economic census of the city. Apart from the problems facing
urban developers, the possibility of errors is high in such surveys.
In the present article, applying the interview technique, it has
been mentioned that utilizing multipurpose cadastre system as a land
information system is essential for urban development plans in Iran.
It can minimize or even remove the failures facing urban
development plans.
Abstract: Increasing energy absorption is a significant parameter
in vehicle design. Absorbing more energy results in decreasing
occupant damage. Limitation of the deflection in a side impact results
in decreased energy absorption (SEA) and increased peak load (PL).
Hence a high crash force jeopardizes passenger safety and vehicle
integrity. The aims of this paper are to determine suitable dimensions
and material of a square beam subjected to side impact, in order to
maximize SEA and minimize PL. To achieve this novel goal, the
geometric parameters of a square beam are optimized using the
response surface method (RSM).multi-objective optimization is
performed, and the optimum design for different response features is
obtained.
Abstract: The purpose of this work is measurement of the
system presampling MTF of a variable resolution x-ray (VRX) CT
scanner. In this paper, we used the parameters of an actual VRX CT
scanner for simulation and study of effect of different focal spot sizes
on system presampling MTF by Monte Carlo method (GATE
simulation software). Focal spot size of 0.6 mm limited the spatial
resolution of the system to 5.5 cy/mm at incident angles of below 17º
for cell#1. By focal spot size of 0.3 mm the spatial resolution
increased up to 11 cy/mm and the limiting effect of focal spot size
appeared at incident angles of below 9º. The focal spot size of 0.3
mm could improve the spatial resolution to some extent but because
of magnification non-uniformity, there is a 10 cy/mm difference
between spatial resolution of cell#1 and cell#256. The focal spot size
of 0.1 mm acted as an ideal point source for this system. The spatial
resolution increased to more than 35 cy/mm and at all incident angles
the spatial resolution was a function of incident angle. By the way
focal spot size of 0.1 mm minimized the effect of magnification nonuniformity.
Abstract: This research investigates the suitability of fuel oil in
improving gypseous soil. A detailed laboratory tests were carried-out
on two soils (soil I with 51.6% gypsum content, and soil II with
26.55%), where the two soils were obtained from Al-Therthar site
(Al-Anbar Province-Iraq).
This study examines the improvement of soil properties using the
gypsum material which is locally available with low cost to minimize
the effect of moisture on these soils by using the fuel oil. This study
was conducted on two models of the soil gypsum, from the Tharthar
area. The first model was sandy soil with Gypsum content of (51.6%)
and the second is clayey soil and the content of Gypsum is (26.55%).
The program included tests measuring the permeability and
compressibility of the soil and their collapse properties. The shear
strength of the soil and the amounts of weight loss of fuel oil due to
drying had been found. These tests have been conducted on the
treated and untreated soils to observe the effect of soil treatment on
the engineering properties when mixed with varying degrees of fuel
oil with the equivalent of the water content.
The results showed that fuel oil is a good material to modify the
basic properties of the gypseous soil of collapsibility and
permeability, which are the main problems of this soil and retained
the soil by an appropriate amount of the cohesion suitable for
carrying the loads from the structure.
Abstract: This paper presents an iterative algorithm to find a
inverse kinematic solution of 5-DOF robot. The algorithm is to
minimize the iteration number. Since the 5-DOF robot cannot give full
orientation of tool. Only z-direction of tool is satisfied while rotation
of tool is determined by kinematic constraint. This work therefore
described how to specify the tool direction and let the tool rotation free.
The simulation results show that this algorithm effectively worked.
Using the proposed iteration algorithm, error due to inverse kinematics
converged to zero rapidly in 5 iterations. This algorithm was applied in
real welding robot and verified through various practical works.
Abstract: One of the potential and effective ways of
storing thermal energy in buildings is the integration of brick with phase change materials (PCMs). This paper presents a two-dimensional model for simulating and analyzing of PCM
in order to minimize energy consumption in the buildings. The numerical approach has been used with the real weather data of a selected city of Iran (Tehran). Two kinds of brick integrated PCM are investigated and compared base on
outdoor weather conditions and the amount of energy
consumption. The results show a significant reduction in
maximum entering heat flux to building about 32.8%
depending on PCM quantity. The results are analyzed by
various temperature contour plots. The contour plots
illustrated the time dependent mechanism of entering heat flux for a brick integrated with PCM. Further analysis is developed to investigate the effect of PCM location on the inlet heat flux. The results demonstrated that to achieve maximum performance of PCM it is better to locate PCM near the outdoor.
Abstract: It is essential to have a uniform and calm flow field
for a settling tank to have high performance. In general, the
recirculation zones always occurred in sedimentation tanks. The
presence of these regions may have different effects. The nonuniformity
of the velocity field, the short-circuiting at the surface and
the motion of the jet at the bed of the tank that occurs because of the
recirculation in the sedimentation layer, are affected by the geometry
of the tank. There are some ways to decrease the size of these dead
zones, which would increase the performance. One of the ways is to
use a suitable baffle configuration. In this study, the presence of
baffle with different position has been investigated by a finite volume
method, with VOF (Volume of Fluid) model. Besides, the k-ε
turbulence model is used in the numerical calculations. The results
indicate that the best position of the baffle is obtained when the
volume of the recirculation region is minimized or is divided to
smaller part and the flow field trend to be uniform in the settling
zone.
Abstract: This paper discusses a genetic algorithm (GA) based optimal load shedding that can apply for electrical distribution networks with and without dispersed generators (DG). Also, the proposed method has the ability for considering constant and variable capacity deficiency caused by unscheduled outages in the bulked generation and transmission system of bulked power supply. The genetic algorithm (GA) is employed to search for the optimal load shedding strategy in distribution networks considering DGs in two cases of constant and variable modelling of bulked power supply of distribution networks. Electrical power distribution systems have a radial network and unidirectional power flows. With the advent of dispersed generations, the electrical distribution system has a locally looped network and bidirectional power flows. Therefore, installed DG in the electrical distribution systems can cause operational problems and impact on existing operational schemes. Introduction of DGs in electrical distribution systems has introduced many new issues in operational and planning level. Load shedding as one of operational issue has no exempt. The objective is to minimize the sum of curtailed load and also system losses within the frame-work of system operational and security constraints. The proposed method is tested on a radial distribution system with 33 load points for more practical applications.
Abstract: This is a cross-cultural study that determines South
African multinational enterprises (MNEs) entry strategies as they
invest in Africa. An integrated theoretical framework comprising the
transaction cost theory, Uppsala model, eclectic paradigm and the
distance framework was adopted. A sample of 40 South African
MNEs with 415 existing FDI entries in Africa was drawn. Using an
ordered logistic regression model, the impact of culture on the choice
of degree of control by South African MNEs in Africa was
determined. Cultural distance was one of significant factors that
influenced South African MNEs- choice of degree of control.
Furthermore, South African MNEs are risk averse in all countries in
Africa but minimize the risks differently across sectors. Service
sectors chooses to own their subsidiaries 100% and avoid dealing
with the locals while manufacturing, resources and construction
choose to have a local partner to share the risk.
Abstract: The approach proposed here is oriented in the direction of fuzzy system for the analysis and the synthesis of intelligent climate controllers, the simulation of the internal climate of the greenhouse is achieved by a linear model whose coefficients are obtained by identification. The use of fuzzy logic controllers for the regulation of climate variables represents a powerful way to minimize the energy cost. Strategies of reduction and optimization are adopted to facilitate the tuning and to reduce the complexity of the controller.
Abstract: Self-compacting concrete (SCC), a new kind of high
performance concrete (HPC) have been first developed in Japan in
1986. The development of SCC has made casting of dense
reinforcement and mass concrete convenient, has minimized noise.
Fresh self-compacting concrete (SCC) flows into formwork and
around obstructions under its own weight to fill it completely and
self-compact (without any need for vibration), without any
segregation and blocking. The elimination of the need for
compaction leads to better quality concrete and substantial
improvement of working conditions. SCC mixes generally have a
much higher content of fine fillers, including cement, and produce
excessively high compressive strength concrete, which restricts its
field of application to special concrete only. To use SCC mixes in
general concrete construction practice, requires low cost materials to
make inexpensive concrete.
Rice husk ash (RHA) has been used as a highly reactive
pozzolanic material to improve the microstructure of the interfacial
transition zone (ITZ) between the cement paste and the aggregate in
self compacting concrete. Mechanical experiments of RHA blended
Portland cement concretes revealed that in addition to the pozzolanic
reactivity of RHA (chemical aspect), the particle grading (physical
aspect) of cement and RHA mixtures also exerted significant
influences on the blending efficiency.
The scope of this research was to determine the usefulness of Rice
husk ash (RHA) in the development of economical self compacting
concrete (SCC). The cost of materials will be decreased by reducing
the cement content by using waste material like rice husk ash instead
of.
This paper presents a study on the development of Mechanical
properties up to 180 days of self compacting and ordinary concretes
with rice-husk ash (RHA), from a rice paddy milling industry in
Rasht (Iran). Two different replacement percentages of cement by
RHA, 10%, and 20%, and two different water/cementicious material
ratios (0.40 and 0.35), were used for both of self compacting and
normal concrete specimens. The results are compared with those of
the self compacting concrete without RHA, with compressive,
flexural strength and modulus of elasticity. It is concluded that RHA
provides a positive effect on the Mechanical properties at age after
60 days.
Base of the result self compacting concrete specimens have higher
value than normal concrete specimens in all test except modulus of
elasticity. Also specimens with 20% replacement of cement by RHA
have the best performance.