Abstract: In this paper, a two-dimensional (2D) numerical
model for the tidal currents simulation in Persian Gulf is presented.
The model is based on the depth averaged equations of shallow water
which consider hydrostatic pressure distribution. The continuity
equation and two momentum equations including the effects of bed
friction, the Coriolis effects and wind stress have been solved. To
integrate the 2D equations, the Alternative Direction Implicit (ADI)
technique has been used. The base of equations discritization was
finite volume method applied on rectangular mesh. To evaluate the
model validation, a dam break case study including analytical
solution is selected and the comparison is done. After that, the
capability of the model in simulation of tidal current in a real field is
represented by modeling the current behavior in Persian Gulf. The
tidal fluctuations in Hormuz Strait have caused the tidal currents in
the area of study. Therefore, the water surface oscillations data at
Hengam Island on Hormoz Strait are used as the model input data.
The check point of the model is measured water surface elevations at
Assaluye port. The comparison between the results and the
acceptable agreement of them showed the model ability for modeling
marine hydrodynamic.
Abstract: Medical applications are among the most impactful
areas of microrobotics. The ultimate goal of medical microrobots is
to reach currently inaccessible areas of the human body and carry out
a host of complex operations such as minimally invasive surgery
(MIS), highly localized drug delivery, and screening for diseases at
their very early stages. Miniature, safe and efficient propulsion
systems hold the key to maturing this technology but they pose
significant challenges. A new type of propulsion developed recently,
uses multi-flagella architecture inspired by the motility mechanism of
prokaryotic microorganisms. There is a lack of efficient methods for
designing this type of propulsion system. The goal of this paper is to
overcome the lack and this way, a numerical strategy is proposed to
design multi-flagella propulsion systems. The strategy is based on the
implementation of the regularized stokeslet and rotlet theory, RFT
theory and new approach of “local corrected velocity". The effects of
shape parameters and angular velocities of each flagellum on overall
flow field and on the robot net forces and moments are considered.
Then a multi-layer perceptron artificial neural network is designed
and employed to adjust the angular velocities of the motors for
propulsion control. The proposed method applied successfully on a
sample configuration and useful demonstrative results is obtained.
Abstract: Content-Based Image Retrieval (CBIR) has been
one on the most vivid research areas in the field of computer vision
over the last 10 years. Many programs and tools have been
developed to formulate and execute queries based on the visual or
audio content and to help browsing large multimedia repositories.
Still, no general breakthrough has been achieved with respect to
large varied databases with documents of difering sorts and with
varying characteristics. Answers to many questions with respect to
speed, semantic descriptors or objective image interpretations are
still unanswered. In the medical field, images, and especially
digital images, are produced in ever increasing quantities and used
for diagnostics and therapy. In several articles, content based
access to medical images for supporting clinical decision making
has been proposed that would ease the management of clinical data
and scenarios for the integration of content-based access methods
into Picture Archiving and Communication Systems (PACS) have
been created. This paper gives an overview of soft computing
techniques. New research directions are being defined that can
prove to be useful. Still, there are very few systems that seem to be
used in clinical practice. It needs to be stated as well that the goal
is not, in general, to replace text based retrieval methods as they
exist at the moment.
Abstract: In this article, a simulation method called the Homotopy Perturbation Method (HPM) is employed in the steady flow of a Walter's B' fluid in a vertical channel with porous wall. We employed Homotopy Perturbation Method to derive solution of a nonlinear form of equation obtained from exerting similarity transforming to the ordinary differential equation gained from continuity and momentum equations of this kind of flow. The results obtained from the Homotopy Perturbation Method are then compared with those from the Runge–Kutta method in order to verify the accuracy of the proposed method. The results show that the Homotopy Perturbation Method can achieve good results in predicting the solution of such problems. Ultimately we use this solution to obtain the other terms of velocities and physical discussion about it.
Abstract: This paper studies the pth moment exponential synchronization of a class of stochastic neural networks with mixed delays. Based on Lyapunov stability theory, by establishing a new integrodifferential inequality with mixed delays, several sufficient conditions have been derived to ensure the pth moment exponential stability for the error system. The criteria extend and improve some earlier results. One numerical example is presented to illustrate the validity of the main results.
Abstract: Threedimensional numerical simulations are conducted on a full scale CANDU Moderator and Transient variations of the temperature and velocity distributions inside the tank are determined. The results show that the flow and temperature distributions inside the moderator tank are three dimensional and no symmetry plane can be identified.Competition between the upward moving buoyancy driven flows and the downward moving momentum driven flows, results in the formation of circulation zones. The moderator tank operates in the buoyancy driven mode and any small disturbances in the flow or temperature makes the system unstable and asymmetric. Different types of temperature fluctuations are noted inside the tank: (i) large amplitude are at the boundaries between the hot and cold (ii) low amplitude are in the core of the tank (iii) high frequency fluctuations are in the regions with high velocities and (iv) low frequency fluctuations are in the regions with lower velocities.
Abstract: This paper presents unified theory for local (Savitzky-
Golay) and global polynomial smoothing. The algebraic framework
can represent any polynomial approximation and is seamless from
low degree local, to high degree global approximations. The representation
of the smoothing operator as a projection onto orthonormal
basis functions enables the computation of: the covariance matrix
for noise propagation through the filter; the noise gain and; the
frequency response of the polynomial filters. A virtually perfect Gram
polynomial basis is synthesized, whereby polynomials of degree
d = 1000 can be synthesized without significant errors. The perfect
basis ensures that the filters are strictly polynomial preserving. Given
n points and a support length ls = 2m + 1 then the smoothing
operator is strictly linear phase for the points xi, i = m+1. . . n-m.
The method is demonstrated on geometric surfaces data lying on an
invariant 2D lattice.
Abstract: In this paper, an analytical approach is used to study the coupled lateral-torsional vibrations of laminated composite beam. It is known that in such structures due to the fibers orientation in various layers, any lateral displacement will produce a twisting moment. This phenomenon is modeled by the bending-twisting material coupling rigidity and its main feature is the coupling of lateral and torsional vibrations. In addition to the material coupling, the effects of shear deformation and rotary inertia are taken into account in the definition of the potential and kinetic energies. Then, the governing differential equations are derived using the Hamilton-s principle and the mathematical model matches the Timoshenko beam model when neglecting the effect of bending-twisting rigidity. The equations of motion which form a system of three coupled PDEs are solved analytically to study the free vibrations of the beam in lateral and rotational modes due to the bending, as well as the torsional mode caused by twisting. The analytic solution is carried out in three steps: 1) assuming synchronous motion for the kinematic variables which are the lateral, rotational and torsional displacements, 2) solving the ensuing eigenvalue problem which contains three coupled second order ODEs and 3) imposing different boundary conditions related to combinations of simply, clamped and free end conditions. The resulting natural frequencies and mode shapes are compared with similar results in the literature and good agreement is achieved.
Abstract: A different concept for designing and detailing of
reinforced concrete precast frame structures is analyzed in this paper.
The new detailing of the joints derives from the special hybrid
moment frame joints. The special reinforcements of this alternative
detailing, named modified special hybrid joint, are bondless with
respect to both column and beams. Full scale tests were performed on
a plan model, which represents a part of 5 story structure, cropped in
the middle of the beams and columns spans. Theoretical approach
was developed, based on testing results on twice repaired model,
subjected to lateral seismic type loading. Discussion regarding the
modified special hybrid joint behavior and further on widening
research needed concludes the presentation.
Abstract: For Seismic design, it is important to estimate,
maximum lateral displacement (inelastic displacement) of the
structures due to sever earthquakes for several reasons. Seismic
design provisions estimate the maximum roof and storey drifts
occurring in major earthquakes by amplifying the drifts of the
structures obtained by elastic analysis subjected to seismic design
load, with a coefficient named “displacement amplification factor"
which is greater than one. Here, this coefficient depends on various
parameters, such as ductility and overstrength factors. The present
research aims to evaluate the value of the displacement amplification
factor in seismic design codes and then tries to propose a value to
estimate the maximum lateral structural displacement from sever
earthquakes, without using non-linear analysis. In seismic codes,
since the displacement amplification is related to “force reduction
factor" hence; this aspect has been accepted in the current study.
Meanwhile, two methodologies are applied to evaluate the value of
displacement amplification factor and its relation with the force
reduction factor. In the first methodology, which is applied for all
structures, the ratio of displacement amplification and force reduction
factors is determined directly. Whereas, in the second methodology
that is applicable just for R/C moment resisting frame, the ratio is
obtained by calculating both factors, separately. The acquired results
of these methodologies are alike and estimate the ratio of two factors
from 1 to 1.2. The results indicate that the ratio of the displacement
amplification factor and the force reduction factor differs to those
proposed by seismic provisions such as NEHRP, IBC and Iranian
seismic code (standard no. 2800).
Abstract: This paper proposes a balance control scheme for a biped robot to trace an arbitrary path using image information. While moving, it estimates the zero moment point(ZMP) of the biped robot in the next step using a Kalman filter and renders an appropriate balanced pose of the robot. The ZMP can be calculated from the robot's pose, which is measured from the reference object image acquired by a CCD camera on the robot's head. For simplifying the kinematical model, the coordinates systems of individual joints of each leg are aligned and the robot motion is approximated as an inverted pendulum so that a simple linear dynamics, 3D-LIPM(3D-Linear Inverted Pendulum Mode) can be applied. The efficiency of the proposed algorithm has been proven by the experiments performed on unknown trajectory.
Abstract: In the paper, the energetic features of the loaded gait
are newly analyzed depending on the trunk flexion change. To
investigate the loaded gait, walking experiments are performed for five
subjects and, the ground reaction forces and kinematic data are
measured. Based on these information, we compute the impulse,
momentum and mechanical works done on the center of body mass,
through the trunk flexion change. As a result, it is shown that the trunk
flexion change does not affect the impulses and momentums during
the step-to-step transition as well. However, the direction of the
pre-collision momentum does change depending on the trunk flexion
change, which is degenerated just after (or during) the collision period.
Abstract: Among many different methods that are used for
optimizing different engineering problems mathematical (numerical)
optimization techniques are very important because they can easily
be used and are consistent with most of engineering problems. Many
studies and researches are done on stability analysis of three
dimensional (3D) slopes and the relating probable slip surfaces and
determination of factors of safety, but in most of them force
equilibrium equations, as in simplified 2D methods, are considered
only in two directions. In other words for decreasing mathematical
calculations and also for simplifying purposes the force equilibrium
equation in 3rd direction is omitted. This point is considered in just a
few numbers of previous studies and most of them have only given a
factor of safety and they haven-t made enough effort to find the most
probable slip surface. In this study shapes of the slip surfaces are
modeled, and safety factors are calculated considering the force
equilibrium equations in all three directions, and also the moment
equilibrium equation is satisfied in the slip direction, and using
nonlinear programming techniques the shape of the most probable
slip surface is determined. The model which is used in this study is a
3D model that is composed of three upper surfaces which can cover
all defined and probable slip surfaces. In this research the meshing
process is done in a way that all elements are prismatic with
quadrilateral cross sections, and the safety factor is defined on this
quadrilateral surface in the base of the element which is a part of the
whole slip surface. The method that is used in this study to find the
most probable slip surface is the non-linear programming method in
which the objective function that must get optimized is the factor of
safety that is a function of the soil properties and the coordinates of
the nodes on the probable slip surface. The main reason for using
non-linear programming method in this research is its quick
convergence to the desired responses. The final results show a good
compatibility with the previously used classical and 2D methods and
also show a reasonable convergence speed.
Abstract: An integrated vehicle dynamics control system is developed in this paper by a combination of active front steering (AFS) and direct yaw-moment control (DYC) based on fuzzy logic control. The control system has a hierarchical structure consisting of two layers. A fuzzy logic controller is used in the upper layer (yaw rate controller) to keep the yaw rate in its desired value. The yaw rate error and its rate of change are applied to the upper controlling layer as inputs, where the direct yaw moment control signal and the steering angle correction of the front wheels are the outputs. In the lower layer (fuzzy integrator), a fuzzy logic controller is designed based on the working region of the lateral tire forces. Depending on the directions of the lateral forces at the front wheels, a switching function is activated to adjust the scaling factor of the fuzzy logic controller. Using a nonlinear seven degrees of freedom vehicle model, the simulation results illustrate considerable improvements which are achieved in vehicle handling through the integrated AFS/DYC control system in comparison with the individual AFS or DYC controllers.
Abstract: In this paper, a comparative study of application of
supervised and unsupervised learning algorithms on illumination
invariant face recognition has been carried out. The supervised
learning has been carried out with the help of using a bi-layered
artificial neural network having one input, two hidden and one output
layer. The gradient descent with momentum and adaptive learning
rate back propagation learning algorithm has been used to implement
the supervised learning in a way that both the inputs and
corresponding outputs are provided at the time of training the
network, thus here is an inherent clustering and optimized learning of
weights which provide us with efficient results.. The unsupervised
learning has been implemented with the help of a modified
Counterpropagation network. The Counterpropagation network
involves the process of clustering followed by application of Outstar
rule to obtain the recognized face. The face recognition system has
been developed for recognizing faces which have varying
illumination intensities, where the database images vary in lighting
with respect to angle of illumination with horizontal and vertical
planes. The supervised and unsupervised learning algorithms have
been implemented and have been tested exhaustively, with and
without application of histogram equalization to get efficient results.
Abstract: The purpose of this research was to study five vital
factors related to employees’ job performance. A total of 250
respondents were sampled from employees who worked at a public
warehouse organization, Bangkok, Thailand. Samples were divided
into two groups according to their work experience. The average
working experience was about 9 years for group one and 28 years for
group two. A questionnaire was utilized as a tool to collect data.
Statistics utilized in this research included frequency, percentage,
mean, standard deviation, t-test analysis, one way ANOVA, and
Pearson Product-moment correlation coefficient. Data were analyzed
by using Statistical Package for the Social Sciences. The findings
disclosed that the majority of respondents were female between 23-
31 years old, single, and hold an undergraduate degree. The average
income of respondents was less than 30,900 baht. The findings also
revealed that the factors of organization chart awareness, job process
and technology, internal environment, employee loyalty, and policy
and management were ranked as medium level. The hypotheses
testing revealed that difference in gender, age, and position had
differences in terms of the awareness of organization chart, job
process and technology, internal environment, employee loyalty, and
policy and management in the same direction with low level.
Abstract: The objective of this research was to study the factors
related to the satisfaction of consumers who purchased a Toyota
SUV Fortuner. This paper was a survey data which collected 400
samples from 65 car dealerships. The survey was conducted mainly
in Bangkok, Thailand. The statistics utilized in this paper included
percentage, mean, standard deviation and Pearson Product-Moment.
The findings revealed that the majority of respondent were male with
an undergraduate degree, married and live together. The average
income of the respondents was between 20,001 - 30,000 baht. Most
of them worked for private companies. Most of them had a family
with the average of 4 members. The hypotheses testing revealed that
the factors of marketing mix in terms of product (ability, gas
mileage, and safety) were related to overall satisfaction at the
medium level. However, the findings also revealed that the factors of
marketing mix in terms of product (image), price, and promotion, and
service center were related to the overall satisfaction at the low level.
Abstract: To achieve accurate and precise results of finite
element analysis (FEA) of bones, it is important to represent the
load/boundary conditions as identical as possible to the human body
such as the bone properties, the type and force of the muscles, the
contact force of the joints, and the location of the muscle attachment.
In this study, the difference in the Von-Mises stress and the total
deformation was compared by classifying them into Case 1, which
shows the actual anatomical form of the muscle attached to the femur
when the same muscle force was applied, and Case 2, which gives a
simplified representation of the attached location. An inverse
dynamical musculoskeletal model was simulated using data from an
actual walking experiment to complement the accuracy of the
muscular force, the input value of FEA. The FEA method using the
results of the muscular force that were calculated through the
simulation showed that the maximum Von-Mises stress and the
maximum total deformation in Case 2 were underestimated by 8.42%
and 6.29%, respectively, compared to Case 1. The torsion energy and
bending moment at each location of the femur occurred via the stress
ingredient. Due to the geometrical/morphological feature of the femur
of having a long bone shape when the stress distribution is wide, as
shown in Case 1, a greater Von-Mises stress and total deformation are
expected from the sum of the stress ingredients. More accurate results
can be achieved only when the muscular strength and the attachment
location in the FEA of the bones and the attachment form are the same
as those in the actual anatomical condition under the various moving
conditions of the human body.
Abstract: Shear walls are used in most of the tall buildings for
carrying the lateral load. When openings for doors or windows are
necessary to be existed in the shear walls, a special type of the shear
walls is used called "coupled shear walls" which in some cases is
stiffened by specific beams and so, called "stiffened coupled shear
walls".
In this paper, a mathematical method for geometrically nonlinear
analysis of the stiffened coupled shear walls has been presented.
Then, a suitable formulation for determining the critical load of the
stiffened coupled shear walls under gravity force has been proposed.
The governing differential equations for equilibrium and deformation
of the stiffened coupled shear walls have been obtained by setting up
the equilibrium equations and the moment-curvature relationships for
each wall. Because of the complexity of the differential equation, the
energy method has been adopted for approximate solution of the
equations.
Abstract: The convergence of heterogeneous wireless access technologies characterizes the 4G wireless networks. In such converged systems, the seamless and efficient handoff between
different access technologies (vertical handoff) is essential and remains a challenging problem. The heterogeneous co-existence of access technologies with largely different characteristics creates a decision problem of determining the “best" available network at
“best" time to reduce the unnecessary handoffs. This paper proposes a dynamic decision model to decide the “best" network at “best"
time moment to handoffs. The proposed dynamic decision model make the right vertical handoff decisions by determining the “best"
network at “best" time among available networks based on, dynamic
factors such as “Received Signal Strength(RSS)" of network and
“velocity" of mobile station simultaneously with static factors like Usage Expense, Link capacity(offered bandwidth) and power
consumption. This model not only meets the individual user needs but also improve the whole system performance by reducing the unnecessary handoffs.