Abstract: Solidification cracking and hydrogen cracking are some defects generated in the fusion welding of ultrahigh carbon steels. However, friction stir welding (FSW) of such steels, being a solid-state technique, has been demonstrated to alleviate such problems encountered in traditional welding. FSW include different process parameters that must be carefully defined prior processing. These parameters included but not restricted to: tool feed, tool RPM, tool geometry, tool tilt angle. These parameters form a key factor behind avoiding warm holes and voids behind the tool and in achieving a defect-free weld. More importantly, these parameters directly affect the microstructure of the weld and hence the final mechanical properties of weld. For that, 3D finite element (FE) thermo-mechanical model was developed using DEFORM 3D to simulate FSW of carbon steel. At points of interest in the joint, tracking is done for history of critical state variables such as temperature, stresses, and strain rates. Typical results found include the ability to simulate different weld zones. Simulations predictions were successfully compared to experimental FSW tests. It is believed that such a numerical model can be used to optimize FSW processing parameters to favor desirable defect free weld with better mechanical properties.
Abstract: The Platform Screen Doors improve Indoor Air Quality
(IAQ) in the subway station; however, and the air quality is degraded
in the subway tunnel. CO2 concentration and indoor particulate matter
value are high in the tunnel. The IAQ level in subway tunnel degrades
by increasing the train movements. Air-curtain installation reduces
dusts, particles and moving toxic smokes and permits traffic by
generating virtual wall. The ventilation systems of the subway tunnel
need improvements to have better air-quality. Numerical analyses
might be effective tools analyze the flowfield inside the air-curtain
installed subway tunnel. The ANSYS CFX software is used for steady
computations of the airflow inside the tunnel. The single-track subway
tunnel has the natural shaft, the mechanical shaft, and the PSDs
installed stations. The height and width of the tunnel are 6.0 m and 4.0
m respectively. The tunnel is 400 m long and the air-curtain is installed
at the top of the tunnel. The thickness and the width of the air-curtain
are 0.08 m and 4 m respectively. The velocity of the air-curtain
changes between 20 - 30 m/s. Three cases are analyzed depending on
the installing location of the air-curtain. The discharged-air through
the natural shafts increases as the velocity of the air-curtain increases
when the air-curtain is installed between the mechanical and the
natural shafts. The pollutant-air is exhausted by the mechanical and the
natural shafts and remained air is pushed toward tunnel end. The
discharged-air through the natural shaft is low when the air-curtain
installed before the natural shaft. The mass flow rate decreases in the
tunnel after the mechanical shaft as the air-curtain velocity increases.
The computational results of the air-curtain installed tunnel become
basis for the optimum design study. The air-curtain installing location
is chosen between the mechanical and the natural shafts. The velocity
of the air-curtain is fixed as 25 m/s. The thickness and the blowing
angles of the air-curtain are the design variables for the optimum
design study. The object function of the design optimization is
maximizing the discharged air through the natural shaft.
Abstract: The study describes chitosan membrane platform
modified with nanostructure pattern which using nanotechnology to
fabricate. The cell-substrate interaction between neuro-2a neuroblasts
cell lines and chitosan membrane (flat, nanostructure and
nanostructure pattern types) was investigated. The adhered
morphology of neuro-2a cells depends on the topography of chitosan
surface. We have found that neuro-2a showed different morphogenesis
when cells adhered on flat and nanostructure chitosan membrane. The
cell projected area of neuro-2a on flat chitosan membrane is larger
than on nanostructure chitosan membrane. In addition, neuro-2a cells
preferred to adhere on flat chitosan surface region than on
nanostructure chitosan membrane to immobilize and differentiation.
The experiment suggests surface topography can be used as a critical
mechanism to isolate group of neuro-2a to a particular rectangle area
on chitosan membrane. Our finding will provide a platform to take
patch clamp to record electrophysiological behavior about neurons in
vitro in the future.
Abstract: With the advantage of wireless network technology,
there are a variety of mobile applications which make the issue of
wireless sensor networks as a popular research area in recent years.
As the wireless sensor network nodes move arbitrarily with the
topology fast change feature, mobile nodes are often confronted with
the void issue which will initiate packet losing, retransmitting,
rerouting, additional transmission cost and power consumption.
When transmitting packets, we would not predict void problem
occurring in advance. Thus, how to improve geographic routing with
void avoidance in wireless networks becomes an important issue. In
this paper, we proposed a greedy geographical void routing algorithm
to solve the void problem for wireless sensor networks. We use the
information of source node and void area to draw two tangents to
form a fan range of the existence void which can announce voidavoiding
message. Then we use source and destination nodes to draw
a line with an angle of the fan range to select the next forwarding
neighbor node for routing. In a dynamic wireless sensor network
environment, the proposed greedy void avoiding algorithm can be
more time-saving and more efficient to forward packets, and improve
current geographical void problem of wireless sensor networks.
Abstract: In the traditional theory of non-uniform torsion the
axial displacement field is expressed as the product of the unit twist
angle and the warping function. The first one, variable along the
beam axis, is obtained by a global congruence condition; the second
one, instead, defined over the cross-section, is determined by solving
a Neumann problem associated to the Laplace equation, as well as for
the uniform torsion problem.
So, as in the classical theory the warping function doesn-t punctually
satisfy the first indefinite equilibrium equation, the principal aim of
this work is to develop a new theory for non-uniform torsion of
beams with axial symmetric cross-section, fully restrained on both
ends and loaded by a constant torque, that permits to punctually
satisfy the previous equation, by means of a trigonometric expansion
of the axial displacement and unit twist angle functions.
Furthermore, as the classical theory is generally applied with good
results to the global and local analysis of ship structures, two beams
having the first one an open profile, the second one a closed section,
have been analyzed, in order to compare the two theories.
Abstract: A full six degrees of freedom (6-DOF) flight dynamics
model is proposed for the accurate prediction of short and long-range
trajectories of high spin and fin-stabilized projectiles via atmospheric
flight to final impact point. The projectiles is assumed to be both rigid
(non-flexible), and rotationally symmetric about its spin axis launched
at low and high pitch angles. The mathematical model is based on the
full equations of motion set up in the no-roll body reference frame and
is integrated numerically from given initial conditions at the firing
site. The projectiles maneuvering motion depends on the most
significant force and moment variations, in addition to wind and
gravity. The computational flight analysis takes into consideration the
Mach number and total angle of attack effects by means of the
variable aerodynamic coefficients. For the purposes of the present
work, linear interpolation has been applied from the tabulated database
of McCoy-s book. The developed computational method gives
satisfactory agreement with published data of verified experiments and
computational codes on atmospheric projectile trajectory analysis for
various initial firing flight conditions.
Abstract: This paper addresses the problems encountered by conventional distance relays when protecting double-circuit transmission lines. The problems arise principally as a result of the mutual coupling between the two circuits under different fault conditions; this mutual coupling is highly nonlinear in nature. An adaptive protection scheme is proposed for such lines based on application of artificial neural network (ANN). ANN has the ability to classify the nonlinear relationship between measured signals by identifying different patterns of the associated signals. One of the key points of the present work is that only current signals measured at local end have been used to detect and classify the faults in the double circuit transmission line with double end infeed. The adaptive protection scheme is tested under a specific fault type, but varying fault location, fault resistance, fault inception angle and with remote end infeed. An improved performance is experienced once the neural network is trained adequately, which performs precisely when faced with different system parameters and conditions. The entire test results clearly show that the fault is detected and classified within a quarter cycle; thus the proposed adaptive protection technique is well suited for double circuit transmission line fault detection & classification. Results of performance studies show that the proposed neural network-based module can improve the performance of conventional fault selection algorithms.
Abstract: To satisfy the need of outfield tests of star sensors, a
method is put forward to construct the reference attitude benchmark.
Firstly, its basic principle is introduced; Then, all the separate
conversion matrixes are deduced, which include: the conversion
matrix responsible for the transformation from the Earth Centered
Inertial frame i to the Earth-centered Earth-fixed frame w according to
the time of an atomic clock, the conversion matrix from frame w to the
geographic frame t, and the matrix from frame t to the platform frame
p, so the attitude matrix of the benchmark platform relative to the
frame i can be obtained using all the three matrixes as the
multiplicative factors; Next, the attitude matrix of the star sensor
relative to frame i is got when the mounting matrix from frame p to the
star sensor frame s is calibrated, and the reference attitude angles for
star sensor outfield tests can be calculated from the transformation
from frame i to frame s; Finally, the computer program is finished to
solve the reference attitudes, and the error curves are drawn about the
three axis attitude angles whose absolute maximum error is just 0.25ÔÇ│.
The analysis on each loop and the final simulating results manifest that
the method by precise timing to acquire the absolute reference attitude
is feasible for star sensor outfield tests.
Abstract: Biometrics methods include recognition techniques
such as fingerprint, iris, hand geometry, voice, face, ears and gait. The gait recognition approach has some advantages, for example it
does not need the prior concern of the observed subject and it can
record many biometric features in order to make deeper analysis, but
most of the research proposals use high computational cost. This
paper shows a gait recognition system with feature subtraction on a
bundle rectangle drawn over the observed person. Statistical results
within a database of 500 videos are shown.
Abstract: The intermittent nature of solar energy and the energy
requirements of buildings necessitate the storage of thermal energy.
In this paper a hybrid system of storing solar energy has been
analyzed. Adding a LHS medium to a commercial solar water heater,
the required energy for heating a small room was obtained in
addition to preparing hot water. In other words, the suggested hybrid
storage system consists of two tanks: a water tank as a SHS medium;
and a paraffin tank as a LHS medium. A computing program was
used to find the optimized time schedule of charging the storage
tanks during each day, according to the solar radiation conditions.
The results show that the use of such system can improve the
capability of energy gathering comparing to the individual water
storage tank during the cold months of the year. Of course, because
of the solar radiation angles and shorten daylight in December &
January, the performance will be the same as the simple solar water
heaters (in the northern hemisphere). But the extra energy stored in
November, February, March & April, can be useful for heating a
small room for 3 hours during the cold days.
Abstract: This research paper presents the CFD analysis of
oscillating airfoil during pitch cycle. Unsteady subsonic flow is
simulated for pitching airfoil at Mach number 0.283 and Reynolds
number 3.45 millions. Turbulent effects are also considered for this
study by using K-ω SST turbulent model. Two-dimensional unsteady
compressible Navier-Stokes code including two-equation turbulence
model and PISO pressure velocity coupling is used. Pressure based
implicit solver with first order implicit unsteady formulation is used.
The simulated pitch cycle results are compared with the available
experimental data. The results have a good agreement with the
experimental data. Aerodynamic characteristics during pitch cycles
have been studied and validated.
Abstract: A hybrid feature based adaptive particle filter algorithm is presented for object tracking in real scenarios with static camera.
The hybrid feature is combined by two effective features: the Grayscale Arranging Pairs (GAP) feature and the color histogram feature. The GAP feature has high discriminative ability even under conditions of severe illumination variation and dynamic background
elements, while the color histogram feature has high reliability to identify the detected objects. The combination of two features covers the shortage of single feature. Furthermore, we adopt an updating
target model so that some external problems such as visual angles can be overcame well. An automatic initialization algorithm is introduced which provides precise initial positions of objects. The experimental
results show the good performance of the proposed method.
Abstract: Controlled release urea has become popular in agricultural industry as it helps to solve environmental issues and increase crop yield. Recently biomass was identified to replace the polymer used as a coating material in the conventional coated urea. In this paper spreading and contact angle of biomass droplet (lignin, cellulose and clay) on urea surface are investigated experimentally. There were two tests were conducted, sessile drop for contact angle measurement and pendant drop for contact angle measurement. A different concentration of biomass droplet was released from 30 mm above a substrate. Glass was used as a controlled substrate. Images were recorded as soon as the droplet impacted onto the urea before completely adsorb into the urea. Digitized droplets were then used to identify the droplet-s surface tension and contact angle. There is large difference observed between the low surface tension and high surface tension liquids, where the wetting and spreading diameter is higher for lower surface tension. From the contact angle results, the data showed that the biomass coating films were possible as wetting liquid (θ < 90º). Contact angle of biomass coating material gives good indication for the wettablity of a liquid on urea surface.
Abstract: In this study, rotating flexible shaft-disk system
having flexible beams is considered as a dynamic system. After
neglecting nonlinear terms, torsional vibration of the shaft-disk
system and lateral and longitudinal vibration of the flexible beam are
still coupled through the motor speed. The system has three natural
frequencies; the flexible shaft-disk system torsional natural
frequency, the flexible beam lateral and longitudinal natural
frequencies. Eigenvalue calculations show that while the shaft speed
changes, torsional natural frequency of the shaft-disk system and the
beam longitudinal natural frequency are not changing but the beam
lateral natural frequency changes. Beam lateral natural frequency
stays the same as the nonrotating beam lateral natural frequency ωb
until the motor speed ωm is equal to ωb. After then ωb increases and
remains equal to the motor speed ωm until the motor speed is equal to
the shaft-disk system natural frequency ωT. Then the beam lateral
natural frequency ωb becomes equal to the natural frequency ωT and
stays same while the motor speed ωm is increased. Modal amplitudes
and phase angles of the vibrations are also plotted against the motor
speed ωm.
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: 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: 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: This paper compares the heuristic Global Search
Techniques; Genetic Algorithm, Particle Swarm Optimization,
Simulated Annealing, Generalized Pattern Search, genetic algorithm
hybridized with Nelder–Mead and Generalized pattern search
technique for tuning of fuzzy PID controller for Puma 560. Since the
actual control is in joint space ,inverse kinematics is used to generate
various joint angles correspoding to desired cartesian space
trajectory. Efficient dynamics and kinematics are modeled on Matlab
which takes very less simulation time. Performances of all the tuning
methods with and without disturbance are compared in terms of ITSE
in joint space and ISE in cartesian space for spiral trajectory tracking.
Genetic Algorithm hybridized with Generalized Pattern Search is
showing best performance.
Abstract: Earth reinforcing techniques have become useful and economical to solve problems related to difficult grounds and provide satisfactory foundation performance. In this context, this paper uses radial basis function neural network (RBFNN) for predicting the bearing pressure of strip footing on reinforced granular bed overlying weak soil. The inputs for the neural network models included plate width, thickness of granular bed and number of layers of reinforcements, settlement ratio, water content, dry density, cohesion and angle of friction. The results indicated that RBFNN model exhibited more than 84 % prediction accuracy, thereby demonstrating its application in a geotechnical problem.
Abstract: Numerical studies have been carried out using a
validated two-dimensional RNG k-epsilon turbulence model for the
design optimization of a thrust vector control system using shock
induced supersonic secondary jet. Parametric analytical studies have
been carried out with various secondary jets at different divergent
locations, jet interaction angles, jet pressures. The results from the
parametric studies of the case on hand reveal that the primary nozzle
with a small divergence angle, downstream injections with a distance
of 2.5 times the primary nozzle throat diameter from the primary
nozzle throat location warrant higher efficiency over a certain range
of jet pressures and jet angles. We observed that the supersonic
secondary jet opposing the core flow with jets interaction angle of
40o to the axis far downstream of the nozzle throat facilitates better
thrust vectoring than the secondary jet with same direction as that of
core flow with various interaction angles. We concluded that fixing
of the supersonic secondary jet nozzle pointing towards the throat
direction with suitable angle at a distance 2 to 4 times of the primary
nozzle throat diameter, as the case may be, from the primary nozzle
throat location could facilitate better thrust vectoring for the
supersonic aerospace vehicles.