Abstract: This paper presents a model for the evaluation of
energy performance and aerodynamic forces acting on a three-bladed
small vertical axis Darrieus wind turbine depending on blade chord
curvature with respect to rotor axis.
The adopted survey methodology is based on an analytical code
coupled to a solid modeling software, capable of generating the
desired blade geometry depending on the blade design geometric
parameters, which is linked to a finite volume CFD code for the
calculation of rotor performance.
After describing and validating the model with experimental data,
the results of numerical simulations are proposed on the bases of two
different blade profile architectures, which are respectively
characterized by a straight chord and by a curved one, having a chord
radius equal to rotor external circumference. A CFD campaign of
analysis is completed for three blade-candidate airfoil sections, that is
the recently-developed DU 06-W-200 cambered blade profile, a
classical symmetrical NACA 0021 and its derived cambered airfoil,
characterized by a curved chord, having a chord radius equal to rotor
external circumference.
The effects of blade chord curvature on angle of attack, blade
tangential and normal forces are first investigated and then the
overall rotor torque and power are analyzed as a function of blade
azimuthal position, achieving a numerical quantification of the
influence of blade camber on overall rotor performance.
Abstract: This paper describes a method to measure and
compensate a 4 axes ultra-precision machine tool that generates micro
patterns on the large surfaces. The grooving machine is usually used
for making a micro mold for many electrical parts such as a light guide
plate for LCD and fuel cells. The ultra precision machine tool has three
linear axes and one rotational table. Shaping is usually used to
generate micro patterns. In the case of 50 μm pitch and 25 μm height
pyramid pattern machining with a 90° wedge angle bite, one of linear
axis is used for long stroke motion for high cutting speed and other
linear axis are used for feeding. The triangular patterns can be
generated with many times of long stroke of one axis. Then 90°
rotation of work piece is needed to make pyramid patterns with
superposition of machined two triangular patterns.
To make a two dimensional positioning error, straightness of two
axes in out of plane, squareness between the each axis are important.
Positioning errors, straightness and squarness were measured by laser
interferometer system. Those were compensated and confirmed by
ISO230-6. One of difficult problem to measure the error motions is
squareness or parallelism of axis between the rotational table and
linear axis. It was investigated by simultaneous moving of rotary table
and XY axes. This compensation method is introduced in this paper.
Abstract: The amplitude response of infrared (IR) sensors
depends on the reflectance properties of the target. Therefore, in
order to use IR sensor for measuring distances accurately, prior
knowledge of the surface must be known. This paper describes the
Phong Illumination Model for determining the properties of a surface
and subsequently calculating the distance to the surface. The angular
position of the IR sensor is computed as normal to the surface for
simplifying the calculation. Ultrasonic (US) sensor can provide the
initial information on distance to obtain the parameters for this
method. In addition, the experimental results obtained by using
LabView are discussed. More care should be taken when placing the
objects from the sensors during acquiring data since the small change
in angle could show very different distance than the actual one.
Since stereo camera vision systems do not perform well under some
environmental conditions such as plain wall, glass surfaces, or poor
lighting conditions, the IR and US sensors can be used additionally to
improve the overall vision systems of mobile robots.
Abstract: This study numerically investigates the effects of Electrohydrodynamic on flow patterns and heat transfer enhancement within a cavity which is on the lower wall of channel. In this simulation, effects of using ground wire and ground plate on the flow patterns are compared. Moreover, the positions of electrode wire respecting with ground are tested in the range of angles θ = 0 - 180o. High electrical voltage exposes to air is 20 kV. Bulk mean velocity and temperature of inlet air are controlled at 0.1 m/s and 60 OC, respectively. The result shows when electric field is applied, swirling flow is appeared in the channel. In addition, swirling flow patterns in the main flow of using ground plate are widely spreader than that of using ground wire. Moreover, direction of swirling flow also affects the flow pattern and heat transfer in a cavity. These cause the using ground wire to give the maximum temperature and heat transfer higher than using ground plate. Furthermore, when the angle is at θ = 60o, high shear flow effect is obtained. This results show high strength of swirling flow and effective heat transfer enhancement.
Abstract: Children with hemiplgic cerebral palsy often walk
with diminished reciprocal arm swing so the purpose of this study
was to describe kinematic characteristics in children with hemiplegic
cerebral palsy (CP) during the gait suphases, and find if there is a
correlation between upper(shoulder and elbow) and lower(hip, knee,
and ankle) limb joints either in involved or uninvolved.48 children
with hemiplegic cerebral palsy (18boys, 30girls) with an average age
of (5.1±0.87) years were selected randomly to evaluate joint angles
during gait by 3D motion analysis system with 6 pro reflex cameras
in a sagittal plane for both sides of the body. The results showed
increased shoulder and elbow flexion, increased hip angular
displacement, decreased knee and ankle arcs during gait cycle, also
there is correlation between shoulder and elbow to hip, knee, and
ankle joints during various subphases of gait.
Abstract: Repairing of the cracks by fiber metal laminates
(FMLs) was first done by some aeronautical laboratories in early
1970s. In this study, experimental investigations were done on the
effect of repairing the center-cracked aluminum plates using the FML
patches. The repairing processes were conducted to characterize the
response of the repaired structures to tensile tests. The composite
patches were made of one aluminum layer and two woven glassepoxy
composite layers. Three different crack lengths in three crack
angles and different patch lay-ups were examined. It was observed
for the lengthen cracks, the effect of increasing the crack angle on
ultimate tensile load in the structure was increase. It was indicated
that the situation of metal layer in the FML patches had an important
effect on the tensile response of the tested specimens. It was found
when the aluminum layer is farther, the ultimate tensile load has the
highest amount.
Abstract: The unsteady wake of an EPPLER 361 airfoil in
pitching motion has been investigated in a subsonic wind tunnel by
hot-wire anemometry. The airfoil was given the pitching motion
about the one-quarter chord axis at reduced frequency of 0182.
Streamwise mean velocity profiles (wake profiles) were investigated
at several vertically aligned points behind the airfoil at one-quarter
chord downstream distance from trailing edge. Oscillation amplitude
and mean angle of attack were varied to determine the effects on
wake profiles. When the maximum dynamic angle of attack was
below the static stall angle of attack, weak effects on wake were
found by increasing oscillation amplitude and mean angle of attack.
But, for higher angles of attack strong unsteady effects were
appeared on the wake.
Abstract: This paper presents the experimental results of
comparison between leakage currents and discharge currents. The leakage currents were obtained on polluted porcelain insulator.
Whereas, the discharge currents were obtained on lightly artificial
polluted porcelain specimen. The conducted measurements were
leakage current or discharge current and applied voltage. The insulator or specimen was in a hermetically sealed chamber, and the
current waveforms were analyzed using FFT.
The result indicated that the leakage current (LC) on low RH condition the fifth harmonic would be visible, and followed by the
seventh harmonic. The insulator had capacitive property. Otherwise,
on 99% relative humidity, the fifth harmonic would also be visible,
and the phase angle reached up to 12.2 degree. Whereas, on discharge current, the third harmonic would be visible, and followed
by fifth harmonic. The third harmonic would increase as pressure reduced. On this condition, the specimen had a non-linear characteristics
Abstract: The main objective of this paper is a comparative
investigate in enhancement of damping power system oscillation via
coordinated design of the power system stabilizer (PSS) and static
synchronous series compensator (SSSC) and static synchronous
compensator (STATCOM). The design problem of FACTS-based
stabilizers is formulated as a GA based optimization problem. In this
paper eigenvalue analysis method is used on small signal stability of
single machine infinite bus (SMIB) system installed with SSSC and
STATCOM. The generator is equipped with a PSS. The proposed
stabilizers are tested on a weakly connected power system with
different disturbances and loading conditions. This aim is to enhance
both rotor angle and power system stability. The eigenvalue analysis
and non-linear simulation results are presented to show the effects of
these FACTS-based stabilizers and reveal that SSSC exhibits the best
effectiveness on damping power system oscillation.
Abstract: Two different superhydrophobic surfaces were
elaborated and their oil repellency behavior was evaluated using
several liquid with different surface tension. A silicone rubber/SiO2
nanocomposite coated (A) on aluminum substrate by “spin-coating"
and the sample B was an anodized aluminum surface covered by
Teflon-like coating. A high static contact angle about ∼162° was
measured for two prepared surfaces on which the water droplet rolloff.
Scanning electron microscopy (SEM) showed the presence of
micro/nanostructures for both sample A and B similar to that of lotus
leaf.
However the sample A presented significantly different behaviour
of wettability against the low surface tension liquid. Sample A has
been wetted totally by oil (dodecan) droplet while sample B showed
oleophobic behaviour. Oleophobic property of Teflon like coating
can be contributed to the presence of CF2 and CF3 functional group
which was shown by XPS analysis.
Abstract: The parametrical study of Shrouded Contra-rotating
Rotor was done in this paper based on 2D axisymmetric simulations.
The calculations were made with an actuator disk as double rotor
model. It objects to explore and quantify the effects of different shroud
geometry parameters mainly using the performance of power loading
(PL), which could evaluate the whole propulsion system capability as
5 Newtontotal thrust generationfor hover demand. The numerical
results show that:The increase of nozzle radius is desired but limited
by the flow separation, its optimal design is around 1.15 times rotor
radius, the viscosity effects greatly constraint the influence of nozzle
shape, the divergent angle around 10.5° performs best for chosen
nozzle length;The parameters of inlet such as leading edge curvature,
radius and internal shape do not affect thrust great but play an
important role in pressure distribution which could produce most part
of shroud thrust, they should be chosen according to the reduction of
adverse pressure gradients to reduce the risk of boundary separation.
Abstract: Wetting characteristics of reactive (Sn–0.7Cu solder)
and non– reactive (castor oil) wetting of liquids on Cu and Ag plated
Al substrates have been investigated. Solder spreading exhibited
capillary, gravity and viscous regimes. Oils did not exhibit noticeable
spreading regimes. Solder alloy showed better wettability on Ag
coated Al substrate compared to Cu plating. In the case of castor oil,
Cu coated Al substrate exhibited good wettability as compared to Ag
coated Al substrates. The difference in wettability during reactive
wetting of solder and non–reactive wetting of oils is attributed to the
change in the surface energies of Al substrates brought about by the
formation of intermetallic compounds (IMCs).
Abstract: Static Var Compensator (SVC) is a shunt type FACTS
device which is used in power system primarily for the purpose of
voltage and reactive power control. In this paper, a fuzzy logic based
supplementary controller for Static Var Compensator (SVC) is
developed which is used for damping the rotor angle oscillations and
to improve the transient stability of the power system. Generator
speed and the electrical power are chosen as input signals for the
Fuzzy Logic Controller (FLC). The effectiveness and feasibility of
the proposed control is demonstrated with Single Machine Infinite
Bus (SMIB) system and multimachine system (WSCC System)
which show improvement over the use of a fixed parameter
controller.
Abstract: The measurement of aerodynamic forces and moments
acting on an aircraft model is important for the development of wind
tunnel measurement technology to predict the performance of the full
scale vehicle. The potentials of an aircraft model with and without
winglet and aerodynamic characteristics with NACA wing No. 65-3-
218 have been studied using subsonic wind tunnel of 1 m × 1 m
rectangular test section and 2.5 m long of Aerodynamics Laboratory
Faculty of Engineering (University Putra Malaysia). Focusing on
analyzing the aerodynamic characteristics of the aircraft model, two
main issues are studied in this paper. First, a six component wind
tunnel external balance is used for measuring lift, drag and pitching
moment. Secondly, Tests are conducted on the aircraft model with
and without winglet of two configurations at Reynolds numbers
1.7×105, 2.1×105, and 2.5×105 for different angle of attacks. Fuzzy
logic approach is found as efficient for the representation,
manipulation and utilization of aerodynamic characteristics.
Therefore, the primary purpose of this work was to investigate the
relationship between lift and drag coefficients, with free-stream
velocities and angle of attacks, and to illustrate how fuzzy logic
might play an important role in study of lift aerodynamic
characteristics of an aircraft model with the addition of certain
winglet configurations. Results of the developed fuzzy logic were
compared with the experimental results. For lift coefficient analysis,
the mean of actual and predicted values were 0.62 and 0.60
respectively. The coreelation between actual and predicted values
(from FLS model) of lift coefficient in different angle of attack was
found as 0.99. The mean relative error of actual and predicted valus
was found as 5.18% for the velocity of 26.36 m/s which was found to
be less than the acceptable limits (10%). The goodness of fit of
prediction value was 0.95 which was close to 1.0.
Abstract: This research paper presents numerical studies of the
characteristics of warhead fragmentation in terms of initial velocities,
spray angles of fragments and fragment mass distribution of high
explosive (HE) warhead. The behavior of warhead fragmentation
depends on shape and size of warhead, thickness of casing, type of
explosive, number and position of detonator, and etc. This paper
focuses on the effects of material properties of warhead casing, i.e.
failure strain, initial yield and ultimate strength on the characteristics
of warhead fragmentation. It was found that initial yield and ultimate
strength of casing has minimal effects on the initial velocities and
spray angles of fragments. Moreover, a brittle warhead casing with
low failure strain tends to produce higher number of fragments with
less average fragment mass.
Abstract: This project focuses on the development of a line
follower algorithm for a Two Wheels Balancing Robot. In this
project, ATMEGA32 is chosen as the brain board controller to react
towards the data received from Balance Processor Chip on the
balance board to monitor the changes of the environment through
two infra-red distance sensor to solve the inclination angle problem.
Hence, the system will immediately restore to the set point (balance
position) through the implementation of internal PID algorithms at
the balance board. Application of infra-red light sensors with the PID
control is vital, in order to develop a smooth line follower robot. As a
result of combination between line follower program and internal self
balancing algorithms, we are able to develop a dynamically
stabilized balancing robot with line follower function.
Abstract: Knowledge is renowned as a significant component
for sustaining competitive advantage and gives leading edge in
business. This study emphasizes towards proper and effectuate
utilization of internal and external (both either explicit or tacit)
knowledge comes from stakeholders, highly supportive to combat
with the challenges and enhance organizational productivity.
Furthermore, it proposed a model under context of IRSA framework
which facilitates the organization including flow of knowledge and
experience sharing among employees. In discussion section an
innovative model which indulges all functionality as mentioned in
analysis section.
Abstract: In a travelling wave thermoacoustic device, the
regenerator sandwiched between a pair of (hot and cold) heat
exchangers constitutes the so-called thermoacoustic core, where the
thermoacoustic energy conversion from heat to acoustic power takes
place. The temperature gradient along the regenerator caused by the
two heat exchangers excites and maintains the acoustic wave in the
resonator. The devices are called travelling wave thermoacoustic
systems because the phase angle difference between the pressure and
velocity oscillation is close to zero in the regenerator. This paper
presents the construction and testing of a thermoacoustic engine
equipped with a ceramic regenerator, made from a ceramic material
that is usually used as catalyst substrate in vehicles- exhaust systems,
with fine square channels (900 cells per square inch). The testing
includes the onset temperature difference (minimum temperature
difference required to start the acoustic oscillation in an engine), the
acoustic power output, thermal efficiency and the temperature profile
along the regenerator.
Abstract: In this work, we perform numerical simulation of fluid
mixing in a floor-grooved micro-channel with wavy sidewalls which
may impose perturbation on the helical flow induced by the slanted
grooves on the channel floor. The perturbation is caused by separation
vortices in the recesses of the wavy-walled channel as the Reynolds
number is large enough. The results show that the effects of the wavy
sidewalls of the present micromixer on the enhancement of fluid
mixing increase with the increase of Reynolds number. The degree of
mixing increases with the increase of the corrugation angle, until the
angle is greater than 45 degrees. Besides, the pumping pressure of the
micromixer increases with the increase of the corrugation angle
monotonically. Therefore, we would suggest setting the corrugation
angle of the wavy sidewalls to be 45 degrees.
Abstract: This paper studies mixed-mode fracture mechanics in
rock based on experimental and numerical analyses. Experiments
were performed on sharp-cracked specimens using the modified
Arcan specimen test loading device. The modified Arcan specimen
test was, in association with a special loading device, an appropriate
apparatus for experimental mixed-mode fracture analysis. By
varying the loading angle from 0° to 90°, pure mode-I, pure mode-II
and a wide range of mixed-mode data were obtained experimentally.
Using the finite element results, correction factors applied to the
rectangular fracture specimen. By employing experimentally
measured critical loads and the aid of the finite element method,
mixed-mode fracture toughness for the limestone under consideration
determined.