Abstract: This paper presents the effect of the orbit inclination
on the pointing error of the satellite antenna and consequently on its
footprint on earth for a typical Ku- band payload system. The performance assessment is examined using both analytical
simulations and practical measurements, taking into account all the
additional sources of the pointing errors, such as East-West station
keeping, orbit eccentricity, and actual attitude control performance. An implementation and computation of the sinusoidal biases in
satellite roll and pitch used to compensate the pointing error of the
satellite antenna coverage is studied and evaluated before and after
the pointing corrections performed. A method for evaluation of the performance of the implemented
biases has been introduced through measuring satellite received level
from a mono-pulse tracking 11.1m transmitting antenna before and
after the implementation of the pointing corrections.
Abstract: In order to investigate the prebiotic potential of
oligosaccharides prepared by chemical hydrolysis of water-soluble
polysaccharides (WSP) from Zizyphus lotus leaves, the effect of
oligosaccharides on bacterial growth was studied. The chemical
composition of WSP was evaluated by colorimetric assays revealed
the average values: 7.05±0.73% proteins and 86.21±0.74%
carbohydrates, among them 64.81±0.42% is neutral sugar and the rest
16.25±1.62% is uronic acids. The characterization of
monosaccharides was determined by high performance anion
exchange chromatography with pulsed amperometric detection
(HPAEC-PAD) was found to be composed of galactose (23.95%),
glucose (21.30%), rhamnose (20.28%), arabinose (9.55%), and
glucuronic acid (22.95%). The effects of oligosaccharides on the
growth of lactic acid bacteria were compared with those of fructooligosaccharide
(RP95). The oligosaccharides concentration was
1g/L of Man, Rogosa, Sharpe broth. Bacterial growth was assessed
during 2, 4.5, 6.5, 9, 12, 16 and 24 h by measuring the optical density
of the cultures at 600 nm (OD600) and pH values. During
fermentation, pH in broth cultures decreased from 6.7 to 5.87±0.15.
The enumeration of lactic acid bacteria indicated that
oligosaccharides led to a significant increase in bacteria (P≤0.05)
compared to the control. The fermentative metabolism appeared to be
faster on RP95 than on oligosaccharides from Zizyphus lotus leaves.
Both RP95 and oligosaccharides showed clear prebiotic effects, but
had differences in fermentation kinetics because of to the different
degree of polymerization. This study shows the prebiotic
effectiveness of oligosaccharides, and provides proof for the selection
of leaves of Zizyphus lotus for use as functional food ingredients.
Abstract: This study was aimed to measure effective transverse
relaxation rates (R2*) in the liver and muscle of normal New Zealand
White (NZW) rabbits. R2* relaxation rate has been widely used in
various hepatic diseases for iron overload by quantifying iron contents
in liver. R2* relaxation rate is defined as the reciprocal of T2*
relaxation time and mainly depends on the constituents of tissue.
Different tissues would have different R2* relaxation rates. The signal
intensity decay in Magnetic resonance imaging (MRI) may be
characterized by R2* relaxation rates. In this study, a 1.5T GE Signa
HDxt whole body MR scanner equipped with an 8-channel high
resolution knee coil was used to observe R2* values in NZW rabbit’s
liver and muscle. Eight healthy NZW rabbits weighted 2 ~ 2.5 kg were
recruited. After anesthesia using Zoletil 50 and Rompun 2% mixture,
the abdomen of rabbit was landmarked at the center of knee coil to
perform 3-plane localizer scan using fast spoiled gradient echo
(FSPGR) pulse sequence. Afterwards, multi-planar fast gradient echo
(MFGR) scans were performed with 8 various echo times (TEs) to
acquire images for R2* measurements. Regions of interest (ROIs) at
liver and muscle were measured using Advantage workstation.
Finally, the R2* was obtained by a linear regression of ln(sı) on TE.
The results showed that the longer the echo time, the smaller the signal
intensity. The R2* values of liver and muscle were 44.8 ± 10.9 s-1 and
37.4 ± 9.5 s-1, respectively. It implies that the iron concentration of
liver is higher than that of muscle. In conclusion, the more the iron
contents in tissue, the higher the R2*. The correlations between R2*
and iron content in NZW rabbits might be valuable for further
exploration.
Abstract: Electrical Muscle Stimulation (EMS) has been
introduced and globally gained increasing attention on its usefulness.
Continuous application of EMS may lead to the increment of muscle
mass and indirectly will increase the strength. This study can be used
as an alternative to help people especially those living a sedentary
lifestyle to improve their muscle activity without having to go
through a heavy workout session. Therefore, this study intended to
investigate the effectiveness of EMS training program in 5 weeks
interventions towards male body composition. It was a quasiexperimental
design, held at the Impulse Studio Bangsar, which
examined the effects of EMS training towards skeletal muscle mass
among the subjects. Fifteen subjects (n = 15) were selected to assist
in this study. The demographic data showed that, the average age of
the subjects was 43.07 years old ± 9.90, height (173.4 cm ± 9.09) and
weight was (85.79 kg ± 18.07). Results showed that there was a
significant difference on the skeletal muscle mass (p = 0.01 < 0.05),
upper body (p = 0.01 < 0.05) and lower body (p = 0.00 < 0.05).
Therefore, the null hypothesis has been rejected in this study. As a
conclusion, the application of EMS towards body composition can
increase the muscle size and strength. This method has been proven
to be able to improve athlete strength and thus, may be implemented
in the sports science area of knowledge.
Abstract: In this study, static and dynamic responses of a typical
reinforced concrete solid slab, designed to British Standard (BS 8110:
1997) and under self and live loadings for dance halls are reported.
Linear perturbation analysis using finite element method was
employed for modal, impulse loading and frequency response
analyses of the slab under the aforementioned loading condition.
Results from the static and dynamic analyses, comprising of the slab
fundamental frequencies and mode shapes, dynamic amplification
factor, maximum deflection, stress distributions among other
valuable outcomes are presented and discussed. These were gauged
with the limiting provisions in the design code with a view of
justifying valid optimization objective function for the structure that
can ensure both adequate strength and economical section for large
clear span slabs. This is necessary owing to the continued increase in
cost of erecting building structures and the squeeze on public finance
globally.
Abstract: The laser-ultrasonic method is realized for
quantifying the influence of porosity on the local Young’s
modulus of isotropic composite materials. The method is based on
a laser thermooptical method of ultrasound generation combined
with measurement of the phase velocity of longitudinal and shear
acoustic waves in samples. The main advantage of this method
compared with traditional ultrasonic research methods is the
efficient generation of short and powerful probing acoustic pulses
required for reliable testing of ultrasound absorbing and
scattering heterogeneous materials. Using as an example samples
of a metal matrix composite with reinforcing microparticles of
silicon carbide in various concentrations, it is shown that to
provide an effective increase in Young’s modulus with increasing
concentration of microparticles, the porosity of the final sample
should not exceed 2%.
Abstract: This paper focuses on the orbit avoidance strategy of
the optical remote sensing satellite. The optical remote sensing
satellite, moving along the Sun-synchronous orbit, is equipped with
laser warning equipment to alert CCD camera from laser attacks. This
paper explores the strategy of satellite avoidance to protect the CCD
camera and also the satellite. The satellite could evasive to several
target points in the orbital coordinates of virtual satellite. The so-called
virtual satellite is a passive vehicle which superposes the satellite at the
initial stage of avoidance. The target points share the consistent cycle
time and the same semi-major axis with the virtual satellite, which
ensures the properties of the satellite’s Sun-synchronous orbit remain
unchanged. Moreover, to further strengthen the avoidance capability
of satellite, it can perform multi-target-points avoid maneuvers. On
occasions of fulfilling the satellite orbit tasks, the orbit can be restored
back to virtual satellite through orbit maneuvers. There into, the avoid
maneuvers adopts pulse guidance. In addition, the fuel consumption is
optimized. The avoidance strategy discussed in this article is
applicable to optical remote sensing satellite when it is encountered
with hostile attack of space-based laser anti-satellite.
Abstract: Pure nickel coatings have been successfully
electrodeposited on copper substrates by the pulse plating technique.
The influence of current density, duty cycle and pulse frequency on
the surface morphology, crystal orientation, and microhardness was
determined. It was found that the crystallite size of the deposit
increases with increasing current density and duty cycle. The crystal
orientation progressively changed from a random texture at 1 A/dm2
to (200) texture at 10 A/dm2. Increasing pulse frequency resulted in
increased texture coefficient and peak intensity of (111) reflection.
An increase in duty cycle resulted in considerable increase in texture
coefficient and peak intensity of (311) reflection. Coatings obtained
at high current densities and duty cycle present a mixed morphology
of small and large grains. Maximum microhardness of 193 Hv was
achieved at 4 A/dm2, 10 Hz and duty cycle of 50%. Nickel coatings
with (200) texture are ductile while (111) texture improves the
microhardness of the coatings.
Abstract: The subject of this paper is to review, comparative
analysis and simulation of selected components of power electronic
systems (PES), consistent with the concept of a more electric aircraft
(MEA). Comparative analysis and simulation in software
environment MATLAB / Simulink were carried out on the base of a
group of representatives of civil aircraft (B-787, A-380) and military
(F-22 Raptor, F-35) in the context of multi-pulse converters used in
them (6- and 12-pulse, and 18- and 24-pulse), which are key
components of high-tech electronics on-board power systems of
autonomous power systems (ASE) of modern aircraft (airplanes of
the future).
Abstract: The photovoltaic (PV) panel with no galvanic
isolation system is well known technique in the world which is
effective and delivers power with enhanced efficiency. The PV
generation presented here is for stand-alone system installed in
remote areas when as the resulting power gets connected to electronic
load installation instead of being tied to the grid. Though very small,
even then transformer-less topology is shown to be with leakage in
pico-ampere range. By using PWM technique PWM, leakage current
in different situations is shown. The results shown in this paper show
how the pico-ampere current is reduced to femto-ampere through use
of inductors and capacitors of suitable values of inductor and
capacitors with the load.
Abstract: Nonlinear evolution of broadband ultrasonic pulses
passed through the rock specimens is studied using the apparatus
“GEOSCAN-02M”. Ultrasonic pulses are excited by the pulses of Qswitched
Nd:YAG laser with the time duration of 10 ns and with the
energy of 260 mJ. This energy can be reduced to 20 mJ by some light
filters. The laser beam radius did not exceed 5 mm. As a result of the
absorption of the laser pulse in the special material – the optoacoustic
generator–the pulses of longitudinal ultrasonic waves are excited with
the time duration of 100 ns and with the maximum pressure
amplitude of 10 MPa. The immersion technique is used to measure
the parameters of these ultrasonic pulses passed through a specimen,
the immersion liquid is distilled water. The reference pulse passed
through the cell with water has the compression and the rarefaction
phases. The amplitude of the rarefaction phase is five times lower
than that of the compression phase. The spectral range of the
reference pulse reaches 10 MHz. The cubic-shaped specimens of the
Karelian gabbro are studied with the rib length 3 cm. The ultimate
strength of the specimens by the uniaxial compression is (300±10)
MPa. As the reference pulse passes through the area of the specimen
without cracks the compression phase decreases and the rarefaction
one increases due to diffraction and scattering of ultrasound, so the
ratio of these phases becomes 2.3:1. After preloading some horizontal
cracks appear in the specimens. Their location is found by one-sided
scanning of the specimen using the backward mode detection of the
ultrasonic pulses reflected from the structure defects. Using the
computer processing of these signals the images are obtained of the
cross-sections of the specimens with cracks. By the increase of the
reference pulse amplitude from 0.1 MPa to 5 MPa the nonlinear
transformation of the ultrasonic pulse passed through the specimen
with horizontal cracks results in the decrease by 2.5 times of the
amplitude of the rarefaction phase and in the increase of its duration
by 2.1 times. By the increase of the reference pulse amplitude from 5
MPa to 10 MPa the time splitting of the phases is observed for the
bipolar pulse passed through the specimen. The compression and
rarefaction phases propagate with different velocities. These features
of the powerful broadband ultrasonic pulses passed through the rock
specimens can be described by the hysteresis model of Preisach-
Mayergoyz and can be used for the location of cracks in the optically
opaque materials.
Abstract: This paper presents the results of a Finite Element
based vibration analysis of a solar powered Unmanned Aerial
Vehicle (UAV). The purpose of this paper was to quantify the free
vibration, forced vibration response due to differing point inputs in
order to predict the relative response magnitudes and frequencies at
various wing locations of vibration induced power generators
(magnet in coil) excited by gust and/or control surface pulse-decays
used to help power the flight of the electric UAV. A Fluid Structure
Interaction (FSI) study was performed in order to ascertain pertinent
design stresses and deflections as well as aerodynamic parameters of
the UAV airfoil. The 10 ft span airfoil is modeled using Mylar as the
primary material. Results show that the free mode in bending is 4.8
Hz while the first forced bending mode is on range of 16.2 to 16.7 Hz
depending on the location of excitation. The free torsional bending
mode is 28.3 Hz, and the first forced torsional mode is range of 26.4
to 27.8 Hz, depending on the location of excitation. The FSI results
predict the coefficients of aerodynamic drag and lift of 0.0052 and
0.077, respectively, which matches hand-calculations used to validate
the Finite Element based results. FSI based maximum von Mises
stresses and deflections were found to be 0.282 MPa and 3.4 mm,
respectively. Dynamic pressures on the airfoil range from 1.04 to
1.23 kPa corresponding to velocity magnitudes in range of 22 to 66
m/s.
Abstract: Wire Electric Discharge Machining (WEDM) is
thermal machining process capable of machining very hard
electrically conductive material irrespective of their hardness.
WEDM is being widely used to machine micro scale parts with the
high dimensional accuracy and surface finish. The objective of this
paper is to optimize the process parameters of wire EDM to fabricate
the micro channels and to calculate the surface finish and material
removal rate of micro channels fabricated using wire EDM. The
material used is aluminum 6061 alloy. The experiments were
performed using CNC wire cut electric discharge machine. The effect
of various parameters of WEDM like pulse on time (TON) with the
levels (100, 150, 200), pulse off time (TOFF) with the levels (25, 35,
45) and current (IP) with the levels (105, 110, 115) were investigated
to study the effect on output parameter i.e. Surface Roughness and
Material Removal Rate (MRR). Each experiment was conducted
under different conditions of pulse on time, pulse off time and peak
current. For material removal rate, TON and Ip
were the most significant process parameter. MRR increases with the increase in
TON and Ip and decreases with the increase in TOFF. For surface
roughness, TON and Ip have the maximum effect and TOFF was found
out to be less effective.
Abstract: One of the most important challenging factors in
medical images is nominated as noise. Image denoising refers to the
improvement of a digital medical image that has been infected by
Additive White Gaussian Noise (AWGN). The digital medical image
or video can be affected by different types of noises. They are
impulse noise, Poisson noise and AWGN. Computed tomography
(CT) images are subjects to low quality due to the noise. Quality of
CT images is dependent on absorbed dose to patients directly in such
a way that increase in absorbed radiation, consequently absorbed
dose to patients (ADP), enhances the CT images quality. In this
manner, noise reduction techniques on purpose of images quality
enhancement exposing no excess radiation to patients is one the
challenging problems for CT images processing. In this work, noise
reduction in CT images was performed using two different
directional 2 dimensional (2D) transformations; i.e., Curvelet and
Contourlet and Discrete Wavelet Transform (DWT) thresholding
methods of BayesShrink and AdaptShrink, compared to each other
and we proposed a new threshold in wavelet domain for not only
noise reduction but also edge retaining, consequently the proposed
method retains the modified coefficients significantly that result good
visual quality. Data evaluations were accomplished by using two
criterions; namely, peak signal to noise ratio (PSNR) and Structure
similarity (Ssim).
Abstract: Space Vector Pulse Width Modulation is popular for
variable frequency drives. The method has several advantages over
carried based PWM and is computation intensive. The
implementation of SVPWM for multilevel inverter requires special
attention and at the same time consumes considerable resources. Due
to faster processing power and reduced over all computational
burden, FPGAs are being investigated as an alternative for other
controllers. In this paper, a space vector PWM algorithm is
implemented using FPGA which requires less computational area and
is modular in structure. The algorithm is verified experimentally for
Neutral Point Clamped inverter using FPGA development board
xc3s5000-4fg900.
Abstract: In this paper, we study the optical nonlinearities of
Silver sulfide (Ag2S) nanostructures dispersed in the Dimethyl
sulfoxide (DMSO) under exposure to 532 nm, 15 nanosecond (ns)
pulsed laser irradiation. Ultraviolet–visible absorption spectrometry
(UV-Vis), X-ray diffraction (XRD), and transmission electron
microscopy (TEM) are used to characterize the obtained nanocrystal
samples. The band gap energy of colloid is determined by analyzing
the UV–Vis absorption spectra of the Ag2S NPs using the band
theory of semiconductors. Z-scan technique is used to characterize
the optical nonlinear properties of the Ag2S nanoparticles (NPs).
Large enhancement of two photon absorption effect is observed with
increase in concentration of the Ag2S nanoparticles using open Zscan
measurements in the ns laser regime. The values of the nonlinear
absorption coefficients are determined based on the local nonlinear
responses including two photon absorption. The observed aperture
dependence of the Ag2S NP limiting performance indicates that the
nonlinear scattering plays an important role in the limiting action of
the sample. The concentration dependence of the optical liming is
also investigated. Our results demonstrate that the optical limiting
threshold decreases with increasing the silver sulfide NPs in DMSO.
Abstract: Concrete is strong in compression however weak in
tension. The tensile strength as well as ductile property of concrete
could be improved by addition of short dispersed fibers. Polyethylene
terephthalate (PET) fiber obtained from hand cutting or mechanical
slitting of plastic sheets generally used as discrete reinforcement in
substitution of steel fiber. PET fiber obtained from the former process
is in the form of straight slit sheet pattern that impart weaker
mechanical bonding behavior in the concrete matrix. To improve the
limitation of straight slit sheet fiber the present study considered two
additional geometry of fiber namely (a) flattened end slit sheet and
(b) deformed slit sheet. The mix for plain concrete was design for a
compressive strength of 25 MPa at 28 days curing time with a watercement
ratio of 0.5. Cylindrical and beam specimens with 0.5% fibers
volume fraction and without fibers were cast to investigate the
influence of geometry on the mechanical properties of concrete. The
performance parameters mainly studied include flexural strength,
splitting tensile strength, compressive strength and ultrasonic pulse
velocity (UPV). Test results show that geometry of fiber has a
marginal effect on the workability of concrete. However, it plays a
significant role in achieving a good compressive and tensile strength
of concrete. Further, significant improvement in term of flexural and
energy dissipation capacity were observed from other fibers as
compared to the straight slit sheet pattern. Also, the inclusion of PET
fiber improved the ability in absorbing energy in the post-cracking
state of the specimen as well as no significant porous structures.
Abstract: These days, the industrial trend is moving away from heavy and bulky passive components to power converter systems that use more and more semiconductor elements. Also, it is difficult to connect the traditional converters to the high and medium voltage. For these reasons, a new family of multilevel inverters has appeared as a solution for working with higher voltage levels. Different modulation topologies like Sinusoidal Pulse Width Modulation (SPWM), Selective Harmonic Elimination Pulse Width Modulation (SHE-PWM) are available for multilevel inverters. In this work, different hybrid modulation techniques which are combination of fundamental frequency modulation and multilevel sinusoidal-modulation are compared. The main characteristic of these modulations are reduction of switching losses with good harmonic performance and balanced power loss dissipation among the device. The proposed hybrid modulation schemes are developed and simulated in Matlab/Simulink for cascaded H-bridge inverter. The results validate the applicability of the proposed schemes for cascaded multilevel inverter.
Abstract: Commercial banks in Nigeria adopted many strategies
to attract fresh deposits including the use of high deposit rate.
However, pricing of banking services moved in favor of the banks at
the expense of customers, resulting in their seeking other investment
alternatives rather than saving their money in the bank. Both deposit
and lending rates were greatly influenced by the Central Bank of
Nigeria (CBN) decision on interest rate. Therefore, commercial bank
effort to attract deposits via manipulation of her rates was greatly
limited, otherwise the banks will be giving out more than it earned.
The study aimed at examining the relationship between interest rate
and fixed fund deposit of commercial banks, how policy-controlled
interest rate affected commercial bank’s fixed fund deposit The
researcher employed ordinary least square technique, using, multiple
linear regression, unrestricted vector auto-regression, correlation
matrix test, granger causality and impulse response graph in the
analysis. Commercial bank’s interest rates affected commercial
bank’s fixed fund deposit significantly while policy-controlled
interest rate did not significantly transmit through the commercial
bank’s interest rates to affect fixed fund deposit. While commercial
banks seek creative ways to expand their fixed fund deposit, policy
authorities in Nigeria should better coordinate interest rate fluctuation
and induce competition in the entire financial sector.
Abstract: In this paper, we report the development of the device
for diagnostics of cardiovascular system state and associated
automated workstation for large-scale medical measurement data
collection and analysis. It was shown that optimal design for the
monitoring device is wristband as it represents engineering trade-off
between accuracy and usability. Monitoring device is based on the
infrared reflective photoplethysmographic sensor, which allows
collecting multiple physiological parameters, such as heart rate and
pulsing wave characteristics. Developed device uses BLE interface
for medical and supplementary data transmission to the coupled
mobile phone, which processes it and send it to the doctor's
automated workstation. Results of this experimental model
approbation confirmed the applicability of the proposed approach.