Abstract: This research proposes an algorithm for the simulation
of time-periodic unsteady problems via the solution unsteady Euler
and Navier-Stokes equations. This algorithm which is called Time
Spectral method uses a Fourier representation in time and hence
solve for the periodic state directly without resolving transients
(which consume most of the resources in a time-accurate scheme).
Mathematical tools used here are discrete Fourier transformations. It
has shown tremendous potential for reducing the computational cost
compared to conventional time-accurate methods, by enforcing
periodicity and using Fourier representation in time, leading to
spectral accuracy. The accuracy and efficiency of this technique is
verified by Euler and Navier-Stokes calculations for pitching airfoils.
Because of flow turbulence nature, Baldwin-Lomax turbulence
model has been used at viscous flow analysis. The results presented
by the Time Spectral method are compared with experimental data. It
has shown tremendous potential for reducing the computational cost
compared to the conventional time-accurate methods, by enforcing
periodicity and using Fourier representation in time, leading to
spectral accuracy, because results verify the small number of time
intervals per pitching cycle required to capture the flow physics.
Abstract: This paper presents a fuzzy logic controlled shunt
active power filter used to compensate for harmonic distortion in three-phase four-wire systems. The shunt active filter employs a
simple method for the calculation of the reference compensation current based of Fast Fourier Transform. This presented filter is able
to operate in both balanced and unbalanced load conditions. A fuzzy
logic based current controller strategy is used to regulate the filter current and hence ensure harmonic free supply current. The validity
of the presented approach in harmonic mitigation is verified via
simulation results of the proposed test system under different loading
conditions.
Abstract: Acoustic Imaging based sound localization using microphone
array is a challenging task in digital-signal processing.
Discrete Fourier transform (DFT) based near-field acoustical holography
(NAH) is an important acoustical technique for sound source
localization and provide an efficient solution to the ill-posed problem.
However, in practice, due to the usage of small curtailed aperture
and its consequence of significant spectral leakage, the DFT could
not reconstruct the active-region-of-sound (AROS) effectively, especially
near the edges of aperture. In this paper, we emphasize the
fundamental problems of DFT-based NAH, provide a solution to
spectral leakage effect by the extrapolation based on linear predictive
coding and 2D Tukey windowing. This approach has been tested to
localize the single and multi-point sound sources. We observe that
incorporating extrapolation technique increases the spatial resolution,
localization accuracy and reduces spectral leakage when small curtail
aperture with a lower number of sensors accounts.
Abstract: In this study, we report the synthesis and
characterization of nanohydroxyapatite (nHAp) in gelatin-starch
matrix via biomimetic method. Characterization of the samples was
performed using X-ray diffraction (XRD) and Fourier Transform
infrared spectroscopy (FT-IR). The Size and morphology of the
nHAp samples were determined using scanning and transmission
electron microscopy (SEM and TEM). The results reveal that the
shape and morphology of nHAp is influenced by presence of
biopolymers as template. Carbonyl and amino groups from gelatin
and hydroxyl from starch play crucial roles in HAp formation on the
surface of gelatin-starch.
Abstract: For broadband wireless mobile communication
systems the orthogonal frequency division multiplexing (OFDM) is a
suitable modulation scheme. The frequency offset between
transmitter and receiver local oscillator is main drawback of OFDM
systems, which causes intercarrier interference (ICI) in the
subcarriers of the OFDM system. This ICI degrades the bit error rate
(BER) performance of the system. In this paper an improved self-ICI
cancellation scheme is proposed to improve the system performance.
The proposed scheme is based on discrete Fourier transform-inverse
discrete Fourier transform (DFT-IDFT). The simulation results show
that there is satisfactory improvement in the bit error rate (BER)
performance of the present scheme.
Abstract: The presence of harmonic in power system is a major
concerned to power engineers for many years. With the increasing
usage of nonlinear loads in power systems, the harmonic pollution
becomes more serious. One of the widely used computation
algorithm for harmonic analysis is fast Fourier transform (FFT). In
this paper, a harmonic analyzer using FFT was implemented on
TMS320C6713 DSK. The supply voltage of 240 V 59 Hz is stepped
down to 5V using a voltage divider in order to match the power
rating of the DSK input. The output from the DSK was displayed on
oscilloscope and Code Composer Studio™ software. This work has
demonstrated the possibility of analyzing the 240V power supply
harmonic content using the DSK board.
Abstract: The bit error rate (BER) performance for ultra-wide
band (UWB) indoor communication with impact of metallic furniture
is investigated. The impulse responses of different indoor
environments for any transmitter and receiver location are computed
by shooting and bouncing ray/image and inverse Fourier transform
techniques. By using the impulse responses of these multipath
channels, the BER performance for binary pulse amplitude
modulation (BPAM) impulse radio UWB communication system are
calculated. Numerical results have shown that the multi-path effect
by the metallic cabinets is an important factor for BER performance.
Also the outage probability for the UWB multipath environment with
metallic cabinets is more serious (about 18%) than with wooden
cabinets. Finally, it is worth noting that in these cases the present
work provides not only comparative information but also quantitative
information on the performance reduction.
Abstract: To successfully provide a fast FIR filter with FTT algorithms, overlapped-save algorithms can be used to lower the computational complexity and achieve the desired real-time processing. As the length of the input block increases in order to improve the efficiency, a larger volume of zero padding will greatly increase the computation length of the FFT. In this paper, we use the overlapped block digital filtering to construct a parallel structure. As long as the down-sampling (or up-sampling) factor is an exact multiple lengths of the impulse response of a FIR filter, we can process the input block by using a parallel structure and thus achieve a low-complex fast FIR filter with overlapped-save algorithms. With a long filter length, the performance and the throughput of the digital filtering system will also be greatly enhanced.
Abstract: This current research focused on development of degradable starch based packaging film with enhanced mechanical properties. A series of low density polyethylene (LDPE)/tapioca starch compounds with various tapioca starch contents were prepared by twin screw extrusion with the addition of maleic anhydride grafted polyethylene as compatibilizer. Palm cooking oil was used as processing aid to ease the blown film process, thus, degradable film can be processed via conventional blown film machine. Studies on their characteristics, mechanical properties and biodegradation were carried out by Fourier Transform Infrared (FTIR) spectroscopy and optical properties, tensile test and exposure to fungi environment respectively. The presence of high starch contents had an adverse effect on the tensile properties of LDPE/tapioca starch blends. However, the addition of compatibilizer to the blends improved the interfacial adhesion between the two materials, hence, improved the tensile properties of the films. High content of starch amount also was found to increase the rate of biodegradability of LDPE/tapioca starch films. It can be proved by exposure of the film to fungi environment. A growth of microbes colony can be seen on the surface of LDPE/tapioca starch film indicates that the granular starch present on the surface of the polymer film is attacked by microorganisms, until most of it is assimilated as a carbon source.
Abstract: An efficient parallel form in digital signal processor can improve the algorithm performance. The butterfly structure is an important role in fast Fourier transform (FFT), because its symmetry form is suitable for hardware implementation. Although it can perform a symmetric structure, the performance will be reduced under the data-dependent flow characteristic. Even though recent research which call as novel memory reference reduction methods (NMRRM) for FFT focus on reduce memory reference in twiddle factor, the data-dependent property still exists. In this paper, we propose a parallel-computing approach for FFT implementation on digital signal processor (DSP) which is based on data-independent property and still hold the property of low-memory reference. The proposed method combines final two steps in NMRRM FFT to perform a novel data-independent structure, besides it is very suitable for multi-operation-unit digital signal processor and dual-core system. We have applied the proposed method of radix-2 FFT algorithm in low memory reference on TI TMSC320C64x DSP. Experimental results show the method can reduce 33.8% clock cycles comparing with the NMRRM FFT implementation and keep the low-memory reference property.
Abstract: This paper presents an algorithm to estimate the parameters of two closely spaced sinusoids, providing a frequency resolution that is more than 800 times greater than that obtained by using the Discrete Fourier Transform (DFT). The strategy uses a highly optimized grid search approach to accurately estimate frequency, amplitude and phase of both sinusoids, keeping at the same time the computational effort at reasonable levels. The proposed method has three main characteristics: 1) a high frequency resolution; 2) frequency, amplitude and phase are all estimated at once using one single package; 3) it does not rely on any statistical assumption or constraint. Potential applications to this strategy include the difficult task of resolving coincident partials of instruments in musical signals.
Abstract: In this paper, we present a new method for
incorporating global shift invariance in support vector machines.
Unlike other approaches which incorporate a feature extraction stage,
we first scale the image and then classify it by using the modified
support vector machines classifier. Shift invariance is achieved by
replacing dot products between patterns used by the SVM classifier
with the maximum cross-correlation value between them. Unlike the
normal approach, in which the patterns are treated as vectors, in our
approach the patterns are treated as matrices (or images). Crosscorrelation
is computed by using computationally efficient
techniques such as the fast Fourier transform. The method has been
tested on the ORL face database. The tests indicate that this method
can improve the recognition rate of an SVM classifier.
Abstract: A frequency grouping approach for multi-channel
instantaneous blind source separation (I-BSS) of convolutive
mixtures is proposed for a lower net residual inter-symbol
interference (ISI) and inter-channel interference (ICI) than the
conventional short-time Fourier transform (STFT) approach. Starting
in the time domain, STFTs are taken with overlapping windows to
convert the convolutive mixing problem into frequency domain
instantaneous mixing. Mixture samples at the same frequency but
from different STFT windows are grouped together forming unique
frequency groups.
The individual frequency group vectors are input to the I-BSS
algorithm of choice, from which the output samples are dispersed
back to their respective STFT windows. After applying the inverse
STFT, the resulting time domain signals are used to construct the
complete source estimates via the weighted overlap-add method
(WOLA). The proposed algorithm is tested for source deconvolution
given two mixtures, and simulated along with the STFT approach to
illustrate its superiority for fairly motionless sources.
Abstract: Five lignin samples were fractionated with
Acetone/Water mixtures and the obtained fractions were subjected to
extensive structural characterization, including Fourier Transform
Infrared (FT-IR), Gel permeation Chromatography (GPC) and
Phosphorus-31 NMR spectroscopy (31P-NMR). The results showed
that for all studied lignins the solubility increases with the increment
of the acetone concentration. Wheat straw lignin has the highest
solubility in 90/10 (v/v) Acetone/Water mixture, 400 mg lignin being
dissolved in 1 mL mixture. The weight average molecular weight of
the obtained fractions increased with the increment of acetone
concentration and thus with solubility. 31P-NMR analysis based on
lignin modification by reactive phospholane into phosphitylated
compounds was used to differentiate and quantify the different types
of OH groups (aromatic, aliphatic, and carboxylic) found in the
fractions obtained with 70/30 (v/v) Acetone/Water mixture.
Abstract: Visualizing sound and noise often help us to determine
an appropriate control over the source localization. Near-field acoustic
holography (NAH) is a powerful tool for the ill-posed problem.
However, in practice, due to the small finite aperture size, the discrete
Fourier transform, FFT based NAH couldn-t predict the activeregion-
of-interest (AROI) over the edges of the plane. Theoretically
few approaches were proposed for solving finite aperture problem.
However most of these methods are not quite compatible for the
practical implementation, especially near the edge of the source. In
this paper, a zip-stuffing extrapolation approach has suggested with
2D Kaiser window. It is operated on wavenumber complex space
to localize the predicted sources. We numerically form a practice
environment with touch impact databases to test the localization of
sound source. It is observed that zip-stuffing aperture extrapolation
and 2D window with evanescent components provide more accuracy
especially in the small aperture and its derivatives.
Abstract: Worldwide many electrical equipment insulation
failures have been reported caused by switching operations, while
those equipments had previously passed all the standard tests and
complied with all quality requirements. The problem is mostly
associated with high-frequency overvoltages generated during
opening or closing of a switching device. The transients generated
during switching operations in a Gas Insulated Substation (GIS) are
associated with high frequency components in the order of few tens
of MHz.
The frequency spectrum of the VFTO generated in the 220/66 kV
Wadi-Hoff GIS is analyzed using Fast Fourier Transform technique.
The main frequency with high voltage amplitude due to the operation
of disconnector (DS5) is 5 to 10 MHz, with the highest amplitude at 9
MHz. The main frequency with high voltage amplitude due to the
operation of circuit breaker (CB5) is 1 to 25 MHz, with the highest
amplitude at 2 MHz.
Mitigating techniques damped the oscillating frequencies
effectively. The using of cable terminal reduced the frequency
oscillation effectively than that of OHTL terminal. The using of a
shunt capacitance results in vanishing the high frequency
components. Ferrite rings reduces the high frequency components
effectively especially in the range 2 to 7 MHz. The using of RC and
RL filters results in vanishing the high frequency components.
Abstract: Solid dispersions (SD) of curcuminpolyvinylpyrrolidone
in the ratio of 1:2, 1:4, 1:5, 1:6, and 1:8 were
prepared in an attempt to increase the solubility and dissolution.
Solubility, dissolution, powder X-ray diffraction (XRD), differential
scanning calorimetry (DSC) and Fourier transform infrared
spectroscopy (FTIR) of solid dispersions, physical mixtures (PM)
and curcumin were evaluated. Both solubility and dissolution of
curcumin solid dispersions were significantly greater than those
observed for physical mixtures and intact curcumin. The powder
X-ray diffractograms indicated that the amorphous curcumin was
obtained from all solid dispersions. It was found that the optimum
weight ratio for curcumin:PVP K-30 is 1:6. The 1:6 solid dispersion
still in the amorphous from after storage at ambient temperature for 2
years and the dissolution profile did not significantly different from
freshly prepared.
Abstract: This report shows the performance of composite
biodegradable film from chitosan, starch and sawdust fiber. The main
objectives of this research are to fabricate and characterize composite
biodegradable film in terms of morphology and physical properties.
The film was prepared by casting method. Sawdust fiber was used as
reinforcing agent and starch as polymer matrix in the casting
solution. The morphology of the film was characterized using atomic
force microscope (AFM). The result showed that the film has
smooth structure. Chemical composition of the film was investigated
using Fourier transform infrared (FTIR) where the result revealed
present of starch in the film. The thermal properties were
characterized using thermal gravimetric analyzer (TGA) and
differential scanning calorimetric (DSC) where the results showed
that the film has small difference in melting and degradation
temperature.
Abstract: Sulfide ion (S2-) is one of the most important ions to be
monitored due to its high toxicity, especially for aquatic organisms. In
this work, [Ca(2,2'-bipyridine)3]2+-intercalated montmorillonite was
prepared and used as a sensor to construct a potentiometric electrode to
measure sulfide ion in solution. The formation of [Ca(2,2'-
bipyridine)3]2+ in montmorillonite was confirmed by Fourier Transform
Infrared spectra. The electrode worked well at pH 4-12 and 4-10 in
sulfide solution 10-2 M and 10-3 M, respectively, in terms of Nernstian
slope. The sensor gave good precision and low cost.
Abstract: The systematic manipulations of shapes and sizes of
inorganic compounds greatly benefit the various application fields
including optics, magnetic, electronics, catalysis and medicine.
However shape control has been much more difficult to achieve.
Hence exploration of novel method for the preparation of differently
shaped nanoparticles is challenging research area. II-VI group of
semiconductor cadmium sulphide (CdS) nanostructure with different
morphologies (such as, acicular like, mesoporous, spherical shapes)
and of crystallite sizes vary from 11 to 16 nm were successfully
synthesized by chemical aqueous precipitation of Cd2+ ions with
homogeneously released S2- ions from decomposition of cadmium
sulphate (CdSO4) and thioacetamide (CH3CSNH2) by annealing at
different radiations (microwave, ultrasonic and sunlight) with matter
and systematic research has been done for various factors affecting
the controlled growth rate of CdS nanoparticles. The obtained
nanomaterials have been characterized by X-ray Diffraction (XRD),
Fourier Transform Infrared Spectroscopy (FTIR),
Thermogravometric (DSC-TGA) analysis and Scanning Electron
Microscopy (SEM). The result indicates that on increasing the
reaction time particle size increases but on increasing the molar ratios
grain size decreases.