Abstract: In this study we focus on improvement performance
of a cue based Motor Imagery Brain Computer Interface (BCI). For
this purpose, data fusion approach is used on results of different
classifiers to make the best decision. At first step Distinction
Sensitive Learning Vector Quantization method is used as a feature
selection method to determine most informative frequencies in
recorded signals and its performance is evaluated by frequency
search method. Then informative features are extracted by packet
wavelet transform. In next step 5 different types of classification
methods are applied. The methodologies are tested on BCI
Competition II dataset III, the best obtained accuracy is 85% and the
best kappa value is 0.8. At final step ordered weighted averaging
(OWA) method is used to provide a proper aggregation classifiers
outputs. Using OWA enhanced system accuracy to 95% and kappa
value to 0.9. Applying OWA just uses 50 milliseconds for
performing calculation.
Abstract: This article presents the development of a neural
network cognitive model for the classification and detection of
different frequency signals. The basic structure of the implemented
neural network was inspired on the perception process that humans
generally make in order to visually distinguish between high and low
frequency signals. It is based on the dynamic neural network concept,
with delays. A special two-layer feedforward neural net structure was
successfully implemented, trained and validated, to achieve
minimum target error. Training confirmed that this neural net
structure descents and converges to a human perception classification
solution, even when far away from the target.
Abstract: In order to provide accurate heart rate variability
indices of sympathetic and parasympathetic activity, the low
frequency and high frequency components of an RR heart rate signal
must be adequately separated. This is not always possible by just
applying spectral analysis, as power from the high and low frequency
components often leak into their adjacent bands. Furthermore,
without the respiratory spectra it is not obvious that the low
frequency component is not another respiratory component, which
can appear in the lower band. This paper describes an adaptive filter,
which aids the separation of the low frequency sympathetic and high
frequency parasympathetic components from an ECG R-R interval
signal, enabling the attainment of more accurate heart rate variability
measures. The algorithm is applied to simulated signals and heart rate
and respiratory signals acquired from an ambulatory monitor
incorporating single lead ECG and inductive plethysmography
sensors embedded in a garment. The results show an improvement
over standard heart rate variability spectral measurements.
Abstract: This paper describes a 2.4 GHz passive switch mixer
and a 5/2.5 GHz voltage-controlled negative Gm oscillator (VCO)
with an inversion-mode MOS varactor. Both circuits are implemented
using a 1P8M 0.13 μm process. The switch mixer has an input
referred 1 dB compression point of -3.89 dBm and a conversion
gain of -0.96 dB when the local oscillator power is +2.5 dBm.
The VCO consumes only 1.75 mW, while drawing 1.45 mA from a
1.2 V supply voltage. In order to reduce the passives size, the VCO
natural oscillation frequency is 5 GHz. A clocked CMOS divideby-
two circuit is used for frequency division and quadrature phase
generation. The VCO has a -109 dBc/Hz phase noise at 1 MHz
frequency offset and a 2.35-2.5 GHz tuning range (after the frequency
division), thus complying with ZigBee requirements.
Abstract: The most common cause of power transformer failures
is mechanical defect brought about by excessive vibration, which is
formed by the combination of multiples of a frequency of 120 Hz. In
this paper, the types of mechanical exciting forces applied to the
power transformer were classified, and the mechanical damage
mechanism of the power transformer was identified using the
vibration transfer route to the machine or structure. The general
effects of 120 Hz-vibration on the enclosure, bushing, Buchholz
relay, pressure release valve and tap changer of the transformer were
also examined.
Abstract: A new estimator for evolutionary spectrum (ES) based
on short time Fourier transform (STFT) and modified group delay
function (MGDF) by signal decomposition (SD) is proposed. The
STFT due to its built-in averaging, suppresses the cross terms and the
MGDF preserves the frequency resolution of the rectangular window
with the reduction in the Gibbs ripple. The present work overcomes
the magnitude distortion observed in multi-component non-stationary
signals with STFT and MGDF estimation of ES using SD. The SD is
achieved either through discrete cosine transform based harmonic
wavelet transform (DCTHWT) or perfect reconstruction filter banks
(PRFB). The MGDF also improves the signal to noise ratio by
removing associated noise. The performance of the present method is
illustrated for cross chirp and frequency shift keying (FSK) signals,
which indicates that its performance is better than STFT-MGDF
(STFT-GD) alone. Further its noise immunity is better than STFT.
The SD based methods, however cannot bring out the frequency
transition path from band to band clearly, as there will be gap in the
contour plot at the transition. The PRFB based STFT-SD shows good
performance than DCTHWT decomposition method for STFT-GD.
Abstract: This paper presents the results of corrosion fatigue
crack growth behaviour of a Ni-Cr-Mn steel commonly used in
marine applications. The effect of mechanical variables such as
frequency and load ratio on fatigue crack growth rate at various
stages has been studied using compact tension (C(T)) specimens
along the rolling direction of steel plate under 3.5% saturated NaCl
aqueous environment. The significance of crack closure on corrosion
fatigue, and the validity of Elber-s empirical linear crack closure
model with the ASTM compliance offset method have been
examined.
Fatigue crack growth rate is higher and threshold stress intensities
are lower in aqueous environment compared to the lab air conditions.
It is also observed that the crack growth rate increases at lower
frequencies. The higher stress ratio promotes the crack growth. The
effect of oxidization and corrosion pit formation is very less as the
stress ratio is increased. It is observed that as stress ratios are
increased, the Elber-s crack closure model agrees well with the crack
closure estimated by the ASTM compliance offset method for tests
conducted at 5Hz frequency compared to tests conducted at 1Hz in
corrosive environment.
Abstract: The binary phase-only filter digital watermarking
embeds the phase information of the discrete Fourier transform of the
image into the corresponding magnitudes for better image authentication.
The paper proposed an approach of how to implement watermark
embedding by quantizing the magnitude, with discussing how to
regulate the quantization steps based on the frequencies of the magnitude
coefficients of the embedded watermark, and how to embed the
watermark at low frequency quantization. The theoretical analysis and
simulation results show that algorithm flexibility, security, watermark
imperceptibility and detection performance of the binary phase-only
filter digital watermarking can be effectively improved with quantization
based watermark embedding, and the robustness against JPEG
compression will also be increased to some extent.
Abstract: Laser engraving is a manufacturing method for those applications where previously Electrical Discharge Machining (EDM) was the only choice. Laser engraving technology removes material layer-by-layer and the thickness of layers is usually in the range of few microns. The aim of the present work is to investigate the influence of the process parameters on the surface quality when machined by laser engraving. The examined parameters were: the pulse frequency, the beam speed and the layer thickness. The surface quality was determined by the surface roughness for every set of parameters. Experimental results on Al7075 material showed that the surface roughness strictly depends on the process parameters used.
Abstract: A new mechanism responsible for structural life
consumption due to resonant fatigue in turbine blades, or vanes, is
presented and explained. A rotating blade or vane in a gas turbine can
change its contour due to erosion and/or material build up, in any of
these instances, the surface pressure distribution occurring on the
suction and pressure sides of blades-vanes can suffer substantial
modification of their pressure and temperatures envelopes and flow
characteristics. Meanwhile, the relative rotation between the blade
and duct vane while the pressurized gas flows and the consequent
wake crossings, will induce a fluctuating thrust force or lift that will
excite the blade.
An actual totally used up set of vane-blade components in a HP
turbine power stage in a gas turbine is analyzed. The blade suffered
some material erosion mostly at the trailing edge provoking a
peculiar surface pressure envelope which evolved as the relative
position between the vane and the blade passed in front of each other.
Interestingly preliminary modal analysis for this eroded blade
indicates several natural frequencies within the aeromechanic power
spectrum, moreover, the highest frequency component is 94% of one
natural frequency indicating near resonant condition.
Independently of other simultaneously occurring fatigue cycles
(such as thermal, centrifugal stresses).
Abstract: A analysis on the conventional the blood pressure estimation method using an oscillometric sphygmomanometer was
performed through a computer simulation using an arterial pressure-volume (APV) model. Traditionally, the maximum amplitude algorithm (MAP) was applied on the oscillation waveforms of the APV model to obtain the mean arterial pressure and the characteristic ratio. The estimation of mean arterial pressure and
characteristic ratio was significantly affected with the shape of the blood pressure waveforms and the cutoff frequency of high-pass filter
(HPL) circuitry. Experimental errors are due to these effects when estimating blood pressure. To find out an algorithm independent from
the influence of waveform shapes and parameters of HPL, the volume
oscillation of the APV model and the phase shift of the oscillation with fast fourier transform (FFT) were testified while increasing the cuff
pressure from 1 mmHg to 200 mmHg (1 mmHg per second). The phase shift between the ranges of volume oscillation was then only observed between the systolic and the diastolic blood pressures. The same results were also obtained from the simulations performed on two different the arterial blood pressure waveforms and one
hyperthermia waveform.
Abstract: A novel robust audio watermarking scheme is
proposed in this paper. In the proposed scheme, the host audio signals
are segmented into frames. Two consecutive frames are assessed if
they are suitable to represent a watermark bit. If so, frequency
transform is performed on these two frames. The compressionexpansion
technique is adopted to generate distortion over the two
frames. The distortion is used to represent one watermark bit.
Psychoacoustic model is applied to calculate local auditory mask to
ensure that the distortion is not audible. The watermarking schemes
using mono and stereo audio signals are designed differently. The
correlation-based detection method is used to detect the distortion
and extract embedded watermark bits. The experimental results show
that the quality degradation caused by the embedded watermarks is
perceptually transparent and the proposed schemes are very robust
against different types of attacks.
Abstract: The wavelet transform is one of the most important
method used in signal processing. In this study, we have introduced
frequency-energy characteristics of local earthquakes using discrete
wavelet transform. Frequency-energy characteristic was analyzed
depend on difference between P and S wave arrival time and noise
within records. We have found that local earthquakes have similar
characteristics. If frequency-energy characteristics can be found
accurately, this gives us a hint to calculate P and S wave arrival time.
It can be seen that wavelet transform provides successful
approximation for this. In this study, 100 earthquakes with 500
records were analyzed approximately.
Abstract: This paper presents results of measurements campaign
carried out at a carrier frequency of 24GHz with the help of TPLINK
router in indoor line-of-sight (LOS) scenarios. Firstly, the
radio wave propagation strategies are analyzed in some rooms with
router of point to point Ad hoc network. Then floor attenuation is
defined for 3 floors in experimental region. The free space model and
dual slope models are modified by considering the influence of
corridor conditions on each floor. Using these models, indoor signal
attenuation can be estimated in modeling of indoor radio wave
propagation. These results and modified models can also be used in
planning the networks of future personal communications services.
Abstract: This paper presents a multiband CPW-fed slot antenna
with L-slot bowtie tuning stub. The proposed antenna has been
designed for PCS 1900, UMTS, WLAN 802.11 a/b/g and bluetooth
applications, with a cost-effective FR4 substrate. The proposed
antenna still radiate as omni-directional in azimuth plane and
sufficient bandwidth for all above mentions. The proposed antenna
works as dual-wideband, bandwidth at low frequency band and high
frequency are about 45.49 % and 22.39 % respectively. The
experimental results of the constructed prototype are presented and
also compared with simulation results using a commercial software
tool.
Abstract: This paper describes an application of a dual satellite
geolocation (DSG) system on identifying and locating the unknown
source of uplink sweeping interference. The geolocation system
integrates the method of joint time difference of arrival (TDOA) and
frequency difference of arrival (FDOA) with ephemeris correction
technique which successfully demonstrated high accuracy in
interference source location. The factors affecting the location error
were also discussed.
Abstract: The demands of taller structures are becoming imperative almost everywhere in the world in addition to the challenges of material and labor cost, project time line etc. This paper conducted a study keeping in view the challenging nature of high-rise construction with no generic rules for deflection minimizations and frequency control. The effects of cyclonic wind and provision of outriggers on 28-storey, 42-storey and 57-storey are examined in this paper and certain conclusions are made which would pave way for researchers to conduct further study in this particular area of civil engineering. The results show that plan dimensions have vital impacts on structural heights. Increase of height while keeping the plan dimensions same, leads to the reduction in the lateral rigidity. To achieve required stiffness increase of bracings sizes as well as introduction of additional lateral resisting system such as belt truss and outriggers is required.
Abstract: Aggression is a behavior that cannot be approved by
the society. Vandalism which is aggression towards objects is an
action that tends to damage public or personal property. The
behaviors that are described as vandalism can often be observed in
the schools as well. According to Zwier and Vaughan (1)
previous research about the reasons of and precautionary measures
for vandalism in schools can be grouped in three tendency categories:
conservative, liberal and radical. In this context, the main aim of this
study is to discover which ideological tendency of the reasons of
school vandalism is adopted by the teachers and what are their
physical, environmental, school system and societal solutions for
vandalism. A total of 200 teachers participated in this study, and the
mean age was 34.20 years (SD = 6.54). The sample was made up of
109 females and 91 males. For the analysis of the data, SPSS 15.00,
frequency, percentage, and t-test were used. The research showed
that the teachers have tendencies in the order of conservative, liberal
and radical for the reasons of vandalism. The research also showed
that the teachers do not have any tendency for eliminating vandalism
physically and general solutions on the level of society; on the other
hand they mostly adopt a conservative tendency in terms of
precautions against vandalism in the school system. Second most,
they adopt the liberal tendency in terms of precautions against
vandalism in the school system. . It is observed that the findings of
this study are comparable to the existing literature on the subject.
Future studies should be conducted with multiple variants and
bigger sampling.
Abstract: Selecting the word translation from a set of target
language words, one that conveys the correct sense of source word
and makes more fluent target language output, is one of core
problems in machine translation. In this paper we compare the 3
methods of estimating word translation probabilities for selecting the
translation word in Thai – English Machine Translation. The 3
methods are (1) Method based on frequency of word translation, (2)
Method based on collocation of word translation, and (3) Method
based on Expectation Maximization (EM) algorithm. For evaluation
we used Thai – English parallel sentences generated by NECTEC.
The method based on EM algorithm is the best method in comparison
to the other methods and gives the satisfying results.
Abstract: This research seeks to investigate the frequency and
profitability of index arbitrage opportunities involving the SET50
futures, SET50 component stocks, and the ThaiDEX SET50 ETF
(ticker symbol: TDEX). In particular, the frequency and profit of
arbitrage are measured in the following three arbitrage tests: (1)
SET50 futures vs. ThaiDEX SET50 ETF, (2) SET50 futures vs.
SET50 component stocks, and (3) ThaiDEX SET50 ETF vs. SET50
component stocks are investigated. For tests (2) and (3), the problems
involve conic optimization and quadratic programming as subproblems.
This research is first to apply conic optimization and
quadratic programming techniques in the context of index arbitrage
and is first to investigate such index arbitrage in the Thai equity and
derivatives markets. Thus, the contribution of this study is twofold.
First, its results would help understand the contribution of the
derivatives securities to the efficiency of the Thai markets. Second,
the methodology employed in this study can be applied to other
geographical markets, with minor adjustments.