Abstract: This paper presents a physics-based model for the
high-voltage fast recovery diodes. The model provides a good
trade-off between reverse recovery time and forward voltage drop
realized through a combination of lifetime control and emitter
efficiency reduction techniques. The minority carrier lifetime can be
extracted from the reverse recovery transient response and forward
characteristics. This paper also shows that decreasing the amount of
the excess carriers stored in the drift region will result in softer
characteristics which can be achieved using a lower doping level. The
developed model is verified by experiment and the measurement data
agrees well with the model.
Abstract: Classification of electroencephalogram (EEG) signals
extracted during mental tasks is a technique that is actively pursued
for Brain Computer Interfaces (BCI) designs. In this paper, we
compared the classification performances of univariateautoregressive
(AR) and multivariate autoregressive (MAR) models
for representing EEG signals that were extracted during different
mental tasks. Multilayer Perceptron (MLP) neural network (NN)
trained by the backpropagation (BP) algorithm was used to classify
these features into the different categories representing the mental
tasks. Classification performances were also compared across
different mental task combinations and 2 sets of hidden units (HU): 2
to 10 HU in steps of 2 and 20 to 100 HU in steps of 20. Five different
mental tasks from 4 subjects were used in the experimental study and
combinations of 2 different mental tasks were studied for each
subject. Three different feature extraction methods with 6th order
were used to extract features from these EEG signals: AR
coefficients computed with Burg-s algorithm (ARBG), AR
coefficients computed with stepwise least square algorithm (ARLS)
and MAR coefficients computed with stepwise least square
algorithm. The best results were obtained with 20 to 100 HU using
ARBG. It is concluded that i) it is important to choose the suitable
mental tasks for different individuals for a successful BCI design, ii)
higher HU are more suitable and iii) ARBG is the most suitable
feature extraction method.
Abstract: Khatunabad area is situated geologically in Urmieh-
Dokhtar magmatic belt in NW of Iran. In this research, studied area
has been investigated in order to recognize the potential copper and
molybdenum-bearing target areas. The survey layers include the
lithologic units, alteration, geochemical result, tectonics and copper
and molybdenum occurrence. As an accurate decision can have a
considerable effect on exploration plans, so in this efforts have been
made to make use of new combination method. For this purpose, the
analytical hierarchy process was used and revealed highly potential
copper and molybdenum mineralization areas. Based on achieved
results, geological perspective in north of studied area is appropriate
for advance stage, especially for subsurface exploration in future.
Abstract: New advancement of technology and never satisfying demands of the civilization are putting huge pressure on the natural fuel resources and these resources are at a constant threat to its sustainability. To get the best out of the automobile, the optimum balance between performance and fuel economy is important. In the present state of art, either of the above two aspects are taken into mind while designing and development process which puts the other in the loss as increase in fuel economy leads to decrement in performance and vice-versa. In-depth observation of the vehicle dynamics apparently shows that large amount of energy is lost during braking and likewise large amount of fuel is consumed to reclaim the initial state, this leads to lower fuel efficiency to gain the same performance. Current use of Kinetic Energy Recovery System is only limited to sports vehicles only because of the higher cost of this system. They are also temporary in nature as power can be squeezed only during a small time duration and use of superior parts leads to high cost, which results on concentration on performance only and neglecting the fuel economy. In this paper Kinetic Energy Recovery System for storing the power and then using the same while accelerating has been discussed. The major storing element in this system is a Flat Spiral Spring that will store energy by compression and torsion.
The use of spring ensure the permanent storage of energy until used by the driver unlike present mechanical regeneration system in which the energy stored decreases with time and is eventually lost. A combination of internal gears and spur gears will be used in order to make the energy release uniform which will lead to safe usage. The system can be used to improve the fuel efficiency by assisting in overcoming the vehicle’s inertia after braking or to provide instant acceleration whenever required by the driver. The performance characteristics of the system including response time, mechanical efficiency and overall increase in efficiency are demonstrated. This technology makes the KERS (Kinetic Energy Recovery System) more flexible and economical allowing specific application while at the same time increasing the time frame and ease of usage.
Abstract: The most suitable Semiconductor detector, Cadmium
Zinc Teloraid , has unique properties because of high Atomic number
and wide Brand Gap . It has been tried in this project with different
processes such as Lead , Diffusion , Produce and Recombination ,
effect of Trapping and injection carrier of CdZnTe , to get hole and
then present a complete answer of it . Then we should investigate the
movement of carrier ( Electron – Hole ) by using above answer.
Abstract: This paper presents a general trainable framework
for fast and robust upright human face and non-human object
detection and verification in static images. To enhance the
performance of the detection process, the technique we develop is
based on the combination of fast neural network (FNN) and
classical neural network (CNN). In FNN, a useful correlation is
exploited to sustain high level of detection accuracy between input
image and the weight of the hidden neurons. This is to enable the
use of Fourier transform that significantly speed up the time
detection. The combination of CNN is responsible to verify the
face region. A bootstrap algorithm is used to collect non human
object, which adds the false detection to the training process of the
human and non-human object. Experimental results on test images
with both simple and complex background demonstrate that the
proposed method has obtained high detection rate and low false
positive rate in detecting both human face and non-human object.
Abstract: The purpose of this paper is applied Taguchi method on the optimization for PEMFC performance, and a representative Computational Fluid Dynamics (CFD) model is selectively performed for statistical analysis. The studied factors in this paper are pressure of fuel cell, operating temperature, the relative humidity of anode and cathode, porosity of gas diffusion electrode (GDE) and conductivity of GDE. The optimal combination for maximum power density is gained by using a three-level statistical method. The results confirmed that the robustness of the optimum design parameters influencing the performance of fuel cell are founded by pressure of fuel cell, 3atm; operating temperature, 353K; the relative humidity of anode, 50%; conductivity of GDE, 1000 S/m, but the relative humidity of cathode and porosity of GDE are pooled as error due to a small sum of squares. The present simulation results give designers the ideas ratify the effectiveness of the proposed robust design methodology for the performance of fuel cell.
Abstract: A SnO2/CdS/CdTe heterojunction was fabricated by
thermal evaporation technique. The fabricated cells were annealed at
573K for periods of 60, 120 and 180 minutes. The structural
properties of the solar cells have been studied by using X-ray
diffraction. Capacitance- voltage measurements were studied for the
as-prepared and annealed cells at a frequency of 102 Hz. The
capacitance- voltage measurements indicated that these cells are
abrupt. The capacitance decreases with increasing annealing time.
The zero bias depletion region width and the carrier concentration
increased with increasing annealing time. The carrier transport
mechanism for the CdS/CdTe heterojunction in dark is tunneling
recombination. The ideality factor is 1.56 and the reverse bias
saturation current is 9.6×10-10A. The energy band lineup for the n-
CdS/p-CdTe heterojunction was investigated using current - voltage
and capacitance - voltage characteristics.
Abstract: This paper investigates vortex shedding processes
occurring at the end of a stack of parallel plates, due to an oscillating
flow induced by an acoustic standing wave within an acoustic
resonator. Here, Particle Image Velocimetry (PIV) is used to quantify
the vortex shedding processes within an acoustic cycle
phase-by-phase, in particular during the “ejection" of the fluid out of
the stack. Standard hot-wire anemometry measurement is also applied
to detect the velocity fluctuations near the end of the stack.
Combination of these two measurement techniques allowed a detailed
analysis of the vortex shedding phenomena. The results obtained show
that, as the Reynolds number varies (by varying the plate thickness
and drive ratio), different flow patterns of vortex shedding are
observed by the PIV measurement. On the other hand, the
time-dependent hot-wire measurements allow obtaining detailed
frequency spectra of the velocity signal, used for calculating
characteristic Strouhal numbers. The impact of the plate thickness and
the Reynolds number on the vortex shedding pattern has been
discussed. Furthermore, a detailed map of the relationship between the
Strouhal number and Reynolds number has been obtained and
discussed.
Abstract: In this paper, the deformation modes of a compact impact absorption member subjected to axial compression are investigated using finite element method and experiments. A multiple combination compact impact absorption member, referred to as a 'compress-expand member', is proposed to substitute the conventional thin-walled circular tube. This study found that the proposed compact impact absorption member has stable load increase characteristics and a wider range of high load efficiency (Pave/Pmax) than the thin-walled circular tube. Moreover, the proposed compact impact absorption member can absorb larger loads in a smaller radius than the thin-walled cylindrical tube, as it can maintain its stable deformation in increased wall thicknesses.
Abstract: The expansion mechanism of a partially ionized plasma produced by laser interaction with solid target (copper) is studied. For this purpose we use a hydrodynamical model which includes a source term combined with Saha's equation. The obtained self-similar solution in the limit of quasi-neutrality shows that the expansion, at the earlier stage, is driven by the combination of thermal pressure and electrostatic potential. They are of the same magnitude. The initial ionized fraction and the temperature are the leading parameters of the expanding profiles,
Abstract: In this paper, we propose a robust controller design method for discrete-time systems with sector-bounded nonlinearities and time-varying delay. Based on the Lyapunov theory, delaydependent stabilization criteria are obtained in terms of linear matrix inequalities (LMIs) by constructing the new Lyapunov-Krasovskii functional and using some inequalities. A robust state feedback controller is designed by LMI framework and a reciprocally convex combination technique. The effectiveness of the proposed method is verified throughout a numerical example.
Abstract: Utilization of diverse germplasm is needed to enhance
the genetic diversity of cultivars. The objective of this study was to
evaluate the genetic relationships of 98 alfalfa germplasm accessions
using morphological traits and SSR markers. From the 98 tested
populations, 81 were locals originating in Europe, 17 were introduced
from USA, Australia, New Zealand and Canada. Three primers
generated 67 polymorphic bands. The average polymorphic
information content (PIC) was very high (> 0.90) over all three used
primer combinations. Cluster analysis using Unweighted Pair Group
Method with Arithmetic Means (UPGMA) and Jaccard´s coefficient
grouped the accessions into 2 major clusters with 4 sub-clusters with
no correlation between genetic and morphological diversity. The SSR
analysis clearly indicated that even with three polymorphic primers,
reliable estimation of genetic diversity could be obtained.
Abstract: Evolvable hardware (EHW) is a developing field that
applies evolutionary algorithm (EA) to automatically design circuits,
antennas, robot controllers etc. A lot of research has been done in this
area and several different EAs have been introduced to tackle
numerous problems, as scalability, evolvability etc. However every
time a specific EA is chosen for solving a particular task, all its
components, such as population size, initialization, selection
mechanism, mutation rate, and genetic operators, should be selected
in order to achieve the best results. In the last three decade the
selection of the right parameters for the EA-s components for solving
different “test-problems" has been investigated. In this paper the
behaviour of mutation rate for designing logic circuits, which has not
been done before, has been deeply analyzed. The mutation rate for an
EHW system modifies the number of inputs of each logic gates, the
functionality (for example from AND to NOR) and the connectivity
between logic gates. The behaviour of the mutation has been
analyzed based on the number of generations, genotype redundancy
and number of logic gates for the evolved circuits. The experimental
results found provide the behaviour of the mutation rate during
evolution for the design and optimization of simple logic circuits.
The experimental results propose the best mutation rate to be used for
designing combinational logic circuits. The research presented is
particular important for those who would like to implement a
dynamic mutation rate inside the evolutionary algorithm for evolving
digital circuits. The researches on the mutation rate during the last 40
years are also summarized.
Abstract: In this paper, based on flume experimental data, the velocity distribution in open channel flows is re-investigated. From the analysis, it is proposed that the wake layer in outer region may be divided into two regions, the relatively weak outer region and the relatively strong outer region. Combining the log law for inner region and the parabolic law for relatively strong outer region, an explicit equation for mean velocity distribution of steady and uniform turbulent flow through straight open channels is proposed and verified with the experimental data. It is found that the sediment concentration has significant effect on velocity distribution in the relatively weak outer region.
Abstract: Increasing growth of information volume in the
internet causes an increasing need to develop new (semi)automatic
methods for retrieval of documents and ranking them according to
their relevance to the user query. In this paper, after a brief review
on ranking models, a new ontology based approach for ranking
HTML documents is proposed and evaluated in various
circumstances. Our approach is a combination of conceptual,
statistical and linguistic methods. This combination reserves the
precision of ranking without loosing the speed. Our approach
exploits natural language processing techniques for extracting
phrases and stemming words. Then an ontology based conceptual
method will be used to annotate documents and expand the query.
To expand a query the spread activation algorithm is improved so
that the expansion can be done in various aspects. The annotated
documents and the expanded query will be processed to compute
the relevance degree exploiting statistical methods. The outstanding
features of our approach are (1) combining conceptual, statistical
and linguistic features of documents, (2) expanding the query with
its related concepts before comparing to documents, (3) extracting
and using both words and phrases to compute relevance degree, (4)
improving the spread activation algorithm to do the expansion based
on weighted combination of different conceptual relationships and
(5) allowing variable document vector dimensions. A ranking
system called ORank is developed to implement and test the
proposed model. The test results will be included at the end of the
paper.
Abstract: Effects of bio-nitrogen fertilizer (bio-N), as a partial
alternative to mineral-nitrogen fertilizer (mineral-N), on growth,
yield and yield quality of broccoli plants were investigated. Bio-N
was applied at 1, 2 or 3 doses in combination with 65% of the
recommended dose of mineral-N (bio-N1, bio-N2 or bio-N3 +
⅔mineral-N). However, 100% of the recommended dose of mineral-
N was applied as a control. Significant positive influences of the bio-
N3 + ⅔mineral-N treatment were observed on growth traits, leaf
contents of nitrogen, phosphorus, potassium, nitrate and nitrite, and
yield quality when compared to the other two combined treatments.
In contrast, there were no significant differences in these parameters
between the bio-N3 + ⅔mineral-N and the control treatments, except
for leaf contents of nitrate and nitrite. They showed lower contents in
the bio-N3 + ⅔mineral-N treatment than the control. Therefore, we
recommend using bio-N as a partial alternative to mineral-N for
healthy nutrition.
Abstract: The process of wafer fabrication is arguably the most
technologically complex and capital intensive stage in semiconductor
manufacturing. This large-scale discrete-event process is highly reentrant,
and involves hundreds of machines, restrictions, and
processing steps. Therefore, production control of wafer fabrication
facilities (fab), specifically scheduling, is one of the most challenging
problems that this industry faces. Dispatching rules have been
extensively applied to the scheduling problems in semiconductor
manufacturing. Moreover, lot release policies are commonly used in
this manufacturing setting to further improve the performance of such
systems and reduce its inherent variability. In this work, simulation is
used in the scheduling of re-entrant flow shop manufacturing systems
with an application in semiconductor wafer fabrication; where, a
simulation model has been developed for the Intel Five-Machine Six
Step Mini-Fab using the ExtendTM simulation environment. The
Mini-Fab has been selected as it captures the challenges involved in
scheduling the highly re-entrant semiconductor manufacturing lines.
A number of scenarios have been developed and have been used to
evaluate the effect of different dispatching rules and lot release
policies on the selected performance measures. Results of simulation
showed that the performance of the Mini-Fab can be drastically
improved using a combination of dispatching rules and lot release
policy.
Abstract: In this paper we propose a new approach for flexible document categorization according to the document type or genre instead of topic. Our approach implements two homogenous classifiers: contextual classifier and logical classifier. The contextual classifier is based on the document URL, whereas, the logical classifier use the logical structure of the document to perform the categorization. The final categorization is obtained by combining contextual and logical categorizations. In our approach, each document is assigned to all predefined categories with different membership degrees. Our experiments demonstrate that our approach is best than other genre categorization approaches.
Abstract: Twenty seven tektites from the Wenchang area, Hainan
province (south China) and five tektites from the Khon Kaen area
(northeast Thailand) were analyzed for major and trace element
contents and Rb-Sr isotopic compositions. All the samples studied are
splash-form tektites. Tektites of this study are characterized by high
SiO2 contents ranging from 71.95 to 74.07 wt% which is consistent
with previously published analyses of Australasian tektites. The trace
element ratios Ba/Rb (avg. 3.89), Th/Sm (avg. 2.40), Sm/Sc (avg.
0.45), Th/Sc (avg. 0.99) and the rare earth elements (REE) contents of
tektites of this study are similar to the average upper continental crust.
Based on the chemical composition, it is suggested that tektites in this
study are derived from similar parental material and are similar to the
post-Archean upper crustal rocks. The major and trace element
abundances of tektites analyzed indicate that the parental material of
tektites may be a terrestrial sedimentary deposit. The tektites from the
Wenchang area, Hainan Island have high positive εSr(0)
values-ranging from 184.5~196.5 which indicate that the parental
material for these tektites have similar Sr isotopic compositions to old
terrestrial sedimentary rocks and they were not dominantly derived
from recent young sediments (such as soil or loess). Based on Rb-Sr
isotopic data, it has been suggested by Blum (1992) [1]that the
depositional age of sedimentary target materials is close to 170Ma
(Jurassic). According to the model suggested by Ho and Chen
(1996)[2], mixing calculations for various amounts and combinations
of target rocks have been carried out. We consider that the best fit for
tektites from the Wenchang area is a mixture of 47% shale, 23%
sandstone, 25% greywacke and 5% quartzite, and the other tektites
from Khon Kaen area is a mixture of 46% shale, 2% sandstone, 20%
greywacke and 32% quartzite.