Abstract: The newest semiconductor devices on the market are MOSFET transistors based on the silicon carbide – SiC. This material has exclusive features thanks to which it becomes a better switch than Si – silicon semiconductor switch. There are some special features that need to be understood to enable the device’s use to its full potential. The advantages and differences of SiC MOSFETs in comparison with Si IGBT transistors have been described in first part of this article. Second part describes driver for SiC MOSFET transistor and last part of article represents SiC MOSFET in the application of buck converter (step-down) and design of simple RC snubber.
Abstract: In recent years, a reconstruction project for sewer
pipelines has been progressing in Japan with the aim of renewing old
sewer culverts. However, it is difficult to secure a sufficient base area
for shafts in an urban area because many streets are narrow with a
complex layout. As a result, construction in such urban areas is
generally very demanding.
In urban areas, there is a strong requirement for a safe, reliable and
economical construction method that does not disturb the public’s
daily life and urban activities. With this in mind, we developed a new
construction method called the “shield switching type micro-tunneling
method,” which integrates the micro-tunneling method and shield
method.
In this method, pipeline is constructed first for sections that are
gently curved or straight using the economical micro-tunneling
method, and then the method is switched to the shield method for
sections with a sharp curve or a series of curves without establishing
an intermediate shaft.
This paper provides the information, features and construction
examples of this newly developed method.
Abstract: A design problem of non-uniform circular antenna arrays for maximum reduction of both the side lobe level (SLL) and first null beam width (FNBW) is dealt with. This problem is modeled as a simple optimization problem. The method of Firefly algorithm (FFA) is used to determine an optimal set of current excitation weights and antenna inter-element separations that provide radiation pattern with maximum SLL reduction and much improvement on FNBW as well. Circular array antenna laid on x-y plane is assumed. FFA is applied on circular arrays of 8-, 10-, and 12- elements. Various simulation results are presented and hence performances of side lobe and FNBW are analyzed. Experimental results show considerable reductions of both the SLL and FNBW with respect to those of the uniform case and some standard algorithms GA, PSO and SA applied to the same problem.
Abstract: This paper describes optimal thinning of an Elliptical
Cylindrical Array (ECA) of uniformly excited isotropic antennas
which can generate directive beam with minimum relative Side Lobe
Level (SLL). The Particle Swarm Optimization (PSO) method, which
represents a new approach for optimization problems in
electromagnetic, is used in the optimization process. The PSO is used
to determine the optimal set of ‘ON-OFF’ elements that provides a
radiation pattern with maximum SLL reduction. Optimization is done
without prefixing the value of First Null Beam Width (FNBW). The
variation of SLL with element spacing of thinned array is also
reported. Simulation results show that the number of array elements
can be reduced by more than 50% of the total number of elements in
the array with a simultaneous reduction in SLL to less than -27dB.
Abstract: Bone hydatidosis is an infection in worldwide distribution. Although there is no evidence in literature on Bone Hydatid disease in Libya, we tried to present the first Epidemiological study of this disease in Eastern Libya through retrospective study from 1995 to 2013. Our data were collected from 3 hospitals in Eastern Libya particularly the sheep-raising areas with total number of musculoskeletal infection cases of two thousand one hundred ninety four (2,194). There were five (5) five cases of bone infection, four (4) of it have been diagnosed after more than three (3) months. Our study is comparable to other international study but this type of bone infection need further studies for effective control strategies for all dogs to avoid serious complications that might happened from the delay in diagnosing this type of disease.
Abstract: Recently, the interest of globalization in the field of
teacher education has increased. In the U.S., the government is trying
to enhance the quality of education through a global approach in
education. To do so, the schools in the U.S. are recruiting teachers with
global capability from countries like Korea where competent teachers
are being trained. Meanwhile, in the case of Korea, although excellent
teachers have been cultivated every year, due to a low birth rate it is
not easy to become a domestic teacher. To solve the trouble that the
two countries are facing, the study first examines the demand and
necessity of globalization in the field of teacher education between
Korea and the U.S. Second, we propose a new project, called the
‘Global Teachers University (GTU)’ program to satisfy the demands
of both countries. Finally, we provide its implications to build the
future educational cooperation for teacher training in a global context.
Abstract: Reconfigurable antennas represent a recent innovation in antenna design that changes from classical fixed-form, fixed function antennas to modifiable structures that can be adapted to fit the requirements of a time varying system.
The ability to control the operating band of an antenna system can have many useful applications. Systems that operate in an acquire-and-track configuration would see a benefit from active bandwidth control. In such systems a wide band search mode is first employed to find a desired signal then a narrow band track mode is used to follow only that signal. Utilizing active antenna bandwidth control, a single antenna would function for both the wide band and narrow band configurations providing the rejection of unwanted signals with the antenna hardware. This ability to move a portion of the RF filtering out of the receiver and onto the antenna itself will also aid in reducing the complexity of the often expensive RF processing subsystems.
Abstract: Bone Anchored Hearing Implants (BAHI) are
routinely used in patients with conductive or mixed hearing loss, e.g.
if conventional air conduction hearing aids cannot be used. New
sound processors and new fitting software now allow the adjustment
of parameters such as loudness compression ratios or maximum
power output separately. Today it is unclear, how the choice of these
parameters influences aided speech understanding in BAHI users.
In this prospective experimental study, the effect of varying the
compression ratio and lowering the maximum power output in a
BAHI were investigated.
Twelve experienced adult subjects with a mixed hearing loss
participated in this study. Four different compression ratios (1.0; 1.3;
1.6; 2.0) were tested along with two different maximum power output
settings, resulting in a total of eight different programs. Each
participant tested each program during two weeks. A blinded Latin
square design was used to minimize bias.
For each of the eight programs, speech understanding in quiet and
in noise was assessed. For speech in quiet, the Freiburg number test
and the Freiburg monosyllabic word test at 50, 65, and 80 dB SPL
were used. For speech in noise, the Oldenburg sentence test was
administered.
Speech understanding in quiet and in noise was improved
significantly in the aided condition in any program, when compared
to the unaided condition. However, no significant differences were
found between any of the eight programs. In contrast, on a subjective
level there was a significant preference for medium compression
ratios of 1.3 to 1.6 and higher maximum power output.
Abstract: In this research, the TRACE/PARCS model of
Lungmen ABWR has been developed for verification of ultimate
response guideline (URG) efficiency. This ultimate measure was
named as DIVing plan, abbreviated from system depressurization,
water injection and containment venting. The simulation initial
condition is 100% rated power/100% rated core flow. This research
focuses on the estimation of the time when the fuel might be damaged
with no water injection by using TRACE/PARCS first. Then, the
effect of the reactor core isolation system (RCIC), control
depressurization and ac-independent water addition system (ACIWA),
which can provide the injection with 950 gpm are also estimated for
the station blackout (SBO) transient.
Abstract: We consider nonlinear uncertain systems such that a
priori information of the uncertainties is not available. For such
systems, we assume that the upper bound of the uncertainties is
represented as a Fredholm integral equation of the first kind and we
propose an adaptation law that is capable of estimating the upper
bound and design a continuous robust control which renders nonlinear
uncertain systems ultimately bounded.
Abstract: This study is conducted to investigate the disparity of between learning styles and cognitive abilities specifically in Vocational Education. Felder and Silverman Learning Styles Model (FSLSM) was applied to measure the students’ learning styles while the content in Building Construction Subject consists; knowledge, skills and problem solving were taken into account in constructing the elements of cognitive abilities. Building Construction is one of the vocational courses offered in Vocational Education structure. There are four dimension of learning styles proposed by Felder and Silverman intended to capture student learning preferences with regards to processing either active or reflective, perception based on sensing or intuitive, input of information used visual or verbal and understanding information represent with sequential or global learner. Felder-Solomon Learning Styles Index was developed based on FSLSM and the questions were used to identify what type of student learning preferences. The index consists 44 item-questions characterize for learning styles dimension in FSLSM. The achievement test was developed to determine the students’ cognitive abilities. The quantitative data was analyzed in descriptive and inferential statistic involving Multivariate Analysis of Variance (MANOVA). The study discovered students are tending to be visual learners and each type of learner having significant difference whereas cognitive abilities there are different finding for each type of learners in knowledge, skills and problem solving. This study concludes the gap between type of learner and the cognitive abilities in few illustrations and it explained how the connecting made. The finding may help teachers to facilitate students more effectively and to boost the student’s cognitive abilities.
Abstract: Progressive collapse of buildings typically occurs
when abnormal loading conditions cause local damages, which leads
to a chain reaction of failure and ultimately catastrophic collapse. The
tie force (TF) method is one of the main design approaches for
progressive collapse. As the TF method is a simplified method, further
investigations on the reliability of the method is necessary. This study
aims to develop an improved TF method to design the cross wall
structures for progressive collapse. To this end, the pullout behavior of
strands in grout was firstly analyzed; and then, by considering the tie
force-slip relationship in the friction stage together with the catenary
action mechanism, a comprehensive analytical method was developed.
The reliability of this approach is verified by the experimental results
of concrete block pullout tests and full scale floor-to-floor joints tests
undertaken by Portland Cement Association (PCA). Discrepancies in
the tie force between the analytical results and codified specifications
have suggested the deficiency of TF method, hence an improved
model based on the analytical results has been proposed to address this
concern.
Abstract: Stirred tanks are widely used in all industrial sectors. The need for further studies of the mixing operation and its different aspects comes from the diversity of agitation tools and implemented geometries in addition to the specific characteristics of each application. Viscous fluids are often encountered in industry and they represent the majority of treated cases, as in the polymer sector, food processing, pharmaceuticals and cosmetics. That's why in this paper, we will present a three-dimensional numerical study using the software Fluent, to study the effect of varying the fluid viscosity in a stirred tank with a Rushton turbine. This viscosity variation was performed by adding carboxymethylcellulose (CMC) to the fluid (water) in the vessel. In this work, we studied first the flow generated in the tank with a Rushton turbine. Second, we studied the effect of the fluid viscosity variation on the thermodynamic quantities defining the flow. For this, three viscosities (0.9% CMC, 1.1% CMC and 1.7% CMC) were considered.
Abstract: In neural networks, when new patters are learned by a network, they radically interfere with previously stored patterns. This
drawback is called catastrophic forgetting. We have already proposed a biologically inspired dual-network memory model which can much reduce this forgetting for static patterns. In this model, information is first stored in the hippocampal network, and thereafter, it is transferred to the neocortical network using pseudopatterns. Because temporal sequence learning is more important than static pattern learning in the real world, in this study, we improve our conventional dual-network memory model so that it can deal with temporal sequences without catastrophic forgetting. The computer simulation results show the effectiveness of the proposed dual-network memory model.
Abstract: Online shopping enables consumers to search for information and purchase products or services through direct interaction with online store. This study aims to examine the effect of Internet marketing environment, product characteristics, familiarity and confidence, and promotional offers on consumer online shopping behavior. 200 questionnaires were distributed to the respondents, who are students and staff at a public university in the Federal Territory of Labuan, Malaysia, following simple random sampling as a means of data collection. Multiple regression analysis was used as a statistical measure to determine the strength of the relationship between one dependent variable and a series of other independent variables. Results revealed that familiarity and confidence was found to greatly influence consumer online shopping behavior followed by promotional offers. A clear understanding of consumer online shopping behavior can help marketing managers predict the online shopping rate and evaluate the future growth of online commerce.
Abstract: Infectious bronchitis virus (IBV) is a very dynamic and evolving virus, causing major economic losses to the global poultry industry. Recently, the Libyan poultry industry faced severe outbreak of respiratory distress associated with high mortality and dramatic drop in egg production. Tracheal and cloacal swabs were analyzed for several poultry viruses. IBV was detected using SYBR Green I real-time PCR detection based on the nucleocapsid (N) gene. Sequence analysis of the partial N gene indicated high similarity (~ 94%) to IBV strain 3382/06 that was isolated from Taiwan. Even though the IBV strain 3382/06 is more similar to that of the Mass type H120, the isolate has been implicated associated with intertypic recombinant of 3 putative parental IBV strains namely H120, Taiwan strain 1171/92 and China strain CK/CH/LDL/97I. Complete sequencing and antigenicity studies of the Libya IBV strains are currently underway to determine the evolution of the virus and its importance in vaccine induced immunity. In this paper we documented for the first time the presence of possibly variant IBV strain from Libya which required dramatic change in vaccination program.
Abstract: This article investigates through experiments the flow characteristics of plane jets from sharp-edged orifice-plate, beveled-edge and radially contoured nozzle. The first two configurations exhibit saddle-backed velocity profiles while the third shows a top-hat. A vena contracta is found for the jet emanating from orifice at x/h » 3 while the contoured case displays a potential core extending to the range x/h = 5. A spurt in jet pressure on the centerline supports vena contracta for the orifice-jet. Momentum thicknesses and integral length scales elongate linearly with x although the growth of the shear-layer and large-scale eddies for the orifice are greater than the contoured case. The near-field spectrum exhibits higher frequency of the primary eddies that concur with enhanced turbulence intensity. Importantly, highly “turbulent” state of the orifice-jet prevails in the far-field where the spectra confirm more energetic secondary eddies associated with greater flapping amplitude of the orifice-jet.
Abstract: When using modern Code Division Multiple Access (CDMA) in mobile communications, the user must be able to vary the transmission rate of users to allocate bandwidth efficiently. In this work, Orthogonal Variable Spreading Factor (OVSF) codes are used with the same principles applied in a low-rate superorthogonal turbo code due to their variable-length properties. The introduced system is the Variable Rate Superorthogonal Turbo Code (VRSTC) where puncturing is not performed on the encoder’s final output but rather before selecting the output to achieve higher rates. Due to bandwidth expansion, the codes outperform an ordinary turbo code in the AWGN channel. Simulations results show decreased performance compared to those obtained with the employment of Walsh-Hadamard codes. However, with OVSF codes, the VRSTC system keeps the orthogonality of codewords whilst producing variable rate codes contrary to Walsh-Hadamard codes where puncturing is usually performed on the final output.
Abstract: The kinetics of Cu(II) transport through a bulk liquid membrane with different membrane materials was investigated in this work. Three types of membrane materials were used: fresh cooking oil, waste cooking oil and kerosene, each of which was mixed with di-2-ethylhexylphosphoric acid (carrier) and tributylphosphate (modifier). Kinetic models derived from the kinetic laws of two consecutive irreversible first-order reactions were used to study the facilitated transport of Cu(II) across the source, membrane and receiving phases of bulk liquid membrane. It was found that the transport kinetics of Cu(II) across the source phase was not affected by different types of membrane materials but decreased considerably when the membrane materials changed from kerosene, waste cooking oil to fresh cooking oil. The rate constants of Cu(II) removal and recovery processes through the bulk liquid membrane were also determined.
Abstract: The concept of myocardial injury, although first recognized from animal studies, is now recognized as a clinical phenomenon that may result in microvascular damage, no-reflow phenomenon, myocardial stunning, myocardial hibernation and ischemic preconditioning. The final consequence of this event is left ventricular (LV) systolic dysfunction leading to increased morbidity and mortality. The typical clinical case of reperfusion injury occurs in acute myocardial infarction (MI) with ST segment elevation in which an occlusion of a major epicardial coronary artery is followed by recanalization of the artery. This may occur spontaneously or by means of thrombolysis and/or by primary percutaneous coronary intervention (PCI) with efficient platelet inhibition by aspirin (acetylsalicylic acid), clopidogrel and glycoprotein IIb/IIIa inhibitors. In recent years, percutaneous coronary intervention (PCI) has become a well-established technique for the treatment of coronary artery disease. PCI improves symptoms in patients with coronary artery disease and it has been increasing safety of procedures. However, peri- and post-procedural myocardial injury, including angiographical slow coronary flow, microvascular embolization, and elevated levels of cardiac enzyme, such as creatine kinase and troponin-T and -I, has also been reported even in elective cases. Furthermore, myocardial reperfusion injury at the beginning of myocardial reperfusion, which causes tissue damage and cardiac dysfunction, may occur in cases of acute coronary syndrome. Because patients with myocardial injury is related to larger myocardial infarction and have a worse long-term prognosis than those without myocardial injury, it is important to prevent myocardial injury during and/or after PCI in patients with coronary artery disease. To date, many studies have demonstrated that adjunctive pharmacological treatment suppresses myocardial injury and increases coronary blood flow during PCI procedures. In this review, we highlight the usefulness of pharmacological treatment in combination with PCI in attenuating myocardial injury in patients with coronary artery disease.