• Journal of Power Electronics
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• v.14 no.1
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• pp.48-60
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• 2014

Multilevel inverters have been widely used for high-voltage and high-power applications. Their performance is greatly superior to that of conventional two-level inverters due to their reduced total harmonic distortion (THD), lower switch ratings, lower electromagnetic interference, and higher dc link voltages. However, they have some disadvantages such as an increased number of components, a complex pulse width modulation control method, and a voltage-balancing problem. In this paper, a novel nine-level reduced switch cascaded multilevel inverter based on a multilevel DC link (MLDCL) inverter topology with reduced switching components is proposed to improve the multilevel inverter performance by compensating the above mentioned disadvantages. This topology requires fewer components when compared to diode clamped, flying capacitor and cascaded inverters and it requires fewer carrier signals and gate drives. Therefore, the overall cost and circuit complexity are greatly reduced. This paper presents modulation methods by a novel reference and multicarrier based PWM schemes for reduced switch cascaded multilevel inverters (RSCMLI). It also compares the performance of the proposed scheme with that of conventional cascaded multilevel inverters (CCMLI). Simulation results from MATLAB/SIMULINK are presented to verify the performance of the nine-level RSCMLI. Finally, a prototype of the nine-level RSCMLI topology is built and tested to show the performance of the inverter through experimental results.

• Asia pacific journal of information systems
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• v.22 no.1
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• pp.1-27
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• 2012

Asynchronous Learning Networks (ALN) has become a kind of prevalent information systems to supplement or even substitute a traditional classroom face-to-face teaching method. In this paper, we investigate the impacts of types of courses, lecturers' instruction models and computer self-efficacy on the ALN effectiveness in teaching from lecturers' perspective. We conducted survey to professors in various faculties such as School of Computing, Faculty of Arts, Science, Business, Law and Engineering in the National University of Singapore. According to the responses from ninety-eight professors, instruction modes positively influence the usage of ALN; types of course and lecturers' computer-efficacy influence lectures' satisfaction of ALN in teaching. Both the usage of ALN and satisfaction of ALN positively influence the effectiveness of ALN. The results of this study fill the gap of ALN researches in education by examining it from lecturers' perspective and enable schools to improve their implementation of ALN systems based on our findings.

• Journal of Ceramic Processing Research
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• v.13 no.spc2
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• pp.270-273
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• 2012

x mol% (x = 0 ~ 20) Na2CO3 excess Bi2.5Na3.5Nb5O18 (BNN) particles were synthesized using molten salt as a flux. The secondary phases were observed at stoichiometric ratio of BNN precursors and their intensity decreased with increasing Na contents. The results of SEM images showed that all particles existed in a platelet shape and the particle increased in size with higher increasing Na contents. Plate-like NaNbO3 particles were developed using BNN precursor obtained by a topochemical microcrystal conversion. XRD analysis of NaNbO3 particles showed that a single perovskite phase and the intensity of (h00) peaks increased with increasing Na contents in BNN precursor. SEM images showed that the size of plate-like NaNbO3 was significantly changed by controlling Na contents in BNN precursors.

• Elastomers and Composites
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• v.37 no.4
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• pp.234-243
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• 2002

A general scheme of a rubber structure is proposed. Using the thermomechanical method(TMA), some changes in the molecular and topological structures for uncured and cured, and unfilled and filled rubbers during processing are shown. In our investigations as region it is understood a complex structure, which is expressed at the thermomechanical curve(TMC) as a zone differed from others in thermal expansion properties. This zone is between the noticed temperatures of relaxation transitions, usually on the level like those determined by DMTA at 1Hz. These regions, which shares, are not stable, and differ in molecular-weight distribution(MWD) of chain fragments between the junctions. Differences in dynamics of the formation of the molecular and topological structures of a vulcanizate are dependent on the rubber formulation, mixing technology and curing time. Some of characteristics of these regions correlate with mechanical properties of vulcanizates what is shown for NR rubbers containing ENR or CPE as a polymeric additive. It is well known that the state of order influences diffusivity of low-molecular substances into the polymer matrix. Because of this, the two topological amorphous regions should influence the distribution of the ingredients and resulting in rubber compounds' heterogeneity, and related properties of cured rubber. Investigation of this problem is expected to be, in the future, one of the essential factors in determining further improvement of polymeric materials properties by compounding with additives and in reprocessing of rubber scrap.

• Korean Journal of Veterinary Research
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• v.47 no.4
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• pp.399-407
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• 2007

Cause of high lethality and dissemination to human being, new development of rapid method for the detection of highly pathogenic Avian Influenza Virus (AIV) is still necessary. For the detection of AIV subtype H5N1, typical pathogenic AIV, new method to confirm sub-typing of this virus is also needed. For the purpose of ultra-rapid detection and sub-typing of hemagglutinin and neuraminidase of AIV, this study was planned. As the results we could demonstrate an ultra-rapid multiplex real-time PCR (URMRT PCR) for the detection of AIV In this study, the URMRT PCR were optimized with synthesized AIV H5- and AIV Nl-specific DNA templates and GenSpector TMC, which is a semiconductor process technology based real-time PCR system with high frequencies of temperature monitoring. Under eight minutes, the amplifications of two AIV subtype-specific PCR products were successfully and independently detected by 30 cycled ultra-rapid PCR, including melting point analysis, from $1{\times}10^3$ copies of mixed template DNA. The URMRT PCR for the detection of AIV H5N 1 developed in this study could be expected to apply not only detections of different AIVs, but also various pathogens. It was also discussed that this kind of the fastest PCR based detection method could be improved by advance of related technology in near future.

• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.2
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• pp.207-218
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• 2017

Improving fuel consumption, particularly that of commercial vehicles, has become a global concern. The reduction in logistics cost has been a key issue in efforts to improve fuel economy and efficiency of transportation equipment. Typical technologies for reducing reduce fuel usage include air resistance reduction technologies, tire rolling resistance technologies, and idle technologies among others. Air resistance technology is a highly effective method that can be easily applied in a short period. As with air resistance technology, several devices involving side skirt, boat tail and gap fairing have been developed based on an analytical 3-D modeling technique for reducing air resistance attributed to the vehicle configuration. The devices were on a 45 feet tractor-trailer and the emission test was done using PEMS equipment. Fuel economy was evaluated by introducing several devices to reduce outer air resistance. The test was conducted by changing the experimental method of SAE J1321 Joint TMC/SAE Fuel Consumption Test Procedure - Type II test. As a result, air resistance decreased by at least 15 % and fuel economy improved by at least 13 %. This study sought to reduce greenhouse gas and improve fuel economy by applying several devices to a test vehicle to lower air resistance.

• Korean Journal of Food Science and Technology
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• v.3 no.3
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• pp.144-149
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• 1971

The sensitive technique of activation analysis is well suited for this study since the elements such as As, Br, and Se in tobaccoes are expected to be high concentration. As, Br, and Hg were determined by Bethge destruction method and subsequent neutron activation analysis. $^{77m}Se$ was also by non-destruction activation analysis. The quantities of the element determined in Korean tobaccoes are given as follows in ppm: As, 0.65 ppm. Hg, 0.74 ppm. Se, 1.18 ppm. Br, 7.1 ppm. From the date given it seems that Korean tobaccoes and foreign tobaccoes contained considerably high concentration of selenium and mercury.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.127-132
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• 2019

In this study, barium strontium titanate (BSTO) with high dielectric perovskite structure was synthesized by liquid-solid solution synthesis and the surface was modified using trimethylsilyl chloride (TMCS) as a silylation agent. Silylation surface modification is a method of reacting -OH ligand on the surface of BSTO nanoparticles with Cl in TMCS to generate HCl and replacing the ligand on the surface of nanoparticles with -Si, -CH₃. Silylation was optimized by varying the concentration of TMCS, and the structure of the silicon network was confirmed by Fourier-transform infrared spectroscopy. In addition, the crystallinity of BSTO nanoparticles was confirmed by X-ray diffractometer and the size of the nanoparticles was calculated using Scherrer equation. The field emission scanning electron microscopic image observed the change of the surface-modified BSTO particle size, and the contact angle measurement confirmed the hydrophobic property of the contact angle of 120.9° in the optimized nanoparticles. Finally, the surface-modified BSTO dispersion experiment in de-ionized water confirmed the hydrophobic degree of the nanoparticles.