• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.21 no.1
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• pp.1-11
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• 2018

The emergence of mucosal healing as a treatment goal that could modify the natural course of Crohn's disease and the accumulating evidence showing that biologics are most effective in achieving mucosal healing, along with the success of early treatment regimens for rheumatoid arthritis, have led to the identification of early Crohn's disease and development of the concept of catching the therapeutic window during the early disease course. Thus, an increasing number of pediatric gastroenterologists are adopting an early biologic treatment strategy with or without an immunomodulator. Although early biologic treatment is effective, cost and overtreatment are issues that limit its early use. Currently, there are insufficient data on who will benefit most from early biologics, as well as on who will not need early or even any biologics. For now, top-down biologics should be considered for patients with currently known high-risk factors of poor outcomes. For other patients, close, objective monitoring and accelerating the step-up process by means of a treat-to-target approach seems the best way to catch the therapeutic window in early pediatric Crohn's disease. The individual benefits of immunomodulator addition during early biologic treatment should be weighed against its risks and decision on early combination treatment should be made after comprehensive discussion with each patient and guardian.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.3
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• pp.230-237
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• 2012

This paper proposes an active-clamp ac-dc converter with direct power conversion that has a simple structure and achieves high efficiency. The proposed converter is derived by integrating the step-down ac chopper and the output-voltage doubler. The proposed converter provides direct ac-dc conversion and dc output voltage without using any full-bridge diode rectifier. The step-down ac chopper using an active-clamp mechanism serves to clamp the voltage spike across the main switches and provides zero-voltage turn-on switching. The resonant-current path formed by the leakage inductance of the transformer and the resonant capacitor of the output-voltage doubler achieves the zero-current turn-off switching of the output diodes. The operation principle of the converter is analyzed and verified. A 500W prototype is implemented to show the performance of the proposed converter. The prototype provides maximum efficiency of 95.1% at the full load.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.34-36
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• 2008

This paper is given a full detail of mathematical analyses of input current for novel active type power factor correction(PFC) AC-DC converter of step up-down added electric isolation. These are compared with harmonics components of input current for a conventional PFC converter of electric isolation type. The proposed PFC converter is constructed in using a new loss-less snubber circuit to achieve a soft switching of control device. Also the proposed converter for discontinuous conduction mode(DCM) eliminates the complicated circuit control requirement and reduces the size of components. The input current waveform in the proposed converter is got to be a sinusoidal form of discontinuous pulse in proportion to magnitude of ac input voltage under the constant duty cycle switching. Therefore, input power factor is nearly unity and the control method is simple. Particularly, the stored energy of loss-less snubber capacitor is recovered with input side and increases input current from resonant operation. The result is that input power factor of the proposed converter is higher than that of a conventional PFC converter. Some simulative results on computer and experimental results are included to confirm the validity of the analytical results.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.5
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• pp.463-467
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• 2003

This paper describes an AC voltage regulator using AC chopper and auxiliary transformer which is series connected with main input. It has many advantages such as fast voltage control, high efficiency and low THD. A detail study of step down AC voltage regulator is described and two kinds of novel step-up/down voltage regulator for AVR application are proposed. The operation principle and PWM method of the proposed regulator are described. Experimental results show that it can be used as AC voltage regulator for special purpose very efficiently.

• Journal of Service Research and Studies
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• v.8 no.1
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• pp.103-122
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• 2018

The purpose of this study is to present the direction of ELS investment by analyzing the actual investment return of the ELS commodities and analyzing the investment effect of ELS that investors have felt unsatisfactory at financial marketing service. The research method is based on the step-down type ELS. We calculated the probability of achieving early redemption condition and maturity repayment condition, early redemption estimated yield, and maturity repayment estimated yield. As the study result, the probability of achieving 100% of the early redemption condition was 74.5%, and the probability of the early redemption condition 95% was 83.0%, 90% was 89.5%, 85% was 92.5%, and 80% was 96.5% respectively. In the case of the lowest 75%, the probability of holding to maturity is analyzed to be 2.5%, and the probability of early redemption is high. The probability of the stock price growth within 65% of the maturity repayment condition was 98.5% and the probability of the stock price growth within 60%~45% of the maturity repayment condition was 100%. 65% of maturity repayment condition was analyzed as 1.5% risk of principal loss, and the probability of achieving the committed yield of maturity was high. As a key measure of ELS investment, it is advantageous to select a commodity with a low rate of maturity repayment and a high rate of early redemption.

• Speech Sciences
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• v.11 no.3
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• pp.37-54
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• 2004

The main goal of this study is to examine the current issue of the deletion of high tone vs. the downstep or upstep of high tone in North Kyungsang Korean (NKK). In this phonetic experiment, five native speakers of North Kyungsang Korean participated and two categories, such as compounds and two-word phrases were included as a test material. This experiment shows that when the first word belongs to the nonfinal class, the high tone of the second word is overwhelmingly deleted. When the first word belongs to the final class, the high tone of it is also overwhelmingly deleted. It is thus concluded that when two words are combined into a phrase, the peak of one word retains, whereas the peak of the other is deleted. It is confirmed that a single high tone prominence in a phonological phrase in NKK is not due to the processes of down step or upstep but the deletion process.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.951-954
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• 1998

This paper proposed that a high power AC-DC buck converter topology of high efficiency using loss-less snubber operates with four chopper connecting a number of parallel circuit. To improve these, a large number of soft switching topologies included a resonant circuit have been proposed. And, some simulative resutls on computer is included to confirm the validity of the analytical results. The partial resonant circuit makes use of a inductor using step-down and a condenser of loss-less snubber. The result is that the switching loss is very low and the efficiency of system is high. And the snubber condenser used in partial resonant circuit makes charging energy regenerated at input power source of rresonant operation. The proposed conversion system is deemed the most suitable for high power applications where the power switching devices are used.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.2
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• pp.305-310
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• 2012

Planetary gear box is a power transmitter having very high gear ratio in compact volume. The planetary step-down gear box converts high speed and low torque into low speed and high torque, which is widely used in constructional and industrial machinery field. And, the planetary step-up gear box does vice versa working, which is used as main gear box of large sized wind mill system. The large sized planetary gear box must be performed the normal-opposite rotation test as a its durability test for achieving the reliability. The large sized planetary gear box is composed by triple gear trains of sun gear, carrier, and ring gear. If input power is supplied into one of them and the other is fixed, and then another becomes the output part. In this paper, we designed a new test equipment which can do rapid normal and opposite rotational change with only small displacement by supplying test power using the above rotation (driving) characteristics and hydraulic cylinder and link, and also compared and analyzed with existing method through various experiments.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.5
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• pp.395-401
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• 2015

This paper proposes a new bidirectional DC-DC converter with high efficiency. The proposed converter is composed of a flyback and a tapped-inductor boost converter to satisfy extreme operating conditions with low cost. The outputs are connected in series to achieve a high-voltage step-up. In the reverse direction, the proposed converter has an extreme step-down voltage. In this study, the proposed converter was employed with a 100 W hardware prototype. To design the controller, a small-signal transfer function of the proposed converter is derived. For PV power conditioning systems, a maximum power point tracking method is applied with perturb and observe method. To verify the operation of the bidirectional power flow, the current controller is applied. All of the controllers are employed with a digital signal processor.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.90-96
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• 2009

In this study, a generic airfoil designed by the inverse method was evaluated with several candidate airfoils as a first step. Each airfoil was compared with respect to aerodynamic performance to meet the requirement of HALE(high altitude long endurance) aircraft. The second step was to optimize the candidate airfoil using the couple of optimization formulations to down select an optimum airfoil. For the analysis of low Reynolds number 2D flow, Drela's MSES was used. After comparing the aerodynamic results, the best airfoil was chosen to construct the baseline 3D wing. The Navier-Stokes code was used to evaluate the overall aerodynamic performance of designed wing with other wings. The results show that the designed wing has the best performance compared with other wings.