• Pediatric Gastroenterology, Hepatology & Nutrition
• /
• 제21권1호
• /
• pp.1-11
• /
• 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.

• 전력전자학회논문지
• /
• 제17권3호
• /
• pp.230-237
• /
• 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.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2008년도 하계학술대회 논문집
• /
• pp.34-36
• /
• 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.

• 전력전자학회논문지
• /
• 제8권5호
• /
• pp.463-467
• /
• 2003

본 논문에서는 교류쵸퍼와 직렬보상변압기로 구성되는 교류전압제어장치에 대하여 연구한다. 먼저, 교류쵸퍼와 직렬보상변압기로 구성되는 기본적인 교류전압제어장치로 출력전압을 입력전압에서 10-20%정도 강압할 수 있는 형태의 강압형 교류전압 제어장치를 제안하고 기본동작원리 및 이의 안전한 운전을 위한 PWM 발생과 초기시퀀스로직을 제시하였다. 또한 이로부터 입력전압변동에 무관하게 일정 출력전압을 발생시키기 위한 자동전압제어장치(AVR: Automatic Voltage Regulator)로 사용가능한 두가지 형태의 직렬보상형 교류전압제어장치를 제안하고 동작원리를 기술하였다. 특히, 입력전압과 반대방향의 극성의 전압을 발생시킬 수 있는 새로운 형태의 양방향 교류쵸퍼를 제안하고, 이의 안전한 운전을 위한 PWM 발생을 위한 스위칭 패턴을 제시하였다. 제안된 교류전압제어회로의 경우 다양한 실험을 통하여 전력절감을 목적으로 하는 강압형 교류전압제어장치와 자동전압조절기의 용도로 효과적으로 적용될 수 있음을 확인하였다.

• 서비스연구
• /
• 제8권1호
• /
• pp.103-122
• /
• 2018

본 연구의 목적은 금융마케팅 서비스에서 투자자들이 미흡하게 느끼는 ELS 상품이 실제로 획득할 수 있는 수익률이 얼마나 되는지를 분석하여 ELS에 대한 투자효과를 규명함으로써 ELS 투자방향을 제시하는데 있다. 연구방법은 스텝다운형 ELS를 대상으로 2001년 1월부터 2017년 8월까지 200개월 동안 만기 3년의 조기상환조건 달성확률, 만기상환조건 달성확률, 조기상환추정수익률, 만기상환추정수익률을 산출하였다. 분석결과는 조기상환조건 100% 달성확률은 74.5%이었으며, 조기상환조건 95%는 달성확률이 83.0%, 90%는 89.5%, 85%는 92.5%, 80%는 96.5%, 75%는 97.5% 이었다. 가장 낮은 75% 경우에 만기까지 보유할 확률은 2.5%인 것으로 분석되어 조기상환조건이 달성될 확률이 높았다. 만기도래했을 때 주가상승률이 만기상환조건 65% 이내에 있을 확률은 98.5%이었으며, 만기상환조건 60%, 58%, 57%, 55%, 50%, 45%는 달성확률이 100% 이었다. 만기상환조건 65%는 원금손실 리스크가 1.5%정도 있는 것으로 분석되어서 만기에 약정된 수익률을 달성할 확률이 높았다. ELS 투자의 유의방안으로는 만기상환조건의 비율이 낮은 상품을 선택하고, 조기상환조건 비율이 높은 상품을 선택해야 하며, 주가지수가 박스권 형성이 예상 될 때 투자하는 것이 유리하다.

• 음성과학
• /
• 제11권3호
• /
• pp.37-54
• /
• 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.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 1998년도 하계종합학술대회논문집
• /
• pp.951-954
• /
• 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.

• 한국생산제조학회지
• /
• 제21권2호
• /
• pp.305-310
• /
• 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.

• 전력전자학회논문지
• /
• 제20권5호
• /
• pp.395-401
• /
• 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
• /
• 한국전산유체공학회 2009년 춘계학술대회논문집
• /
• pp.90-96
• /
• 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.