• Advances in Computational Design
• /
• 제8권3호
• /
• pp.237-253
• /
• 2023

Torque ripple content and variable switching frequency operation of conventional direct torque control (DTC) are reduced by the integration of space vector modulation (SVM) into DTC. Integration of space vector modulation to conventional direct torque control known as SVM-DTC. It had been more frequently used method in renewable energy and machine drive systems. In this paper, SVM-DTC is used to control the rotor side converter (RSC) of a wind driven doubly-fed induction generator (DFIG) because of its advantages such as reduction of torque ripples and constant switching frequency operation. However, flux and torque ripples are still dominant due to distorted current waveforms at different operations of the wind turbine. Therefore, to smoothen the torque profile a Neural Network Controller (NNC) based SVM-DTC has been proposed by replacing the PI controller in the speed control loop of the wind turbine controller. Also, stability analysis and simulation study of DFIG using process reaction curve method (RRCM) are presented. Validation of simulation study in MATLAB/SIMULINK environment of proposed wind driven DFIG system has been performed by laboratory developed prototype model. The proposed NNC based SVM-DTC yields superior torque response and ripple reduction compared to other methods.

• 한국작물학회지
• /
• 제45권5호
• /
• pp.335-338
• /
• 2000

The technology of direct-seeding in rice cultivation is an innovation mainly induced by factors in market economy and is rapidly diffused among individual farmhouses. Because the effect of technology can be affected by many factors under various farming circumstances, the impact and stability of the direct-seeding technology compared with transplanting was analyzed under various topographical regions. Yield in direct-seeding was higher in plains, although the farm size producing higher yield was quite different depending on the topographical regions. In the direct-seeding cultivation of rice, man-labor hours was reduced by about 38 percent and the reduction rate showed little difference among topographical regions. Fertilizer was used about 11 percent more but the increase rate varied from 3 to 17 percent depending on regions with higher rates in plains. Application of agricultural chemicals was also increased about 9 percent in direct-seeding, but the increase rate was as high as 12 percent in suburbs. More fertilizer and agricultural chemicals were used in direct-seeding cultivation by farmhouses implementing both direct-seeding and transplanting than by those implementing direct-seeding only. Use of more fertilizers and agricultural chemicals in direct-seeding in all regions may indicate its technical instability. Major problems causing the technical instability of direct-seeding cultivation should be solved by comprehensive research considering various farming circumstances such as topographical features rather than just a top-down style research and extension.

• 한국안전학회지
• /
• 제32권5호
• /
• pp.41-46
• /
• 2017

The coefficient of derailment and the rate of wheel load reduction were used as the index of train running safety that was directly affected the train derailment safety. In aspects of track, the train running safety depends on the complex interaction between wheel and rail, and the track-vehicle conditions (i.e., the curvature, cant, track system, vehicle speed and the operation conditions, etc). In this study, the relationship between the train running safety and the track curvature and vehicle speed for direct fixation concrete tracks currently employed in Korean light rapid transit was assessed by performing field tests using actual vehicles running along the service lines. The measured dynamic wheel load, lateral wheel load and lateral displacement of rail head were measured for same train running on four tested tracks under real conditions, which included curved and tangent tracks placed on the tunnel and bridge, thus increasing the train speed by approximately maximum design speed of each test site. Therefore, the measured dynamic track response was applied to the running safety analysis in order to evaluate the coefficient of derailment, the rate of wheel load reduction and the track gauge widening at each test site, and compare with the corresponding Korean train running safety standard. As the results, the lateral track response of direct fixation concrete track appeared to increase with the decreased track curvature; therefore, it was inferred that the track curvature directly affected the train running safety.

• 한국전자통신학회논문지
• /
• 제9권11호
• /
• pp.1233-1240
• /
• 2014

1980년 Toffoli 가역게이트 출현 이후 지난 30년 간 적당한 함수 상에 가역 임베딩을 하는 많은 가역회로 합성법들이 발표되어 오는 동안 소수의 논문만이 가역 임베딩 없이 직접적인 비가역-가역 회로 매핑 방법을 채택해 왔다. 본 논문에서는 가역 임베딩 없는 직접적 가역 매핑에 대한 효과적인 게이트비용 절감 정책을 개발하였다. 새로운 비용절감 정책을 개발하기 위해 고전회로에서 NOT 게이트 배치에 따른 Toffoli 모듈 비용의 영향을 고찰하고, 이것을 기초로 하여 고전적 AND(OR)게이트에 대한 반전입력 추가가 가역 Toffoli 모듈의 비용을 증가(감소)시킨다-라는 고전 게이트 반전입력 수와 가역 Toffoli 모듈 비용 사이의 반비례적 성질을 이끌어내었다. 직접적 가역 매핑에 선행한 반전입력 재배치 정책은 현존하는 팬-아웃 및 슈퍼셀 정책들과 병행할 경우에 가역 Toffoli 모듈의 비용과 복잡성을 개선할 수 있는 효과적인 방법이다.

• 전력전자학회논문지
• /
• 제5권6호
• /
• pp.620-631
• /
• 2000

본 논문에서는 인버터의 스위칭 주파수가 0.5-1kHz로 제한되는 3레벨 인버터로 구동되는 고전압 대용량 유도 전동기 직접토크제어의 토크리플 저감법을 제안한다. 기존의 토크리플 저감법은 인버터 스위칭 주파수가 비교적 높은 2-3kHz에서 동작하는 알고리즘으로 1kHz이하의 낮은 인버터 스위칭 주파수의 시스템에 적용하면 만족할만한 토크 라플 저감 성능블 얻을 수 없다. 새로운 직접토크제어 기법은 특히 낮은 스위칭 주파수를 갖는 시스템에 적용하기 위한 것이며, 모든 동작 속도 구간에서 토크리플 저감 성능을 나티낸다. 시뮬레이션과 실험을 통해 세안한 알고리즘의 타당성을 입증한다.

• Journal of Oral Medicine and Pain
• /
• 제23권3호
• /
• pp.281-288
• /
• 1998

The authors treated a 30-years old female patient who visited the Department of Oral Medicine, PNUH due to the chief complaint of limitation of mouth opening. The magnetic resonance imaging following clinical examination was used for establishing an accurate and reliable diagnosis and the patient was diagnosed as having anterior disc displacement without reduction in the right joint and anterior disc displacement with reduction in the left joint. For managing acute anterior disc displacement without reduction, mandible manipulation was applied first focusing on pain control and then stabilization appliance was used for maintenance of joint stabilization. With time, the sign and symptom was remarkably reduced and an active exercise program was recommended to maintain of normal muscle length, increase joint range of motion and develop normal coordination arthrokinematics. As a result of treatment, the patient did not complain discomfort of normal daily activities and it was difficult to consider that the displace disc was not reduced completely, but the improvement in range of motion and joint mobility were remarkably found. Therefore, an exercise program should be considered to maintain joint mobility and be effective as a self-care.

• 현장농수산연구지
• /
• 제3권1호
• /
• pp.30-47
• /
• 2001

This research was performed to develope a stable direct seeding method in rice cultivation using by a direct seeder with soil application. A principle of this methodology was introduced from seeding nursery system of machine transplanting enable to increase high seeding establishment direct seeding method with soil application was high of 89-95% while that of water seeding was 68%. During seeding growth plant height was ralatively small but seeding health was high. A total soil consumption of this methodology was 145kg/10a in dirll seeding and 26kg/10a in hill seeding respectively, there was 100% erected in direct seeding with soil application while water seeding was 45% in erected seeding stand. In direct seeding method with soil application total carbohydrate content was higher than that of water seeding. This machine was manufactured to attach and/or detach to a machine transplanter with riding type and machine cultivator with multipurpose. In the farmer's demonstrated rice field this method was well performed like machine transplanting in terms of rice growth and development. There was highly cost reduction for rice production like other direct seeding methods.

• 한국유변학회:학술대회논문집
• /
• 한국유변학회 2000년도 춘계 학술발표회 논문집
• /
• pp.15-18
• /
• 2000

• 대한수학회보
• /
• 제45권3호
• /
• pp.485-494
• /
• 2008

There are two well known reduction formulae for structural constants of the cohomology ring of Grassmannians, i.e., Littlewood-Richardson coefficients. Two reduction formulae are a conjugate pair in the sense that indexing partitions of one formula are conjugate to those of the other formula. A nice bijective proof of the first reduction formula is given in the authors' previous paper while a (combinatorial) proof for the second reduction formula in the paper depends on the identity between Littlewood-Richardson coefficients of conjugate shape. In this article, a direct bijective proof for the second reduction formula for Littlewood-Richardson coefficients is given. Our proof is independent of any previously known results (or bijections) on tableaux theory and supplements the arguments on bijective proofs of reduction formulae in the authors' previous paper.

• 한국방사성폐기물학회:학술대회논문집
• /
• 한국방사성폐기물학회 2005년도 Proceedings of The 6th korea-china joint workshop on nuclear waste management
• /
• pp.86-91
• /
• 2005

A metal product obtained from an electrolytic reduction process, possesses less volume and radioactivity than those of the unprocessed spent oxide fuels. The chemical composition of the metal product varies according to the process condition. In this work, a basic study was performed to evaluate the chemical forms of the spent oxide fuel components in an electrolytic reduction process with the operation conditions. One of the most important operation conditions is the cell potential applied for the reduction cell. It is expected that $PU_{2}O_3$ is difficult to reduce even though the cell potential is negative enough to reduce the lithium oxide when the activity of $Li_{2}O$ exceeds 0.003. The reduction of actinide oxides via the reduction of $Li_{2}O$ is assumed to have a greater reduction yield than a direct reduction of the actinide oxides.