• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.169-172
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• 2006

This paper presents the single-stage High Power Factor AC/DC Two-Switch Forward Converter (TSFC). Recently, due to growing concern about the harmonic pollution of power distribution systems and the adoption of standards such as ICE 61000-3-2 and IEEE 519, There is a need to reduce the harmonic contents of AC line currents of power supplies. This research proposed the single-stage two switch forward circuit for low voltage and high current output. The principle of operation, feature and design considerations are illustrated and verified through the simulation with a 200W(5V, 40A) 200kHz MOSFET based experimental circuit.

• 한국정밀공학회지
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• 제17권3호
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• pp.158-164
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• 2000

In recent year, desire and request fer micro automation are growing rapidly covering the whole range of the industry. This has been caused mainly by request of more accurate manufacturing process due to a higher density of integrated circuits in semiconductor industry. This paper presents a six d.o.f fine motion stage using magnetic levitation technique, which is one of actuating techniques that have the potential for achieving such a micro motion. There is no limit in motion resolution theoretically that the magnetically levitated part over a fixed stator can realize. In addition, it Is possible to manipulate the position and the force of the moving part at the same time. Then, the magnetic levitation technique is chosen into the actuating method. However, we discuss issues of design, kinematics, dynamics, and control of the proposed system. And a few experimental results fur step input are given.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 봄 학술발표회 논문집
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• pp.233-240
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• 2001

Artificial neural networks(ANN) have been exploited where the relationship among information is very complicated and nonlinear. It is appropriate to computerize the information and knowledge used in the preliminary design stage where it lacks of formality of representation of designers' experience and intuition. However, most designers start the preliminary design stage with very little information. Therefore, the ANN model for this stage must be designed to have input much less than output. This case usually causes big troubles such as in learning time, convergence and reliability of solutions. To address this problem, this paper proposes multi-level neural networks for progressive structural design considering that all the design information can not be obtained at a time but are growing gradually. The use of multi-level networks developed in this paper has been proved its validity by applying it to the preliminary design of cable-stayed bridges.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.226-228
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• 2005

This paper presents the single-stage High Power Factor TTFC(Two-Transistor Forward Converter). Recently, due to growing concern about the harmonic pollution of power distribution systems and the adoption of standards such as ICE 61000-3-2 and IEEE 519, There is a need to reduce the harmonic contests of AC line currents of power supplies. This research proposed the single-stage two switch forward circuit for low voltage and high current output.

• Journal of Biosystems Engineering
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• 제41권3호
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• pp.263-272
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• 2016

Purpose: Pulse crop damage due to wild birds is a serious problem, to the extent that the rate of damage during the period of time between seeding and the stage of cotyledon reaches 45.4% on average. This study investigated a method of fundamentally blocking birds from eating crops by conducting vinyl mulching after seeding and identifying the growing locations for beans to perform punching. Methods: Infrared (IR) sensors that could measure the temperature without contact were used to recognize the locations of soybean cotyledons below vinyl mulch. To expand the measurable range, 10 IR sensors were arranged in a linear array. A sliding mechanical device was used to reconstruct the two-dimensional spatial variance information of targets. Spatial interpolation was applied to the two-dimensional temperature distribution information measured in real time to improve the resolution of the bean coleoptile locations. The temperature distributions above the vinyl mulch for five species of soybeans over a period of six days from the appearance of the cotyledon stage were analyzed. Results: During the experimental period, cases where bean cotyledons did and did not come into contact with the bottom of the vinyl mulch were both observed, and depended on the degree of growth of the bean cotyledons. Although the locations of bean cotyledons could be estimated through temperature distribution analyses in cases where they came into contact with the bottom of the vinyl mulch, this estimation showed somewhat large errors according to the time that had passed after the cotyledon stage. The detection results were similar for similar types of crops. Thus, this method could be applied to crops with similar growth patterns. According to the results of 360 experiments that were conducted (five species of bean ${\times}$ six days ${\times}$ four speed levels ${\times}$ three repetitions), the location detection performance had an accuracy of 36.9%, and the range of location errors was 0-4.9 cm (RMSE = 3.1 cm). During a period of 3-5 days after the cotyledon stage, the location detection performance had an accuracy of 59% (RMSE = 3.9 cm). Conclusions: In the present study, to fundamentally solve the problem of damage to beans from birds in the early stage after seeding, a working method was proposed in which punching is carried out after seeding, thereby breaking away from the existing method in which seeding is carried out after punching. Methods for the accurate detection of soybean growing locations were studied to allow punching to promote the continuous growth of soybeans that had reached the cotyledon stage. Through experiments using multiple IR sensors and a sliding mechanical device, it was found that the locations of the crop could be partially identified 3-5 days after reaching the cotyledon stage regardless of the kind of pulse crop. It can be concluded that additional studies of robust detection methods considering environmental factors and factors for crop growth are necessary.

• Fisheries and Aquatic Sciences
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• 제6권2호
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• pp.51-58
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• 2003

The gonadal development and the gametogenic cycle and the fine structure of ripe germ cells of the cultured Pacific oyster, Crassostrea gigas were investigated using oysters monthly collected from the southern coast of Korea from October 2000 to September 2001. Monthly changes in the condition index were similar to that of meat weight rate and the highest value was observed in between April and May, and the lowest value in August. The external colors of the testis and the ovary were milky white and yellowish, respectively. The spawning period of the Pacific oyster was continued from May to September, with a peak in July. The gametogenic cycle could be classified into five successive stages: multiplicative stage (December to March), growing stage (March and April), mature stage (April to June), spawning stage (June to August) and resting stage (August to January). Variety of egg yolk granules, lipid granules, mitochondria, and endoplasmic reticula were observed in cytoplasm of ripe oocyte. The spermatozoon consisted of the head, middle piece and tail; including cap-shaped acrosome with domed structure, elliptical shaped nucleus, four mitochondria, two centrioles and flagellum.

• 스마트미디어저널
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• 제11권2호
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• pp.53-62
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• 2022

산업화 이후 가속화된 지구 온난화 현상으로 인해 기존환경 변화 및 이상기후 발생 빈도가 증가하고 있다. 농업은 기후변화에 매우 민감한 분야의 산업으로 지구 온난화는 작물의 생산량을 감소시키고 재배 지역이 변하는 등의 문제를 발생시킨다. 또한, 환경 변화는 작물의 생육 시기를 불규칙하게 만들어 숙련된 농사꾼들도 작물의 생육단계를 쉽게 추정할 수 없도록 만들어 여러 문제를 발생시킨다. 이에 본 논문에서는 작물의 생육단계를 추정하기 위한 CNN(Convolution Neural Network) 모델을 제안한다. 제안한 모델은 ResNet의 Pooling Layer를 수정한 모델로 ResNet, DenseNet 모델의 생육단계 추정보다 높은 성능 결과를 확인하였다.

• 벤처창업연구
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• 제9권3호
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• pp.75-88
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• 2014

본 연구는 벤처기업이 겪는 성장통이 경영성과에 미치는 영향과 성장통이 발생하는 요인을 분석하여 벤처기업에 정책적 시사점을 제시하는데 그 목적이 있다. 연평균복합성장률을 사용하여 추출한 경영성과와 성장통을 상관관계분석한 결과 통계적으로 유의적인 부(-)의 관계가 있었다. 성장통에 영향을 미치는 요인을 분석하기 위해 회귀분석을 실시한 7개의 변수 중 CEO의 업무능력과 리더십, 조직 구조적 역량, 조직 문화적 역량은 성장통과 유의미한 관계가 있으나 분석요인 중 CEO의 업무능력은 성장통을 악화시키는 것으로 나타나, 기업이 일정한 성장기에 들어서는 경우 CEO의 개인적 역량에 의존하기보다 관리시스템을 구축하는 것이 필요한 것으로 분석되었다. 또한 기업의 관리역량과 관련된 CEO의 강한 리더십 발휘와 조직구조의 적정한 편제 및 고객 지향적이고 책임감 있는 기업문화의 조성은 성장통을 감소시키는 요인으로 조사되었다.

• 한국산림과학회지
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• 제106권1호
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• pp.40-53
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• 2017

본 연구에서는 느티나무, 물푸레나무 및 졸참나무를 대상으로 시설양묘 과정에서 요구되는 적정 용기의 생육밀도 및 용적을 구명하고자, 16 종류의 용기[4 생육밀도(100, 144, 196, 256본/$m^2$)${\times}4$ 용적(460, 380, 300, 220 $cm^3$/구)]에서 생산된 용기묘의 생리 특성을 조사 분석하였다. 생육밀도 및 용적에 따른 용기묘의 광합성 특성, 광화학 효율 및 엽록소 함량변화를 알아보기 위해 이원분산분석과 다중회귀분석을 이용하였다. 세 수종 모두 용기의 생육밀도와 용적은 묘목의 광합성 기구에 영향을 미치며, 두 요인간의 상호작용이 졸참나무의 기공전도도를 제외하고 광합성 속도, 수분이용효율, 기공전도도 및 엽록소 함량에서 확인되었다. 그러나 광화학 효율은 생육밀도와 용적에 따른 상호작용이 없었다. 또한, 물푸레나무와 졸참나무의 광합성 속도는 생육밀도와 부의 상관관계를 보였으며, 세 수종 모두 광합성 속도와 용적과는 정의 상관관계를 보였다. 광합성 속도를 기준으로 다중회귀분석기법을 적용한 결과, 느티나무는 160~210본/$m^2$과 430~460 $cm^3$/구, 물푸레나무는 130~150본/$m^2$과 390~440 $cm^3$/구, 졸참나무는 130~170본/$m^2$과 420~460 $cm^3$/구가 최적 용기 규격으로 판단된다. 향후, 수종별 적정 용기 적용으로 양묘과정에서 우량 용기묘 생산뿐만 아니라, 조림 후에도 우수한 생장을 기대할 수 있다.

• 대한임상검사과학회지
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• 제49권1호
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• pp.40-47
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• 2017

난포 내 난자를 둘러싸고 있는 과립세포는 난자를 위한 성장상태 및 난포의 발달에 중요하다. Solute carrier family 유전자는 스테로이드 호르몬, 다양한 약물, 몇몇 다른 기질을 유입시킨다. 연구에서 획득한 서로 다르게 발현하는 유전자들 (DEGs) 중 일부를 in situ hybridization을 통해 분석하였다. 분석한 결과 SLC23A3과 SLC39A10이 난소에서 높게 발현하였다. SLC39A10 유전자는 원시난포에서 높게 발현하였고, SLC23A3은 일차, 이차 난포에서 높게 발현하였다. 특히 성장하는 난포의 과립막 세포에서 발현하였다. SLC23A3과 SLC39A10은 원시난포와 일차난포에서 다르게 발현하는 것은 각 난포의 분리를 통해 좀 더 확인해야 할 것이다. 본 연구에서는 유전자 발현 정보를 통해 원시난포의 개시와 성장을 위한 전환에 관여하는 기전을 이해하는데 기초정보와 난포발달 촉진을 위한 난소기능부전의 기전을 규명하는데 정보를 제공할 것으로 기대된다.