• 한국전자통신학회논문지
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• 제18권3호
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• pp.397-404
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• 2023

본 논문은 풍력터빈의 시제품 인증을 위한 국제 규정에 근거하여 풍력터빈 시험장을 설계하였다. 시험장에 설치되는 기상탑의 최대 높이는 140m이며, 5MW 이상 풍력터빈을 최대 3대까지 시험할 수 있는 전력설비가 구성되어 있다. 설치된 기상탑에서 측정한 기상자원은 감시시스템을 이용하여 기록 및 분석이 가능함을 확인하였다. 풍력터빈 제조업체는 이 시험장을 인증기간 동안 사용할 수 있고 설치된 풍력터빈은 지속적인 발전사업도 가능하다. 따라서, 장기적으로 풍력터빈의 성능 및 내구성을 측정하여 모델을 개량하거나 새로운 풍력터빈을 개발하기 위한 기초자료를 얻을 수 있다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제3권3호
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• pp.208-215
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• 2011

A full-scale field trial in ice-covered sea is one of the most important tasks in the design of icebreaking ships. The first Korean icebreaking research vessel 'ARAON', after her delivery in late 2009, had a sea ice field trial in the Arctic Sea during July-August, 2010. This paper describes the test procedures and data analysis on the icebreaking performance of the IBRV ARAON. The data gathered from the icebreaking performance test in the Chukchi Sea and the Beaufort Sea during the Arctic voyage of ARAON includes the speed and engine power of the ship as well as sea ice thickness and strength data. The air temperature, wind speed and heading of the ship were also measured during each sea ice trial. The ARAON was designed to break 1 m thick level ice with a flexural strength of 630kPa at a continuous speed of 3knots. She is registered as a KR POLAR 10 class ship. The principal dimensions of ARAON are 110 m, 19 m and 6.8 m in length, breadth and draft respectively. She is equipped with four 3,500kW diesel-electric main engines and two Azipod type propulsion motors. Four sea ice trials were carried out to understand the relationship between the engine power and the ship speed, given the Arctic ice condition. The analysis shows that the ARAON was able to operate at 1.5knots in a 2.5m thick medium ice floe condition with the engine power of 5MW, and the speed reached 3.1 knots at the same ice floe condition when the power increased to 6.6MW. She showed a good performance of speed in medium ice floe compared to the speed performance in level ice. More detailed analysis is summarized in this paper.

• 한국컴퓨터그래픽스학회논문지
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• 제15권4호
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• pp.1-11
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• 2009

본 연구에서는 다각형 메쉬 모델들에 대한 시뮬레이션 수행시 주요 병목현상으로 제기되는 충돌감지의 효율성을 높이기 위하여, 연속 시간사이에서 이산시간 스위프트로 형성된 프리즘을 단위로 하는 효율적 메쉬 컬링 기법을 제안한다. 제안 기법에서는 우선, 연속 시간사이에서 대응되는 두 삼각형을 이용하여 프리즘을 정의하고, 프리즘 단위의 폐쇄검사(Occlusion Query) 기반 가시성 테스트(Visibility Test)를 실시하여, 교차 가능성이 없는 프리즘을 세부 충돌테스트의 대상에서 제외시킨다. 또한, 가시성 테스트 결과로 추출된 프리즘의 충돌가능 집합(PCS: Potential Colliding Set)에서 충돌 가능성이 없는 프리즘의 쌍들을 분리축 테스트(SAT: Separating Axis Test)을 기반으로 분류하는 협대역 컬링(Narrow Band Culling)을 수행한다. 분리축 테스트 시, 두 프리즘의 영역을 각각의 반공간(Half Space)에 포함시키는 평면을 정의하고 이에 수직인 주축을 정의하여, 단일 주축에 대한 분리 검사를 수행함으로써 수행 효율성을 높인다. 제안기법의 성능을 평가하기 위하여 서로 다른 크기의 벤치마크 모델을 선정하고, 제안 기법 적용 전후의 세부 층돌검사 대상 프리즘 쌍의 수를 비교하였다. 또한, 단일 주축에 대한 분리축 테스트 기반 컬링의 효율성을 입증하기 위하여, 프리즘 쌍에 대한 가시성테스트 실험 결과와 비교하였다. 2916개와 2731개의 삼각형으로 구성된 두 메쉬모델에 대한 컬링 실험에서, 제안 컬링기법 적용시 99%의 효과적인 컬링결과를 얻었다.

• Journal of Biosystems Engineering
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• 제43권1호
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• pp.1-13
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• 2018

Purpose: The development of compact tractors that can be used in dry fields, greenhouses, and orchards for pest control, weeding, transportation, and harvesting is necessary. The development and performance evaluation of power transmission units are very important when it comes to tractor development. This study evaluates the performance of a driving power transmission unit of a 50 kW multi-purpose narrow tractor. Methods: The performance of the transmission and forward-reverse clutch, which are the main components of the driving power transmission unit of multi-purpose narrow tractors, was evaluated herein. The transmission performance was evaluated in terms of power transmission efficiency, noise, and axle load, while the forward-reverse clutch performance was evaluated in terms of durability. The transmission's power transmission efficiency accounts for the measurement of transmission losses, which occur in the transmission's gear, bearing, and oil seal. The motor's power was input in the transmission's input shaft. The rotational speed and torque were measured in the final output shaft. The noise was measured at each speed level after installing a microphone on the left, right, and upper sides. The axle load test was performed through a continuous equilibrium load test, in which a constant load was continuously applied. The forward-reverse clutch performance was calculated using the engine torque to axle torque ratio with the assembled engine and transmission. Results: The loss of power in the transmission efficiency test of the driving power unit was 6.0-9.7 kW based on all gear steps. This loss of horsepower was equal to 11-18% of the input power (52 kW). The transmission efficiency of the driving power unit was 81.5-89.0%. The noise of the driving power unit was 50-57 dB at 800 rpm, 70-77 dB at 1600 rpm, and 76-83 dB at 2400 rpm. The axle load test verified that the input torque and axle revolutions were constant. The results of the forward-reverse clutch performance test revealed that hydraulic pressure and torque changes were stably maintained when moving forward or backward, and its operation met the hydraulic design standards. Conclusions: When comprehensively examined, these research results were similar to the main driving power transmission systems from USA and Japan in terms of performance. Based on these results, tractor prototypes are expected to be created and supplied to farmhouses after going through sufficient in-situ adaptability tests.

• Structural Engineering and Mechanics
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• 제46권2호
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• pp.179-196
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• 2013

An experimentally measured single footfall trace (SFT) from a walking subject needs to be extended into a continuous force curve, which can then be used as load for floor vibration serviceability assessment, or on which further analysis like discrete Fourier transform can be conducted. This paper investigates the accuracy, applicability and parametrical sensitivity of four extension methods, Methods I to IV, which extends the SFT into a continuous time history by the walking step rate, stride time, double support proportion and the double support time, respectively. Performance of the four methods was assessed by comparing their results with the experimentally obtained reference footfall traces in the time and frequency domain, and by comparing the vibrational response of a concrete slab subjected to the extended traces to that of reference traces. The effect of the extension parameter on each method was also explored through parametrical analysis. This study finds that, in general, Method I and II perform better than Method III and IV, and all of the four methods are sensitive to their extension parameter. When reliable information of walking rate or gait period is available in the test, Methods I or II is a better choice. Otherwise, Method III, with the suggested extension parameter of double support time proportion, is recommended.

• 농업과학연구
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• 제49권4호
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• pp.785-793
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• 2022

In this study, tomato maturity was estimated based on deep learning for a harvesting robot. Tomato images were obtained using a RGB camera installed on a monitoring robot, which was developed previously, and the samples were cropped to 128 × 128 size images to generate a dataset for training the classification model. The classification model was constructed based on convolutional neural networks, and the mean-variance loss was used to learn implicitly the distribution of the data features by class. In the test stage, the tomato maturity was estimated as a continuous index, which has a range of 0 to 1, by calculating the expected class value. The results show that the F1-score of the classification was approximately 0.94, and the performance was similar to that of a deep learning-based classification task in the agriculture field. In addition, it was possible to estimate the distribution in each maturity stage. From the results, it was found that our approach can not only classify the discrete maturation stages of the tomatoes but also can estimate the continuous maturity.

• Asia pacific journal of information systems
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• 제19권3호
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• pp.151-179
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• 2009

The purpose of this study is to make an empirical analysis on the factors affecting the intention for the continuous use of the BSC system, which has been recently spread in the public sector. Because the object of acceptance is the performance management system based on BSC (Balanced Scorecard) implemented in the form of information systems, this study proposes a research model by applying TAM (Technology Acceptance Model). Independent variables are factors affecting the acceptance of BSC system such as training, communication, IS support, CEO support and personal innovativeness, and we examine their effects on the dependent variable, namely, intention on continuous use via mediating variables: perceived usefulness and perceived ease of use. A questionnaire survey was conducted with public institutions(firms) that had introduced and were operating the BSC system; 264 valid questionnaires are adopted. Collected data are analyzed using SPSS 16.0 and AMOS 7.0. Results of reliability test show that all analyzed data are reliable. In validity test, one item regarding communication was excluded; 9 latent variables and 34 observed variables are used in the final analysis. Based on the results of the hypothesis test through path analysis using a structural equation model, 10 out of 16 hypotheses are accepted. Factors affecting perceived usefulness are training and IS(Information System) support. The analysis results indicate that perceived ease of use is mainly affected by IS support, CEO support, and personal innovativeness among the factors related to the acceptance of the BSC system. This suggests that, contrary to the expectation that the BSC system may be used without difficulty, the management's active support is required in order to attain expected improvement in productivity and work efficiency. This was also pointed out in case studies on the construction of the BSC system in public sectors. On the other hand, perceived ease of use is found to affect perceived usefulness. This supports the results of previous researches on TAM. Perceived ease of use and perceived usefulness are found to affect the attitude towards the use of the system. The intention on continuous use is affected more by perceived usefulness than by the attitude towards the use of system. This result supports the results of previous researches on TAM, showing that the BSC system is utilized substantially in worksites. This study is considered meaningful in that it was actually performed on users at public institutions(firms) that had introduced the BSC system and that it empirically tested hypotheses on the acceptance of the BSC system by applying TAM to the research model.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.88-91
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• 2001

Our knowledge about their long-term performance in an outdoor environment is still very limited. The electrical stress caused the surface of these insulators to become degradation. In order to evaluate leakage current patterns caused by surface aging on polymeric insulators, we utilized the combined aging test facility and leakage current monitoring system. And we get the continuous leakage current values from each sample. After completing the 3000h combined aging cycle test, leakage current measurement were conducted for these samples and carried out harmonics analysis for its data.

• 한국생산제조학회지
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• 제20권5호
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• pp.653-658
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• 2011

In general, the purpose of packaging fasteners is a series of management activities to maintain the condition at the time of production until they get delivered to the end user. An automatic packing system for fasteners is consisted of bucket conveyor, slide feeder, vision inspection system, box-magazine conveyor system and automatic packing machine. Also, the automatic packing machine is consisted of six modules including charging device, clamping/opening device, sealing/cutting device, feeding/air-shower device, supplying/adjusting device and device frame, etc. In this paper, we proposed an automatic packing mechanism of the one station concept for packing work of fastener objects where the continuous batch work is performed in a finite space. The proposed one-station packing mechanism has been optimized through mechanical, dynamical, structural and fluid analyses. And it had been manufactured as the prototype of automatic packing machine. The field test for validation of performance was performed directly at the production line of bolt and screw. In the field test, this packing machine showed an efficiency of about 4.5 times the manual operation. It also showed 30% reduction in the consumption of packing materials compared to the manual operation. This automatic packing machine for fastener objects will be commercialized soon.

• 생물정신의학
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• 제9권2호
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• pp.112-119
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• 2002

Object:This study was to investigate the difference of speech perception ability in schizophrenic patients, and depression patients in order to explore trait-dependent speech perception ability of each disorder. Methods:The speech perception ability was assessed with masked speech tracking test(MST) in schizophrenic patients(N=31), depression patients(N=25), and normal controls(N=21). The continuous performance test(CPT) and sentence repetition test(SRT) were also used for assessment of attention and working memory. Results:The schizophrenic patients showed significant impaired MST performance, compared with depressive patients and normal controls. The performances of CPT and SRT were also more impaired in schizophrenic patients. The difference of MST performances between two patient group was cancelled out after consideration of differences in CPT & SRT performances. Conclusions:These results imply that schizophrenic patients have the impaired speech perception ability compared with depressive patients and normal controls. But speech perception ability was significantly influenced with CPT and SRT. For evaluation of pure speech perception ability, the more elaborate controlled study that excluded factors such as attention, working memory and intelligence is needed.