• 한국기계가공학회지
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• 제11권3호
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• pp.116-121
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• 2012

In recent years, world is faced with a transportation energy dilemma, and the transportation is dependent on a single fuel - petroleum. However, Hybrid Electric Vehicle(HEV) technology holds more advantages to reduce the demand for petroleum in the transportation by efficiency improvements of petroleum consumption. Therefore, there is a trend that lower gear noise levels are demanded in HEV for drivers to avoid annoyance and fatigue during operation. And meshing transmission error(T.E.) is the excitation that leads to the tonal noise known as gear whine, and radiated gear whine is also the dominant source of noise in the whole gearbox. This paper presents a method for the analysis of gear tooth profile and lead modification, and the predictions of transmission error and load distribution are shown under one loaded torque for the 1st gear pair of HEV gearbox. The test is also obtained before tooth micro-modification under the torque. At last, the appropriate tooth modification is used to minimize the transmission error and load distribution under the loaded torque. It is a good approach which the simulated result is used to improve the design in order to minimize the radiation gear whine noise.

• 한국정밀공학회지
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• 제21권7호
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• pp.62-69
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• 2004

This paper presents an experimental study on the dimensional error in ball-end milling. In the 3D free-formed surface machining using ball-end milling, while machining conditions are varied due to the Z component of the feed and existing hemisphere part of the ball-end mill, the mechanics of ball-end milling are complicated. In the finishing, most of cutting is performed the ball part of the cutter and the machined surface are required the high quality. But the dimensional errors in the ball-end milling are inevitably caused by tool deflection, tool wear, thermal effect and machine tool errors and so on. Among these factors, the most significant one of dimensional error is usually known as tool deflection. Tool deflection is related to the instantaneous horizontal cutting force and varied the finishing cutting path. It lead to decrease cutting area, thus resulting cutting forces but the dimensional precision surface could not be obtained. So the machining experiments are conducted fur dimensional error investigation and these results may be used for decrease dimensional errors in practice.

• The Journal of Asian Finance, Economics and Business
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• 제9권10호
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• pp.105-113
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• 2022

The purpose of this paper is to analyze the relationship between the ratio of non-controlling shareholder interests (minority equity ratio, MER) and the measurement error in real activities manipulation (RM) proxy for Japanese firms. Many Japanese firms have practiced stakeholder-oriented corporate governance systems. Previous studies suggest that the higher the MER, the more Japanese businesses tend to employ management techniques for the group's sales growth while also reallocating resources inside the group to reduce principal-principal conflicts. Such differences in management strategies by firms could lead to measurement error in the RM proxy. The analysis uses 16,450 firm-years listed on the Tokyo Stock Exchange. The results of our analysis show that there is a positive relationship between MER and the RM proxy, and high persistence of RM proxies, suggesting that the RM proxies may contain measurement error. We also find that MER is correlated with variables associated with management strategy and that controlling for these variables can reduce the measurement error of RM proxy in firms with large MER. This study extends previous research on measurement error in RM proxy by relating them to ownership structure and corporate governance. This paper would contribute to researchers examining issues related to RM.

• 로봇학회논문지
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• 제19권1호
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• pp.23-30
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• 2024

This paper studies a GPS error filtering method that takes into account the continuity of the ongoing path to enhance the safety of autonomous agricultural mobile robots. Real-Time Kinematic Global Positioning System (RTK-GPS) is increasingly utilized for robot position evaluation in outdoor environments due to its significantly higher reliability compared to conventional GPS systems. However, in orchard environments, the robot's current position obtained from RTK-GPS information can become unstable due to unknown disturbances like orchard canopies. This problem can potentially lead to navigation errors and path deviations during the robot's movement. These issues can be resolved by filtering out GPS information that deviates from the continuity of the waypoints traversed, based on the robot's assessment of its current path. The contributions of this paper is as follows. 1) The method based on the previous waypoints of the traveled path to determine the current position and trajectory. 2) GPS filtering method based on deviations from the determined path. 3) Finally, verification of the navigation errors between the method applying the error filter and the method not applying the error filter.

• 한국산업정보학회논문지
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• 제27권2호
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• pp.71-82
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• 2022

자동차용 배터리 제조공정 가운데 하나인 Tab Welding 공정에서 생산된 제품의 샘플링 인장검사를 대체하기 위해 현재 비전검사기를 개발하여 사용하고 있다. 그러나, 비전검사는 검사 위치 오차 문제와 이를 개선하기 위해 발생하는 비용 문제를 가지고 있다. 이러한 문제점들을 해결하기 위해 최근 딥러닝 기술을 적용하는 사례들이 발생하고 있다. 본 논문도 그런 사례 중 하나로 기존 제품 검사에 딥러닝 기술 중 하나인 Faster R-CNN을 적용하여 그 유용성을 파악하고자 하였다. 기존 비전검사기를 통해 획득한 이미지들을 학습 데이터로 사용하여 Faster R-CNN ResNet101 V1 1024x1024 모델을 사용하여 학습하였다. 검사 기준인 미검률 0%, 과검률 10%의 기준으로 기존 비전검사와 Faster R-CNN 검사결과를 비교 분석하였다. 미검출률은 기존 비전검사에서 34.5%, Faster R-CNN 검사에서 0%였다. 과검출률은 기존 비전검사에서 100%, Faster R-CNN에서 6.9%였다. 결론적으로 자동차용 배터리 리드탭 암흔 오류 검출에 딥러닝 기술이 매우 유용함을 확인할 수 있었다.

• 대한전자공학회논문지TC
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• 제44권2호
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• pp.55-61
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• 2007

본 논문에서는 곱의 상관방식과 차분상관방식의 OFDM 심벌 동기타이밍방식에 있어서 멀티패스 채널 지연프로필의 각 수신지연파에서 OFDM 심벌 동기타이밍으로 검출될 확률식을 나타내 보인다. 여러 가지 지연확산의 채널들에 대해 행해본 컴퓨터시뮬레이션의 결과 상관의 동기타이밍 검출방식에서는 진폭이 가장 큰 지연파의 선두에서 동기타이밍을 취할 확률이 높게 나타나는데 대하여 차분방식에서는 언제나 제 1수신지연파의 선두에서 동기타이밍을 취할 확률이 높게 나타나는 특성을 보여준다. 이러한 결과를 통하여 본 논문에서는 채널의 지연확산 길이에 관계없이 OFDM신호의 동기타이밍을 0점과 -1점 심벌 동기타이밍을 취하는 것에서 BER의 성능차이를 보여준다.

• 한국전자통신학회논문지
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• 제12권5호
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• pp.837-844
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• 2017

조석수조에서 수위를 조절하기 위한 위어는 자체에 부착된 2대의 전동실린더에 의해 상하로 이송된다. 이때 발생되는 좌 우 전동실린더의 이동거리 차는 위어의 불균형과 마찰을 일으키므로, 위어는 목표지점으로 이송될 수 없게 된다. 본 연구에서는 위어를 신속하고 정확하게 이송하기 위한 동기제어시스템이 구축된다. 교차결합구조에 기초한 이 동기제어시스템은 두 개의 I-PD제어기와 한 개의 진상보상기로 구성된다. 각 I-PD제어기는 전동실린더가 오버슈트와 입력포화를 발생시키지 않고 위치지령을 정확히 추종하도록, 그리고 진상보상기는 신속하고 안정적으로 동기가 되도록 설계된다. 끝으로 시뮬레이션을 통해 설계된 동기제어시스템이 동기오차의 제거에 효과적임을 나타낸다.

• Progress in Superconductivity
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• 제5권2호
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• pp.98-104
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• 2004

We analyzed a noise-sensitivity profile of a specific SQUID sensor system for the localization of brain activity. The location of a neuromagnetic current source is estimated from the recording of spatially distributed SQUID sensors. According to the specific arrangement of the sensors, each site in the source space has different sensitivity, that is, the difference in the lead field vectors. Conversely, channel noises on each sensor will give a different amount of the estimation error to each of the source sites. e.g., a distant source site from the sensor system has a small lead-field vector in magnitude and low sensitivity. However, when we solve the inverse problem from the recorded sensor data, we use the inverse of the lead-field vector that is rather large, which results in an overestimated noise power on the site. Especially, the spatial sensitivity profile of a gradiometer system measuring tangential fields is much more complex than a radial magnetometer system. This is one of the causes to make the solutions of inverse problems unstable on intervening of the sensor noise. In this study, in order to improve the localization accuracy, we calculated the noise-sensitivity profile of our 40-channel planar SQUID gradiometer system, and applied it as a normalization weight factor to the source localization using synthetic aperture magnetometry.

• 대기
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• 제25권2호
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• pp.271-281
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• 2015

The objectives of this study are to develop a hydrological drought outlook system using GloSea5 (Global Seasonal forecasting system 5) which has recently been used by KMA (Korea Meteorological Association) and to evaluate the forecasting capability. For drought analysis, the bilinear interpolation method was applied to spatially downscale the low-resolution outputs of GloSea5 and PR (Predicted Runoff) was produced for different lead times (i.e., 1-, 2-, 3-month) running LSM (Land Surface Model). The behavior of PR anomaly was similar to that of HR (Historical Runoff) and the estimated values were negative up to lead times of 1- and 2-month. For the evaluation of drought outlook, SRI (Standardized Runoff Index) was selected and PR_SRI estimated using PR. ROC score was 0.83, 0.71, 0.60 for 1-, 2- and 3-month lead times, respectively. It also showed the hit rate is high and false alarm rate is low as shorter lead time. The temporal Correlation Coefficient (CC) was 0.82, 0.60, 0.31 and Root Mean Square Error (RMSE) was 0.52, 0.86, 1.20 for 1-, 2-, 3-month lead time, respectively. The accuracy of PR_SRI was high up to 1- and 2-month lead time on local regions except the Gyeonggi and Gangwon province. It can be concluded that GloSea5 has high applicability for hydrological drought outlook.

• 한국수자원학회논문집
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• 제44권7호
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• pp.537-551
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• 2011

본 연구에서는 앞선 연구를 통해 선정된 최적 입력 자료 조합을 이용하여 한강수계의 왕숙천과 금강유역의 갑천에 대한 Takagi-Sugeno 퍼지기법과 신경망을 연계한 뉴로-퍼지 홍수예측 모형을 구축하였다. 구축된 뉴로-퍼지 홍수예측 모형을 한강수계의 왕숙천과 금강유역의 갑천에 적용하여 30분, 60분, 90분, 120분, 150분, 180분의 선행시간에 대해 각각 홍수예측을 수행하였다. 선행시간별 예측수위를 관측수위와 비교한 결과 안정되고 정확도 높은 홍수예측을 하는 것을 확인할 수 있었다. 추가적으로 정량적 평가를 위해 평균제곱근 오차(Root Mean Square Error)와 같은 통계지표를 산정하여 모형의 적용성을 검증하였다. 검증 결과 모든 통계지표에서 큰 오차 없이 성공적으로 홍수예측이 모의됨을 확인할 수 있었다. 본 연구결과는 향후 중소하천에서 충분한 선행시간을 확보한 정확도 높은 홍수정보시스템의 구축에 활용할 수 있을 것으로 판단된다.