• Journal of the Korean Magnetics Society
• /
• v.12 no.2
• /
• pp.68-72
• /
• 2002

In this research, the effects of capacitance to the access time were studied at the junction area of tunneling magnetoresistance when these were used as memory devices. These results were obtained by applying electric signal input and magnetic field was not used. We applied bipolar square waves of 1MHz to the MTJ samples to obtain the results and time constant ($\tau$) calculated by observing wave responses utilizing an oscilloscope. And time constant was compared with junction area. Each part of MTJ sample, such as electrical pad, lead and contact area, was modeled as an electrical equivalent circuit based on experimental results. For the 200㎛$\times$200㎛ cell, junction capacitance was 90 pF. Also, measurement and simulation results were compared, which showed those similarity.

• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.824-825
• /
• 2015

본 논문은 Switched Reluctance Motor(SRM)의 보다 정확한 제어를 위한 인덕턴스 측정에 대해 설명한다. 기존의 인덕턴스 측정방법에는 등가회로를 이용하여 측정하는 방법과 시정수를 이용하여 측정하는 방법이 사용되어왔고 본 논문에서는 기존의 인덕턴스 측정방법과 자동화된 전압적분법을 이용하여 인덕턴스를 측정하였고 실제 측정 데이터 및 유한요소해석(FEA : Finite Element Analysis) 데이터와의 비교를 통하여 타당성을 입증하였다.

• Korean Journal of Optics and Photonics
• /
• v.26 no.2
• /
• pp.73-82
• /
• 2015

This work demonstrates the indoor SI-traceable calibration of a transmissometer with a 75-m baseline for the measurement of visibility in MOR (Meteorological Optical Range). The calibration is performed using a set of neutral density (ND) filters (OD 0.1-2.5) and a set of high-transmission quartz glass plates (a bare quartz glass plate and antireflective-coated quartz glass plates), the collection consisting of 20 artifacts in total. The luminous transmittance values of the reference artifacts had been calibrated traceable to the KRISS spectral transmittance scale, which ranges from 0.2 % to 99.5 %. The transmissometer to be calibrated typically consists of a loosely collimated light source based on a white LED (CCT ~5000 K) and a luminous intensity detector with a CIE 1924 V(${\lambda}$) spectral response. As a result of calibration, we obtained the MOR error and its uncertainty for the transmissometer in 20 m - 40 km of MOR. Based on the results, we investigated the applicability of the calibration method and the conformity of the transmissometer to the ICAO's (International Civil Aviation Organization) accuracy requirement for meteorological visibility measurement. We expect that this work will establish the standard procedure for the SI-traceable calibration of a transmissometer.

• Korean Journal of Optics and Photonics
• /
• v.6 no.1
• /
• pp.56-61
• /
• 1995

본 연구에서는 펄스형 고반복 Nd:YAG 레이저를 이용한 거리측정기의 설계 및 그에 따른 제작 성능을 기술하고자 한다. 제작 결과로 얻어진 측정 최대거리는 지상표적에 대하여 약 19km이다. 이 때 대기의 시정거리는 약 23km이다.

• Proceedings of the Korea Air Pollution Research Association Conference
• /
• 2003.05b
• /
• pp.111-112
• /
• 2003

자외선의 영역에서 에너지 흡수를 일으키는 기준 가스들을 측정하는 방법은 여러 가지가 있다. 근래에 이르러 분광학적인 방법으로 이들을 측정하는 시도가 늘어나고 있다. 유럽에서 널리 이용중인 도아즈는 현재는 위성에 응용되어 개발되고 있으며 가스의 파장에 대하여 흡수선을 이용하여 해당가스를 검출해내는 기술을 그 원리로 하고 있다. 지점 측정 방법에 대하여 많은 장점을 가지고 있으나 현재로서는 지속적으로 개발되고 있고 응용 기술의 난해함 등으로 그 응용범위가 한정되어 있다. 본 연구는 국내에서 개발된 도아즈 시스템으로부터 시정 거리를 산출하는 데 필요한 550 nm 에서의 광 감쇄도 측정을 내용으로 한다. (중략)

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2022.11a
• /
• pp.214-216
• /
• 2022

본 논문에서는 시정계에 비해서 낮은 가격으로 개발이 가능한 카메라 시스템과 촬영한 사진으로 해무 강도를 측정하는 방안을 제안한다. 항로표지에 부착이 가능하고 360도 촬영이 가능한 카메라 시스템 구현 내용을 설명하고 해무의 강도를 측정하기 위해 안개 모델과 Dark Channel Prior(DCP)를 이용해 해무 강도를 측정하는 알고리즘을 개발하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2019.05a
• /
• pp.176-178
• /
• 2019

부산항은 초미세먼지 기준으로 세계 10대 오염항만으로 보고되어, 우리나라 항만도시의 대기오염도가 심각한 수준임을 알 수 있다. 이처럼 선박, 하역장비, 대형화물차 등 항만오염배출원에서 발생하는 미세먼지는 항만지역 내외를 가리지 않고 배후도시 지역민의 삶의 질에 큰 영향을 미친다. 이외 하역장비, 대형화물차 등 항만운영으로 인해 발생하는 소음 또한 지역민 주거생활환경에 영향을 미치는 주요 요인이다. 이 연구는 부산항 신항의 배후도시인 창원시 항만배후지역(웅동생활권)의 주민이 겪고 있는 환경피해실태를 파악하고자 항만배후지역의 생활환경 중 체감오염도가 높은 미세먼지($PM_{10}$)와 소음에 대한 기초 영향조사 수행하였다. 연구결과 신항(창원) 배후지역의 미세먼지($PM_{10}$) 농도는 인근 지역인 창원시 경화동, 부산시 녹산동보다 높게 조사되었고, 경남지역 대기측정소(21개)의 평균보다 최대 $25{\mu}g/m^3$ 이상 높게 측정 되었다. 또한, 신항(창원) 배후지역의 소음도는 환경관리기준을 초과하는 것으로 조사되었다.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.21 no.2
• /
• pp.101-115
• /
• 2022

This study compared the performance of LiDAR in detecting objects in rough weather with that in clear weather. An experiment that reproduced rough weather divided the fog visibility into four stages from 200 m to 50 m and controlled the rainfall by dividing it into 20 mm/h and 50 mm/h. The number of points cloud and intensity were used as the performance indicators. The difference in performance was statistically investigated by a T-Test. The result of the study indicates that the performance of LiDAR decreased in the order in situations of 20 mm/h rainfall, fog visibility less than 200 m, 50 mm/h rainfall, fog visibility less than 150 m, fog visibility less than 100 m, and fog visibility less than 50 m. The decreased performance was greater when the measurement distance was greater and when the color was black rather than white. However, in the case of white, there was no difference in performance at a measurement distance of 10 m even at 50 m fog visibility, which is considered the worst situation in this experiment. This no difference in performance was also statistically significant. These performance verification results are expected to be utilized in the manufacture of road facilities in the future that improve the visibility of sensors.

• Journal of the Korean earth science society
• /
• v.44 no.2
• /
• pp.105-118
• /
• 2023

In this study, we predicted the presence of fog with a one-hour delay using the XGBoost DART machine learning algorithm for Andong, which had the highest occurrence of fog among inland stations from 2016 to 2020. We used six datasets: meteorological data, agricultural observation data, additional derived data, and their expanded data. The weather phenomenon numbers obtained through naked-eye observations and the visibility distances measured by visibility meters were classified as fog [1] or no-fog [0]. We set up twelve machine learning modeling experiments and used data from 2021 for model validation. We mainly evaluated model performance using recall and AUC-ROC, considering the harmful effects of fog on society and local communities. The combination of oversampled meteorological data features and the target induced by weather phenomenon numbers showed the best performance. This result highlights the importance of naked-eye observations in predicting fog using machine learning algorithms.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.10 no.1
• /
• pp.27-35
• /
• 1973

The electronic states of carrier capture centers in reverse biased point-contact germanium diodes have been investigated through the tomperature-and reverse voltage-characteristics of burst noise. The measured values of the time constants wllich represent the electronic states of the centers are extended up to greater than ten minutes, which are about 10,000 times greater than the ones obtained by other investigators. From the relation between these time constants and temperatures, the quasi-Peymi level and the activation energy of the center have been obtained.