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405 nm 살균용 UV LED 등기구의 청색광 위해에 관한 연구
허현석,김충혁,남기호,김진사 한국전기전자재료학회 2023 전기전자재료학회논문지 Vol.36 No.3
Recently, sterilization technology has received increasing interest due to the COVID-19 pandemic and required safety precautions. Particularly, sterilization devices using near ultraviolet (UV) with a 405 nm wavelength are also drawing attention. It has a UV-C wavelength and other sterilization effects. Its blue-colored light on the boundary between UV and visible light is used as a light-emitting diode (LED) lamp for 405 nm sterilization, owing to its longer wavelengths than UV rays. However, the 405 nm wavelength contains blue light that can damage the eyes and skin during prolonged exposures and affect the emotional and biological parts of the body. Currently, 405 nm sterilization LED light registers are circulating in the market. However, they have not undergone safety tests for blue-light hazards. Thus, with the active distribution of sterilization LED lights, solid safety standards and management systems are essential to protect users from blue-light hazards. Accordingly, in this study, we conducted spectral radiance and spectral radiative luminance tests on 405 nm sterilization LED registers available in the market by the measurement criteria of IEC 62471. Safety standards must be established to secure users' safety against blue light hazards at a time when 405nm sterilization LED lights are actively distributed due to COVID-19.
고속 푸리에 합성곱을 이용한 파지 조건에 강인한 촉각센서 기반 물체 인식 방법
허현석,김정중,고두열,김창현,이승철 한국로봇학회 2022 로봇학회 논문지 Vol.17 No.3
The accurate object recognition is important for the precise and accurate manipulation. To enhance the recognition performance, we can use various types of sensors. In general, acquired data from sensors have a high sampling rate. So, in the past, the RNN-based model is commonly used to handle and analyze the time-series sensor data. However, the RNN-based model has limitations of excessive parameters. CNN-based model also can be used to analyze time-series input data. However, CNN-based model also has limitations of the small receptive field in early layers. For this reason, when we use a CNN-based model, model architecture should be deeper and heavier to extract useful global features. Thus, traditional methods like RN N -based and CN N -based model needs huge amount of learning parameters. Recently studied result shows that Fast Fourier Convolution (FFC) can overcome the limitations of traditional methods. This operator can extract global features from the first hidden layer, so it can be effectively used for feature extracting of sensor data that have a high sampling rate. In this paper, we propose the algorithm to recognize objects using tactile sensor data and the FFC model. The data was acquired from 11 types of objects to verify our posed model. We collected pressure, current, position data when the gripper grasps the objects by random force. As a result, the accuracy is enhanced from 84.66% to 91.43% when we use the proposed FFC-based model instead of the traditional model.
도달시간차 기반의 음원 위치 추정법의 정확도 향상을 위한 딥러닝 적용 연구
정일주,허현석,정인지,이승철 한국음향학회 2024 韓國音響學會誌 Vol.43 No.2
This study introduces an enhanced sound source localization technique, bolstered by a data-driven deep learning approach, to improve the precision and accuracy of direction of arrival estimation. Focused on refining Time Difference Of Arrival (TDOA) based sound source localization, the research hinges on accurately estimating TDOA from cross-correlation functions. Accurately estimating the TDOA still remains a limitation in this research field because the measured value from actual microphones are mixed with a lot of noise. Additionally, the digitization process of acoustic signals introduces quantization errors, associated with the sampling frequency of the measurement system, that limit the precision of TDOA estimation. A deep learning-based approach is designed to overcome these limitations in TDOA accuracy and precision. To validate the method, we conduct comprehensive evaluations using both two and three-microphone array configurations. Moreover, the feasibility and real-world applicability of the suggested method are further substantiated through experiments conducted in an anechoic chamber.
박범수,정해동,허현석,김민섭,이승철 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.11
The advent of smart factories has resulted in the frequent utilization of industrial robots within factories to increase production automation and efficiency. Due to the increase in the number of industrial robots, it has become more important to prevent any unexpected breakdowns of the factory. As a result, the lifespan prediction of machinery has become a crucial factor because such failures can be directly associated with factory productivity resulting in significant losses. Most of the failures occur within one of the core components of the robot arm, the servo motor, and thus we will focus on the analysis of the servo motor in this study. However, sensor attachment to such equipment is considered difficult due to the dynamic movement of the robot arm, meaning that internal instrumentation should be utilized during analysis. In addition, no definite measure to determine the degradation of the motor exists, and thus a new degradation index is proposed in this study. Therefore, in this study, the lifespan of the servo motor will be estimated through accelerated degradation testing methods based on a new system degradation assessment method, which estimates the fault of the system using observer-based residuals with encoder data obtained from internal instrumentation.
특발성 청소년 척추측만증 환자의 척추변형에 따른 사회심리적 상태
김은주,김한승,허현석,문재호 대한재활의학회 2004 Annals of Rehabilitation Medicine Vol.28 No.3
Objective: To determine the relation of Radiographic Scoring System and Scoliosis Research Society-22 (SRS-22), a revised form of health-related quality-of-life (HRQL) questionnaire in idiopathic adolescent scoliosis patients. Method: A patient group was made up of 41 adolescents who were diagnosed as idiopathic scoliosis. A control group of 17 persons with Cobb's angle <10o was established. To evaluate psychosocial condition, SRS-22 was used to collect the data on both patient and control group. Roentgenographic study was conducted to obtain the Radiographic Deformity Score and evaluate the curve pattern. Results: Pain, self image/appearance, mental health and total score of SRS domains were found to be significantly different between patient and control group (p<0.05). Radiog raphic Deformity Score was positively correlated with pain and self image of SRS domains (p<0.05). However, the pattern of curve was found to be not correlated with SRS score. Conclusion: We could evaluate a psychologic condition of idiopathic adolescent scoliosis using Scoliosis Research Society-22 (SRS-22) health-related quality-of-life (HRQL) questionnaire. The more severe spinal deformity, it had the more negative influence on psychologic conditions in idiopathic adolescent scoliosis patients. Therefore, the clinician who is managing idiopathic adolescent scoliosis patients should consider their psychosocial conditions.