• 한국환경보건학회지
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• 제49권2호
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• pp.78-88
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• 2023

Background: Exposure to volatile organic compounds (VOCs) can have acute and chronic health effects on human beings in general and in working environments. In particular, VOCs are often emitted in large quantities in industrial settings. In such circumstances, there is a need to improve the indoor air quality at workplaces. Objectives: The purposes of this study were to verify the effectiveness of air cleaning devices in workplaces and provide alternative solutions for improving working environments. Methods: Personal exposure and area level of VOCs for workers were evaluated in a car-part adhesive process before and after installing an air cleaning device with a TiO₂-coated filter. Passive samplers and direct reading instruments were used to collect and analyze the VOCs, and the removal efficiency and improvement of air quality were evaluated. We also calculated the exposure index (EI) to assess the risk level in the workplace. Results: The removal efficiency for VOCs through the installation of the air cleaning device was approximately 26.9~69.0% as determined by the concentration levels before and after installation. The measured substances did not exceed the exposure limits for the work environment and the EI was less than 1. However, carcinogenic substances such as benzene, formaldehyde, carbon tetrachloride, and trichloroethylene were detected. Conclusions: The application of an air cleaning device can be a solution for controlling the indoor air quality in a workplace, particularly in cases where ventilation systems cannot be installed due to process limitations.

• 한국패류학회지
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• 제28권3호
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• pp.187-196
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• 2012

폐쇄 사육 시스템에서 고착성 무척추동물 특히 연체동물의 부착용 재료로서 이용되고 있는 dead rock과 live rock이 수질에 부가적으로 미치는 영향을 파악하고자 인도네시아로부터 수입된 dead rock과 live rock을 인공해수를 이용한 실험수조에 투입 한 후 수질변화를 관찰하였다. 두 종류의 rock들은 모두 pH 안정에 영향을 주었으며 질소화합물의 분해에도 일정한 영향을 주는 것으로 나타났다. dead rock의 경우 사용전 충분한 안정화 기간을 거침으로써 부착용 도구로서 뿐만 아니라 훌륭한 보조여과 기능을 담당할 수 있는 것으로 사료된다. live rock의 경우에는 이미 부착되어 서식하고 있는 조류나 박테리아에 의해 dead rock에 비해 더욱 높은 질소화합물 분해 능력을 나타냈으며 초기 투입 시 부착되어 있는 생물의 폐사나 해적생물의 유입에 따른 위험성을 제거 할 경우 사육시스템 내에서 단순한 부착용 재료로서 뿐만 아니라 다양한 목적에 이용가능 할 것으로 사료된다.

• 한국전자파학회논문지
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• 제28권5호
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• pp.410-418
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• 2017

본 연구에서는 항공기 기반 FMCW-SAR(Frequency Modulated Continuous Wave-Synthetic Aperture Radar) 시스템의 연속이동효과를 분석하고, 이를 보정하기 위한 신호처리 연구 결과를 설명하며, 보정된 레이다 신호를 back-projection 알고리즘 기반으로 복원시킨 SAR 영상 품질 개선 결과를 포함한다. FMCW 신호기반 SAR 시스템의 연속이동효과를 FMCW 신호 모델을 이용하여 항공기 이동 속도와 샘플링 주기 등의 영향을 분석하고, 이를 개선시키기 위해 시간-도플러(t, $k_u$) 영역에서의 레이다 신호처리 기법을 적용하였다. 이때, FMCW-SAR 영상 복원을 위해 back-projection 알고리즘과 수정된 정합필터를 활용하였으며, 항공기 기반으로 수집된 실제 X-밴드 대역 데이터에 적용하여 연속이동효과 개선 결과를 확인/검증하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.480-480
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• 2000

In this paper, we proposed a fuzzy-neuro controller to control the speed of wound rotor induction motor with slip energy recovery. The speed is limited at some range of sub-synchronous speed of the rotating magnetic field. Control speed by adjusting resistance value in the rotor circuit that occurs the efficiency of power are reduced, because of the slip energy is lost when it passes through the rotor resistance. The control system is designed to maintain efficiency of motor. Recently, the emergence of artificial neural networks has made it conductive to integrate fuzzy controllers and neural models for the development of fuzzy control systems, Fuzzy-neuro controller has been designed by integrating two neural network models with a basic fuzzy logic controller. Using the back propagation algorithm, the first neural network is trained as a plant emulator and the second neural network is used as a compensator for the basic fuzzy controller to improve its performance on-line. The function of the neural network plant emulator is to provide the correct error signal at the output of the neural fuzzy compensator without the need for any mathematical modeling of the plant. The difficulty of fine-tuning the scale factors and formulating the correct control rules in a basic fuzzy controller may be reduced using the proposed scheme. The scheme is applied to the control speed of a wound rotor induction motor process. The control system is designed to maintain efficiency of motor and compensate power factor of system. That is: the proposed controller gives the controlled system by keeping the speed constant and the good transient response without overshoot can be obtained.

• 한국산업보건학회지
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• 제7권2호
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• pp.171-180
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• 1997

The objectives of this study were both 10 discuss the sampling method for airborne metalworking fluids(MWF)' mist and 10 suggest measures to minimize worker's exposure to carcinogen contained in metalworking fluids. In order to measure airborne MWF mist, it seems to be appropriate to use NIOSH Method #0500(filler weight) rather than NIOSH Method # 5026(analysis by FTIR). Because MWF mist on PVC filter evaporated and migrated during sampling, worker's exposure to MWF could be underestimated. So, when evaluating worker's exposure to MWF mist, other environmental conditions also must be considered. Enclosure and local exhaust ventilation system seems to he the most effective measure and must be constructed with process facility. In order to control worker exposure to carcinogens contained in MWF, distillation type and condition for crude oil, PAH concentration in MWF, and viscosity index of MWF must legally be described.

• 방송공학회논문지
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• 제18권4호
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• pp.599-608
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• 2013

움직임 보상 보간 기법은 동영상 정보의 프레임율 증가 뿐 아니라 분산 동영상 부호화 시스템에서 부가 정보 생성에 사용된다. 본 논문에서는 움직임 보상 보간 기법의 성능을 효율적으로 향상시키기 위하여 DCT(Discrete Cosine Transform) 혹은 LiftLT를 이용하여 영상의 크기를 두 배 확대 변환한 후 움직임 보상 보간을 수행하여 생성된 두 배 크기의 영상을 다시 축소 변환하여 원래 크기의 보간 프레임을 생성하는 기법을 제안한다. 또한 보간 필터를 사용하여 부화소 단위의 세밀한 움직임 보상 보간을 수행한 경우의 성능도 분석한다. 모의 실험 결과 제안하는 기법이 기존의 보간 필터를 이용한 기법에 비해서 우수한 성능을 보임을 확인하였다.

• 한국의학물리학회지:의학물리
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• 제6권1호
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• pp.65-77
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• 1995

A new gamma camera using a-Si : H photodetectors has been designed for the imaging of heart and other small organs. In this new design the photomultiplier tubes and the position sensing circuitry are replaced by 2-D array of a-Si : H p-i-n pixel photode tectors and readout circuitry which are built on a substrate. Without the photomultiplier tubes this camera is light weight, hence can be made portable. To predict the characteristics and the performance of this new gamma camera we did Monte Carlo simulations. In the simulations 128${\times}$128 imaging array of various pixel sixes were used. $\^$99m/Tc(140keV)and $\^$201/Tl(70keV) were used as radiation sources. From the simulations we could obtain the resolution of the camera and ther overall system, and the blurring effects due to scattering in the phantom. Using the Wiener filter for image processing, restoration of the blurred image could be achieved. Simulation results of a-Si : H based gamma camera were compared with those of a conwentional gamma camera.

• Journal of Power Electronics
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• 제11권4호
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• pp.471-478
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• 2011

This paper addresses the establishment of a kVA-range plug-in hybrid electrical vehicle (PHEV) integration test platform and associated issues. Advancements in battery and power electronic technology, hybrid vehicles are becoming increasingly dependent on the electrical energy provided by the batteries. Minimal or no support by the internal combustion engine may result in the vehicle being occasionally unable to recharge the batteries during highly dynamic driving that occurs in urban areas. The inability to sustain its own energy source creates a situation where the vehicle must connect to the electrical grid in order to recharge its batteries. The effects of a large penetration of electric vehicles connected into the grid are still relatively unknown. This paper presents a novel methodology that will be utilized to study the effects of PHEV charging at the sub-transmission level. The proposed test platform utilizes the power hardware-in-the-loop (PHIL) concept in conjunction with high-fidelity PHEV energy system simulation models. The battery, in particular, is simulated utilizing a real-time digital simulator ($RTDS^{TM}$) which generates appropriate control commands to a power electronics-based voltage amplifier that interfaces via a LC-LC-type filter to a power grid. In addition, the PHEV impact is evaluated via another power electronic converter controlled through $dSPACE^{TM}$, a rapid control systems prototyping software.

• 컴퓨터교육학회논문지
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• 제5권1호
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• pp.109-115
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• 2002

인터넷이 교육에 사용됨으로써 학습자의 자기주도학습, 개별학습, 완전학습, 그리고 탐구형 학습 등이 효과적으로 이루어질 수 있다. 특히 이러한 장점을 취하기 위하여 게시판 시스템이 웹 기반 학습에 널리 사용되고 있다. 그러나, 게시판의 활용은 인터넷이 가지는 익명성으로 인해 자유로운 의견의 교환이라는 장점 외에, 부정적이거나 폭력적인 언어 사용이 쉽게 일어난다는 단점을 가진다. 본 연구는 인터넷을 활용한 학습에서 커뮤니케이션 도구로 널리 사용되고 있는 게시판이 유해단어 관리 기능을 가지도록 함으로써, 유해한 내용을 포함하는 내용의 게시를 제재하고 학생들의 언어 습관을 교정 할 수 있게 하였다.

• Journal of Power Electronics
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• 제18권6호
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• pp.1659-1669
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• 2018

An improved circulating current suppression control method is proposed in this paper. In the proposed controller, an outer loop of the average capacitor voltage control model is used to balance the sub-module capacitor voltage. Meanwhile, an individual voltage balance controller and an arm voltage balance controller are also used. The DC and harmonic components of the circulating current are separated using a low pass filter. Therefore, a multiple quasi-proportional-resonant (multi-quasi-PR) controller is introduced in the inner loop to eliminate the circulating harmonic current, which mainly contains second-order harmonic but also contains other high-order harmonics. In addition, the parameters of the multi-quasi-PR controller are designed in the discrete domain and an analysis of the stability characteristic is given in this paper. In addition, a simulation model of a three-phase MMC system is built in order to confirm the correctness and superiority of the proposed controller. Finally, experiment results are presented and compared. These results illustrate that the improved control method has good performance in suppressing circulating harmonic current and in balancing the capacitor voltage.