• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.293-302
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• 2002

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.4
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• pp.390-396
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• 2004

A double-inlet pulse tube refrigerator was fabricated as a U-shape with $\Phi$19.0 mm${\times}$125 mm regenerator packed by #200 stainless steel mesh and $\Phi$12.7 mm${\times}$125 mm pulse tube. A pressure sensor was installed at the inlet of the regenerator and a differential pressure sensor was installed across the bypass. Amplitude of the pulsating pressure was independent of the opening of the orifice and the bypass valves. Helium flow through the orifice and the bypass was calculated based on the measured pressure. Energy loss through the orifice and the bypass was evaluated with the measured pressure and the calculated helium flow rate. The energy loss, which is equivalent to the refrigeration capacity at the cold end of the ideal pulse tube refrigerator, was mainly generated through the orifice. It was proportional to the opening of the orifice valve, but the real refrigerator displayed the best performance at the optimized opening of the orifice valve. This optimized performance of the tested pulse tube refrigerator can be explained by additional refrigeration losses. As an example, the shuttle heat transfer loss of the pulse tube was calculated from the measured experimental data.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.12
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• pp.668-673
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• 2013

In this study, specimens with nano-sized porous thin films were manufactured by injecting fluorescence solution into the pores. We intended to find out the difference of the fluorescence intensity in each region of the specimen through an experimental apparatus that makes a temperature field. Before conducting experiments, the optimized manufacturing conditions were determined by analysis of all parameters that influence the emission intensity, and the experiments were carried out with the specimens produced in the optimized conditions. Then, the calibration curves of the fluorescence intensity versus temperature were performed by taking the intensity distributions from the specimen in various temperature fields. The surfaces of specimens were coated with Rhodamine-B (Rh-B) fluorescent dye and measured based on the fluorescence intensity. Silica (SiO2) nanoporous structure with 1-um thickness was constructed on a cover glass, and fluorescence dye was absorbed into these porous thin films.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.7
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• pp.508-516
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• 2008

Fault detection and diagnosis(FDD) system is beneficial in equipment management by providing the operator with tools which can help find out a failure of the system. An experimental study has been performed on fault detection and diagnosis method for a water chiller. Bayes classifier, which is one of classical pattern classifiers, is adopted in deciding whether fault occurred or not. Failure modes in this study include refrigerant leakage, decrease in mass flow rate of the chilled water and cooling water, and sensor error of the cooling water inlet temperature. It is possible to detect and diagnose faults in this study by adopting FDD algorithm using only four parameters(compressor outlet temperature, chilled water inlet temperature, cooling water outlet temperature and compressor power consumption). Refrigerant leakage failure is detected at 20% of refrigerant leakage. When mass flow rate of the chilled and cooling water decrease more than 8% or 12%, FDD algorithm can detect the faults. The deviation of temperature sensor over $0.6^{\circ}C$ can be detected as fault.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.2198-2202
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• 2005

In this paper we have presented a condition monitoring method of check valve using neural network. The acoustic emission sensor was used to acquire the condition signals of check valve in direct vessel injection (DVI) test loop. The acquired sensor signal pass through a signal conditioning which are consisted of steps; rejection of background noise, amplification, analogue to digital conversion, extract of feature points. The extracted feature points which represent the condition of check valve was utilized input values of fault diagnosis algorithms using pre-learned neural network. The fault diagnosis algorithm proceeds fault detection, fault isolation and fault identification within limited ranges. The developed algorithm enables timely diagnosis of failure of check valve’s degradation and service aging so that maintenance and replacement could be preformed prior to loss of the safety function. The overall process has been experimented and the results are given to show its effectiveness.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.404-408
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• 2009

Gas pipelines in bridges, roads and subway construction sections can undergo abrupt stress and vibration changes. To protect human life from any gas leakage accidents induced by the abrupt stress and vibration, the gas pipeline system needs to be continuously monitored. The estimation method of pipeline stress using MEMS wireless tilt sensor has been developed and its validity has been evaluated using a lab test bench.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.08a
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• pp.185-188
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• 2000

Heart sound contains rich information regarding the dynamics of the heart and the auscultation has been a first choice of routine procedures for diagnosis of the heart. However, heart sounds captured using a conventional stethoscope are not often loud or clear enough for doctors to precisely classify their characteristics, especially, under the noisy environments of the hospital. A simple auscultation device that removed shortcomings of the conventional stethoscope was constructed in the study. The device employed a polymer based adherent differential output sensor which was on contact with skin through a coupling medium and appropriated electronic circuits for signal amplification and conditioning. An ordinary headphone is taken to hear the captured heart sounds and the volume can be adjusted to hear well. It is also possible that the device sends the captured heart sound signals to a PC where the signals are further processed and viualized.

• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.982-987
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• 2006

고전의 관현악기에서부터 현대의 각종 전자악기까지, 인류는 그 문화와 시대의 변화에 따라 다양한 형태의 악기를 개발하고 활용하였다. 최근에는 전기전자 기술의 발달로 다양한 센서와 프로그램을 활용해서 여러 가지 음색과 효과를 내는 악기가 개발되고 있다. 그 중에서 사람의 움직임을 직접 감지해서 음악적 도구로 활용하는 기술이 주목 받고 있다. 이를 위해 터치 센서(touch sensor), 비젼 센서(vision sensor), 자기장 센서(magnetic sensor), 초음파 센서(ultrasonic sensor) 등이 응용되고 있다. 그러나 지금까지의 센서 기술로는 사람의 움직임과 관련된 위치, 속도, 가속도 등에 대한 정보를 직접 추출하기가 어렵고, 구현된 시스템도 공간의 제약을 받거나 혹은 구현된 부피가 크거나 복잡한 구성형태를 지니고 있는 문제점이 있었다. 그래서 본 논문에서는 사람의 움직임과 관련된 가속도 정보를 직접 감지해서 새로운 형태의 악기로 활용될 수 있는 시스템을 연구하고 개발하였다. 이를 위해 6개의 가속도 정보를 처리하는 기술과 DSP(Digital Signal Processor) 활용 기술, Max/MSP 활용 기술이 응용 되었으며, 소형의 시스템을 개발하기 위해 시그널 컨디셔닝(signal conditioning) 회로와 DSP 보드를 자체 개발하였다. 실험을 통해 사람의 움직임과 관련된 각종 정보가 적절한 소프트웨어의 활용으로 다양한 음색의 변화는 물론 음높이, 음량의 변화까지도 제어할 수 있음을 확인하였고, 새로운 형태의 악기로써 무대 공연이나 노래방 등에 폭넓게 활용될 수 있는 가능성을 확인하였다.

• Journal of Sensor Science and Technology
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• v.12 no.1
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• pp.24-33
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• 2003

This research is about a comfort sensing system for human environmental monitoring using a one-bodied humidity and temperature sensor and an air flow sensor. The thermal comfort that a human being feels in indoor environment has been known to be influenced mostly by six parameters, i.e. air temperature, radiation, air flow, humidity, activity level and clothing thermal resistance. Considering an environmental monitoring, we have designed and fabricated a one-bodied humidity and temperature sensor and an air flow sensor that detect air relative humidity, temperature and air flow in human environment using surface micromachining technologies. Micro-controller calculates a PMV (predicted mean vote) and CSV (comfort sensing vote) with sensing signals and display a PMV on LCD (liquid crystal display) for human comfort on indoor climate. Our work has demonstrated that a comfort sensing system can provide an effective means of measuring and monitoring the indoor comfort sensing index of a human being. Experimental results with simulated environment clearly suggest that our comfort sensing system can be used in many applications such as air conditioning system, feedback controlling in automobile, home and hospital etc..

• Journal of the Korean Society for Precision Engineering
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• v.24 no.9
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• pp.60-67
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• 2007

A signal conditioning circuit for capacitive displacement sensors was developed using a high frequency modulation/demodulation method, and its performance was evaluated. Since capacitive displacement sensors can achieve high resolution and linearity, they have been widely used as precision sensors within the range of several hundred micrometers. However, they inherently have a limitation in low frequency range and some nonlinearity characteristics and so a specially designed signal conditioning circuit is needed to handle these properties. The developed signal processing circuit consists of three parts: linearization, modulation/demodulation, and nonlinearity compensation. Each part was constructed discretely using several IC chips and passive elements. An evaluation system for precision displacement sensors was developed using a laser interferometer, a precision stage, and a PID position controller. The signal processing circuit was tested using the evaluation system in the respect of resolution, repeatability, linearity, and so on. From the experimental results, we know that a highly linear voltage output can be obtained successfully, which is proportional to displacement and the nonlinearity of output is less than 0.02% of full range. However, in the future, further investigation is required to reduce noise level and phase delay due to a low-pass filter. The evaluation system also can be applied effectively to calibration and evaluation of precision sensors and stages.