• Journal of the Korean Society for Precision Engineering
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• v.11 no.2
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• pp.120-133
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• 1994

홀로그래픽 간섭계측기로터 나오는 영상 데이터를 해석하는 전문가시스템에 대하여 기술하였다. 그동안 간섭 띠무늬(fringe)를 해석하는 방법들이 어느 정도의 자동화를 이룩하며 개발되어왔다. 그러나, 복잡한 간섭 띠무늬 패턴(fringe pattern)및 심한 잡음이 생기게 되는 고속도 항공공학 분야 또는 실험기계공학 분야에서는 신뢰할 만한 자동화를 이룩하기가 매우 힘들었다. 현재 사용가능한 방법중에는 간섭띠무늬 추적, 위상전이, 푸리에 변환, 회귀분석 등이 있는데, 이들은 소음제거나 데이터 수정을 하는데 있어서 극히 국부적인 정보에만 의존하였다. 결과적으로, 특별히 심한 소음이 있는 경우, 부정확한 위상중첩이나 간섭띠무늬 순차배열문제에 부딪히게 되고 따라서 작업자의 수작업이 심각하게 필요하게 된다. 본 논문에서는 간섭띠무늬 추적방법의 자동화 를 위한 새롭고 포괄적인, 규칙기반 전문가시스템에 대하여 기술하였다. 새로 개발된 전문가 시스템은 간섭띠무늬 패턴에 대한 전체적인 또는 지연적인 정보를 추출해 내고 또 전문가가 가지고 있는 지식을 이용한다. 이 전문가 시스템은 저수준 및 고수준 처리를 동시에 할 수 있도록 상호연결기구를 채택하여 간섭띠무늬를 해석하는 적절한 해결책을 마련하였다. 또한 위상전이나 푸리에 변환 방법에서 문제가 되는 자동위상 중첩에 대해 개발된 전문가 시스템의 응용의 가능성에 대해서도 기술하였다.

• Journal of Advanced Navigation Technology
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• v.13 no.1
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• pp.34-40
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• 2009

The phase delay of output signal of APD(avalanche photo diode) caused by intensity of reflected light which comes from target. These difference of phase delay is an one of the main reason of measurement error, but there is no reasonable measurement meter and method to detect it. In this paper, to solve the problem, we propose and implement a method to measure the intensity of radiation. The method measures DC voltage which is proportional to the reflected intensity of radiation and come out from APD in receiver by realtime.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.9
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• pp.879-888
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• 2009

Unsteady three-dimensional reacting flowfield generated by transverse hydrogen injection into a supersonic mainstream is numerically investigated using DES and finite-rate chemistry model. Comparisons are made with experimental results to investigate the turbulent reacting flow physics. The numerical OH distribution describes well the experimental OH-PLIF result, while the numerical ignition delay time shows some disparity due to the restricted available experimental data. The intermittency phenomena are identified by the comparative analysis between RANS and DES. Those effects are also quantified by the temperature distributions along streamlines and superimposed OH mass fraction along with time.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.6
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• pp.120-127
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• 1995

A nonlinear empirical state-space model of the Artificial Neural Network(ANN) has been developed. The nonlinear model structure incorporates characteristic, so as to enable identification of the transient response, as well as the steady-state response of a dynamic system. A hybrid feedfoward/feedback neural network, namely a Local Time Delayed Recurrent Multi-layer Perception(RMLP), is the model structure developed in this paper. RMLP is used to identify nonlinear dynamic system in an input/output sense. The feedfoward protion of the network architecture provides with the well-known curve fitting factor, while local recurrent and cross-talk connections provides the dynamics of the system. A dynamic learning algorithm is used to train the proposed network in a supervised manner. The derived dynamic learning algorithm exhibit a computationally desirable characteristic; both network sweep involved in the algorithm are performed forward, enhancing its parallel implementation. RMLP state-space and its associate learning algorithm is demonstrated through a simple examples. The simulation results are very encouraging.

• Journal of the korean academy of Pediatric Dentistry
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• v.49 no.3
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• pp.241-252
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• 2022

The purpose of this study was to evaluate the relationship between sella turcica morphology and delayed dental age. In total, 389 participants under 16 years old were selected. Dental age was evaluated by the Demirjian method and age discrepancy (AD), the value subtracted from dental age to chronological age, was calculated. The participants were divided into 8 groups based on the sella turcica type. Bridging ratio (BR) was defined as interclinoid distance divided by sella turcica length to determine the degree of sella turcica bridging (STB) and the participants were classified into 4 groups by BR. The data were statistically analyzed using the Kruskal Wallis test and the Mann Whitney test. Some groups with sella turcica abnormality showed lower AD than that of the normal group and the AD differences varied from 4 months to 1.3 year. As the STB severity increased, AD decreased. AD differences varied from 7 months to 1.19 year. No distinct differences were observed in sella turcica type and STB groups according to sex. The results indicate that sella turcica morphology is associated with delayed dental age. Sella turcica can be used as a supplementary indicator to predict dental development.

• Journal of Power System Engineering
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• v.15 no.3
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• pp.5-11
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• 2011

디젤기관의 경우는 종래부터 직분식이 주류를 이루었고, 근래에는 분사압력의 고압화가 진행중이다. 분사압력의 고압화에 의해 연소효율의 향상 및 배출가스중의 입자상물질(PM:Particulate Matter)의 저감을 유도하고 있으나, 연소가스의 고온화로 인해 질소산화물(NOx:Nitrogen Oxides)은 증가한다. 따라서, 분사기간의 지연(Retard)이나 파일럿분사(Pilot injection)등의 혼합기제어에 의해 질소산화물의 저감을 꾀하고 있다. 이와 같이 디젤기관에 있어서도 혼합기 형성의 최적화에 의한 연소제어를 시도하는 수법이 중시되고 있고, 이를 위해서는 디젤분무 구조에 기초한 혼합기의 형성기구에 대한 규명이 매우 중요하다. 그러므로 본 연구에서는 보다 고도의 혼합기형성 제어를 위한 기초연구로서 고온 고압장에서의 증발디젤자유분무구조를 해석하였으며, 계측영역은 연료와 주위기체와의 혼합이 활발히 진행되는 분무의 하류영역으로 설정하고, 입자화상속도측정법(particle Image Velocimetry:PIV)을 이용한 분무의 유동해석을 기초로 증발 디젤분무의 구조 해석을 행하였다. 실험조건으로서 분사압력을 72MPa, 112MPa로 각각 변화시켰다.

• Proceedings of the IEEK Conference
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• 2009.05a
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• pp.19-21
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• 2009

The reflectometry for locating the fault at a cable is the same as a problem estimating the time delay between the incident and the reflected signals. In this paper, we propose a method for estimating the time delay between the two signals. The proposed method is based on the modeling of the Gaussian enveloped linear chirp signal in the Gaussian noise environment. The phase and the instantaneous frequency of the received signal are estimated by linear Kalman filtering. From the estimated instantaneous frequency, we can measure the time interval between the center frequencies of the incident and the reflected signals. The time interval is the same as the time delay between the incident and the reflected signals. In a simulation assuming that the cable has open fault at the end of the cable, the proposed method showed a good result in estimating the time delay.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.171-176
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• 2003

A Test Facility was established to carry out the integrated propulsion performance tests(IPPT). To perform IPPT's with maximum safety, an emergency blockage system was investigated. An emergency blockage system using combustion chamber pressure and acceleration signals was set up to monitor ignition delay and fail, flame out, propellant feeding status, unstable combustion and excessive structural vibration. With such system, the maximum safety could be secured by rapid judgement and follow-up measures, which made IPPT's be safely completed.

• Journal of the Korean Geotechnical Society
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• v.16 no.5
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• pp.203-212
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• 2000

샌드파일 주변지반은 교란으로 스미어 영향과 베수저항에 의해 압밀지연 현상이 발생하는 것으로 알려져 있다. 이와 같이 샌드파일 주변지반의 압밀특성에 미치는 영향을 파악하기 위하여 지반물성치에 따른 예측치와 계측을 통한 실측치에 대한 비교검토를 실시하였다. 압밀계수 특성인 압밀소요기간은 수평과 연직압밀계수를 동일하게 평가할 경우 예측과 실측치가 매우 유사한 결과를 보여주는 것으로 나타났다. 압축지수 특성인 침하량 분석결과 예측치에 비해 60~90%정도로 작게 평가되는데 이것은 공동확장이론에 의한 초기 방사(측)방향 압축을 고려할 경우 유사한 값을 얻을 수 있다. 따라서 샌드파일 주변지반에서의 거동특성을 파악하기 위하여 스미어 배수저항뿐 아니라, 초기 방사(측)방향 압축을 고려한 개량특성으로서의 평가도 필요한 것으로 판단된다.

• Journal of the Korean Institute of Gas
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• v.24 no.5
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• pp.29-38
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• 2020

It is practically difficult to accurately measure the temperature and concentration of a large combustion systems at industrial sites in real time. Temperature measurement using thermocouple, which are mainly used, is a point-measuring method that is less accurate and less reliable to analyze the wide area range of inner combustion system, and has limitations to internal accessibility. In terms of concentration analysis, most measurement methods use sampling method, which are limited by the difficulty of real-time measurement. As a way to overcome these limitations, laser-based measurement methods have been developed continuously. Laser-based measurement are line-average measurement methods with high representation and precision, which are beneficial for the application of large combustion systems. In this study the temperature and concentration were measured in real time by water vapor and oxygen generated during combustion using Tunable Diode Laser Absorption Spectroscopy (TDLAS). The results showed that the average temperature inside the combustion system was 1330℃ and the mean oxygen concentration was 3.3 %, which showed similar tendency with plant monitoring data.