• 한국대기환경학회지
• /
• 제17권4호
• /
• pp.313-319
• /
• 2001

The development of ozone SRP (Standard Reference Photometer) designated as a G-7 project by the Korean Ministry of Environment began 1997 and is now nearly completed. With the completion of the ozone SRP we will not only acquire a qualification to participate in the international ozone calibration system but also enhance calibration credibility of ozone similarly to that of other ambient air pollution monitors. As the ozone SRP uses highly cleaned blank air that can be distinguished from general ozone analyzer, it is possible to reduce errors associated with the determination of ozone via elongation of the absorption length as long as 1 meter In addition, gas chopping method hat been adopted to cut down interference of other substances and time drift. Furthermore, the system has also been modified to minimize the strayed ultra-violet noise along the light path. In this paper, a new method for uncertainty evaluation has been introduced, which is guided by the ISO (International Standard Organization) GUM (Guide to the Expression of Uncertainty in Measurement) through assessments of the uncertainty type B (that was impossible to estimate before) as well as the uncertainty type A (based on statistics).

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제50권9호
• /
• pp.456-465
• /
• 2001

In this paper, breakdown voltages in $SF_6-N_2$ mixtures were experimentally investigated to understand characteristics of dielectric strength and physical phenomena in nonuniform field disturbed by a needle shape protrusion. The test voltages are the lightning impulse$(\pm1.2/44 \mus)$ and the damped oscillatory impulse$(\pm400 ns / 0.83 MHz)$ voltages which can be occurred by the operation of disconnecting switches in gas-insulated switchgears(GIS). The effects of the polarity and wave shape of the test voltages, and the gas pressure on the V-t characteristics were in detail examined. The V-t characteristic curves were measured in different two ways : (1) one is the method by taking the maximum voltage recorded at or prior to breakdown against the time to breakdown, that is, the Procedures recommended in IEC 60060-1, (2) the other is the method by taking the voltage at the instant of chopping against the time to breakdown. As a result, the V-t characteristics of $SF_6-N_2$ mixtures in nonuniform electric field were significantly affected by the polarity and wave shape of the applied voltages. The positive breakdown voltages resulted in lower breakdown voltages in the time ranges considered, and the V-t curves for the negative oscillatory impulse voltage were extended over the longer time range. For the lightning impulse voltages, the V-t curves obtained by IEC Pub. 60060-1 were nearly same with the V-t curves obtained by the voltage at the instant of chopping against the time to breakdown. It is clear that the actual breakdown voltages were much lower than the maximum voltages appearing at or prior to breakdown because of the displacement current produced as a result of the dV/dt during the oscillatory transient voltage app1ication. The scattering of the negative actual breakdown voltages was much larger than that of the positive.

• 대한기계학회논문집B
• /
• 제33권2호
• /
• pp.133-140
• /
• 2009

A fast-response $CO_2$ analyzer has been developed for measuring the $CO_2$ concentration during transient condition of a SI engine. The analyzer consists of the non-dispersive infrared absorption method, electrical chopping system and water cooling system. The analyzer has good repeatability, linearity and permissible drift characteristic. Besides, it showed 18ms of a response to measure the $CO_2$ concentration. The fast-response $CO_2$ analyzer was applied to a single cylinder SI engine and the $CO_2$ emission was examined during engine start. Simultaneously, the standard exhaust gas analyzer, which has slow response time, was used for confirming the accuracy of the exhaust gas analysis using the fast-response $CO_2$ analyzer. The developed analyzer showed much faster responsive characteristic than that of a standard analyzer and made cycle by cycle exhaust gas analysis possible. The transient engine operating characteristics will be estimated from the $CO_2$ concentration of engine-out emissions and engine operating variables.

• 대한기계학회논문집B
• /
• 제34권10호
• /
• pp.947-955
• /
• 2010

대부분의 석유 가스전은 탄화수소혼합물과 일반기체 등 저류층 내부 유체의 성분조성에 따라 저류층내 상거동 특성이 매우 민감하게 변화한다. 석유 가스전의 평가와 개발 생산계획을 수립함에 있어, 이러한 상거동에 따른 기체와 액체의 성분비 결정과 석유와 가스의 이상유동 해석을 위한 저류유체의 PVT관계 및 포화물성의 규명은 필수적이다. 이중에서 특히, 포화물성의 계산은 수렴성이 나빠, 이상 유동의 해석적 연구에 있어서 많은 어려움을 초래하는 원인이 되고 있다. 이에 본 연구에서는 포화물성 의 계산에 있어서 수렴도 향상을 위한 새로운 초기값 추정 방법과 근 탐색 알고리듬을 제안하고, 성능비교 등을 통한 수렴도 영향인자에 대한 분석을 시도하였다. 결과적으로, 제안된 방법을 통해 포화물성 해석 수렴성을 개선하였고 GUI 기반의 새로운 다성분 다상거동해석 시뮬레이터의 개발에 적용하였다.

• 센서학회지
• /
• 제10권5호
• /
• pp.279-285
• /
• 2001

본 논문에서는 동맥혈중 이산화탄소 분압을 실시간으로 추정하는 capnograph 시스템에 상용되는 대부분 NDIR 흡수식(non-dispersive infrared absorption) 광챔버와 신호처리회로를 설계 및 구현하였다. 광챔버 설계시 일반 정상인의 capnogram을 주파수 분석하여 적합한 광쵸핑 주파수를 결정한 뒤, 이에 근거하여 시간응답을 고려한 광챔버를 설계하였으며, 열잡음에 대한 영향을 줄이기 위해 2광원 1센서 방식의 $CO_2$ 농도 신호처리회로를 구현하였다. 구현된 광챔버에 대한 가스배출시간을 조사하였으며 신호처리회로를 외부 온도 변화 실험에 적용한 결과 2광원 1센서 방식이 안정된 출력 신호를 얻을 수 있음을 확인하였고, 실제 사람의 호흡에 대한 실험결과 정상적인 capnogram 형태의 $CO_2$ 농도 변화 곡선을 보였다.