• 오토저널
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• 제15권3호
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• pp.1-9
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• 1993

디젤 엔진의 연소 과정에서 흡입공기와 분사된 연료의 최적 혼합기 형성이 배기성분, 연료효율 등 엔진의 성능을 향상시키는데 있어 매우 중요한 과제중의 하나이다. 이를 위하여 연료분무 현상에 대한 연구와 더불어 연소실내 공기유동 현상에 대한 연구가 주요 관심대상이 되어왔다. LDV를 이용한 3-D 유속측정 및 각종 CFD Code를 이용한 유동해석등의 방법으로 엔진 실린더 내부의 유동현상을 이해하는데 많은 도움이 되고 있으나 아직도 엔진연소실설계 등 엔진 개발에 있어서는 종래의 방법에 의한 실린더내 와류 강도의 비교평가에 크게 의존하고 있으므로 여기서는 디젤 엔진의 와류를 측정 평가하는 방법으로 Paddle Wheel회전을 이용한 Paddle Wheel식 Swirl Meter방식과 실린더내 흡입공기의 각 운동량을 측정하는 Impulse식 Swirl Meter 방식에 대해 고찰하고자 한다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.338-343
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• 2005

We have evaluated the structural integrity of a sandwich composite train roof which can find a lightweight, cost saving solution to large structural components for rail vehicles in design stages. The sandwich composite train roof was 11.45 meter long and 1.76 meter wide. The reinforced frame was inserted in sandwich panels to improve the structural performance of train roof structure and had the shape of hollow rectangular box. The finite-element analysis was used to calculate the stresses, deflections and natural frequencies of the sandwich composite train roof against the weight of air-condition system. The 3D sandwich FE model was introduced to simulate the hollow aluminum frames which jointed to both sides of the sandwich train roof. The results shown that the structural performance of a sandwich composite train roof under load conditions specified was proven and the use of aluminum reinforced frame was beneficial with regard to weight savings in comparison to steel reinforced frame.

• Tuberculosis and Respiratory Diseases
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• 제48권5호
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• pp.773-780
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• 2000

연구배경 : 흉수의 pH 측정은 흉막천자시 흉수의 원인 진단을 위해 시행되는 중요한 검사항목이며, 특히 부폐렴흉막염이 농흉화되는지를 확인할 수 있는 지표중 하나이다. 흉수의 pH 측정은 혈액가스분석기계를 이용하는 것이 표준이나, 상황에 따라서는 pH meter나 pH strip을 이용하기도 한다. 본 연구에서는 흉수중 삼출액을 대상으로 위의 세가지 방법으로 pH를 측정하고 측정치들을 비교하여 보았다. 방법 : 1999년 8월부터 2000년 3월까지 중앙대학교 부속 용산의료원에 입원하여 삼출성 흉수로 의심되어 흉막 천자를 시행한 34례 (결핵성 흉막염 16명, 부폐렴성 흉수 9명, 폐암 5명, 농흉 3명, 심부전 1명)의 흉수에서 혈액가스분석기계, pH meter, pH strip의 세 가지 방법으로 pH를 측정하였다. 혈액가스분석기계와 pH meter에 의한 측정은 천자후 $0^{circ}C$로 유지하면서 30분 내에 시행하였으며, pH strip 측정은 흉막천자 직후에 pH strip으로 pH를 측정하고, 상온 상태로 검사실에 내려서 보고되는 결과를 이용하였다. 결과 : 34례 흉수의 pH 값 (평균값$\pm$표준편차)은 혈액가스 분석법 7.34$\pm$0.12, pH meter 법 7.52$\pm$0.25, pH strip 법 중, 흉막천자후 즉시검사의 경우에는 7.37$\pm$0.16 였으며, 검사실에서 측정한 pH strip법은 6.93$\pm$0.20으로, 혈액가스분석법을 기준으로 한 평균치 분석에서 검사실에서 측정한 pH strip 법은 의미있는 차이를 보였다(p<0.05). 혈액가스분석법과 pH meter 방법, 그리고 혈액가스 분석법과 천자직후 pH strip법의 사이에는 의미있는 상관관계가 있었고, 혈액가스분석법과 pH strip 법 사이에는 의미있는 상관관계가 없었다. 결론 : 흉수천자 직후에 측정한 pH strip 법은 비교적 간단하고 정확하게 흉수의 pH를 측정할 수 있을 것으로 판단된다.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2000년도 학술발표회 발표논문집
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• pp.333-339
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• 2000

This study was performed to investigate the performance of heat recovery device attached to exhaust gas funnel connected to combustion chamber of greenhouse heating system. The experiment heat recovery system is mainly consisted of LPG combustion chamber and two heat recovery units; unit-A is attached directly to the exhaust gas funnel, and unit-B is connected with unit-A. Heat recovery performance was evaluated by estimating total energy amount by using enthalpy difference between two measurement points together with mass flow rate of gas and/or air passing through each heat recovery unit depending on 5 different flow rates controlled by voltage meter. The results of this experimental study, such as heat exchange behavior of supply air pipes and exhaust air passages crossing the pipes, pressure drop between inlet and outlet, heat recovery performance of exchange unit, etc., will be used as fundamental data for designing optimum heat recovery device to be used for fuel saving purpose by reducing heat loss amounts mostly wasted outside of greenhouse through funnels.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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• pp.2508-2510
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• 2001

Frequency of cavity vibration in air flowing tube is closely related to a velocity of air. In this research, an instrumentation system to estimate frequency of cavity vibration for measurement of the velocity and quantity of a moving fluid is implemented by using DSP TMS320C32. Measurement of the generated sound wave frequency in cavity is difficult because of environmental noise. Adaptive filters are used to eliminate this noise effectively. The estimated velocity and quantity of a moving fluid by proposed system is compared with the results measured by a standard flow meter.

• 한국해양공학회지
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• 제13권3B호
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• pp.14-21
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• 1999

As an effective means to convey crushed materials from seabed to onboard ship and to raise hazardous or abrasive liquids, air-lift pump provides a reliable mechanism due to its simple configuration and easy-to-operate principle. The present study is focused on investigation of related performance by the analysis program based on the gas-liquid two-phase flow in circular pipes. The program covers pump operating in isothermal and vertical two-phase flow with Newtonian liquids. It is summarized as important result that an optimum air mass flow rate exists for the maximum lifted liquid mass flow rate in terms of a given submergence rates. The comparison between riser performance of the conveyed liquid flow rate calculated by the computer program and measured data with large scale air lift pump system constructed in 200 meter depth vertical tank reveals similar distribution.

• KIEAE Journal
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• 제15권4호
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• pp.29-35
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• 2015

Purpose: Double skin facade is a representative advantageous passive technology of building skin in the aspect of energy saving and environment improvement, reduces heat loss with buffer space in winter season and enhances indoor air and comfort of residents by activating natural ventilation in mid-season. However, in summer season, temperature increase in the intermediate space due to solar energy from exterior transparent skin could be a potential problem; also, relatively weak buoyancy of air caused by low density difference between double-skin facade could increase cooling load as air of intermediate space in high temperature hangs. However, proof data is insufficient to objectify such phenomenon. Method: In this study, researchers surveyed air temperature of intermediate space and airflow and diagnosed its cause targeting on applied multistory facade in the building which gives thermal uncomfort to residents. Also, the researchers produced Solar-air heat transfer coefficient meter, measured thermal boundary condition of double-skin facade, and presented the result of measurement as an objectified verification material regarding overheating phenomenon in the intermediate space of double-skin facade in summer season. Result: Inefficient condition was verified that total heat increases and overheating due to insufficient natural ventilation in multistory facade. In addition, logic behind preceding research was objectified and verified regarding high temperature phenomenon in the intermediate space which could increase cooling load in summer season.

• KIEAE Journal
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• 제16권6호
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• pp.109-114
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• 2016

Purpose: The underground air is the warm air discharged from the porous volcano bedrock 30-50m underground in Jeju, including excessive humidity. The temperature of the underground air is $15-20^{\circ}C$ throughout the year. In Jeju, the underground air was used for heating greenhouses by supplying into greenhouses directly. This heating method by supplying the underground air into greenhouses directly had several problems. The study was conducted to develop the heat pump system using underground air as heat source for resolving excessive humidity problem of the underground air, adopting the underground air as a farm supporting project by Ministry of Agriculture, Food and Rural Affairs(MAFRA) and saving heating cost for agricultural facilities. Method: 35kW scale(10 RT) heat pump system using underground air installed in a greenhouse of area $330m^2$ in Jeju-Special Self-Governing Province Agricultural Research & Extension Services, Seogwipo-si, Jeju. The inlet and outlet water temperature of the condenser, the evaporator and the thermal storage tank and the underground air temperature and the air temperature in the greenhouse were measured by T type thermocouples. The data were collected and saved in a data logger(MV200, Yokogawa, Japan). Flow rates of water flowing in the condenser, the evaporator and the thermal storage tank were measured by an ultrasonic flow meter(PT868, Panametrics, Norway). The total electric power that consumed by the system was measured by a wattmeter(CW240, Yokogawa, Japan). Heating COP, rejection heat of condenser, extraction heat of evaporator and heating cost were analyzed. Result: The underground air in Jeju was adopted as a farm supporting project by Ministry of Agriculture, Food and Rural Affairs(MAFRA) in 2010. From 2011, the heat pump systems using underground air as a heat source were installed in 12 farms(16.3ha) in Jeju.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.2018-2023
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• 2003

An experiment is conducted for measuring the performance of an air tool, which is operated at 100,000 RPM at the unloaded state with the low torque. An experimental apparatus is developed as the power absorption type dynamometer. Inlet static pressure, flow rate, RPM and force are measured simultaneously. Torque, output power and specific output power are obtained. Those experimental results are compared with the experimental results obtained on a commercial dynamometer. However, no commercial dynamometers are available for measuring the torque above 30,000RPM. In order to use the commercial dynamometer, a reduction gear is applied to the shaft of dynamometer. Torque and power obtained on the commercial dynamometer show 50% lower than those obtained on a power absorption type dynamometer, because the inertia force is added to the air tool rotor for the braking system. Moreover, the starting RPM on the commercial dynamometer is less than 40,000RPM. From the compared results, they show that the power absorption type dynamometer should be applied for measuring the performance of an air tool operating at low torque and high RPM.

• 한국대기환경학회지
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• 제32권2호
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• pp.167-175
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• 2016

In this study, we estimate air pollutants emission from agricultural waste burning. We investigated activities related to agricultural waste burning such as crop burning rates, location, and time by region. The average crop burning rates per square meter farmland of fruits, pulses, barleys, cereals, vegetables, and special crops were $273.1g/m^2$, $105.7g/m^2$, $7.4g/m^2$, $121.0g/m^2$, $290.7g/m^2$, and $392.9g/m^2$, respectively. We estimated air pollutants emissions with pre-developed emission factors. The estimated air pollutant emission of agricultural biomass burning were CO 148,028 ton/year, $NO_x$ 5,220 ton/year, $SO_x$ 11 ton/year, VOC 59,767 ton/year, TSP 21,548 ton/year, $PM_{10}$ 8,909 ton/year, $PM_{2.5}$ 7,405 ton/year, and $NH_3$ 5 ton/year. When these results compared with the entire emissions of national inventory (CAPSS), CO, VOC, $PM_{10}$ account for about 17.8%, 6.2%, 6.7% of the total, respectively.