• 한국분무공학회지
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• 제29권2호
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• pp.53-59
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• 2024

Cars are one of the main causes of air pollution in large cities, and 34.6% of domestic air pollution emissions come from mobile sources, of which cars account for 69.6%. In particular, the importance of nitrogen oxides (NOx) and particulate matter (PM), which are major pollutants in diesel vehicles, is increasing due to their high contribution to emissions. Therefore, in this study, the problem of natural regeneration caused by low exhaust gas temperature during low speed and low load operation was solved by applying a complex regeneration DPF that is not affected by temperature conditions to large diesel vehicles with higher driving time and engine displacement than small and medium-sized vehicles. And the feasibility of application to large diesel vehicles was reviewed by measuring the emission reduction efficiency. As a result of the reduction efficiency test on the actual vehicle durability product, PM showed a reduction efficiency of 84% to 86%, and the reduction efficiency of gaseous substances showed a high reduction efficiency of over 90%. The actual vehicle applicability test was completed with three driving patterns: village bus vehicle, police car, and road-going construction equipment vehicle, and no device problems occurred until the end of the test. Both load and no-load smoke measurement results showed a smoke reduction efficiency of over 96%.

• 한국농공학회논문집
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• 제65권4호
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• pp.1-10
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• 2023

As a result of climate change, non-point source pollution (NPS) from farmland with the steep slope during the rainy season is expected to have a significant impact on the water system. This study aimed to evaluate the effect of furrow mulching using alfalfa and PAM (Polyacrylamide) materials for each rainfall event, while considering the load characteristics of NPS. The study was conducted in Wanju-gun, Jeollabuk-do, in 2022, with a testbed that had a slope of 13%, sandy loam soil, and maize crops. The testbed was composed of four plots: bare soil (Bare), No mulching (Cont.), Vegetation mulching (VM), and PAM mulching (PM). Runoff was collected from each rainfall event using a 1/40 sampler and the NPS load was calculated by measuring the concentrations of SS, T-N, T-P, and TOC. During farming season, the reduction efficiency of NPS load was 37.1~59.5% for VM and 38.2~75.7% for PM. The analysis found that VM had a linear regression correlation (R²=0.28~0.86, P-value=0.01~0.1) with elapsed time of application, while PM had a quadratic regression correlation (R²=0.35~0.80, P-value=0.1). These results suggest that the selection of furrow mulch materials and the appropriate application method play a crucial role in reducing non-point pollution in farmland. Therefore, further studies on the time-series reduction effect based on the application method are recommended to develop more effective preemptive reduction technologies.

• 한국지반공학회지:지반
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• 제12권6호
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• pp.51-64
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• 1996

축하중계측장치가 부착된 모형 개단 강관 말뚝을 상대밀도 49%인 초세립질 포화 모래지반을 담고 있는 압력 토조속에 타입한 후 정적압축재하시험을 실시하여 극한지지력을 결정하였다. 극한지지력의 임의 수준의 압축하중을 말뚝머리에 재재하한 후 유사지진 진동 및 Sine정현파 진동을 작용시켜 동적 진동에 의한 개단말뚝의 압축지지력 저감특성을 연구하였다. 유사화된 지진진 동과 Sine정현파진동에 의한 개단말뚝의 지지력 저감특성은 큰 차이를 보였다. 유사화된 지진 진동중 지지력 저감율은 작용하중의 크기에 따라 크게 달라지는데, 작용하중의 크기가 약 70% 이하일 경우에는 지지력 감소율이 8%이하였으며, 극한하중의 90%이상을 지지하는 개단말뚝의 극한지 지력은 약 15%이상 감소되었다. 또한, 외주면 마찰력 성분의 감소량은 감소된 총 지지력의 약 80%를 차지하였다. Sine정현파 진동중 지지력의 감소율은 작용하중의 크기에 따라 달라지지 않으며, 진폭과 진동수에 의해 크게 영향을 받았다. 즉, 진폭이 클수록, 진동수가 적을수록 지지력은 크게 감소되었다. 관내토 폐색응력의 감소양상은 진동의 종류에 따라 크게 달랐다. 유사 지진 진동에 의한 관내토 폐색응력의 감소는 작용하중의 크기에 상관없이 말뚝 선단으로 부터 약 3.0D, 이내의 관내 토에서 발생되었다. Sine정현파 진동에 의한 판내토 폐색응력의 감소는 말뚝 선단으로 부터 약 1.0D,이내의 관내토에서 크게 감소하고, 1.0-3.0D,의 관내토 부분에서는 거의 감소되지 않았다. 또한, 관내토 폐색력은 크게 감소되어졌고, 작용하중의 크기에 따라 감소율도 크게 달랐다.

• International Journal of Automotive Technology
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• 제6권6호
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• pp.591-598
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• 2005

A three-way catalyst system of a natural gas vehicle (NGV) has characteristics of higher fuel consumption and higher thermal load than a lean-bum catalyst system. To meet stringent emission standards in the future, NGV with the lean-bum engine may need a catalyst system to reduce the amounts of HC, CO and NOx emission, although natural gas system has low emission characteristics. We conducted experiments to evaluate the conversion efficiency of the NOx reduction catalyst for the lean-burn natural gas engine. The NOx reduction catalysts were prepared with the ${\gamma}-Al_{2}O_3$ washcoat including Ba based on Pt, Pd and Rh precious metal. In the experiments, effective parameters were space velocity, spike duration of the rich condition, and the temperature of flowing model gas. From the results of the experiments, we found that the temperature for maximum NOx reduction was around $450^{\circ}C$, and the space velocity for optimum NOx reduction was around $30,000\;h^{-1}$ And we developed an evaluation model of the NOx reduction catalyst to evaluate the conversion performance of each other catalysts.

• Journal of Advanced Marine Engineering and Technology
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• 제31권1호
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• pp.44-50
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• 2007

Diesel engines have high thermal efficiency, and they have less CO & HC emissions than another engines. while NOx & Soot emissions are very much. compared with exhaust emission standards. However, the limit level is more and more strengthened yearly due to the importance of environmental protection. So, the optimal countermeasures for the reduction of NOx & Soot emissions below limit level are required. Therefore. the author has investigated the effects of emulsified fuel on the characteristics of exhaust emissions. using an four-cycle, four-cylinder and direct injection diesel engine because the using of emulsified fuel among various methods for reducing NOx & Soot emissions is simple in installation low in cost and high in efficiency. The results of investigation according to various operating conditions are as follows : 1) Specific fuel consumption increase maximum 19.8% at low load. but is not affected at full load. 2) In case of emulsion ratio 25%, NOx emission decrease 32% at 75% load. 30% at full load. 3) In case of emulsion ratio 25%, Soot emission decrease 84% at 75% load, 59% at full load.

• 한국식품저장유통학회지
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• 제6권3호
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• pp.276-280
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• 1999

항균력이 있는 것으로 확인된 대황 및 황련추출물을 오이, 호박, 상치 및 고추에 처리하였을 때 총균수가 감소하였다. 채소의 종류에 따라서 적절한 처리농도는 달랐는 데, 호박, 상치 및 고추는 100 ppm, 오이는 500 ppm 처리가 적절한 것으로 나타났다. 채소를 침지할 때의 시간은 10분 정도가 적절한 것으로 나타났으며, 세척수의 온도를 4$0^{\circ}C$로 높일 경우에도 채소류 표면의 총균수 감소 효과는 실온의 세척수와 비슷하였다. 또한 오이와 호박을 대황 및 황련 추출물로 처리한 다음 1$0^{\circ}C$에서 건조하고 PVC랩으로 포장하여 저장한 결과 대조구에 비하여 총균수가 낮은 것으로 나타났다. 저장 기간 중 무게는 지속적으로 감소하였으며, 처리구와 대조구간에 큰 차이를 나타내지는 않았다. Ascorbic acid의 함량은 저장 기간 중 지속적으로 감소하는 것으로 나타났는데, 대황 및 황련추출물을 처리한 시험구가 대조구에 비하여 ascorbic acid의 함량이 높은 것으로 나타났다

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 학술대회 논문집 전문대학교육위원
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• pp.147-153
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• 2006

Voltage unbalance will be generated by the load unbalance operation such as combination operation of single & three phase load and current unbalance will be more severe by the deteriorated voltage quality. Under the these unbalance conditions, all power electronic converters used in different types of electronic systems can increase harmonic disturbances by injecting harmonic currents directly into the feeder grid of three phase 4-wire. Harmonic current may cause torque to decrease. it may also overheat or become noisy and torque oscillation in the rotor can lead to mechanical resonance and vibration. This paper presents a scheme on the characteristics of induction motor under the combination of linear & non-linear loads at the three phase 4-wire power distribution system by the unbalance and harmonic components. It was able to confirm that the number of torque pulsation decreased and torque ripple values increased by the harmonics that reduction was difficult by five harmonics filters at additional driving time of single-phase non-linear load.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1530-1535
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• 2003

The automatic load transfer switch (ALTS) typically automatically transfers electrical loads from a normal electrical power source to an emergency electrical power source upon reduction or loss of normal power source voltage. It can also automatically re-transfer the load to the normal power source when the normal voltage has been restored within acceptable limits. The transfer operation of ALTS is accomplished by a spring-driven linkage mechanism. In this paper we build a dynamic model of driving mechanism for ALTS using ADAMS and checked the characteristics of the transfer operation. Finally we performed a detailed design of the driving mechanism through results of analysis and confirmed it to satisfy design requirements.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.302-307
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• 2004

This paper reviewed characteristics of fatigue crack behavior observed by changing various shapes of initial crack and magnitudes of loading in compact tension shear(CTS) specimen subjected to shear loading. In the high-loading condition, fatigue crack under shear loading propagated branching from the pre-crack tip. Meanwhile, the secondary fatigue crack in the low-loading condition which was created in the notch root due to friction on the pre-crack face grew to a main crack. Influenced by the mode II loading condition, fatigue crack propagation retardation appeared in the initial propagation region due to the reduction of crack driving force and friction on crack face. In both cases, however, fatigue cracks grew in tensile mode type. Propagation path of fatigue crack under the shear loading was 70 degree angle from the initial crack regardless of its shape and load magnitude.

• 한국안전학회지
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• 제13권2호
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• pp.13-21
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• 1998

This is a study on the natural vibration characteristics of Vehicle frame. Nowadays, many trucks freight the over-load, do the car designers consider the over-load about 200% in the design. It's necessary to make the model of a vehicle and simulate it for the test of driving condition, durability and vibration behavior before the vehicle is manufactured. If it is possible to make a simulation using the static and dynamic analysis, this is very useful in accomplishing an optimal design of the vehicle. In this paper, we studied the vibration characteristics of a truck body frame. The automobile body frame model for experiment is made smaller than real size frame with the ratio of 1/10. The vibration characteristics of a frame is considered as one of main factors in analyzing and improving the problem for ride comfort, noise and vibration reduction. Therefore, we experimented two method to neglect the nonlinearity. First is bolting and second is welding at the joint section. We compared computer simulation results and experimental data.