• International Journal of Automotive Technology
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• 제6권5호
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• pp.445-451
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• 2005

Most of the pollutants from passenger cars are emitted during the cold-transient phase of the FTP-75 test. In order to reduce the exhaust emissions during the cold-transient period, it is essential to warm up the catalyst as fast as possible after the engine starts, and the Unburned Exhaust Gas Ignition (UEGI) technology was developed through our previous studies to help close-coupled catalytic converters (CCC) reach the light-off temperature within a few seconds after cold-start. The UEGI system operates by igniting the unburned exhaust mixture by glow plugs installed upstream of the catalyst. The flame generates a high amount of heat, and if the heat is concentrated on a specific area of monolith surface, then thermal crack or failure of the monolith could occur. Therefore, it is very important to monitor the temperature distribution in the CCC during the UEGI operation, so the local temperatures in the monolith were measured using thermocouples. Experimental results showed that the temperature of CCC rises faster with the UEGI technology, and the CCC reaches the light-off temperature earlier than the baseline case. Under the conditions tested, the light-off time of the baseline case was 62 seconds, compared with 33 seconds for the UEGI case. The peak temperature is well under the thermal melting condition, and temperature distribution is not so severe as to consider thermal stress. It is noted that the UEGI technology is an effective method to warm up the catalyst with a small amount of thermal stress during the cold start period.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.35.1-35.1
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• 2009

Vertically aligned zinc oxide (ZnO) nanorods (NRs) with different surface morphology were grown by metal organic chemical vapor deposition (MOCVD) on sapphire substrate. The films thus prepared were characterized by measuring X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) studies. To study the effect of surface morphology on wettability, the contact angle (CA) of water was measured. It was demonstrated that the CA of the deposited ZnO NRs varied between $104^{\circ}$ and $135^{\circ}$ depending upon the surface morphology. Variable temperature photoluminescence (PL) have employed to probe the exciton recombination in high density and vertically aligned ZnO Nanorod arrays. The low-temperature PL characterizes the dominant near-band-edge excitonic emissions from such nanorod arrays.

• 한국분무공학회지
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• 제27권1호
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• pp.11-17
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• 2022

In upcoming Post Stage-V and Tier 5 regulations of construction machineries, nitrogen oxide (NOx) emissions are strictly limited in cold start conditions. In response to this, a method of improving NOx conversion efficiency has been applied by installing an electric heating catalyst (EHC) in front of conventional urea-SCR systems so that the evaporation and thermal decomposition of urea-water solution can be promoted in cold start conditions. In this strategy, the evaporation and thermal decomposition of urea-water solution and corresponding NOx conversion efficiency are governed by temperature conditions inside the EHC. Therefore, characterizing the temperature distribution in the EHC under various operating conditions is crucial for the optimized operation and control of the EHC in Urea-SCR systems. In this study, a 1-D modeling analysis was performed to predict the heater surface temperature distribution in EHC under various operating conditions. The reliability of prediction results was verified by comparing them with measurement results obtained using an infrared (IR) camera. Based on 1-D analysis results, the effects of various EHC operation parameters on the heater surface temperature distribution were analyzed and discussed.

• 분석과학
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• 제24권4호
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• pp.282-289
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• 2011

자동차 내장재에서 방출되는 오염물질들을 평가하는 간편한 방법으로 백을 이용하는 방법이 ISO 12219-2의 방법으로 개발중에 있다. 백을 사용하는 정적 시험방법은 방출시험 시 습도를 조절하지 않기 때문에 습도조건에 민감한 포름알데하이드의 방출시험에는 적당하지 않다. 따라서 이 연구에서는 백을 사용하는 정적 시험방법에서 추가로 수분을 공급하여 시험백안의 상대습도를 조절할 수 있는 가능성 및 상대습도가 포름알데하이드 방출농도에 미치는 영향에 대해 알아보았다. 시험 백 안의 상대습도는 주입한 수분의 양뿐만 아니라 시험백의 재질과 시험편의 종류에 큰 영향을 받았다. 그리고 시험 백 안의 상대습도가 증가할수록 포름알데하이드의 방출강도는 증가했지만 과다한 수분이 공급되면 백 내부 표면이나 시험편의 표면에 여분의 수분이 응축하여 여기에 방출된 포름알데하이드가 재흡수되어 측정된 포름 알데하이드의 방출강도가 낮게 나타났다.

• 한국대기환경학회지
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• 제27권6호
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• pp.663-671
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• 2011

Although a scooter is a convenient transportation means for a short distance traveling with a light package in the congested urban center, it might be one of the significant sources of air pollutants to which many people can easily be exposed during its passing-by. In this paper, we measured concentrations of gases and particles emitted from a scooter at roadside with no other traffic. To understand the characteristics of scooter emissions with respect to driving speed (idling, 30 km/h) at the roadside, total particle number concentration, particle size distribution, average surface area of particles deposited in the alveolar region, and concentrations of black carbon, CO, and $NO_x$ were measured. The concentrations of the particle number, surface area of deposited particles, CO, and $NO_x$ were highly fluctuated in the scooter's idling condition. The trends of particle number concentration, CO, and $NO_x$ generation were similar to one another. When the scooter started to move, all of $NO_x$, CO and particle number concentrations increased and after it passed by at the speed of 30 km/h, the concentration peaks of the particles and gases appeared at the same time. Unimodal size distribution with ~70 and ~93 nm mode diameters was observed for the idling and cruising condition, respectively. From this work, we found that emission from a passing vehicle could be characterized using a roadside monitoring technique.

• Journal of Animal Science and Technology
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• 제58권6호
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• pp.22.1-22.15
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• 2016

Background: Dietary manipulation is a common practice to mitigate gaseous emission from livestock production facilities, and the variation of fat level in the diet has shown great influence on ruminal volatile fatty acids (VFA) and enteric methane generation. The changes in dietary fat levels influence rumen chemistry that could modify manure nutrient composition along with odor and gaseous emissions from manure management facilities. Methods: A field experiment was carried out on beef cattle feedlots to investigate the effect of four levels of dietary fat concentrations (3 to 5.5 %) on the manure composition and gaseous emissions (methane-$CH_4$, nitrous oxide-$N_2O$, carbon dioxide-$CO_2$ and hydrogen sulfide-$H_2S$) from the feedlot pen surface. The experiment was carried out over a 5-month period from June to October during North Dakota's summer-fall climatic condition. Air and manure sampling was conducted five times at a 20-30 day intervals. Results: Overall, this research indicated that fat levels in diet have no or little effect on the nutrient composition of manure and gaseous emission from the pens with cattle fed with different diet. Though significant variation of gaseous emission and manure composition were observed between different sampling periods, no effect of high fat diet was observed on manure composition and gaseous emission. Conclusions: It can be concluded that addition of fat to animal diet may not have any impact on gaseous emission and manure compositions.

• 신재생에너지
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• 제19권1호
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• pp.1-11
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• 2023

A large amount of carbon monoxide (CO) is generated in circulating fluidized bed combustion, the process whereby a hot cyclone separates unburned fuel. However, calcium sulfate (CaSO₄), when combined with a high CO content, can cause fouling on the surface of the steam tube installed inside the integrated recycle heat exchangers (INTREX). In this study, CaSO₄ decomposition was investigated using 0.2-3.2 vol.% CO and 1-3 vol.% oxygen (O₂) at 850℃ for 20 min in a lab-scale fluidized bed reactor. The results show that CaSO₄ decomposes into CaS and CaO when CO gas is supplied, and SO₂ emissions increase from 135 ppm to 1021 ppm with increasing CO concentration. However, the O₂ supply delayed SO₂ emissions because the reaction between CO and O₂ is faster than that of CaSO₄; nevertheless, when supplied with CaCO₃, the intermediate product, SO₂ was significantly released, regardless of the CO and O₂ supply. In addition, agglomerated solids and yellow sulfur power were observed after solid recovery, and the reactor distributor was corroded. Consequently, a sufficient O₂ supply is important and can prevent fouling formation on the INTREX surface by suppressing CaSO₄ degradation.

• 한국기계가공학회지
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• 제21권7호
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• pp.53-63
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• 2022

Recently, the use of aluminum components in the reduction of the vehicle weight to improve fuel efficiency and reduce carbon dioxide emissions has increased. In the aluminum machining cutting process, hole-making is an important process that accounts for 30% of the machining process. Although many studies have been conducted using the continuously advancing hole processing technology, studies on the machinability of the tool depending on the type of chuck on the workpiece are still lacking. In this study, the machining performance of cemented carbide burnishing drills was compared and analyzed according to chuck type. The burnishing drill was used to create a hole in the AL6061 workpiece, and the surface roughness and dimensional accuracy of the hole were examined according to the type of chuck while monitoring the spindle load.

• 한국산림과학회지
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• 제101권2호
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• pp.286-290
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• 2012

산불은 전 세계적으로 다량의 온실가스를 배출하여 지구온난화에 기여한다. 본 연구에서는 산불로 인한 지표층 연료의 연소량과 이로 인한 온실가스 배출량을 분석하고자 하였다. 이를 위해 51개 산불을 대상으로 소나무림과 활엽수림으로 구분하고, 다시 지표화와 수관화 피해 지역으로 나누어 잔존 연료량을 채취하여, 미연소 지역의 연료량과 일원분산분석을 수행하였다. 그 결과 활엽수 지표화 지역은 8,361 kg/ha, 소나무 지표화 지역은 8,055 kg/ha, 소나무 수관화 지역은 12,333 kg/ha이 연소되어, 수종별 산불행태별로 차이가 있었다. 이때의 연소율은 각각 78, 59, 90%이었다. 이산화탄소, 메탄, 아산화질소 등의 온실가스 배출량은 활엽수 지표화 연소지역 15,856 kg/ha, 소나무 지표화 연소지역 14,834 kg/ha, 소나무 수관화 연소지역은 약 22,709 kg/ha이었다.

• 한국환경농학회지
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• 제28권1호
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• pp.15-19
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• 2009

대기중으로 휘산되는 대부분의 암모니아는 농경지에서 시용하는 가축분뇨 퇴비와 질소비료에서 유래한다. 본 연구는 밭 토양에서 돈분 퇴비 시용방법에 따른 암모니아 휘산량을 소형원드터널 방법을 이용해서 정량적으로 평가하였다. 돈분 퇴비(20 Mg/ha) 표층살포(SA), 표층살포 후 즉시 경운(IRA), 표층 살포 3일 후 경운(RA-3d) 처리의 13일 동안 암모니아 휘산량은 각각 28.7, 8.7, 24.3 kg N/ha로 IRA 처리구는 SA 처리구에 비해 70% 저감효과를 가져왔다. 그리고 SA 처리구의 퇴비 처리 후 24시간 이내 휘산된 암모니아 양은 총 휘산량의 61%로 대부분의 암모니아는 시용 초기 짧은 시간 내에 휘산됨을 알 수 있었다. 석회와 퇴비 혼용시용 후 교반(L+C mix), 퇴비표층 살포 3일후 석회시용 교반(C+L3D), 석회시용 3일 후 퇴비시용 교반(L+C3D) 처리구의 22일 동안 총 암모니아 휘산량은 각각 40.1, 31.4, 27.7 kg/ha이었다. 따라서 가축분 퇴비 시용시 석회를 혼용하는 것은 피해야 하며, 만일 동일 작기내 시용이 불가피할 경우는 퇴비시용에 앞서 석회를 먼저 충분한 일수를 앞두고 시용하는 것이 암모니아 휘산량을 저감시킬 수 있다는 결론을 얻었다.