• 대한기계학회논문집B
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• 제35권2호
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• pp.121-127
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• 2011

희박 공연비에서 동작하는 디젤 엔진은 NOx 를 저감시키기 위해서 주기적으로 과농한 분위기를 형성해 주어야 한다. 최근 배기관 내에 환원제로서 경유를 직접 분사하는 HC-LNT 방식이 활발히 연구되고 있다. 이러한 연구는 NOx 저감을 위해 HC 의 농도를 제어하는 기술로서, 실제 배기관내에 HC 가 균일하게 분포하여야 촉매의 정화효율이 향상되므로 HC 를 균일하게 분사하는 방법의 최적화가 가장 중요하다. 본 연구에서는 저압에서 미립화 특성이 양호한 가솔린 흡기포트 분사용 인젝터를 이용하여, 가시화 방법으로 실제 배기관내에서의 환원제 분무 거동 특성을 측정하였고 NOx 정화 특성간의 관계를 실험적으로 비교함으로써, 인젝터의 최적 부착 조건과 분사 조건을 파악하였다.

• International Journal of Automotive Technology
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• 제3권1호
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• pp.41-46
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• 2002

Effect of secondary air injection (SAI) on hydrocarbon reduction has been investigated in a single cylinder Sl engine operating at cold-steady/cold-start conditions. The hydrocarbon emission and exhaust gas temperature with and without catalytic converter were compared with continuous and synchronized SAIs, which injected secondary air intermittently into exhaust port. Effects of SAI location, SAI pressure, SAI timing, and location of catalytic converter have been investigated and the results are compared for both SAls with base condition. At cold-steady condition, the rate of HC reduction increased as the location of SAI was closer to the exhaust valve for both synchronized and continuous SAls. The emission of HC decreased with increasing exhaust-A/F when it was rich, and was relatively insensitive when it was lean. The timing of SAI in synchronized SAI had significant effect on HC reduction and exhaust gas temperature and the synchronized SAI was found to be more effective in HC reduction and exhaust gas temperature compared to the continuous SAI . At cold-start condition, when the catalytic converter was located 20 cm downstream from the exhaust port exit, the catalytic converter warm-up period for both SAls decreased by about 50%, and the accumulated hydrocarbon emission during the first 120 s decreased about by 56% and 22% with the synchronized and continuous SAIs, respectively, compared to that of the base condition.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3108-3113
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• 2008

This paper investigated the behaviors of combustion characteristics at part load condition with various intake charge motions induced by the port masking schemes in the CVVT (Continuously Variable valve Timing) engine. Time resolved in-cylinder and exhaust emissions were measured by the fast response HC and NOx analyzers to examine their formation mechanisms and behavior characteristics. As a result, in-cylinder HC decreased with the advanced intake valve timings but HC at the exhaust port increased due to the worse combustion stabilities. However HC reduction could be achieved by the application of the port maskings with a enhancement of the engine stability. NOx also decreased with early intake timings by internal EGR but increased with the charge motion controls which enhance the combustion behavior.

• 한국수소및신에너지학회논문집
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• 제23권3호
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• pp.199-206
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• 2012

HC-SCR was conducted over Co-Pt/ZSM5 catalyst coated over 200 cpsi cordierite in the condition of atomspheric pressure and $200^{\circ}C-500^{\circ}C$. Weight ratio of Co/Pt determined from EDX analysis was 8/2, which was almost equal to the weight ratio at preparation step. XPS showed that nitrates within cobalt precursor and chlorine withn Pt precursor were removed. TEM result demonstrated that crystallite size of cobalt and Pt was under 5nm. Among these tested hydrocarbon reductants, isobutane ($i-C_4H_{10}$) showed the highest de-$NO_x$ yield of 80% under the condition of the mole ratio of reductant/NOx=1.0 at $180^{\circ}C$. De-$NO_x$ yield from HC-SCR was increased as the carbon number of hydrocarbon reductant was increased. The decrease of bonding energy between C and H of HC reductant played a role to increase of de-$NO_x$ yield, which indicated that the dissociation step of C-H bond of hydrocarbon molecule might be the rate determining step of HC-SCR. The increase of oxygen concentration in the feed resulted in the decrease of de-$NO_x$ yield but the increase of CO and $N_2O$ yield.

• 한국자동차공학회논문집
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• 제20권5호
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• pp.130-137
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• 2012

Automotive engines need strategies to satisfy with the emission regulations in terms of PM and NOx. HC-LNT (Hydrocarbon-Lean NOx Trap) with secondary injection system is considered as more practical technology in order to cope with emission regulations. The HC-LNT system, which is using diesel fuel itself as a reducing agent, absorbs NOx in lean exhaust gas condition and releases NOx in rich exhaust gas conditions. In this system, inappropriate amounts of reducing agent will slip through the LNT without the profits of conversion and cause additional emission problems. Therefore, the suitable amount of reducing agent should be supplied into the catalytic converter. In this research, engine emission test was conducted to optimize injection quantity at the various engine test conditions. Different exhaust layouts and catalyst shapes have been studied and extension unit which makes better uniformity of exhaust gas was used for HC-LNT system. From this results, the effect of secondary injection conditions on NOx conversion characteristics of HC-LNT was clarified.

• 한국식품영양과학회지
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• 제20권2호
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• pp.94-102
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• 1991

This study was directed to further clarify the effect of resting time or dietary condition for the improvement of exercise capacity and physical fitness, and the changes of some body consitiuents and physiological functions which are related to the exercise metabolism. Sixteen male students(8 athletes and 8 nonathletes)were participated during 3 weeks(Aug. 20-Sep.9, 1989). Each subject performed two treadmill running trials at an absolute intensity (1 mintute in 3.4mph/15% slope and 2 minutes in 5.5mph/20% slope). In the resting time trials, general diet was fed before 1, 2, 4 and 12 hours of the treadmill exercise loaded. in the dietary condition trials, high carbohydrate(HC), high fat(HF) and high protein(HP) diet were fed before 2 hours of the treadmill exercise loaded. Control trial was that of resting time before treadmill exercise loaded after 12 hours of general diet feeding. Measurement were made to study the change of blood glucose, palmitate, lactate, blood pressure and heart rate. The results obtained are summarized as follows: Mean daily metabolizable period. In resting time trial, the blood glucose concentration of athlete and nonathlete from 2 hours group was similar to control group. The blood palmitate concentration of athlete was increased in 1 and 2 hours group but those of nonathlete was not only increased in 1 and2 hours group but was more increased in 12 hours group, compared with both control group. The blood lactate concentration was increased in all experimental group, compared with both control group and those of nonathlete was much higher than athlets. The elevation rate of blood pressure in pre-and after-exercise of athlete was lower than those of nonathlete. In dietary composition trial, the blood glucose concentration of athlete and nonathlete in HC group was higher than other diet groups. The blood lactate concentration of athlete and nonathlete in HC group was lower than other diet groups. There was no remarkable change of the blood palmitate concentration and heart rate in each dietary composition trial, but those of nonathlete was low in HC and high in HP group. In above results, it was suggested that the effective condition of resting time and dietary composition for the improvement of exercise capacity of nonathlete may be 2 hours and HC diet, respectively. But it was showed that the exercise capacity of athlete may not be affected by experimental condition of resting time, except 1 hour after feeding or of dietary composition because of well adaptation in new exercise condition.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.945-949
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• 2001

This study is an experimental study on the characteristics of emission by changing catalytic converter position for cold-start. The measurements are done a changing of the distance between exhaust manifold and catalytic converter. It measured temperature of exhaust manifold, before and after catalytic converter at each position of experimental condition. and measured the characteristics of emission which is HC, CO, $CO_{2}$ and lambda at each position of experimental condition. The results show a few advantage about reduction of HC and CO as catalytic converter's temperature is raised quickly as closed exhaust manifold. but $CO_{2}$ has not the same trend of HC and CO. From measurement value of lambda, reduction effects of $NO_{x}$ are known a few advantage as increase of the distance between exhaust manifold and catalytic converter.

• 한국응용곤충학회지
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• 제28권3호
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• pp.105-112
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• 1989

누에(Bombyx mori)와 흰불나방(Hyphantria cunea)으로 부터 분리된 핵다각체병바이러스(nuclear polyhedrosis virus: NPV)를 동정하기 위하여 전자현미경 관찰한 결과, BmNPV 다각체의 크기는 $3 \mu\textrm{m}$ 정도의 18면체로 외형이 균일하였으나, HcNPV는 1.5-$2 \mu\textrm{m}$ 정도이며 부정형이었다. Alkaline protease를 부활화시킨 후 SDS-PAGE한 다각체 단백질의 分子물은 BmNPV가 30 KD, HcNPV는 31 KD인 major band와 이들의 중합체(polymer)로 생각되는 57 KD, 112 KD의 minor band들이 관찰되었다. 또한 virion 단백질을 SDS-PAGE한 후 은염색한 결과, BmNPV는 분자량 9.6~112 KD인 47개의 band, HcNPV 경우는 분자량 9.4~l11 KD인 48개는 band가 관찰되었다. BmNPV와 HcNPV DNA의 제한효소 처이에 의한 전기영동 패턴을 관찰했으며, 각각의 genome 크기는 BmNPV가 약 116.4 Kb, HcNPV의 약 114.6 Kb였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2910-2915
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• 2008

This paper was investigated the behaviors of the engine and combustion phenomena for various LPG compositions in the semi-return type system, which is not recircurated to LPG tank through furl rail, applied LPi engine during a cold idle condition and including a cold start of the engine. Cyclic HC and NOx emissions were measured at exhaust port to examine their formation mechanical and reduction mechanical with fast response gas analyzers. Various ignition timing is experimented to study the characteristics of combustion phenomena, HC/NOx emissions during fast idle. Also, this study was investigated start delay time, cylinder pressure, HC/NOx emissions, Mass Fraction Burned, starting time to evaluate performance of transient cold startability. Compared to the return type system, the semi-return type system have advantages in point of production cost and equivalent performance of engine starting time and pressure settling time.

• The Korean Journal of Physiology and Pharmacology
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• 제24권3호
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• pp.249-257
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• 2020

The aim of the present study was to investigate the pathophysiological etiology of osteoarthritis that is mediated by the apoptosis of chondrocytes exposed to 25-hydroxycholesterol (25-HC), an oxysterol synthesized by the expression of cholesterol-25-hydroxylase (CH25H) under inflammatory conditions. Interleukin-1β induced the apoptosis of chondrocytes in a dose- dependent manner. Furthermore, the production of 25-HC increased in the chondrocytes treated with interleukin-1β through the expression of CH25H. 25-HC decreased the viability of chondrocytes. Chondrocytes with condensed nucleus and apoptotic populations increased by 25-HC. Moreover, the activity and expression of caspase-3 were increased by the death ligand-mediated extrinsic and mitochondria-dependent intrinsic apoptotic pathways in the chondrocytes treated with 25-HC. Finally, 25-HC induced not only caspase-dependent apoptosis, but also induced proteoglycan loss in articular cartilage ex vivo cultured rat knee joints. These data indicate that 25-HC may act as a metabolic pathophysiological factor in osteoarthritis that is mediated by progressive chondrocyte death in the articular cartilage with inflammatory condition.