• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2012년도 한국컴퓨터종합학술대회논문집 Vol.39 No.1(A)
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• pp.179-181
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• 2012

본 연구는 NAND 플래시 기반의 임베디드 시스템에 warm-start 개념을 도입하여 재부팅 시간을 단축시키는 방법에 관한 연구이다. NAND 플래시 기반의 임베디드 시스템에서는 부팅 시 커널 이미지를 NAND 플래시에서 DRAM으로 로드하는 과정이 필요하다. 최근 SoC (System-On-Chip)는 "software reset" 기능을 지원하며 DRAM의 내용을 훼손하지 않고 시스템을 리셋하는 것이 가능하다. 우리는 이 기능을 이용하여 DRAM 상에 이미 로드되어 있는 커널 요소를 재부팅 시에도 다시 사용하도록 구현하고, 그에 따라 중복된 커널 요소의 로드를 제거했다. 이 기법을 우리는 KWS(Kernel-Warm-Start) 라는 이름으로 정의했다. KWS 에서는 부팅이 재부팅인 경우 필요한 커널 요소만을 로드한다. 결과적으로 재부팅 시 커널 요소의 로드 크기를 89.29% 감소시킬 수 있었고, 재부팅 시간을 첫 번째 부팅에서 75.47% 단축할 수 있었다.

• 경영과학
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• 제21권1호
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• pp.77-86
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• 2004

In this paper, we present a methodology for solving the multicommodity network flow problems using interior point methods. In our method, the minimum cost network flow problem extracted from the given multicommodity network flow problem is solved by primal-dual barrier method in which normal equations are solved partially using preconditioned conjugate gradient method. Based on the solution of the minimum cost network flow problem, a warm-start point is obtained from which Castro's specialized interior point method for multicommodity network flow problem starts. In the computational experiments, the effectiveness of our methodology is shown.

• 한국전문물리치료학회지
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• 제3권2호
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• pp.49-54
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• 1996

The purposes of this study were to measure skin temperature and blood flow on the contralateral upper extremity when heat is applied to one upper extremity, were to compare the effect of contrast bath. The subjects were 38 healthy adults with no history of peripheral vascular disease. The subjects of contrast bath were 18 persons and the subjects of warm bath were 20 persons. The subjects of one group were seated with their right arm in water($42^{\circ}C$) up to the mid-forearm. The subjects of the other group were seated with their right arm up to the mid-forearm in water which was changed from warm to cold using the contrast bath technique. The continually changing temperatures and blood flow were measured by an independent observer at intervals of 10, 15, 20, 25 and 30 minutes respectively after the start of the procedure. The results were as follows. The temperature of the warm bath group rose 4.28% over the pre-experimental temperatures and the temperature of the contrast bath group rose 3.41%. There was no statistically significant difference between the two groups. The blood flow of the warm bath group rose 8.31% over the pre-experimental blood flow and the blood flow of the contrast bath group rose 17.24%. There was a statistically significant between the two groups 20 minutes after the start of the procedure. Thus the contrast bath is a more effective method than the warm bath to increase blood flow.

• 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.

• 한국자동차공학회논문집
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• 제20권4호
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• pp.25-32
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• 2012

Cold start driving cycles exhibit an increases in friction losses due to the low temperatures of metal components and media compared to the normal operating engine conditions. These friction losses are adversely affected to fuel economy. Therefore, in recent years, various techniques for the improvement of fuel economy at cold start driving cycles have been introduced. The main techniques are the upward control of coolant temperature and the fast warm-up techniques. In particular, the fast warm-up techniques are implemented with the coolant flow-controlled water pump and the WHRS (waste heat recovery system). This paper deals with an effect of fast ATF (automatic transmission fluid) warm-up on fuel economy using a recovery system of EGR gas waste heat in a diesel engine. On a conventional diesel engine, two ATF coolers have been connected in series, i.e., an air-cooled ATF cooler is placed in front of the condenser of air conditioning system and a water-cooled one is embedded into the radiator header. However, the new system consists of only a water-cooled heat exchanger that has been changed into the integrated structure with an EGR cooler to have the engine coolant directly from the EGR cooler. The ATF cooler becomes the ATF warmer and cooler, i.e., it plays a role of an ATF warmer if the temperature of ATF is lower than that of coolant, and plays a role of an ATF cooler otherwise. Chassis dynamometer experiments demonstrated the fuel economy improvement of over 2.5% with rapid increase in the ATF temperature.

• 한국자동차공학회논문집
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• 제9권6호
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• pp.103-111
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• 2001

During cold-start period, the reduction of exhaust emissions is a challenging task. To decrease harmful gaseous substances such as HC, it is necessary to realize a fast catalyst warm-up. In this study, the performance of dual pipe exhaust system have been carried out through different test mode. From measurement of gas temperature and HC concentration, the following conclusions were derived ; 1) Compared with single pipe, dual pipe exhaust system remarkably increase temperature of exhaust gas going through M.C.C(Main Catalytic Converter). 2) W.C.C.(Warm-up Catalytic Converter) also decreases HC emission. To reduce HC emission, it is helpful to use W.C.C. as well as dual pipe exhaust system. 3) Using finite element method, it is shown that inner parts have much higher distribution of temperature than outer parts.

• 한국자동차공학회논문집
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• 제19권6호
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• pp.53-60
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• 2011

The effect of exhaust heat recovery system can be evaluated by two well known method. First method is to measure the time duration from engine start under cold coolant temperature till coolant get warmed. By this methodology coolant warming duration can be index of warm-up effect. Second method is to analyze heat balance of the engine during warm-up phase under steady engine operation so that wasted energy by losses such as cooling and exhaust can be index of warm-up effect. This study focused on evaluation of warming-up effect by both methodology above mentioned using 2L SI engine under from idle to 2000rpm steady condition. Results, idle operation showed low heat recovery efficiency but under higher engine speed condition, remarkable heat recovery efficiency improvement was observed. In 2000rpm steady condition, warm-up duration of engine is decreased by exhaust heat recovery system.

• 플랜트 저널
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• 제10권1호
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• pp.47-53
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• 2014

1887년 경복궁 건천궁에서 최초로 전기점등 행사를 시행한 이후 2012년 11월 기준의 대한민국 발전설비 용량은 81,737 MW, 그리고 2012년도 최대전력 수요는 71,230 MW로 이전기록을 경신한 바 있다. 이렇게 급속하게 증가하는 전력수요를 충족하기 위하여 정부에서는 대용량 유연탄 화력과 원자력발전소를 건설하여 운영 중에 있으나 전력수요는 주중에 집중되고 주말에는 급감하여 주말의 예비률이 40% 이상을 상회하고 있어 양수발전기를 이용하여 주말수요를 창출하는 한편 감소된 주말의 전력수요에 맞추어 서울화력발전소을 포함한 고원가 발전소에 대한 주말정지를 시행하고 있다. 서울화력발전소는 전력수요지의 중심지인 수도 서울에 위치하였음에도 발전원가가 높아 2008년도 이후 매년 30회 이상의 주말정지를 시행함으로 기동정지 과정에서 많은 비용을 지출하고 있어 본 연구에서는 1969년 준공하여 열병합설비로 개조한 서울화력발전소 제5호기를 대상으로 온간기동 과정에서 보일러 강제순환펌프 입구 관수온도 상승률을 증가시켜 온도상승 공정에 소요되는 시간을 약 35% 단축하고 기동시간 종합관리 프로그램을 구성하여 운영함으로써 전체적으로 온간기동 시간을 23% 단축할 수 있음을 확인하였다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2001년도 제23회 KOSCO SYMPOSIUM 논문집
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• pp.169-178
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• 2001

Among the recent research ideas to reduce hydrocarbon emissions emitted from SI engines till light-off of catalyst since cold start are those exploiting non-thermal plasma technique and photo-catalyst that draws recent attention by virtue of its successful application to practical use to clean up the atmosphere using the feature of its relative independence on temperature. Based on the previous research results obtained with model exhaust gases using an experimental emissions reduction system that utilizes the non-thermal plasma and photo-catalyst technique, further investigation was conducted on a production N/A 1.5 liter DOHC engine during cold start to warm-up. For the effects of non-thermal plasma-photocatalyst combined reactor, 10% concentration reduction was achieved with the fuel component paraffins, and the large increase in non-fuel paraffinic components and acetylene concentrations were similar to those of base condition. However the absolute value was locally a bit higher than those of base condition since the products was made from the dissociation and decomposition of highly branched paraffins by plasma-photocatalyst reactor. Olefinic components were highly decomposed by about 75%, due to these excellent decompositions of olefins which have relatively high MIR values, and the SR value was 1.87 that is 30% reduction from that of base condition, then, the photochemical reactivity was lowered.

• International Journal of Automotive Technology
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• 제7권7호
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• pp.763-768
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• 2006

Emission reduction in the cold start period of SI engines is crucial to meet stringent emission regulations such as SULEV Emissoin reduction is the starting point of the study in the which the variable valve timing (VVT) technology may be one promising method to minimize cold start emissions while maintaining engine performance. This is because it is possible to change valve overlap and residual gas fraction during cold start and idle operations. Our previous study showed that spark timing is another important factor for reducing cold-start emissions since it affects warm-up time of close-coupled catalysts (CCC) by changing exhaust gas temperature. However, even though these factors may be favorable for reduction of emissions, they may deteriorate combustion stability in these operating conditions. This means that the two variables should be optimized for best exhaust emissions and engine stability. This study investigated the effects of valve and spark timings in idle performance such as combustion stability and exhaust emissions. Experiments showed that valve timings significantly affected engine stability and exhaust emissions, especially CO and $NO_x$, due to change in residual gas fraction within the combustion chamber. Spark timing also affects HC emissions and exhaust gas temperature. Yet it has no significant effects on combustion stability. A control strategy of proper valve timing and spark timing is suggested in order to achieve a reduction in exhaust emissions and a stable operation of the engine in a cold start and idle operation.