• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.04a
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• pp.41-46
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• 1996

The engine intake system noise has been recognized as a problem for many years. Acoustic design of intake system has traditionally been a trial and error process. This has resulted in the development of computer simulation program for a acoustic analysis and acoustic modeling. In this study, we developed the program based on the transfer matrix method which analyze and predict the performance of a intake noise. The program was verified by experiments on a real intake system. By using of the simulation program, we analyzed acoustic characteristics and, made proposals of improvement to reduce the intake noise and was verified by the SYSNOISE software.

• Korean Journal of Community Nutrition
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• v.20 no.1
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• pp.61-72
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• 2015

Objectives: This study was performed to examine nutrition problems and causes/contributing risk factors. Methods: This study was conducted using data 1,863 adults visited Asan health screening & promotion center located in Seoul, Korea during May to June of 2013. We used Nutrition Care Process Model developed by the International Dietetics & Nutrition Terminology (IDNT). Results: The most frequent nutrition problem in male subjects was excessive alcohol intake. Men in fifties showed the highest rate of excessive alcohol intake among the age groups examined (22.4%). By comparison, the most frequent nutrition problem in women was inadequate protein intake. Women in fifties exhibited the highest rate of inadequate protein intake (22.5%). The most common contributing factors for these observations were a low preference for dairy products followed by high preference for alcohol and a deficit in food-and nutrition-related knowledge, regardless of the sex and age. The most common nutrition problem observed among the group diagnosed with hyperglycemia or hypertriglyceridemia or hyperuricemia or fatty liver was excessive alcohol intake (p < 0.001), whereas the group diagnosed with hyperglycemia or hypercholesterolemia showed significantly higher rate of inappropriate intake of carbohydrate (fructose) compared to the group not diagnosed with such disease conditions (p < 0.05). The group diagnosed with hypercholesterolemia, hyperuricemia and fatty liver showed significantly higher occurrence of inappropriate intake of fat (saturated fat) than the group free of such diseases (p < 0.001). The osteopenia group showed higher rate of inadequate protein intake (p < 0.001) and the fatty liver group with excessive energy intake (p < 0.001). Overall, the results suggest that there is a significant relationship between nutrition problems and health conditions found in groups diagnosed with a diverse array of medical conditions. Conclusions: Therefore, we strongly suggest that dieticians should implement nutrition interventions with people visiting health screening & promotion center based on nutrition problems and the contributing factors diagnosed by dietitions in order to prevent chronic diseases in this population.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.1
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• pp.15-26
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• 1997

The present study is mainly motivated to numerically simulate the autoignition and combustion process of a diesel spray in RCM and effects of design parameters on combustion and engine performance in the DI diesel engine using EGR. In case of the burning spray in RCM, special emphasis is given to the autoignition process coupled with the fluid mechanics and chemical reaction. Computations are carried out for a wide range of operating condition in terms of temperature, concentration of oxygen and carbon dioxide of the intake gas in the DI diesel engine. Numerical results indicate that the mixing process along the edges of spray jet has a crucial role for autoignition and combustion process. Temperature and concentration of O2 and CO2 of intake gas significantly influence the combustion characteristics and engine performance in the diesel/EGR environment.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.992-997
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• 2003

The flow characteristics along a intake/compression process are very important for the combustion process. The intake/compression flow fields are related to the piston shape of engine. The flow fields are analysed by using the ICEM-CFD IC3M code for the rapid mesh-generation and by using the STAR-CD code for the calculations. The influences of the piston bowl shapes were investigated. The results showed that piston shapes had influences on a intake/compression flow and offered the definite basic data in a design side.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.77-83
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• 1996

Noise control process of an air intake system for a four-cylinder automotive engine is described. The objective of the process is reduction of induction noise without losing engine performance and changing package layout. The theory and feasibility for noise control elements are also discussed. In general, four-cylinder engines generate a lower frequency induction noise around 80-150 Hz (2400-4500 rpm) and firing frequency, valve impact noise are the main sources. In this paper, the most problematic noise source is identified first and better position of air inlet is selected between inside-fender and out-of-fender layouts. Secondly, the possible noise control approach and CAE analysis results are compared to those from speaker excitation tests. Finally, the effect of the controlled intake system after the installation to an automobile is presented.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.10
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• pp.761-768
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• 2008

This paper is the first of 2 companion papers which investigate in-cylinder swirl generation characteristics in helical port engine with wide valve angle. Two wide valve-angle engines, which are same ones and have slightly different rig swirl number, were used to compare the characteristics of cylinder-flow. One intake port is deactivated to induce swirl flow. A PIV (Particle Image Velocimetry) was applied to measure in-cylinder velocity field during intake stroke. The results show that the intake flow component passing through valve area near the cylinder wall is not negligible in helical port engine with wide valve angle contrary to conventional one. The effect of this velocity component on in-cylinder increases as the swirl ratio rises and intake process progresses. Consequently, this component interferes the formation of in-cylinder swirl flow resulting in lower actual swirl.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.2
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• pp.391-398
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• 1998

The intake noise, a major source of vehicle noises, has rapidly become a noticeable, and has been studied to reduce the level. Traditionally, the intake system has been developed through the road test and the experiment using a engine dynamo, namely, the trial and error process. This approach require very high cost and long time consuming to develop the system. In this study, the simulator which had a speaker in the cylinder head was presented. It was easy to analyze the acoustic characteristic of the intake system in laboratory environment. This study presented a improvement to reduce the level of the intake noise using the Transfer Matrix Method and NIT/SYSNOISE, FE analysis commercial software. It was to select optimum position of a resonator and verified by the simulator. This simulator can be used early in the design stage of development of the intake system.

• Journal of Power System Engineering
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• v.10 no.3
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• pp.11-16
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• 2006

The pressure fluctuation in the intake and exhaust pipe of 4 stroke-cycle diesel engine is caused by reciprocating motion of piston for suction of fresh air and exhaust of burned gas. this gas dynamic effect can be utilized for increase the volumetric efficiency. Many empirical studies have been carried out to investigate the effects of intake pulsating flow on the volumetric efficiency. However, when the gas dynamic effects are utilized for the variable speed engine to increase its performance, The speed range in which the maximum volumetric efficiency is limited and there occurs some difficulties in lay-out of intake system because it become too long. During induction process, as waves travel both directions, they are reflected and interacted each other and pressure waves are transmitted through it. Hence, the flow becomes more complex and unsteady flow. These pressure waves act upon intake pulsating flow and affects on the volumetric efficiency. In this paper the effects of pulsating flow of intake and exhaust pipes on volumetric efficiency were examined and evaluated. It was found that volumetric efficiency was affected by pulsating flow of intake and exhaust pipes.

• Nutrition Research and Practice
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• v.16 no.sup1
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• pp.47-56
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• 2022

This paper examines the process and evidence used to create the Dietary Reference Intake (DRI) of alpha-linolenic acid (ALA) and eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) for Koreans. ALA (18:3n3) is an essential fatty acid, and EPA and DHA are known to have beneficial effects on cardiovascular disease risk and reduction of triglyceride levels. Various international organizations have suggested dietary recommendations for n-3 polyunsaturated fatty acids (PUFAs), including ALA, EPA, and DHA. A DRI for Koreans was established for the first time in 2020, specifically for the adequate intake (AI) of ALA and EPA + DHA. This recommendation was based on the average intake of ALA and EPA + DHA from the Korea National Health and Nutrition Examination Survey 2013-2017. For Korean infants, the AI of ALA and DHA was based on the fatty acid composition of maternal milk. Estimated average requirement and a tolerable upper intake level have not been set for n-3 PUFA due to insufficient evidence. In addition, the intake level of n-3 PUFA for prevention of chronic disease has also not been determined. Future studies and randomized controlled trials are required to establish the UL and to define the level for disease prevention.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.3
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• pp.24-32
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• 1995

The scavenging characteristics have a great influence on the performance of a diesel engine, especially slow-speed two-stroke diesel engines which are usually used as a marine propulsion power plant, and they are greatly affected by the conditions in the cylinder, intake and exhaust manifolds, and the opening and closing timing of scavenging ports or exhaust valves during the gas exchange process. Besides, there are many other factors to affect the scavenging characteristics and these factors interact each other very complicatedly. Therefore the simulation program of the gas exchange process is very useful to improve and predict the scavenging characteristics, due to the high costs associated with redesign and testing. In this paper it was attenpted to investigate the effect of the variation of the pressure ratio of intake to exhaust manifolds, and the variation of the opening and closing timing of a exhaust valve by using a computational program for a three-zone scavenging model which was developed by authors. The computed results showed that the scavenging efficiency and delivery ratio increased considerably, but the trapping efficiency decreased with increasing of the pressure ratio of intake to exhaust manifolds. The scavenging efficiency, trapping efficiency, and th conditions of the cylinder gases were affected by the opening timing of the exhaust valve, but the delivery ratio by the closing timing.