• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.4
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• pp.47-55
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• 2008

Turbocharger has a main purpose on recycling of the exhaust gas from the engine cylinder. On the basis of the facility characteristics, the turbocharger supported on floating ring bearings has some problems such as the large volume, oil supplement for lubrication and high power loss due to high operating torque. The air foil bearing has been studied as the bearing element to be able to alternate the floating ring bearing without the problems of the floating ring bearing. In this study, the air foil bearing has 2 parts; journal and thrust bearings, and the test facility consists of the engine, exhaust and intake parts. In addiction, the specification of the turbocharger follows a small turbocharger for SUV engine. The engine speed is varied from 750 (idle rpm) to 2,500 rpm and then, the rotating speed of the turbocharger rotor is accelerated from 0 to 100,000 rpm. From those experiments, the comparison between the performances of the air foil bearing and floating ring bearing is conducted and the results show that the air foil bearing has less power loss, maximum 770 watt, than the floating ring bearing, maximum 5,110 watt. This result verifies that the air foil bearing is more efficient and able to output more power under the same condition of the input power.

• Journal of Nutrition and Health
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• v.31 no.5
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• pp.939-948
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• 1998

To investigate the relationship between eating behavior and the prevalence of adolescents drug abuse and smoking, this survey was conducted among 349 male students(mean age ; 16.0 $\pm$0.9yrs) at technical high schools in Kyunggi-Do. It was shown that 58.7% of total subjects were smoking and 11.2% were abusing drugs. Drug abusers weighed Less than non-abusers especially, student smokers were 2.7kg lighter than non-smokers despite the same height. Although parents' education showed no relationship with drug abuse, educational level of student smokers' fathers was significantly lower than that of non-smokers' fathers. Drug abusers and smokers showed significantly higher incidence of runaway from home, absence from school without notice, and parents' divorce than non-abusers and non-smokers. Drugs abused were sleeping pills(n=20), bonds and butane gas(n=9), marijuana(n=3), tranquilizer(n=3), morphine and cocaine(n=2), and pep pills like amphetamine(n=2) 76.9% of the drug abusers had their first experience in junior high school and 81% of the smokers stared smoking as early as in junior high school. Also, 44% of the smokers reported that they smoke daily. The drug abusers tended to have more irregular eating habits than the non-abusers. The smokers showed irregular mealtime, ate either too fast or too slow, and especially, often skipped lunch or dinner. The drug abusers and smokers took little vegetable in their meals and often ate bread or noodles instead of rice for staples. In addition, they preferred taste to nutrition when they had meals. The smokers tended to ingest smaller amount of calcium source such as milk or dinner food and fish with bone although they consume more volume of total foods than the non-smokers. All subjects took less in calorie, calcium, iron, vitamin A, vitamin E, riboflavin, and folic acid than the Recommended Dietary Allowance Those findings suggest that drug abuse and smoking cause bad eating habits that influence unbalanced nutritional state. Therefore, nutrition education should be provided to the adolescents so that they can recognize the disadvantages of drug and smoking and its relation to dietary relation. (Korean J Nutrition 31(5) : 939-948, 1998)

• Clinical and Experimental Pediatrics
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• v.45 no.4
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• pp.529-534
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• 2002

Interstitial pneumonia is a heterogenous group of inflammatory and fibrosing lesions that manifest themselves as infiltrative lung disease. Of these, nonspecific interstitial pneumonia is characterized as a variable degree of interstitial inflammation with or without fibrosis and is distinguished from usual interstitial pneumonia and desquamative interstitial pneumonia, histologically. The influx of inflammatory cells and the responses of immune effector cells injury to the alveolar wall and these initial injuries results in alveolitis and fibrosis. Consequently, the gas exchange throughout the alveolar wall is impaired and the patients suffer from lung diseases of a restrictive pattern. The chief complaints represented are dyspnea and dry cough. We experienced a case of nonspecific interstitial pneumonia in a 10-year old girl. The patient had been healthy and had not been exposed to organic dusts or other toxic materials. The pathology of lung biopsy tissue showed that the alveoli were thickened by a mixture of chronic inflammatory cells and collagen type fibrosis. High resolution computed tomography(HRCT) found the patchy areas of ground-glass opacity with patchy consolidation and irregular reticular opacity, and diffuse distribution without zonal predominance. The forced vital capicity(FVC) was 31%, forced expiratory volume in one second ($FEV_1$) 29% and $FEV_1/FVC$ 90%, so a restrictive pulmonary insufficiency was found.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.1
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• pp.16-27
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• 2002

A level-set method is used for analyzing the behaviors of gas bubbles in two fluids incompressible viscous flow domain. The governing equations are solved by using a finite volume method. The numerical results are verified by comparing with the experimental and other computational results. Computations for the deformations and motions of one or multi-bubbles in the flow domain with the initial undisturbed free interface are conducted. It can be seen that numerical results for different surface tension and density ratio arise very different behaviors of bubbles. When bubbles rise near the free interface, the free interface gives some great influence on the behaviors of bubbles. The present results computed by a level-set method give useful information about the properties of bubble motions and deformations.

• Korean Journal of Materials Research
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• v.21 no.1
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• pp.21-27
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• 2011

A nano-porous structure of tin oxide was prepared using an anodic oxidation process and the sample's electrochemical properties were evaluated for application as an anode in a rechargeable lithium battery. Microscopic images of the as-anodized sample indicated that it has a nano-porous structure with an average pore size of several tens of nanometers and a pore wall size of about 10 nanometers; the structural/compositional analyses proved that it is amorphous stannous oxide (SnO). The powder form of the as-anodized specimen was satisfactorily lithiated and delithiated as the anode in a lithium battery. Furthermore, it showed high initial reversible capacity and superior rate performance when compared to previous fabrication attempts. Its excellent electrode performance is probably due to the effective alleviation of strain arising from a cycling-induced large volume change and the short diffusion length of lithium through the nano-structured sample. To further enhance the rate performance, the attempt was made to create porous tin oxide film on copper substrate by anodizing the electrodeposited tin. Nevertheless, the full anodization of tin film on a copper substrate led to the mechanical disintegration of the anodic tin oxide, due most likely to the vigorous gas evolution and the surface oxidation of copper substrate. The adhesion of anodic tin oxide to the substrate, together with the initial reversibility and cycling stability, needs to be further improved for its application to high-power electrode materials in lithium batteries.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.1
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• pp.29-36
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• 2014

Hybrid rocket displays many different low frequency pressure oscillations during combustion. Thermal lag between solid and gas phase is the primary mechanism to trigger low frequency pressure oscillations of around 10Hz, and Helmholtz or $L^*$ mode also produces other types of low frequency oscillations above 10 Hz which is associated with the change in combustion volume. Since the flow characteristics in hybrid rocket is very similar to those in solid rocket combustion, it is not surprising to observe similar pressure oscillation behaviors. Experimental test shows that combustion pressure suddenly turns into to a big amplitude oscillation around 10Hz then followed by returning to an original pressure level after a short period combustion. Further investigations show that this instability is independent of the change in O/F ratio at all. One of the possible candidates is the vortex shedding dynamics over the backward step in the post combustion chamber. It is required to investigate the low frequency oscillation mechanism in the future study.

• Journal of Korea Port Economic Association
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• v.34 no.1
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• pp.35-49
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• 2018

Busan Port handles more than 75% of the domestic freight volume and is ranked at 6th for global shipping in the world. This paper aims to estimate ship emission in North Port that is the center of Busan Port and located near the residential area. The emission for each type of ship is calculated applying a emission model proposed by U.S. EPA and the atmospheric diffusion pattern of the exhaust gas according to the season, the weather condition and the time was identified using CALPUFF Model. As a result, the major pollutants of $NO_x$, $SO_x$ and PM10 were 30,853 tons, 36,281 tons and 6,856 tons, respectively, and the highest rate was 42% in oil tankers. On clear days, air pollution was stagnant around the harbor, spread widely on windy days, and tended to be thinner on rainy days. The research contributes to recognizing the seriousness of air pollution and can be used as basic data for policy making in the future.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.613-617
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• 2001

The test items like as endurance, air leakage and oil endurance test is requested for reliability evaluation about O-ring which is a kind of core machinery accessories of semi-conduct manufacturing equipment. For verification of these, we design and manufactured a test system for endurance, air leakage and oil endurance of O-ring for semi-conduct manufacturing equipment, and also performed the test for two kinds of O-ring, as it were Viton and Kalretz. The characteristics of this test equipment consist in realization of the test conditions of semi-conduct manufacturing equipment and satisfying the test method. The test conditions are cut gas, vacuum grade, temperature and revolution numbers in the endurance test system, vacuum grade and temperature in the air leakage test system, temperature and time in the oil endurance test system. The separating test results for wearing which is an oil endurance test item, the wearing index of domestic produced Viton O-ring is higher than foreign product by 2%, wearing rate of Kalretz O-ring better than Viton O-ring by 17%, and particles existed in various place. The test result of air leakage which is measured through the RGA sensor used Helium, the vacuum grade was $10^-3$Torr. And the test result of oil endurance, the volume change rate was 7~15%. Hereafter, we intend to analysis the reliability test evaluation and to utilize for domestic manufacturing companies by establishing data base and developing reliability softwares.

• Journal of Environmental Health Sciences
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• v.19 no.2
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• pp.23-33
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• 1993

The anaerobic digestion of organic synthetic wastewater in anaerobic fluidized bed bioreactor (AFBBR) and anaerobic fluidized packed bed bioreactor (AFPBBR) was studied. This study was conducted to evaluate efficiency and reliability of two reactor. Experiment was performed to find the effect of upflow rate with AFBBR and the height of packed bed with AFPBBR. As a result, this program obtained several conclusion. These are given as follows: As applied the upflow rate increased in AFBBR the produced volume of biogas increased, while the gas production and COD removal decreased at above 0.3 m$^3$/h. When a upflow rate is 0.4 m$^3$/h in AFBBR the volatile suspended solid (VSS) became significantly increased. At an organic loading rate from 0.1 to 0.4 of upflow rate in AFBBR, the methane yield was 1.5584 m$^3$CH$_4$/kgCOD removed, and the observed cell yield coefficient was 0.0933 gVSS/gCOD. In case of AFPBBR, the results showed also that 20 cm of height of packed bed was superior to other in the aspect ot biogas production, the content of methane and COD removal. At 20 cm of height, the profile of microorganisms was stable, while at 30 cm the VSS of effluent became higher than AFBBR. Though COD removal of AFPBBR increased with packed bed, COD removal deteriorate with over packing because the loss of pressure became higher in the reactor. At an organic loading rate from 20 to 40 cm of packed bed in-AFPBBR, the methane yield was 2.5649 m$^3$CH$_4$/kgCOD removed, and the observed cell yield coefficient was 0.0506 gVSS/gCOD. Based upon the results obtained, it is suggested that AFBBR and AFPBBR is the most effective conditions at 0.3 m3/h of upflow rate, the 20cm of packed bed, respectively. The rate constant are summarized as follow:

• Carbon letters
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• v.13 no.2
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• pp.109-114
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• 2012

A nuclear, biological, chemical (NBC) canister was indigenously developed using active carbon impregnated with ammoniacal salts of copper (II), chromium (VI) and silver (I), and high efficiency particulate aerosol filter media. The NBC canister was evaluated against carbon tetra chloride ($CCl_4$) vapours, which were used as a simulant for persistent chemical warfare agents under dynamic conditions for testing breakthrough times of canisters of gas masks in the National Approval Test of Respirators. The effects of $CCl_4$ concentration, test flow rate, temperature, and relative humidity (RH) on the breakthrough time of the NBC canister against $CCl_4$ vapour were also studied. The impregnated carbon that filled the NBC canister was characterized for surface area and pore volume by $N_2$ adsorption-desorption isotherm at liquid nitrogen temperature. The study clearly indicated that the NBC canister provides adequate protection against $CCl_4$ vapours. The breakthrough time decreased with the increase of the $CCl_4$ concentration and flow rate. The variation in temperature and RH did not significantly affect the breakthrough behaviour of the NBC canister at high vapour concentration of $CCl_4$, whereas the breakthrough time of the NBC canister was reduced by an increase of RH at low $CCl_4$ vapour concentration.