• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.677-684
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• 2013

A mixed refrigerant cycle (MRC) has been widely used in liquefaction of natural gas because it is simple and easily operable with reasonable equipment costs. One of the important techniques in MRC is selection of a refrigerant mixture and decision of its optimum mixing ratio. In this work, it is examined whether mixture components (refrigerants) and their mixing ratio influence performance of general MRC processes. In doing this, mixture design and response surface method, which are well-known statistical techniques, are used to find optimal mixture refrigerants and their optimal mixing ratio that minimize total energy consumption of the entire liquefaction process. A MRC process using several refrigerants and various mixing ratios is simulated by Aspen HYSYS and mixture design and response surface method are implemented using Minitab. According to the results, methane ($C_1$), ethane ($C_2$), propane ($C_3$) and nitrogen ($N_2$) are selected as best mixture refrigerants and the determined mixture ratio (mole ration) can reduce total energy consumption by up to 50%.

• Journal of Community Nutrition
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• v.4 no.3
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• pp.187-194
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• 2002

This study was investigated the effects of exercise and supplementation of L-carnitine and antioxidants on hepatic mitochondrial function, especially oxidative phosphorylation (OXPHOS). Isolated hepatic mitochondria from 4 rat groups were functionally tested by an analysis of respiration and the coupling of this process to ATP synthesis in the presence of ADP. Four groups were non-trained, non-supplemented group (NTNS), non-trained, supplemented group (NTS), long term-trained, non-supplemented group (LTNS) , and long term-trained, supplemented group (LTS). The trained rats run on a treadmill (grade 10°,20 m/min) for 60min/day for 8 weeks. The supplemented rats were treated with L-carnitine (0.5% diet), vitamin E(0.5mg/g BW), vitamin C (0.5mg/g BW) and melatonin (1 $\mu$ g/g BW) for 8 weeks. There were exercise effects on improving mitochondrial OXPHOS. Within non-supplemented groups, exercised rats resulted in a significant decrease in state 4 oxygen consumption, which increased the respiratory control (RC) ratio and ADP : O (P/O) ratio. There were supplementation effects on improving mitochondrial OXPHOS, too. Within non-exercised rats, supplemented rats resulted in a significant decrease in state 4 oxygon consumption. which increased the RC ratio and P/O ratio. There were additive effects of exercise and supplementation on OXPHOS. Within supplemented rats, exercise resulted in an increase in RC ratio. Significant effects of exercise-supplement interaction on improving OXPHOS were identified. It suggests that exercise and supplementation of L-carnitine and antioxidants might improve more efficiently the impaired OXPHOS efficiency in mitochondrial dysfunction that recognized as is an important cause of degenerative diseases. (J Community Nutrition 4(3) : 187∼194, 2002)

• Journal of Korean Society of Water and Wastewater
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• v.32 no.6
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• pp.527-533
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• 2018

Microorganisms detected in the biofilm not only cause secondary pollution of drinking water such as taste, odor and pathogenic disease but also increase the amount of disinfectant due to microbial regrowth during the transportation of tap water. In this work, the influence of C/N ratio in tap water on the characteristics of biofilm growth was examined. The C/N ratio of the tap water sample was controlled at 100:5, 100:10, 100:20, 100:30, and 100:40 by adding appropriate amounts of dextrose and $(NH_4)_2SO_4$. Of the five C/N ratios, heterotrophic plate counts (HPC) was highest at the ratio of 100:10. Following the initial formation in all the five experimental conditions, natural detachment of the biofilm was observed. Extracellular enzyme activity (EEA) analyses showed that the change of the EEA during the experimental period was similar to that of the HPC, demonstrating a positive correlation between HPC and EEA. For TOC concentration in the tap water sample, approximately 75% of the TOC was consumed in 7 days of the experiment and 96% in 28 days. The TOC appeared to be relatively rapidly consumed at the initial phase of the biofilm growth. Consumption pattern of the ammonia nitrogen was different from the TOC consumption pattern showing the different role of ammonia nitrogen on the growth of biofilm.

• Health Policy and Management
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• v.30 no.3
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• pp.366-375
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• 2020

Background: The purpose of this study is to investigate association between harms from the alcohol consumption of others and depression measured by Patient Health Questionnaire-9, perceived stress among Korean adults. Methods: This study used data from the 7th Korea National Health and Nutrition Examination Survey (2016-2018; n=9,668). We used multivariate survey logistic regression analysis in order to investigate the association. Results: Among participants, 5.55% had experience for harms from the alcohol consumption of others. Among them, 15.25% had depression and 8.97% had perceived stress. Multivariate survey logistic regressions revealed that objective depression and perceived stress were associated with harms from the alcohol consumption of others (objective depression: odds ratio [OR], 3.30; 95% confidence interval [CI], 2.32-4.70; perceived stress: OR, 2.04; 95% CI, 1.62-2.56). Conclusion: Objective depression and perceived stress was significantly associated with harms from the alcohol consumption of others. This study suggests that government agencies and policy makers should recognize current status, further, develop a plan to identify the causes of harms from the alcohol consumption of others and protect vulnerable groups.

• Journal of Nutrition and Health
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• v.30 no.10
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• pp.1211-1218
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• 1997

This study was performed to assess the consumption of various seasonings (SNG), which are usually omitted from food frequency questionnaire(FFQ), and their contributions to nutrient intake levels. A dietary survey with FFQ , which surveyed the intake of 65 mainly uncooked food items, was conducted for 493 adults over 30 years of age from 373 households in a rural area of Korea. Household consumption of major SNG items-garlic , red pepper powder, fermented soy bean paste, oil, soy sauce , salt, etc- were estimated by a questionnaire completed by the housewives of the survey participants. The daily consumption of SNG items by each subject was determined by 3 methods ; dividing daily household consumption by \circled1 the number of household members. \circled2 the number of household members over 10 years of age and \circled3 the weighted number of houshold members calculated by the ratio of the RDA for energy. All three methods for calculating the daily personal consumption of seasoning gave similar results, which may have been partly due to the homogenity of family age distribution of the households in the study area. Therefore, the results of method \circled1 were used to determine the contribution of SNG to nutrient intake of subjects in this study. Daily intake of all nutrients were significantly increased by including SNG consumption in the measurements as compared to measuring intake by FFQ alone (p0.01). Percentages of total daily nutrient intake from SNG ranged from 2.3% in carbohydrate to 34.4% in fat. Nutrients with higher contributions from SNG were energy (8.4%), fat (34.4%), Fe(20.55) and $\beta$-carotene(17.9%). These results indicate that SNG consumption can contribute significantly to the intake of several nutrients and must be considered in surveys using FFQ.

• Korean Journal of Community Nutrition
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• v.29 no.4
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• pp.253-264
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• 2024

Objectives: This study investigated the association between eating habits and the utilization of dietary supplements (DSs) according to food-related lifestyle (FRL) among Korean adults. Methods: This study included a total of 300 participants (150 men and 150 women) in their 20s to 60s living in Seoul and Gyeonggi Province. We identified two groups by factor and cluster analysis: an 'active pursuit' group and a 'passive pursuit' group. Differences in eating habits and DS utilization between the two groups were analyzed by chi-square test and t-test. Logistic regression analysis was used to analyze the effect of variables on DS consumption according to FRL. Results: There were significant differences between the two groups in terms of age, alcohol drinking frequency, total dietary score, change in DS consumption after coronavirus disease 2019, and current DS consumption (P < 0.05). The proportion who perceived many health benefits of DSs was higher in the 'active pursuit' group than in the 'passive pursuit' group (P = 0.003). The most commonly consumed type of DSs was multivitamins & minerals for the 'active pursuit' group, and omega-3 fatty acids for the 'passive pursuit' group. The 'an active pursuit' group consumed DSs 2.93 times more (95% confidence interval [CI]: 1.44-5.97) compared to the 'passive pursuit' group, after adjusting for confounders. In the 'active pursuit' group, the health pursuit (odds ratio [OR] = 6.54, 95% CI: 1.44-29.61) and rational consumption pursuit factors (OR = 0.26, 95% CI: 0.08-0.83) were associated with DS consumption, whereas only the health pursuit factor had a significant association (OR = 5.37, 95% CI: 2.08-13.88) within the 'passive pursuit' group. However, total dietary score and DSs consumption did not show a relationship. Conclusions: By understanding the consumption characteristics of DSs according to FRL, this can serve as basic data necessary for promoting health through the utilization of DSs and healthy behaviors.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.05a
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• pp.57-60
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• 2002

Recently, the coal ash production has been increased by increase of consumption of electric power. So it is important to find a reclaimed place and treatment utility for treating coal ash. Accordingly, in this study we performed an experimental study to compare and analyze the Properties of concrete according to W/C and bottom ash replacement ratio. As a result of this study, it was found that the bleeding content was decreased according to decrease of W/C and increase of bottom ash replacement ratio, and the compressive strength of concrete using bottom ash was similar to plain concrete(replacement ratio 0%).

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.699-704
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• 2002

Recently, the coal ash production has been increased by increase of consumption of electric power. So it is important to find a reclaimed place and treatment utility for treating coal ash. Accordingly, in this study we performed an experimental study to compare and analyze the properties of concrete according to W/C and bottom ash replacement ratio. As a result of this study, it was found that the bleeding content was decreased according to decrease of W/C and increase of bottom ash replacement ratio, and the compressive strength of concrete using bottom ash was similar to plain concrete(replacement ratio 0%).

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.4
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• pp.27-33
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• 2001

In this study, it is observed that the distribution of combustion chamber volume affects the volumetric efficiency. The distribution ratio was adjusted by controlling combustion chamber volume of head and piston bowl one. Four cases were investigated, which are the combination of different distribution ratios and different compression ratios (9.8-10.0). A commercial SOHC 3-valve engine was modified by cutting the bottom face of the head and/or replacing the piston by the one that has different volume. The result shows that the less the head side volume, the more volumetric efficiency is achieved under the same compression ratio. It is also observed that increasing volumetric efficiency results in early knock occurrence due to increased "real" compression ratio. To consider reliability in estimating the volumetric efficiency, we examined the sensitivity of the AFR equation to possible errors in emission measurements. It is shown that the volumetric efficiency, which is calculated by measuring AFR and fuel consumption, can be controlled in 1% error. 1% error.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.2
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• pp.57-62
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• 2000

The effect of exhaust gas recirculation(EGR) on the characteristics of exhaust gas emissions, and SFC are experimentally investigated by four-cylinder, four-cycle and direct injection marine diesel engine. In order to reduce the soot contents in the recirculated exhaust gas to intake system of the engines, a soot removal system of a cylinderical-type scrubber is specially designed and manufactured for the experimental system. (1) SFC is increased in downward convex curve style with increasing excess air ratio, it is increased with increasing EGR rate at the same excess air ratio. (2) NOx emission is reduced in downward convex curve style with increasing excess air ratio, it is reduced with increasing EGR rate at the same excess air ratio. (3) Soot emission is decreased in downward convex curve style with increasing excess air ratio, it is reduced with increasing EGR rate at the same excess air ratio. (4) CO emission is increased in nearly straight line style with increasing excess air ratio, it is increased with increasing EGR rate at the same excess air ratio. (5) HC emission is not constant tendency with increasing excess air ratio, it is increased with increasing EGR rate at the same excess air ratio.