• 한국환경보건학회지
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• 제28권2호
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• pp.183-192
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• 2002

Indoor air quality is affected by source strength of pollutants, ventilation rate, decay rate, outdoor level and so on. Although technologies exist to measure these factors directly, direct measurements of all factors are impractical in most field studies. The purpose of this study was to develop an alternative methods to estimate these factors by multiple measurements. Daily indoor and outdoor NO$_2$concentrations for 21 days in 20 houses in summer and winter, Seoul. Using a mass balance model and linear regression analysis, penetration factor (ventilation divided by sum of air exchange rate and deposition constant) and source strength factor(emission rate divided by sum of air exchange rate and deposition constant) were calculated. Subsequently, the ventilation and source strength were estimated. During sampling period, geometric mean of natural ventilation was estimated to be 1.10$\pm$1.53 ACH, assuming a residential NO$_2$decay rate of 0.8 hr$^{-1}$ in summer. In winter, natural ventilation was 0.75$\pm$1.31 ACH. And mean source strengths in summer and winter were 14.8ppb/hr and 22.4ppb/hr, respectively. Although the method showed similar finding previous studies, the study did not measure ACH or the source strength of the house directly. As validation of natural ventilations, infiltrations were measured with $CO_2$tracer gas in 18 houses. Relationship between ventilation and infiltration was statistically correlated (Pearson r=0.63, p=0.02).

• Journal of Korean Society for Atmospheric Environment
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• 제24권E1호
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• pp.32-43
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• 2008

Source samples were collected to construct source profiles for 9 different source types, including soil, road dust, gasoline/diesel-powered vehicles, a municipal incinerator, industrial sources, agricultural/biomass burning, marine aerosol, and a coal-fired power plant. Seasonal profiles for 'Chinese aerosol', aerosols derived from the urban area of China, were reconstructed from seasonal $PM_{2.5}$ compositions reported in Beijing, China. Ambient $PM_{2.5}$ at a receptor site was also measured during each of the four seasons, from April 2001 to February 2002, in Seoul. The Chemical Mass Balance receptor model was applied to quantify source contributions during the study period using the estimated source profiles. Consequently, motor vehicle exhaust (33.0%), in particular 23.9% for diesel-powered vehicles, was the largest contributor affecting the $PM_{2.5}$ levels in Seoul, followed by agricultural/biomass burning (21.5%) and 'Chinese aerosol' (13.1%), indicating contributions from long-range transport. The largest contributors by season were: for spring, 'Chinese aerosol' (31.7%); for summer, motor vehicle exhaust (66.9%); and for fall and winter, agricultural/biomass burning (31.1% and 40.1%, respectively). These results show different seasonal patterns and sources affecting the $PM_{2.5}$ level in Seoul, than those previously reported for other cities in the world.

• 한국환경과학회지
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• 제15권10호
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• pp.913-918
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• 2006

Despite the wide distribution of air pollutants, the concentrations of indoor air pollutants may be the dominant risk factor in personal exposure due to the fact that most people spend an average of 80% of their time in enclosed buildings. Researches for improvement of indoor air quality have been developed such as installation of air cleaning device, ventilation system, titanium dioxide$(TiO_2)$ coating and so on. However, it is difficult to evaluate the magnitude of improvement of indoor air quality in field study because indoor air quality can be affected by source generation, outdoor air level, ventilation, decay by reaction, temperature, humidity, mixing condition and so on. In this study, evaluation of reduction of formaldehyde and nitrogen dioxide emission rate in indoor environments by $TiO_2$ coating material was carried out using mass balance model in indoor environment. we proposed the evaluation method of magnitude of improvement in indoor air quality, considering outdoor level and ventilation. Since simple indoor concentration measurements could not properly evaluate the indoor air quality, outdoor level and ventilation should be considered when evaluate the indoor net quality.

• Journal of Obesity & Metabolic Syndrome
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• 제27권4호
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• pp.203-212
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• 2018

Dynamic energy balance can give clinicians important answers for why obesity is so resistant to control. When food intake is reduced for weight control, all components of energy expenditure change, including metabolic rate at rest (resting energy expenditure [REE]), metabolic rate of exercise, and adaptive thermogenesis. This means that a change in energy intake influences energy expenditure in a dynamic way. Mechanisms associated with reduction of total energy expenditure following weight loss are likely to be related to decreased body mass and enhanced metabolic efficiency. Reducing calorie intake results in a decrease in body weight, initially with a marked reduction in fat free mass and a decrease in REE, and this change is maintained for several years in a reduced state. Metabolic adaptation, which is not explained by changes in body composition, lasts for more than several years. These are powerful physiological adaptations that induce weight regain. To avoid a typically observed weight-loss and regain trajectory, realistic weight loss goals should be established and maintained for more than 1 year. Using a mathematical model can help clinicians formulate advice about diet control. It is important to emphasize steady efforts for several years to maintain reduced weight over efforts to lose weight. Because obesity is difficult to reverse, clinicians must prioritize obesity prevention. Obesity prevention strategies should have high feasibility, broad population reach, and relatively low cost, especially for young children who have the smallest energy gaps to change.

• Journal of Biosystems Engineering
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• 제37권2호
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• pp.82-89
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• 2012

Purpose: The simulation model of a pneumatic conveying drying (PCD) for sawdust was developed and verified with the experiments. Method: The thermal behavior and mass transfer of a PCD were modeled and investigated by comparing the experimental results given by a reference (Kamei et al. 1952) to validate the model. Momentum, energy and mass balance, one dimensional first order ordinary differential equations, were coded and solved into Matlab V. 7.1.0 (2009). Results: The simulation results showed that the moisture content reduced from 194% to 40% (dry basis), air temperature decreased from $512^{\circ}C$ to $128^{\circ}C$ with the particle residence time of 0.7 seconds. The statistical indicators, root mean square error and R-squared, were calculated to be 0.079, and 0.998, respectively, between the measured and predicted values of moisture content. The relative error between the measured and predicted values of the final pressured drop, air temperature, and air velocity were only 8.96%, 0.39% and 1.05% respectively. Conclusions: The predicted moisture content, final temperature, and pressure drop values were in good agreement with the experimental results. The developed model can be used for design and estimation of PCD system for drying of wood dust particles.

• 한국지하수토양환경학회지:지하수토양환경
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• 제24권4호
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• pp.11-19
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• 2019

This paper examines an assessment method for terminating the post-closure maintenance of a landfill using a simplified landfill gas model. The case study site is the Sudokwon Landfill in Incheon city, which was closed in 2000. The deviations of the results obtained by the regular model and the simplified model were both slightly over 10% from the measured data. Also, the deviation of the simplified model from the regular model has been less than 5% since 2005. Thus, the simplified model could be applied to other landfills that have been closed for at least 5 years. Additionally, the results of the mass balance analysis using the simplified landfill gas model indicated that 39% of the organic carbon was discharged, leading to organic carbon and organic matter content of 7.2 and 17.6%, respectively, in the landfill by the end of 2018.

• Journal of Microbiology and Biotechnology
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• 제21권12호
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• pp.1257-1263
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• 2011

This paper is dedicated to the study on the external and internal mass transfers of glucose for succinic acid fermentation under substrate and product inhibitions using a bioreactor with stirred bed of immobilized Actinobacillus succinogenes cells. By means of the substrate mass balance for a single particle of biocatalysts, considering the kinetic model adapted for both inhibitory effects, specific mathematical models were developed for describing the profiles of the substrate concentration in the outer and inner regions of biocatalysts and for estimating the substrate mass flows in the liquid boundary layer surrounding the particle and inside the particle. The values of the mass flows were significantly influenced by the internal diffusion velocity and rate of the biochemical reaction of substrate consumption. These cumulated influences led to the appearance of a biological inactive region near the particle center, its magnitude varying from 0 to 5.3% of the overall volume of particles.

• 대한기계학회논문집B
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• 제28권1호
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• pp.24-30
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• 2004

Analysis model for the two-phase catalytic reactor is presented. With the progress in development of micro thermofluidic devices, needs fur understanding of the phenomena in two phase reaction in cm scale has been arisen. To investigate thermal and reactive performance of down scaled two phase reactor simple analysis model that is a kind of lumped flow model is proposed. Analysis model presented is based on the experiment on mm scale model reactor. Target experiment is catalytic decomposition of 70wt％ hydrogen peroxide with existence of perovskite L $a_{0.8}$S $r_{0.2}$Co $O_3$ catalyst. It is composed of balance equations of mass and energy. Each phase is considered to be a species fur the simplicity. Axial diffusion and transversal distribution of properties are neglected. Two phase catalytic reaction is modeled as successive gasification of liquid lump around catalyst and reaction in gas phase. Heat transfer is modeled by model function ofNu number. Modeled Nu is expressed as Nu=N $u_{0}$ (1＋ $a_1$( $a_2$ $T^{-}$ $a_3$)exp( $a_4$ $T^{-1}$)exp( $a_{5}$ z). Transfer coefficients are determined by the comparison of experimental results. With the model, heat transfer characteristics are investigated. Also by the mass transfer coefficient, characteristics in mass transfer is investigated. With the result basic understanding on design and analysis of mm scale two-phase reactive device is obtained. Also it can be further applied to micro scale reactive device fabricated by micromachining.ing..

• 한국수자원학회논문집
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• 제38권3호
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• pp.223-233
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• 2005

본 연구에서는 분포형 모형과 셀의 유입, 유출 및 저류량에 대한 질량보존의 법칙을 이용하여 토사의 이송 및 퇴적분포예측기법을 개발하였다. 모형은 (a) 토사침식 예측 (b) 흐름방향 및 유출량 산정 그리고 (c) 토사에 대한 질량보존의 법칙에 따른 셀별 토사이동량 산정의 세 단계로 구성되었다. 토양침식은 범용토양손실공식(USLE)을 활용하였으며 분포형 모형에서의 경사장(L) 산정은 일방향(SF)과 다방향 흐름 알고리즘(MF)을 사용하였다. 경사(S) 산정을 위해서는 Maximum Downhill Slope Method (MDS) and the Neighborhood Method (NBH) 기법을 활용하였고 셀별 토양의 이동은 Ferro등(1998)과 Swift (2000)의 토사전달률(DR)개념을 적용하였다. 개발된 모형은 시험유역의 실측 토사량과의 비교검토를 통하여 검증하였다. 3개의 농업용 저수지 유역에 적용한 결과, Ferro의 토사전달률 산정공식과 MDS, MF 기법을 이용한 해석이 저수지의 운영기록과 가장 유사한 결과를 제시한다는 사실을 확인할 수 있었다.

• 대한한의학회지
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• 제42권4호
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• pp.185-196
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• 2021

Objectives: Many symptoms of cold and heat patterns are related to the thermoregulation of the body. Thus, we aimed to study the association of cold and heat patterns with anthropometry/body composition. Methods: The cold and heat patterns of 2000 individuals aged 30-55 years were evaluated using a self-administered questionnaire. Results: Among the anthropometric and body composition variables, body mass index (-0.37, 0.39) and fat mass index (-0.35, 0.38) had the highest correlation coefficients with the cold and heat pattern scores after adjustment for age and sex in the cold-heat group, while the correlation coefficients were relatively lower in the non-cold-heat group. In the cold-heat group, the most parsimonious model for the cold pattern with the variables selected by the best subset method and Lasso included sex, body mass index, waist-hip ratio, and extracellular water/total body water (adjusted R² = 0.324), and the model for heat pattern additionally included age (adjusted R² = 0.292). Conclusions: The variables related to obesity and water balance were the most useful for predicting cold and heat patterns. Further studies are required to improve the performance of prediction models.