• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.263-270
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• 2010

In this study, an air cleaner is considered to improve comfort, safety, and health of automobile passengers. The performance and installation conditions of the air cleaner have been studied to investigate their effects on the air quality in the cabin room using numerical analysis. A five-passenger sedan and a seven-passenger minivan that have comparatively large indoor volume have been considered. The distributions of the local mean age and the volume averaged age of indoor air are calculated according to the variation of the placement and the air flow of the air cleaner. In addition, a decrease of contamination concentration, especially VOCs(volatile organic compounds), by the air cleaner is numerically analyzed with time-accurate unsteady calculation to quantify the effect of the air cleaner on the indoor air quality. As a result, the effective installation and operation conditions of the air cleaner for the automobile cabin room could be suggested.

• Journal of Environmental Health Sciences
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• v.23 no.4
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• pp.57-66
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• 1997

Successful energy conservation and good indcfor air quality (IAQ) are highly dependent on ventilation system. Air filtration is a primary solution of indoor air control strategies in terms of reducing energy consumption and improving ihdoor air quality. A conventional system with bypass filter, as it is called variable-air-volume/bypass filtration system (VAV/BPFS), is a variation of the conventional variable air volume (VAV) systems, which is designed to eliminate indoor air pollutant and to save energy. Bypass filtration system equipped with a high-efficiency particulate filter and carbon absorbent provides additional cleaned air into indoor environments and maintain good IAQ for human health. The objectives of this research were to compare the relative total decay rate of indoor air pollutant concentrations, and to develop a mathematical model simulating the performance of VAV/BPFS. All experiments were performed in chamber under the controlled conditions. The specific conclusions of this research are: 1. The VAV/BPFS system is more efficient than the VAV system in removing indoor air pollutant concentration. The total decay rates of aerosol, and total volatile organic compound (TVOC) for the VAV/BPFS system were higher than those of the conventional VAV system. 2. IAQ model predictions of each pollutant agree closely with the measured values. 3. According to IAQ model evaluation, reduction of outdoor supply air results in decreased dilution removal rate and on increased bypass filtration removal rate with the VAV/BPFS. As a results, we recommends the VAV/BPFS as an alternative to conventional VAV systems.

• Steel and Composite Structures
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• v.50 no.2
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• pp.183-199
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• 2024

In this paper, a closed-form rigorous solution for interfacial stress in continuous steel beam with variable section strengthened with bonded prestressed FRP plates and subjected to a uniformly distributed load is developed using linear elastic theory and including the variation of fiber volume fractions with a longitudinal orientation of the fibers of the FRP plates. The results show that there exists a high concentration of both shear and normal stress at the ends of the laminate, which might result in premature failure of the strengthening scheme at these locations. The theoretical predictions are compared with other existing solutions. Overall, the predictions of the different solutions agree closely with each other. A parametric study has been conducted to investigate the sensitivity of interface behavior to parameters such as laminate and adhesive stiffness, the thickness of the laminate and the fiber volume fractions where all were found to have a marked effect on the magnitude of maximum shear and normal stress in the composite member. This research gives a numerical precision in relating to the others studies which neglect the effect of prestressed plate and the shear lag impact. The physical and geometric properties of materials are taken into account, and that may play an important role in reducing the interfacial stresses magnitude.

• Environmental Engineering Research
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• v.13 no.4
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• pp.184-191
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• 2008

Long term monitoring was conducted to investigate a surface runoff of pollution from urban highway. The monitoring data was collected for 18 rainfall events and was used to correlate pollution load to various parameters, such as rainfall intensity, antecedent dry days and total discharge flow. Runoff coefficient and seasonal variation were also evaluated. The mean runoff coefficient of the highway was 0.823(range; $0.4687{\sim}0.9884$), and wash-off ratio for $COD_{Mn}$ and SS loads was 72.6% and 64.3%, respectively. For the initial rainfall event, the runoff EMC of $COD_{Mn}$ was high in summer and the EMC of SS was high in autumn season. However the seasonal variation of T-N and T-P was not significant. The discharged $COD_{Mn}$-EMC was $147.6\;mg/L{\sim}9.0\;mg/L$ on the generated $COD_{Mn}$-EMC of $98.8\;mg/L{\sim}8.9\;mg/L$. While the generated EMC of SS was in $285.7\;mg/L{\sim}20.0\;mg/L$ and its discharged EMC was in $190.4\;mg/L{\sim}8.0\;mg/L$. EMC of pollutants was not directly related to the first flush rainfall intensity and the antecedent dry days. But the correlation was relatively high between EMC and cumulative runoff flow volume. The trend of EMC was reduced with the cumulative runoff flow volume.

• Journal of Korea Water Resources Association
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• v.31 no.2
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• pp.209-219
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• 1998

Sea water volume intruded from the lock gated was compted by a one-dimensional numerical model and the extent of diffusion of sea water was evaluated for that. The volume of intruded sea water, in the exchange processes of salt and fresh waters, was computed by the conceptual model considering the tidal level, volume of chamber, volume of canal, and operation period only, It was divided into some cases according to whether ships enter or leave the canal and whether the level of tide is lower or higher than that of water level in canal. The model, developed in this work, assumed that intruded sea water is well mixed in the canal; and complete is the exchange of waters between sea and canal. The simulation case was divided into two categories according to whether the water was added from the Han River or not.

• Journal of Pharmaceutical Investigation
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• v.22 no.4
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• pp.317-321
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• 1992

A high-performance liquid chromatographic (HPLC) method was developed for the determination of diltiazem (DTZ) and its major metabolite, deacetyldiltiazem (DAD), in rat plasma. DTZ, DAD and imipramine, the internal standard, were selectively fractionated from plasma on a $C_{18}$ reversedphase column $({\mu}-Bondapak,\;10\;{\mu}m\;silica,\;300{\times}3.9\;mm\;ID)$. The composition of the mobile phase was methanol: acetonitrile: 0.04 M ammonium bromide: triethylamine (40:24:36:0.06 in volume). The pH of the mobile phase of their method was lowered to 6.4. The eluents from the column were detected for DTZ and DAD using a UV detector at 237 nm. The recovery was >85% for DTZ and DAD, and average intra-day and inter-day coefficients of variation were <6% for DTZ and DAD at the concentration ranges of 20-1000 ng/ml. Detection limit of DTZ and DAD in plasma was 20 ng/ml with signal-to-noise ratio of 3. This method would be applicable to practical pharmacokinetic studies without detriment to the HPLC column.

• YAKHAK HOEJI
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• v.34 no.3
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• pp.206-211
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• 1990

Total suspended particles were collected and size-fractionated by an Andersen high-volume air sampler at Chungang University located near the Han River, Seoul, Korea, during the period form March, 1986 to August, 1986 and from March, 1987 to February, 1988. The concentrations and the particle size distributions of anions such as chloride, nitrate and sulfate were determined by ion chromatography. The averages of concentrations were $125.43\;{\mu}g/m^3$ in 1986 and $189.19\;{\mu}g/m^3$ in 1987 for total suspended particles (TSP), $2.12\;{\mu}g/m^3$ in 1986 and $4.14\;{\mu}g/m^3$ in 1987 for chloride, $4.39\;{\mu}g/m^3$ in 1986 and $5.95\;{\mu}g/m^3$ in 1987 for nitrate and $11.98\;{\mu}g/m^3$ in 1986 and $19.29\;{\mu}g/m^3$ in 1987 for sulfate. Size distribution of TSP was found to be generally bimodal. Chloride exhibited a seasonal variation in the distribution; fine particles were predominant in the winter whereas the concentration of coarse ones was almost same through four seasons. Nitrate showed a distribution similar to that of chloride. Such variation was less significant for sulfate. For chloride and nitrate, the relationship between the monthly averaged distribution pattern and air temperature was analyzed in terms of fine fraction (FF). The FF decreased with increasing air temperature.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.3 s.234
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• pp.330-339
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• 2005

An experimental study on the behavior of droplets impinging on a solid flat surface was carried out in the present study. Breakup of a liquid droplet impinging on a solid surface has been investigated experimentally for various liquids with different properties. The liquid droplet temperature and incident angle were chosen as major parameters. Liquid droplet temperature and incident angle varied in the range from $-20{\circ}C\;to\;30{\circ}C\;and\;from\;30{\circ}\;to\;60{\circ},$ respectively. It was found that the variation of droplet temperature influences upon the mean diameter and uniformity of droplets which were bounced out from the solid surface. With increase of incident angle the dispersion mass fraction increases, causing the decrease of liquid film flow rate. As the liquid temperature increases, dispersion mass fraction increases since the surface tension decreases.

• Journal of Korean Society of Forest Science
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• v.103 no.1
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• pp.105-112
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• 2014

The main purpose of this study is to measure spatio-temporal variation of forest tree volume based on the RCP(Representative Concentration Pathway) 8.5 scenario, targeting on Pinus densiflora forests which is the main tree species in South Korea. To estimate nationwide scale, $5^{th}$ forest type map and National Forest Inventory data were used. Also, to reflect the impact of change in place and climate on growth of forest trees, growth model reflecting the climate and topography features were applied. The result of the model validation, which compared the result of the model with the forest statistics of different cities and provinces, showed a high suitability. Considering the continuous climate change, volume of Pinus densiflora forest is predicted to increase from $131m^3/ha$ at present to $212.42m^3/ha$ in the year of 2050. If the climate maintains as the present, volume is predicted to increase to $221.92m^3/ha$. With the climate change, it is predicted that most of the region, except for some of the alpine region, will have a decrease in growth rate of Pinus densiflora forest. The growth rate of Pinus densiflora forest will have a greater decline, especially in the coastal area and the southern area. With the result of this study, it will be possible to quantify the effect of climate change on the growth of Pinus densiflora forest according to spatio-temporal is possible. The result of the study can be useful in establishing the forest management practices, considering the adaptation of climate change.

• The Korean Journal of Pharmacology
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• v.12 no.1
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• pp.15-22
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• 1976

The clinical abuse of C.N.S. stimulants during recent years has directed particular attention. Effect of various organs other than C.N.S. was also extensively investigated with those agents. It has been shown that, although there is a wide variation in sensitivity between species, caffeine stimulates gastric secretion in man, cat, guinea pig and dog. Roth and Ivy(1944) reported that caffeine and histamine acted synergistically in stimulating gastric secretion in the cat. Vaille et al(1966) studied that production of pancreatic juice in the rat was enhanced, but bile secretion was not affected by caffeine. In clinical study the effect of chlorpromazine on the external pancreatic secretion in the 24 subjects, the volume fell more than 20% in 7 subjects. (Skajaa et al 1960) It is widely known that C.N.S. stimulants enhanced spontaneous motor activity in the mice, while tranquilizers depressed the activity. Woo (1975) reported that the group of mice treated with chlorpromazine showed markedly inhibited motor activity and in the group of mice treated with amphetamine, there was a significant increase in the motor activity. The purpose of the present experiment was to study the effects of C.N.S. stimulants and depressant on the exocrine pancreas, and on the spontaneous motor activity in the rats. The results obtained are summarized as follows. 1. In animals treated with xanthine derivatives, the volume of pancreatobiliary secretion was markedly increased. 2. Total bilirubin output was elevated markedly in the xanthine derivatives and imipramine treated animals. The bilirubin concentration was increased in xanthine derivatives treated group. 3. The concentration of cholate in the bile was decreased in the chlorpromazine treated group. 4. The activity of lipase in the pancreatobiliary juice was elevated markedly in the xanthine derivatives treated group only. 5. In the all experimental groups, the activity of amylase in pancreatobiliary juice was significantly elevated. 6. In the caffeine treated group, spontaneous motor activity was markedly increased in $30{\sim}60$ minutes, and the amphetamine treated group showed the increased motor activity in first 30 minutes. 7. The group of rats treated with chlorpromazine showed markedly inhibited motor activity after 30 minutes, and the imipramine treated group showed similar result but less inhibition.