• Journal of the Korean Society of Industry Convergence
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• v.4 no.2
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• pp.193-198
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• 2001

2성분계 혼합물(1,2-dichloropropane + 2-methoxyethanol)에 대해 과잉몰 부피(excess molar volumes) $V^E$ 및 과잉 몰엔탈피(excess molar enthalpies) $H^E$를 298.15K에서 측정하였다. 혼합물의 밀도측정은 digital vibrating tube densimeter를 이용하였고, 과잉 몰엔탈피는 isothermal flow microcalorimeter를 이용하였다. 측정한 과잉 몰부피는 전 조성 영역에서 양의 편차를 나타내었으며, 과잉 몰엔탈피는 S 자형용 보였다. 또한 얻어진 data는 Nelder- Mead의 simplex method를 이용하여 Redlich-Kister 다항식에 접합 (fitting)하였다.

• Applied Chemistry for Engineering
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• v.8 no.1
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• pp.140-145
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• 1997

Carbon dioxide hydrogenation reaction was carried out over hybrid catalyst composed of $Cu/ZnO/ZrO_2$, and MFI zeolites such as HZSM-5, H-Ga-Silicate and H-Fe-Silicate. The hybrid catalyst composed of $Cu/ZnO/ZrO_2$, catalyst and HZSM-5 showed the highest yield and selectivity to $C_2{^+}$ hydrocarbon, which seemed to be due to the largest amount of Br nsted acid sites. Higher yield to $C_2{^+}$ hydrocarbon was obtained over HZSM-5 with lower $SiO_2/Al_2O_3$ ratio and also with longer ion exchange time, which showed larger amount of Br nsted acid sites, respectively. When a metal ion was exchanged into HZSM-5, the highest yield to $C_2{^+}$ hydrocarbon was obtained with descending order $Ga/HZSM-5{\simeq}HZSM-5>Zn/HZSM-5$, i.e., with the amount of $Br\ddot{o}nsted$ acid sites.

• Archives of Pharmacal Research
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• v.26 no.3
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• pp.224-231
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• 2003

The anti-thrombotic effects of LB30057, a direct thrombin inhibitor, were evaluated with in vivo rat and dog thrombosis models. In rats, 1 mg/kg of LB30057 inhibited half of the clot formations in the inferior vena cava at 5 minutes after intravenous application. When measured at 2 hours after oral application, 100 mg/kg prevented approximately half of the clot formations in the inferior vena cava and 50 mg/kg prolonged the mean occlusion time from $15.6{\pm}1.3$ minutes to $47.2{\pm}8.3$ minutes in the carotid artery. In dogs, the formation of thrombus in the jugular vein was reduced to half at a dose range of 20-30 mg/kg at 6 hours after oral application. In addition, the LB30057 dosage required to reduce venous clot formation by approximately 80-90% in dogs was only about 10% of that required for the same reduction in rats. This is probably due to the variation in its time-dependent blood concentration profiles in each species; for example, the plasma half-life of LB71350 in dogs was longer than that in rats ($153.0{\pm}3.0$ vs. $129.7{\pm}12.7$ min at 30 mg/kg, i.v., respectively). AUG, $T_{max},{\;}G_{max}$, and BA in dogs were 59, 8.9, 9.17, and 13.3 times higher than those in rats at oral 30 mg/kg, respectively. Taken together, these results suggest that LB30057 administered orally is effective in the prevention of arterial and venous thrombosis in rats and dogs. It therefore represents a good lead compound for investigations to discover a new, orally available, therapeutic agent for treating thrombotic diseases.

• Applied Chemistry for Engineering
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• v.7 no.3
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• pp.464-472
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• 1996

The mechanism of thin-film formation by Ionized Cluster Beam Deposition(ICBD) was investigated. A simulation program based on the Monte-Carlo method was developed in order to investigate the effects of the acceleration voltage, substrate temperature, activation energy for the surface migration, and critical nuclei size on grain size and surface roughness. Studies of the effect of kinetic energy of clusters on the film formation processes revealed that high acceleration voltage enhanced the surface-migration of adatoms and made it easier for an epitaxial film to be formed. The relaxation time of kinetic energy of adatoms increased with the substrate temperature, which in turn increased the grain size of the crystalline film. This effect was more clearly distinguished when the critical nuclei size was large. The surface-migration activation energy was found to affect the interaction between the adatoms and the substrate and thus the relaxation time of kinetic energy. Investigations of the surface roughness revealed that the acceleration voltage, the substrate temperature, and the surface-migration activation energy exerted a collective effect on the morphology of the film surface.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.31 no.3 s.52
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• pp.227-235
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• 2005

Skin aging is not a disease nor an abnormal phenomenon but a collection of degenerative changes with age, characterized by skin dryness, wrinkle formation, and loss of skin elasticity. The skin wrinkles are caused by either genetically predisposed factors or environmental factors such as UV irradiation or physical/chemical stimulus. The histological manifestations of wrinkles are changes in both amount and integrity of elastic and collagen fibers. Here we report the isolation and characterization of 3 active compounds, prangenidin, 8-hydroxybergapten, and xanthotoxol from Angelica dahurica root. The anti-wrinkle activities of these compounds were also investigated.

• Membrane Journal
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• v.10 no.1
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• pp.39-46
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• 2000

To predict the absorption behavior of carbon dioxide on membrane contactor, an aqueous potassium carbonate solution as an absorbent. The reversible reactions of carbon dioxide with chemicals were considered, and the physicochemical properties of reaction rate constants, equilibrium constants, solubilities and diffusion coefficients were used as a function of concentration of carbon dioxide and the temperature. A non-wetted mode was also used as an operating condition of the membrane contactor. In these operation conditions, the effect of the following system parameters were studied : the concentration of potassium carbonate, the velocity of the absorbent and the pressure of the mixture gas. The absorption behavior of carbon dioxide caused by a facilitated transport was observed as the increment of the concentration of the absorbent. The absorption rate of carbon dioxide was increased as the absorbent velocity was increased. Furthermore, it was found that the pressure if the mixture gas and the reuse number of absorbent affect severely the absorption rate of carbon dioxide. The absorption behavior was successfully predicted by the computer simulation using the system parameters which are important for design and operation of the membrane contactor.

• Solar Energy
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• v.15 no.3
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• pp.29-38
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• 1995

The heat-storage characteristics accompanied by exothermic reaction at the regeneration of $Ca(OH)_2$ in tile heat-storage mode of a chemical heat pump system using a $Ca(OH)_2/CaO$ reversible thermochemical reaction was examined in a lab-scale unit. In this heat-storage mode, the particle bed of CaO could be regenerated by heating the $Ca(OH)_2$ packed bed to the higher temperature at which the equilibrium pressure in the reactor is greater than the water vapor pressure in the condenser. The results are i) the dehydration, thermal decomposition, rate of $Ca(OH)_2$ was higher at the lower part of particle bed than at the upper part, ii) in the reactor, the dehydration was proceeded along radial and axial direction, from inner part to the outer part, which explains heat transfers from the center to wall and from the tenter to lower or upper part of reactor.

• Journal of Environmental Health Sciences
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• v.43 no.3
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• pp.223-232
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• 2017

Objectives: In response to increased interest in the safety of children's products, a risk management system is being prepared through exposure assessment of hazardous chemicals. To estimate exposure levels, risk assessors are using deterministic and probabilistic approaches to statistical methodology and a commercialized Monte Carlo simulation based on tools (MCTool) to efficiently support calculation of the probability density functions. This study was conducted to analyze and discuss the usage patterns and problems associated with the results of these two approaches and MCTools used in the case of probabilistic approaches by reviewing research reports related to exposure assessment for children's products. Methods: We collected six research reports on exposure and risk assessment of children's products and summarized the deterministic results and corresponding underlying distributions for exposure dose and concentration results estimated through deterministic and probabilistic approaches. We focused on mechanisms and differences in the MCTools used for decision making with probabilistic distributions to validate the simulation adequacy in detail. Results: The estimation results of exposure dose and concentration from the deterministic approaches were 0.19-3.98 times higher than the results from the probabilistic approach. For the probabilistic approach, the use of lognormal, Student's T, and Weibull distributions had the highest frequency as underlying distributions of the input parameters. However, we could not examine the reasons for the selection of each distribution because of the absence of test-statistics. In addition, there were some cases estimating the discrete probability distribution model as the underlying distribution for continuous variables, such as weight. To find the cause of abnormal simulations, we applied two MCTools used for all reports and described the improper usage routes of MCTools. Conclusions: For transparent and realistic exposure assessment, it is necessary to 1) establish standardized guidelines for the proper use of the two statistical approaches, including notes by MCTool and 2) consider the development of a new software tool with proper configurations and features specialized for risk assessment. Such guidelines and software will make exposure assessment more user-friendly, consistent, and rapid in the future.

• Journal of Food Hygiene and Safety
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• v.35 no.6
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• pp.607-617
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• 2020

Human bio-monitoring (HBM) data is a very important resource for tracking total exposure and concentrations of a parent chemical or its metabolites in human biomarkers. However, until now, it was difficult to execute the integration of different types of HBM data due to incompatibility problems caused by gaps in study design, chemical description and coding system between different sources in Korea. In this study, we presented a standardized code system and HBM knowledge model (KM) based on relational database modeling methodology. For this purpose, we used 11 raw datasets collected from the Ministry of Food and Drug Safety (MFDS) between 2006 and 2018. We then constructed the HBM database (DB) using a total of 205,491 concentration-related data points for 18,870 participants and 86 chemicals. In addition, we developed a summary report-type statistical analysis program to verify the inputted HBM datasets. This study will contribute to promoting the sustainable creation and versatile utilization of big-data for HBM results at the MFDS.

• Applied Chemistry for Engineering
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• v.8 no.5
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• pp.860-865
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• 1997

Brown rice oil contains palmitic acid, linolenic acid, linoleic acid, oleic acid, stearic acid, tocopherol, squalene, etc. The oil including essential fatty acids was extracted from the domestic brown rice bran using supercritical carbon dioxide(SCC) process, and the extracts were analyzed with GC-MSD. The extraction amount of brown rice oil was dependent upon the operating pressure and temperature, and the fatty acid composition of oil was varied with the reduced density(${\rho}_{\gamma}$) of the SCC. About 70~80% of brown rice oil was extracted in 4 hours. Especially, squalene which was not found in solvent extract phase was identified in supercritical fluid extraction phase only.