• Journal of Korean Society for Atmospheric Environment
• /
• v.24 no.1
• /
• pp.91-99
• /
• 2008

A multilayer tower-type photoreactor, in which $TiO_2$-coated glass-tubes were installed, was used to measure the vapor-phase BTEX removal efficiencies by ozone oxidation ($O_3$/UV), photocatalytic oxidation ($TiO_2$/UV) and the combination of ozone and photocatalytic oxidation ($O_3/TiO_2$/UV) process, respectively. The experiments were conducted under various relative humidities, temperatures, ozone concentrations, gas flow rates and BTEX concentrations. As a result, the BTEX removal efficiency and the oxidation rate by $O_3/TiO_2$/UV system were highest, compared to $O_3$/UV and $TiO_2$/UV system. The $O_3/TiO_2$/UV system accelerated the low oxidation rate of low-concentration organic compounds and removed organic compounds to a large extent in a fixed volume of reactor in a short time. Therefore, $O_3/TiO_2$/UV system as a superimposed oxidation technology was developed to efficiently and economically treat refractory VOCs. Also, this study demonstrated feasibility of a technology to scale up a photoreactor from lab-scale to pilot-scale, which uses (i) a separated light-source chamber and a light distribution system, (ii) catalyst fixing to glass-tube media, and (iii) unit connection in series and/or parallel. The experimental results from $O_3/TiO_2$/UV system showed that (i) the highest BTEX removal efficiencies were obtained under relative humidity ranging from 50 to 55% and temperature ranging from 40 to $50^{\circ}C$, and (ii) the removal efficiencies linearly increased with ozone dosage and decreased with gas flow rate. When applying Langmuir-Hinshelwood model to $TiO_2$/UV and $O_3/TiO_2$/UV system, reaction rate constant for $O_3/TiO_2$/UV system was larger than that for $TiO_2$/UV system, however, it was found that adsorption constant for $O_3/TiO_2$/UV system was smaller than that for $TiO_2$/UV system due to competitive adsorption between organics and ozone.

• Korean Journal of Food Science and Technology
• /
• v.42 no.6
• /
• pp.733-738
• /
• 2010

The leaves of Zizyphus jujuba have been used for various purposes including medicine and nutrition. In this study, the conditions for the ethanol extraction of antioxidant from Zizyphus jujuba were optimized using response surface methodology (RSM). A Box-Behnken design containing 15 experimental runs with three replicates was employed to study the effects of solvent extraction conditions such as extraction temperature ($^{\circ}C$, $X_1$), extraction time (min, $X_2$), and ethanol concentration (%, $X_3$) on the extraction yield of antioxidants from Zizyphus jujuba. The yields of total polyphenols and total flavonoid, and electron donating activity (EDA) were considered as response variables. The second-order polynomial model gave a satisfactory description of the experimental results showing different patterns of extraction conditions with variation in the linear, quadratic, and interaction effects of the independent variables. Based on four-dimensional RSM, one of the optimized sets of conditions was 45% ethanol, $45^{\circ}C$, and an extraction time of 15 min. Under the optimal conditions, the predicted values were 177.64 mg/g dry basis, 35.99 mg/g dry basis, and 86.14% Vit.C equivalents for total polyphenols, total flavonoids, and EDA, respectively. The experimental values showed good agreements with the predicted values.

• The Journal of Korean Academy of Prosthodontics
• /
• v.44 no.1
• /
• pp.20-28
• /
• 2006

Statement of problem: The titanium has advantages of a high biocompatibility, a corrosion resistence, low density, and cheep price, so it is focused as a substituted alloy But it is quite difficult to cast with the tranditional method due to the high melting point, reacivity with element at, elevated temperature. By using the CAD-CAM system for the crown construction, it is possible to reduce the errors while proceeding the wax-up, investing, and casting procedure Purpose: The purposes of this study were to measure the marginal adaptation of the casting titanium coping and machine-milled titanium coping according to the casting methods and the marginal configurations. Material and method: The marginal configurations were used chamfer shoulder, and beveled shoulder. The total 30 copings were used, and these are divided into 6 groups according to the manufacturing method and marginal configuration. The gap between margin of the model and the restoration was measured with 3-dimensional measuring microscope. Results: The following results were obtained; 1. casting gold coping demonstrated the best marginal seal, followed by casting titanium coping finally machine-milled titanium copings. 2. In casting titanium coping, chamfer demonstrated the best marginal seal, followed by shoulder and beveled shoulder. There was no significantly difference in shoulder and beveled shoulder. But all margin form has clinically acceptable 3. In machine-milled titanium copings, chamfer demonstrated the best marginal seal, followed by shoulder and beveled shoulder. Beveled shoulder show large and uneven marginal gap Conclusions: Above result revealed that marginal adaptation of the titanim coping is avail able in the clinical range, it can be used as an alternative metal and it is prefered especially in chamfer or shoulder margin during implant superstructure fabrication. But there should be more research on machine-milled titanium in order to use it in the clinics.

• Journal of Sensor Science and Technology
• /
• v.24 no.6
• /
• pp.404-411
• /
• 2015

A stoichiometric mixture of evaporating materials for $BaAl_2Se_4$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $BaAl_2Se_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperatures were $610^{\circ}C$ and $410^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $BaAl_2Se_4$ single crystal thin films measured from Hall effect by van der Pauw method are $8.29{\times}10^{-16}cm^{-3}$ and $278cm^2/vs$ at 293 K, respectively. The temperature dependence of the energy band gap of the $BaAl_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=3.4205eV-(4.3112{\times}10^{-4}eV/K)T^2/(T+232 K)$. The crystal field and the spin-orbit splitting energies for the valence band of the $BaAl_2Se_4$ have been estimated to be 249.4 meV and 263.4 meV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}so$ definitely exists in the ${\Gamma}_5$ states of the valence band of the $BaAl_2Se_4/GaAs$ epilayer. The three photocurrent peaks observed at 10 K are ascribed to the $A_1$-, $B_1$-exciton for n =1 and $C_{31}$-exciton peaks for n=31.

• Journal of Pharmaceutical Investigation
• /
• v.20 no.4
• /
• pp.223-228
• /
• 1990

The contribution of endogenous transport systems to the blood-brain barrier (BBB) transport of basic and acidic drugs was studied by using a carotid injection technique in rats and an isolated bovine cerebrovascular disease state were compared between the normotensive rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP) which have been well established as an animal model with pathogenic similarities to humans. Basic drugs such as eperisone, thiamine and scopolamine inhibited, in a concentration dependent manner the in vivo uptake of $[{^3}H]choline$ through BBB, whereas amino acids and acidic drugs such as salicylic acid and valproic acid did not inhibit the uptake. The uptake of $[^3H]choline$ by B-CAP increased with time and showed a remarkable temperature dependency. The uptake of $[^3H]choline$ by B-CAP showed the very similar inhibitory effects as observed in the in vivo brain uptake, and was competitively inhibited by a basic drug, eperisone. The in vivo BBB uptakes of $[^3H]acetic$ acid and $[^{14}C]salicylic$ acid were dependent on pH of the injectate and the concentration of drugs. Several acidic drugs such such as salicylic acid, benzoic acid and valproic acid inhibited the in vivo uptake of $[^3H]acetic$ acid, whereas amino acid, choline and a basic drug such as eperisone did not inhibit the uptake. The uptake of acetic acid by B-CAP was competitively inhibited by salicylic acid. The permeability surface area product (PS) through BBB for $[^3H]choline$ in SHRSP was significantly lower than that in WKY. The concentration of choline in the brain dialysate in SHRSP was about half of that in WKY, while no significant difference was observed in the plasma concentration of choline between SHRSP and WKY. No significant difference was observed in the transport of monocarboxylic acids, glucose and neutral amino acid through BBB between SHRSP and WKY. From these results, it was concluded that BBB transport system of choline contributes to the transport of basic drugs through BBB, that acidic drugs can be transported via a moncarboxylic acid BBB transport system and that the specific dysfuntion of the BBB choline transport in SHRSP was ascribed to the reduction of the maximum velocity of choline concentration in the brain interstitial fluids.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.5
• /
• pp.723-730
• /
• 2016

Solar cells in a PV module are connected in series and parallel to produce a higher voltage and current. The PV module has performance characteristics depending on solar radiation and temperature. In addition, the PV system causes power loss by special situations, including the shadows of the surrounding environment, such as nearby buildings and trees. In other words, an increase in power loss and a decrease in life cycle can occur because of the partial shadow and hot-spot effect. Therefore, this paper proposes the optimal configuration algorithm of a bypass diode to improve the output of a PV module and one of a PV array to minimize the loss of the PV array. In addition, this paper presents a model of a PV module and PV array based on the PSIM S/W. The simulation results confirmed that the proposed optimal configuration algorithms are useful tools for improving the performance of PV system.

• Restorative Dentistry and Endodontics
• /
• v.25 no.1
• /
• pp.91-108
• /
• 2000

Most of cervical abrasion and erosion lesions show gingival margin where the cavosurface angle is on cementum or dentin. Composite resin restoration of cervical lesion shrink toward enamel margin due to polymerization contraction. This shrinkage has clinical problem such as microleakage and secondary caries. Several methods to diminish contraction stress of composite resin restoration, such as modifying cavity form and building up restorations in several increments have been attempted. The purpose of this study was to compare polymerization contraction stress of composite resin in Class V cavity subjected to cavity forms and placement methods. In this study, finite element model of 5 types of Class V cavity was developed on computer tomogram of maxillary central incisor. The types are : 1) Box cavity 2) Box cavity with incisal bevel 3) V shape cavity 4) V shape cavity with incisal bevel 5) Saucer shape cavity. The placement methods are 1) Incisal first oblique incremental curing 2) Bulk curing. An FEM based program for light activated polymerization is not available. For simulation of curing dynamics, time dependent transient thermal conduction analysis was conducted on each cavity and each placement method. For simulation of polymerization shrinkage, thermal stress analysis was performed with each cavity and each placement method. The time-temperature dependent volume shrinkage rate, elastic modulus, and Poisson's ratio were determined in thermal conduction data. The results were as follows : 1. With all five Class V cavifies, the highest Von Mises stress at the composite-tooth interface occurred at gingival margin. 2. With box cavity, V shape cavity and saucer cavity, Von Mises stress at gingival margin of V shape cavity was lower than the others. And that of box cavity was lower than that of saucer cavity. 3. Preparing bevel at incisal cavosurface margin decreased the rate of stress development in early polymerization stage. 4. Preparing bevel at incisal cavosurface margin of V shape cavity increased the Von Mises stress at gingival margin, but decreased at incisal margin. 5. At incisal margin, stress development by bulk curing method was rapid at early stage. Stress development by first increment of incremental curing method was also rapid but lower than that by bulk curing method, however after second increment curing final stress was the same for two placement methods. 6. At gingival margin, stress development by incremental curing method was suddenly rapid at early stage of second increment curing, but final stress was the same for two placement methods.

• The KIPS Transactions:PartB
• /
• v.9B no.5
• /
• pp.663-672
• /
• 2002

In this paper, Using an automatic tracking system, behavior of an aquatic insect, Chironomus sp. (Chironomidae), was observed in semi-natural conditions in response to sub-lethal treament of a carbamate insecticide, carbofuran. The fourth instar larvae were placed in an observation cage $(6cm\times{7cm}\times{2.5cm)}$ at temperature of $18^\circ{C}$ and the light condition of 10 time (light) : 14 time (dark). The tracking system was devised to detect the instant, partial movement of the insect body. Individual movement was traced after the treatment of carbofuran (0.1ppm) for four days 2days : before treatment, 2 days : after treatment). Along with the other irregular behaviors, "ventilation activity", appearing as a shape of "compressed zig-zag", was more frequently observed after the treatment of the insecticide. The activity of the test individuals was also generally depressed after the chemical treatment. In order to detect behavioral changes of the treated specimens, wavelet analysis was implemented to characterize different movement patterns. The extracted parameters based on Discrete Wavelet Transforms (DWT) were subsequently provided to artificial neural networks to be trained to represent different patterns of the movement tracks before and after treatments of the insecticide. This combined model of wavelets and artificial neural networks was able to point out the occurrence of characteristic movement patterns, and could be an alternative tool for automatically detecting presences of toxic chemicals for water quality monitoring. quality monitoring.

• Journal of Korea Water Resources Association
• /
• v.32 no.6
• /
• pp.617-625
• /
• 1999

Global warming has begun since the industrial revolution and it is getting worse recently. Even though the increase of greenhouse gases such as $CO_2$ is thought to be the main cause for global warming, its impact on global climate has not been revealed clearly in rather quantitative manners. However, researches using General Circulation Models(GCMs) has shown the accumulation of greenhouse gases increases the global mean temperature, which in turn impacts on the global water circulation pattern. This changes in global water circulation pattern result in abnormal and more frequent meteorological events such as severe floods and droughts, generally more severe than the normal ones, which are now common around the world and is referred as a indirect proof of global warming. Korean peninsula also cannot be an exception and have had several extremes recently. The main objective of this research is to analyze the impact of global warming on the change of flood and drought frequency. Based on the assumption that now is a point in a continuously changing climate due to global warming, we analyzed the observed daily rainfall data to find out how the increase of annual rainfall amount affects the distribution of daily rainfall. Obviously, the more the annual rainfall depth, the more frequency of much daily rainfall, and vice versa. However, the analysis of the 17 points data of Keum river basin in Korea shows that especially the number of days of under 10mm or over 50mm daily rainfall depth is highly correlated with the amount of annual rainfall depth, not the number of dry days with their correlation coefficients quite high around 0.8 to 0.9.

• Applied Chemistry for Engineering
• /
• v.9 no.5
• /
• pp.742-748
• /
• 1998

Experiments have been conducted to investigate synergistic effects and mechanisms of the Alaskan subbituminous coal/polypropylene (PP). Coliquefaction of coal/PP gave the synergistic effect in yields by 17% compared to independent liquefactions of coal or PP at $430^{\circ}C$. To analyse coliquefaction mechanisms, the second and zeroth order kinetic models were developed for coal and PP conversions respectively. When the models were simulated to fit coliquefaction results, those represented results successfully with the correlation coefficient of 0.99. The amount of tetralin needed to liquefy unit mass of coa 1(${\beta}$) was also calculated using the developed model. According to the calculated results, $\beta$ increased from 0.4 to 1.0 as the coliquefaction temperature increased from $410^{\circ}C$ to $470^{\circ}C$. This indicated that tetralin lowered the molecular weight of oil produced, and this phenomenon was recognized by the GPC analyses. Furthermore, it was found that tetralin prohibited the liquefaction of PP when coal was not added. On the other hand, tetralin was believed to act as a hydrogen-donor solvent to coal rather than prohibit PP liquefaction during coliquefaction. Therefore, the liquefaction rate of PP increases and synergistic effects in oil yields are mainly due to the increase in PP liquefaction during coal/PP coliquefaction.