• Journal of Environmental Health Sciences
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• v.35 no.3
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• pp.169-177
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• 2009

In the past decade there has been increasing concern about the atopic dermatitis (AD) associated with environmental diseases. AD has been increased in the last decade and known as one of the multifactoral diseases, which has the genetic background and environmental factors at the same time. The purposes of this study were to investigate the prevalence rate and etiologic risk factors of atopic dermatitis in preschool children in Changwon, which is a one of the Korean cities and has a large industrial complex. We reviewed and analyzed the statistical data, obtained from Korea National Health Insurance Corporation, related to prevalence rate by age and administrative district. A cross-sectional questionnaire survey, based on ISAAC (International Study of Allergy and Asthma in Childhood), was conducted on random samples of preschool children (5 to 8 years old) of large sized kindergartens in Changwon. The lifetime and last one years prevalence of AD in preschool children in Changwon was increased from 1998 to 2008. The prevalence rate of AD in the preschool children in Changwon city was 9.6%. The prevalence rate in boys was 9.7% and that in girls was 9.4%. The one year prevalence of AD was ranked as middle among other provincial cities in Korea in 2008. This study showed that the prevalence rate of the atopic disease in Changwon was 9% in 2008, which was increased especially compare to 2000. More active governmental approaches for control and prevention of atopic dermatitis for children are recommended. Further studies are needed for more accurate estimation of the prevalence of AD in Korea including different regional and age population.

• Journal of Environmental Health Sciences
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• v.39 no.1
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• pp.83-89
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• 2013

Objectives: The purpose of this experiment was to illuminate the relationship between the phosphorus removal rate of unit operation and the phosphorus removal rate of phosphorus volume loading in the Ferrous Nutrient Removal process, which consists of an anoxic basin, oxic basin, and iron precipitation apparatus. Methods: This study was conducted in order to improve the effect of nitrogen and phosphorus removal in domestic wastewater using the FNR (Ferrous Nutrient Removal) process which features an iron precipitation reactor in anoxic and oxic basins. The average concentration of TN and TP was analyzed in a pilot plant ($50m^3/day$). Results: The removal rate of T-N and T-P were 66.5% and 92.8%, respectively. The $NH_3-N$ concentration of effluent was 2.62 mg/l with nitrification in the oxic basin even though the influent was 17.7 mg/l. The $NO_3$-N concentration of effluent was 5.83 mg/l through nitrification in oxic basin even though the influent and anoxic basin were 0.82 mg/l and 1.00 mg/l, respectively. The specific nitrification of the oxic basin ($mg.NH_3$-Nremoved/gMLVSSd) was 16.5 and specific de-nitrification ($mg.NO_3$-Nremoved/gMLVSSd) was 90.8. The T-P removal rate was higher in the oxic basin as T-P of influent was consumed at a rate of 56.3% in the anoxic basin but at 90.3% in the oxic basin. The TP removal rate (mg.TP/g.MLSS.d) ranged from 2.01 to 4.67 (3.06) as the volume loading of T-P was increased, Conclusions: The test results showed that the electrolysis of iron is an effective method of phosphorus removal. Regardless of the temperature and organic matter content of the influent, the quality of phosphorus in the treated water was both relatively stable and high due to the high removal efficiency. Nitrogen removal efficiency was 66.5% because organic matter from the influent serves as a carbon source in the anoxic basin.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.4
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• pp.665-670
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• 2020

Buffer layer in CIGS thin-film solar cells improves energy conversion efficiency through band alignment between the absorption layer and the window layer. ZnS is a non-toxic II-VI compound semiconductor with direct-transition band gaps and n-conductivity as well as with excellent lattice matching for CIGS absorbent layers. In this study, the structural and optical properties of ZnS thin films, deposited by RF magnetron sputtering method and subsequently performed by the rapid thermal annealing treatment, were investigated for the buffer layer. The zincblende cubic structures along (111), (220), and (311) were shown in all specimens. The rapid thermal annealed specimens at the relatively low temperatures were polycrystalline structure with the wurtzite hexagonal structures along (002). Rapid thermal annealing at high temperatures changed the polycrystalline structure to the single crystal of the zincblende cubic structures. Through the chemical analysis, the zincblende cubic structure was obtained in the specimen with the ratio of Zn/S near stoichiometry. ZnS thin film showed the shifted absorption edge towards the lower wavelength as annealing temperature increased, and the mean optical transmittance in the visible light range increased to 80.40% under 500℃ conditions.

• Journal of the Korean Ceramic Society
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• v.39 no.4
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• pp.352-358
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• 2002

The variations of the properties of Sr and Mg added $LaGaO_3$ system electrolyte with the amount of the additive and the sintering condition were studied. Main phase was (La$_{1-x}Sr_x)(Ga_{1-y}Mg_y)O_{3-\delta}$ phase for each compositions and the single phases $(La_{0.85}Sr_{0.15})(Ga_{0.85}Mg_{0.15})O_{3-\delta},(La_{0.85}Sr_{0.15})(Ga_{0.8}Mg_{0.2})O_{3-\delta}$ and $(La_{0.8}Sr_{0.2})(Ga_{0.8}Mg_{0.2})O{3-\delta}$ were obtained with the decrease in the sintering temperature and Mg addition. Thermal expansion coefficient of the $(La_{0.8}Sr_{0.2})(Ga_{0.8}Mg_{0.2})O_{3-\delta}$ decreased with the increase in the sintering temperature. Electric conductivity of electrolyte sintered at $1500^{circ}C$ for 1h was 0.14 S/cm at $800^{circ}C$ with 1 mA.

• Journal of the Korean Ceramic Society
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• v.39 no.4
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• pp.346-351
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• 2002

The electrical conductivity and phase stability of $ZrO_2$ doped with $Sc_2O_3$ and $CeO_2$ were investigated in order to search for better solid electrolyte material for solid oxide fuel cell. Present study showed that $ZrO_2$ doped with $Sc_2O_3$ and $CeO_2$ exhibited no phase transition during the heat treatment up to $1350^{Circ}C∼1550^{Circ}C$ and was stable as a cubic phase in whole temperature ranges. The $ZrO_2$ doped with $Sc_2O_3$ and $CeO_2$ showed much higher electrical conductivity than YSZ in the temperature range of $300∼^{Circ}C$ and better long term stability than other sc-$ZrO_2$ based electrolyte that showed the possibility as a strong candidate electrolyte material for intermediate-or low-temperature SOFC.

• Journal of the Korean Ceramic Society
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• v.47 no.5
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• pp.467-473
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• 2010

The objective of this study is to prepare lead-free thick film resistor (TFR) paste compatible with AlN substrate for hybrid microelectronics. For this purpose, CaO-ZnO-$B_2O_3-Al_2O_3-SiO_2$ glass system was chosen as a sintering aid of $RuO_2$. The effects of the weight ratio of CaO to ZnO in glass composition, the glass content and the sintering temperature on the electrical properties of TFR were investigated. $RuO_2$ as a conductive and glass powder were dispersed in an organic binder to obtain printable paste and then thick-film was formed by screen printing, followed by sintering at the range between $750^{\circ}C$ and $900^{\circ}C$ for 10 min with a heating rate of $50^{\circ}C$/min in an ambient atmosphere. The addition of ZnO to glass composition and sintering at higher temperature resulted in increasing sheet resistance and decreasing temperature coefficient of resistance. Using $RuO_2$-based resistor paste containing 40 wt%glass of CaO-20.5%ZnO-25%$B_2O_3$-7%$Al_2O_3$-15%$SiO_2$ composition, it is possible to produce thick film resistor on AlN substrate with sheet resistance of $10.6\Omega/\spuare$ and the temperature coefficient of resistance of 702ppm/$^{\circ}C$ after sintering at $850^{\circ}C$.

• Journal of Biomedical Engineering Research
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• v.21 no.3 s.61
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• pp.273-277
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• 2000

The galvanostatic anodization of commercially Pure titanium plate (c.p.Ti, grade 2) was investigated in various concentrations of aqueous $H_3PO_4$ from 0.05M to 0.7M. The surfaces of anodic oxide films, formed by the current density in the range between 0.3 and $l.0 A/dm^2$. were analyzed by SEM and XRD. The voltage-time (V-T) curves displayed an initial linear part and a subsequent parabolic part, and the initial slopes increased with an increase in the current density in 0.05M $H_3PO_4$. As the concentration of the electrolyte increased, the V-T corves exhibit no change but the final voltage decreased. The anodic oxide film of titanium developed from fine grains to snowflake-like grains in a layered structure with an increase in the concentration of the electrolyte and current density. Sparking at the interface of the oxide/electrolyte accompanied the local deposition and dissolution of the oxide film through discharging. The crystallinity of the anodic oxide film increased with the anodizing voltage and decreased with an increase in the concentration of the electrolyte.

• Journal of Biomedical Engineering Research
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• v.25 no.6
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• pp.565-573
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• 2004

In this paper, we proposed a heart activity control model for simulation of the aortic sinus baroreceptor, which was the most representative baroreceptor sensing the variance of pressure in the cardiovascular system. And then, the heart activity control model composed electric circuit model of the cardiovascular system with baroreflex control and time delay sub-model to observe the effect of time delay in heart period and stroke volume under the regulation of baroreflex in the aortic sinus. The mechanism of time delay in the heart activity baroreflex control model is as follows. A control function is conduct sensing pressure information in the aortic sinus baroreceptor to transmit the efferent nerve through central nervous system. As simulation results of the proposed model, we observed three patterns of the cardiovascular system variability by the time delay. First of all, if the time delay over 2.5 second, aortic pressure and stroke volume and heart rate was observed non-periodically and irregularly. However, if the time delay from 0.1 second to 0.25 second, the regular oscillation was observed. And then, if time delay under 0.1 second, then heart rate and aortic pressure-heart rate trajectory were maintained in stable state.

• Journal of Biomedical Engineering Research
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• v.18 no.3
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• pp.273-283
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• 1997

Electrogastrography(EGG), the cutaneous recording of the myoelectrical activity of the stomach using surface electrodes, is attactive due to its non-invasiveness. Despite many attempts made over the decades, analysis of surface EGG has not led to identification of contraction-related electrical response activity of the stomach that would help the clinician to diagnose motility disorders of the stomach. We propose feasible methods to detect the gastric contraction by spectrum analysis and vector analysis of the surface EGG signal. A running spectral analysis(RSA) based on the fast Fourier transform (FFT) was applied to the filtered EGG signal. The powers of dominant frequency and its harmonics were compared with gastric contraction signals such as the strain gauge signal from the gastric serosa in dog or the antropyloric pressure in human. And we also carried out vector analysis of the filtered EGG signals obtained from three paired electrodes. The amplitude and direction of the calculated EGG vector were analyzed and compared with the gastric contraction signals. From the spectrum analysis, we found that the increase of the power of the first harmonic of the dominant frequency was highly correlated with the gastric contraction. And from the vector analysis of the EGG signal, we found a typical change of the amplitude and direction of the EGG vector, which can indicate occurrences of the gastric contraction.

• Journal of Life Science
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• v.16 no.1
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• pp.114-119
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• 2006

The purpose of this study was to determine effects of the Ga-As (Gallium-Arsenide) Dens-Bio laser on mechanically injured sciatic nerves of rats. The improvement of the injured rat sciatic nerve was evaluated by measuring of nerve conduction velocity and amplitude of compound muscle action potential. The sciatic nerves of forty male Sprague-Dawley rats were compressed with hemostatic forceps for 30 seconds. The experimental group was divided into 4 subgroups according to the duration of treatment. Lower power infrared laser irradiation was done transcutaneously to the injured sciatic nerve area, 3 minutes daily to each of four treatment groups for 1, 3, 5, and 7 weeks, respectively. Compound muscle action potential and nerve conduction velocity of sciatic nerve were obtained before nerve injury and at 1, 3, 5, and 7 weeks after injury. There were significant difference of the nerve conduction velocity and amplitudes of compound muscle action potential between the treatment group and non-treatment group at 1, 3, and 5 weeks after laser treatment. However, there were no differences found between the electrophysiologic parameters that were measured after 7 weeks in two groups. There was significant correlation between the increment of compound muscle action potential and nerve conduction velocity after time course according to laser treatment. In conclusion, the low power laser treatment had improved the sciatic nerve function, and therefore these results may provide the basic data to clarify the neurological recovery and treatment after incomplete peripheral nerve injury.