• Safety and Health at Work
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• v.14 no.2
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• pp.215-221
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• 2023

Background: There is little information about the airborne hazardous agents released during the heat treatment when manufacturing a welding material. This study aimed to evaluate the airborne hazardous agents generated at welding material manufacturing sites through area sampling. Methods: concentration of airborne particles was measured using a scanning mobility particle sizer and optical particle sizer. Total suspended particles (TSP) and respirable dust samples were collected on polyvinyl chloride filters and weighed to measure the mass concentrations. Volatile organic compounds and heavy metals were analyzed using a gas chromatography mass spectrometer and inductively coupled plasma mass spectrometer, respectively. Results: The average mass concentration of TSP was 683.1±677.4 ㎍/m³, with respirable dust accounting for 38.6% of the TSP. The average concentration of the airborne particles less than 10 ㎛ in diameter was 11.2-22.8×10⁴ particles/cm³, and the average number of the particles with a diameter of 10-100 nm was approximately 78-86% of the total measured particles (<10 ㎛). In the case of volatile organic compounds, the heat treatment process concentration was significantly higher (p < 0.05) during combustion than during cooling. The airborne heavy metal concentrations differed depending on the materials used for heat treatment. The content of heavy metals in the airborne particles was approximately 32.6%. Conclusions: Nanoparticle exposure increased as the number of particles in the air around the heat treatment process increases, and the ratio of heavy metals in dust generated after the heat treatment process is high, which may adversely affect workers' health.

• Journal of the Korean earth science society
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• v.37 no.7
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• pp.389-397
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• 2016

In order to investigate the light curve difference in visual and infrared wavelength of ${\delta}$ Scuti variable Bo Lyn, observations were performed using BOAO 1.8m reflecting telescope and an infrared detector, KASINICS, with J, H, and Ks filters. Infrared light curves of total 7 nights were obtained between March and April in 2011, and those were compared to the V-filter light curve to examine the differences in period, time of maximum light, amplitude, and shape. From the periodic analysis of infrared light curve, a single frequency of $f_1=10.712cycle/day$, $P=0.09335{\pm}0.00002days$ was obtained, and there was no difference in the period along different wavelengths. In the infrared light curve, a frequency of $2f_1$ was detected. This frequency well explains the asymmetric shape of light curve, one of the characteristics of high-amplitude ${\delta}$ Scuti variables. We compared the locations of the measured infrared maxima and the predicted maxima of V-filter, finding that the times of maxima were delayed about 0.3 phase at infrared wavelengths. Amplitude ratios were adopted to be ${\Delta}J/{\Delta}V=0.328$, ${\Delta}H/{\Delta}V=0.216$, and ${\Delta}Ks/{\Delta}V=0.211$, with the range of variation being smaller at longer wavelengths. It seems that the differences in the times of maxima and amplitude occurred because the changes in brightness of a pulsating variable star are mainly caused by the change in temperature.

• Applied Chemistry for Engineering
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• v.19 no.1
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• pp.80-85
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• 2008

Catalytic filter is capable of performing shallow bed dust filtration plus a catalytic reaction, promoted by a catalyst deposited in its inner structure. Such a feature may allow potential cost and space reduction in several environmental applications. Dust filtration and halogenated volatile organic compound (1,2-dichlorobenzene) destruction were carried out in a lab-scale reactor. $WO_3-V_2O_5/TiO_2$ supplied by MaGreen, which showed high catalytic acitivity at low temperature, was used as a catalyst. P-84 that can be operated under $250^{\circ}C$ was used as a felt. The catalytic activity and filtration efficiency of catalytic filters were investigated under the operating conditions, including temperature, face velocity, and dust concentration. The catalytic activity of catalytic filter increased with increasing temperature and the amount of catalyst loaded. The test results showed that the filtration efficiency was primarily affected by the face velocity. Pressure drop variations as a function of time were investigated for a variety of conditions. In case of virgin filter, a dramatic decrease in the pulse interval and a slightly increase in the base line pressure drop were observed. A relatively slow pressure drop build-up was recorded for the catalytic filter due to smooth and slippery surface characteristics of nanofiber. The catalytic filter indicated that high filtration efficiency over 99.98% and high catalytic activity over 90% at 1 m/min and $210^{\circ}C$.

• Korean Journal of Clinical Pharmacy
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• v.13 no.2
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• pp.82-90
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• 2003

Dopamine is an effective pressor for the treatment of shock and hypotension when patients do not respond to plasma volume expansion. Two dopamine intravenous delivery systems are currently available in Korea. The objective of this study was to compare dopamine premixed with prefilled system in terms of supply costs (preparation costs + personnel time), contamination rates and convenience. Time-and-motion studies were conducted to determine the time and costs associated with preparation and administration of the two systems. They were analyzed and compared by Mann-Whitney test. To evaluate the contaminaton rates of the two systems, both systems were prepared in an open environment similar to that of practical situations. Premixed and compounded solutions were then filtered by $0.22{\mu}m$ membrane filters, which were cultured at $37^{\circ}C$ for 10 days and their contents were visually checked for bacterial contamination. The convenience of the two systems was compared by itemized user assessments on preparation, dose calculation, admixture, administration and disposal of waste matters. They were analyzed by Wilcoxon's signed rank test and 100 part percentage. It was found that the preparation costs $(mean{\pm}SD)$ for premixed and prefilled systems were $271.70\pm293.55\;Won$ (Korean currency) and $1521.04\pm510.63\;Won$, respectively. The preparation time $(mean{\pm}SD)$ for premixed system was $68.10\pm35.69\;sec.$ while at for prefilled system was $154.03\pm50.06\;sec.$ (n=59 each, p<0.001). No bacterium was observed in the samples of both systems (n=20, each). User assessments indicated that the premixed system was more convenient than the prefilled system except for the item of dose calculation (n=24, p<0.001). Subjective evaluations have proven that the use of the dopamine premixed system resulted in increased efficiency of intravenous preparation by allowing personnel to devote more time to other labor-intensive duties and lower total medical costs.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.669-678
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• 1994

The BOD removal characteristics of submerged biofilters filled with three kinds of filter media respectively were experimentally examined with constant temperature, pH value and variable BOD loading and recirculation ratio. Obtained results are as follows; 1. The BOD removal ratio decreases with the increasing $BOD_5$ volumetric loading rate, and the loading rate for the BOD removal over 90% is lower thean $1.6kg{\cdot}BOD_5/m^3{\cdot}d$ for the plastic media of Netring and cubic wire meshes. This is a much large value than $0.3{\sim}0.8kg{\cdot}BOD_5/m^3{\cdot}d$ for conventional activated sludge process. The required submerged biofilter volume is found to be much samller than that of conventional activated sludge process. 2. The decreasing order of BOD removal is Netring (random plastic media), cubic wire meshes (plastic module), and then gravel (stone media). This is mainly due to the media characteristics such as void ratio, specific surface area and media shapes. 3. The $BOD_5$ removal rate increases with the recircuration ration, but the rate of increases becomes samaller as the recirculation ratio increases over 20. When $BOD_5$ loading is $1.8kg{\cdot}BOD_5/m^3{\cdot}d$, the required recirculation rationto obtain 90% $BOD_5$ removal is about 20 for Netring and it was about 30 for cubic wire meshes. 4. Reynold's Number increases with recirculation ratio, and the Reynold's Numbers corresponding to the recircuration ratio of 10~50 are less than 52, showing laminar up flows in the filter. The settled and effluent sludges increase with increase of Reynol's Number, and there are the definite Reynold's Numbers at which the settling sludge concentrations become nearly constant respectively in each filters. 5. In this submerged biofilter system, small volume of sludge hopper can be substituted for a separated settling tank.

• Journal of Astronomy and Space Sciences
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• v.24 no.3
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• pp.209-218
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• 2007

In this paper, we have presented the observational result for the photometric quality of main telescopes in Gimhae Astronomical Observatory. Also we performed the observation of searching new minor planets as competitive work in public observatories. The observation was carried out using 60cm telescope of Gimhae Astronomical Observatory on 2007 January 13. And, $Sch\ddot{u}ler$ BVI filters and 1K CCD camera (AP8p) were used. To define the quality of CCD photometry, we observed the region of well-known standard stars in the open cluster M67. From observed data, The transformation coefficients and airmass coefficients were obtained, and the accuracy of CCD photometry was investigated. From PSF photometry, we obtained the color-magnitude diagram of M67, and considered the useful magnitude limit and the physical properties of M67. This method can be successfully used to confirm the photometric quality of main telescope in public observatories. To investigate the detection possibility of unknown object as astroid, we observed the near area of the opposition in the ecliptic plane. And we discussed the result. Our result show that it can be possible to detect minor planets in solar system brighter than $V{\sim}18.3mag$. and it can carry out photometric study brighter than V 16mag. in Gimhae Astronomical Observatory. These results imply that the public observatories can make the research work.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.12 s.115
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• pp.1156-1163
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• 2006

This paper presents an ultra wideband(UWB) direct conversion mixer for IEEE 802.15.3a applications with simulation and measurement results. Since the direct conversion mixing causes dc-offset and even-order distortion, the proposed mixer adopts an anti-parallel diode pairs(APDPs) to solve these problems. The proposed mixer consists of an in-phase wilkinson power divider over $3.1{\sim}4.8GHz$, a wideband $45^{\circ}$ power divider over $1.5{\sim}2.4GHz$, and miniatured band pass filters(BPFs) for RF-LO isolations. The conversion loss is optimized with impedance matchings between APDPs and wideband components. The measured mixer shows the conversion loss of 13.5 dB, input third-order intercept-point($IIP_3$) of 7 dBm, and 1-dB gam compression point($P_{1dB}$) of -4 dBm. Quadrature(I/Q) outputs have the magnitude difference of about 1 dB and phase difference of ${\pm}3^{\circ}$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.4
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• pp.362-370
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• 2010

In this paper, a compact RF Front-end module for Wireless Fidelity(Wi-Fi) and Worldwide Interoperability for Microwave Access(WiMAX) applications is realized by low temperature co-fired ceramic(LTCC) technology. The RF Front-end module is composed of three LTCC band-pass filters, a Film Bulk Acoustic Resonator(FBAR) filter, fully embedded matching circuits, an SPDT switch for mode selection, an SPDT switch for Tx/Rx selection, and an SP4T switch for band selection. The parasitic elements of 0.2~0.3 pF are generated by the structure of stacking in the top pad pattern for DC block capacitor of SPDT switch for mode selection. These kinds of parasitic elements break the matching characteristic, and thus, the overall electrical performance of the module is degraded. In order to compensate it, we insert a parallel lumped-element inductor on capacitor pad pattern for DC block, so that we obtain the optimized performance of the RF Front-end module. The fabricated RF front-end module has 12 layers including three inner grounds and it occupies less than $6.0mm{\times}6.0mm{\times}0.728mm$.

• Journal of Korean Society on Water Environment
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• v.35 no.2
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• pp.145-151
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• 2019

The purpose of this study was to investigate treatment characteristics of diatomite filtration, that would allow water recovery from biologically-treated effluent for reuse. Diatomite, Celpure 100, and acid clay were used as filter-aids, with a support filter manufactured from polyethylene (PE), and polypropylene (PP). This pre-coating process using diatomite filter-aids, is used in the filtration range of pressure filters, and has consistently provided high-quality separation. The results showed that variations in average removal efficiency of SS, and T-P from biologically treated effluent by the diatomite-coated PE filter, were approximately 82.2 ~ 88.9 % and 4.8 ~ 21.1 %, respectively. T-P treatment efficiency of the PP filter pre-coated with diatomite and $Celpure^{(R)}100$ at $57.64g/m^2$, was approximately $24{\pm}10%$ and $40{\pm}15%$ on average, respectively. Particle size distribution of secondary effluent varied from 0.05 to $200{\mu}m$, and $d_{50}$ value was $20.76{\mu}m$. The size distribution of particles in the diatomite filtrate ranged from 1.26 to $101.1{\mu}m$ when pre-coated with diatomite filter-aid, at a content of $57.64g/m^2$. Diatomite filter aids, i.e., the particles that form the pre-coating layer, capture very fine particles as well as macromolecules, owing to their complex structure with numerous fine microscopic pores, and surface properties. The filtration process using diatomite and $Celpure^{(R)}100$ as filter aids, has been successfully applied, to recover water from sewage for reuse. The disadvantage of the process, is that the particle size of the filter-aid is spent, because of pressurization.

• The Korean Journal of Nuclear Medicine
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• v.32 no.3
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• pp.298-304
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• 1998

Purpose: We evaluated the usefulness of Re-188 sulfur colloid for radiation synovectomy and therapy of intraperitoneal metastasis. Materials and Methods: We investigated the labeling efficiency of Re-188 sulfur colloid on various conditions. The stability of Re-188 sulfur colloid was observed at room temperature for 24 h and in human serum and synovial fluid for 72 h. The particle size distribution of Re-188 sulfur colloid was measured by filtering with various pore size filters. Animal experiment was performed in mice and rabbits. Results: The labeling efficiency of Re-188 sulfur colloid was $64.5{\pm}5.8%$ (n=5) at the conditions of sodium thiosulfate 40 mg, EDTA $Na_2.2H_2O$ 0.8 mg, $KReO_4$ 0.8 mg at pH 1. After purification, the radiochemical purity was higher than 99%. The stability of Re-188 sulfur colloid was high (>99%) at room temperature for 24 h and in human serum and synovial fluid for 72 h. The particle size distribution of Re-188 sulfur colloid was 0.3% ($<1{\mu}m$), 11.2% ($1{\sim}5{\mu}m$), 25.8% ($5{\sim}10{\mu}m$) and 52.8% ($>10{\mu}m$). In mice, 1 h postinjection of Re-188 sulfur colloid into tail vein, uptakes in lung, liver and muscle were $37.30{\pm}5.36$, $32.33{\pm}1.79$, $6.60{\pm}0.02%$ ID/organ respectively. After i.p. injection in mice, the uptakes of extraperitonial organs of Re-188 sulfur colloid at 1 and 24 h were $0.1{\pm}0.1$, $0.4{\pm}0.1%$ ID/organ, and the excretions through urine and feces (${\sim}70 h$) were low ($2.68{\pm}0.80$, $0.95{\pm}0.17%$). When Re-188 sulfur colloid was injected to synovial space of rabbit, the uptake in other organs except knee was very low. Conclusion: Re-188 sulfur colloid showed high labeling efficiency, stability and potency for clinical use.