• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.1
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• pp.109-116
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• 2011

To measure the traffic pollutants with high temporal and spatial resolution under real conditions a mobile emission laboratory (MEL) was designed and built in KIST with close-cooperation with KIMM and Yonsei university. The equipment of the mini-van provides gas phase measurements of CO, NOx, $CO_2$, THC (Total hydrocarbon) and number density & size distribution measurements of fine and ultra-fine particles by a fast mobility particle sizer (FMPS) and a condensation particle counter (CPC). The inlet sampling port above the bumper enables the chasing of different type of vehicles. This paper introduces the construction and technical details of the MEL and presents data from the car chasing experiment of diesel and CNG city bus. The dilution ratio was increased rapidly according to the chasing distance. Most particles from the diesel city bus were counted under 300 nm and the peak concentration of the particles was located between 40-60 nm. However, the most particles from the CNG city bus were nano particle counted under 50 nm.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.1
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• pp.20-26
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• 2015

Objectives: To evaluate the biodurability of Korean Chrysotile(KC), the changes in fibers numbers and changes in the element composition of fibers from the lung of Sprague-Dawley rats instilled KC(average size $4.74{\mu}m$, $59,043{\times}10^6$ fibers/mg) was estimated. Methods: Rats were administered 1 mg KC(low group) or 2 mg KC(high group) by a single intratracheal instillation. At each time point(5 days, 5 weeks, 10 weeks), the numbers of KC fibers and the changes of element composition(atomic %) of KC fibers from the lung of the rats were analyzed with transmission electron microscope equipped with energy dispersive X-ray spectrometer. Results: Over time, the number of fibers within the lungs of animals were reduced. The average length of the low and high group is significantly reduced from 5 days after administration. Over time, the fiber ratio of at least $5{\mu}m$ remaining in the lung tissue of the low concentration group was up but the high group was reduced. From day 5 after administration, the composition ratio(Mg) was significantly decreased in all groups. Conclusions: Size and composition of Korean Chrysotile in the lung tissue of rats was changed from 5 days.

• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1830-1837
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• 2023

The thermal cutting of contaminated or activated metals during decommissioning nuclear power plants inevitably results in the release of radioactive aerosol. Since radioactive aerosols are pernicious particles that contribute to the internal dose of workers, air conditioning units with a HEPA filter are used to remove radioactive aerosols. However, a HEPA filter cannot be used permanently. This study evaluates the efficiency and lifetime of filters in actual metal cutting condition using a plasma arc cutter and a high-resolution aerosol detector. The number concentration and size distribution of aerosols from 6 nm to 10 ㎛ were measured on both the upstream and downstream sides of the filter. The total aerosol removal efficiency of HEPA filter satisfies the standard of removing at least 99.97% of 0.3 ㎛ airborne particles, even if the pressure drop increases due to dust feeding load. The pressure drop and particle size removal efficiency at 0.3 ㎛ of the HEPA filter were found to increase with repeated cutting experiments. By contrast, the efficiency of used HEPA filter reduced in removing nano-sized aerosols by up to 79.26%. Altogether, these results can be used to determine the performance guidance and replacement frequency of HEPA filters used in nuclear power plants.

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.119-128
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• 2004

Environmental impact of waste tires as gound-reinforcing material is studied. Analysis for chemical compounds and toxic effect were performed on effluents from twelve lysimeters in which waste tires were mixed with sand and three initially different environmental solutions of acidic, neutral, and basic circulated through the mixture. The test results of effluents collected from the lysimeters provided that the contaminant concentrations were lower than those of Korean drinking water standards for all the selected and tested metal elements. While iron concentration increased slightly with the exposure period, other metal concentrations decreased with the number of circulation times. From the comparison with previous investigations, the contaminant concentration decreased with the increase of tire size, i.e. increases with the increase of the exposed surface of tire metals. From the toxicity tests, no deteriorative effect was observed and it could be concluded that waste tires are not biologically hostile materials.

• Journal of Korean Society on Water Environment
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• v.34 no.3
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• pp.251-269
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• 2018

In 1997, the environmental score (Q) corresponding the tolerance value of Korean benthic macroinvertebrate species and the related biotic score, the ecological score of benthic macroinvertebrates (ESB) were proposed; ESB was similar to Beck's biotic index or Chandler's biotic score. This study was carried out to revise the Q values of individual species and the assessment scheme of ESB based on the taxonomic performance and ecological information accumulated since then. The original ESB was renamed as TESB (total ESB), and AESB (average ESB) was newly proposed. AESB is calculated by dividing the TESB (for a given station) by the number of species present in the sample. In this study, TESB showed a positively skewed distribution, while AESB showed a negatively skewed distribution. The correlation between TESB and the concentration of $BOD_5$ was a little stronger than that of the original ESB. TESB showed a very strong correlation (correlation coefficient r = 0.98) with Margalef's species richness, of which correlation coefficient was higher than that of AESB (r = 0.85). AESB showed a strong correlation (r = -0.79) with the concentration of $BOD_5$, while TESB showed a weaker correlation (r = -0.67). Applying TESB and AESB together in an assessment of the environment may be comprehensive because the physical and chemical states of the environment can be evaluated together. AESB is less dependent on the sample size, while TESB tends to increase as the sample size increases. In the evaluation of the environment using TESB, it is necessary to standardize the methods on monitoring.

• Journal of the Korean Applied Science and Technology
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• v.28 no.3
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• pp.306-312
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• 2011

In this study, we are crystallized to the low density polyethylene (LDPE) micro-particles in $n$-dodecanol solution by thermally induced phase separation(TIPS) method. The Low density polyethylene micro-particles is used in a wide variety of polymer coatings and industrial application. The utility of that for a particular application depends on a number of factors such as the particle size and distribution, and chemical composition of the materials. However, there are still needs for new methods of preparation which will provide the structure with unique sizes. The widely used processes for micro-size particles are crystallization method and thermally induced phase separation. TIPS process based on the phase separation mechanism was performed for the LDPE system which undergoes liquid-solid phase separation. Effects of various operating parameters were examined on the structure variation of the particles. Professionality, take-up speed and crystallization rate depended on temperature and concentration of polymer in solution.

• The Korean Journal of Zoology
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• v.23 no.1
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• pp.13-24
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• 1980

The germarium contains the apical complex consisting of a multinucleated syncytium. Apical complex has a nutritive role for the early spermatogonia. Trophocytes are irregularly shaped and are distributed throughout the space from spermatogonial cysts to sperm bundles, and they increase in size by endopolyploidization. As meiotic divisions are not complete until the final moult, spermatogenesis continues even in the adult. Chromosome number is 2n=24. Spermiogenesis is divided into seven stages in terms of chromatin concentration, cytoplasmic granules, and the nuclear size and shape. These stages could be grouped into the spherical, the elongating and the rodform spermatids in shape.

• Polymer(Korea)
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• v.32 no.2
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• pp.183-188
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• 2008

Reinforced open cell micro structured foams were prepared by the polymerization of high internal phase emulsions incorporating inorganic thickeners. Organoclays were used as oil phase thickener, and sodium montmorillonite was used as aqueous phase thickener. Rheological properties of emulsions increased as oil phase thickener concentration and agitation speed increased, due to the reduced drop size reflecting both competition between continuous and dispersed phase viscosities and increase of shear force. Drop size variation with thickener concentration could be explained by a dimensional analysis between capillary number and viscosity ratio. Upon the foams polymerized by the emulsions, compression properties, such as crush strength and Young's modulus were measured and compared. Among the microcellular foams, the foam incorporated with an organoclay having reactive group showed outstanding properties. It is speculated that the exfoliated silicate layers inside polystyrene matrix, resulting in nanocomposite foam, are the main reason why this foam has enhanced properties.

• Clinical and Experimental Reproductive Medicine
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• v.13 no.1
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• pp.39-51
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• 1986

This experiment has been done to evaluate the relationship between the follicular atresia and the protein patterns on electrophoreais of the follicular fluids in porcine ovary. The protein concentration of the follicular fluids was lower than that of serum, and gradually decreased as the follicle siae became larger. The number of protein bands of follicular fluid on electrophoresis was less than that of serum, and gradually increased as follicle size became larger. Three specific bands were detected on disc PAGE and one band(M W. 75,000) on SDS PAGE in the follicular fluids, while not in serum. One band (A) at ${\beta}$-globulin region on disc PAGE became heavier, as follicles became atretic. Two bands less than(M. W. 20,000) were detected only in the large follicular fluid. Another band(M. W. 43,000) was not detected in necrotic group, whereas all other groups showed it. It could be concluded that the component and composition of the proteins follicular fluids changes according to the follicular size during atresia. Therefore detection of the changing pattern of proteins in the follicular fluid can be used as a basic criterion for the identification of follicular atretic stage.

• Macromolecular Research
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• v.12 no.5
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• pp.519-527
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• 2004

Stable poly(methyl methacrylate-co-divinylbenzene) (poly(MMA-co-DVB)) microspheres were prepared by precipitation polymerization using acetonitrile as the main medium under various polymerization conditions, including modifications of the agitation speed, monomer and initiator concentrations, DVB content in the monomer mixture, and the use of various cosolvents. Gentle agitation was required to obtain smooth spherical particles. The individually stable microspheres were obtained at monomer concentrations of up to 15 vol% in an acetonitrile medium. The number-average diameter increased linearly with respect to increases in the monomer and initiator concentrations. We found, however, that the uniformity of the microspheres was independent of the variation of the polymerization ingredients because nuclei formation was solely influenced by the crosslinking reaction of the monomers. We obtained higher yields for the polymerization at higher concentrations of monomer and initiator. The concentration of DVB in the monomer mixture composition played an important role in determining not only the size of the microspheres but also the yield of the polymerization. In addition, although we employed various cosolvents as the polymerization medium, we found that acetonitrile/2-methoxyethanol was the only system that provided spherical particles without coagulation. This finding indicates that the precipitation polymerization is strongly dependent on the solvent used as the medium.