• Proceedings of the Korean Geotechical Society Conference
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• 1998.05a
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• pp.35-81
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• 1998

Distinct Element Method(DEM) has a great advantage to model the discontinuous behaviour of jointed rock masses such as rotation, sliding, and separation of rock blocks. Geometrical data of joints by a field monitoring is not enough to model the jointed rock mass though the results of DE analysis for the jointed rock mass is most sensitive to the distributional properties of joints. Also, it is important to use a properly joint law in evaluating the stability of a jointed rock mass because the joint is considered as the contact between blocks in DEM. In this study, a stochastic modelling technique is developed and the dilatant rock joint is numerically modelled in order to consider th geometrical and mechanical properties of joints in DE analysis. The stochastic modelling technique provides a assemblage of rock blocks by reproducing the joint distribution from insufficient joint data. Numerical Modelling of joint dilatancy in a edge-edge contact of DEM enable to consider not only mechanical properties but also various boundary conditions of joint. Preprocess Procedure for a stochastic DE model is composed of a statistical process of raw data of joints, a joint generation, and a block boundary generation. This stochastic DE model is used to analyze the effect of deviations of geometrical joint parameters on .the behaviour of jointed rock masses. This modelling method may be one tool for the consistency of DE analysis because it keeps the objectivity of the numerical model. In the joint constitutive law with a dilatancy, the normal and shear behaviour of a joint are fully coupled due to dilatation. It is easy to quantify the input Parameters used in the joint law from laboratory tests. The boundary effect on the behaviour of a joint is verified from shear tests under CNL and CNS using the numerical model of a single joint. The numerical model developed is applied to jointed rock masses to evaluate the effect of joint dilation on tunnel stability.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.2
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• pp.153-162
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• 2014

Purpose: This study was assessed to investigate the change of subjective and/or objective symptoms and the light transmittance of lens caused by the use longer than recommended wearing time of daily disposable circle contact lenses (circle lens) in dry eyes. Methods: Three daily disposable circle lenses made of etafilcon A, hilafilcon B, and nelfilcon A were applied on 30 dry eyes with smaller tear volume than normal eyes in their twenties free from any eye diseases by when subjects complained any kind of discomfort. On the first and the last days of lens wearing, subjective discomfort, blinking rate, lens centration on corneal surface and visible light transmittance of lens were recorded at every case and compared. Results: The circle lens wearers complained subjective discomfort and quit the lens wearing when they wore the circle lens longer than 10 hours even though there were some difference according to the lens materials of daily disposable circle lens. However, around 20% of dry eyes could wear the circle lens made of non-ionic materials longer than 40 hours. Dry eyes showed most sensitive feeling of subjective discomfort against the circle lens made of etafilcon A among three different lens materials. On the last day of lens wearing, the representative subjective discomforts were irritation, stiffness, dryness and tiredness. When the subjects wore circle lens more than the recommended time, blinking rate was significantly increased about 20~30% regardless of lens materials when it compared with the values right after lens wearing. On the last day of lens wearing, the vertical direction of lens centration was shifted to pupil center however, its distribution in horizontal direction was wide compared with the distribution right after lens wearing. Especially, the centration of etafilcon A lens was unstable. Furthermore, the visible light transmittance of 3 different circle lenses in dry eyes has significantly been reduced around 15% averaged. Conclusions: From these results, it was known that the increase of dryness and stiffness caused by overusage of daily disposable circle lens induced excess irritation and decreased visible light transmittance and caused significant more blinking, which provoked lens decentration. It was also revealed that dry eyes showed sensitive reaction subjectively and objectively against the overusage of circle lens made of high water content/ionic lens material even there were some difference of the degree depending on the individual and the lens material. Thus, this research can be suggested as the basic reference for the education about some unexpected problems and the side effect caused by the wearing of circle lens in dry eyes.

• Journal of Food Hygiene and Safety
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• v.28 no.3
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• pp.272-278
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• 2013

To evaluate the effect of surface contaminated with Escherichia coli O157:H7 (E. coli O157:H7) on the microbiological safety of lettuce, this study was conducted to investigate the attachment, biofilm producing, survival, and cross-contamination of E. coli O157:H7 on stainless steel and polyvinyl chloride (PVC). The attachment rate of E. coli O157:H7 on PVC was 10 times higher than that on stainless steel after exposure 1 h in cell suspension. However, there was not a difference between two types of surface after exposure for 6 h and 24h. The biofilm producing of E. coli O157:H7 was TSB > 10% lettuce extracts > 1% lettuce extracts > phosphate buffer. When two kinds of materials were stored at various conditions ($20^{\circ}C$ and $30^{\circ}C$, relative humidity (RH) 43%, 69%, and 100%), the numbers of E. coli O157:H7 at $30^{\circ}C$, RH 43% or RH 69% were reduced by 5.0 log CFU/coupon within 12 h regardless of material type. Conversely, the survival of E. coli O157:H7 at RH 100% was lasted more than 5 days. In addition, the reduction rate of E. coli O157:H7 was decreased in the presence of organic matter. The transfer efficiency of E. coli O157:H7 from the contaminated surface to lettuce was dependent upon the water amount of the surface of lettuce. Especially, the transfer rate of E. coli O157:H7 was increased by 10 times in the presence of water on the lettuce surface. From this study, the retention of E. coli O157:H7 on produce contact surfaces increase the risk cross-contamination of this pathogen to produce. Thus, it is important that the surface in post harvest facility is properly washed and sanitized after working for prevention of cross-contamination from surface.

• Journal of Veterinary Clinics
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• v.29 no.4
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• pp.283-296
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• 2012

Allergic contact dermatitis (ACD) is an inflammatory skin disease and regarded as a prototype of T-cell mediated delayed-type hypersensitivity reactions. Poly-${\gamma}$-glutamic acid (PGA) is a biodegradable polymer that is produced by Bacillus subtilis. This study was performed to assess the effects of PGA in a canine model of ACD. ACD was induced on the back of dogs induced by sensitization and repeated application by 2,4-dinitro-1-chlorobenzene (DNCB). Topical treatment of PGA was applied once a day for 12 days and skin biophysical parameters including transepidermal water loss (TEWL), skin hydration, skin pH, skin thickness and erythema index, were measured every two days during experimental periods. Histopathology and immunohistochemistry were performed to evaluate the antiinflammatory effect. In skin biophysical parameters, TEWL, skin hydration, skin thickness and erythema index were significantly increased, with a maximum increase appeared on day 2 (p < 0.05). On the other hand, skin pH was significantly decreased, with a maximum decrease appeared on day 2 (p < 0.01). After the completion of PGA treatment, skin biophysical parameters were significantly reached those of baseline in a time-dependent manner (p < 0.05). In histopathology, marked increases of epidermal thicknesses were induced after DNCB challenge with numerous inflammatory cell infiltrations and edematous changes, decreases of connective tissue occupied regions in dermis. In addition, marked increases of cytokine - tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$) and interferon-${\gamma}$ (IFN-${\gamma}$)-immunoreactivities in the dermis and of apoptotic markers - caspase-3 and PARP-immunoreactivities in the epidermis were observed in DNCB-PBS control as compared with intact control, respectively (p < 0.01). It means, the ACD and related apoptotic changes were induced by DNCB in the present study. However, these ACD induced by DNCB and related apoptosis in epidermis were significantly inhibited by treatment of PGA treated skin, the decreases of infiltrated inflammatory cells and related decreases of pro-inflammatory cytokine immunoreactivities were also observed (p < 0.01). Based on these findings, PGA may have anti-inflammatory and alleviatory effects in the allergic contact dermatitis.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.1
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• pp.51-57
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• 2014

Purpose: The present study was conducted to establish the experimental condition for the proper evaluation of protein removal efficacy when developing protein removal agents. Its protein removal efficacy was further analyzed and compared with the result from protein removal efficacy against protein deposition on contact lens to suggest the evaluation method for efficacy of protein removal agents. Methods: Protein digestibility assay presented in the Korean pharmacopoeia was selected to establish the evaluation method for efficacy of papain, pancreatin, subtilisin A and protease itself as a ingredient and protein removal tablets or solution containing those enzymes and find a suitable test conditions. Furthermore, the cleaning efficacy of commercially available protein removal tablets and solution on balafilcon A lens deposited with protein artificially was measured and the correlation between two evaluation methods was further analyzed. Results: When pancreatin itself and the product containing pancreatin was evaluated by protein digestibility assay, both reached 28 IU/mg, the standard value of protein digestibility suggested by the Korean pharmacopoeia. In case of protease and subtilisin A tested with trichloroacetic acid B solution, both of them met the enzyme activity level proposed by the manufacturers when they were evaluated by protein digestibility assay however, papain and subtilisin A tested with trichloroacetic acid A solution were not reached the enzyme activity level. Among protein removal agents, three products except a product containing pancreatin did not meet the enzyme activity value specified by the manufacturer when they were evaluated by protein digestibility assay. However, actual protein removal efficacy of three products except a papain-containing product on the lens was greater than 90% protein removal. In the case of papain-containing protein removal product, its effect was not measured by protein digestibility assay however, its actual protein removal efficacy on the lens reached 73.72%. Conclusions: From the results, it was confirmed that the efficacy of protein removal agents for contact lens should be evaluated by different method according to the type of proteolytic enzyme contained. That is, the protein removal agents containing pancreatin, protease and subtilisin A can be evaluated by protein digestibility assay and protein removal efficiency evaluation and the products containing papain can be effectively evaluated by only the evaluation method for protein removal efficiency employing the lens.

• Korean Journal of Optics and Photonics
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• v.18 no.6
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• pp.452-460
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• 2007

Ultra-low loss ZERODUR and fused silica mirrors were manufactured and their light scattering characteristics were investigated. For this purpose, ZERODUR and fused silica substrates were super-polished by the bowl feed method. The surface roughness were 0.292 ${\AA}$ and 0.326 ${\AA}$ in rms for ZERODUR and fused silica, respectively. To obtain the high reflectivity, 22 thin film layers of $SiO_2$ and $Ta_2O_5$ were deposited by Ion Beam Sputtering. The measured light scattering of ZERODUR and fused silica mirror were 30.9 ppm and 4.6 ppm, respectively. This shows that the substrate surface roughness is not the only parameter which determines the light scattering of the mirror. In order to investigate the mechanism for additional light scattering of the ZERODUR mirror, the surface roughness of the mirror was measured by AFM and was found to be 2.3 times higher than that of the fused silica mirror. It is believed that there is some mismatch at the interface between the substrate and the first thin film layer which leads to the increased mirror surface roughness. To clarify this, the contact angle measurements were performed by SEO 300A, based on the Giriflaco-Good-Fowkes-Young method. The fused silica substrates with 0.46 ${\AA}$ in its physical surface roughness shows lower contact angle than that of the ZERODUR substrate with 0.31 ${\AA}$. This indicates that the thin film surface roughness is determined by not only its surface roughness but also the surface energy of the substrate, which depends on the chemical composition or crystalline orientation of the materials. The surface energy of each substrate was calculated from a contact angle measurement, and it shows that the higher the surface energy of the substrate, the better the surface roughness of the thin film.

• The Journal of Korean Academy of Prosthodontics
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• v.49 no.4
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• pp.300-307
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• 2011

Purpose: This study evaluated PostGraft$^{TM}$ which enhances implant stability and bone density. Materials and methods: Forty eight implants were installed at the tibia of ovariectomized rats. The group administrated with PostGraft$^{TM}$ was the experimental group, and the control group was not administrated. Implant stability was evaluated at the $2^{nd}$, $4^{th}$ and $6^{th}$ week by Periotest value, bone mineral density, bone-to-implant contact. These values were analyzed statistically with Mann-Whitney U test (P<.05). Histological analysis was evaluated at the $2^{nd}$, $4^{th}$ and $6^{th}$ week. Results: According to the Periotest$^{(R)}$ measurement, both experimental and control groups showed decrease in values as time elapsed. Greater decrease was observed in the experimental group but there was no significant difference. By examining the radiographic images, both experimental and control groups showed tendency of increase in bone density. Greater increase was seen in the experimental group but there was no significant difference. According to the bone-to-implant contact measurement, both experimental and control groups showed increase in values as time elapsed. Greater increase was seen in the experimental group. At the $2^{nd}$ and $4^{th}$ week, there was no significant difference. But at the $6^{th}$ week, there was significant difference (P<.05). By histological analysis, both experimental and control groups showed increase in bone formation as time elapsed. In addition, greater increase was seen in the experimental group. Conclusion: It could be concluded that the PostGraft$^{TM}$ medicated group showed better results in the bone density and osseointegration.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.7
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• pp.483-490
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• 2009

The aims of this study were to evaluate the removal efficiency for various pollutants in urban storm runoff by a filtration device, and to determine design parameters depending on filter media properties. Appropriate selection of filter media will affect the size and life time of the filtration device. Sets of column tests were performed in order to evaluate the removal efficiency by perlite and a synthetic resin. An investigation of surface properties including CEC (cation exchange capacity) and zeta-potential suggested that the perlite had a superior adsorption capability for cationic pollutants. TCODcr and turbidity were analyzed to investigate the removal characteristic of particulate pollutant. In both columns, the particles in the collected storm runoff was almost completely capture with a small EBCT (empty bed contact time) of 2.5 minutes. Complete clogging at the EBCT of 2.5 minutes occurred after 630 minutes in the perlite column and 810 minutes in the resin column. The removal efficiency of TCODcr and turbidity at the EBCT of 2.5 minutes decreased to below 70% due to an wall effect. The removal efficiency for dissolved pollutant (SCODcr) was negligible due to the insufficient contact time for adsorption. The removal of heavy metals (Cu, Zn, Pb) was mostly ascribed to the filtration of particles containing metals, since the relationship between CEC and the removal efficiency was not apparent. The result of this study would be valuable for the application of filtration device to control of urban storm runoff.

• Journal of Astronomy and Space Sciences
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• v.26 no.2
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• pp.141-156
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• 2009

Through the photometric observations of the near-contact binary, XZ CMi, new BV light curves were secured and seven times of minimum light were determined. An intensive period study with all published timings, including ours, confirms that the period of XZ CMi has varied in a cyclic period variation superposed on a secular period decrease over last 70 years. Assuming the cyclic change of period to occur by a light-time effect due to a third-body, the light-time orbit with a semi-amplitude of 0.0056d, a period of 29y and an eccentricity of 0.71 was calculated. The observed secular period decrease of $-5.26{\times}10^{-11}d/P$ was interpreted as a result of simultaneous occurrence of both a period decrease of $-8.20{\times}10^{-11}d/P$ by angular momentum loss (AML) due to a magnetic braking stellar wind and a period increase of $2.94{\times}10^{-11}d/P$ by a mass transfer from the less massive secondary to the primary components in the system. In this line the decreasing rate of period due to AML is about 3 times larger than the increasing one by a mass transfer in their absolute values. The latter implies a mass transfer of $\dot{M}_s=3.21{\times}10^{-8}M_{\odot}y^{-1}$ from the less massive secondary to the primary. The BV light curves with the latest Wilson-Devinney binary code were analyzed for two separate models of 8200K and 7000K as the photospheric temperature of the primary component. Both models confirm that XZ CMi is truly a near-contact binary with a less massive secondary completely filling Roche lobe and a primary inside the inner Roche lobe and there is a third-light corresponding to about 15-17% of the total system light. However, the third-light source can not be the same as the third-body suggested from the period study. At the present, however, we can not determine which one between two models is better fitted to the observations because of a negligible difference of $\sum(O-C)^2$ between them. The diversity of mass ratios, with which previous investigators were in disagreement, still remains to be one of unsolved problems in XZ CMi system. Spectroscopic observations for a radial velocity curve and high-resolution spectra as well as a high-precision photometry are needed to resolve some of remaining problems.

• Pediatric Infection and Vaccine
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• v.9 no.1
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• pp.61-66
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• 2002

Purpose : To determine wether varicella can be prevented by administration of oral acyclovir(ACV) during the incubation period of the disease. Methods : Starting 9 days after exposure to the index case in their families, ACV(40 mg/kg/day in four divided doses) was given orally to 20 exposed children for 5 days. Their clinical features was compared with those of 20 control subjects. Antibody titers to VZV were measured in both group 1 week and 4 weeks after finishing the oral ACV administration. Results : The mean age of family members with varicella(51.4 months) were significantly high compared to that of ACV prophylaxis group(28.5 months) and control group(31 months) (P<0.05). Among the 12 children with ACV prophylaxis who completed follow up blood sampling, nine children were diagnosed as VZV infection on the serologic test(75%). Among them six children showed positive VZV IgM on the first blood sample and two children showed serocoversion to positive IgM on the second test after ACV prophylaxis. One child who was negative on both IgM and IgG, showed positive IgG on the second test. The incidence of fever and severity of skin rashes were significantly low in children received oral ACV than in the control group. No or reduced number of maculopapular eruption were observed in the oral ACV group compared to multiple vesicles of the control group. Conclusion : In the present study, we observed that oral ACV prophylaxis to the family contacts is effective in reducing severity of skin lesion. It is likely that oral ACV 9 days after contact prevents or reduces blood dissemination of VZV. Little is known about clinical effect and immunity to the virus in exposed children with no varicella symptom after treatment. We propose the checking up antibody to VZV some period after oral ACV, and considering vaccination to whom with no antibody. But further more studies are needed to practical application of oral ACV for the postexposure prophylaxis of varicella.