• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.42-46
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• 2008

Even though fuel cell have high efficiency when pure hydrogen from gas tank is used as a fuel source, it is more beneficial to generate hydrogen from city gas (mainly methane) in residential application such as domestic or office environments. Thus hydrogen is generated by reforming process using hydrocarbon. Unfortunately, the reforming process for hydrogen production is accompanied with unavoidable impurities. Impurities such as CO, $CO_2$, $H_2S$, $NH_3$, $CH_4$, and $CH_4$ in hydrogen could cause negative effects on fuel cell performance. Those effects are kinetic losses due to poisoning of the electrode catalysts, ohmic losses due to proton conductivity reduction including membrane and catalyst ionomer layers, and mass transport losses due to degrading catalyst layer structure and hydrophobic property. Hydrogen produced from reformer eventually contains around 73% of $H_2$, 20% or less of $CO_2$, 5.8% of less of $N_2$, or 2% less of $CH_4$, and 10ppm or less of CO. This study is aimed at investigating the effect of carbon dioxide on fuel cell performance. The performance of PEM fuel cell was investigated using current vs. potential experiment, long run(10 hr) test, and electrochemical impedance measurement when the concentrations of carbon dioxide were 10%, 20% and 30%. Also, the concentration of impurity supplied to the fuel cell was verified by gas chromatography(GC).

• Journal of Periodontal and Implant Science
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• v.30 no.2
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• pp.305-324
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• 2000

This study compared the short-term(4 months) clinical results of regenerative therapy with bioabsorbable membranes($BioMesh^{(R)}$) and bone allograft for the treatment of periodontal(intrabony and furcation) defects in smokers and nonsmokers.(16 smokers) 32 subjects with 92 defects participated in the study(46 in smokers and 46 in non-smokers). This study also evaluated a bioresorbable barrier with and without decalcified freeze-dried bone allograft(DFDBA). The 92 periodontal defects were randomly treated with either the resorbable barrier alone or resorbable barrier in combination with DFDBA following thorough defect debridement and root preparation with tetracycline. Each patient received both types of treatment modalities. Clinical examinations(probing depth, gingival recession, clinical attachment level, plaque index and gingival index) were carried out immediately before and 4 months after surgery. Significant(p<0.001) gains in mean attachment level were observed for both smokers(2.93mm) and non-smokers(3.30mm) but there were not significant difference between two groups. Similarly, significant reductions in mean probing depthshowed for smokers(4.52mm) and non-smokers(4.26mm). However, when comparing gingival recession, smokers were found to exhibit significantly poorer treatment results(1.59mm vs 0.96mm, p<0.05). Using the split-mouth-design, no statistically significant difference between the two modalities could be detected with regard to pocket depth reduction, gingival recession, or attachment gain. These results illustrate that the attachment gain is better in the non-smoker and the best in the non-smoker with the combination therapy of resorbable barrier and DFDBA than with resorbable barrier alone but smoking had no significant effect on clinical treatment outcome, even though smokers show more significant gingival recession. In addition, both treatments, either resorbable barrier plus DFDBA or resorbable barrier alone, promoted significant resolution of periodontal defects but the addition of DFDBA with a bioabsorbable membrane appears to add no extra benefit to the only membrane treatment.

• Journal of the Korea Organic Resources Recycling Association
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• v.9 no.1
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• pp.90-98
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• 2001

The slow degradation rate of sewage sludge in anaerobic digesters is due to the rate limiting step of sludge hydrolysis. Therefore, the pre-treatment process had been carried out using acidic(pH 1.5, 3, 4, 5) and alkaline(pH9, 10, 13), thermal(50, 100, 150, $200^{\circ}C$) and ultrasonic treatment(400W, 20kHz, 15, 20, 25, 30, 35, 40, 50, 60min). In the best conditions of each treatment, the SCOD ratio(%) of treated/untreared samples were increased 102% in acid(pH5), 986% in alkali(pH13), 959% in thermal($200^{\circ}C$) and 1123% in ultrasonic(35min) treatment. As the result, the ultrasonic treatment was most effective, followed by alkali, thermal, acidic treatment. In the effects of total gas productivity, the thermal($200^{\circ}C$) pretreatment was the highest, followed by thermal($150^{\circ}C$), ultrasonic(90min), alkaline(pH9) and ultrasonic(50min).

• The Journal of Engineering Geology
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• v.3 no.1
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• pp.21-37
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• 1993

In order to investigate the correlation of sedimentary rock properties. specific gravity, porosity, water content, sonic wave velodty, and point4oad strength index of core samples of limestones, sandstones and shales were measured. The relationships between density and velocity show $V_p=16300d-38719.3,{\;}V_s1896.4d-29225.1$ of regression equation for sandstones and $Vp=4085d-10264.8,{\;}V_s=3519d-7841.3$ for shales and <$Vp=4085d^2-20747d+303,{\;}V_s=3899d^2-21442d+318$ for limestones. Seismic wave velocity of shales which have high density is lower than that of sandstones, and this seems to be an effect of bedding in shale. P-wave velocity and S-wave velocity of limestones, sandstones and shales show the linear relationships as a whole. The regression equations are respectively calculated V_s=0.26V_p+1041.6m/sec,{\;}V_s=0.43V_p+424.2m/sec,{\;}and{\;}Vs=0.51V_p+261.9m/sec$ and the correlation coefficients of the velocity show r= 0.86 in sandstones, r= 0.75 in limestones and r=0.86 in shales. According to the point4oad strength test for limestones, point4ord strength anisotropy was not so dear even though the specimens show generally the banded structure. Variations of dip angle of bedding whihin the range $30^{\circ}-60^{\circ}$ does not have much influence upon the diametral strength index and axial strength index. From the result of point load test, P-wave velocity increases with point4ord strength index but the regression equations are $V_p=98.5lI{s_d}+4082.1m/sec,{\;}V_p=106.41{s_a}+3954m/sec$ and their correlation coefficient is low.

• Childhood Kidney Diseases
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• v.1 no.2
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• pp.151-154
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• 1997

Purpose : The prevalence of renal malformation in Turner syndrome has been quoted as being greater than 50% in older series. Recently in 1988, Lippe's review gave a prevalence of 33%, significantly lower than all previous reports. In 1996, Flynn reported that renal malformation occurs in approximately 24% of all girls with Turner syndrome, and that it is seldom seen in girls with mosaic karyotype who form the predominant subgroup. The aim of this study was to evaluate prevalence of renal malformation by karyotype in Turner syndrome in Korea. Method : We evaluated 81 patients with Turner sundrome diagnosed in Yonsei University from Jan. 1987 to Dec. 1996. The patient entered in this study were those for whom both karyotype and ultrasound examination of the kidney were available. Result : 1) The karyotype showed: 45,X ; 29 cases (38%), mosaicism : 32 cases (40%), structural aberration ; 17 cases (22%). 2) Of the 29 cases of pure 45,X karyotype, 5(17%) had abnormal renal findings, while these were found in only 1 of the 30 mosaic cases(3.3%), and in 1 of the 17 structural aberration cases(6%). The malformation included 3 cases of horseshoe kidney, 2 cases of axial malrotation, hypoplastic kidney and simple cyst each one. There was no statistical significance between 3 groups (p=0.09). Conclusion : We conclude that renal malformation occurs in 9.2% in this study, therefore Korean girls with Turner syndrome have lower rates of renal malformation.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.30 no.2
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• pp.134-152
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• 2020

Objectives: The objective of this study was to evaluate volatile organic compounds (VOCs) and toluene diisocyanates (TDIs) exposure among polyurethane waterproofing workers in the construction industry. Methods: Task-based personal air samplings were carried out at seven construction sites using organic vapor monitor for VOCs (n=88) and glass fiber filters coated with 1-(2-pyridyl)piperazine(1-2PP) for TDIs (n=81). The concentration of VOCs and TDIs were shown for four different work types(mixing paint, primer roller painting, urethane resin spread painting, painter assistant) at five different worksites (rooftop, ground parking lot, piloti, bathroom, and swimming pool). The two TDI sampling methods (filter vs impinger) were evaluated in parallel to compare the concentrations. Results: The geometric mean(GM) concentration of VOCs Exposure Index (EI) was highest for primer roller painting (1.4), followed in order by, urethane resin spread painting (0.85), mixing paint (0.53), and painter assistant (0.35) by work types. The GM of VOCs EI was highest for bathroom (1.4) followed in order by, swimming pool (0.85), piloti (0.89), ground parking lot (0.82) and rooftop (0.57) by worksites. The GM of 2,4-/2,6-TDI concentration was 0.052 ppb and 0.432 ppb each. There was no statistical difference in TDIs concentrations among worksites. The concentration of 2,6-TDI was ten times higher than that of 2,4-TDI. The concentration of 2,6-TDI by impinger method was 5.7 times higher than that by filter method. Conclusions: In this study, we found 38.6% of the VOCs samples exceeded the occupational exposure limits and 19.8% of the 2,6-TDI samples exceeded 1 ppb among polyurethane waterproofing workers. The most important determinants that increase the concentration of VOCs and TDIs was indoor environment and primer painting work.

• Korean Journal of Animal Reproduction
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• v.25 no.4
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• pp.399-407
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• 2001

The microinjection of retroviral vectors into the perivitelline spaces of MII-stage oocytes increased production of transgenic bovine embryos. However, oocytes have various sizes of perivitelline space, and there is the tendency that the oocyte membranes are damageable by micropipettes during the injection of retroviral vectors into perivitelline spaces or oocytes. Thus, it was not always possible to stably inject retroviral vector into perivitelline spaces of oocytes. Here we used sucrose to minimize the damage of the oocyte membrane. When the oocytes were suspended in 0.5% sucrose, poor quality oocytes showed rough cytoplasmic membranes, while good quality oocytes maintained smooth membranes. However, when the tatters were subjected to in vitro fertilization, no significant differences were observed in cleavage rates (82% of control Vs. 84% of sucrose treated oocytes). The Same trends were obtained from the oocytes fertilized after microinjection of LN$\beta$-EGFP and LNC-hGH genes into the perivitelline spares. The rates of cleavage and blastocyst from microinjection of LN$\beta$-EGFP genes were 81 and 25%, and from microinjection of LNC-hGM genes were 53 and 30%, respectively. The result indicated that microinjected oocytes could develop to the blastocyst stages after in vitro fertilization with no significant difference from control group. Moreover, the integration of hGH-gene (by PCR analysis) was detected in 52% of infected cleaved embryos and the expression of EGFP-gene (under a fluoresrence microscope) was also observed in 34% of infected blastocyst. These results indicated that 0.5% sucrose treatment could be an efficient method not only to select good quality embryos but also to inject retroviral vectors into perivitelline spares without any harm and hence improving developmental rates.

• Korean Journal of Clinical Laboratory Science
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• v.36 no.1
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• pp.27-32
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• 2004

Bone marrow transplantation(BMT) is widely used as curative means of various malignant and nonmalignant hematologic disorders, and early and accurate determination of engraftment is very important for critical management decisions. Reticulocyte counts performed by automated flow cytometric methods is a good indicator of erythropoietic activity and its evaluation has been proposed as an early predictor of bone marrow regeneration. Some reports highlighted the usefulness of the percentage of highly fluorescent reticulocytes and the sum of highly and medium fluorescent reticulocytes(immature reticulocyte fraction, IRF). In Asan Medical Center, the criteria for engraftment following BMT or PBSCT was defined as the first day of a 3-day trend of absolute neutrophil count(ANC)${\geq}500/uL$ and platelet count${\geq}30{\times}10^3/uL$. In 1999, Grotto et al proposed an indidator of bone marrow recovery as the first day on which the IRF was twice the minimum value after bone marrow transplantation. To compare the both criterias, we got consecutive datas of immature reticulocyte fraction, absolute neutrophil count(ANC), WBC count, platelet count and reticulocyte count by XE-2100 automated hematology analyzer(Sysmex Co. Japan) from 33 patients daily after BMT. When compared to standard neutrophil engraftment(10-30 days, $16.2{\pm}4.6days$), IRF engraftment (5-21 days, $11.0{\pm}3.9days$) occured significantly earlier in 87.9% of patients(P<0.05). The mean engraftment day for WBC count(11-29 days, $16.4{\pm}4.3days$) was similar to ANC, but platelet count and reticulocyte count revealed more delayed data (10-49 days, $19.1{\pm}7.4days$ vs 17-64 days, $31.4{\pm}14.1days$). In conclusion, our results confirm that an increase in the immature reticulocyte population is the earliest sign of the hematopoietic recovery after BMT and that automated reticulocyte quantification including immature fraction may be integrated into clinical protocols to evaluate bone marrow reconstitution.

• Korean Journal of Food Science and Technology
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• v.19 no.6
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• pp.486-491
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• 1987

The performance and applicability to food concentration of heat pump were investigated. During heating the water of spa from $43^{\circ}C$ to $51^{\circ}C$, COP's of heat pump (R-12, 150 HP) were 4.03 at heating part and 3.5 at cooling part. And, the efficiency of compressor (${\alpha}$) was 0.477 While the city water was heated to $39^{\circ}C$ by heat pump (R-22, 10 HP), its COP's were 3.0 at heating part and 1.87 at cooling part. During concentrations sucrose solution by centrifugal evaporator (ALFA-LAVAL CO, CTIB) with heat pump, heat capacity for condensating water vapor was required greater 15% than the latent heat for concentrating and then the overall heat transfer coefficient was $1196\;Kcal/m^{2}.\;h.\;^{\circ}C$. When low temperature concentration ($30-35^{\circ}C$, 28-40 Torr) of garlic extract was carried out by the water of $60^{\circ}C$ and $15^{\circ}C$ adjusted by heat pump, the ratio of heat capacity for concentrating vs. that for condensating of water vapor was 0.961.

• KSBB Journal
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• v.20 no.2 s.91
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• pp.106-111
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• 2005

The functional relationship between the number of mole of an i-fatty acid (Si) included in fish oil and the hydrolysis time(t) was expressed as a mathematical model, $S_i=-{\alpha_i}1n(t)+\beta_i$. The average errors of calculated values on the basis of the measured values were distributed in the range of less than $5\%$ for all the 15 fatty aids composing of fish oil. The equation of hydrolysis rate of each fatty acid was deduced as $v_i={\gamma_i}exp(\frac{S_i}{\alpha_i})$ from the above-mentioned $S_i=-{\alpha_i}ln(t)+{\beta_i}$. Therefore the hydrolysis yields of fatty acids were analyzed using the equation of $S_i\;Vs.\;t.$. The 15 fatty acids were categorized into 4groups from the view point of hydrolysis yield. The hydrolysis yields of the first group, including C14:0, C16:0, C16:1, C18:0, C18:1 (n-7) and 1l8:1 (n-9), were higher than $70\%$ at 48 hr of hydrolysis. Those of the second group, C20:1, C22:1, C18:3, C20:4 and C20:5, were distributed from $40\%,\;to\;60\%$, and third group were around $30\%$. The final group containing only C22:6 was very hard to be hydrolyzed and the yield was less than $20\%$ at the same time.