• Journal of Korea Water Resources Association
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• v.51 no.3
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• pp.263-272
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• 2018

For the design of hydraulic structures, the design flood discharge corresponding to a specific frequency is generally used by using the design storm calculated according to the rainfall-runoff relationship. In the past, empirical equations such as rational equations were used to calculate the peak flow rate. However, as the duration of rainfall is prolonged, the outflow patterns are different from the actual events, so the accuracy of the temporal distribution of the probability rainfall becomes important. In the present work, Huff's quartile method is used for the temporal distribution of rainfall, and the third quartile is generally used. The regression equation for Huff's quadratic curve applies a sixth order polynomial equation because of its high accuracy throughout the duration of rainfall. However, in statistical modeling, the regression equation needs to be concise in accordance with the principle of simplicity, and it is necessary to determine the regression coefficient based on the statistical significance level. Therefore, in this study, the statistical significance test for regression equation for temporal distribution of the Huff's quartile method, which is used as the temporal distribution method of design rainfall, is conducted for 69 rainfall observation stations under the jurisdiction of the Korea Meteorological Administration. It is statistically significant that the regression equation of the Huff's quartile method can be considered only up to the 4th order polynomial equation, as the regression coefficient is significant in most of the 69 rainfall observation stations.

• Journal of the Mineralogical Society of Korea
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• v.27 no.3
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• pp.107-114
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• 2014

In this study, we tried to determine the origin of fine-grained sediments in Southeastern Yellow Sea Mud patch (SEYSM) using principal component analysis coupled with semi-quantitative X-ray diffraction analysis for 4 major clay minerals. We used 51 marine surface sediments from SEYSM and 33 surface sediments of rivers flowing into the Yellow Sea. We made bioplot diagram using R program with principal component 1 and component 2 because the two components might contain about 98% of all data. The content of each clay mineral in the south and north regions of SEYSM are almost similar. In the biplot, SEYSM sediments distribute close to Korean rivers sediments than Huanghe and Changjiang sediments. Based on these results, we suggest that SEYSM is originated from the Korean rivers sediments. The higher accumulation rate in the SEYSM compared to the sediment discharge from neighboring Korean rivers can be explained by erosion and reworking of surface sediments in this area. The principal component analysis can be used for the provenance research of marine sediments around the Korean Peninsula.

• Korean Journal of Clinical Pharmacy
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• v.26 no.4
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• pp.318-323
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• 2016

Background: Multidisciplinary team care (MTC) is a collaborative approach to treatment plan and ongoing care. We aimed to evaluate the clinical effect of MTC on the regulation of chronic kidney disease-mineral and bone disorder (CKD-MBD) complications in dialysis patients. Methods: This retrospective observational study was approved by the institutional review board. Among patients who have undergone dialysis at admission, the patients admitted to the nephrology ward were allocated to MTC group, and the others to usual care (UC) group. The MTC group had collaborative care by nephrologists, nurses, pharmacists, and nutritionists. The endpoints were the regulation of corrected calcium (cCa) and phosphate (P), the percent of patients in target level of cCa-P product ($cCa{\times}P$), and the prescription rate of non-calcium based P-binders. Results: A total of 163 patients were included from January to December 2009. A significant difference was shown in the percentage of patients in target $cCa{\times}P$ level at admission (MTC vs. UC, 81.40% vs. 91.67%; P = 0.038), but there was no significant difference at discharge. During admission, the cCa and P levels of patients in only UC group were significantly changed. In addition, compared with UC group, patients in MTC group were more likely prescribed appropriate P-binders, when they had higher $cCa{\times}P$ levels than $55mg^2/dL^2$ (P <0.001). Conclusion: It was found that MTC had beneficial effect on improving the regulation of CKD-MBD and the appropriate phosphate binder uses. Therefore, application of the MTC is anticipated to enhance quality of clinical care in chronic diseases.

• Korean Chemical Engineering Research
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• v.54 no.6
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• pp.746-752
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• 2016

In this study, soft carbon was prepared by carbonization of carbon precursor (pitch) obtained from PFO (pyrolysis fuel oil) heat treatment. Three carbon precursors prepared by the thermal reaction were 3903 (at $390^{\circ}C$ for 3 h), 4001 (at $400^{\circ}C$ for 1 h) and 4002 (at $400^{\circ}C$ for 2 h). After the prepared soft carbon was ground to a particle size of $25{\sim}35^{\circ}C$, the soft carbon was synthesised by the chemical treatment with boric acid ($H_3BO_3$). The prepared soft carbon were analysed by XRD, FE-SEM and XPS. Also, the electrochemical performances of soft carbon were investigated by constant current charge/discharge test, cyclic voltammetry and impedance tests in the electrolyte of $LiPF_6$ dissolved inorganic solvents (EC:DMC=1:1 vol%+VC 3 wt%). The coin cell using soft carbon of $25{\sim}35^{\circ}C$ with 3903 soft carbon ($H_3BO_3$/Pitch=3:100 in weight) has better initial capacity and efficiency (330 mAh/g, 82%) than those of other coin cells. Also, it was found that the retention rate capability of 2C/0.1C was 90% after 30 cycles.

• Journal of the Korean Electrochemical Society
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• v.9 no.1
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• pp.1-5
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• 2006

Lithium titanium oxide $(Li_4Ti_5O_{12})$ with spinel-framework structures as anode material for lithium-ion battery was prepared by sol-gel and high energy ball milling (HEBH) method. According to the X-ray diffraction (XRD), Particle Size Analyses(PSA) and scanning electron microscopy (SEM) analysis, uniformly distributed $Li_4Ti_5O_{12}$ particles with grain sizes of 100 nm were observed. Half cells, consisting of $Li_4Ti_5O_{12}$ as working electrode and lithium foil as both counter and reference electrodes showed the high performance of high rate discharge capacity and 173 mAh/g at 0.2C in the range of $1.0\sim2.5 V$. Furthermore, the crystalline structure of $Li_4Ti_5O_{12}$ didn't transform during the lithium intercalation and deintercalation process.

• Journal of the Korean Electrochemical Society
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• v.19 no.3
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• pp.101-106
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• 2016

In this study, we prepared an ionic liquid composite solid polymer electrolyte (PEO-LiTFSI-$Pyr_{14}TFSI$) with poly(ethylen oxide), lithium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide by blending-cross linking process. Although the PEO-LiTFSI-$Pyr_{14}TFSI$ composite solid polymer electrolyte displayed a small peak at 4.4 V, it had high electrochemical oxidation stability up to 5.7 V. Ionic conductivity of the PEO-LiTFSI-$Pyr_{14}TFSI$ composite solid polymer electrolyte increased with increasing temperature from $10^{-6}S\;cm^{-1}$ at $30^{\circ}C$ to $10^{-4}S\;cm^{-1}$ at $70^{\circ}C$. To investigate the electrochemical properties, the PEO-LiTFSI-$Pyr_{14}TFSI$ composite solid polymer electrolyte assembled with $LiFePO_4$ cathode and Li-metal anode. At 0.1 C-rate, the cell delivered $40mAh\;g^{-1}$ for $30^{\circ}C$, $69.8mAh\;g^{-1}$ for $40^{\circ}C$ and $113mAh\;g^{-1}$ for $50^{\circ}C$, respectively. The PEO-LiTFSI-$Pyr_{14}TFSI$ solid polymer electrolyte exhibited good charge-discharge performance in Li/SPE/$LiFePO_4$ cells at $50^{\circ}C$.

• Journal of the Korean Electrochemical Society
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• v.11 no.4
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• pp.268-272
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• 2008

$LiFePO_4$ material was synthesized by electrospinning method to obtain optimal particle size($50{\sim}100\;nm$) without carbon coating or ball milling. This material showed an orthorthombic structure with Pnma space group without any impurities, such as FeP or $Fe_2P$, in the XRD pattern. The particle morphology and particle shape were observed by SEM analysis. Li/$LiFePO_4$ cell showed a high initial discharge capacity of 135 mAh/g, at current density of $0.1\;mA/cm^2$ with a cut-off voltage of 2.8 to 4.0V. This cell exhibited a perfect cycle performance over 99.9% cycle retention rate up to 50 cycles.

• Korean Journal of Agricultural Science
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• v.11 no.2
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• pp.284-294
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• 1984

Effects of orifice diameter, operating angle and swirl chamber distance were examined to study a reasonable distribution pattern on the maximum available travel distance in the triple nozzle system. The results of the study were as follows; 1. Discharge rate was increased with increase of orifice diameter, and a quadratic line for the 1st nozzle and linear lines for the 2nd or the 3rd nozzle. 2. The operating angle of $15^{\circ}$ had showed the maximum available travel distance, and 17m in orifice diameter of 3.0mm and operating pressure of $24.5{\times}10^5pa$ ($25Kg/cm^2$). 3. Nozzle setting methods (reference Table 6.) for improvement of uniformity of deposit distribution were varied depending on the size of orifice diameter of the 1st nozzle, nevertheless coefficients of uniformity were improved about 6 percents. 4. Adjustment of the swirl chamber distance of the 2nd nozzle could improve the minimum area of about 6m from the triple nozzle.

• Radiation Oncology Journal
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• v.6 no.1
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• pp.55-61
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• 1988

Fifty patients with residual, unresectable or recurrent rectal cancer were treated with external irradiation using a 6-MV linear accelerator at the Division of Therapeutic Radiology, Department of Radiology, Kangnam St. Mary's Hospital, Catholic University Medical College during the period of April 1983 to December 1987. This paper describes the results of a retrospective analysis of the results of external irradiation for the residual, unresectable and recurrent rectal cancer in 46 patients. Four patients were lost to follow-up. Of the 46 patients, $18 (39\%)$ presented with unresectable primary lesions and $28 (61\%)$ with residual or recurrent rectal cancer. In $93\%$, the pathologic diagnosis was adenocarcinoma. Resonse to irradiation was observed in $22 (73\%)$ out of 30 patients who were treated for pain, $12 (86\%)$ out of 14 patients who were treated for mass, and $17 (77\%)$ out of 22 patients who were treated for bloody discharge. The actuarial postoperative 2-year and 3-year survival rates in recurrent and unresectable patients were $43\%$ and $22\%$, respectively. However, the post-RT 2-year survival rate was $13\% (6/46)$.

• Journal of Soil and Groundwater Environment
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• v.17 no.3
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• pp.76-85
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• 2012

Geochemical and ecological properties of remediated soil and gas exhausted from a low-temperature thermal desorption (LTTD) process were analyzed to assess the environmental impact of LTTD treatment. Soil characteristics were examined with regard to the chemical (EC, CEC, and organic matter) and the ecological (dehydrogenase activity, germination rate of Brassica juncea, and growth of Eisenia andrei) properties. The exhaust gases were analyzed based on the Air Quality Act in Korea as well as volatile organic compounds (VOCs) and mixed odor. Level of organic Organic matter of the soil treated by LTTD process was slightly decreased compared to that of the original soil because the heating temperature ($200^{\circ}C$) and retention time (less than 15 minutes) were neither high nor long enough for the oxidation of organic matter. The LTTD process results in reducing TPH of the contaminated soil from $5,133{\pm}508$ mg/kg to $272{\pm}107$ mg/kg while preserving soil properties. Analysis results of the exhaust gases from the LTTD process satisfied discharge standard of Air Quality Law in Korea. Concentration of VOCs including acetaldehyde, propionaldehyde, butyraldehyde and valeraldehyde in circulation gas volatilized from contaminated soil were effectively reduced in the regenerative thermal oxidizer and all satisfied the legal standards. Showing ecologically improved properties of contaminated soil after LTTD process and environmentally tolerable impact of the exhaust gas, LTTD treatment of TPH-contaminated soil is an environmentally acceptable technology.