• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.3
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• pp.165-172
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• 2017

In this study, centrifugal fan blades used to circulate cold air inside a household refrigerator were optimized to achieve high performance and low noise by using the response surface method, which is frequently employed as an optimization algorithm when multiple independent variables affect one dependent variable. The inlet and outlet blade angles, and the inner radius, were selected as the independent variables. First, the fan blades were optimized to achieve the maximum volume flow rate. Based on this result, a prototype fan blade was manufactured using a 3-D printer. The measured P-Q curves confirmed the increased volume flow rate of the proposed fan. Then, the rotation speed of the new fan was decreased to match the P-Q curve of the existing fan. It was found that a noise reduction of 1.7 dBA could be achieved using the new fan at the same volume flow rate.

• Biomolecules & Therapeutics
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• v.5 no.4
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• pp.419-425
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• 1997

The pharmacokinetics of DWP20364 (1-cyclopropyl -5-amino-6,8-difluoro-7-(2,7-diazabiclo [3,3,0] oct-4-ene-7-yl)-1,4-dihydro-4-oxoquinoline-3-carboxylic acid), a novel fluoroquinolone containing C7-bicyc-talc structure, were compared with those of ciprofloxacin (CPFX) after single intravenous (i.v.) and oral (p.o.) administration to rats using microbiological assay (bioassay). After i.v. administration to rats, the plasma concentrations of the two drugs declined biexponentially. The terminal half-lives (t$_{1}$2$\beta$/) of DWP20364 were 110$\pm$ 13.2 min and 117$\pm$3.09 min after i.v. and p.o. administration, respectively, and they were significantly higher than those of CPFX (45.5$\pm$9.52 min and 48.3$\pm$ 12.1 min, respectively). Similar results were also obtained from plasma concentrations and area under the plasma concentration-time curves. The total body clearance of DWP20364, 7.82$\pm$0.37 ml/min/kg was significantly slower than that of CPFX, 27.3 $\pm$ 11.1 m1/ min/kg. Above data suggested that the antimicrobial activity of DWP20364 could be longer than that of CPFX. The urinary recovery after i.v. and p.o. administration of DWP20364 was significantly lower than those of CPFX suggesting that the effect of DWP20364 on urinary tract infection could be lower than that of CPFX. The serum protein binding values of DWP20364 at 2$\mu$g/ml were apparently 91.5~93.1% in rats and human. DWP20364 was distributed by the order of liver, lung, kidney, sf)leon, heart, muscle and brain collected at 30 min after orally administered.

• Journal of the Korean Magnetics Society
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• v.20 no.6
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• pp.228-233
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• 2010

The microwave permeability was measured in order to analyze the thickness dependence of loss properties in CoFeHfO thin films with varying thickness of t = 57~1368 nm. A single resonance peak (P1) at 2.95 GHz was appeared in the samples with thickness less than 405 nm, while second resonance peak (P2) at 547MHz was additionally appeared in the samples with thickness greater than 405 nm. The P2 was originated by the angle distribution of the easy axis, which was confirmed from the measured results of the change of imaginary permeability with applied magnetic field in the sample of 1368 nm thickness and low field torque curves. If the second peaks can be reduced by minimizing the angle distribution of the easy axis, the CoFeHfO thin films with thickness greater than 400 nm can be used for the compact microwave devices operated at up to 2 GHz ranges.

• Journal of Korean Society on Water Environment
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• v.33 no.5
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• pp.538-545
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• 2017

The purpose of this study is to investigate growth response and toxigenicity under various temperature and nutritional conditions, in order to understand the physioecological characteristics of Aphanizomenon flos-aquae, which is a bloom-forming cyanobacterium in the Nakdong River. The strain was inoculated into media under combinations of four temperatures (4, 12, 21, $30^{\circ}C$) and three nutrients (modified CB medium, P-depleted CB medium, N-depleted CB medium) for 28 days. The algae-inhibition tests were performed to assess the potential allelopathic effects of the strains' filtrates on the growth of four algae strains (Microcystis aeruginosa, Aulacoseria ambigua f. spiralis, Aphanizomenon flos-aquae, Scenedesmus obliquus). Toxin production of a strain was measured by Enzyme-Linked ImmunoSolbent Assay (ELISA). The optimal growth temperature (Topt) of strains was $19.9^{\circ}C$ ($18.3-21.2^{\circ}C$), and the temperature range for growth was from $-0.3^{\circ}C$ to $34.3^{\circ}C$. Specific growth rate (${\mu}$) in modified CB medium varied from 0.10 to $0.16day^{-1}$, and the maximum growth rate (${\mu}_{max}$) was $0.17day^{-1}$. Although growth curves under N-existed and N-depleted conditions were almost the same, growth under N-depleted condition was relatively slowed (${\mu}=0.09$ to $0.14day^{-1}$), with a decreased maximum cell density. However, growth under the P-depleted condition was restricted for all temperatures, Two stains of Aphanizomenon flos-aquae were confirmed as not producing toxins, because saxitoxin and cylindrospermopsin were not detected by ELISA. The exudates or filtrates from the Aphanizomenon flos-aquae (DGUC003) resulted in significant inhibition of algal growth on the Aulacoseira ambigua f. spiralis (DGUD001) and Aphanizomenon flos-aquae (DGUC001) (p < 0.01).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1705-1713
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• 2010

The reliable fatigue life for hybrid composite joint structures was estimated by a statistical method for evaluating fatigue life; the results of the fatigue test varied widely. Cyclic bending tests were performed on a cantilever beam with a hybrid composite joint, which was developed for the body of a low-floor bus. In order to estimate the fatigue life of the hybrid composite joint structure by comparing the data obtained during the fatigue tests, the most suitable probabilistic density function among the normal, lognormal, and Weibull distributions was selected. The probabilistic-stress-life (P-S-N) curves calculated by using the selected Weibull distribution was suggested for process of statistical fatigue life estimation and reliability design.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.26 no.2
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• pp.121-132
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• 1996

The purpose of this study was to aid in the prediction of tumor cell tolerance to radiotherapy and/or chemotherapy. For this study, cell surviving curves were obtained for human osteosarcoma MG-63 cell line using semiautomated MTT assay. 2,4, 6, 8, 10Gy were irradiated at a dose rate of 210cGy/min using /sup 60/Co Irradiator ALDORADO 8. After irradiation, MG-63 cell lines(3×10⁴ cells/ml) were exposed to bleomycin and cisplatin at concentration of 0.2, 2, 20㎍/㎖ for 1 hour respectively. The viable cells were determined for each radiation dose and/or each concentration of drug. And they were compared to control values. The obtained results were as follows : 1. There was significant difference of surviving fraction at 4, 6, 8, 10Gy on MG-63 cell line(p<0.05). 2. There was significant difference of cytotoxicity of bleomycin or cisplatin at all concentration of 0.2, 2, 20㎍/㎖ (p<0.05) on MG-63 cell line. The cytotoxicity of cisplatin was more effective than bleomycin at concentration of 20㎍/㎖ on MG-63 cell line. 3. There was significant difference of cytotoxicity of bleomycin or cisplatin at all concentration after irradiation of 2Gy on MG-63 cell line. 4. There was significant difference of cytotoxicity of bloemycin or cisplatin at concentration of 20㎍/㎖ after irradiation than that of irradiation alone(p<0.01). But there was no significant difference of cytotoxicity of bleomycin at concentration of 20㎍/㎖ after irradiation of l0Gy than that of irradiation alone.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.22 no.4
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• pp.246-252
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• 2011

Background : The objective of this study was to evaluate the diagnostic efficiency of the Comprehensive Attention Test (CAT) by comparing the results of the continuous performance test (CPT) and the CAT in children and adolescents with attention-deficit hyperactivity disorder (ADHD). Method : A total of 110 children and adolescents with ADHD (mean age : 11.2${\pm}$2.9 years, 76 boys) and 36 children and adolescents without ADHD (mean age : 12.0${\pm}$2.7 years, 25 boys) completed the CAT. We compared the specificity and sensitivity of the CPT and CAT at two different cut-off points via the McNemar test. The areas under the receiver operating characteristic curves (AUC) between the two groups were compared using Medcalc software. Results : The sensitivity and specificity of the CPT were .419 and .806, respectively. The sensitivity of the CAT was .827, which was significantly higher than that of the CPT (p<.001), and the specificity of CAT is .444, which was significantly lower than that of CPT (p<.001). The AUC of the CPT and CAT was .664 and .692, respectively, and there were no significant difference between the two groups on the paired comparison (p=.513). Conclusions : The results of this study suggest that the CAT has moderate specificity and high sensitivity. The CAT can be used as a useful tool to evaluate the neuropsychological function of children and adolescents with ADHD.

• Corrosion Science and Technology
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• v.5 no.5
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• pp.168-172
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• 2006

Alloy 600 having a superior resistance to a corrosion is used as a steam generator tubing in nuclear power plants. In spite of its high corrosion resistance, there are many tubings which experience corrosion problems such as a SCC under the high temperature and high pressure environments of nuclear power plants. The Alloy 600 tubing can be repaired by using a Ni electroplating having an excellent SCC resistance. In order to carry out a successful Ni electrodeposition inside a steam generator tubing, the effects of various parameters on the material properties of the electrodeposit should be elucidated. Hence this work deals with the effects of an applied current density, duty cycle($T_{on}/(T_{on}+T_{off})$) of a pulse current, bath temperature and solution pH on the material properties of Ni electrodeposit obtained from a Ni sulphamate bath by analyzing the current efficiency, potentiodynamic curve, hardness and stress-strain curve. Hardness, YS(yield strength) and TS(tensile strength) decreased whereas the elongation increased as the applied current density increased. This was thought to be by a concentration depletion at the interface of the electrodeposit/solution, and a fractional decrease of the hydrogen reduction reaction. As the duty cycle increased, the hardness, YS and TS decreased while the elongation increased. During an off time at a high duty cycle, the concentration depletion could not be recovered sufficiently enough to induce a coarse grain sized electrodeposit. With an increase of the solution temperature and pH, the YS and TS increased while the elongation decreased. The experimental results of the hardness and the stress-strain curves can be supplemented by the results of the potentiodynamic curve.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1119-1129
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• 2011

Shot-peening effects on the fatigue behavior of bearing steel were investigated under the high cyclic loading. Hourglass shape specimens were made of bearing steel(JIS-SUJ2) for rotary bending fatigue tests. Two kinds of treatments were performed : a heat treatment and a shot-peened surface treatment after the heat treatment. The fracture surfaces of specimens were classified into two types of fracture mode : the surface fracture mode induced by a surface defect and the internal fracture mode induced by a nonmetallic inclusion. Inclusion depth and shape affected considerably the fatigue life. Shot-peening treatment improved much the fatigue life of the bearing steel under low and high levels of cyclic loads. Probabilistic-stress-life (P-S-N) curves were suggested for the reliable fatigue life estimation of the improved bearing steel.

• Advances in environmental research
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• v.3 no.2
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• pp.163-172
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• 2014

Magnetite was chosen as a typical adsorbent to study its phosphate adsorption capacity in water body with low concentration of phosphorus (below $2mg\;PL^{-1}$). Magnetite was collected from Luoyang City, Henan Province, China. In this research, three factors have been studied to describe the adsorption of phosphate on magnetite, which was solution concentration (concentration ranging from 0.1 to $2.5mg\;PL^{-1}$), suspension pH (1 to 13) and temperature (ranging from $10^{\circ}C$ to $40^{\circ}C$). In addition, the modified samples had been characterized with XRD and FE-SEM image. The results show that iron ions contains in magnetite were the main factors of phosphorus removal. The behavior of phosphorus adsorption to substrates could be fitted to both Langmuir and Freundlich isothermal adsorption equations in the low concentration phosphorus water. The theoretical saturated adsorption quantity of magnetite is 0.158 mg/g. pH has great influence on the phosphorus removal of magnetite ore by adsorption. And pH of 3 can receive the best results. While temperature has little effect on it. Magnetite was greatly effective for phosphorus removal in the column experiments, which is a more practical reflection of phosphorous removal combing the adsorption isotherm model and the breakthrough curves. According to the analysis of heavy metals release, the release of heavy metals was very low, they didn't produce the secondary pollution. The mechanism of uptake phosphate is in virtue of chemisorption between phosphate and ferric ion released by magnetite oxidation. The combined investigation of the magnetite showed that it was better substrate for water body with low concentration of phosphorus.