• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.2
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• pp.147-152
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• 2015

We designed, fabricated, and tested the capacitive microsensors for skin piloerection monitoring. The performance of the skin piloerection monitoring sensor was characterized using the artificial bump, representing human skin goosebump; thus, resulting in the sensitivity of $-0.00252%/{\mu}m$ and the nonlinearity of 25.9 % for the artificial goosebump deformation in the range of $0{\sim}326{\mu}m$. We also verified two successive human skin piloerection having 3.5 s duration on the subject's dorsal forearms, thus resulting in the capacitance change of -6.2 fF and -9.2 fF compared to the initial condition, corresponding to the piloerection intensity of $145{\mu}m$ and $194{\mu}m$, respectively. It was demonstrated experimentally that the proposed sensor is capable to measure the human skin piloerection objectively and quantitatively, thereby suggesting the quantitative evaluation method of the qualitative human emotional state for cognitive human-machine interfaces applications.

• Journal of Welding and Joining
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• v.9 no.1
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• pp.40-47
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• 1991

The most fatigue tests carried out under the either stress or strain control, but machines and structures had taken variable stress. This variable stress was treated as statistics based on p-type distributions. In this paper, the cumulative fatigue damage of SM45C round bar specimens having a center hole resulting from block loading with p-distributions in rotating bending conditions, is presented. The value of p was changed in the range from 0.25 to 1; 0.25, 0.5, 0.75, 1. The following conclusions were obtained through the constant stress amplitude experiments and the block loading experiments. (1) In constant loading test, fatigue life was affected by cyclic rate. From experimental data, N$_{f}$ (100cpm)/N$_{f}$(3000cpm)equal to 0.56. (2) In case of the cyclic rate 100cpm and 3000cpm, at the high stress amplitude level the crack propagation life N$_{*}$f is longer than the low stress amplitude level. (3) Miner's hypothesis may be valid for p=0.75 and prediction of fatigue life by Haibach's method agree with experimental data well for the case p=0.5, while the modified Miner's method agree with experimental data well for the case p=0.25.5.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.8 s.239
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• pp.895-902
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• 2005

Lock-on characteristics of flow around a circular cylinder oscillating rotationally with a relatively high forcing frequency have been investigated experimentally. Dominant governing parameters are Reynolds number (Re), angular amplitude of oscillation (${\theta}_A$), and frequency ratio $F_R=f_f/f_n,\;where\;f_f$ is a forcing frequency and $f_n$ is a natural frequency of vortex shedding. Experiments were carried out under the conditions of $Re=4.14{\times}10^3,\;{\pi}/90{\leq}{\theta_A}{\leq}{\pi}/3,\;and\;F_R=1.0$. The effect of this active flow control technique on the lock-on flow characteristics of the cylinder wake was evaluated with wake velocity measurements and spectral analysis of hot-wire signals. The rotational oscillation modifies the flow structure of near wake significantly. The lock-on phenomenon always occurs at $F_R=1.0$, regardless of the angular amplitude ${\theta}_A$. In addition, when the angular amplitude is less than a certain value, the lock-on characteristics appear only at $F_R=1.0$,. The range of lock-on phenomena expands and vortex formation length is decreased, as the angular amplitude increases. The rotational oscillation create a small-scale vortex structure in the region just near the cylinder surface. At ${\theta}_A=60^{\circ}$, the drag coefficient was reduced about $43.7\%$ at maximum.

• Journal of Korean Public Health Nursing
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• v.12 no.2
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• pp.67-88
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• 1998

Present study was attempt to explore the relationship between perceived family support and depression and to emphasize the importance or needs of family support in psychological care especially among adolescents. Study subjects comprized of 308 high school students including vocational students in part, and data collection was done in the Kwangju City area in April. 1998. The Moos Family Environment Scale and the Zung's Self-Rating Depression Scale modified by investigators were used as measurement tools of 59 item questionnaire and in data analysis, statistical methods of T-test, ANOVA. and Pearson Correlation Coefficient were utilized. The study findings are as follows 1. The hypothesis of the study, 'the higher the degree of perceived family support among adolescents, the lower the level of depression', was supported (r=-0.4469, p<.001). 2. Some variables in demographic characteristics related to the degree of family support with statistical significance were school division of vacational vs non-vocational(t=-2.02, p<.05), age(f=5.47, p<.01), family monthly income (f=2.49, p<.05), mother's level of education (f=3.01. p<.05), residence at developmental stage (f=2.87, p<.05), personal problem of highest priority at present(f=7.73, p<.001), and family problem perceived by adolescents(f=7.38, p< .001). 3. Items In general characteristics related to the level of depression with statistical significance were sex(t=-2.91, p<.0l). mother's level of education(f=2.53. p<.05). residence at developmental stage (f=3.95. p<.0l). present personal problem of highest priority (f=3.68. p<.1l). and perceived in-family problem (f=4.58. p<.001). 4. The mean score of the degree of perceived family support was 61.26 $(SD=\pm14.45)$ in a range of 21.00 to 96.00 ; that of the level of depression. 43.74 $(SD=\pm8.04)$ in a range of 23.00 to 67.00. which demonstrated that the higher the degree of perceived family support, the lower the level of depression. In conclusion. it was found that the degree of family support perceived by adolescents is a variable affecting the level of depression. Based on the study outcome, further research suggestions can be made as such that repeated studies are needed in order to delineate the various factors affecting family support and depression, and a study involving family support implementation program is required as a nursing intervention for the development of emotional security among adolescents, perceived family support, depression, adolescence.

• Journal of the Korean Ceramic Society
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• v.38 no.11
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• pp.1046-1054
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• 2001

Effects of B$_2$O$_3$and CuO addition on the microwave dielectric properties of the PbWO$_4$-TiO$_2$ceramics were investigated in order to use this material as an LTCC material for fabrication of a multilayered RF passive components module. We found that PbWO$_4$could be used as an LTCC material because of its low sintering temperature (8$50^{\circ}C$) and fairy good microwave dielectric properties($\varepsilon$$_{r}$=21.5, Q$\times$f$_{0}$=37200 GHz and $\tau$$_{f}$ =-31 ppm/$^{\circ}C$). In order to stabilize $\tau$$_{f}$ of PbWO$_4$, TiO$_2$was added to the PbWO$_4$and the mixture was sintered at 8$50^{\circ}C$. A near zero $\tau$$_{f}$ value (+0.2 ppm/$^{\circ}C$) was obtained with 8.7 mol% TiO$_2$addition. $\varepsilon$r and Q$\times$f$_{0}$ values were 22.3 and 21400 GHz, respectively. It was believed that the decrement of Q$\times$f$_{0}$ value with TiO$_2$addition was resulted from increasing grain boundary. In order to improve Q$\times$f$_{0}$, various amounts of B$_2$O$_3$and CuO were added to the 0.913PbWO$_4$-0.087TiO$_2$mixture. The optimum amount of CuO was 0.05 wt%. At this addition, the 0.913PbWO$_4$-0.087TiO$_2$ceramic showed $\varepsilon$$_{r}$=23.5, $\tau$$_{f}$ =-2.2ppm/$^{\circ}C$, and Q$\times$f$_{0}$=32900 GHz after sintered at 8$50^{\circ}C$. In case of B$_2$O$_3$addition, the optimum amount range was 1.0~2.5 wt% at which we could obtain following results; $\varepsilon$$_{r}$=20.3~22.1, Q$\times$f$_{0}$=48700~54700 GHz, and $\tau$$_{f}$ =+2.4~+8.2ppm/$^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.6029-6038
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• 2013

In this study we attempt to modify the backbone structure and improve processibility of PBO having high melting and glass transition temperature. A series of aromatic poly(o-hydroxyamide)s(PHAs) were synthesized by direct polycondensaton of diacides containing diimide unit with two types of bis(o-aminophenol)s including 3,3'-dihydroxybenzidine and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane. PHAs were studied by FT-IR, $^1H$-NMR, DSC and TGA. PHAs exhibited inherent viscosities in the range of 0.34~0.65 dL/g at $35^{\circ}C$ in DMAc solution. The PHA 1 and 6F-PHA 6, introducing o-phenylene unit in the main chain showed excellent solubilities in aprotic solvents such as NMP etc. However, the PHA 3, having p-phenylene unit was not even dissolved perfectly with LiCl salt. 6F-PHAs were readily soluble at room temperature in aprotic solvents except 6F-PHA 3. But they showed better solubility than that of PHAs. The polybenzoxazoles(PBOs) were quite insoluble in other solvents except partially soluble in sulfuric acid. PBOs exhibited relatively high glass transition temperatures(Tg) in the range of 306~$311^{\circ}C$ by DSC. The maximum weight loss temperature and char yields of PHA3 and 6F-PHA3 showed the highest values of $658^{\circ}C$ and $653^{\circ}C$, 62.6 % and 62.1 %, respectively.

• KSBB Journal
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• v.19 no.4
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• pp.269-273
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• 2004

A simple, fast and reproducible quantitative analysis method for sugar concentration composed in oligosaccharide mixture was developed. Two glass TLC plates were prepared per sample. After dipping one plate into the copper bicinchoninate reagent and the other plate into 5% sulfuric acid solution, both plates were baked in microwave oven until sugar spots were developed or the surface temperature of TLC plate becomes 60 to 70 $^{\circ}C$. The corrective factor values [F value =(the value of total sugar concentration converted as glucose unit/the value of reducing sugar concentration converted as glucose unit)/(polymerization degree of sugar)] of different molecular weight sugars were determined. Within the concentration of 0.25∼1.0 $\mu\textrm{g}$ in each sample loaded, the fructose-F (corrective factor value of fructose) was 0.45, yet for the higher concentration (2.5∼7.5 $\mu\textrm{g}$) fructose-F was 1.0. In case of glucose, in the range of 0.5∼7.5 $\mu\textrm{g}$, glucose-F was same as fructose-F, 1.0. However, as the molecular weight of sugar was increased, the F values were decreased in both maltodextrin and isomaltodextrin oligosaccharides in 0.5∼7.5 $\mu\textrm{g}$ of each sample loaded. Interestingly, F values were equal for the same molecular weight sugars, although the structures were different from each other. Using F value of each sugar, we could determine and compare the exact total sugar concentration of different molecular weight maltooligosaccharide and isomaltooligosaccharide. We also could determine if the unknown sugar was a reducing or non-reducing compound by using optimized TLC with microwave oven method.

• Korean Journal of Optics and Photonics
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• v.15 no.4
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• pp.325-330
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• 2004

We fabricated a vacuum ultraviolet spectre-reflectometer which consists of a deuterium light source, a vacuum monochromator, and a sample chamber and detector module. The operation was performed in the ultraviolet spectral ranges between 115 nm and 330 nm at the vacuum pressure of 3.0 ${\times}$ 10$^{-4}$ Pa. The wavelength of the vacuum monochromator was calibrated with the line spectrum of a low pressure Mercury lamp of 253.652 nm and 184.95 nm wavelengths, and its resolution was 0.012 nm, and the precision of wavelength was $\pm$ 0.03 nm. With this reflectometer and a deuterium lamp, we measured the spectral regular transmittance and reflectance of materials(MgF$_2$, CaF$_2$, BaF$_2$, SiO$_2$, Sapphire) used as optical components over the spectral range between 115 nm and 230 nm.

• Journal of the Korean Magnetics Society
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• v.5 no.2
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• pp.119-122
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• 1995

We have measured the magnetic susceptibilities of a CuF/sub 2/ .center dot. 2H/sub 2/O sample by means of the SQUID(superconducting quantum interference device) at the magnetic fields of 0.5 T and 1 mT, in the temperature range 5-300 K. The sample was found to contain some nonmagnetic calcium and magnesium impurities by the elemental analysis. Our measurements differ from known results for pure Cu F/sub 2/ .center dot. 2H/sub 2/O and are well explained by the effect of the nonmagnetic impurities in our sample. The purity of our sample derived from the temperature dependence of the susceptibilities was compared with that from the elemental analysis.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.134-137
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• 2009

Combustion tests of a low thrust rocket engine was performed to get combustion characteristics, which used a high concentrated hydrogen peroxide and kerosene as the oxidizer and fuel. The engine consisted of multi injector(six coaxial swirl injectors), chamber, nozzle and catalyst ignition system. The test was carried out by changing O/F ratio from 3.8 to 11.0. The experimental results showed that combustion efficiency was highest at O/F ratio from 5 to 6 and pressure fluctuations of all the range were lower than 5%.