• Journal of Astronomy and Space Sciences
• /
• v.21 no.4
• /
• pp.283-294
• /
• 2004

New BV RI photometric observations of the contact binary AH Tau were performed with the 61 cm reflector and a 2K CCD camera at the Sobaeksan Optical Astronomy Observatory during seven nights from September to December, 2001. A total of 144 times of minima observed up to date, including three times of minima obtained from our observation, were analyzed. It is found that the orbital period of AH Tau has varied in a cyclic way superposed on a secular period decrease. The rate of the secular period decrease is calculated to be $1^s$ .04 per century, implying that a mass of about $3.8{\times}10^{-8}M{\odot}/yr$ from the more massive primary flows into the secondary if a conservative mass transfer is assumed. Assuming that the sinusoidal period variation is produced by a light-time effect due to an unseen third body, the resultant semi-amplitude, period, and eccentricity for the deduced light-time orbit are obtained as 35.4 years, 0.014 day and 0.52, respectively. The mass of the third-body is calculated as a tout $0.24M{\odot}$ when the third body is assumed to be coplanar with AH Tau system.

• Macromolecular Research
• /
• v.9 no.2
• /
• pp.107-115
• /
• 2001

Poly(L-lactide-co-glycolide)(PLGA) was blended with poly[$\omega$-methacryloyloxyethyl phospho-rylcholine-co-ethylhexylmethacrylate (PMEH)] (PLGA/PMEH) to endow with new functionality i.e., to improve the cell-, tissue- and blood-compatibility. The characteristics of surface properties were investigated by measurement of contact angle goniometer, Fourier-transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) and electron spectroscopy for chemical analysis (ESCA). NIH/3T3 fibroblast and bovine aortic endothelial cell were cultured on control and PLGA/PMEH surfaces for the evaluation of ceil attachment and proliferation in terms of surface functionality such as the concentration of phosphoryl-choline. Also, the behavior of platelet adhesion on PLGA/PMEH was observed in terms of the surface functionality. The contact angles on control and PLGA/PMEH surfaces decreased with increasing PMEH content from 75$^{\circ}$ to about 43$^{\circ}$. It was observed from the FTIR-ATR spectra that phosphorylcholine groups are gradually increased with increasing blended amount of MPC. The experimental P percent values from ESCA analysis were more 3.28∼7.4 times than that of the theoretical P percent for each blend films. These results clearly indicated that the MPC units were concentrated on the surface of PLGA/PMEH blend. The control and PLGA/PMEH films with 0.5 to 10.0 wt% concentration of PMEH were used to evaluate cell adhesion and growth in terms of phosphorylcholine functionality and wettability. Cell adhesion and growth on PLGA/PMEH surfaces were less active than those of control and both cell number decreased with increasing PMEH contents without the effect of surface wettability. It can be explained that the fibronectin adsorption decreased with an increase in the surface density of phosphorylcholine functional group. One can conclude the amount of the protein adsorption and the adhesion number of cells can be controlled and nonspecifically reduced by the introduction with phosphorylcholine group. Morphology of the adhered platelets on the PLGA/PMEH surface showed lower activating than control and the number of adhered platelets on the PLGA/PMEH sample decreased with increasing the phosphorylcholine contents. The amount of fibrinogen adsorbed on the PLGA/PMEH surface demonstrated that the phospholipid polar group played an important role in reducing protein adsorption on the surface. In conclusion, this surface modification technique might be effectively used PLGA film and scaffolds for controlling the adhesion and growth of cell and tissue, furthermore, blood compatibility of the PLGA was improved by blending of the MPC polymer for the application of tissue engineering fields.

• Polymer(Korea)
• /
• v.37 no.3
• /
• pp.316-322
• /
• 2013

In this study, poly(ethylene terephthalate) (PET) was treated with fluorination and ultrasonic washing treatment for hydrophilic modification of PET film. We measured the change of surface modified PET film surface characteristics using contact angle, surface free energy, FE-SEM, AFM and XPS. After direct fluorination and ultrasonic washing treatment, the water contact angle was measured to be $10.81^{\circ}$, 85% reduction compared to the untreated PET film. Total surface free energy has been measured to be $42.25mNm^{-1}$, 650% increase compared to the untreated PET film. Also RMS roughness has been measured to be 1.965 nm, 348% increase compared to the untreated PET film. Hydrophilic functional group C-OH bond concentration has increased approximately 3 times. These results are attributed to the hydrophilic functional group and cavitation due to chemical etching. From this result, it was suggested that the fluorination-ultrasonic washing treatment method could be useful to make PET film surface hydrophilic.

• The Journal of Korean Society for School & Community Health Education
• /
• v.1 no.1
• /
• pp.119-130
• /
• 2000

The purpose of this study was to serve as a basis for more effective sex education, by examining the influence of obscene media on elementary school student's sex consciousness. For attaining the purpose, the research questions were posed as follows: 1) What's general characteristics of elementary school students? 2) How much are elementary school students exposed to obscene media? 3) Is their sex consciousness different according to the degree of being exposed to obscene media and the appearance of secondary sex characteristic? The subject of study were the 400 male and female students who were in the sixth grade at elementary school in the city of Paju. The questionnaire survey was conducted to find out their general characteristics, sex consciousness and degree of being exposed to obscene media. The conclusions were as follows; 1) Basic Information 94% of the students investigated were living with their parents. The greatest number of their parents were in their fourties. Concerning the religion of their families, 47.5% belonged to Christianity or Catholicism. 47.3% got in touch with obscene media, which indicated that the harmful influence of that media was great. Their basic knowledge of pregnancy was very poor, as 27.2% weren't sure whether being pregnant could be caused only by shaking hands, hugging or kissing. 34.7% considered it a natural behavior to contact the other sex. Regarding their practice of sexual behavior, they'd have an experience of hugging or kissing. 2) Group Comparison The female students underwent the appearance of secondary sex characteristic faster than the male students. As a result of examining if their degree of being exposed to obscene media was affected by the presence or absence of secondary sex characteristic, no statistically significant difference existed in all the groups: the entire group, male student group and female student group. There appeared, however, statistically significant differences between male and female students, as the number of male student who hadn't yet been exposed to obscene media was less than that of female student who hadn't. And the number of male student who had been much exposed to obscene media was more than that of female student who had. 3) Sex Knowledge, Sex Attitude and Sex Practice The extent of making contact with obscene media didn't make statistically significant difference to the sex knowledge of all the groups. But more extent of getting in touch with obscene media led to more sex attitude and sex practice in the entire group. However, as a result of analyzing these things by the presence or absence of secondary sex characteristic, it's found in general that the group that had secondary sex characteristic possessed statistically better sex knowledge than the other group that hadn't. For the male students, there appeared little disparities in three subareas of sex knowledge, sex attitude and sex practice. For the female students, however, the group that had secondary sex characteristic owned better sex knowledge than the other group that hadn't, and the former group looked upon sex attitude as more natural.

• Journal of the Korean Magnetics Society
• /
• v.14 no.1
• /
• pp.33-37
• /
• 2004

Cu$_{0.1}$Fe$_{0.9}$Cr$_2$S$_4$ has been studied with Mossbauer spectroscopy, x-ray diffraction, vibrating sample magnetometer (VSM), and magnetoresistance (MR) measurement. The crystal structure was determined to be a cubic spinel with lattice parameter a$_{0}$=9.9880 $\AA$. The MR measurements show a semiconductor behavior below 110 K and metal behaved above 100 K. The temperature dependence of magnetization of Cu$_{0.1}$Fe$_{0.9}$Cr$_2$S$_4$ was reported. In addition to a large irreversibility between the zero-field-cooling (ZFC) and the field-cooling (FC) magnetization at applied field H=100 Oe, a cusp-like anomaly was observed in both the FC and ZFC curves. It shifted toward the lower temperature region with increasing magnetic field, and then showed convex type maximum at 110 K, under the applied field of 5 kOe. The Mossbauer spectra were measured from 15 K to room temperature. The asymmetric line broadening was observed for the sample Cu$_{0.1}$Fe$_{0.9}$Cr$_2$S$_4$, and it was considered to be dynamic Jahn-Teller relaxation. The charge state of Fe ions was ferrous in character. The unusual reduction of magnetic hyperfine field below 110 K was interpreted in terms of cancellation effect between the mutually opposite orbital current field (H$_{L}$) and Fermi contact field (H$_{C}$).

• Journal of the Microelectronics and Packaging Society
• /
• v.11 no.2 s.31
• /
• pp.23-28
• /
• 2004

We utilized Ag capping layer for fluxless bonding. To investigate the effect of Ag capping layer, two sets of sample were used. One set was bare In and Sn solders. The other set was In and Sn solders with Ag capping layer. In ($10{\mu}m$) and Sn ($10{\mu}m$) solders were deposited on Cu/Ti/Si substrate using thermal-evaporation, and Ag ($0.1{\mu}m$) capping layers were deposited on In and Sn solders. Solder joints were made by joining two In and Sn deposited specimens at $130^{\circ}C$ for 30 s under 0.8, 1.6, 3.2 MPa using thermal compression bonder. The contact resistance was measured using four-point probe method. The shear strength of the solder joints was measured by the shear test of cross-bar sample in the direction. The microstructure of the solder joints was characterized with SEM and EDS. In and Sn solders without Ag capping layers were only bonded at $130^{\circ}C$ under high bonding pressure. Also the shear strength of the In-Sn solder joints under was lower than that of the Ag/In-Ag/Sn solder joints. The resistance of the solder joints was $2-4\;m{\Omega}$ The solder joints consisted of In-rich phase and Sn-rich phase and the intermixed compounds were found at the interface. As bonding pressure increased, the intermixed compounds formed more.

• Journal of the Korea Concrete Institute
• /
• v.18 no.5 s.95
• /
• pp.695-702
• /
• 2006

The stress distribution and the critical stresses in concrete pavements were analyzed using formulations in the transformed field domains when dual-wheel single-, tandem-, and tridem-axle loads were applied. First the accuracy of the transformed field domain analysis results was verified by comparing with the finite element analysis results. Then, the stress distribution along the longitudinal and transverse directions was investigated, and the effects of slab thickness, concrete elastic modulus, and foundation stiffness on the stress distribution were studied. The effect of the tire contact pressure related to the tire print area was also studied, and the location of the critical stress occurrence in concrete pavements was finally investigated. From this study, it was found that the critical concrete stress due to multi-axle loads became larger as the concrete elastic modulus increased, the slab thickness increased, and the foundation stiffness decreased. The number of axles did not tend to affect the critical stress ratio except for a small foundation stiffness value with which the critical stress ratio became significantly larger as the number of axles increased. The critical stress location in the transverse direction tended to move into the interior as the tire contact pressure increased, the concrete elastic modulus increased, the slab thickness increased, and the foundation stiffness decreased. The critical stress location in the longitudinal direction was under the axle for single- and tandem-axle loads, but for tridem-axle loads, it tended to move under the middle axle from the outer axles as the concrete elastic modulus and/or slab thickness increased and the foundation stiffness decreased.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.14 no.7
• /
• pp.914-919
• /
• 2004

When the motor is rotating, the torque and rpm are varying as the loads or the driving status connecting through reduction units are changing. On the contrary, one can monitor the changes of the loads or the driving status in the manner of measuring motor torque and rpm. There is a torque measuring method using the strain gauge and bridge circuit. But, because this is the contact method, it has the life time which is dependent on rotating velocity and used time. So this system demands on replacement of some Parts or whole system itself for maintenance. And this system is also relatively big and expensive, requiring preceding annoying process. In this paper, we are going to suppose non-contact method to measure torque and rpm using the Hall effects sensor For this we have made the planetary geared reduction motor with Hall sensors and with the monitoring system. The monitoring system displays the sensing data(torque, rpm) and calculated data( power) and also has the network capability with Bluetooth protocol. Our solution is much more inexpensive ;md simple method to measure torque and rpm than before.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.34 no.1
• /
• pp.12-16
• /
• 2012

Purpose: The purpose of this study is to evaluate the effect of exposure of hydroxyapatite coating on the amount of bone formation and stability in the dogs. Methods: In this study, hydroxyapatite coated implants (HAPTITE) was placed over the femur bone surface of four dogs about 1 mm. The experimental group was divided into 4 weeks group of 8 implants and 8 weeks group of 8 implants, and then they were sacrificed. The stability of implants was evaluated twice with Osstell$^{TM}$ mentor (Osstell AB, Goteborg, Sweden) at right after placement and sacrifice. The amount of bone formation was evaluated through histomorphometric examination. Results: The stability of implants was in normal range, and tended to increase as time goes by. Mean percentages of new bone formation rates were $90.5{\pm}6.6$ at uppermost 1 mm bone level adjacent to soft tissues (level 1) and $92.9{\pm}4.1$ at next 1 mm bone level (level 2) in 4 weeks group, $90.1{\pm}11.5$ at level 1 and $95.9{\pm}2.3$ at level 2 in 8 weeks group. Mean percentages of bone-implant contact rates were $85.1{\pm}10.8$ at level 1 and $88.1{\pm}13.8$ at level 2 in 4 weeks group, $88.5{\pm}14.4$ at level 1 and $95.3{\pm}3.1$ at level 2 in 8 weeks group. There was no statistically significant difference of new bone formation rate and bone-implant contact rate between uppermost 1 mm bone level adjacent to soft tissues and next 1 mm bone level. However, there was no significant difference in bone formation between 4 and 8 weeks groups. Conclusion: These results suggested that exposed hydroxyapatite coated implants to soft tissue showed favorable bone formation and implant stability.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.8
• /
• pp.722-727
• /
• 2016

In this study, we attempted to reduce the generation of waste acids in the electropolishing process by improving the current efficiency. The optimum conditions of the electropolishing process when using the round bus bar were determined by the Taguchi method. The current density, polishing time, electrolyte temperature and flow rate were selected as the control factors for the current efficiency in the electropolishing process. An orthogonal array was created by considering three levels for each factor and experiments were carried out. The larger-the-better SN ratios were calculated by the Taguchi method. The current density was the most important factor affecting the current efficiency and the polishing time was the least important one. The optimum conditions to minimize the generation of waste acids were a current density of $45A/dm^2$, polishing time of 4 min, electrolyte temperature of $65^{\circ}C$ and flow rate of 7 L/min. The results of the ANOVA confirmed that the effects of the current density, electrolyte temperature and flow rate are significant at the 95% confidence level. The increase in the contact area and contact force afforded by using the round bus bar improved the current efficiency which, in turn, reduced the amount of waste acids generated. Further research is planned to investigate the effect of the type of bus bar on the current efficiency.