• Investigative Magnetic Resonance Imaging
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• v.19 no.2
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• pp.76-87
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• 2015

Purpose: There is an ongoing search for a stent material that produces a reduced susceptibility artifact. This study evaluated the effect of manganese (Mn) content on the MRI susceptibility artifact of ferrous-manganese (Fe-Mn) alloys, and investigated the correlation between MRI findings and measurements of Fe-Mn microstructure on X-ray diffraction (XRD). Materials and Methods: Fe-Mn binary alloys were prepared with Mn contents varying from 10% to 35% by weight (i.e., 10%, 15%, 20%, 25%, 30%, and 35%; designated as Fe-10Mn, Fe-15Mn, Fe-20Mn, Fe-25Mn, Fe-30Mn, and Fe-35Mn, respectively), and their microstructure was evaluated using XRD. Three-dimensional spoiled gradient echo sequences of cylindrical specimens were obtained in parallel and perpendicular to the static magnetic field (B0). In addition, T1-weighted spin echo, T2-weighted fast spin echo, and $T2^*$weighted gradient echo images were obtained. The size of the low-intensity area on MRI was measured for each of the Fe-Mn binary alloys prepared. Results: Three phases of ${\alpha}^{\prime}$-martensite, ${\gamma}$-austenite, and ${\varepsilon}$-martensite were seen on XRD, and their composition changed from ${\alpha}^{\prime}$-martensite to ${\gamma}$-austenite and/or ${\varepsilon}$-martensite, with increasing Mn content. The Fe-10Mn and Fe-15Mn specimens comprised ${\alpha}^{\prime}$-martensite, the Fe-20Mn and Fe-25Mn specimens comprised ${\gamma}+{\varepsilon}$ phases, and the Fe-30Mn and Fe-35Mn specimens exhibited a single ${\gamma}$ phase. The size of the low-intensity areas of Fe-Mn on MRI decreased relative to its microstructure on XRD with increasing Mn content. Conclusion: Based on these findings, proper conditioning of the Mn content in Fe-Mn alloys will improve its visibility on MR angiography, and a Mn content of more than 25% is recommended to reduce the magnetic susceptibility artifacts on MRI. A reduced artifact of Fe-Mn alloys on MRI is closely related to the paramagnetic constitution of ${\gamma}$-austenite and/or ${\varepsilon}$-martensite.

• Korean Journal of Radiology
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• v.25 no.6
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• pp.511-517
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• 2024

Objective: To prospectively investigate the influence of the menstrual cycle on the background parenchymal signal (BPS) and apparent diffusion coefficient (ADC) of the breast on diffusion-weighted MRI (DW-MRI) in healthy premenopausal women. Materials and Methods: Seven healthy premenopausal women (median age, 37 years; range, 33-49 years) with regular menstrual cycles participated in this study. DW-MRI was performed during each of the four phases of the menstrual cycle (four examinations in total). Three radiologists independently assessed the BPS visual grade on images with b-values of 800 sec/mm² (b800), 1200 sec/mm² (b1200), and a synthetic 1500 sec/mm² (sb1500). Additionally, one radiologist conducted a quantitative analysis to measure the BPS volume (%) and ADC values of the BPS (ADC_BPS) and fibroglandular tissue (ADC_FGT). Changes in the visual grade, BPS volume (%), ADC_BPS, and ADC_FGT during the menstrual cycle were descriptively analyzed. Results: The visual grade of BPS in seven women varied from mild to marked on b800 and from minimal to moderate on b1200 and sb1500. As the b-value increased, the visual grade of BPS decreased. On b800 and sb1500, two of the seven volunteers showed the highest visual grade in the early follicular phase (EFP). On b1200, three of the seven volunteers showed the highest visual grades in EFP. The BPS volume (%) on b800 and b1200 showed the highest value in three of the six volunteers with dense breasts in EFP. Three of the seven volunteers showed the lowest ADC_BPS in the EFP. Four of the seven volunteers showed the highest ADC_BPS in the early luteal phase (ELP) and the lowest ADC_FGT in the late follicular phase (LFP). Conclusion: Most volunteers did not exhibit specific BPS patterns during their menstrual cycles. However, the highest BPS and lowest ADC_BPS were more frequently observed in EFP than in the other menstrual cycle phases, whereas the highest ADC_BPS was more common in ELP. The lowest ADC_FGT was more frequent in LFP.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.4
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• pp.429-437
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• 2007

This study aims to develop a sulfur-using denitrification process which is possible a renovation to advanced treatment plant submerging a simple module in activated sludge aeration tank. At first, the impact factor of sulfur-using denitrification was appreciated by the batch test. Secondly, reflecting a dissolved oxygen effect of sulfur-using denitrification that was confirmed by the batch test, in a continuous nitrification/sulfur-using denitrification, high-rate nitrogen removal reaction was induced at optimum condition controlling DO concentration according to phases. Also, inside and outside of sulfur-using denitrification module was covered with microfilter and the module was considered as an alternative of clarifier. Result of batch test for sulfur-using denitrification, $NO_2{^-}N$ was lower for consumption of alkalinity and sulfur than that of $NO_3{^-}-N$. These results revealed the accordance of theoretical prediction. In continuous nitrification/sulfur-using denitrification experiment, actual wastewater was used as a influent, and influent nitrogen loading rates were increased 0.04, 0.07, 0.11, $0.14kg\;N/m^3-day$ by changing hydraulic retention times. At this time, nitrogen loading rates of packed sulfur were increased 0.23, 0.46, 0.69, $0.93kg\;N/m^3-day$. As a result, nitrification efficiency was about 100% and denitrification efficiency was 93, 81, 79, 72%. Accordingly, nitrogen removal was a high-rate. Also the module of sulfur-using denitrification covered with microfilter did not make a fouling phenomena according to increased flux. And the module was achieved effluent suspended solids of below 10 mg/L without a clarifier. In conclusion, it is possible a renovation to advanced treatment plant submerging a simple module packed sulfur in activated sludge aeration tank of traditional facilities. And the plant used the module packed sulfur is expected as a effective facilities of high-rate and the smallest.

• Clinical and Experimental Reproductive Medicine
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• v.14 no.2
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• pp.127-137
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• 1987

Steroid hormone profiles during luteal phases after in vitro fertilization(IVF) and embryo transfer(ET) have been evaluated in 83 cycles stimulated by pure follicle-stimulating hormone/human menopausal gonadotropin/human chorionic gonadotropin, in which 13 patients became pregnant. Serum estradiol($E_2$) and progesterone($P_4$) levels were determined on days 2, 5, 7 and 9 after laparoscopic follicle aspiration. The follicular $E_2$ peak was slightly higher in pregnancies than in failures. Positive correlations were observed between the follicular $E_2$ peaks and the $P_4$ levels on days 5 and 7 of the luteal phase in pregnancies, but no correlation was found in failures. The $E_2$ and $P_4$ levels on days 5 and 7 of the luteal phase were significantly higher in pregnancies than in failures, but not different on days 2 and 9. Values of the $P_4/E_2$ ratio were similar between the two groups. The luteal phase durations were 12 to 19 days and no correlation was observed between the lengths of luteal phase and the luteal $E_2$ or $P_4$ concentrations. These data suggest that high $P_4$ levels in the mid-luteal phase, which have positive correlations with the follicular $E_2$ peaks, might have a favorable influence on the pregnancy success in human IVF.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.1B
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• pp.133-144
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• 2004

This research aimed to do an empirical study, by comparing the relationships of service quality, customer satisfaction and customer loyalty in mobile telecommunications between Korea and China which possess different growth phases. For this purpose, six factors in service quality, customer satisfaction and customer loyalty have been under a regression analysis to verify the causal relationship. The key findings of this study are as follows. Both Korea and China showed the causal relationship between customer satisfaction and customer loyalty; the service support which applies as the core services, have been found to be the most important factors in customer satisfaction and customer loyalty. And this study has been able to establish strategic views on reinforcing customer bases in mobile telecommunication service markets in both countries.

• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.280-286
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• 2015

Two series of unsymmetric dimesogenic compounds containing a butylene or pentamethylene group as the flexible spacer were synthesized and their thermal and mesomorphic properties were studied. Mesogenic groups of the synthesized compounds consisted of a cholesteryl and an azobenzene group with lateral substituent. Chemical structures and mesomorphic properties of the synthesized compounds were investigated by FT-IR, $^1H$-NMR, differential scanning calorimeter (DSC), and polarizing optical microscope (POM). All synthesized compounds, apart from $D5-OCH_3$, showed enantiotropic liquid crystal phases. Compounds having an even number of carbon atoms in the flexible spacer exhibited wide mesophase temperature ranges and high isotropic transition temperatures. Regarding the effect of lateral substituents, compounds with bulky substituents exhibited decreased mesophase temperature ranges and isotropic transition temperatures, while those with polar substituents showed the increased thermal stability of the smectic phase.

• Journal of The Korean Association of Information Education
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• v.11 no.1
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• pp.59-66
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• 2007

This study is aimed at developing a curriculum in relation to programming learning by using robot, for it has been judged as a scientific learning tool to help elementary school children as well as gifted children among them improve their creativity. Based on this concept, teaching aids and materials were developed, and then applied to the locale of education, and results therefrom were analyzed ccordingly. Curriculum and contents of teaching aids were classified into two processes, i.e. the assembling process of robot to fit the varied problematic situations and the programming process (all six phases), and edited so much as to entice elementary school children to get interests and attentions to robot and programming by compiling the contents to suit their level of learning. Results from the evaluation of the application of robot education curriculum to the locale for learning revealed that it was a positive teaching tool that helped children improve their creativity. Also conclusions were derived from the analysis and evaluation that several aspects should be complemented as for teaching and learning tool to achieve the objective of excellence education.

• Journal of Digital Convergence
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• v.13 no.11
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• pp.441-448
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• 2015

The purpose of the study was to perform a comparative analysis of the success and failure cases to increase the completeness of vault "Shirai-Kim Hee Hoon" technique. The subject of the study was "K" a male gymnast from Korean Artistic Gymnastic National team. The results obtained through the three-dimensional analysis during international as well as practice session are as follows: Firstly, excluding BC, the lead time in each PrF, HC and PoF phases were shorter during successful trials than in failure trials. Secondly, during successful trials, the horizontal and vertical velocity appeared to be higher during taking off, which contributed positively to the leaping motion in the horizontal direction. Thirdly, when compared with successful and failure trials, the body's angular rotation was highly maintained during the takeoff from the spring board followed by larger thigh angular displacement at the vault before actually attempting the backward rotation.

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.717-722
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• 2004

A design was done, and all characteristic of photodetectr of the web pattern type which a standard process of the Bipolar which Si PIN structure was used in this paper, and was used for the current amplifier design was used, and high-speed, was used as receiving optcal area of high altitude, and the module which had a low dark current characteristic was implemented with one chip with a base. Important area decreases an area of Ie at the time of this in order to consider an electrical characteristic and economy than the existing receiving IC, and performance of a product and confidence are got done in incense. First of all, the receiving IC which a spec, pattern of a wafer to he satisfied with the following electrical optical characteristic that produced receiving IC of 5V and structure are determined, and did one-chip is made. On the other hand, the time when AR layer of double is $Si_{3}N_{4}/SiO_{2}=1500/1800$ has an optical reflectivity of less than $10{\%}$ on an incidence optical wavelength of 660 ,and, in case of photo detector which reverse voltage made with 1.8V runs in 1.65V, an error about a change of thickness is very the thickness that can be improved surely. And, as for the optical current characteristic, about 5 times increases had the optical current with 274nA in 55nA when Pc was -27dBm. A BJT process is used, and receiving IC running electricity suitable for low voltage and an optical characteristic in minimum 1.8V with a base with two phases is made with one chip. IC of low voltage operates in 1.8V and 3.0V at the same time, and optical link receiving IC is going to be implemented

• Journal of The Korean Astronomical Society
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• v.50 no.3
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• pp.41-49
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• 2017

We conduct BVRI and R band photometric observations of asteroid (5247) Krylov from January 2016 to April 2016 for 51 nights using the Korea Microlensing Telescope Network (KMTNet). The color indices of (5247) Krylov at the light curve maxima are determined as $B-V=0.841{\pm}0.035$, $V-R=0.418{\pm}0.031$, and $V-I=0.871{\pm}0.031$ where the phase angle is $14.1^{\circ}$. They are acquired after the standardization of BVRI instrumental measurements using the ensemble normalization technique. Based on the color indices, (5247) Krylov is classified as a S-type asteroid. Double periods, that is, a primary period $P_1=82.188{\pm}0.013h$ and a secondary period $P_2=67.13{\pm}0.20h$ are identified from period searches of its R band light curve. The light curve phases with $P_1$ and this indicate that it is a typical Non-Principal Axis (NPA) asteroid. We discuss the possible causes of its NPA rotation.