• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.238-239
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• 2001

sub-30fs 펄스폭의 상용 Ti：sapphire 레이저시스템에 대한 펄스압축기 및 2차 조화파 발생기를 제작하여 특성을 평가하였다. 그림la에서 82MHz의 주파수로 모드록되는 상용 Ti：sapphire 레이저 (Spectra-Physics Millennia/Tsunami laser)의 출력이 반사경 Ml, M2를 거쳐 펄스압축기에 입사되고 압축되어 나온 펄스가 다시 M6, M7를 거쳐 2차 조화파발생기로 입사되는 2단구조로 설계되었다. 압축기에 입사되기전 평균파워는 파장 800nm에서 520mW로 측정되었으며, 측정된 스펙트럼 반치폭 47nm에 (그림 2a)에 대해 chirp-free sech$^2$t 펄스로 가정할 경우 본 레이저시스템의 변환한계 펄스폭은 14.5fs로 계산된다. (중략)

• Journal of dental hygiene science
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• v.15 no.4
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• pp.407-412
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• 2015

This study investigated flexural properties of indirect Gum-shade composite resins for esthetic improvement. The material utilized in this study was Crea.lign, Twiny flow and Twiny paste (TP). Ten specimens were fabricated with a dimension of $25{\times}2{\times}2mm$ according to the ISO 4049. After fabrications, specimens were stored in the distilled water for 24 hours at the temperature of $37^{\circ}C$. Three-point bending test was performed in universal testing machine (Instron 3344; Instron, USA) at a crosshead speed of 1 mm/min until the failure occurred. TP exhibited a higher flexural strength (FS) and flexural modulus (FM) compared to the flowable materials. There were significant differences among the three materials in FS and FM. However, there was no significant difference in work of fracture (WOF) in all tested materials (p>0.05). In Weibull analysis, TP showed the greatest Weibull modulus which means a higher reliability of the materials. Also, Gum-shade composite resins revealed a strong correlation in all flexural properties. There was a positive correlation in FS-FM ($r^2=0.99$) and a negative correlation between FS-WOF and FM-WOF ($r^2>0.97$). Therefore, this confirmed that flexural property was important for mechanical behavior evaluation and useful information. To addition, this improved among mechanical properties correlation of materials as important factor.

• Defense and Technology
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• no.4 s.230
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• pp.22-29
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• 1998

현재 개발이 완료되고 비행시험이 진행중인 FS-X의 개발기간중 FS-X의 운용요구라면 기존의 미국 전투기인 F-15, F-16 또는 F/A-18을 재설계하거나 개조하면 충분히 만족할 수 있고 적은 비용으로 획득할 수 있다는 미국의 주장에 대항한 일본의 대응책과 기술개발력 육성의 문제를 일본의 안전보장이라는 관점에서 정리함으로써 향후 한국의 항공산업 발전에 참고가 되었으면 한다

• Asian-Australasian Journal of Animal Sciences
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• v.29 no.2
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• pp.195-203
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• 2016

This study was conducted to evaluate the effect of dietary supplementation with rice bran, flax seed, or sunflower seed to finishing native Korean cattle (Hanwoo) on growth performances, carcass characteristics, fatty acid composition, free amino acid and peptide contents, and sensory evaluations of Longissimus muscle (LM). A total of 39 Hanwoo steers (average age of 22.2 mo and average body weight (BW) of 552.2 kg) were randomly divided into Control, rice bran (RB), flax seed (FS), or Sunflower seed (SS) groups. The steers were group fed for 273 d until they reached an average age of 31.2 mo. Final BW was 768.2, 785.8, 786.2, and 789.0 kg, and average daily gain was 0.79, 0.85, 0.82, and 0.84 kg for the Control, RS, FS, and SS groups, respectively (p>0.05). Fat thickness of the FS group (19.8 mm) was greater (p<0.05) than that of the other groups. Final yield grade converted into numerical values was 2.0 for the RB group, 1.7 for the Control and SS groups, and 1.4 for the FS group. Marbling degrees for the Control, SS, RB, and FS groups were 5.3, 5.1, 4.7, and 4.6, respectively. Percentages of palmitic acid ($C_{16:0}$), stearic acid ($C_{18:0}$), and arachidic acid ($C_{20:0}$) in the LM were not different among the groups. Palmitoleic ($C_{16:1}$) acid was higher (p<0.05) in the SS group. The concentration of oleic acid was highest (p<0.05) in the Control group (47.73%). The level of linolenic acid ($C_{18:3}$) was 2.3 times higher (p<0.05) in the FS group compared to the other groups. Methionine concentration was (p<0.05) higher in FS (1.7 mg/100 g) and SS (1.2 mg/100 g) steers than in the Control or RB groups. Glutamic acid and ${\alpha}$-aminoadipic acid (${\alpha}$-AAA) contents were (p<0.05) higher in the FS group compared to the other groups. LM from the FS group had numerically higher (p>0.05) scores for flavor, umami, and overall palatability in sensory evaluations. In conclusion, supplementation of flax seed to diets of finishing Hanwoo steers improved sensory evaluations which might have been caused by increases in flavor related amino acids such as methionine, glutamic acid and ${\alpha}$-AAA and peptides, anserine and carnosine, and their complex reactions.

• International Journal of Industrial Entomology and Biomaterials
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• v.39 no.1
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• pp.9-13
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• 2019

In this study, 4 different types of GBR membrane were undergone for bio-degradability test; Silk mat from silkworm cocoon (TDI), silk mat from flatwise-spun (FS), collagen membrane (OssGuide), and dPTFE membrane (Cytoplast). Each material was segmented in 10.00 mm length and 0.3 mm thickness. The samples were put into the normal saline at $37^{\circ}C$ for 2 weeks. After that, yield strength and tensile strain were measured and compared them with those of before treatment. The morphology of the membranes was observed by SEM. Tensile strain of FS was significantly increased at 2 weeks' normal saline treatment (P=0.018). When compared to OssGuide, TDI and FS showed significantly higher tensile strain at 2 weeks' normal saline treatment (P<0.05). In the SEM images, there were no significant changes in Cytoplast, TDI, and FS after 2 weeks' treatment. However, OssGuide showed damaged surface after 2 weeks' treatment. In conclusion, both TDI and FS did not have any evidence of biodegradability at 2 weeks' observation in normal saline treatment. However, OssGuide showed more than 20 % decrease in yield strength and tensile strain.

• Journal of Environmental Science International
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• v.10 no.6
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• pp.431-436
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• 2001

Variations in phytoplankton concentrations result from changes of the ocean color caused by phytoplankton pigments. Thus, ocean spectral reflectance for low chlorophyll waters are blue and high chlorophyll waters tend to have green reflectance. In the Korea region, clear waters and the open sea in the Kuroshio regions of the East China Sea have low chlorophyll. As one moves even closer In the northwestern part of the East China Sea, the situation becomes much more optically complicated, with contributions not only from higher concentration of phytoplankton, but also from sediments and dissolved materials from terrestrial and sea bottom sources. The color often approaches yellow-brown in the turbidity waters (Case Ⅱ waters). To verify satellite ocean color retrievals, or to develop new algorithms for complex case Ⅱ regions requires ship-based studies. In this study, we compared the chlorophyll retrievals from NASA's SeaWiFS sensor with chlorophyll values determined with standard fluorometric methods during two cruises on Korean NFRDI ships. For the SeaWiFS data, we used the standard NASA SeaWiFS algorithm to estimate the chlorophyll_a distribution around the Korean waters using Orbview/ SeaWiFS satellite data acquired by our HPRT station at NFRDl. We studied In find out the relationship between the measured chlorophyll_a from the ship and the estimated chlorophyll_a from the SeaWiFs satellite data around the northern part of the East China Sea, in February, and May, 2000. The relationship between the measured chlorophyll_a and the SeaWiFS chlorophyll_a shows following the equations (1) In the northern part of the East China Sea. Chlorophyll_a =0.121Ln(X) + 0.504, R²= 0.73 (1) We also determined total suspended sediment mass (55) and compared it with SeaWiFS spectral band ratio. A suspended solid algorithm was composed of in-.situ data and the ratio (L/sub WN/(490 ㎚)L/sub WN/(555 ㎚) of the SeaWiFS wavelength bands. The relationship between the measured suspended solid and the SeaWiFS band ratio shows following the equation (2) in the northern part of the East China Sea. SS = -0.703 Ln(X) + 2.237, R²= 0.62 (2) In the near future, NFRDI will develop algorithms for quantifying the ocean color properties around the Korean waters, with the data from regular ocean observations using its own research vessels and from three satellites, KOMPSAT/OSMl, Terra/MODIS and Orbview/SeaWiFS.

• Environmental Engineering Research
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• v.12 no.2
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• pp.55-63
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• 2007

PCDD/Fs monitoring was carried out to estimate the contamination level in soil samples taken in the vicinity of the various incinerators throughout South Korea from July 2003 to December 2004. The levels ranged from N.D. to 130.39 pg I-TEQ/g (d.w.) with an average concentration of 11.38 pg I-TEQ/g (d.w.). The level of PCDD/Fs in this study is similar to that of other countries. Overall, the highest mean concentration in the soil was found at 250 m from the stack. In addition, the flue gases were analyzed in order to obtain the congener profiles of the PCDD/Fs emitted from the incinerators. The concentration of I-TEQ in the flue gas ranged from 0.33 to 21.5 ng TEQ/$Sm^3$. These levels were much lower than the concentration stipulated in the Korean emission criterion(40 ng TEQ/$Sm^3$ until 2005). The comparison of the congener patterns using cluster analysis showed that the incinerators and PCP are sources of PCDD/Fs in the soil samples according to the sampling point, but the possibility of unidentified combustion sources and vehicles exists in the case of complex industrial regions.

• Korean Journal of Digital Imaging in Medicine
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• v.14 no.1
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• pp.31-35
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• 2012

To test the real image quality of a spectral attenuated inversion-recovery (SPAIR) fat-suppression (FS) techniquein clinical abdominal MRI by comparison to turbo spin echo inversion-recovery (TSEIR) fat-suppression (FS) technique. 3.0T MRI studies of the abdomen were performed in 30 patients with liver lesions (hemangiomas n: 15; HCC n: 15). T2W sequences were acquired using SPAIR TSEIR. Measurements included retroperitoneal and mesenteric fat signal-to-noise (SNR) to evaluate FS; liver lesion contrast-to-noise (CNR) to evaluate bulk water signal recovery effects; and bowel wall delineation to evaluate susceptibility and physiological motion effects. SPAIR-TSEIR images produce significantly improved FS and liver lesion CNR. The mean SNR of the retroperitoneal and mesenteric fat for SPAIR were 20.5, 10.2 and TSEIR were 43.2, 24.1 (P<0.05). SPAIR-TSEIR images produced higher CNR for both hemangiomas CNR 164.88 vs 126.83 (P<0.05) and metastasis CNR 75.27 vs 53.19 (P<0.05). Bowel wall visualization was significantly improved using in both SPAIR-TSEIR (P< 0.05). The real image quality of SPAIR was better than over conventional TSEIR FS on clinical abdominal MRI scans.

• Journal of Advanced Navigation Technology
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• v.12 no.2
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• pp.115-121
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• 2008

In this paper, we analysis the error performance improvement of the FS MC-CDMA, whose information data are spread spectrum with direct sequences(DS), and each subband signal is transmitted using a subcarrier frequency, combining BCH code in Mobile communication channels which is characterized by Nakagami fading. The effect of co-channel interference on the block error performance is also studied in this paper. As a results of study, the coding techniques provides more efficient improvement than non-coding, but the coding techniques are required more band as many coding rate. Our study demonstrates that the system is combined coding techniques, the amount of improvement is capable of efficiently exploiting over the Nakagami fading.

• Journal of Power Electronics
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• v.12 no.6
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• pp.895-903
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• 2012

This paper presents a fast switching direct torque control (FS-DTC) using only a single DC-link current sensor. In FS-DTC, six new active voltage complex space vectors (CSVs) are synthesized by the conventional active voltage space vectors (SVs). The corresponding sectors are rotated in the anticlockwise direction by 30 degrees. A selection table is defined to select the CSVs. Based on the "Different Phase Mode", the output sequence of the selected CSV is optimized. Accordingly, a reconstruction method is proposed to acquire the phase currents. The core of the FS-DTC is that all of the three phase currents can be reliably reconstructed during every two sampling periods, which is the result of the fast switching between different phases. The errors between the reconstructed and actual currents are strictly limited in one sampling period. The FS-DTC has the advantages of the standard DTC scheme such as simple structure, quick torque response and robustness. As can be seen in the analysis, the FS-DTC can be thought of as an equivalent standard DTC scheme with 86.6% of the maximum speed, 173.2% of the torque ripple, and 115% of the response time of the torque. Based on a dSPACE DS1103 controller, the FS-DTC is implemented in an induction machine drive system. The results verify the effectiveness of the FS-DTC.