• Korean Journal of Optics and Photonics
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• v.11 no.1
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• pp.43-46
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• 2000

We generated 9-fs pulses from a Kerr-lens mode-locked Ti:sapphire laser only using commercial optical components. Two sets of prisms pair made of fused silica were used to compensate group delay dispersion inside and outside the laser oscillator respectively, and broadband mirrors were used to obtain a broad spectrum. By comparison between reflectance curves of the broadband mirrors and those of previous ones, broadband mirrors which have high reflectance bandwidth of over 180 nm were found to be essential to produce sub-IO-fs pulses. ulses.

• Applied Chemistry for Engineering
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• v.9 no.3
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• pp.457-461
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• 1998

The vesicle system of DPPC(dipalmitoylphosphaticylcholine)/Chol(Cholesterol) has been modified by incorporating various mole fractions of flourinated surfactant($C_8F_{17}(CH_2)_2OCO-CH_2CH(SO_3Na)COO(CH_2)_2C_8F_{17}$. Sodium bis(1H,1H,2H,2H-heptadecaflurododecyl)-2-sulfosuccinate, FS)/fluorinated fatty acid salt ($C_7F_{15}COONH_4$, ammoniumpentadecaflurooctyrate, FFS), and their physicochemical properties have been investigated in an attempt to enhance the stability of phospholipid vesicle system. The ${\zeta}$-potential measurement by use of Zetamaster sub-micron Particle Electrophoresis Analyzer (Malvern Co.) showed that a charged homogeneous DPPC/Chol/FS vesicle has been formed owing to the incorporated FFS effect on the membrane, playing a role as a cosurfactant in the bilayer between DPPC and FS components. With increase in the concentration of FFS, it was found that the particle size and also surface charge of the DPPC/Chol/FS vesicle decreased. The stability of DPPC/Chol/FS/FFS liposome was found to be enhanced significantly compared to that of DPPC/Chol/FS according to the dispersity change as a function of time. The release rate of dye molecule of Methylene Blue from the DPPC/Chol/FS/FFS vesicle was determined to be slower than that of DPPC/Chol/FS system, and it may be attributed to the increase in microviscosity of the hydrophobic region in the bilayer. The affinfinity of DPPC/Chol/FS/FFS vesicles to albumin was found to be slightly lowered compared to that of DPPC/Chol/FS. Based on these findings, it was confirmed that a more stable and homogeneous vesicle system of DPPC/Chol/FS could be prepared by addition of FFS, acting as a cosurfactant in the aggregate formation.

• Korean Journal of Community Nutrition
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• v.10 no.3
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• pp.319-330
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• 2005

College foodservice (FS) demands highly-developed operation technique which can provide adequate nutrients to their students, as well as to guide better eating habits and to meet students' various desires. The purpose of this study was to provide basic data to improve college FS satisfaction with food items by comparing 2 contract-managed and 2 self-operated college FS in Daejeon and Chungnam area. According to the results, $\59.1%$ of students frequently (over 3 times per week) took meals at college cafeteria and the main reason for using college cafeteria was the low-price of meal, although the students' Satisfaction degree with price of meal was lower in contract-managed FS than in self-operated FS. There were no differences in the food satisfaction degrees with overall appraisal of food items between 2 operating systems of college FS, but the satisfaction degrees with all food items were high in male as compared with female. The higher the negative self-perceived clinical symptoms scores, the lower the satisfaction with foods, which suggests that the health state of students was one of the factors that influenced college FS satisfaction. According to stepwise multiple regression analysis,'taste of boiled rice', 'overall appraisal of boiled rice', 'overall appraisal of soup', and 'variety of side dish', in decreasing order, were the most relatively important attributes for overall customer satis-faction with food taste of college FS. Finally, there should be further studies on important management factors to improve college FS satisfaction according to 2 operating system.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.8
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• pp.472-483
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• 2002

This paper presents the design and implementation of a cache file system, umcFS, which is specifically designed to provide an efficient caching and transmission of streaming media. The proposed file system is based on the concept of file disk and implemented as an application level on top of a general-purpose file system. The file disk favors the continuity of cached media and provides an efficient I/O mechanism for cache server. umcFS statically allocates control blocks as well as media cache blocks. These blocks are referenced by the single-level indirect management structure. As the file system is designed as an application level, it is easy to develop and port to other systems. The performance of the implemented system shows that umcFS performs about 13% better than the native file system in randomly accessing the cache blocks of 1024KB.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.7
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• pp.427-431
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• 2017

In this paper, we discuss ${\beta}-Ga_2O_3$ thin films that have been grown on freestanding GaN (FS-GaN) using furnace oxidation. A GaN template was grown by horizontalhydride vapor phase epitaxy (HVPE), and FS-GaN was fabricated using the laser lift off (LLO) system. To obtain ${\beta}-Ga_2O_3$ thin film, FS-GaN was oxidized at $900{\sim}1,100^{\circ}C$. Surface and cross-section of prepared ${\beta}-Ga_2O_3$ thin films were observed by field emission scanning electron microscopy (FE-SEM). The single crystal FS-GaNs were changed to poly-crystal ${\beta}-Ga_2O_3$. The oxidized ${\beta}-Ga_2O_3$ thin film at $1,100^{\circ}C$ was peel off from FS-GaN. Next, oxidation of FS-GaNwas investigated for 0.5~12 hours with variation of the oxidation time. The thicknesses of ${\beta}-Ga_2O_3$ thin films were measured from 100 nm to 1,200 nm. Moreover, the 2-theta XRD result indicated that (-201), (-402), and (-603) peaks were confirmed. The intensity of peaks was increased with increased oxidation time. The ${\beta}-Ga_2O_3$ thin film was generated to oxidize FS-GaN.

• Journal of Nutrition and Health
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• v.36 no.2
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• pp.211-222
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• 2003

This study on satisfaction with school food service (FS) programs was conducted with 485 middle school students and 515 high school students based on FS management type. There were four types of FS management: independent-conventional (IC), independent-commissary (ICM), contract-conventional (CC), and contract-delivery (CD). About seventy percent of the students expressed satisfaction with the food quantity of the school lunches. But one third of the students, who felt the quantity was insufficient, cited the small size of the rice serving. Many high school students cited the small size of the side dishes as well as the rice serving. It is suggested that the meal quantity should be determined in consideration of the students' physical development. The satisfaction with FS sanitation was lower than that with the meal quality, eating environment, and environment of dining room with respect to all four types of FS management, and was lowest in the CD. It is suggested that FS sanitation should be managed more thoroughly for the students' safety, and that the school FS Committee should carefully monitor the sanitary management of the contract FS companies by means of a well-designed and monitored management system. Most of middle and high school students expected good taste and a diversity of foods in their school lunches. Food taste should be improved, and various food materials and cooking methods should be used for balanced nutrition and greater student satisfaction, particularly in contract FS types (CC and CD).

• KIISE Transactions on Computing Practices
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• v.22 no.2
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• pp.95-100
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• 2016

In the current era of big data and cloud computing, the amount of data utilized is increasing, and various systems to process this big data rapidly are being developed. A distributed file system is often used to store the data, and glusterFS is one of popular distributed file systems. As computer technology has advanced, NAND flash SSDs (Solid State Drives), which are high performance storage devices, have become cheaper. For this reason, datacenter operators attempt to use SSDs in their systems. They also try to install glusterFS on SSDs. However, since the glusterFS is designed to use HDDs (Hard Disk Drives), when SSDs are used instead of HDDs, the performance is degraded due to structural problems. The problems include the use of I/O-cache, Read-ahead, and Write-behind Translators. By removing these features that do not fit SSDs which are advantageous for random I/O, we have achieved performance improvements, by up to 255% in the case of 4KB random reads, and by up to 50% in the case of 64KB random reads.

• 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.

• Korean Journal of Remote Sensing
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• v.18 no.4
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• pp.201-207
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• 2002

Radiative transfer model was used to detect the yellow sand using KOMPSAT-1/0SMI data. With OSMI and SeaWiFS data, spectrum analysis for spatial and channel were carried out to investigate the characteristics of sensor for the detection of yellow sand. It was compared and analyzed the optical depth of OSMI and SeaWiFS data. Spectral characteristics of x-axis is similar in 765 and 865nm according to spectral analysis for OSMI and SeaWiFS data. It is considered that band 7 and 8(765 and 865nm) of OSMI is suitable for detecting the yellow sand. Compared the yellow sand images by OSMI and MODIS, the data of OSMI are applicable to monitor the yellow sand phenomena. The optical depth of yellow sand event was about 0.8 with 1.0 maximum.