• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.2
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• pp.115-121
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• 2002

This report summarized the static test of the rudder system for the KTX-1 basic trainer. The test loads are applied up to the limit and ultimate loads in a stepping sequence. Test loads and test results matt the strength and stiffness requirements of the rudder control system.. Using #004 full scale structure test airframe.

• JSTS:Journal of Semiconductor Technology and Science
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• v.3 no.1
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• pp.47-54
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• 2003

New efficiency enhancement techniques have been devised and implemented to InGaP/GaAs HBT MMIC power amplifiers for W-CDMA mobile terminals applications. Two different types of bias current control circuits that select the efficient quiescent currents in accordance with the required output power levels are proposed for overall power efficiency improvement. A dual chain power amplifier with single matching network composed of two different parallel-connected power amplifier is also introduced. With these efficiency enhancement techniques, the implemented MMIC power amplifiers presents power added efficiency (PAE) more than 14.8 % and adjacent channel leakage ratio(ACLR) lower than -39 dBc at 20 dBm output power and PAE more than 39.4% and ACLR lower than -33 dBc at 28 dBm output power. The average power usage efficiency of the power amplifier is improved by a factor of more than 1.415 with the bias current control circuits and even up to a factor of 3 with the dual chain power amplifier.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.7 s.110
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• pp.648-658
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• 2006

We propose a thin frequency selective surface(FSS) superstrate etched on a substrate for dual-band directivity enhancement, and present a design method of the superstrate. In the proposed new design, two FSS arrays with the same periodicity, but with different alignments are placed above and below a thin dielectric layer to overcome the problem of conventional superstrates for dual band directivity enhancements. Based on the unit-cell simulation, several important parameters that characterize the thin FSS superstrate are investigated, and the procedure for designing such a superstrate is described. We compare the resonant frequencies and the qualify factors of the unit cell with those of three FSS antenna composites with different quality factors, and identify the quality factors which support similar directivity enhancement at the dual-band directivity enhancement. It was found that there is an optimum FSS array size of a superstrate to enhance the directivity most efficiently. Measured results for a fabricated superstrate show a good agreement with the simulated ones.

• Journal of Korean Dental Hygiene Science
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• v.6 no.2
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• pp.51-64
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• 2023

Background: This study was conducted to determine the association with dual jobbing on dental hygienists' job satisfaction and to identify the factors that lead to dual jobs. Methods: This study was an online survey of 110 currently employed dental hygienists conducted during the month of May 2022. To determine job satisfaction, we used the 20-item Korea-Minnesota Satisfaction Questionnaire (K-MSQ). Survey questions related to dual job were adapted and supplemented from the dual job survey instrument for dental hygienists to identify intention to dual job and future intention to dual job. Descriptive statistics, independent t-test, ANOVA and Scheffe's post hoc analysis, and multiple logistic regression were performed. Results: The dual job rate and future dual job rate of the participants in this study were about 27% and 47%, respectively. The means for Intrinsic job satisfaction, Extrinsic job satisfaction, and job satisfaction were 3.44, 3.15, and 3.36, respectively. It was statistically significant that extrinsic job satisfaction increased with increasing position, and intrinsic job satisfaction, extrinsic job satisfaction, and job satisfaction increased with increasing salary. Those currently working dual jobs cited "self-actualization" as a reason for doing so, and those who intended to work dual jobs in the future cited "not being paid enough in their primary job" as a reason. We found that a one-unit increase in intrinsic job satisfaction and job satisfaction increases the odds of future intention to dual job by about 1.07 and 1.05 times, respectively (p<0.05). Conclusion: This study confirmed the influence of dental hygienists' job satisfaction on intention to dual job and future intention to dual job, and self-actualization was found to be the main factor. Therefore, the consideration of dual jobs in the future will affect the improvement of dental hygienists as professionals and the reduction of turnover through better working conditions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.269-273
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• 2003

There is a growing interest to replace the commercial steels with non-heat treated steels, which does not involve the spheroidization and quenching-tempering treatment. However, Non-heat treated steels should satisfy high strength and good formability without performing heat treatment. Therefore, it is important to investigate optimum materials showing a good combination of strength and formability after the drawing process. In this study, Dual-Phase Steels were studied as candidate materials for non-heat treated steels, which have different martensite morphologies and volume fractions obtained through heat-treatment of intercritical quenching (IcQ), intermediate quenching (ImQ) and step quenching (SQ). The mechanical properties of DP steels were measured by tension and compression tests. Also, the cold formability of three DP steels which have similar tensile strength value was investigated by estimating the deformation resistance and the forming limit. The deformation resistance which is important factor in determining die life was estimated by calculating the deformation energy. And the forming limit was estimated by measuring the critical strain revealing crack initiation at the notch tip of the specimens.

• Journal of Welding and Joining
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• v.11 no.2
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• pp.42-52
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• 1993

The corrosion fatigue fracture behaviour of dual phase steel was investigated in 3% NaCl solution at 302MPa and 137MPa. Fatigue test was conducted by cantilever type of self-made rotary bending fatigue testing machine. The fatigue strength increased with increasing the hardness of 2nd phase. Corrosion pit originated at the boundary of the 2nd phase. The size and number of corrosion pits were influenced by the 2nd phase hardness, and pits remained constant in size just after they were transited into cracks. The life of crack initiation was effected by stress level. The shape of relation of .DELTA. K and da/dN has smaller scattering in it in 3% NaCl solution than that in air. The higher the 2nd phase hardness is, the greater the corrosion fatigue life becomes. Corrosion fatigue fracture behaviour was primarily effected by mechanical factor in case of high stress(302MPa), but by electro-chemical reaction in a lower stress(137MPa). As stress level got lower and hardness of the 2nd phase got higher, the roughness of fracture surface increased.

• Transactions of Materials Processing
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• v.13 no.1
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• pp.84-89
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• 2004

There is a growing interest to replace the commercial steels with non-heat treated steels, which does not involve the spheroidization and quenching-tempering treatment. However, Non-heat treated steels should satisfy high strength and good formability without performing heat treatment. Therefore, it is important to investigate optimum materials showing a good combination of strength and formability after the drawing process. In this study, Dual-Phase Steels were studied as candidate materials for non-heat treated steels, which have different martensite morphologies and volume fractions obtained through heat-treatment of intercritical quenching (IcQ), intermediate quenching (ImQ) and step quenching (SQ). The mechanical properties of DP steels were measured by tension and compression tests. Also, the cold formability of three DP steels which have similar tensile strength value was investigated by estimating the deformation resistance and the forming limit. The deformation resistance which is important factor in determining die life was estimated by calculating the deformation energy. And the forming limit was estimated by measuring the critical strain revealing crack initiation at the notch tip of the specimens.

• Journal of the Korean Society of Clothing and Textiles
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• v.32 no.2
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• pp.179-189
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• 2008

The purposes of this study were to segment surrogate internet shopping mall consumers by fashion leadership and to find the differences among the segmented groups in regard to surrogate internet shopping perceived risks, selection criteria, dissatisfactions with surrogate shopping malls, and other purchase behavior. The subjects of this study were female consumers who were users of surrogate internet shopping malls. The data were collected during October, 2005. The respondents returned the questionnaires and 283 questionnaires were finally used in the data analysis. The statistical analyses used for the study were factor analysis, ANOVA, Duncan test, and $X^2$-test. The results showed that consumers were segmented by four groups: fashion dual leaders, fashion leaders, fashion followers, and fashion laggards. These segmented groups were significantly different in regard to surrogate internet shopping mall perceived risks, selection criteria, dissatisfactions with surrogate shopping malls, and other purchase behavior. Generally, fashion dual leaders had less perceived risks, considered diverse selection criteria important, and were less dissatisfied with surrogate shopping malls. Also, the fashion dual leaders had a higher purchase frequency and paid a higher price on surrogate internet shopping malls.

• Journal of Korean Vacuum Science & Technology
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• v.6 no.2
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• pp.62-66
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• 2002

Hydraulic pumps are used to control the landing wheels of aircrafts, and their proper operation is vital to plane safety It is well hewn that adhesive wear failure is a major cause of pump failure. A dual nitrogen plasma immersion ion implantation process calling for the implantation of nitrogen at two different energies and doses has been developed to enhance the surface properties of the disks in the pumps. The procedures meet the strict temperature requirement of <200$^{\circ}C$, and after the treatment, the working lifetime of the pumps increases by more than a factor of two. This experimental protocol has been adopted by the hydraulic pump factory as a standard manufacturing procedure.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3473-3478
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• 2007

A dual side cooling annular fuel having internal and external coolant channels has many advantages basically due to low fuel temperature and high DNBR margin, which can make a significant increase of core power density possible. So recently a 12x12 square annular fuel array was proposed for the fuel assembly to be reloaded without structural interference with operating reactors of OPR-1000s. Even through the inherent potential of the annular fuel on the high power density, it may be seriously eroded in the case of a severe unbalanced mass flux split to the internal and external channels in standpoint of DNB. Mass flux split is determined pressure drop characteristics between inner and outer channels. The spacer grids binding fuel array influence greatly the pressure drop in outer channels and the mass flux split. As an important factor of DNB behavior, the enthalpy differences at both channel exits were evaluated using the mass flux splits.