• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1999.05a
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• pp.14-15
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• 1999

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.2
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• pp.75-83
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• 2016

Since a turbomachine has complex flow characteristics, which are caused by adverse pressure gradient and high speed motion, an elaborate turbulence model is needed to accurately predict the flow. Some turbulence models such as an algebraic or a two-equation eddy viscosity model have been used for in-house RANS-code, but it is difficult to obtain good result for several complex flows. In this study, Durbin's V2-F turbulence model, which has been known for better prediction for severe flow separation, is applied to T-Flow. It was validated for simple cases such as channel and compressor cascade, and its applicability to turbomachinery was shown by analyzing internal flow of a single rotor. As a result, the V2-F turbulence model shows better blade surface pressure distribution than the one-and-two equation turbulence model.

• Journal of Plant Biology
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• v.29 no.1
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• pp.19-40
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• 1986

A study on the species description, enumeration and interspecific relationships of genus Filipendula was undertaken for four Korean and two Japanese species. The use of scanning electron miroscope(SEM) has made possible a detailed study of foliar trichomes, pollen grains and fruit surface features. A new method for the preparation of SEM samples was developed in this study. Filipendula glaberrima, F. formosa, and F. korean were reliable endemic species. Among them, F. glaberrima shares many characteristics with F. formosa. F. gloaberrima can be divided into tow types based on leaf, seed, flower and pollen characters. Type I is characterized by ciliated fruits, many branched vascular bundles on the petal, dense trichomes on the leaf vein of abaxial surface, and many foveolate pollen surface. Type II possesses glabrous fruits, a few vascular bundles on the petal, rare trichomes on the leaf vein and a few foveolate pollen surface. The significant taxonomic characteristics in the classification of genus Filipendula are their lengths of fruit stalks, the densities of marginal trichomes of fruits, and textures of stipules.

• Nuclear Engineering and Technology
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• v.36 no.1
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• pp.47-52
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• 2004

Recently, a new sintered pellet-type LiF:Mg,Cu,Na,Si TL detector which has a high sensitivity and good reusability, named KLT-300(KAERI LiF:Mg,Cu,Na,Si TL detector), was developed by the variation of the dopants concentrations and the parameters of the preparation procedure at KAERI (Korea Atomic Energy Research Institute). In this study, the thermoluminescent characteristics of the newly developed TL detectors were investigated. The sensitivity of the TL detector was compared with that of the TLD-100 by light integration. The dose linearity of the detector was tested from $10^{-6}$ Gy up to 30 Gy. The dose response was very linear up to 10 Gy and a sublinear response was observed at higher doses. The energy response of the detector was studied for photon energies from 20 keV to 662 keV. The result shows that a maximum response of 1.004 at 53 keV and a minimum response of 0.825 at 20 keV were observed. The reproducibility study for the TL detector was also carried out. The coefficients of variation for each detector separately did not exceed 0.016, and for all the 10 detectors collectively was 0.0054. Lower limit of detection for the detector was investigated at 70 nGy by the Harshaw 4500 TLD Reader and the residual signal of the TL detector was found to be $0.57\%$.

• Speech Sciences
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• v.12 no.1
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• pp.37-43
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• 2005

The phenomenon of vocal vibrato may be regarded as an acoustic representation of one of the most rapid and continuous changes in pitch and intensity that the human vocal mechanism is capable of producing. Singers are likely to use vibrato effectively to enrich their voice. The purpose of this study was to obtain acoustic measurements (vF0 and vAm) of 45 subjects (15 trot and 15 ballad singers and 15 non-singers) and to compare acoustic measurements of the vowel /a/ produced by 3 groups on 2 voice sampling conditions (prolongation and singing of /a/). Thirty singers of trot and ballad were selected by a producer and a concert director working for the KBS (Korean Broadcasting System). The MDVP was used to measure the acoustic parameters. A two-way MANOVA was used for statistical analyses. The results were as follows; Firstly, there was no significant difference among the 3 groups in vF0 and vAm in prolongation of /a/, but in singing voice, there was a significant difference among 3 groups in vF0 and vAm. Secondly, there was an interaction between music genre and voice sampling condition in vF0, and vAm. Finally, trot singers sing with more vibrato than ballad singers. It was concluded that it is very important to analyze singers' voice including various voice conditions (prolongation, reading, conversation, and singing) and to identify differences of singing voice characteristics among music genre.

• International Journal of Automotive Technology
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• v.3 no.4
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• pp.171-176
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• 2002

A bench test set-up is employed to simulate the friction characteristics of a paper-based friction material operating against a steel plate. Dry friction tests are run as well as tests with transmission fluids. Glazed friction material produces a negative coefficient of friction versus sliding velocity (f-v) curve for both dry friction and lubrication with transmission fluids. At low sliding speeds, the coefficient of friction when operating in transmission fluids for glazed friction materials is greater than that under dry friction. An appreciable negative f-v slope occurs at low sliding speeds for glazed friction materials when running with the transmission fluid. The friction material after running in produces a constant f-v curve under dry friction and a negative slope when lubricated with transmission fluid. At low sliding speeds, the coefficient of friction of the run-in friction material is lower than that of the glazed wet material. On the other hand, the run-in friction material has a larger friction coefficient than does the glazed friction material at higher sliding speeds.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1619-1622
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• 2001

Recently many researches on the diagnosis of stator winding insulation for large rotating machines have been developed sine the 1970s. Capacitive coupler has been the most widely used sensor for on-line partial discharge(PD) in rotating machines. The 105 [pF] ceramic coupler(CC) has been developed to continuously measure the PD activity in operating motor stator windings. This paper presents frequency characteristics and laboratory test to compare traditional 80 [pF] epoxy-mica coupler(EMC) and 105 [pF] CC for PD measurement in 6.6 [kV] stator windings.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.131-134
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• 1991

In order to determine an operating pattern of SLIM in an experimental MAGLEV vehicle, operating characteristics of SLIM are obtained using a disk type test facility. The test results are compared with the pre-estimated values. It is found that a closed loop control is required for operating at a constant slip-frequency condition which makes the normal force minimum.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.6
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• pp.470-477
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• 2004

This study shows the design process of a MR damper for semi-active suspension systems. Damping force characteristics of the designed damper was predicted through the flow analysis and magnetic analysis. The predicted results were compared with the experimental results and the initial design specification was modified according to the results.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.50-52
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• 1995

This paper deals with the dynamic characteristics of LIM which is controlled by constant V/f ratio and the characteristics of the Inverter acted as interface between the utility power system and LIM. Though open-loop control method is less reliable than closed-loop control method, it's commonly used because it is simple and cheap. This paper shows the consideration for dynamic characteristics of LIM under open-loop control and for Inverter.