• Journal of computational fluids engineering
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• v.4 no.1
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• pp.27-33
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• 1999

Spiral tube heat exchangers can find numerous applications in many engineering fields. Flow in spiral tubes is interest to engineers due to occurrence of secondary flow which enhances the cross-sectional mixing and the heat transfer rate. In the present study, an incompressible viscous 3-D flow in spiral tubes with rectangular cross-section of various torsion rate and Reynolds number is studied by using a finite volume method. It is shown that the axial velocity profile is affected by the secondary flow motion. Because there is some difference from correlation proposed by Hur et al., a lot of analysis and arrangement of experimental results are needed. This study showed the results of variation of hydrodynamic entry length for torsion and Re numbers.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.144-148
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• 2001

A proper estimation of the mechanical properties for composites has been required for better design/selection of constituents for composite materials. Present investigation shows the simulation results for ceramic reinforced metal matrix composite under uniaxial transverse tensile loading. The resulting transverse mean stress with the transverse mean strain was described for composites as a function of the volume fraction with two different types of interfacial bonding: (1)strongly bonded interface, and (2)no bonded interface. A two-dimensional finite element modeling and analysis were conducted based on the unit-cell concept with an assumption of a regular square arrangement of the reinforcement within the composite. The mean stress was generally increased with the ceramic volume fraction for composite with strong interface bonding. The micromechanics concept combined with finite element modeling for composite can be used in order to predict the transverse properties of composites with a priori known properties of constituents.

• IEIE Transactions on Smart Processing and Computing
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• v.3 no.1
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• pp.35-39
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• 2014

This paper proposes a Modified Minimum Mean Square Error (M-MMSE) estimator for an Orthogonal Frequency Division Multiplexing (OFDM) System over fast fading Rayleigh channel. The proposed M-MMSE estimator considered the effects of the efficient placement of pilots based on the channel energy distribution. The pilot symbols were placed in a non-linear manner according to the density of the channel energy. Comparative analysis of the MMSE estimator for a comb-type pilot arrangement and M-MMSE estimator for the proposed pilot insertion scheme revealed significant performance improvement of the M-MMSE estimator over the MMSE estimator.

• 한국전산유체공학회:학술대회논문집
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• 1998.11a
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• pp.62-69
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• 1998

Spiral tube heat exchangers can find numerous applications in many engineering field. Flow in spital tubes is interest to engineers due to occurrence of secondary flow which enhances the cross-sectional mixing and the heat transfer rate. In the present study, an incompressible viscous 3-D flow in spiral tubes with rectangular cross-section of various torsion rate and Reynolds number is studied by using a finite volume method. It is shown that the axial velocity profile is affected by the secondary flow motion. Because there is some difference from correlation proposed by Hur et al., a lot of analysis and arrangement of experimental results are needed. This study showed the results of variation of hydrodynamic entry length for torsion and Re numbers.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.453-458
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• 2001

The stability of turbulent nonpremixed interacting flames is investigated in terms of nozzle configuration shapes which depend on the existence of the center nozzles. Six nozzle arrangements which are cross 4, 5, 8, 9, square 8 and circular 8 nozzles are used for the experiment. Those are arranged to see the effect of the center nozzle out of multi-nozzle. There are many parameters that affect flame stability in multi-nozzle flame such as nozzle separation distance, fuel flowrates and nozzle configuration, but the most important factor is the existence of nozzles in the center area from the nozzle arrangement. As the number of nozzle in the area is reduced, more air can be entrained into the center of flame base and then tag flame is formed. In the case of circular 8 nozzles, blowout flowrates are above 5.4 times compared with that of single equivalent area nozzle.

• Journal of Korean Home Economics Education Association
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• v.5 no.1
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• pp.121-132
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• 1993

The purpose of this study is to evaluate the state and problems on sex education of junior & senior high schools in Taegu city & Kyungbuk province and then to try to find the solutions. This article is consisted of four parts: the present state of sex education, how to improve sex education, the problems of teacher training and the actual condition of educational materials for that. The item of questionnaires was analyzed by SAS-PC program. the results are marked with frequency, percentage, mean and $\chi$$^2$(chi-square). For effective and better sex education in high schools, development & distribution of various audio-visual teaching material, and systematic & correlative arrangement of educational contents are to be first requisite. Concerning about the teacher training it is needed that to establish the standard o general management and equipment of instruction system.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.5
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• pp.425-432
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• 2012

Viscous flow fields of side-by-side arranged two-dimensional floating bodies are numerically simulated by a Navier-Stokes equation solver. Two identical bodies with a narrow gap are forced to heave and sway motions. Square and rounded bilge hull forms are compared to find out the effects of vortex shedding on damping force. Wave height, force RAOs, added mass and damping coefficients including non-diagonal cross coefficients are calculated and a similarity between the wave height and force RAOs is discussed. CFD which can take into account of viscous damping and vortex shedding shows better results than linear potential theory.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.50 no.3
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• pp.117-124
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• 2001

The aim of this paper is to develop a controller of multi-phase bipolar brushless DC (MPB BLDC) motors for an electric bicycle. A MPB BLDC motor has a Permanent magnet rotor in which the magnetic arrangement is radial to the shaft and integral to the rotor laminations. This technique concentrates flux, giving a higher flux density than a surface-mounted PM motor and increases reluctance torque. The stator of MPB BLBC motor has parallel winding, allowing multi-phase separate independent controllability. It gets much more high power than wye-connection at same low voltage. The conventional techniques of exited with modulation(EWM), bidirection control, and partial square wale control are Proposed with one H-bridge and two photo sensors per phase. The Proposed controller is satisfied for the limited speed control and designed for system stability Experimental results show the performance of the proposed controller of MPB BLDC motors for an electric bicycle.

• Bulletin of the Korean Chemical Society
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• v.33 no.12
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• pp.4069-4073
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• 2012

Metallacyclodimeric complexes of $[(Me_4en)Pd(L)]_2(ClO_4)_4$ ($Me_4en$ = N,N,N',N'-tetramethylethylenediamine; L = dimethylbis(4-pyridyl)silane (dmps), methylvinylbis(4-pyridyl)silane (mvps)) have been synthesized, and their structures have been characterized by X-ray single crystallography. The skeletal structures consist of one 20-membered metallamacrocycle, two 5-membered metallacycles, and four pyridyl groups. The local geometry around the palladium(II) ion approximates to a typical square planar arrangement with four nitrogen donors. Delicate difference in catalytic effects on hydrogenation was investigated based on the structure of catalyst and substrates.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1669-1670
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• 2006

LED have many problem as narrow light view angle, high price, drift phenomenon of color coordinate, high heating problem for lower power, lower weight and small size. But, with the development of blue LEDs and the improvement of LED brightness, color variation are becoming more and more popular as lighting and application devices in this page, 1 used the Light Tools which was a simulation program in order to recognize optical a few characteristic of LEDs arrangement along reflector matrial and designed LED Arranged 5 phi LED in 5mm interval In the square that was $10{\times}10$ And designs a reflection board on pcb, structural design of PCB changed as five type. - Aluminum, Gold. Chromium, Nickel, Copper.