• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.6
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• pp.607-613
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• 2010

A seawater distiller, in which the waste heat from a portable electric generator was used, with a multiple-effect diffusion still was designed. The waste gas from small generators commonly used in islands has not yet been used because it has less thermal energy; however, this waste gas can be used as a heat source for small-capacity distillers and as an additional heat source for solar stills. The proposed distiller comprises a series of closely spaced parallel partitions that are placed in contact with saline-soaked wicks. In the distiller, evaporation and condensation processes are repeated to recycle the thermal energy for increasing the distillate productivity. Experimental results show that the proposed distiller with only one-effect still can produce at least 6.7 kg/day of distilled water; the proposed distiller with a ten-effect still is expected to produce 43 kg/day of distilled water. This amount of distillate is approximately four times the maximum daily productivity of the solar stills, as determined in outdoor experiments.

• Journal of Sensor Science and Technology
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• v.9 no.2
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• pp.120-126
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• 2000

This paper dealt with the developed portable electric field meter which consisted of planar-type sensor, analog amplifier with gain controller, A/D convertor, and display unit. The principle of the planar-type sensor for detecting time-varying electric field of extremely low frequency (ELF) bandwidth was described, and a calibration system using cylindrical guard electrodes and parallel-plate electrodes was proposed. From the calibration experiment, the frequency bandwidth and the sensitivity of the developed electric field meter was $17[Hz]{\sim}7[kHz]$, and 4.45[mV/V/m], respectively. Also it can measure the electric field strength up to 10[kV/m], and the measured result was displayed on the liquid crystal display in digit. The electric field meter can be widely applied to measure electric field strength radiated from power lines, computers, and home appliances such as hair dryer, heater, etc.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.2
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• pp.247-256
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• 1999

The leaky wave emanated from the dielectric-coated parallel-plate waveguide with finite periodic thick slot in its upper plate is investigated theoretically for H-polarization case. For this structure, fields in slot regions are expressed as a summation of the parallel-plate waveguide TM modes, and in other regions are expressed in the spectral domain by use of the inverse Fourier transform. Boundary conditions at the interfaces are enforced, and the simultaneous linear equations are derived. The influences of the slot width, slot thickness, thickness of a dielectric coating, and finite slot number on the radiation characteristics (phase constant, leakage constant, radiation pattern) are examined. The results of the finite periodic slot are compared with those of the infinite extent structure and good agreement has been found.

• Journal of Radiation Protection and Research
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• v.24 no.4
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• pp.195-203
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• 1999

It is difficult to determine dosimetric characteristics for small field photon beams since such small fields do not achieve complete lateral electronic equilibrium and have steep dose gradients. Dosimetric characteristics of small field 4, 6, and 10 MeV photon beams have been measured in water with a diamond detector and compared to measurements using small volume cylindrical and plane parallel ionization chambers. Percent depth dose (PDD) and beam profiles for 6 and 10 MeV photon beams were measured with diamond detector and cylindrical ion chamber for small fields ranging from $1{\times}1\;to\;4{\times}4cm^2$. Total scatter factors($S_{c,p}$) for 4, 6, and 10 MeV photon beams were measured with diamond detector, cylindrical and plane parallel ion chambers for small fields ranging from $1{\times}1\;to\;4{\times}4cm^2$. The $S_{c,p}$ factors obtained with three detectors for 4, 6, and 10 MeV photon beams agreed well ($\pm1.2%$) for field sizes greater than $2{\times}2,\;2.5{\times}2.5,\;and\;3{\times}3\;cm^2$, respectively. For smaller field sizes, the cylindrical and plane parallel ionization chambers measure a smaller $S_{c,p}$ factor, as a result of the steep dose gradients across their sensitive volumes. The PDD values obtained with diamond detector and cylindrical ionization chamber for 6 and 10MeV photon beams agreed well ($\pm1.5%$) for field sizes greater than $4{\times}4\;cm^2$. For smaller field sizes, diamond detector produced a depth-dose curve which had a significantly shallower falloff than that obtained from the measurements of relative depth-dose with a cylindrical ionization chamber. For the measurements of beam profiles, a distortion in terms of broadened penumbra was observed with a cylindrical ionization chamber since diamond detector exhibited higher spatial resolution. The diamond detector with small sensitive volume, near water equivalent, and high spatial resolution is suitable detector compared to ionization chambers for the measurements of small field photon beams.

• Journal of Power System Engineering
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• v.9 no.2
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• pp.33-39
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• 2005

Experiments are performed to study the mixed convection flow and heat transfer in an inclined parallel plates with the upper part cooled and the lower part heated uniformly. The Reynolds number ranges from $4.0{\times}10^{-3}\;to\;6.2{\times}10^{-2}$, the angle of inclination, ${\theta}$, from 0 to 45 degree from the horizontal line, and Pr of the high viscosity fluid is 909. In this paper, the PIV(Particle image velocimetry) with TLC(Thermo-sensitive liquid crystal) tracers is used for visualizing and analysis. This method allows simultaneous measurement of velocity and temperature field at a given instant of time. Quantitative data of the temperature and velocity are obtained by applying the color-image processing to a visualized image, and neural network is applied to the color-to-temperature calibration. This paper describes the methods, and presents the quantitative visualization of mixed convection. From this study, it is found that the flow pattern can be classified into three patterns which are affected by Reynolds number and the angle of inclination.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.9
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• pp.698-706
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• 2006

Experiment and numerical calculation have been peformed to investigate mixed convection heat transfer between inclined parallel plates. Particle image velocimetry (PIV) with thermo-sensitive liquid crystal (TLC) tracers is used for visualizing and analysis. This method allows simultaneous measurement of velocity and temperature fields at a given instant of time. Quantitative data of the temperature and velocity are obtained by applying the color-image processing to a visualized image, and neural network is applied to the color-to-temperature calibration. The governing equations are discretized using the finite volume method. The results are presented for the Reynolds number ranges from 0.004 to 0.062, the angle of inclination, ${\Theta}$, from 0 to 45 degree and Prandtl number of the high viscosity fluid is 909. The results show velocity, temperature and mean Nusselt numbers distributions. It is found that the periodic flow of mixed convection between inclined parallel plates is shown at $0^{\circ}{\leq}{\Theta}<30^{\circ}$, Re<0.062, and the flow pattern can be classified into three patterns which depend on Reynolds number and the angle of inclination. The minimum Nusselt numbers occur at Re=0.05 regardless of the angle of inclination.

• Journal of Navigation and Port Research
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• v.27 no.5
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• pp.473-478
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• 2003

Numerical study was made on the flow characteristics around a circular pipeline between parallel walls. The incompressible Navier-Stokes equations were solved by using a third-order upwind differential scheme. When the distance near a wall is small enough, the vortex shedding is almost completely suppressed because of the interaction with the wall boundary layer separation. This study aims to clarify the characteristics of the vortex shedding regime as the body approaches a wall as Reynolds number varies. The feature of separated vorticity dynamics is analyzed at different conditions with particular attention to the interaction between the pipeline wake and the induced separation on the plane walls.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.3
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• pp.181-188
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• 2008

The effect of inclination angle on the heat transfer and pressure drop characteristics of the brazed aluminum heat exchangers is experimentally investigated. Three samples having different fin pitches(1.25, 1.5 and 2.0 mm) were tested. Results show that heat transfer coefficient is not affected by the inclination angle. However, the friction factor increases as the inclination angle increases with negligible difference between the forward and backward inclination. Both the heat transfer coefficient and the friction factor are the smallest at $F_p=1.5mm$, followed by $F_p=2.0mm$ and 1.25mm. Possible explanation is provided considering the louver layout. Comparison with existing correlations is also made.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.2
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• pp.56-65
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• 1989

In this paper, a new model is presented which characterizs the coupling of the radiating edges between two rectangular microstrip patch antennas. This model, namely Radiating Edges-Coupling (REC) model, is derived from the equivalent circuit of the slitted parallel-plate waveguide filled with homogeneous dielectric. Applying the REC model to two coupled rectangular microstrip patch antennas, we obtain numerical S-parameter values of |$S_{11}$| and |$S_{12}$|for the various coupling separations, $S_e$=0.5, 1.0, 1.5, and 2.0mm. Theoretical results are in fairly good agreement with experimental results.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.493-493
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• 2012

평행평판 축전 결합 플라즈마는 증착이나 식각 등 많은 공정장비에서 사용된다. 이때 구동주파수를 높여주거나 리액터의 크기를 증가시킬 경우, 플라즈마 밀도가 불균일해진다. 플라즈마 밀도는 플라즈마 내 전기장 분포의 균일도와 관련이 있는 것으로 전기장 분포를 균일하게 만드는 것은 매우 중요하다. 이전 연구에서는 충돌 주파수(공정 압력)가 전기장의 분포에 미치는 영향에 대해 발표하였다 [1]. 본 연구에서는 구동 주파수, 충돌 주파수(공정 압력), 플라즈마 주파수(플라즈마 밀도)가 전기장 분포에 미치는 영향을 알아보았고, 이들의 상관관계를 분석하였다. 플라즈마 주파수(플라즈마 밀도)와 충돌 주파수(공정 압력)는 전기장 분포의 균일도에 영향을 주는 변수이지만 이 둘은 반대 영향을 미쳤다. 따라서 두 주파수가 전기장 분포에 미치는 영향이 균형을 이룰 때 균일한 전기장 분포를 얻을 수 있었다. 이 때 구동 주파수가 증가할수록 균일하게 하는 두 주파수의 영역이 줄어들어 높은 구동 주파수에서는 전기장 분포를 균일하게 하기 어려웠다. 이러한 관계를 이용하여 일정한 구동 주파수와 플라즈마 주파수에서 전기장 분포의 균일도를 10% 이내로 하기 위해 충돌 주파수를 결정할 수 있는 방정식을 구하고, 충돌 주파수와 플라즈마 주파수, 그리고 구동 주파수가 전기장 분포를 균일하게 하는 이들의 관계를 살펴 보았다.