• 한국진공학회지
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• 제8권3B호
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• pp.353-360
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• 1999

The global balance model is applied to investigate the transient behavior of the electron density and temperature in helicon plasmas. The power absorption calculated from the solutions of the Maxwell equations is used in solving the power balance equation. A balance model for the neutral gas is also considered to fins its density self-consistently. It is turned out that the numerical results reasonably explain consequences of the ion pumping effect including the occurrence of two distinct modes of pulsed helicon discharge which have been observed experimentally. The behavior of the discharge parameters are fond to be primarily dependent on the power absorption and the gas flow rate, but the pressure controls the electron density and temperature of the final steady state as well as the transient state even with the same flow rate. Finally, it is shown that the electron density virtually the linear relationship between the density and the magnetic field is retained for a higher pressure when the effect of the ion pumping is negligible.

• 전자공학회논문지B
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• 제28B권5호
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• pp.335-342
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• 1991

A real-tme nonlinear parameter tomography is pumping wave method. This tomorgraphy has a merit which requires no 180$^{\circ}$ projection datum, while the ray-bending effect is remrkably remained on the reconstructed image. In this paper we intend to compensate this ray-bending effect using the perturbation method. Impulsive pumping wave makes derived compensative term simple form, nad the compensative image is easily obtained. We perform computer simulation to confirm the improvement of corrected imate.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.1895-1899
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• 2006

해안지역에서는 해수와 담수의 밀도차, 조석에 의한 해수면변화등과 같은 자연적 요인과 양수, 하구에서의 골재채취, 대규모 간척사업등의 인위적 요인에 의해서 해수가 육지부로 침투되는 현상이 발생한다. 본 연구에서는 양수가 지하수의 염분농도변화에 미치는 영향을 분석하였다. 모의결과, $200m^3/day$이상 양수시에는 지하수위의 저하보다는 횡방향흐름이 가속화 됨에 따라 밀도차에 의한 흐름과 횡방향흐름 유속이 합쳐져서 해수의 급격한 유입으로 TDS농도가 증가하는 것으로 나타났다. 결론적으로 기 관측된 점자료를 이용하여 3차원 공간분포상에서 양수에 따른 염분농도의 변화를 가시적으로 확인 할 수 있으며, 이를 통하여 해안지역에서 해수침투로 인한 재해를 막고 지하수를 보다 안전하게 이용하기위한 적정양수량을 제안할 수 있을 것으로 기대된다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.331-331
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• 2012

With the NAND Flash scaling down, it becomes more and more difficult to follow Moore's law to continue the scaling due to physical limitations. Recently, three-dimensional (3D) flash memories have introduced as an ideal solution for ultra-high-density data storage. In 3D flash memory, as the process reason, we need to use poly-Si TFTs instead of conventional transistors. So, after combining charge trap flash (CTF) structure and poly-Si TFTs, the emerging device SONOS-TFTs has also suffered from some reliability problem such as hot carrier degradation, charge-trapping-induced parasitic capacitance and resistance which both create interface traps. Charge pumping method is a useful tool to investigate the degradation phenomenon related to interface trap creation. However, the curves for charge pumping current in SONOS TFTs were far from ideal, which previously due to the fabrication process or some unknown traps. It needs an optimization and the important geometrical effect should be eliminated. In spite of its importance, it is still not deeply studied. In our work, base-level sweep model was applied in SONOS TFTs, and the nonideal charge pumping current was optimized by adjusting the gate pulse transition time. As a result, after the optimizing, an improved charge pumping current curve is obtained.

• 한국전기전자재료학회논문지
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• 제13권10호
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• pp.822-827
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• 2000

The Si-SiO$_2$interface trap and nitride bulk trap distribution of SONOSFET(polysilicon-oxide-nitride-oxide-semiconductor field effect transistor) NVSM (nonvolatile semiconductor memory) cell is investigated by single junction charge pumping method. The device was fabricated by 0.35㎛ standard logic fabrication process including the ONO stack dielectrics. The thickness of ONO dielectricis are 24$\AA$ for tunnel oxide, 74 $\AA$ for nitride and 25 $\AA$ for blocking oxide, respectively. By the use of single junction charge pumping method, the lateral profiles of both interface and memory traps can be calculated directly from experimental charge pumping results without complex numerical simulation. The interface traps were almost uniformly distributed over the whole channel region and its maximum value was 7.97$\times$10$\^$10/㎠. The memory traps were uniformly distributed in the nitride layer and its maximum value was 1.04$\times$10$\^$19/㎤. The degradation characteristics of SONOSFET with write/erase cycling also were investigated.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1703-1708
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• 2004

In this study, we are investigated experimentally the pumping characteristics about the pumping channel shapes of disk-type drag pump (DTDP). We are experimented the pumping performance about the rotors which have channel or do not exist. The channel disk-type rotor has spiral channels both upper and lower part, and stator is planar. The planar disk-type rotor hasn't channel and stator has spiral channels both upper and lower part. The flow-meter method is adopted to calculate the pumping speed. Compression ratio and pumping speeds for the nitrogen gas are measured under the inlet pressure range of 0.001 ${\sim}$ 4 Torr. The maximum of compression ratio was about 3300 for three-stage DTDP (channel disk-type rotor), 1000 for four-stage (planar disk-type rotor) and two-stage DTDP (channel disk-type rotor) at zero throughput. The ultimate pressure was $1.6{\times}10^{-6}$ Torr for three-stage DTDP (channel disk-type rotor), $2.5{\times}10^{-6}$ Torr for four-stage DTDP (planar disk-type rotor).

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.916-919
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• 2004

The monopole theory has long been used to model air-pumped effect from the elastic cavities in car tire. This approach models the change of an air as a piston moving backward and forward on a spring and equates local air movements exactly with the volume changes of the system. Thus, the monopole theory has a restricted domain of applicability due to the usual assumption of a small amplitude acoustic wave equation and acoustic monopole theory. This paper describes an approach to predict the air-pumping noise of a car ave with CFD/Kirchhoff integral method. The type groove is simply modeled as piston-cavity-sliding door geometry and with the aid of CFD technique flow properties in the groove of rolling car tyre are acquired. And these unsteady flow data are used as a air-pumping source in the next Cm calculation of full tyre-road geometry. Acoustic far field is predicted from Kirchhoff integral method by using unsteady flow data in space and time, which is provided by the CFD calculation of full tyre-road domain. This approach can cover the non-linearity of acoustic monopole theory with the aid of using Non-linear governing equation in CFD calculation. The method proposed in this paper is applied to the prediction of air-pumping noise of modeled car tyre and the predicted results are qualitatively compared with the experimental data.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1640-1645
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• 2004

The pumping characteristics of a single-stage disk-type drag pump ( DTDP ) are calculated,for the variation of the vertical clearance between a rotor and stator and of the radial clearance between a rotor and casing wall, by the three-dimensional direct simulation Monte Carlo (DSMC)method. The gas flow mainly belongs to the molecular transition flow region. Spiral channels of a DTDP are cut on the both the upper and lower sides of a rotating disk, but the stationary disks are planar. As a consequence of results, the vertical and radial clearances have a significant effect on the pumping performance. Experiments are performed under the outlet pressure range of 0.4 $^{\sim}$ 533 Pa. When the numerical results are compared to the experimental data, the numerical results agree well qualitatively.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2003년도 추계학술발표회
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• pp.217-221
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• 2003

Variation of decision variables for optimal remediation using the pump-and-treat method is examined to estimate the effect of the degree of concentration constraint. Simulation-optimization method using genetic algorithm is applied to minimize the total pumping volume. In total volume minimization strategy, the remediation time increases rapidly prior to significant increase in pumping rates. When the concentration constraint is set severer, the more wells are required and the well on the down-gradient direction from the plume hot-spot gives more efficient remediation performance than that on the hot-spot position. These results show that the more profitable strategy for remediation can be achieved by increasing the required remediation time than raising the pumping rate until the time reaches a certain limitation level. So, the remediation time has to be considered as one of the essential decision variables fer optimal remediation design.

• 한국정밀공학회지
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• 제16권12호
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• pp.31-39
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• 1999

Previous researches and experiments have already verified that the primary noise source of high pressure tandem axial thpe piston pump is fluid-borne noise from the process of oil distribution between the kidney-shaped port and valve plate. So, many researchers have improved pressure gradients and reduced sound levels by applying pre-compression and pre-decompression metering grooves to valve plate. In practice however, the sound level of th high pressure tandem axial type piston pump is still undesirable. This paper testified the effect of pumping phase of the piston on vibration and noise of th high pressure tandem axial type piston pump on the best of theoretical research in $this^(1)$. Therefore considering the pumping phase of the piston when assembling the tandem axial type piston pump, it is possible to reduce 1.5~2[dB]of sound level.