• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.386-390
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• 2004

하천은 자연 상태에서 내부분 단일 하천이 아닌 몇 개의 지류가 본류와 만나는 복잡한 하천망을 구성하며 하류로 흘러간다. 이 때 본류와 지류가 만나는 합류부에서는 본류와 지류의 합류각도나 유량에 의해 수리학적인 특성이 매우 민감하게 변화한다. 수리학적 특성에서는 수심이나 유속 등의 흐름에 대한 분석이 있을 뿐 아니라, 유사이동에서의 침식이나 퇴적과 같은 하상변동도 중요하게 고려되어야 한다. 그러나, 지금까지 합류점에 내한 연구가 대부분 물의 흐름 해석에 관한 연구이며, 하상변화에 대한 연구가 상당히 부족하다. 본 실험 연구에서는 본류와 지류의 접근각도를 $60^{\circ},\;75^{\circ},\;90^{\circ}$로 변화시키면서 분석하였으며, 유량비는 1:0.2, 1:0.35, 1:0.5로 변화시키면서 분석하였다. 이때 사용한 모형수로는 본류와 지류의 폭을 1:0.8로 하였으며, 이동상 실험을 위해 입경 1mm인 균일 모래를 이용하여 실험하였다. 그 결과 침식되는 길이는 유량비 및 접근각도가 증가함에 따라 커지는 경향을 나타내고 있으며, 이는 합류부에서의 하상침식에 대한 개선방향으로 활용될 수 있을 것으로 판단되고 있으며, 또한 접근각도가 증가함에 따라서는 최심경사는 점차 증가하는 것으로 나타났으나, 유량비가 증가함에 따라 감소하는 것으로 나타났다.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.4 s.23
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• pp.57-65
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• 2006

In this study, hydraulic model same as natural channel with junction area and curved reach is constructed, and after that the variation of difference of the water surface elevation at cross section in junction area is analyzed using constructed hydraulic model. In junction area, the variation of maximum water level based on downstream section is more affected in discharge ratio at upstream than downstream. The maximum water level increased as closed to junction and the peak level appeared at just downstream of junction. The slope of water elevation at cross section is affected in section shape and decreased as discharge ratio is reduce. The expressed formulas developed in the channel consist of constant curvature and section shape showed difference of 60% with measured value, but the suggested formula in this study to compute difference of water surface elevation showed difference of 10% with measured value.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.156-161
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• 2002

It depends on the joint configuration, dimensions and constraints on the joint whether the residual stress at the root of single-sided butt weld is tensile or not. Therefore, recommendation is generally made that high R ratio should be used in the fatigue test of this type of joint in order to prevent excessively long life caused by compressive residual stress. in this research, the residual stress profile in butt weld joint was obtained through compliance method, using successive extension of a slot and measurement of the variation of strain during the slot extension. The residual stress profile was firstly assumed to be the linear summation of Legendre polynomials up to 9th order excluding 0th and 1st order. Strain variation on the surface was measured while the slot was being extended by cutting to find out the 8 unknown coefficients of each polynomial tenn. The cut was made by the electric discharge machine. It was concluded that the residual stress near the surface stayed positive, however, it turned into the negative value as soon as it passed through 2 or 3 mm depth. Several fatigue tests were also carried out under zero stress ratio. Test results showed that fatigue life coincides well with the design cuive of butt joint in British Standards, which supports that it is tensile residual stress that exists near the weld root.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.7
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• pp.649-658
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• 2000

Thermodynamic modeling of low-pressure scroll compressor was developed by combining continuity and energy conservation equation. Suction gas heating was considered using energy balance inside the low pressure shell. Pressure, temperature and mass of refrigerant-22 as a function of orbiting angle were calculated by solving the governing equations using fourth order Rung-Kutta scheme. Motor efficiency was taken by experiments with a variation of frequency. The developed model was applied to the analysis of an inverter driven scroll compressor with a variation of frequency, pressure ratio and operating conditions. The model was verified with the experimental results at the same operating conditions. The developed model was adequate to predict performance of the inverter driven scroll compressor as a function of operating conditions. Calculated parameters from the model were discharge temperature, mass flow rate, power input, COP, and thermodynamic properties with respect to orbiting angle. To enhance the performance of a scroll compressor, it is essential to diminish leakage at low frequency level and improve the mechanical efficiency at high frequency level.

• Journal of Digital Convergence
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• v.13 no.12
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• pp.245-257
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• 2015

This study was to develop the predictive model for severity-adjusted mortality of inpatients with multiple chronic conditions and analyse the factors on the variation of hospital standardized mortality ratio(HSMR) to propose the plan to reduce the variation. We collect the data "Korean National Hospital Discharge In-depth Injury Survey" from 2008 to 2010 and select the final 110,700 objects of study who have chronic diseases for principal diagnosis and who are over the age of 30 with more than 2 chronic diseases including principal diagnosis. We designed a severity-adjusted mortality predictive model with using data-mining methods (logistic regression analysis, decision tree and neural network method). In this study, we used the predictive model for severity-adjusted mortality ratio by the decision tree using Elixhauser comorbidity index. As the result of the hospital standardized mortality ratio(HSMR) of inpatients with multiple chronic conditions, there were statistically significant differences in HSMR by the insurance type, bed number of hospital, and the location of hospital. We should find the method based on the result of this study to manage mortality ratio of inpatients with multiple chronic conditions efficiently as the national level. So we should make an effort to increase the quality of medical treatment for inpatients with multiple chronic diseases and to reduce growing medical expenses.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.4
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• pp.72-79
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• 1997

A study is a experiment which is figure out to optimum discharge cutting condition of the surface roughness, electronic discharging speed and electrode wear ration with Ton , Toff and V(voltage) as an input condition according to the current(Ip) in an electric spark machine : 1) Electrode is utilized Cu and Graphite. 2) Work piece is used the material of carbon steel. The condition of experiment is : 1) Current is varied 0.7(A) to 50(A) and the time of electric discharging to work piece in each time is 30(min) to 60(min). 2) After the upper side of work piece was measured in radius(5$\mu$m) of stylus analyzed the surface roughness to ade the table and graph of Rmax by yielding data. 3) Electro wear ratio is : \circled1Cooper was measured ex-machining and post-machining by the electronic balance. \circled2The ex-machining of graphite measured by it, the post-machining was found the data from volume $\times$specific gravity and analyzed to made its table and graph on ground the data. 4) In order to keep the accuracy of voltage affected to the work piece was equipped with the A.V. R and the memory scope was sticked to the electric spark machine. 5) In order to preserve the precision of current, to get rid of the noise occured by internal resistance of electric spark machine and to force injecting for the discharge fluid , it made the fixed table for a work piece to minimize the work error by means of one's failure during the electric discharging.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.6
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• pp.317-323
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• 2013

A multi-perforated tube indicates the existence of multiple holes of various shapes on the surface of a long cylinder-type or rectangular tube, and a hole installed on the surface is called an orifice, as it is relatively small in size, compared with the surface area of the tube. In this study, the flow characteristics of a circular multi-perforated tube with many orifices on the surface were investigated experimentally and numerically. The volume flowrate issuing from each orifice, discharge angle, effective flow area ratio, and the flow fields around the orifices were measured and visualized, with the variation of the orifice area ratio, at the same blockage ratio. The volume flowrate distributions along the flow direction of the multi-perforated tube tends to be more uniform, as larger orifices were positioned at the inlet side of the multi-perforated tube, compared with no orifice area change along the flow direction.

• Transactions on Electrical and Electronic Materials
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• v.5 no.3
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• pp.98-103
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• 2004

The plasma properties in the facing target sputtering system during carbon nitride film deposition have been investigated. The ionized nitrogen species of the deposited films increased with increasing discharge current and were independent of the nitrogen pressure. The nitrogen content in the films did not vary significantly with the variation of nitrogen gas. The electron temperature was high close to that in the inter-cathode region, reduced as the electrons moved away from the most intense region of magnetic confinement and increased again outside this region. Calculations based on the film composition showed that the ion to carbon atom ratio at the substrate was about 50 and that the ratio between the ionized and neutral nitrogen molecules was about 0.25.

• Journal of the Semiconductor & Display Technology
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• v.17 no.2
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• pp.16-19
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• 2018

The development speed of semiconductor and display device manufacturing technology is growing faster than the development speed of process equipment. So, there is a growing need for process diagnostic technology that can measure process conditions in real time and directly. In this study, a plasma diagnosis was carried out using impedance variation due to the plasma discharge. Variation of the measurement impedance appears as a voltage change at the reference impedance, and the plasma density is calculated using this. The above experiment was conducted by integrating the plasma diagnosis system and the linear atmospheric pressure DBD plasma source. It was confirmed that plasma density varies depending on various parameters (gas flow rate, $Ar/O_2$ mixture ratio, Input power).

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.48-51
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• 2000

We proposed the new driving waveform which has changed the waveform of sustain division to improve luminous efficiency in plasma display panel. This sustain waveform is to add the ramp to the rectangular waveform, resulting in self-erasing discharge in the falling edge region. The proposed waveform has improved the luminous efficiency of 30％ even in low driving frequency(25kHz), whereas the conventional driving waveform using the self-erasing discharge can improve the luminous efficiency only in high driving frequency( >150kHz). Front the results of this paper, we hope that the variety study on frequency and duty ratio, ramp waveform will increase the luminous efficiency.