• 한국연초학회지
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• 제22권2호
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• pp.151-156
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• 2000

The variability of a ventilated filter cigarette depends on the details of its construction and on the variabilities of its components. Variations in filter ventilation arise from many sources, including variations in tobacco rod pressure drop, filter tip pressure drop, tipping paper permeability, and plugwrap permeability. To reduce the filter ventilation variability, the variability of filter ventilation levels in ventilated cigarettes is studied by Monte Carlo Analysis. For each trials a value is selected for tobacco rod pressure drop, filter tip pressure drop, tipping paper permeability, and plugwrap permeability. These values are selected randomly from a normal distribution based on the target and coefficient of variation for each input variable. The results of this analysis for filter ventilation variation suggest that the variations of filter ventilation are dependent on the details of cigarette designs studied and reducing the variability of any cigarette component will reduce filter ventilation variability. For typical cigarettes, variation in the permeability of tipping paper is usually the most significant contributor to filter ventilation variability. Results of a Monte Carlo Analysis could provide both general insights and specific practical guidance about the design of ventilated filter cigarettes.

• 한국산업융합학회 논문집
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• 제25권1호
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• pp.61-70
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• 2022

Fire damage time in high-rise buildings and wildland fire increasing every year. The use of high-pressure fire pumps is required to effectively extinguish fires. Reflecting the curvature effect of the fire hose occurring at the actual fire fighting site, this study provides a database of pressure drop, discharge velocity and maximum discharge height through C FD numerical analysis and it can provide using standards for fire extinguishing. Two Reynolds numbers of 200000 and 400000 were numerically analyzed at 0° -180° bending with water of 25℃ as a working fluid in hoses with a diameter of 65mm, a length of 15m, and a radius of curvature of 130mm. Realizable k-ε turbulence model was used and standard wall function was used. The pressure drop increases as the bending angle increases, and the maximum value at 90° and then decreases. The increasing rate is greater than the decrease. The velocity of the secondary flow also decreases after having the maximum value at 90°. The decreasing rate is greater than the increase. The turbulent kinetic energy increases to 120° and decreases with the maximum value. Pressure drop, velocity of the secondary flow, and turbulence kinetic energy are measured larger in the second bending region than in the first bending region.

• 한국분무공학회지
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• 제4권4호
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• pp.30-37
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• 1999

The breakup characteristics of liquid sheet formed by the liquid rocket injector has a close relation with the combustion efficiency. In this paper, basic characteristics of droplet size and velocity distribution were measured with PDPA for the Like Doublet Impinging Injector. Test variables were the angle of impact, the diameter of orifice and jet velocity. Water was used as test fluid. As a result, for impingement angle less than 90 degree, following correlations were obtained between drop size and design parameters : $D_{32}({\mu}m)=295.0{\times}V^{-0.09}\times(2\theta)^{-0.1}{\times}d^{0.072}$. For impingement angle greater than 100 degree, drop sizes were increased but eventually converged to a certain limiting value.

• 전기화학회지
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• 제3권4호
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• pp.241-245
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• 2000

비정질 $MnO_2\;nH_2O$ 전극재료를 사용한 pseudo-capacitor를 설계 제작하여 특성을 평가하였다. 100mV/s의 cyclic voltammogram으로부터 측정한 결과, 이 전극재료의 안정한 potential window는 1V이고 비용량은 250F/g이었다. TDMA(Time Division Multiplex Algorithm) pulse 시험에서 TDMA 시스템 (2 parallel-pseudo-capacitor systems) 은 0.22V의 ohmic voltage drop과 0.38V의 capacitor voltage drop을 보여주었다. 이 TDMA system의 total voltage drop이 0.60V이므로 TDMA 위성통신 휴대전화의 요건인 1V maximum voltage drop을 충족하였다. 또한, 이 system의 ESR과 비용량은 각각 $55m{\Omega}$과 105mF이었다. 따라서 이 TDMA system이 위성통신 휴대전화를 위한 load-leveling 캐패시터로 응용 가능함을 확인하였다.

• 대한기계학회논문집B
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• 제20권6호
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• pp.2023-2035
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• 1996

In the present study, the characteristics of the electrical deformation of a bubble and a drop under a uniform electric field have been investigated to understand EHD heat transfer enhancement by an electric field. The deformation of the bubble and the drop have been studied theoretically using an electric normal stress acting on their interfaces and assured by the numerical analysis and the experiment. From the variation of bubble volume and free energy, it is found that a bubble is compressed in an electric field and free energy had larger value with increasing W and the permittivity of a dielectric fluid. The electric normal stress induced on the interface of the bubble and the drop is different. Because of the surface charge induced at the drop interface, the electric normal stress acting on the drop is much larger than that of the bubble. The drop is, therefore, deformed much more than the bubble. In addition, the experimental and numerical results show that the aspect ratio and the contact angle of the bubble increase with increasing W.

• 복식문화연구
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• 제20권4호
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• pp.529-534
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• 2012

An analysis of adult women's somatotypes classified by drop values can provide important preliminary data in determining standard clothing sizes for mass production of ready-made clothes. This is because the values are based on measurements of girth, which is essential information in the size-setting process. Adult women's body types are classified according to drop values in a standard clothing size system adopted by Korea and several other countries. This study aims to identify somatotype characteristics of adult women aged 20 to 69 by using five types of drop values: bust-waist, hip-waist, hip-bust, abdomen-waist, and hip-abdomen. Statistical cluster analysis of collected data revealed four somatotypes among adult women. Type R, with a developed lower body, accounted for 36.6%, and its bodyline was found to be closest to the average adult woman. Type X, constituting 25.4%, had the curviest contours of all and relatively large hip measurements, with the thinnest figure. Flat abdomen and hips characterized type Y, which accounted for 18.9%. Lastly, 19.0% fell into type H, the most obese figure, in which abdomen girth exceeded hip measurements. Since type H has excess fat deposits in the abdomen, not only hip measurements but also abdomen girth should be considered when designing top longer than torso-length and bottoms.

• 설비공학논문집
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• 제16권5호
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• pp.414-420
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• 2004

The heat transfer and pressure drop characteristics associated with the gas cooling of the supercritical carbon dioxide in a horizontal tube have been investigated experimentally. This problem is of particular interest in the design of a gas cooler of cooling systems using $CO_2$refrigerant. The test section is consisted of 6 series of 455 mm in length, 4.15 mm ID copper tube, respectively. The effects of the inlet temperature, pressure and mass flow rate on the heat transfer and pressure drop of $CO_2$in a horizontal tube is studied in detail. The heat transfer coefficient of $CO_2$is varied by temperature, inlet pressure, and mass flow rate of $CO_2$. This has maximum value at near the pseudocritical temperature. The pressure drop is changed by inlet pressure and mass flow rate of $CO_2$. The results have been compared with those of previous work. The heat transfer correlation at the supercritical gas cooling process is also suggested.

• Journal of Advanced Marine Engineering and Technology
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• 제31권6호
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• pp.715-722
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• 2007

Experiments were conducted for the investigation of pressure drop inside horizontal micro-fin tubes during the condensation of R-22 and ternary refrigerant. R-407C(HFC-32/125/134a 23/25/62 wt%) as a substitute of R-22. The condenser is a double-tube and counterflow type heat exchanger which is consisted with micro-fin tubes having 60 fins with a length of 4000mm, outer diameter of 9.53mm and fin height of 0.2mm. The mass velocity varied from 102.1 to $301.0kg/(m^2{\cdot}s)$ and inlet quality was fixed as 1.0. From the experimental results. the pressure drop for R-407C was considerably higher than that for R-22. The value of PF(penalty factor) for both of refrigerants was not bigger than the ratio of micro-fin tube area to smooth tube area. Based on the experimental data. correlation was Proposed for the prediction of frictional pressure drop during the condensation of R-22 and R-407C inside horizontal micro-fin tubes.

• 전력전자학회논문지
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• 제20권1호
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• pp.81-90
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• 2015

This paper investigates the droop control-based real and reactive power load sharing with a virtual inductor when the line impedance between inverter and Point of Common Coupling (PCC) is partly and unequally resistive in high-capacity systems. In this paper, the virtual inductor method is applied to parallel inverter systems with resistive and inductive line impedance. Reactive power sharing error has been improved by applying droop control after considering each line impedance voltage drop. However, in high capacity parallel systems with large output current, the reference output voltage, which is the output of droop controller, becomes lower than the rated value because of the high voltage drop from virtual inductance. Hence, line impedance voltage drop has been added to the droop equation so that parallel inverters operate within the range of rated output voltage. Additionally, the virtual inductor value has been selected via small signal modeling to analyze stability in transient conditions. Finally, the proposed droop method has been verified by MATLAB and PSIM simulation.

• 대한기계학회논문집
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• 제16권4호
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• pp.795-802
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• 1992

본 연구에서는 일정한 각도의 분사를 갖는 평씨일(plain seal)에 대하여 각 인자들이 누수성능에 미치는 영향을 수치적으로 조사하였다. 인자들로는 축방향 레 이놀즈수, 축회전속도, 분사의 유입속도, 간극비, 분사의 위치 및 유입각 등이 고려되 었다.