• 한국자동차공학회논문집
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• 제23권1호
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• pp.112-121
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• 2015

In this paper, powertrain of output split type plug-in hybrid electric vehicle is analyzed for the operation range of speed, torque, and power. First, it is assumed that the efficiency of motor is 100%. And, the speed and torque equations are derived based on the lever analogy. With the above equations, the simulations are performed for the powertrain of output split type plug-in hybrid electric vehicle. From the simulation results, it is found that the output torques of EV1 and series modes are larger than the EV2 and power split modes' ones. It means the EV1 and series modes can be used for the rapid acceleration. But the EV1 and series modes can be used only the velocity of under the 120 km/h. It is because the motor reaches its maximum speed when the velocity is over the 120 km/h for the EV1 and series modes. When the engine is turned on, the engine power is transmitted through the two motors. But, the power split mode shows the power split of engine at the output shaft, and it has the point of zero motor power. Thus, the transmission efficiency of the power split mode can be higher than the series mode's one, it the motor efficiency is considered.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.100-105
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• 2000

The present work describes the prediction method for the unsteady flow field and the acoustic pressure field of a ducted axial fan. The prediction method is comprised of time-marching free-wake method, acoustic analogy. and the Helmholtz-Kirchhoff BEM. The predicted sound signal of a rotor is similar to the experiment one. We assume that the rotor rotates with a constant angular velocity and the flow field around the rotor is incompressible and inviscid. Then, a time-marching free-wake method is used to model the fan and to calculate the flow field. The force of each element on the blade is calculated by the unsteady Bernoulli equation. Lawson's method is used to predict the acoustic source. The newly developed Helmholtz-Kirchhoff BEM for thin body is used to calculate the sound field of the ducted fan. The ducted fan with 6 blades is analysed and the sound field around the duct is calculated.

• 반도체디스플레이기술학회지
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• 제21권4호
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• pp.39-44
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• 2022

Using a CFD (computational fluid dynamics) simulation tool, we have offered a design guideline of a slot-die head having a simple T-shaped cavity through an analysis of the fluid dynamics in terms of cavity pressure and outlet velocity, which affect the uniformity of coated thin films. We have visualized the fluid flow with a transparent slot-die head where poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) is injected. We have shown that the fluid dynamics inside the slot-die head depends sensitively on the cavity depth, cavity length, land length, and channel gap (i.e., shim thickness). Of those, the channel gap is the most critical parameter that determines the uniformity of the pressure and velocity distributions. A pressure drop inside the cavity is shown to be reduced with decreasing shim thickness. To quantify it, we have also calculated the coefficient of variation (CV). In accordance with Hagen-Poiseuille's laws and electron-hydraulic analogy, the CV value is decreased with increasing cavity depth, cavity length, and land length.

• 대한토목학회논문집
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• 제12권2호
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• pp.1-10
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• 1992

이 논문에서는 철근 콘크리트 부재의 전단 해석을 위한 트러스 유사법이 발전된 형태인 '빗 구조' 해석 모델을 부분 프리스트레스트 콘크리트 부재의 전단 해석을 위해 수정하여 제안 하였다. 제안된 '빗 구조' 모델은 콘크리트 압축대의 위치와 경사 및 사압축대의 경사가 하중과 프리스트레스의 크기에 따라서 변하는 것이다. 역학적 모델의 구성을 위하여 비선형 보, 트러스 요소를 사용하였으며, 사압축대의 경사를 결정하기 위한 식을 '압축대' 이론을 수정하여 유도하였다. '빗구조' 모델에 의한 해석 결과를 부분 프리스트레스트 콘크리트 부재의 재하 실험 결과와 비교하였다. 이에 따르면 '빗 구조' 해석 결과에 의한 전단 철근의 응력은 수정 M$\ddot{o}$rsch이론과 고전 M$\ddot{o}$rsch 이론에 의한 계산치의 중간 정도의 값이다. 처짐과 전단철근의 응력값을 비교한 결과, 본 논문에서 제안된 '빗 구조' 모델이 부분 프리스트페스트 콘크리트 부재의 전단 해석에 사용될 수 있음을 알 수 있었다.

• 한국분무공학회지
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• 제10권1호
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• pp.17-23
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• 2005

Even though a relatively complete knowledge base has been established for diesel sprays, much of the knowledge cannot be directly translated to correlate the characteristics of gasoline spray. The macroscopic characteristics of gasoline impingement spray was investigated with photographic and image processing technique by Particle Motion Analysis System. The injector with single hole nozzle diameter of 0.28 mm was used in this experiment and the injection duration was selected as 10 msec. The injection pressure with 0.3, 0.35, and 0.4 MPa, impingement distance or 70, 100 and 130m, impingement angle or 0.15, 30 and $45^{\circ}$ were employed for the variables to affect the spray characteristics of impinging spray. It is clear that there is the analogy on the spray tip penetration between the gasoline impinging jet and diesel free jet. The spray tip penetration of impinging gasoline spray is proportional to the quarter power of the time after start of injection. The maximum height of impinging gasoline spray is also proportional to the quarter power of the time regardless of impingement distance, impingement angle and injection pressure. In addition, the effect of impingement angle on the spray tip penetration is significant according to the time after start of injection, even though there is minor effect in the initial stage of time after start of injection. Moreover, there is no remarkable effect of injection pressure on the spray tip Penetration under the experimental condition used in this study.

• Journal of Astronomy and Space Sciences
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• 제31권2호
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• pp.131-140
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• 2014

Lava caves could be useful as outposts for the human exploration of the Moon. Lava caves or lava tubes are formed when the external surface of the lava flows cools more quickly to make a hardened crust over subsurface lava flows. The lava flow eventually ceases and drains out of the tube, leaving an empty space. The frail part of the ceiling of lava tube could collapse to expose the entrance to the lava tubes which is called a pit crater. Several pit craters with the diameter of around 100 meters have been found by analyzing the data of SELENE and LRO lunar missions. It is hard to use these pit craters for outposts since these are too large in scale. In this study, small scale pit craters which are fit for outposts have been investigated using the NAC image data of LROC. Several topographic patterns which are believed to be lunar caves have been found and the similar pit craters of the Earth were compared and analyzed to identify caves. For this analysis, the image data of satellites and aerial photographs are collected and classified to construct a database. Several pit craters analogous to lunar pit craters were derived and a morphological pit crater model was generated using the 3D printer based on this database.

• ETRI Journal
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• 제38권2호
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• pp.376-386
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• 2016

Currently, web applications are gaining in prevalence. In a web application, an input may not be appropriately validated, making the web application susceptible to cross-site scripting (XSS), which poses serious security problems for Internet users and websites to whom such trusted web pages belong. A taint inference is a type of information flow analysis technique that is useful in detecting XSS on the client side. However, in existing techniques, two current practical issues have yet to be handled properly. One is URL rewriting, which transforms a standard URL into a clearer and more manageable form. Another is HTML sanitization, which filters an input against blacklists or whitelists of HTML tags or attributes. In this paper, we make an analogy between the taint inference problem and the molecule sequence alignment problem in bioinformatics, and transfer two techniques related to the latter over to the former to solve the aforementioned yet-to-be-handled-properly practical issues. In particular, in our method, URL rewriting is addressed using local sequence alignment and HTML sanitization is modeled by introducing a removal gap penalty. Empirical results demonstrate the effectiveness and efficiency of our method.

• 대한기계학회논문집B
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• 제25권9호
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• pp.1165-1174
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• 2001

The objective of this study is to understand the generation mechanism of sound and to develop a prediction method for the acoustic pressure field of a centrifugal fan. If the fan is operating at the free field without the casing, the acoustic analogy is a good method to predict the acoustic of the fan. But, the casing gives a dominant effect to the radiated sound field and the scattering effect of casing should be considered. So, in this paper the Kirchhoff-BEM is developed, which can consider the scattering effect of the rigid body. In order to consider the scattering and diffraction effects owing to the casing, BEM is introduced. The source of BEM is newly developed, so the sound field of the centrifugal fan can be obtained. In order to compare the predicted one with experimental data, a centrifugal impeller and a wedge are used in the numerical calculation and the results are compared with the experimental data. Reasonable results are obtained not only for the peak frequencies but also for the amplitudes of the tonal sound. The radiated acoustic field shows the diffraction and scattering effects of the wedge clearly.

• 천문학회보
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• 제38권1호
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• pp.46.2-46.2
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• 2013

The neutral component of the interstellar medium (ISM) is segregated into the cold neutral medium (CNM) and warm neutral medium (WNM) as a result of thermal instability. It was found that the CNM--WNM evaporation interface, across which the CNM undergoes thermal expansion, is linearly unstable to corrugational disturbances, in complete analogy with the Darrieus-Landau instability (DLI) in terrestrial flames. To explore dynamical consequences of the DLI in the ISM, we perform a linear stability analysis of the DLI including the effect of thermal conduction as well as nonlinear hydrodynamic simulations. We find that the DLI is suppressed at short length scales via heat transport. The linear growth time of the fastest growing mode is proportional to the square of the evaporation flow speed of the CNM relative to the interface and is typically >10 Myr. In the nonlinear stage, perturbations grow into cusp-like structure protruding toward the WNM, and soon reach a steady state where the evaporation rate is increased by a factor of 2 compared to the initial state. We demonstrate that the amplitude of the interface distortion and enhancement in evaporation rate are determined primarily by the density ratio between the CNM and WNM. Given quite a long growth time and highly subsonic velocities at saturation, the DLI is unlikely to play an important role in the ISM dynamics.

• 대한전기학회논문지:전력기술부문A
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• 제48권5호
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• pp.508-516
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• 1999

This paper presents a method for constructing composite power system effective load duration curves(CMELDC) at load points by Monte Carlo method. The concept of effective load duration curves(ELDC) in power system planning is useful and important in both HLII. CMELDC can be obtained from convolution integral processing of the probability function of unsupplied power and the load duration curve at each load point. This concept is analogy to the ELEC in HLI. And, the reliability indices (LOLP, EDNS) for composite power system are evaluated using CMELDC. Differences in reliability levels between HLI and HLII come from considering with the uncertainty associated with the outages of the transmission system. It is expected that the CMELDC can be applied usefully to areas such as reliability evaluation, probabilistic production cost simulation and analytical outage cost assessment, etc. in HLII, DC load flow and Monte Carlo method are used for this study. The characteristics and effectiveness of thes methodology are illustrated by a case study of the IEEE RTS.