• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
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• pp.191-198
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• 2009

There are almost no studies on verification of requirements for high speed rolling stocks by means of RAM goals and on setting RAM goals by means of verification on practical reliability, availability and maintainability for high speed rolling stocks though they are covered in specification of an order that RAM goals asked of rolling stocks are shown for gaining high quality of them and availability when they are in operation. This study is for estimating number of high speed train-sets that would be supplementarily placed an order through verification of RAM goals of a project for the introduction of KTX-II 100 cars. It verify that optimized requirements for high speed rolling stocks by relatively comparison with between requirements for train-sets through setting RAM goals and requirements for train-sets through analysis of prospects for management balance with high speed rolling stocks.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2000년도 춘계학술대회 논문집(Proceeding of the KOSME 2000 Spring Annual Meeting)
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• pp.165-170
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• 2000

A fundamental experimental study for a substitute proposal to super-speed craft propulsion system called underwater ram-jet propulsion by high pressure air ejection as driving force was investigated. for basic study of effect of ram-jet propulsion performances ismple underwater ram-jet flow field was established and PIV(Particle Image Velocimetry) method was adopted to analyse the jet-induced flow appearing at ram intake mixing chamber and nozzle. Some flow dynamics relating to the high-speed ejector effect were discussed for the basic understanding for the ram-jet propulsion principle.

• Journal of Advanced Marine Engineering and Technology
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• 제24권3호
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• pp.36-42
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• 2000

A fundamental experimental study for an alternative proposal to super-speed craft propulsion system called underwater ram-jet propulsion by high pressure air ejection as driving force was investigated. For basic study of the effects of ram-jet propulsion performance, a simple underwater ram-jet flow field was established and PIV(Particle Image Velocimetry) method was adopted to analyse the jet-induced flow appearing at ram intake, mixing chamber and nozzle. Some flow dynamics relating to the high-speed ram-jet effect were discussed for the basic understanding of the its propulsion principle.

• Korean Chemical Engineering Research
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• 제55권5호
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• pp.668-678
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• 2017

Intermolecular interactions were studied for binary mixtures of 2-propanol + cyclohexane, n-hexane, benzene, toluene, o-, m- and p-xylenes by measuring ultrasonic speeds (u) over the entire range of composition at 298.15 K and 308.15 K. From these results the deviation in ultrasonic speed was calculated. These results were fitted to the Redlich-Kister equation to derive the binary coefficients along with standard deviations between the experimental and calculated data. Acoustic parameters such as excess isentropic compressibility ($K_s^E$), intermolecular free length ($L_f$) and available volume ($V_a$) were also derived from ultrasonic speed data and Jacobson's free length theory. The ultrasonic speed data were correlated by Nomoto's relation, Van Dael's mixing relation, impedance dependence relation, and Schaaff's collision factor theory. Van Dael's relation gives the best prediction of u in the binary mixtures containing aliphatic hydrocarbons. The ultrasonic speed data and isentropic compressibility were further analyzed in terms of Jacobson's free length theory.

• 대한기계학회논문집
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• 제19권4호
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• pp.896-907
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• 1995

Titanium 6242(.alpha. + .betha.) alloy has a good strength/weight ratio and is used for aircraft components such as engine disks and compressor blades. When this material is forged at an elevated temperature, the process parameters should be carefully controlled because the process window of this material is quite narrow. In the present investigation, a rigid-thermoviscoplastic finite element method is used to predict the deformation behavior and temperature/strain distributions in an engine disk during near-net shape hot forging. The purpose of the investigation is to obtain a proper ram speed profile, assuming the hydraulic press used in the forging is capable of varying ram speed during loading. In result, it was found that the ram speed at constant strain-rate of 0.5/sec shows a sound deformation behavior, a relatively uniform deformation and a good temperature distribution. This information is also valuable in predicting resulting microstructures in the disk.

• 열처리공학회지
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• 제34권4호
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• pp.185-190
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• 2021

The extrusion experiments using the 7075 aluminum billet have been performed to investigate the effects of die cooling and ram speed on the occurrence of surface defects on the extrudate. The purpose of die cooling was to suppress overheating of the extrudate at the moment of extrusion. In the present die cooling system, liquid nitrogen has been injected in to the die and sprayed to the surface of extrudate. Ram speed was either kept or varied in the range of 1.1~1.7 mm/sec. throughout one extrusion shot to check the occurrence of surface defects. Every extrusion started at a ram speed of 1.25 mm/sec. The temperature of extrudate was measured using a laser thermometer. The 7075 billet of 180 mm in diameter and 550 mm in length was preheated at 390℃ and extruded to get a single plate of 8000 mm in length, 150 mm in width and 10 mm in thickness. Each extrudate was checked by eye to find the surface defects. The microstructures were obtained in the specimen cut from each corner of the extrudate using the EBSD micrographs.

• Tribology and Lubricants
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• 제5권2호
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• pp.77-82
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• 1989

The influences of ram pressure on the performances of tilting-pad journal bearings are investigated experimentally. The test rig consists of a single tilting-pad and a rotating journal. Film thicknesses and pressure distribution of the lubricating film are measured continuously for several values of coordinate of the pivot position and journal speed. The findings of the investigation are as follows: (]) According as the journal speed increases the ram pressure increases, maximum pressure decreases and the pivot position which maximize the minimum film thickness shifts toward the leading edge. (2) The ram pressure makes it possible to generate the converging wedge and the positive pressure between the pad and the journal even when the pad is supported at the points between the leading edge and the center of the pad. (3) The influence of the ram pressure on the performance of tilting pad bearings is significant and must be considered in the design of these bearings.

• 한국군사과학기술학회지
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• 제24권2호
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• pp.228-236
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• 2021

In order to understand the underwater noise source factor of the linear pump type forced ejection system, a reduced-model compressed water experiment device was developed. The reduced-model compressed water experiment device consists of a reverberation tank, a linear pump type forced ejection device, and an underwater vehicle. The underwater noise source was selected from the hydraulic ram moving speed, the hydraulic ram/piston pipe spacing, the ejection pipe inlet/water ram area ratio, and the number of water ram inlets. The underwater vehicle was ejected into the reverberation tank by the device. The source level was derived from the measured sound pressure. The source level tends to increase as the hydraulic ram/piston tube spacing and the hydraulic ram moving speed increase. The source level tended to increase as the area ratio was increased, but the level was weak. The number of water ram inlet did not affect the source level.

• Korean Chemical Engineering Research
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• 제56권5호
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• pp.663-678
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• 2018

Refractive index and speeds of sound for the binary mixture of isomer of butanol (1) + cyclohexane, benzene and toluene (2) were measured at 308.15 K. The measured data were used to calculate deviation in refractive index ${\Delta}n$, ultrasonic speed ${\Delta}u$, isentropic compressibility $K_s^E$, available volume $V_a$, excess intermolecular free length $L_f$ and molecular association $M_A$. All the derived properties were correlated with polynomial equation. Ultrasonic speed data were predicted using various empirical correlations like Nomoto, van Dael, impedance dependence and theoretically with Schaaff's collision factor theory (CFT). Jacobson free length theory (FLT) was used to calculate $L_f$. The measured refractive index was also correlated with various mixing rules. The deviation in refractive index Δn and ultrasonic speed ${\Delta}u$ was used to determine the intermolecular interactions.

• 한국멀티미디어학회논문지
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• 제10권5호
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• pp.604-611
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• 2007

자바카드는 스마트카드와 (U)SIM기술의 표준 기술로 받아들여지고 있으며, 그것은 하드웨어 독립성과 이를 통해 구현 가능한 어플리케이션의 사후발행기능으로 Native카드와 구별된다. 그러나 자바카드의 가장 큰 단점 중 하나는 하드웨어 자인의 제약과 자바 언어 자체에서 야기되는 늦은 실행 속도 문제이다. 본 논문에서는 카드 터미널 또는 SMS를 통한 어플리케이션 동적 다운로드시 속도를 개선하기 위해 논리주소를 물리주소로 바꾸는 Resolution작업에서 애플릿의 다운로드시 기존의 EEPROM 기반 심볼릭 참조를 EEPROM에 비해 약 100,000배 빠른 RAM에서의 직접참조가 가능한 자바카드 인스톨러를 설계 및 구현하였다. 실험을 통해 확인한 결과 제안된 Resolution_In_RAM기법이 적용된 자바카드 인스톨러를 통해 애플릿을 다운로드하면 EEPROM 기록 횟수가 37%, 다운로드 시간이 30% 이상 감소됨을 알 수 있었다.