• 한국자동차공학회논문집
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• 제6권1호
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• pp.213-221
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• 1998

The investigation regarding the ignition system of a plasma jet explored by using a constant volume vessel. The purpose of this study is to elucidate relation between the characteristics of the configuration and jet ejection of plasma jet plug, when the sub energy were supplied at plasma jet ignition system. From the results of a visualization by the schlieren system, the jut ejection for plasma jet ignition are depended on the jet plug configuration and sub energy, but the configuration of plasma jet plug is more influenced than the sub energy on the plasma jet ejection. And the plasma jet ignition strongly influences upon the combustion enhancement than the conventional spark ignition.

• 한국추진공학회지
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• 제16권3호
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• pp.69-76
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• 2012

본 논문에는 유도탄 사출시스템의 사출성능 향상을 위해 침식연소 현상이 발생하지 않는 상태에서 가스발생기의 압력 기울기를 증가시키는 방법에 대해 기술하였다. 안정연소를 얻기 위해 그레인에 반경방향홀을 뚫는 방법과 그레인의 길이대 직경비를 줄이는 방법을 고안하여 이를 적용, 연소시험을 실시하였다. 시험결과 반경방향홀 그레인을 적용했을 경우 침식연소 방지효과는 좋았으나 사출성능을 저하시키는 쪽으로 성능이 변화하였다. 반면에, 다열형 그레인을 적용시 침식연소 방지효과와 함께 사출성능을 향상시키는데 유용한 것으로 나타났다.

• Journal of Mechanical Science and Technology
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• 제17권12호
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• pp.2107-2115
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• 2003

A supersonic dual coaxial jet has been employed popularly for various industrial purposes, such as gasdynamic laser, supersonic ejector, noise control and enhancement of mixing. Detailed characteristics of supersonic dual coaxial jets issuing from an inner supersonic nozzle and outer sonic nozzles with various ejection angles are experimentally investigated. Three important parameters, such as pressure ratios of the inner and outer nozzles, and outer nozzle ejection angle, are chosen for a better understanding of jet structures in the present study. The results obtained from the present experimental study show that the Mach disk diameter becomes smaller, and the Mach disk moves toward the nozzle exit, and the length of the first shock cell decreases with the pressure ratio of the outer nozzle. It was also found that the highly underexpanded outer jet produces a new oblique shock wave, which makes jet structure much more complicated. On the other hand the outer jet ejection angle affects the structure of the inner jet structure less than the pressure ratio of the outer nozzle, relatively.

• Nuclear Engineering and Technology
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• 제30권3호
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• pp.273-286
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• 1998

As there has arisen a concern that failure of the high burnup fuel under the reactivity-insertion accident(RIA) may occur at the energy lower than the expected, fuel behavior under the rod ejection accident in a typical Westinghouse-designed 950 MWe PWR was analyzed by using the three dimensional nodal transient neutronics code, PANBOX2 and the transient fuel rod performance analysis code, FRAP-T6. Fuel failure criteria versus the burnup was conservatively derived taking into account available test data and the possible fuel failure mechanisms. The high burnup and longer cycle length fuel loading scheme of a peak rod turnup of 68 MWD/kgU was selected for the analysis. Except three dimensional core neutronics calculation, the analysis used the same core conditions and assumptions as the conventional zero dimensional analysis. Results of three dimensional analysis showed that the peak fuel enthalpy during the rod ejection accident is less than one third of that calculated by the conventional zero dimensional analysis methodology and the fraction of fuel failure in the core is less than 4 %. Therefore, it can be said that the current design limit of less than 10 percent fuel failure and maintaining the core coolable geometry would be adequately satisfied under the rod ejection accident, even though the conservative fuel failure criteria derived from the test data are applied.

• 한국항공우주학회지
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• 제47권12호
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• pp.904-912
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• 2019

본 연구는 항공기에 근접하여 폭발하는 고폭형 위협 무기의 파편 발사속도 및 발사각을 수치 해석적으로 추정한 결과이다. 고폭형 위협 무기에 대한 항공기의 취약성을 평가하기 위하여 탄두 구성품의 물리량을 이해하는 것은 매우 중요하다. 일반적으로 고폭형 위협 무기에 대한 구성품의 질량, 길이 및 직경 등 물리적 변수는 알려져 있지 않다. Terrier, Sparrow 등 유사 위협 무기들의 데이터를 이용하여 charge to mass 비율, 길이와 직경 비율 등과 관련된 경험식을 수치 해석적으로 유도하였다. 근접신관에 의하여 외부에 폭발하는 탄두에서 탄두 덮개 구성비는 20% 수준으로 나타났으며, 고폭 화약의 양쪽 끝부분에서 방사되는 파편의 발사속도 구배 현상이 뚜렷이 나타났지만 법선 방향에 대한 발사각은 6° 이내로 나타났다.

• The Korean Journal of Physiology and Pharmacology
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• 제4권3호
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• pp.253-261
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• 2000

Head-out water immersion induces marked increase in the cardiac stroke volume. The present study was undertaken to characterize the stroke volume change by analyzing the aortic blood flow and left ventricular systolic time intervals. Ten men rested on a siting position in the air and in the water at $34.5^{circ}C$ for 30 min each. Their stroke volume, heart rate, ventricular systolic time intervals, and aortic blood flow indices were assessed by impedance cardiography. During immersion, the stroke volume increased 56%, with a slight (4%) decrease in heart rate, thus cardiac output increased ${\sim}50%.$ The slight increase in R-R interval was due to an equivalent increase in the systolic and diastolic time intervals. The ventricular ejection time was 20% increased, and this was mainly due to a decrease in pre-ejection period (28%). The mean arterial pressure increased 5 mmHg, indicating that the cardiac afterload was slightly elevated by immersion. The left ventricular end-diastolic volume index increased 24%, indicating that the cardiac preload was markedly elevated during immersion. The mean velocity and the indices of peak velocity and peak acceleration of aortic blood flow were all increased by ${\sim}30%,$ indicating that the left ventricular contractile force was enhanced by immersion. These results suggest that the increase in stroke volume during immersion is characterized by an increase in ventricular ejection time and aortic blood flow velocity, which may be primarily attributed to the increased cardiac preload and the muscle length-dependent increase in myocardial contractile force.

• 한국정밀공학회지
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• 제32권4호
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• pp.369-375
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• 2015

This paper presents ejection of high viscosity fluids with magnetostrictive inkjet printhead(Magjet), which is not common with any other printhead. The MagJet uses a magnetostrictive material, Terfenol-D rod with 10-mm in diameter and 50-mm in length, as an actuation mechanism. It has been known that high viscosity is often an obstacle in ejecting small and mono-disperse droplets. We calculated required pressure with fluidic inertia (Bernoulli equation) and viscous loss (Hagen Poiseuille equation). The required pressure for ejecting a droplet is 1300kPa. The generated force and displacement with Terfenol-D rod are estimated to be 480N (2600kPa) and $28{\mu}m$, respectively. It was enough that Magjet eject high viscosity fluid (Max 1000cP). The experiments are performed to eject the high viscosity fluid with Magjet. The ejection of high viscosity fluids is successful with the aid of Terfenol-D's high performance.

• 한국유체기계학회 논문집
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• 제15권4호
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• pp.33-41
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• 2012

In the present work, a parametric study on double-jet film-cooling has been carried out to enhance the film-cooling effectiveness using three-dimensional Reynolds-averaged Navier-Stokes analysis. The shear stress transport turbulence model is used as the turbulence closure. The lateral ejection angles and the lateral and streamwise distance between the centers of the cooling holes are chosen as the geometric parameters. The spatially averaged film-cooling effectiveness averaged over an area of 8 hole diameters in width and 30 hole diameters in streamwise length is used to evaluate the performance of film-cooling. The parameter of the lateral distance has the largest impact on the film cooling effectiveness compared to the others. On the other hand, the parameter of streamwise distance gives the least influence on the film cooling effectiveness.

• 터널과지하공간
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• 제21권4호
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• pp.320-327
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• 2011

본 연구는 ○○ 석회석 광산의 화강암 폐석을 이용한 부순 모래를 전색재로 이용하기 위하여 그 현장의 주변에서 쉽게 구할 수 있는 바다 모래, 강 모래, 점토와 물의 전색재와 동일한 조건으로 모르타르 블록의 시험발파를 통해 전색효과에 대한 비교가 이루어졌다. 이때 모르타르 블록은 폭 50 cm, 길이 50 cm와 높이 70 cm로 제작하였다. 전색재료들에 대한 물리.역학적 특성을 알아보기 위하여 체가름 시험, 직접전단시험과 압출시험이 수행되었다. 모르타르 발파시험에서 전색길이 10 cm 및 20 cm에 대하여 폭발 충격압에 따른 강봉의 축방향 변형율과 전색재의 분출속도가 동적 변형율 측정기에 의해 측정되었다. 강봉의 축방향 변형율은 화강암 부순 모래가 가장 크게 나타났으며, 전색재의 분출속도는 물을 전색재로 사용하였을 때 가장 작은 값을 보이고 있다. 이 결과는 사용된 전색재의 발파 공내 다짐단위중량, 입도분포, 전단저항 및 압출시험결과와 상호 연관성을 보이고 있다. 전색재의 분출속도와 축방향 변형률은 서로 지수적으로 반비례하는 경향을 나타낸다.

• Design & Manufacturing
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• 제14권3호
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• pp.57-62
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• 2020

In the drug delivery system industry, the technology with even split injection becomes important for maximizing efficiency and minimizing the side effects. In conventional drug delivery system, infection can occur due to pain and splashing. Also, various applications are impossible due to disposable use, and it is the reason to avoid to use this system because of the complexity of the driving method. Therefore, in this study, a painless drug delivery device is developed for non-pain with electrical insulation breakdown method. Finite elements analysis was used to evaluate the ejection characteristics of drugs according to the shape of the micro ejection nozzle. The effect of the number of holes in the micro nozzle, the length of the nozzle and the inner shape of the nozzle on the drug discharge characteristics were analyzed.