• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.439-442
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• 2009

In this study, the residual strength of CFRP filament winding pressure vessel after low velocity impact was evaluated quantitatively. After impact test, the pressure vessel was sectioned to produce 25 mm-wide ring specimen and the bursting pressure of this specimen was measured. A finite element model was also fabricated to investigate the deformation and stress distribution characteristics of the impacted CFRP vessel. The degradation of the residual strength along with the increase of impact energy was successfully measured and reviewed.

• Journal of the Korean Chemical Society
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• v.27 no.2
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• pp.102-110
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• 1983

The effect of pressure and temperature on the stabilities of the benzene-iodine charge transfer complex have been investigated through ultraviolet spectrophotometric measurements in n-hexane. The stabilities of the complexes were measured at temperatures of 25, 40 and $60^{\circ}C$ up to 1600 bars. The equilibrium constant of the complex formation was increased with pressure and decreased with temperature raising. The absorption coefficient was increased with both pressure and temperature. Changes of volume, enthalpy, free energy and entropy for the formation of complexes were obtained from the equilibrium constants. The red-shift at a higher pressure, the blue-shift at a higher temperature and the relation between pressure and oscillator strength were discussed by means of thermodynamic functions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.2
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• pp.17-24
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• 2003

This paper presents results from steady wind tunnel test conducted on a $65^{\circ}$ delta wing at a root chord Reynolds number of $1.76{\times}10^6$. In these experiments, the wing was instrumented with 188 pressure taps, conjunction with powerful multi-channel data logging system, allowed the wing upper surface pressure distribution to be measured. Analysis indicates that the wing upper surface distribution can provide considerable insight into the comvined aerodynamic effects of angle of attack and sideslip on the wing. In a sideslip condition, the strength of the vortex on the windward side is much stronger than that of leeward side. This asymmetric pressure disstribution betwwen each side of wings result in a negative value of rolling moment. However, at a certatin range of angle of attck and sideslip angle(${\alpha}$=$24^{\circ}{\sim}36^{\circ}C$, ${\beta}$=$-5^{\circ}{\sim}-15^{\circ}C$) abrupt change of sign of rolling monent, rolling monent reversal, was observed.

• The Journal of the Korea Contents Association
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• v.15 no.1
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• pp.462-474
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• 2015

This article is aimed to investigate the role of social pressure in the influential relationship of user motivation on user commitment in social media. On this purpose, user motivation in social media was divided into 3 sub-dimensions as social motivation, functional motivation and hedonic motivation and social pressure was also categorized into informational isolation pressure and conformity pressure and then it was explored that how the social pressure makes differential effects in the relationship of each dimensions of user motivation and user commitment. Major findings are as follows. First, user's social motivation and hedonic motivation in social media had significant positive influence on user commitment. Second, the informational isolation pressure showed moderating effect in the relation of functional motivation and commitment. Third, conformity pressure displayed moderating effect in the relation of social motivation and commitment. This article suggests empirical supports about the role of social pressure in the phenomena of social media use and commitment, but requires to explore more specific factors and multi-dimensional studies in regard of social pressure in social media.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.2
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• pp.51-58
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• 2001

Supersonic, axisymmetric, jets issuing from several kinds of dual, coaxial, nozzles were experimentally investigated. Four different kinds of coaxial, dual nozzles were employed to characterize the major. features of the supersonic, coaxial, dual jets. Two convergent-divergent supersonic nozzles with different impinging angle on the jet axis of were designed to have the Mach number 2.0 and used to compare the coaxial jet flows with those discharging from two sonic nozzles. The primary pressure ratio was changed in the range from 4.0 to 10.0 and the assistant jet ratio from 1.0 to 4.0. The results obtained show that the assistant jets from the annular. nozzle affect the coaxial jet flows and an increase of both the primary jet pressure ratio and assistant jet pressure ratio lead to a longer supersonic length of the dual, coaxial jet.

• Aerospace Engineering and Technology
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• v.9 no.2
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• pp.185-192
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• 2010

Design of velocity-compounded turbine for 75ton class LRE turbopump application and pressure compounded turbine for 30ton class LRE turbopump has been performed. 1D calculation and CFD analysis were conducted in determining blade and flow passage shape of velocity compounded turbine iteratively. Finally, 23.1% improved specific power and 5% reduced weight turbine to the original design was developed. In case of pressure-compounded supersonic turbine design, rotational speed was increased by 50% and the effect of carryover ratio, 2nd nozzle installation angle, leakage flow of 2nd nozzle, and work sharing factor was studied. Final 1D design resulted 36% increased specific power and 51% reduced weight comparing to the original single-row impulse turbine. It is anticipated that nozzle flow path design will be very important for the accomplishment of expected performance of pressure-compounded turbine and nozzle shape optimization will be conducted through the CFD analysis.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.280-280
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• 2011

유도결합 플라즈마를 이용한 식각 장치에서 플라즈마 균일도 향상에 대한 수많은 연구가 이뤄지고 있다. 안테나의 디자인, 인가 전력과 주파수, 안테나와 기판간의 거리, 기판과 챔버 외벽간의 거리 등 다양한 변수들이 변화되어 왔다. 또한, 최근에는 식각 균일도뿐만 아니라 식각 속도 향상에도 많은 관심이 모아지면서 유동에 영향을 주는 GDP 구조가 다시 중요해지고 있다. 본 연구에서는 300 mm 식각장치를 형상화하고, GDP의 구조와 유량비에 따라 플라즈마의 균일도에 어떻게 영향을 끼지는지 사용 유체역학 전산모사 프로그램인 CFD-ACE+를 이용하여 예측해 보았다. 안테나는 2중 직렬방식으로 안쪽과 바깥쪽의 안테나에 각기 다른 전력을 인가 할 수 있는 구조를 사용했으며, 압력은 10에서 60 mTorr까지 변화시켰다. GDP의 구조는 안쪽 입구와 바깥쪽 입구가 있으며 역시 따로 유량을 조절할 수 있도록 설계하였다. 안쪽 입구는 수직방향을 향하고 있으며, 바깥쪽 입구는 90도 이내의 각을 갖도록 꺾여 있는 것과 수평방향으로 주입할 수 있는 구조, 두 가지를 사용하였다. 유량 비율은 안쪽 입구와 바깥쪽 입구를 2:8, 5:5, 8:2로 고정하였다. 우선 GDP의 구조가 90이내의 각을 갖도록 주입되는 구조에서는 어떤 유량비율에서도 약간의 vortex가 발생했다. 수직방향의 유량이 감소될수록 기판에서 멀리서 발생했으며 강도 또한 감소했다. 기판 표면에서의 압력분포 균일도도 8:2에서 2.8%, 2:8에서 0.6%로 향상되었다. 2:8의 유량 비율에서 압력을 10에서 60 mTorr까지 향상시키면 vortex 효과는 감소되나 기판에서의 압력 균일도가 0.8%까지 약간 나빠졌다. 여기서 발생되는 vortex는 GDP 구조를 수평방향으로 주입되기 함으로서 해결할 수 있었으며, 압력 균일도도 0.2%까지 향상시킬 수 있었다. 또한, 강한 수직방향의 유량은 중심에 발생하는 플라즈마의 중앙을 밀어내는 효과를 확인했으며, 실험적 증명이 추후 연구단계로 진행될 예정이다. 식각 균일도나 식각 속도를 예측하려면 CF계열의 복잡한 가스를 사용해야하기 때문에 유량이 플라즈마에 미치는 영향을 보기 위해서 본 연구에서는 단일종인 Ar 가스만을 사용하였다. 첫 단계로 이와 같이 최적화시킨 유동조건에서 복잡한 식각가스를 이용한 플라즈마 계산은 다음 단계로 준비 중에 있다.

• Journal of the Korean Institute of Gas
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• v.11 no.2 s.35
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• pp.1-4
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• 2007

Natural gas has different gas composition according to imported gas region, and the difference of gas composition affects pressure loss value occurred in pipe networks, Therefore, using real gas composition instead of averaged gas composition can obtain more reliable results for pipe network analysis. In this study, the effect of real gas composition at gas supply points on the demand pressure has been analyzed. To compare the results, the calculated pressure values for averaged gas composition at all the supply points have been used. From the results, we found that the effect of real gas composition consideration on demand pressure was considerable, and the real gas composition has to be considered for reliable pipe network analysis in gas industry.

• Journal of Digital Convergence
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• v.16 no.11
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• pp.543-551
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• 2018

This study investigated the effects of corrective exercise and TECAR on cervical alignment, pain threshold, and pain in forward head posture patients. The subject includes 30 forward head posture patients. In the intervention methods, the experimental group combined corrective exercise and TECAR treatment. Only the corrective exercise was applied to the control group. Assessments were made on cervico vertebra angle (CV angle), pain pressure threshold (PPT) and neck disability index (NDI) visual analog scale (VAS). The intervention was conducted six times a week for two weeks. Both groups showed significant differences in CV angle, PPT, NDI, and VAS. Also, PPT, NDI, and VAS excluding CV angle were significantly improved in the study group compared to the control group. These results suggest that the intervention method that combines corrective exercise and TECAR treatment has a more positive effect on pain and ADL ability of forward head posture patient.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1992.10a
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• pp.31-35
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• 1992

자동차 관련 소음 및 진동중 엔진과 관련된 것은 흡.배기계 소음과 엔진 자 체의 각 구동 부위 및 연소실 소음으로 대별하여 볼수 있다. 특히 연소실 소 음의 경우에는 엔진 내부에서 발생하는 진동과 압력파가 엔진을 진동시키고, 이러한 엔진의 진동이 방사음을 발생시켜 형성되는 만큼 그 해석 및 공학적 접근 방법이 용이하지 않다. 연소실 소음은 압력의 갑작스런 변화에 의한 폭 발소음과 피스톤과 실린더 벽면의 충돌에 의한 피스톤 슬랩(piston slap)으로 크게 구분할 수 있으며 압력이 높지 않고 압력의 변화가 빠르지 않을 경우 에는 피스톤 슬랩이 기계적 소음의 주 원인이 되는 것으로 알려져 있다. 본 고에서는 피스톤 슬랩에 의한 진동 현상을 예측하기 위한 이론적 접근 방법 을 제시하고 이의 타당성을 검증하기 위한 실험적 방법을 제시하고자 한다. 또한, 피스톤과 실린더의 간극 진단을 위해 슬랩 신호를 이용하는 방법에 대 해 살펴보고, 피스톤과 실린더의 충돌 속도를 통해 슬랩 신호를 줄이기 위한 엔진의 설계 방법에 대해 살펴보고자 한다.