• 한국자동차공학회논문집
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• 제4권2호
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• pp.137-146
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• 1996

Behaviour of ultra-high pressure diesel spray and its structure in a constant-volume pressure chamber were studied with injection pressure ranging from 35 to 110MPa. Sprays were observed by using the back illumination scattering method and righ angle scattering method. The spray process mechanism were investigated with both photographs. As a result, the spray angle and air entrainment angle was larger as injection pressure and back pressure increase. It becomes clear that mean air-fuel ratio is increased by increasing the injection pressure.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.687-689
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• 2014

This paper deals with the optimal muffler model by using acoustic analysis and CFD(computational fluid dynamics) analysis. The complicated muffler model could be better noise reduction performance. However, it could be worse affected to back-pressure performance by pressure drop in working fluid. High back-pressure is caused to low system efficiency. Therefore, it is important for the muffler design to consider the pressure drop. The muffler models are changed their partition plate position. Acoustic power transmission loss(TL) and pressure drop of working fluid are calculated by using computational analysis and used to build database for finding their trends. The optimal muffler model in user-interested frequency range could be selected by analyzing this database.

• 대한기계학회논문집B
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• 제41권9호
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• pp.563-570
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• 2017

본 연구에서는 이차목 디퓨저의 배압에 따른 특성과 디퓨저 내부의 유동을 확인하기 위해서 실험과 수치해석을 통하여 살펴보았다. 디퓨저의 배압($P_a$)조건을 모사하기 위해 이젝터를 사용하였으며, 디퓨저와 이젝터는 상온 고압기체질소를 사용하였다. 그 결과, 노즐전단압력($P_0$)이 동일할 때 배압($P_a$)을 낮추어 압력비($P_0/P_a$)를 높게 할수록 압력회복이 디퓨저 후단에서 이루어짐을 확인하였다. 노즐전단압력($P_0$)이 다르더라도 압력비($P_0/P_a)$가 동일하다면 디퓨저 내부의 유동특성이 거의 동일함을 확인하였으며, 시동압력비($(P_0/P_a)_{st}$) 또한 일치함을 확인하였다.

• 한국의류학회지
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• 제13권2호
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• pp.103-108
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• 1989

The purpose of this study was to confirm the difference of garment pressure and comfort depend on age group wearing the Korean skirt-band. A loadcell was used for measuring garment pressure, and 25 female subjects were chosen for each of young, middle, and old age groups. Garment pressure was measured in front, side, and back parts of the body. The results were as follows: 1. The younger the subjects, the greater the garment pressure. This suggests that the young age group wear the Korean skirt-band more tightly than needed. 2. The measurements of the pressure in 3 parts of the body were different. In young and middle age groups, pressure decreased from side to back, while in the old age group the order was side, back, and (rent. 3. The young age group felt high restriction of pressure. And the pressure in side part of body is the greatest among the three measurement.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.173-176
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• 2007

The characteristics of the tool system give many effects into the costs and qualities for the finished components. This study proposes a new method for manufacturing of high manufacturing productivity, production process reduction and low cost through back pressure forming. The Lock-up hub is manufactured through many processes, such as upsetting($1^{st}$ Forming), piercing, direct extrusion($2^{nd}$ Forming), final sizing process($3^{rd}$ Forming). In this study, process design for closed-die forging of a Lock-up hub used for a component of automobile transmission was made using three-dimensional finite element simulations, and the strain distributions and velocity distributions are investigated through the post processor. The rigid-plastic finite-element method for back pressure forging has been used in order to reduce development time and die cost. Using the FEM simulation, we found the optimum value of back pressure. The prototypes of Lock-up hub parts were forged into the net-shape. In the experiment, lead precision of tooth are measured by the CCMM(Contact Coordinate Measuring Machine). The dimensional accuracy of forged part was improved up to the 40% when back press was applied.

• 대한정형도수물리치료학회지
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• 제26권2호
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• pp.11-18
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• 2020

Background: The purpose of this study is to examine the correlation between high heels and body imbalance among female college students in their twenties who mainly wear high heels and prevent associated problems. Methods: The subjects included 89 female college students in their twenties. They were measured in plantar pressure with a gait analyzer. Their legs were measured in length with a tape measure. Their pain intensity and pain frequency were measured in visual analog scale and in pain rating score. Results: There were statistically positive correlations between right leg length and low back pain frequency (p<.05) and negative correlations between the left hindfoot and low back pain frequency (p<.05). There were statistically positive correlations between right leg length and knee pain frequency (p<.05) and positive correlations between the ankle pain intensity and right leg length (p<.05). Conclusion: The stronger the pain was in the ankle, the stronger and more frequent their lumber pain was. When the pressure of the left heel was lower, the frequency of lumbar pain increased.

• 한국철도학회논문집
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• 제19권6호
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• pp.765-776
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• 2016

본 연구에서는 철도 교대를 위한 표준단면을 선정하고, 선정된 단면에 대하여 토압산정방법과 내부마찰각에 따른 직배면과 가상배면에 작용하는 주동토압을 비교 분석하였다. 또한, 기존토압과 개량시행쐐기법의 토압을 이용하여 내부마찰각에 따른 교대의 외적 안정성, 부재력 및 경제성을 분석하였다. 본 연구로부터 가상배면에서의 주동토압은 직배면에서의 주동토압보다 크며, 내부마찰각이 증가함에 따라 감소한다는 것을 알 수 있었다. 기존토압(Rankine, Coulomb, 시행쐐기법) 및 개량토압(개량시행쐐기법) 모두 내부마찰각이 증가함에 따라 부재력은 크게 감소하였고, 경제성은 향상되는 것으로 평가되었다.

• 한국가시화정보학회지
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• 제10권1호
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• pp.47-54
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• 2012

Single Stage To Orbit (SSTO) missions which require its engines to be operated at varying back pressure conditions, use engines operate at high combustion chamber pressures (more than 100bar) with moderate area ratios (AR 70~80). This ensures that the exhaust jet flows full during most part of the operational regimes by optimal expansion at each altitude. Aero-spike nozzle is a kind of altitude adaptation nozzle where requirement of high combustion chamber pressures can be avoided as the flow is adapted to the outside conditions by the virtue of the nozzle configuration. However, the thrust prediction using the conventional thrust equations remains to be a challenge as the nozzle plume shapes vary with the back pressure conditions. In the present work, the performance evaluation of a new aero-spike nozzle is being carried out. Computational studies are carried out to predict the thrust generated by the aero-spike nozzle in varying back pressure conditions which requires the unsteady pressure boundary conditions in the computational domain. Schlieren pictures are taken to validate the computational results. It is found that the flow in the aero-spike nozzle is mainly affected by the base wall pressure variation. The aerospike nozzle exhibits maximum performance in the properly expanded flow regime due to the open wake formation.

• 소성∙가공
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• 제30권1호
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• pp.35-42
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• 2021

Magnesium alloys are used in electronic devices such as laptops due to their lightweight features as well as vibration absorption and electromagnetic shielding properties. However, the precision of electronics is limited by the large number of small and precise ribs, the cost-effective manufacture of which requires appropriate technology. Plate forging is an efficient manufacturing process that can address these challenges. In this study, plate forging of magnesium alloys was investigated specifically for the fabrication of laptop cover. The plate forging process with back-pressure was used for near-net shape formation. Finite element analysis was used to select appropriate variables for back-pressure formation to generate ribs of various sizes and shapes without defects. The reliability of the analysis was verified to manufacture the prototype. The effect of back-pressure can be verified via fabrication of prototypes as well as structure and forming analysis based on finite element method. The process design factor of back-pressure increases formability without defects of under-filling and flow-through. Moreover, the tensile strength was maintained even after high temperature plate forging at 370 ℃, and the elongation was improved.

• 한국의류학회지
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• 제27권5호
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• pp.485-495
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• 2003

This study was to compare and analyze the clothing pressure according to arms movements of 4 brands jacket for middle-aged women group by measuring clothing pressure of each brand. The results were as follows: 1. According to the analysis of jackets of 4 brands, in general, jacket C had the largest ease amount. while jacket A had a large ease amount in waist, hip areas compared with bust area. Also jacket B had a small ease amount in bust, waist areas and jacket D had a small ease amount in hip areas. Therefore the ease amount is different between each brand, each size even though jacket designs are similar. 2. It was found that clothing pressure was affected by arm movements than jackets. Since this study was limited to the arm movement for motion variation, it was recognized that a significant difference among each jacket and each movement at shoulder, waist parts existed with relation to this motion. 3. Parts showing a significant difference among each size were bust point, abdomen point, center back point of abdomen level, angulus superior scapulae point and center back point of waist level. Also clothing pressure of size B91 was bigger than size B88 except Center back point of waist level. 4. Clothing pressure in shoulder point, front armpit point, back armpit point, upper arm point areas increased as the angle of the arms movement increased. Also, individual variation of clothing pressure in front armpit point, back armpit point, armpit point and upper arm point was large, and clothing pressure in abdomen point was high in M5(sitting posture).