• 한국기계가공학회지
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• 제5권3호
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• pp.92-98
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• 2006

In this study, the behavior characteristics of a hydrostatic thrust bearing used in hydraulic equipment was analyzed using a commercial finite element program, ADINA. The solid domain was modeled with the fluid domain simultaneously to solve the fully coupled problem, because this is a problem where a fully coupled analysis is needed in order to model the fluid-structure interaction(FSI). The results such as bearing deformation, stress, film thickness and lifting bearing force were obtained through FSI analysis, and then they were compared with the results calculated from the classical method, a single step sequential analysis. It was found that the result difference between two analyses was increased according to the injection pressure. Therefore, in case of high pressure loading, it is desirable to conduct the FSI analysis to examine the deformation characteristics of a hydrostatic slipper bearing.

• 한국식품과학회지
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• 제30권3호
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• pp.596-601
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• 1998

비열처리공법 중 하나로 새롭게 주목받고 있는 초고압 처리를 동치미에 적용하여 미생물의 살균정도, 효소 활성과 hardness의 변화를 관찰하였다. 제조한 동치미를 $30^{\circ}C$ 배양기에서 발효 적숙기라고 판단되는 pH 4.0까지 발효시킨 후, 이를 시료로 사용하여 $200{\sim}686\;MPa$ 범위의 압력에서 5분간 처리하였다. 무처리군의 균체수는 호기성 세균, 젖산균, 효모 및 곰팡이가 각각 $4.05{\times}10^8,\;3.25{\times}10^8,\;3.55{\times}10^4\;CFU/mL$ 존재하였으나, 호기성 세균은 600 MPa, 젖산균과 효모 및 곰팡이는 400 MPa 이상에서 완전히 살균되었다. 젖산균의 압력에 따른 내압성을 관찰해 본 결과 380 MPa에서 Leuconostoc mesenteroides가 유일하게 검출되어 가장 강한 내압성을 나타내었으며, 김치의 주 산패균으로 알려진 Lactobacillus plantarum은 300 MPa로 처리한 시료에서도 발견되지 않아 압력에 약한 균주로 판단되었다. 조직감에 관계하는 효소인 pectinesterase (PE)와 polygalacturonase (PG)는 압력에 의해 모두 활성이 증가하였다. 초고압 처리를 하지 않은 시료의 효소 활성을 100으로 했을 때, PE는 500 MPa에서 193으로 가장 활성이 높았으며, PG는 압력이 증가함에 따라 활성이 서서히 증가하여 686 MPa에서 191이었다. 동치미에 있는 무의 조직감은 초고압 처리했을 때 hardness가 증가하여 400 MPa에서 5분간 처리한 시료는 무처리군에 비해 약 0.065kg이 높았다.

• 드라이브 ㆍ 컨트롤
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• 제10권1호
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• pp.14-20
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• 2013

In the high rotational speed and pressure state, the leakage flow rate of the axial piston pump is one of the serious problems and make great reasons to decrease the volume efficiency. In this study, tribology characteristics is clarified for the hydrostatic slipper bearing in the swash plate type axial piston pump, by means of theoretical analysis for the different shape of the hydrostatic slipper bearing. It was analyzed by Mathcad software and used equal conditions at $0^{\circ}$ swash plate angle in each model. The results show that performance characteristics of the swash plate type axial piston pump are significantly influenced by the shape of the hydrostatic slipper bearing.

• 동력기계공학회지
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• 제15권5호
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• pp.5-9
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• 2011

The hydraulic piston using a hydrostatic bearing has been used widely due to its satisfying performance at very high pressurized circumstance and relative higher power density in comparison to conventional one. For high pressurization, enhanced efficiency and long durability of the hydraulic piston, the design of hydrostatic bearing is at issue, which is installed between piston shoe and swash plate. The performance of the hydrostatic bearing is influenced significantly by the assembly of the piston shoe consisting of circular land and recess. In this study, to estimate the performance of the hydrostatic bearing, the characteristics for lubrication of the assembly of the piston shoe were investigated by measuring a leakage rate of hydraulic fluid under an experimental condition, where a rotating velocity of the piston, hydraulic pressure and temperature of the hydraulic fluid were changed systematically. In addition, a film thickness of the hydraulic fluid on the piston shoe was measured and compared to theoretical one.

• Preventive Nutrition and Food Science
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• 제20권4호
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• pp.253-259
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• 2015

Chronic low-grade inflammation is associated with obesity. This study investigated effect of high hydrostatic pressure extract of red ginseng (HRG) on inflammation in rats with high-fat (HF) diet induced obesity. Male, Sprague-Dawley rats (80~110 g) were randomly divided into two groups, and fed a 45% HF diet (HF) and a 45% HF diet containing 1.5% HRG (HF+HRG) for 14 weeks. At the end of the experiment, the serum leptin level was reduced by the HRG supplementation. The mRNA expression of genes related to adipogenesis including peroxisome proliferator-activated receptor-gamma and adipocyte protein 2 was down-regulated in the white adipose tissue (WAT). The mRNA levels of major inflammatory cytokines such as tumor necrosis factor-${\alpha}$, monocyte chemoattractant protein 1, and interleukin-6 were remarkably down-regulated by the HRG in WAT. These results suggest that HRG might be beneficial in ameliorating the inflammation-associated health complications by suppressing adipogenic and pro-inflammatory gene expression.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.117-123
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• 2003

This paper deals with pressure ripple and noise reduction characteristics for a hydrostatic transmission(HST) consisting of a variable axial piston pump connected in an open loop to a fixed displacement axial piston motor. Pressure ripples in HST is major source of vibration, which can lead to fatigue failure of components and cause noise. In order to reduce the pressure ripple, an annular tube type hydraulic filter proposes to absorb pressure ripples with the high frequencies components to achieve better noise attenuation in HST. The basic principle tube is applied to propagation of pressure wave, reflection, absorption in cross section of discontinuity and resonance in the hydraulic pipeline. It is experimently confirmed that a hydraulic filter is absorbed to be about 30∼40dB of pressure ripple with high frequencies. These results will assist in modeling and design of noise reduction in hydraulic control systems, and here, should provide a means of designing a quieter HST.

• 한국축산식품학회지
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• 제21권1호
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• pp.32-37
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• 2001

The study investigated the effects of protein concentration, EGTA and strength of hydrostatic pressure on pH, viscosity and turbidity for ultra filtrated skim milk retentates. The results showed that hydrostatic pressure treatments up to 600 MPa did not affect the viscosity of skim milk, while the turbidity of skim milk increased at higher than 200 MPa. Addition of EGTA caused reduction in turbidity of skim milk, two times (2SR) and three times (3SR) concentrated skim milk retentates. Viscosity for 2SR and 3SR increased proportionally to the amount of EGTA, but viscosity of skim milk was not influenced by EGTA. High pressure treatment also did not cause any difference in viscosity and turbidity of skim milk. However, this treatment decreased viscosity and turbidity for 2SR and 3SR. In particular, 200 MPa treatment showed to induce a higher decrease in turbidity compared with 400 MPa.

• Journal of Advanced Marine Engineering and Technology
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• 제22권5호
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• pp.609-616
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• 1998

Structural analyses are preformed for the high pressure steam turbine casings of the nuclear and the fossil power plants. An axisymmetric boundary element program for analysis of the casings is developed and applied in the process of practical structural design. To show the useful-ness and accuracy of the developed program results of the analysis are compared with those of the finite element analysis under hydrostatic test pressure, To check the validity of the axisymmetric numerical analysis of the casings the stresses resulting from the hydrostatic test pressure are measured using the strain gate. The results of the numerical analyses are compared and discussed with those of the experiments.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 추계학술대회 논문요약집
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• pp.191-191
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• 2003

It is well-known that the mechanical behavior of fiber-reinforced composites under hydrostatic pressure environment is different from that of atmospheric pressure environment. It is also known that the mechanical behavior of fiber-reinforced composites is affected by strain rate. In this work, we investigated the effect of strain rate on the compressional elastic modulus and fracture stress of fiber-reinforced composites under hydrostatic pressure environment. The material used in the compressional test was unidirectional carbon/epoxy composites and the hydrostatic pressures applied was 250 MPa. Compressional tests were performed applying various strain rates of 0.05 %/sec, 0.25 %/sec, 0.45 %/sec, and 0.75 %/sec. The results showed that the elastic modulus increased with increasing strain rate while the fracture stress was little affected by the strain rate.

• 한국해양공학회지
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• 제23권5호
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• pp.39-44
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• 2009

The hydrostatic slipper bearing is generally used in high pressure axial piston pumps to support the load generated from two surfaces which are sliding relatively at low speed. The object of the bearing is to remove the possibility of direct contact by maintenance of an adequate oil film thickness between two metal surfaces. Because the bearing performance is influenced by the bearing deformation, it is highly dependent on the injection pressure, the bearing surface profile and so on. In this study, the deformation characteristics of a hydrostatic slipper bearing is investigated according to the injection pressure by the finite element analysis. In the analysis, the special boundary condition to take the fluid-structure interaction (FSI) into account is used on the interactive surface. The results, such as bearing deformation, stress and lifting force, obtained from the fully coupled analysis are compared with those from the single step sequential method.