• Journal of Power System Engineering
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• v.15 no.5
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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.

• Transactions of The Korea Fluid Power Systems Society
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• v.2 no.4
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• pp.14-22
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• 2005

The safety factor of hydraulic piston pumps & motors due to high pressurization, high speedization and low weight/volume realization to enhance the output density shows a tendency to decrease. Therefore more effective test methods are necessary to predict the exact life. The failure of hydraulic pumps & motors operating in high pressure and high speed mainly occurs in piston-shoe assemblies, and the major failure mode is wearout of the shoe surface. The sensitive parameters in the endurance life test are speed, pressure and temperature, and the failure production increases in proportion to the operating time. In this research, the authors propose the combined accelerated life test model using the analysis method of the combined accelerated life test results of piston-shoe assemblies by applying simultaneously high speed, high pressure and high temperature in accordance with variation of speed, pressure and temperature to reduce the life test time.

• Journal of the Korean Geotechnical Society
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• v.28 no.7
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• pp.17-30
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• 2012

A new trenchless tunneling method using pressurizing support has been developed. As it overcomes shortcomings of conventional methods, it is applied to the field. The main concept of the new method is the pressurization system which, by means of pressurization bag between outer flange of steel ribs and excavated perimeter, applies the pressure corresponding to the magnitude of the relaxed earth pressure caused by excavation to the ground to prevent ground displacement. The stability of the support members and effect of displacement control of the new method were verified through several ways such as numerical tests and various model tests. The new method was applied to the construction of a 10.7 m wide, 7.9 m high and 85 m long road tunnel that passes under Yeongdong Expressway. By applying the new method, the tunnel construction was successfully completed in 13.5 months. It decreases the construction period to 35% compared to that of conventional methods, and ground displacement was almost negligible.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.4
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• pp.397-419
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• 2012

The pressurizing support tunneling method has been developed that overcomes shortcomings of conventional trenchless methods and applied to the field. The main concept of the new method is the pressurization system which, by means of pressurization bag between outer flange of steel ribs and excavated perimeter, applies higher pressure than the pressure relaxed by excavation to the ground to prevent ground displacement. The stability of the support members and effect of displacement control of the new method were verified through 3D numerical analyses. The new method was applied to the construction of a 10.7 m wide, 7.9 m high and 85 m long ramp tunnel that passes under ${\bigcirc}{\bigcirc}$ Expressway. By applying the new method, the tunnel construction was successfully completed in 13.5 months which decreases construction time to 35% compared to conventional methods, and ground displacement was almost negligible.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.25 no.4
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• pp.300-311
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• 2022

Purpose: Dysphagia, vomiting and feeding difficulties are common symptoms, with which children present. Esophageal function testing with high resolution manometry can help in diagnosing and treating these patients. We aim to access the clinical utility of high-resolution manometry of esophagus in symptomatic pediatric patients. Methods: A retrospective chart review was done on all symptomatic patients who underwent esophageal high-resolution manometry between 2010 and 2019 at Sydney Children's Hospital, Australia. Manometry results were categorized based on Chicago classification. Demographic data, indication of procedure, manometric findings, and details of treatment changes were obtained and analyzed. Results: There were 62 patients with median age of 10 years (9 months-18 years). The main indication for the procedure was dysphagia (56%). Thirty-two percent of patients had a co-morbid condition, with esophageal atresia accounting for 16%. The majority (77%) of patients had abnormal manometry which included, ineffective esophageal motility in 45.2%. In esophageal atresia cohort, esophageal pressurization was seen in 50%, aperistalsis in 40% and 10% with prior fundoplication had esophago-gastric junction obstruction. Patients with esophago-gastric junction obstruction or achalasia were treated by either pneumatic dilation or Heller's myotomy. Patients with ineffective esophageal motility and rumination were treated with a trial of prokinetics/dietary texture modification and diaphragmatic breathing. Conclusion: Esophageal high-resolution manometry has a role in the evaluation of symptomatic pediatric patients. The majority of our patients had abnormal results which led to change in treatments, with either medication, surgery and/or feeding modification with resultant improvement in symptoms.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.8
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• pp.1221-1226
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• 2003

High hydrostatic Pressure was applied to Foxtail Millet Yakju to investigate the effects of high pressure on inactivation of microorganisms and enzymes. Total bacteria, lactic acid bacteria and yeast in untreated Yakju were $1.5{\times}$10$^4$,1.9${\times}$10$^4$ and 1.4${\times}$10$^4$ CFU/mL, respectively. Total bacterial count was reduced to 4.1${\times}$l0$^2$ CFU/mL, while lactic acid bacteria and yeast were sterilized completely in Yakju heated at $65^{\circ}C$ for 15 min. Lactic acid bacteria and yeast decreased greatly with the increase of treatment pressure, and were sterilized completely in Yakju treated at more than 300 ㎫ for 10 min/$25^{\circ}C$. Total bacteria were not completely sterilized with pressurization of even 600 ㎫ at room temperature and reduced to 2 log cycle even at $65^{\circ}C$. Total bacteria decreased by 2∼3 log cycle with the increase of treatment time from 10 to 60 min at $25^{\circ}C$/300 ㎫. Pressurization of Yakju caused a partial inactivation of $\alpha$ -amylase and glucosamylase, and the activities of $\alpha$ -amylase and glucoamylase decreased by 18.1% and 21.1%, respectively at $25^{\circ}C$/600 ㎫/10 min. Activities of $\alpha$ -amylase and glucoamylase decreased with the increase of temperature, and 22.2% and 32.1% of the original activity were remained with the treatment at $65^{\circ}C$/300 ㎫/10 min, respectively. Enzyme activities decreased slightly with the increase of treatment time at $65^{\circ}C$/300 ㎫.

• Asian-Australasian Journal of Animal Sciences
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• v.31 no.8
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• pp.1336-1344
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• 2018

Objective: This study aimed to observe whether high-pressure processing (HPP) affected aroma development and the degradation rate of umami taste-related ATP breakdown products, specifically inosinic acid in grass-fed beef during vacuum aging. Methods: Strip loin (longissimus lumborum) cuts obtained from six grass-fed Friesian Holstein steers (32 months old) on day 4 post slaughter were vacuum-packed and subjected to pressurization at 300 and 500 MPa for 180 s at $15^{\circ}C{\pm}2^{\circ}C$. The samples were then stored for 4 weeks at $5^{\circ}C{\pm}0.5^{\circ}C$ under vacuum and compared with the control (0.1 MPa). Results: HPP increased the shear force value, promoted moisture loss and lipid oxidation, induced surface paleness, stabilized pH during aging, and reduced bacterial load and growth. The shear force value of 500 MPa-treated samples remained higher than the control after aging, while no significant differences were found between the control and 300 MPa-treated samples. Degradation of inosinic acid and inosine occurred during pressurization, resulting in an increase in hypoxanthine content. However, the degradation rate in HPP-treated samples during aging was slower; therefore, inosinic acid and inosine content remained higher than in control samples. No significant differences were found in hypoxanthine content at the end of aging. HPP intensified the levels of hexanal, octanal, 2-methylbutanal, 3-methylbutanal, benzaldehyde, and 2,5-dimethylpyrazine in cooked-aged beef samples. Conclusion: HPP induced aroma development and delayed the degradation of inosinic acid. However, it also reduced the postmortem tenderization rate.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.6
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• pp.81-86
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• 2017

The high-pressure resin transfer molding (HP-RTM) process has a very effective for the mass production of carbon fiber reinforced plastic (CFRP) for light weight in the automotive industry. In developing robust equipment, new process and fast cure matrix systems reduces significantly the cycle time less than 5 minutes in recent years. This paper describes the cavity pressure, temperature and molding characteristics of the HP-RTM process. The HP-RTM mold was equipped with two cavity pressure sensors and three temperature sensors. The cavity pressure characteristics of the HP-RTM injection, pressurization, and curing processes were studied. This experiment was conducted with selected process parameters such as mold cap size, maximum press force, and injection volume. Consequently, this monitoring method provides correlations between the selected process parameters and final forming characteristics in this work.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.241-244
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• 2006

The analysis of propellant feeding sub-system is performed using a commercial code SINDA/FLUINT, the comprehensive finite-difference, one-dimensional, lumped parameter tool. With the code, cryogenic helium supply system, liquid oxygen supply system, helium injection cooling system are evaluated. The code gave satisfactory estimation scheme for propulsion system characterized by cryogenic temperature and high pressure, two phase flow. This paper focuses on presenting calculation scheme of propulsion sub-system using one-dimensional code like SINDA/FLUINT.

• 한국전산유체공학회:학술대회논문집
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• 1999.05a
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• pp.205-212
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• 1999

Safety Depressurization System of the Korean Next Generation Reactor prevents the Reactor Coolant System from over-pressurization by discharging the coolant with high pressure and temperature into the In-containment Refueling Water Storage Tank(IRWST) during an accident. If temperature in the IRWST rises above the temperature limit of $200\;^{\circ}F$ due to the discharged coolant, an unstable steam condensation may occur and cause large load on the IRWST wall. To investigate whether this condition can be reached or not for the design basis accident, the flow and temperature distributions of water in the IRWST wire calculated by using CFX 4.2 computer code. The results show that the local water temperature does not exceeds the temperature limit within the transient time of 5 seconds.