• Journal of Korea Water Resources Association
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• v.47 no.12
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• pp.1177-1185
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• 2014

This study suggests a new hydrostatic pressure distribution corrected for nonuniform flow over a channel of large slope. For analyzing shallow-water flows over large slope accurately, it is developed a finite-volume model incorporating the pressure distribution to the shallow water equations. Traveling speed of the hydraulic jump downstream a parabolic bump in the drain case is quite reduced by the weakened bottom gradient source term in the model with the pressure correction. In simulating the dam-break flow over a triangular sill, it is identified that the model with pressure correction could capture the water surface by the digital imaging measurements more than the model without that. Due to the pressure correction decreasing the reflected flows on and increasing overflows over the sill, there are good agreements in the experiment and the simulation with that. Therefore, this model is expected to be applied to such practical problems as flows in the spillway of dam or run-up on the beach.

• The Korean Journal of Food And Nutrition
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• v.29 no.3
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• pp.371-381
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• 2016

The present study investigated the effects of processing parameters such as time (10, 20, 30, 40 min), pressure (25, 50, 75, 100 MPa), and the salinity of brine (0~10%(w/v)) on jacopever (Sebastes schlegeli Hilgendorf) in order to establish optimization of the three factors using a high hydrostatic pressure (HHP) machine. To do so, it analyzed the quality characteristics of volatile basic nitrogen (VBN), trimethylamine (TMA), total bacterial counts, dynamic viscoelasticities, and differential scanning calorimetry (DSC) properties. First, when the time increased to 40 mins, by 10 min intervals, the total bacterial counts in HHP groups under $25^{\circ}C$, 100 MPa, and 4%(w/v) brine were significantly decreased except for the first 10 min in comparison to the control group. In regards to DSC properties, the onset temperature ($T_O$) of the first endothermal curve was significantly reduced. Second, when the pressure level increased up to 100 MPa by 25 MPa increments, the total bacterial counts in the HHP samples significantly decreased for 20 min at 50 MPa or higher. As the pressure increased, G', G" and the slope of tan ${\delta}$ decreased (except for 50 MPa). Third, in regards to the salinities of brine, when the HHP processing was treated at 100 MPa, $25^{\circ}C$ for 20 min, the total bacterial counts of all the HHP groups significantly decreased in comparison to those of the control group. A significant difference was found in the enthalpy of the second endothermic curve in the 6~10%(w/v) (except 7%(w/v)) HHP groups. Therefore, the salinity of the immersion water under the HHP condition was appropriate when it was lower than 6%(w/v). The present study demonstrated that the optimum parameter condition according to/under the condition of the microbial inhibition and economic effects using an HHP would be the reaction time for 20 min, reaction pressure at 100 MPa, and the salinity of 4%(w/v) brine.

• Korean Journal of Food Science and Technology
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• v.32 no.1
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• pp.111-116
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• 2000

Effects of ultra-high pressure treatment on viable cell count and quality characteristics of low salt fermented anchovy under different operating conditions such as pressure$(200{\sim}500\;MPa)$, temperature$(20{\sim}50^{\circ}C)$ and treatment time$(5{\sim}20\;min)$ were investigated. Viable cell count decreased gradually with the increase of pressure and suddenly at 400 MPa. It also decreased by seven folds at $50^{\circ}C$ and logarithmically with the increase of treatment time. Peroxide value increased with the increase of pressure, temperature and treatment time, and temperature played a major role. Thiobarbituric acid value was higher by two folds in samples treated than in the untreated regardless of any conditions investigated. Volatile basic nitrogen was almost the same in all samples except the one at $50^{\circ}C$. The sample treated at greater than $30^{\circ}C$ under high hydrostatic pressure indicated higher value in amino nitrogen. Treatment at $20^{\circ}C/300$ MPa/15 min showed greater reductions in viable cell counts, remaining better quality of low salt fermented anchovy.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.5
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• pp.535-544
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• 2009

Signals from the Global Positioning System(GPS) satellite are used to retrieve the integrated amount of water vapor or the precipitable water vapor(PWV) along the path between a transmitting satellite and ground-based receiver. In order to retrieve the PWV from GPS signal delay in the troposphere, the actual zenith wet delay, which can be derived by extracting the zenith total delay and subtracting the actual zenith hydrostatic delay computed using surface pressure observing, will be needed. Since it has been not co-located between GPS permanent station and automated weather station, the air-pressure on the mean sea level has been used to determine the actual zenith hydrostatic delay. The directly use of this air-pressure has been caused the dilution of precision on GPS PWV retrieval. In this study, Korean reverse sea level correction method of air-pressure was suggested for the improving of GPS PWV retrieval capability and the accuracy of water vapor estimated by GPS was evaluated through a comparison with radiosonde PWV.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.1
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• pp.89-97
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• 2009

Jujube wine was treated with hydrostatic pressure (500 MPa, 5 min) or freezing ($-20^{\circ}C$, 3 days and thawed $20^{\circ}C$, 4 hr) and their microbial counts, physicochemical properties, and sensory characteristics were investigated during storage at $35^{\circ}C$ for 60 days. Microorganisms in pressure-treated jujube wine were not detected during the whole period and chemical compositions as well as color were slightly changed. Sensory quality was significantly preserved until 20 days without increasing sweet aroma and taste. In freezing-treated wine, bacterial counts were decreased after 10 days and remained below 10 CFU/mL while lactic acid bacteria and yeast were not detected. Changes of chemical composition were smaller than those of the untreated wine but bigger than those of the pressure-treated or heat-treated wine. Instrumental color was changed after $10{\sim}20$ days resulting from the increase of L value and the reduction of a value. Sensory quality was significantly similar with the fresh wine for 10 days, suggesting that pressure treatment would be the most effective sterilization method to improve the shelf life of jujube wine whereas freezing treatment would be insufficient.

• Korean Journal of Food Science and Technology
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• v.29 no.5
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• pp.974-981
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• 1997

A combined treatment of high hydrostatic pressure and carbonation was used to inactivate pectinesterase (PE) and sterilize microorganisms in Valencia orange juice without major changes in its nutritive components. Quality characteristics of Valencia orange juice, such as microorganisms, PE activity, vitamin C content and color, were evaluated after it was treated with pressure, carbonation-and-pressure, and heat. Quality changes during storage at $4^{\circ}C$ and $30^{\circ}C$ after the treatments were also investigated. Pressurized orange juice (pressurized at 600 MPa for 10 min at $20^{\circ}C$) showed 7.0% residual PE activity, while the carbonated-and-pressurized orange juice (207 $kPa-CO_2$ gas pressure, pressurized at 600 MPa for 10 min at $20^{\circ}C$) showed 0%. Pressurization at 400 MPa or higher decreased the population of microorganisms in the orange juice to less than 10 CFU/mL. Carbonated-and-pressurized orange juice showed slight decrease in vitamin C content when stored at both $4^{\circ}C\;and\;30^{\circ}C$. While heat-treated ($90^{\circ}C$ for 60 sec) orange juice showed 75% decrease in vitamin C content when stored at $30^{\circ}C$. L value (lightness) and b value (yellowness) of carbonated-and-pressurized orange juice were higher than those of heat-treated orange juice when they were stored at $4^{\circ}C$ for 30 days.

• Korean Journal of Food Science and Technology
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• v.33 no.2
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• pp.226-230
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• 2001

High hydrostatic pressure was applied to Foxtail Millet Takju to investigate the effects of high pressure on inactivation of microorganisms and enzymes. Total bacteria, lactic acid bacteria and yeast in untreated Takju were $6.8{\times}10^7,\;1.3{\times}10^8\;and\;8.4{\times}10^7\;CFU/mL$, respectively. Total bacterial count in Takju reduced to $2.2{\times}10^5\;CFU/mL$, while lactic acid bacteria and yeast were sterilized completely when heated at $65^{\circ}C$ for 30 min. Lactic acid bacteria and yeast decreased with the increase of treatment pressure, and pressurization of 400 MPa for 10 min at room temperature sterilized completely the lactic acid bacteria and yeast in Takju. Total bacteria were not sterilized with pressurization of even 600 MPa at room temperature. Total bacteria were completely sterilized at $66^{\circ}C/400\;MPa/60\;min\;and\;66^{\circ}C/600\;MPa/10\;min$. Pressurization of Takju caused a partial inactivation of ${\alpha}-amylase$, and after pressurization at 600 MPa for 10 min at room temperature, 73.2% of the original activity remained. The activity of glucoamylase increased with the increase of treatment pressure. Treatment at $66^{\circ}C/400\;MPa/10\;min$ reduced the activity of ${\alpha}-amylase$ by 59.7% and glucoamylase by 20.5%. ${\alpha}-Amylase$ was inactivated to less than 1.2% of the original activity at $66^{\circ}C/600\;MPa/30\;min$.

• Journal of Drive and Control
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• v.14 no.4
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• pp.9-16
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• 2017

In this study, the force tracking performance of the single-rod and double-rod type EHAs (Electro-Hydrostatic Actuators) was compared by computer simulation and experiments. The force-controlled EHAs exhibit non-linear behavior that are significantly dependent on operation conditions. The investigation focused on localizing the parameters that provide significant rise to the non-linearity. For this, the single-rod and double-rod type EHAs were mathematically expressed to derive their linear models. In parallel, they were modeled by a commercial simulation program including non-linear properties based on experimental results. It was shown that the dependency of the bulk modulus of oil with entrapped air on working pressure dominated the non-linearity in force control performance in case of the double-rod type EHA. The force control of the single-rod type EHA was influenced by much more elements. Besides the asymmetrical piston geometry and the non-linear bulk modulus of oil, its pilot-operated check valves made it dependent not only on the magnitude of reference input but also on its direction.

• Journal of Navigation and Port Research
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• v.43 no.5
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• pp.328-334
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• 2019

Underwater architecture in providing a comfortable living space underwater is mandated to survive prevailing environmental loads, especially hydrostatic ambient water pressure exerted on the structure of individual habitat hulls at depth and hydrodynamic fluctuation of external forces that perturb the postural equilibrium and mooring stability of the underwater housing system, for which the design including the hull shape and mooring system constraint the responses. In this study, the postural stability of a proposed underwater floating housing system with three vertically connected ellipsoidal-shape habitat hulls of different sizes are theorized and calculated for hydrostatic stability, using MATLAB in the volumetric integration of a hull and the weight of operational loads under assumed scenarios. The assumptions made in the numerical method to estimate the stability of the habitat system include the fixed weight of the hulls, and their adjustable loads within operational limits for the set meteorological oceanic conditions. The purpose of this study was to numerically manipulate a) The buoyancy and b) The adjusted center of mass of the system within the range of designed external and internal load changes, by which the effective mooring system capability and postural equilibrium requirements were argued with the quantitative analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.799-800
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• 2012