• Journal of Energy Engineering
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• v.15 no.1 s.45
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• pp.23-27
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• 2006

This paper presents the evaluation of LPG (Liquefied petroleum gas) regulators for home use. For the evaluation, several properties of the regulators were experimentally analyzed, such as the operation of safety device, the adjusting and lock-up pressure, the adjusting spring and the diaphragm, with respect to the used time of the regulators. Experimental results showed that the initial operation performance of regulators were degraded with increase of the service time and also showed that the degradation of the performance and material property could become serious after six-year-use of the regulator.

• Magazine of the Korean Society of Agricultural Engineers
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• v.17 no.2
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• pp.3763-3771
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• 1975

This study was attempted to investigate the changes of specific fuel consumption, compression pressure and power output, consequently to obtain basic data on farm kerosene engine. The samples which are used in this study are a 4 cycle water cooled korosene engine for the use of K6-CT83 power tiller and a 4 cycle air-cooled kerosene engine for the use of G5L-3A water pump. The Korean Industrial Standards (K.S)KS-B 6002 "Test code of small internal combustion engine" was referred in carrying out this study, and its results are as follows. 1. According to load increasing, the speific fuel consumption of the engines generally decreases, however, in case of 10% over-loading it increases. 2. As a result of full load consecutive operation, according to passing of operating time, the amount of wear generally increases, consequently the speific fuel consumption also increases, and inversly the compression pressure decreases. 3. The changes of specific fuel consumption and compression pressure were closely related with time of piston ring exchange, and periodically about 100 hours the engines show the increase of specific fuel consumption and the decrease of compression pressure. 4. After about 300 hours, although the engine had new piston rings, the specific fuel consumption increase, consequently the engine needs boring. In actual use, it is impossible to operate consecutively on full load, therefore the boring time of engine is expected to come later.

• The Journal of Korean Physical Therapy
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• v.25 no.2
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• pp.71-75
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• 2013

Purpose: Although use of a tilt table is recommended in clinical practice, there are no published guidelines regarding pressure and inclination for tilt table use. The aim of the current study was to assess the changes of pressure on sacrum and buttock according to different inclination of the tilt table in healthy subjects. Methods: Thirty two healthy subjects participated in this study. Subjects were positioned supine on the tilt table and safety straps were secured across the chest, pelvic, and knee with sufficient tension to prevent the subjects from falling. Pressure and peak pressure of sacrum and buttock were measured using pressure mapping system with the tilt table standing at $0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $75^{\circ}$, and $85^{\circ}$ inclination. Results: A significant decrease in the pressure of sacrum and buttock was achieved by increasing tilt table inclination (p<0.05): $0^{\circ}{\sim}15^{\circ}$ (8.16%), $15^{\circ}{\sim}30^{\circ}$ (8.02%), $30^{\circ}{\sim}45^{\circ}$ (11.61%), $45^{\circ}{\sim}60^{\circ}$ (16.18%), $60^{\circ}{\sim}75^{\circ}$ (16%), and $75^{\circ}{\sim}85^{\circ}$ (11.48%). A significant decrease in the peak pressure was achieved by increasing tilt table inclination (p<0.05): $30^{\circ}{\sim}45^{\circ}$ (9.91%), $45^{\circ}{\sim}60^{\circ}$ (19.24%), $60^{\circ}{\sim}75^{\circ}$ (19.93%), and $75^{\circ}{\sim}85^{\circ}$ (11.48%). No significant peak pressure change was observed in $0^{\circ}{\sim}15^{\circ}$, $15^{\circ}{\sim}30^{\circ}$ tilt table inclination (p>0.05). Conclusion: The results of this study showed that the pressure of sacrum and buttock were decreased according to increasing tilt table inclination in healthy subjects. Guidelines are needed in order to optimize patient safety and overall outcome for tilt table standing.

• Transactions of the Korean Society of Mechanical Engineers
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• v.1 no.2
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• pp.65-72
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• 1977

Major problems in the design and use of refief valve are (a) chattering because of instability, (b) excessive pressure differential which makes the valves crack far below maximum pressure diminishing useful flow in the system. In this study, A magnet-coupled relief valve is investigated theoretically and experimentally in order to improve the performance of a conventional direct type reliefvalve. A theory is developed to predict the performance, response, and stability of the magnet-coupled valve taking into account the delivery line response. In the experiment, a typical magnet-coupled relief valve is designed on the basis of the analytical results; the discharge rates are measured varying the supply pressure, and both the pressure-time curves and valve displacament-time curves are recorded providing the supply pressures greater than the setting pressure. The measured override characteristic curves are then compared with those of conventional pilot type and direct type releif valves. It is showm that the excessive pressure differential of a magnet-coupled relief valve becomes less than that of a conventional direct type valve. It is also shown that the most important chatacteristic of a magnet-coupled relief valve is to eliminate valve chattering due to instability regardless of the magnitude of setting pressures and discharge rates, which suggests wide applications of the idea of the use of a magnet in the design of hydraulic valves.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.491-495
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• 2004

The industries use polymer materials for many purposes for they have many merits. The costs of these materials take up too great a proportion of the overall cost of products that use these materials as their major material. It is advantage for polymer industries to reduce these costs. The microcellular foaming process was developed in the early 1980s to solve this problem and proved to be quite successful. Microcellular foaming process uses inert gases such as $CO_2$, $N_2$. As these gases solve into polymer matrices, many properties are changed. The microcellular foaming process makes the glass transition temperature of polymers to low, and diminish the residual stress of polymer matrices. Besides, the microcellular foaming process has several merits, impact strength elevation, thermal insulation, noise insulation, and raw material saving etc. This characteristic of microcellular foaming process has influenced by cell morphology. The cell morphology means cell size and cell density. The cell morphology has influenced by many factors. The examples of factor are pressure drop rate, foaming temperature, foaming time, saturation pressure, saturation time etc. Among their factors, pressure drop rate is the most important factor for cell morphology in microcellular foaming injection molding process. This paper describes about the cell morphology change in accordance with the pressure drop rate of microcellular foaming injection molding process.

• Journal of Power System Engineering
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• v.17 no.4
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• pp.45-50
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• 2013

This paper presents the comparison of heat transfer and pressure drop of various secondary refrigerants (single-phase and two-phase) in the indirect refrigeration system. The main results were summarized as follows: In case of heat transfer, it is useful to use secondary refrigerants in low evaporating temperature region and the heat transfer coefficient of single-phase is larger than two-phase secondary refrigerants. In case of pressure drop, it is useful to use secondary refrigerants in high evaporating temperature region and the pressure drop of two-phase is smaller than single-phase secondary refrigerant. Also, $CO_2$ is the best useful because pressure drop of $CO_2$ among the secondary refrigerants is the smallest.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.4
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• pp.55-63
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• 2009

This paper reports on the theoretical and experimental study of the pressure ripples in a pressure unbalanced type vane pump which have widespread use in industry. Because they can infinitely vary the volume of the fluid pumped in the system by a control. Pressure ripples occur due to the flow ripples induced by geometry of side plate, leakage flow, reverse flow from the outlet volume produced by pressure difference between pumping chamber and outlet volume when the pumping chamber connected with the outlet volume. In this paper, we measured the pressure variation of a pumping chamber, reaction force on a cam ring, the mathematical model for analyzing the pressure ripples which included vane detachment and fluid inertia effects in notch area has been presented, and was applied to predict the level and the wave form of the pressure ripples according to operating conditions.

• Korean Journal of Medicinal Crop Science
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• v.19 no.1
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• pp.54-65
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• 2011

This study was performed to investigate the enhancement of cosmeceutical activities of Berberis koreana bark by different extraction processes. The extracts are WE (water extract at $100^{\circ}C$, control), USE (ultrasonification for 1 hours at $60^{\circ}C$ with water), HPE (high pressure for 5 minutes at $60^{\circ}C$ with water) and USE + HPE (ultrasonification process for 1 hours after high pressure for 5 minutes at $60^{\circ}C$ with water), respectively. The cytotoxicity of the extracts was in the range of 24.02~26.94% at 1.0 mg/ml concentration. The USE + HPE showed the lowest cytotoxicity. Compared to the WE, total phenolic and flavonoid contents in the USE + HPE increased to 121.5% and 154.2%. The USE + HPE showed the highest activity at 1.0 mg/ml concentration in 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging, inhibition activity of xanthine oxidase and superoxide dismutase (SOD)-like test, respectively. Tyrosinase inhibition of WE, USE, HPE and USE + HPE at 1.0 mg/ml concentration was measured as 17.72, 19.62, 22.83 and 24.16%, respectively. Hyaluronidase inhibition activities of the USE + HPE were higher than 20.8%~29.5% of the WE. Our results suggested that the extracts from ultrasonification process after high pressure extraction has relatively high cosmeceutical activities, and that the bark of Berberis koreana could be considered as a candidate of new functional cosmetic agents.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.8
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• pp.947-953
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• 2007

Occurrence of pressure pulsation in positive displacement hydraulic turbine is one of the principal problems which should be cleared to improve the turbine performance and to put the turbine to practical use. Therefore, present study is tried to examine the occurrence mechanism and characteristics of the pressure pulsation CFD analysis and experimental measurement are implemented in this study to clarify the phenomena of unsteady pressure pulsation. The results show that occurrence reason of the pressure pulsation is not only due to a series of opening and closing of the chamber formed between rotor and casing wall but also due to the variation of rotational speed of following rotor. The pressure pulsation causes torque variation and the curve patterns of the torque variation conforms to that of the pressure pulsation. Pressure in the chamber is equal to the averaged value of inlet and outlet pressures. Sudden pressure decrease by accelerated through-flow between lobe and casing wall results in torque loss.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.2
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• pp.130-136
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• 2001

This paper presents an of a brake pressure restriction valve to a motorcycle anti-lock brake system(ABS). In the conventional anti-lock brake system of automobiles, slip ratio as a control variable is actively controlled, which requires wheel speed sensors, ECU, and a pressure modulator. In the ABS valve that has been developed for use in motorcycles, however, the brake pressure that is close to the wheel locking pressure is preset by simple exercises and then the valve just allows to pass the wheel locking pressure and cutoff the remaining pressure. Simulation studies with a single wheel braking dynamics and lumped chassis model show that the pressure restriction valve has basic ABS functions as well as some robustness properties for the uncertain load and road conditions as well as various initial braking speeds. Field tests also show that the pressure restriction valve avoids the wheel locking effectively.