• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.111-117
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• 2003

In the design of the split type free displacer Stilting cryocooler the motion of the displacer is very important to decide the cooling capacity, which depends upon the working gas pressure, the swept volume in the compression space and the expansion space, operating frequency, the phase shift between piston and displacer, etc. In this study, Stirling cryocooler actuated by the electric farce of the dual linear motor is designed and manufactured. Cool down characteristics of the cold end with laser displacement sensor in the expander of the Stilting cryocooler is evaluated. The charging pressure was 15kg$_{f}$/$\textrm{cm}^2$ and operating frequency was 50Hz. Input power and the lowest temperature were about 32W and 67K, respectively. And, displacement of the piston is measured by LVDTs (Linear Variable Differential Transformers), displacement of thedisplacer is measured by laser optic method, and phase shift between piston and displacer is discussed. As the peak-to-peak pressure of the compressor was increased, peak-to-peak displacement of the displacer was increased. The peak-to-peak displacement of the displacer increases in the range of 0 - 64.5Hz(resonant frequency of the displacer), but decreases steeply when the operating frequency is bigger than the resonant frequency. Finally when the phase shift between displacements of the Piston and displacer is 45。, operating frequency is optimum and is decided by resonant frequency of the expander, mass and cross section area of the displacer and constant by friction and flow resistance.e.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.157-171
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• 1990

The heat transfer problem associated with pulse technique for measuring thermal diffusivity was solved by means of Green function. The obtained general solution was discussed so as to apply for all possible cases; kinds of boundary condition and heat source, irradiation positions of heat pulse, radius of heat pulse, one-and two-dimensional heat flow, finite pulse time effects and radiation heat loss systems. Experimentally, the laser flash lamp was used as heat source for measuring thermal diffusivity of low carbon, aluminium chilled steel plate, which was heavily rolled in order to measure the variation of thermal diffusivity in the temperature range from room temperature through 500.deg. C. The derived results are (1) materials produced from same furnace showed a somewhat different thermal diffusivity values. (2) the thermal diffusivity value of rolled material was smaller than unrolled material and the difference decreased as increasing temperature. (3) the thermal diffusivity value of an annealed and temper rolled material was larger than the value of a cold rolled material, even thought smaller than unrolled material. (4) In case of heavy rolled material, there was no consistent relationships between the thermal diffusivity and the reduction in thickness.

• The Journal of Korean Medical History
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• v.23 no.1
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• pp.23-41
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• 2010

Greater yang disease(太陽病) is a syndrome induced by peripheral obstruction. One of them is "wind stroke(中風)" with the obstruction in lymphatic system. The other obstruction appearing on circulatory system is called "cold damage(傷寒)." Kyejitang(桂枝湯) is the formula prescribed for greater yang wind stroke pattern(太陽中風證) which is caused by peripheral lymphatic duct obstruction. Ramulus Cinamoni acts as a vasodilator and Radix Paeoniae relieves the abdominal tension. They make blood move to the internal organ and this can remove the retention of peripheral lymphatic system. Covering the patient with a blanket and getting him/her to have hot and thin rice gruel causes slight Diaphoresis, contributing to relieving the retention of lymphatic system. Disharmony between nutrient and defense(營衛不和) means that pressure becomes different between lymphatic system and vascular system. Kyejitang(桂枝湯) is called releasing muscles formula(解肌劑) because it can resolve such pressure difference. Diaphoresis is not a means to eliminate pathogenic qi(邪氣) from the body. That is the syndrome proving that the body fluid has moved around when disordered fluid distribution is corrected. Therefore, diaphoresis should be induced weakly all the time. If diaphoresis is induced excessively, body fluid will move more than desired and then illness cannot be cured. In Sanghanlun(傷寒論), dispersing drugs aim at addressing the retention in the exterior field, but it actually applies to the entire exterior and interior to make body fluid move. Therefore, diaphoresis does not just act on exterior field, and freeing the stool does not only apply to interior field. Distribution of body fluid changed by pathogenic qi(邪氣) influences the whole body because the human body has a closed circulatory system. Sanghanlun(傷寒論) has included treatments for pathogenic disease. However, its value should not be limited to pathogenic disease. It is because controlling blood flow by sending body fluid to the place a doctor wants is certainly worth using for treatment of non-exogenous disease or chronic illnesses.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.4
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• pp.82-91
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• 2003

Experiments to investigate the mixing performance of unlike doublet impinging jets are conducted. Reynolds number of simulants used in this study rages from 1.0 to 1.5 Cold flow test is performed to investigate the hydrodynamic effect and spray of the impinging jets are collected locally and calculated by using Rupe's mixing efficiency equation. Momentum exchanges and relative velocity ratio between two jets are taken as the main parameter to represent the effect of enlargement of the orifice diameter. As diameter ratio increases, the corresponding momentum ratio where maximum mixing efficiency occurs and relative velocity at the maximum mixing efficiency ranges 0.6 to 0.7, respectively. Penetration depth can be taken as a prominent parameter to estimate the mixing efficiency.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.7
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• pp.619-625
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• 2015

Swirl injectors are widely used for Liquid Rocket Engine(LRE) as fuel injection system and following researches are also being carried out throughout the world. Especially, solving combustion instability problem is essential for every type of LREs. In this study, cold test was carried out for open type swirl injector as a fundamental research to solve combustion instability problem. Pressure fluctuation was applied to the inlet flow coming into the injector and the following response characteristics were observed. The effect of swirl chamber geometry was also studied by changing both swirl chamber length and diameter.

• Food Science of Animal Resources
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• v.38 no.2
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• pp.251-258
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• 2018

We investigated microbial and quality changes in wrap-packaged dry-aged beef after completion of aging and subsequent storage in a refrigerator. After 28 days of dry aging (temperature, $4^{\circ}C$; RH, approximately 75%; air flow velocity, 2.5 m/s), sirloins were trimmed, wrap-packaged, and stored at $4^{\circ}C$ for 7 days. Analyses of microbial growth, pH, volatile basic nitrogen (VBN), 2-thiobarbituric acid-reactive substance (TABRS), and instrumental color, myoglobin, and sensory evaluation were conducted on days 0, 3, 5, and 7. The results show that the number of total aerobic bacteria (TAB), yeast, and lactic acid bacteria increased with an increase in storage days, whereas no change in the growth of mold was observed during 7 days of storage. Based on the legal standard for TAB count, the estimated shelf-life of wrap-packaged dry-aged beef was predicted to be less than 12.2 days. However, the shelflife should be less than 6.3 days, considering the result of sensory quality (odor, taste, and overall acceptance). No significant change in visible appearance was also observed during 7 days of storage. The results suggest that the present quality indicators for meat spoilage (pH, VBN, and TBARS) should be re-considered for dry-aged beef, as its characteristics are different from those of fresh and/or wet-aged beef.

• Korean Journal of Food Science and Technology
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• v.26 no.6
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• pp.819-823
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• 1994

For the development of rice-derived fat replacing ingredient, low dextrose equivalent (D.E.) malto dextrin was prepared by enzyme hydrolysis, and its physical and rheological properties were studied. The molecular sizes of rice maltodextrin were measured by gel permeation chromatography on Sephadex G-50. Gel permeation column chromatograms showed a large single peak, suggesting a limited hydrolysis, and the average degree of polymerization decreased from 72.8 for 3 D.E. maltodextrin to 48.7 for 6 D.E. maltodextrin. Cold water solubility of maltodextrin was increased with increasing D.E. value and its values ranged from 47.3% to 71.3%. 8% solution of rice maltodextrin showed pseudoplastic behavior. Flow behavior index was decreased as D.E. value was increased.

• Korean Journal of Food Science and Technology
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• v.20 no.6
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• pp.845-849
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• 1988

A laboratory scale storage facility consisting of a cold room, sample jars and a ventilation device was designed and built. Storaging sample jars (1.7 l) for fruit were fabricated with transparent acryl and provided with a constant air flow. For the supplying of air to sample jars, the air distributing system was built with solenoid valves, an air precooling coil and a pressure equalizing tank. To provide the programmable storaging environment of the facility a microprocessor-based controller was designed and installed. The controller was built with the 8 bit microprocessor (Z-80), EPROM, RAM, programmable peripheral interface(8255 PPI), and A/D converter. Softwares for the auto-temperature measurement and control of the storage system were developed and systemized in ROM. The automated storage system was applied to citrus storage, and the temperature of the storage facilities was successfully acquisited to the computer and controlled.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.2
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• pp.235-251
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• 1997

A numerical simulation on the combined natural convection and radiation is carried out in a partially open rectangular enclosure with a heater by using the finite volume and the S-8 discrete ordinate methods. The fluid inside the enclosure is considered as an absorbing, emitting and anisotropic scattering media. The heater causes a natural circulation of the fluid (10$^{5}$ $^{9}$ ) which results in significant in-flow of the ambient cold fluid through the partially open wall. Comparing the results of pure convection with those of the combined convection- radiation, the combined heat transfer results with small Planck numbers (P$_{l}$ <1.0) show much stronger circulation than those of the pure convection, and the fluid circulation is more evident for larger Rayleigh numbers. When one of three radiative properties - the medium absorption coefficient, the wall reflectivity, and the scattering albedo - increases, the fluid circulation and the heat transfer in the enclosure are reduced. The location of the heater and the open ratio of the right wall are also shown to affect the fluid circulation and heat transfer significantly. However, the anisotropy of the scattering phase function is shown to be unimportant for the fluid circulation and heat transfer within the enclosure considered in this study.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.8
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• pp.687-693
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• 2018

In this paper, we studied on the thermal design of the active antenna system for stable performance considering thermal reliability. The active antenna has high performance and heat flux elements in T/R modules. Thermal heating of elements in T/R modules has to be dissipated effectively and the antenna has to be operated over the range of suggested temperature by the thermal design. T/R modules of high heat flux in the active antenna can be dissipated effectively by liquid cooling. In this study, we studied on the thermal design including the liquid cooling system to optimize the thermal performance of the active antenna. And the thermal design was verified by numerical analysis.