• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.6
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• pp.773-778
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• 2007

This study was performed to develop a more simple and convenient heat treatment process for increasing heating temperature than the traditional 9-times steaming process for Rehmanniae radix Preparata (R. radix P.). The R. radix was heated to various temperatures (110, 120, 130, 140 and $150^{\circ}C$) for different lengths of time (1, 2, 3, 4 and 5 hr). Chromaticity, free sugar, amino acid, catalpol and 5-HMF (5-hydroxy-methyl-2-furaldehyde) content of water extracts of R. radix P. were analysed. With increasing heating temperature and time, the L, a and b-value of samples gradually decreased. Fructose and glucose contents were increased to $120^{\circ}C$ for 5 hr (5.21 and 6.67%, respectively) with no changes afterward. Sucrose content was not detected after $130^{\circ}C$. Total amino acid was increased to $140^{\circ}C$ and decreased afterward. The maximum total amino acid content was 4,172 mg/100 g at $140^{\circ}C$ for 2 hr (R. radix L.: 3,029 mg/100 g). The catalpol was decreased to $130^{\circ}C$ for 1 hr and not detected afterward. The 5-HMF content increased with increasing heating temperature and time. The maximum content of 5.HMF was 2.5% in $150^{\circ}C$ for 5 hr. Hence, it can be suggested that the heat treatment at $130^{\circ}C$ for 2 hr or more is the most optimum processing conditions, instead of the traditional 9.times steaming process.

• Applied Biological Chemistry
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• v.47 no.4
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• pp.409-413
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• 2004

We have studied quality changes of fully ripe fruit of Korean native pumpkin 'Yangsan' regarding the following parameters: pH, sugar content, weight, water content, contents of crude protein and amino acids during 60 days storage at room temperature. As the results, there was no changes in sugar contents according to the storage period, but pH was changing to a little acidic direction with slight decrease in weight and water content. Contents of total crude proteins and comprising amino acids were increased during the storage period. The main contents of amino acids of the Korean native pumpkin, Yangsan, were glutamic acid (15.5%), aspartic acid (10.1%), lysine (8.7%), valine (7.5%), leucine (7.1%) and alanine (6.6%), which were not highly influenced during storage period. Additionally we have investigated the content of free amino acids and color changes during processing of Yangsan under high temperature at $121^{\circ}C$ and high pressure at $1\;kg/cm^2$. In fully ripe fruits, a total of 29 kinds of free amino acids were detected including 8 kinds of essential amino acids (histidine, isoleucine, leucine, lysine, phenylalanine, methionine, threonine and valine). More than 35% of total free amino acids were aspartic acid (20.3%) and asparagine (15.4%); ornithine, citrullin, and arginine, which are related to Ornithine cycle, were also detected in fully ripe fruits. But when treated with high temperature and high pressure, glutamic acid and arginine were decreased rapidly whereas ammnonium chloride was relatively increased. Moreover "b" value as yellow color indicator was decreased from 17.45 to 9.14 while treated for 60 minutes with high temperature and pressure, caused by the degradation of ${\beta}-carotene$ and other yellowish pigments in Yangsan.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.4
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• pp.38-45
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• 2007

A liquid rocket engine fuel-rich gas generator has been developed for the first time in the country, which can produce combustion gas over the rate of 4 kg/s at 900 K and 58 bar. The gas is not only for driving a turbopump but also for providing heat source for propellant supply tanks. The final design of the gas generator had been fixed based on the concept and preliminary development tests, and was validated through structure and heat transfer analysis. The manufacturing involved precision machining, surface finish, and special welding technique. The final assessment on the characteristics of ignition and combustion had been carried out for two different versions of injector heads. This concluded that the present product satisfies the development requirements such as spatial temperature distribution and the development has been successful.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.561-565
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• 2009

The performance of supersonic impulse turbine was investigated experimentally. Experiment was performed with the compressed air instead of the high temperature burned gas because of the limitation of test facility and danger. As a result of the experiment with the compressed air, the performance in the real gas(burned gas) was predicted by the similarity method. The nozzle area of prototype turbine was calculated based on the real gas. So, it is difficult to satisfy the similarity conditions completely. Two similarity conditions were set and the design point for real gas was existed between two similarity conditions. And, the new turbine test model with calculated nozzle area based on the compressed air was tested. Therefore, similarity point of the new turbine test model was also existed between above two similarity points. It means that the design point for real gas was similar to the test point with the new turbine model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.7
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• pp.653-658
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• 2016

High pressure components of a gas turbine engine are generally made of nickel-base superalloys, using precision casting process due to complicated geometries with intricate channels and cooling holes. Turbine components manufactured from directionally solidified and single crystal materials have columnar grains; however, it is found that the crystals do not grow in its preferred direction, although the orientation can be controlled. This anisotropy can lead to the variations of elastic and Hill's parameters in constitutive equations, and they alter stress distributions and the low cycle fatigue life. We aims to evaluate the effects of perturbed crystal orientations on the structural integrity of a directionally solidified nozzle using low cycle fatigue life. We also attempt to show the necessity for the control of allowed manufacturing errors and stochastic analysis. Our approaches included conjugate heat transfer and structural analysis, along with low cycle fatigue life assessment.

• Analytical Science and Technology
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• v.6 no.2
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• pp.149-156
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• 1993

The formation of the graphite spherulites has been studied experimentally in the Ni-C liquid under high pressure and temperature. In the diamond-stable region the graphite spherulites were formed and grew stably. They were not the polycrystalline particles but the single crystals of the fullerene-type, respectively, grown spirally with much imperfection. And they were proved to be in a mixture state of carbon atoms with $sp^2$- and $sp^3$-bonding by an Auger electron spectroscope and a high resolution transmission electron microscope. As the pressure decreased from the diamond-stable region to the graphite-stable region, the shape of the graphite particles changed gradually from the sphere to the flaky shape. The formation of the graphite spherulites was attributed to the stable existence of the carbon atoms with $sp^3$ bonding in the diamond-stable region. The formation of the large fullerene-type graphite spherulites with much imperfection is well agreed with Kroto's prediction for growth of the giant fullerene.

• Polymer(Korea)
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• v.35 no.1
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• pp.1-6
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• 2011

Pressurized high temperature plastic resin flows into the cavity of mold and is solidified in injection molding process. Residual stress is being developed in injection molded part because of high temperature variations and high pressure. Developed residual stress relaxes as time goes. Consequently this makes part deformed and deteriorates quality of product. A measurement method of residual stress for injection molded transparent articles has been investigated using photoelasticity. Light, a composite of electromagnetic waves, is purified into a single wave by a polarized film. When this wave passes through the specimen, birefringence is developed according to the level of residual stress in the specimen and color fringed pattern appears after the second polarized film. Residual stress in the injection molded transparent flat a part has been measured quantitatively using the color fringed pattern. Optical characteristics have been a part also predicted by computer simulation and compared with experimental results.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.2
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• pp.39-45
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• 2006

In liquid rocket engine turbopump, it is difficult to evaluate turbine performance for high pressure, high temperature circumstance. Turbine test is often done by using air at similarity condition so that the turbine can be tested at lower risk. This paper describes an air similarity test program of liquid rocket engine turbopump turbine. A test facility has been built to evaluate aerodynamic performance of turbines. The test facility consists of high pressure air supply system, mass flow rate measuring nozzle, test section, hydraulic break, exit orifice for pressure control, instrumentation and control system. This paper also presents how to decide the similarity conditions of the turbine test and describes how to control test conditions. Relative standard deviation of measurement parameter was less than 1% and measured turbine efficiency corresponded with analysis result within 2%.

• Aerospace Engineering and Technology
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• v.1 no.1
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• pp.163-172
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• 2002

The turbine system composed of a nozzle and a rotor is used to drive turbopumps while gas passes through the nozzle, potential energy is converted to kinematic energy, which forces the rotor blades to spin. In this study, an aerodynamic design of a turbine system is investigated using compressible fluid dynamic theories with some pre-determined design requirements (i.e.,pressure ratio, rotational speed, required power etc.) obtained from a liquid rocket engine (L.R.E.) system design. For simplicity of a turbine system, impulse-type rotor blades for open type L.R.E. have been chosen. Usually, the open-type turbine system requires low mass flow rate compared to the close-type system. In this study, a partial admission nozzle is adopted to maximize the efficiency of the close-type turbine system. A design methodology of the a turbine system has been introduced. Especially, a partial admission nozzle has been designed by means of simple empirical correlations between efficiency and configuration of the nozzle. Finally, a turbine system design for a 10 ton thrust level of L.R.E is presented.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.5
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• pp.79-86
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• 2014

A turbopump real-propellant test facility(TPTF) is to verify the performance of a turbopump unit(TPU) based on liquid oxygen and kerosene. One of the most important sub-facilities is a hot-gas generation system which makes the driving force of the TPU with an alcohol burner. The alcohol burner generates the required flow rates and temperature at the facility using high pressure air and ethanol. In the study, the verification tests of the alcohol burner which was manufactured entirely with domestic technology were performed and fabrication technique and operation skill for the burner could be obtained ahead of the construction of the facility. Two burners will be operated simultaneously for the real-propellant test of 75tf class turbopump and satisfy the power requirement from the turbine of the TPU.