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Effects of Supercritical Environment on Hydrocarbon-fuel Injection

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Journal of Thermal Science 2017年第2期26卷 183-191页

作者： Bongchul Shin Dohun Kim min.son.Jaye Koo Graduate School Korea Aerospace UniversityGoyangRepublic of Korea School of Aerospace and Mechanical Engineering Korea Aerospace UniversityGoyangRepublic of Korea

In this study, the effects of environment conditions on decane were investigated. Decane was injected in subcritical and supercritical ambient conditions. The visualization chamber was pressurized to 1.68 MPa by using nitrogen gas at a temperature of 653 K for subcritical ambient conditions. For supercritical ambient conditions, the visualization chamber was pressurized to 2.52 MPa by using helium at a temperature of 653 K. The decane injection in the pressurized chamber was visualized via a shadowgraph technique and gradient images were obtained by a post processing method. A large variation in density gradient was observed at jet interface in the case of subcritical injection in subcritical ambient conditions. Conversely, for supercritical injection in supercritical ambient conditions, a small density gradient was observed at the jet interface. In a manner similar to that observed in other cases, supercritical injection in subcritical ambient conditions differed from supercritical ambient conditions such as sphere shape liquid. Additionally, there were changes in the interface, and the supercritical injection core width was thicker than that in the subcritical injection. Furthermore, in cases with the same injection conditions, the change in the supercritical ambient normalized core width was smaller than the change in the subcritical ambient normalized core width owing to high specific heat at the supercritical injection and small phase change at the interface. Therefore, the interface was affected by the changing ambient condition. Given that the effect of changing the thermodynamic properties of propellants could be essential for a variable thrust rocket engine, the effects of the ambient conditions were investigated experimentally.

关键词： Decane Jet Subcritical Supercritical Visualization

Deformation prediction of porcelain-enameled steels with strain history by press formin. and high-temperature behavior of coating layer

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中国有色金属学会会刊：英文版 2012年第S3期22卷 838-844页

作者： Young-Ki son.Chan-Joo LEE Jung-min.LEE Byung-min.KIM School of Mechanical Engineering Pusan National University Dongnam Regional Division Korea Institute of Industrial Technology

Porcelain enamel coatings were widely applied for the protection of steel products because they offered high corrosion protection,resistance to heat and abrasion,high hardness,hygiene and ease of *** typical process to produce enameled steels is roughly divided into two stages:the first stage consists of a formin. process to give the desired shape to a steel substrate,and the second stage consists of a firing process to bond enamel frits on the *** firing process requires a high temperature above 800 °C,which may lead to austenitic transformation and severe thermal deformation of the steel *** aim of this study is to develop a finite element analysis (FE analysis) technique to predict the mechanical and thermal deformations of the enameled steels during formin. and any further enameling process,including *** FE analysis involves analyzing the strain history of the steel substrate,which comprises the stress and thickness distributions of the substrate and its deformed shape,and the high-temperature behavior of the enamel coating *** validity of the FE analysis is verified through the U-bending test and firing test with various numbers and positions of enamel coating layers on the *** results reveal that the FE analysis results agree well with the experimental results with 8% error.

关键词： porcelain enamel firing process finite element analysis enameled steel thermal deformation

Conceptual Design for a Kerosene Fuel-rich Gas-generator of a Turbopump-fed Liquid Rocket Engine

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Journal of Thermal Science 2012年第5期21卷 428-434页

作者： min.son.Jaye Koo Won Kook Cho Eun Seok Lee Graduate Student Korea Aerospace UniversityGoyang Republic of Korea School of Aerospace and Mechanical Engineering Korea Aerospace UniversityGoyang Republic of Korea Korea Aerospace Research Institute Daejeon Republic of Korea

A design method for a kerosene fuel-rich gas-generator of a liquid rocket engine using turbopumps to supply propellant was performed at a conceptual level. The gas-generator creates hot gases, enabling the turbine to operate the turbopumps. A chemical non-equilibrium analysis and a droplet vaporization model were used for the estimation of the burnt gas properties and characteristic chamber length. A premixed counter-flow flame analysis was performed for the prediction of the burnt gas properties, namely the temperature, the specific heat ratio and heat capacity, and the chemical reaction time. To predict the vaporization time, the Spalding model, using a single droplet in convective condition, was used. The min.mum residence time in the chamber and the characteristic length were calculated by adding the reaction time and the vaporization time. Using the characteristic length, the design methods for the fuel-rich gas-generator were established. Finally, a parametric study was achieved for the effects of the O/F ratio, mass flow rate, chamber pressure, initial droplet temperature, initial droplet diameter and initial droplet velocity.

关键词： Liquid rocket engine Conceptual design Fuel-rich gas-generator Sensitivity analysis

Development of Prelimin.ry Design Program for Combustor of Regenerative Cooled Liquid Rocket Engine

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Journal of Thermal Science 2011年第5期20卷 467-473页

作者： Won Kook Cho Woo Seok Seol min.son.min.Kyo Seo Jaye Koo Korea Aerospace Research Institute DaejoenRepublic of Korea Graduate Student Korea Aerospace UniversityGoyangRepublic of Korea School of Aerospace and Mechanical Engineering Korea Aerospace UniversityGoyangRepublic of Korea

An integrated program was established to design a combustor for a liquid rocket engine and to analyze regenerative cooling results on a prelimin.ry design *** of burnt gas from a kerosene-LOx mixture in the combustor and rocket performance were calculated from CEA which is the code for the calculation of chemical *** heat transfer of regenerative cooling was analyzed by using SUPERTRAPP code for coolant properties and by one-dimensional correlations of the heat transfer coefficient from the combustor liner to the *** of the combustors of F-1 and RS-27A engines were designed from similar input data and the present results were compared to actual data for ***,the combustors of 30 tonf class,75 tonf class and 150 tonf class were designed from the required thrust,combustion chamber,exit pressure and mixture ratio of *** wall temperature,heat flux and pressure drop were calculated for heat transfer analysis of regenerative cooling using the profiles.

关键词： Liquid rocket engine Prelimin.ry design of Combustor Regenerative cooling

Corticoreticular tract lesion in children with developmental delay presenting with gait dysfunction and trunk instability

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Neural Regeneration Research 2017年第9期12卷 1465-1471页

作者： Yong min.Kwon Jessica Rose Ae Ryoung Kim Su min.son Department of Physical Medicine and Rehabilitation College of Medicine Yeungnam University Department of Orthopedic Surgery College of Medicine Stanford University

The corticoreticular tract （CRT） is known to be involved in walking and postural control. Using diffusion tensor tractography （DTT）, we investigated the relationship between the CRT and gait dysfunction, includ- ing trunk instability, in pediatric patients. Thirty patients with delayed development and 15 age-matched, typically-developed （TD） children were recruited. Fifteen patients with gait dysfunction （bilateral trunk instability） were included in the group A, and the other 15 patients with gait dysfunction （unilateral trunk instability） were included in the group B. The Growth Motor Function Classification System, Functional Ambulation Category scale, and Functional Ambulation Category scale were used for measurement of functional state. Fractional anisotropy, apparent diffusion coefficient, fiber number, and tract integrity of the CRT and corticospinal tract were measured. Diffusion parameters or integrity of corticospinal tract were not significantly different in the three study groups. However, CRT results revealed that both CRTs were disrupted in the group A, whereas CRT disruption in the hemispheres contralateral to clinical mani- festations was observed in the group B. Fractional anisotropy values and fiber numbers in both CRTs were decreased in the group A than in the group TD. The extents of decreases of fractional anisotropy values and fiber numbers on the ipsilateral side relative to those on the contralateral side were greater in the group B than in the group TD. Functional evaluation data and clinical manifestations were found to show strong correlations with CRT status, rather than with corticospinal tract status. These findings suggest that CRT status appears to be clinically important for gait function and trunk stability in pediatric patients and DTT can help assess CRT status in pediatric patients with gait dysfunction.

关键词： nerve regeneration corticoreticular tract corticospinal tract gait trunk diffusion tensor Trunk Control Measurement Scale Functional Ambulation Category Growth Motor Function Classification System cerebral palsy motor neural regeneration

Verification on Spray Simulation of a Pintle Injector for Liquid Rocket Engine

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Journal of Thermal Science 2016年第1期25卷 90-96页

作者： min.son.Kijeong Yu Kanmaniraja Radhakrishnan Bongchul Shin Jaye Koo Korea Aerospace University GoyangRepublic of Korea School of Aerospace and Mechanical Engineering Korea Aerospace UniversityGoyangRepublic of Korea

The pintle injector used for a liquid rocket engine is a newly re-attracted injection system famous for its wide throttle ability with high efficiency. The pintle injector has many variations with complex inner structures due to its moving parts. In order to study the rotating flow near the injector tip, which was observed from the cold flow experiment using water and air, a numerical simulation was adopted and a verification of the numerical model was later conducted. For the verification process, three types of experimental data including velocity distributions of gas flows, spray angles and liquid distribution were all compared using simulated results. The numerical simulation was performed using a commercial simulation program with the Eulerian multiphase model and axisymmetric two dimensional grids. The maximum and min.mum velocities of gas were within the acceptable range of agreement, however, the spray angles experienced up to 25% error when the momentum ratios were increased. The spray density distributions were quantitatively measured and had good agreement. As a result of this study, it was concluded that the simulation method was properly constructed to study specific flow characteristics of the pintle injector despite having the limitations of two dimensional and coarse grids.

关键词： Spray characteristics Pintle injector Simulation Experiment Liquid rocket engine

The effect of fertilization on early growth of konara oak and Japanese zelkova seedlings planted in a harvested pitch pine plantation

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Journal of Forestry Research 2016年第4期27卷 863-870页

作者： A-Ram Yang Jaehong Hwang min.Seok Cho Yowhan son Forest Practice Research Center National Institute of Forest Science Department of Environmental Science and Ecological Engineering Graduate School Korea University

We determin.d a suitable amount of fertilizer for konara oak（Quercus serrata） and Japanese zelkova（Zelkova serrata） planted in a harvested pitch pine（Pinus rigida） plantation. Two-year-old bare-root seedlings of konara oak and one-year-old containerized seedlings of Japanese zelkova were planted in April 2011. Three plots were established for each tree species to evaluate each of three fertilization applications. Solid compound fertilizer（N：P：K = 3：4：1） was applied yearly in three amounts（control： no fertilization, F1： 180 kg ha-1, and F2：360 kg ha-1）, every May from 2011 to 2013. We measured the root collar diameter and height, and analyzed the compartmental N and P concentrations. Compartmental N concentrations of konara oak and Japanese zelkova were not consistent based on amount of fertilization. However,the compartmental P concentrations of konara oak and Japanese zelkova were significantly different in the order of F2, F1, and control. Although the differences in growth of konara oak appeared after 3 years of fertilization,Japanese zelkova showed differences after only 2 years of fertilization owing to differences in seedling type. Growth of konara oak was affected by fertilization at F1 and F2 in2013. However, growth of Japanese zelkova was affected only at F2. Nutrient demand of Japanese zelkova appeard to be higher than that of konara oak, at least during the early growing period. Results from this study could be practically used in harvested pitch pine plantations to determin. appropriate fertilization regimes.

关键词： fertilization Japanese plantation fertilizer pitch planted seedling practically collar yearly

Simultaneous surface modification method for 0.4Li2MnO3-0.6LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion batteries： Acid treatment and LiCoPO4 coating

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Nano Research 2017年第12期10卷 4210-4220页

作者： min.Joon Lee Eunsol Lho Pilgun Oh Yoonkook son.Jaephil Cho Department of Energy Engineering School of Energy and Chemical Engineering Ulsan National Institute of Science and Technology(UNIST) Ulsan 44919 Republic of Korea

Li-rich layered cathode materials have been considered the most promising candidates for large-scale Li-ion batteries due to their low cost and high reversible capacity. However, these materials have many drawbacks that hinder commercialization, such as low initial efficiency and cyclability at elevated temperatures. To overcome these barriers, we propose an efficient and effective surface modification method, in which chemical activation （acid treatment） and LiCoPO4 coating were carried out simultaneously. During the synthesis, the lithium ions were extracted from the lattice, leading to improved Columbic efficiency, and these ions were used for the formation of LiCoPO4. The Ni and Co doped spinel phase was formed at the surface of the host material, which gives rise to the facile pathway for lithium ions. The LiCoPO4 and highly doped spinel on the surface acted as double protection layers that effectively prevented side reactions on the surface at 60℃. Moreover, the transition metal migration of the modified cathode was weakened, due to the presence of the spinel structure at the surface. Consequently, the newly developed Li-rich cathode material exhibited a high 1st efficiency of 94%, improved capacity retention of 82% during 100 cycles at 60℃, and superior rate capability of 62% at 12C （1C = 200 mA/g） rate at 24℃. In addition, the thermal stability of the modified cathode was significantly improved as compared to that of a bare counterpart at 4.6 V, showing a 60% decrease in the total heat generation.

关键词： lithium ion battery cathode material Li-rich material electrochemistry surface modification

Improved speech absence probability estimation based on environmental noise classification

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Journal of Central South University 2012年第9期19卷 2548-2553页

作者： son.Young-ho LEE Sang-min Department of Electronic Engineering Inha University Institute for Information and Electronics Research Inha University

An improved speech absence probability estimation was proposed using environmental noise classification for speech enhancement.A relevant noise estimation approach,known as the speech presence uncertainty tracking method,requires seeking the "a priori" probability of speech absence that is derived by applying microphone input signal and the noise signal based on the estimated value of the "a posteriori" signal-to-noise ratio(SNR).To overcome this problem,first,the optimal values in terms of the perceived speech quality of a variety of noise types are ***,the estimated optimal values are assigned according to the determin.d noise type which is classified by a real-time noise classification algorithm based on the Gaussian mixture model(GMM).The proposed algorithm estimates the speech absence probability using a noise classification algorithm which is based on GMM to apply the optimal parameter of each noise type,unlike the conventional approach which uses a fixed threshold and smoothing *** performance of the proposed method was evaluated by objective tests,such as the perceptual evaluation of speech quality(PESQ) and composite *** was then evaluated by a subjective test,namely,mean opinion scores(MOS) under various noise *** proposed method show better results than existing methods.

关键词： speech enhancement soft decision speech absence probability Gaussian mixture model (GMM)