• 대한기계학회논문집B
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• 제27권9호
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• pp.1273-1281
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• 2003

The present study is mainly motivated to investigate the vaporization, auto-ignition, and combustion of liquid fuel spray injected into high pressure environment. The unsteady, multi-dimensional models were used for realistic simulation of spray as well as prediction of accurate ignition delay time. The Separated Flow (SF) model which considers the finite rate of transport between liquid and gas phases was employed to represent the interactions between spray and gas field. Among the SF models, the Discrete Droplet Model (DDM) which simulates the spray using finite number of representative samples of discrete droplets was adopted. The Eulerian-Lagrangian formulation was used to analyze the two-phase interactions. In order to predict an evaporation rate of droplet in high pressure environment, the high pressure vaporization model was applied using thermodynamic equilibrium and phase equilibrium at droplet surface. The high pressure effect as well as high temperature effect was considered in the calculation of liquid and gas properties. In case of vaporization, an interaction between droplets was studied through the simulation of spray. The interaction is shown up differently whether the ambient gas field is at normal pressure or high pressure. Also, the characteristics of spray behavior in high pressure environment were investigated through the comparison with normal ambient pressure case. In both cases, the spray behaviors are simulated through the distributions of temperature and reaction rate in gas field.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.1511-1516
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• 2009

In recent years, the large-scale shaft have been appling in domestic mine for mass production using a large machine, the safety of mine also have been increasing. And the new trial that shotcrete of tunnel field was apply to mine support was progressed. But, the conditions of domestic mine was different from that of tunnel, so, the batch plant of tunnel could not be installed in mine field because of low economical efficiency and difficulty for selection of site. Ready-mixed Shotcrete that mixed with high quality materials and could be controled shotcrete quality is producted in plants and transported to field, so do not need to batch plant. In this study, The Field test of the Ready-mixed Shotcrete was performed in the large-scale mine and was compared with the quality of Field mix shotcrete. As the result of the Field test, compressive strength and rebound of Ready-mixed Shotcrete were superior to these of Field mix shotcrete.

• 한국초전도ㆍ저온공학회논문지
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• 제21권1호
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• pp.1-5
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• 2019

The pulsed field magnetization of the short-circuited soldered double pancake coil made of stabilized commercial high-Tc superconductor (HTS) tape is experimentally studied. The evolution of the shielding current induced by the pulsed field and the trapped field after the pulsed magnetization was measured at 77 K. It is shown that the trapped field in the coil is close to the value reached in the field cooling process and reduces weakly at 5-fold increasing of pulsed field amplitude. The current relaxation at t~2 ms after the pulse is defined by the current sharing between the tape's copper coating and the $YBa_2Cu_3O_{7-d}$ layer. In the intermediate time scale (1 s < t < 100 s) the flux creep in HTS layer dominates. At t > 100 s the current's relaxation is defined by the resistance of soldered joint between tapes.

• Wind and Structures
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• 제28권4호
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• pp.239-253
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• 2019

Accurate numericalsimulation of wind field over complex terrain is an important prerequisite for wind resource assessment. In this study, numerical simulation of wind field over complex terrain was further carried out by taking the complex terrain around Siu Ho Wan station in Hong Kong as an example. By artificially expanding the original digital model data, Gambit and ICEM CFD software were used to create high-precision complex terrain model with high-quality meshing. The equilibrium atmospheric boundary layer simulation based on RANS turbulence model was carried out in a flat terrain domain, and the approximate inflow boundary conditions for the wind field simulation over complex terrain were established. Based on this, numerical simulations of wind field over complex terrain under different inflow wind directions were carried out. The numerical results were compared with the wind tunnel test and field measurement data for land and sea fetches. The results show that the numerical results are in good agreement with the wind tunnel data and the field measurement data which can verify the accuracy and reliability of the numerical simulation. The near ground wind field over complex terrain is complex and affected obviously by the terrain, and the wind field characteristics should be fully understood by numerical simulation when carrying out engineering application on it.

• 한방비만학회지
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• 제22권1호
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• pp.21-29
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• 2022

Objectives: This study aimed to examine the changes in ingredients according to its cultivation method by examining the content of saponin and non-saponin components of ginseng. Methods: Ginseng saponin component analysis was compared and reviewed using the high-performance liquid chromatography method, and acidic polysaccharide component was measured using the carbazole sulfuric acid method. Results: The comparative analysis of ginseng saponin content of 4 and 6 years old fresh ginseng showed the following results. According to the cultivation method, upland field cultivation fresh ginseng showed higher average content of crude saponin than paddy field cultivation fresh ginseng. Whereas, paddy field cultivation fresh ginseng showed higher average content of total saponin than upland field cultivation fresh ginseng. Ginsenoside Rb1 showed higher content of paddy field cultivation fresh ginseng than upland field cultivation fresh ginseng in 6 years old ginseng. However, it showed higher content of upland field cultivation fresh ginseng than paddy field cultivation fresh ginseng in 4 years old ginseng. Additionally, ginsenoside Rg1 showed higher content of paddy field cultivation fresh ginseng than upland field cultivation fresh ginseng in 6 years old ginseng, whereas upland field cultivation fresh ginseng showed higher content of paddy field cultivation fresh ginseng in 4 years old ginseng. The effect on the content of ginseng saponins and acidic polysaccharides according to paddy field and upland field cultivation methods is considered to be small. Conclusions: The paddy field cultivation method, which is more efficient in production cost due to depletion of farmland and long-distance cultivation, is considered to be an economical cultivation method.

• Journal of Ginseng Research
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• 제15권3호
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• pp.197-199
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• 1991

Growth of ginseng and physical properties of soil were compared with bed height in experimental plots of sand loam for four year and clay loam soil for three year old ginseng plants, respectively. Field survey was also carried out to compare yield and soil physical properties with bed height in the same fold of six years old ginseng fields. High yield of ginseng root was observed at high bed both in the experimental plots and field survey as well. The rate of rusty root was significantly reduced at high bed. Soil porosity increased but soil hardness decreased at high bed.

• Investigative Magnetic Resonance Imaging
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• 제11권2호
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• pp.95-102
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• 2007

목적: 3.0 Tesla와 같은 고 자장에서 고해상도의 나선주사영상을 얻기 위해서는 주자장을 균일하게 만들어야 한다. 특히, 나선주사영상인 경우 스핀-에코펄스 시퀀스(SE)나 경사자계 에코 펄스 시퀀스(GE)에 비하여 측정 시간이 길기 때문에 주자장이 균일하지 못하다면, off-resonance 현상으로 영상의 blur가 심해진다. 본 연구에서는 빠른 시간 안에 주자장을 균일하게 할 수 있는 고차(Higher-order) shimming방법을 모색했다. 대상 및 방법: 3 Tesla 자기 공명 영상시스템에서 고해상도의 나선주사영상을 얻기에 적합할 정도의 균일한 주자장을 빠른 시간 안에 만들기 위해, 한번의 스캔으로 axial, sagittal, coronal 방향의 불균일도 map을 구할 수 있는 펄스 시퀀스를 제안하였고, 불균일도 map으로부터 spherical harmonics 분석를 통해 shim 코일에 적절한 전류를 인가하여 주자장을 균일하게 만들었다. 결과: 3 Tesla 자기 공명 영상 시스템에서 주자장의 불균일도는 주자장의 크기에 비례하게 된다. 제안한 펄스 시퀀스로 얻은 영상을 이용하여 불균일도 Map을 만들 수 있었고, 이를 spherical harmonics 분석을 하여 2-3회의 고차 shimming으로 불균일한 자장을 균일하게 만들 수 있었다. 제안된 고차 shimming 방법은 전체 영상 영역 뿐만 아니라 선택한 영역에 대해서만 적용도 가능하기 때문에 국부 영역에 대한 고차 shimming이 가능하다. 고차 shimming이 적용되어 주자장이 균일하게 개선된 상태에서 고해상도의 나선주사영상을 얻을 수 있었다. 결론: 3 Tesla 고자장 자기 공명 영상 시스템에서 주자장의 불균일도를 개선하기 위한 펄스 시퀀스와 알고리즘을 통해 주자장의 불균일도를 빠른 시간 안에 개선할 수 있었다. 주자장의 불균일도를 효과적으로 개선함으로써, 고해상도의 나선주사 영상을 얻을 수 있었다.

• 한국생산제조학회지
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• 제4권3호
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• pp.25-30
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• 1995

A new finishing process, magnetic-electrolytic-abrasive polishing(MEAP), combining Lorentz' force effect in the traditional electrolytic finishing process was developed to realize the high efficiency as well as high surface quality of finishing . The paper describes the theoretical basis about the modification of electrolytic ions motion by the magnetic field. The effect of magnetic field on the electrolytic process was discussed was and analyzed from the result of model test.

• 대한수학회논문집
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• 제22권3호
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• pp.453-464
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• 2007

A computationally efficient numerical scheme is presented for the phase-field model of two-phase systems for anisotropic interfacial energy. The scheme is solved by using a nonlinear multigrid method. When the coefficient for the anisotropic interfacial energy is sufficiently high, the interface of the system shows corners or missing crystallographic orientations. Numerical simulations with high and low anisotropic coefficients show excellent agreement with exact equilibrium shapes. We also present spinodal decomposition, which shows the robustness of the pro-posed scheme.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2009년도 정보통신설비 학술대회
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• pp.227-230
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• 2009

In this paper, the results of field testing of high-speed power line in-home networking in Korea are reported. When multiple networks share a common channel, they can interfere destructively and reduce system capacity. This is major problem in-home power line communications, especially in MDU deployments. The effects of neighboring network interference in power line communications are reported.