• Tunnel and Underground Space
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• v.27 no.5
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• pp.324-332
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• 2017

In this paper, a numerical analysis of one-dimensional viscous fluid flow in a rock joint using UDEC code is performed to evaluate the effect of design parameters on injection performance. We consider injection pressure, fluid compressibility, time dependence of yield strength and viscosity of injected grout fluid, and mechanical deformation of joint as the design parameters, and penetration length and flow rate of injection are investigated as the injection performance. Numerical estimations of penetration length and flow rate were compared to analytical solution and were well comparable with each other. We showed that cumulative injection volume can be over-estimated by 1.2 times than the case that the time-dependent viscosity evolution is not considered. We also carried out a coupled fluid flow and mechanical deformation analysis and demonstrated that injection-induced joint opening may result in the increment of cumulative volume by 4.4 times of that from the flow only analysis in which joint aperture is kept constant.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.267-268
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• 2013

본 논문에서는 아날로그 필터회로의 신호 증폭비에 따른 센서리스 각추정 성능에 대해 분석 하였다. 신호 주입 센서리스에서 높은 주파수 신호 주입 방법이 선호되는데, 주입 주파수가 커질수록 시스템 임피던스가 증가한다. 따라서 낮은 주파수 주입방법과 동일한 각추정 성능을 얻기 위해서는 상대적으로 큰 주입전압이 필요하다. 특히 전동기의 돌극성이 작거나 ADC의 정밀도가 낮으면 각추정이 불가능한 경우도 존재 한다. 하지만 아날로그 필터회로를 이용하여 주입 주파수 신호를 증폭할 경우 작은 크기의 전압주입으로 각추정이 가능하다. 아날로그 대역통과필터의 신호 증폭비에 따른 최대 각에러 값을 모의 실험을 통해 비교하고, 실제 회로를 설계하여 센서리스 각추정 성능을 시험평가 하였다.

• Economic and Environmental Geology
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• v.43 no.2
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• pp.177-184
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• 2010

When cement grout is used for waterproofing of grounds, important roles are played by fluidity, particle size and bleeding. The most important element which determines their characteristics is the water/cement ratio of grout. Moreover in order to improve the efficiency of soil permeation, micro cement with a smaller average diameter is used in addition to ordinary portland cement. Besides the mixing ratio and cement diameter, the condition of ground is also of fundamental importance in the efficiency of permeation. In order to evaluate grout in terms of permeation ability into ground, we need a field test of grounting, which is cost and time consuming. In this paper we present a laboratory test method in which the suitability and efficiency of grouts are simply and more practically tested. In Korea neither a test standard nor devices are available to simulate grouting in a laboratory. We devised a grout injection equipment in which grouting was reproduced in the same condition with different materials, and suggested a standard for the production of specimens. Our tests revealed that the efficiency of injection increases with the water/cement ratio. We also found that more efficiently injected is the grout with the order of decreasing size; MS8000, micro cement, and ultra fine cements, and colloidal super cement.

• Journal of the Korean Geotechnical Society
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• v.33 no.9
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• pp.23-34
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• 2017

In order to develop urban underground spaces, even microcracks should be reinforced. In this paper, the grouting injection performance for microcracks was investigated considering the viscosity and particle size of the grouting materials, injection pressure, and crack width. There are two types of typical grouting materials used for filling micro-cracks. One is a chemical liquid grouting material which is a solution type and the other is a cementitious grouting material which is a suspension type. The injection performance of the grouting materials for microcracks is generally influenced by the viscosity, and the injection performance of the cementitious grouting material is additionally affected by the particle size. From laboratory tests, the viscosity was calculated inversely to provide a suitable viscosity measurement method for each grouting material. The groutability ratio based on the relationship between the crack width and the particle size was evaluated to estimate the grouting feasibility of the cementitous grouting material through microcracks.

• Journal of Energy Engineering
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• v.17 no.2
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• pp.67-76
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• 2008

A thermal-hydraulic integral effect test facility, ATLAS (Advanced Thermal-hydraulic Test Loop for Accident Simulation), has been constructed at KAERI (Korea Atomic Energy Research Institute). Recently several integral effect tests for the reflood period of a LBLOCA (Large Break LOss of Coolant Accident) of the APR1400 have been performed with the ATLAS. In the APR1400 a high flow condition is changed to a low flow condition due to an fluidic device during an operation of the SIT. As the self-controlled fluidic device was not installed in the ATLAS, a set of characterization tests was performed to simulate its injection capability from the SIT for the APR1400 simulation. In the ATLAS the required SIT flow rate in the high flow condition was acquired by installing orifices with an optimized flow area to throttle the SIT discharge line and the low flow condition was achieved by changing the opening of the flow control valve in the SIT injection line. The test results showed that the safety injection systems of the ATLAS could simulate the required high and low flow rates of the SIT for the APR1400 simulation efficiently.

• Journal of the Korean GEO-environmental Society
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• v.17 no.10
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• pp.23-31
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• 2016

Grout is generally operated with low viscous material similar to water, but grout for micro crack with high viscous materials and high injection pressure is gradually increased under the development of underground and subsea space. In order to estimate grouting injection performance considering crack width, viscosity of grouting materials, and injection pressure, there should be a reliable standard laboratory testing method. In this paper, theoretical injection mechanisms of grouting materials are presented as radial and linear flows, and laboratory testing apparatus are introduced to simulate each flow case. Radial flow is simulated by using acrylic disk plates which are able to spread grouting material radially from the center of the disk plates, and linear flow is simulated by using stainless parallel plane plates which are able to spread grouting material linearly. Apparatus are consist of upper and lower plates and industrial films with different thickness are placed between plates in order to simulate various crack widths. Laboratory verification tests with these apparatus were conducted with tap water (1cP at $20^{\circ}C$) as an injection material. Through the laboratory testing results, the best laboratory testing method is recommended in order to estimate grouting injection performance.

• Journal of Biomedical Engineering Research
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• v.25 no.3
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• pp.165-169
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• 2004

In Magnetic Resonance Electrical Impedance Tomography (MREIT), we inject current through electrodes placed on the surface of a subject and measure the induced magnetic flux density distribution using an MRI scanner. This requires a constant current source whose output pulses are synchronized with MR pulse sequences. In this paper, we present a design and performance analysis of a current source used in a 3.0T MREIT system. The developed current source was tested using a saline phantom. We found that its performance is satisfactory for the current MREIT system. We suggest future improvements for better SNR(signal-to-noise ratio).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1595-1602
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• 2010

A disposable drug infuser is used to provide drugs to patients who are not hospitalized; in this infuser, an elastic recovery force is exerted by a diaphragm made of a rubber-like materialsuch that a constant amount of drugs is provided to a patient. The drug infuser has to control the speed and amount of drugs to be released, as well as the overall duration for which they are to be administered. However, in a drug infuser with an elastic diaphragm, the infusion pressure depends on the amount of drug remaining within the infuser, and the amount of drug infused gradually decreases as the amount remaining in the infuser decreases. In this study, a finite element procedure involving the application of the fluid-structure interaction technique was developed and the performance of the elastic type disposable drug infuser was analyzed. The optimum design for ensuring that the infusion pressure remains constant throughout the duration of usage, including during infusion and discharge, was determined by this procedure.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.465-481
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• 2022

Rock grouting is important to improve the waterproof efficiency and mechanical strength of rock medium with joint for utilizing the underground rock space such as tunnel. The grouting materials typically has been used the cement materials, which represent Bingham fluid model. This model can express the relationship of viscosity and yield strength. In addition, it is dependent with elapsed time. The grouting injection performance can be deteriorated with an increase of viscosity and yield strength in the grouting process if the time dependence is ignored. Therefore, in this study, the characteristics of viscosity and yield strength were investigated according to water-cement ratio and time dependence in the laboratory test. Numerical simulation was carried out to investigate the grouting performance according to the time dependence of characteristics in terms of the viscosity model. Given the results, the grouting injected distance and cumulative grout volume were significantly decreased when the time dependence of grouting material was considered. This study, considering the characteristics according to the time dependence of viscosity and yield strength, will be meaningful to the design of grouting injection in field applications.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1998.10a
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• pp.193-208
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• 1998

본 논문에서는 써모싸이폰식 히트파이프의 열수송한계와 작동유체의 주입량이 파이프의 직경, 가열량 및 증발부와 응축부의 길이비 등에 따라 변화하므로 이러한 인자에 따른 적정 작동유체의 주입량과 가열량의 한계에 대해 고찰하였다. 특히 각종 전자부품의 냉각에 사용되는 히트파이프가 써모사이폰식이므로 사용작동유체에 대해 가열량에 따라 파이프의 직경예측이 가능토록 열수송한계특성에 대해 검토하고, 싸이리스터용은 증발부와 응축부의 길이비 변동이 심하므로 작동유체의 주입량이 중요한 성능인자로 작용하므로 길이비에 따른 작동유체의 주입량범위에 대해 기술하였다. 그리고 최적의 작동유체범위와 히트파이프의 증발열전달계수 및 응축열전달계수에 대한 실험으로부터 성능자료를 도출하여 이론해석과 비교검토하였다.