• Computers and Concrete
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• 제14권1호
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• pp.91-107
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• 2014

Using the principle of damage mechanics, zero-thickness pore pressure cohesive elements (PPCE) are used to simulate the casing-cement interface (CCI) and cement-rock interface (CRI). The traction-separation law describes the emergence and propagation of the PPCE. Mohr-coulomb criteria determines the elastic and plastic condition of cement sheath and rock. The finite element model (FEM) of delamination fractures emergence and propagation along the casing-cement-rock (CCR) interfaces during hydraulic fracturing is established, and the emergence and propagation of fractures along the wellbore axial and circumferential direction are simulated. Regadless of the perforation angle (the angle between the perforation and the max. horizontal principle stress), mirco-annulus will be produced alonge the wellbore circumferential direction when the cementation strength of the CCI and the CRI is less than the rock tensile strength; the delamination fractures are hard to propagate along the horizontal wellbore axial direction; emergence and propagation of delamination fractures are most likely produced on the shallow formation when the in-situ stresses are lower; the failure mode of cement sheath in the deep well is mainly interfaces seperation and body damange caused by cement expansion and contraction, or pressure testing and well shut-in operations.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.769-772
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• 2009

Diaphragm compressors are used for a hydrogen compression because it can achieve high gas pressure with high purity. But diaphragm's lifetime may depend on the shape of the cavity and deflection from fluctuation the pressure change, which is necessary to monitored. In this study, the gas and hydraulic oil pressure in the cavity were measured as piston speed varies for diaphragm compressor. The results show pressure change quantities were reduced and maximum pressure points are delayed as the piston moves faster. And the hydraulic pressure were elevated as gas pressure elevated. And the compression period was more faster than expansion period.

• 유공압시스템학회논문집
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• 제2권3호
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• pp.12-17
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• 2005

This paper presents a theoretical study of the delivery flow ripple produced by a swash plate type hydraulic piston pump for the purpose of developing a computer simulation program capable of predicting the pump source flow ripple accurately at the design stage. Particular attention has been paid to the development of the theoretical model by clarifying quantitatively the design influences of key parts of valve plate such as relief groove and pre-compression/expansion.

• 환경위생공학
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• 제12권3호
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• pp.103-109
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• 1997

As the quality of raw water deteriorates, a number of additional treatment techniques have been developed and adapted to water treatment for producing a safe and aesthetically satisfactory drinking water. So, BACFB process as pretreatment in water supply is to be effective to remove dissolved organics. This study performed to find out the effects of HRT and hydraulic characteristics on BACFB reactors in water supply. The flow type in reactor was a high dispersion with complete mixing. As superficial velocity was increased, bed expansion was closed to theoretical values. It was considered that below 30 min HRT could operated to ensure the removal of dissolved organics.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1995년도 가을 학술발표회 논문집
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• pp.61-67
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• 1995

The steam generator, one of the major components in the reactor coolant system, plays an important role in transferring the thermal energy made in the reactor during normal operation to the secondary side and producing steam to drive turbine. A hydraulic snubber system is used in order to protect the steam generator under the dynamic loading condition and to absorb the thermal expansion transmitted by the reactor coolant piping due to high temperature and pressure during normal operation. In this study, the model for a geometrical linkage system is presented to analyze the snubber stroke of the steam generator and the parameters in the snubber stroke analysis are investigated. A method to analyze lever ratio of the linkage system which is required in the process of determining the snubber stiffness value is also presented. To discuss the validation of the suggested analysis, the analysis results are compared with the measured data during the hot functional test for the standardized 1000 Mwe pressurized water reactor plant under the construction.

• 터널과지하공간
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• 제26권4호
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• pp.327-337
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• 2016

본 연구에서는 화강암 내부의 미세균열 분포에 따른 이방성이 수압파쇄실험 결과에 미치는 영향을 평가하였다. 압력증가율을 일정하게 설정하여 수압파쇄실험을 수행한 결과, 원주방향(주입정 방향과 직교)으로 리프트면이 분포한 시료의 파쇄압력이 가장 낮게 측정되었고, 이는 미세균열의 밀도가 높기 때문이다. 수압파쇄실험과정에서 시료 내부의 변화가 발생하는 주입압력의 크기와 유체 주입속도의 변화 또한 결방향에 따라 분포한 미세균열의 밀도와 관계가 있는 것으로 판단된다. 유체주입속도를 일정하게 설정하여 수압파쇄실험을 수행하였을 경우, 상대적으로 미세균열의 밀도가 높은 리프트면이 원주방향으로 분포된 시료에서 주입압력증가율이 낮게 나타났고, 유체가 침투될 수 있는 균열망이 상대적으로 적게 형성된 그레인면 및 하드웨이면이 원주방향으로 분포된 시료에서는 압력증가율이 높게 나타났다. X-ray CT 촬영을 통해 시료 내부에 생성된 균열의 방향을 확인한 결과, 대부분의 시료에서 리프트면 혹은 그레인면과 평행한 방향으로 균열이 생성된 것을 확인하였고, 이는 암석 내에 상대적으로 미세균열의 밀도가 높아서 분리성이 크기 때문이다.

• 한국구조물진단유지관리공학회 논문집
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• 제26권5호
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• pp.43-48
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• 2022

본 논문에서는 신축량이 크고 내구성이 우수한 모듈러 신축이음장치의 내진성능을 평가하기 위해 지진응답 거동해석과 지진거동모사실험을 수행하였다. 지진응답 거동해석은 한국(KS), 미국(AASHTO LRFD), 그리고 유럽(Eurocode)의 설계기준 응답스팩트럼을 적용하여 인공지진파를 생성하였다. 해석대상 교량은 경간 1,000m 사장교를 대상으로 각 기준에 대해 세가지의 인공지진파를 생성하였으며, 지진거동모사실험은 축방향과 횡방향의 동적 유압가력기를 사용하여 인공지진파를 재현하였다. 실험결과 축방향, 횡방향 및 양방향에 인공지진파를 재하하였을 때 신축이음의 거동 이상이나 파괴는 발생하지 않았으며, 신축이음장치의 지진거동에 대한 내구성 및 안전성을 확인하였다.

• 대한토목학회논문집
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• 제29권4D호
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• pp.483-489
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• 2009

진동 소음을 저감시키는 Fe-Mn 제진 금속을 이용하여 제작된 핑거형 신축이음장치의 피로 내구성을 평가하고자 유한 요소해석과 수직하중 피로시험을 실시하였다. 피로실험은 Fe-Mn 제진금속을 이용한 신축이음장치와 유압가력기(25tonf)를 사용하여 진행되었으며, 그 결과에 따르면 핑거형 신축이음장치에 수직하중을 인가하였을 경우 핑거에서 측정된 최대 응력은 237.6MPa 이며, 이는 제진 금속의 항복강도인 420MPa의 56.6%이였다. 제진 금속을 이용한 신축이음의 피로시험은 도로교 설계기준에 따라 재하위치(KS F 4425)와 재하판($57.7cm{\times}23.1cm$)의 크기가 설정되었고, 그에 따른 200만회 수직하중 피로 시험에 있어서 파괴거동을 나타내지 않았으며 그 내구성과 안전성을 확인하였다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.173-179
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• 1998

The piping system of a power plant suffers not only thermal expansion according to the temperature variation, but also many kinds of load: steady state vibrations due to the equipment operation or fluid flow, and transient vibrations due to the earthquake or explosion, etc. The snubbers are usually installed on the piping system to allow thermal expansion, and to reduce dynamic responses. Most snubbers are kinds of hydraulic and mechanical type, which can be degraded by leakage and abrasion, and required much cost for maintenance and replacement. Recently the wire rope type snubbers are developed and applied to the power plant, and proved as effective to reduce piping system vibration. Wire rope type snubber uses the bending rigidity and energy dissipation properties of ropes. This paper presents the procedure of design, and the method to apply hysteresis curve to the dynamic response analysis. Experiments were also conducted to confirm design results.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.815-824
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• 2013

Pneumatic exciters can be good replacements of electrodynamic, piezoelectric and hydraulic exciters owing to simple structure and large exciting force. One problem to be solved is a slow response caused by compressibility of air. Desirable frequency response characteristics of exciter are constant magnitude and zero degree phase, because users want no time delay between input signal and output force. For this reason, frequency range of pneumatic exciters is limited about 0~1 Hz. Therefore, expansion of frequency range is an important issue when designing the pneumatic exciter. In this paper, the pneumatic exciter which has same structure with active pneumatic isolator is dealt with. The dynamic characteristics are presented, and its limitation of expanding frequency range is shown based on analytical studies. Then the pneumatic exciter with dual-chamber is suggested to overcome this problem. Based on simulation study, a design method is presented.