• Geomechanics and Engineering
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• 제22권1호
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• pp.1-9
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• 2020

This paper presents an investigation of the ground response of a gob-side gateroad suffering mining stress induced by a 21 m-thick coal seam extraction. A field observation, including entry convergence and stress changes monitoring, was first conducted in the tailgate 8209. The observation results of entry convergence showed that, during the adjacent panel 8210 retreating period, the deformation of the gob-side gateroad experienced a continuous increase stage, subsequently, an accelerating increase stage, and finally, a slow increase stage. However, strong ground response, including roof bending deflection, rib extrusion and floor heave, occurred during the current panel 8209 retreating period, and the maximum floor heave reached 1530 mm. The stress changes within coal mass of the two ribs demonstrated that the gateroad was always located in the stress concentrated area, which responsible for the strong response of the tailgate 8209. Subsequently, a hydraulic fracture technique was proposed to pre-fracture the two hard roofs above the tailgate 8209, thus decreasing the induced disturbance on the tailgate. The validity of the above roof treatment was verified via field application. The finding of this study could be a reference for understanding the stability control of the gob-side gateroad in extra thick coal seams mining.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 추계학술대회 논문집
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• pp.141-144
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• 1998

The electrical characteristics of poly-Si TFT's with offset structure by negative bias stress are systematically investigated as a function of offset length. The changes of electrical characteristics, V$\_$th/, off-current, on/off ratio, in the offset structured poly-Si TFT's are smaller than that of the conventional structured poly-Si TFT's under the stress condition (V$\_$ds/=20V, V$\_$gs/=-20V). It is found that the hot carrier effect by negative bias stress is suppressed by the offset structured poly-Si TFT's because the local electric field near the drain region is decreased by offset region.

• 한국해안해양공학회지
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• 제12권4호
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• pp.168-180
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• 2000

In the Part I, the three dimensional model testing with NNW deep water wave direction gave the results such that the occurrence of breaking waves over the peak of Ear-Do caused very small wave height at the structure position. But the measured wave forces were rather greater than the calculated forces based on deep water wave height. Furthermore, It was also perceived that the time series of the forces looked like corresponding to the case that waves were superimposed by an unidirectional current. In the present Part II, the current is presumed to be a flow secondly induced by breaking waves, and an extensive study to clarify the current in a quantitative sense is performed through numerical analysis and hydraulic experiment. The results showed that a strong circulation can surely occur in the vicinity of the structure due to radiation stress differentials given by the breaking waves. It was also recognized that the velocity of the induced current varied with the magnitude of energy dissipation rate introduced in the numerical analysis. The numerical analysis was tuned adjusting the dissipation rate so that the calculated wave field could closely match with the experimental results of Part I. The fluid force (in prototype) for the optimal match showed approximately 2.2% increased over the calculated value based on the deep water wave height (24.6m) whereas the force corresponding to the average of the experimental values showed the increase of about 13.0%.

• 대한전기학회논문지
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• 제37권1호
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• pp.10-17
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• 1988

The torsional resonance of the generator shaft system has the possibility of inducing voltages across the stator winding because it is a carrier with the field excitation. And these torsional induced stator currents inducs the eddy current in the rotor. This paper describes the eddy current based on the double Fourier series method. The forces generating during the torsional interaction are computed using the Maxwell's magnetic stress tensor for each of the Fouriercomponennts. And then, these forces of the Fourier components are evaluated by the Parseval's theorem.

• Geomechanics and Engineering
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• 제11권6호
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• pp.805-820
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• 2016

A fully coupled non-linear effective stress response finite difference (FD) model is built to survey the counter-intuitive recent findings on the reliance of pore water pressure ratio on foundation contact pressure. Two alternative design scenarios for a benchmark problem are explored and contrasted in the light of construction emission rates using the EFFC-DFI methodology. A strain-hardening effective stress plasticity model is adopted to simulate the dynamic loading. A combination of input motions, contact pressure, initial vertical total pressure and distance to foundation centreline are employed, as model variables, to further investigate the control of permanent and variable actions on the residual pore pressure ratio. The model is verified against the Ghosh and Madabhushi high acceleration field test database. The outputs of this work are aimed to improve the current computer-aided seismic foundation design that relies on ground's packing state and consistency. The results confirm that on seismic excitation of shallow foundations, the likelihood of effective stress loss is greater in deeper depths and across free field. For the benchmark problem, adopting a shallow foundation system instead of piled foundation benefitted in a 75% less emission rate, a marked proportion of which is owed to reduced materials and haulage carbon cost.

• 한국초전도ㆍ저온공학회논문지
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• 제25권3호
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• pp.34-37
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• 2023

The practical application of REBCO coated conductor (CC) tapes, vital for energy transmission (e.g., cable application) and high-field magnets (e.g., coil application), necessitates efficient and simple quality assessment procedures. This study introduces a systematic approach to assess the electromechanical properties of REBCO CC tapes under 77 K and self-field conditions. The approach involves customized tensile and bending tests that clarify the critical current (I_c) response of the CC tapes under mechanical loads induced by tension and bending. This study measures the retained Ic values of commercially available GdBCO CC tapes under 250 MPa tensile stress and 40 mm bending diameter. Through experimentation, the study demonstrates the resilience of these tapes and their suitability for applications. By presenting a simplified stress-based analysis and a bending test of the tapes, the study contributes to effective quality assessment methods for the development of practical superconducting products.

• 한국자기학회지
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• 제16권6호
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• pp.305-308
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• 2006

Magnetic flux leakage(MFL) 신호를 이용하여 비파괴 검사 신호를 획득하는데 주로 사용하는 감지기 또는 금속 덩어리를 의미하는 pig 이용 기술은 일반적으로 천연 가스 전송에 사용되는 강철 파이프라인 상의 대량 부식 흔적을 감지하는데 널리 이용 되어지고 있다. 이를 대체할 수 있는 비파괴 검사 기술의 양상에 대하여 소개 하자면, 지하에 매설된 가스 파이프라인의 바깥 면에 가로축을 따라 난, 부식에 의한 결함에 일반적으로 동반하는 '압력에 의한 부식 흠집(Stress Corrosion Crack : SCC)'을 탐지하는 기술이 있다. 본 논문은 가스 파이프라인 상의 가능성 있는 SCC 검출 장치로서 탐촉자의 원거리에 형성된 다상 회전 전자장 활용 기술에 대하여 논하고 있다. Pig 원형에 대한 묘사와 비파괴 신호 검사용 탐촉자에 대한 설명이 덧붙여져 있으며 결함 검지장치의 유한 요소 모델링과 연관한 부분에 관하여도 발전적으로 논하였다. 테스트 용 pig를 이용한 초기 실험 결과는 본 논문에서 보이고 있는 비파괴 검사 양식이 가스 파이프 라인의 가로축을 따라 발생한 결함에 매우 민감하게 반응하고 있음을 보이고 있다.

• 한국암반공학회:학술대회논문집
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• 한국암반공학회 2008년도 춘계학술발표회 논문집
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• pp.79-88
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• 2008

1994년 처음으로 국내 지반공학자들에게 소개된 수압파쇄 시험법은, 측정장비 및 해석방법에 있어서 많은 발전을 이루어 왔다. 파이프라인 타입이었던 제1세대 수압파쇄 시험장비는 다루기가 쉽지 않았고 파이프 연결부위에서의 압력 누설 문제가 대두되면서, 제2세대라 불리는 와이어라인 타입으로 보완된 바 있으나, 기존의 시스템에 비해 많은 장점을 가짐에도 불구하고 공기압축기를 별도로 설치해야 하는 문제점을 여전히 안고 있어, 2004년 이후 이를 모두 포함하는 현재의 제3세대 all-in-one 시스템으로 보완된 바 있다. 장비의 발전과 함께, 응력해석을 위한 소프트웨어의 발전도 꾸준히 진행되어온 바, 불확실한 결정값으로 인해 가장 다루기 어려운 균열폐쇄압력에 대하여 여러 가지 기법을 적용함으로써 가장 합리적인 값을 도출해내는 방법의 개발이 그 한 예가 될 것이다. 이러한 지난 10여년 간의 기술발전과 함께 국내 대부분의 지역에서 수행된 수압파쇄시험을 통하여 대한민국의 거의 전 지역에 대한 측정결과들을 축적할 수 있었으며, 현재 이 결과값은 터널굴착을 위한 기초설계단계에서 널리 활용되고 있다. 향후 해저터널의 건설과 관련하여 해상에서의 수압파쇄 초기응력측정법 또한 꾸준히 개발되고 있으나, 지금까지 축적된 내륙에서의 초기응력 측정값이 해저터널의 안전한 설계를 위해 직간접적으로 사용되어지길 기대하며, 현재까지 수압파쇄시험을 통해 얻어진 한반도의 초기응력의 평균 크기와 방향을 지질학적 특성결과와 관련 지어 제시하고자 한다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.37.1-37
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• 2001

Electric plating is used in various industry field. Specially, pulse plating is able to deposit material at high current density compared to conventional DC plating. For example, pulse plating can get more fine grain, can improve adhesion and metal distribution and current efficiency, can reduce internal stress and crack. Therefore, we developed bidirection pulse power supply(BPPS) which has high speed pulse current and high current density and improve deposition quality and increase plating speed in this paper. BPPS(Bidirection pulse power supply) needs high speed rising time, falling time and output current accuracy. BPPS consists of rectifier part, chopper part, invertor part, and control part. Rectifier part changes outprt current direction.

• Advances in materials Research
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• 제7권3호
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• pp.203-220
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• 2018

This investigation is focused on the study of effect of hall current in transversely isotropic magneto thermoelastic homogeneous medium with fractional order heat transfer and rotation. As an application the bounding surface is subjected to normal force. The research becomes more interesting due to interaction of Hall current with the effect of rotation as it has found various applications. Laplace and Fourier transform is used for solving field equations. The analytical expressions of temperature, displacement components, stress components and current density components are computed in the transformed domain. The effects of hall current and fractional order parameter at different values are represented graphically.