• 한국자동차공학회논문집
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• 제7권7호
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• pp.258-267
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• 1999

The aim of the study is to provide fundamental information for the development of magneticfluid actuator. To achieve the aim, the force and dynamic characteristics of magenticfluid are investigated by experiment for the various of tube diameter, height and position of magneticfluid column in magneticfield according to supplied voltage of solenoid coil, wave form and frquency. From this study, actuating force of magneticfluid is generated by magneticfield. The magnitude of force increases as the intensity of magneticfield becomes strong and the center of magneticfield becomes lower than the center of magneticfluid column. And the force of magneticfluid relates to the volume of magneticfluid more than the height and diameter. The response delay time decreases as the height of magmeticfluid more than the height and diameter. The response delay time decrease as the height of magneticfluid column becomes longer and the center of magneticfield becomes lower than the center of magniticfluid column. But, the approaching time increases as supplied voltage becomes higher and the center of magneticfiled becomes higher than the center of magniticfluid column. The frequency generating maximum force is 1Hz and the critical frequency is about 4Hz.

• Computers and Concrete
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• 제4권3호
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• pp.221-241
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• 2007

Based on the experiment results, the damage and fracture behavior of concrete at the ages of 1d, 2d, 7d and 28d, in three-point bending and uniaxial tensile tests, were simulated with a finite element program, ABAQUS. The critical stress intensity factor $K_{IC}^s$ and the critical crack tip opening displacement ($CTOD_C$) of concrete were calculated with effective-elastic crack approach for the three-point bending test of grade C30 concrete. Based on the crack band model, a bilinear strain-softening curve was derived to simulate the LOAD-CMOD curves and LOAD-Displacement curves. In numerical analysis of the uniaxial tension test of concrete of grade C40, the damage and fracture mechanics were combined. The smeared cracking model coupling with damaged variable was adopted to evaluate the onset and development of microcracking of uniaxial tensile specimen. The uniaxial tension test was simulated by invoking the damage plastic model which took both damage and plasticity as inner variables with user subroutines. All the numerical simulated results show good agreement with the experimental results.

• 한국지반공학회논문집
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• 제16권1호
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• pp.221-226
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• 2000

단일 균열시스템에서 간극 크기에 따른 상대투과도의 변화 특성을 측정하기 위해 본 연구에서는Hele-Shaw평판 형태의 유리 평판을 제작하여 실험을 수행하였다. 평판의 재질은 유동 양상 관찰을 위해 유리를 사용하였고, 간극 크기는 실제 현장에서 관측되는 30에서 $120\mum$ 사이의 범위에서 7가지 경우를 설정하여 정상유동법에 의한 실험을 수행하였다. 또한 실험 측정결과에 대한 보다 정확한 포화도 계산 및 분석의 편의를 위해 디지털 영상 편집법 (digital image process technique)을 이용한 해석모델을 개발ㆍ이용하였으며, 균열에서의 2상 유체유동 양상에 직접적인 영향을 미치는 간극크기와 매질의 표면 특성을 나타내는 임계포화도를 이용하여 단일 균열에 대한상대투과도 실험관계식을 도출하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.474-477
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• 2002

We performed a continuous heat treatment experiment for long Si$_2$Sr$_2$CaCuO$_{x}$ (Bi2212) superconductor tapes on copper substrates. A precursor that contains a mixture of Bi$_2$O$_3$, SrCO$_3$, and CaCO$_3$ powders was prepared and screen-printed on Cu tapes. The screen- printed tapes were thermally treated by consecutive processes with various temperature settings using an air-filled tube furnace. The diffraction patterns and the microstructures of the high temperature superconductor thick films were analyzed by X-ray diffractometry (XRD) and optical Microscopy respectively, and the critical temperatures of the superconducting thick films were measured. The critical temperatures of the superconducting films were measured to be about 77K, and the films'crystallographic c-axes were confirmed to be normal to the film surfaces by XRD and morphology observation. We also observed that the thick superconducting layer is formed and aligned on the copper substrate via partial melted state that consists of a liquid phase and a secondary phase.e.

• 마이크로전자및패키징학회지
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• 제6권3호
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• pp.45-50
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• 1999

동(CU)은 전기전자부품에 널리 사용되어 왔는데, 특히 점 저항용접된 동은 콘덴서나 저항의 리드부분에 사용되고 있다. 그러나 일반적으로 동은 전기 저항이 낮아 저항용접이 어렵다. 본 연구에서는 동의 점 용접성을 개선하기 위하여, 상대적으로 전기 저항이 높은 Sn-37%Pb 솔더를 동 표면에 도금하였다. 실험변수로, 가 압력은 100kgf에서 200kgf, 용접시간은 20ms에서 50ms, 용접전류는 100A에서 2500A까지 변화시켰다. 실험결과, 솔더 도금된 동박판은 용접전류 400~2200A, 가압력 100~200kgf, 용접시간 20~50ms범위에서 저항용접이 가능하였다. 점 용접부의 인장전단 강도는 임계 전류값까지는 용접전류가 증가함에 따라 증가하고, 임계 전류값 이후부터는 용접전류에 따라 인장전단 강도가 감소하였다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제39권5호
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• pp.203-206
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• 2013

Statistics is the science of data. As the foundation of scientific knowledge, data refers to evidentiary facts from the nature of reality by human action, observation, or experiment. Clinicians should be aware of the conditions of good data to support the validity of clinical modalities in reading scientific articles, one of the resources to revise or update their clinical knowledge and skills. The cause-effect link between clinical modality and outcome is ascertained as pattern statistic. The uniformity of nature guarantees the recurrence of data as the basic scientific evidence. Variation statistics are examined for patterns of recurrence. This provides information on the probability of recurrence of the cause-effect phenomenon. Multiple causal factors of natural phenomenon need a counterproof of absence in terms of the control group. A pattern of relation between a causal factor and an effect becomes recognizable, and thus, should be estimated as relation statistic. The type and meaning of each relation statistic should be well-understood. A study regarding a sample from the population of wide variations require clinicians to be aware of error statistics due to random chance. Incomplete human sense, coarse measurement instrument, and preconceived idea as a hypothesis that tends to bias the research, which gives rise to the necessity of keen critical independent mind with regard to the reported data.

• 한국소음진동공학회논문집
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• 제22권7호
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• pp.642-649
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• 2012

This paper deals with a copper die casting induction motor which has several advantages of motor performance. The developed motor is used as spindle motor in machining center. The dynamic characteristic analysis of rotor is dealt with for precision machining. The critical speed of rotor considering rotation and gyroscopic effect should be above operating speed, 18,000 rpm, and have a 201 % sufficient separation margin. Also, the 3-D unbalance vibration response analysis is performed and enabled the prediction of the expected vibration amplitude by unbalance in high speed. The unbalance vibration responses of each position on the rotor are satisfied with allowable vibration displacement of API 611 standard according to balancing G grade(G 0.4, G 2.5, G 6.3). Copper die casting high speed induction motor is successfully developed and verified by experiment.

• 대한기계학회논문집
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• 제17권11호
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• pp.2762-2772
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• 1993

The paper deals with the flutter of a cantilevered beam subjected to a rocket thrust generated by a solid rocket motor. It is saaumed that the rocket thrust is to be a constant follower thrust, and produced by the installation of a solid rocket motor to the tip end of the cantilevered beam. The rocket motor is considered to be a rigid body having finite sizes, but not a mass point as it has been assumed so far. Governing equations are derived through the extended Hamilton's principle, and finite element method is applied to obtain the theoretical prediction for critical follower thrust. The maximum follower thrust is also calculated through the change of shear deformation parameter of the beam in the numerical simulation. The theoretical prediction for flutter or stability is verified by experiment. The experimental results show that critical follower thrust in theory agrees well with the experimental value taking account of the magnitude, rotary inertia of the rocket motor and the distance from the tip end of the beam to the center of gravity of the rocket motor.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.850-853
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• 2008

In the motorized retractor of the smart seat belt system, anti-overload clutch is a very important element to prevent the excessive belt tensional force. Anti-overload clutch is the essential device to protect drivers from chest damage by the excessive belt tension. It generates slipping motion under excessive webbing moment and the belt tensional force is limited below critical value. In this study, slipping mechanism in the antioverload clutch is investigated by analysis and experiment. On the prototype model, finite element analysis is performed to identify the slipping condition and to determine the critical load. Analysis result is compared with the experimental result and the validity of the analysis model is verified. The purpose of the study is to provide the analytical background for the systematic design of the anti-overload clutch mechanism.

• Journal of Welding and Joining
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• 제33권1호
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• pp.80-86
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• 2015

The purpose of this study is to establish the predictive method of the angular distortion caused by the line heating process with high frequency induction heating. In order to do it, the heat input model for the high frequency induction heating system was established through comparing the temperature evaluation results obtained by both FEA and experiment. The critical heating conditions to prevent the degradation of the work piece with various thicknesses were identified by FEA and microstructure test results. Under the critical heating conditions, the extensive line heating tests were performed. According to the test results, it was found that the angular distortion behavior of the heated plates could be defined as the function of heat intensity and the rigidity of heated plate. In addition, it was clarified that the angular distortion strongly depended on the size of test specimen such as the length and the width of the heated plate. Based on these results, the predictive equation for the angular distortion was established with the function of heat intensity, bending rigidity and size of heated plate.