• Journal of the Korean Mathematical Society
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• v.49 no.5
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• pp.927-945
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• 2012

An approximation of singular source terms in elliptic problems is developed and analyzed. Under certain assumptions on the curve where the singular source is defined, the second order convergence in the maximum norm can be proved. Numerical results present its better performance compared to previously developed regularization techniques.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.59-60
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.647-648
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• 2009

• Journal of Cerebrovascular and Endovascular Neurosurgery
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• v.26 no.3
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• pp.260-264
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• 2024

Objective: We sought to investigate how priming the tube between air versus air mixed with saline ex vivo influenced suction force. We examined how priming the tube influenced peak suction force and time to achieve peak suction force between both modalities. Methods: Using a Dwyer Instruments (Dwyer Instruments Inc., Michigan City, IN, USA), INC Digitial Pressure Gauge, we were able to connect a .072 inch aspiration catheter to a rotating hemostatic valve and to aspiration tubing. We recorded suction force measured in negative inches of Mercury (inHg) over 10 iterations between having the aspiration tube primed with air alone versus air mixed with saline. A test was used to compare results between both modalities. Results: Priming the tube with air alone compared to air mixed with saline was found to have an increased average max suction force (-28.60 versus -28.20 in HG, p<0.01). We also identified a logarithmic curve of suction force across time in which time to maximal suction force was more prompt with air compared with air mixed with saline (13.8 seconds versus 21.60 seconds, p<0.01). Conclusions: Priming the tube with air compared to air mixed with saline suggests that not only is increased maximal suction force achieved, but also the time required to achieve maximal suction force is less. This data suggests against priming the aspiration tubing with saline and suggests that the first pass aspiration primed with air may have the greatest suction force.

• Smart Structures and Systems
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• v.20 no.4
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• pp.461-472
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• 2017

Explicit design formulae of liquid column vibration absorber (LCVA) for suppressing harmonic vibration of structures with small inherent structural damping are developed in this study. The developed design formulae are also applicable to the design of a tuned mass damper (TMD) and a tuned liquid column damper (TLCD) for damped structures under harmonic force excitation. The optimum parameters of LCVA for suppressing harmonic vibration of undamped structures are first derived. Numerical searching of the optimum parameters of tuned vibration absorber system for suppressing harmonic vibration of damped structure is conducted. Explicit formulae for these optimum parameters are then obtained by a series of curve fitting techniques. The analytical result shows that the control performance of TLCD for reducing harmonic vibration of undamped structure is always better than that of non-uniform LCVA for same mass and length ratios. As for the effects of structural damping on the optimum parameters, it is found that the optimum tuning ratio decreases and the optimum damping ratio increases as the structural damping is increased. Furthermore, the optimum head loss coefficient is inversely proportional to the amplitude of excitation force and increases as the structural damping is increased. Numerical verification of the developed explicit design expressions is also conducted and the developed expressions are demonstrated to be reasonably accurate for design purposes.

• Structural Engineering and Mechanics
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• v.46 no.2
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• pp.179-196
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• 2013

An experimentally measured single footfall trace (SFT) from a walking subject needs to be extended into a continuous force curve, which can then be used as load for floor vibration serviceability assessment, or on which further analysis like discrete Fourier transform can be conducted. This paper investigates the accuracy, applicability and parametrical sensitivity of four extension methods, Methods I to IV, which extends the SFT into a continuous time history by the walking step rate, stride time, double support proportion and the double support time, respectively. Performance of the four methods was assessed by comparing their results with the experimentally obtained reference footfall traces in the time and frequency domain, and by comparing the vibrational response of a concrete slab subjected to the extended traces to that of reference traces. The effect of the extension parameter on each method was also explored through parametrical analysis. This study finds that, in general, Method I and II perform better than Method III and IV, and all of the four methods are sensitive to their extension parameter. When reliable information of walking rate or gait period is available in the test, Methods I or II is a better choice. Otherwise, Method III, with the suggested extension parameter of double support time proportion, is recommended.

• Geomechanics and Engineering
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• v.8 no.5
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• pp.741-756
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• 2015

The prediction of impending collapse of deep tunnel is one of the most difficult problems. Collapse mechanism of deep tunnel in layered soils is derived using a new curved failure mechanism within the framework of upper bound theorem, and effects of seepage forces are considered. Nonlinear failure criterion is adopted in the present analysis, and the possible collapse shape of deep tunnel in the layered soils is discussed in this paper. In the layered soils, the internal energy dissipations along velocity discontinuity are calculated, and the external work rates are produced by weight, seepage forces and supporting pressure. With upper bound theorem of limit analysis, two different curve functions are proposed for the two different soil stratums. The specific shape of collapse surface is discussed, using the proposed curve functions. Effects of nonlinear coefficient, initial cohesion, pore water pressure and unit weight on potential collapse are analyzed. According to the numerical results, with the nonlinear coefficient increase, the shape of collapse block will increase. With initial cohesion of the upper soil increase, the shape of failure block will be flat, and with the lower soil improving, the size of collapsing will be large. Furthermore, the shape of collapsing will decrease with the unit weight decrease.

• The Korean Journal of Nuclear Medicine
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• v.21 no.1
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• pp.55-60
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• 1987

$Digoxin^{(R)}$을 복용하고 있지 않는 각27명의 만성 신부전 환자 및 신생아의 혈청에서 Gammacoat $Digoxin^{(R)}$ kit와 Amerlex Digoxin $RIA^{(R)}$ kit를 이용하여 digoxin과 교차 면역반응을 보이는 내인성 물질(이하 DLI: Digoxin-like Immunoreactivity)을 측정하여 다음의 결과를 얻었다. 1) Gammacoat $Digoxin^{(R)}$ kit로 측정시 27명의 만성 신부전 환자중 12명에서 신생아의 경우는 27명 전원에서 측정 하한치 이상의 DLI가 검출된 반면, Amerlex Digoxin $RIA^{(R)}$ kit로는 1명을 제외한 양 군의 전원에서 DLI가 관찰되지 않았다. 만성 신부전 환자에서 Gammacoat $Digoxin^{(R)}$ kit로 측정된 DLI와 혈청 BUN/Creatinine 값 사이에는 유의한 상관 관계가 없었다. 2) 만성 신부전 환자 및 신생아의 pooled sera에 가한 digoxin의 수거율은 각각 49%, 40%였다. 3) 만선 신부전 환자 및 신생아의 pooled sera에서 측정되는 DLI의 희석 curve는 정상 희석 curve와 다르다고 할 수 없었다. 4) 만성 신부전 환자의 pooled sera에서 측정되는 DLI의 16%, 그리고 신생아의 pooled sera 에서 측정되는 DLI의 20%가 trypsin에 sensitive하였다. 5) 만성 신부전 환자의 pooled sera에서 측정되는 DLI의 56%가, 그리고 신생아의 pooled sera에서 측정되는 DLI의 경우는 전체의 20%미만이 methylene chloride로 추출되었다. 이상에서 만성 신부전 환자 및 신생아의 혈청에서는 방사면역 kit의 증류에 따라 DLI가 검출되며 그 실체를 알기 위해서는 더욱 연구가 필요하다고 할 수 있었다.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.05a
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• pp.93-98
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• 1999

Generally, the - life of die is limited by fatigue fracture or dimensional inaccuracy originated from wear. In this paper, to predict the fatigue life of the dissimilar materials die, the stress and stxain histories of die can be predicted by the analysis of elasto-plastic finite element neth hod and the elastic analysis of die during the process analysis of workpiece. Using heat shrink fit analysis, initial stress of the k r t die is computed. Also, the stress-life curve of die material can be obtained through experiment. With the above two facts, we propose the analysis method of predicting fatigue life in die. In the proposed model, tlz analysis of elastic-plastic finite element method for material is carried out by using ABAQUS. Surface force resulted from the contacting border of the die and workpiece is tmnsformed into the nodal force of die to implement elastic analysis. Besides, the proposed analysis model of die is applied to the one material and the dissimilar materials extrusion die.

• Journal of Korean Association for Spatial Structures
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• v.21 no.4
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• pp.31-38
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• 2021

The precast-buckling restrained braces(PC-BRB) reinforced with engineering plastics that can compensate for the disadvantages in the manufacturing process of the existing buckling restrained brace. In this study, to examine the applicability of PC-BRB to actual structures, example structures similar to school facilities were selected and the reinforcement effect was analyzed analytically according to the damping design procedure of PC-BRB. Load-displacement curve through the incremental loading test appeared similar to the bilinear curve. Applying test result, Analytical model of PC-BRB model was constructed and applied to the example structure. As a result of the analysis, the PC-BRB showed stable hysteresis behavior without lowering the strength, and the inter story drift ratio and the shear force were reduced due to the damping effect. In addition, the reduction ratio of the shear force was similar to the reduction ratio assumed when designing the damping device.