• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.838-843
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• 2001

Internal damping plays an important role in some rotor dynamic systems with the use of various materials for shafts, for example, composite material. However, although the effects of internal damping have been investigated for a couple of decades, there are several different internal damping models in use, none of which are accepted as the most reliable model. The purpose of this paper is to compare the results of dynamic analysis of rotor systems with several different internal damping models. The exact dynamic element method is used to formulate and analyze the problem. The simulation results provided in this paper may be useful for the dynamic analysis of high rotor systems subject to significant internal damping.

• 대한전기학회논문지
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• 제39권7호
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• pp.740-748
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• 1990

In this paper, we consider the problem of parameter estimation, i.e., definding the internal structure of a linear distribution parameter system from its input/output data. First, a linear partial differential equation describing the system is double-integrated with respect to two variables and then transformed into an integral equation. Next the Walsh Operation Matrix for Walsh function and their integration are introduced to transform the integral equation into algebraic simultaneous equations. Finally, we develop an algorithm to estimate the parameters of the linear distributed parameter system from the simple linear algebraic simultaneous equations. It is also shown that our algorithm could be effective in real time data processing since it uses the Fast Walsh Transform.

• Kidney Research and Clinical Practice
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• 제36권1호
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• pp.48-57
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• 2017

Background: Hepatic steatosis measured with controlled attenuation parameter (CAP) using transient elastography predicts metabolic syndrome in the general population. We investigated whether CAP predicted metabolic syndrome in chronic kidney disease patients. Methods: CAP was measured with transient elastography in 465 predialysis chronic kidney disease patients (mean age, 57.5 years). Results: The median CAP value was 239 (202-274) dB/m. In 195 (41.9%) patients with metabolic syndrome, diabetes mellitus was more prevalent (105 [53.8%] vs. 71 [26.3%], P < 0.001), with significantly increased urine albumin-to-creatinine ratio (184 [38-706] vs. 56 [16-408] mg/g Cr, P = 0.003), high sensitivity C-reactive protein levels (5.4 [1.4-28.2] vs. 1.7 [0.6-9.9] mg/L, P < 0.001), and CAP (248 [210-302] vs. 226 [196-259] dB/m, P < 0.001). In multiple linear regression analysis, CAP was independently related to body mass index (${\beta}=0.742$, P < 0.001), triglyceride levels (${\beta}=2.034$, P < 0.001), estimated glomerular filtration rate (${\beta}=0.316$, P = 0.001), serum albumin (${\beta}=1.386$, P < 0.001), alanine aminotransferase (${\beta}=0.064$, P = 0.029), and total bilirubin (${\beta}=-0.881$, P = 0.009). In multiple logistic regression analysis, increased CAP was independently associated with increased metabolic syndrome risk (per 10 dB/m increase; odds ratio, 1.093; 95% confidence interval, 1.009-1.183; P = 0.029) even after adjusting for multiple confounding factors. Conclusion: Increased CAP measured with transient elastography significantly correlated with and could predict increased metabolic syndrome risk in chronic kidney disease patients.

• Applied Microscopy
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• 제29권1호
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• pp.75-81
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• 1999

본 실험에서 얻어진 결론을 요약하면 아래와 같다. (1) 저진공도의 sputter coater를 이용하여 Au 내부 표준시편을 제작하는 최적 조건은 9mA의 전류로 100 초간 coating하는 것이다. (2) 고진공도의 evaporation coater를 이용하여 Al 내부 표준시편을 제작하는 최적 조건은 7kV의 전압으로 10분간 coating하는 것이다. (3) Au 내부 표준시편을 이용하여 측정한 홍주석 격자상수 값의 측정오차는 정밀도가 1.2% 이하이고, 정확도는 0.3% 이하이다. (4) Au 내부 표준시편을 이용하여 측정한 알바이트 장석 격자상수 값의 측정오차는 정밀도가 0.5% 이하이고, 정확도는 1.1% 이하이다. (5) 내부 표준시편을 사용하여 격자상수를 측정할 때 가장 심각한 오차는 전자회절도형의 거리 및 각도 측정시 발생한다. 체계적인 측정 방법과 정밀도 높은 측정 도구의 사용이 필요하다. (6) 시료나 TEM 조건 때문에 분말 XRD 방법이나 수렴성빔 전자회절법으로 격자상수를 구할 수 없는 경우에는 내부 표준시편을 이용한 TEM 격자상수 측정법이 좋은 대안이 된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.862-870
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• 2010

This thesis has been researched on optimized design method for the total cross section of embankment considering the fact that the size of embankment cross section is directly related with economic efficiency when dam designing. In general, embankment cross section of fill dam is either determined by cohesion and angle of internal friction, a strength parameter of embankment materials or by permeability of embankment. Therefore the size of embankment cross section depending on strength parameter of embankment materials was determined by using MIDAS-GTS program through stress-seepage coupled analysis at the time of fill dam design. As a result, determination of embankment cross section was more affected by the size of central core and permeability rather than by slope stability by shear strength and it was revealed that in case of embankment height being over 20m, stability against infiltration and slope action could be secured only when embankment slope is at least over 1:2.5. In addition, it was also revealed that in case of making the size of central core exceeding specification standard, total cross section of embankment could be reduced considerably and at the time of embankment design, adequate size and appropriateness of embankment cross section could be determined with referring the table suggested by this study.

• Journal of Astronomy and Space Sciences
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• 제22권4호
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• pp.513-526
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• 2005

본 연구의 목적은 회전안정화 우주비행체 내부에 탑재된 유동질량의 운동을 보다 광범위한 파라미터 영역에 대해 해석하고, 관련 분야에서 활용할 수 있는 적정한 설계 기준을 제공하기 위한 것이다. 문제의 해석을 위해 perturbation 기법을 이용하였고, 그 결과로 파라미터 공간에서의 안정-불안정 영역을 결정할 수 있는 Ince-Strutt 선도를 구하였다. 해석 방법 및 확보된 결과의 적정성을 입증하기 위하여 선도에서 취한 여러 파라미터 값에 대한 수치적 시뮬레이션을 수행하였다. 유동체 운동의 위상평면 분석을 통하여 수행된 해석 과정 및 결과가 적정한 것으로 입증되었으며, 회전 비행체에 탑재된 유동질량의 운동은 파라미터 값의 선택에 따라 여러 가지 형태의 안정-불안정 현상을 유발함을 알 수 있었다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 가을 학술발표회 논문집
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• pp.413-420
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• 1998

In this study, an expert system is developed to evaluate a safety of tunnel structures. Using a dynamic finite element analysis module, this expert system predicts dynamic responses of a concrete lining surface which a transient force is applied on and estimates the condition between the concrete lining and surrounding ground. The evaluation parameter values of the module are multi-reflected wave frequency and amplitude of the dynamic responses. The multi-reflected wave frequency represents the depth of concrete lining, and the other parameter, the amplitude of the frequency, is utilized for detecting the internal flaws. A comparison of the dynamic responses between numerical and experimental model test verifies an effectiveness of this system. By this expert system, the safety of tunnel structures and the detection of internal flaws of concrete linings are estimated quantitatively.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.416-417
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• 2017

본 연구에서는 PMD 내부 유동 해석을 위한 3차원 착화기 모델링 및 전산 해석을 수행하였다. Lumped parameter method를 이용하여 착화기 모델링을 진행하였고, 이를 상용 프로그램과 연동하여 전산 해석을 수행하였다. 전산 해석의 결과는 CBT 및 PMD 실험 결과값과 비교하였다.

• Nuclear Engineering and Technology
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• 제39권1호
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• pp.75-84
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• 2007

This paper presents a closed-form model for evaluating the restraint effect of pressure induced bending on the opening of a circumferential through-wall crack, which is considered plastic deformation behavior. Three-dimensional finite element analyses with different crack lengths, restraint conditions, pipe geometries, magnitudes of internal pressure, and tensile properties were used to investigate the influence of each parameter on the pressure-induced bending restraint on the crack opening displacement. From these investigations, an analytical model based on elastic-perfectly plastic material was developed in terms of the crack length, symmetric restraint length, mean radius to thickness ratio, axial stress corresponding to the internal pressure, and normalized crack opening displacement evaluated from a linear-elastic crack opening condition. Finite element analyses results demonstrate that the proposed analytical model reliably estimated the restraint effect of pressure-induced bending on the plastic crack opening of a circumferential through-wall crack and properly reflected the dependence on each parameter within the range over which the analytical expression was derived.

• Korean Journal of Chemical Engineering
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• 제36권3호
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• pp.356-367
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• 2019

This work presents an advanced and systematic approach to analytically design the optimal parameters of a two parameter second-order internal model control (IMC) filter that satisfies operational constraints on the output process, the manipulated variable as well as rate of change of the manipulated variable, for a first-order plus dead time (FOPDT) process. The IMC parameters are designed to minimize a control objective function composed of the weighted sum of the error between the process variable and the set point, and the rate of change of the manipulated variable, and to satisfy the desired constraints. The feasible region of the constrained IMC control parameters was graphically analyzed, as the process parameters and the constraints varied. The resulting constrained IMC control parameters were also used to find the corresponding industrial proportional-integral controller parameters of a Smith predictor structure.