• 비파괴검사학회지
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• 제21권5호
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• pp.532-541
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• 2001

재료의 노화에 의한 강도 및 인성 감소치를 정량적으로 평가하는 비파괴적 기법의 개발이 시도되고 있으며 전기비저항법도 그 중의 하나이다. 본 연구에서는 전기비저항법의 열화도 평가에의 적용성을 살펴보기 위해 먼저 6종 10 가지의 비자성 금속을 측정시료로 선택하여 직류 two-point probe법(혹은 2탐침법)으로 전기비저항을 계산한 결과와 비접촉식 와전류 방법으로 전기비저항을 측정한 결과를 서로 비교하였다. 또한, 1Cr-1Mo-0.25V강에 대하여 비파괴적 측정 방법인 four-point probe 방법(혹은 4탐침법)을 사용하여 얻은 결과와 기존의 2탐침법을 사용하여 얻은 결과를 서로 비교하여 현장에서의 4탐침 기술의 적용 가능성을 살펴보았다. 1Cr-1Mo-0.25V강에 대하여 2탐침법으로 구한 비저항 값과 4탐침법으로 구한 비저항 측정값의 차이는 0.6%였다. 따라서 4탐침법을 사용하여 현장에서 금속소재의 열화도의 비파괴적 평가가 가능하다고 사료된다.

• 한국정밀공학회지
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• 제22권11호
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• pp.135-141
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• 2005

Measurement of five DOF motion errors in a ultra precision feed table was attempted in this study. Yaw and pitch error were measured by using a laser interferometer and roll error was measured by using the reversal method. Linear motion errors in the vertical and horizontal directions were measured by using the sequential two point method. In this case, influence of angular motion errors was compensated by using the previously measured ones by the laser interferometer and the reversal method. The capacitive type sensors and an optical straight edge were used in the reversal method and the sequential two point method. Influence of thermal deformation on sensor jig was investgated and minimized by the periodic measurement according to the variation of room temperature. Deviation of gain between sensors was also compensated using the step response data. 5 DOF motion errors of a hydrostatic table driven by the linear motor werer tested using the measurement method. In the horizontal direction, measuring accuracies for the linear and angular motion were within ${\pm}0.02\;{\mu}m$ and ${\pm}0.04$ arcsec, respectively. In the vertical direction, they were within ${\pm}0.02{\mu}m$ and ${\pm}0.05$ arcsec. From these results, it was found that the introduced measurement method was very effective to measure 5 DOF motion errors of the ultra precision feed tables.

• Smart Structures and Systems
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• 제15권3호
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• pp.751-767
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• 2015

A new procedure is proposed for assessing probabilistic condition of structures considering effect of measured data uncertainty. In this procedure, multiple Finite Element (FE) models are identified by using weighting vectors that represent the uncertainty conditions of measured data. The distribution of structural parameters is analysed using a Principal Component Analysis (PCA) in relation to uncertainty conditions, and the identified models are classified into groups according to their similarity by using a K-means method. The condition of a structure is then assessed probabilistically using FE models in the classified groups, each of which represents specific uncertainty condition of measured data. Yeondae bridge, a steel-box girder expressway bridge in Korea, is used as an illustrative example. Probabilistic condition of the bridge is evaluated by the distribution of load rating factors obtained using multiple FE models. The numerical example shows that the proposed method can quantify uncertainty of measured data and subsequently evaluate efficiently the probabilistic condition of bridges.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1998년도 학술발표회 발표논문집
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• pp.449-454
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• 1998

This study was performed of the research for accurate prediction of consolidation settlement at initial consolidation time. In order to analysis the program is developed which is able to analysis behavior of settlement caused by gradual load increment, and simulated consolidation using whole measured settlement data and that from beginning of embankment to end of it. The former result agrees with measured data and the latter it overestimated 13% larger than measured data. It was found the time which takes to be eliminated effect of gradual step load. This method is compared with the results from Asaoka, Hyperbolic and Tan's hyperbolic method respectively Asaoka and Tan's hyperbolic methods we in good agreement with this method. But classical hyperbolic method overestimated about 32%.

• 소음진동
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• 제8권2호
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• pp.306-312
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• 1998

This paper proposes a method for estimating the vibrational power supplied by a machine that generates excitation force to its supporting structure via the coupling points. The basis of the method is that the vibrational power can be calculated using the mechanical impedance and the velocity at the coupling points on the supporting structure. First, a method is described to estimate the mobilities at the coupling points when the machine is not separable from the supporting structure, then the vibrational power is calculated using the estimated mobilities and measured velocities at the coupling points. The mobilities are estimated from the result of impulsive testing of the coupled structure. The method is investigated using an experimental model. The estimated and measured values of the mobilities and the vibrational power are compared. It is shown that the estimated values agree well with the measured values.

• 한국정보통신학회논문지
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• 제5권7호
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• pp.1263-1271
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• 2001

There are two methods in blood pressure measurement ; Invasive methode and Non-invasive method. The Invasive methode can get the 띠cod pressure measurement but, patient feel uncomfortable. So Non-invasive methode used generally. The Oscillometric method is typical Non-Invasive method. This method is commonly used to measure BP in electric sphygmomanometer and has various algorithm. In this paper it is described about a algorithm, it controls, determinates the cuff pressure, and fillers the measured BP data. This system can interface with PC(personal computer) by RS-232 and save the measured data in PC. This system deflates the cuff pressure by Solenoid valve. The main algorithm are oscillometric and maximum amplitude algorithm(MAA). MAA has various measured oscillation, it depends on patient's age, height, weight and arm circumference size. In this paper proposed system can measure Systolic BP, Diastolic BP, and Mean BP using Interpolation, Auto Reinflation algorithm.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2008년도 추계학술발표대회 논문집
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• pp.69-74
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• 2008

This study is to analyze and compare on the sky condition of cloud amount and measured solar horizontal irradiation in Seoul. Sky cover method is determination of sky condition used by cloud amount of the Meteorological Administration. And HCI method is determination of sky condition used by measured solar horizontal irradiation. The HCI methods of Erbs et al.(1982), Orgill and Hollands(1977) appear a lot of error because of the air pollution such as smog phenomenon or yellow sand phenomenon and so on. Therefore, The purpose of this study is to improve the method for determination of sky condition.

• 한국공작기계학회논문집
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• 제10권2호
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• pp.56-63
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• 2001

The objective of this research is to develop a measurement error compensation method for On-Machine Measurement (OMM) process based on a closed-loop configuration. Geometric errors of vertical machining center are measured using ball-bar system, and probing errors are measured using master ball. The errors are represented using homogeneous trans-formation matrices and the closed-loop configuration method is applied to calculate 3-dimensional errors. To verify the effectiveness of the method proposed in this research, compensated results are compared to the data using CMM process, and the results are analyzed. The results show the proposed method can be applied in OMM process to make the measured data more reliable.

• 전기학회논문지P
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• 제57권3호
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• pp.291-295
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• 2008

We have developed an evaluation technique for ratio errors of current transformer (CT) comparator by using the precise standard capacitors. By applying this technique for equivalent circuit of CT comparator evaluation system, we can obtain the calculated and measured ratio errors in the CT comparator. Thus we can evaluate ratio errors of CT comparator by comparing the calculated and measured ratio errors. Because this method requires only the standard capacitors, it is simple and easy method to reliability and accuracy maintenance of CT comparator. The method was applied to CT comparator under test with the ratio error ranges of $0{\sim}{\pm}10%$. The ratio error of the CT comparator under test theoretically obtained in this method are consistent with that measured for same CT comparator under test by using wide ratio error CT within an estimated expanded uncertainty (k = 2) in the overall ratio error ranges.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.96-101
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• 2001

The development of a new experimental method is required to easily observe the growth behavior of fatigue cracks. To satisfy the requirement, an image processing technique was introduced to fatigue testing. The length of surface fatigue crack could be successfully measured by the image processing system. At first, the image data of cracks were stored into the computer while the cyclic loading was interrupted. After testing, crack length was determined using image processing software which was developed by ourselves. Block matching method was applied to the detection of surface fatigue cracks. By comparing the data measured by image processing system with the data measured by manual measurement with a microscope, the effectiveness of the image processing system was established. If the proposed method is used to monitor and observe the crack growth behavior automatically, the time and efforts for fatigue test could be dramatically reduced.