• 한국과학교육학회지
• /
• 제31권1호
• /
• pp.115-127
• /
• 2011

본 연구에서는 탐구 기능 가운데 자료 수집, 자료처리, 자료 해석과 관련하여 실험보고서 분석틀을 개발하였다. 또한 개발한 분석틀을 대학생들의 보고서 분석에 적용하여 오차와 불확도 개념을 중심으로 대학생들이 보고서 작성에서 어려움을 겪고 있는가에대해 알아보았다. 물리실험 수업을 수강한 30명의 학생들에게 실시한 설문지와 학생들이 작성한 실험보고서를 분석하였다. 학생들은 자료 수집과 관련하여 반복 측정에 대해 인식을 하고 있으나 보고서에서는 이를 명확하게 표현하지 못하였다. 극값이나 기울기가급하게 변하면 더욱 정밀한 측정을 해야 하지만 학생들은 이 부분에서도 어려움을 지니고 있었다. 특히, 오차와 불확도와 관련하여 학생들은 많은 어려움을 표출하고 있었다. 오차와 불확도의 전파에 대한 이해도가 매우 낮은 상태에서 단순한 오차 전파공식도 이용하지 못하는 학생이 많았다. 오차와 불확도를 분석을 통해 자료를 해석하는 과정에서도 많은 어려움을 겪고 있었는데, 오차의 원인들이 결과에 어떻게 영향을 주는지를 정량적으로 분석할 수 있는 학생은 거의 없었다. 반면에 학생 대부분이 오차와 불확도 분석이 중요하다고 응답하였다. 학생들이 중요성을 인식하고 있으나 올바른 개념을 지니지 못하여 보고서 작성에서 어려움을 겪고 있다는 결론을 내릴 수 있었다. 실험 수업에서 보고서를 통해 과학적 의사소통을 해야하는 학생들에게 물리 개념뿐만 아니라 자료를 수집하고 처리하고 해석하는 데 필요한 기본 개념에 대한 교육이 필요할 것이다.

• 한국전자파학회논문지
• /
• 제23권12호
• /
• pp.1365-1372
• /
• 2012

본 논문에서는 임펄스 발생기로부터 계측 시스템으로 전달되는 펄스 신호의 주파수 성분을 매우 정밀하게 측정하고 관련 불확도를 평가하는 시스템과 방법을 다루었다. 임펄스 신호의 스펙트럼 진폭 불확도를 결정짓는 복잡한 요소들과 그 해석적 분석 방법 및 실측을 통한 평가 결과를 제시하였다. 측정 시스템의 확장 불확도는 0.015이고, 이는 국내 최고 수준이며 세계적 교정기관의 결과와도 대등한 수준이다.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 1993년도 수공학연구발표회논문집
• /
• pp.343-350
• /
• 1993

• 한국가시화정보학회지
• /
• 제3권2호
• /
• pp.71-78
• /
• 2005

Uncertainty introduced by a cross-correlation algorithm based on FFT has been investigated using PIV standard images. The standard images were generated by the Monte Carlo simulation method. Both bias and random errors from the velocity vector have been analyzed with regard to the particle diameter, displacement, and the number of particles. The uncertainty of velocity is evaluated based upon the IS0/IEC standard. As a result, a total error of $0.26\%$ is included in the PIV cross-correlation algorithm. In addition, the uncertainty budget is presented, where the effect of the above three variables is examined. According to the budget, the variation of the number of particles within the interrogation window mainly contributes to the combined standard uncertainty of the real measured velocity field when excluding the effect of errors by the experiments itself. Finally, the expanded uncertainty is found to be about $12\%$ at the $95\%$ confidence level.

• 한국정밀공학회지
• /
• 제32권5호
• /
• pp.415-422
• /
• 2015

Ballscrews are important motion transfer and positioning units of industrial machinery and precision machines. Positioning accuracy of the feed drive system depends upon axial stiffness of ballscrew systems. As the nut stiffness depends upon preload and operating conditions, analytical modeling of the stiffness is performed through the contact and body deformation analysis. For accurate contact analysis, the contact angle variation between balls and grooves is incorporated in the developed model. To verify the developed mathematical stiffness model, experiments are conducted on the test-rig. Through the uncertainty analysis according to GUM (Guide to the expression of Uncertainty in Measurement), it is confirmed that the formulated stiffness model has over 85% estimation accuracy. After constructing the ballscrew DB, a quick turnaround system for the nut stiffness estimation has been developed in this research.

• 한국정밀공학회지
• /
• 제26권4호
• /
• pp.91-99
• /
• 2009

Because of both precise measurement and efficient quality control, coordinate measuring machines(CMMs) have been widely used in the industry. The purpose of this paper is to present a method to estimate the CMM measurement uncertainty using design of experiments. A factorial design is applied to carry out the performance test proposed by ISO 10360 and to investigate CMM measurement errors associated to orientation and length of the length bar. In order to assess the measurement uncertainty for the performance test, an analysis of the uncertainty components that make up the uncertainty budget has been carried out. The procedure for evaluating the uncertainty of it follows GUM ("Guide to the expression of uncertainty in measurement"). The results show that the proposed method is suitable to investigate CMM performance and determine the contribution of machine variables to measurement uncertainty.

• 한국정밀공학회지
• /
• 제23권8호
• /
• pp.72-79
• /
• 2006

We measured grating pitch standards using optical diffractometry and analyzed measurement uncertainty. Grating pitch standards have been used widely as a magnification standard for a scanning electron microscope (SEM) and a scanning probe microscope (SPM). Thus, to establish the meter-traceability in nano-metrology using SPM and SEM, it is important to certify grating pitch standards accurately. The optical diffractometer consists of two laser sources, argon ion laser (488 nm) and He-Cd laser (325 nm), optics to make an incident beam, a precision rotary table and a quadrant photo-diode to detect the position of diffraction beam. The precision rotary table incorporates a calibrated angle encoder, enabling the precise and accurate measurement of diffraction angle. Applying the measured diffraction angle to the grating equation, the mean pitch of grating specimen can be obtained very accurately. The pitch and orthogonality of two-dimensional grating pitch standards were measured, and the measurement uncertainty was analyzed according to the Guide to the Expression of Uncertainty in Measurement. The expanded uncertainties (k = 2) in pitch measurement were less than 0.015 nm and 0.03 nm for the specimen with the nominal pitch of 300 nm and 1000 nm. In the case of orthogonality measurement, the expanded uncertainties were less than $0.006^{\circ}$. In the pitch measurement, the main uncertainty source was the variation of measured pitch values according to the diffraction order. The measurement results show that the optical diffractometry can be used as an effective calibration tool for grating pitch standards.

• 한국정밀공학회지
• /
• 제24권9호
• /
• pp.68-75
• /
• 2007

The pitch and orthogonality of two-dimensional (2D) gratings have been measured by using a metrological atomic force microscope (MAFM) and measurement uncertainty has been analyzed. Gratings are typical standard artifacts for the calibration of precision microscopes. Since the magnification and orthogonality in two perpendicular axes of microscopes can be calibrated simultaneously using 2D gratings, it is important to certify the pitch and orthogonality of 2D gratings accurately for nano-metrology using precision microscopes. In the measurement of 2D gratings, the MAFM can be used effectively for its nanometric resolution and uncertainty, but a new measurement scheme was required to overcome some limitations of current MAFM such as nonnegligible thermal drift and slow scan speed. Two kinds of 2D gratings, each with the nominal pitch of 300 nm and 1000 nm, were measured using line scans for the pitch measurement of each direction. The expanded uncertainties (k = 2) of measured pitch values were less than 0.2 nm and 0.4 nm for each specimen, and those of measured orthogonality were less than 0.09 degree and 0.05 degree respectively. The experimental results measured using the MAFM and optical diffractometer were coincident with each other within the expanded uncertainty of the MAFM. As a future work, we also proposed another scheme for the measurements of 2D gratings to increase the accuracy of calculated peak positions.

• 한국정밀공학회지
• /
• 제22권4호
• /
• pp.84-91
• /
• 2005

We measured the pitch of one-dimensional (ID) grating specimens using a metrological atomic force microscope (M-AFM). The ID grating specimens a.e often used as a magnification standard in nano-metrology, such as scanning probe microscopy (SPM) and scanning electron microscopy (SEM). Thus, we need to certify the pitch of grating specimens fur the meter-traceability in nano-metrology. To this end, an M-AFM was setup at KRISS. The M-AFM consists of a commercial AFM head module, a two-axis flexure hinge type nanoscanner with built-in capacitive sensors, and a two-axis heterodyne interferometer to establish the meter-traceability directly. Two kinds of ID grating specimens, each with the nominal pitch of 288 nm and 700 nm, were measured. The uncertainty in pitch measurement was evaluated according to Guide to the Expression of Uncertainty in Measurement. The pitch was calculated from 9 line scan profiles obtained at different positions with 100 ㎛ scan range. The expanded uncertainties (k = 2) in pitch measurement were 0.10 nm and 0.30 nm for the specimens with the nominal pitch of 288 nm and 700 nm. The measured pitch values were compared with those obtained using an optical diffractometer, and agreed within the range of the expanded uncertainty of pitch measurement. We also discussed the effect of averaging in the measurement of mean pitch using M-AFM and main components of uncertainty.

• 한국기계가공학회지
• /
• 제13권1호
• /
• pp.16-22
• /
• 2014

Resonance refers to the magnification of a structural response which occurs when a linear lightly damped system is driven with a sinusoidal input at its natural frequency. An exploratory vibration test (a natural frequency measurement test) is very important for the vibration testing of machine parts, as the value measured in an actual laboratory affects test results. For this reason, it is necessary to estimate the measurement uncertainty to verify the reliability of this type of test. In this study, measurement uncertainty is estimated based on three uncertainty factors. The uncertain factors are the measured points in the machine parts, the resolution of the vibration equipment, and uncertainty of the calibration certificate.