• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.831-836
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• 2006

In the process of accurate manufacture and measurement, it is necessarily required to isolate external or internal vibration due to external disturbance and internal actuators. The higher vibration isolation system gets damping around resonance, the better it is generally. This paper analyzes the performance of an existing passive air-spring for vibration isolation table by using experiment and simulation. Optimal design for a passive air spring can be obtained by tuning the size of the orifice. Also design for an active isolation system is carried out by applying PID controller and considering non-linearity of pneumatic characteristics with help of look-up table. We have developed the active vibration isolation table with the better isolation performance.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.2
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• pp.208-213
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• 2012

In this paper, the radial error of a rotary table at five-axis machine tool is evaluated by utilizing ISO 230-2 and estimation method using double ball-bar. The geometric error of a rotary table is defined as position dependent geometric errors or position independent geometric errors according to their physical character. Then estimation method of geometric errors using double ball-bar is simply summarized including measurement path, parametric modeling and least squares approach. To estimate representative radial error, offset error, set-up error which affect to the double ball-bar data, mean value of measured data including CCW/CW-direction are used at estimation process. Radial errors are separated from measured data and used for evaluation with ISO 230-2. Finally, suggested evaluation method is applied to a rotary table at five-axis machine tool and its result is analyzed to improve the accuracy of the rotary table.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.8 s.185
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• pp.72-79
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• 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.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.862-874
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• 1989

A phase evil method and spectrum analysis were instrument error which is originated from measurement system and the form error of standard specimens. An instrument with a rotating table supported by an air bearing is calibrated using standard specimens. The phase of standard specimens was measured 12 times on the rotating table with rotating 30 in turn and its measurement magnification was set by 100000 times. As a result of data analysis of all the observations, read out at each of 144 orientations(per 2.5) from recorded datafiles, the error of the performance of the instrument and those of the standard specimens are evaluated and a systematic deviation of the instrument is determined. In the particular instrument used in the present experiment, the deviation of the instrument is determined with the accuracy of 15nm and those of standard specimens with the accuracy of 23, 13 n, respectively. The reproducibility of the instrument is investigated, too. If the instrument is calibrated by using the above standard specimens, then the accuracy of the measurement of roundness error can be improved to about 15nm.

• Journal of Auto-vehicle Safety Association
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• v.10 no.1
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• pp.45-51
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• 2018

There are some ambiguities of the information on the fuel economy provided to the consumers because the standard and the detailed regulations for the fuel economy of the two-wheeled vehicle have not been established in Korea. Since Korea has been a signatory of World Forum for Harmonization of Vehicle Regulations since 1998, it is possible to remove the ambiguities by adopting the WMTC (Worldwide-harmonized Motorcycle Test Cycle) measurement method for the fuel economy of the two-wheel vehicle. As a preliminary study on the WMTC mode fuel economy, road loads measured by coast down method and table method were compared for the two types of two-wheeled motorcycles on sales in domestic market. In the same model, it was confirmed that the deviation of WMTC mode fuel efficiency was below -5% between products. On the other hand, the difference of WMTC fuel economy exceeded 5% between the coast down method and table method.

• Journal of the Korean Society of Physical Medicine
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• v.8 no.2
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• pp.209-217
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• 2013

PURPOSE: The purpose of this study was to investigate the clinical availability of the pendulum test (through reliability and validity) using a NK table attached electrogoniometer for spasticity measurement in patients with brain lesions. METHODS: Thirty-one stroke and traumatic brain injury subjects participated in the study. Intraclass correlation coefficient (ICC) was used to verify the test-retest reliability of spasticity measures of the pendulum test. Pearson's product correlation coefficient was used to examine the validity of the pendulum test through the amplitude of the deep tendon reflex (DTR) test known for objective and quantitative measure of spasticity. RESULTS: In these results, the test-retest reliability was showed significantly high correlation between pendulum tests (ICCs=.95~.97, p<.01). There were significant negative correlations between the amplitude of the DTR test and all measures of spasticity of the pendulum test(r=-.77~-.85, p<.01). CONCLUSION: Thus, it is possible to use the pendulum test using a NK table as an objective measure of spasticity, rather than other expensive equipment, which is more complicated to use. Further studies are needed to explore the therapeutic effects of spasticity using a newly designed pendulum test equipment in this study.

• Korean Journal of Agricultural Science
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• v.7 no.2
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• pp.109-118
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• 1980

This test was carried out to present criterion to measure the liquid limit of weathered granite soil by using the flow-table method whose operation is easier and more convenient than slump test. The results are as follows. 1. Since liquid limit of weathered granite soil depends upon the particle size distribution, weatheredness and content of colored minerals, maximum particle size should be prescribed when the testing rule of liquid limit by flow-table method is enacted. 2. If take the averaged water content as liquid limit where the height and width of flow are 1 cm respectively by 10 times dropping, this liquid limit is slightly less than the one by slump test. The differance of liquid limit between flow table method and slump test is about 10%. 3. Correlation curves of flow width-water content and flow hight-water content show similar shapes. Those are straight lines in semi-logarithm paper just as liquid limit test. 4. This flow-table method is more convenient and has less personal error of measurement than slump test does. So flow-table method would be favourably utilized for judging the engineering properties of soil.

• International Journal of Quality Innovation
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• v.5 no.1
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• pp.68-84
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• 2004

The measured values of a same object should remain constant regardless of the object's position in the image. In other words, its measured values should not vary as its position in the image changes. However, lens' image distortion, heterogeneous light source, varied angle between the measuring apparatus and the object, and different surroundings where the testing is set up will all cause variation in the measurement of the object when the object's position in the image changes. This research attempts to compensate the machine vision image distortion caused by the object's position in the image by developing the compensation table. The compensation is accomplished by facilitating users to obtain the correcting object and serves the objective of improving the precision of measurement.

• Applied Science and Convergence Technology
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• v.23 no.3
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• pp.103-112
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• 2014

The Korea Research Institute of Standards and Science (KRISS) has three major vacuum systems: an ultrasonic interferometer manometer (UIM; Section II, Figs. 1 and 2) for a low vacuum, a static expansion system (SES; Section III, Figs. 3 and 4) for a medium vacuum, and an orifice-type dynamic expansion system (DES, Section IV, Figs. 5 and 6) for high and ultra-high vacuum systems. For each system, explicit measurement model equations with multiple variables are given. According to ISO standards, all of these system variable errors were used to calculate the expanded uncertainty (U). For each system, the expanded uncertainties (k = 1, confidence level = 95%) and relative expanded uncertainty (expanded uncertainty/generated pressure) levels are summarized in Table 4. Within the uncertainty limits, our bilateral and key comparisons [CCM.P-K4 (10 Pa to 1 kPa)] are extensive and in good agreement with those of other nations (Fig. 8 and Table 5).

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.5
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• pp.23-31
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• 2010

In this study, a shaking table test was performed for the evaluation of the failure capacity of an anchor foundation system in the case of an aged condition. For the shaking table test, three kinds of specimens were manufactured as follows: 1) a non-damaged anchor; 2) a specimen with cracks running through the anchor; and 3) a specimen with cracks along the expected corn-shape fracture away from the anchor. A dynamic characteristic was determined through a measurement of the frequency response function (FRF), and the seismic capacity was evaluated by using a shaking table test. Failure capacities were calculated using an acceleration response and it was compared with the anchor design code.