• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1433-1437
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• 2005

Until now, strain gage technique and accelerometer for the diagnosis safety of constructions are used widely. However, the limits of these methods are revealed. But Electronic Speckle Pattern Interferometry(ESPI) that uses Pulse Laser is noncontact, whole-field, real-time measuring method also dull to disturbance and can achieve test result in a very short time. It has various strong point in spot application, swift establishment, and dynamic conduct analysis for the entire field of Laser illuminate. This author analyzed vibration characteristic of using the Pulse ESPI System, the diagnosis safety of bridges, to simplify the analysis of the dynamic conduct of a large construction.

• Journal of Astronomy and Space Sciences
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• v.24 no.4
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• pp.431-450
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• 2007

In the auto-guiding system for obtaining a long exposure astrophotography, CCD camera is usually used for measuring guide errors which are affected by optical dispersion and mechanical disturbances. In this paper, a discrete time dynamic model and a performance index are proposed for analysing the auto-guiding system. The optimal gain for proportional control is derived considering the optical dispersion and the disturbances. Some experiments are provided to illustrate that the optimal control gain is lower as the optical dispersion is higher.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.1084-1088
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• 1995

In this paper, an electrostatic plate resonator with four corrugated bridges and another with four flat ones have been fabricated and tested by the electrostatic actuation. The resonators consist of one rigid plate and four bridges. Boron diffusion process and anisotropic etch process with EPW are mainly used to fabricate the resonators. The dynamic characteristics of the fabricated resonators are obtained by measuring the velocity of the center of the rigid plate using a laser vibrometer. The results show that the deflection of the resonator with the corrugated bridges is larger than the resonator with the flat ones. It has been confirmed that the corrugated structure releases the residual tensile stress in the bridges resulted from the diffusion process.

• Journal of Sensor Science and Technology
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• v.17 no.3
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• pp.223-228
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• 2008

A more accurate method of measuring the electrical conductivity (L) of solutions was developed by applying dynamic temperature compensation for measurement of L. Temperature changes of a sample were induced by a heater probe and the changes in L per unit temperature were measured. An equation for L with respect to temperature change was developed and L at the standard temperature ($25^{\circ}C$) was computed. Based on our proposed method, it is possible to have temperature compensation without having the temperature coefficients in advance.

• Geomechanics and Engineering
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• v.12 no.1
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• pp.1-8
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• 2017

An experimental technique for determining the spalling strength of rock-like materials under a high strain rate is developed. It is observed that the spalling strength of a specimen can be determined by only knowing the wavelength, loading peak value and length of the first spallation of an incident wave under a specific loading waveform. Using this method in combination with a split-Hopkinson pressure bar (SHPB) and other experimental devices, the spalling strength of granite specimens under a high strain rate is tested. Comparisons with other experimental results show that the new measuring method can accurately calculate the dynamic tensile strength of rock materials under a high strain rate.

• Journal of Advanced Marine Engineering and Technology
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• v.16 no.5
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• pp.17-28
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• 1992

During the last decade, engine makers have developed new types or increasing power rate engines to enlarge theirs marketing shear in two stroke, low-speed diesel engines. As the results, these engines have increased the additional stresses due to torsional vibration more than old model engines. The torsional vibration dampers are necessary in order to reduce heigher additional stresses of intermediate and crank shaft in these engine. In this paper, the optimum designing of Geislinger type torsional Damper has been carried out, based on the theoretical conception. The dynamic characteristics and performance fo dampers are estimated by the measuring results obtained with the monitoring system of dampers and additional stresses of propulsion shafts.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.863-868
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• 2001

It is necessary to design th anti-vibration system of precision machinery for a sound operation and a quality assurance. However, in general. the allowable vibration limit is not well known. In the paper, the vibration criteria for foundation of vibration sensitive machinery is proposed and anti-vibration system is designed by using vibration measurement results of foundation. Also, the F.E. analysis is performed to verify the effectiveness of a designed anti-vibration system and to determine allowable dynamic load of machinery

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1062-1067
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• 2007

This study presents an experimental technique to monitor the dynamic behavior of the railway bridge system simultaneously using multiplexed fiber Bragg grating (FBG) sensors. The measuring quantities include stains, curvatures, vertical deflections, and vertical accelerations. The strains are directly measured from multiplexed FBG sensors at various locations of the test bridge followed by curvature calculations based on the plane section assumption. Vertical deflections are then estimated using the Bernoulli beam theory and regression analysis. Finally, vertical accelerations are obtained from the numerical differentiation in time domain. In order to verify the proposed method, several conventional electric strain gauges, displacement transducers, and accelerometers are installed at the mid-span of the bridge for comparisons. A test train is passed over the bridge to monitor the dynamic response of the bridge. The monitoring results show that the multiplexed FBG sensing system is able to capture the essential behavior of the test bridge while resolving wiring problem in practice.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.947-953
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• 2010

The KTX-Sancheon has been commercially operating on the high-speed line since March. 2. In order to verify the performance of high-speed train and core equipments such as current collection system, sophisticated tests and evaluating procedures should have been considering. In this paper, the load cell with a built-in strain-gauge which developed to improve measuring method of contact force between the pantograph and catenary system is introduced. The static test results of the load cell shows that its design is very suitable and applicable for the dynamic test and on-line test. After the test and evaluation of load cell's dynamic calibration with pantograph, we will be applied to test interaction characteristics between the pantograph and catenary system on the high-speed line.

• Tribology and Lubricants
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• v.23 no.2
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• pp.56-60
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• 2007

The main object of this study is to compare the results that have been concluded by the experiment and to estimate the temperature rise that can cause the contacting surface to be damaged. The former studies are based on the Blok and Jaeger formula. By these formulas we assume that two of the contacted objects are a kind of semi-infinite solid and with this assumption we can make a temperature analysis. But this method doesn't consider lubrication conditions and the calculation time requires a lot of time in that we have to face many difficulties in measuring the actual temperature rise. In this study we combines the semi-infinite solid method and the finite volume method to analyze the temperature of the contacting surface. And we measure temperature rise of the contact surface by dynamic thermocouple.