• Journal of Conservation Science
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• v.31 no.3
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• pp.267-278
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• 2015

In this study, the elastomer cover, a new contact material, was developed to establish the customized ultrasonic measurement considering surface irregularities of stone cultural heritages. The cover exhibits high elastic force and wear resistance because it has tensile strength of 17MPa and elongation of 625%. In addition, as a result of comparative experiments for the seven types according to transducers and contact materials including the elastomer cover, rock surface irregularities significantly affect attenuation of ultrasonic velocity. The phenomenon was more noticeable in the chiseling finish and indirect transmission measurement rather than the dabbed finish and direct transmission measurement. However, the Type F using the exponential transducer and elastomer cover showed stable P-wave velocity and high amplitude regardless of the surface irregularities. This because the elastomer cover sufficiently sticks to surface irregularities and removes pores between a transducer and a rock specimen. Therefore, the Type F should be used for the ultrasonic measurement of stone cultural heritages with surface irregularities.

• Proceedings of the KSR Conference
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• 1999.05a
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• pp.390-397
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• 1999

This paper investigates about the prediction of rail bending fatigue lifes for the purpose of the effective maintenance of surface irregularities of rail welded parts. The rail bending stresses are calculated using a track dynamic analysis program. The rail surface irregularities measured in situ are given as inputs in the analyses. On the other hand, the S-N curves are derived based on the results of bending fatigue tests. Using data found so far, rail fatigue lifes are estimated adopting a modified Miner's rule. The useful guides for maintenance of rail welded part are proposed in terms of grinding period and grinding depth of rail surface irregularities.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.539-545
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• 2009

KTX trains which began passenger service between Seoul and Busan in April 2004 have gained very high evaluation for their safe operation. Track is one of the most important means to keep KTX safety, it has not been a fail of safe structure. The track failure during operation may lead to a severe accident. So, it is to be verified the confidence of track maintenance management on the high speed line. This paper would like to find a track deformation trend through a comparative analysis on actual measurement data at these times. It discusses the effect of cyclic dynamic load at welding part. KTX dynamic impact load was measured in accordance with a rail surface irregularity and analyzed some track irregularities according to the condition of rail profile at welding part in the Gyeongbu high speed line.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.3
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• pp.23-31
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• 1995

The sending characteristics of the non-contact type displacement transducers can affect the performances of the magnetic bearing systems when they support the rotating shaft. The probe type displacement sensor detects not only the displacement of the rotor at the sensing position but also the surface irregularitis of the rotor such as surface roughnessand roundness errors. If there exist such measuring errors, the magnetic bearing can not apply proper force against the rotor displacements for the detected signal is the input to the magnetic bearing controllers. The cylindrical shape capacitive transducer can detect the rotor displacement by the integral sum of the charges which are formed between the sensor plates and rotor so that it can reduce the detecting errors induced by the surface irregularities of the rotor. By theore- tical analysis, we compared the sensing characteristics of the cylindrical shape capacitive transducers for the rotors that have some sinusoidal irregularities with that of the ideal probe type displacement transducers.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.291-295
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• 2007

The irregularities in the guideways used in the Maglev transportation system that result from surface roughness and deflection of guideway have strong effects on the dynamic characteristics of Maglev vehicles, because the electromagnetic suspension of Maglev vehicles strongly interacts with the guideway. For this reason, a numerical prediction of air gap responses to these irregularities is desirable to improve aspects of running performance, such as stability and passenger comfort, while minimizing aesthetic impact and construction cost. This paper presents a procedure to predict the air gap response which is a criteria for stability, and investigates the responses with the goal of attaining higher travel speeds in the urban Maglev vehicle UTM-01 utilizing electromagnetic suspension.

• Geophysics and Geophysical Exploration
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• v.8 no.1
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• pp.7-17
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• 2005

The determination of seismic velocities in refractors for near-surface seismic refraction investigations is an ill-posed problem. Small variations in the computed time parameters can result in quite large lateral variations in the derived velocities, which are often artefacts of the inversion algorithms. Such artefacts are usually not recognized or corrected with forward modelling. Therefore, if detailed refractor models are sought with model based inversion, then detailed starting models are required. The usual source of artefacts in seismic velocities is irregular refractors. Under most circumstances, the variable migration of the generalized reciprocal method (GRM) is able to accommodate irregular interfaces and generate detailed starting models of the refractor. However, where the very-near-surface environment of the Earth is also irregular, the efficacy of the GRM is reduced, and weathering corrections can be necessary. Standard methods for correcting for surface irregularities are usually not practical where the very-near-surface irregularities are of limited lateral extent. In such circumstances, the GRM smoothing statics method (SSM) is a simple and robust approach, which can facilitate more-accurate estimates of refractor velocities. The GRM SSM generates a smoothing 'statics' correction by subtracting an average of the time-depths computed with a range of XY values from the time-depths computed with a zero XY value (where the XY value is the separation between the receivers used to compute the time-depth). The time-depths to the deeper target refractors do not vary greatly with varying XY values, and therefore an average is much the same as the optimum value. However, the time-depths for the very-near-surface irregularities migrate laterally with increasing XY values and they are substantially reduced with the averaging process. As a result, the time-depth profile averaged over a range of XY values is effectively corrected for the near-surface irregularities. In addition, the time-depths computed with a Bero XY value are the sum of both the near-surface effects and the time-depths to the target refractor. Therefore, their subtraction generates an approximate 'statics' correction, which in turn, is subtracted from the traveltimes The GRM SSM is essentially a smoothing procedure, rather than a deterministic weathering correction approach, and it is most effective with near-surface irregularities of quite limited lateral extent. Model and case studies demonstrate that the GRM SSM substantially improves the reliability in determining detailed seismic velocities in irregular refractors.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.34 no.2
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• pp.73-83
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• 2002

Gloss is very important optical property influencing the perceived quality of the paper surface as well as the surface after printing. Although the average gloss level of paper products or printed images is important to meet end use specifications, the occurrence of gloss mottle, or non-uniformity of gloss, is often of greater concern for meeting quality requirements, especially for the high gloss paper. Gloss variation originates from the irregularities of paper surface, especially surface roughness of paper. Roughness of paper can be divided into micro-roughness (under $1\mu m$ scale in variation) and macro-roughness (over $1\mu m$ scale in variation) depending on the scale of the irregularities. A clearer understanding of the gloss variation of paper can be achieved by separating the contributions of these two scales of roughness, and characterizing them independently. In order to do this, a novel gloss measuring method was introduced. This can detect local gloss with very high resolution. The effect of macro-roughness on gloss variation, which was identified by the measurable surface topography, was separated from the total gloss variation by using this method. The effect of micro-roughness was then estimated indirectly. The local gloss variations of various paper samples were then evaluated to demonstrate the utility of this approach.

• Journal of the Korean Society for Railway
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• v.18 no.1
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• pp.63-70
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• 2015

Track irregularities have a strong influence on the safety and the ride comfort of trains as well as track maintenance work. A statistical analysis was conducted for track irregularities data measured in Kyoungbu high speed line using a track recording car(EM120). First, the characteristics of EM120, which adopted versine measurement system, were investigated and the transfer function of EM120 was examined. The distributions of the surface and the alignment which have short wavelength were considerably high and the distribution decreased as wavelength increases. A distribution analysis of the wavelength was carried out according to EN standards and most of the track irregularities were in a D1 wavelength range. The distributions of the amplitude of track irregularities were also investigated and the results show that the distributions of track irregularities decrease rapidly as amplitude increases. These results may be helpful in making track maintenance plans and revising track irregularities criteria.

• Journal of the Korean Society for Railway
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• v.4 no.4
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• pp.138-146
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• 2001

For the purpose of the effective maintenance of surface irregularities of rail, this paper investigates the rail service life to a bending fatigue failure of welding parts of rail on the slab track by the structures laboratory testing to derive S-N curves, a GTDAP(General Track Dynamic Analysis Program) to calculate the stresses and a modified Miner's rule to predict a fatigue life. The useful guides for maintenance of rail welded parts on the slab track are proposed in terms of a grinding period and the depth of rail surface irregularities. This study also proposed the guides for maintenance of rail welded part on the ballast track. The effects of fatigue service lives are compared one another.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1028-1033
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• 2004

The open deck steel bridge is the most common type in railway bridges. Steel I-shaped girders are connected with sleepers directly without ballast and moving train loads are transmitted directly to the girder, so this bridge has weak characteristics on impact. Therefore, considerable accelerations can cause unsatisfactory dynamic behavior of the open deck steel bridge. Especially, Impact created at rail joints can increase the dynamic response of the bridge and this phenomenon would be injurious to passenger comfort. In the present study, dynamic behavior of the open deck steel bridge which has a rail joint is estimated through experimental studies and bridge-train interaction analysis considering surface irregularities by rail joints.