• Structural Engineering and Mechanics
• /
• v.60 no.2
• /
• pp.175-191
• /
• 2016

The present article is aimed at an investigation of stresses produced in a microstretch elastic half-space due to a moving load. The expressions of normal stress, shear stress and tangential couple stress produced in this case have been obtained in closed form. To find the displacement fields the perturbation method is applied. Significant effect of moving load on variation of stresses developed at different depths below the surface due to the depth of substrate and frictional coefficient of the rough surface of the medium has been observed. The effects of different shapes of irregularity and depth of irregularity on normal, shear and tangential couple stresses have been discussed. Some particular cases have also been deduced from the present investigation. Finally, the analytical developments have been illustrated numerically for aluminium-epoxy-like material substrate under the action of moving load.

• Proceedings of the KSR Conference
• /
• 2008.06a
• /
• pp.2173-2178
• /
• 2008

Railroad is the major factor of vibration source in railway vehicles, and it must carefully maintained the original condition to secure the safety and good ride comfort of passenger. Measuring the condition of rail irregularities such as surface, alignment, gauge, twist and cant etc is required to maintain the good performance of railroad. Currently, the various rail irregularity measurement systems(EM120, ROGER1000K and the Total Rail Irregularity Measurement system of Korea High Speed Train) are operated in Korea to estimate the rail irregularity. It is hard to verify the correlation of one rail irregularity data of a measurement system with the other, because they have been adopted different rail irregularity estimation methods. The best method securing the reliability of the irregularity data is the direct confirmation on the ground where the measurement system had detected as a fault section, but it is impossible to apply all sections simultaneously due to limitation of time, labor, cost and equipments. There is a method to secure the reliability of the data by using acceleration values. Rail irregularities, the major factor of vibration in railway vehicle, are transmitted to the vehicle acceleration through masses, springs, dampers and joints as the system dynamic formation. In this study, Transition Function has been adopted by using the rail irregularity and the acceleration value regarding as input & output parameters respectively. It has been verified by comparing the analyzed results with real measured irregularity data from the Total Rail Irregularity Measurement system of Korea High Speed Train. Also various methods has been accomplished to verify the correlation between rail irregularities and acceleration values.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.983-986
• /
• 2007

The absorption power of a surface depends on the surface irregularity which has been known as an important factor in determining scattering coefficient. This study investigates the effect of increase in surface area on the absorption and scattering coefficients of a diffuse surface. The surface irregularity or surface pattern can be compared to the wavelengths and the random-incidence scattering coefficient of surface is measured by ISO 17497-1. The scattering coefficients of increasing the surface area in linear pattern of v-cut groove on rubber plate were measured in 1:10 scale model reverberation chamber. It is found that the scattering and absorption coefficients increase with increasing surface area. At 60% of increased surface area the spacing between the hemisphere diffuser and the v-cut groove acts similar with results of absorption coefficient. The results show that absorption coefficient depends on surface area and the spacing where as scattering coefficient depends on surface area and texture.

• Korean Journal of Optics and Photonics
• /
• v.16 no.1
• /
• pp.71-78
• /
• 2005

A null lens system of autostigmatic type, consisting of two mirrors, is designed for testing a large aspherical mirror. The system is theoretically analyzed to determine the limitation of measurement accuracy according to the manufacturing and alignment errors. We confirmed that irregularity of the null lens surface is the principal factor among tolerances in limiting measurement accuracy. Consequently, we can predict that measurement accuracy will be from 5λ/100 to 4λ/1000 according to the amount of this irregularity. That is, we can present the limitation of possible measurement accuracy with actual alignment and manufacturing errors.

• Fibers and Polymers
• /
• v.6 no.1
• /
• pp.66-71
• /
• 2005

The surface evenness and texture are closely related with the irregularity of yam thickness. Besides, yam thickness variation has an important role to influence the yam performance and the textile process efficiency. Thus, the information not only on the yam thickness, but also on the short- term irregular characteristics that have not been known before is required for enhancing the qualities of textile products. This paper reports the results of a study about the yam thickness and its variation for various types of yam on the basis of a new measurement system applying a laser slit beam as a light source. The new method delivers effective information on the irregularity. The analysis of the measured signal confirms that the visual shade created by the yam doubling and twisting can be measured and the yam thickness characteristics can be represented by corre­lograms. Depending on yam types, correlograms have different shapes and can be approximated to an exponentially decaying function with or without fluctuating magnitude. In addition, the effective information on the yam irregularity can be influ­enced by the sampling length interval of the measuring device used for tests.

• Journal of the Korean Society for Railway
• /
• v.13 no.6
• /
• pp.583-588
• /
• 2010

Track irregularities is one of key factors influencing running behavior of train. In order to ensure safety and ride comfort, it is highly important that relationship between track irregularity and running behavior of vehicle is identified and the criteria for track irregularities is adequately established. Numerical analysis was conducted to investigate influence of surface on running behavior of KTX and various wavelength and amplitude of surface were considered in numerical analysis. Derailment, lateral load, bogie acc., body acc. of numerical analysis results were investigated to evaluate the effect on track profile on safety and ride comfort of KTX.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.22 no.3
• /
• pp.155-166
• /
• 2019

Road infrastructure has increased explosively due to economic development after industrialization and at present road infrastructure is being changed and increased by construction of new roads and maintenance and expansion of existing roads. Such road infrastructure should support safe driving. Road management plays an important role in safe driving. The purpose of this dissertation is to verify predictability of dangerous sections by analyzing road geometrical structure such as surface irregularity and superelevation for some sections in Central Inland Expressway by MMS and present ways of managing roads using MMS. Having analyzed surface irregularity of roads by using MMS, it was found that over 50 percent of all eight sections, targets of this study need betterments and for superelevation, over 50 percent of two sections goes against superelevation standard. Targets of this study are sections that accidents occurred frequently based on history of past accidents and predictability of dangerous sections can be verified through analysis of road geometrical structure using MMS. Using MMS data created by construction of high definition maps which are being undergone for all roads and methods proposed by this study will help investigate dangerous sections efficiently according to road environment. A result of MMS can be used for maintenance of road furniture.

• Journal of the Korean Society for Railway
• /
• v.14 no.6
• /
• pp.535-544
• /
• 2011

The rail surface defects can cause the high impact load on the track and lead to the progress of the rail fatigue damage and the rail break. In case of the rail break, there is a great deal of risk for derailment, and thus the maintenance criteria for the rail surface defects are of great importance. In this study, using the dynamic train-track interaction analysis program, the impact wheel loads and rail bending stresses according to the depths of the surface defects have been calculated with the input data of the rail surface irregularities measured at 43 spots with surface defects in the ballasted track of high-speed railway. Considering the irregularity of track geometry, the allowable limits of wheel load and rail bending stress have been set, and the maintenance criteria for the rail surface defects was suggested by analyzing the relationship of the maximum values of wheel load and rail bending stress versus depth and width of rail surface defect. The analysis results suggest that the allowable depth of the surface defect is determined approximately 0.2mm from the limit of the impact wheel load.

• Journal of Information Technology Services
• /
• v.13 no.2
• /
• pp.251-259
• /
• 2014

Outdoor cultural properties have been damaged by natural weathering and air pollution for a long time. For this reason, there are many characteristics it is hard to decipher some carved inscription on the surface of damaged outdoor cultural properties. Until now, Rubbed copy has been widely used to decode engraved inscription. A investigation for epigraph has been made by the rubbing that has resulted in a lower resolution from the viewpoints of extraction process and used materials. Rubbing's results are not satisfied in the damaged inscriptions which are weathered by natural environment and pollution for a long time and in the narrowed one. The main analysis presented in this paper is a cross section analysis method using 3d scanning technique for epigraph not read. Cross section analysis is a study on readability improvement method for ancient inscription of irregularity monument surface. Cross section analysis confirms information that separated the inscription information of monument and the ground information to read a ancient inscription and decode the inscription information. The proposed character identification method contributed to decoding an ancient inscription on Silla Monument in Jungseong-ri of Pohang.

• Proceedings of the Korean Fiber Society Conference
• /
• 2003.10a
• /
• pp.77-78
• /
• 2003

The surface evenness and texture of textile products are closely related with the irregularity of yarn thickness which has an important role to influence the quality and the process efficiency. For measuring yam thickness the capacitive method is known to dominate the market, delivering results that are in a close relation with the mechanical properties of yarn, while the optical method offers information that seems related rather with the apparent quality of yarn. If a thin light beam is applied for the optoelectrical measurement, it is very possible that this method can provide us with important information which is not obtainable from the capacitive type measurement. This paper reports the results of a study about the yarn thickness and its variation on the basis of a new measurement system using a laser slit beam. Analysis of the new system confirms that we can extract new information on the yarn irregularity ranging into much short wavelengths. Even the visual shade created by the yam doubling and twisting can be measured and represented well. Depending on the yam types, the thickness measurements show their own characteristics.