• Proceedings of the KSR Conference
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• 2010.06a
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• pp.507-513
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• 2010

This paper is described the analysis of time-varying low-frequency electric magnetic field emitted from electric rolling stocks fed by VVVF inverter, in reference to allowable magnitude for exposures to time-varying electromagnetic field issued by International Commission on Non-Ionizing Radiation Protection(ICNIRP). The level of the magnetic field strength was measured, in reference to the standard for occupational environments, which takes into account the public person's protection against the excessive emission of the low-frequency magnetic field, 5 Hz ~ 2 kHz.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.365-370
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• 2007

Foundation settlements(settlements at the embankment surface and ground) has been evaluating to satisfy the strict allowable residual settlement level from the start of the construction of Gyungbu high speed railway. This is because both embankment and ground settlement could be important to minimize the residual settlement after the construction of concrete track. Ground settlement is caused by the increase of effective stress resulting from embankment. The causes of embankment settlement could be come from different sources, for example, the increase of effective stress, rainfall, creep behaviors. Based on the field measured data, this paper analysed the settlement of ground and embankment settlement. The biggest settlement at the embankment surface was 9.7mm during 246days at the STA 000k922.5. The calculated settlement of embankment itself was 8.6mm at the same places. These results conclude that the compressive settlement of embankment could not negligible.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.500-504
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• 2007

Database are developed to control measured settlement data under construction in Gyungbu High Speed Railway from Daegu to Busan. This means that data having different type at different site could be managed in a unified way. The database includes algorithm to evaluate embankment settlement with settlement data at the surface of embankment and ground settlement data. And also, it has a function to analyse the causes of large settlement over allowable level and high settlement speed based on the log data, embankment specification, physical characteristics of embankment materials.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1005-1011
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• 2007

The brake system of train must posses the large braking effort in order to stop the train safely within the limited traveling distance. But, the excessive braking effort has been deteriorated the ride comfort due to high level of deceleration and jerk, and sometimes occurred the skid, because the applied braking force exceeds the allowable adhesive force. This skid causes not only to increase the stopping distance but also to deteriorate the safety of train and damage the rail surface by wheel flat. In the present paper, the braking force for disc brake of Korea High Speed Train (HSR350x) was measured through on-line test and the adhesion force was estimated by using the analytic model in the skid condition. Also, we have discussed the relationship between the actual disc brake force and the adhesion force in real skid condition.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.736-741
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• 2004

In high-capacity disk drives with ever-growing track density, the allowable level of position error signal (PES) is becoming smaller and smaller. In order to achieve the high TPI disk drive, it is necessary to improve the writing accuracy during the STW(servo track writing) process through the reduction of TMR sources. Among the main contributors of the NRRO(Non-Repeatable Run-out) PES, the disk vibration and the HSA(head-stack assembly) vibration is considered to be one of the most significant factors. Also the most contributors of RRO(Repeatable Run- out) come from the contributors of NRRO which is written-in at the time of STW(servo track writing) process. In this paper, the experimental test result shows that the effect of NRRO on servo written-in RRO effectively can be reduced through a STW process under low dense medium condition such as semi-vacuum.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.4
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• pp.7-13
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• 1992

Diffraction loss occurs when the propagation path is obstructed by mountains and hills between a base station antenna and a moving vehicle antenna in mobile-radio communication. In this paper an approximate mathematical model using Fresnel-Kirchhoff diffraction theory is considered to predict propogation attenuation by natural obstacles with lateral profiles having general shapes. Field tests are conducted using helical and crossed drooping dipole antenna at 820 MHz. The theoretical analysis used in estimating the effects of hills agrees reasonably with experimental data. The results seem to be useful for estimating the level of received power, the minimum allowable input power, the optimum site of base station and consequently, planning terrestrial microwave links.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.28 no.1
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• pp.83-89
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• 2020

Personal air vehicle (PAV) is considered by aviation engineers as a solution to provide fast urban mobility. The purpose of designing a optionally piloted PAV (OPPAV) is to provide an individual air vehicle. The airframe structure is designed with high strength carbon fiber composite to reduce the aircraft weight. This paper presents an overview of sizing process for OPPAV at the conceptual design level. It consists of load analysis, structural sizing and development of efficient design allowable values for composite material. The weight is estimated based on sizing process, including strength and stiffness requirements. The objective of this study is to present a overview of structural sizing procedure and fast tool for preliminary design phases.

• Tunnel and Underground Space
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• v.4 no.1
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• pp.38-46
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• 1994

This paper concerns the design of blasts adjacent to structures and facilities. In order to investigate the site characteristics, measurements of in-situ wave propagation and laboratory tests of rock cores taken from the boreholes were carried out. Effects of rock media and delay intervals on ground vibration levels were identified from over sixty measurements of three times of test blasts. For practical use in the field, an empirical propagation equation was derived so as to reflect the characteristics of rock media and delay effects. Safe limits of vibration level for structures were conservatively established based on various suggested criteria. Safe limits for facilities were adopted so that vibration levels induced by blasting should not exceed the allowable limits specified in the manufacturer's installation condition. Suggested were blast pattern and operation to enhance the rock fracturing and to reduce the ground vibration levels under the restricted conditions.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.15 no.3
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• pp.70-76
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• 2007

The benefits for using reduced takeoff thrust are many, ranging from lower maintenance and operating costs to improved engine and dispatch reliabilities. Some pilots, however, are apprehensive about using reduced thrust. They are particularly reluctant to use the maximum permissible level of reduced thrust. Two common arguments are (1)If reduced thrust is used, then the airplane will not be able to clear the obstacles if an engine fails during takeoff, and (2)If the maximum allowable assumed temperature is used, then there will be no stopping margin left if the takeoff is aborted. There is the notion that using reduced thrust sacrifices safety. The intent of this discussion is to: (1)Show that reduced thrust performance meets all regulatory requirements (2)Show that the Assumed Temperature method includes inherent extra performance margins (3)Show how to maximize performance margins while maximizing thrust reduction.

• Journal of the Korea institute for structural maintenance and inspection
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• v.1 no.2
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• pp.107-113
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• 1997

Nondesructive test and structural analysis have been conducted to assess the safety of weld defective steel bridges in service. In the nondestructive test, using the radioactive ray and ultrasonic, the defective welding patterns in the steel bridges are identified. A major defective welding pattern is identified as the lack of welding area due to the insufficient welding penetration. By considering the welding defect in the above, structural analysis is conducted to evaluate the influence of welding defect on the safety of steel bridges. The results indicate that, due to the insufficient welding penetration, the stress obtained in the analysis is over the allowable fatigue stress level, and its influence on safety of the bridges is significant.