• Proceedings of the KSR Conference
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• 2000.05a
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• pp.479-486
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• 2000

There has been recently an on-going effort in railway community to improve the dynamic performance of on-site railroad track with limited track possession time. In this paper, train running test lateral resistant force test and static/dynamic analyses are conducted before and after sprinkle of the ballast stabilizer in order to investigate the dynamic behaviors and parameters of the railroad track. Based upon the above results, effects of the stabilizer is verified, and a table for the track modulus representing on-site track condition and the methods to reduce the vibration and the transmitting forces of the ballasted track components to the infrastructures are suggested. It is thought that the suggestions made in this paper could be used as the preliminary data for the condition assessment and the maintenance of the track in the future.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.04a
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• pp.28-28
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• 2002

가스터빈 엔진을 운용하는 데 있어서 가/감속율을 크게 하면 엔진성능 천이 시간은 짧으나 압축기에서의 서지나 터빈 입구온도의 급격한 상승이 발생할 수 있으며 가/감속율을 작게 하면 엔진은 안정적이나 천이시간이 길어지게 되어 결과적으로 엔진의 동적 응답성이 나빠지게 된다. 또한 압축기에서 발생할 수 있는 서지를 방지하기 위하여 압축기 서지 마진이 l0%∼20%인 서지 한계선(조정선)을 설정하여 엔진이 서지 한계선을 넘지 않도록 제어한다.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.125-130
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• 2005

The railway shall be verified with the view point of dynamic performances before delivering to the Customer and the verification procedure shall be followed the Customer's demands or relevant international standard, UIC 518 (Testing and approval of railway vehicles from the point of view of their dynamic behavior-Safety-Track fatigue-Ride quality). In this paper, verification procedures in UIC 518 and the test results for domestic project are summarized.

• Journal of the Society of Disaster Information
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• v.16 no.4
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• pp.638-649
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• 2020

Purpose: The objective of this study is to evaluate the load carrying capacity of a target bridge structure based on the simple slab bridge of concrete over 20 years of public service. Method: By performing static loading test and dynamic loading test, the displacement, strain, impact factor, and natural frequency values were measured and evaluated through analysis method. Result: The main results of this study are as follows. First, the maximum displacement and maximum strain of S1 were assessed at 2.917 mm and 44.720 𝜇ε( tensile) and -13.760 𝜇ε(compression), respectively, with S2 maximum displacement and maximum strain being 2.100 mm and 4.870 𝜇ε(tensile), respectively. Second, the maximum measured impact factor was 0.191 in section S1 A-A, and the maximum measured impact factor was 0.155 in section S2 C-C. Third, the natural frequency was assessed at 6.086 Hz, and the measurement was found to be within the range of 6.152 Hz to 6.738 Hz. Conclusion: The tested bridge may be evaluated to show good behavior and characteristics for the design load.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.11a
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• pp.33-34
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• 1997

장비나 부품이 비행 또는 수송 등 실제상황에서 겪게되는 진동환경에 얼마만큼 견디는지 여부를 확인하고, 예상되는 동적 하중에 의한 성능저하나 오 동작이 일어나지 알는지 확인하기 위해 환경진동시험(environmental vibration test)이 수행된다. 이러한 환경진동시험의 경우에는 대형(대용량)의 진동시험기(shaker 또는 exciter)가 이용되며 진동시험기로부터 에너지를 시험물에 기계적으로 전달시켜줄 수 있는 진동 시험치구(이하, "치구(fixture)")가 필요하게 된다. 따라서 치구의 설계문제가 대두되며, 환경진동시험의 성공여부를 좌우하는데 대단히 중요한 역할을 하게 된다. 치구의 설계시 가장 중요한 점은 시험규격에 정해진 기준스펙트럼(specified reference spectrum)이 치구 위에 설치될 여러 시험물부착점들에 그대로 전달될 수 있는 강체치구(rigid fixture)를 설계하는 것이 가장 이상적이지만 치구의 공진 및 반공진 특성으로 인해 시험물부착점들 마다 스펙트럼이 달라지게 된다. 따라서 시험물은 과대시험(overtest) 또는/그리고 과소시험(undertest)를 겪게된다.최근의 진동시험제어 기법으로서는 다채널시스템을 이용한 여러 시험부착점들에서의 진동레벨의 평균을 제어하는 평균제어기법(average control technique)이 이용되므로서 시험주파수 범위에서 공진진동수(resonance frequency)들은 기준스펙트럼과 동일하게 제어가 가능하나 반공진 진동수(antiresonance frequency)들에서는 반공진 진동수들이 갖는 물리적 특성으로 인해 기준스펙트럼과 동일하게 제어가 이루어지지 않으므로시험규격에 정해진 정확한 진동시험이 수행되지 못하게된다.본 연구에서는 치구의 설계단계에서 치구 위의 여러 시험물 부착점들- 평균제어점(average control points)- 에서의 반공진 진동수들을 고려하여 그 감도를 게산하고, 치구의 구조변경을 수행하여 시험물 부착점들에서의 반공진 진동수를 일치시키므로서 종래의 진동시험제어시 나타나는 반공진진동수에서의 문제점을 제거할 수 있고, 그 결과 시험물 부착점들에서의 스펙트럼이 시험규격에 정해진 스펙트럼대로 진동시험이 수행될 수 있게 하는데 있다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.3
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• pp.95-101
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• 2004

Stability rating of KSR-III rocket engine is conducted based on stability rating tests in the course of development of KSR-III rocket engine. Rocket engine is approved to have combustion stabilization ability when it can suppress the external perturbation or pressure oscillation with finite amplitude and recover the original stable combustion. Rocket engine in flight may be perturbed by unexpectedly large-amplitude pressure oscillation and thus a designer should not only assure combustion stabilization ability of the engine but also quantify the stabilization capacity. For this, principal quantitative parameters and their evaluation are introduced. To verify dynamic stability of KSR-III rocket engine, six stability rating tests have been conducted. Based on these test results, such parameters are quantified and thereby, the stabilization capacity of KSR-III rocket engine is evaluated.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.2
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• pp.20-28
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• 1998

To accurately predict the motion of a submergible, the nonlinear structure of dynamic model should be selected and corresponding parameters should be estimated using model test. Providing the model structure, only the values of parameters are unknown and the estimation can thus be formulated as a standard least square problem. Unfortunately, the nonlinear model structure of submersibles is rarely known a prior and method of model structure determination from measurement data of model test should be developed and included as a vital part of the estimation procedure. In this study, the well-known linear least square algorithm for the analysis of model tests and a way to measure the goodness are reviewed, and the identification algorithm based on an orthogonal decomposition method of Gram-Schmidt is extended to combine structure selection and maneuvering coefficients estimation in a very simple and efficient manner. Finally, the efficiency of this algorithm is verified by using simulation and applying to the analysis of model test of a submerged body. As a result, it was verified that this combined method might be very erective in selecting the structure of dynamic model estimating the maneuvering coefficients from measurement fiat of model test.

• The Journal of Engineering Geology
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• v.22 no.3
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• pp.293-307
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• 2012

Shear wave velocity is commonly invoked in explaining geophysical phenomena and in solving geotechnical engineering problems. In particular, the importance of shear wave velocity in geotechnical earthquake engineering has been widely recognized for seismic design and seismic performance evaluation. In the present study, various insitu seismic tests were performed to evaluate geotechnical dynamic characteristics at 183 sites in Korea, and shear wave velocity profiles with depth were determined to be representative of the dynamic properties at the investigated sites. Subsurface soil and rock layers at the target sites were reclassified into five geotechnical layers: fill, alluvial soil, weathered soil, weathered rock, and bedrock, taking into account their general uses in geotechnical earthquake engineering practice. Average shear wave velocity profiles for the five geotechnical layers were obtained by synthesizing the shear wave velocity profiles from seismic tests in the field. Based on the profiles, a representative shear wave velocity value was determined for each layer, for use in engineering seismology and geotechnical earthquake engineering.

• Journal of the Korean Geosynthetics Society
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• v.13 no.3
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• pp.39-47
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• 2014

In this study, the full scale model tests were performed with track-roadbed system such as Ho-nam high speed railway. The measured data gives good similar a roadbed pressure with equivalent depth to the Odemark's theory. In the case of earth pressures have a under 50 kPa at upper-subgrade applying 330 kN static loading. Results of cyclic loading tests did not differ significantly from those of static loading test. The elastic displacement at HSB layer has a level of 1/100 compared to the 1 mm that it was evaluation criteria for speed up of High Speed Railway. Elastic displacement at subgrade layer was measured a level of 1/175. The dynamic characteristics of track-roadbed with loading frequency level were linearly increased under 35 Hz, while the wheel loading, displacement and acceleration of roadbed were decreased loading frequency above 35 Hz.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.183-188
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• 2008

Engine control/performance model for helicopter simulator is one of the most important models which affect flight performance and handling quality. It is typical to develop the model based on the raw data and models from the engine designers/manufacturers. The approaches in this study were to develop the basic model based on the available resources and to tune and verify it based on the ground/flight test results. The maintenance manuals of TB3-117 which is installed in KA-32T were reviewed and the components to be simulated for the engine control model were categorized and modeled. Piece-wise linear modeling method was used for the engine performance model. The engine performance data in the engine maintenance manuals were incorporated into the engine steady state performance tables, which were incorporated with the transfer functions for the dynamic performance. Engine control/performance model was compared and tuned with the ground/flight test results. It was verified that the fidelity of the model was within the tolerances in FAA AC120-63.