• Proceedings of the KSR Conference
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• 2003.05a
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• pp.567-573
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• 2003

Korean High Speed Train (KHST) has been tested on high speed line in JungBu site since it was developed in 2002. The data acquisition system was developed to accomplish successfully this on-line test for proving the dynamic Performance of KHST. This system was consist of the personal computers based on National Instrument PXI modules and the test programs based on Labview 6i. This paper shows that this system is efficient to acquire the test data through the multi-channels connected the accelerometers which located in long distance places and flexible to change and add channels for data acquisition. The dynamic analysis of an on-line test is very complicate because the environmental conditions, as examples radius of curve, inclination of the track, tunnels, bridges, and so forth, and running conditions, as examples driving, braking, the number of working motors, and so forth, have an effect on the results. Therefor, the analysis method is important and this paper proposes the efficient procedure graphically, showing the proposed method simplify the accelerations of 5th bogie frame acquired during the on-line test for KHST.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.114-128
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• 2016

The development of operational performance indicators is of utmost importance for nuclear power plants, since they measure, track, and trend plant operation. Leading indicators are ideal for reducing the likelihood of consequential events. This paper describes the operational data analysis of the information contained in the Corrective Action Program. The methodology considers human error and organizational factors because of their large contribution to consequential events. The results include a tool developed from the data to be used for the identification, prediction, and reduction of the likelihood of significant consequential events. This tool is based on the resilience curve that was built from the plant's operational data. The stress is described by the number of unresolved condition reports. The strain is represented by the number of preventive maintenance tasks and other periodic work activities (i.e., baseline activities), as well as, closing open corrective actions assigned to different departments to resolve the condition reports (i.e., corrective action workload). Beyond the identified resilience threshold, the stress exceeds the station's ability to operate successfully and there is an increased likelihood that a consequential event will occur. A performance indicator is proposed to reduce the likelihood of consequential events at nuclear power plants.

• Journal of Power Electronics
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• v.16 no.1
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• pp.287-296
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• 2016

Conventional maximum power point tracking (MPPT) methods are ineffective under partially shaded conditions because multiple local maximum can be exhibited on power-voltage characteristic curve. This study proposes an improved cuckoo search (ICS) MPPT method after investigating the cuckoo search (CS) algorithm applied in solving multiple MPPT. The algorithm eliminates the random step in the original CS algorithm, and the conception of low-power, high-power, normal and marked zones are introduced. The adaptive step adjustment is also realized according to the different stages of the nest position. This algorithm adopts the large step in low-power and marked zones to reduce search time, and a small step in high-power zone is used to improve search accuracy. Finally, simulation and experiment results indicate that the promoted ICS algorithm can immediately and accurately track the global maximum under partially shaded conditions, and the array output efficiency can be improved.

• Tribology and Lubricants
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• v.37 no.5
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• pp.179-188
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• 2021

Reputed for their low friction coefficient and wear protection effect, diamond-like carbon (DLC) materials are considered amongst the most important lubricant coatings for tribological applications. In this framework, this investigation aims to elucidate the effect of a few operating parameters, such as applied stress and sliding amplitude on the friction lifetime of DLC coatings. Fretting wear tests are conducted using a 12.7 mm radius counterpart of 52100 steel balls slid against a substrate of the same material coated with a 2 ㎛ thickness DLC. Approximately, 5 to 57 N force is applied, generating a maximum Hertzian contact pressure of 430 to 662 MPa, corresponding to the applied force. The coefficient of friction (CoF) generates three regimes, first a running-in period regime, followed by a steady-state evolution regime, and finally a progressive increase of the CoF reaching the steel CoF value, as an indicator of reaching the substrate. To track the wear scenario, interrupted tests are performed with analysis combining scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), 3D profilometer and micro-Raman spectroscopy. The results show two endurance values: one characterizing the coating failure (Nc₁), and the other (Nc₂) indicating the friction failure which is situated where the CoF reaches a threshold value of μ_th = 0.3 in the third regime. The Archard energy density factor is used to determine the two endurance values (Nc₁, Nc₂). Based on this approach, a master curve is established delimitating both the coating and the friction endurances.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.11
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• pp.604-613
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• 2018

In recent years, numerous train derailment accidents caused by deterioration and high speed technology of railways have increased. Guardrails or barriers of railway bridges are installed to restrain and prevent the derailment of the train body level. On the other hand, it can result in a high casualties and secondary damage. Therefore, a Derailment Containment Provision (DCP) within the track at the wheel/bogie level was developed. DCP is designed for rapid installation because it reduces the impact load on the barrier and inertia force on the steep curve to minimize turnover, fall, and trespass on the other side track of the bridge. In this paper, DCP was analyzed using LS-Dyna with a parameter study as the impact loading location and interface contact condition. The contact conditions were analyzed using the Tiebreak contact simulating breakage of material properties and Perfect bond contact assuming fully attached. As a result, the Tiebreak contact behaved similarly with the actual behavior. In addition, the maximum displacement and flexural failure was generated on the interface and DCP center, respectively. The impact analysis was carried out in advance to confirm the DCP design due to the difficulties of performing the actual impact test, and it could change the DCP anchor design as the analysis results.

• The Journal of the Korea Contents Association
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• v.7 no.4
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• pp.234-240
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• 2007

The purpose of this paper was to architecture optimal model of the scooped swing in high bar. The scooped swing was modeled to the double pendulum and was simulated with the Lagrange's equation of motion. Lagrange's method based on a energy approaching method was implemented as a equation of motion. The subject was a national man-gymnast(age 18yrs, height 153 cut mass 48 kg) and the high bar of SPIETH company was used to measure the scooped swing. Qualisys system(six MCU-240 cameras, QTM software)was used to capture data for imaging analysis. The solution of a model and data processing were solved in Mathematica5.0. The results were as follows: First model value of maximum bar displacement was longer than experimental value, that is, 0.02 m. Second, both angular pattern of segment1(HAT) had a increasing curve but curve patterns had a different concave and convex me. Third the experimental value of maximum angular angle of segment2(total leg) had larger than model value, that is, $4^{\circ}$. Conclusively, model parameters were quasi-optimized to obtain a quasi-match between simulated and actual performances. It hopes to simulate a human model by means of integrating musculoskeletal and neuromuscular system in the future study.

• Journal of the Korean Society for Railway
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• v.20 no.2
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• pp.165-172
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• 2017

High frequency squeal noise can be generated when a railroad vehicle runs a sharp curved section; this noise causes environmental complaints and excessive wear on the wheel and the railroad track. In this paper, curved squeal noise experiments on a commercial railway were carried out to investigate this phenomenon. The relationship of the squeal noise pressure level, the frequency characteristics, the railway running speed, and the modal behavior of the wheel were investigated. At the same time, the lateral motion of the wheel relative to the rail was captured using a video camera; wheel movement was calculated when the noise was generated. queal noise occurred at the highest level at the inner front wheel; this phenomena is considered to be related to the lateral vibration response characteristics of the wheel. It can be seen that the magnitude of this squeal noise is not directly related to the increase in vehicle speed.

• Journal of the Korean Society for Railway
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• v.15 no.4
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• pp.343-351
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• 2012

With the cooperation of many research institutes and railway companies, the next generation high speed train is under development for many years. To confirm the safety requirement of the developed high speed train, multibody dynamic analysis is implemented. Through this analysis, railway derailment and lateral guiding force simulation was evaluated according to UIC code 518 OR for international railway vehicle. Test results were compared by limit value of safety criteria. Safety evaluation results, according to international standards, would provide basic reference data of ensuring safety speed and track radius curve. The safety of the train at the maximum speed is verified by numerical analysis results.

• Korean Journal of Applied Biomechanics
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• v.22 no.3
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• pp.269-276
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• 2012

The purpose of This study's aim is to examine the difference in the changes of body segment movement, variables for ball quality, and carry at golf driver swing according to the ball quality using comparative analysis. Regarding the impact variables according to the ball quality using the track man and carry, club speed was the fastest at draw shot, ball speed was the fastest at straight shot, and smash factor was the lowest at draw shot. About the vertical launch angle, the fade shot showed the highest launch angle while the max height of the ground and ball was the highest at fade shot. And carry was the longest at draw shot. For the flight time, it was the longest at draw shot. The landing angle was the largest at fade shot. About the club head position change and trajectory, at the overall event point, the fade shot drew a more outer trajectory at the point of the follow through(E6) than the straight or draw shot. Regarding the angular speed of shoulder rotation, at the overall event point, the fade shot showed the greatest angular speed change in the follow through(E6). Also, about the angular speed of pelvic rotation, at the overall event point, the draw shot showed the greatest angular speed change at the point of down swing(E4). Concerning the stance angle change, both straight and fade shots were open as the concept of open stance whereas the draw shot was close as that of close stance. Regarding the previous study, the most important factor of deciding Ball Quality is the club face angle's open and close state at Impact. In short, the Ball Quality and carry were decided by this factor.

• Journal of Astronomy and Space Sciences
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• v.29 no.1
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• pp.51-55
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• 2012

A few high-mass X-ray binaries-consisting of an OB star plus compact companion-have been observed by Fermi and ground-based Cerenkov telescopes like High Energy Stereoscopic System (HESS) to be sources of very high energy (VHE; up to 30 TeV) ${\gamma}$-rays. This paper focuses on the prominent ${\gamma}$-ray source, LS 5039, which consists of a massive O6.5V star in a 3.9-day-period, mildly elliptical ($e{\approx}0.24$) orbit with its companion, assumed here to be an unmagnetized compact object (e.g., black hole). Using three dimensional smoothed particle hydrodynamics simulations of the Bondi-Hoyle accretion of the O-star wind onto the companion, we find that the orbital phase variation of the accretion follows very closely the simple Bondi-Hoyle-Lyttleton (BHL) rate for the local radius and wind speed. Moreover, a simple model, wherein intrinsic emission of ${\gamma}$-rays is assumed to track this accretion rate, reproduces quite well Fermi observations of the phase variation of ${\gamma}$-rays in the energy range 0.1-10 GeV. However for the VHE (0.1-30 TeV) radiation observed by the HESS Cerenkov telescope, it is important to account also for photon-photon interactions between the ${\gamma}$-rays and the stellar optical/UV radiation, which effectively attenuates much of the strong emission near periastron. When this is included, we find that this simple BHL accretion model also quite naturally fits the HESS light curve, thus making it a strong alternative to the pulsar-wind-shock models commonly invoked to explain such VHE ${\gamma}$-ray emission in massive-star binaries.