• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.1
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• pp.57-64
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• 2017

In order to reduce damages to major railroad components, which have the potential to cause interruptions to railroad services and safety accidents and to generate unnecessary maintenance costs, the development of rolling stock maintenance technology is switching from preventive maintenance based on the inspection period to predictive maintenance technology, led by advanced countries. Furthermore, to enhance trust in accordance with the speedup of system and reduce maintenances cost simultaneously, the demand for fault diagnosis and prognostic health management technology is increasing. The objective of this paper is to propose a highly reliable learning model using various machine learning algorithms that can be applied to critical rolling stock components. This paper presents a model for railway rolling stock component fault diagnosis and conducts a mechanical failure diagnosis of motor components by applying the machine learning technique in order to ensure efficient maintenance support along with a data preprocessing plan for component fault diagnosis. This paper first defines a failure diagnosis model for rolling stock components. Function-based algorithms ANFIS and SMO were used as machine learning techniques for generating the failure diagnosis model. Two tree-based algorithms, RadomForest and CART, were also employed. In order to evaluate the performance of the algorithms to be used for diagnosing failures in motors as a critical railroad component, an experiment was carried out on 2 data sets with different classes (includes 6 classes and 3 class levels). According to the results of the experiment, the random forest algorithm, a tree-based machine learning technique, showed the best performance.

• Nuclear Engineering and Technology
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• v.52 no.4
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• pp.721-733
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• 2020

In nuclear engineering, the occurrence of critical heat flux (CHF) is complicated for rod bundle, and it is much more difficult to predict the CHF when it is in natural circulation under motion condition. In this paper, the dryout-type CHF is investigated for the rod bundle in a natural circulation loop under rolling motion condition based on the coupled analysis of subchannel method, a one-dimensional system analysis method and a CHF mechanism model, namely the three-fluid model for annular flow. In order to consider the rolling effect of the natural circulation loop, the subchannel model is connected to the one-dimensional system code at the inlet and outlet of the rod bundle. The subchannel analysis provides the local thermal hydraulic parameters as input for the CHF mechanism model to calculate the occurrence of CHF. The rolling motion is modeled by additional motion forces in the momentum equation. First, the calculation methods of the natural circulation and CHF are validated by a published natural circulation experiment data and a CHF empirical correlation, respectively. Then, the CHF of the rod bundle in a natural circulation loop under both the stationary and rolling motion condition is predicted and analyzed. According to the calculation results, CHF under stationary condition is smaller than that under rolling motion condition. Besides, the CHF decreases with the increase of the rolling period and angular acceleration amplitude within the range of inlet subcooling and mass flux adopted in the current research. This paper can provide useful information for the prediction of CHF in natural circulation under motion condition, which is important for the nuclear reactor design improvement and safety analysis.

• Journal of the Korean Institute of Navigation
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• v.23 no.2
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• pp.23-27
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• 1999

When a ship is running in following and quartering seas and on a crest with the ship′s length being nearly the same as the wave length, ship′s stability will be lost most; "T" shape crests with highly concentrated energy will appear during the process of transformation from irregular waves to regular ones, and the ship may be under continuous impact of large waves for a long period of time; Synchronism will also appear when the ship′s natural period of rolling and period of encounter are close to each other. For safe navigation, proper stability should be well ensured, proper speed and course chosen with speed under 1.8L1/2 kn (L is the ship′s length), initial listing avoided, special attention paid to steering.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.5
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• pp.538-542
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• 2015

The transverse moment of inertia is an indispensable factor in analyzing the roll motion characteristics of ships and the calculating method needs to be based on the more reasonable theories when deciding the value as the results and reliability of analysis could be much affected by the correctness. However, the mass distribution and shape of hulls are quite complicated and give much difficulties in case of calculating the value directly from the ship design data, furthermore even acquiring the detailed design data for calculation is almost impossible. Therefore some simpler ways are practically adopted in the assumption that the gyradius of roll moment can be decided by a given ratio and hull width. It is well known that the responses of the free roll decay are varied according to the value of roll moment in view of roll period and amplitude decay ratio, so that the general formula to get the moment value can be derived also from the observation of roll decay responses. This study presents how the roll period and decay ratio are interrelated each other from the roll motion characteristics with suggesting a general formula to be able to calculate roll moment from it. Finally, the obtained general formula has been applied to a ship data to check the resultant characteristics through analyzing graphs and showed that the roll moment becomes more accurate when rolling period and decay ratio are considered together in calculation.

• Journal of the Korean Society for Railway
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• v.20 no.5
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• pp.569-576
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• 2017

The electromagnetic valve of pneumatic doors of EMUs has a high failure rate due to air leakage because it supplies air on and off to operate the doors repeatedly. The electromagnetic valve is a very important safety component for which a very high reliability is required because failure makes it impossible to operate the passenger cars. However, domestic urban railway operators maintain electronic valves of the EMU door under a fixed cycle with a spare period according to the full overhaul cycle of the EMU. An improvement of the current maintenance cycle was suggested based on the reliability function and mission reliability. Using the statistical program MINITAB for the operational data of EMU line 6, we analyzed the characteristics of the fault distribution and derived the shape and scale parameters of the reliability function. If we limit the specific reliability probability to under a certain failure rate and calculate its statistical parameters, we can calculate the allowable inspection period with mission reliability. Through this study, we suggested a maintenance period based on RCM (reliability centered-maintenance) to improve the reliability of electromagnetic valves from 68% to 95%.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.761-766
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• 2004

This paper describes how to measure the running safety using vibration accelerometers theoretically, and considers the effect of vibration parameters, such as amplitude and period, on the running safety by numerical analysis, which shows that the running safety are decreased as those parameters are increased.

• Journal of Veterinary Clinics
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• v.19 no.2
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• pp.243-246
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• 2002

An acute colic in a 6-month-old Thoroughbred filly is described. The filly was presented with acute colic haracterized by rolling and pawing. Over a period of days she suffered from severe abdominal pain and subsequently died. ost mortem examination revealed the ileocecal intrssusception as a part invagination of the ileum into the cecum. It seems ogical to assume that the invagination occurred at the start of the illness. In addition, it is also noted the presence of Parascaris quorum in the stomach.

• Journal of Navigation and Port Research
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• v.37 no.2
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• pp.221-229
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• 2013

To find the influence of incident angle of wave on the moment of 3 storied steel moment resisting frame which is placed on the concrete rectangular pontoon, the fluid dynamic analysis is carried out, varying the period of wave from 5 to 15 second by 2 seconds. As increasing incident angle of wave to longitudinal axis, the influence of RAO-rolling is increased. The moment of longitudinal frame is increased apparently by the wave pressure when the incident angle is $0^{\circ}$. And the moment of the frame due to the wave pressure is decreased as the incident angle is increased. But the moment of frame due to acceleration caused from pitching and rolling is increased. It is shown that the increased moment when incident angle is $90^{\circ}$ is much greater than that of incident angle $0^{\circ}$.

• Smart Structures and Systems
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• v.23 no.1
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• pp.91-106
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• 2019

Adopting sloped rolling-type isolation devices underneath a raised floor system has been proved as one of the most effective approaches to mitigate seismic responses of the protected equipment installed above. However, pounding against surrounding walls or other obstructions may occur if such a base-isolated raised floor system is subjected to long-period excitation, leading to adverse effects or even more severe damage. In this study, real-time hybrid simulation (RTHS) is adopted to assess the control performance of a smart base-isolated raised floor system as it is an efficient and cost-effective experimental method. It is composed of multiple sloped rolling-type isolation devices, a rigid steel platen, four magnetorheological (MR) dampers, and protected high-tech equipment. One of the MR dampers is physically tested in the laboratory while the remainders are numerically simulated. In order to consider the effect of input excitation characteristics on the isolation performance, the smart base-isolated raised floor system is assumed to be located at the roof of a building and the ground level. Four control algorithms are designed for the MR dampers including passive-on, switching, modified switching, and fuzzy logic control. Six artificial spectrum-compatible input excitations and three slope angles of the isolation devices are considered in the RTHS. Experimental results demonstrate that the incorporation of semi-active control into a base-isolated raised floor system is effective and feasible in practice for high-tech industry.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1479-1485
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• 2008

This paper shows the result of study on the detailed applicable procedure of software Escrow account applied for rolling stock. The customer as end-user requires software source code, related critical technical documents etc. about software based system of train for maintenance purpose through software modification and enhancement after completion of warranty period. Otherwise, it is not easy to keep up with the customer's requirement of demanding supplier's exclusive information because it is considered as intellectual property rights of supplier as software developer. Therefore, the main contractor(normally called as Car-builder) need to introduce software Escrow service in order to coordinate the different a standpoint between software developer and end-user. Software Escrow is a legal arrangement in which an software Escrow packages (software source code, software development tool, build process, proprietary information, copyright and etc.) is deposited into and Escrow account under the trust of a reliable third party (Escrow agent) depending on mutual agreement on Escrow contract condition as signing off Escrow agreement document. This paper deals with the study on the detailed procedure about the following general category of Escrow procedure and purpose to apply this specific procedure of Escrow into the future project onward.