• Wind and Structures
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• v.24 no.3
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• pp.223-247
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• 2017

By using numerical simulation, vast and detailed information and observation of the physics of flow over a train model can be obtained. However, the accuracy of the numerical results is questionable as it is affected by grid convergence error. This paper describes a systematic method of computational grid refinement for the Unsteady Reynolds Navier-Stokes (URANS) of flow around a generic model of trains using the OpenFOAM software. The sensitivity of the computed flow field on different mesh resolutions is investigated in this paper. This involves solutions on three different grid refinements, namely fine, medium, and coarse grids to investigate the effect of grid dependency. The level of grid independence is evaluated using a form of Richardson extrapolation and Grid Convergence Index (GCI). This is done by comparing the GCI results of various parameters between different levels of mesh resolutions. In this study, monotonic convergence criteria were achieved, indicating that the grid convergence error was progressively reduced. The fine grid resolution's GCI value was less than 1%. The results from a simulation of the finest grid resolution, which includes pressure coefficient, drag coefficient and flow visualization, are presented and compared to previous available data.

• Proceedings of the KSR Conference
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• 2003.05a
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• pp.718-723
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• 2003

The acceptance test of KTX has been performed in Korea. During the test lateral vibration of carbody over the accepted value called sway was found. Many activities have been taken to find the cause of the vibration and the counter-measure. KTX has 20 car trainset formation whose trailer cars are linked by articulate bogies. So this study is performed to see the effects of long trainset formation on vehicle dynamics and the train stability by 16 car vehicle model. Firstly the reliable vehicle model which shows well the tendencies appeared in the tests on the high speed test line is required to find the cause of lateral vibration and the countermeasure. Vehicle model was made for the analysis with VAMPIRE. The analysis results show that secondary air spring lateral stiffness is the most significant parameter to cause carbody lateral vibration. Mode analysis results show that the least damped mode shape is similar to the vibration pattern shown in the tests that the amplitude of the motion increases along the train set and decreases in the tail part. The lateral vibration was appeared at the speed range between 100km/h and 200km/h and disappeared at the low speed and the high speed.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.2
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• pp.319-328
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• 2021

In this paper, we perform prediction of amount of electric power plant for complex of wind plant using multi-layer perceptron in order to calculate exact calculation of capacity of ESS to maximize profit through generation and to minimize generation cost of wind generation. We acquire wind speed, direction of wind and air density as variables to predict the amount of generation of wind power. Then, we merge and normalize there variables. To train model, we divide merged variables into data as train and test data with ratio of 70% versus 30%. Then we train model by using training data, and we alsouate the prediction performance of model by using test data. Finally, we present the result of prediction in amount of wind power.

• Journal of the Korea Society of Computer and Information
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• v.21 no.5
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• pp.91-98
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• 2016

We propose a method to train a model that can predict the probability of a crime being committed. CCTV data by matching criminal events are required to train the crime prediction model. However, collecting CCTV data appropriate for training is difficult. Thus, we collected actual criminal records and converted them to an appropriate format using variables by considering a crime prediction environment and the availability of real-time data collection from CCTV. In addition, we identified new specific crime types according to the characteristics of criminal events and trained and tested the prediction model by applying neural network partial least squares for each crime type. Results show a level of predictive accuracy sufficiently significant to demonstrate the applicability of CCTV to real-time crime prediction.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.6
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• pp.97-108
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• 1996

A modeling technique is proposed for dynamic simulations of OHC valve trains with HLA(hydraulic lash adiuster). HLA is expressed by an air-oil mixture model considering HLA leak-down and aeraton effects. A compact nonlinear equation is derived which describe the short term dynamic behavior of the HLA. Valve spring is analyzed by a distributed parameter model including nonlinear characteristics in the spring surge phenomena. Global behavior of the remaining valve train is expressed by a lumped mass model. The experiental results prove that the simulation model developed here is accurate and useful for the dynamic simulations of OHC valve trains with HLA.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.216-221
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• 2000

In this study, two mathematical models are first constructed to analyze vibration characteristics of a gear train - spindle system of an NC lathe gear box. One is a lumped parameter model which is used for calculating natural frequencies of the torsional vibration, the other is a finite element model for analyzing lateral vibration and critical speeds of the spindle system. In addition, this study examines some possible resonance conditions such as gear mesh frequencies, 1X shaft rpm frequencies over whole operating speed range, and so on. The results may be helpful to design a machine tool gear box with low noise and vibration.

• Structural Engineering and Mechanics
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• v.38 no.3
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• pp.301-314
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• 2011

The paper constitutes the second part of the author's study. The first part (Podworna 2010) formulates four fundamental tasks in dynamics of the bridge-track-train systems. The following cyclic moving loads are considered: a concentrated forces stream (model P), an unsprung masses stream (model M), a single-mass viscoelastic oscillators stream (model $M_o$) and a double-mass viscoelastic oscillators stream (model $MM_o$). Three problems precluding to the numerical simulations have been developed, i.e., prediction of the forced resonances, the parameters of integration of equations of motion, the output results. A computer programme was written in Pascal and numerical research in the scope of the fundamental tasks was worked out. The investigations were focused on adequacy evaluation of the moving load models, P, M, $M_o$, $MM_o$, in predicting dynamic processes in railway bridges.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.164-169
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• 2005

The TTX(Tilting Train eXpress) is designed to achieve high driving speed up to 200 km/h and to run on conventional curved rails without speed reduction. In order to maintain power collection between catenary and pantograph collector while train body is tilted, the TTX pantograph must have tilting structure (or Sledge). The power quality is determined by the tilting structure. Static and dynamic characteristics of tilting structure, therefore, are important to evaluate the pantograph performance. The current prototype of the tilting structure is overweight model and its structural characteristics have not been investigated. In this study, the finite element model of TTX tilting structure is established and static analysis is performed. Finally, using this result, a light weight model is proposed.

• Journal of Korea Multimedia Society
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• v.24 no.12
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• pp.1614-1623
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• 2021

In this paper, the purpose is evaluation of the effect of using fractal feature in machine learning based pancreatic tumor classification. We used the data that Pancreas CT series 469 case including 1995 slice of benign and 1772 slice of malignant. Feature selection is implemented from 109 feature to 7 feature by Lasso regularization. In Fractal feature, fractal dimension is obtained by box-counting method, and hurst coefficient is calculated range data of pixel value in ROI. As a result, there were significant differences in both benign and malignancies tumor. Additionally, we compared the classification performance between model without fractal feature and model with fractal feature by using support vector machine. The train model with fractal feature showed statistically significant performance in comparison with train model without fractal feature.

• Journal of the Korean Society for Railway
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• v.15 no.6
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• pp.537-542
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• 2012

Rolling stocks are often subjected to the effects of natural strong wind or wind pressure caused by the crossing train. These wind pressure cause the falling-off in running stability and overturn safety. It is sometimes reported that trains are blown over by a gust of wind. So, many countries enact regulations to secure the overturn safety for wind speed. In this study, theoretical equations of overturn safety based on multi-body model are derived and analyzed the difference between the result of the solid model and that of multi-body model. In case of multi-body model, it is assumed that the degrees of freedom for carbody and bogie are assigned an independent values respectively. The results show that the latter approach based on multi-body model can access the overturn safety of train and replace the conventional method by using commercial software which is accessing with decrement of wheel load.