• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.9
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• pp.799-807
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• 2005

The flow characteristics and the heat transfer rate on a surface by the interaction of a pair of vortices are studied numerically. To analyze the common flow up produced by vortex generators in a rectangular channel flow, the pseudo-compressibility viscous method is introduced into the Reynolds-averaged Navier-Stokes equation for 3-dimensional unsteady, incompressible viscous flows. To predict turbulence characteristics, a two-layer $k-\varepsilon$ turbulence model is used on the flat plate 3-dimensional turbulence boundary The computational results predict accurately Reynolds stress, turbulent kinetic energy and flow field generated by the vortex generators. The numerical results, such as thermal boundary layers, skin friction characteristics and heat transfers, are also reasonably close to the experimental data.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1177-1182
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• 2004

The physical model considered here is a horizontal layer of fluid heated below and cooldabove with a heat-generating conducting body placed at the center of the layer. The body genrates a constant amount of heat as initial condition. Two-dimensional solution for unsteady natural convection is obtained using an accurate and efficient Chebyshev spectral methodology for various of Rayleigh number from $10^3$ to $10^6$. Multi-domain Technique is used to handle heat-generating conducting body. The results for the case of heat-generating body are also compared to those of adaibatic body.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.4 s.235
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• pp.441-452
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• 2005

The physical model considered here is a horizontal layer of fluid heated below and cold above with heat-generating conducting body placed at the center of the layer. The dimensionless thermal conductivities of body considered in the present study are 0.01, 1 and 150. The dimensionless temperature difference ratios considered are 0.25, 2.5 and 25. Two-dimensional solution for unsteady natural convection is obtained using an accurate and efficient Chebyshev spectral methodology for variety of Rayleigh number from $10^{3}\;to\;10^{6}.$ Multi-domain technique is used to handle square- shaped heat-generating conducting body. The results for the case of conducting body with heat generation are also compared to those without heat generation.

• Computers and Concrete
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• v.27 no.3
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• pp.269-282
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• 2021

A dynamic analytical solution for a simply supported, rectangular functionally graded plate with a porous middle layer under time-dependent load based on a refined third-order shear deformation theory with a cubic variation of in-plane displacements according to the thickness and linear/quadratic transverse displacement is presented. The solution achieved in the trigonometric series form and rests on the Green's function method. Two porosity types and their influence on material properties, and mechanical behavior are considered. The network of pores is assumed to be empty or filled with low-pressure air, and the material properties are calculated using the power-law distribution idealization. Numerical calculations have been carried out to demonstrate the accuracy of the kinematic model for the dynamic problem, the effect of porosity, thickness of porous layers, power-law index, and type of loading on the dynamic response of an imperfect functionally graded material plate.

• Advances in nano research
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• v.13 no.5
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• pp.427-435
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• 2022

Static stability behaviors of annular sandwich plates constructed from two layers of particle-reinforced nanocomposites have been investigated in the present article. The type of nanoscale particles has been considered to be graphene oxide powders (GOPs). The particles are assumed to have uniform and graded dispersions inside the matrix and the material properties have been defined according to Halpin-Tsai micromechanical model. The core layer is assumed to have honeycomb configuration. Annular plate has been formulated according to thin shell assumptions considering geometrical nonlinearities. After solving the governing equations via Galerkin's technique, it is showed that the post-buckling curves of annular sandwich plates rely on the core wall thickness, amount of GOP particles, sector radius, and thickness of layers.

• ETRI Journal
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• v.46 no.3
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• pp.526-537
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• 2024

Monitoring fetal growth in utero is crucial to anomaly diagnosis. However, current computer-vision models struggle to accurately assess the key metrics (i.e., head circumference and occipitofrontal and biparietal diameters) from ultrasound images, largely owing to a lack of training data. Mitigation usually entails image augmentation (e.g., flipping, rotating, scaling, and translating). Nevertheless, the accuracy of our task remains insufficient. Hence, we offer a U-Net fetal head measurement tool that leverages a hybrid Dice and binary cross-entropy loss to compute the similarity between actual and predicted segmented regions. Ellipse-fitted two-dimensional ultrasound images acquired from the HC18 dataset are input, and their lower feature layers are reused for efficiency. During regression, a novel region of interest pooling layer extracts elliptical feature maps, and during segmentation, feature pyramids fuse field-layer data with a new scale attention method to reduce noise. Performance is measured by Dice similarity, mean pixel accuracy, and mean intersection-over-union, giving 97.90%, 99.18%, and 97.81% scores, respectively, which match or outperform the best U-Net models.

• Structural Engineering and Mechanics
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• v.92 no.1
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• pp.81-88
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• 2024

In the present work generalized thermoelasticity of a piezoelectric layer is analysed under various shock loading conditions. The generalized thermoelasticity is based on the Lord-Shulman model. The governing equations are solved in the space domain using the finite element method and for solving the equations in the time domain the Newmark method is used. Two kinds of shock loading, temperature shock, and stress shock loading are considered. The results are compared with same results presented in other works and a very close agreement is observed. Finally, the results for each loading condition are presented in various locations and times.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.6
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• pp.1291-1300
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• 2020

Recently, a deep learning-based non-profiling side-channel analysis was proposed. The deep learning-based non-profiling analysis is a technique that trains a neural network model for all guessed keys and then finds the correct secret key through the difference in the training metrics. As the performance of non-profiling analysis varies greatly depending on the neural network training model design, a correct model design criterion is required. This paper describes the two types of loss functions and eight labeling methods used in the training model design. It predicts the analysis performance of each labeling method in terms of non-profiling analysis and power consumption model. Considering the characteristics of non-profiling analysis and the HW (Hamming Weight) power consumption model is assumed, we predict that the learning model applying the HW label without One-hot encoding and the Correlation Optimization (CO) loss will have the best analysis performance. And we performed actual analysis on three data sets that are Subbytes operation part of AES-128 1 round. We verified our prediction by non-profiling analyzing two data sets with a total 16 of MLP-based model, which we describe.

• Computers and Concrete
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• v.25 no.6
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• pp.551-563
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• 2020

This paper investigates the artificial neural network (ANN) to predict the dimensionless parameters for the maximum contact pressures and contact areas of a contact problem. Firstly, the problem is formulated and solved theoretically by using Theory of Elasticity and Integral Transform Technique. Secondly, the contact problem has been extended based on the ANN. The multilayer perceptron (MLP) with three-layer was used to calculate the contact distances. External load, distance between the two quarter planes, layer heights and material properties were created by giving examples of different values were used at the training and test stages of ANN. Program code was rewritten in C++. Different types of network structures were used in the training process. The accuracy of the trained neural networks for the case was tested using 173 new data which were generated via theoretical solutions so as to determine the best network model. As a result, minimum deviation value (difference between theoretical and C++ ANN results) of was obtained for the network model. Theoretical results were compared with artificial neural network results and well agreements between them were achieved.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1989.04a
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• pp.38-43
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• 1989

An improved model for predicting the reinforced concrete element behavior under dynamic strain rates was developed using the layer modeling technique. The developed strain rate sensitive model for axial/flexural analysis of reinforced concrete elements was uses to predict the test results, performed at different loading rates, and the predictions were reasonable. The developed analysis technique was used to study the loading rate sensitivity of reinforced concrete beams and columns with different geometry and material properties. Two design formulas for computing the loading rate dependent axial and flexural strengths of reinforced concrete sections were also suggested.