• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.2
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• pp.305-314
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• 2017

Recently, user authentication through biometric traits such as fingerprint and iris raise more and more attention especially in mobile commerce and fin-tech fields. In particular, commercialized authentication methods using fingerprint recognition are widely utilized mainly because customers are more adopted and used to fingerprint recognition applications. In the meantime, the security issues caused by fingerprint falsification bring lots of attention. In this paper, we propose a new method to improve the performance of fake fingerprint detection using CNN(Convolutional Neural Network). It is common practice to increase the amount of learning data by using affine transformation or horizontal reflection to improve the detection rate in CNN characteristics that are influenced by learning data. However, in this paper we propose an effective data augmentation method based on the database difficulty level. The experimental results confirm the validity of proposed method.

• The KSFM Journal of Fluid Machinery
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• v.13 no.5
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• pp.43-53
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• 2010

This study investigates a design optimization of a rotating two-pass rectangular cooling channel with staggered arrays of pin-fins. The radial basis neural network method is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer with shear stress transport turbulent model. The ratio of the diameter to height of the pin-fins and the ratio of the streamwise spacing between the pin-fins to height of the pin-fin are selected as design variables. The optimization problem has been defined as a minimization of the objective function, which is defined as a linear combination of heat transfer related term and friction loss related term with a weighting factor. Results are presented for streamlines, velocity vector fields, and contours of Nusselt numbers, friction coefficients, and turbulent kinetic energy. These results show how fluid flow in a two-pass square cooling channel evolves a converted secondary flows due to Coriolis force, staggered arrays of pin-fins, and a $180^{\circ}$ turn region. These results describe how the fluid flow affects surface heat transfer. The Coriolis force induces heat transfer discrepancy between leading and trailing surfaces, having higher Nusselt number on the leading surface in the second pass while having lower Nusselt number on the trailing surface. Dean vortices generated in $180^{\circ}$ turn region augment heat transfer in the turning region and in the upstream region of the second pass. As the result of optimization, in comparison with the reference geometry, thermal performance of the optimum geometry shows the improvement by 30.5%. Through the optimization, the diameter of pin-fin increased by 14.9% and the streamwise distance between pin-fins increased by 32.1%. And, the value of objective function decreased by 18.1%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.9
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• pp.947-954
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• 2011

Drive-train friction loss in a vehicle may account for 4% of its total fuel consumption loss. An ATF W/C (auto-transmission fluid warmer/cooler) plate-fin heat exchanger is a type of heat exchanger that uses metal plates to transfer heat between the auto-transmission fluid and coolant. The use of an ATF W/C heat exchanger can result in a fuel economy improvement of about 1% in vehicles. An experimental setup for testing the thermal performance of an ATF W/C plate-fin heat exchanger is developed. In this study, the influence of the ATF and coolant, flow rates, and temperature on the efficiency of an ATF W/C heat exchanger are investigated experimentally. From the experimental data, a simple correlation for predicting the efficiency of an ATF W/C heat exchanger is proposed. On the basis of this correlation, the fuel economy of a vehicle with and without an ATF W/C heat exchanger is compared by using Simulink. Finally, it is shown that the fuel economy is improved by 0.992% when an ATF W/C heat exchanger is installed in the vehicle.

• Advanced Industrial SCIence
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• v.1 no.1
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• pp.7-15
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• 2022

To adopt the development in the medical scenario IoT developed towards the advancement with the processing of a large amount of medical data defined as an Internet of Medical Things (IoMT). The vast range of collected medical data is stored in the cloud in the structured manner to process the collected healthcare data. However, it is difficult to handle the huge volume of the healthcare data so it is necessary to develop an appropriate scheme for the healthcare structured data. In this paper, a machine learning mode for processing the structured heath care data collected from the IoMT is suggested. To process the vast range of healthcare data, this paper proposed an MTGPLSTM model for the processing of the medical data. The proposed model integrates the linear regression model for the processing of healthcare information. With the developed model outlier model is implemented based on the FinTech model for the evaluation and prediction of the COVID-19 healthcare dataset collected from the IoMT. The proposed MTGPLSTM model comprises of the regression model to predict and evaluate the planning scheme for the prevention of the infection spreading. The developed model performance is evaluated based on the consideration of the different classifiers such as LR, SVR, RFR, LSTM and the proposed MTGPLSTM model and the different size of data as 1GB, 2GB and 3GB is mainly concerned. The comparative analysis expressed that the proposed MTGPLSTM model achieves ~4% reduced MAPE and RMSE value for the worldwide data; in case of china minimal MAPE value of 0.97 is achieved which is ~ 6% minimal than the existing classifier leads.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.1
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• pp.35-42
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• 2020

Electromechanical Actuator(EMA) for flight vehicles generally serves to control the fin deflection angle or the thrust vector angle. This paper deals with design and development of EMA for both aerodynamic control and thrust vector control. In this paper, a novel compact EMA is proposed that can simultaneously control both the tail fin and the jet vane with one actuator and detach the jet vane after vertical launch and rapid turn of the flight vehicle so as to increase efficiency during flying to target. To do this, we designed the EMA using a push-push link mechanism and derived a mathematical model. The mathematical model is validated by comparing simulation result and experimental data. The performance and reliability of the proposed EMA have been verified through performance test, environmental test and ground test. The proposed EMA is expected to be useful as an EMA for flight vehicles because of its simple and compact structure, as well as its performance and reliability.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2666-2671
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• 2007

This work presents microchannel heat sink shape optimization procedure using Kriging method. Design variables relating to microchannel width, depth and fin width are selected, and thermal resistance has been taken as objective function. Design points are selected through a three-level fractional factorial design of sampling method. Navier-Stokes and energy equations for laminar flow and conjugate heat transfer are solved at these design points using a finite volume solver. Solutions are carefully validated with experimental results. Using the numerically evaluated objective function, a surrogate model (Kriging) is constructed and optimum point is searched by sequential quadratic programming. The process of shape optimization greatly improves the thermal performance of microchannel heat sink under constant pumping power.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.9
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• pp.853-859
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• 2000

In this study, low temperature waste heat recovery heat exchanger was developed using a principle of self-excited oscillating heat pipe. The heat exchanger of serpentine type was composed of extruded flat aluminum tube with 6 channels (3 nm$\times$ 2.75nm) and louvered fin. The heat transfer area density of heat exchanger was $331.9 m^2/m^3$. Working fluid is R141b and charge ratio was 40% by volume. Heat transfer rate and the effectiveness of heat exchanger was primary concern of this study. As a result, the effectiveness of heat exchanger was about 0.4-0.67, and recovered waste heat rate was about 4.5 kW per one unit of heat exchanger.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.329-339
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• 2002

In ship operation the consequency of roll motions can seriously degrade the performance of mechanical and personnel effectiveness. So many studies for the roll stabilization control system design have been performed and very good results have been achieved. In many studies, the stabilizing fins are used. Recently rudders, which have been extensively modified, have been used to exclusively to stabilize the roll. This paper examines the two-degree-of-freedom servosystem design technique to synthesize the yaw control system which achieves the course keeping object of the ship and the H$_{\infty}$ control approach to suppress the roll motion, respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.9
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• pp.733-740
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• 2007

Microchannel heat sink shape optimization is performed using Kriging method. Design variables relating to microchannel width, depth and fin width are selected, and thermal resistance has been taken as objective function. Design points are selected through a three-level fractional factorial design of sampling method. Navier-Stokes and energy equations for laminar flow and conjugate heat transfer are solved at these design points using a finite volume solver. Solutions are carefully validated with experimental results. Using the numerically evaluated objective function, a surrogate model (Kriging) is constructed and optimum point is searched by sequential quadratic programming. The process of shape optimization greatly improves the thermal performance of microchannel heat sink under constant pumping power.

• Journal of Welding and Joining
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• v.11 no.2
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• pp.13-20
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• 1993

The object of the research is to develop the flux for aluminum brazing. Five kinds of flux were applied to brazing joint with fin and tube structure using same filler metal. To estimate the performance of the developed flux, products analysis, differential thermal test, grain size test, observation of crystalline structure, tensile test, corrosion test were made. From the results of experiment, the following conculsions were obtained. 1. The optimum composition ratio (Wt) of AlF$_3$ and KF was 50-60% : 40-50% 2. The optimum melting point of the flux was 567-578$^{\circ}C$.