• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.56.1-56.1
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• 2018

Tidal disruption events (TDEs) provide evidence for quiescent supermassive black holes (SMBHs) in the centers of inactive galaxies. TDEs occur when a star on a parabolic orbit approaches close enough to a SMBH to be disrupted by the tidal force of the SMBH. The subsequent super-Eddington accretion of stellar debris falling back to the SMBH produces a characteristic flare lasting several months. The theoretically expected bolometric light curve decays with time as proportional to $t^{-5/3}$. However, the light curves observed in most of the optical-UV TDEs deviate from the $t^{-5/3}$ decay rate especially at early time, while the light curves of some soft-X-ray TDEs are overall in good agreement with the $t^{-5/3}$ law. Therefore, it is required to construct the theoretical model for explaining these light curve variations consistently. In this paper, we revisit the mass fallback rates analytically and semi-analytically by taking account of the structure of the star, which is simply modeled by the polytrope. We find the relation between a polytropic index and the power law index of the mass fallback rate. We also discuss whether and how the decay curves, which we derived, fit the observed ones.

• IEMEK Journal of Embedded Systems and Applications
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• v.10 no.6
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• pp.363-372
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• 2015

Recent some SoC FPGA Releases that integrate ARM processor and FPGA fabric show better performance compared to the ASIC SoC used in typical embedded image processing system. In this study, using the above advantages, we implement a SoC FPGA-based Real-Time Object Recognition and Tracking System. In our system, the video input and output, image preprocessing process, and background subtraction processing were implemented in FPGA logics. And the object recognition and tracking processes were implemented in ARM processor-based programs. Our system provides the processing performance of 5.3 fps for the SVGA video input. This is about 79 times faster processing power than software approach based on the Nios II Soft-core processor, and about 4 times faster than approach based the HPS processor. Consequently, if the object recognition and tracking system takes a design structure combined with the FPGA logic and HPS processor-based processes of recent SoC FPGA Releases, then the real-time processing is possible because the processing speed is improved than the system that be handled only by the software approach.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.2
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• pp.99-106
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• 2006

In this paper, the new method that estimates a sensing ability of smart sensor will be proposed. A study is estimation method that evaluates sensing ability about smart sensor respectively. According to acceleration(g) and displacement changing, we estimated sensing ability of smart sensor using SAI(Sensing Ability Index) method respectively. Smart sensors was made fer experiment. The types of smart sensor are two types(hard and soft smart sensor). Smart sensors developed for recognition of material. Experiment and analysis are executed for estimate the SAI method. In develop a smart sensor, the SAI method will be useful for finding optical design condition of smart sensor that can sense a material. And then dynamic characteristics of smart sensors(frequency changing, acceleration changing, critical point, etc.) are evaluated respectively through new method(SAI) that use the power spectrum density. Dynamic characteristic of sensor is evaluated with SAI method relatively. We can use the SAI for finding critical point of smart sensor, too.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.2B no.3
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• pp.125-132
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• 2002

PMSMS (permanent magnet synchronous motors) are widely used in industrial applications and home appliances because of their high torque to inertia ratio, superior power density, and high efficiency. For high performance control, accurate informations about the rotor position is essential. Sensorless algorithms have lately been studied extensively due to the high cost of position sensors and their low reliability in harsh environments. A novel position sensorless speed control for PMSMs uses indirect flux estimation and is presented in this paper. Rotor position and angular velocity are estimated by the proposed indirect flux estimation. Linkage flux and magnetic field flux are calculated by the voltage equations and the measured phase current without any integration. Instead of linkage flux calculation with integral operation, indirect flux and differential magnetic field are used for the estimation of rotor position. A proper rejection technique fur current noise effect in the calculation of differential linkage flux is introduced. The proposed indirect flux detecting method is free from the integral rounding error and linkage flux drift problem, because differential linkage flux can be calculated without any integral operation. Furthermore, electrical parameters of the PMSM can be measured by the proposed TCM (time compression method) for soft starting and precise estimation of rotor position. The position estimator uses accurate electrical parameters that are obtained from the proposed TCM at starting strategy. In the operating region, a proper compensation method fur temperature effect can compensate fir the estimation error from the variation of electrical parameters. The proposed novel position sensorless speed control scheme is verified by the experimental results.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.2
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• pp.69-74
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• 1999

This paper presents about a example of circuit design and characteristics of proposed circuit in the case of adopted the high frequency resonant Inverter of SEPP type using ZVS(Zero-Voltage-Switching) to the Induction heating load. The soft switching technology known as ZVS is used to reduce turn on and off loss at switching. Also, this paper realizes quantitative circuit analysis which has change the equivalent of Induction heating load to the electric circuit. According to the calculated characteristics value, a method of the circuit designs and operation characteristics of the Inverter is proposed. In addition, this paper proves the propriety of theoretical analysis through the experiment. The proposed inverter shows it can be practically used as power source system for induction heating Jar etc.

• Structural Engineering and Mechanics
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• v.75 no.5
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• pp.633-642
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• 2020

Artificial neural networks (ANNs) are known as intelligent methods for modeling the behavior of physical phenomena because of it is a soft computing technique and takes data samples rather than entire data sets to arrive at solutions, which saves both time and money. ANN is successfully used in the civil engineering applications which are suitable examining the complicated relations between variables. Functionally graded materials (FGMs) are advanced composites that successfully used in various engineering design. The FGMs are nonhomogeneous materials and made of two different type of materials. In the present study, the bending analysis of functionally graded material (FGM) beams presents on theoretical based on combination of mixed-finite element method, Gâteaux differential and Timoshenko beam theory. The main idea in this study is to build a model using ANN with four parameters that are: Young's modulus ratio (E_t/E_b), a shear correction factor (k_s), power-law exponent (n) and length to thickness ratio (L/h). The output data is the maximum displacement (w). In the experiments: 252 different data are used. The proposed ANN model is evaluated by the correlation of the coefficient (R), MAE and MSE statistical methods. The ANN model is very good and the maximum displacement can be predicted in ANN without attempting any experiments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.5
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• pp.1766-1784
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• 2014

Finger vein images contain rich oriented features. Local line binary pattern (LLBP) is a good oriented feature representation method extended from local binary pattern (LBP), but it is limited in that it can only extract horizontal and vertical line patterns, so effective information in an image may not be exploited and fully utilized. In this paper, an orientation-selectable LLBP method, called generalized local line binary pattern (GLLBP), is proposed for finger vein recognition. GLLBP extends LLBP for line pattern extraction into any orientation. To effectually improve the matching accuracy, the soft power metric is employed to calculate the matching score. Furthermore, to fully utilize the oriented features in an image, the matching scores from the line patterns with the best discriminative ability are fused using the Hamacher rule to achieve the final matching score for the last recognition. Experimental results on our database, MMCBNU_6000, show that the proposed method performs much better than state-of-the-art algorithms that use the oriented features and local features, such as LBP, LLBP, Gabor filter, steerable filter and local direction code (LDC).

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.1107-1112
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• 2009

Ground anchor should not be used in soft clay, because anchor resistance can not be guaranteed. However, there is a way to increase the capacity of anchors. The pulse powered anchor is an underreamed anchor by using high voltage electrokinetic pulse energy. In this study, a series of field test were carried out in order to find expansion rate related in number of pulse charge. and Anchor pull-out tests were performed at the Geotechnical Experimentation Site at Sungkyunkwan University in Suwon, Korea. Data were analyzed in order to define a relation between expansion rate and ultimate pullout load.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.132-135
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• 2002

MI(Magneto-Impedance) sensor which is made by thin films has significantly high detecting sensitivity in weak magnetic field. It also has a merit to be able to build in the low power system. Its structure is simple, which makes it easier to prepare a miniature. In this study, its magnetic permeability and anisotropy field($H_{k}$) as a function of a thickness of sputtered amorphous CoZrNb films with zero-magnetostriction and soft magnetic property are investigated. In order to make a uniaxial anisotropy, film was subjected to the post annealing in a static magnetic field with 1KOe intensity at 250, 300, and $320^{\circ}C$ respectively for 2 hours. Magnetic properties of film are measured by using a MH loop tracer. Its magnetic permeability of a film is measured over the frequency range 1 MHz to 750MHz. And, it was examined on the permeability and impedance to design the MI sensor which acts at 50MHz by thickening a CoZrNb film relatively, and fabricated the MI sensor which acts at the 50MHz.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.719-721
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• 2013

A thinning stage of fingerprint algorithm occupies 39% cycle of microprocessor system for identification processing of image from fingerprint sensor. Hardware block processing is more effective than software one in speed and power consumption, because a thinning algorithm is iteration of simple instructions without a transcendental function. This paper describes an effective hardware scheme for thinning stage processing using Verilog-HDL in $64{\times}64$ Pixel Array. The hardware scheme is designed and simulated in RTL. The logic is also synthesized by XST in FPGA environment and tested. Experimental results show the performance of the proposed scheme and possibility of application for a soft microprocessor and thinning processor embedded fingerprint SoC.