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Papers

Total Posts 53
12

Mathematical Basis for the Chaining of Lossy Interface Adapters

정유철 | IET Software 4/1 (2010)

Despite providing similar functionality, multiple network services may require the use of different interfaces to access the functionality, and this problem will only get worse with the widespread deployment of ubiquitous computing environments. One way around this problem is to use interface adapters that adapt one interface into another. Chaining these adapters allows flexible interface adaptation with fewer adapters, but the loss incurred due to imperfect interface adaptation must be considered. This paper outlines a matrix-based mathematical basis for analyzing the chaining of lossy interface adapters. We also show that the problem of finding an optimal interface adapter chain is NP-complete with a reduction from 3SAT.?

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11

Gravitational collapse of the shells with the smeared gravitational source in noncommutative geometry

오정근 | JHEP 1003 (2010)

We study the formation of the (noncommutative) Schwarzschild black hole from collapsing shell of the generalized matters containing polytropic and Chaplygin gas. We show that this collapsing shell depending on various parameters forms either a black hole or a naked singular shell with the help of the pressure. Furthermore, by considering the smeared gravitational sources, we investigate the noncommutative black holes formation. Though this mild noncommutative correction of matters cannot ultimately resolve the emergence of the naked singularity, we show that in some parameter region the collapsing shell evolves to a noncommutative black hole before becoming a naked singular shell.

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10

Stochastic Quantization of Brownian Particle Motion Obeying Kramers Equation

최연택 | J PHYS SOC JPN 79/6 (2010)

The stochastic quantization problem of Brownian particle motion that follows Kramers equation is investigated in one-dimension using invariant related unitary transformation method. The explicit Hamiltonians for Langevin equation are constructed separately for the systems that have several different types of the external forces. In the case which does not have external forces, the spectrum of Schro?dinger solution is continuous since the particles are unbound in a finite region. However, when a external force is given by the (time-dependent) harmonic potential, the particles are bound inside the potential leading the spectrum of quantum wave functions to be discrete. The bound?unbound transitions are important since it is connected to metal?insulator transitions that can be achievable for certain compound semiconductors by increasing the doping concentrations at low temperatures. Additionally, when the Hamiltonian involves a higher order term of x as well as harmonic potential term, we have executed the ordinary perturbation expansion in order to obtain the approximate quantum solutions.

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9

Helicity and geometric nature of particle trajectories in homogeneous isotropic turbulence

최연택 | INT J HEAT FLUID FL 31 (2010)

The role of helicity in Lagrangian turbulence is investigated using direct numerical simulation of homogeneous isotropic turbulence. Probability density functions and autocorrelations along a fluid particle trajectory associated with geometric quantities such as curvature and torsion of the Lagrangian trajectory are provided. The relationship between helicity and the ratio of torsion to curvature is investigated. We found that probability density functions of torsion and torsion normalized by curvature clearly show well-established slope in log?log plots. Finally, the relationship between helicity, acceleration and geometric quantities are discussed.

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8

Absorption cross section in the topologically massive gravity at the critical point

오정근 | Euro. Phys. J. C 65 (2010)

The absorption cross section for the warped AdS3 black hole background shows that it is larger than the area even if the s-wave limit is considered. It raises some question whether the deviation from the areal cross section is due to the warped configuration of the geometry or the rotating co- ordinate system, where these two effects are mixed up in the warped AdS3 black hole. So, we study the low-frequency scattering dynamics of propagating scalar fields under the warped AdS3 background at the critical point which reduces to the BTZ black hole in the rotating frame without the warped factor, which shows that the deformation effect at the critical point does not appear.

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7

Gaze Tracking System at a Distance for Controlling IPTV

이의철 | IEEE T CONSUM ELECTR 56/4 (2010)

Although many kinds of methods for tracking human gaze position in order as human-computer interface and virtual reality have been developed and applied, there has no method of gaze tracking as human-TV interface of internet protocol television (IPTV) at a distance. That is due to many limitations of camera optics and illumination since the natural viewing distance is relatively far as almost 2m. To overcome such limitation, a new gaze tracking system and method at a distance for controlling IPTV is proposed. Our method is novel in the following four ways compared to previous work. First, this research is the first one of gaze tracking at a distance. Second, in order to solve the limitation of camera optics at a distance, we use a zoom lens for acquiring enough eye image resolution. Third, in order to directly estimate gaze position without complicate camera calibrations, we used only geometric information about pupil and four cornea specular reflections from 2D eye image. Fourth, by using infrared illuminators and NIR pass filter, the pupil region becomes distinctive in the input image irrespective of the change of environmental visible light. Experimental results with an IPTV of 60 inch wide screen (16:9) showed that the proposed system could be used as a new interface for controlling IPTV.

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6

Eye Blink Detection Robust to Various Facial Poses

이의철 | J NEUROSCI METH 193/2 (2010)

Applications based on eye-blink detection have increased, which requires eye-blink detection to be robust and non- intrusive irrespective of the changes in the user’s facial pose. However, most previous studies of camera based blink detection have the disadvantage that the performances were affected by the facial pose. They also focused on blink detection using only frontal facial images. To overcome them, we propose a new method of blink detection robust to the facial pose. This research is novel in the following four ways compared to previous studies. First, the face and eye regions are detected by using both AdaBoost face detector and Lucas-Kanade-Tomasi (LKT) based method in order to be robust to facial pose. Second, the state of the eye being open or closed needed for blink detection is determined based on two features, the ratio of the height to the width of the eye region in a still image, and the cumulative difference of the number of black pixels of the eye region using an adaptive threshold in successive images. These two features are robustly extracted irrespective of the illumination variations by using illumination normalization. Third, the accuracy of determining eye state, open or close is increased by combining the above two features based on the support vector machine (SVM). Finally, the SVM classifier for determining the eye state is adaptively selected according to the facial rotation. Experimental results with three databases showed that the blink detection by the proposed method was robust to various facial poses.

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5

The Comparative Measurements of Eyestrain Caused by 2D and 3D Displays

이의철 | IEEE T CONSUM ELECTR 56/3 (2010)

The problem of eyestrain caused by 3D display becomes a major topic of discussion. However, there has been no previous research to compare the eyestrain caused by 2D and 3D displays, objectively. In this study, we measured the frequency of blinking using a near-infrared pupil detection device to quantitatively compare the amount of eyestrain caused when watching the two types of displays, on the basis that more frequent blinking indicates greater eyestrain. Our research is novel in the following three ways. First, the eyestrain that occurs when watching 2D and 3D displays are quantitatively compared by using eye blink frequency. Second, the significances of two factors (kind of display, and the Z distance of watching display) and their interaction effect are calculated by using 2k factorial design analysis. Third, the correlation between objective tests based on blink frequency and subjective tests based on a survey is measured. The experimental results showed that the amount of eyestrain when watching a 3D display, especially at short viewing distances, was higher. High correlation between the quantitative results and subjective assessments collected using a questionnaire survey showed that blinking frequency is a reliable measure. Further, the developed pupil tracking device and blinking-rate-based measurement can be easily adapted to commercial glasses-based 3D display systems.

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4

A Realistic Game System Using Multi-Modal User Interfaces

이의철 | IEEE T CONSUM ELECTR 56/3 (2010)

This study is to propose a realistic game system using a multi-modal interface, including gaze tracking, hand gesture recognition and bio-signal analysis based on the photoplethysmogram (PPG), the galvanic skin response (GSR), and the skin temperature (SKT). Our research is novel in the following four ways, compared to previous game systems. First, a highly immersive and realistic game is implemented on a head mounted display (HMD), with a gaze tracker, a gesture recognizer and a bio-signal analyzer. Second, since the camera module for eye tracking is attached below the HMD, the user’s gaze position onto the HMD display can be calculated without wearing any additional eye tracking devices. Third, an aiming cursor in the game system is controlled by the gaze tracking. The grabbing and throwing behaviors toward a target are performed by the user’s hand gestures using a data glove. Finally, the level of difficulty in the game system is adaptively controlled according to the measurement and analysis of the user’s bio- signals. The experimental results show that the proposed method provides more effect on experience of immersion and interest than conventional interaction method such as a keyboard and or a mouse.

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