• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.107-107
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• 2012

Recently, large-area synthesis of high-quality but polycrystalline graphene has been advanced as a scalable route to applications including electronic devices. The presence of grain boundaries (GBs) may be detrimental on some electronic, thermal, and mechanical properties of graphene, including reduced electronic mobility, lower thermal conductivity, and reduced ultimate mechanical strength, yet on the other hand, GBs might be beneficially exploited via controlled GB engineering. The study of graphene grains and their boundary is therefore critical for a complete understanding of this interesting material and for enabling diverse applications. I present that scanning electron diffraction in STEM mode makes possible fast and direct identification of GBs. We also demonstrate that dark field TEM imaging techniques allow facile GB imaging for high-angle tilt GBs in graphene. GB mapping is systematically carried out on large-area graphene samples via these complementary techniques. The study of the detailed atomic structure at a GB in suspended graphene uses aberration-corrected atomic resolution TEM at a low kV.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.425-428
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• 2004

In this paper, we study the discretization behaviors of the equivalent control based sliding-mode control (SMC) systems. The investigation is carried out via studying the second order linear system and some interesting dynamic properties are explored. Especially, according to the variation of system parameters, the inherent dynamical behavior of the trajectories within some specified boundaries are studied. From this result, the boundaries of system state using symbolic dynamics approach are first proposed. Simulations are presented to verify the theoretical results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.85-91
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• 2000

The smallest value of the load when the equilibrium condition becomes to be unstable is defined as the buckling load. The primary objective of this paper is to analyse stability boundaries for star dome under combined loads and is to investigate the iteration diagram under the independent loading parameter In numerical procedure of the geometrically nonlinear problems, Arc Length Method and Newton-Raphson iteration method is used to find accurate critical point(bifurcation point and limit point). In this paper independent loading vector is combined as proportional value and star dome was used as numerical analysis model to find stability boundary among load parameters and many other models as multi-star dome and arches were studied. Through this study we can find the type of buckling mode and the value of buckling load.

• Proceedings of the IEEK Conference
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• 2001.06c
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• pp.13-16
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• 2001

In reinforcement teaming, Q-learning converges quite slowly to a good policy. Its because searching for the goal state takes very long time in a large stochastic domain. So I propose the speedup method using the Q-value initialization for model-free reinforcement learning. In the speedup method, it learns a naive model of a domain and makes boundaries around the goal state. By using these boundaries, it assigns the initial Q-values to the state-action pairs and does Q-learning with the initial Q-values. The initial Q-values guide the agent to the goal state in the early states of learning, so that Q-teaming updates Q-values efficiently. Therefore it saves exploration time to search for the goal state and has better performance than Q-learning. 1 present Speedup Q-learning algorithm to implement the speedup method. This algorithm is evaluated. in a grid-world domain and compared to Q-teaming.

• Phonetics and Speech Sciences
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• v.1 no.2
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• pp.105-110
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• 2009

This paper introduces the technique of semi-automatically identifying different types of noise in the frequency domain. Given the lower cutoff frequency of the frication noise, and a user-specified constant, the technique identifies the boundary between the frication and aspiration noise in a Korean lax fricative followed by the vowel /a/ by comparing the upper and lower sums of energy with respect to the cutoff frequency. The user-specified constant can be adjusted for different speakers. When the technique was applied to distinguish the two types of noise of Korean lax fricatives from the same speaker, the average and standard deviation of the difference between the manually inserted boundaries and the automatically inserted boundaries were 2.67ms and 1.80ms respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.2
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• pp.278-284
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• 2001

In this paper, the slanted metallic boundaries is analyzed for the triangular cell grid method and compared with staircase approximation. Specially, this paper is derived an error range to the angle of inclination between the metal and the dielectric from the triangular cell grid method. That result, when the angle of inclination is from 30˚ to 60˚, the triangular cell grid method improves the accuracy, the computer memory and time requirement in comparison with the staircase approximation. But, out of this range, we do not expect the accuracy because a side of cell size lengthen.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.05a
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• pp.9-13
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• 1995

The effect of WO$_3$ addition and sintering condition on the electrical properties of SrTiO$_3$ceramic have been investigated. Resistivity and capacitance of grains and grain boundaries were obtained by applying impedance spectroscopy. From the result it could be concluded that the temperature dependance of capacitance of WO$_3$doped specimens were influenced directly by the variation of grain boundary capacitance. It was also found that the dispersion frequency increased as the degree of reduction of the specimen increased. The dispersion frequency characteristics showed discernably that the resistivity of the specimen varied with WO$_3$ content. The dielectric properties were influenced directly by the reduction of the specimens. The dielectric constant of grain boundaries of BL capacitor could be obtained by Cole-Cole plot and was influeneced by the amount of WO$_3$ added.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.2
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• pp.89-96
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• 1998

Conventional block-based video coders induce annoying blocking artifacts in very low bitarte coding. We propose a delocking filter which is appropriate for real time operation in a conventional video decoder. The proposed algorithm uses on dimensional filtering across block boundaries horizontally and vertiaclly with two separate filtering modes. The mode decision is quite simple but is fully based on the characteristics of human visual system and video sequences. In flat regions, a strong smoothing filter is appliced; and in the other regions, a moew sophisticated smoothing filter, which is based on the frequency information around block boundaries, is used to reduce blocking artifacts without introuducing undesired blur. Eeven though the proposed deblocking filter is quite simple, simulation results show that it improves both subjective and objective image quality for various image features.

• Journal of the Korean Ceramic Society
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• v.29 no.4
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• pp.265-272
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• 1992

Role of CaO in the sintering of 12Ce-TZP ceramics was studied. The addition of small amounts of CaO increase the densification rate of 12Ce-TZP by altering lattice defect structure and the diffusion coefficient of the rate controlling species, namely cerium and zirconium cations. CaO also inhibits grain growth during sintering and allows the sintering process to proceed to theoretical density by maintaining a high diffusion flux of vacancies from the pores to the grain boundaries. The inhibition of grain growth is accomplished by the segregation of solute at the grain boundaries, causing a decrease in the grain boundary mobility. The segregation of calcium was revealed by AES study.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.06a
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• pp.358-363
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• 1998

An algorithm for representing the cubic spline interpolation of differentiable functions by a fuzzy system is presented in this paper. The cubic B-spline functions which form a basis for the interpolation function are used as the fuzzy sets for input fuzzification. The ordinal number of the coefficient cKL in the list of the coefficient cij's as sorted in increasing order, is taken to be the output fuzzy set number in the (k, l) th entry of the fuzzy rule table. Spike functions are used for the output fuzzy sets, with cij's as support boundaries after they are sorted. An algorithm to compute the support boundaries explicitly without solving the matrix equation involved is included, along with a few properties of the fuzzy rule matrix for the designed fuzzy system.