• Journal of KIISE:Computing Practices and Letters
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• v.6 no.2
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• pp.265-273
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• 2000

In relational database management systems(RDBMS), a table consIn relational database management systems(RDBMS), a table consists of sets of records which are composed of a set of attributes. The number of distinct values(NDV) of an attribute denotes the number of distinct attribute values that actually appear in the database records, and is widely used in optimizing queries and supporting statistic queries. Object-relational database management systems(ORBBMSS), however, support the inheritance between tables which enforces an attribute defined in a super-table to be inherited in sub-tables automatically. Hence, in ORDBMSS, not only NDV of an attribute In a single table but also NDV of an attribute in multiple tables(HNDV) is needed. In this paper, we propose a method that calculates HNDV using arrays of attribute value intervals. In this method, an array of attribute value intervals is created for an attribute of interest In each table in a table hierarchy, and HNDV can be calculated or estimated by merging the arrays of attribute value intervals. The proposed method accurately calculates HNDV using small additional storage space and is efficient for an environment where only some of the tables in a table hierarchy are frequently updated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.536-539
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• 2002

In this paper, we developed the automatic optical fiber aligner by image processing and automatic loading system. Optical fiber is indispensable for optical communication systems that transmit large volumes of data at high speed, but super-precision technology in sub-micron units is required for optical axis adjustment, we have developed 6-axis micro stage system for I/O optical fiber arrays, the initial automatic aligning system/software for a input optical array by the image processing technique, fast I/O-synchronous aligning strategy, the automatic loading/unloading system and the automatic UV bonding mechanism. In order to adjust the alignment it used on PC based motion controller, a $10\mu\textrm{mm}$ repeat-detailed drawing of automatic loading system is developed by a primary line up for high detailed drawing. Also, at this researches used the image processing system and algorithm instead of the existing a primary hand-line up. and fiber input array and waveguide chip formed in line by automatic. Therefore, the developed and manufactured optical aligning system in this research fulfills the great role of support industry for major electronics manufacturers, telecommunications companies, universities, government agencies and other research institutions.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.2
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• pp.81-87
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• 2000

This paper presents a new approach to the synthesis of two-dimensional arrays such as Atmel 6000 series FPGAs using internal don't cares. Basically complex terms which fits to the linear array of cells without further routing wires are generated and they are collected by OR/XOR operations. In previous methods, complex terms are collected only by XOR operations, which may not be effective for nearly unate functions. In this paper, we allow complex terms to be collected by OR operations in addition to XOR operations. First, complex terms that lies in the ON-set of the function are generated and collected by OR operations. The sub-function realized by the first stage becomes an internal don't cares and they are exploited in the second stage which generates complex terms collectable by XOR operation. Experimental results shows the efficacy of the proposed method compared to the previous methods.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.95.2-95.2
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• 2017

Anodic TiO2 nanostructures have wide applications due to their various functional properties such as wide band-gap, chemical stability, and anti-corrosiveness. In order to enhance the properties, several approaches to fabricate TiO2 structures have been developed. Especially, TiO2 nanotube arrays prepared by anodization in a fluoride electrolyte show impressive properties for dye sensitized solar cells1 and photocatalyst. In this presentation, we introduce new types of TiO2 nanostructures beyond TiO2 nanotubes that are fabricated by anodization at high temperature in a glycerol/phosphate electrolyte. We show that depending on the anodization parameters different self-organized morphologies - of highly aligned, high aspect ratio oxide structures can be formed. Critical factor for growth and the use for dye sensitized solar cells and photocatalyst will be discussed.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.146-146
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• 2017

산화비스무트는 리튬이온과의 반응에서 현재 상용화된 그래파이트보다 높은 이론용량을 가지고 있으나, 리튬이온과의 반응에서 비교적 큰 부피팽창 특성을 가져 리튬이차전지의 음극재로서 상용화가 어려운 단점이 있다. 본 연구에서는, 이러한 문제점을 개선하기 위하여 양극산화법을 통해 충 방전시 부피팽창 변화가 매우 적은 타이타니아 나노튜브를 제조한 후, 그 위에 스프레이 방법으로 산화비스무트를 코팅하여 두 물질의 복함체를 만듦으로써 용량과 구조적 안정성을 향상시키는 방법을 소개한다. 음극재의 구조적 특성은 고분해능 주사전자현미경 (HR-SEM), 고분해능 엑스선 회절분석기(XRD)를 통해 조사하였으며, 전기화학 임피던스 분광법 (EIS), 순환전류법 (CV), 충 방전 싸이클 분석을 통해 리튬이차전지의 작동원리와 보다 향상된 성능을 규명하였다.

• Journal of the Korean Statistical Society
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• v.34 no.1
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• pp.21-33
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• 2005

Let ｛X/sun ni/ ｜ 1 ≤ i ≤ n, n ≥ 1 ｝ be an array of rowwise negatively associated random variables. We in this paper discuss the conditions of n/sup -1/p/ (equation omitted) →0 completely as n → ∞ for some 1 ≤ p < 2 under not necessarily identically distributed setting. As application, it is obtained that n/sup -1/p/ (equation omitted) →0 completely as n → ∞ if and only if E｜X/sub 11/｜/sup 2p/ < ∞ and EX/sub ni=0 under identically distributed case such that the corresponding results on i. i. d. case are extended and the strong convergence for weighted sums of rowwise negatively associated arrays is also considered.

• Advances in Energy Research
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• v.3 no.1
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• pp.45-57
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• 2015

This article is addressed to define a new composite electrode constituted by porous nickel and an array of highly ordered $TiO_2$ nanotubes obtained by a previous galvanostatic anodization treatment in an ethylene glycol solution. The electrochemical performances of the composite anode were evaluated in a photo-electrolyser, which showed good solar conversion efficiency with respect to the UV irradiance together with a reduction of energy consumption. Such a combination of materials makes our system simple and able to work both in dark and under solar light exposure, thus opening new perspectives for industrial-scale applications.

• Journal of the Korean institute of surface engineering
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• v.51 no.6
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• pp.365-371
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• 2018

1D core-shell nanostructures have attracted great attention due to their enhanced physical and chemical properties. Specifically, oriented single-crystalline $TiO_2$ nanorods or nanowires on a transparent conductive substrate would be more desirable as the building core backbone. However, a facile approach to produce such structure-based hybrids is highly demanded. In this study, a three-step hydrothermal method was developed to grow NiMn-layered double hydroxide-decorated $TiO_2$/carbon core-shell nanorod arrays on transparent conductive fluorine-doped tin oxide (FTO) substrates. XRD, SEM, TEM, XPS and Raman were used to analyze the obtained samples. The in-situ fabricated hybrid nanostructured materials are expected to be applicable for photoelectrode working in water splitting.

• Korean Journal of Optics and Photonics
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• v.34 no.6
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• pp.235-240
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• 2023

The optical signal injected into an end-fire optical phased array propagates along the waveguides inside the device and is emitted from the edge of the antenna. In general, reflection and scattering occur at the boundary, thereby reducing the emission efficiency of the optical signal. In this article, we propose a silicon nitride (Si₃N₄) tapered waveguide antenna structure whose width is tapered toward the emitting edge, achieving high emission efficiency operating at the 1,550 nm wavelength. The Si₃N₄ tapered waveguide antenna was numerically designed using the 3D finite-difference time-domain method. The optical signal emission efficiency increased from 78% to 96.3%, while reflectance decreased from 22% to 3.7% compared with the untapered waveguide antenna counterpart. This result will not only boost the optical signal intensity but also mitigate optical noise resulting from back reflection along the waveguide in the end-fire optical phased array device.

• Journal of the Korean Electrochemical Society
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• v.12 no.1
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• pp.47-53
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• 2009

In this study, highly ordered AAO (Anodic Aluminum Oxide) with nanopores was prepared by commercial grade Al substrate containing 3.5 wt.% impurities through two step anodizing method. Nanopores of prepared AAO arrays were used as templates for preparing nanofiber. $TiO_2$ was deposited by using DP (deposition-precipitation) method into AAO pores to grow nanofiber. Au particles were loaded on this $TiO_2$ nanofiber which was grown vertically. Prepared 2 wt.% $Au/TiO_2$ nanofiber was characterized by XRD, SEM and Raman. The crystal structure was analyzed by the XRD. SEM was used to observe pore size and pore wall thickness. Photocatalytic activity of co-oxidation was compared with $TiO_2$ and $Au/TiO_2$ nanofiber on AAO arrays.