• Title/Summary/Keyword: lattice structures

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Optimization of 1-3 Type Piezocomposite Structures Considering Inter-Pillar Vibration Modes (Inter-Pillar 진동 모드를 고려한 1-3형 압전복합체의 구조 최적화)

  • Pyo, Seonghun;Kim, Jinwook;Roh, Yongrae
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.26 no.6
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    • pp.434-440
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    • 2013
  • With polymer properties and ceramic volume fraction as design variables, the optimal structure of 1-3 piezocomposites has been determined to maximize the thickness mode electromechanical coupling factor. When the piezocomposite vibrates in a thickness mode, inter-pillar resonant modes are likely to occur between lattice-structured piezoceramic pillars and polymer matrix, which significantly deteriorates the performance of the piezocomposite. In this work, a new method to design the structure of the 1-3 type piezocomposite is proposed to maximize the thickness mode electromechanical coupling factor while preventing the occurrence of the inter-pillar modes. Genetic algorithm was used for the optimal design, and the finite element analysis method was used for the analysis of the inter-pillar mode.

Biosynthesis of Silver Nanoparticles by Phytopathogen Xanthomonas oryzae pv. oryzae Strain BXO8

  • Narayanan, Kannan Badri;Sakthivel, Natarajan
    • Journal of Microbiology and Biotechnology
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    • v.23 no.9
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    • pp.1287-1292
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    • 2013
  • Extracellular biogenic synthesis of silver nanoparticles with various shapes using the rice bacterial blight bacterium Xanthomonas oryzae pv. oryzae BXO8 is reported. The synthesized silver nanoparticles were characterized by UV-Vis spectroscopy, powder X-ray diffractometry (XRD), scanning electron microscopy, energy dispersive X-ray spectrometry, and high-resolution transmission electron microscopy (HR-TEM). Based on the evidence of HR-TEM, the synthesized particles were found to be spherical, with anisotropic structures such as triangles and rods, with an average size of 14.86 nm. The crystalline nature of silver nanoparticles was evident from the bright circular spots in the SAED pattern, clear lattice fringes in the high-resolution TEM images, and peaks in the XRD pattern. The FTIR spectrum showed that biomolecules containing amide and carboxylate groups are involved in the reduction and stabilization of the silver nanoparticles. Using such a biological method for the synthesis of silver nanoparticles is a simple, viable, cost-effective, and environmentally friendly process, which can be used in antimicrobial therapy.

Synthesis of GaN by Direct Reaction Method and Vapor Phase Epitaxy (직접반응법에 의한 GaN의 한성과 기상에피텍시)

  • 김선태;문동찬
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1995.11a
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    • pp.71-73
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    • 1995
  • In this work, we synthsized GaN powders by the direct reactions of Ga with NH$_3$at the temperature range of 950∼1150$^{\circ}C$ and we growth the GaN thin films on Si and sapphire substrates using the synthesized GaN powders by the vapor phase epitaxy method. The synthesized powder had hexagonal crystal structures with lattice constants of a$\sub$0/=3.1895${\AA}$, c$\sub$0/=5.18394${\AA}$. The reaction rates of GaN were increased with both reaction time and temperature, however it did not depends on the flow rates of NH$_3$. The island type GaN crystals were grown on (0001) sapphire substrates and fast lateral growth of GaN on (111) Si substrate than sapphire was observed in our experiments.

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Residual Stress Measurement on Welded Specimen by Neutron Diffraction (중성자 회절을 이용한 용접부위의 잔류응력 측정)

  • 박만진;장동영;최희동
    • Journal of Welding and Joining
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    • v.20 no.2
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    • pp.50-58
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    • 2002
  • Residual stress is generated in the structures as a result of irregular elastic-plastic deformation during fabrication processes such as welding, heat treatment, and mechanical processing. There are several factors attributed to the origin of residual stresses, tensile or compressive. The stresses can be determined by destructive ways or nondestructive ways using X-ray or neutron diffraction. Although X-ray diffraction is a well established technique, it is practically limited to near-surface stresses. Neutrons penetrate easily into most materials and neutron diffraction permits non-destructive evaluation of lattice strain within the bulk of large specimens because the radiation is more deeply penetrating for metallic engineering components. This paper presented application of neutron diffraction technique to the residual stress measurement using 20 mm thick welded stainless steel plate($100{\times}100 \textrm{mm}^2$)

A study of multiple-exposure nanosphere lithography for photonic quasi-crystals fabrication (광자 준결정 제작을 위한 다중 노광 나노구 리소그라피 연구)

  • Yeo, Jong-Bin;Lee, Hyun-Yong
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2010.06a
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    • pp.62-62
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    • 2010
  • Photonic quasi-crystals(PQCs) have been fabricated by a multiple-exposure nanosphere lithography (MENSL) method using the self-assembled nanospheres as lens-mask patterns. The multiple-exposing source is collimated laser beam and rotation, tilting system. The arrays of the PQCs exhibited variable lattice structures and shape the control of ratating angle ($\theta$), tilting angle ($\gamma$) and the exposure conditions. The used nanosphere size is upto the $1\;{\mu}m$. Images of prepared 2D PQCs were observed by SEM. We believe that the MENSL method is a suitable useful tool to realize the PQCs arrays of large area.

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The Fast Lifting Wavelet Transform for Image Coding

  • Shin, Jonghong;Jee, InnHo
    • Proceedings of the IEEK Conference
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    • 2002.07b
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    • pp.1015-1018
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    • 2002
  • We show how any discrete wavelet transform or two band subband filtering with finite filters can be decomposed onto a finite sequence of simple filtering steps, which we call lifting steps but that are also known as ladder structures, We present a self-contained derivations, building the decomposition from the basic principles such as the Euclidean algorithm, with a focus on a applying it to wavelet filtering. This factorization provides an alternative for the lattice factorization, with the advantage that it can also be used in the bi-orthogonal, i.e, non-unitary case. Lifting leads to a speed-up when compared to the standard implementation. We show that this lifting scheme can be applied in image compression efficiently

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The FPGA Implementation of Wavelet Transform Chip using Daubechies′4 Tap Filter for DSP Application

  • Jeong, Chang-Soo;Kim, Nam-Young
    • Proceedings of the IEEK Conference
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    • 1999.11a
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    • pp.376-379
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    • 1999
  • The wavelet transform chip is implemented with Daubechies' 4 tap filter. It works at 20MHz in Field Programmable Gate array (FPGA) implementation of Quadrature Mirror Filter(QMF) Lattice Structure. In this paper, the structure contains taro-channel quadrature mirror filter, data format converter(DFC), delay control unit(DCU), and three 20$\times$8 bits real multiplier. The structures for the DFC and DCU need to he regular and scalable, require minimum number of regular, and thereby lead to an efficient and scalable architecture for the Discrete Wavelet Transform(DWT). These results present the possibility that it can be used in Digital Signal Processing(DSP) application faster than Fourier transform at small area with lour cost.

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Fabrication and Optical Characterization of Colloidal 3-D Photonic Crystals

  • N. Y. Ha;Y. Woo;Park, Byungchoo;J. W. Wu
    • Journal of the Korean Vacuum Society
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    • v.12 no.S1
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    • pp.15-16
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    • 2003
  • 3-D photonic band-gap structures are fabricated from dielectric colloidal polystyrene beads through a centrifuge method. The fabricated photonic crystals exhibit opalescent colors under white light and show a clear diffraction peak dependent on the incident angle of the light beam. Also the scanning electron microscope image was taken to verify the face-centered cubic crystal structure. Bragg's law and Snell's law are employed to describe the position of angle resolved diffraction peaks. It was shown that the optically deduced effective refractive index and lattice constants were in good agreement with the crystal structure identified by scanning electron microscope.

Topology optimization of nonlinear single layer domes by a new metaheuristic

  • Gholizadeh, Saeed;Barati, Hamed
    • Steel and Composite Structures
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    • v.16 no.6
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    • pp.681-701
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    • 2014
  • The main aim of this study is to propose an efficient meta-heuristic algorithm for topology optimization of geometrically nonlinear single layer domes by serially integration of computational advantages of firefly algorithm (FA) and particle swarm optimization (PSO). During the optimization process, the optimum number of rings, the optimum height of crown and tubular section of the member groups are determined considering geometric nonlinear behaviour of the domes. In the proposed algorithm, termed as FA-PSO, in the first stage an optimization process is accomplished using FA to explore the design space then, in the second stage, a local search is performed using PSO around the best solution found by FA. The optimum designs obtained by the proposed algorithm are compared with those reported in the literature and it is demonstrated that the FA-PSO converges to better solutions spending less computational cost emphasizing on the efficiency of the proposed algorithm.

Frequency Domain Pre-Processing for Automatic Defect Inspection of TFT-LCD Panels (TFT-LCD 패널의 자동 결함 검출을 위한 주파수영역 전처리)

  • Nam, Hyun-Do;Nam, Seung-Uk
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.57 no.7
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    • pp.1295-1297
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    • 2008
  • Large-sized flat-panel displays are widely used for PC monitors and TV displays. In this paper, frequency domain pre-filter algorithms are presented for detection of defects in large-sized Thin Film Transistor-Liquid Crystal Display(TFT-LCD) panel surfaces. Frequency analysis with 1-D, 2-D FFT methods for extract the periodic patterns of lattice structures in TFT-LCD is performed. To remove this patterns, frequency domain band-stop filters were used for eliminating specific frequency components. In order to acquire only defected images, 2-D inverse FFT methods to inverse transform of frequency domain images were used.