• Title/Summary/Keyword: Transmission matrix

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Universal SSR Small Signal Stability Analysis Program of Power Systems and its Applications to IEEE Benchmark Systems

  • Kim, Dong-Joon;Nam, Hae-Kon;Moon, Young-Hwan
    • KIEE International Transactions on Power Engineering
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    • v.3A no.3
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    • pp.139-147
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    • 2003
  • The paper presents a novel approach of constructing the state matrix of the multi-machine power system for SSR (subsynchronous resonance) analysis using the linearized equations of individual devices including electrical transmission network dynamics. The machine models in the local d-q reference frame are integrated with the network models in the common R-I reference frame by simply transforming their output equations into the R-I frame where the transformed output is used as the input to the network dynamics or vice versa. The salient feature of the formulation is that it allows for modular construction of various component models without rearranging the overall state space formulation. This universal SSR small signal stability program provides a flexible tool for systematic analyses of SSR small-signal stability impacts of both conventional devices such as generation systems and novel devices such as power electronic apparatus and their controllers. The paper also presents its application results to IEEE benchmark models.

Mechanical Properties with Aging Time in High Nitrogen Steel for Transmission Line (가공송전선용 고질소강의 시효시간에 따른 기계적 특성의 변화)

  • Kim, Bong-Seo;Yoo, Kyung-Jae;Kwon, Hae-Woong;Lee, Hee-Woong;Kim, Byung-Geol
    • Proceedings of the KIEE Conference
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    • 1999.07d
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    • pp.1664-1666
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    • 1999
  • In order to study the mechanical properties of high nitoren steel with ageing time, hardness, tensile stress several basic properties of Fe-Mn-Cr-Ni-N steel have been studied. With increasing partial pressure of nitrogen and ageing time to 10h, hardness and tensile stress are increased, but decreased beyond 10h because of over ageing. It is considered that the main factor related with mechnical properties is carbide precipitate, M7C3 which is precipitated with ageing time in matrix and optimum ageing time is 10h in 60C.

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An Efficient Scheme to Achieve Differential Unitary Space-Time Modulation on MIMO-OFDM Systems

  • Liu, Shou-Yin;Chong, Jong-Wha
    • ETRI Journal
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    • v.26 no.6
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    • pp.565-574
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    • 2004
  • Differential unitary space-time modulation (DUSTM) has emerged as a promising technique to obtain spatial diversity without intractable channel estimation. This paper presents a study of the application of DUSTM on multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems with frequency-selective fading channels. From the view of a correlation analysis between subcarriers of OFDM, we obtain the maximum achievable diversity of DUSTM on MIMO-OFDM systems. Moreover, an efficient implementation strategy based on subcarrier reconstruction is proposed, which transmits all the signals of one signal matrix in one OFDM transmission and performs differential processing between two adjacent OFDM blocks. The proposed method is capable of obtaining both spatial and multipath diversity while reducing the effect of time variation of channels to a minimum. The performance improvement is confirmed by simulation results.

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Long-term AC Electrical Treeing Behaviors of Epoxy/Layered Silicate Nanocomposites Prepared by a 3-Roll Mill

  • Park, Jae-Jun
    • Transactions on Electrical and Electronic Materials
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    • v.13 no.2
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    • pp.85-88
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    • 2012
  • Studies on the effects of layered silicate content on the AC electrical treeing and breakdown behaviors of epoxy/layered silicate nanocomposites were carried out in needle-plate electrode geometry. Wide-angle X-ray diffraction (WAXD) analysis and transmission electron microscopy (TEM) observation showed that 1 wt% of the multilayered silicate was fully exfoliated into nano-sized monolayers in the epoxy matrix however, over 3 wt% of the silicate was in an intercalated state. When 1 wt% layered silicates were incorporated, an electrical tree was initiated in 439 min and propagated at a speed of 2.3 μm/min after applying 781.4 kV/mm, representing a decreased in starting initiation time by a factor of 11.0 and increase in propagation speed by a factor 8.2 in comparison with neat epoxy resin. These values were in great decline after the layered silicate content was increased to 3wt% which implies that the exfoliated silicate blocked the tree initiation and propagation processes effectively. However the effect was largely decreased in the intercalated state.

Distributed Quasi-Orthogonal Space-Time Block Code for Four Transmit Antennas with Information Exchange Error Mitigation

  • Tseng, Shu-Ming;Wang, Shih-Han
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.7 no.10
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    • pp.2411-2429
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    • 2013
  • In this paper, we extend the case of information exchange error mitigation for the distributed orthogonal space-time block code (DOSTBC) for two transmit antennas to distributed quasi-orthogonal space-time block code (DQOSTBC) for four transmit antennas. A rate 1 full-diversity DQOSTBC for four transmit antennas is designed. The code matrix changes according to different information exchange error cases, so full diversity is maintained even if not all information exchange is correct. We also perform analysis of the pairwise error probability. The performance analysis indicates that the proposed rate 1 DQOSTBC outperforms rate 1/2 DOSTBC for four transmit antennas at the same transmission rate, which is confirmed by the simulation results.

A Pathway to Microdomain Alignment in Block Copolymer/Nanoparticle Thin Films under Electric Field

  • Bae, Joonwon
    • Bulletin of the Korean Chemical Society
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    • v.35 no.9
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    • pp.2689-2693
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    • 2014
  • The control over microstructure in block copolymer thin films using external electric fields has become an interesting research topic. In this article, the effect of nanoparticle on the microdomain alignments in block copolymer (polystyrene-b-poly(2-vinylpyridine)/nanoparticle (Au) thin films under electric fields has been examined with transmission electron microscopy. The homogeneous dispersion of Au nanoparticles into the block copolymer matrix was achieved by surface modification of nanoparticles with compatible ligands. Compared with the phenomenon seen in the pristine block copolymer thin films, a peculiar alignment behavior was observed in the block copolymer/nanoparticle hybrid thin films under electric fields. In addition, the different pathways observed in the pristine and nanoparticle incorporated block copolymer thin films were also monitored as a function of exposure time. This work can provide the fundamental information for understanding microdomain alignment in block copolymer/nanoparticle thin films under external electric fields.

High-Speed Signaling in SDARM Bus Interface Channels : Review

  • Park, Hong-June;Sohn, Young-Soo;Park, Jin-Seok;Bae, Seung-Jun;Park, Seok-Woo
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.1 no.1
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    • pp.50-69
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    • 2001
  • Three kinds of high-speed signaling methods for synchronous DRAM (SDRAM) bus interface channels (PC-133, Direct-Rambus, and SSTL-2) were analyzed in terms of the timing budget and the physical transmission characteristics. To analyze the SDRAM bus interface channels, loss mechanisms and the effective characteristic impedance method were reviewed and the ABCD matrix method was proposed as an analytic and yet accurate method. SPICE simulations were done to get the AC responses and the eye patterns of the three SDRAM bus interface channels for performance comparisons. Recent progress and future trend for SDRAM bus interface standards were reviewed.

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Designing a Microphone Array for Acoustical Inverse Problems (음향학적 역문제를 위한 마이크로폰의 정렬방법)

  • Kim, Youngtea
    • The Journal of the Acoustical Society of Korea
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    • v.23 no.1E
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    • pp.3-9
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    • 2004
  • An important inverse problem in the field of acoustics is that of reconstructing the strengths of a number of sources given a model of transmission paths from the sources to a number of sensors at which measurements are made. In dealing with this kind of the acoustical inverse problem, strengths of the discretised source distribution can be simply deduced from the measured pressure field data and the inversion of corresponding matrix of frequency response functions. However, deducing :he solution of such problems is not straightforward due to the practical difficulty caused by their inherent ill-conditioned behaviour. Therefore, in order to overcome this difficulty associated with the ill-conditioning, the problem is replaced by a nearby well-conditioned problem whose solution approximates the required solution. In this paper a microphone array are identified for which the inverse problem is optimally conditioned, which can be robust to contaminating errors. This involves sampling both source and field in a manner which results in the discrete pressures and source strengths constituting a discrete Fourier transform pair.

Crystallography Analysis of the β-Mg17Al12 Precipitates by the Secondary Constrained Coincident Site Lattice Model

  • Huang, Xuefei;Huang, Weigang
    • Applied Microscopy
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    • v.45 no.4
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    • pp.230-235
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    • 2015
  • Crystallographic models are effective tools to interpret, calculate and even to predict the preferred crystallographic morphologies of precipitates in various precipitation systems. The present study gives an introduction on the recently developed secondary constrained coincident site lattice (II-CCSL) model. Using the II-CCSL model, the interface matching condition of the βMg17Al12 precipitates with αMg matrix in an aged AZ91 alloy has been analyzed to rationalize the morphologies of the precipitates. The results show that the characteristic crystallographic features of the observed βMg17Al12 precipitates, i.e., the habit plane of the βMg17Al12 lath with a Burgers orientation relationship (OR) and the growth direction of the βMg17Al12 with a Crawley OR exhibit a better lattice matching degree than their vicinal orientations. Moreover, the Crawley OR is preferred to the Burgers OR due to a better lattice match.

Hybrid Nanocomposites: Processing and Properties

  • Shi, Y.;Kanny, K.;Jawahar, P.
    • Advanced Composite Materials
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    • v.18 no.4
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    • pp.365-379
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    • 2009
  • Epoxy/S2-glass reinforced composites (SGRPs) infused with Cloisite 30B nanoclays were manufactured using the vacuum assisted resin infusion molding (VARIM) process. Prior to infusion, the matrix and clays were thoroughly mixed using a direct mixing technique (DMT) and a high shear mixing technique (HSMT) to ensure uniform dispersion of the nanoclays. Structures with varying clay contents (1-3 wt%) were manufactured. Both pristine and SGRP nanocomposites were then subjected to mechanical testing. For the specimens manufactured by DMT, the tensile, flexural, and compressive modulus increased with increasing the clay content. Similarly, the tensile, flexural, compressive, interlaminate shear and impact strength increased with the addition of 1 wt% clay: however the trend reversed with further increase in the clay content. Specimens manufactured by HSMT showed superior properties compared to those of nanocomposites containing 1 wt% clay produced by DMT. In order to understand these phenomena a morphological study was conducted. Transmission electron microscopy (TEM) micrographs revealed that HSMT led to better dispersion and changed the nanoclay structure from orderly intercalation to disorderly intercalation giving multi-directional strength.