• Title/Summary/Keyword: Sigma-delta

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The DWA Design with Improved Structure by Clock Timing Control (클록 타이밍 조정에 의한 개선된 구조를 가지는 DWA 설계)

  • Kim, Dong-Gyun;Shin, Hong-Gyu;Cho, Seong-Ik
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.59 no.4
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    • pp.401-404
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    • 2010
  • In multibit Sigma-Delta Modulator, DWA(Data Weighted Averaging) among the DEM(Dynamic Element Matching) techniques was widely used to get rid of non-linearity that caused by mismatching of unit capacitor in feedback DAC path. this paper proposed the improved DWA architecture by adjusting clock timing of the existing DWA architecture. 2n Register block used for output was replaced with 2n S-R latch block. As a result of this, MOS Tr. can be reduced and extra clock can also be removed. Moreover, two n-bit Register block used to delay n-bit data code is decreased to one n-bit Register. In order to confirm characteristics, DWA for the 3-bit output with the proposed DWA architecture was designed on 0.18um process under 1.8V supply. Compared with the existing architecture. It was able to reduce the number of 222 MOS Tr.

Sigma-Delta A/D Converter for ADSL Modems (ADSL 모뎀용 시그마-델타 아날로그/디지털 변환기)

  • Han, Seung-Yub;Yu, Sang-Dae;Lee, Ju-Sang
    • Proceedings of the KIEE Conference
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    • 2003.11c
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    • pp.950-953
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    • 2003
  • In this paper, sigma-delta A/D converter for ADSL modems using oversampling technique is designed. Conventionally, the oversampling A/D converter is consist of opamps, switched capacitors, quantizers, infernal D/A converters, and decimation filters. 3-bit flash A/D converter, 3-bit thermometer-based D/A converters, and sub-blocks are used for high speed operation. HSPICE simulator and CADENCE tool are used for verification and layout of the designed modulator. The internal A/D converter and D/A converters are operated at 130 MHz. In design of decimation filter Matlab is used for calculating coefficients and ModelSim and VHDL are used for design.

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OSCILLATION OF ONE ORDER NEUTRAL DIFFERENTIAL EQUATION WITH IMPULSES

  • Cheng, Jinfa;Chu, Yuming
    • Communications of the Korean Mathematical Society
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    • v.26 no.2
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    • pp.197-205
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    • 2011
  • Explicit sufficient conditions are established for the oscillation of the one order neutral differential equations with impulsive $(x(t)+{\sum\limits^n_{i=1}}c_ix(t-{\sigma}_i))'+px(t-{\tau})=0$, $t{\neq}t_{\kappa}$, ${\Delta}(x(t_{\kappa})+{\sum\limits^n_{i=1}}c_ix(t_{\kappa}-{\sigma}_i))+p_0x(t_{\kappa}-{\tau})=0$, $c_i{\geq}0$, $i=1,2,{\ldots}n$, $p{\tau}$>0, $p_0{\tau}$>0, ${\Delta}(x_{\kappa})=x(t^+_{\kappa})-x(t_{\kappa})$. Explicit sufficient and necessary condition are established when $c_i$ = 0, i = 1, 2, ${\ldots}$, n.

Source Parameters of the Southern Yellow Sea Earthquake Occurred on July 25, 1994 (1994년 7월 25일 발생한 황해남부 지진의 지진원 요수)

  • 김성균;김민선
    • Journal of the Earthquake Engineering Society of Korea
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    • v.2 no.1
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    • pp.113-118
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    • 1998
  • 1994년 7월 25일 발생한 황해남부 지진(Mb=5.5)의 지진원 요소들을 결정하였다. 지진원 요소들을 결정하기 위하여 이 지진에 대하여 이전의 연구에서 얻어진 지진발생기구를 사용하였다. 지진발생기구에 의하면, 이 지진은 거의 동서방향의 압축응력장에 주향이동성분이 가미되어 발생한 것을 암시한다. 지진원 요소들은 단주기 및 장주기 P파에 대한 원지장 스펙트럼으로부터 계산되었다. 지진모멘트(M0), 코너주파수(f0), 지진원 반경(r) 및 응력강하량($\Delta$$\sigma$)은 각각 M0 = 3.18$\times$1024 dyne-cm, f0=0.3 Hz, r=3.7km, $\Delta$$\sigma$=27bar로 구해졌다. 지진모멘트로부터 산정한 모멘트 규모는 5.6으로 나타났다.

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THE NEUMANN PROBLEM FOR A CLASS OF COMPLEX HESSIAN QUOTIENT EQUATIONS

  • Yuying Qian;Qiang Tu;Chenyue Xue
    • Bulletin of the Korean Mathematical Society
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    • v.61 no.4
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    • pp.999-1017
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    • 2024
  • In this paper, we study the Neumann problem for the complex Hessian quotient equation ${\frac{{\sigma}_k({\tau}{\Delta}uI+{\partial}{\bar{\partial}u)}}{{\sigma}_l({\tau}{\Delta}uI+{\partial}{\bar{\partial}u)}}}={\psi}$ with 0 ≤ 𝑙 < k ≤ n. We prove a priori estimate and global C1 estimates, in particular, we use the double normal second derivatives on the boundary to establish the global C2 estimates and prove the existence and the uniqueness for the Neumann problem of the above complex Hessian quotient equation.

THE ANALYTIC FEYNMAN INTEGRAL OVER PATHS ON ABSTRACT WIENER SPACE

  • Yoo, Il
    • Communications of the Korean Mathematical Society
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    • v.10 no.1
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    • pp.93-107
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    • 1995
  • In their paper [2,3], Cameron and Storvick introduced some classes $S"+m$ and of functionals on classical Wiener spaces $C_0[a,b]$. For such functionals, they showed that the analytic Feynman integral exists and they gave some formulas for this integral. Moreover they obtained that the functionals of the form $$ (1.1) F(x) = exp {\int^b_a{\theta(s,x(x))dx} $$ are in S" where they assumbed that the potential $\delta : [a,b] \times R \to C$ satisfies (i) for each $s \in [a,b], \theta(s,\cdot)$ is the Fourier-Stieltjes transform of $\sigma_s \in M(R)$, (ii) for each Borel subset E of $[a,b] \times R, \sigma_s (E^{(s)})$ is a Borel measurable function of s on [a,b], and (iii) the total variation $\Vert \sigma_s \Vert$ of $\sigma_s$ is bounded as a function of s.tion of s.

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Characterization of Weak Asplund Space in Terms of Positive Sublinear Functional

  • Oh, Seung Jae
    • Journal of the Chungcheong Mathematical Society
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    • v.1 no.1
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    • pp.71-76
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    • 1988
  • For each continuous convex function ${\phi}$ defined on an open convex subset $A_{\phi}$ of a Banach space X, if we define a positively homogeneous sublinear functional ${\sigma}_x$ on X by ${\sigma}_x(y)=\sup{\lbrace}f(y)\;:\;f{\in}{\partial}{\phi}(x){\rbrace}$, where ${\partial}{\phi}(x)$ is a subdifferential of ${\phi}$ at x, then we get the following characterization theorem of Gateaux differentiability (weak Asplund) sapce. THEOREM. For every ${\phi}$ above, $D_{\phi}={\lbrace}x{\in}A\;:\;\sup_{||u||=1}\;{\sigma}_x(u)+{\sigma}_x(-u)=0{\rbrace}$ contains dense (dense $G_{\delta}$) subset of $A_{\phi}$ if and only if X is a Gateaux differentiability (weak Asplund) space.

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A study on the characteristics of corrosion-fatigue-crack propagation in the welded parts of high tensile steels under sea water (고장력강 용접부의 해수중 부식피로균열 성장특성에 관한 연구)

  • 김영식;박무창
    • Journal of Ocean Engineering and Technology
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    • v.1 no.2
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    • pp.113-122
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    • 1987
  • Ships and offshore strrctures are exposed to the corrosive surroundings, and the extablishment of the design criteria and the elucidation on the influence by this environment are requested to maintain the safety and to demonstrate the function of the structure. In this paper, the fatigue-crack-growth behavior on the compact tension specimens of quenched, tempered HT80 grade steels and RA36 high tensile steels having a single edge fatigue cracked notch respectively, were investigated under the repeated tensile stress with constant stroke in sea water for the welded parts by shielded metal arc welding. Main results obtained are summerized as follows; 1. The fatigue-crack-growth rates da/dN in sea water appeared to be greater behavior than those in air environment at the same stress intensisy factor range $\DeltaK$. 2. The correlation data of da/dN$\DeltaK$ of the two kinds of high tensile steels in sea water showed no great difference, however, the correlation data of da/dN$\DeltaK/\sigma_y$($\sigma_y$ stands for yield strength of the material) showed that the fatigue-crack-growth behavior of RA36 plate is affected by active path corrosion(APC) mechanism, while that of HT80 grade plate is mainly affected by hydrogen embrittlement mechanism.

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Planar harmonic mappings and curvature estimates

  • Jun, Sook-Heui
    • Journal of the Korean Mathematical Society
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    • v.32 no.4
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    • pp.803-814
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    • 1995
  • Let $\Sigma$ be the class of all complex-valued, harmonic, orientation-preserving, univalent mappings defined on $\Delta = {z : $\mid$z$\mid$ > 1}$ that map $\infty$ to $\infty$.

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Initiation and Propagation Behaviors of Micro-Surface-Fatigue Cracks under In-Plane Tension Fatigue Tests (引張 軸荷重 疲勞 에 의한 微小表面 균열 의 發생 . 成長擧動)

  • 서창민
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.9 no.1
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    • pp.1-9
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    • 1985
  • In-plane tension fatigue tests (R = 0.05) were carried out to investigate the initiation and propagation behaviors of micro-surface-fatigue cracks on smooth surfaces of a mild steel. Also, the investigations of saturated cyclic strain which can be obtained by the fatigue tests have been made via the cyclic strain intensity factor, .DELTA. $K_{\epsilon}$/, for the purpose of unifying two approaches of the study of fatigue; the one approach is based on the fracture mechanics concept and the other on lowcycle fatigue concept. Some of the results are as follows; The growth rate, d(2a)/dN, of small cracks cannot be represented by one straight line as a function of .DELTA.K for various of the nominal stress range, .DELTA..sigma., and is higher than that of a larger through crack. The rearrangement of the d(2a)/dN by .DELTA..epsilon..root..pi.s( = .DELTA. $K_{\epsilon}$/) with the stress range .DELTA..epsilon. in .DELTA.K replaced by .DELTA..epsilon., strain range, gives one straight line of the .DELTA. $K_{\epsilon}$-d(2a)/dN relation for various values of stress range .DELTA.$_{\epsilon}$../.X>../.