• Title/Summary/Keyword: linear approximation

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Improved Differential-Linear Cryptanalysis Using DLCT (DLCT를 활용한 향상된 차분선형 분석)

  • Kim, Hyunwoo;Kim, Seonggyeom;Hong, Deukjo;Sung, Jaechul;Hong, Seokhie
    • Journal of the Korea Institute of Information Security & Cryptology
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    • v.28 no.6
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    • pp.1379-1392
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    • 2018
  • The complexity of the differential-linear cryptanalysis is strongly influenced by the probability of the differential-linear characteristic computed under the assumption of round independence, linear approximation independence, and uniformity for the trail that does not satisfy differential trail. Therefore, computing the exact probability of the differential-linear characteristic is a very important issue related to the validity of the attack. In this paper, we propose a new concept called DLCT(Differential-Linear Connectivity Table) for the differential-linear cryptanalysis. Additionally, we propose an improved probability computation technique of differential-linear characteristic by applying DLCT. By doing so, we were able to weaken linear approximation independence assumption. We reanalyzed the previous results by applying DLCT to DES and SERPENT. The probability of 7-round differential-linear characteristic of DES is $1/2+2^{-5.81}$, the probability of 9-round differential-linear characteristic of SERPENT is computed again to $1/2+2^{-57.9}$, and data complexity required for the attack is reduced by $2^{0.2}$ and $2^{2.2}$ times, respectively.

Application of the nonlinear transformation and linear state state feedback control to nonlinear hydraulic servo system (비선형 유압 서보시스템의 비선형 변환 및 이에 대한 선형제어에 관한 연구)

  • 김영준;장효환
    • 제어로봇시스템학회:학술대회논문집
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    • 1989.10a
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    • pp.272-275
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    • 1989
  • In this paper feedback linearization of valve-controlled nonlinear hydraulic velocity control system is studied. The $C^{\infty}$ nonlinear transformation T is obtained, and it is shown that this transformation is global one. Linear equivalence of nonlinear hydraulic velocity control system is obtained by this global nonlinear transformation, and linear state feedback control law is applied to this linear model. It is shown that this transformation method is to the linear approximation by simulation study..

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Testing Homogeneity for Random Effects in Linear Mixed Model

  • Ahn, Chul H.
    • Communications for Statistical Applications and Methods
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    • v.7 no.2
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    • pp.403-414
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    • 2000
  • A diagnostic tool for testing homogeneity for random effects is proposed in unbalanced linear mixed model based on score statistic. The finite sample behavior of the test statistic is examined using Monte Carlo experiments examine the chi-square approximation of the test statistic under the null hypothesis.

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On Testing Fisher's Linear Discriminant Function When Covariance Matrices Are Unequal

  • Kim, Hea-Jung
    • Journal of the Korean Statistical Society
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    • v.22 no.2
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    • pp.325-337
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    • 1993
  • This paper propose two test statistics which enable us to proceed the variable selection in Fisher's linear discriminant function for the case of heterogeneous discrimination with equal training sample size. Simultaneous confidence intervals associated with the test are also given. These are exact and approximate results. The latter is based upon an approximation of a linear sum of Wishart distributions with unequal scale matrices. Using simulated sampling experiments, powers of the two tests have been tabulated, and power comparisons have been made between them.

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An improved linear sampled-data output regulators (개선된 선형 샘플치 출력 조절기)

  • 정선태
    • 제어로봇시스템학회:학술대회논문집
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    • 1997.10a
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    • pp.1726-1729
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    • 1997
  • In general, the solvability of linear robust output regulation problem are not preserved under time-sampling. Thus, it is found that the digital regulator implemented by itme-sampling of anlog output regulator designed based on the continuous-time linear system model is nothing but a 1st order approximation with respect to time-sampling. By the way, one can design an improved sampled-data regulator with respect to sampling time by utilizing the intrinsic structure of the system. In this paper, we study the system structures which it is possible to design an improved sampled-data regulator with respect to sampling time.

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A Note on Positive Invariant Set for Linear Uncertain Discrete-Time Systems

  • Matsumoto, H.;Otsuka, N.
    • 제어로봇시스템학회:학술대회논문집
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    • 2005.06a
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    • pp.571-574
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    • 2005
  • This paper gives some sufficient conditions for a given polyhedral set which is represented as a set of linear inequalities to be positive D-invariant for uncertain linear discrete-time systems in the case such that the systems matrices depend linearly on uncertain parameters whose ranges are given intervals. Further, the results will be applied to uncertain linear continuous systems in the sense of the above by using Euler approximation.

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Fractal Image Compression Using Adaptive Selection of Block Approximation Formula (블록 근사화식의 적응적 선택을 이용한 프랙탈 영상 부호화)

  • Park, Yong-Ki;Park, Chul-Woo;Kim, Doo-Young
    • The Transactions of the Korea Information Processing Society
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    • v.4 no.12
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    • pp.3185-3199
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    • 1997
  • This paper suggests techniques to reduce coding time which is a problem in traditional fractal compression and to improve fidelity of reconstructed images by determining fractal coefficient through adaptive selection of block approximation formula. First, to reduce coding time, we construct a linear list of domain blocks of which characteristics is given by their luminance and variance and then we control block searching time according to the first permissible threshold value. Next, when employing three-level block partition, if a range block of minimum partition level cannot find a domain block which has a satisfying approximation error, we choose new approximation coefficients using a non-linear approximation of luminance term. This boosts the fidelity. Our experiment employing the above methods shows enhancement in the coding time more than two times over traditional coding methods and shows improvement in PSNR value by about 1-3dB at the same com- pression rate.

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The Semi-Analytic Structural Sensitivity Using Pade Approximation (Pade근사를 이용한 준해석 구조 민감도의 해석)

  • Dan, Ho-Jin;Lee, Byung-Chai
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.12
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    • pp.2631-2635
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    • 2002
  • The semi-analytic sensitivity analysis using Pade approximation is presented for linear elastic structures. Although the semi-analytic method has several advantages, accuracy of the method prevents it from practical application. One of promising remedies is the use of geometric series for the matrix inversion. Though series expansion of order three has been successfully applied to the calculation of the structural sensitivity in the most range of the design perturbation, it is prone to have a slow convergence for large perturbation. To overcome this shortage, Pade approximation is introduced so that it can broaden the trust region of the perturbation without adding expansion terms. Numerical results show that the confident sensitivity can be obtained with tiny expenses of computation effort.

Feature curve extraction from point clouds via developable strip intersection

  • Lee, Kai Wah;Bo, Pengbo
    • Journal of Computational Design and Engineering
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    • v.3 no.2
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    • pp.102-111
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    • 2016
  • In this paper, we study the problem of computing smooth feature curves from CAD type point clouds models. The proposed method reconstructs feature curves from the intersections of developable strip pairs which approximate the regions along both sides of the features. The generation of developable surfaces is based on a linear approximation of the given point cloud through a variational shape approximation approach. A line segment sequencing algorithm is proposed for collecting feature line segments into different feature sequences as well as sequential groups of data points. A developable surface approximation procedure is employed to refine incident approximation planes of data points into developable strips. Some experimental results are included to demonstrate the performance of the proposed method.