• Title/Summary/Keyword: random vectors

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Probabilistic Strength Assessment of Ice Specimen considering Spatial Variation of Material Properties (물성치의 공간분포를 고려한 빙 시험편의 확률론적 강도평가)

  • Kim, Hojoon;Kim, Yooil
    • Journal of the Society of Naval Architects of Korea
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    • v.57 no.2
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    • pp.80-87
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    • 2020
  • As the Arctic sea ice decreases due to various reasons such as global warming, the demand for ships and offshore structures operating in the Arctic region is steadily increasing. In the case of sea ice, the anisotropy is caused by the uncertainty inside the material. For most of the research, nevertheless, estimating the ice load has been treated deterministically. With regard to this, in this paper, a four-point bending strength analysis of an ice specimen was attempted using a stochastic finite element method. First, spatial distribution of the material properties used in the yield criterion was assumed to be a multivariate Gaussian random field. After that, a direct method, which is a sort of stochastic finite element method, and a sensitivity method using the sensitivity of response for random variables were proposed for calculating the probabilistic distribution of ice specimen strength. A parametric study was conducted with different mean vectors and correlation lengths for each material property used in the above procedure. The calculation time was about ten seconds for the direct method and about three minutes for the sensitivity methods. As the cohesion and correlation length increased, the mean value of the critical load and the standard deviation increased. On the contrary, they decreased as the friction angle increased. Also, in all cases, the direct and sensitivity methods yielded very similar results.

ECG-based Biometric Authentication Using Random Forest (랜덤 포레스트를 이용한 심전도 기반 생체 인증)

  • Kim, JeongKyun;Lee, Kang Bok;Hong, Sang Gi
    • Journal of the Institute of Electronics and Information Engineers
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    • v.54 no.6
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    • pp.100-105
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    • 2017
  • This work presents an ECG biometric recognition system for the purpose of biometric authentication. ECG biometric approaches are divided into two major categories, fiducial-based and non-fiducial-based methods. This paper proposes a new non-fiducial framework using discrete cosine transform and a Random Forest classifier. When using DCT, most of the signal information tends to be concentrated in a few low-frequency components. In order to apply feature vector of Random Forest, DCT feature vectors of ECG heartbeats are constructed by using the first 40 DCT coefficients. RF is based on the computation of a large number of decision trees. It is relatively fast, robust and inherently suitable for multi-class problems. Furthermore, it trade-off threshold between admission and rejection of ID inside RF classifier. As a result, proposed method offers 99.9% recognition rates when tested on MIT-BIH NSRDB.

A Robust Digital Watermarking based on Virtual Optics (가상 광학에 기반한 강인한 디지털 워터마킹)

  • Lee, Geum-Boon;Cho, Beom-Joon
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.15 no.5
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    • pp.1073-1080
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    • 2011
  • In this paper, we propose a novel digital watermarking method by virtual optics which secures multimedia information such as images, videos and sounds. To secure the multimedia data, we use Fresnel transform which describes the diffraction phenomena of the waves. Also, this method attaches the random phase function to Fresnel transform so that original image and watermark image would be gaussian random vectors. The complex numbers of watermark by Fresnel transform are separated the real part and the imaginary part. The former is embedded in original image as a encoding key imperceptibly and the latter is used for detecting the watermark as a decoding key. This method for digital watermarking ensures that watermark can be successfully registered and extracted from the watermarked image. Further, it provides the robustness to signal processing operation and geometric distortion and proves the strong resilience against cropping attack. The performance evaluation of the experiment is carried out with PSNR, and the numerical simulation results show the efficiency of the proposed method.

Geometrically non-linear dynamic analysis of plates by an improved finite element-transfer matrix method on a microcomputer

  • Chen, YuHua
    • Structural Engineering and Mechanics
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    • v.2 no.4
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    • pp.395-402
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    • 1994
  • An improved finite element-transfer matrix method is applied to the transient analysis of plates with large displacement under various excitations. In the present method, the transfer of state vectors from left to right in a combined finite element-transfer matrix method is changed into the transfer of generally incremental stiffness equations of every section from left to right. Furthermore, in this method, the propagation of round-off errors occurring in recursive multiplications of transfer and point matrices is avoided. The Newmark-${\beta}$ method is employed for time integration and the modified Newton-Raphson method for equilibrium iteration in each time step. An ITNONDL-W program based on this method using the IBM-PC/AT microcomputer is developed. Finally numerical examples are presented to demonstrate the accuracy as well as the potential of the proposed method for dynamic large deflection analysis of plates with random boundaries under various excitations.

Practical Schemes for Tunable Secure Network Coding

  • Liu, Guangjun
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.9 no.3
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    • pp.1193-1209
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    • 2015
  • Network coding is promising to maximize network throughput and improve the resilience to random network failures in various networking systems. In this paper, the problem of providing efficient confidentiality for practical network coding system against a global eavesdropper (with full eavesdropping capabilities to the network) is considered. By exploiting a novel combination between the construction technique of systematic Maximum Distance Separable (MDS) erasure coding and traditional cryptographic approach, two efficient schemes are proposed that can achieve the maximum possible rate and minimum encryption overhead respectively on top of any communication network or underlying linear network code. Every generation is first subjected to an encoding by a particular matrix generated by two (or three) Vandermonde matrices, and then parts of coded vectors (or secret symbols) are encrypted before transmitting. The proposed schemes are characterized by tunable and measurable degrees of security and also shown to be of low overhead in computation and bandwidth.

Enhanced least square complex frequency method for operational modal analysis of noisy data

  • Akrami, V.;Zamani, S. Majid
    • Earthquakes and Structures
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    • v.15 no.3
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    • pp.263-273
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    • 2018
  • Operational modal analysis is being widely used in aerospace, mechanical and civil engineering. Common research fields include optimal design and rehabilitation under dynamic loads, structural health monitoring, modification and control of dynamic response and analytical model updating. In many practical cases, influence of noise contamination in the recorded data makes it difficult to identify the modal parameters accurately. In this paper, an improved frequency domain method called Enhanced Least Square Complex Frequency (eLSCF) is developed to extract modal parameters from noisy recorded data. The proposed method makes the use of pre-defined approximate mode shape vectors to refine the cross-power spectral density matrix and extract fundamental frequency for the mode of interest. The efficiency of the proposed method is illustrated using an example five story shear frame loaded by random excitation and different noise signals.

Efficient robust path delay fault test generation for combinational circuits using the testability measure (테스트 용이도를 이용한 조합회로의 효율적인 로보스트 경로 지연 고장 테스트 생성)

  • 허용민;임인칠
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.33A no.2
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    • pp.205-216
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    • 1996
  • In this paper we propose an efficient robust path delay fault test genration algorithm for detection of path delay faluts in combinational ligic circuits. In the proposed robust test genration approach, the testability measure is computed for all gates in the circuit under test and these computed values are used to genrate weighted random delay test vetors for detection of path delay faults. For genrated robust test vectors, we perform fault simulation on ISCAS '85 benchmark circuits using parallel pattern technqieus. The results indicate that the proposed test genration method not only increases the number of detected robust path delay faults but also reduces the time taen to genrate robust tests.

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Flowfield Calculation around Two Circular Cylinders by a Discrete Vortex Method (이산와법에 의한 2원주 주위의 유동장 수치계산)

  • Ro Ki-Deok;Kang Ho-Keun;Choi Hyeong-Doo
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.345-348
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    • 2002
  • The Flow patterns around two cylinders in various arrangements were studied by a discrete vortex method. The flow for the surface of each cylinder was represented by arranging bound vortices at adequate intervals. The viscous diffusion of fluid was represented by the random walk method. The vortex distributions, streaklines, timelines and velocity vectors around two cylinders were calculated for centre-to-centre pitch ratios of $P/D=1.5 and 2.5$, attack angles of ${\alpha}=0^{\circ},\;30^{\circ},\;60^{\circ}\;and\;90^{\circ}$, and Reynolds number of Re=1200. The results of simulation correspond to the photographs by flow visualization and the flow intereference between two cylinders in various arrangements was clearly visualized by a numerical simulation.

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RELSYS: A computer program for structural system reliability

  • Estes, Allen C.;Frangopol, Dan M.
    • Structural Engineering and Mechanics
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    • v.6 no.8
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    • pp.901-919
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    • 1998
  • Most reliability-based analyses focus on the reliability of the individual components of a structure. There are many advantages to examining the components in combination as an entire structural system. This paper illustrates an algorithm used in the computer program RELSYS (RELiability of SYStems) which computes the system reliability of any structure which can be modeled as a series-parallel combination of its components. A first-order method is used to initially compute the reliability of each individual component. The system reliability is computed by successively reducing the series and parallel systems until the system has been simplified to a single equivalent component. Equivalent alpha vectors are used to account for the correlation between failure modes during the system reduction process.

A Flowfield Calculation around Two Circular Cylinders in Various Arrangements by a Discrete Vortex Method (이산와법에 의한 다양한 배열에서 2원주 주위의 유동장 계산)

  • 노기덕;박지태;강호근
    • Journal of Advanced Marine Engineering and Technology
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    • v.27 no.3
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    • pp.365-372
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    • 2003
  • The Flow patterns around two cylinders in various arrangements were studied by a discrete vortex method. The flow for the surface of each cylinder was represented by arranging bound vortices at adequate intervals. The viscous diffusion of fluid was represented by the random walk method. The vortex distributions. streaklines. timelines and velocity vectors around two cylinders were calculated for centre-to-centre pitch ratios of P/D=1.5 and 2.5, attack ang1es of $a=0^{circ}, 30^{circ}, 60^{circ} and 90^{\circ}$. and Reynolds number of Re= 1200. The results of simulation correspond to the photographs by flow visualization and the flow intereference between two cylinders in various arrangements were clearly visualized by a numerical simulation.