• Journal of Astronomy and Space Sciences
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• 제23권4호
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• pp.303-310
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• 2006

We model the aspherical dust envelopes around O-rich AGB stars. We perform the radiative transfer model calculations for axisymmetric dust distributions. We simulate what could be observed from the aspherical dust envelopes around O-rich AGB stars by presenting the model spectral energy distributions and images at various wave-lengths for different optical depths and viewing angles. The model results are very different from the ones with spherically symmetric geometry.

• Communications for Statistical Applications and Methods
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• 제9권1호
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• pp.101-113
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• 2002

In this paper we introduce a new score generating (unction for the rank regression in the linear regression model. The score function compares the $\gamma$'th and s\`th power of the tail probabilities of the underlying probability distribution. We show that the rank estimate asymptotically converges to a multivariate normal. further we derive the asymptotic Pitman relative efficiencies and the most efficient values of $\gamma$ and s under the symmetric distribution such as uniform, normal, cauchy and double exponential distributions and the asymmetric distribution such as exponential and lognormal distributions respectively.

• 대한수학회지
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• 제35권1호
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• pp.225-234
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• 1998

We compute genus distributions for bouquets of dipoles by using the method concerning the cycle structure of permutations in the symmetric group. From this, we can deduce that every bouquet of dipoles is upper embeddable. We find a foumula for computing the embedding polynomials for bouquets of dipoles.

• Structural Monitoring and Maintenance
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• 제6권2호
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• pp.147-159
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• 2019

In present article, a size-dependent refined thick beam element has been established based upon nonlocal elasticity theory. Next, it is used to explore vibration response of porous metal foam nanobeams on elastic medium. The established beam element introduces ten degrees of freedom. Different porosity distributions called uniform, symmetric and asymmetric will be employed. Herein, introduced thick beam element contains shear deformations without using correction factors. Convergence and verification studies of obtained results from finite element method are also provided. The impacts of nonlocality factor, foundation factors, shear deformation, slenderness ratio, porosity kinds and porosity factor on vibration frequencies of metal foam nano-sized beams have been explored.

• Nuclear Engineering and Technology
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• 제53권2호
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• pp.357-367
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• 2021

In general, common cause failures (CCFs) have been modeled with the assumption that components within the same group are symmetric. This assumption reduces the number of parameters required for the CCF probability estimation and allows us to use a parametric model, such as the alpha factor model. Although there are various asymmetric conditions in nuclear power plants (NPPs) to be addressed, the traditional CCF models are limited to symmetric conditions. Therefore, this paper proposes the copulabased CCF model to deal with asymmetric as well as symmetric CCFs. Once a joint distribution between the components is constructed using copulas, the proposed model is able to provide the probability of common cause basic events (CCBEs) by formulating a system of equations without symmetry assumptions. In addition, Bayesian inferences for the parameters of the marginal and copula distributions are introduced and Markov Chain Monte Carlo (MCMC) algorithms are employed to sample from the posterior distribution. Three example cases using simulated data, including asymmetry conditions in total failure probabilities and/or dependencies, are illustrated. Consequently, the copula-based CCF model provides appropriate estimates of CCFs for asymmetric conditions. This paper also discusses the limitations and notes on the proposed method.

• 전기의세계
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• 제29권11호
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• pp.742-750
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• 1980

The problem of nonlinear time-invariant system identification by estimation of Wiener kernels is studied for discrete time systems with inputs having symmetric probability distributions. G-functionals are constructed. It is further shown that under idealized conditions, these seemingly different techniques yield the same results. The results of identification of asimulated second degree system is presented.

• 대한전자공학회논문지
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• 제21권4호
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• pp.7-12
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• 1984

DFT로 대각선화 할 수 있는 circulant matrix가 대칭이고 실수인 경우에 이를 대각선화 할 수 있는 CDFT(composite DFT)를 유도했다. 일반적인 실수 신호의 대칭 covariance matrix에 대하여 DFT와 CDFT 변환했을 경우의 variance 분포를 분석했고, 이를 토대로 rate distortion 이론에 의하여 이들의 성능을 비교한 결과 CDFT가 DFT보다 bit rate면에서 효과적임을 볼 수 있었다. 그리고 f(q)=(0.95)q인 covariance matrix(64×64)에 대해 CDFT가 DFT에 비해. 계산결과, 평균적으로 0.0095bit가 감소될 수 있었다.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제9권1호
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• pp.81-90
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• 2002

The least informative (favorable) distributions, minimizing Fisher information for a multivariate location parameter, are derived in the parametric class of the exponential-power spherically symmetric distributions under the following characterizing restrictions; (i) a bounded variance, (ii) a bounded value of a density at the center of symmetry, and (iii) the intersection of these restrictions. In the first two cases, (i) and (ii) respectively, the least informative distributions are the Gaussian and Laplace, respectively. In the latter case (iii) the optimal solution has three branches, with relatively small variances it is the Gaussian, them with intermediate variances. The corresponding robust minimax M-estimators of location are given by the $L_2$-norm, the $L_1$-norm and the $L_{p}$ -norm methods. The properties of the proposed estimators and their adaptive versions ar studied in asymptotics and on finite samples by Monte Carlo.

• Communications for Statistical Applications and Methods
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• 제27권4호
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• pp.397-412
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• 2020

In this paper, a notion of data depth is used to propose nonparametric multivariate two sample tests for difference between scale parameters. Data depth can be used to measure the centrality or outlying-ness of the multivariate data point relative to data cloud. A difference in the scale parameters indicates the difference in the depth values of a multivariate data point. By observing this fact on a depth vs depth plot (DD-plot), we propose nonparametric multivariate two sample tests for scale parameters of multivariate distributions. The p-values of these proposed tests are obtained by using Fisher's permutation approach. The power performance of these proposed tests has been reported for few symmetric and skewed multivariate distributions with the existing tests. Illustration with real-life data is also provided.

• 대한기계학회논문집B
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• 제26권10호
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• pp.1378-1386
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• 2002

In the present study, velocity profile and wall shear stress distributions of developing turbulent oscillatory flows in an oscillator connected to straight duct located in exit region of a curved duct was investigated experimentally. The experimental study for air flows was conducted to measure axial velocity profiles, shear stress distributions by using the Laser Doppler Velocimetry(LDV) system with the data acquisition and processing system of Rotating Machinery Resolver(R.M.R) and PHASE software. The results obtained from experimental studies are summarized as follows. The critical Reynolds number for a change from transitional oscillatory flow to turbulent flow was about 7500, in the 60region of dimensionless axial position which was considered as a fully developed flow region. The turbulent oscillatory flow, velocity profiles of the inflow period in the entrance region were gradually developed, but those of the outflow period were not changed nearly. Velocity profiles of inflow and outflow were shown as a symmetric form in a fully developed flow region. The wall shear stress distributions of turbulent oscillatory flow increase rapidly as the flow proceeds to downstream and flow was in good agreement with the theoretically.