• Title/Summary/Keyword: gaussian model

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Geostrophic Velocities Derived from Satellite Altimetry in the Sea South of Japan

  • Kim, Seung-Bum
    • Korean Journal of Remote Sensing
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    • v.18 no.5
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    • pp.243-253
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    • 2002
  • Time-mean and absolute geostrophic velocities of the Kuroshio current south of Japan are derived from TOPEX/Poseidon altimeter data using a Gaussian jet model. When compared with simultaneous measurements from a shipboard acoustic Doppler current profiler (ADCP) at two intersection points, the altimetric and ADCP absolute velocities correlate well with the correlation coefficient of 0.55 to 0.74. The accuracy of time-mean velocity ranges from 1 cm s$^{-1}$ to 5 cm s$^{-1}$. The errors in the absolute and the mean velocities are similar to those reported previously for other currents. The comparable performance suggests the Gaussian jet model is a promising methodology for determining absolute geostrophic velocities, noting that in this region the Kuroshio does not meander sufficiently and thus provides unfavorable environment for the performance of the Gaussian jet model.

The Analysis of Breakdown Voltage for the Double-gate MOSFET Using the Gaussian Doping Distribution

  • Jung, Hak-Kee
    • Journal of information and communication convergence engineering
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    • v.10 no.2
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    • pp.200-204
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    • 2012
  • This study has presented the analysis of breakdown voltage for a double-gate metal-oxide semiconductor field-effect transistor (MOSFET) based on the doping distribution of the Gaussian function. The double-gate MOSFET is a next generation transistor that shrinks the short channel effects of the nano-scaled CMOSFET. The degradation of breakdown voltage is a highly important short channel effect with threshold voltage roll-off and an increase in subthreshold swings. The analytical potential distribution derived from Poisson's equation and the Fulop's avalanche breakdown condition have been used to calculate the breakdown voltage of a double-gate MOSFET for the shape of the Gaussian doping distribution. This analytical potential model is in good agreement with the numerical model. Using this model, the breakdown voltage has been analyzed for channel length and doping concentration with parameters such as projected range and standard projected deviation of Gaussian function. As a result, since the breakdown voltage is greatly changed for the shape of the Gaussian function, the channel doping distribution of a double-gate MOSFET has to be carefully designed.

An Approximation Method for the Estimation of Exposed dose due to Gamma - rays from Radioactive Materials dispersed to the Atmoshere (대기로 확산된 방사성물질로부터 방출되는 감마선에 의한 피폭선량을 계산하기 위한 근사화 방법)

  • Kim, T.W.;Park, C.M.;Ro, S.G.
    • Journal of Radiation Protection and Research
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    • v.15 no.2
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    • pp.51-56
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    • 1990
  • The dispersing model of radioactive plume in the atmosphere was assumed to form finite ellipseshaped volumes rather than a single plume and gamma absorbed doses from the plume were computed using the proposed model. The results obtained were compared with those computed by the Gaussian plume and the circular approximation models. The results computed by the proposed ellipse-shaped approximation model were close to those by the Gaussian plume model. and more accurate than those by the circular approximation model. The computing time for the proposed approximation model was one fortieth of that for the Gaussian plume model.

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Analytic study on the realization of partially coherent Gaussian Schell-model beams with isotropic cross section and anisotropic degree of coherence function (등방성 빔 단면과 비등방성 공간 부분 코히어런스 특성을 갖는 가우시안 셀 모델 빔의 구현에 대한 해석적 연구)

  • Kim, Hwi;Kim, Tae-Soo;Choi, Kyung-Sik;Lee, Byung-Ho
    • Korean Journal of Optics and Photonics
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    • v.15 no.3
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    • pp.200-213
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    • 2004
  • The realization of partially coherent Gaussian Schell-model beams with isotropic cross section and anisotropic degree of coherence function is investigated theoretically. An optical system is devised to transform diffused light generated by passing the Gaussian beam of the He-Ne laser thorough a rotating holographic diffuser to the partially coherent Gaussian Schell-model beam with isotropic cross section and anisotropic degree of coherence function. Analytic design equations are formulated and design examples are presented.

Development of a novel fatigue damage model for Gaussian wide band stress responses using numerical approximation methods

  • Jun, Seock-Hee;Park, Jun-Bum
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.12 no.1
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    • pp.755-767
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    • 2020
  • A significant development has been made on a new fatigue damage model applicable to Gaussian wide band stress response spectra using numerical approximation methods such as data processing, time simulation, and regression analysis. So far, most of the alternative approximate models provide slightly underestimated or overestimated damage results compared with the rain-flow counting distribution. A more reliable approximate model that can minimize the damage differences between exact and approximate solutions is required for the practical design of ships and offshore structures. The present paper provides a detailed description of the development process of a new fatigue damage model. Based on the principle of the Gaussian wide band model, this study aims to develop the best approximate fatigue damage model. To obtain highly accurate damage distributions, this study deals with some prominent research findings, i.e., the moment of rain-flow range distribution MRR(n), the special bandwidth parameter μk, the empirical closed form model consisting of four probability density functions, and the correction factor QC. Sequential prerequisite data processes, such as creation of various stress spectra, extraction of stress time history, and the rain-flow counting stress process, are conducted so that these research findings provide much better results. Through comparison studies, the proposed model shows more reliable and accurate damage distributions, very close to those of the rain-flow counting solution. Several significant achievements and findings obtained from this study are suggested. Further work is needed to apply the new developed model to crack growth prediction under a random stress process in view of the engineering critical assessment of offshore structures. The present developed formulation and procedure also need to be extended to non-Gaussian wide band processes.

A Study on Fatigue Analysis of Non-Gaussian Wide Band Process using Frequency-domain Method (주파수 영역 해석 기법을 이용한 비정규 광대역 과정의 피로해석에 관한 연구)

  • Kim, Hyeon-Jin;Jang, Beom-Seon
    • Journal of the Society of Naval Architects of Korea
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    • v.55 no.6
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    • pp.466-473
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    • 2018
  • Most frequency domain-based approaches assume that structural response should be a Gaussian random process. But a lot of non-Gaussian processes caused by multi-excitation and non-linearity in structural responses or load itself are observed in many real engineering problems. In this study, the effect of non-Normality on fatigue damages are discussed through case study. The accuracy of four frequency domain methods for non-Gaussian processes are compared in the case study. Power-law and Hermite models which are derived for non-Gaussian narrow-banded process tend to estimate fatigue damages less accurate than time domain results in small kurtosis and in case of large kurtosis they give conservative results. Weibull model seems to give conservative results in all environmental conditions considered. Among the four methods, Benascuitti-Tovo model for non-Gaussian process gives the best results in case study. This study could serve as background material for understanding the effect of non-normality on fatigue damages.

An Effective Denoising Method for Images Contaminated with Mixed Noise Based on Adaptive Median Filtering and Wavelet Threshold Denoising

  • Lin, Lin
    • Journal of Information Processing Systems
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    • v.14 no.2
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    • pp.539-551
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    • 2018
  • Images are unavoidably contaminated with different types of noise during the processes of image acquisition and transmission. The main forms of noise are impulse noise (is also called salt and pepper noise) and Gaussian noise. In this paper, an effective method of removing mixed noise from images is proposed. In general, different types of denoising methods are designed for different types of noise; for example, the median filter displays good performance in removing impulse noise, and the wavelet denoising algorithm displays good performance in removing Gaussian noise. However, images are affected by more than one type of noise in many cases. To reduce both impulse noise and Gaussian noise, this paper proposes a denoising method that combines adaptive median filtering (AMF) based on impulse noise detection with the wavelet threshold denoising method based on a Gaussian mixture model (GMM). The simulation results show that the proposed method achieves much better denoising performance than the median filter or the wavelet denoising method for images contaminated with mixed noise.

Gaussian Process Regression and Its Application to Mathematical Finance (가우시언 과정의 회귀분석과 금융수학의 응용)

  • Lim, Hyuncheul
    • Journal for History of Mathematics
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    • v.35 no.1
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    • pp.1-18
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    • 2022
  • This paper presents a statistical machine learning method that generates the implied volatility surface under the rareness of the market data. We apply the practitioner's Black-Scholes model and Gaussian process regression method to construct a Bayesian inference system with observed volatilities as a prior information and estimate the posterior distribution of the unobserved volatilities. The variance instead of the volatility is the target of the estimation, and the radial basis function is applied to the mean and kernel function of the Gaussian process regression. We present two types of Gaussian process regression methods and empirically analyze them.

A revised Hermite peak factor model for non-Gaussian wind pressures on high-rise buildings and comparison of methods

  • Dongmei Huang;Hongling Xie;Qiusheng Li
    • Wind and Structures
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    • v.36 no.1
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    • pp.15-29
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    • 2023
  • To better estimate the non-Gaussian extreme wind pressures for high-rise buildings, a data-driven revised Hermitetype peak factor estimation model is proposed in this papar. Subsequently, a comparative study on three types of methods, such as Hermite-type models, short-time estimate Gumbel method (STE), and new translated-peak-process method (TPP) is carried out. The investigations show that the proposed Hermite-type peak factor has better accuracy and applicability than the other Hermite-type models, and its absolute accuracy is slightly inferior to the STE and new TPP methods for non-Gaussian wind pressures by comparing with the observed values. Moreover, these methods generally overestimate the Gaussian wind pressures especially the STE.

Semi-Supervised Learning by Gaussian Mixtures (정규 혼합분포를 이용한 준지도 학습)

  • Choi, Byoung-Jeong;Chae, Youn-Seok;Choi, Woo-Young;Park, Chang-Yi;Koo, Ja-Yong
    • The Korean Journal of Applied Statistics
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    • v.21 no.5
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    • pp.825-833
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    • 2008
  • Discriminant analysis based on Gaussian mixture models, an useful tool for multi-class classifications, can be extended to semi-supervised learning. We consider a model selection problem for a Gaussian mixture model in semi-supervised learning. More specifically, we adopt Bayesian information criterion to determine the number of subclasses in the mixture model. Through simulations, we illustrate the usefulness of the criterion.