• 제목/요약/키워드: Kernel models

검색결과 197건 처리시간 0.028초

境界積分法에 의한 軸對稱 彈性 問題의 解析 (Boundary Integral Equation Analysis of Axisymmetric Linear Elastic Problems)

  • 공창덕;김진우
    • 대한기계학회논문집
    • /
    • 제10권5호
    • /
    • pp.787-797
    • /
    • 1986
  • 본 논문에서는 축대칭 선형 문제의 경계적분법에 대한 일반화한 정식화 과정 및 수치적 접근방법이 제시되었으며 정식화 과정 중 Navier 방정식의 기본해로부터 도 출되는 변위 및 표면적 Kernel을 구하는 Hankel 변환법을 이용한 $\ulcorner$직접축대칭접근법 $\lrcorner$과 3차원 Kevin 해로부터 원주경로 따라 적분한 $\ulcorner$3차원 접근법$\lrcorner$이 비교 검토되었 다.

벼의 리올러지 특성(特性)(II) -곡립(穀粒)의 압축(壓縮)크리이프- (Rheological Properties of Rough Rice (II) -Compressive Creep of Rough Rice Kernel-)

  • 김만수;김성래;박종민
    • Journal of Biosystems Engineering
    • /
    • 제15권3호
    • /
    • pp.219-229
    • /
    • 1990
  • The compression creep behavior of grains when loaded depends not only on load but also on duration of load application. The most common methods of studying the load-time characteristics of agricultural products is by employing rheological models such as Burger's model. However it is sometimes not sufficient to describe the viscoelastic behavior of grains to be Burger's model. For this reason, this study was conducted to develop the rheological model which represented the creep compliance response of the rough rice kernel and was a function of initial stress applied and time. The effects of the initial stress applied and the moisture content on the compression creep behavior of the rough rice kernel were analyzed. The results were obtained from the study as follows: 1. Since the viscoelastic behavior of the rough rice kernel was nonlinear, the transient and steady state creep compliance was satisfactorily modelled as follows: $$J({\sigma},t)=A{\sigma}^B[C+Dt-exp(-Ft)]$$ But, for the every stress applied, the compression creep behavior of the samples tested can be well described by Burger's model respectively. 2. The creep compliance, the instantaneous elastic strain, the retarded elastic strain and the viscous strain of the sample tested generally increased in magnitude with increasing the applied initial stress and the moisture content used in the tests. At low moisture content, the creep compliance for the Japonica-type rough rice kernel Was a little higher than those for Indica-type and at high moisture content, vice versa at high moisture content. 3. The retardation times of the samples had not an uniform tendency by the initial stress and the moisture content. The retardation times ranged from 0.66 to 6.76 seconds, and the creep progressed from transient to steady state at a relatively high rate. 4. The less viscous strain than the instantaneous elastic strain for the samples tested indicated that rough rice kernel behaved as a viscoelastic body characterized by elasticity than viscosity.

  • PDF

KOSPI지수와 원-달러 환율의 변동성의 비대칭성에 대한 실증연구 (Empirical Analyses of Asymmetric Conditional Heteroscedasticities for the KOSPI and Korean Won-US Dollar Exchange Rate)

  • 맹혜영;신동완
    • 응용통계연구
    • /
    • 제24권6호
    • /
    • pp.1033-1043
    • /
    • 2011
  • 본 논문에서는 KOSPI지수와 원-달러 환율의 로그수익률을 사용하여 비대칭 이분산성에 대해 연구한다. 커널 density plot과 상승기와 하강기의 평균, 분산을 검토하여 이들 시계열의 변동의 비대칭성에 대한 윤곽을 파악하고 GARCH군의 여러 비대칭 모형을 적합하여 비대칭성을 실증적으로 파악한다. 또한 최종선택 모형인 EGARCH 모형을 바탕으로 부트스트래핑을 사용하여 미래 시점의 변동성인 조건부 분산의 기대치를 예측하고 예측표준오차를 구해본다.

Assessment of compressive strength of high-performance concrete using soft computing approaches

  • Chukwuemeka Daniel;Jitendra Khatti;Kamaldeep Singh Grover
    • Computers and Concrete
    • /
    • 제33권1호
    • /
    • pp.55-75
    • /
    • 2024
  • The present study introduces an optimum performance soft computing model for predicting the compressive strength of high-performance concrete (HPC) by comparing models based on conventional (kernel-based, covariance function-based, and tree-based), advanced machine (least square support vector machine-LSSVM and minimax probability machine regressor-MPMR), and deep (artificial neural network-ANN) learning approaches using a common database for the first time. A compressive strength database, having results of 1030 concrete samples, has been compiled from the literature and preprocessed. For the purpose of training, testing, and validation of soft computing models, 803, 101, and 101 data points have been selected arbitrarily from preprocessed data points, i.e., 1005. Thirteen performance metrics, including three new metrics, i.e., a20-index, index of agreement, and index of scatter, have been implemented for each model. The performance comparison reveals that the SVM (kernel-based), ET (tree-based), MPMR (advanced), and ANN (deep) models have achieved higher performance in predicting the compressive strength of HPC. From the overall analysis of performance, accuracy, Taylor plot, accuracy metric, regression error characteristics curve, Anderson-Darling, Wilcoxon, Uncertainty, and reliability, it has been observed that model CS4 based on the ensemble tree has been recognized as an optimum performance model with higher performance, i.e., a correlation coefficient of 0.9352, root mean square error of 5.76 MPa, and mean absolute error of 4.1069 MPa. The present study also reveals that multicollinearity affects the prediction accuracy of Gaussian process regression, decision tree, multilinear regression, and adaptive boosting regressor models, novel research in compressive strength prediction of HPC. The cosine sensitivity analysis reveals that the prediction of compressive strength of HPC is highly affected by cement content, fine aggregate, coarse aggregate, and water content.

비다양체 모델을 수용하는 CAD 시스템 커널을 위한 불리안 조직의 개발 (Development of Boolean Operations for CAD System Kernel Supporting Non-manifold Models)

  • 김성환;이건우;김영진
    • 한국CDE학회논문집
    • /
    • 제1권1호
    • /
    • pp.20-32
    • /
    • 1996
  • The boundary evaluation technique for Boolean operation on non-manifold models which is regarded as the most popular and powerful method to create and modify 3-D CAD models has been developed. This technique adopted the concept of Merge and Selection in which the CSG tree for Boolean operation can be edited quickly and easily. In this method, the merged set which contains complete information about primitive models involved is created by merging primitives one by one, then the alive entities are selected following the given CSG tree. This technique can support the hybrid representation of B-rep(Boundary Representation) and CSG(Constructive Solid Geometry) tree in a unified non-manifold model data structure, and expected to be used as a basic method for many modeling problems such as data representation of form features, and the interference between them, and data representation of conceptual models in design process, etc.

  • PDF

자동분류기반 성격 유형별 도서추천시스템 개발을 위한 실험적 연구 (A Experimental Study on the Development of a Book Recommendation System Using Automatic Classification, Based on the Personality Type)

  • 조현양
    • 한국도서관정보학회지
    • /
    • 제48권2호
    • /
    • pp.215-236
    • /
    • 2017
  • 이 연구의 목적은 개인별 성향이나 성격 유형에 따라 선호하는 도서에 차이가 있음을 전제로, 어린이 청소년을 위한 추천도서의 책소개 정보를 활용하여 개인별 성격유형에 적합한 도서를 합리적으로 추천할 수 있는 서평 자동분류시스템을 개발하는 것이다. 연구에서 사용한 데이터는 국립어린이청소년도서관에서 제공하는 501권의 유아 및 아동도서를 대상으로 하였다. 실험에 활용된 2가지 기계학습 모델(비선형 커널 및 선형 커널) 각각에 대해서 총 6가지의 색인어 가중치 계산 방법과 자질 선택 방법, 그리고 10가지의 자질 선정 임계치 조합으로 구성된 360개의 분류 모델들을 구성하고 각각의 성능을 측정하였다. 전체적으로는 선형 커널을 이용한 SVM 기반 학습 방법(LIBLINEAR)이 비선형 분류를 지원하는 LibSVM(RBF 커널) 모델보다 더 나은 성능을 보이는 것으로 나타났다. 다만 성능 측정 결과는 뉴스 기사나 논문을 대상으로 한 문헌 분류 성능에 비해서 낮은 것으로 나타났으나, 합리적인 분류 기준이 존재하는 뉴스기사나 주제 분류에 비해서 성격 유형 기반 분류는 그 난이도가 높다는 것을 감안할 때, 초기 실험 결과로서의 의미는 있다.

An Efficiency Assessment for Reflectance Normalization of RapidEye Employing BRD Components of Wide-Swath satellite

  • Kim, Sang-Il;Han, Kyung-Soo;Yeom, Jong-Min
    • 대한원격탐사학회지
    • /
    • 제27권3호
    • /
    • pp.303-314
    • /
    • 2011
  • Surface albedo is an important parameter of the surface energy budget, and its accurate quantification is of major interest to the global climate modeling community. Therefore, in this paper, we consider the direct solution of kernel based bidirectional reflectance distribution function (BRDF) models for retrieval of normalized reflectance of high resolution satellite. The BRD effects can be seen in satellite data having a wide swath such as SPOT/VGT (VEGETATION) have sufficient angular sampling, but high resolution satellites are impossible to obtain sufficient angular sampling over a pixel during short period because of their narrow swath scanning when applying semi-empirical model. This gives a difficulty to run BRDF model inferring the reflectance normalization of high resolution satellites. The principal purpose of the study is to estimate normalized reflectance of high resolution satellite (RapidEye) through BRDF components from SPOT/VGT. We use semi-empirical BRDF model to estimated BRDF components from SPOT/VGT and reflectance normalization of RapidEye. This study used SPOT/VGT satellite data acquired in the S1 (daily) data, and within this study is the multispectral sensor RapidEye. Isotropic value such as the normalized reflectance was closely related to the BRDF parameters and the kernels. Also, we show scatter plot of the SPOT/VGT and RapidEye isotropic value relationship. The linear relationship between the two linear regression analysis is performed by using the parameters of SPOTNGT like as isotropic value, geometric value and volumetric scattering value, and the kernel values of RapidEye like as geometric and volumetric scattering kernel Because BRDF parameters are difficult to directly calculate from high resolution satellites, we use to BRDF parameter of SPOT/VGT. Also, we make a decision of weighting for geometric value, volumetric scattering value and error through regression models. As a result, the weighting through linear regression analysis produced good agreement. For all sites, the SPOT/VGT isotropic and RapidEye isotropic values had the high correlation (RMSE, bias), and generally are very consistent.

GMM-supervector를 사용한 SVM 기반 화자분류에 대한 연구 (A Study on SVM-Based Speaker Classification Using GMM-supervector)

  • 이경록
    • 전기전자학회논문지
    • /
    • 제24권4호
    • /
    • pp.1022-1027
    • /
    • 2020
  • 본 논문에서는 GMM-supervector를 특징 파라미터로 하는 SVM 기반 화자 분류에 대해서 실험하였다. 실험을 위한 화자 클러스터를 생성하기 위해서 기존의 SNR 기반 가중치를 반영한 KL거리 기반 화자변화검출을 실행하였다. SVM 기반 화자 분류는 2단계로 이루어져있다. 1단계는 UBM과 화자 모델들간의 SVM 기반 분류를 시행하여 각 클러스터에 화자 정보를 인덱싱한 다음 화자별로 그룹핑한다. 2단계는 화자 클러스터 그룹에 UBM과 화자모델들간의 SVM 기반 분류를 시행한다. SVM의 커널 함수로는 Linear와 RBF를 사용하였다. 실험결과, 1단계에서는 Linear 커널이 화자 클러스터 148개, MDR 0, FAR 47.3, ER 50.7로 좋은 성능으로 보였다. 2단계 실험결과도 Linear 커널이 화자 클러스터 109개, MDR 1.3, FAR 28.4, ER 32.1로 좋은 성능을 보였다.

An efficient reliability analysis strategy for low failure probability problems

  • Cao, Runan;Sun, Zhili;Wang, Jian;Guo, Fanyi
    • Structural Engineering and Mechanics
    • /
    • 제78권2호
    • /
    • pp.209-218
    • /
    • 2021
  • For engineering, there are two major challenges in reliability analysis. First, to ensure the accuracy of simulation results, mechanical products are usually defined implicitly by complex numerical models that require time-consuming. Second, the mechanical products are fortunately designed with a large safety margin, which leads to a low failure probability. This paper proposes an efficient and high-precision adaptive active learning algorithm based on the Kriging surrogate model to deal with the problems with low failure probability and time-consuming numerical models. In order to solve the problem with multiple failure regions, the adaptive kernel-density estimation is introduced and improved. Meanwhile, a new criterion for selecting points based on the current Kriging model is proposed to improve the computational efficiency. The criterion for choosing the best sampling points considers not only the probability of misjudging the sign of the response value at a point by the Kriging model but also the distribution information at that point. In order to prevent the distance between the selected training points from too close, the correlation between training points is limited to avoid information redundancy and improve the computation efficiency of the algorithm. Finally, the efficiency and accuracy of the proposed method are verified compared with other algorithms through two academic examples and one engineering application.

Spatial Downscaling of MODIS Land Surface Temperature: Recent Research Trends, Challenges, and Future Directions

  • Yoo, Cheolhee;Im, Jungho;Park, Sumin;Cho, Dongjin
    • 대한원격탐사학회지
    • /
    • 제36권4호
    • /
    • pp.609-626
    • /
    • 2020
  • Satellite-based land surface temperature (LST) has been used as one of the major parameters in various climate and environmental models. Especially, Moderate Resolution Imaging Spectroradiometer (MODIS) LST is the most widely used satellite-based LST product due to its spatiotemporal coverage (1 km spatial and sub-daily temporal resolutions) and longevity (> 20 years). However, there is an increasing demand for LST products with finer spatial resolution (e.g., 10-250 m) over regions such as urban areas. Therefore, various methods have been proposed to produce high-resolution MODIS-like LST less than 250 m (e.g., 100 m). The purpose of this review is to provide a comprehensive overview of recent research trends and challenges for the downscaling of MODIS LST. Based on the recent literature survey for the past decade, the downscaling techniques classified into three groups-kernel-driven, fusion-based, and the combination of kernel-driven and fusion-based methods-were reviewed with their pros and cons. Then, five open issues and challenges were discussed: uncertainty in LST retrievals, low thermal contrast, the nonlinearity of LST temporal change, cloud contamination, and model generalization. Future research directions of LST downscaling were finally provided.