期刊文献+
共找到159篇文章
< 1 2 8 >
每页显示 20 50 100
Dimensionality Reduction of High-Dimensional Highly Correlated Multivariate Grapevine Dataset
1
作者 Uday Kant Jha Peter Bajorski +3 位作者 Ernest Fokoue Justine Vanden Heuvel Jan van Aardt Grant Anderson 《Open Journal of Statistics》 2017年第4期702-717,共16页
Viticulturists traditionally have a keen interest in studying the relationship between the biochemistry of grapevines’ leaves/petioles and their associated spectral reflectance in order to understand the fruit ripeni... Viticulturists traditionally have a keen interest in studying the relationship between the biochemistry of grapevines’ leaves/petioles and their associated spectral reflectance in order to understand the fruit ripening rate, water status, nutrient levels, and disease risk. In this paper, we implement imaging spectroscopy (hyperspectral) reflectance data, for the reflective 330 - 2510 nm wavelength region (986 total spectral bands), to assess vineyard nutrient status;this constitutes a high dimensional dataset with a covariance matrix that is ill-conditioned. The identification of the variables (wavelength bands) that contribute useful information for nutrient assessment and prediction, plays a pivotal role in multivariate statistical modeling. In recent years, researchers have successfully developed many continuous, nearly unbiased, sparse and accurate variable selection methods to overcome this problem. This paper compares four regularized and one functional regression methods: Elastic Net, Multi-Step Adaptive Elastic Net, Minimax Concave Penalty, iterative Sure Independence Screening, and Functional Data Analysis for wavelength variable selection. Thereafter, the predictive performance of these regularized sparse models is enhanced using the stepwise regression. This comparative study of regression methods using a high-dimensional and highly correlated grapevine hyperspectral dataset revealed that the performance of Elastic Net for variable selection yields the best predictive ability. 展开更多
关键词 HIGH-DImeNSIONAL data MULTI-STEP Adaptive Elastic Net MINIMAX CONCAVE Penalty sure Independence Screening Functional data Analysis
暂未订购
Censored Composite Conditional Quantile Screening for High-Dimensional Survival Data
2
作者 LIU Wei LI Yingqiu 《应用概率统计》 CSCD 北大核心 2024年第5期783-799,共17页
In this paper,we introduce the censored composite conditional quantile coefficient(cC-CQC)to rank the relative importance of each predictor in high-dimensional censored regression.The cCCQC takes advantage of all usef... In this paper,we introduce the censored composite conditional quantile coefficient(cC-CQC)to rank the relative importance of each predictor in high-dimensional censored regression.The cCCQC takes advantage of all useful information across quantiles and can detect nonlinear effects including interactions and heterogeneity,effectively.Furthermore,the proposed screening method based on cCCQC is robust to the existence of outliers and enjoys the sure screening property.Simulation results demonstrate that the proposed method performs competitively on survival datasets of high-dimensional predictors,particularly when the variables are highly correlated. 展开更多
关键词 high-dimensional survival data censored composite conditional quantile coefficient sure screening property rank consistency property
在线阅读 下载PDF
基于3D-CNN和融合Transformer的步态识别算法 被引量:1
3
作者 李金成 代雪晶 闫睿骜 《科学技术与工程》 北大核心 2025年第17期7276-7284,共9页
当前,步态识别的主流方法常依赖堆叠卷积层来逐步扩大感受野,以融合局部特征,这种方法大多采用浅层网络,在提取步态图像的全局特征时存在一定的局限性,并缺乏对时序周期特征信息的关注。因此提出一种融合Transformer和3D卷积的深层神经... 当前,步态识别的主流方法常依赖堆叠卷积层来逐步扩大感受野,以融合局部特征,这种方法大多采用浅层网络,在提取步态图像的全局特征时存在一定的局限性,并缺乏对时序周期特征信息的关注。因此提出一种融合Transformer和3D卷积的深层神经网络算法(3D convolutional gait recognition network based on adaptFormer and spect-conv,3D-ASgaitNet)。首先,初始残差卷积层将二进制轮廓数据转换为浮点编码特征图,以提供密集的低级结构特征;在此基础上,光谱层通过频域和时域的联合处理增强特征提取能力,并使用伪3D残差卷积模块进一步提取高级时空特征;最后融合AdaptFormer模块,通过轻量级的下采样-上采样网络结构,以适应不同的数据分布和任务需求,提供灵活的特征变换能力。3D-ASgaitNet分别在4个公开的室内数据集(CASIA-B、OU-MVLP)、室外数据集(GREW、Gait3D)上进行,分别取得99.84%、87.83%、45.32%、72.12%的识别准确率。实验结果表明,所提出方法在CASIA-B、Gait3D数据集中的识别准确率接近SOTA性能。 展开更多
关键词 步态识别 融合Transformer 3D残差卷积 二进制轮廓数据
在线阅读 下载PDF
ALMOST SURE GLOBAL WELL-POSEDNESS FOR THE FOURTH-ORDER NONLINEAR SCHR?DINGER EQUATION WITH LARGE INITIAL DATA
4
作者 陈明娟 张帅 《Acta Mathematica Scientia》 SCIE CSCD 2023年第5期2215-2233,共19页
We consider the fourth-order nonlinear Schr?dinger equation(4NLS)(i?t+εΔ+Δ2)u=c1um+c2(?u)um-1+c3(?u)2um-2,and establish the conditional almost sure global well-posedness for random initial data in Hs(Rd)for s∈(sc-... We consider the fourth-order nonlinear Schr?dinger equation(4NLS)(i?t+εΔ+Δ2)u=c1um+c2(?u)um-1+c3(?u)2um-2,and establish the conditional almost sure global well-posedness for random initial data in Hs(Rd)for s∈(sc-1/2,sc],when d≥3 and m≥5,where sc:=d/2-2/(m-1)is the scaling critical regularity of 4NLS with the second order derivative nonlinearities.Our proof relies on the nonlinear estimates in a new M-norm and the stability theory in the probabilistic setting.Similar supercritical global well-posedness results also hold for d=2,m≥4 and d≥3,3≤m<5. 展开更多
关键词 fourth-order Schrodinger equation random initial data almost sure global well-posedness M-norm stability theory
在线阅读 下载PDF
Linear manifold clustering for high dimensional data based on line manifold searching and fusing 被引量:1
5
作者 黎刚果 王正志 +2 位作者 王晓敏 倪青山 强波 《Journal of Central South University》 SCIE EI CAS 2010年第5期1058-1069,共12页
High dimensional data clustering,with the inherent sparsity of data and the existence of noise,is a serious challenge for clustering algorithms.A new linear manifold clustering method was proposed to address this prob... High dimensional data clustering,with the inherent sparsity of data and the existence of noise,is a serious challenge for clustering algorithms.A new linear manifold clustering method was proposed to address this problem.The basic idea was to search the line manifold clusters hidden in datasets,and then fuse some of the line manifold clusters to construct higher dimensional manifold clusters.The orthogonal distance and the tangent distance were considered together as the linear manifold distance metrics. Spatial neighbor information was fully utilized to construct the original line manifold and optimize line manifolds during the line manifold cluster searching procedure.The results obtained from experiments over real and synthetic data sets demonstrate the superiority of the proposed method over some competing clustering methods in terms of accuracy and computation time.The proposed method is able to obtain high clustering accuracy for various data sets with different sizes,manifold dimensions and noise ratios,which confirms the anti-noise capability and high clustering accuracy of the proposed method for high dimensional data. 展开更多
关键词 linear manifold subspace clustering line manifold data mining data fusing clustering algorithm
在线阅读 下载PDF
Ultra-High Dimensional Feature Selection and Mean Estimation under Missing at Random
6
作者 Wanhui Li Guangming Deng Dong Pan 《Open Journal of Statistics》 2023年第6期850-871,共22页
Next Generation Sequencing (NGS) provides an effective basis for estimating the survival time of cancer patients, but it also poses the problem of high data dimensionality, in addition to the fact that some patients d... Next Generation Sequencing (NGS) provides an effective basis for estimating the survival time of cancer patients, but it also poses the problem of high data dimensionality, in addition to the fact that some patients drop out of the study, making the data missing, so a method for estimating the mean of the response variable with missing values for the ultra-high dimensional datasets is needed. In this paper, we propose a two-stage ultra-high dimensional variable screening method, RF-SIS, based on random forest regression, which effectively solves the problem of estimating missing values due to excessive data dimension. After the dimension reduction process by applying RF-SIS, mean interpolation is executed on the missing responses. The results of the simulated data show that compared with the estimation method of directly deleting missing observations, the estimation results of RF-SIS-MI have significant advantages in terms of the proportion of intervals covered, the average length of intervals, and the average absolute deviation. 展开更多
关键词 Ultrahigh-Dimensional data Missing data sure Independent Screening mean Estimation
在线阅读 下载PDF
Nonparametric Feature Screening via the Variance of the Regression Function
7
作者 Won Chul Song Michael G. Akritas 《Open Journal of Statistics》 2024年第4期413-438,共26页
This article develops a procedure for screening variables, in ultra high-di- mensional settings, based on their predictive significance. This is achieved by ranking the variables according to the variance of their res... This article develops a procedure for screening variables, in ultra high-di- mensional settings, based on their predictive significance. This is achieved by ranking the variables according to the variance of their respective marginal regression functions (RV-SIS). We show that, under some mild technical conditions, the RV-SIS possesses a sure screening property, which is defined by Fan and Lv (2008). Numerical comparisons suggest that RV-SIS has competitive performance compared to other screening procedures, and outperforms them in many different model settings. 展开更多
关键词 sure Independence Screening Nonparametric Regression Ultrahigh-Dimensional data Variable Selection
在线阅读 下载PDF
NON-PARAMETRIC ESTIMATION IN CONTAMINATED LINEAR MODEL 被引量:1
8
作者 Chai Genxiang Sun Yan Yang XiaohanDept.ofAppl.Math.,TongjiUniv.,Shanghai200092 《Applied Mathematics(A Journal of Chinese Universities)》 SCIE CSCD 2001年第2期195-202,共8页
In this paper, the following contaminated linear model is considered:y i=(1-ε)x τ iβ+z i, 1≤i≤n,where r.v.'s { y i } are contaminated with errors { z i }. To assume that the errors have the fin... In this paper, the following contaminated linear model is considered:y i=(1-ε)x τ iβ+z i, 1≤i≤n,where r.v.'s { y i } are contaminated with errors { z i }. To assume that the errors have the finite moment of order 2 only. The non parametric estimation of contaminated coefficient ε and regression parameter β are established, and the strong consistency and convergence rate almost surely of the estimators are obtained. A simulated example is also given to show the visual performance of the estimations. 展开更多
关键词 Contaminated data non parametric estimation strong consistency convergence rate almost surely.
在线阅读 下载PDF
Sure feature screening for high-dimensional dichotomous classification 被引量:2
9
作者 SHAO Li YU Yuan ZHOU Yong 《Science China Mathematics》 SCIE CSCD 2016年第12期2527-2542,共16页
The curse of high-dimensionality has emerged in the statistical fields more and more frequently.Many techniques have been developed to address this challenge for classification problems. We propose a novel feature scr... The curse of high-dimensionality has emerged in the statistical fields more and more frequently.Many techniques have been developed to address this challenge for classification problems. We propose a novel feature screening procedure for dichotomous response data. This new method can be implemented as easily as t-test marginal screening approach, and the proposed procedure is free of any subexponential tail probability conditions and moment requirement and not restricted in a specific model structure. We prove that our method possesses the sure screening property and also illustrate the effect of screening by Monte Carlo simulation and apply it to a real data example. 展开更多
关键词 ultra-high dimensional data dichotomous classification sure screening property
原文传递
A ground-based dataset and diffusion model for on-orbit low-light image enhancement
10
作者 Yiman ZHU Lu WANG +1 位作者 Jingyi YUAN Yu GUO 《Frontiers of Information Technology & Electronic Engineering》 2025年第7期1083-1098,共16页
On-orbit service is important for maintaining the sustainability of the space environment.A space-based visible camera is an economical and lightweight sensor for situational awareness during on-orbit service.However,... On-orbit service is important for maintaining the sustainability of the space environment.A space-based visible camera is an economical and lightweight sensor for situational awareness during on-orbit service.However,it can be easily affected by the low illumination environment.Recently,deep learning has achieved remarkable success in image enhancement of natural images,but it is seldom applied in space due to the data bottleneck.In this study,we first propose a dataset of BeiDou navigation satellites for on-orbit low-light image enhancement(LLIE).In the automatic data collection scheme,we focus on reducing the domain gap and improving the diversity of the dataset.We collect hardware-in-the-loop images based on a robotic simulation testbed imitating space lighting conditions.To evenly sample poses of different orientations and distances without collision,we propose a collision-free workspace and pose-stratified sampling.Subsequently,we develop a novel diffusion model.To enhance the image contrast without over-exposure and blurred details,we design fused attention guidance to highlight the structure and the dark region.Finally,a comparison of our method with previous methods indicates that our method has better on-orbit LLIE performance. 展开更多
关键词 Satellite capture Low-light image enhancement(LLIE) data collection Diffusion model fused attention
原文传递
Feature Screening for Ultrahigh-dimensional Censored Data with Varying Coefficient Single-index Model 被引量:1
11
作者 Yi LIU 《Acta Mathematicae Applicatae Sinica》 SCIE CSCD 2019年第4期845-861,共17页
In this paper, we study the sure independence screening of ultrahigh-dimensional censored data with varying coefficient single-index model. This general model framework covers a large number of commonly used survival ... In this paper, we study the sure independence screening of ultrahigh-dimensional censored data with varying coefficient single-index model. This general model framework covers a large number of commonly used survival models. The property that the proposed method is not derived for a specific model is appealing in ultrahigh dimensional regressions, as it is difficult to specify a correct model for ultrahigh dimensional predictors.Once the assuming data generating process does not meet the actual one, the screening method based on the model will be problematic. We establish the sure screening property and consistency in ranking property of the proposed method. Simulations are conducted to study the finite sample performances, and the results demonstrate that the proposed method is competitive compared with the existing methods. We also illustrate the results via the analysis of data from The National Alzheimers Coordinating Center(NACC). 展开更多
关键词 censored data consistency in ranking PROPERTY FEATURE selection HIGH-DImeNSIONAL data sure SCREENING PROPERTY VARYING COEFFICIENT single-index model
原文传递
Feature Screening for High-Dimensional Survival Data via Censored Quantile Correlation 被引量:1
12
作者 XU Kai HUANG Xudong 《Journal of Systems Science & Complexity》 SCIE EI CSCD 2021年第3期1207-1224,共18页
This paper proposes a new sure independence screening procedure for high-dimensional survival data based on censored quantile correlation(CQC).This framework has two distinctive features:1)Via incorporating a weightin... This paper proposes a new sure independence screening procedure for high-dimensional survival data based on censored quantile correlation(CQC).This framework has two distinctive features:1)Via incorporating a weighting scheme,our metric is a natural extension of quantile correlation(QC),considered by Li(2015),to handle high-dimensional survival data;2)The proposed method not only is robust against outliers,but also can discover the nonlinear relationship between independent variables and censored dependent variable.Additionally,the proposed method enjoys the sure screening property under certain technical conditions.Simulation results demonstrate that the proposed method performs competitively on survival datasets of high-dimensional predictors. 展开更多
关键词 Censored quantile correlation feature screening high-dimensional survival data rank consistency property sure screening property
原文传递
Polymer design for solvent separations by integrating simulations,experiments and known physics via machine learning
13
作者 Janhavi Nistane Rohan Datta +4 位作者 Young Joo Lee Harikrishna Sahu Seung Soon Jang Ryan Lively Rampi Ramprasad 《npj Computational Materials》 2025年第1期2016-2027,共12页
This study guides the discovery of sustainable high-performance polymer membranes for organic binary solvent separations.We focus on solvent diffusivity in polymers,a key factor in quantifying solvent transport.Tradit... This study guides the discovery of sustainable high-performance polymer membranes for organic binary solvent separations.We focus on solvent diffusivity in polymers,a key factor in quantifying solvent transport.Traditional experimental and computational methods for determining diffusivity are time-and resource-intensive,while current machine learning(ML)models often lack accuracy outside their training domains.To overcome this,we fuse experimental and simulated diffusivity data to train physics-enforced multi-task ML models,achieving more robust predictions in unseen chemical spaces and outperforming single-task models in data-limited scenarios.Next,we address the challenge of identifying optimal membranes for a model toluene-heptane separation,identifying polyvinyl chloride(PVC)as the optimal membrane among 13,000 polymers,consistent with literature findings,thereby validating our methodology.Expanding our search,we screen 1 million publicly available and 7 million chemically recyclable polymers,identifying greener halogen-free alternatives to PVC.This capability is expected to advance membrane design for solvent separations. 展开更多
关键词 machine learning ml models machine learning multi task models organic binary solvent separationswe DIFFUSIVITY solvent separations fuse experimental simulated diffusivity data experimental computational methods
原文传递
基于融合相关性的协同分摊噪声软测量建模
14
作者 梁楠 高世伟 +2 位作者 张伟 田添 薛瑞争 《电子测量与仪器学报》 北大核心 2025年第9期172-181,共10页
基于数据驱动的软测量建模方法在流程工业中有着广泛的应用。流程工业中,辅助数据常常会受到异构、杂糅的噪声的污染,且工业数据中线性相关与非线性相关共存,而噪声问题和不合理的相关关系表达均会严重影响软测量模型的预测结果。在协... 基于数据驱动的软测量建模方法在流程工业中有着广泛的应用。流程工业中,辅助数据常常会受到异构、杂糅的噪声的污染,且工业数据中线性相关与非线性相关共存,而噪声问题和不合理的相关关系表达均会严重影响软测量模型的预测结果。在协同分摊噪声算法的基础上提出一种基于融合相关性的协同分摊噪声算法进行软测量建模。首先,采用融合了关注线性相关性的Pearson系数和关注非线性相关性的Spearman系数的融合相关性系数优化协同分摊噪声算法,使协同分摊噪声算法中数据可信度计算更合理,更符合工业数据中线性相关与非线性相关共存的情况。然后,结合卷积神经网络(convolutional neural networks,CNN)搭建软测量模型。在脱丁烷塔数据集上进行多降噪方法、多模型和多回归方法的交叉组合实验,结果表明,该优化后的降噪算法较基础的协同分摊噪声算法、小波变换降噪、降噪自编码器有着较强的降噪能力;所搭建的软测量模型有着较优的预测精度及较小的预测误差,其中决定系数(r-square,R~2)指标和均方误差(mean squared error,MSE)分别为0.9716和0.0011。 展开更多
关键词 数据驱动建模 软测量 融合相关性 协同分摊噪声 HCAN-CNN
原文传递
基于循环神经网络的非失速和近失速飞行数据气动参数辨识
15
作者 惠哲 都东岳 +2 位作者 刘雨亭 昌敏 白俊强 《航空学报》 北大核心 2025年第23期194-206,共13页
提出了一种结合门控循环单元(GRU)神经网络模型和高斯-牛顿(GN)优化算法的气动参数辨识方法,旨在分别从自主研发的小型无人机和ATTAS飞机生成的纵向飞行数据中准确辨识未知的气动参数。经过设计和训练的GRU网络模型用以表征所选飞机系... 提出了一种结合门控循环单元(GRU)神经网络模型和高斯-牛顿(GN)优化算法的气动参数辨识方法,旨在分别从自主研发的小型无人机和ATTAS飞机生成的纵向飞行数据中准确辨识未知的气动参数。经过设计和训练的GRU网络模型用以表征所选飞机系统的动力学,同时避免对其假设的动力学模型进行数值积分。GN优化算法结合训练完毕的GRU网络模型,通过迭代最小化与未知气动参数相关的代价函数来获得高置信度的参数辨识结果。本文用到的实测飞行数据包括:自研无人机的非失速飞行数据和ATTAS飞机的近失速飞行数据。研究结果表明:GRU网络模型可以通过调整相应的网络参数(诸如,隐藏层的数量、单个隐藏层中的单元数量、丢弃率、时间步长和学习率)来保持对非失速和近失速飞行数据的可靠预测效果。此外,通过将所选飞机气动参数的辨识值与相对应的风洞测量值或参考值进行比较,证实了所提参数辨识方法的有效性。 展开更多
关键词 气动参数辨识方法 GRU网络模型 GN优化算法 实测飞行数据 网络参数
原文传递
基于深度学习与D-S理论的多模态数据特征融合算法 被引量:1
16
作者 张燕 《吉林大学学报(理学版)》 北大核心 2025年第3期855-860,共6页
针对传统多模态数据特征融合算法存在融合效果较差的问题,提出一种基于深度学习与D-S(Dempster-Shafer)理论的多模态数据特征融合算法.首先,在深度学习框架内,采用受限Boltzmann机(RBM)对多模态数据进行训练,根据数据的特性和任务需求,... 针对传统多模态数据特征融合算法存在融合效果较差的问题,提出一种基于深度学习与D-S(Dempster-Shafer)理论的多模态数据特征融合算法.首先,在深度学习框架内,采用受限Boltzmann机(RBM)对多模态数据进行训练,根据数据的特性和任务需求,构建RBM模型结构进行多模态数据特征选择.其次,根据选取的特征选择计算同类模态数据之间的距离,确定信任函数,并设定阈值以删除异常数据,实现同类模态数据初步融合.最后,通过计算异类模态数据与不同等级特征之间的距离,确定异类数据的信任函数,结合D-S理论实现多模态数据特征融合.实验结果表明,该算法的纯度最高达1.0,标准化互信息最高达0.3,表明该算法可以获取精准的多模态数据特征融合结果. 展开更多
关键词 深度学习 D-S理论 多模态数据特征 融合
在线阅读 下载PDF
异质面板计数数据的子群识别和估计
17
作者 黄云舒 谭春辉 《统计与决策》 北大核心 2025年第24期47-51,共5页
文章针对具有异质性的面板计数数据构建了一种半参数均值回归模型,该模型通过对协变量回归系数进行差异化定义,能够同时捕捉个体间的同质效应与异质效应。在建模过程中,采用样条函数对基准非参数均值函数进行逼近,从而将原模型中的非参... 文章针对具有异质性的面板计数数据构建了一种半参数均值回归模型,该模型通过对协变量回归系数进行差异化定义,能够同时捕捉个体间的同质效应与异质效应。在建模过程中,采用样条函数对基准非参数均值函数进行逼近,从而将原模型中的非参数部分参数化,转化为可估计的半参数形式。基于这一参数化估计空间,进一步构建了关于待估半参数的极大似然函数。在此基础上,通过在负对数似然函数中引入融合非凸惩罚函数,构建出一个正则化的目标函数,并将该目标函数的极小值点作为模型参数的估计量,从而实现了基于数据驱动的子群划分与稳健的参数估计。在数值计算方面,由于目标函数整体结构非凸,因此直接进行优化求解极为复杂。为提升计算效率与可行性,提出主ADMM算法。该算法将原问题转化为一系列易于处理的子问题,从而实现对目标函数的高效优化。将所提方法应用于膀胱肿瘤临床试验数据的实证分析中,通过对患者面板计数数据的建模与子群识别,评估了不同治疗方案对膀胱肿瘤复发的影响,识别出对特定治疗反应不同的患者亚组,说明所提方法是有效的。 展开更多
关键词 面板计数数据 子群识别 样条 融合惩罚 主ADMM算法
原文传递
基于干预注意力的细粒度图像识别
18
作者 陈建锟 王永雄 潘志群 《上海理工大学学报》 北大核心 2025年第2期209-219,共11页
注意力机制在细粒度识别任务中具有关键作用。为了让模型更加关注判别性区域,提出一种新的基于干预注意力的方法,为监督注意力学习特征提供关键线索。具体地,在训练过程中加入干预注意力,并将注意力应用于数据裁剪和擦除过程,进而提高... 注意力机制在细粒度识别任务中具有关键作用。为了让模型更加关注判别性区域,提出一种新的基于干预注意力的方法,为监督注意力学习特征提供关键线索。具体地,在训练过程中加入干预注意力,并将注意力应用于数据裁剪和擦除过程,进而提高模型的学习效率。同时,将融合注意力应用于特征提取网络,帮助网络学习更加有效的特征。此外,引入标签平滑损失函数以及中心正则化损失函数,有效地提升分类精度。实验表明,提出的方法具有优异性能,分别在CUB-200-2011、Stanford Cars和FGVC Aircraft数据集上实现了89.8%、95.7%和94.7%的分类准确率,相比多个细粒度分类算法具有更好的分类效果。 展开更多
关键词 细粒度图像识别 干预注意力 数据增强 融合注意力 标签平滑
在线阅读 下载PDF
机理-数据融合的造斜率智能预测方法
19
作者 白佳帅 钟尹明 +4 位作者 王立伟 李臻 宋先知 刘子豪 祝兆鹏 《石油机械》 北大核心 2025年第5期1-9,共9页
造斜率的准确预测是进行井眼轨迹调控的基础,直接影响定向井钻井效率,但由于井下力学行为的复杂性,传统预测方法存在一定限制,难以实现精确预测。为此,提出了一种力学-智能模型融合的造斜率预测方法。利用力学模型计算钻头侧向力、钻头... 造斜率的准确预测是进行井眼轨迹调控的基础,直接影响定向井钻井效率,但由于井下力学行为的复杂性,传统预测方法存在一定限制,难以实现精确预测。为此,提出了一种力学-智能模型融合的造斜率预测方法。利用力学模型计算钻头侧向力、钻头转角和极限造斜率并作为主控因素,通过自动化机器学习框架联合其他参数进行拟合预测,从而取代传统方法反演经验系数的过程,使其充分发挥力学模型宏观规律描述准确和智能模型非线性拟合能力强的优势。利用新疆玛湖区块14口井数据进行训练和测试。结果显示,融合力学参数后,模型造斜率最大误差、均方根误差和平均绝对误差分别下降了17%、12%和8%,其中均方根误差和平均绝对误差均小于每30 m 1.00°,表明该方法能够有效提升造斜率预测精度,尤其在造斜率急剧变化的井段表现出更优的预测性能。研究结果可为造斜率的准确预测提供新的思路,同时也可为井眼轨迹的精确调控提供一定的技术支撑。 展开更多
关键词 智能钻井 自动化机器学习 造斜率预测 机理-数据融合 力学参数
在线阅读 下载PDF
城乡劳动力流动、城镇就业与收入差异——理论与实证研究 被引量:8
20
作者 蔡武 程小军 《经济与管理》 CSSCI 2012年第11期15-20,共6页
鉴于我国现实情况,对H-T模型的基本假设进行修定,采用动态递归方法从理论上推导了城乡劳动力流动、城镇就业与城乡居民实际收入差距的相互均衡关系,并从动态内生系统的角度建立Panel Data的联立方程模型,采用似无关(SURE)方法实证研究... 鉴于我国现实情况,对H-T模型的基本假设进行修定,采用动态递归方法从理论上推导了城乡劳动力流动、城镇就业与城乡居民实际收入差距的相互均衡关系,并从动态内生系统的角度建立Panel Data的联立方程模型,采用似无关(SURE)方法实证研究三者之间的直接和间接影响。研究发现:城乡劳动力流动缩小了城乡收入差距,而城乡差距的缩小也促进了城乡劳动力流动,两者形成良性互动;城乡差距加剧了城镇失业,城镇失业也扩大了城乡差距,两者存在恶性循环;城乡劳动力流动和城镇失业相互之间均具有很微小的且不显著的促进作用。 展开更多
关键词 城乡劳动力流动 城镇失业 城乡实际收入差距 PANEL data联立方程 sure
在线阅读 下载PDF
上一页 1 2 8 下一页 到第
使用帮助 返回顶部