期刊文献+
共找到1,048篇文章
< 1 2 53 >
每页显示 20 50 100
Using Multiple Risk Factors and Generalized Linear Mixed Models with 5-Fold Cross-Validation Strategy for Optimal Carotid Plaque Progression Prediction
1
作者 Qingyu Wang Dalin Tang +5 位作者 Liang Wang Gador Canton Zheyang Wu Thomas SHatsukami Kristen L Billiar Chun Yuan 《医用生物力学》 EI CAS CSCD 北大核心 2019年第A01期74-75,共2页
Background Cardiovascular diseases are closely linked to atherosclerotic plaque development and rupture.Plaque progression prediction is of fundamental significance to cardiovascular research and disease diagnosis,pre... Background Cardiovascular diseases are closely linked to atherosclerotic plaque development and rupture.Plaque progression prediction is of fundamental significance to cardiovascular research and disease diagnosis,prevention,and treatment.Generalized linear mixed models(GLMM)is an extension of linear model for categorical responses while considering the correlation among observations.Methods Magnetic resonance image(MRI)data of carotid atheroscleroticplaques were acquired from 20 patients with consent obtained and 3D thin-layer models were constructed to calculate plaque stress and strain for plaque progression prediction.Data for ten morphological and biomechanical risk factors included wall thickness(WT),lipid percent(LP),minimum cap thickness(MinCT),plaque area(PA),plaque burden(PB),lumen area(LA),maximum plaque wall stress(MPWS),maximum plaque wall strain(MPWSn),average plaque wall stress(APWS),and average plaque wall strain(APWSn)were extracted from all slices for analysis.Wall thickness increase(WTI),plaque burden increase(PBI)and plaque area increase(PAI) were chosen as three measures for plaque progression.Generalized linear mixed models(GLMM)with 5-fold cross-validation strategy were used to calculate prediction accuracy for each predictor and identify optimal predictor with the highest prediction accuracy defined as sum of sensitivity and specificity.All 201 MRI slices were randomly divided into 4 training subgroups and 1 verification subgroup.The training subgroups were used for model fitting,and the verification subgroup was used to estimate the model.All combinations(total1023)of 10 risk factors were feed to GLMM and the prediction accuracy of each predictor were selected from the point on the ROC(receiver operating characteristic)curve with the highest sum of specificity and sensitivity.Results LA was the best single predictor for PBI with the highest prediction accuracy(1.360 1),and the area under of the ROC curve(AUC)is0.654 0,followed by APWSn(1.336 3)with AUC=0.6342.The optimal predictor among all possible combinations for PBI was the combination of LA,PA,LP,WT,MPWS and MPWSn with prediction accuracy=1.414 6(AUC=0.715 8).LA was once again the best single predictor for PAI with the highest prediction accuracy(1.184 6)with AUC=0.606 4,followed by MPWSn(1. 183 2)with AUC=0.6084.The combination of PA,PB,WT,MPWS,MPWSn and APWSn gave the best prediction accuracy(1.302 5)for PAI,and the AUC value is 0.6657.PA was the best single predictor for WTI with highest prediction accuracy(1.288 7)with AUC=0.641 5,followed by WT(1.254 0),with AUC=0.6097.The combination of PA,PB,WT,LP,MinCT,MPWS and MPWS was the best predictor for WTI with prediction accuracy as 1.314 0,with AUC=0.6552.This indicated that PBI was a more predictable measure than WTI and PAI. The combinational predictors improved prediction accuracy by 9.95%,4.01%and 1.96%over the best single predictors for PAI,PBI and WTI(AUC values improved by9.78%,9.45%,and 2.14%),respectively.Conclusions The use of GLMM with 5-fold cross-validation strategy combining both morphological and biomechanical risk factors could potentially improve the accuracy of carotid plaque progression prediction.This study suggests that a linear combination of multiple predictors can provide potential improvement to existing plaque assessment schemes. 展开更多
关键词 Multiple Risk FACTORS generalized Linear 5-Fold cross-validation STRATEGY AUC
在线阅读 下载PDF
Generalized weighted functional proportional mean combining forecasting model and its method of parameter estimation
2
作者 万玉成 盛昭潮 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2004年第1期7-11,18,共6页
A new kind of combining forecasting model based on the generalized weighted functional proportional mean is proposed and the parameter estimation method of its weighting coefficients by means of the algorithm of quadr... A new kind of combining forecasting model based on the generalized weighted functional proportional mean is proposed and the parameter estimation method of its weighting coefficients by means of the algorithm of quadratic programming is given. This model has extensive representation. It is a new kind of aggregative method of group forecasting. By taking the suitable combining form of the forecasting models and seeking the optimal parameter, the optimal combining form can be obtained and the forecasting accuracy can be improved. The effectiveness of this model is demonstrated by an example. 展开更多
关键词 combining forecasting generalized weighted functional proportional mean parameter estimation quadratic programming
在线阅读 下载PDF
PM_(2.5) probabilistic forecasting system based on graph generative network with graph U-nets architecture
3
作者 LI Yan-fei YANG Rui +1 位作者 DUAN Zhu LIU Hui 《Journal of Central South University》 2025年第1期304-318,共15页
Urban air pollution has brought great troubles to physical and mental health,economic development,environmental protection,and other aspects.Predicting the changes and trends of air pollution can provide a scientific ... Urban air pollution has brought great troubles to physical and mental health,economic development,environmental protection,and other aspects.Predicting the changes and trends of air pollution can provide a scientific basis for governance and prevention efforts.In this paper,we propose an interval prediction method that considers the spatio-temporal characteristic information of PM_(2.5)signals from multiple stations.K-nearest neighbor(KNN)algorithm interpolates the lost signals in the process of collection,transmission,and storage to ensure the continuity of data.Graph generative network(GGN)is used to process time-series meteorological data with complex structures.The graph U-Nets framework is introduced into the GGN model to enhance its controllability to the graph generation process,which is beneficial to improve the efficiency and robustness of the model.In addition,sparse Bayesian regression is incorporated to improve the dimensional disaster defect of traditional kernel density estimation(KDE)interval prediction.With the support of sparse strategy,sparse Bayesian regression kernel density estimation(SBR-KDE)is very efficient in processing high-dimensional large-scale data.The PM_(2.5)data of spring,summer,autumn,and winter from 34 air quality monitoring sites in Beijing verified the accuracy,generalization,and superiority of the proposed model in interval prediction. 展开更多
关键词 PM_(2.5)interval forecasting graph generative network graph U-Nets sparse Bayesian regression kernel density estimation spatial-temporal characteristics
在线阅读 下载PDF
Statistical analysis of generalized exponential distribution under progressive censoring with binomial removals 被引量:11
4
作者 Weian Yan Yimin Shi +1 位作者 Baowei Song Zhaoyong Mao 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2011年第4期707-714,共8页
The estimation of generalized exponential distribution based on progressive censoring with binomial removals is presented, where the number of units removed at each failure time follows a binomial distribution. Maximu... The estimation of generalized exponential distribution based on progressive censoring with binomial removals is presented, where the number of units removed at each failure time follows a binomial distribution. Maximum likelihood estimators of the parameters and their confidence intervals are derived. The expected time required to complete the life test under this censoring scheme is investigated. Finally, the numerical examples are given to illustrate some theoretical results by means of Monte-Carlo simulation. 展开更多
关键词 binomial removal progressive censoring maximumlikelihood estimator expected experiment time generalized exponential distribution.
在线阅读 下载PDF
Elevation estimation for low-angle target based on reffection paths suppression 被引量:2
5
作者 Hou Yuguan Shen Yiying Zhang Zhongzhao 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2008年第1期71-75,共5页
In the signal processing for metrewave radar, the reflection paths of target echoes can cause severe error in the elevation estimation for the low-angle target tracking. The exact angles of the reflection paths are un... In the signal processing for metrewave radar, the reflection paths of target echoes can cause severe error in the elevation estimation for the low-angle target tracking. The exact angles of the reflection paths are unknown beforehand, and therefore, the reflection paths can not be suppressed easily. Therefore, in this article, an improved reflection paths suppression approach is presented. A block matrix aggregate is constructed based on the possible angles of the reflection paths. Combined with the beamforming-like processing, a generalized maximum likelihood estimation is derived to optimize the estimation. Moreover, the noise reduction method based on the Toeplitz covariance matrix is used for better performance. This approach is applied to the real data collected by the low-angle tracking radar with 8-channel vertical array. The experiment results show that the reflection effects are reduced and the accuracy of the elevation estimate is improved. 展开更多
关键词 elevation estimation low-angle target tracking reflection paths suppression generalized maximum likelihood estimation.
在线阅读 下载PDF
A statistical inference for generalized Rayleigh model under Type-Ⅱ progressive censoring with binomial removals 被引量:2
6
作者 REN Junru GUI Wenhao 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2020年第1期206-223,共18页
This paper considers the parameters and reliability characteristics estimation problem of the generalized Rayleigh distribution under progressively Type-Ⅱ censoring with random removals,that is,the number of units re... This paper considers the parameters and reliability characteristics estimation problem of the generalized Rayleigh distribution under progressively Type-Ⅱ censoring with random removals,that is,the number of units removed at each failure time follows the binomial distribution.The maximum likelihood estimation and the Bayesian estimation are derived.In the meanwhile,through a great quantity of Monte Carlo simulation experiments we have studied different hyperparameters as well as symmetric and asymmetric loss functions in the Bayesian estimation procedure.A real industrial case is presented to justify and illustrate the proposed methods.We also investigate the expected experimentation time and discuss the influence of the parameters on the termination point to complete the censoring test. 展开更多
关键词 Type-Ⅱprogressive censoring with random removals generalized Rayleigh distribution reliability characteristic maximum likelihood estimation Markov chain Monte Carlo method expected experimentation time
在线阅读 下载PDF
H _ index based fault estimation for micro quad-rotor 被引量:1
7
作者 Pu Yang Zhixia Yin Bin Jiang 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2014年第3期483-488,共6页
Taking the attitude control system of micro quad-rotor as a research object, a design scheme of fault estimator based on generalized Kalman-Yakubovic-Popov (GKYP) lemma is put forward to deal with the problem of est... Taking the attitude control system of micro quad-rotor as a research object, a design scheme of fault estimator based on generalized Kalman-Yakubovic-Popov (GKYP) lemma is put forward to deal with the problem of estimating multiple actuators malfunctions with couplings. Using an H_index and an appropriate algorithm, the goal of weakening the coupling can be achieved by limiting the fault frequency to a certain range, then different kinds of actuator faults can be estimated correctly. The simulations demonstrate the reliability and validity of the proposed method. 展开更多
关键词 micro quad-rotor fault estimation generalized Kalman-Yakubovic-Popov (GKYP) lemma.
在线阅读 下载PDF
Hypothesis testing analysis and unknown parameter estimation of GPS signal detection 被引量:3
8
作者 张文 M.Ghogho 《Journal of Central South University》 SCIE EI CAS 2012年第5期1290-1301,共12页
Hypothesis testing analysis and unknown parameter estimation of both the intermediate frequency(IF) and baseband GPS signal detection are given by using the generalized likelihood ratio test(GLRT) approach,applying th... Hypothesis testing analysis and unknown parameter estimation of both the intermediate frequency(IF) and baseband GPS signal detection are given by using the generalized likelihood ratio test(GLRT) approach,applying the model of GPS signal in white Gaussian noise,It is proved that the test statistic follows central or noncentral F distribution,It is also pointed out that the test statistic is nearly identical to central or noncentral chi-squared distribution because the processing samples are large enough to be considered as infinite in GPS acquisition problem.It is also proved that the probability of false alarm,the probability of detection and the threshold are affected largely when the hypothesis testing refers to the full pseudorandom noise(PRN) code phase and Doppler frequency search space cells instead of each individual cell.The performance of the test statistic is also given with combining the noncoherent integration. 展开更多
关键词 global positioning system (GPS) signal detection parameter estimation generalized likelihood ratio test (GLRT) probability of false alarm probability of detection THRESHOLD
在线阅读 下载PDF
Dependence Rayleigh competing risks model with generalized censored data 被引量:1
9
作者 WANG Liang MA Jin’ge SHI Yimin 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2020年第4期852-858,共7页
The inference for the dependent competing risks model is studied and the dependent structure of failure causes is modeled by a Marshall-Olkin bivariate Rayleigh distribution. Under generalized progressive hybrid censo... The inference for the dependent competing risks model is studied and the dependent structure of failure causes is modeled by a Marshall-Olkin bivariate Rayleigh distribution. Under generalized progressive hybrid censoring(GPHC), maximum likelihood estimates are established and the confidence intervals are constructed based on the asymptotic theory. Bayesian estimates and the highest posterior density credible intervals are obtained by using Gibbs sampling. Simulation and a real life electrical appliances data set are used for practical illustration. 展开更多
关键词 dependence competing risks bivariate distribution generalized progressive hybrid censoring(GPHC) likelihood estimation Bayesian analysis
在线阅读 下载PDF
H_∞ fault estimation for a class of linear time-delay systems in finite frequency domain
10
作者 Quanchao Dong Maiying Zhong Steven X. Ding 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2010年第5期835-841,共7页
This paper deals with the problem of H∞ fault estimation for linear time-delay systems in finite frequency domain.First a generalized coordinate change is applied to the original system such that in the new coordinat... This paper deals with the problem of H∞ fault estimation for linear time-delay systems in finite frequency domain.First a generalized coordinate change is applied to the original system such that in the new coordinates all the time-delay terms are injected by the system's input and output.Then an observer-based H∞ fault estimator with input and output injections is proposed for fault estimation with known frequency range.With the aid of Generalized Kalman-Yakubovich-Popov lemma,sufficient conditions on the existence of the H∞ fault estimator are derived and a solution to the observer gain matrices is obtained by solving a set of linear matrix inequalities.Finally,a numerical example is given to illustrate the effectiveness of the proposed method. 展开更多
关键词 fault estimation TIME-DELAY generalized coordinate change generalized Kalman-Yakubovich-Popov lemma finite frequency domain.
在线阅读 下载PDF
基于Generalized-Hyperbolic分布的VaR和CVaR拟合实证研究
11
作者 张亮亮 杨青 熊国兵 《郑州轻工业学院学报(自然科学版)》 CAS 2011年第5期121-124,共4页
基于Generalized-Hyperbolic分布模型,采用极大似然方法,利用中国市场数据对VaR和CVaR进行了动态拟合、实证结果以及模型的后测检验.结果表明:使用Generalized-Hyperbolic分布比使用正态分布可以有效地降低VaR计算失败的次数,且置信度... 基于Generalized-Hyperbolic分布模型,采用极大似然方法,利用中国市场数据对VaR和CVaR进行了动态拟合、实证结果以及模型的后测检验.结果表明:使用Generalized-Hyperbolic分布比使用正态分布可以有效地降低VaR计算失败的次数,且置信度越高其拟合效果越好,是一种很好的静态VaR,CVaR估计方法. 展开更多
关键词 generalized-Hyperbolic分布 VAR CVAR 拟合
在线阅读 下载PDF
Empirical Analysis of Value-at-Risk Estimation Methods Using Extreme Value Theory
12
作者 Zhao Yuanrui & Tian Hongwei School of Management, Finance Center, Tianjin University, 300072, P. R. China 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2001年第1期13-21,共9页
This paper investigates methods of value-at-risk (VaR) estimation using extreme value theory (EVT). It compares two different estimation methods, 'two-step subsample bootstrap' based on moment estimation and m... This paper investigates methods of value-at-risk (VaR) estimation using extreme value theory (EVT). It compares two different estimation methods, 'two-step subsample bootstrap' based on moment estimation and maximum likelihood estimation (MLE), according to their theoretical bases and computation procedures. Then, the estimation results are analyzed together with those of normal method and empirical method. The empirical research of foreign exchange data shows that the EVT methods have good characters in estimating VaR under extreme conditions and 'two-step subsample bootstrap' method is preferable to MLE. 展开更多
关键词 Value-at-risk (VaR) Extreme value theory (EVT) generalized extreme value distribution Twr-step subsample bootstrap Maximum likelihood estimation.
在线阅读 下载PDF
含类虚拟同步发电机和柔性负荷的直流微电网大信号稳定控制方法 被引量:2
13
作者 王慧 赵书强 +3 位作者 陈旭博 孟建辉 田艳军 高本锋 《电工技术学报》 北大核心 2025年第3期705-716,共12页
直流微电网稳态工作点切换、负荷变化较大时经常会出现暂态失稳现象,属于比较典型的“大信号失稳”工况,传统基于小信号的解决方法难以应对。为此,该文提出一种考虑类虚拟同步发电机(AVSG)控制参数和柔性负荷灵活调节的稳定控制方法。... 直流微电网稳态工作点切换、负荷变化较大时经常会出现暂态失稳现象,属于比较典型的“大信号失稳”工况,传统基于小信号的解决方法难以应对。为此,该文提出一种考虑类虚拟同步发电机(AVSG)控制参数和柔性负荷灵活调节的稳定控制方法。首先建立直流微电网的Takagi-Sugeno(TS)模糊模型。然后,借助线性矩阵不等式(LMI)工具构建Lyapunov函数以估计目标稳态点的吸引域。若目标稳态点的最大估计吸引域(LEDA)包含初始稳态点,则系统是渐近稳定的;否则存在失稳的风险。此时,利用灵活可调的虚拟阻尼、虚拟惯量和柔性负荷等资源,让目标稳态点的LEDA直接或者间接包含初始稳态点,从而消除振荡失稳的风险。研究结果表明:基于吸引域理论改进虚拟阻尼和虚拟惯量等控制参数以及工作点运行轨迹,是一种实用且有效保障系统稳定运行的方法。最后,通过硬件在环仿真(HIL)进行了验证。 展开更多
关键词 直流微电网 大信号稳定 吸引域估计 类虚拟同步发电机 柔性负荷
在线阅读 下载PDF
面向高比例新能源并网的多智能体协同自动发电控制算法 被引量:1
14
作者 苏寅生 刘蔚 +3 位作者 张野 赵利刚 马骞 任建宇 《高压电器》 北大核心 2025年第5期80-92,共13页
具有强随机性的新能源大规模接入电网,给电网带来愈来愈差的控制性能。具有马尔可夫随机过程特性的强化学习对解决随机性问题具有优势,而面向新能源规模化接入时,其仍面临着无法获取最优解的问题,控制性能并不理想。因此,提出一种价值... 具有强随机性的新能源大规模接入电网,给电网带来愈来愈差的控制性能。具有马尔可夫随机过程特性的强化学习对解决随机性问题具有优势,而面向新能源规模化接入时,其仍面临着无法获取最优解的问题,控制性能并不理想。因此,提出一种价值估计矫正的软演员—评论家多智能体协同深度强化学习算法来获取多区域协同最优解。通过状态—动作的分布值函数减轻价值的过估计问题,从而获取全局最优解。对改进的IEEE标准两区域模型和西南三区域电网模型进行仿真,验证了所提算法的有效性,且与多种控制方法相比,具有更优的控制性及频率稳定性。 展开更多
关键词 自动发电控制 价值估计 软演员—评论家 分布值函数
在线阅读 下载PDF
噪声标签回归的泛化误差估计及过滤算法
15
作者 姜高霞 李政莹 王文剑 《小型微型计算机系统》 北大核心 2025年第1期72-80,共9页
当回归数据中存在数值型标签噪声时,传统泛化误差估计方法不再适用,回归模型的泛化性能缺乏保障.本文提出一种面向标签噪声的回归模型泛化误差估计方法,并设计了自适应高斯核噪声估计与样本召回过滤(adaptive Gaussian kernel noise est... 当回归数据中存在数值型标签噪声时,传统泛化误差估计方法不再适用,回归模型的泛化性能缺乏保障.本文提出一种面向标签噪声的回归模型泛化误差估计方法,并设计了自适应高斯核噪声估计与样本召回过滤(adaptive Gaussian kernel noise estimator and sample recall filtering, AGKSRF)算法.在所提Craven-Wahba(CW)泛化误差估计的基础上,提出一种CW样本选择框架.基于最大后验估计思想和自适应近邻方法,提出标签噪声的自适应高斯核(adaptive Gaussian kernel, AGK)估计方法.结合所提框架,AGKSRF首先过滤大噪声样本,同时考虑到初次过滤时可能有部分干净样本被误删,AGKSRF根据模型在过滤样本上的误差对样本进行召回再过滤.标准数据集上的实验结果表明,AGKSRF降低模型误差的能力提升了6~51个百分点.AGKSRF还可以识别年龄估计数据上的错误标签.因此,AGKSRF算法可以有效提升数据质量. 展开更多
关键词 噪声标签回归 泛化误差估计 自适应高斯核估计 样本召回过滤
在线阅读 下载PDF
基于树结构Parzen估计器的自动驾驶仿真测试关键场景生成方法
16
作者 秦琴 杨志胜 +2 位作者 李道鑫 沈知玮 曹晓琳 《汽车技术》 北大核心 2025年第5期39-46,共8页
针对高维空间中生成关键场景场景数量呈指数增长,传统人工构造或随机搜索方法难以兼顾覆盖率与效率问题,提出基于单目标树结构Parzen估计器(TPE)和多目标树结构Parzen估计器(MOTPE)的搜索方法。通过CARLA模拟器搭建软件在环自动化仿真... 针对高维空间中生成关键场景场景数量呈指数增长,传统人工构造或随机搜索方法难以兼顾覆盖率与效率问题,提出基于单目标树结构Parzen估计器(TPE)和多目标树结构Parzen估计器(MOTPE)的搜索方法。通过CARLA模拟器搭建软件在环自动化仿真测试框架,以天气要素为例,对比不同搜索算法的关键场景生成效果。试验结果表明:基于TPE的搜索方法和基于MOTPE的方法相较于随机搜索方法生成的关键场景数量分别提高3.11倍和2.06倍,MOTPE方法的场景质量方面是TPE的1.53倍,配合场景自动化生成与测试框架,可有效解决场景数量爆炸问题,发现具有高测试价值的场景。 展开更多
关键词 自动驾驶 场景生成 TPE MOTPE CARLA
在线阅读 下载PDF
腹部浅表超声引导下介入治疗中晚期胰腺癌的近期疗效及其对患者免疫水平的影响
17
作者 王君 姜路 +1 位作者 熊芹 骆洪浩 《中国免疫学杂志》 北大核心 2025年第7期1586-1592,I0001-I0003,共10页
目的:探究腹部浅表超声引导下介入治疗对中晚期胰腺癌患者的近期疗效及其对免疫水平的影响。方法:选择2018年5月至2020年3月于岳池县人民医院确诊的中晚期胰腺癌患者152例为研究对象,其中84例采用联合化疗方式治疗,68例采用单纯化疗方... 目的:探究腹部浅表超声引导下介入治疗对中晚期胰腺癌患者的近期疗效及其对免疫水平的影响。方法:选择2018年5月至2020年3月于岳池县人民医院确诊的中晚期胰腺癌患者152例为研究对象,其中84例采用联合化疗方式治疗,68例采用单纯化疗方式治疗,通过倾向性评分匹配(PSM)法按1∶1匹配后两组各60例。比较匹配后两组临床资料,并采用广义估计方程评价不同治疗方法对中晚期胰腺癌近期疗效及免疫水平的影响。结果:匹配后两组年龄、BMI、肿瘤部位、性别、肿瘤大小、肿瘤分期差异均无统计学意义(P>0.05)。匹配后两组患者经治疗后局部控制率(LCR)呈下降趋势(P<0.05),联合化疗组局部无进展生存期(LPFS)、总生存期(OS)中位数均高于单纯化疗组(P<0.05)。联合化疗组和单纯化疗组治疗前CA19-9水平差异无统计学意义(P>0.05)。联合化疗组患者治疗后CA19-9水平呈连续下降趋势,6个月随访结果较治疗前显著降低;单纯化疗组治疗后CA19-9水平整体变化呈先降后升,1个月为最低点,CA19-9水平比治疗前明显降低,其余时期随访结果与治疗前差异无统计学意义(P>0.05)。单纯化疗组与联合化疗组治疗后7 d、14 d CA19-9水平差异无统计学意义(P>0.05),联合化疗组1个月、3个月、6个月CA19-9水平明显低于单纯化疗组(P<0.05)。联合化疗组所有免疫指标均呈先升后降趋势,1个月达到最高点,治疗后6个月总T细胞数较治疗前显著降低(P<0.05),CD3^(+)T、NK细胞、IL-2、IFN-γ仍高于治疗前(P<0.05),其余指标与治疗前差异无统计学意义(P>0.05)。单纯化疗组CD4^(+)T/CD8^(+)T变化趋势不显著,其余指标与联合化疗组趋势一致(P<0.05),治疗后6个月总T细胞、CD3^(+)T细胞、NK细胞数、IL-2水平较治疗前更低(P<0.05),其余指标与治疗前差异无统计学意义(P>0.05)。随访期内,联合化疗组总T细胞数、CD3^(+)T细胞数、NK细胞数、IL-2、IFN-γ、IL-6水平较单纯化疗组偏高(P>0.05)。随访14 d和3个月联合化疗组CD4^(+)T/CD8^(+)T显著高于单纯化疗组(P<0.05),其余随访时间差异无统计学意义(P>0.05)。广义估计方程评估结果显示,所有指标差异均有统计学意义。结论:腹部浅表超声引导下介入治疗能够有效提高中晚期胰腺癌近期疗效和免疫水平。 展开更多
关键词 腹部浅表超声 介入治疗 微波消融 胰腺癌 广义估计方程
在线阅读 下载PDF
基于误差扩展卡尔曼滤波的火箭回收索状态估计
18
作者 宋晓东 孔芝权 +2 位作者 陈彤 周立梁 张欢 《宇航学报》 北大核心 2025年第6期1252-1262,共11页
针对火箭回收索的高维非线性时变柔性特性和强干扰问题,提出了一种基于多体动力学模型和广义-α积分法的误差扩展卡尔曼状态估计器,用于火箭回收索的捕获状态精准估计。基于任意拉格朗日欧拉(ALE)描述的索单元,建立火箭回收索多体动力... 针对火箭回收索的高维非线性时变柔性特性和强干扰问题,提出了一种基于多体动力学模型和广义-α积分法的误差扩展卡尔曼状态估计器,用于火箭回收索的捕获状态精准估计。基于任意拉格朗日欧拉(ALE)描述的索单元,建立火箭回收索多体动力学事件驱动动态模型,给出了时变尾焰冲击作用和动态非物质状态估计点的动态网格直接表达形式,降低了模型规模的同时保证了状态变量的拓扑不变性。对回收索上可能捕获位置和速度进行状态估计,基于误差扩展卡尔曼滤波框架对状态变量和误差变量采用不同的预测更新策略。状态变量采用广义-α积分法在满足约束条件前提下进行一步预测精准计算,误差变量和误差协方差矩阵采用扩展卡尔曼方法进行预测和更新。状态误差更新后再次进行约束违约修正提高估计准确性。仿真分析表明,所提状态估计器在不改造多体动力学模型的前提下,实现了高维非线性时变火箭回收索的高效精准状态估计。 展开更多
关键词 误差扩展卡尔曼滤波 多体动力学模型 状态估计 任意拉格朗日欧拉法 广义-α积分法
在线阅读 下载PDF
基于多源数据的配变低压侧谐波估计方法
19
作者 张逸 林楠 +2 位作者 刘必杰 欧杰宇 黄雁 《中国电机工程学报》 北大核心 2025年第11期4305-4317,I0016,共14页
针对配变低压侧缺乏谐波量测的问题,该文结合短时测试数据和长期功率数据,提出一种基于深度学习的配变低压侧谐波估计方法。首先,采用Fisher最优分割法和导数动态时间弯曲算法相结合的方法对谐波主导用户进行识别;其次,提出一种变分模... 针对配变低压侧缺乏谐波量测的问题,该文结合短时测试数据和长期功率数据,提出一种基于深度学习的配变低压侧谐波估计方法。首先,采用Fisher最优分割法和导数动态时间弯曲算法相结合的方法对谐波主导用户进行识别;其次,提出一种变分模态分解和格拉姆角场相结合的电气数据转化方法,将谐波主导用户的功率信号和配变低压侧谐波信号转化为伪彩色格拉姆功率图像和灰色格拉姆谐波图像;最后,将两种图像输入到改进的PSRGAN(pix2pix-super-resolution generative adversarial network)模型中训练学习,学习谐波源用户功率数据与配变低压侧谐波数据间的映射关系,迁移生成配变低压侧谐波长期监测数据。通过仿真模型与实测算例验证所提方法的准确性,且所需数据易于获取,具有工程实用性。 展开更多
关键词 多源数据 变分模态分解 格拉姆变换 改进生成对抗模型 谐波估计
在线阅读 下载PDF
数字经济对绿色创新与经济韧性耦合协调效应的影响研究
20
作者 李玲 吴雨婷 孟仲修 《生态经济》 北大核心 2025年第5期63-70,共8页
在数字经济逐步成为未来经济增长新引擎的背景下,促进绿色创新与经济韧性的深度融合与协调发展是未来发展的主旋律。基于2013—2021年我国28个省份的面板数据,构建绿色创新与经济韧性的耦合协同模型,运用Dagum基尼系数解析绿色创新与经... 在数字经济逐步成为未来经济增长新引擎的背景下,促进绿色创新与经济韧性的深度融合与协调发展是未来发展的主旋律。基于2013—2021年我国28个省份的面板数据,构建绿色创新与经济韧性的耦合协同模型,运用Dagum基尼系数解析绿色创新与经济韧性耦合协调度的时空演变特征,并构建系统广义矩估计模型和空间杜宾模型检验数字经济对绿色创新与经济韧性耦合协调度的影响效应。研究结果表明:(1)我国绿色创新与经济韧性耦合协调度呈现“上升—下降—上升”的发展趋势,并存在明显的“东高西低”发展格局,具有显著的区域差异性。(2)数字经济对绿色创新与经济韧性耦合协调度具有正向促进作用。(3)数字经济对绿色创新与经济韧性耦合协调度的影响具有显著的空间溢出效应,且不同地区表现出显著的区域异质性。 展开更多
关键词 数字经济 绿色创新 经济韧性 系统广义矩估计模型 空间杜宾模型
在线阅读 下载PDF
上一页 1 2 53 下一页 到第
使用帮助 返回顶部