结节性甲状腺肿和甲状腺腺瘤的超声造影定量参数、血流动力学参数及与Ang-1关系
Zhongguo shiyan zhenduanxue, 2023 目的 探索结节性甲状腺肿和甲状腺腺瘤的超声造影定量参数、血流动力学改变观察及其与Ang-1表达的关系。方法 在2019年2月至2021年3月期间选取经病理活检确诊的61例甲状腺腺瘤(甲状腺腺瘤组),64例结节性甲状腺肿(结节性甲状腺肿组)为试验对象，均进行超声造影检查，采用ROC曲线分析超声各参数和血流动力学参数的AUC值，并运用Pearson法分析Ang-1表达与超声造影定量参数、血流动力学之间关系。结果 甲状腺腺瘤组内部回声以实性为主，多存在包膜；结节性甲状腺肿组主要以混合性为主，无包膜 ...
马素红, 张萌萌, 韩紫娜, 韩冰
doaj
GARCH model and the Autoregressive Conditional Density modeling application in Chinese stock market [PDF]
, 2013 从事于金融时间序列预测的研究工作者发现，金融时间序列数据往往存在异方差的现象。为了刻画预测误差的条件方差中可能存在的某种相关性，恩格尔(Engle，1982)提出了自回归条件异方差模型，即ARCH模型。后由博勒斯莱文(Bollerslev，T.1986)发展成为GARCH模型-广义自回归条件异方差模型。ARCH/GARCH族模型对误差的方差进行了建模，特别适用于波动性的分析和预测，这样的分析对投资者的决策以及政策的制定者都能起到非常重要的指导性作用，其意义已不单单只是对数值本身的分析和预测 ...
陈艺宣
core
Research on position variability of HILL statistics estimated Extreme Value Index [PDF]
, 2014 极值理论对样本尾部分布的极值指数的估计方法主要有两类：半参数方法和全参数方法，前者主要是基于分布尾部的Hill估计量，后者则主要基于广义帕累托分布。本文对两类Hill型估计量进行如下研究：由于Hill估计量对正极值指数的估计是位置可变的，本文对其位置平移后估计的变化和特点采用蒙特卡罗随机模拟方法进行模拟分析；另外，本文对位置不变的改进型Hill估计量的估计效果与Pickands估计、Hill估计进行比较分析并得出的结论：针对Frechet-Pareto型分布样本，在一般情况下 ...
刘坤宾
core
Driving Rhythm Method for Driving Comfort Analysis on Rural Highways [PDF]
, 2017 Driving comfort is of great significance for rural highways, since the variation characteristics of driving speed are comparatively complex on rural highways.
Bo Yu, Yuren Chen
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Spatial sampling method for crop acreage based on remote sensing in hilly area in Minhou County,Fujian Province [PDF]
, 2017 以福建闽侯县作为研究区,采用传统抽样(简单随机抽样、系统抽样、分层抽样); 、空间抽样(空间随机抽样、空间系统抽样、空间分层抽样)等方法对研究区农作物种植面积进行样本抽选、总体推算及误差估计,结果表明: 1 500; m*1 500; m格网为最优抽样单元尺寸,空间分层抽样方法的相对误差为3.86%,变异系数为6.03%,抽样成本为6.03,抽样效率高.与传统抽样方法相比,空间; 抽样方法显著减少样本容量,节约调查成本.Traditional sampling methods of simple ...
刘金福 +5 more
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Probabilistic load flow calculation for three-phase unbalanced droop-regulated islanded microgrids based on low-rank approximation method [PDF]
, 2020 For the characteristics of unbalanced nodes and constant frequency in the sagging control island microgrid, taking into account its three-phase asymmetry and the influence of uncertainty factors, a three-phase probability trend calculation method based ...
Fu, H. +4 more
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Gaoya dianqi, 2019 变压器绕组变形与等效电参数变化的对应关系对变压器绕组变形诊断精度有重要影响。通过建立变压器绕组等效电路模型,得到了绕组结构与等效电参数之间的对应关系。在此基础上,以某变压器为例,运用电磁—结构耦合有限元方法,根据弹塑性力学原理,计算了变压器绕组在短路电磁力作用下发生的塑性变形状态、应力分布及绕组的轴向和辐向位移;然后,运用能量法计算得到了不同类型和程度的绕组变形与绕组等效电路电参数之间的对应关系。研究结果可以为从等效电路参数变化的角度诊断变压器绕组变形状态提供依据,从而提高变压器绕组变形诊断精度。
毛辰 +10 more
doaj
Traffic measurement algorithm based on least recent used and Bloom filter [PDF]
, 2013 Aiming at the naïve algorithm’s deficiency of high false negative probability,a novel scheme called LRU-BF(least recent used ＆amp;Bloom filter) was presented.In order to achieve high accuracy,the algorithm adopted mechanisms of LRU eliminating and Bloom ...
Bin-qiang WANG +3 more
core
SAR image despeckling using nonsubsampled Contourlet transform [PDF]
, 2008 中文摘要: 提出了一种基于无下采样 Cont ourlet变换 (NSCT)的合成孔径雷达 ( S AR)图像去噪方法。首次在理论上证实了 S AR图像取对数后无下采样 Cont ourlet系数服从广义高斯分布 ,从而提出采用贝叶斯阈值方法估计不含噪声的无下采样 Cont ourlet系数 ,达到去除噪声的目的。仿真和实际实验结果表明 ,该方法在噪声平滑、 边缘和纹理保护等方面优于其他方法。由于无下采样 Cont ourlet变换不进行下采样 ...
丁兴号, 连学强, 闫敬文
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Outage performance analysis for vehicular communications assisted by intelligent reflecting surfaces [PDF]
To address the vehicle-to-vehicle (V2V) link failure caused by severe shadowing in vehicular networks, roadside-based intelligent reflecting surfaces (IRS) were considered to assist the V2V communications, and the outage performance of the vehicular ...
SUN Yanshi +3 more
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