Hormesis has emerged as a more common and fundamental dose-response model than the threshold or linear-no-threshold(LNT) models

在回顾传统的有阈和线性无阈的剂量-反应关系的基础上,分析此类该模型被毒理学领域认同的主要原因和其在预测低剂量效应中的缺陷,进而提出了高剂量接触呈现抑制效应,而低剂量却呈现促进或刺激作用这一全面的激效兴奋性剂量-反应关系,弥补了现有模型的不足,并充分论证这种激效性剂量-反应关系在不同种属、接触因素和生物学终点中的普遍性,并探讨了不同物质的激效兴奋作用的可能机制以及激效兴奋模型的三大优点,最后提出了激效模型谋求广泛接受的现实困难和发展趋势。

数字经济影响农村产业融合的机理研究——基于中国省域面板数据的实证研究

基于2011—2021年中国省级面板数据,采用固定效应模型、面板门槛回归模型等实证检验数字经济对农村产业融合发展的影响及其非线性关系。研究发现:(1)数字经济显著促进了我国农村产业融合发展,该结论经过一系列稳健性检验、内生性处理后依然成立。(2)数字经济对农村产业融合发展的促进作用存在边际效应递减的非线性特征,资本积累水平、居民消费水平、高质量人力资本水平在这一促进作用中发挥门槛效应。(3)随着农村产业融合发展水平的提高,数字经济对农村产业融合发展的促进作用呈现出由弱逐渐变强再弱化的趋势,相较于西部地区,数字经济在东、中部地区对农村产业融合发展的促进作用较弱。为充分发挥数字经济促进农村产业融合发展的积极效应,需要在加快发展数字经济、推进数字乡村建设的同时,促进金融创新、缓解金融约束,推进共同富裕、提振消费信心,重视人才培养与引进、保障人才供给。

卫星用高能激光防护技术发展现状

高能激光技术不断发展,逐渐成为卫星在轨安全的威胁。介绍了高能连续激光和脉冲激光武器对卫星损伤机制的研究进展。针对卫星太阳电池阵、相机、星敏感器等光学系统以及热控多层、复合材料推进剂储箱等非光学关键结构防护特点,总结分析了线性光学防护薄膜、非线性光学防护薄膜、相变材料、机械快门、高损伤阈值薄膜和防护罩等各种高能激光防护技术的主要原理、发展现状和技术特点。

基于复杂网络的复杂产品系统关键节点辨识

复杂产品系统具有规模大、结构复杂等特点,从系统结构的视角辨识复杂产品系统关键节点,对于“事前”定位潜在风险源具有重要意义。针对目前“事后”追溯风险源难以保证复杂产品系统可靠运行及风险管理前瞻性等问题,考虑复杂产品系统的层级结构和子系统间风险的相互影响,提出了一种可用于“事前”风险管理的关键节点辨识方法。首先依据系统结构建立复杂网络;然后,构造零模型并结合网络统计特征初步划分节点集合,在此基础上引入线性阈值模型分析节点风险传播影响力,并基于风险的动态传播特征选取关键节点;最后,采用新舟700飞机的系统结构进行实证分析。结果表明,提出的方法有效地辨识了复杂产品系统的关键节点。

气候变化背景下西藏高原地区界限温度时空变化特征

受全球气候变化影响,农牧业生产面临较大风险,研究界限温度时空变化对调整农业种植结构,实现农业可持续发展具有重要意义。利用近40a(1981-2020年)西藏38个气象站点逐日平均气温观测数据,采用线性倾向估计、Person系数、Mann-Kendall、优势分析等方法,分析了气候变暖背景下近40a西藏≥0℃、≥5℃和≥10℃界限温度(初日、终日、持续日数和活动积温)的时空变化特征。结果表明:(1)西藏≥0℃、≥5℃和≥10℃界限温度分布总体上表现为自东南向西北初日推迟、终日提早、持续日数缩短和积温减少的特征,并具有明显的海拔垂直地带性特征。1991-2020年与1981-2010年平均值比较,西藏各站三种积温均增加,以≥10℃积温增幅较大;绝大部分站点初日偏早、终日偏晚、持续日数偏多。(2)近40a西藏≥0℃、≥5℃和≥10℃初日、终日和持续日数的变幅以≥0℃最大,平均每10a初日提早3.2d、终日推迟3.5d、持续日数延长5.4d;积温增幅以≥10℃最大,为86.1℃·d·10a^(-1)。≥0℃、≥5℃持续日数增加是由于初日明显提早造成的,而≥10℃持续日数的增加因终日显著推迟导致。(3)≥0℃界限温度的线性倾向率(LTR),低海拔地区明显大于高海拔地区;≥5℃初日、积温LTR的最大值在低海拔地区,终日、持续日数LTR的最大值在中高海拔地区(3500-4000m);≥10℃初日LTR在中高海拔地区最大,终日、持续日数和积温LTR最大值出现在海拔4000-4500m地区。(4)20世纪80年代≥0℃、≥5℃和≥10℃初日偏晚、终日偏早、持续日数偏短、积温偏低;90年代初日、终日和持续日数正常,积温仍偏低;进入21世纪后,初日偏早、终日偏晚、持续日数增加、积温明显偏高,以21世纪10年代最明显。(5)≥5℃终日突变最早,发生在20世纪90年代初;≥10℃终日突变最晚,在21世纪10年代中期;初日、积温的突变分别出现在20世纪90年代中后期和21世纪初,持续日数突变点发生在20世纪90年代后期至21世纪中前期。

基于标幺化三阈值事件检测与LDA分类器的工商业负荷辨识方法

非侵入式负荷辨识技术能够低成本的获取用户各类设备使用情况,实现电力负荷的在线监测与分析,对支撑负荷预测、需求响应等应用开展有着重要意义。针对一般工商业用户类型多样、负荷种类繁多、设备运行特性复杂的特点,提出了一种基于标幺化三阈值事件检测与LDA分类器的工商业负荷辨识方案。首先针对不同能耗级别、不同启停特性的设备设计了参数可调的统一负荷事件检测框架,提升了缓变型、分段型、震荡型负荷事件的检出准确度。随后提出了基于多元特征与LDA线性判别的设备类型判断算法,在兼顾边缘端计算效率的同时取得了与随机森林等非线性分类器相同的辨识性能。

CRB:A new rumor blocking algorithm in online social networks based on competitive spreading model and influence maximization

The virtuality and openness of online social platforms make networks a hotbed for the rapid propagation of various rumors.In order to block the outbreak of rumor,one of the most effective containment measures is spreading positive information to counterbalance the diffusion of rumor.The spreading mechanism of rumors and effective suppression strategies are significant and challenging research issues.Firstly,in order to simulate the dissemination of multiple types of information,we propose a competitive linear threshold model with state transition(CLTST)to describe the spreading process of rumor and anti-rumor in the same network.Subsequently,we put forward a community-based rumor blocking(CRB)algorithm based on influence maximization theory in social networks.Its crucial step is to identify a set of influential seeds that propagate anti-rumor information to other nodes,which includes community detection,selection of candidate anti-rumor seeds and generation of anti-rumor seed set.Under the CLTST model,the CRB algorithm has been compared with six state-of-the-art algorithms on nine online social networks to verify the performance.Experimental results show that the proposed model can better reflect the process of rumor propagation,and review the propagation mechanism of rumor and anti-rumor in online social networks.Moreover,the proposed CRB algorithm has better performance in weakening the rumor dissemination ability,which can select anti-rumor seeds in networks more accurately and achieve better performance in influence spread,sensitivity analysis,seeds distribution and running time.

基于矩阵乘法关联的分级图像秘密共享方案

针对目前图像秘密共享中缺乏集合内或集合间多级权限控制的细粒度问题,提出一种基于矩阵乘法构造分级恢复的图像秘密共享方案。利用图像所具有的矩阵属性,在对原始像素干扰最小的情况下,通过矩阵可逆乘法构建秘密图像之间的关联矩阵,引入效率较高的矩阵运算进行共享份额生成与秘密恢复。当参与者集合中必要参与者满足对应门限时,可恢复第一级秘密图像;当全体参与者满足整体门限时,可恢复第二级秘密图像。仿真结果表明,该加密算法具有良好的安全性与鲁棒性。

基于曲波变换与联合方法的地震数据重建

野外地震数据采集通常会受地形等不可控因素的影响,导致采集到不规则缺失的地震数据,为了不影响后续地震资料处理,需要对缺失的地震数据进行重建。传统的重建算法往往收敛速度较慢,为此,提出将快速阈值迭代法和线性Bregman方法进行联合,在快速阈值迭代加速的基础上进一步提高了算法的效率,得到了一种快速高精度重建方法。在重建的过程中,以曲波域作为稀疏变换域,采用硬阈值函数和指数阈值模型。通过理论数据的模拟和实际数据的检验表明,相较于传统的地震数据重建方法,该方法重建的效果明显,重建效率更高。此外,该方法具有一定的抗噪性,在快速阈值迭代法高效收敛的基础上进一步加快了重建的效率。

Influence of salinity and moisture on the threshold shear velocity of saline sand in the Qarhan Desert, Qaidam Basin of China: A wind tunnel experiment

Determination of the threshold shear velocity is essential for predicting sand transport,dust release and desertification.In this study,a wind tunnel experiment was conducted to evaluate the influence of salinity and moisture on the threshold shear velocity of saline sand.Saline sand samples(mean particle size of 164.50–186.08μm and the total silt,clay and salt content of 0.80%–8.25%)were collected from three saline sand dunes(one barchan dune and two linear dunes)in the Qarhan Desert,Qaidam Basin of China.Original saline sand samples were placed in two experimental trays for wet and dry processing to simulate deliquescence and desiccation,respectively.Surface moisture content ranging from 0.30% to 1.90% was generated by the steam method so that the saline sand can absorb water in a saturated water vapor environment.The motion of sand particles was determined by the observers with a solid laser.The laser sheet(0.80 cm thick),which was emitted by the solid laser,horizontally covered the sand surface and was bound to the sand.Results show that the cohesion of saline sand results from a combination of salt and water.The threshold shear velocity increases exponentially with the increase in crust thickness for the linear sand dunes.There is a positive linear correlation between the original moisture content and relative threshold shear velocity.The threshold shear velocity of dewatered sand is greater than that of wet sand with the same original moisture content.Our results will provide valuable information about the sand transport of highly saline soil in the desert.

Iterative learning based fault diagnosis for discrete linear uncertain systems

In order to detect and estimate faults in discrete lin-ear time-varying uncertain systems, the discrete iterative learning strategy is applied in fault diagnosis, and a novel fault detection and estimation algorithm is proposed. And the threshold limited technology is adopted in the proposed algorithm. Within the chosen optimal time region, residual signals are used in the proposed algorithm to correct the introduced virtual faults with iterative learning rules, making the virtual faults close to these occurred in practical systems. And the same method is repeated in the rest optimal time regions, thereby reaching the aim of fault diagnosis. The proposed algorithm not only completes fault detection and estimation for discrete linear time-varying uncertain systems, but also improves the reliability of fault detection and decreases the false alarm rate. The final simulation results verify the validity of the proposed algorithm.

Research of optical rainfall sensor based on CCD linear array

Rainfall monitoring is one of the most important meteorological observation elements for the disaster weather. The maintenance of current tipping bucket rain gauge and weighing type rain gauge is a critical issue. The optical rainfall sensor based on CCD linear array is mainly studied in this paper. Because of the maintenance-free time and good adaptability,it can be widely used in the automatic rainfall monitoring in severe environment and have a good perspective in using.

胜利油田高89地区特低渗透油藏CO_(2)驱非线性渗流规律研究

特低渗透油藏储层物性差,流体流动困难,常表现出非线性渗流特征。以往非线性渗流规律的研究以水驱为主,对CO_(2)驱的研究较少。针对胜利油田高89地区特低渗透油藏CO_(2)驱非线性渗流规律认识不足的问题,开展了渗流规律实验研究,揭示了CO_(2)与原油相互作用对原油渗流特征的影响规律,建立了不同渗透率下CO_(2)驱最小启动压力梯度计算公式及CO_(2)驱非线性渗流规律表征模型。结果表明:特低渗透油藏CO_(2)驱存在启动压力,原油最小启动压力梯度与流度呈良好的幂函数关系,随着流度的增加,启动压力梯度显著降低;CO_(2)驱渗流曲线呈现“曲线段+直线段”的两段式特征,直线段的流速与压力梯度呈良好的线性关系,曲线段的流速与压力梯度呈良好的二次函数关系;CO_(2)溶于原油后有显著的膨胀降黏效果,使得原油最小启动压力梯度明显降低,原油渗流能力增强,渗流曲线非线性段变短。

Comparative Methodical Assessment of Established MOSFET Threshold Voltage Extraction Methods at 10-nm Technology Node

Threshold voltage (VTH) is the most evocative aspect of MOSFET operation. It is the crucial device constraint to model on-off transition characteristics. Precise VTH value of the device is extracted and evaluated by several estimation techniques. However, these assessed values of VTH diverge from the exact values due to various short channel effects (SCEs) and non-idealities present in the device. Numerous prevalent VTH extraction methods are discussed. All the results are verified by extensive 2-D TCAD simulation and confirmed through analytical results at 10-nm technology node. Aim of this research paper is to explore and present a comparative study of largely applied threshold extraction methods for bulk driven nano-MOSFETs especially at 10-nm technology node along with various sub 45-nm technology nodes. Application of the threshold extraction methods to implement noise analysis is briefly presented to infer the most appropriate extraction method at nanometer technology nodes.

Parameter Estimation of Multiple Frequency-Hopping Signals Based on Space-Time-Frequency Analysis by Atomic Norm Soft Thresholding with Missing Observations

In this paper,we address the problem of multiple frequency-hopping(FH)signal parameters estimation in the presence of random missing observations.A space-time matrix with random missing observations is acquired by a uniform linear array(ULA).We exploit the inherent incomplete data processing capability of atomic norm soft thresholding(AST)to analyze the space-time matrix and complete the accurate estimation of the hopping time and frequency of the received FH signals.The hopping time is obtained by the sudden changes of the spatial information,which is implemented as the boundary to divide the time domain signal so that each segment of the signal is a superposition of time-invariant multiple components.Then,the frequency of multiple signal components can be estimated precisely by AST within each segment.After obtaining the above two parameters of the hopping time and the frequency of signals,the direction of arrival(DOA)can be directly calculated by them,and the network sorting can be realized.Results of simulation show that the proposed method is superior to the existing technology.Even when a large portion of data observations is missing,as the number of array elements increases,the proposed method still achieves acceptable accuracy of multi-FH signal parameters estimation.

收入对老年人抑郁水平的非线性影响研究——来自CHARLS数据的经验证据

文章采用2018年中国健康与养老追踪调查数据,实证分析收入对老年人抑郁水平的影响。研究发现,随着收入的增加,老年人的精神抑郁水平显著降低。多重门槛回归估计结果表明,收入对老年人抑郁水平的影响存在双重门槛效应。收入的影响呈现非线性,随着收入水平的提高,收入对老年人精神健康的影响水平降低。进一步研究显示,城市老年人和男性老年人具有更高的收入门槛值,同时农村老年人和男性老年人表现出更加复杂的非线性变化。建议提高老年人保障水平,共享经济社会发展成果;开发老年人力资源,保障低龄老年人群体再就业;鼓励老年人参与社会活动,提供非现金方式的社会支持。

A General(k,n)Threshold Secret Image Sharing Construction Based on Matrix Theory

Shamir proposed a classic polynomial-based secret sharing(SS)scheme,which is also widely applied in secret image sharing(SIS).However,the following researchers paid more attention to the development of properties,such as lossless recovery,rather than the principle of Shamir’s polynomial-based SS scheme.In this paper,we introduce matrix theory to analyze Shamir’s polynomial-based scheme as well as propose a general(k,n)threshold SIS construction based on matrix theory.Besides,it is proved that Shamir’s polynomial-based SS scheme is a special case of our construction method.Both experimental results and analyses are given to demonstrate the effectiveness of the proposed construction method.

一种NLF-对数小波阈值的脉冲干扰降噪方法

在脉冲噪声背景下,传统信号降噪方法性能退化,无法去除强脉冲噪声,而且会出现计算复杂度增加的问题.本文提出一种基于非线性滤波(Nonlinear Filtering, NLF)和小波阈值去噪的联合算法,该方法利用非线性滤波算法抑制强脉冲噪声点干扰,通过改进的对数小波阈值函数去噪方法进行全局处理,快速而且高质量的完成对信号降噪.实验结果表明,本文所提算法对脉冲噪声背景下的多种信号类型都具有可行性,能够获得更高的峰值信噪比,具有很好的降噪效果.

基于拟合优化的多传感器测距误差残差补偿修正算法设计

在复杂环境下,多传感器协同测距过程,受信号强弱、传感器性能、光照的影响,测距过程存在一定误差。为解决上述问题,提出一种多传感器测距误差补偿算法。该算法首先利用小波变换将多传感器信号分解成低频和高频信号,并对高频信号采取阈值量化处理。将处理后的高频信号与低频信号重构,完成信号降噪。其次采用坐标投影法构建误差模型,并在模型中采用带有拟合优化的残差补偿法修正误差。最后将灰度重心算法与电荷耦合原理结合消除光斑,完成多传感器测距误差补偿。实验结果显示:这种算法的残差平均值在0.37附近波动、标准差平均值为0.42、信号采集误差平均值小于1 Hz,能够实现多传感器测距误差的准确补偿。

杭州湾围垦耕地土壤生态系统服务变化特征及阈值分析

研究目的:尝试构建长时间序列下的围垦耕地土壤生态系统服务评估方法体系,通过杭州湾围垦区实证研究,探索围垦耕地土壤生态系统服务的长期变化特征和关键阈值,为存量围垦耕地资源的可持续利用和适应性治理提供参考。研究方法:时空替代法、分段线性回归模型。研究结果:(1)根据土壤生态系统服务理论,构建基于“人类需求—服务类别—关键服务—评价指标”的围垦耕地土壤生态系统服务评价指标体系;(2)由于持续的土壤改良和农业管理措施,围垦耕地土壤生态系统服务显著高于自然滩涂土壤,并随围垦时间延长不断提高;(3)杭州湾围垦耕地土壤生态系统服务对围垦时间的响应呈现显著阈值效应,在围垦后74 a左右,土壤生态系统服务出现“急剧提高—稳定增长”突变特征。研究结论:(1)本文评价体系与方法为沿海围垦耕地评价和耕地保护研究提供了一种新的思路,也为围垦土地的农业生产管理提供有益借鉴;(2)围垦耕地土壤生态系统服务变化具有阶段性,应根据不同围垦年限对围垦耕地采取差异性的管控措施。