分布式环境中基于协商的虚拟网映射算法

网络虚拟化技术可以在共享的底层物理网络上为用户同时提供多种可定制的服务网络。目前的虚拟网映射算法比较依赖于集中式的管理节点,使其在可靠性和适用范围等方面存在诸多问题。为此,提出了一种分布式环境下的虚拟网映射算法,该算法通过多个节点之间的相互协商来完成虚拟网的映射,并且在降低通信开销和缩短虚拟链路的路径长度方面进行了相应改进。实验结果表明,该算法与同类型算法相比,在资源利用率和通信开销方面具有一定的优越性。

测度熵计算中映射不变分布的应用

构造计算测度熵（ＭｅｔｒｉｃＥｎｔｒｏｐｙ）的马尔可夫划分（ＭａｒｋｏｖＰａｒｔｉｔｉｏｎ）时，对于非线性映射采取等似然假设，影响精度。提出用计算映射的不变分布来进行改进；对逻辑映射导出映射不变分布的算式及迭代格式，进行了测度熵的计算；计算表明，迭代次数不多时即能得出较好结果。

时间延迟函数耦合一致分布混沌映射的视频流加密算法研究

由于现有的视频流加密算法都没考虑时间延迟特征而导致加密序列的自相关性较高,降低其安全性;且其在计算效率与安全性之间存在矛盾。对此,设计了时间延迟函数和一致分布Logistic映射,并将MEPG技术引入进来,提出了时间延迟函数与一致分布混沌映射相融合的MEPG视频流加密算法。采用块加密结合流加密,可解决加密速度与安全性之间的矛盾;并将时间延迟引入到超混沌序列中,消除该序列的自相关性;在加密过程中嵌入MEPG编码,实现实时性。利用MATLAB对该算法以及其他几种算法进行对比仿真,结果显示:与其他算法相比,该加密算法的安全性更高;考虑时间延迟特征的超混沌序列的自相关性更低。

可数度量空间上的完全分布混沌映射

设X={x_0,x_1,…}是一个自密的可数度量空间.则对任意0<δ<diamX,存在X上的同胚φ满足:(a)X={φ~ix_0:i∈Z}且{φ~ix_0:i≥0},{φ^(-i)x_0:i≥0}均为X的稠密子集;(b)φ,φ^(-1)均以X为其一个分布式δ-混沌集.

基于映射-归约分布式架构的城市轨道交通信号系统检测平台

城市轨道交通信号系统的检测工作多由设备厂商自行实施并进行评价,部分测试过程相对封闭,如何从第三方角度对信号系统进行检测并得到一个可信的结论,成为急需解决的问题。采用分布式文件系统,并结合映射-归约架构,可很好地解决信号系统的检测问题。基于映射-归约分布式架构的信号系统检测通过并行运算、负载均衡、就近冗余储存等技术,可提升运算资源效率,平台所采用的容错机制也可提升系统鲁棒性。该平台的优势还在于其结论具有可信度,并由此提出了采用映射-归约分布式架构的实施方法。

分布式SOM结合K-均值聚类的软件定义网络泛洪攻击检测方法

针对软件定义网络(SDN)泛洪攻击导致的上层性能瓶颈和过载问题,提出一种分布式自组织映射(DSOM)结合K-均值聚类的网络流量攻击检测方法。首先,位于应用层的DSOM控制器将现有数据集发送给集成了DSOM扩展包的交换机,在每个交换机上分别训练DSOM映射;然后,在预定时间内合并DSOM映射;最后,DSOM控制器将合并后的DSOM映射发送到所有OpenFlow交换机,利用K-均值聚类完成最终的分类。实验结果表明,DSOM方案能够有效检测异常流量、解决瓶颈问题,相比传统方法具有一定的优势。此外,该方法提高了系统对攻击流量的反应速度,同时给网络系统带来较小的开销。

宫颈癌放疗分次间剂量分布映射方法的现状与难点

目的总结宫颈癌联合治疗中远距离外照射放疗(EBRT)与近距离放疗(BT)联合放疗分次间剂量分布映射方法的现状与难点,特别侧重于基于图像配准的方法、剂量与图像配准的区别及关注点。方法检索PubMed、中国知网及万方期刊全文数据库建库至2023-09-20收录的相关文献,中文关键词为“宫颈癌、剂量分布映射、剂量叠加、图像配准”,英文关键词为“cervical cancer、dose distribution mapping、dose accumulation、image registration”。纳入标准:(1)宫颈癌剂量叠加;(2)宫颈癌分次间剂量分布映射;(3)基于图像配准的宫颈癌剂量叠加。排除标准:(1)低质量文献;(2)内容相似或重复。最终共纳入文献51篇。结果在宫颈癌治疗中,EBRT与BT联合的分次间剂量分布映射存在挑战。治疗过程中由于多器官的复杂厘米级位移和形变,可能导致分次间剂量递送误差。将不同放疗阶段的剂量分布映射传递至参考阶段可能引起误差放大效应,增加了精准放疗的难度。结论准确剂量分布映射方法是精确评估累积生物等效剂量的前提条件,直接利用图像配准将组织/肿瘤剂量分布图映射至参考阶段存在局限性,建议深入研究联合放疗分次间剂量分布映射方法。

基于卷积神经网络的智能机器人信息安全访问控制方法

针对智能机器人接收的多样模态访问信息,文章提出了基于卷积神经网络的访问控制方法。通过量化处理图像、文本、语音数据,引入卷积神经网络分析“超平面”中的映射分布,确定访问控制函数输出。测试显示,该方法下异常访问对系统安全态势影响小,参数稳定在90.0以上,显著优于对照组,展现了可靠性方面的优势。

基于改进的最小二乘法伺服液压PID控制系统设计

为了有效解决液压传动系统应用中存在的元件控制复杂度高和容积流量动态性导致的系统工作效率低下问题,在建立基于最小二乘法的液压控制模型基础上,设计了具有高效稳定的伺服液压PID控制系统。首先,针对大功率负载下的阀门控制损耗和容积不稳定性,结合最小二乘法拟合的传感器控制向量,提出基于最小二乘法的液压控制模型;接着,通过横切柱面推动模块结合混动曲轴以及液压传感器设计电动机伺服液压PID控制系统的传动组,并建立了伺服液压PID控制系统;最后,通过现场测试和实验分析所得结果,证明了所设计的伺服液压PID控制系统在减小阀门位移、输出液压力抖动和传感器故障次数以及提高液压泵容积效率等方面均具有良好的表现。

日地系统多物理耦合机制的设计与实现

以日地系统活动规律研究为背景,通过对SCIRUN提出的PRMI进行4点改进,提出一种高效的日地系统多物理耦合交互机制PRMI++,能够在物理模型组件进行并行远程方法调用实现耦合交互的同时,自动实现网格重映射和数据并行分布重映射。实验结果证明PRMI++具有较好的性能。

陶瓷基复合材料力学性能计算及涡轮导叶宏观响应分析方法

针对涡轮导叶宏观热力学响应,将化学气相沉积工艺2D编织SiC_(f)/SiC陶瓷基复合材料完成拉伸试验并将该试件进行分割,对分割后的试样进行断面电镜扫描,测量统计细观编织结构参数,建立考虑缺陷位置和形状的代表性体积单元模型。采用细观有限元方法,应用该模型计算得到SiC_(f)/SiC陶瓷基复合材料的宏观弹性常数。结果表明:面内拉伸模量预测值比试验值低4.4%,剪切模量预测值比试验值高7.8%。结合陶瓷基复合材料涡轮导叶的加工工艺,建立了材料分布映射模型,对导叶典型特征结构件在给定热载荷下的宏观响应进行预测。结果表明:涡轮导叶典型结构加热段尾缘第1主应变预测值比试验值低5.5%。

不同降水产品在长江流域的偏差校正研究

基于长江流域135个站点1983-2020年的月降水量观测数据,分别对ERA5-Land、PERSIANN-CDR和M SWEP等三种降水产品进行了适用性评估,并对比使用了多种偏差校正方法来提高降水产品的观测精度。结果表明,MSWEP对于长江流域的降水模拟效果较好,空间相关系数高达0.91,相对偏差仅为1.64%;ERA5-Land则对长江流域降水高估严重,精度较差。经偏差校正处理后,三种降水产品的适用性均得到了不同程度的提升,尤其是ERA5-Land,KGE(Kling-Gupta Efficiency)指标值从校正前的0.72增加到了0.82。对比不同偏差校正方法的应用效果发现,线性缩放法和分段伽玛分布校正法在长江流域表现最优,且后者更加稳健。本研究可为降水产品及气候模式输出等的后处理工作提供指导。

Realization of finite precision chaotic systems via internal perturbation

A method of controllable internal perturbation inside the chaotic map is proposed to solve the problem in chaotic systems caused by finite precision.A chaotic system can produce large amounts of initial-sensitive,non-cyclical pseudo-random sequences.However,the finite precision brings short period and odd points which obstruct application of chaos theory seriously in digital communication systems.Perturbation in chaotic systems is a possible efficient method for solving finite precision problems,but former researches are limited in uniform distribution maps.The proposed internal perturbation can work on both uniform and non-uniform distribution chaotic maps like Chebyshev map and Logistic map.By simulations,results show that the proposed internal perturbation extends sequence periods and eliminates the odd points,so as to improve chaotic performances of perturbed chaotic sequences.

一种基于频率的GCM日降水偏差校正方法改进及其在长江流域的应用

对全球气候模式(GCM)数据进行偏差校正是气候影响评估的前提和基础。通过在等比分布映射(ERCDFm)校正法中引入对降水频率的校正,增补了降水日数偏少情况下的小雨日数,保留了降水频率的长期变化信号,提高降水日数及总降水量的模拟效果。以长江流域1961—2005年的格点化日降水资料作为观测数据,对5个GCM模式历史期以及RCP4.5情景下未来日降水进行校正。结果表明:改进后的ERCDFm校正方法明显改善了降水频率及降水量的模拟。降水频率与年降水量的RMSE分别较改进前降低了83%和58%,偏差值小于50 mm/a的格点占比由改进前31%提高至49%,解决了由于降水频率模拟偏低导致的降水量低估。校正后的预估结果表明:RCP4.5情景下,相对于1986—2005年,2030—2050年长江流域降水呈增加趋势(平均增幅为6.1%),春、夏、秋、冬各季节降水量的平均增幅为8.2%、6.4%、4.7%和0.7%。

ON HARMONIC MAPS INTO SYMPLECTIC GROUPS Sp(N)

By means of the theory of harmonic maps into the unitary group U(N), the authors study harmonic maps into the symplectic group Sp(N). The symplectic uniton and symplectic ex--tended uniton are introduced. The method of the symplectic Backlund transformation and the Darboux transformation is used to construct new symplectic unitons from a known one.

Bounding species distribution models

Species distribution models are increasing in popularity for mapping suitable habitat for species of management con- cern. Many investigators now recognize that extrapolations of these models with geographic information systems （GIS） might be sensitive to the environmental bounds of the data used in their development, yet there is no recommended best practice for ＂clamping＂ model extrapolations. We relied on two commonly used modeling approaches： classification and regression tree （CART） and maximum entropy （Maxent） models, and we tested a simple alteration of the model extrapolations, bounding ex- trapolations to the maximum and minimum values of primary environmental predictors, to provide a more realistic map of suit-able habitat of hybridized Africanized honey bees in the southwestern United States. Findings suggest that multiple models of bounding, and the most conservative bounding of species distribution models, like those presented here, should probably replace the unbounded or loosely bounded techniques currently used [Current Zoology 57 （5）： 642-647,2011].

Spatially distributed modelling and mapping of soil organic carbon and total nitrogen stocks in the Eastern Mau Forest Reserve,Kenya

Detailed knowledge about the estimates and spatial patterns of soil organic carbon(SOC) and total nitrogen(TN) stocks is fundamental for sustainable land management and climate change mitigation.This study aimed at:(1) mapping the spatial patterns,and(2) quantifying SOC and TN stocks to 30 cm depth in the Eastern Mau Forest Reserve using field,remote sensing,geographical information systems(GIS),and statistical modelling approaches.This is a critical ecosystem offering essential services,but its sustainability is threatened by deforestation and degradation.Results revealed that elevation,silt content,TN concentration,and Landsat 8 Operational Land Imager band 11 explained 72% of the variability in SOC stocks,while the same factors(except silt content) explained 71% of the variability in TN stocks.The results further showed that soil properties,particularly TN and SOC concentrations,were more important than that other environmental factors in controlling the observed patterns of SOC and TN stocks,respectively.Forests stored the highest amounts of SOC and TN(3.78 Tg C and 0.38 Tg N) followed by croplands(2.46 Tg C and 0.25 Tg N) and grasslands(0.57 Tg C and 0.06 Tg N).Overall,the Eastern Mau Forest Reserve stored approximately 6.81 Tg C and 0.69 Tg N.The highest estimates of SOC and TN stocks(hotspots) occurred on the western and northwestern parts where forests dominated,while the lowest estimates(coldspots) occurred on the eastern side where croplands had been established.Therefore,the hotspots need policies that promote conservation,while the coldspots need those that support accumulation of SOC and TN stocks.

Mapping carbon distribution in 35SiMn steel by energy-filtered transmission electron microscopy

In this study,the three-windows method,the jump-ratio method and the R-map method in energy-filtered transmission electron microscopy(EFTEM) have been applied to mapping carbon distribution in 35SiMn steel after a quenching-partitioning treatment.The carbon contamination is successfully suppressed by using EFTEM and plasma-cleaning TEM samples.Compared to the three-windows method and the jump-ratio method,the R-map method provides carbon distribution with less noises,and is insensitive to changes in sample thickness.We have demonstrated that the R-map method is a better way for carbon mapping in middle-carbon steel without the influence of carbon contamination.

Mapping paddy rice with multi-date moderate-resolution imaging spectroradiometer (MODIS) data in China

The objective of this study was to obtain spatial distribution maps of paddy rice fields using multi-date moderate-resolution imaging spectroradiometer(MODIS) data in China.Paddy rice fields were extracted by identifying the unique char-acteristic of high soil moisture in the flooding and transplanting period with improved algorithms based on rice growth calendar regionalization.The characteristic could be reflected by the enhanced vegetation index(EVI) and the land surface water index(LSWI) derived from MODIS sensor data.Algorithms for single,early,and late rice identification were obtained from selected typical test sites.The algorithms could not only separate early rice and late rice planted in the same fields,but also reduce the uncertainties.The areal accuracy of the MODIS-derived results was validated by comparison with agricultural statistics,and the spatial matching was examined by ETM+(enhanced thematic mapper plus) images in a test region.Major factors that might cause errors,such as the coarse spatial resolution and noises in the MODIS data,were discussed.Although not suitable for monitoring the inter-annual variations due to some inevitable factors,the MODIS-derived results were useful for obtaining spatial distribution maps of paddy rice on a large scale,and they might provide reference for further studies.

Mapping Nuclear Decay to a Complex Network

Nuclear decay is investigated by the view of network science and the relationship of nuclear decay among different radionuclide can be mapped to a network topology directly.The network includes 1410 nodes and 1275 edges.The average degree of the network of nuclear decay is about 1.8,the cumulative degree distribution still meets the typical power-law distribution,and the corresponding exponent is about 4.1.Not considering their dynamic behavior,the fitting parameters of the nuclear decay network are obtained according to the LUHNM theory proposed by our group before.Their cumulated degree distributions of the nuclear decay network match well.The idea and method may provide a new way to study some other problems of nuclear physics.