PET image reconstruction with a system matrix containing point spread function derived from single photon incidence response

A point spread function（PSF） for the blurring component in positron emission tomography（PET） is studied. The PSF matrix is derived from the single photon incidence response function. A statistical iterative reconstruction（IR） method based on the system matrix containing the PSF is developed. More specifically, the gamma photon incidence upon a crystal array is simulated by Monte Carlo（MC） simulation, and then the single photon incidence response functions are calculated. Subsequently, the single photon incidence response functions are used to compute the coincidence blurring factor according to the physical process of PET coincidence detection. Through weighting the ordinary system matrix response by the coincidence blurring factors, the IR system matrix containing the PSF is finally established. By using this system matrix, the image is reconstructed by an ordered subset expectation maximization（OSEM） algorithm. The experimental results show that the proposed system matrix can substantially improve the image radial resolution, contrast,and noise property. Furthermore, the simulated single gamma-ray incidence response function depends only on the crystal configuration, so the method could be extended to any PET scanner with the same detector crystal configuration.

Global Dynamics Analysis of a Cholera Transmission Model with General Incidence and Multiple Modes of Infection

This paper develops an SIBR cholera transmission model with general incidence rate. Necessary and sufficient conditions for local and global asymptotic stability of the equilibria are established by Routh Hurwitz criterium, Lyapunov function, and the second additive composite matrix theorem. What is more, exploiting the DED is cover simulation tool, the parameter values of the model are estimated with the 1998-2021 cholera case data in China. Finally, we perform sensitivity analysis for the basic reproduction number to seek for effective interventions for cholera control. .

Comprehensive multivariate grey incidence degree based on principal component analysis

To overcome the too fine-grained granularity problem of multivariate grey incidence analysis and to explore the comprehensive incidence analysis model, three multivariate grey incidences degree models based on principal component analysis （PCA） are proposed. Firstly, the PCA method is introduced to extract the feature sequences of a behavioral matrix. Then, the grey incidence analysis between two behavioral matrices is transformed into the similarity and nearness measure between their feature sequences. Based on the classic grey incidence analysis theory, absolute and relative incidence degree models for feature sequences are constructed, and a comprehensive grey incidence model is proposed. Furthermore, the properties of models are researched. It proves that the proposed models satisfy the properties of translation invariance, multiple transformation invariance, and axioms of the grey incidence analysis, respectively. Finally, a case is studied. The results illustrate that the model is effective than other multivariate grey incidence analysis models.

鼻咽癌放化疗患者营养补充认知度的影响因素及其重要性矩阵分析

目的分析鼻咽癌同期放化疗患者营养补充认知度的影响因素及其重要性矩阵。方法选取216例鼻咽癌同期放化疗患者为研究对象。采用问卷调查鼻咽癌放化疗患者营养补充认知度,收集患者一般资料。采用多元线性回归分析法分析鼻咽癌放化疗患者营养补充认知度的影响因素,并对各因素进行重要性矩阵分析。结果放化疗2个月时,鼻咽癌患者的血红蛋白、前白蛋白水平低于放化疗前和放化疗结束后2个月,营养状况评分、营养不良发生率高于放化疗前和放化疗结束后2个月,差异有统计学意义(P<0.01)。问卷评估结果显示,鼻咽癌患者营养补充认知总分为(37.44±6.10)分。年龄、农村居住、回避应对、肿瘤分期、社会支持、学历和心理弹性是鼻咽癌患者营养补充认知度的影响因素(P<0.05)。重要性矩阵分析结果显示,回避应对、心理弹性、社会支持重要性较高,改善难度较低,进入优先改进区域;年龄、农村居住、肿瘤分期、学历的重要性、改善难度均较高,进入次优改进区域。结论鼻咽癌患者的营养补充认知度的影响因素为农村居住、年龄、回避应对、学历、心理弹性、肿瘤分期和社会支持,临床工作中应针对上述因素改善患者营养认知行为。

基于ISMM方法的非均匀磁化等离子体湍流中电磁波传播特性研究

由于传统散射矩阵法(scattering matrix method, SMM)在计算过程中会产生奇异矩阵,本文基于改进的SMM (improved SMM, ISMM)结合一维磁化等离子体湍流模型,计算了等离子体湍流介质对电磁波在不同入射角下的反射系数和透射系数,同时分析了电磁波在非均匀磁化等离子体中的传播特性。结果表明,湍流的出现极大地影响了等离子体鞘套中电子的运动规律,使其运动过程中能量衰减增多,因此其在0~35 GHz的透射系数增大;另一方面外部磁场的增大,对左旋圆极化波与右旋圆极化波的传播特性影响相反,这是因为在左旋情况下,左旋圆极化波的旋转方向正好与电子的旋转方向相同,右旋圆极化波相反;随着入射角度的增大,相当于电磁波在等离子体湍流中的传播距离增大,导致更多的电磁波能量被吸收;此外,考虑非均匀磁化情况后,电磁波在0~35 GHz频段内的右旋圆极化的透射系数更大。这些结果为研究电磁波在非均匀磁化等离子体湍流介质的传播特性提供了理论依据。

ERAD: Enhanced Ransomware Attack Defense System for Healthcare Organizations

Digital integration within healthcare systems exacerbates their vulnerability to sophisticated ransomware threats, leading to severe operational disruptions and data breaches. Current defenses are typically categorized into active and passive measures that struggle to achieve comprehensive threat mitigation and often lack real-time response effectiveness. This paper presents an innovative ransomware defense system, ERAD, designed for healthcare environments that apply the MITRE ATT&CK Matrix to coordinate dynamic, stage-specific countermeasures throughout the ransomware attack lifecycle. By systematically identifying and addressing threats based on indicators of compromise (IOCs), the proposed system proactively disrupts the attack chain before serious damage occurs. Validation is provided through a detailed analysis of a system deployment against LockBit 3.0 ransomware, illustrating significant enhancements in mitigating the impact of the attack, reducing the cost of recovery, and strengthening the cybersecurity framework of healthcare organizations, but also applicable to other non-health sectors of the business world.

Study of Differential Cross-Section and S-Matrix Using Volkov Function and Taylor Series Expansion for Elastic Scattering

This paper deals with S-matrix, born first approximation, amplitude, and differential cross-section (DCS), using Volkov function and Taylor series expansion in laser field, scattering. Equation (30) copes-with DCS and Equation (36) deals with S-matrix, with different parameters, moreover, both equations contain real and imaginary parts. The DCS increases with increasing angle and polarizabilities, constant with dipole distance for both emission and absorption of single-photon. The DCS for both emission and absorption is responded to low incidence energy (30 eV - 60 eV) and photon energy (15 eV) while at high energy only emission and absorption are responded for DCS. The DCS between absorption and emission of a photon with angle variation, dipole distance, and atomic polarizabilities was found 1.098 a.u.2 and at high incidence, energies were found 0.1 a.u.2.

基于综合游走策略的边嵌入链路预测算法

针对网络分析方法中研究的图数据默认使用节点图,只能得到节点的向量表示,不能直接将边表示成向量的问题,设计了一种基于有偏+无偏的图嵌入算法Line2Vec,并在此基础上提出基于边嵌入的链路预测框架(Line2Vec-L).首先,基于综合游走策略重新定义采样域节点的采样概率,并结合Word2Vec模型得到信息未被稀释、表示性强的节点图的边嵌入向量;然后,结合关联矩阵得到不存在边或未知边的向量表示,并将得到的边向量用于链路预测.实验结果表明Line2Vec在边向量表示上的有效性,并验证了Line2Vec-L的AUC值更高,由此说明采用Line2Vec可得到表示性更强的边向量,有助于提升链路预测的性能.

斜入射下1/4波片补偿能力的优化

本文使用理论与实验相结合的方法研究了斜入射下液晶涂布型C-plate(Liquid crystal coated C-plate,LCC)对逆分散1/4波片(Reverse wavelength dispersion quarter wave plate,RQWP)补偿能力的优化特性。使用扩展琼斯矩阵比较了偏振光以任意角度通过RQWP、RQWP+LCC两种架构后出射光的椭圆率,探究了不同相位延迟RTH的LCC对出射光椭圆率的影响;测试了上述两种架构的圆偏光片在OLED(Organic light emitting-diode display)上的环境光反射率以及反射颜色色坐标。结果表明,LCC能够使45°斜入射时出射光的椭圆率提升10%以上,且在红、绿、蓝三色光条件下,调整LCC的RTH可使膜材架构的总折射率系数NZ趋近于0.5,获得最佳效果。使用RQWP+LCC架构的圆偏光片可使45°极角下OLED的环境光反射率降低3%。在工业生产中直接生产NZ=0.5的膜材拥有较高的技术难度,本文结论对开发NZ=0.5的膜材提供了新的可行方案。

含缺陷一维声子晶体斜入射声波的透射特性研究

声波在声子晶体周期结构中的传播具有能带效应,含缺陷声子晶体可在原有禁带中形成新的缺陷模式。文中通过传递矩阵法分别计算声波斜入射含缺陷和无缺陷声子晶体的全向透射谱,经对比分析发现了由固体缺陷引起的缺陷模式。在此基础上,研究了缺陷层厚度、位置对缺陷态透射率的影响。通过水下声传输实验对固体缺陷引起的缺陷模式的存在及其随角度变化的特征进行验证。实验结果表明,在含缺陷结构的全向透射谱第一Bragg禁带中存在新的透射通带,且在一定范围内随入射角度的增大,该通带对应的频率向高频方向偏移。文中完善了含缺陷一维声子晶体中斜入射声波的传播特性,为缺陷态实际应用提供了理论和实验基础。

基于模糊ISM的铁路机务行车安全风险关联性分析

为提升铁路机务行车安全能力,保障铁路运输牵引动力的可靠性,首先,基于对某路局机务系统安全风险问题库的统计分析,提取出了5类共18项导致该类事故发生的致因要素,以此类要素作为评价铁路机务行车安全的风险指标;其次,运用改进的解释结构模型,建立了各风险因素间的邻接矩阵和可达矩阵,绘制了影响机务行车安全的各类风险因素演化过程的解释结构图;最后,结合对风险因素及其演化路径的剖析,找出了风险因素间的层级关联关系。研究结果表明:机车疲劳驾驶、机车火灾、车辆伤害等是影响机务行车安全的最直接因素;设备标准执行力、检修标准执行力是影响机务行车安全的间接因素;而制度执行力和管理执行力是影响机务行车安全的最深层次因素。

基于AHP的水利工程项目管理课程考核评价权重优化

该文主要目的是建立水利工程项目管理考核量化指标体系,使课程评价更具科学性、合理性。主要应用层次理论分析法,确立水利工程项目管理评价层次结构,给出了水利工程项目管理课程考核的量化指标。随着课程量化指标的给出,科学地考核水利工程项目管理课程的评价体系。使得评价指标权重合理化,评价结果科学、公正和易操作。

Analytical Calculation Method of Reliability Sensitivity Indexes for Distribution Systems Based on Fault Incidence Matrix

An analytical calculation method for the reliability sensitivity indexes of distribution systems is proposed to explicitly quantify the impact of various influence factors on system reliability.Firstly,the analytical calculation formulas for the reliability indexes of distribution systems are derived based on the fault incidence matrix(FIM).Secondly,the factors that affect system reliability are divided into two categories:quantifiable parameter factors and non-quantifiable network structure factors.The sensitivity indexes for the quantifiable parameter factors are derived using the direct partial derivation of the reliability calculation formulas.The sensitivity indexes for the nonquantifiable network structure factors are derived using the transformation of FIMs.Finally,the accuracy and efficiency of the proposed sensitivity calculation method are verified by applying them to an IEEE 6-bus RBTS system.This paper sums up the factors that influence system reliability in detail and gives the explicit analytical calculation method for the sensitivity of each factor.Repetitive calculation of the reliability index can be avoided during the sensitivity analysis.The bottleneck that affects the reliability level of distribution systems can be identified efficiently,and valuable information and guidance can be provided to enhance the reliability of distribution systems.

有向符号网络的边能控性研究

符号网络是一类具有正负符号特征的网络.在多智能体系统中,符号网络能够描述智能体之间的合作与对抗交互关系,因此受到学者的广泛关注.本文主要研究有向符号网络的边能控性.首先,对具有符号网络的多智能体系统边动力学进行建模,得到边能控性模型.其次,从网络拓扑结构角度对边能控子空间进行定量刻画,利用有向符号网络的距离和等价划分得到能控子空间的上下界估计.进一步,讨论了符号网络边能控性与顶点能控性的关系.所得结果表明:当顶点符号图为结构非平衡时,符号网络的边能控性与顶点能控性等价.最后,通过仿真结果验证所得理论的有效性.

基于逆向搜索的模糊Petri网分层算法

模糊Petri网(FPN)是知识库系统(KBS)表示、建模与分析的主要工具之一。针对部分FPN层次结构不清晰、库所/变迁间从属关系不明确的问题,提出一种基于逆向搜索的FPN分层算法(HFPN-RS)以实现非层次化FPN到层次化FPN(HFPN)的自动转换。首先,从终结库所开始对整个FPN进行逆向搜索,将所有输入库所的前集、输出库所的后集分别划分在同一层;其次,通过添加虚库所-虚变迁对的方式明确整个模型的层次结构;同时提出两条相关定理以明确HFPN分层层数的下确界和层次化操作中需要添加的最少虚库所-虚变迁对数,并给出经层次化操作后具有完整分层结构的FPN模型关联矩阵维度计算公式。在实验部分,通过对几类各具特点的FPN模型进行层次化操作,并利用所提定理进行验证。实验结果表明,添加虚库所-虚变迁对后新FPN模型具有清晰的层次结构,为下一步FPN泛化能力等研究内容的深入提供了理论基础。

一种求解度约束最小生成树问题的混合整数线性规划方法

针对含有度约束的最小生成树问题,区别于传统启发式算法和智能算法,提出了一种将度约束最小生成树问题线性化的方法。通过邻接矩阵和关联矩阵处理各节点的出线度约束,以电力系统中直流潮流节点功率平衡思想处理网络的辐射性约束,并基于CPLEX平台调用yalmip求解MILP模型。以8节点系统,9节点系统,旅行商问题的eil51系统进行算例测试,证明线性模型能够有效求解含有度约束生成树规划问题。

On region crossing change and incidence matrix

In a recent work of Ayaka Shimizu, she studied an operation named region crossing change on link diagrams, which was proposed by Kishimoto, and showed that a region crossing change is an unknotting operation for knot diagrams. In this paper, we prove that the region crossing change on a 2-component link diagram is an unknotting operation if and only if the linking number of the diagram is even. Besides, we define an incidence matrix of a link diagram via its signed planar graph and its dual graph. By studying the relation between region crossing change and incidence matrix, we prove that a signed planar graph represents an n-component link diagram if and only if the rank of the associated incidence matrix equals c n + 1, where c denotes the size of the graph.

树状网的潮流算法

本文以在根节点处增加虚拟零阻抗支路和按一定规律对节点、支路编号的方法，使网络的节点──支路关联矩阵成为易于处理的正方阵。用此关联降，可以很简洁地表示树状网潮流计算的过程，使编程工程简单。以ＩＥＥＥ３３节点试例的网络计算表明，方法简单有效。

作战协同关系超图模型

在分析超图和作战协同相关概念基础上,采用形式化方式对抽象化的作战协同关系进行了描述,定义了协同关系矩阵,创新性地根据超图相关概念构建了作战协同超图模型,并根据模型定义了顶点度和关联系数等支持作战协同关系分析的特征参数。通过实验建立了某想定数据中的火力协同关系超图模型,并进行了度和关联系数的分析,实验结果证明了作战协同关系超图模型的可用性。

描述变胞机构构态变换的关联矩阵法

基于变胞机构的变拓扑结构特性,提出了3种基本变胞过程:构件数目变化、运动副数目变化和连接方式变化,这些过程的组合使用可实现全部变胞要求。为了完整、简便、清晰地描述构态变换过程,提出运用含有运动副类型的关联矩阵及其逻辑运算对变胞过程进行描述,同时给出了构态变换方程的逻辑表达式和实现变胞过程的4种基本变胞矩阵。该方法能直观地描述出构态变换的过程和目的,变胞矩阵构造简便,与传统数学运算相比运算次数少,且变换过程中不需要对构件重新编号,有利于形成变胞机构计算机辅助设计方法。