Investigation on the dynamic behaviors of the coupled memcapacitor-based circuits

In this paper, by referring to the concept of coupled memristors(MRs) and considering the flux coupling connection,the constitutive relations for describing the coupled memcapacitors(MCs) are theoretically deduced. The dynamic behaviors of dual coupled MCs in serial and parallel connections are analyzed in terms of identical or opposite polarities for the first time. Based on the derived constitutive relations of the two coupled MCs, the modified relaxation oscillators(ROs)are obtained with the purpose of achieving controllable oscillation frequency and duty cycle. In consideration of different parameter configurations, the experimental investigation is carried out by using practical off-the-shelf circuit components to verify the correction of the theoretical calculation with numerical simulation of the coupled MCs and its application in ROs.     

Expansion of EYM amplitudes in gauge invariant vector space

Motivated by the problem of expanding the single-trace tree-level amplitude of Einstein-Yang-Mills theory to the BCJ basis of Yang-Mills amplitudes, we present an alternative expansion formula in gauge invariant vector space. Starting from a generic vector space consisting of polynomials of momenta and polarization vectors, we define a new sub-space as a gauge invariant vector space by imposing constraints on the gauge invariant conditions. To characterize this sub-space, we compute its dimension and construct an explicit gauge invariant basis from it. We propose an expansion formula in this gauge invariant basis with expansion coefficients being linear combinations of the Yang-Mills amplitude, manifesting the gauge invariance of both the expansion basis and coefficients. With the help of quivers, we compute the expansion coefficients via differential operators and demonstrate the general expansion algorithm using several examples.     

物理教育的衔接现状及教师策略研究

近年来全国多省份陆续进行高考改革,在学生从高中过渡到大学的过程中,高中选科制度衍生出了在心理、学习方式、学习内容等方面的一系列问题,也成为教师必须面对的问题.基于以上出现的新情况,设计了关于物理衔接的调查问卷,以中央民族大学物理专业大一学生为研究对象,探究了大学物理与高中物理衔接在教师方面的影响因素,并辅以大学生学习动机的调查问卷,进一步探索了如何提升物理衔接的教学效果,并结合教育心理学关于内部动机与外部动机的研究理论,从教师的角度提出了大中衔接过程中的实施建议及策略.     

凸显“本质联系证据推理”的离子键与共价键教学

针对离子键与共价键在教学中存在本质分离、联系割裂和忽视“证据推理”素养发展目标的问题,依据元素周期律中金属性和非金属性的递变规律进行推理,并寻找证据进行证实或证伪,以认清离子键与共价键的静电作用的成键本质和辩证统一的关系,发展学生证据推理的核心素养,提高学生的逻辑思维能力。     

Synthesis of phosphonic acid silver-graphene oxide nanomaterials with photocatalytic activity through ultrasonic-assisted method

In this article, phosphonic acid silver-graphene oxide nanomaterials (Nano-PAS-GO) was synthesized from silver nitrate (AgNO₃) solution and phosphoric graphene oxide (PGO) via the convenient ultrasonic-assisted method, and the structure and morphology were characterized, and the photocatalytic activity and recyclability were evaluated through photocatalyzing degradation of Rhodamin B (RhB) aqueous solution, and the possible photocatalytic mechanism was also discussed. Based on those, it was confirmed that Nano-PAS-GO has been synthesized from AgNO₃ solution and PGO colloidal suspension under ultrasonic-assisted condition, and Nano-PAS-GO has consisted of phosphoric acid silver nanoparticles and GO with 2D lattice (2D GO lattice) connected in the form of C-P bonds, and the photodegradation rate of Nano-PAS-GO for RhB aqueous solution has reached 93.99%, and Nano-PAS-GO has possessed the nicer recyclability when the photocatalytic time was 50 min. From those results, the strong and stable interface _.between PAS nanoparticles and 2D GO lattice connected in the form of the covalent bonds has effectively inhibited the occurrence of the photocorrosion phenomenon.     

Hermitian Yang-Mills Metrics on Higgs Bundles over Asymptotically Cylindrical Kähler Manifolds

Let V be an asymptotically cylindrical Kahler manifold with asymptotic cross-section     

基于2D DenseU-net的核磁共振海马体分割

针对深层U-net网络易出现梯度消失以及存在特征重用率低的问题，本文提出一种2D DenseU-net海马体分割算法框架，融合了DenseNet和U-net两种网络结构。通过在U-net中构建当前层与前面所有层的密集连接，有效缓解了深层U-net易出现梯度消失的问题，并加强了特征传播与特征复用；DenseU-net在发挥密集连接优势的同时，保持了U-net网络中下采样和上采样的长连接结构，有助于保存浅层信息。此外，针对海马体存在比例少、体积小、边缘不清晰等特点，本文对数据样本依次进行正样本数据增强、尺寸均等剪切以及去除无效样本、边缘采样的特殊处理，有效解决了正负样本失衡问题并强化了海马体细节信息，保证获取完整的特征用于网络训练。在公开数据集ADNI（Alzheimer's Disease Neuroimaging Initiative）上的实验结果表明，本文方法能够达到92.63%的平均分割Dice精度，优于传统的海马体分割方法以及目前流行的一些基于深度学习的海马体分割模型。     

电光调Q驱动电源与晶体之间的引线研究

分析了高重频电光调Q驱动电源与晶体之间的最佳引线。由于调Q晶体和引线都存在分布电容和电感,如果晶体两端阻抗不匹配,电压脉冲就会出现阻尼振荡,从而影响激光脉冲。针对这一问题,使用脉冲反射法和分布参数电路法,以平行导线作为引线,分析了脉冲在引线中的传输、晶体高压波形和引线所要求的驱动电源的最小功率。使用脉冲反射法,以同轴线作为引线,分析了简单连接晶体和阻抗匹配后连接晶体的两种情况,得出了晶体两端电压波形和同轴引线阻抗匹配后的电路对快速开关的要求。根据以上分析,得出了电光调Q中引线的选择原则。     

Characterization of Levi-Civita and Newton–Cartan connections in dimension 2

In dimension 2, we give a local characterization of Levi-Civita connections, improving a result by G. Thompson (1991), and of Newton–Cartan connections (connections which are limit of Levi-Civita connections).