Five-fold local symmetry in metallic liquids and glasses

The structure of metallic glasses has been a long-standing mystery. Owing to the disordered nature of atomic structures in metallic glasses, it is a great challenge to find a simple structural description, such as periodicity for crystals, for establishing the structure–property relationship in amorphous materials. In this paper, we briefly review the recent developments of the five-fold local symmetry in metallic liquids and glasses and the understanding of the structure–property relationship based on this parameter. Experimental evidence demonstrates that five-fold local symmetry is found to be general in metallic liquids and glasses. Comprehensive molecular dynamics simulations show that the temperature evolution of five-fold local symmetry reflects the structural evolution in glass transition in cooling process, and the structure–property relationship such as relaxation dynamics, dynamic crossover phenomena, glass transition, and mechanical deformation in metallic liquids and glasses can be well understood base on the simple and general structure parameter of five-fold local symmetry.

Growth mechanism of icosahedral and other five-fold symmetric diamond crystals

Five-fold symmetric diamond crystals（FSDCs） were synthesized by hot filament chemical vapour deposition（HFCVD） methods. Their surface morphologies and defects were characterised by scanning electron microscopy（SEM）. From the perspective of nucleation-growth, a growth mechanism for icosahedral and other five-fold symmetric diamond crystals was discussed. Computer modelling was also carried out. The results show that the dodecahedrane（C20H20） molecule is proposed as a nucleus for the growth of icosahedral diamond crystals（IDCs）, wherein the 20 {111} surface planes develop orthogonal to the direction of the original 20 C—H bonds by sequential H abstraction and CH3 addition reactions. IDC can be pictured as an assembly of isosceles tetrahedra, with each tetrahedron contributing a {111} plane to the surface of the IDC and the remainder of the tetrahedral surfaces forming twin planes with neighbouring tetrahedra. The small mismatch（1.44°） between the {111} surface dihedral angle of a perfect icosahedron and that of a twinned icosahedron reveals itself via twin planes in the IDC grain. The modelling suggests how the relief of strain induced by this distortion could lead to the formation of defects such as concave pentagonal cavities at vertices and grooves along the grain edges that accord well with those observed experimentally. Similar arguments based on growth from the hexacyclo pentadecane（C15H20） nucleus can also account for the observed formation of star and rod shaped FSDCs, and some of their more obvious morphological defects.

New solutions from nonlocal symmetry of the generalized fifth order KdV equation

The nonlocal symmetry of the generalized fifth order KdV equation(FOKdV) is first obtained by using the related Lax pair and then localizing it in a new enlarged system by introducing some new variables. On this basis, new Ba¨cklund transformation is obtained through Lie’s first theorem. Furthermore, the general form of Lie point symmetry for the enlarged FOKdV system is found and new interaction solutions for the generalized FOKdV equation are explored by using a symmetry reduction method.

Bifurcated overtones of one-way localized Fabry-Pérot resonances in parity-time symmetric optical lattices

Since the first observation of parity-time（PT） symmetry in optics, varied interesting phenomena have been discovered in both theories and experiments, such as PT phase transition and unidirectional invisibility, which turns PT-symmetric optics into a hotspot in research. Here, we report on the one-way localized Fabry-Pérot（FP） resonance, where a welldesigned PT optical resonator may operate at exceptional points with bidirectional transparency but unidirectional field localization. Overtones of such one-way localized FP resonance can be classified into a blue shifted branch and a red shifted branch. Therefore, the fundamental resonant frequency is not the lowest one. We find that the spatial field distributions of the overtones at the same absolute order are almost the same, even though their frequencies are quite different.

ONE FERMION-LOOP CORRECTION AND SUPERSYMMETRY IN THE SUPERSYMMETRIC σ-MODEL WITH WESS-ZUMINO TERMS

It is shown that the local counterterms which simultaneously restore local Lorentz and gauge invariance of the σ-model do not satisfy the criteria of(2,0)supersymmetry.But local counterterms and the non-local part of one-loop effective action together are invariant under the(2,0)supersymmetry transformation.

A Test for the Local Intrinsic Lorentz Symmetry

Basing on a generalization of Wong＇s equations, the problem of motions for particles in the Lorentz gauge field configuration, which is Schwarzschild-like solution of Yang-Mills equations, is studied. The picture of interaction between particles with the Lorentz gauge field is described in an analogous manner to that between isotopic-spin-carrying particles and Yang-Mills field. By examining the effective potential and the equations of orbits for particles, it is found that the considered motions possess some qualitative features resembling to motions of particles in a centrally symmetric gravitational field.

结合相位对称与基于排序LSS的多模态遥感影像匹配

针对多模态遥感影像存在非线性辐射畸变的问题,本文提出了一种结合相位对称特征与基于排序局部自相似性的多模态遥感影像匹配方法.首先,利用影像的局部相位信息构造相位对称图,在此基础上利用加速分段测试特征提取算法(features from accelerated segment test,FAST)对相位对称图进行特征提取.然后结合基于排序的局部自相似性与相位一致性构造一种新的特征描述符RPCLSS(combining rank,phase congruency and local self-similarity descriptor).最后利用快速抽样一致性算法(fast sample consensus,FSC)进行误匹配点剔除.将本文方法在公开的多源遥感影像数据集上与现有的5种先进匹配方法进行对比实验.实验结果表明,本文方法在正确匹配点数量、匹配精度和匹配正确率方面,优于现有的先进多模态遥感影像匹配方法.

混合局部-非局部椭圆方程奇异解的单调性和对称性

该文运用移动平面法研究了一类混合局部-非局部半线性椭圆方程奇异解的单调性和对称性.

Local Geometric Proof of Riemann Conjecture

Riemann hypothesis (RH) is a difficult problem. So far one doesn’t know how to go about it. Studying ζ and using analysis method likely are two incor-rect guides. Actually, a unique hope may study Riemann function , , by geometric analysis, which has the symmetry: v=0 if β=0, and basic expression . We show that |u| is single peak in each root-interval of u for fixed β ∈(0,1/2]. Using the slope ut, we prove that v has opposite signs at two end-points of Ij. There surely exists an inner point such that , so {|u|,|v|/β} form a local peak-valley structure, and have positive lower bound in Ij. Because each t must lie in some Ij, then ||ξ|| > 0 is valid for any t (i.e. RH is true). Using the positivity of Lagarias (1999), we show the strict monotone for β > β0 ≥ 0 , and the peak-valley structure is equiva-lent to RH, which may be the geometric model expected by Bombieri (2000). This research follows Liuhui’s methodology: “Computing can detect the un-known and method”.

A ROBUST EYE LOCALIZATION ALGORITHM FOR FACE RECOGNITION

The accuracy of face alignment affects greatly the performance of a face recognition system. Since the face alignment is usually conducted using eye positions, the algorithm for accurate eye lo- calization is essential for the accurate face recognition. In this paper, an algorithm is proposed for eye localization. First, the proper AdaBoost detection is adaptively trained to segment the region based on the special gray distribution in the region. After that, a fast radial symmetry operator is used to pre- cisely locate the center of eyes. Experimental results show that the method can accurately locate the eyes, and it is robust to the variations of face poses, illuminations, expressions, and accessories.

Weak antilocalization and interaction-induced localization of Dirac and Weyl Fermions in topological insulators and semimetals

Weak localization and antilocalization are quantum transport phenomena that arise from the quantum interference in disordered metals.At low temperatures,they can give distinct temperature and magnetic field dependences in conductivity,allowing the symmetry of the system to be explored.In the past few years,they have also been observed in newly emergent topological materials,including topological insulators and topological semimetals.In contrast from the conventional electrons,in these new materials the quasiparticles are described as Dirac or Weyl fermions.In this article,we review our recent efforts on the theories of weak antilocalization and interaction-induced localization for Dirac and Weyl fermions in topological insulators and topological semimetals.

Explicit solutions from residual symmetry of the Boussinesq equation

The Bcklund transformation related symmetry is nonlocal, which is hard to be applied in constructing solutions for nonlinear equations. In this paper, the residual symmetry of the Boussinesq equation is localized to Lie point symmetry by introducing multiple new variables. By applying the general Lie point method, two main results are obtained： a new type of Backlund transformation is derived, from which new solutions can be generated from old ones; the similarity reduction solutions as well as corresponding reduction equations are found. The localization procedure provides an effective way to investigate interaction solutions between nonlinear waves and solitons.

A Design Flow for Robust License Plate Localization and Recognition in Complex Scenes

In this paper, we present a new design flow for robust license plate localization and recognition. The algorithm consists of three stages: 1) license plate localization;2) character segmentation;and 3) feature extraction and character recognition. The algorithm uses Mexican hat operator for edge detection and Euler number of a binary image for identifying the license plate region. A pre-processing step using median filter and contrast enhancement is employed to improve the character segmentation performance in case of low resolution and blur images. A unique feature vector comprised of region properties, projection data and reflection symmetry coefficient has been proposed. Back propagation artificial neural network classifier has been used to train and test the neural network based on the extracted feature. A thorough testing of algorithm is performed on a database with varying test cases in terms of illumination and different plate conditions. Practical considerations like existence of another text block in an image, presence of dirt or shadow on or near license plate region, license plate with rows of characters and sensitivity to license plate dimensions have been addressed. The results are encouraging with success rate of 98.10% for license plate localization and 97.05% for character recognition.

面向虹膜识别的多方向中心对称局部二值模式

为了提升虹膜纹理的表征效果,获得稳定的局部纹理信息表达,提出基于多方向中心对称局部二值模式的虹膜识别算法.首先通过眼睑边缘快速定位生成掩膜,抑制眼睑区域噪声;然后在多方向的基础上,提出多方向中心对称的局部二值模式完成虹膜纹理特征的表征;最后利用汉明距离判定虹膜是否匹配.针对由于类内与类间匹配次数失衡导致评价指标正确识别率存在的不足,提出修正的正确识别率.在CASIA.V1,CASIA.V3-Interval,JUL6.0和CASIA.V4-Lamp虹膜库上的实验结果表明,所提算法的修正的正确识别率分别为99.857%,99.940%,99.640%和97.973%,等错误率下降0.03%~5.96%;该算法能够有效地表征虹膜纹理信息,具有良好的识别性能和鲁棒性.

稀土掺杂无序结构晶体的局域位置对称性与发光调控

稀土掺杂的无序结构晶体具有优异的下转移和上转换发光性能,通过对材料的发光调控可使其广泛应用于各种光学和光电子学领域。稀土离子的光学性质与所处的晶体场环境密切相关,因此,使用稀土离子作为灵敏的结构探针,可以确定无序结构发光材料中稀土离子掺杂的局域结构和位置对称性;同时,通过改变稀土离子掺杂的无序结构晶体的局域位置对称性也可以进行一系列发光调控。本文首先介绍了稀土离子掺杂无序结构材料的晶体学格位对称性和光谱学格位对称性;其次,系统总结了通过改变局域结构来调控稀土离子掺杂的下转移/上转换发光的最新成果,包括组分调节和外场调节;最后,深入探讨了稀土掺杂无序结构发光材料面临的挑战和发展前景。

液态Ta快凝过程中团簇的遗传及其与局域对称性的关联

金属玻璃是液态金属在某种程度上的“冻结”,探明液态金属的结构特征及其在快凝过程中的演化特性,有助于理解玻璃转变和玻璃形成能力的微结构机制.为此,本文采用分子动力学,模拟研究了液态金属Ta的快凝过程.并用双体分布函数、最大标准团簇、遗传跟踪等方法,对快凝Ta的微结构特征及其演化特性进行了表征和分析.结果表明,快凝金属Ta的原子组态是各种Kasper团簇及变形结构,其中占比最高的是Z13 Kasper团簇.连续遗传起始温度和阶段遗传分数均可用来表征团簇结构遗传能力的大小.最大标准团簇的对称性可以采用局域对称性参数(LSP)来定量表征,局域五次对称参数(LSP_(5))越大其遗传能力越强.各类团簇在能量区间出现的频率均服从高斯分布,其平均原子势能期望值(E^(j)_(exp))与LSP呈近似线性关系,且E^(j)_(exp)随LSP_(5)的增大而降低.高的局域五次对称性降低了团簇的平均原子势能,从而增强了这类团簇的结构遗传能力.

局部支撑平台高空对称网架施工安装技术研究与应用

钢网架作为一种空间杆系结构,适用于大跨度建筑的屋盖及屋架,近年来在体育场馆、机场、车站等工程中得到广泛应用。科学的网架安装,不但节约材料、缩短工期、降低安装成本,还保证动态安装过程受力和变形可控,确保施工过程安全。本文以某工程体育馆项目为例,重点介绍了局部支撑平台高空对称正放三角锥螺栓球节点钢结构网架安装施工工艺,并利用有限元软件对其网架安装过程进行虚拟仿真施工模拟,模拟结果表明局部支撑平台高空对称网架安装技术可行。该技术不但解决了大跨度网架高空拼接关键性技术问题,还节约了材料、缩短了工期,为工程取得了重大经济效益。

颧骨复合体骨折定量复位校正仪的研制及临床应用

目的:研制颧骨复合体骨折定量复位校正仪。用其指导手术复位,提高疗效。方法:视头颅为一整体,根据镜像对称性原理,制成由面弓、滑动定位尺、轨限、耳杆和额托等附件构成的颧骨复合体骨折定量复位校正仪。对40名成年人(男女各20人)颧骨、颧弓突点的测量。结果:建立了正常人群颧骨、颧弓突点测量均值(Ar-mp)男性:左11.09±1.20/右11.55±1.35 mm;女性:左13.38±1.40/右12.85±1.20 mm。(Ar-ztu)男性:左31.12±1.85/右31.6±1.88 mm;女性:左35.33±0.87/右34.97±1.04 mm。以该校正仪用于临床单侧和双侧颧骨复合体骨折术中骨折块的复位,提高了准确性。结论:临床上该校正仪指导骨折块复位固定,对颧骨颧弓突点和颅面部对称性的恢复有一定意义。

基于方向对称变换的人脸定位方法

本文定义了一种新的对称变换———方向对称变换，它与常用的广义对称变换相比能够提供更多的信息来描述物体的形状．在此基础上提出了一种快速的人脸定位方法，与应用广义对称变换方法相比不仅可以提高定位准确率，而且能够大幅减小计算量．

基于平滑轮廓对称轴法的苹果目标采摘点定位方法

果实采摘点的精确定位是采摘机器人必须解决的关键问题。鉴于苹果目标具有良好对称性的特点,利用转动惯量所具有的平移、旋转不变性及其在对称轴方向取得极值的特性,提出了一种基于轮廓对称轴法的苹果目标采摘点定位方法。为了解决分割后苹果目标边缘不够平滑而导致定位精度偏低的问题,提出了一种苹果目标轮廓平滑方法。为了验证算法的有效性,对随机选取的20幅无遮挡的单果苹果图像分别利用轮廓平滑和未进行轮廓平滑的算法进行试验,试验结果表明,未进行轮廓平滑算法的平均定位误差为20.678°,而轮廓平滑后算法平均定位误差为4.542°,比未进行轮廓平滑算法平均定位误差降低了78.035%,未进行轮廓平滑算法的平均运行时间为10.2ms,而轮廓平滑后算法的平均运行时间为7.5ms,比未进行轮廓平滑算法平均运行时间降低了25.839%,表明平滑轮廓算法可以提高定位精度和运算效率。利用平滑轮廓对称轴算法可以较好地找到苹果目标的对称轴并实现采摘点定位,表明将该方法应用于苹果目标的对称轴提取及采摘点定位是可行的。