中子半影成像的计算机断层重建技术

实际用于中子半影成像重建的方法都是线性方法,而计算机断层重建是一种能够用于中子半影成像重建的新方法.介绍了中子半影成像的断层重建原理,将半影成像的诊断图像沿径向等角度提取、微分后就可以使用断层重建方法重建.给出了使用卷积反投影方法重建不同噪声诊断图像的结果,并分析了断层重建的优缺点.重建结果表明,断层重建方法能够重建出...     

Hyperconifold transitions,mirror symmetry,and string theory

Multiply-connected Calabi–Yau threefolds are of particular interest for both string theorists and mathematicians. Recently it was pointed out that one of the generic degenerations of these spaces (occurring at codimension one in moduli space) is an isolated singularity which is a finite cyclic quotient of the conifold; these were called hyperconifolds. It was also shown that if the order of the quotient group is even, such singular varieties have projective crepant resolutions, which are therefore smooth Calabi–Yau manifolds. The resulting topological transitions were called hyperconifold transitions, and change the fundamental group as well as the Hodge numbers. Here Batyrev?s construction of Calabi–Yau hypersurfaces in toric fourfolds is used to demonstrate that certain compact examples containing the remaining hyperconifolds — the Z₃${\mathbb{Z}}_3$ and Z₅${\mathbb{Z}}_5$ cases — also have Calabi–Yau resolutions. The mirrors of the resulting transitions are studied and it is found, surprisingly, that they are ordinary conifold transitions. These are the first examples of conifold transitions with mirrors which are more exotic extremal transitions. The new hyperconifold transitions are also used to construct a small number of new Calabi–Yau manifolds, with small Hodge numbers and fundamental group Z₃${\mathbb{Z}}_3$ or Z₅${\mathbb{Z}}_5$. Finally, it is demonstrated that a hyperconifold is a physically sensible background in Type IIB string theory. In analogy to the conifold case, non-perturbative dynamics smooth the physical moduli space, such that hyperconifold transitions correspond to non-singular processes in the full theory.     

Linearization of vector fields and embedding of diffeomorphisms in flows via Nash–Moser theorem

In the first part of this paper we give suitable spectral properties of the adjoint operators induced by appropriate perturbations of some hyperbolic linear vector fields. These properties are useful to prove general facts based on the Nash–Moser inverse function theorem. In the second part of this work we study circumstances where a global linearization of a vector field X$X$ in a real numerical space is feasible and where some diffeomorphisms which are close to exp(X)$exp\left(X\right)$ can be embedded in a flow.     

惯性约束聚变反应速率测量

 聚变反应速率是表征惯性约束聚变热核反应的重要参数,为测量聚变反应速率,研制了一套由闪烁体及鼻锥部分、光学系统和条纹相机组成的测量系统。在神光Ⅲ原型装置上利用新研制的聚变反应速率测量系统进行了聚变反应速率测量。在DT中子产额约为10¹⁰条件下,首次获得了聚变反应速率随时间的变化过程。对影响聚变反应速率测量的相关因素进行详细分析后表明,系统的时间分辨力优于30 ps。     

Some isoperimetric inequalities and eigenvalue estimates in weighted manifolds

In this paper we prove general inequalities involving the weighted mean curvature of compact submanifolds immersed in weighted manifolds. As a consequence we obtain a relative linear isoperimetric inequality for such submanifolds. We also prove an extrinsic upper bound to the first non-zero eigenvalue of the drift Laplacian on closed submanifolds of weighted manifolds.     

Integral manifolds of impulsive fractional functional differential systems

In this paper, a class of impulsive Caputo fractional functional differential systems with variable impulsive perturbations is investigated. Sufficient conditions for the existence of integral manifolds are obtained. The main results are proved by means of piecewise continuous Lyapunov functions and the fractional comparison principle. The demonstrated techniques can be applied in studying properties of many applied problems of diverse interest.     

求解两块可分离凸极小化问题的惯性交替方向乘子法

The alternating direction method of multipliers(ADMM)is a widely used method for solving many convex minimization models arising in signal and image processing.In this paper,we propose an inertial ADMM for solving a two-block separable convex minimization problem with linear equality constraints.This algorithm is obtained by making use of the inertial Douglas-Rachford splitting algorithm to the corresponding dual of the primal problem.We study the convergence analysis of the proposed algorithm in infinite-dimensional Hilbert spaces.Furthermore,we apply the proposed algorithm on the robust principal component analysis problem and also compare it with other state-of-the-art algorithms.Numerical results demonstrate the advantage of the proposed algorithm.     

机载平台式惯导系统导电环故障机理分析及解决措施

导电环是平台式惯导系统惯性平台的重要组成部分,主要承担惯性平台台体内各种信号与系统的传输和交联,导电环发生故障直接会导致惯导系统失效。针对导电环三种故障模式:接触电阻变大、绝缘强度降低以及烧坏,本文采用微动磨损和电接触理论,结合作者的实际工作经验,对故障机理进行了分析,提出了相应的改进措施。这些措施均在生产中得到落实。落实措施后的故障统计表明,采取的改进措施有效,导电环的故障率与原来相比降低了38%。