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Search Results: 1 - 10 of 315724 matches for " 先验边界条件<br>optical coherence tomography "
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Coronary vessel intimal sequence extraction based on prior boundary constraints in optical coherence tomography image

- , 2018, DOI: 10.7507/1001-5515.201712058
Abstract: 光学相干断层影像(OCT)是一种应用于血管的影像新技术,其高分辨率和可量化分析等特点,使其能够检测血管内膜和斑块表面的特殊结构并发现微小病变。特别是随着其在识别冠状动脉粥样硬化斑块、优化经皮冠状动脉介入(PCI)治疗、辅助医生制定相关诊断和治疗策略以及支架术后评估等方面的应用相继展开,OCT 已经成为心血管疾病诊断的有效工具。本文提出了一种基于先验边界条件的冠脉 OCT 内膜轮廓序列提取算法,在 Chan-Vese 模型基础上通过改进演化权函数把轮廓曲线的局部信息引入模型,控制曲线边界演化速度,并在模型中加入梯度能量项和基于先验边界条件的内膜轮廓形状限制项,进一步约束曲线演化轮廓的形状,最终实现冠脉血管内膜轮廓的序列提取。与作为金标准的专业医生手动分割结果进行实验对比,结果表明本算法在冠脉 OCT 内膜轮廓模糊、失真、有导丝阴影及有斑块干扰等情况下均能准确提取冠脉血管内膜轮廓,提示本研究成果或可应用于临床辅助诊断和精确诊疗之中。
Optical coherence tomography (OCT) is a new technique applied in cardiovascular system. It can detect vessel intimal, small structure of plaque surface and discover small lesions with its high axial resolution and quantification character. Especially with the application of OCT in characterization of coronary atherosclerotic plaque, diagnosis and treatment strategy making, optimizing percutaneous coronary intervention therapy and assessment after stent planting make the OCT become an efficient tool for cardiovascular disease diagnosis and treatment. This paper presents a novel coronary vessel intimal sequence extraction method based on prior boundary constraints in OCT image. On the basis of conventional Chan-Vese model, we modified the evolutionary weight function to control the evolutionary rate of boundary by adding local information of boundary curve. At the same time, we added the gradient energy term and intimal boundary constraint term based on priori boundary condition to further control the evolutionary of boundary curve. At last, coronary vessel intimal is extracted in a sequence way. The comparison with vessel intimal, manual segmented by clinical scientists (golden standard), indicates that our coronary vessel intimal extraction method is robust to intimal boundary blur, distortion, guide wire shadow and plaque disturbs. The results of this study can be applied to clinical aid diagnosis and precise diagnosis and treatment.
Positive Solutions for Second-Order Nonlinear Boundary Value Problems with Integral Boundary Conditions

刘健, 封汉颍
Pure Mathematics (PM) , 2014, DOI: 10.12677/PM.2014.41009
In this article, a second-order nonlinear boundary value problem with integral boundary conditions is investigated. By calculating, the Green’s function for boundary value problem subject to homogeneous boundary conditions and its properties are given. By using the fixed point theory in cones, the existence results for at least one positive solution for the problem are established when f is superlinear or sublinear.
- , 2019,
Abstract: 缠绕式提升系统悬绳的横向振动是钢丝绳多层缠绕有序排绳和工程安全的主要评价指标。为了研究悬绳在不同形式绳槽激励下的横振响应,基于Hamilton原理建立提升系统振动方程,推导不同形式绳槽的激励函数,用Galerkin法离散振动方程,以某布莱尔式钢丝绳提升试验台运行状态曲线作为运动参数输入分析不同形式绳槽激励下的横振响应,用高速相机记录钢丝绳振动,并提出一种有效的图像处理方法,得到悬绳固定点处横振时域图,比较模型的数值仿真解与实验结果发现:在本实验台参数下,对称绳槽激励的悬绳横振大于非对称绳槽布置;悬绳横振的实测曲线与数值仿真变化趋势基本一致,实测频率与计算频率也非常接近,说明本文建立的边界激励下悬绳的横振模型是有效的。模型可为将来超深井提升卷筒绳槽型式的选择提供可靠的理论依据。
Abstract:The transverse vibration of a winding hoist system’s hanging rope is the main evaluating index for multi-layer winding wire rope orderly arrangement and engineering safety.In order to study transverse vibration response of hanging rope under excitations of different types rope grooves, the vibration equation of the hoisting system’s hanging rope was established with Hamilton principle, excitation functions of different types rope grooves were deduced, the vibration equation was discretized using Galerkin method.The operational state curve of a certain Blair rope hoisting test platform was taken as the imported motion parameter to analyze lateral vibration responses of the hanging rope under excitations of different types rope grooves.The hanging rope’s transverse vibrations were recorded with a high speed camera, and an effective image-processing method was proposed to obtain time history figures of transverse vibration responses of the rope’s fixed point.The results of the theoretical model’s numerical simulation were compared with the test ones, it was shown that the hanging rope’s transverse vibrations under excitations of symmetric grooves are larger than those under excitations of non-symmetric grooves; the changing trend of actually measured curves of the rope’s transverse vibrations is consistent to that of the numerical simulation curves, the actually measured vibration frequencies are close to the calculated vibration ones, so the transverse vibration model established here for the hanging rope is effective, it provides a reliable theoretical basis for grooves types choosing of extremely deep well hoisting systems.
Blow-Up and Asymptotic Behavior of Global Solution of Damped Wave Equation with Dynamic Boundary Conditions

靳妞, 张宏伟, 呼青英
Pure Mathematics (PM) , 2012, DOI: 10.12677/PM.2012.23023
Abstract: 本文讨论动力边界条件的阻尼波动方程解的爆破性和渐近性。利用凸性分析和不稳定集,分别给出了初始能量为负和正时,解爆破的充分条件;借助Nakao不等式和位势井理论得到了解的衰减估计。
In this paper, the blow-up and asymptotic behavior of global solution of damped wave equation with dynamic boundary condition are discussed. By the convexity lemma and unstable set, the sufficient con- dition of the solution of the wave equation with negative and positive initial energy respectively are obtained. With the help of Nakao and stable set, the energy decay of the solution is given.
New Solution of Cubic Spline Interpolation Function

刘永春, 王强
Pure Mathematics (PM) , 2013, DOI: 10.12677/PM.2013.36055
>In this article, based on analysis of three turning angles algorithm of cubic spline interpolation, the cubic spline interpolation is generalized on the condition of the second boundary. The methods are presented on the condition that the second derivative of arbitrary two nodes is given. At the end of the article, this cal- culation method is illustrated through an example.
一类含临界对流项的拟线性椭圆方程Neumann问题正解的先验估计与可解性 A priori estimates and existence of positive solutions to quasilinear elliptic equations with critical convection terms and nonlinear Neumann boundary conditions
- , 2017,
Abstract: 讨论了带有非线性Neumann边界条件的m-Laplacian方程正解的先验估计与存在性,其中非线性项含有临界对流项.利用解的爆破方法和相应的Liouville定理得到解的先验估计,运用不动点定理得到解的存在性
Entanglement in an anisotropic spin-1 Heisenberg chain
Zhu Yan,Zhu Shi-Qun,Hao Xiang,
朱 燕
,朱士群,郝 翔

中国物理 B , 2007,
Abstract: The entanglement in an anisotropic spin-1 Heisenberg chain with a uniform magnetic field is investigated. The ground-state entanglement will undergo two different kinds of transitions when the anisotropy \Delta and the amplitude of the magnetic field B are varied. The thermal entanglement of the nearest neighbour always declines when B increases no matter what the value of the anisotropy is. It is very interesting to note that the entanglement of the next-nearest neighbour can increase to a maximum at a certain magnetic field. Regardless of the boundary condition, the nearest-neighbour entanglement always decreases and approaches to a constant value when the size of the system is very large. The constant value of open boundary condition is much larger than that of periodic boundary condition.

Zhou Jianyi,Yang Quanrang,

电子与信息学报 , 1997,
Abstract: A high accuracy stable Dispersive Boundary Condition(DBC) is presented, which can be used to model wave propagation in transmission lines by the finite-difference time-domain method. The differential factor in the boundary condition is replaced by a new two-order difference scheme. The new DBC has the same absolute stability as that proposed by P. Y. Zhao, et al. (1994), but it has a much better absorbing performance.
Breakup of spiral wave under different boundary conditions
Zhao Ying-Kui,Wang Guang-Rui,Chen Shi-Gang,

中国物理 B , 2007,
Abstract: In this paper, we investigate the breakup of spiral wave under no-flux, periodic and Dirichlet boundary conditions respectively. When the parameter \varepsilon is close to a critical value for Doppler-induced wave breakup, the instability of the system caused by the boundary effect occurs in the last two cases, resulting in the breakup of spiral wave near the boundary. With our defined average order measure of spiral wave (AOMSW), we quantify the degree of order of the system when the boundary-induced breakup of spiral wave happens. By analysing the AOMSW and outer diameter R of the spiral tip orbit, it is easy to find that this boundary effect is correlated with large values of R, especially under the Dirichlet boundary condition. This correlation is nonlinear, so the AOMSW sometimes oscillates with the variation of \varepsilon.
带有Neumann条件的对流扩散方程的两层紧差分格式 A Two-level Finite Difference Scheme for Convection Diffusion Equations with Neumann Boundary Conditions
- , 2018,
Abstract: 对带有Neumann边界条件的常系数对流扩散方程,建立了一个两层有限差分格式,利用离散能量分析法给出了差分解的先验估计式,分析了差分格式解存在唯一性、收敛性以及稳定性.并得出了差分格式在L_∞范数下的收敛阶数为O(τ~2+h~4).通过数值算例,验证了理论分析结果是正确的.
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