多尺度几何活动曲线及MR图像边界提取

活动曲线方法是 80年代末发展起来的基于模型的图像分割方法 ,主要有两大类 ,能量活动曲线方法和几何活动曲线方法 .几何活动曲线方法在数学上比较完备 ,较好地克服了能量方法的许多缺点 ,但是在医学图像分割中 ,尤其在结构性噪声比较严重的情况下 ,几何活动曲线向边界的演化会受到一定程度的影响 .为了解决这个问题 ,作者利用基于小波变换的多尺度边缘检测算法 ,提出了多尺度几何活动曲线模型 .在人体头部 MR图像脑边界的提取中 ,多尺度几何活动曲线比较好地克服了灰质和白质之间复杂边界的影响 ,较好地提取出了有突出形状的人脑边界 .

直线导轨表面误差建模及多尺度曲线拟合方法研究

针对直线导轨的表面误差问题,建立了直线导轨表面误差模型。采用多尺度曲线拟合法,将直线导轨表面误差分解为形状误差、波纹度误差和粗糙度误差,并使用三坐标测量机获取实际的直线导轨表面误差,然后分别采用多尺度曲线拟合法和二次多项式对表面误差进行拟合。结果表明,建立的直线导轨表面误差模型和多尺度曲线拟合方法比传统的模型和拟合方法更精确。

基于相依数据的非参数回归函数和尺度函数的联立稳健估计

该文将Hrdle和Tsybakov的结果推广到数据来自α-混合的严平稳序列的情形,得到了估计的相合性和渐近正太性.在小样本的情形下给出了随机模拟结果,以检查所提出估计的表现.

区域地表水热通量遥感的空间不均匀性分析

针对区域地表水热通量遥感的尺度问题,详细分析了地表水热过程的空间异质性成因,阐明由于对地表水热过程的机理认识和参数化的水平限制,脱离具体问题而严格遵循水热机理过程来模拟空间绝对详尽的区域水热通量不可行也不必要.文中引入尺度曲线,分析了地表参数空间异质性和遥感观测能力之间的空间尺度权衡关系,定性解释了二者尺度曲线的交点有助于确定区域地表水热通量遥感的尺度.最后通过实例建议了基于多尺度一致性指数比较的方法,可用以判断地表水热通量的空间异质性.研究表明,可行并可信地估算区域尺度地表水热通量,须考虑地表参数的空间尺度特征,权衡遥感观测的有限性与水热过程的复杂性.

Analysis of semi-solid response under rapid compression tests using multi-scale modelling and experiments

Simulating semi-solid metal forming requires modelling semi-solid behaviour.However, such modelling is difficult because semi-solid behavior is thixotropic and depends on the liquid-solid spatial distribution within the material.In order to better understand and model relationships between microstructure and behavior, a model based on micromechanical approaches and homogenisation techniques is presented.This model is an extension of a previous model established in a pure viscoplastic framework to account for elasticity.Indeed, experimental load-displacement signals reveal the presence of an elastic-type response in the earlier stages of deformation when semi-solids are loaded under rapid compression.This elastic feature of the behaviour is attributed to the response of the porous solid skeleton saturated by incompressible liquid.A good quantitative agreement is found between the elastic-viscoplastic predicted response and the experimental data.More precisely, the strong initial rising part of the load-displacement curve, the peak load and the subsequent fall in load are well captured.The effect of solid fraction on mechanical response is in qualitative agreement with experiments.

Effect of surface nanocrystallization and PPEC time on complex nanocrystalline hard layer fabricated by plasma electrolysis

Size distribution of nano-carbides produced by duplex treatments of surface nanocrystallization(by surface severe plastic deformation) and plasma electrolytic carburizing on CP-Ti was investigated.Skewness and kurtosis of Gussian shape distribution curves were studied and the effect of time was determined.The usage of longer time is more suitable for achieving less size of complex nano-carbides.Surface roughness of treated samples was measured.It is observed that there is an optimum level for time on surface roughness increasing(difference between two measured data).

矢量曲线数据的网络渐进传输

提出了一种保持拓扑一致性的曲线多尺度表达方法,并基于此方法实现了曲线数据的网络渐进传输。该方法首先将曲线结点的重要程度、公共约束点和单调链等信息组织成单调线性BLG树结构,然后基于该结构按需实时生成多尺度曲线,利用优化的单调链求交算法维护拓扑一致性。曲线数据网络渐进传输实验验证了此方法的有效性。

桩基非线性轴向受迫振动稳态幅频响应分析

用多时间尺度法得到了一端固定、另一端自由的桩基非线性轴向受迫振动系统主共振时的稳态幅频响应曲线。研究表明:桩基非线性轴向受迫振动的幅频响应曲线不仅与派生线性振动系统的固有频率、土刚度和阻尼系数有关,而且也与振幅、相位和非线性特征量有关。幅频响应曲线中会出现一种典型的振幅跳跃的非线性现象,当激励频率接近线性系统固有频率时,系统产生共振从而响应幅值增大,而且同一激励频率可能会对应于振幅的多个不同值,运动状态具有不稳定性。随着非线性系数的增大,响应曲线峰值侧向弯曲;粘性阻尼会抑制响应振幅的增大;激励振幅增大会导致响应振幅增大。