高速铁路轮轨滚动噪声的分形描述及分形维估计

提出基于分形分析的轮轨滚动噪声研究方法,研究了不同尺度下轮轨滚动噪声增量的统计特性,证明轮轨滚动噪声具有分形特性,可由分形布朗运动描述。在此基础上,利用分形布朗运动的小波系数方差与分形维的幂律关系估计了轮轨滚动噪声的分形维,并估计了以裂纹扩展为代表的钢轨伤损声发射信号的分形维,对比研究发现:轮轨滚动噪声分形维本身具有随机性,不同车速下的轮轨滚动噪声分形维估计以1.5666为均值随机分布在小于2的小区间内;分形维是轮轨滚动噪声的固有特征,与车速无关,不同车速的轮轨滚动噪声可由统一的分形布朗运动模型描述;裂纹扩展信号与轮轨滚动噪声不同,其分形维估计大于2,不满足分形布朗运动模型的要求,但分形维可作为二者的区别特征。研究提取了轮轨滚动噪声的分形维作为固有特征,为高速轮轨滚动噪声描述及轮轨伤损检测提供了有效的分析方法。      

A thermal flux-diffusing model for complex networks and its applications in community structure detection

We introduce a thermal flux-diffusing model for complex networks. Based on this model, we propose a physical method to detect the communities in the complex networks. The method allows us to obtain the temperature distribution of nodes in time that scales linearly with the network size. Then, the local community enclosing a given node can be easily detected for the reason that the dense connections in the local communities lead to the temperatures of nodes in the same community being close to each other. The community structure of a network can be recursively detected by randomly choosing the nodes outside the detected local communities. In the experiments, we apply our method to a set of benchmarking networks with known pre-determined community structures. The experiment results show that our method has higher accuracy and precision than most existing globe methods and is better than the other existing local methods in the selection of the initial node. Finally, several real-world networks are investigated.     

联合谱域与深度域光谱相位显微方法

提出了一种联合谱域与深度域光谱相位显微方法, 该方法利用谱域相位信息克服2π歧义, 并结合深度域相位信息, 以实现高动态范围、高灵敏度的相位检测. 首先通过理论推导和信号模拟, 进行了深度域相位和谱域相位的灵敏度比较, 证明了深度域相位在灵敏度上要高于谱域相位. 进而详细介绍了联合谱域与深度域光谱相位显微方法. 最后通过盖玻片和光学分辨率板实验验证了所提出的联合谱域 与深度域光谱相位显微方法能够在实现高动态测量范围的同时保持高相位灵敏度. 关键词： 光谱相位显微方法 动态范围 灵敏度     

安徽高中数学竞赛题的变式与推广

<正>文[1]和文[2]分别给出了2006年安徽省高中数学竞赛初赛中的题目:"设x,y是实数,且满足x~2+xy+y~2=3.则x~2-xy+y~2的最大值和最小值是__."的三种思路三种解法与二种思路三种解法.笔者拜读了之后颇有感想,下面给出这个题目的一个变式,供大家参考.由于xy=x~2·y/x,y~2=xy·y/x,于是我们可     

CHAID方法在居民卫生服务需求研究中的应用

CHAID(Chi-squared Automatic Interaction Detector)方法可以用于解决回归和分类问题,能处理非线性、具有交互作用及缺失值等较为复杂的数据,特别适用于大样本和多维频数表资料的研究,被广泛用于医学科研、市场分析及质量控制等多个领域。本文通过对浙江省海岛居民两周患病率的分析,介绍CHAID方法在居民卫生服务需求研究中的应用。     

Registering multiple medical images using the shared chain mutual information

A new approach to the simultaneous registration of multiple medical images is proposed using shared chain mutual information(SCMI)as the matching measure.The presented method applies SCMI to measure the shared information between the multiple images.Registration is achieved by adjusting the relative position of the floating image until the SCMI between all the images is maximized.Using this measure,we registered three and four simulated magnetic resonance imaging(MRI)images using downhill simplex optimization to search for the optimal transformation parameters.Accuracy and validity of the proposed method for multiple-image registration are testified by comparing the results with that of two- image registration.Furthermore,the performance of the proposed method is validated by registering the real ultrasonic image sequence.     

Photoacoustic microscopy image resolution enhancement via directional total variation regularization

Photoacoustic microscopy(PAM) is recognized as a powerful tool for various microcirculation system studies. To improve the spatial resolution for the PAM images, the requirements of the system will always be increased correspondingly. Without additional cost of the system, we address the problem of improving the resolution of PAM images by integrating a deconvolution model with a directional total variation regularization. Additionally, we present a primal-dual-based algorithm to solve the associated optimization problem efficiently. Results from both test images and some PAM images studies validate the effectiveness of the proposed method in enhancing the spatial resolution. We expect the proposed technique to be an alternative resolution enhancement tool for some important biomedical applications.     

基于受激辐射信号的谱域光学相干层析分子成像方法

鉴于不同生理病理状态下组织复折射率实部的变化不大,传统光学相干层析(OCT)成像技术在分子特异性识别上存在先天不足.为此,本文提出了基于受激辐射信号的OCT成像方法,可在实现传统散射成像的同时,实现基于受激辐射信号的分子成像.在超高分辨率谱域OCT系统的基础上,通过增设光谱分光与调制抽运光支路,建立了基于单宽谱光源的抽运探测谱域OCT系统,详细推导了调制抽运下受激辐射信号的获取与成像公式.利用搭建的抽运探测谱域OCT系统,实现了瞬态受激辐射信号的相干探测.基于同时获取的受激辐射OCT信号和传统OCT信号,成功重构了氮化物粉末构建样品的基于受激辐射信号的分子对比OCT图像.     

ZnO-P2O5:Tb3+玻璃的热释光研究

采用高温熔融法制备了ZnO-P2O5：Tb^3＋玻璃,并以热释光为手段,研究了基质组成、Tb^3＋掺杂浓度、熔制气氛、Tb^3＋与其他稀土离子共掺等因素对ZnO-P2O5：Tb^3＋玻璃的发光中心、陷阱浓度及陷阱能级分布的影响。结果表明：ZnO含量的增加,使得与Zn^2＋配位的氧空位的数量增多,导致50-150℃低温区对应的陷阱浓度增加;还原气氛下,Tb^3＋掺杂后,一方面形成发光中心使得热释光强度提高,另一方面,可能由于不等价取代基质中的Zn^2＋离子产生新的缺陷使得陷阱能级加深;空气气氛下,大部分Tb^3＋被氧化成Tb^4＋,发光中心浓度降低;Ce^3＋,Eu^3＋,Dy^3＋,Nd^3＋,Pr^3＋和Er^3＋与Tb^3＋共掺时,陷阱能级深度与陷阱中心的电荷密度发生了不同程度的变化。     

声发射技术在铁路系统检测中的研究和应用

高速铁路的快速发展,给我国经济和社会发展带来了巨大的推动作用,同时对铁路系统的安全性提出了更高的要求。针对声发射技术在铁路系统安全检测中的研究和应用,介绍了声发射技术及其在检测应用中的优点,综述了目前国内外声发射技术在铁路系统检测研究中的情况,包括钢轨伤损检测、车轮伤损检测、轮轴轴承伤损检测、铁路结构安全监测以及车体材料安全监测等,特别针对钢轨裂纹伤损引起的钢轨断裂这一铁路安全中的主要事故,着重分析了声发射技术在钢轨裂纹伤损检测研究中的情况,并介绍了在高速铁路方面的应用探索。最后在上述分析总结的基础上,指出了声发射技术在铁路系统特别是高速铁路检测研究中的前景及研究难点。