平方阻尼项的力学振动问题论析

本文根据定常运动的临界情形的理论,对平方阻尼项的力学振动在大幅度振动情况下进行研究和探讨。得到了角速度的定量表述,并具体分析了力学振动系统的相平面轨迹的性质和特点及平衡点的物理性质。     

基于分形参数的B超图像纹理分析

利用离散分形布朗随机场模型对Ｂ超图像的分布特征进行顾分析和讨论。鉴于一般的图像不是完全的分形体,文中给出了计算分维数的尺度范围公式,根据上述模型和尺度范围公式,对正常肝脏和有癌变肝脏的两组Ｂ超图像的分维数进行了计算,结果表明在未考虑尺度范围时两组图像的分维数差别不大;而考虑了尺度范围时两幅图像的分维数就有明显的差别,即正常肝脏图像的分维数大于有癌变肝脏图像的分维数。     

用维数公式证明有关矩阵的(不)等式

把线性空间中的维数公式推广到一般的矩阵上，并应用它来证明了几个常见的有关矩阵秩的不等式和等式，其证明过程非常简捷。     

再论TH320型全洛氏硬度计的示值误差调整

TH320型全洛氏硬度计采用分段数字化调整的方法,有效克服了普通洛氏硬度计因示值线性不好而造成的调整困难,使示值调整变得简捷、方便。同时,全洛氏硬度计的每一个硬度范围段的示值误差调整是完全独立的,即调整某一个范围段的示值误差修正量对其他范围段示值的修正幅度毫无影响。如何利用手中的有限的标准块,修正标尺整个测试范围内的数据,该文通过实际数据的测试,进一步认识了TH320全洛氏硬度计在示值误差调整方面的特点。     

基于四阶累积量的近场源多参数联合估计

提出了一种近场窄带信源多参数联合估计新方法,通过所构造四阶累积量矩阵的特征值及其特征向量就可以直接获得近场源频率、方位及距离三维参数的联合估计,无须峰值搜索,适用于任意高斯噪声环境．与现有方法相比,所提方法有效地避免了阵列孔径损失,而且算法简单高效．仿真综合结果表明了新方法的有效性．     

多维层次聚集cube的可扩展存储结构

采用多维层次式B ＋树作为多维数据集的索引结构,并在此基础上创建了一种可扩展的存储结构——多维层次聚集cube(MH-cube).基于MH-cube的层次特性,可以高效地对多维数据集进行快速查询、数据更新与模式更新,分析表明MH-cube在性能上优越于其他cube.     

Heterogeneous Asymmetric Dynamic Conditional Correlation Model with Stock Return and Range

The paper considers the return and range model with dynamic conditional correlations (DCC). The paper suggests the new specifications for the asymmetric effects on log‐volatilities and dynamic correlations, combined with long‐run dependences. The new DCC model can be estimated by the quasi‐maximum likelihood method. Empirical analysis on Nikkei 225, Hang Seng and Straits Times indices shows the daily, weekly and monthly pattern of asymmetric effects. For the period including the global financial crisis, the new DCC model provides plausible one‐step‐ahead forecasts of the VaR thresholds, and yields positive economic values of switching from other DCC models. Copyright © 2013 John Wiley & Sons, Ltd.     

Financial volatility modeling: The feedback asymmetric conditional autoregressive range model

An implied assumption in the asymmetric conditional autoregressive range (ACARR) model is that upward range is independent of downward range. This paper scrutinizes this assumption on a broad variety of stock indices. Instead of independence, we find significant cross‐interdependence between the upward range and the downward range. Regression test shows that the cross‐interdependence cannot be explained by leverage effect. To include the cross‐interdependence, a feedback asymmetric conditional autoregressive range (FACARR) model is proposed. Empirical studies are performed on a variety of stock indices, and the results show that the FACARR model outperforms the ACARR model with high significance for both in‐sample and out‐of‐sample forecasting.     

Genetic and morphometric variation of the Blackcap (Sylvia atricapilla) on the Azores Archipelago reveals a recent range expansion

ABSTRACT

The Blackcap, Sylvia atricapilla, is one of the few passerine species that breeds in all the Macaronesian archipelagos. The sedentary habits of these populations contrast with the migratory populations from the Western Europe. However, little is known for Azorean populations. We assessed the phylogeography of populations from the Azores based on sequences of two mitochondrial genes and one nuclear gene in the Z-chromosome. We also analysed differences in eight morphometric characters from a total of 282 Blackcaps from all the Azores islands. Our results suggest the occurrence of historical and/or current gene flow among birds from all the islands. Blackcaps from the Azores are close relatives of those from Madeira and Portugal, indicating a recent range expansion to the Azores in the last 0.1 million years. The analysis of morphometric data showed a high morphological diversity among and within the islands, probably related to ecological traits.     

Small giants from Madagascan caves: autapomorphic giantism in the new cave-dwelling planthopper Tsingya clarkei gen. nov., sp. nov. (Hemiptera: Fulgoroidea: Meenoplidae)

A new giant cave-dwelling species of planthopper of the family Meenoplidae (Fulgoromorpha) is described from the Tsingy de Bemaraha National Park in western Madagascar, with information on its distribution and ecology. As the new species could not be placed in any of the previously described genera, a new genus is established. This is the first record of a cavernicolous meenoplid from the Afrotropical Region, and the second cave-dwelling Fulgoromorphan species from Madagascar. It is also the second example of island gigantism in the Fulgoromorpha from Madagascar.