面向可扩展集群环境的快速虚拟机迁移方法

在集群环境下,为了提高虚拟机Xen的迁移效率,提出了一种面向可扩展集群环境的快速可靠的虚拟机迁移方法.通过在分布式文件系统GlusterFS中增加Heartbeat监测模块,实时监测集群环境中物理机节点的加入与退出,动态创建或修改GlusterFS文件系统的配置文件.为了使GlusterFS文件系统能够自动管理节点,设...     

城市化背景下中国虚拟水流动空间变化特征及其驱动因素研究

为了解决日益增涨的水资源需求导致的缺水问题, 从投入产出视角进行合理的虚拟水调动已成为缓解地区水资源压力的新途径。基于1997 年与2010年区域间投入产出表以及水资源公报数据, 构建虚拟水多区域投入产出计算模型, 并细化用水产业, 计算得出区域间虚拟水相互交换关系与转移量。同时, 将区域虚拟水空间流动量与区域间人口迁移和产业转移特征进行关联分析, 结果表明, 研究时段的中国城市化进程中, 虚拟水主要由内陆地区向沿海地区输送, 且区域间人口迁移特征与虚拟水空间转移特征的关联性很强。人口流动带动消费品转移, 进而引起虚拟水流动, 产业空间转移通过生产要素的空间转移与聚集, 持续影响虚拟水的流动量和流动方向。因此, 基于中国城市化特征, 未来区域发展应考虑结合实体水调动以及虚拟水流动与人口迁移和产业转移的关联关系, 保证经济活动密集区域的水资源供给。     

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.     

Arthropods associated with nests of Cacicus sp. and Psarocolius sp. (Passerida: Icteridae) in varzea forest near the meeting of the rivers Negro and Solimões (Central Amazonia,Brazil) at high water

We analysed the arthropod fauna from nine nests of Cacicus sp. and nine nests of Psarocolius sp. (Passerida: Icteridae), in the varzea forest of Central Amazonia, Brazil, during high water, establishing these nests as one of the probable refuges for several arthropods performing vertical migration during periods of flooding and high water, besides discussing the role of these arthropods in the nests. We also evaluate the effectiveness of the extraction of arthropods from nests using an apparatus based on the Berlese–Tullgren funnel. We obtained 15,128 arthropods from three subphyla, five classes and 16 orders. The nests were shown as complex ecosystems sheltering groups from different functional and trophic categories and revealed striking differences from those of terra firma, remarkably in Blattaria, Arachnida and Pseudoscorpiones. The increasing volume of the funnel and time of heat exposure was shown to be appropriate for extraction of the arthropods from the bulky nests of these birds.     

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.     

氮在饱和土壤层中迁移转化特征研究

通过室内土柱实验，研究了氮在包气带不同土质层中饱水条件下迁移转化的特征；建立了一维饱和土壤层中氮迁移的预测模型。研究结果表明：氮对地下水的污染因子是硝酸根；土质是影响土壤氮迁移的重要因素之一。在迁移转化环境条件相同的情况下，随着土壤颗粒中粘粒含量的增加，土层的净化容量增加，其中土层的反硝化反应速率的增加是硝酸根去除的决定性因素。     

废胎胶粉复合改性高黏沥青复配体系

为研究胶粉复合改性高黏沥青复配体系的显著性影响程度及机理,选择废胎胶粉种类、废胎胶粉掺量、SBS掺量、补强剂掺量、增塑剂掺量5个试验变量制备复合改性高黏沥青。设计五因素四水平正交试验,通过极差分析研究各因素对改性沥青针入度、延度、软化点、黏韧性和60 ℃动力黏度5个技术指标的影响。结果表明：补强剂掺量对针入度影响最大,增塑剂次之;胶粉掺量对60 ℃动力黏度影响最大,与补强剂协同作用于软化点;SBS掺量对延度影响最大;粘韧性无明显规律。综合考虑各因素,得出胶粉合金添加剂的较优制备方案是：选择卡车轮胎胶粉,各物料以质量分数计,废胎胶粉：SBS：补强剂：增塑剂=100:24:10:19。较优制备方案下,通过双螺杆挤出工艺制备胶粉合金高黏添加剂,且掺量为25%时,废胎胶粉复合改性高黏沥青表现出优秀的高低温性能,沥青黏度和路用性能明显提升。