资金流冲击、投资者情绪与股票流动性的异质性变化

利用我国A股样本股票2005~2016年的月度数据,分析了交易资金流对个股流动性的冲击效应,以及投资者情绪和股票个体特征在其中所起的作用。研究结果表明:个股交易资金流对其流动性具有显著负向冲击效应,随着交易资金流的增加,个股流动性会下降,而投资者悲观情绪在这种冲击中具有显著的放大效应;将资金流对流动性的冲击程度界定为股票流动性的敏感度并分析其异质性变化,结果表明收益率对情绪、账面市值比、规模因子更敏感,其流动性敏感度更高,更易受到资金流的冲击;融资融券制度加剧了交易资金流对股票流动性的冲击效应。

基于复杂网络异质性的节点重要性评估方法

对于复杂网络的结构特殊性,用加权拓扑熵为理论基础,提出了基于复杂网络结构异质性变化率的节点重要程度评估方法。首先,本文给出了复杂网络加权拓扑熵的概念,阐述了基于BBV网络的反向演化原理,其次,在反向演化原理的基础上提出了节点重要程度取决于网络结构异质性变化率的观点,并提出了网络割点的异质性变化率的计算方法;最后,以一个例子来说明节点重要程度的评估过程,并对特殊节点进行了处理分析。

Spatio-temporal Variation of Landscape Heterogeneity under Influence of Human Activities in Xiamen City of China in Recent Decade

Xiamen is an economically competitive and highly urbanized city along the coastal area of Fujian Province, China. The research on spatio-temporal variation of landscape heterogeneity under the influence of human activities is of great importance to the further study on the relationship of landscape pattern and ecological process. It is also crucial to the discovery of spatial variation and intensity distribution of human activities. The research analyzed the intensity of human impacts and the spatial variation features and dynamics of landscape patterns by introducing statistical theories and approaches. We analyzed spatio-temporal variation of landscape heterogeneity using the geostatistical techniques, such as semivariogram and Kriging interpolation.Results show that there is a higher correlation between landscape heterogeneity indexes and human impact index. Both the indexes show a moderate spatial autocorrelation as well as an obvious characteristic of anisotropy. From 1998 to 2008, the spatial differentiation of the changes in the intensity of human activities and the changes in landscape heterogeneity shows that the landscape patterns in Xiamen are closely related with the urban land utilization methods, the condition of traffic and geographical location and the physical geographical condition such as the terrain and the ecological environment. The process of urbanization has a significant impact on the urban landscape pattern.

Heterogeneity in supraglacial debris thickness and its role in glacier mass changes of the Mount Gongga

In the Tibetan Plateau, many glaciers have extensive covers of supraglacial debris in their ablation zones, which affects glacier response to climate change by altering ice melting and spatial patterns of mass loss. Insufficient debris thickness data make it difficult to analyze regional debris-cover effects. Maritime glaciers of the Mount Gongga have been characterized by a substantial reduction in glacier area and ice mass in recent decades. The thermal property of the debris layer estimated from remotely sensed data reveals that debris-covered glaciers are dominant in this region, on which the proportion of debris cover to total glacier area varies from 1.74% to 53.0%. Using a physically-based debris-cover effect assessment model, we found that although the presence of supraglacial debris has a significant insulating effect on heavily debris-covered glaciers, il accelerates ice melting on -10.2% of total ablation zone and produces rapid wastage of -25% of the debris-covered glaciers, leading to the similar mass losses between the debris-covered and debris-free glaciers. Widespread debris cover also facilitates the development of active terminus regions. Regional differences in debris-cover effects are apparent, highlighting the im- portance of debris cover for understanding glacier mass changes in the Tibetan Plateau and other mountain ranges around the world.

Urban Expansion and Spatiotemporal Relationships with Driving Factors Revealed by Geographically Weighted Logistic Regression

Urbanization improves our lives but also threatens human health and sustainable development. Revealing the spatiotemporal pattern of urban expansion and spatiotemporal relationships with driving forces, especially in terms of the ubiquitous and fast growing small city, is a crucial prerequisite to solving these problems and realizing sustainable development. Kunshan, China was used as a case study here. Eleven variables from four aspects covering physical, socioeconomic, accessibility and neighborhood were selected, and logistic regression and geographically weighted logistic regression modeling were employed to explore spatiotemporal relationships from 1991-2014. Results reveal that urban expansion in Kunshan shows an accelerating tendency with annual expansion from 2000-2014 four times higher than for 1991-2000. More importantly, the annual expansion rate of Kunshan of 28.42% in 2000-2014 is higher than that of a large city. Urban expansion and related factors have spatiotemporal varying relationships. From a global perspective, the closer to a city, town, main road and the higher the GDP, the more likely a region will undergo urbanization. Interestingly, the effect of population on urban expansion is decreasing, especially in developed areas, and the effect of distance to lake is enhanced. From a local perspective, the magnitude and even the sign of the coefficients vary across the study area. However, the range of the coefficient of GWLR is around that of the corresponding variable in LR, and the sign of most variables in GWLR is consistent with that of corresponding variables in LR. GWLR surpasses LR with the same explanatory variables in revealing regional differences and improving model reliability. Based on these findings, more attention should be given to small cities in China. Promoting the connotation of city culture and public services to realize New-type Urbanization and regional diversity policy in order to manage urban expansion scientifically are also recommended.

Variation in regrowth ability in relation to land-use intensity in three common grassland herbs

Aims Plant populations in managed grasslands are subject to strong selection exerted by grazing,mowing and fertilization.Many previous studies showed that this can cause evolutionary changes in mean trait values,but little is known about the evolution of phenotypic plasticity in response to land use.In this study,we aimed to elucidate the relationships between phenotypic plasticity—specifically,regrowth ability after biomass removal—and the intensity of grassland management and levels of temporal variation therein.Methods We conducted an outdoor common garden experiment to test if plants from more intensively mown and grazed sites showed an increased ability to regrow after biomass removal.We used three common plant species from temperate European grasslands,with seed material from 58 to 68 populations along gradients of land-use intensity,ranging from extensive(only light grazing)to very intensive management(up to four cuts per year).Important Findings In two out of three species,we found significant population differentiation in regrowth ability after clipping.While variation in regrowth ability was unrelated to the mean land-use intensity of populations of origin,we found a relationship with its temporal variation in Plantago lanceolata,where plants experiencing less variable environmental conditions over the last 11 years showed stronger regrowth in reproductive biomass after clipping.Therefore,while mean grazing and mowing intensity may not select for regrowth ability,the temporal stability of the environmental heterogeneity created by land use may have caused its evolution in some species.

Overcoming maladaptive plasticity through plastic compensation

Most species evolve within fluctuating environments, and have developed adaptations to meet the challenges posed by environmental heterogeneity. One such adaptation is phenotypic plasticity, or the ability of a single genotype to produce multiple environmentally-induced phenotypes. Yet, not all plasticity is adaptive. Despite the renewed interest in adaptive phenotypic plas- ticity and its consequences for evolution, much less is known about maladaptive plasticity. However, maladaptive plasticity is likely an important driver of phenotypic similarity among populations living in different environments. This paper traces four strategies for overcoming maladaptive plasticity that result in phenotypic similarity, two of which involve genetic changes （standing genetic variation, genetic compensation） and two of which do not （standing epigenetic variation, plastic compensation）. Plastic compensation is defined as adaptive plasticity overcoming maladaptive plasticity. In particular, plastic compensation may increase the likelihood of genetic compensation by facilitating population persistence. We provide key terms to disentangle these aspects of phenotypic plasticity and introduce examples to reinforce the potential importance of plastic compensation for under- standing evolutionary change