企业员工社会网络度中心性对个人绩效的影响——度异质性的调节作用

内嵌在经济活动中的社会关系对企业员工绩效的影响是绩效研究的重点之一,近年来的实证研究却并未获得一致的结论。为揭示网络结构与员工绩效间的关系,本文引入一个新的概念——度异质性。度中心性反映个体在网络中的绝对权利大小,而度异质性反映了这种权利在网络中的分布。利用2009年西安调查数据研究发现,正式网络中的度中心性没有对员工个人绩效产生影响;非正式网络度中心性对个人绩效产生显著正向影响,且受到度异质性的反向调节作用。

中国制造业出口技术结构与就业性别歧视关系研究——基于区域和要素密集度异质性视角的实证检验

时值中国经济转型关键时期,在实现出口技术对发达经济体追赶与赶超目标下,维持男女就业良性平稳增长是确保经济发展方式稳定转变的必要条件,也是实现社会长治久安的重要基础要求。为此文章借助动态面板差分GMM估计法,从区域和要素密集度异质性视角揭示出口技术结构与就业性别歧视两者之间的关系,结果表明:首先不同区域出口技术结构水平不同对就业性别歧视的作用效应不同,东部过高和西部过低的出口技术结构水平使得其出口技术水平提升均会加剧就业性别歧视,仅有中部保持在中等区间的出口技术结构水平提升有利于缓解就业性别歧视;其次不同区域两类要素密集型出口技术结构变动对就业性别歧视的作用力度不同,东部资本密集型出口技术结构提升对其的负向作用大于劳动密集型,西部则相反,而中部劳动密集型出口技术结构水平提升对就业性别歧视的正向作用大于资本密集型;最后城镇化和工业化水平提升,能够缓解就业性别歧视,劳动力需求和人力资本的作用则存在区域差异。

基于节点度异质性惩罚的链路预测方法

针对大部分现存的链路预测方法仅关注规则网络以及偏好连接现象而导致在稀疏网络获得低质量性能,提出一种节点度异质性惩罚的链路预测框架(NDHP),该框架最优预测准确度与网络拓扑特征有密切关联。首先,计算整个网络节点度获得所有节点对的度异质性相似度;其次,采用惩罚节点度较大机制去惩罚度异质性权重较大的节点抑制节点间差异;最后,通过可调参数将平均节点聚类系数和平均最短路径分别和基于度异质性惩罚框架相关联,获取网络结构信息来弥补网络稀疏信息不足,并提出基于节点度异质性惩罚的平均聚类系数指标(NDHP_AC)和基于节点度异质性惩罚的平均距离指标(NDHP_AD)。此外,在8个真实无向无权网络上与最近代表性的方法相比较,所提两个指标在预测缺失链接和鲁棒性两方面性能优于基准指标。尤其在高度稀疏网络中,所提指标的AUC和AUPR分别最大提高了15.3%和8.6%。

成本上升、外需疲软与制造业技术复杂度演进——基于内外资和要素密集度异质性视角

制造业技术复杂度的升级与赶超是我国经济发展方式转变的根本途径与核心内容,那么制造业当前面临的两大困境(成本上升与外需疲软)会对中国制造业技术复杂度动态演进产生什么样的影响呢?本文通过拓展林毅夫的研究方法,构建了判断企业技术复杂程度的微观识别工具,并借助965992组微观企业数据,在判定2000-2007年企业技术复杂度的基础上,从内外资和要素密集度异质性视角探索上述问题的答案。得到的结论与启示主要有:首先内资制造业技术复杂度赶超呈现显著的"逆水行舟"特征,内外资企业在技术复杂度动态演进过程中具有显著的"赶超惰性";其次外需疲软会改变资本密集型内资企业技术复杂度演进的原有"轨迹",对其他类型企业的影响不明显,非要素型成本上升给制造业技术复杂度深化带来的"损害"大于要素型成本上升;最后资本积累和技术复杂度演进的"沉没成本"对制造业技术复杂度具有显著的促进作用,现有的补贴制度并不具备调节制造业技术复杂度升级和赶超的功能。

外商直接投资独资化挤出国内投资吗?:基于工业行业要素密集度异质性的视角

近年来我国外商直接投资(FDI)日益明显的独资化趋势引起了学者的关注。文章阐述了外商独资相对合资、合作对国内投资的挤入挤出效应差别和影响机制,并利用工业领域37个主要行业2003~2015年的面板数据进行了实证检验。对全行业及资本技术密集型行业而言,当期的外商独资对国内投资有挤出作用,但滞后一期的外商独资则会减弱FDI对国内投资的负向作用,挤入国内投资;而在劳动密集型行业,外商直接投资对国内投资的挤入挤出效应并不受投资方式的影响。

出口对中国制造业工资差距的影响研究——基于要素密集度和所有制异质性视角的S-S定理检验

借助中国2000-2007年制造业27个行业120余万组微观企业数据,基于拓展后的Feenstra&Hanson(2003)模型,运用系统GMM估计从要素密集度和所有制异质性视角验证S-S定理在中国的适用性。得到结论与启示主要有:首先以往认为S-S定理在中国不适用的推断是不准确的,S-S定理关于发展中国家的基本观点与中国劳动密集型制造业出口效应的估计结果是吻合的;其次提高高端熟练劳动力的供给数量和加大后发型企业技术赶超能够有效地降低中国制造业工资差距;最后企业所得税对制造业工资差距表现出一定的调节功能,补贴则并未表现出显著的调节功能。

社会资本对区域创新能力的影响——兼论地区差异和空间效应的分析

培育创新能力、实现创新驱动发展是保持区域竞争优势的关键所在,社会资本通过增进主体合作、促进知识溢出、营造创新环境塑造区域创新能力。选用2010—2020年省级面板数据,结合经济距离矩阵和空间杜宾模型研究社会资本如何影响区域创新能力。研究发现,社会资本对区域创新能力具有正效应,并同时存在维度异质性与区域异质性,其中结构维度社会资本具有更加显著的促进效用。空间效应分析发现,邻近地区社会资本的积累同样有利于本地创新能力的提高。区域异质性检验发现,社会资本在经济发达地区具有更加强劲的创新效应,而经济欠发达地区的社会资本对创新能力呈现抑制作用。因此,各地区要重视本地社会资本的积累,积极构建通达的社会网络结构,充分发掘社会资本在提高创新能力中的优势。

Seismic wave propagation in Kelvin visco-elastic VTI media

In this article,under the assumption of weak anisotropy and weak attenuation, we present approximate solutions of anisotropic complex velocities and quality-factors for Kelvin visco-elastic transverse isotropy（KEL-VTI） media,based on the complex physical parameter matrix.Also,combined with the KEL-VTI media model,the propagation characteristics of the qP-,qS V-,and qSH-wave phases and energies are discussed.Further, we build a typical KEL-VTI media model of the Huainan coal mine to model the wave propagation.The numerical simulation results show that the PP- and PSV-wave theoretical wave-fields are close to the wave-fields of three-component P- and converted-waves acquired in the work area.This result proves that the KEL-VTI media model gives a good approximation to this typical coalfield seismic-geologic conditions and is helpful to the study of attenuation compensation of multi-component seismic data.

Electronic Structures and Thermoelectric Properties of Two-Dimensional MoS2/MoSe2 Heterostructures

Thermoelectric properties of bulk and bilayer two-dimensional （2D） MoS2/MoSe2 het- erostructures are investigated using density functional theory in conjunction with semi- classical Boltzmann transport theory. It is predicted that the bulk 2D heterostructures could considerably enhance the thermoelectric properties as compared with the bulk MoSe2. The enhancement originates from the reduction in the band gap and the presence of interlayer van der Waals interactions. We therefore propose the 2D MoS2/MoSe2 heterostructures as a possible candidate material for thermoelectric applications.

Spatial-temporal Heterogeneity of Industrial Structure Transformation and Carbon Emission Effects in Xuzhou Metropolitan Area

Employing decoupling index and industrial structure characteristic bias index methods, this study analyzed the spatial-temporal characteristics of industrial structure transformations and their resulting carbon emissions in the Xuzhou Metropolitan Area from 2000 to 2014, with a focus on their relationships and driving factors. Our research indicates that carbon emission intensity from industrial structures in the Xuzhou Metropolitan Area at first showed an increasing trend, which then decreased. Furthermore, the relationship between emissions and industrial economic growth has been trending toward absolute decoupling. From the perspective of the center-periphery, the Xuzhou Metropolitan Area formed a concentric pattern, where both progress towards low emissions and the level of technological advancement gradually diminished from the center to the periphery. In terms of variation across provinces, the ISCB index in the eastern Henan has decreased the slowest, followed by the southern Shandong and the northern Anhui, with the northern Jiangsu ranking last. During this period, resource-and labor-intensive industries were the primary growth industries in the northern Anhui and the eastern Henan, while labor-intensive industries dominated the southern Shandong and capital-intensive industries dominated the northern Jiangsu. In terms of city types, the spatial pattern for industrial structure indicates that recession resource-based cities had higher carbon emission intensities than mature resource-based cities, followed by non-resource-based cities and regenerative resource-based cities. Generally, the industrial structure in the Xuzhou Metropolitan Area has transformed from being resource-intensive to capital-intensive, and has been trending toward technology-intensive as resource availability has been exploited to exhaustion and then been regenerated. Industrial structure has been the leading factor causing heterogeneity of carbon emission intensities between metropolitan cities. Therefore, the key to optimizing the industrial structure and layout of metropolitan areas is to promote industrial structure transformation and improve the system controlling collaborative industrial development between cities.

Spatial heterogeneity in a deep artificial lake plankton community revealed by PCR-DGGE fingerprinting

To explore the spatial heterogeneity of plankton communities in a deep artificial lake （Songhua Lake, China）, samples were collected at seven sites. Samples were investigated by denaturing gradient gel electrophoresis （DGGE） analysis of the PCR-amplified 16S and 18S rRNA genes and specific bands were sequenced. Cluster analysis of the DGGE profiles revealed that all of the samples grouped into two distinct clusters, in accordance with sampling site; while in each cluster, the divergence of sub-clusters correlated with sampling depth. Sequence analysis of selected dominant DGGE bands revealed that most sequenced phylotypes （84%） exhibited 〉97% similarity to the closest sequences in GenBank, and were affiliated with ten common freshwater plankton phyla （Proteobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria, Bacillariophyta, Pyrrophyta, Cryptophyta, Ciliophora, Stramenopiles, and Rotifera）. Several of these groups are also found worldwide, indicating the cosmopolitan distribution of the phylotypes. The relationships between DGGE patterns and environmental factors were analyzed by redundancy analysis （RDA）. The results suggested that, total nitrogen, nitrate, nitrite, temperature were strongly correlated with the variation ammonia, and CODMn concentrations, and water in plankton composition.

Modeling of forest soil and litter health using disturbance and landscape heterogeneity indicators in northern Iran

This paper focuses on the indicators of soil and litter health, disturbance, and landscape heterogeneity as a tool for prediction of ecosystem sustainability in the northern forests of Iran. The study area was divided into spatial homogenous sites using slope, aspect, and soil humidity classes. Then a range of sites along the disturbance gradient was selected for sampling. Chemical and physical indicators of soil and litter health were measured at random points within these sites. Structural equation modeling(SEM) was applied to link six constructs of landscape heterogeneity, three constructs of disturbance(harvest, livestock, and human accessibility), and soil and litter health. The results showed that with decreasing accessibility, the total N and organic matter content of soil increased and effective bulk density decreased. Harvesting activities increased soil organic matter. Therefore, it is concluded that disturbances through harvesting and accessibility inversely affect the soil health. Unexpectedly, it was found that the litter total C and C:N ratio improved with an increase in the harvest and accessibility disturbances, whereas litter bulk density decreased. Investigation of tree composition revealed that in the climax communities, which are normally affected more by harvesting activities, some species like Fagus orientalis Lipsky with low decomposition rate are dominant. The research results showed that changes in disturbance intensity are reflected in litter and soil indicators, whereas the SEM indicated that landscape heterogeneity has a moderator effect on the disturbance to both litter and soil paths.

Riparian plant community structure and assembly processes differed by variations in riverbank curvatures:implications for restoring habitats along the Three Gorges Reservoir

A meandering riverbank plays a vital role in maintaining natural river ecosystems,providing habitats for riparian vegetation.However,dams have significantly altered riverbank shapes.To restore the riparian ecosystems,it is imperative to understand how different riverbank curvatures influence them.This study aims to uncover the ecological impacts of riverbank curvature on the structure and assembly process of plant communities in the riparian zone of the Yangtze River,regulated by the Three Gorges Dam(TGD)in China.We categorized the riparian zones into four types:cove,lobe,wavy and linear shapes.We documented the composition and diversity of riparian plant communities.Our findings revealed that wavy and cove riverbanks exhibited greater species diversity(with Shannon–Wiener diversity index values 1.5×higher)compared to communities along linear riverbanks.Furthermore,the analysis of functional traits indicated that wavy riverbanks promoted the differentiation of plant functional traits,thus enhancing ecosystem functions,with functional dispersion index(FDis)values 1.3 times higher than those of linear riverbanks.Significant variations in the assembly of riparian communities were also observed among different riverbanks,with standardized effect size(SES)values indicating a higher degree of niche differentiation in cove riverbanks(SES=0.4)compared to linear riverbanks(SES=–0.6).These results highlight the ecological importance of diverse riverbank curvatures in influencing the diversity,structure and assembly of riparian communities along the waterway.In summary,this study underscores the necessity of maintaining or restoring various natural morphological curvatures when rehabilitating riparian communities along rivers impacted by human activities.

股票还是彩票:博彩偏好与IPO之谜

本文试图通过个人投资者的"赌性"——博彩偏好来解释我国IPO的诸多异象,即上市首日暴涨;长期收益反转;换手率超高等。基于累积前景理论,本文从理论上阐述并从实证上验证了博彩偏好对IPO首日暴涨和长期收益反转有着显著的影响。以我国证券市场2009-2012年所有发行新股作为研究样本,实证结果表明博彩偏好每增加一个标准差,首日涨幅显著提高5.5%,并且当市场环境较好时,投资者的乐观情绪会使博彩偏好的效应增强。从长期来看,博彩偏好越强的公司,长期风险溢酬为负,机构投资者继续持有新股的可能性越低。

Soil Macrofaunal Communities are Heterogeneous in Heathlands with Different Grazing Intensity

Moderate grazing by cattle increases the heterogeneity of soil and vegetation. This has been suggested as an ecologically sustainable mean of managing natural environments endangered by tree encroachment, such as heathlands. Our study was performed to test the impact of grazing intensity on soil macroinvertebrate communities in heterogeneous landscapes in a private property eligible to the Natura 2000 European Network of Special Protection Areas within the Brenne Natural Regional Park （Indre, ~rance）. We sampled macroinvertebrates along a broken line crossing 5 different land-use types, from pasture to pine forest, passing through a besom heath （Erica scoparia） heathland at 3 levels of cattle pressure. We hypothesized that： i） litter-dwelling （mostly arthropods and mollusks） and soil-dwelling macroinvertebrates （mostly earthworms） would respond in an opposite manner to various grazing intensities, and ii） intermediate cattle pressure （pastured heath） would increase soil and community heterogeneity. The results supported the first hypothesis, which was explained by land-use impacts mediated by soil properties. However, our results supported only partly the second hypothesis since maximum dissimilarity （whether in the composition of soil macroinvertebrate communities or in soil features） was observed in only one out of the two pastured heaths where cattle pressure was intermediate.

Temperature dependent Raman and photoluminescence of vertical WS2/MoS2 monolayer heterostructures

Heterostructures from two-dimensional transition-metal dichalcogenides MX2 have emerged as a hot topic in recent years due to their various fascinating properties. Here, we investigated the temperature dependent Raman and photoluminescence （PL） spectra in vertical stacked WS2/MoS2 monolayer heterostructures. Our result shows that both E^g and Alg modes of WS2 and MoS2 vary linearly with tem- perature increasing from 300 to 642 K. The PL measurement also reveals strong temperature dependencies of the PL intensity and peak position. The activation energy of the thermal quenching of the PL emission has been found to be equal to 69.6 meV. The temperature dependence of the peak energy well follows the band- gap shrinkage of bulk semiconductor.

Homogenization for Periodic Heterogeneous Materials with Arbitrary Position-Dependent Material Properties

We present a rigorous homogenization approach for elcient computation of a class of physical problems in a one-dimensional periodic heterogeneous material. This material is represented by a spatially periodic array of unit cells with a length of More specifically, the method is applied to the diffusion, heat conduction, and wave propagation problems. Heterogeneous materials can have arbitrary position-dependent continuous or discontinuous materials properties （for example heat conductivity） within the unit cell. The final effective model includes both effective properties at the leading order and high-order contributions due to the microscopic heterogeneity. A dimensionless heterogeneity parameter ~ is defined to represent high-order contributions, shown to be in the range of [-1/12, 0], and has a universal expression for all three problems. Both effective properties and heterogeneity parameter 13 are independent oft, the microscopic scale of heterogeneity. The homogenized solution describing macroscopic variations can be obtained from the effective model. Solution with sub-unit-cell accuracy can be constructed based on the homogenized solution and its spatial derivatives. The paper represents a general approach to obtain the effective model for arbitrary periodic heterogeneous materials with position-dependent properties.

Dielectric and insulating properties of SrTiO_3/Si heterostructure controlled by cation concentration

SrTiO3 films with different cation concentration were deposited on Si（001） substrates by oxide molecular beam epitaxy. An amorphous layer was observed at the interface whose thickness depends on the oxygen pressure and the substrate temperature during growth. Although lowering the oxygen vacancy concentration in SrTiO3 led to better insulating performance as indi- cated by the lowered leakage current density of the heterostructure, the dielectric performance was deteriorated because of the thickened interracial layer that dominated the capacitance of SrTiO3/Si heterostructure. Instead of adjusting the oxygen vacan- cy concentration, we propose that controlling the film cation concentration is an effective way to tune the dielectric and insu- lating properties of SrTiO3/Si at the same time.

Stiffness heterogeneity-induced double-edged sword behaviors of carcinoma-associated fibroblasts in antitumor therapy

Carcinoma-associated fibroblasts(CAFs) function as a double-edged sword in tumor progression. However,factors affecting the transition between tumor promotion and inhibition remain to be investigated. Here, we found that the transition was determined by stiffness heterogeneity of the tumor stroma in which tumor cells and CAFs were grown.When tumor cells were grown on a rigid plastic substrate,supernatants from CAFs inhibited the cytotoxic effects of 5-fluorouracil. In contrast, when tumor cells were grown on a soft substrate(5.3 kPa), supernatants from CAFs grown on a soft substrate increased the cytotoxicity of 5-fluorouracil. The diverse effects of CAFs were mediated by mechanotransduction factors, including stroma stiffness-induced cytokine expression in CAFs and signal transduction associated with stress fiber formation of CAFs. Moreover, we found that the cytokine expression in CAFs was regulated by nuclear Yesassociated protein, which changed according to cell stiffness,as characterized by atomic force microscopy. Overall, these findings suggested that modulating the mechanotransduction of the stroma together with CAFs might be important for increasing the efficacy of chemotherapy.