“流空间”视角下淮河生态经济带网络结构研究

论文以“流空间”为研究视角,构建了淮河生态经济带人口、物流、资金及信息流联系网络,结合社会网络分析揭示了区域联系网络特征。研究发现,区域内资金和信息联系高于人口和物流联系,徐州市各类要素联系总强度都较高且3种中心性指标均为最高,为区域要素联系的枢纽性城市;扬州市与其附近单元联系紧密因而要素联系总强度也较高但与其他单元联系强度较弱。淮河生态经济带28个单元可划分为4个凝聚子群,由江苏板块和山东板块组成的子群内部凝聚力最强且对其他子群具有相对较强的凝聚力,其他子群内部凝聚力较弱且对其他子群影响也较弱。淮河生态经济带城市可划分为核心城市、次核心城市、一般城市和边缘城市,其中核心城市为徐州,次核心城市为阜阳、蚌埠和淮安,边缘城市往往在区域内处于边缘位置且本身经济发展水平较低。最后,基于区域网络结构特征提出政策建议,以期为淮河生态经济带争创“中国发展第四极”提供有益指导。

从“流空间”视角看加强政府对进城农民工的制度安排

改革开放的环境、市场经济体制与机制形成了巨大的人力资源"流空间",越来越多的农民工涌向城市,成为诸多行业和城市化进程的主力军。文章分析了"流空间"产生的背景,剖析了"流空间"的概念,并深入探讨了进城农民工面临的问题及产生问题的原因,指出了政府应在完善法律法规体系、建立面向农民工的社会保障制度、提高农民工的组织化程度等方面,开展对进城农民工的制度安排。

基于“流空间”理论的南沙区域交通枢纽建设策略

为优化交通区位、探讨南沙区域发展动力以及发展方向,首先,从“流空间”理论分析出发,结合“流空间”与城市实体空间的联系,借助手机信令数据以及地铁、道路流量等交通流数据,分析南沙区域“流空间”的主要特征;其次,通过对比交通流向、用地开发等数据,验证南沙区域交通枢纽具有交通流量规模仍较小、跨区就业少而通勤圈仍然相对独立以及枢纽流量小而周边开发少等特征,总结出南沙区域交通枢纽建设存在处于交通网络末梢、与中心城区的交互少且缺乏中心城区支撑、枢纽功能引导不足等问题;最后,提出了大湾区南沙区域交通枢纽建设应从强化其区域交通网络的地位,融入中心城区通勤圈以及加强交通枢纽周边开发等建议。

基于空间要素流动的海岸带规划响应机制与路径

海岸带是具有陆海双重属性的特殊地理区域,通过要素跨系统、多维度的流动实现空间演变。深入掌握海岸带空间演变规律,对于推动陆海协调发展具有重大意义。本文引入“空间要素流动”相关理论,聚焦陆海统筹背景下的海岸带空间要素流动概念,探索其流动特征,落实于规划与管理。首先,概述了陆海统筹研究背景,并梳理了“流空间”、区域要素流动以及地理流研究等相关理论;其次,从概念界定、要素分类和空间格局等方面,阐述了海岸带空间要素流动的理念内涵及其空间格局分布;最后,基于流动耦合特点,探讨海岸带规划响应机制和路径,旨在为实现陆海协调发展提供理论支撑。

“流空间”视角下区域空间结构研究进展

通过对国外近几年关于"流空间"视角下区域空间结构研究的文献梳理,发现研究领域集中在区域中心性测度方法,从功能性角度识别多中心空间结构,传统腹地和网络腹地的划分以及中心地理论、城市网络理论和引力模型等理论验证四个方面。四个方面的研究深入都与"流"类型及其测度方法演变密切相关。不同类型的"流"数据在区域空间结构研究中起到了重要推动作用,尤其是手机信令数据、互联网数据、手机通话数据等大数据能更好地反映区域城市之间的空间相互作用,为"流空间"视角下的区域空间研究提供了新的机遇。以"物流"数据测度的"流"分析、整合大数据和传统数据、进一步认识不同类型"流"差异及适用环境将是未来的研究方向。

基于提升空间“辐射力”的城市节点更新策略研究——以重庆巫山神女市场改造为例

城市商业节点作为城市发展的重要引擎,其辐射效应对于区域经济发展具有重要意义。当前众多老城区节点因环境恶劣、功能滞后成为了城市中的“失落空间”,不仅自身活力不足,还严重制约着周边地区的发展。该文以重庆巫山县神女市场改造为例,以提升空间“辐射力”为目标,基于“增长极”理论和“流空间”理论,提出了集中生产要素、空间赋能增效、整序空间结构、建构作用路径四个更新策略,并对环境、文化、公共空间以及交通的改造提升措施进行了探讨,可为城市节点更新提供新的视角和方法。

Spatial Differences in the Response of Runoff to Climate and Land Use Changes in the Yiluo River Basin

Accurately identifying the spatial differences in the response of regional runoff to climate and land use changes can clarify the mechanism of regional runoff changes and provide a scientific basis for adopting the appropriate water resource protection policies.In this study,based on the Budyko theory,we quantitatively evaluated the spatial differences in the response of runoff to climate and land use changes in the Yiluo River Basin after 2000;calculated the sensitivity of runoff changes to precipitation(P),potential evapotranspiration(E_(0))and land use changes;and quantified the contributions of those three factors to runoff changes.The findings revealed that with decreasing elevation,precipitation gradually decreases,potential evapotranspiration gradually increases,and runoff gradually decreases in the Yiluo River basin.Influenced by the population density,both cultivated land and construction land are widely distributed with the middle and lower reaches of the basin,while the upper reaches are dominated by forest land.Compared with the base period(1985-1989),precipitation and potential evapotranspiration in the watershed during the change period(2000-2017)basically showed decreasing and increasing trends,respectively,with obvious spatial differentiation.P increased significantly in the upper reaches of the Yi River,with an average of 35.2 mm(-83.8-84.7 mm),while P increased and decreased in the other five subbasins,but the decreasing trend was more prominent.Among the subbasins,the upper and middle reaches of the Luo River showed the largest reductions in P,with an average of-34.2 mm(-145.9-20.6 mm),whereas the middle reaches of the Yi River showed the smallest reduction in P,with an average of-10.9 mm(-84.2-59.5 mm).The E_(0)in the different regions during the change period showed an increasing trend,and the increase in E_(0)gradually decreased from the upper reaches to the lower reaches.The E_(0)in the upper reaches of the Luo River showed the largest change,with an average of 45.3 mm(38.2-48.3 mm),while the lower reaches of the Yiluo River showed the smallest change,with an average of 7.3 mm(-3.2-17.1 mm).Land use changes were primarily from cultivated to construction land in the middle and lower reaches.Runoff changes were positively correlated with precipitation changes and negatively correlated with potential evapotranspiration and land use changes.The absolute values of the sensitivity coefficients of runoff to these environmental factors decreased with lower altitude,indicating a reduced responsiveness of the basin runoff under a warming and drying climate trend.Reductions in precipitation and changes in potential evapotranspiration have led to reductions in runoff ranging from 4.7 to 17.4 mm and from 0.7 to 9.1 mm,respectively,while land use changes led to corresponding runoff reductions of 23.0 to 46.5 mm,suggesting that land use changes are more likely to trigger runoff changes in the basin than climatic fluctuations.Given the dominance of cultivated land,especially in the middle and lower reaches,and the region’s high susceptibility to human activities,there has been a significant reduction in runoff in recent years.The contribution of land use change to the runoff reduction in the Yiluo River Basin was greater at lower elevations,up to 86.1%,while climatic effects were more significant at higher elevations,up to 27.8%.Therefore,promoting the implementation of projects such as water ecological restoration and returning farmland to forests are of great significance to curb the over-exploitation of groundwater,to formulate scientific management and scheduling policies in order to realize the transformation of the water balance in the river basin from a non-steady state to a steady state,and to promote the integrity of the ecosystem of the lower reaches of the Yellow River and ensure its sustainable development.

On Self-dual 4-dimensional Pseudo-Riemannian Manifolds

For a 4-dimensional Riemannian manifold(M,g),Atiyah et al.in[Proc.Roy.Soc.London Ser.A,1978,362(1711):425-461]used the kernel of twistor operator D to construct a distribution V(D)on the dual bundle of the anti-self-dual spinor bundle on M.Now V(D)forms an almost complex structure on dual bundle.Moreover,they showed that this almost complex structure is integrable if and only if M is self-dual.In this paper,we extend the construction of V(D)to 4-dimensional pseudo-Riemannian manifolds of signature(2,2).And we give a new method to prove the curvature condition in the integrability condition of V(D).Using this new method,we study the integrability conditions and structure of V(D)when the signature of g is(2,2).

Characteristic analysis of 1.06μm long-cavity diode lasers based on asymmetric waveguide structures

In long-cavity edge-emitting diode lasers,longitudinal spatial hole burning(LSHB),two-photon ab⁃sorption(TPA)and free carrier absorption(FCA)are among the key factors that affect the linear increase in out⁃put power at high injection currents.In this paper,a simplified numerical analysis model is proposed for 1.06μm long-cavity diode lasers by combining TPA and FCA losses with one-dimensional(1D)rate equations.The ef⁃fects of LSHB,TPA and FCA on the output characteristics are systematically analyzed,and it is proposed that ad⁃justing the front facet reflectivity and the position of the quantum well(QW)in the waveguide layer can improve the front facet output power.

站-城视角下长三角高铁网络“流”空间结构特征研究

站-城关系是我国高铁网络快速发展中的一个关键空间治理问题,而当前高铁网络“流”空间研究中针对站-城关系特征的研究相对较少。为此,基于城市和高铁站点两个尺度空间分析单元,利用复杂网络理论与方法,分析了长三角高铁网络发展的“流”空间特征。研究结果表明:(1)从城市尺度来看,上海市、南京市、杭州市以及合肥市在高铁网络中处于核心地位。长三角地区被划为4个子网络,反映了高铁网络联系的不同地区紧密性特征。(2)从站-城关系的分析视角来看,一个城市中多站点特征总体可归纳总结为4种类型,并且多数城市一般只有一个高铁站点处于核心地位,且核心站点的类型存在较大差异。因此,本研究建议高铁站点地区发展应从统筹城市网络和站-城关系两个视角进行综合考虑。结论对于高铁网络“流”空间的多尺度和跨尺度空间特征分析具有一定的参考价值。

Flow equation and similarity criterion during centrifugal casting in micro-channel

Liquid metal filling flow process in the microscale during the centrifugal casting process was studied by means of similar physical simulation. The research was focused on derived similarity criterion. Based on the traditional flow equations, the flow equation and the Bernoulli＇s equation for liquid metal flows in micro-scale space were derived, which provides a mathematical model for numerical simulation of micro-scale flow. In the meanwhile, according to the micro-flow equation and the similarity theory, the similarity criterion for the physical simulation of the mold filling behaviors was presented under centrifugal force field, so as to achieve the visual observation and quantitative analysis of micro-flow process.

INTERNET TRAFFIC DATA FLOW FORECAST BY RBF NEURAL NETWORK BASED ON PHASE SPACE RECONSTRUCTION

Characteristics of the Internet traffic data flow are studied based on the chaos theory. A phase space that is isometric with the network dynamic system is reconstructed by using the single variable time series of a network flow. Some parameters, such as the correlative dimension and the Lyapunov exponent are calculated, and the chaos characteristic is proved to exist in Internet traffic data flows. A neural network model is construct- ed based on radial basis function （RBF） to forecast actual Internet traffic data flow. Simulation results show that, compared with other forecasts of the forward-feedback neural network, the forecast of the RBF neural network based on the chaos theory has faster learning capacity and higher forecasting accuracy.

Nonlinear Current-Voltage Characteristics and Electroluminescence of cBN Crystal

The current-voltage（I-V） characteristics of cBN crystal sandwiched between two metallic electrodes are measured and found to be nonlinear. Over 20 samples are measured at room temperature with various electrodes, and the resulting curves are all similar in shape. When a voltage of about 560V is applied to the cBN crystal, the emitted light is visible to the naked eye in a dark room. We explain these phenomena by the space charge limited current and the electronic transition between the X and Г valleys of the conduction band.

Influence of Collective Boulder Array on the Surrounding Time-averaged and Turbulent Flow Fields

Arrays of large immobile boulders,which are often encountered in steep mountain streams,affect the timing and magnitude of sediment transport events through their interactions with the approach flow.Despite their importance in the quantification of the bedload rate,the collective influence of a boulder array on the approach timeaveraged and turbulent flow field has to date been overlooked.The overarching objective is,thus,to assess the collective effects of a boulder array on the time-averaged and turbulent flow fields surrounding an individual boulder within the array,placing particular emphasis on highlighting the bed shear stress spatial variability.The objective of this study is pursued by resolving and comparing the timeaveraged and turbulent flow fields developing around a boulder,with and without an array of isolated boulders being present.The results show that the effects of an individual boulder on the time-averaged streamwise velocity and turbulence intensity were limited to the boulder's immediate vicinity in the streamwise(x/d c < 2-3) and vertical(z/d c < 1) directions.Outside of the boulder's immediate vicinity,the time-averaged streamwise velocity was found to be globally decelerated.This global deceleration was attributed to the form drag generated collectively by the boulder array.More importantly,the boulder array reduced the applied shear stress exerted on theindividual boulders found within the array,by absorbing a portion of the total applied shear.Furthermore,the array was found to have a "homogenizing" effect on the near-bed turbulence thus significantly reducing the turbulence intensity in the near-bed region.The findings of this study suggest that the collective boulder array bears a portion of the total applied bed shear stress as form drag,hence reducing the available bed shear stress for transporting incoming mobile sediment.Thus,the effects of the boulder array should not be ignored in sediment transport predictions.These effects are encapsulated in this study by Equation(6).

Population structure of the blacklegged tick Ixodes scapularis revealed by SSCP data using the mitochondrial Cyt b and the nuclear ITS1 markers

The population genetic structure of the blacklegged tick Ixodes scapularis was analyzed using 853 individual ticks collected from 12 sites along the eastern seaboard of the United States. PCR-based DNA single strand conformation polymorphism(SSCP) was used for analysis of one haploid locus, the mitochondrial cytochrome b(Cyt b), and one diploid locus, the internal transcribed spacer 1(ITS1) of nuclear ribosomal RNA. Seven haplotypes in the Cyt b locus and 13 genotypes in the ITS1 locus were identified. Population differentiation and isolation by distance were found. Distribution of haplotype and genotype frequencies across geographic regions suggests that two distinct populations exist along the Eastern Coast of the US. However, genetic variation among individuals within regions was large. This degree of variation suggests frequent gene flow between regions. Moreover, overall genetic diversity among individuals was much higher in ticks from the southern population.

Investigation of oil-air two-phase mass flow rate measurement using Venturi and void fraction sensor

Oil-air two-phase flow measurement was investigated with a Venturi and void fraction meters in this work. This paper proposes a new flow rate measurement correlation in which the effect of the velocity ratio between gas and liquid was considered. With the pressure drop across the Venturi and the void fraction that was measured by electrical capacitance tomography apparatus, both mixture flow rate and oil flow rate could be obtained by the correlation. Experiments included bubble-, slug-, wave and annular flow with the void fraction ranging from 15% to 83%, the oil flow rate ranging from 0.97 kg/s to 1.78 kg/s, the gas flow rate ranging up to 0.018 kg/s and quality ranging nearly up to 2.0%. The root-mean-square errors of mixture mass flow rate and that of oil mass flow rate were less than 5%. Furthermore, coefficients of the correlation were modified based on flow regimes, with the results showing reduced root-mean-square errors.

Spatial Effect of Mineral Resources Exploitation on Urbanization:A Case Study of Tarim River Basin,Xinjiang,China

Mineral resources exploitation significantly affects the spatial structure and evolutive trend of urbanization in arid areas.In this study,the spatial autocorrelation method and the spatial computation model were used to investigate the spatial impacts of mineral resources excavation and processing on comprehensive level of urbanization in the Tarim River Basin,Xinjiang,China for the years of 2000,2006 and 2008.The results are as follows:1)There was a spatial correlation of the development of mineral resources industry and the comprehensive level of urbanization in 2006 and 2008,with the spatial concentration trend rising significantly in 2006 and decreasing in 2008.2)The patterns of local spatial concentration of mineral resources industry and of the comprehensive level of urbanization were relatively stable,and the two patterns showed signs of spatial correlationship.The higher was the degree of the concentration of mineral resources industry,the stronger was its impact on the spatial clustering of urbanization.3)In 2000, mineral resources excavation and processing had a significant positive impact on the comprehensive level of urbanization in the region but not in its adjacent regions.However,in 2008,mineral resources excavation and processing significantly raised the comprehensive level of urbanization not only in the region but also in its neighboring regions.This research demonstrates that the development of mineral resources industry can strongly affect the trends and spatial patterns of urbanization.

MAGE ANALYSIS OF GEOSTATIONARY METEOROLOGICAL SATELLITE FOR MONITORING MOVEMENT OF MESOSCALE CONVECTIVE SYSTEMS OVER TIBETAN PLATEAU

Disaster weather forecasting is becoming increasingly important. In this paper, the trajectories of Mesoscale Convective Systems （MCSs） were automatically tracked over the Chinese Tibetan Plateau using Geostationary Meteorological Satellite （GMS） brightness temperature （Tbb） from June to August 1998, and the MCSs are classified according to their movement direction. Based on these, spatial data mining methods are used to study the relationships between MCSs trajectories and their environmental physical field values. Results indicate that at 400hPa level, the trajectories of MCSs moving across the 105°E boundary are less influenced by water vapor flux divergence, vertical wind velocity, reIative humidity and K index. In addition, if the gravity central longitude locations of MCSs are between 104°E and 105°E, then geopotential height and wind divergence are two main factors in movement causation. On the other hand, at 500hPa level, the trajectories of MCSs in a north-east direction are mainly influenced by K index and water vapor flux divergence when their central locations are less than 104°E. However, the MCSs moving in an east and south-east direction are influenced by a few correlation factors at this level.

Some Inequalities for Submanifolds in Cosymplectic Space Forms

For submanifolds in a cosymplectic space form tangent to the structure vector field ξ, two important inequalities with Ricci curvature, scalar curvature and the squared mean curvature are obtained. These results are also applied to get corresponding consequences for anti-invariant submanifolds.

Gallbladder function and dynamics of bile flow in asymptomatic gallstone disease

AIM： To investigate the effects of gallbladder stones on motor functions of the gallbladder and the dynamics of bile flow in asymptomatic gallstone disease. METHODS： Quantitative hepatobiliary scintigraphy was performed to detect the parameters of gallbladder motor function [gallbladder ejection fraction （GBEF）, gallbladder visualization time （GBVT）, gallbladder time to peak activity （GBTmax）, gallbladder half emptying time （GBT1/2）, and transit time of bile to duodenum （TTBD）] in 24 patients with asymptomatic cholelithiasis who were diagnosed incidentally during routine abdominal ultrasonographic examination and 20 healthy subjects with normal gallbladder. RESULTS： Even though there was no significant difference in the clinical and laboratory parameters between the patient and control groups, all parameters of gallbladder function except TTBD were found to differ significantly between the two groups. GBEF in the patient group was decreased （P = 0.000） and GBVT, GBT GBT1/2 in the patient group were longer （P = 0.000, P = 0.015, P = 0.001, respectively）.there were not any clinical and laboratory findings, gallbladder filling and emptying could be impaired in patients with gallstone disease.