企业采购组织的绩效评价研究 ——以宁波市上市企业为例

通过构建超效率BCC模型和Malmquist指数模型,对2015-2019年10家宁波市上市企业采购组织的绩效进行评价分析.结果显示:10家宁波市上市企业采购组织的综合技术效率均值为0.849,整体表现较好,但仍存在较大的提升空间;全要素生产指数年均增长率为4.4％,技术进步增长率为8.4％,表明技术进步对全要素生产指...     

山东省十七地市可持续发展能力分析

结合国内外可持续发展指标体系的研究成果,运用主成分分析法构建山东省十七地市可持续发展能力综合评价指标体系和评价模型.该体系共分3层,涉及经济、社会、资源与环境3个方面共32项指标,运用2012年数据和评价模型,对山东省可持续发展能力进行了综合评价.     

“双碳”目标下区域生态效率评价及提升路径研究——以长江经济带为例

长江经济带的城市生态效率表现出明显的区域性特征。通过非期望产出超效率SBM模型，对2012—2020年长江经济带11个省市的城市生态效率进行测算，采用Malmquist指数和Tobit模型，对测算结果进行分析，并探究影响城市生态效率的因素。结果表明，区域的生态效率整体上自东向西逐渐降低，空间集聚效应明显；科学技术是长江经济带生态效率的主要增长点；同时，人均国内生产总值对长江经济带城市生态效率的影响通过1%的显著性检验，影响明显。应处理好经济发展与生态保护的关系，控制来自生活、工业的污染；要发展信息和自动化产业，以绿色、集约、高科技为重点，加快传统产业转型升级；坚持绿色发展、生态优先的理念，依靠科技进步提高资本和人力的产出效率。     

基于SE-DEA的山东省城市物流效率评价分析

山东省各地市经济基础不同,物流业的发展水平与效率也有较大差异,而这种差异会阻碍山东省经济的持续、协调、健康发展.以山东省17地市的物流业为研究对象,通过构建科学的物流效率指标评价体系,结合2012年山东省经济发展的相关数据,应用DEA和SE-DEA模型对各地市物流效率进行研究,并提出相应发展建议.     

基于GM(1,1)模型的国内旅游需求规模预测

利用灰色模型对2012-2015年国内旅游需求规模进行了预测。通过计算,预测出2012-2015年国内旅游人数每年以2亿人次左右的数量增长,年均增长率为9%。研究表明:中国国内旅游需求规模是不断上升的,国内旅游将呈现良好发展的势头。     

新常态下我国工业技术进步的测度及影响研究——基于省际面板数据的实证分析

利用我国经济发展步入新常态时期的2012—2014年的工业数据,增加涵盖人口、环境变化的产出变量,使用DEA数据包络的Malmquist指数法测算我国各省市工业技术进步状况,并基于省际面板数据使用Cobb-Douglas生产函数估计工业技术进步对工业产出的影响,结果表明:2012—2014年期间我国工业技术年均进步5.3%,相比1999—2009年期间,我国工业技术进步平均增长率从4.5%提高了0.8%.采用固定效应模型和随机效应模型,估计技术进步对工业产出的弹性分别为0.35%和0.38%.     

基于DEA和Malmquist指数的河南省技术 创新效率评价研究

科学评价河南省技术创新效率有利于推动河南省的经济发展.运用DEA模型和Malmquist指数分解法测算了河南省2010—2017年各市技术创新效率.研究结果表明,研究期间内各市的综合效率大部分呈上升趋势,个别有下降趋势;从Malmquist指数分解法来看,随着年份的增加,全要素生产前期有下降趋势,从2013年开始呈现上升趋势且受技术进步影响较大.最后根据研究结果提出相应的建议及措施.     

西部地区农业生态效率评价及影响因素研究

目的 分析2010-2019年西部地区农业生态效率水平并探讨农业生态效率的影响因素。方法 运用非期望超效率SBM模型和Malmquist指数测度农业生态效率，并运用面板Tobit模型对农业生态效率的影响因素进行研究。结果 (1)2011-2019年，西部地区农业生态效率整体呈现出“N”型趋势，且地区间差异较大；(2)2019年甘肃、内蒙古、宁夏、青海、四川和云南的生产要素投入和碳排放产出均存在不同程度冗余；(3)西部地区全要素生产率呈现出“U”型趋势，且全要素生产率增长主要由技术进步驱动；(4)西部地区农业生态效率受到规模化水平、机械化水平、受灾率、农民收入水平、环境规制水平与技术投资水平等多方面影响。结论 需从农业要素节约、高效投入，严格控制农业碳排放和加大农业技术投资与环境污染治理投资3方面对西部地区农业生态效率进行提高和改进。     

基于DEA交叉模型的西部地区生态效率时空变化

建立基于DEA模型的生态效率投入产出指标体系,以2005-2009西部地区11个省份截面数据为样本,采用DEA交叉评价模型和空间对比分析方法,对西部地区生态效率进行时空差异研究.结果表明:从时间上看,西部地区生态效率总体上呈现出增加的趋势,省份之间的差异进一步扩大,其中,陕西一直处于首位,而宁夏一直处于末位.从空间上看,西部地区生态效率存在着明显的区域差异,东南区域整体上要高于西北区域,但是区域间的这种差异呈现出增大的趋势,生态效率分布的重心逐渐向区域中心集中,经济条件好的省份生态效率水平相对较高.最后,依据以上研究发现,提出了相应的建议.     

基于边际分析方法的生态效率驱动因子识别与趋势预测

以安徽省为例,运用熵值TOPSIS方法及生态效率测度模型,对生态效率进行测算;采用偏最小二乘与通径分析方法,对生态效率驱动因子边际直接与间接效应进行考察;通过作散点图的最佳拟合优充方法,对生态效率演化趋势进行预测.结果表明:1)生态效率指数由2005年的0.545 4提升至2015年的0.8061,整体呈波动上升态势,年均升幅3.98%;2)科技创新、产业结构、固定资产投资、城镇化水平、外商投资、规制政策边际弹性系数分别为-0.006 78、-0.026 84、-0.062 79、-0.001 71、0.069 11、0.130 06;3)若按既有惯性发展模式,2020年生态效率指数将降至0.005 3,生态文明建设将面临较大挑战.基于研究结果,提出提升生态效率的政策建议.     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

英文诗歌中的喻类修辞

为了有助于提高英文爱好者的个人情操、文化素养和学习兴趣,以及专业人员对英语学习和研究进行多途径的探索,本文通过一些精选诗歌的引证和分析,着重论述了喻类修辞法在英文诗歌中的运用其及效果。     

Man Is Unable to Change the Miserable Life——Analysis of the Arrangement of Four Characters in The Glass Menagerie

Tennessee Williams is considered as one of the most important American playwrights since World War II.The Glass Menagerie is his first successful drama,which describes a tragic situation of family and means to say that Man is unable to change the miserable life,no matter whatever means he try,This essay focuses on the analysis of the arrangement of the four main characters:Laura.Amanda,Jim and Tom to reveal the theme.Laura is fragile.Amanda is brave.Jim is vital.Tom is sensible.And all of them develop and try the different means to struggle against life,but fail tragically.With the evidence,the paper comes to conclusion naturally that Man is unable to change the miserable life,and he dooms to fail.     

Characterization of root-nodulating bacteria on Retama raetam in arid Tunisian soils

The aim of this study is to investigate the diversity of Retama raetam root-nodule bacteria isolated from arid regions of Tunisia. Twelve isolates, chosen as representative for different 16S rRNA gene patterns, were characterized by 16S rRNA gene sequencing and phenotypic analysis. Isolates were assigned to Sinorhizobium, Rhizobium and Agrobacterium. Symbiotic properties of Sinorhizobium and Rhizobium isolates showed a large diversity in their capacity to infect their host plant and fix atmospheric nitrogen. Strain RK 22 identified as Rhizobium was the most effective isolate.     

An Affordable Accurate Evaluation of the Binding Conformations Predicted by Molecular Docking Studies in Bio-System

正Recently,docking has been widely used to predict the binding-modes of protein-inhibitors,when the crystal complexes structure was absent.Most docking algorithms are able to generate a large number of probable conformations,it,however,is difficult to effectively evaluate these docking poses and identify the most reasonable bindingmode.In the present study,on the basis of the crystallographic data of human 3-hydroxy-3-methylglutaryl coenzyme     

WIMAX与WI-FI技术分析及联合组网

介绍了WiMAX与Wi-Fi两种无线宽带接入技术,并对两者之间的关系及相互之间的影响做了对比及分析,并对WiMAX的关键技术进行了详细说明,最后对两者的联合组网方式做了简单的探讨。