城市公园不同植物群落内空气负离子变异格局及影响因素

选取上海市中心城区中山公园中9个不同配置的植物群落,通过1年内连续监测空气负离子浓度,分析得到了各群落中负离子的变异格局,并探索了不同群落结构、不同郁闭度、周边水体等因素对空气负离子浓度的影响.结果表明:中山公园不同群落类型负离子浓度大多在200～700个/cm3,日变化呈单峰形, 1年内在7月至10月间保持较高水平且波动程度较大;群落结构与负离子浓度的关系大致为草乔灌≈乔草乔灌草,群落结构越复杂,负离子变异性越小;负离子浓度变异系数与郁闭度间呈负相关关系,即郁闭度越高,群落中空气负离子浓度的变异系数越低,在每日植物发生光合作用的7:00～19:00,植物郁闭度与负离子浓度变异系数的负相关性更为显著.此外,城市公园中常见的静态水体对负离子浓度的影响不显著.可为城市公园中营造适宜健康的植物群落提供基础数据和科学依据.     

六种城市绿地内夏季空气负离子与颗粒物

为合理规划城市绿地、有益于人们户外活动,研究了6种类型城市绿地空气负离子和颗粒物浓度的日变化、空气质量的差异,分析了负离子与不同粒径颗粒物之间的关系。结果表明:空气负离子和颗粒物浓度日变化均较明显;不同类型绿地空气负离子浓度存在显著差异,其浓度从大到小的顺序为阔叶乔草、乔灌草、阔叶乔木、篱草、针叶乔草、草坪;不同类型绿地空气颗粒物浓度没有显著差异。由枝叶茂盛的高大乔木组成的林地,其空气负离子水平和空气质量较好。总体上空气负离子与颗粒物的相关关系不显著,相比之下,空气负离子对细颗粒物的中和能力较强。     

城市人工林空气负离子变化特征及其主要影响因子

由于空气负离子存在瞬时性,1 h或2 h的间断性监测很难准确反映其变化趋势。为获得空气负离子的实时变化趋势并准确分析其影响因子,以上海崇明岛5种人工林为研究对象,开展单层结构人工林空气负离子实时监测及主要影响因子的研究。结果表明:人工林空气负离子浓度日变化曲线呈双峰型曲线,但峰值出现的具体时间和大小因优势种不同而有所差异;人工林空气负离子浓度存在季节性差异,不同季节空气负离子浓度的均值大小次序为夏季((1 476±17.1)ions/cm~3)冬季((1 310±25.2)ions/cm~3)春季((1 197±12.6)ions/cm~3)秋季((1 089±12.7)ions/cm~3);5种林分空气负离子浓度的年均值大小次序为池杉林((1 405±16.5)ions/cm~3)混交林((1 269±18.1)ions/cm~3)臭椿林((1 259±23.2)ions/cm~3)水杉林((1 257±210)ions/cm~3)香樟林((1 093±16.6)ions/cm~3);在一定范围内,林分空气负离子浓度与优势树种树高和环境相对湿度呈正相关,与温度和风速呈负相关;当光照度小于20 000 lx时,林分负离子浓度与光照度呈显著正相关;主成分分析表明,相对湿度和光照度是影响林分空气负离子浓度的主要因素。通过比较优势种光合作用日变化和林分空气负离子浓度日变化相似的"M"形双峰曲线,认为植物光合作用也是影响林分空气负离子浓度的重要因子。     

城市绿地对空气负离子的影响

为研究城市绿地对空气负离子的影响,在南昌市选择有典型特征的城市绿地,对其在不同环境状况下的空气正、负离子浓度进行监测.结果表明:1)城市绿地能有效的提高空气负离子数量;2)乔、灌、草3种不同类型的绿地中,乔木林片对提高空气负离子浓度和改善空气质量的作用最为显著;3)在城市环境下,不同林分结构类型的乔木片林对空气负离子水平以及空气质量评价指数的影响差异不显著;4)天气条件对绿地的空气负离子水平存在显著的影响;5)喷泉对空气负离子有显著的影响.     

夏季干旱半干旱城市公园绿地空气负离子与空气颗粒物变化特征

【目的】观测北方干旱半干旱城市公园绿地不同植被结构空气负离子浓度与空气颗粒物浓度,并评价影响因素及其交互影响,为北方城市居民选择游憩时间及公园建设提供科学依据。【方法】于2020年7—8月,同步观测呼和浩特市敕勒川公园5种植被结构及对照点空气负离子浓度、空气颗粒物浓度,分析空气负离子与空气颗粒物变化特征及其影响因素。【结果】不同植被结构空气负离子浓度基本呈“V”形变化特征,空气颗粒物浓度最高值出现在早晨,最低值出现在下午;不同植被结构空气负离子浓度均值均高于对照点,且复层植被结构产生的负离子浓度要高于单层植被结构,不同植被结构对空气颗粒物浓度的调控存在着削减和集聚并存的效应;气象因子是影响空气负离子和空气颗粒物浓度的主要因素,风速与空气负离子浓度间显著负相关,温度与空气负离子浓度、总悬浮颗粒物(TSP)和PM₁₀浓度间显著负相关,相对湿度与空气负离子浓度、TSP和PM₁₀浓度间显著正相关,露点温度与PM_2.5和PM_1.0浓度间显著正相关;空气负离子浓度与PM_1.0浓度间显著负相关。【结论】复层植被结构较单层植被结构对提高空气负离子浓度有更加显著的作用,疏密适当的植被对减少空气颗粒物浓度起到积极作用;依据观测结果,建议城市周边居民开展休闲娱乐活动的最佳时间选择在9:00—10:00和14:00—17:00。     

鸡公山空气负离子分布规律及其与环境因子的关系

利用空气负离子测定仪对鸡公山不同生境、不同天气条件下的空气负离子分布状况进行连续的定位观测,探讨鸡公山空气负离子浓度的日变化和季节变化规律,并进一步分析空气负离子浓度与气温、空气相对湿度等环境因子之间的关系.研究结果表明:(1)不同生境的空气负离子浓度大小依次为瀑布>溪流>湖泊>阔叶林>针叶林>针阔混交林>灌丛;(2)不同天气条件下空气负离子浓度大小为:雨过天晴>晴天>阴天;(3)空气负离子浓度的日变化规律呈现出先降低再升高的趋势,即早晨最高,中午降至最低,下午又逐渐升高;(4)空气负离子浓度的季节差异显著,夏季>秋季>春季>冬季;(5)空气负离子浓度与气温和空气湿度均呈现出正相关的趋势.     

长沙市不同功能区空气负离子水平研究

空气负离子浓度的高低反映了空气质量的好坏.文章选择了长沙市代表性的4个功能区进行了空气负离子浓度监测,并进行了空气质量的评价.结果表明:(1)空气负离子浓度日变化幅度较大,空气负离子水平和空气质量出现峰谷交替的现象;(2)不同植被的城市绿地空气负离子水平差异较为明显,以乔木为主的岳麓山空气负离子浓度最高,空气质量最佳;(3)不同功能区的空气负离子水平差异较为明显,城市绿地的空气负离子浓度最高,空气质量最好.     

城市绿地植物群落空气负离子浓度及影响要素研究

通过对上海市6种典型城市绿地植物群落夏、秋两季空气负离子浓度的测定,分析了季节因素和群落因素对空气负离子浓度的影响关系,并重点进行了群落因素对空气负离子浓度影响的定量分析研究.研究结果表明:(1) 城市绿地植物群落空气负离子浓度受到季节和群落两个因素的协同作用;(2)城市绿地植物群落夏季的平均负离子浓度高于秋季;(3)...     

空气负离子浓度的实验研究

测试了周围生活环境中的空气负离子浓度，并通过实验测试了衰减距离、摩擦、风速、温度、湿度等影响因素对材料产生负离子的影响．实验结果表明，周围生活环境中空气负离子浓度小于500个／cm^2，外界空气负离子浓度大于1500个／cm^2，空气负离子在环境中的衰减距离为20cm左右．当临界风速处于3m／s-10m／s之间，风速的摩擦可以产生负离子；相对于摩擦，温度、湿度的变化对材料产生负离子的影响较小．     

植物源负离子发生器室内应用的研究

为研究植物源负离子发生器在室内应用的效果,探明植物源负离子与室内气象因子的关系,以龙舌兰作为负离子源进行研究,结果表明:①植物源负离子发生器能高效持续释放负离子,浓度均值为1 256 156.53ion·cm-3,可有效提高室内空气质量;②当植物源负离子发生器运行时,在无人状态下室内CO2浓度的降幅是关机状态下的2.2倍;③当1人在室内活动,且植物源负离子发生器开启时,负离子浓度与温度呈极显著正相关;当发生器关闭时,相关性不明显.当室内没有人活动,植物源负离子发生器开启和关闭时,负离子浓度与温度均呈极显著负相关,与湿度均呈极显著正相关;④人的因素对室内负离子浓度具有重要影响,在植物源负离子发生器开启状态下,当室内有1人活动时,负离子浓度均值为223 556.42 ion·cm-3,与无人活动的状态相比下降了82.2%,且能显著改变气象因子与空气负离子浓度的相关性.     

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。