基于交叉覆盖算法的文本分类

分类是文本信息搜索和挖掘的核心内容,被广泛应用于搜索引擎的设计以及数据挖掘的研究中。首先对文本进行分词,对分词的结果采用x2统计量的方法提取特征,再使用前向神经网络的交叉覆盖算法作为分类器进行文本分类。实验表明,x2统计量可大规模降低特征维数,在此基础上结合交叉覆盖算法的优秀分类能力,可在特征维数较低的情况下获得一个性能较好的文本分类器。     

遥感图像在土地覆盖和温度分布之间对应关系研究中的应用(英文 )

利用遥感手段探讨土地覆盖类型和温度之间的对应关系有新意。以日本东京地区１９９８年１０月１４日接收的ＴＭ遥感图像为主要数据，在地面实际调查的基础上，利用图像处理方法，进行了土地覆盖类型和温度分布之间关系的探讨。以该区几种代表性的土地覆盖类型作为训练区，利用ＴＭ图像的第１，２，３，４，５五个波段数据进行分类处理，获得了很好的分类结果，ＴＭ图像第６波段（１０．４０～１２．５μｍ）是探测地面温度分布最佳波段，利用第６波段数据通过一系列的转换，获得了该区温度分布。温度分布和土地覆盖类型之间具有很好的对应性，如：白天的城区温度与郊区相比普遍偏高，但城区中植被覆盖率高的居民区和公园，温度偏低；城区的商业区（新宿、银座等）、机场和大型工厂等温度偏高。     

Connectivity of core habitat in the Northeastern United States: Parks and protected areas in a landscape context

The exurbanization process, particularly rural residential development, is reducing the amount of roadless areas and remote habitat across the nation, with implications for biodiversity and ecosystem integrity of parks and protected areas. The need for connecting protected areas via existing habitat centers, or relatively undisturbed core areas, is greater than ever as exurbanization expands. Our objective was to make use of nationally available data sets on roads as well as information derived from satellite imagery, including impervious cover of the built environment and forest canopy density, to identify core habitat of the northeastern and mid-Atlantic USA. The identified core habitat areas, which covered 73,730 km² across 1177 discrete units, were stratified in terms of land ownership and management, and then analyzed in a landscape context using connectivity metrics derived from graph theory. The connectivity analysis made use of a suitability surface, derived from the land cover information, which approximated the costs incurred by hypothetical animals traversing the landscape. We show that protected areas are frequently identified as core habitat but are typically isolated, albeit sometimes buffered by adjacent multi-use lands (such as state or national forests). Over one third of the core habitat we identified has no protection, and another 42% is subject to motorized recreation or timber extraction. We provide maps showing the relative importance of core habitat areas for potentially connecting existing protected areas, and also provide an example of the vulnerability of connectivity to projected future residential development around one greater park ecosystem.     

径向可开启板式结构几何协调性研究

介绍了一种新型开合结构--径向可开启板式结构.针对它在几何协调性方面存在的缺陷,分析了这种结构的基本构成并给出基本几何方程;运用欧式几何分析方法研究了开启时具有圆形开口的结构各单元之间的拓扑关系,得到了临界方程和限制方程,据此绘制了一些常用参数下的临界曲线和限制曲线,以便设计者选用;给出了两种开启时可形成梅花形开口或多边形开口的新型结构,解决了特定参数下屋面设计的几何协调性问题.研究结果为径向可开启板式结构的设计提供了有价值的参考.     

一种折叠式地沟盖板的设计与应用

通过介绍一种折叠式、收纳占用空间小的地沟盖板的设计与应用,阐明了未设置盖板的早期冷轧机运卷地沟、及长而狭小的收纳空间地沟盖板架设的一种思路。     

Assessing the landscape context and conversion risk of protected areas using satellite data products

Since the establishment of the first national park (Yellowstone National Park in 1872) and the first wildlife refuge (Pelican Island in 1903), dramatic changes have occurred in both ecological and cultural landscapes across the U.S. The ability of these protected areas to maintain current levels of biodiversity depend, at least in part, on the integrity of the surrounding landscape. Our objective was to quantify and compare the extent and pattern of natural land cover, risk of conversion, and relationships with demographic and economic variables in counties near National Park Service units and U.S. Fish and Wildlife Service refuges with those counties distant from either type of protected area in the coterminous United States. Our results indicate that landscapes in counties within 10 km of both parks and refuges and those within 10 km of just parks were more natural, more intact, and more protected than those in counties within 10 km of just refuges and counties greater than 10 km from either protected area system. However, they also had greater human population density and change in population, indicating potential conversion risk since the percent of landscape protected averaged < 5% in both groups and human population dynamics are primary drivers of change in many landscapes. Conversion outweighed protection by at least two times (Conservation Risk Index > 2) in 76% of counties near both parks and refuges, 81% of counties near just parks, 91% of counties near just refuges, and 93% of distant counties. Thirteen percent of counties in the coterminous U.S. had moderate to high amounts of natural land cover (> 60%), low protection (< 20%), and the greatest change in population (> 20%). Although these areas are not the most critically endangered, they represent the greatest conservation opportunity, need, and urgency. Our approach is based on national level metrics that are simple, general, informative, and can be understood by broad audiences and by policy makers and managers to assess the health of lands surrounding parks and refuges. Regular monitoring of these metrics with satellite data products in counties surrounding protected areas provides a consistent, national level assessment of management opportunities and potentially adverse changes on adjacent lands.     

面向对象的土地覆盖信息提取方法研究

利用遥感方法提取土地覆盖信息时,常用的自动分类方法只能利用遥感数据的光谱信息,而面向对象的分类方法在综合利用遥感数据光谱信息、纹理特征、拓扑关系和加入专题信息进行多尺度分割获取对象后的基础上,通过对对象的目视识别建立模糊判别函数来进行分类。利用面向对象的方法成功提取了三峡库区奉节县中部的土地覆盖信息,得到了较为满意的结果,利用野外采样数据进行验证其精度达89.2%。     

冰盖下桥墩局部冲刷新型防冲组合结构试验研究

河流冰盖的形成改变了桥墩周围的水力特性,导致桥墩局部冲刷加剧。基于动床冲刷,在冰盖及明流条件下进行了螺纹式减冲索与钩环式护圈组合的新型防冲结构室内模型试验,探究其对桥墩局部冲刷的防冲效果。试验结果表明：新型防冲组合结构改变了桥墩的局部冲刷模式,延缓了冲刷过程;通过极差分析与方差分析可知,螺纹直径为6.0 mm、螺纹角为15°、螺纹排数为3的新型防冲组合结构的防护效果最优;与无防护工况相比,在粗糙冰盖条件下新型防冲组合结构桥墩最大冲刷深度减小了59.03%;螺纹式减冲索增大了桥墩表面的粗糙度,可以更好地削弱下潜流和分离墩前迎面水流,从而达到有效防冲的目的。     

春播与复播油葵产量形成及群体生理参数比较研究

在新疆石河子地区,在滴灌、种植密度和田间配置方式相同的条件下,比较了春播与复播油葵品种新葵20号产量形成及群体生理参数。结果表明,春播条件下,生育期、生物产量、籽实产量、收获指数分别为97d、9271．9kg／hm^2、4349．Okg,／hm^2、0．47,复播条件下则分别为94d、14413．5kg／hm^2、4106．4kg／hm^2、0．35。春播和复播的最大叶面积指数（LAImax）分别为4．54和5．52。每公顷春播的光合势（LAD）为93．25m。d,开花后占77．6％;复播则为94．12m。d,开花后占82．9％。春、复播全生育期平均净同化率（NAR）分别为3．67、5．26g／（m^2·d）。采用更早熟的品种,提早播种,使灌浆提前,加之使用植物生长调节剂以增强光合产物向籽实转移,有望进一步提高复播油葵产量。     

失效混凝土保护层的修复加固技术

结合某特大桥一墩柱出现的钢筋骨架偏移、混凝土保护层厚度薄厚不均的质量问题,介绍了对混凝土保护层的再认识、保护层失效后的修复加固措施和施工方法以及减缩剂在修复用混凝土中的应用。