Principles of the eradication or control of tsetse flies

The success of attempts to control African trypanosomiasis afflicting both men and animals through the destruction of the tsetse vector depends on a realistic assessment of human and ecological factors in infested regions. The complete eradication of tsetse is at present possible only in limited areas, and elsewhere the advantages of periodic control campaigns have to be weighed carefully against their cost.     

Genetic mechanisms and constraints governing the evolution of correlated traits in drosophilid flies

Some morphological traits differ greatly between related species, but it is not clear whether diversity evolves through changes in the same genes and whether similar, independent (that is, convergent) changes occur by the same mechanism. Pigmentation in fruitflies presents an attractive opportunity to explore these issues because pigmentation patterns are diverse, similar patterns have arisen in independent clades, and numerous genes governing their formation have been identified in Drosophila melanogaster. Here we show that both evolutionary diversification and convergence can be due to evolution at the same locus, by comparing abdominal pigmentation and trichome patterns and the expression of Bric-à-brac2 (Bab2), which regulates both traits in D. melanogaster, in 13 species representing the major clades of the subfamily Drosophilinae. Modifications of Bab2 expression are frequently correlated with diverse pigmentation and trichome patterns that evolved independently in multiple lineages. In a few species, Bab2 expression is not correlated with changes in pigmentation but is correlated with a conserved pattern of trichomes, indicating that this locus can be circumvented to evolve new patterns when a correlated trait is under different constraints.     

卫星位置误差相关时的三星编队系统时差定位精度

为使三星编队卫星系统的时差定位数学模型更真实地反映现实,该文充分考虑编队星座系统联合观测定轨中存在的卫星位置误差相关性的特点,首次从星座系统整体出发,将单星误差变量转换为可反映误差相关性的具有明确物理意义的星间距离等独立变量,推导出辐射源定位精度的数学模型,并对星座系统整体漂移、几何构形畸变、星座平面旋转、翘动误差对定位精度影响进行分析和数值计算,指出引起星座翘动的非相关误差因素对定位精度影响最大、相关性误差对精度影响最小,并给出了满足系统定位精度达到4km、等精度曲线包含星下点附近直径为3000km区域的条件。     

基于密度依赖模型的建筑企业死亡率

基于密度依赖理论及其分析方法,研究建筑企业死亡率密度依赖过程及其影响因素,并以江苏省建筑企业1989--2007年数据为例,建立企业一年数据结构,运用Cox比例风险模型进行实证分析.研究结果表明,产业层面的演化过程对建筑企业的死亡具有显著影响,但这种影响并不符合一般产业中密度依赖模型所得出的结果.种群密度对建筑企业死亡率的影响主要表现为随种群密度的增大而不断上升,但这一过程也同时受到组织年龄的影响.除此之外,建筑企业规模、宏观环境因素等也对企业死亡率有影响作用.     

Strong population substructure is correlated with morphology and ecology in a migratory bat

Examining patterns of inter-population genetic diversity can provide valuable information about both historical and current evolutionary processes affecting a species. Population genetic studies of flying and migratory species such as bats and birds have traditionally shown minimal population substructure, characterized by high levels of gene flow between populations. In general, strongly substructured mammalian populations either are separated by non-traversable barriers or belong to terrestrial species with low dispersal abilities. Species with female philopatry (the tendency to remain in or consistently return to the natal territory) might show strong substructure when examined with maternally inherited mitochondrial DNA, but this substructure generally disappears when biparentally inherited markers are used, owing to male-mediated gene flow. Male-biased dispersal is considered typical for mammals, and philopatry in both sexes is rare. Here we show strong population substructure in a migratory bat species, and philopatry in both sexes, as indicated by concordance of nuclear and mtDNA findings. Furthermore, the genetic structure correlates with local biomes and differentiation in wing morphology. There is therefore a close correlation of genetic and morphological differentiation in sympatric subspecific populations of this mammalian species.     

国家铁路网密度与人口密度、人均GNP关系的统计分析

利用1996年世界116个国家的截面数据,分析了铁路网密度与人口密度,人均GDP的关系,建立了一个统计模型来反应国家铁路网建设的宏观需求,提出了依赖－偏好指数的概念,分析了地理环境,资源产业结构,建设历史及政策偏好等因素对国家铁路网建设的影响,解释了模型值与统计之间的偏差。     

高分辨率卫星影像物理模型与有理函数模型转换

高分辨率卫星遥感影像的物理模型描述影像与地面之间的严格几何成像关系,其参数具有可理解的物理意义,但其形式复杂且与传感器类型相关,出于技术保密其物理参数通常不被提供。有理函数模型作为通用传感器模型,解决了物理模型的缺陷,但缺点是其参数不具有可理解性。因此,拟以Quickbird立体影像为例,研究物理模型和有理函数模型的转换,以综合利用两者的优点。研究结果表明,从物理模型得到的有理函数模型,具有与物理模型相近的精度,这与已有研究结果一致;从有理函数模型可以在一定假设条件上恢复重建严格物理模型,恢复的严格物理模型的定位精度不受假设条件影响。     

论人口密度场地图编制的几个问题

在分析人口密度地图的特点和编制意义的基础上，以宝鸡市为例，采用加权圆法编制了宝鸡市人口密度场地图，并且阐明了与人口密度场地图编制有关的加权圆半径及权系数的确定、控制点的布局、人口密度高度带的选择等技术问题     

Survival variability and population density in fish populations

To understand the processes that regulate the abundance and persistence of wild populations is a fundamental goal of ecology and a prerequisite for the management of living resources. Variable abundance data, however, make the demonstration of regulation processes challenging. A previously overlooked aspect in understanding how populations are regulated is the possibility that the pattern of variability--its strength as a function of population size--may be more than 'noise', thus revealing much about the characteristics of population regulation. Here we show that patterns in survival variability do provide evidence of regulation through density. Using a large, global compilation of marine, anadromous and freshwater fisheries data, we examine the relationship between the variability of survival and population abundance. The interannual variability in progeny survival increases at low adult abundance in an inversely density-dependent fashion. This pattern is consistent with models in which density dependence enters after the larval stage. The findings are compatible with very simple forms of density dependence: even a linear increase of juvenile mortality with adult density adequately explains the results. The model predictions explain why populations with strong regulation may experience large increases in variability at low densities. Furthermore, the inverse relationship between survival variability and the strength of density dependence has important consequences for fisheries management and recovery, and population persistence or extinction.     

聊城市人口密度空间化方法探讨与运用

人口的空间分布是指一定时点上人口在各地区的分布状况,是人口过程在空间的表现形式.在考虑人口分布受自然、社会、经济等因子影响的情况下,文章采用相关分析法,得出聊城市人口密度分布与道路密度分布关系密切的结论,其相关系数为0.829 5;在此基础上采用属性数据栅格化、数字人口模型(DPM)、数据内插,尤其是点内插与面内插相结合的方法对聊城地区人口密度空间分布进行模拟,进而得出区域内部人口密度空间分布的连续变化规律并对该分布规律进行相应分析.     

城市园林鸟类种群密度研究

采用距离抽样法在成都市区中心地带对西南民族大学校园(老校区)鸟种类和数量进行了研究,共记录到鸟类13种,隶属于12属,8科,3目,共2087只.其中优势种6种,个体数占总数的83.04%;普通种2种,个体数占总数的11.64%;稀有种5种,个体数占总数的5.32%;包括留鸟、夏侯鸟、繁殖鸟.研究结果基本上反映了市区的生态环境状况,为城市环境建设和环境质量评估提供了科学依据.     

城市密度分布与异速生长定律的空间复杂性探讨

从空间复杂性及空间尺度和空间维数方面研究了异速生长定律与Clark定律存在的模型相容性和模型参数一致性问题.结果表明,城市人口密度分布与城市人口-城区面积异速生长幂次定律的矛盾,本质上是一种空间复杂性问题.三维的空间投影到二维必然导致复杂的结果,不同维数的空间逻辑链接也会表现出复杂行为,解决这个问题的办法是将研究对象的维度保持一致.     

秦巴山系部分地区蚊虫种类及密度调查

对秦岭和巴山部分地区的蚊虫种类及密度进行了初步调查，共记录了７属２５种，其中陕西新记录１２种；利用人工小时法对畜舍和人房两种生境进行了成蚊密度测定，发现畜舍成蚊密度高于人房．     

结合Gabor滤波和同质性判定的高光谱图像分类

针对传统高光谱图像分类算法多利用目标类别光谱信息而忽略空间信息的问题,提出了一种综合利用空间信息与光谱信息的分类算法．首先,利用主成分分析（PCA）和无参数加权特征提取（NWFE）分别对高光谱数据进行特征提取;然后,在PCA第一主成分的基础上进行二维Gabor滤波得到像元纹理特征,结合纹理信息与光谱信息利用支持向量机对图像分类;最后利用多尺度区域同质性判定进一步改进图像分类精度．实验表明,该算法能够消除“噪声”像元,有效地提高图像分类精度．     

武汉城市圈人口密度的时空分布分析

基于1991—2011年湖北统计年鉴及第六次人口普查数据,分析武汉城市圈9个城市人口密度分布.分析结果显示：圈内人口密度呈逐年增长趋势,各地区增长不平衡,且存在空间集聚现象,人口主要聚集于城市中心;远离核心城市武汉市的地区,人口密度较小,人口密度的空间分布不均匀且随时间变化;圈内人口密度总体呈现中部密集两侧稀疏,西部密集东部稀疏的特征.     

Cox risk model with correlated classes of business

A correlated aggregate claim model with m dependent classes of insurance business is constructed, in which claim occurrences of m classes relate to Cox process and these claim processes are correlated. This Cox risk model with correlated classes of business is first transformed to the Cox model of n independent risk processes. Then the generalized Lundberg exponent and Lundberg inequality are obtained by the martingale approach. Finally, the explicit expression of Lundberg exponent under a special condition is derived.     

城市人口空间分布密度衰减模型的一个理论证明

基于理想地表形态和圆形城市假设,借助最大熵方法导出了关于城市人口空间分布密度衰减规律的Clark模型ρ(r)=ρoexp(-r/r0),从而解决了该模型的理论来源问题.式中P(r)为距离市中心为r处的人口密度,参数ρ0=P0/2πγ02在理论上为市中心(r=0)的人口密度,O0为城市总人口,γ0被定义为城市人口空间分布的特征半径.     

栓皮栎种群的生物量与材积动态及其密度调节

以河南省广泛分布的栓皮栎种群为对象 ,通过对该种群在不同程度干扰下的生物量与材积进行Logistic模型模拟 ,说明了其增长与环境之间的关系 ;同时通过其密度调节的 - 3/ 2法则拟合 ,说明了种群能够保持其稳定性的机制。本文可以为栓皮栎种群的管理与保护提供依据     

一种与色度相关的图像质量评价方法

由于采用色差方式度量视觉色度阈值,不能直接与色调和饱和度参数对应,限制了与色度图的接轨以及视觉相关方法的进一步研究,为此作者依据电视学色度信号的定义,通过产生色度信号模长与相角变化的测试图像,依据JND思路,分别观察这些不同模长和相角的测试图像,获取与色调和饱和度相关的视觉阈值,确定与色度视觉相关的图像质量评价方法.实验给出了与色调和饱和度相关的视觉阈值,验证了方案的可行性和有效性.