点格局分析函数的边缘校正及其在昆虫种群格局分析中的应用

点格局分析函数是分析种群空间分布格局的常用方法之一,其关键问题是边缘效应的校正.将边缘效应的权重值定义为以分布点为圆心,尺度距离为半径作圆,圆在样地内的面积部分与整个圆面积之比.利用该面积比定义的边缘效应系数分析了越冬水稻二化螟幼虫在不同尺度下的空间分布型.研究结果显示点格局分析函数能够反映出不同尺度下昆虫种群空间格局,其分析结果对合理制定抽样计划具有重要的指导作用. 点格局分析函数在水稻越冬二化螟幼虫的应用分析中表明:在田间研究中其取样尺度不应小于2m.     

Ripley's K(d)函数分析种群空间分布格局的边缘校正

Ripley’sK(d)函数是分析种群空间分布格局最常用的方法,边缘校正是此方法的关键问题。传统的边缘校正包括3种情形：(i)圆完全包含在样地内;(ii)圆与样地的一条边相交;(iii)圆与样地的两条边相交,并有2个或3个交点。实际上,还存在第(iv)种情形,即圆与样地两条边相交有4个交点的情形。本文从数学上证明,传统边缘校正中,当边缘校正属于第(iv)种情形时,仍按第(iii)种情形进行校正,必然导致权重估计偏大,L(d)值偏高,从而影响结果分析。采用我国东北长白山天然云冷杉林样地资料验证了此结论。结果表明,天然云冷杉林中,3个优势种群林木分布格局特点是：鱼鳞云杉和臭冷杉的分布格局曲线非常相近,而与椴木的差异较大。原因是鱼鳞云杉和臭冷杉具有相似的生态学特性。椴木在小尺度显著聚集,因为椴木常在林隙更新。相比较而言,建群种云冷杉分布的均匀程度要比椴木高。     

应用加权TOPSIS法综合评价某院医疗质量的报告

目的:探讨加权TOPSIS法在医疗质量综合评价中的应用价值.方法:根据该院2002-2006年统计资料筛选评价指标并给予权重,建立数据矩阵和规范化矩阵;确定最优向量和最劣向量,计算各年度医疗质量评价指标与最优、最劣向量的加权欧氏距离和相对接近度.结果:根据该院原始数据成功建立了数据矩阵和规范化矩阵,确定的最优向量z+=(0.4479,0.4485,0.4486,0.4515,0.4474,0.4528,0.4737,0.4714,0.4970),最劣向量Z-=(0.4466,0.4452,0.4458,0.4420,0.4467,0.4397,0.3778,0.4254,0.3568),各年度与最优及最劣向量的加权欧氏距离、相对接近度及排序结果表明该院医疗质量逐年提高,2006年最好,2005年次之,2002年最差.结论:加权TOPSIS法考虑了各指标的权重,从而使评价结果更趋于合理,适用于医院医疗质量综合评价.     

边缘效应的空间尺度与测度

综述了边缘效应的空间尺度类型以及在不同尺度上的测度方法.基于大量的研究整合,认为边缘效应空间尺度的划分,可以根据空间尺度的不同以及边缘效应形成和维持因素,分为大中小3个尺度类型,即大尺度的生物群区交错带、中尺度的景观类型之间的生态交错带和小尺度的斑块(生态系统)之间的群落交错区.大尺度主要是以植被气候带为标志的生物群区间的边缘效应,这种地带性的交错区主要受大气环境条件的影响.中尺度类型主要包括城乡交错带、林草交错带、农牧交错带等类型,是不同生态系统要素的空间交接地带,在物质能量等相互流动的作用下变得更为复杂.小尺度水平上是指斑块之间的交错所形成的边缘效应,受小地形等微环境条件及生物非生物等因子的制约,研究主要集中在群落边缘、林窗边缘和林线交错带等方面.对边缘效应测度的定量化研究有助于更加深入理解边缘效应.在大尺度水平上,边缘效应测度的研究主要是应用数量生态学等方法,研究不同气候带之间界线的划分及其物种分布的梯度规律性.中尺度水平上应用景观生态学的3S技术等方法,侧重于研究交错带的动态变化趋势及位置宽度的判定.小尺度水平上通过对距离边缘的长度,各群落中种群的数量、结构、多样性等定量指标的测定来构建测度公式,从而对边缘效应的强度进行量化,并反映边缘对群落的正负效应.总体上看,主要集中于中小尺度上,未来应该强化大尺度边缘效应测度的研究.     

中国中东部平原亚热带湿润区湖泊营养物生态分区

湖泊营养物生态分区是实现湖泊分区控制的前提和基础。以中国中东部平原亚热带湿润区为案例区,根据区域特点,从自然地理要素、生态系统和人类活动三方面建立指标体系,对各指标进行归一化得到各指标数据的分值;采用AHP方法确定各指标的权重值,结合各指标分值计算栅格尺度上湖泊营养物生态分区综合评价分值;根据研究区域DEM数据划分小流域,将栅格尺度的湖泊营养物生态分区综合评价分值投影到小流域尺度上,采用双约束空间聚类算法对小流域尺度上湖泊营养物生态分区评价分值进行聚类得到湖泊营养物生态分区结果。结果表明:(1)AHP可以用来确定复杂指标体系中各指标的权重,适合用于确定湖泊营养物生态分区指标体系中各指标的权重;(2)采用双约束空间聚类进行湖泊营养物生态分区,保证了分区结果在空间上的连续性和评价分值上的接近性;(3)根据自然地理条件、土地利用和人类活动强度的不同,可以将中东部平原亚热带湿润区划分为长江中下游平原湖区、湘赣平原丘陵湖区、湘渝山地湖区、四川盆地湖区、川西—大巴山山地湖区5个营养物生态区。     

基于局部调整动态轮廓模型提取超声图像乳腺肿瘤边缘

提出一种基于局部调整动态轮廓模型提取超声图像乳腺肿瘤边缘的算法。该算法在Chan—Vese（CV）模型基础上,定义了一个局部调整项,采用基于水平集的动态轮廓模型提取超声图像乳腺肿瘤边缘。将该算法应用于89例临床超声图像乳腺肿瘤的边缘提取实验,结果表明：该算法比CV模型更适用于具有区域非同质性的超声图像的分割,可有效实现超声图像乳腺肿瘤边缘的提取。     

多年平均降水资源空间变化模拟方法的研究

区域多年平均降水量的研究是集水农业工程规划的基础,也是有限的降水资源合理利用和配置的依据。研究利用ＡＲＣ／ＩＮＦＯ地理信息系统,建立了研究区的栅格数字高程模型（ＤＥＭ）及近３０年的年均降水量空间数据库;采用９种算法（距离权重法、趋势面法、样条函数法、普通Ｋｒｉｇｉｎｇ法、通用Ｋｒｉｇｉｎｇ方法１、通用Ｋｒｉｇｉｎｇ方法２、泰森多边形法、多元回归法和综合方法）,计算并比较分析了研究区多年平均降水量的     

基于侧柏液流的测定对Granier原始公式系数进行校正

为研究Granier原始公式计算单株树木蒸腾耗水量的准确性,以侧柏作为研究对象,采用热消散方法测定在15、30、50、70和90cm水柱高度形成不同压力梯度下的树干液流通量密度,并以称重法作为对照,利用回归分析方法拟合称重法测定的液流通量密度与热消散法测定的树干液流温差系数(K值),进而建立校正公式.结果表明:基于侧柏校正的Granier公式为Fd=0.0115K0.5581(R2=0.8319).与称重法测定的液流通量密度相比,校正的Granier公式计算的结果略高(6.70±0.02)％,而Granier原始公式计算的则低估(78.53±0.04)％.由此可知,采用校正的Granier公式计算侧柏的液流通量密度具有较高的精度.     

大兴安岭林火发生的时空聚集性特征

林火是大兴安岭林区重要的干扰因子之一,揭示其发生的时空分布特征和规律,对林火安全管理和未来气候变化下的林火预测具有重要作用。本文以大兴安岭1967—2006年发生的林火为研究对象,将其视为一个在时间和空间上完全随机的点过程。采用时间点过程方法中的变异系数和阿伦因子及空间点格局分析中的Ripley K函数和Kernel空间密度函数等估算方法,分别对大兴安岭林火时间和空间分布的聚集性范围和尺度进行分析。结果表明:在较小的时间尺度上,林火分布趋向随机过程,随着观测时间长度增大,分布的聚集性表现越显著;空间分布上,林火在一定距离尺度内表现为聚集分布,超过该尺度则为随机泊松分布;林火的分布往往聚集在某些特定区域,存在明显的林火高发区。这些结果进一步揭示了大兴安岭林火时空的内在分布规律,但对于导致这些林火时空分布格局的机制还有待进一步研究。     

植被叶面积指数遥感反演的尺度效应及空间变异性

遥感作为宏观生态学研究中数据获取的一种便捷手段,有助于把握较大尺度内生态学现象的特征.应用遥感数据反演LAI时,由于像元的异质性,不同尺度遥感数据之间的转换是遥感发展的一个重要问题.以河北省黄骅市为研究区,在利用TM和MODIS遥感数据对芦苇LAI反演误差产生原因进行分析的基础上,利用半变异函数对像元空间异质性进行了定量描述.发现NDVI算法的非线性带给LAI尺度转换的误差很小,而LAI的空间异质性则是引起LAI尺度效应的根本原因.并且当像元内空间异质性很大时半变异函数的基台值比纯像元要大得多,空间自相关的程度是引起LAI尺度转换误差的主要原因;反之,像元内空间异质性不大时,随机误差是引起LAI尺度转换误差的主要原因.当像元为纯像元时,由像元异质性引起的反演误差基本可以忽略.此外,研究区芦苇的空间相关有效尺度约为360m,超过此距离空间相关性则不复存在.     

Edge-corrected Estimators for the Reduced Second Moment Measure of Point Processes

A new edge-corrected estimator is proposed for the second moment cumulative function K(t) introduced by Ripley (1977, Journal of the Royal Statistical Society, Series B 39, 172–212). This new estimator is compared by simulation methods with existing edge-corrected estimators in the context of both K(t) and L(t) functions which are used to study point patterns. The results of the simulation study suggests that the new estimator provides almost unbiased estimates of K(t) and L(t) and has a smaller mean squared error than its predecessors.     

植物空间分布格局中邻体距离的概率分布模型及参数估计

最近邻体法是一类有效的植物空间分布格局分析方法,邻体距离的概率分布模型用于描述邻体距离的统计特征,属于常用的最近邻体法之一。然而,聚集分布格局中邻体距离(个体到个体)的概率分布模型表达式复杂,参数估计的计算量大。根据该模型期望和方差的特性,提出了一种简化的参数估计方法,并利用遗传算法来实现参数优化,结果表明遗传算法可以有效地估计的该模型的两个参数。同时,利用该模型拟合了加拿大南温哥华岛3个寒温带树种的空间分布数据,结果显示:该概率分布模型可以很好地拟合美国花旗松(P.menziesii)和西部铁杉(T.heterophylla)的邻体距离分布,但由于西北红柏(T.plicata)存在高度聚集的团簇分布,拟合结果不理想;美国花旗松在样地中近似随机分布,空间聚集参数对空间尺度的依赖性不强,但西北红柏和西部铁杉空间聚集参数具有尺度依赖性,随邻体距离阶数增加而变大。最后,讨论了该模型以及参数估计方法的优势和限制。     

A new method of estimating gauge length for porcine aortic valve test specimens

Porcine aortic valve (PAV) cusps are folded and wrinkled in the in vitro state. In the tensile testing of PAV specimens, estimating gauge length (the length at which a specimen starts to offer measurable resistance to load) is often difficult and subjective. We have therefore developed a new method for estimating the gauge length of such tissues. The method is based on the observation that the specimen's gauge length can be associated with a stationary point on the slope of its load-length curve if loaded from a wrinkled state, or a state of slight compression. We represented the load-length response of test specimens in the low-load, high-compliance region by a cubic function and determined the stationary point on the slope of the function using elementary calculus. The cubic function representation is fine-tuned by reducing or expanding an originally selected "test region" until the correlation coefficient of the cubic fit is maximized. The new method was applied to data obtained from the tensile testing of strips of heart valve tissue and was found to be objective, repeatable and robust.     

The Contraction-Expansion Algorithm and Its Use in Fitting Nonlinear Equation

1IntroductionMostadequatenumeriMrelationshipbetweencovarlate扯dresPOnsearenonlinear．Howev·er,applicationofnonlinearequationappearedfarlessthanlinearregression．ThedifficultyInesti·mail呛theparametersIncomplicatednonllnearmodelingmaybethemainreasoninbl     

Detecting phylogenetic incongruence using BIONJ: an improvement of the ILD test

The problem of testing for congruence between phylogenetic data has long been debated among phylogeneticists, but reaches a critical point with the availability of large amount of biological sequences. Notably in prokaryotes, where the amount of lateral transfers is believed to be important, the inference of phylogenies using multiple genes requires testing for incongruence before concatenating the genes. On another scale, incongruence tests can be used to detect recombination points within single gene alignments. The incongruence length difference test (ILD), based on parsimony, has been proved to be useful for finding incongruent data sets, but its application remains limited to small data sets for computational time reasons. Here, we have adapted the principle of ILD to the BIONJ algorithm. This algorithm is based on a tree length minimisation criterion and is suitable to replace parsimony in this test when used with uncorrected distance (model-free approach). We show that this new test, ILD-BIONJ, while being much faster, is often more accurate than the ILD test, especially when the alignments compared are simulated under different evolutionary models.     

Unbiased estimation of evolutionary distance between nucleotide sequences

A new algorithm for estimating the number of nucleotide substitutions per site (i.e., the evolutionary distance) between two nucleotide sequences is presented. This algorithm can be applied to many estimation methods, such as Jukes and Cantor's method, Kimura's transition/transversion method, and Tajima and Nei's method. Unlike ordinary methods, this algorithm is always applicable. Numerical computations and computer simulations indicate that this algorithm gives an almost unbiased estimate of the evolutionary distance, unless the evolutionary distance is very large. This algorithm should be useful especially when we analyze short nucleotide sequences. It can also be applied to amino acid sequences, for estimating the number of amino acid replacements.      

Statistical Model for Locating Fragile Points on Nucleic-ACID Molecules

Breakage is an important behavioral characteristic of nucleic-acid molecules. This paper concerns the problem of estimating the location of fragile (F) points on biological macromolecules such as DNA or RNA. We assume that the original length of the macromolecules is a random variable, breakage occurs more likely at some points of the macromolecules than others, and the number of breakages, except for those occurring at such points, is according to a Poisson process. Under these assumptions, the density function of the length of a randomly chosen segment has been derived. The Maximum Likelihood Estimation (MLE) is suggested for estimating the parameters. The model is applied to the data available on RNA of Avian Myeloblostosis Virus (AMV), and three possible F-points have been located. The robustness of the model is discussed.     

Gonad development and filleting yield of common carp Cyprinus carpio L. reared in ponds in Eastern France

The processing of 232 common carp Cyprinus carpio made it possible to study the correlation between gonad maturation and filleting yield. The study was undertaken between April and August 1992 and was carried out on 4-year-old carp cultured in extensive ponds. Morphological parameters were recorded and relations between total weight and length, biomass of fillet, and biomass of gonad were determined. The histology of male and female gonads was examined in relation to the gonadosomatic index (GSI: up to 16% for females and less than 11% for males) and condition indices (total K or somatic K1). Filleting yields (32–36% of the total weight) decreased for females just prior to spawning and corresponded to a decline of K1. A rematuration phenomenon was observed, although females weighing less than 1200g were still immature. We suggest avoiding the filleting of large females before spawning and suggest estimating the date of appearance of this stage by referring to the positive correlation established in this paper between the number of degree-days and total fish weight.     

Detecting protein sequence conservation via metric embeddings

MOTIVATION: Comparing two protein databases is a fundamental task in biosequence annotation. Given two databases, one must find all pairs of proteins that align with high score under a biologically meaningful substitution score matrix, such as a BLOSUM matrix (Henikoff and Henikoff, 1992). Distance-based approaches to this problem map each peptide in the database to a point in a metric space, such that peptides aligning with higher scores are mapped to closer points. Many techniques exist to discover close pairs of points in a metric space efficiently, but the challenge in applying this work to proteomic comparison is to find a distance mapping that accurately encodes all the distinctions among residue pairs made by a proteomic score matrix. Buhler (2002) proposed one such mapping but found that it led to a relatively inefficient algorithm for protein-protein comparison. RESULTS: This work proposes a new distance mapping for peptides under the BLOSUM matrices that permits more efficient similarity search. We first propose a new distance function on peptides derived from a given score matrix. We then show how to map peptides to bit vectors such that the distance between any two peptides is closely approximated by the Hamming distance (i.e. number of mismatches) between their corresponding bit vectors. We combine these two results with the LSH-ALL-PAIRS-SIM algorithm of Buhler (2002) to produce an improved distance-based algorithm for proteomic comparison. An initial implementation of the improved algorithm exhibits sensitivity within 5% of that of the original LSH-ALL-PAIRS-SIM, while running up to eight times faster.