GWLS-SVR模型的红枣树叶片叶绿素含量估算

叶绿素含量是红枣树光合作用能力、生长状况、营养状况的指示剂,不同地理位置种植的红枣树受到自然、人为等因素的影响,叶绿素含量分布有所不同,该研究实地测定了若羌县枣树叶片高光谱反射率及表征叶绿素含量的枣树叶片SPAD(soil plant analysis development)值.为了高效无损地估算红枣树叶片SPAD值...     

非对称距离的旅行商问题的构造算法

章分析了非对称距离的旅行商问题,讨论了节约算法与最小生成树算法两种启发式方法,并用实例进行了说明,最后对算法的有效性进行了说明。     

基于FTA方法的COVID-19疫情应急防控决策研究

鉴于新型冠状病毒肺炎(COVID-19)的易感染性与聚集性等特点,基于COVID-19的传播机制,应用故障树分析(FTA)方法,研究了具有不同特征的疫情突发事件风险决策问题,包括疫情突发事件的动态演化过程、多种情景以及应急方案对突发事件的影响。通过分析COVID-19疫情突发事件的演化过程,构建故障树来描述导致突发事件演变的条件与因素之间的逻辑关系,给出了不同的可行应急方案。利用FTA预估出疫情突发事件发生的概率,计算出可行应急方案的整体排序值,获得最优应急方案。最后通过一个COVID-19确诊患者的案例分析,验证了所提出的方法的可行性和有效性。     

树网络上f模式最优广播问题的线性算法

网络G的一个结点v上的一次广播是指从它将一个消息传递给若干相邻结点.所谓f模式广播,是指结点v在一次广播中至多向f(v)个相邻结点传递信息(f为给定的整值函数).假定每一次广播的执行时间为一单位.网络G的广播过程是广播的时间安排,使所有结点均获得消息.最优广播问题是求总时间最少的广播过程.在G是树网络情形,文献中已给出时间界为O(n2)的算法.本文给出线性时间的简捷算法.     

A note on generating finer‐grain parallelism in a representation tree

The representation tree lies at the heart of the algorithm of Multiple Relatively Robust Representations for computing orthogonal eigenvectors of a symmetric tridiagonal matrix without Gram–Schmidt. A representation tree describes the incremental shift relations between relatively robust representations of eigenvalue clusters of an unreduced tridiagonal matrix, which are needed to strongly separate close eigenvalues in the relative sense. At the bottom of the representation tree, each leaf defines a relatively isolated eigenvalue to high relative accuracy. The shape of the representation tree plays a pivotal role for complexity and available parallelism: a deeper tree consisting of multiple levels of nodes involves tasks associated to more work (i.e., eigenvalue refinement to resolve eigenvalue clusters) and less parallelism (i.e., a longer critical path as well as potential data movement and synchronization). An embarrassingly parallel, ideal tree on the other hand consists of a root and leaves only. As highly parallel hybrid graphics processing unit/multicore platforms with large memory now become available as commodity platforms, exploiting parallelism in traditional algorithms becomes key to modernizing the components of standard software libraries such as LAPACK. This paper focuses on LAPACK's Multiple Relatively Robust Representations algorithm and investigates the critical case where a representation tree contains a long sequential chain of large (fat) nodes that hamper parallelism. This key problem needs to be addressed as it concerns all sorts of computing environments, distributed computing, symmetric multiprocessor, as well as hybrid graphics processing unit/multicore architectures. We present an improved representation tree that often offers a significantly shorter critical path and finer computational granularity of smaller tasks that are easier to schedule. In a study of selected synthetic and application matrices, we show that an average 75% reduction in the length of the critical path and 82% reduction in task granularity can be achieved. Copyright © 2011 John Wiley & Sons, Ltd.     

Bubble tree convergence for the harmonic sequence of harmonic surfaces in ℂℙ n

We show that any harmonic sequence determined by a harmonic map from a compact Riemannian surface M to CP^n has a terminating holomorphic （or anti-holomorphic） map from M to CP^n, or a ＂bubble tree limit＂ consisting of a harmonic map f： M → CP^n and a tree of bubbles hλ^μ： S^2 --→ CP^n.     

The maximum multiplicity of an eigenvalue in a matrix whose graph is a tree

We study the maximum possible multiplicity of an eigenvalue of a matrix whose graph is a tree, expressing that maximum multiplicity in terms of certain parameters associated with the tree.     

ECONOMIC EVALUATION OF BIOTECHNOLOGICAL PROGRESS: THE EFFECT OF CHANGING MANAGEMENT BEHAVIOR

Abstract The paper assesses the welfare effects of biotechnological progress, as exemplified by tree improvements, using a partial equilibrium model. Timber demand is assumed to be stochastic and the distributions of its coefficients known. The coefficients of a log‐linear supply function are determined by maximizing the expected present value of the total surplus of timber production, both in the presence and in the absence of genetically improved regeneration materials. The supply functions are then used to estimate the expected present values of the total surplus in different cases through simulation. These estimates enable us to assess the direct effect and the effect of changing harvest behavior on the expected present value of the total surplus. The main results of the study are (i) the presence of genetically improved regeneration materials has significant impacts on the aggregate timber supply function; (ii) the application of genetically improved regeneration materials leads to a significant increase in the expected present value of the total surplus; and (iii) a considerable proportion of the welfare gain results from the change in harvest behavior. A conclusion we draw from this study is that ignoring the influences of technological and policy changes on behavior can lead to significantly biased welfare estimates. We view the model as a potential approach to conducting counterfactual policy comparisons in economics without forward‐looking data.     

Lotka-Volterra树系统全局渐近稳定性的判据

本文通过引入种群度的概念,给出一组很容易验证的判断n维Lotka-Volterra树系统存在全局渐近稳定非负平衡点的充分条件。     

Countably categorical coloured linear orders

In this paper, we give a classification of (finite or countable) ?₀‐categorical coloured linear orders, generalizing Rosenstein's characterization of ?₀‐categorical linear orderings. We show that they can all be built from coloured singletons by concatenation and ?_n‐combinations (for n ≥ 1). We give a method using coding trees to describe all structures in our list (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)