PHYSICAL AND NUMERICAL MODELLING OF THE DYNAMIC BEHAVIOR OF A FLY LINE

The planar equations of motion for a tapered fly line subjected to tension, bending, aerodynamic drag, and weight are derived. The resulting theory describes the large non-linear deformation of the line as it forms a propagating loop during fly casting. A cast is initiated by the motion of the tip of the fly rod that represents the boundary condition at one end of the fly line. At the opposite end, the boundary condition describes the equations of motion of a small attached fly (point mass with air drag). An efficient numerical algorithm is reviewed that captures the initiation and propagation of a non-linear wave that describes the loop. The algorithm is composed of three major steps. First, the non-linear initial-boundary-value problem is transformed into a two-point boundary-value problem, using finite differencing in time. The resulting non-linear boundary-value problem is linearized and then transformed into an initial-value problem in space. Example results are provided that illustrate how an overhead cast develops from initial conditions describing a perfectly laid out back cast. The numerical solutions are used to explore the influence of two sample effects in fly casting, namely, the drag created by the attached fly and the shape of the rod tip path.     

Stability of a simple Levi–Civitá functional equation on non-unital commutative semigroups

In this paper, we study the Hyers–Ulam stability of a simple Levi–Civitá functional equation f(x+y)=f(x)h(y)+f(y) and its pexiderization f(x+y)= g(x) h(y)+k(y) on non-unital commutative semigroups by investigating the functional inequalities |f(x+y)?f(x)h(y)?f(y)|≤?? and |f(x+y)?g(x)h(y)?k(y)|≤??, respectively. We also study the bounded solutions of the simple Levi–Civitá functional inequality.     

LINEAR VIBRATION CHARACTERISTICS OF CABLE-BUOY SYSTEMS

A theoretical model for the linear vibration of a cable tensioned by a subsurface buoy is developed. The equilibrium of the cable-buoy system subject to drag is evaluated using an approximate closed-form solution whose range of validity is confirmed through comparison with numerical solutions. The three-dimensional equations of cable-buoy motion are linearized about this equilibrium and then used to assess vibration characteristics. The characteristic equations for the natural frequencies of both in-plane and out-of-plane vibration modes are derived. The in-plane natural frequency spectrum exhibits the curve veering phenomena due to asymmetry of the associated mode shapes. Parameter studies reveal the dependencies of the in-plane and out-of-plane vibration modes on the cable tension, the buoy mass, and the current velocity.     

不相交主成分分析(PCA)和遗传算法(GA)用于差异表达基因的识别

建立了一种基于不相交主成分分析(Disjoint PCA)和遗传算法(GA)的特征变量选择方法, 并用于从基因表达谱(Gene expression profiles)数据中识别差异表达的基因. 在该方法中, 用不相交主成分分析评估基因组在区分两类不同样品时的区分能力; 用GA寻找区分能力最强的基因组; 所识别基因的偶然相关性用统计方法评估. 由于该方法考虑了基因间的协同作用更接近于基因的生物过程, 从而使所识别的基因具有更好的差异表达能力. 将该方法应用于肝细胞癌(HCC)样品的基因芯片数据分析, 结果表明, 所识别的基因具有较强的区分能力, 优于常用的基因芯片显著性分析(Significance analysis of microarrays, SAM)方法.     

A HABITAT BASED MODEL FOR THE DISTRIBUTION OF FOREST INTERIOR NESTING BIRDS IN A FRAGMENTED LANDSCAPE

ABSTRACT. Increased awareness of the plight of many forest dwelling species has made necessary the development of methods for projecting the spatial distribution of these populations. This is particularly important for populations that currently occupy forest fragments and that are likely to be exposed to further disruption of their natural habitat. In this paper we develop a model for predicting the distribution of a bird population that evolved as forest interior dwellers. This model uses as its basis knowledge of the relationship between demographic characteristics of the population and the qualities of the habitat where individuals reside. We make the assumption that individuals will be naturally drawn to areas where they might expect greater reproductive success and repelled from areas where there is a high degree of intraspecific competition (high density). We apply the model to the ovenbird population in a large region of the Midwest. We use the model to examine the relative extent to which the surplus production from two major source areas supports extensive sink populations. The basic diffusion model parameterized by county forest cover data projects a population distribution which compares favorably with the results from the breeding bird count.