Focus-center problem of planar degenerate system

In this paper we discuss how to determine a degenerate equilibrium of planar analytic systems to be focus-center type. A method of generalized normal sectors is used to determine orbits in exceptional directions near high degenerate equilibria. We obtain a sufficient and necessary condition for the existence of orbits going to origin in a generalized normal sector in class III. Thus, together with some criterions of orbits going to origin in a generic quasi-sector, we can characterize whether the degenerate equilibrium is of focus-center type in every case. The effectiveness of our methods is shown in an example which has a high degenerate equilibrium.     

Long-time asymptotics of the focusing Kundu–Eckhaus equation with nonzero boundary conditions

The long-time asymptotics of the focusing Kundu–Eckhaus equation with nonzero boundary conditions at infinity is investigated by the nonlinear steepest descent method of Deift and Zhou. Three asymptotic sectors in space–time plane are found: the plane wave sector I, plane wave sector II and an intermediate sector with a modulated one-phase elliptic wave. The asymptotic solutions of the three sectors are proposed by successively deforming the corresponding Riemann–Hilbert problems to solvable model problems. Moreover, a time-dependent g-function mechanism is introduced to remove the exponential growths of the jump matrices in the modulated one-phase elliptic wave sector. Finally, the modulational instability is studied to reveal the criterion for the existence of modulated elliptic waves in the central region.     

Heuristic methods for the sectoring arc routing problem

The sectoring arc routing problem (SARP) is introduced to model activities associated with the streets of large urban areas, like municipal waste collection. The aim is to partition the street network into a given number of sectors and to build a set of vehicle trips in each sector, to minimize the total duration of the trips. Two two-phase heuristics and one best insertion method are proposed. In the two-phase methods, phase 1 constructs the sectors using two possible heuristics, while phase 2 solves a mixed capacitated arc routing problem (MCARP) to compute the trips in each sector. The best insertion method determines sectors and trips simultaneously. In addition to solution cost, some evaluation criteria such as imbalance, diameter and dispersion measures are used to compare algorithms. Numerical results on large instances with up to 401 nodes and 1056 links (arcs or edges) are reported and analysed.     

灰色关联度分析在投入产出关联度中的应用

产业经济学常用投入产出方法中的影响力系数和感应度系数来评价部门的拉动和推动作用,从而作为确定国民经济中关键部门最重要的参考指标。本文针对影响力系数和感应度系数的缺陷,采用灰色关联度曲线相似的思想对中国1997年17部门的投入产出表作了实证分析,并和传统的方法作了比较,结果表明,用本方法确定关键部门更符合实际,具有重要的参考价值。     

Isoperimetric inequalities and conjugate points on Lorentzian surfaces

Recently, an isoperimetric inequality for a sector on the Minkowski 2-spacetime has been derived by the method of parallels and the relativistic Gauss-Bonnet formula. In the present paper, we derive an isoperimetric inequality for a sector on a Lorentzian surface with curvatureK ≤ C. As a sector can be modeled by a geodesic variation of a timelike geodesic, our isoperimetric inequality gives an upper bound for the spacelike boundary of a sector. As an application of our results, we give an elementary proof of the existence of conjugate points on a Lorentzian surface with curvatureK ≤ C < 0 and we obtain an upper bound for the (timelike) diameter of a globally hyperbolic Lorentzian surface withK ≤ C < 0 by comparison of sectors.     

Goal programming: Application in the management of the miombo woodland in Mozambique

Community-based management of natural resources (CBNRM) is a priority in Mozambique's policy on forestry and wildlife resources. In essence the government's policy is to manage the natural resources in partnership with the rural communities and the private sector. This represents a change in policy in the agricultural and natural resources sectors, and has potential for significant impact in economic development. This paper demonstrates the potential for employing goal programming as a planning tool in participatory natural resource management in Mozambique. The focus is on the miombo woodlands, which are the main natural forest resources in the country and which most of the local communities, the forestry and tourist industries depend on for a variety of forest products and services.     

亚纯函数族的一个正规定则

本文研究了涉及一类微分多项式的亚纯函数族的正规性问题.利用Zalcman-Pang的方法,得到一个正规定则,推广了2011年袁文俊等得到的结果.     

Liénard系统的同宿轨族与闭轨族

本文讨论Lienard系统解的一些定性性质，得到了存在同宿轨族、闭轨族、双曲扇形和椭圆扇形、正负半轨有界及其与等倾线相交的充要条件或充分条件．     

Lienard系统的同宿轨族与闭轨族

本文讨论Ｌｉｅｎａｒｄ系统解的一些定性性质，得到了存在同宿轨族、闭轨族、双曲扇形和椭圆扇形、正负半轨有界及其与等倾线相交的充要条件或充分条件．     

DEA在投入产出表中的应用及其对建筑业的分析

将DEA(Data Envelopment Analysis)应用于投入产出表,这将有助于从投入产出表的使用和投入角度计算各个部门的相对效率,以此分析了经济系统各部门之间的相对依赖程度.为了证明这一点,本文从使用和投入的角度设定了五个目标对建筑业进行分析.结果表明建筑业对其他部门的使用相对依赖程度很小,而建筑产品的生产对其他部门的中间投入有很强的依赖性.此外,建筑业与制造业基本上是同相的.     

回转对称结构应力分析新方法

提出了回转对称结构在任意荷载作用下的应力分析新方法。先利用离散Ｆｏｕｒｉｅｒ变换,将整个回转对称的分析等价地分解为一系列带有复数约束条件的单个扇区分析。然后以再构造了由两个完全相同扇区的构成的虚拟结构,并证明了吸要在虚拟结构上施加适当的外力实数约束条件,那么虚拟结构的位移结果与原来单个扇 区在复数约束条件的解答是完全一致的。虚拟结构在实数约束条件下的应力分析几乎所有的通用有限元素程序都可以解决。因     

区间数权向量排序方法研究

通过引入二元分布函数对一对区间数权重进行排序,从而确定一系列权重相对重要区间的次序.并对此方法给出了实例计算.     

Influence of predator mutual interference and prey refuge on Lotka–Volterra predator–prey dynamics

A Lotka–Volterra predator–prey model incorporating a constant number of prey using refuges and mutual interference for predator species is presented. By applying the divergency criterion and theories on exceptional directions and normal sectors, we show that the interior equilibrium is always globally asymptotically stable and two boundary equilibria are both saddle points. Our results indicate that prey refuge has no influence on the coexistence of predator and prey species of the considered model under the effects of mutual interference for predator species, which differently from the conclusion without predator mutual interference, thus improving some known ones. Numerical simulations are performed to illustrate the validity of our results.     

Humanitarian aid logistics: supply chain management in high gear

This paper builds on the idea that private sector logistics can and should be applied to improve the performance of disaster logistics but that before embarking on this the private sector needs to understand the core capabilities of humanitarian logistics. With this in mind, the paper walks us through the complexities of managing supply chains in humanitarian settings. It pinpoints the cross learning potential for both the humanitarian and private sectors in emergency relief operations as well as possibilities of getting involved through corporate social responsibility. It also outlines strategies for better preparedness and the need for supply chains to be agile, adaptable and aligned—a core competency of many humanitarian organizations involved in disaster relief and an area which the private sector could draw on to improve their own competitive edge. Finally, the article states the case for closer collaboration between humanitarians, businesses and academics to achieve better and more effective supply chains to respond to the complexities of today's logistics be it the private sector or relieving the lives of those blighted by disaster.     

The variance equity measure in locational decision theory

Classical location theories and models were initially developed for the private sector, so that the related operational research literature has emphasized performance measures of efficiency and effectiveness. For public sector applications, measures of equity become important, yet such measures have received little formal treatment. This paper suggests a locational equity measure, the variance measure, and investigates its properties for tree networks. A fast algorithm (O(M)) to locate the minimum variance point on a tree network is developed, and some numerical results illustrate the variance optimal location.This work is dedicated to the memory of Professor Jonathan Halpern     

The sources of productivity change in Spanish banking

In this paper we examine the pattern of productivity change in Spanish banking over the period 1986–1993. Two sectors dominate Spanish banking, commercial banks and the faster-growing savings banks. We begin by examining productivity change separately within each sector. However since the two sectors are gradually becoming more competitive, we continue by merging the two sectors, and by examining productivity change in the industry. The merging procedure follows a methodology originally proposed by Charnes, Cooper and Rhodes (1981), in which intra-sectoral managerial inefficiency is eliminated prior to merging. This procedure allows us to distinguish differences in managerial efficiency within each sector from differences in the institutional efficiency of the two sectors. It also enables us to decompose potential productivity change into institutional efficiency change, technical change, and the impact of scale economies. We find the commercial banks to have had a slightly lower rate of productivity growth, but a slightly higher rate of potential productivity growth. We attribute this phenomenon to differences in both managerial efficiency and institutional efficiency, to differences in the rate of technical progress, and to the adverse impact of diseconomies of scale in the commercial banking sector.     

The power‐of‐pull of economic sectors: A complex network analysis

To compare the relative power of individual sectors to pull the entire economy, i.e., the power‐of‐pull, this article utilizes a complex system perspective to model the economy as a network of economic sectors connected by trade flows. A sector's power‐of‐pull is defined and calculated as a function of the powers‐of‐pull of those sectors that it pulls through network linkages, and their powers‐of‐pull are, in turn, functions of those sectors that they further pull ad infinitum throughout the network. Theoretically, boosting activities in sectors with a higher power‐of‐pull will generate greater network effects while stimulating the entire economy, especially during recessions. This method is applied to the United States in the years before and after the 2008 financial crisis. The results provide a fresh look at the U.S. government's economic revival policies and reveal fundamental changes in the economic structure of the U.S. This work advocates a network‐based analysis of the economy as a complex system. © 2013 Wiley Periodicals, Inc. Complexity 18: 37–47, 2013     

中间逻辑中的良构范式

本文在中间逻辑中引入了良构范式的概念,为该类范式的研究提出了一个通用方法,并应用该方法证明了HT逻辑是存在一般蕴含范式的最弱中间逻辑,经典命题逻辑CPL是存在限制蕴含范式的仅有中间逻辑.     

On the strong smoothness of weak solutions of an abstract evolution equation i. differentiability

For the evolution equation y' ^′(t)=Ay(t) with a normal operator A in a Hilbert space, conditions on A are found which are necessary and sufficient for all weak solutions of the equation to be strongly differentiable. Certain effects of smoothness improvement of the weak solutions are analyzed. The strong infinite differentiability of weak solutions of the equation with a symmetric operator is proved.     

The sector design and assignment problem for snow disposal operations

Winter road maintenance operations involve a host of decision-making problems at the strategic, tactical, operational, and real-time levels. Those operations include spreading of chemicals and abrasives, snow plowing, loading snow into trucks, and hauling snow to disposal sites. In this paper, we present a model and two heuristic solution approaches based on mathematical optimization for the problem of partitioning a road network into sectors and allocating sectors to snow disposal sites for snow disposal operations. Given a road network and a set of planned disposal sites, the problem is to determine a set of non-overlapping subnetworks, called sectors, according to several criteria related to the operational effectiveness and the geographical layout, and to assign each sector to a single snow disposal site so as to respect the capacities of the disposal sites, while minimizing relevant variable and fixed costs. Our approach uses single street segments as the units of analysis and we consider sector contiguity, sector balance and sector shape constraints, hourly and annual disposal site capacities, as well as single assignment requirements. The resulting model is based on a multi-commodity network flow structure to impose the contiguity constraints in a linear form. The two solution approaches were tested on data from the city of Montreal in Canada.