Network Structure and Dynamics of Chinese Regional Incubation

Networks and Spatial Economics - In recent years, the structure of incubation networks has attracted much attention. However, the intricacy of network has limited the discussions on its structure...     

八叉树结构的虚拟动力学检测算法

描述了物体间交互的FV和EE两种基本接触模式,在此基础上提出了用八叉树结构来构建虚拟环境的几何模型和动力学模型,给出了不但考虑刚度．而且考虑惯性和阻尼的虚拟仿真机器人与虚拟环境交互的虚拟力检测的一般算法。对于模型空间中的任何形状的实体都可以由八叉树法分割的立方体序列来表示。而其实体的总的虚拟交互力是在FV和EE两种基本接触模式下所分割的所有立方体间的矢量和。实验显示了所给出的算法的可行性。该算法对虚拟现实临场感遥操作机器人系统控制结构和控制算法的分析和设计,特别是系统中人机接口的设计具有重要价值．     

Exact Largest and Smallest Size of Components

Golomb and Gaal [15] study the number of permutations on n objects with largest cycle length equal to k . They give explicit expressions on ranges n/(i+1) < k ≤ n/i for i=1,2, ldots, derive a general recurrence for the number of permutations of size n with largest cycle length equal to k , and provide the contribution of the ranges (n/(i+1),n/i] for i=1,2,ldots, to the expected length of the largest cycle. We view a cycle of a permutation as a component. We provide exact counts for the number of decomposable combinatorial structures with largest and smallest components of a given size. These structures include permutations, polynomials over finite fields, and graphs among many others (in both the labelled and unlabelled cases). The contribution of the ranges (n/(i+1),n/i] for i=1,2,ldots, to the expected length of the smallest and largest component is also studied. Received June 27, 2000; revised October 8, 2000.     

Exploiting Model Structure to Solve the Dynamics of a Macro Model

This paper considers alternative numerical approaches to solvingthe time-path of a nonlinear representative agent model.     

结构未建模系统的变结构自适应控制器设计

本文对一类结构未建模的动态不确定系统，采用变结构控制与自适应控制相结合的方法，给出了一种鲁棒控制器设计方案。所提方案适用于系统已建模部分为非最小相位的系统，并能保证系统输入输出全局有界稳定。     

自动驾驶仪动特性的局部收敛变结构导引律

针对拦截弹末制导全局收敛设计难度大等特点,在考虑导弹自动驾驶仪动态特性的前提下,提出局部收敛的变结构导引律.在设计过程中,先对局部收敛稳定性理论进行数学描述,然后将控制系统分解为两个子系统,且只考虑视线角速率的变化,使得设计过程大大简化,设计的导引律有效地克服了自动驾驶仪动态延迟对制导精度的影响.仿真结果表明,在目标做正弦机动,自动驾驶仪存在较大滞后情况下,局部收敛变结构导引律仍具有较高的制导精度.     

Size of the Largest Antichain in a Partition Poset

Partitions {(k ₁,..., k )} of a given set are considered as a partially ordered set (poset) with a natural partial ordering with respect to inclusion. Asymptotics for the size of the largest antichain in this poset is found for fixed.     

Interval-Related Talks at the Annual Conference of the North American Fuzzy Information Processing Society NAFIPS'02

Reliable Computing -     

Validation of North American Forest Disturbance dynamics derived from Landsat time series stacks

The North American Forest Dynamics (NAFD) study is a core project of the North American Carbon Program (NACP). The NAFD project is evaluating forest disturbance patterns and rates of disturbance by integrating U.S. Department of Agriculture (USDA) Forest Service Inventory and Analysis (FIA) field observations with temporally dense time series Landsat imagery. In Phase I of NAFD forest disturbance history was derived for 23 U.S. sample locations over the time period 1984 to 2005 from biennial Landsat time series stacks (LTSS). This study evaluates the accuracy of these Phase I NAFD disturbance history maps for 6 selected sample locations. We evaluate the disturbance maps using 2 reference datasets: 1) a design-based approach incorporating visual analysis of the LTSS in tandem with high resolution imagery and 2) the USDA FIA field observations. Overall accuracy for the NAFD disturbance product assessed at the individual time step level range from 77% to 86%. We examine the success rates of the mapping approach for capturing different types of disturbance and find that 82% of stand clearing events were detected. When we aggregate the data into change and no change categories the accuracy of stand clearing disturbance samples improved to over 92%. The majority of error in the disturbance maps was due to misclassification of partial disturbance as unchanged forest. We analyze the resulting errors of commission and omission as related to both reference datasets for each LTSS and present examples to illustrate the strengths and weaknesses of Phase I NAFD approach. In addition, we discuss the map biases observed in this work and what this may imply for estimating national forest disturbance rates with this approach.     

Land surface phenology of North American mountain environments using moderate resolution imaging spectroradiometer data

Monitoring and understanding plant phenology is becoming an increasingly important way to identify and model global changes in vegetation life cycle events. High elevation biomes cover twenty percent of the Earth's land surface and provide essential natural resources. These areas experience limited resource availability for plant growth, development, and reproduction, and are one of the first ecosystems to reflect the harmful impact of climate change. Despite this, the phenology of mountain ecosystems has historically been understudied due to the rough and variable terrain and inaccessibility of the area. In addition, although numerous studies have used synoptically sensed data to study phenological patterns at the continental and global scales, relatively few have focused on characterizing the land surface phenology in mountainous areas. Here we use the MODIS/Terra + Aqua satellite 8-day 500 m Nadir BRDF Adjusted Reflectance product to quantify the land surface phenology. We relate independent data for elevation, slope, aspect, solar radiation, and temperature as well as longitude and latitude with the derived phenology estimates. We present that satellite derived SOS can be predicted based on topographic and weather variables with a significant R²adj between 0.56 and 0.62 for the entire western mountain range. Elevation and latitude exhibit the most significant influences on the timing of SOS throughout our study area. When examined at both the local and regional scales, as well as when accounting for aspect and temperature, SOS follows closely with Hopkins' Bioclimatic Law with respect to elevation and latitude.     

Stability Analysis of Linear Shift‐Invariant Dynamics in Honeycomb Structure

This paper deals with the stability of linear shift‐invariant multidimensional dynamical systems defined on honeycomb structure. Two different honeycomb structures are discussed. The local dynamical states are assumed to be distributed to honeycomb cells in the first consideration, and they are assumed to be distributed to the nodes of honeycomb mesh in the second consideration. In each honeycomb structure, the fundamental linear shift‐invariant dynamics is introduced and then the stability criterion is presented.     

Computational Experience with a Large-Scale,Multi-Period,Spatial Equilibrium Model of the North American Natural Gas System

In this paper we describe numerical results for a market equilibrium model for the North American natural gas system. The model is based on the notion of maximizing total surplus less transportation costs (Takayama and Judge, 1971; Samuelson, 1952) resulting in a large-scale nonlinear program (Gabriel et al., 2000). The model relies on building up supply curves from the bottom up using a data base of some 17,000 natural gas reservoirs. This feature provides a good deal of realism in simulating the effects of technology, market forces, and policy considerations on the supply side of the market while making the computations challenging due to the lack of closed form supply curves. A successive linear programming strategy is employed to solve the overall nonlinear problem. We describe several mathematical algorithms that are employed in the successive LP approach to efficiently compute market equilibrium values. These algorithms are heuristic in nature with excellent convergence results. In the numerical results section of this paper, we describe several experiments regarding schemes to accelerate the overall convergence based on iterative smoothing (similar to a Gauss-Seidel strategy) as well as tests aimed at optimal spatial and temporal aggregation.     

Kinematics and Dynamics of the Fulleroid

This paper presents, besides a new synthesis, the kinematic and dynamic analysis of a complex spatial mechanism, called Fulleroid, which initially has been synthesized on the basis of the generalized Heureka Oktahedron. This mechanism consists of 24 equal triangular bodies interconcected by simple or double rotary joints. It is a highly overconstrained linkage which is, however, movable with one global degree of freedom due to its special dimensions. The six symmetry planes of the Fulleroid clearly define a center and allow introducing a central co-ordinate system in relation to which all of its rigid bodies perform Schoenfließ motions. With these special (relative) motions it becomes possible to determine the (absolute) motion of each link within a second (absolute) co-ordinate system fixed to one of these bodies. Knowing the positions of the bodies within this co-ordinate system and knowing the (absolute) velocities of all points of the Fulleroid as functions of the input parameter and its time derivative, the ruling differential equation can be established for a given input force or moment.     

Logic and the Dynamics of Information

We discuss how issues of information and computation interact with logic today, and what might be a natural extended agenda of investigation.