Designing sound in cybercartography: from structured cinematic narratives to unpredictable sound/image interactions

In this paper we draw on the analysis of sound in film theory in order to explore the potential that sound offers cybercartography. We first argue that the theoretical body developed in film studies is highly relevant to the study of sound/image relationships in mapmaking. We then build on this argument to develop experimental animated and interactive sound maps for the Cybercartographic Atlas of Antarctica that further explore the potential of sound for integrating emotional, cultural and political dimensions in cartography. These maps have been designed to recreate cinematic soundscapes, to provide contrapuntal perspectives on the cartographic image and to generate an aural identity of the atlas. As part of this experimental mapping, an innovative sound infrastructure is being developed to allow complex sound designs to be transmitted over the Internet as part of atlas content. Through this infrastructure the user can select as well as contribute his own sounds. The overall cartographic message is becoming less predictable, thus opening new perspectives on the way we design, interact with, and modify sounded maps over the Internet.     

Developing parallel procedures for line simplification

Abstract

This paper explores parallel programming issues that are relevant to the efficient implementation of spatial data handling procedures on current parallel computers through sample implementations of the Douglas line simplification procedure. Using source code-equivalent implementations of the Douglas procedure, this paper analyses the performance characteristics of two parallel implementations, compares their performance characteristics to those of a sequential implementation, and identifies critical components of the parallel implementations that enhance or inhibit their overall performance values. The results of this work show that the selection of appropriate interprocessor communication and load balancing strategies are crucial to obtaining large speedup values over comparable sequential implementations.     

A Voronoi neighborhood-based search heuristic for distance/capacity constrained very large vehicle routing problems

Local search heuristics for very large-scale vehicle routing problems (VRPs) have made remarkable advances in recent years. However, few local search heuristics have focused on the use of the spatial neighborhood in Voronoi diagrams to improve local searches. Based on the concept of a k-ring shaped Voronoi neighbor, we propose a Voronoi spatial neighborhood-based search heuristic and algorithm to solve very large-scale VRPs. In this algorithm, k-ring Voronoi neighbors of a customer are limited to building and updating local routings, and rearranging local routings with improper links. This algorithm was evaluated using four sets of benchmark tests for 200–8683 customers. Solutions were compared with specific examples in the literature, such as the one-depot VRP. This algorithm produced better solutions than some of the best-known benchmark VRP solutions and requires less computational time. The algorithm outperformed previous methods used to solve very large-scale, real-world distance constrained capacitated VRP.     

A local stability analysis of astronomical disks

Abstract

A fifth-order dispersion relation describing the local stability of a differentially rotating flow against small perturbations is derived. Finite viscosity and conductivity and both vertical (parallel to the rotation axis) and radial gradients in density, temperature and pressure are included. A general form is assumed for the equation of state, although this is not exploited in the paper. A number of special cases are studied: with negligible viscosity and conductivity, it is shown that modes can often be separated into two high frequency (modified acoustic), two intermediate frequency (combined inertial and internal waves) and a low frequency mode. In convectively unstable situations the intermediate frequency modes may be replaced by a damped/growing pair of instablities. Various criteria for mode excitation are given. It is shown that viscosity always inhibits instability at very short wavelengths, while non-zero conductivity may destabilize the flow. At intermediate wavelengths viscosity could also play a destabilizing role. A parameter study of the effects of fluctuations in the conductivity shows that it could cause mode excitation under certain circumstances.     

作为复杂适应系统的农业文化遗产：复杂性的挑战

本文首先阐述了农业系统的复杂性,并对农业系统所面对不确定性,以及外部系统的冲击和压力而形成的动态性进行了分析,提出“复杂适应性系统理论”为研究活态的农业系统,尤其为研究中国的全球重要农业文化遗产（GIAHS）提供了可能,而这些农业文化遗产系统（或其中某些部分）对于研究抵抗力和自我良性管理具有重要的意义.本文认为当前研究中的相关方法将会对整个系统的认识产生新的见解,同时避免把系统分解为各组分进行微观研究再重新还原成整体的研究思路.本文通过综述与GIAHS相关的方法并将旅游引入农村系统（作为一种扰动）,认为可以创造新的方法来认识农村发展干预措施对古老景观的影响,特别是分布在中国农村的许多景观.     

Zonal shear flows with a free surface: Hamiltonian formulation and linear and nonlinear stability

General theoretical results via a Hamiltonian formulation are developed for zonal shear flows with the inclusion of the vortex stretching effect of the deformed free surface (equivalent barotropic model). These results include a generalization of the Flierl–Stern–Whitehead zero angular momentum theorem for localized nonlinear structures (whether or not on a β-plane), and sufficient conditions for linear and nonlinear stability in the Liapunov sense–the latter are given as estimates in terms of an L ²-type perturbation norm which are global in time and are derived via bounds on the equilibrium potential vorticity gradient.     

On the nonlinear evolution of columnar vortices in a rotating environment

We examine the three-dimensional, nonlinear evolution of columnar vortices in a rotating environment. As the initial vorticity distribution, a wavetrain of finite amplitude Kelvin-Helmholtz vortices in shear is employed. Through direct numerical simulation of the Navier-Stokes equations we seek to better understand the process of maturation of the various three-dimensional modes of instability to which such vortical flows are subject, especially those which exist as a consequence of the action of the Coriolis force. In the absence of rotational influence, we thereby demonstrate that the nonlinear evolution of columnar vortices is most strongly controlled by one or the other of two mechanisms. One mechanism of instability is identifiable as a so-called elliptical instability, which promotes the initial bending of vortex tubes in a sinusoidal fashion, while the other is a hyperbolic mode, which is responsible for the development of streamwise vortex streaks in the "braids" between adjacent vortex cores. In the rotating case, anticyclonic vortices are strongly destabilized by weak background rotation, while rapid rotation stabilizes both the cyclones and anticyclones. The strong anticyclones are subject to two distinct forms of instability, namely a Coriolis force modified elliptical instability and an inertial (centrifugal) instability. The former instability is very similar to the nonrotating form of the elliptical instability as it promotes bending of vortex tubes, while the latter instability grows on the edge of the vortex core and generates streaks of vorticity, which surround the vortex core itself. These results of direct numerical simulation fully verify the results of previous linear stability analyses. Taken together, they provide a simple explanation for the broken symmetry that is often observed to be characteristic of the von Karman vortex streets that develop in the atmospheric lee of oceanic islands.     

Simple laminar dynamos: from two rolls to one

The study of laminar flows with simple streamlines in conducting fluids that might support kinematic dynamo action has a long history. Early successful examples include the Gailitis (1970 Gailitis, A. 1970. Self-excitation of a magnetic field by a pair of annular vortices. Mag. Gidrod, 6: 19–22. (English translation: Magnetohydrodynamics, 6:14–17) [Google Scholar]) dynamo, which has two meridional rolls. We show here that a single meridional roll, considered as a limit of a modified Gailitis-like dynamo, can also support kinematic dynamo action in a deep spherical shell. This flow has a claim to be the simplest such flow possible.     

Kinematic dynamo action in a sphere: Effects of periodic time-dependent flows on solutions with axial dipole symmetry

Choosing a simple class of flows, with characteristics that may be present in the Earth's core, we study the ability to generate a magnetic field when the flow is permitted to oscillate periodically in time. The flow characteristics are parameterised by D, representing a differential rotation, M, a meridional circulation, and C, a component characterising convective rolls. The dynamo action of all solutions with fixed parameters (steady flows) is known from earlier studies. Dynamo action is sensitive to these flow parameters and fails spectacularly for much of the parameter space where magnetic flux is concentrated into small regions, leading to high diffusion. In addition, steady flows generate only steady or regularly reversing oscillatory fields and cannot therefore reproduce irregular geomagnetic-type reversal behaviour. Oscillations of the flow are introduced by varying the flow parameters in time, defining a closed orbit in the space ( D,?M ). When the frequency of the oscillation is small, the net growth rate of the magnetic field over one period approaches the average of the growth rates for steady flows along the orbit. At increased frequency time-dependence appears to smooth out flux concentrations, often enhancing dynamo action. Dynamo action can be impaired, however, when flux concentrations of opposite signs occur close together as smoothing destroys the flux by cancellation. It is possible to produce geomagnetic-type reversals by making the orbit stray into a region where the steady flows generate oscillatory fields. In this case, however, dynamo action was not found to be enhanced by the time-dependence. A novel approach is being taken to solve the time-dependent eigenvalue problem where, by combining Floquet theory with a matrix-free Krylov-subspace method, we can avoid large memory requirements for storing the matrix required by the standard approach.     

不同掏蚀深度下古城墙的稳定性数值分析

以浙江良渚古城的宽顶古场面墙稳定性问题为研究对象,本文针对古城墙可能出现的不同深度的风沙掏蚀的实际工况,通过有限差分软件FLAC3D,建立计算模型进行了稳定性分析,探讨了不同掏蚀深度下城墙破坏机理和规律.研究表明:当城墙墙根掏蚀深度不是很大时,城墙整体稳定,土体开始出现比较小的位移量,掏蚀部位及其周围出现局部塑性破坏现象.随着掏蚀深度的增加,城墙塑性破坏区域不断向城墙体内部、顶部及顶部后缘范围发展,城墙上的土体位移量随着掏蚀深度的增加而呈数量级的增加,直至城墙出现整体崩塌破坏.掏蚀作用加剧了地震作用下城墙体的破坏,在掏蚀部位形成潜在破坏口,内部形成塑性贯通区,造成墙体整体崩塌.