Measuring Spatial Correspondence among Network Paths

Measuring the spatial correspondence among geographic features is an important component of many analyses such as those seeking to identify similar or dissimilar features, explore the extent to which change has taken place, and explain the processes influencing spatial change. In networked systems, the paths providing connectivity between pairs of nodes are often the geographic features among which spatial correspondence is to be assessed. That is, given a set of paths between a pair of nodes, the extent to which they share portions of the network and spatially deviate from one another can provide insight on the factors underlying the use of a system. While methods for measuring the spatial correspondence among specific types of network paths have been devised, this article proposes a methodology for measuring the spatial correspondence among the topology of network paths of any type, including those involving redundant use of network space. By basing comparisons upon the topologic relationships among the paths, the proposed approach better accounts for average spatial deviation as well as the asymmetric spatial relationship between pairs of paths, enabling greater stability and consistency in the analysis of their spatial characteristics. The developed methodology is applied to evaluate variability in spatial correspondence among a set of network paths to demonstrate its utility.     

Lower ionosphere effect observed during the 30 June 1992 total solar eclipse

VLF radio signals (12.9 kHz) transmitted from Ω-Argentina (43°12′S, 65°24′W) were received in Atibaia, Brazil (23°11 'S, 46°33'W) during the total solar eclipse of 30 June 1992. The surface path of the totality crossed the VLF propagation path in the sunrise transition period causing a phase delay of 6.4 μs and an amplitude change of 1.3 dB. The ionospheric response to the Sun's obscuration was compared with the phase delays reported for several solar eclipses that occurred from 1966 to 1979. The results are mainly discussed in terms of the length of VLF propagation path affected. Some similarities between a sudden phase anomaly and a reversed eclipse effect are also raised.     

Shortest Distances in a Modified Transportation Network

Taking as the starting point an undirected source network and a set of possible new links that can be used to extend the source network, a method is proposed to determine, by simple inspection of a matrix tableau, all shortest distances in any extended network, without using a shortest path algorithm. In consequence, this method may be a useful tool for analyzing and judging network extensions. In particular, computation time can be saved in many complex network optimization methods that use shortest path algorithms. The computer experiments show that the method is feasible even when an extended network may differ from the source network by several dozens of branches.     

Spatial Filtering for Identifying a Shortest Path Around Obstacles

The shortest path between two locations is crucial for location modeling, spatial analysis, and wayfinding in complex environments. When no transportation system or network exists, continuous space movement adds substantial complexity to identifying a best path as there are increased travel options as well as barriers inhibiting potential movement. To derive the shortest path, various methods have been developed. Recent work has attempted to exploit spatial knowledge and geographic information system functionality, representing significant advantages over existing methods. However, a high density of obstacles increases computational complexity making real‐time solution difficult in some situations. This article presents a spatial filtering method to enhance Euclidean shortest path derivation in complex environments. The new approach offers substantial computational improvement while still guaranteeing an optimal path is found. Application results demonstrate the effectiveness of the approach and its comparative superiority.     

Policy Networks in Complex Governance Subsystems: Observing and Comparing Hyperlink,Media, and Partnership Networks

Methods for observing policy networks have not kept up with the development of new network analytic techniques required to understand governance in complex settings. We compare three unobtrusive methods for observing policy networks based on hyperlinks between policy actor web sites, on media reports, and on public policy partnerships. Observations of one complex local water policy arena with all three methods provide a comparison of the general as well as actor‐specific network characteristics in the three observed networks. The core network of actors observed by all methods has similar network level statistics, highly correlated relationships measured by Quadratic Assignment Procedures models, and the same significant network microstructures as measured by Exponential Random Graph Models. The full networks including actors observed by any method also exhibit similar actor‐level characteristics, although the correlations across networks are stronger for bridging capital measures than for bonding capital measures, and each method has different apparent biases. Once biases are accounted for, similarities suggest that these methods may provide useful proxies for each other and for other relationships that are more difficult or impossible to measure, particularly when combined to offset each method's biases. If so, they can extend the range of policy networks observable with limited resources across space and time.     

Propagation characteristics of night-time whistlers in the region of equatorial anomaly

In this paper results of simultaneous multi-station observations of night-time whistlers obtained at very low latitudes for the last three years are presented. The propagation mechanism of these whistlers is also discussed. Some records can be shown to have the characteristics of ducted propagation by calculating the dispersion of the whistlers along a ducted path and by noticing the feature of strong intensity, as well as the existence of three-hop echoes. Whistlers in some other records, however, can be shown to be propagating along a non-ducted path by numerical ray-tracing, in which a non-dipole field (IGRF) is used and a negative horizontal gradient of ionization in the equatorial ionosphere is taken into account. The agreement of the results of calculation with observed facts seems to confirm the existence of a definite whistler path at very low latitudes. Finally, based on analysis of typical events, the effects of magnetic storms on the parameters of low latitude whistlers due to variations in the equatorial ionosphere are also discussed.     

The K‐Function Method on a Network and Its Computational Implementation

This paper proposes two statistical methods, called the network K‐function method and the network cross K‐function method, for analyzing the distribution of points on a network. First, by extending the ordinary K‐function method defined on a homogeneous infinite plane with the Euclidean distance, the paper formulates the K‐function method and the cross K‐function method on a finite irregular network with the shortest‐path distance. Second, the paper shows advantages of the network K‐function methods, such as that the network K‐function methods can deal with spatial point processes on a street network in a small district, and that they can exactly take the boundary effect into account. Third, the paper develops the computational implementation of the network K‐functions, and shows that the computational order of the K‐function method is O(n²_Q log n_Q) and that of the network cross K‐function is O(n_Q log U3Q), where n_Q is the number of nodes of a network.     

A Minimax Method for Finding the k Best “Differentiated” Paths

In real-world applications, the k-shortest-paths between a pair of nodes on a network will often be slight variations of one another. This could be a problem for many path-based models, particularly those on capacitated networks where different routing alternatives are needed that are less likely to encounter the same capacity constraints. This paper develops a method to solve for k differentiated paths that are relatively short and yet relatively different from one another, but not necessarily disjoint. Our method utilizes the sum of a path's distance plus some fraction of its shared distance with each other path. A minimax algorithm is used to select the path whose largest sum of length, plus shared length vis-à-vis each previously selected path, is as small as possible. We present computational results for the Chinese railway system, comparing the paths generated by a standard k-shortest-path algorithm with those from our new model.     

基于网络分析的交通网络评价及其与区域经济发展关系研究

以网络分析为基础,使用节点连通性和可达性等指标,评价研究甘肃省的交通网络以及交通网络与区域经济发展之间的内在关系,提出了平均经济--网络直径概念、功能及其计算方法。研究结果表明,节点连通性和可达性指标与区域经济发展水平具有密切的相关性,且跨区域交通对区域经济发展的贡献率大于仅邻域交通对区域经济发展的贡献率;使用节点连通性和可达性指标可界定出各区域经济之间的空间相互作用范围,为整个区域的交通规划和经济区划提供有力的科学依据;甘肃省交通呈聚团模式,具有空间自相关性。     

AN ALGORITHM FOR THE SPATIAL PRICE EQUILIBRIUM PROBLEM ON A GENERAL NETWORK IN THE SPACE OF THE PATH FLOWS*

ABSTRACT. The spatial price equilibrium on a general network may be formulated as a nonlinear-cost mathematical programming problem with simple constraints, when the decision variables are the path flows. The solution of this problem is difficult due to the very large number of variables (paths) and the impracticality of generating all the paths from all the origins to all the destinations. In this paper, we develop a Gauss-Seidel-Newton Projection algorithm and combine it with a restriction strategy. That makes it unnecessary to generate a priori all the paths. This algorithm may be further improved by exploiting the equivalence between the spatial price equilibrium on a general network and the network equilibrium. Computational results that we present in this paper demonstrate the efficiency of the proposed solution algorithms.     

Measuring the Structure of Road Networks

Spatial networks display both topologic and geometric variations in their structure. This study investigates the measurement of a road network structure. Existing measures of heterogeneity, connectivity, accessibility, and interconnectivity are reviewed and three supplemental measures are proposed, including measures of entropy, connection patterns, and continuity. The proposed measures were applied to 16 test networks, which were derived from four idealized base networks: 90°, 45°, 30°, and completely connected. The results show that the differentiated structures of road networks can be evaluated by the measure of entropy; predefined connection patterns of arterial roads can be identified and quantified by the measures of ringness, webness, beltness, circuitness, and treeness. A measure of continuity evaluates the quality of a network from the perspective of travelers. Proposed measures could be used to describe the structural attributes of complicated road networks quantitatively, to compare different network structures, and to explore the structural evolution of networks in the spatial and temporal context. These measures can find application in urban planning and transportation practice.     

Dispersion of Nodes Added to a Network

For location problems in which optimal locations can be at nodes or along arcs but no finite dominating set has been identified, researchers may desire a method for dispersing p additional discrete candidate sites along the m arcs of a network. This article develops and tests minimax and maximin models for solving this continuous network location problem, which we call the added-node dispersion problem (ANDP). Adding nodes to an arc subdivides it into subarcs. The minimax model minimizes the maximum subarc length, while the maximin model maximizes the minimum subarc length. Like most worst-case objectives, the minimax and maximin objectives are plagued by poorly behaved alternate optima. Therefore, a secondary MinSumMax objective is used to select the best-dispersed alternate optima. We prove that equal spacing of added nodes along arcs is optimal to the MinSumMax objective. Using this fact we develop greedy heuristic algorithms that are simple, optimal, and efficient (O( mp )). Empirical results show how the maximum subarc, minimum subarc, and sum of longest subarcs change as the number of added nodes increases. Further empirical results show how using the ANDP to locate additional nodes can improve the solutions of another location problem. Using the p-dispersion problem as a case study, we show how much adding ANDP sites to the network vertices improves the p-dispersion objective function compared with (a) network vertices only and (b) vertices plus randomly added nodes. The ANDP can also be used by itself to disperse facilities such as stores, refueling stations, cell phone towers, or relay facilities along the arcs of a network, assuming that such facilities already exist at all nodes of the network.     

New path development between innovation systems and individual actors

ABSTRACT

This special issue is devoted to studying mechanisms that may stimulate or hamper the renewal of existing industry paths and the growth of new paths. In this guest editorial, we look closely at the role of policy instruments in situations where the majority of regional industries are embedded in strong regional and/or national innovation systems. This theme is currently very relevant in (parts of) Norway, where the dominant oil sector is downsizing and new growth paths are required to maintain employment and welfare. The guest editorial presents a theoretical framework for new regional industrial path development, followed by a discussion on how two Norwegian policy tools contribute to new path development. The 10 articles of the special issue study different aspects of new regional industrial path development based on cases in Norway, Sweden and Spain. Some papers also discuss the role of policy in new path development. Based on the findings from these articles, we believe that new path development is fostered by policies that incorporate both actor-based and system-based elements. Such policy mix could provide a vital push towards new path development.     

Chaoplexic warfare or the future of military organization

Scientific methods and concepts have been exerting a powerful influence on the exercising of armed force since the Scientific Revolution and the dawn of the modern era. In association with the respective technologies of the clock, engine and computer, the scientific theories of mechanism, thermodynamics, and cybernetics have all in turn been recruited to shape distinct approaches to the challenges of imposing order on the chaos of the battlefield. Today, it is on the basis of the new sciences of chaos and complexity that the latest regime of the scientific way of warfare is being erected. Chaoplexic warfare draws on the study of nonlinear phenomena of self‐organization to propose a radical decentralization of armed forces through the adoption of the network form. For all its present flaws, network‐centric warfare and its operational concepts of self‐synchronization and swarming mark an important step on the path to chaoplexic warfare.     

Remembering and Forgetting: The Relationship Between Memory and the Abandonment of Graves in Nineteenth- and Twentieth-Century Greek Cemeteries

This paper examines the concept of commemoration as an expression of social memory and its relationship to time and space as manifested through the mortuary evidence from Modern Greek cemeteries. Of particular interest is the act of commemoration itself: who remembers whom and the length of time that this type of memory endures. Based on evidence collected from a number of different cemeteries in northern Kythera and the eastern Corinthia, I argue that memory at the nuclear family level determines the length of time a grave is remembered as a physical location. Once this memory ceases to exist, the grave gradually enters a process of neglect, which ultimately leads to its abandonment. Some abandoned graves are recycled for use by other families who, in the absence of any recollection or memory of the grave, remove and destroy the old monuments (if they exist) and the remains of the previous occupants. Particular burial spaces are, thus, reclaimed by new groups.     

中国外资银行空间网络演化的结构特征及其影响因素

本文基于外资银行网点数据,借鉴连锁型网络模型,构建了1990年、2001年和2015年中国外资银行空间网络并分析演化结构特征,最后借助条件Logit模型探讨了外资银行空间分布的影响因素。研究表明：①中国外资银行空间网络小世界网络特征明显,具有较大的集聚系数和较小的平均路径长度,网络中局域小集团网络化特征和核心-边缘结构明显。②随着网络规模的平稳增长,网络的有序性呈现出增强趋势,网络中金融连接度和金融可达性增加,金融传输效率和组织效率进一步提高,核心-边缘结构现象有所加剧。③外资银行空间分布的主导因素在不同时期不一样,1990年主导因素是市场机会和区位效应,2001年和2015年的主导因素是金融集聚,但指标的具体影响概率有所降低。     

中国妇女发展脆弱性：测度、时空演化及驱动机制

借鉴人类发展指数（HDI）,从健康、教育及就业三大维度构建中国妇女发展脆弱性评估模型。以妇女发展脆弱性指数为测度指标,运用变异系数、LISA时间路径和时空跃迁等方法,对2006—2016年中国妇女发展状况的区域差异、空间分布和时空交互特征进行分析,并利用计量经济学模型探讨其影响机制。结果表明：①2006—2016年,中国妇女发展脆弱性总体上呈下降趋势,区域差异在波动中逐渐扩大。在区域尺度上,东部地区较低,中部和东北地区次之,西部地区最高。东部地区内部差异显著,呈现两极化;②脆弱性类型以低和较低脆弱类型为主,大致以“胡焕庸线”为界,西北半壁妇女发展脆弱性显著偏高;③中国妇女发展脆弱性空间分布具有较强的稳定性,存在一定的路径依赖和空间锁定特征。相对长度由东部沿海向西北内陆及西南地区递增,弯曲度表现出相似的空间分异特征;④妇女发展脆弱性是多因素交互作用的结果。经济发展水平、城镇化、全球化和教育事业发展对于降低妇女发展脆弱性具有积极作用。政府行为的驱动效应对脆弱性存在抑制作用,但未通过显著性检验。     

Nonparametric Significance Test for Discovery of Network‐Constrained Spatial Co‐Location Patterns

Spatial co‐location patterns are useful for understanding positive spatial interactions among different geographical phenomena. Existing methods for detecting spatial co‐location patterns are mostly developed based on planar space assumption; however, geographical phenomena related to human activities are strongly constrained by road networks. Although these methods can be simply modified to consider the constraints of networks by using the network distance or network partitioning scheme, user‐specified parameters or priori assumptions for determining prevalent co‐location patterns are still subjective. As a result, some co‐location patterns may be wrongly reported or omitted. Therefore, a nonparametric significance test without priori assumptions about the distributions of the spatial features is proposed in this article. Both point‐dependent and location‐dependent network‐constrained summary statistics are first utilized to model the distribution characteristics of the spatial features. Then, by using these summary statistics, a network‐constrained pattern reconstruction method is developed to construct the null model of the test, and the prevalence degree of co‐location patterns is modeled as the significance level. The significance test is evaluated using the facility points‐of‐interest data sets. Experiments and comparisons show that the significance test can effectively detect network‐constrained spatial co‐location patterns with less priori knowledge and outperforms two state‐of‐the‐art methods in excluding spurious patterns.     

国外区域经济研究的一个新趋势——区域经济网络研究

现代区域经济发展呈现出网络化的趋势。国外区域经济学者将复杂网络理论和方法引入到区域经济学中,逐渐开拓出区域经济网络研究这个新领域,形成了解释区域经济现象和揭示区域经济规律的网络分析路径。目前,国外的研究工作主要是运用复杂网络理论和分析方法,对区域经济中的各类网络进行规范的定义和描述,研究这些网络的形成与演化,揭示区域经济增长和发展中的网络效应,分析知识、技术等要素在网络中的流动和扩散。     

Experimental daytime VLF ionospheric parameters

Measured field strengths from VLF transmitters are used to determine improved daytime values of ionospheric parameters to enable improved VLF propagation predictions. These parameters are the traditional H′ (height in km) and β (sharpness in km⁻¹) as used by Wait and by NOSC in their Earthionosphere waveguide computer program. They are found by comparing the predictions of the NOSC program with the observed VLF field strengths over both long and short paths.Experimental observations from two nearly north-south paths are used to determine the solar zenith angle dependence of both H′ and β for low latitude (or summer mid-latitude) conditions. These results are then used to predict the daytime variations in VLF field strengths with solar zenith angle (and hence time) on other suitable paths and good agreement is found with measurements made on these paths.The absolute value of β for overhead Sun is found to be 0.45 km⁻¹ and is principally determined by the attenuation on the very long, west to east, fully sunlit, 14.4 Mm path from NWC (Australia, 22°S) to San Francisco (37°N), after applying small corrections for the solar zenith angle variations along the path at midday. Further support is obtained from results from the 8.6 Mm path NDT (Japan) to San Francisco, an 8.2 Mm path NPM (Hawaii) to New Zealand, and an east to west 7.5 Mm path from NPM to Townsville, Australia. The conditions studied are solar maximum. The frequencies studied are 15–30 kHz.