Contiguity Criteria Research Articles

Mathematical political districting taking care of minority groups

Political districting (PD) is a wide studied topic in the literature since the 60s. It typically requires a multi-criteria approach, and mathematical programs are frequently suggested to model the many aspects of this difficult problem. This implies that exact models cannot be solved to optimality when the size of the territory is too large. In spite of this, an exact formulation can also be exploited in a heuristic framework to find at least a sub-optimal solution for large size problem instances. We study the design of electoral districts in Mexico, where the population is characterized by the presence of minority groups (“indigenous community”) who have a special right to be represented in the Parliament. For this, the Mexican electoral law prescribes that a fixed number of districts must be designed to support the representation of the indigenous community. We formulate mixed integer linear programs (MILP) following these two principles, but also including the basic PD criteria of contiguity and population balance. The district map is obtained in two stages: first we produce the fixed number of indigenous districts established by the Law; then we complete the district map by forming the non-indigenous districts. This two-phase approach has two advantages: a dedicated objective function can be formulated in Phase 1 to form indigenous districts at best; in the second phase the instance size is reduced (both in the number of territorial units and in the number of districts) so that the computational effort to solve the problem is reduced as well. We test our procedure on the territory of Chiapas in Mexico and on some fictitious problem instances in which the territory is represented by a grid graph. We also compare our district map with the Institutional one currently adopted in Chiapas.

Enhancing an unsupervised clustering algorithm with a spatial contiguity constraint for river habitat analysis

AbstractThe spread of two‐dimensional numerical hydrodynamic tools for ecohydraulic applications allowed for the development of automatic habitat detection methods, adopted as predicting tools for river habitat analysis. These automatic approaches differ for the employed identification rules, such as preference curves, fuzzy rules and clustering methods. Previous research has shown promising results in the automatic identification of mesoscale habitat patches by using clustering algorithms together with numerical hydrodynamic model results. These algorithms attempt to implement and simulate some of the expert‐based requirements adopted in the field to delineate habitat patches. Spatial contiguity is one of such expert‐based requirements that has not been enforced and exploited in automatic mesohabitat identification so far. In this work, we propose a novel tool (BASEmeso) based on an agglomerative hierarchical clustering algorithm where we enforced a spatial contiguity criteria. We compare our approach with a more established method without spatial constraints, considering a synthetic river reach where the composition of mesohabitat patches is known a priori, and on three experimental river reaches, to investigate the effects of different river morphologies. Our results show that when employing a contiguity constraint, a patch's extent is better captured, different patches can be distinguished better and the distribution of patch characteristics is smoother. This holds for all investigated morphologies. Together, it suggests that including a spatial contiguity constraint can improve the automatic delineation of river mesohabitat patches. The proposed methodology could positively contribute in the development of automatic, objective and predictive meso‐scale habitat assessment workflows.

Simultaneous node and link districting in transportation networks: Model, algorithms and railway application

Partitioning a large network into multiple subnetworks is adopted extensively in various practical applications involving the architecture of distributed management. In this study, we consider strategic simultaneous node and link districting to partition the nodes and links of a given transportation network into a fixed number of mutually disjoint districts, based on the districting criteria of integrity, contiguity, balance, and independence. We first formulate the resulting problem as a mixed integer linear programming model to minimize the weighted sum of the total size deviation of districts and total cooperation between districts. An improved network flow-based technique is proposed to incorporate the complicated contiguity criterion by using a polynomial number of constraints. Valid inequalities, which break the symmetry within and between districts, are designed to strengthen the model. To solve this challenge problem, we reformulate it as a binary linear programming model, and develop a column generation-based algorithm to find tight lower bounds and good-quality solutions. Then, an iterative search algorithm is designed to obtain good-quality solutions rapidly. Furthermore, a more efficient hybrid algorithm is proposed by using the results of the iterative search algorithm to initialize the column generation-based algorithm. We assess the proposed model and algorithms by using various scales of instances derived from the train dispatcher desk districting problem, which is a practical application of the investigated problem in the context of railway. The computational results reveal that our approaches outperform existing approaches and a commercial solver, and our best algorithm can solve almost all the investigated instances to optimality within a considerably short average computation time. The districting solutions of our approaches are also better than the empirical solutions designed by railway managers mainly based on experience.

Designing Zoning Systems for Freight Transportation Planning: A GIS-based approach for Automated Zone Design using Public Data Sources

The first step in transportation planning studies is the discretization of study area into numerous zones. Zoning systems are expected to reflect the characteristics of the area they divide and is of crucial importance to the planning process. In order to obtain zones appropriate for freight demand modelling, the zoning process needs to be incorporated with zonal characteristics that account for inter-zone variability of freight movements. These zones can be termed as Freight Traffic Analysis Zones (FTAZs). Although these zones will ease the task of freight data collection, compatibility should exist between zoning systems for passenger and freight movements. The existing zoning systems, such as census boundaries, lacks the generalizability to use in passenger and freight transportation planning framework, hence needs to be updated. Rather than using the existing zones or completely changing them on an administrative scale, the alternative option could be to update the zones by regrouping them using an automated zone design methodology. The objective of automated zone design is to maximize the homogeneity in FTAZs using a cluster analysis while effectively incorporating the essential contiguity criteria. This could be efficiently done on a Geographic Information System (GIS) platform. This research aims to demonstrate the design of FTAZs by performing clustering analysis of basic spatial units in a GIS platform. Jaipur Metropolitan region is taken as a case study in this paper to execute the methodology with the use of publicly available data sources. The analyses and findings presented in this paper should be helpful for identifying appropriate zone delineation strategies for developing freight demand models.

G-STAR Model for Forecasting Space-Time Variation of Temperature in Northern Ethiopia

Among many indicators of climate change, the temperature is a key indicator to take remedial action for world global warming. This finding provides application of space-time models for temperature data, which is selected in three meteorology stations (Mekelle, Adigrat and Adwa) of Northern Ethiopia. The objectives of this research are to see the space-time variations of temperature and to find better forecasting model. The steps for building this model starting from order selection of space and autoregressive order, parameters estimation, a diagnostic check of errors and finally forecasting for the long term. The preliminary model is identified by VAR (vector autoregressive) model and tentatively selects the order by using MIC (minimum information criteria) and uses the autoregressive order for the model and fixes the spatial effect, model parameters are estimated using the least square method. Weighted matrix computed by using queen contiguity criteria. It is found that the model STAR(1,1) and GSTAR(1,1) are two options, finally the best-fitted model is GSTAR(1,1) which has high forecasting performance and smallest RMSEF. The outcome of the forecast indicated that in northern Ethiopia, the weather conditions especially temperature of future is increasing trend in dry seasons in all 3 stations in similar fashion but more consistent and has less variation across the region, and less consistent and high variation within the region and the researcher found that spatial effect has high impact on prediction of models.

Evaluation of left atrial linear ablation using contiguous and optimized radiofrequency lesions: the ALINE study.

Achieving block across linear lesions is challenging. We prospectively evaluated radiofrequency (RF) linear ablation at the roof and mitral isthmus (MI) using point-by-point contiguous and optimized RF lesions. Forty-one consecutive patients with symptomatic persistent AF underwent stepwise contact force (CF)-guided catheter ablation during ongoing AF. A single linear set of RF lesions was delivered at the roof and posterior MI according to the 'Atrial LINEar' (ALINE) criteria, i.e. point-by-point RF delivery (up to 35 W) respecting strict criteria of contiguity (inter-lesion distance ≤ 6 mm) and indirect lesion depth assessment (ablation index ≥550). We assessed the incidence of bidirectional block across both lines only after restoration of sinus rhythm. After a median RF time of 7 min [interquartile range (IQR) 5-9], first-pass block across roof lines was observed in 38 of 41 (93%) patients. Final bidirectional roof block was achieved in 40 of 41 (98%) patients. First-pass block was observed in 8 of 35 (23%) MI lines, after a median RF time of 8 min (IQR 7-12). Additional endo- and epicardial (54% of patients) RF applications resulted in final bidirectional MI block in 28 of 35 (80%) patients. During a median follow-up of 396 (IQR 310-442) days, 12 patients underwent repeat procedures, with conduction recovery in 4 of 12 and 5 of 10 previously blocked roof lines and MI lines, respectively. No complications occurred. Anatomical linear ablation using contiguous and optimized RF lesions results in a high rate of first-pass block at the roof but not at the MI. Due to its complex 3D architecture, the MI frequently requires additional endo- and epicardial RF lesions to be blocked.

La evolución espacial de los subcentros de empleo en Ciudad Juárez, Chihuahua (1994-2004): un análisis con indicadores de autocorrelación espacial global y local / The Spatial Evolution of Employment Subcenters in Ciudad Juárez, Chihuahua (1994-2004): An Analysis Using Global and Local Spatial Autocorrelation Indicators

El objetivo del artículo es identificar los subcentros de empleo total mediante el uso de indicadores de autocorrelación espacial global y local en Ciudad Juárez, Chihuahua, en el periodo 1994-2004. Esta metodología usa matrices de pesos espaciales e incorpora la noción de unidades vecinas y no está limitada al criterio de contigüidad del método de doble umbral. La variable usada fue la densidad bruta de empleo total (manufactura, comercio y servicio) en los años 1994 y 2004 a nivel de AGEB, obtenida de los Censos Económicos (INEGI, 1994 y 2004). Mediante el uso de dos indicadores de autocorrelación espacial, en específico el I de Moran y los indicadores locales de asociación espacial (LISA por sus siglas en inglés), fue posible identificar varios centros y subcentros de empleo total. Los resultados muestran la presencia de dependencia y heterogeneidad espacial que se manifiestan en la forma de agrupamientos de alta densidad de empleo (alto-alto) tanto en el distrito central de negocios (DCN) como en el subcentro de empleo mixto localizado en el corredor industrial de la avenida Rafael Pérez Serna. Asimismo, existen varios subcentros de empleo manufacturero aislados de alta densidad (alto-alto) localizados sobre las principales vialidades dirigidas a puertos internacionales. En este contexto, se puede concluir que la distribución del empleo fuera del DCN, producto de economías de aglomeración, implica la presencia de una estructura urbana policéntrica.Abstract:The objective of this article is to identify total employment subcenters through the use of global and local spatial autocorrelation indicators in Ciudad Juárez, Chihuahua, during the period from 1994-2004. This methodology uses spatial weights matrices, includes the notion of neighboring units and is not restricted to the contiguity criterion of the double threshold method. The variable used was the gross density of total employment (manufacturing, trade and service) in 1994 and 2004 at the ageb level, obtained from the Economic Census (INEGI, 1994 and 2004). Two spatial autocorrelation indicators, specifically Moran’s I and local indicators of spatial association (LISA) were used to identify several centers and sub-centers of total employment. The results show the presence of dependence and spatial heterogeneity expressed in the form of groups of high density employment (high-high) in both the central business district (CBD) and the mixed employment subcenter located in the industrial corridor of Avenida Rafael Pérez Serna. Likewise, there are several isolated high density manufacturing employment subcenters (high-high) located on the main roads leading to international ports. In this context, one can conclude that employment distribution outside the CBD, resulting from agglomeration economies, implies the presence of a polycentric urban structure.

Spatial Econometric Model of Poverty in Java Island

This paper gives the concept of spatial econometric model and applies it to analyze the spatial dimensions of poverty and its determinants using data from Java Island 2010 census survey, for 105 districts of Java Island. Dependent variable used in this research is percentage of poverty rate at particular district and predictors are some selected variables that are correlated to poverty. Weighted matrix is obtained by using queen contiguity criteria and four statistical models are applied to the data, Ordinary Least Square regression model, Spatial Error Model, Spatial Lag Model and Spatial Durbin Model. It is shown that the OLS estimates of the poverty function suffer from spatial effects that indicated the OLS model are miss specified since Moran Index test also confirmed the existence of spatial autocorrelation. LM and Robust LM are used for testing the existence of spatial effect. The Likelihood Ratio common factor test and AIC are used for model selection criteria. Gauss Markov Assumptions are done and the Spatial Lag model proved to be better than other model for a given data and the result shows that Education and Working hours has significant impact on poverty.

Persistent extreme precipitation events in China during 1951-2010

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 57:143-155 (2013) - DOI: https://doi.org/10.3354/cr01171 Persistent extreme precipitation events in China during 1951-2010 Yang Chen, Panmao Zhai* State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, CMA, Beijing, P. R. China *Corresponding author. Email: pmzhai@cma.gov.cn ABSTRACT: Persistent extreme precipitation events (PEPEs) in China are investigated in the context of a new definition that considers both the persistence and the extremity of daily precipitation at individual stations. An identification method for regional PEPEs is designed based on joint application of this definition and a spatial contiguity criterion. Between 1951 and 2010, individual-station-based PEPEs occurred mainly in Central-Eastern China (26-34°N) and South China (south of 26°N). Relatively few PEPEs were observed in the northern part of China (north of 34°N). Individual-station-based PEPEs in Central-Eastern China and South China were also typically of higher intensity and longer duration than those observed in the northern part of China. Altogether, 74 regional events are identified. The stations involved in these regional events correspond to the centers of intense precipitation associated with the event. These areas are prone to severe flooding. Of the 74 identified PEPEs, 70 occurred in the central and southern parts of eastern China (primarily the Yangtze-Huai River Valley and South China). Only 4 events occurred in the northern part of China. Regional PEPEs occurred more frequently after 1990, with higher mean intensity, longer mean duration, and larger affected areas. The 74 regional PEPEs are classified and analyzed according to occurrence time, geographical location, and the influence of typhoons. KEY WORDS: Persistent extreme precipitation · Regional event · Disaster · Climate change Full text in pdf format PreviousNextCite this article as: Chen Y, Zhai P (2013) Persistent extreme precipitation events in China during 1951-2010. Clim Res 57:143-155. https://doi.org/10.3354/cr01171 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 57, No. 2. Online publication date: August 20, 2013 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2013 Inter-Research.

Age-related cerebral white matter changes and pulse-wave encephalopathy: observations with three-dimensional MRI

Our purpose was to investigate leukoaraïosis (LA) using three-dimensional MR imaging combined with advanced image-processing technology to attempt to group signal abnormalities according to their etiology. Coronal T2-weighted fast fluid-attenuated inversion-recovery (FLAIR) sequences and three-dimensional T1-weighted fast spoiled gradient recalled echo sequences were used to examine cerebral white matter changes in 75 elderly people with memory complaint but no dementia. They were otherwise healthy, community-dwelling subjects. Three subtypes of LA were defined on the basis of their shape, geography and extent: the so-called subependymal/subpial LA, perivascular LA and "bands" along long white matter tracts. Subependymal changes were directly contiguous with ventricular spaces. They showed features of "water hammer" lesions with ventricular systematisation and a more frequent location around the frontal horns than around the bodies (P=.0008). The use of cerebrospinal fluid (CSF) contiguity criterion allowed a classification of splenial changes in the subpial group. Conversely, posterior periventricular lesions in the centrum ovale as well as irregular and extensive periventricular lesions were not directly contiguous with CSF spaces. The so-called perivascular changes showed features of small-vessel-associated disease; they surrounded linear CSF-like signals that followed the direction of perforating vessels. Distribution of these perivascular changes appeared heterogeneous (P ranging from .04 to 5.10(-16)). These findings suggest that subependymal/subpial LA and subcortical LA may be separate manifestations of a single underlying pulse-wave encephalopathy.

Specificity of Atrial Mode Switching in Detecting Atrial Fibrillation Episodes:

The number of automatic mode switch (AMS) has been used to measure the efficacy of atrial pacing in limiting atrial fibrillation (AF). We investigated the impact of length and contiguity on the specificity of AMS in detecting AF episodes in 24 recipients of dual chamber pacemakers with sick sinus syndrome and paroxysmal AF. An AMS algorithm and intracardiac electrogram recordings (IEGM) were activated in all patients to distinguish true arrhythmic events from unnecessary AMS. The length of AMS and the contiguity, that is, the probability of occurrence of another AMS within 5 minutes before or after AMS were examined to increase the specificity of the AMS. During a mean follow-up of 5 +/- 3 months, 250 AMS were collected. The IEGM analysis confirmed a true AF episode in 193 of 250 AMS (77.2%). Using the contiguity criterion, 47 of 57 (82.5%) inappropriate AMS episodes were isolated (there were no other AMS within 5 minutes), whereas 54 of 193 (27.9%) appropriate AMS episode were isolated. Adopting both length and contiguity criteria the specificity of AMS in detecting true AF episodes increased from 77.2% to 93.2% at the cost of 11.9% loss of original sensitivity. Combining the length and contiguity criteria, we were able to improve the specificity of the AMS in the detection of AF.

Solar Feature Identification using Contrasts and Contiguity

We present a new technique for the rapid, automatic identification of solar features on full-disk photometric images. The technique permits the detection of features whose contrasts are only slightly above the noise level. Contrast and contiguity criteria are used to identify pixels belonging to an individual feature. The criteria used are simple and objective, and do not require one to guess at the contrast distribution of the features. Comparison of Ca ii K images with magnetograms shows excellent agreement between the identified features and observed magnetic features. In addition, we can now reliably identify faculae on continuum images. Since this technique can be rapidly applied to a large set of images, it allows us to compile a database of the physical and photometric properties of individual solar features.

Asymptotic arbitrage in large financial markets

A large financial market is described by a sequence of standard general models of continuous trading. It turns out that the absence of asymptotic arbitrage of the first kind is equivalent to the contiguity of sequence of objective probabilities with respect to the sequence of upper envelopes of equivalent martingale measures, while absence of asymptotic arbitrage of the second kind is equivalent to the contiguity of the sequence of lower envelopes of equivalent martingale measures with respect to the sequence of objective probabilities. We express criteria of contiguity in terms of the Hellinger processes. As examples, we study a large market with asset prices given by linear stochastic equations which may have random volatilities, the Ross Arbitrage Pricing Model, and a discrete-time model with two assets and infinite horizon. The suggested theory can be considered as a natural extension of Arbirage Pricing Theory covering the continuous as well as the discrete time case.

Large Financial Markets: Asymptotic Arbitrage and Contiguity

We introduce a large financial market as a sequence of ordinary security market models (in continuous or discrete time). An important property of such markets is the absence of asymptotic arbitrage, i.e., a possibility to obtain “essential” nonrisk profits from “infinitesimally” small endowments. It is shown that this property is closely related to the contiguity of the equivalent martingale measures. To check the no asymptotic property one can use the criteria of contiguity based on the Hellinger processes. We give an example of a large market with correlated asset prices where the absence of asymptotic arbitrage forces the returns from the assets to approach the security market line of the CAPM.

MOVIES-B: an acoustic detection description software. Application to shoal species' classification

Resume Software, MOVIES-B, developed by lFREMER (Institut francais de recherche pour l'exploitation de la mer), enables the recognition of echogram features as acoustic detection structures according to spatial-energetic contiguity criteria. These structures (shoals, plankton layers) are described by energetic, morphological, spatial and temporal descriptors. Specifying acoustic detections as individual shoals will allow shoal by shoal echo-integration and may lead to better biomass estimation and shoal species description. The conceptual and operational framework of MOVIES-B is presented in the first part of this paper. The second part presents preliminary work performed in order to assess the feasibility of classification and possible species identification of shoals using MOVIES-B software. This research has studied the data set obtained from four fisheries acoustic surveys, in the Bay of Biscay. The data set is a matrix of 29 descriptors from 13,122 shoals. A limited knowledge of species composition was obtained from trawling. Eight species were captured: Sardina pilchardus, Clupea harengus, Sprattus sprattus, Engraulis encrasicolus, Micrornesistius poutassou, Trachurus sp., Scomber sp. and Capros aper. Cluster analysis and linear discriminant analysis were performed on trawled identified shoals data (808 shoals), after a reduction of the space descriptors by a stepwise technique. A partition into 6 clusters was carried out and clusters are described by species composition and continuous variables values. After grouping the six species shoals in two groups, 84% of shoals from the testing data set could be correctly classified using the linear discriminant function.

Three-dimensional knowledge driven reconstruction of coronary trees

A knowledge-driven approach to the three-dimensional reconstruction of coronary artery trees by means of two X-ray projections is proposed. The spatial reconstruction of the tree skeleton is discussed. A binary tree model of the arterial structure and its projections is employed. Consequently, the reconstruction of the three-dimensional tree skeleton is achieved by (a) matching the skeletons of corresponding pairs of vascular segments in the two views and (b) back-projecting the coupled skeleton projections. From a geometrical point of view, the matching problem is, in general, ill-conditioned. For this reason, additional information sources were used. Thus, the matching phase is accomplished by using both the imaging geometry information, as well as anatomical and topological knowledge, about the coronary arteries coded in a rule base. As far as the back-projection phase is concerned, an algorithm was developed based on: (1) the imaging geometry, (2) the bounding of the back-projection error and (3) a contiguity criterion.

A second stage trigger for track reconstruction based on contiguity ideas

A fast modular processor to search for tracks from wire chamber arrays is presented. The processor works out the track search by applying an algorithm based on contiguity criteria.