Spatial Dependence Research Papers - Academia.edu (original) (raw)

This paper examines the per capita income convergence process among 23 Argentinian provinces over the period 1983-2002. The purpose of this work is to apply new estimation methods following two-step procedure as in Badinger et al. (2004).... more

This paper examines the per capita income convergence process among 23 Argentinian provinces over the period 1983-2002. The purpose of this work is to apply new estimation methods following two-step procedure as in Badinger et al. (2004). We combine a spatial filtering of variables to remove the spatial correlation (Getis and Griffith, 2002) and suitable estimators for dynamic panels (using first-differenced and system GMM estimators). Our estimations on filtered variables reveal a conditional convergence process between Argentinian provinces and a positive and significant impact of agglomeration variables on growth rate. Hence, our results show that ignoring spatial distortions due to geographic proximity misleads estimations and underestimates the speed of convergence specifically for provinces which are distant from Buenos Aires. Moreover, we improve estimations of agglomeration effects when spatial autocorrelation is removed.

Selecting a the sampling design in experimental plots on the basis of the study of the spatial soil variability Data obtained by using a systematic sampling in two contrasting soils in the Venezuelan central plains were used to identify... more

Selecting a the sampling design in experimental plots on the basis of the study of the spatial soil variability Data obtained by using a systematic sampling in two contrasting soils in the Venezuelan central plains were used to identify the spatial soil variation and to optimize the sample design for monitoring changes induced by soil management. One of the soils

ABSTRACT Friction stir welding (FSW) has been widely used to metals with moderate melting temperatures, primarily Al alloys. Recently, tool materials that withstand high stresses and temperatures necessary for FSW of materials with high... more

ABSTRACT Friction stir welding (FSW) has been widely used to metals with moderate melting temperatures, primarily Al alloys. Recently, tool materials that withstand high stresses and temperatures necessary for FSW of materials with high melting temperatures have been developed. In the present Study tungsten carbide (WC) was used for FSW of dissimilar monel 400 alloy and 316 stainless steel, and a defect-free weld was successfully produced. Microstructural characteristics, and mechanical properties in the weld were examined. The work included microstructure examination, microhardness, tensile and fatigue tests of all joints. This study shows that the friction stir welded dissimilar joint present better mechanical properties when compared with each base material. Microhardness and tensile strength increased by more than 30% and 20%, respectively, as compared to base metal.

We develop a general space–time filter applied to panel data models in order to control for heterogeneity as well as both time and spatial dependence. Treatment of initial period observations is analyzed when the number of time periods... more

We develop a general space–time filter applied to panel data models in order to control for heterogeneity as well as both time and spatial dependence. Treatment of initial period observations is analyzed when the number of time periods is small. A second issue relates to a restriction implied by the filter specification on the space–time cross-product term that can greatly

Relationships between habitat structure and spatial variations in vegetation composition were determined in catenas of central Argentina salt marsh landscapes. Vegetation was classified following a multi-technique strategy. An analysis of... more

Relationships between habitat structure and spatial variations in vegetation composition were determined in catenas of central Argentina salt marsh landscapes. Vegetation was classified following a multi-technique strategy. An analysis of species distributions along an environmental gradient was made and a redundancy analysis was used to relate the environmental variables to vegetation data. The spatial covariation was evaluated through fractal analysis. The vegetation can be divided into four discrete noda that correspond to different topographic positions (summit, backslope, footslope and toeslope, respectively): nodum of Stipa trichotoma + St. tenuissima, nodum of Distichlis scoparia, nodum of Distichlis spicata and nodum of Spartina densiflora. Each of these nodum is characterized by a definite combination of floristic groups. Symmetric aggregation of vegetation borders was observed in all three sites. The existence of vegetation discontinuities along the catenas depended largely on water table depth and salinity which in turn controlled the edaphic salinity. The arrangement of sites by multivariate analysis reflected the influence of a complex gradient representing halomorphic and hydromorphic factors. β-diversity was associated with abrupt changes in the physical structure of the catena for a reduced spatial dimension (300-m scale). Absolute diversity and evenness were higher on the summit and declined progressively toward the toeslope. The rate of change was higher on the backslope and the dominant species have different ecological amplitudes overlapping along the gradient. The main operational factors associated with the floristic differences are: (i) the variations in the chemical composition and the seasonal dynamics of the soil solution in the aerated layer of soils, (ii) the salinity and dynamics of groundwater, and (iii) the length of time that the soil is flooded during the rainy season (summer). The fractal dimension was close to 2, implying weak spatial dependence. Fractal dimension varied as a function of scale. The fractogram only revealed a significant spatial dependence on the summit. This spatial dependence was associated with short distances of gradient showing that the organizational pattern of Distichlis spp.- Spartina was related to combinations of underlying environmental factors rather than to a specific position in the catena. The catenas are highly structured spatially, floristic compositions are inextricably linked to this structure. Habitat complexity may directly affect associated vegetation by regulating the hydrohalomorphic conditions in the aerated layer of the soils. The relationships of the habitat-floristic groups are not simple, hydromorphism interacts in a complex way with halomorphism.

This article has four aims. First is to clarify the origins and different meanings of place, space, and other basic concepts in spatial analysis. The second aim is to reiterate the illogicality of the spatial homogeneity assumption in... more

This article has four aims. First is to clarify the origins and different meanings of place, space, and other basic concepts in spatial analysis. The second aim is to reiterate the illogicality of the spatial homogeneity assumption in ordinary least squares (OLS) regression. An illustration of the comparison between traditional OLS and geographically weighted regression modeling is included for this purpose. The third aim is to explain that place matters in crime analysis not only when crime data are spatially clustered, but when relationships between correlates are found to be conditional upon place. The final aim is to convince criminology and criminal justice faculty to begin discussing the inclusion of spatial modeling as a compulsory topic in the curriculum.

Background Although there are inequalities in child health and survival in the Democratic Republic of Congo (DRC), the influence of distal determinants such as geographic location on children's nutritional status is still unclear. We... more

Background Although there are inequalities in child health and survival in the Democratic Republic of Congo (DRC), the influence of distal determinants such as geographic location on children's nutritional status is still unclear. We investigate the impact of geographic location on child nutritional status by mapping the residual net effect of malnutrition while accounting for important risk factors. Methods We examine spatial variation in under-five malnutrition with flexible geo-additive semi-parametric mixed model while simultaneously controlling for spatial dependence and possibly nonlinear effects of covariates within a simultaneous, coherent regression framework based on Markov Chain Monte Carlo techniques. Individual data records were constructed for children. Each record represents a child and consists of nutritional status information and a list of covariates. For the 8,992 children born within the last five years before the survey, 3,663 children have information on anthropometric measures. Our novel empirical approach is able to flexibly determine to what extent the substantial spatial pattern of malnutrition is driven by detectable factors such as socioeconomic factors and can be attributable to unmeasured factors such as conflicts, political, environmental and cultural factors. Results Although childhood malnutrition was more pronounced in all provinces of the DRC, after accounting for the location's effects, geographic differences were significant: malnutrition was significantly higher in rural areas compared to urban centres and this difference persisted after multiple adjustments. The findings suggest that models of nutritional intervention must be carefully specified with regard to residential location. Conclusion Childhood malnutrition is spatially structured and rates remain very high in the provinces that rely on the mining industry and comparable to the level seen in Eastern provinces under conflicts. Even in provinces such as Bas-Congo that produce foods, childhood malnutrition is higher probably because of the economic decision to sell more than the population consumes. Improving maternal and child nutritional status is a prerequisite for achieving MDG 4, to reduce child mortality rate in the DRC.