spatial process
Recently Published Documents

This study presents the results of a landslide susceptibility analysis applied to the Vrancea-Buzău seismogenic region in the Carpathian Mountains, Romania. The target area is affected by a large diversity of landslide processes. Slopes are made-up of various types of rocks, climatic conditions can be classified as wet, and the area is a seismically active one. All this contributes to the observed high landslide hazard. The paper analyses the spatial component of the landslide hazard affecting the target area, the regional landslide susceptibility. First, an existing landslide inventory was completed to cover a wider area for the landslide susceptibility analysis. Second, two types of methods are applied, a purely statistical technique, based on correlations between landslide occurrence and local conditions, as well as the simplified spatial process-based Newmark Displacement analysis. Landslide susceptibility maps have been produced by applying both methods, the second one also allowing us to simulate different scenarios, based on various soil saturation rates and seismic inputs. Furthermore, landslide susceptibility was computed both for the landslide source and runout zones—the first providing information about areas where landslides are preferentially triggered and the second indicating where landslides preferentially move along the slope and accumulate. The analysis showed that any of the different methods applied produces reliable maps of landslide susceptibility. However, uncertainties were also outlined as validation is insufficient, especially in the northern area, where only a few landslides could be mapped due to the intense vegetation cover.

Spatial statistics is concerned with the analysis of data that have spatial locations associated with them, and those locations are used to model statistical dependence between the data. The spatial data are treated as a single realization from a probability model that encodes the dependence through both fixed effects and random effects, where randomness is manifest in the underlying spatial process and in the noisy, incomplete measurement process. The focus of this review article is on the use of basis functions to provide an extremely flexible and computationally efficient way to model spatial processes that are possibly highly nonstationary. Several examples of basis-function models are provided to illustrate how they are used in Gaussian, non-Gaussian, multivariate, and spatio-temporal settings, with applications in geophysics. Our aim is to emphasize the versatility of these spatial-statistical models and to demonstrate that they are now center-stage in a number of application domains. The review concludes with a discussion and illustration of software currently available to fit spatial-basis-function models and implement spatial-statistical prediction. Expected final online publication date for the Annual Review of Statistics and Its Application, Volume 9 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

PurposeThe purpose of this paper is to estimate crop yield densities considering time trends in the first three moments and spatially varying coefficients.Design/methodology/approachYield density parameters are assumed to be spatially correlated, through a Gaussian spatial process. This study spatially smooth multiple parameters using Bayesian Kriging.FindingsAssuming that county yields follow skew normal distributions, the location parameter increased faster in the eastern and northwestern counties of Iowa, while the scale increased faster in southern counties and the shape parameter increased more (implying less left skewness) in southwestern counties. Over time, the mean has increased sharply, while the variance and left skewness increased modestly.Originality/valueBayesian Kriging can smooth time-varying yield distributions, handle unbalanced panel data and provide estimates when data are missing. Most past models used a two-stage estimation procedure, while our procedure estimates parameters jointly.

A kernel conditional quantile estimate of a real-valued non-stationary spatial process is proposed for a prediction goal at a non-observed location of the underlying process. The originality is based on the ability to take into account some local spatial dependency. Large sample properties based on almost complete and \(L^q\)-consistencies of the estimator are established. A numerical study is given in order to illustrate the performance of our methodology.

Barrett’s esophagus (BE) is a benign condition of the distal esophagus that initiates a multistage pathway to esophageal adenocarcinoma (EAC). Short of frequent intrusive (and costly) surveillance, effective screening for neoplasia in BE populations is yet to be established since progressors are rare and virtually undetectable without routine biopsies, which often sample only a small portion of the BE tissue. As a result, reliable estimation of the true prevalence of dysplasia in a BE population and evidence-based optimization of screening for at-risk individuals is challenging. Data-driven microsimulations, i.e., model-generated instances of disease history in a predefined virtual population, have found utility in the EAC screening literature as low-overhead alternatives to real-world hypothesis testing of optimal interventions for dysplasia. Despite the successes, computational limitations, paucity of knowledge and data on Barrett’s dysplasia, and the complexities of disease progression as a multiscale multiphysics process have hindered the treatment of disease progression in BE as a spatial process. Agent-based modeling of nucleation and proliferation processes in dysplasia warrants exploration in this context as an approximation that operates at a trade-off between computational tractability and precise representation of the composition and physics of the substrate (tissue). In this study, we describe spatially resolved simulations of premalignant progression toward EAC in a coarse-grained model of Barrett’s tissue that resolves the metaplastic tissue at a length scale of 0.42 mm (~3300 crypts/mm2). The model is calibrated to reproduce historical high-grade dysplasia prevalence when model-generated patients are screened using the Seattle protocol.

The engagement of people in extremely low-wage work in major cities of the Global South and their withdrawal from labour-organising activities arise from several factors. Among these is the hegemonic meaning construction of work as ‘timepass’ or leisure and as an opportunity for sociality and neighbourliness that is central to the social reproduction of everyday life. Drawing on ethnographic fieldwork in Delhi, this article examines how work regimes are marked by a ‘commission economy’, whereby various stakeholders in the chain of surplus accumulation demand a commission for their services. The possibility of undertaking informal economic activities is contingent on a host of improvisations that are founded upon discipline, violence and also solidarity. In this respect, various stakeholders possess what they refer to as a ‘setting’, which alludes to an active process of economic and non-economic relationship-building with both state and non-state agencies within both formal and informal arenas. To ‘do setting’ is a dynamic spatial process that draws on negotiations with the aim of shaping favourable relationships and outcomes in particular urban spaces. It entails the use of social and cultural resources, everyday political negotiations and extra-judicial solutions.

Clustering in spatial data is very common phenomena in various fields such as disease mapping, ecology, environmental science and so on. Analysis of spatially clustered data should be different from conventional analysis of spatial data because of the nature of clusters in the data. Because it is expected that the observations of same cluster are more similar than the observations from different clusters. In this study, a method has been proposed for the analysis of spatially clustered areal data based on generalized estimating equations which were originally developed for analyzing longitudinal data. The performance of the model for known clusters is tested in terms of how well it estimates the regression parameters and how well it captures the true spatial process. These results are presented and compared with the conditional auto-regressive model which is the most frequently used spatial model. In the simulation study, the proposed generalized estimating equations approach yields better results than the popular conditional auto-regressive model from the both perspectives of parameter estimation and spatial process capturing. A real life data on the vitamin A supplement coverage among postpartum women in Bangladesh is then analyzed for demonstration of the method. The existing divisional clustering behavior of vitamin A supplement coverage in Bangladesh is identified more accurately by the proposed approach than that by the conditional auto-regressive model.

A great number of various factors to a different extent impact iron ore treatment, properties of mineral composition of ore and parameters of technological equipment being some of them. To solve the problem of improving performance of a concentration plant in terms of the concentrate, it is required to elaborate effective scheduled procedures, upgrade technological equipment, develop methods of control over concentration processes considering technological properties of ore fed. There is suggested a method of improving efficiency of magnetic concentration of iron ore under the action of high-intensity ultrasound. There are established dependencies between physical-mechanical and chemical-mineralogical characteristics of iron ore slurry solids and their behavior in technological flows under controlled ultrasonic vibrations, this enabling simulation modelling of the process and specification of optimal controlling actions. The research object is assessment of characteristics and control of iron ore magnetic concentration on the technological line of the ore concentration plant. The research subject is the cyber-physical system based on using impacts of highintensity ultrasound on slurry solids to assess characteristics of iron ore magnetic concentration. Obtained dependencies and mathematical models of the non-linear spatial process of high-intensity ultrasound propagation in the iron ore slurry enable implementing the method of assessing characteristics of iron ore magnetic concentration and due to this increase efficiency of the mentioned operations. There are suggested methods of calculating intensity of high-intensity ultrasound in a certain point of the measurement area in order to perform forecast displacement of ground ore particles and changes of the fraction composition of slurry solids under the controlled action of high-intensity ultrasonic vibrations. The developed method and the software-engineering complex for its implementation enable restoring a function of distributing ground ore particles by sizes, forecasting results of technological operations and forming controlling actions.