Spreading Direction Research Articles

Analyzing spatiotemporal species spread by three declustering methods utilizing monitoring data based on national programs and citizen science

Systematic and dynamic monitoring of species is often performed at preferential locations. Thus, while models of spatial distributions assume evenly distributed spatial sampling, sampling designs are often clustered, resulting in biased estimates. Therefore, spatial declustering methods should be used to reduce bias, for example when quantifying the spread of invasive species. However, little is known about the relative efficiency of such methods. In this study, the spatiotemporal spread of a species was estimated from synthetic data and from field-collected data, using three alternative declustering methods. We compared two grid-based methods that involve data depletion, and a polygon area weighting method (Multiplicatively Weighted Buffer-Thiessen Polygons; MWBTP), in which constrained weights account for spatial redundancy without any loss of data. We applied the effective range radius method to estimate spread rate from range areas in different time steps. The spread rate was determined as a linear regression slope between the effective range radius (range area/π) and time. Range areas were produced using 95% isopleth of kernel density estimation, with either fixed or adaptive bandwidths. Directional spread was quantified using the displacement of the population's weighted mean centers over time, and the direction of spread was determined using their standard deviational ellipse. We simulated spatially clustered sampling data, and compared the spread rates based on each of the three declustering methods, relative to that measured under an evenly distributed sampling. MWTBP best estimated the spread rate using adaptive-bandwidth KDE (−2.2% relative difference from the even distribution), whereas the clustered distribution produced a −34.4% relative difference. The grid-based methods produced relative differences of −19.6% and −28.5%. Our field data span two years from an Israeli national monitoring program of the invasive red palm weevil, Rhynchophorus ferrugineus, in which weevil traps were distributed in clusters. The grid-based methods showed small relative differences of up to 2% in spread rate, compared to uncorrected estimates, with MWBTP resulting in the greatest difference (−7% relative difference). The spread direction as evaluated by MWBTP deflected 18.3° from that of the uncorrected method and best reflected the actual spread direction. In conclusion, MWBTP appears to best overcome clustering, and yields superior or similar results to those of the other, more commonly-used methods. Databases from field monitoring programs are accumulating at accelerating rates, commonly with spatial clustering. Thus, we suggest further development and application of declustering methods on such spatial data to reduce biases in ecological and agricultural research and practice.

Link between melt-impregnation and metamorphism of Atlantis Massif peridotite (IODP Expedition 357)

IODP Expedition 357 drilled 17 shallow sites scattered over ~ 10 km in the west to east spreading direction across the Atlantis Massif oceanic core complex (OCC, MAR, 30 ºN). Mantle exposed in the footwall of the Atlantic Massif OCC is nearly wholly serpentinized (80–100%) harzburgite and subordinate dunite. A recent whole-rock chemistry study by Whattam et al. (Chemical Geology 594. 10.1016/j.chemgeo.2021.120681, 2022) subdivides Atlantis Massif peridotites into: Type I fluid–rock dominated serpentinite, which exhibits almost nil evidence of melt-impregnation or silica metasomatism; Type II melt–rock dominated, mafic melt-impregnated serpentinite; and Type III melt–rock dominated Si-metasomatized serpentinite. In this study, on the basis of EPMA, three kinds of Cr–spinel are distinguished in Expedition 357 serpentinite: (I) primary, unmetamorphosed mantle array, (II) low-Ti metamorphosed, and (III) high-Ti melt reacted. All Cr–spinel of western site Type I serpentinite is unmetamorphosed (n = 34) and comprises 68% of all unmetamorphosed Cr–spinel. Metamorphosed Cr–spinel (n = 100) are the most abundant and occur in the central and eastern site Type II and Type III serpentinite, whereas melt-reacted Cr–spinel and chromite are restricted to the central sites and occur predominantly in serpentinized dunite. Estimates of the degree of melt extraction of Type I serpentinite using F = 10ln(spinel Cr#) + 24 are ~ 9–17%. Fugacity calculations of primary, unmetamorphosed Cr–spinel yield Δlog(fO2)FMQ of − 1.7 to + 1.0 and calculations using olivine–spinel Mg–Fe exchange thermometry yield a mean closure temperature of 808 ± 39 °C. Mafic melt-impregnation resulted in Cr–spinel with anomalously high TiO2 of 0.27–0.68 wt.% and production of Ti-rich chromite (up to 1.23 wt.% TiO2). Greenschist facies metamorphism (< 500 °C) resulted in Mg–Fe2+ exchange between Cr–spinel and forsterite and anomalously low Cr–spinel Mg#; higher degrees of amphibolite facies metamorphism (~ 500–700 °C) also resulted in anomalously high Cr# due to Al–Cr exchange. As has been previously established, significant Al loss from chromite cores above 550 °C is the result of equilibration with fluids in equilibrium with chlorite, which may be valid for our samples. On the basis of Cr–spinel vs. whole-rock compositions, a clear relationship exists between melt-impregnation and metamorphism of central and eastern serpentinite, which we postulate to be the result of heat associated with magma injection and subsequent localized contact metamorphism. To our knowledge, such a relation between mafic melt-impregnation of peridotite and metamorphism (of peridotite) has not previously been established in general and specifically for the Atlantis Massif peridotite. Closure temperatures of 440–731 °C of metamorphosed Cr–spinel approximate greenschist to amphibolite facies metamorphic conditions.

Asymmetric Soft‐Structure Functional Surface for Intelligent Liquids’ Distinction, Transportation, and Reaction Mixer

AbstractStructured surfaces have attracted wide attention because of their great potential in directional transport, liquid collection or separation, microfluidics, etc. However, it remains a big challenge to design a surface that can distinguish various liquids, utilize their inherent properties to control their transportation, and realize functional applications. Herein, it is presented an asymmetric soft‐structure functional surface (ASFS) with arrayed curvature units that can make the Laplace pressure as a driving force to determine the preferential spreading direction and show abundant transport behaviors for liquids with different surface tensions. With good deformability, the proposed ASFS can directionally transport liquids along complex terrains, e.g., 1D‐tilted, 2D‐curved, and 3D‐helical trajectories. It is also demonstrated that the ASFS can achieve synchronous or asynchronous liquid mixing by choosing appropriate liquids. Moreover, the intelligent response ability allows the ASFS to be a portable contact angle discriminator. This study proposes a new strategy to manipulate liquids via their intrinsic properties and opens new avenues for application‐oriented liquid operation surfaces.

Predicting the rate of forest fire spread toward any directions based on a CNN model considering the correlations of input variables

ABSTRACT Modeling forest fire spread rate is a complex problem, and the existing models are unable to accurately predict the rate of fires spreading towards any directions. In this paper, a convolutional neural network (CNN)-based model is designed to predict the spread rate of forest fires spreading in any directions and using the spread direction as one of the model’s inputs. Several outdoor burning experiments were designed and conducted in order to obtain a dataset on which the model can be trained and validated. Correlation analysis was performed on the variables, and their positions are arranged in a fourth-order matrix according to the strength of their correlations to reflect the correlations in space for feature extraction by the CNN. A deep neural network (DNN)-based model is also designed for comparison to demonstrate the advantages of considering the correlation between variables. The comparison with the improved Wang’s model proves that the model proposed in this paper has higher prediction accuracy compared with the traditional model. The validation experiments were carried out in terms of fire spread rate or fire line’s position. The proposed spread model can provide the technical support for managing the forest fires.

Spatially weak syncronization of spreading pattern between Aedes Albopictus and dengue fever

Understanding the response of dengue fever to climate change remains a global public health concern. A rich array of mathematical models have been proposed to help estimate future population exposure and vulnerability. While these models have proved helpful in modeling mosquito distribution and/or revealing dengue transmission mechanism, they have rarely been incorporated into distribution estimates, particularly at large spatial and temporal scales, to evaluate dengue response to long-term environmental change. Here, we develop a novel mechanistic phenology model that explicitly describes the dengue epidemic process completion (DPEC) according to empirically derived responses to environmental conditions. Further, we apply this model to Aedes albopictus and dengue transmission in mainland China. We validate the model with recorded indigenous dengue cases, and reveal the power of model prediction. Results suggest that future temperature rise promotes geographic expansion of mosquitoes and dengue fever, respectively around 3–15% and 4–10% increment in the area by 2080, compared to nowadays. Results also indicate a more extended season (1–2 months increment) and stronger intensity (up to 4 DEPC increment) of dengue transmission by 2080. Most importantly, our model discloses a weak correlation between the spreading pattern of dengue and Aedes albopictus. Using the spatial expansion trend of mosquito to infer the risk of dengue to the human population is likely to bring about strong bias in spreading direction and/or overestimate dengue distribution. Our study paves a way to provide a useful tool and precise information for predicting dengue dynamics. It also helps design control strategies to prevent arbovirus outbreaks worldwide in areas colonized by Aedes mosquitoes.

Distress-Mediated Remodeling of Cardiac Connexin-43 in a Novel Cell Model for Arrhythmogenic Heart Diseases.

Gap junctions and their expression pattern are essential to robust function of intercellular communication and electrical propagation in cardiomyocytes. In healthy myocytes, the main cardiac gap junction protein connexin-43 (Cx43) is located at the intercalated disc providing a clear direction of signal spreading across the cardiac tissue. Dislocation of Cx43 to lateral membranes has been detected in numerous cardiac diseases leading to slowed conduction and high propensity for the development of arrhythmias. At the cellular level, arrhythmogenic diseases are associated with elevated levels of oxidative distress and gap junction remodeling affecting especially the amount and sarcolemmal distribution of Cx43 expression. So far, a mechanistic link between sustained oxidative distress and altered Cx43 expression has not yet been identified. Here, we propose a novel cell model based on murine induced-pluripotent stem cell-derived cardiomyocytes to investigate subcellular signaling pathways linking cardiomyocyte distress with gap junction remodeling. We tested the new hypothesis that chronic distress, induced by rapid pacing, leads to increased reactive oxygen species, which promotes expression of a micro-RNA, miR-1, specific for the control of Cx43. Our data demonstrate that Cx43 expression is highly sensitive to oxidative distress, leading to reduced expression. This effect can be efficiently prevented by the glutathione peroxidase mimetic ebselen. Moreover, Cx43 expression is tightly regulated by miR-1, which is activated by tachypacing-induced oxidative distress. In light of the high arrhythmogenic potential of altered Cx43 expression, we propose miR-1 as a novel target for pharmacological interventions to prevent the maladaptive remodeling processes during chronic distress in the heart.

A Framework for Burnt Area Mapping and Evacuation Problem Using Aerial Imagery Analysis

The study aims to develop a holistic framework for maximum area coverage of a disaster region during a bushfire event. The monitoring and detection of bushfires are essential to assess the extent of damage, its direction of spread, and action to be taken for its containment. Bushfires limit human’s access to gather data to understand the ground situation. Therefore, the application of Unmanned Aerial Vehicles (UAVs) could be a suitable and technically advanced approach to grasp the dynamics of fires and take measures to mitigate them. The study proposes an optimization model for a maximal area coverage of the fire-affected region. The advanced Artificial Bee Colony (ABC) algorithm will be applied to the swarm of drones to capture images and gather data vital for enhancing disaster response. The captured images will facilitate the development of burnt area maps, locating access points to the region, estimating damages, and preventing the further spread of fire. The proposed algorithm showed optimum responses for exploration, exploitation, and estimation of the maximum height of the drones for the coverage of wildfires and it outperformed the benchmarking algorithm. The results showed that area coverage of the affected region was directly proportional to drone height. At a maximum drone height of 121 m, the area coverage was improved by 30%. These results further led to a proposed framework for bushfire relief and rescue missions. The framework is grounded on the ABC algorithm and requires the coordination of the State Emergency Services (SES) for quick and efficient disaster response.

An Acoustic Study of Emphasis Spread in Najdi Arabic

As with other varieties of Arabic, Najdi Arabic (NA), spoken in central Saudi Arabia, contains a set of emphatic consonants, /? – ? – ð?/, which have an uncontrollable phonological effect on neighboring segments whereby the presence of an emphatic in a word entails “emphasis spread” to the adjacent non-emphatic segments. Acoustically, emphasis is manifested by lowering the frequency of the second formant (F2) of vowels in the vicinity of an emphatic. The purpose of this study is investigate the domain and directionality of emphasis spread in NA and whether it is blocked by any opaque phonemes by measuring and comparing the F2 frequencies of vowels in minimal pairs contrasting on the basis of the presence/absence of emphatics. The results show that the domain of emphasis spread in NA is the entire phonological word consisting of the stem plus any inflectional/derivational affixes. In addition, emphasis spreads rightward and leftward throughout the phonological word in a gradient manner in an inverse relationship, where emphasis peaks in the syllable containing the emphatic and gradually decreases as it moves into the following/preceding syllables. Finally, the high front phonemes /y – ? – ?/ act as opaque segments as they block rightward spread but not leftward spread.

Gray Matter Volume Loss in Proposed Brain-First and Body-First Parkinson's Disease Subtypes.

α-Synuclein pathology is associated with neuronal degeneration in Parkinson's disease (PD) and considered to sequentially spread across the brain (Braak stages). According to a new hypothesis of distinct α-synuclein spreading directions based on the initial site of pathology, the "brain-first" spreading subtype would be associated with a more asymmetric cerebral and nigrostriatal pathology than the "body-first" subtype. Here, we tested if proposed markers of brain-first PD (ie, higher dopamine transporter [DaT] asymmetry; absence of rapid eye movement sleep behavior disorder [RBD]) are associated with a greater or more asymmetric reduction in gray matter volume (GMV) in comparison to body-first PD. Data of 255 de novo PD patients and 110 healthy controls (HCs) were retrieved from the Parkinson's Progression Markers Initiative. Structural magnetic resonance images were preprocessed, and GMVs and their hemispherical asymmetry were obtained for each of the neuropathologically defined Braak stages. Group and correlation comparisons were performed to assess differences in GMV and GMV asymmetry between PD subtypes. PD patients demonstrated significantly smaller bilateral GMVs compared to HCs, in a pattern denoting stage-dependent disease-related brain atrophy. However, the degree of putaminal DaT asymmetry was not associated with reduced GMV or higher GMV asymmetry. Furthermore, RBD-negative and RBD-positive patients did not demonstrate a significant difference in GMV or GMV asymmetry. Our findings suggest that putative brain-first and body-first patients do not present diverging brain atrophy patterns. Although certainly not disproving the brain-first/body-first spreading hypothesis, this study fails to provide evidence in support of it. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Composition regulation of composite materials in laser powder bed fusion additive manufacturing

Understanding and controlling the composition segregation during powder spreading is of key importance in the additive manufacturing (AM) of composite materials. Under this circumstance, the segregation behavior of WC/316 L composite powders during spreading in laser powder bed fusion (LPBF) AM was numerically investigated by the discrete element method. The effects of process conditions (i.e., spreader velocity and geometry) and powder properties (i.e., size and shape of the WC powder) on the powder bed composition segregation and related characteristics were systematically analyzed. Corresponding mechanisms were identified from microscopic scale in terms of particle velocity, motion trajectory, mechanical behavior, and energy information. Finally, proper solutions in designing and constructing WC/316 L composite materials with desired gradient structures were proposed. The results show that the small blade velocity ( V ) will enhance the negative segregation, increase the average packing density ρ ¯ , and decrease uniformity ρ vc in the WC/316 L composite powder bed. Compared with the blade, the roller can increase the negative segregation ( Se roller = −0.027 < Se blade = −0.019) and the average packing density ( ρ ¯ roller = 0.31> ρ ¯ blade = 0.20). When the WC/316 L size ratio increases from 25 μm/45 μm to 45 μm/45 μm, the negative segregation becomes weaker, and its value increases from −0.084 to −0.007. When the size ratio increases to 65 μm/45 μm, the powder behaves positive segregation with Se max = 0.017; in this case, the packing density is the lowest (0.14), and the uniformity is the worst (0.17). In comparison with spherical shape, polyhedral WC powder can reduce the negative segregation of the powder bed ( Se sphere = −0.019 < Se polyhedron = −0.008), while the WC shape has less effect on the packing density and uniformity. The density difference of the WC and 316 L powders leads to the difference in energy and force, resulting in different motion and segregation behaviors in the composite powder bed. For WC/316 L composite powder with a fixed composition, the condition of V = 0.025 m/s, WC/316 L size ratio = 25 μm/45 μm, roller spreader, and spherical WC can realize the proper composition gradient along the spreading direction in the composite powder bed. • The spreading of binary WC/316L composite powders was numerically investigated. • The parametric studies on segregation behavior were systematically conducted. • The underlying mechanisms were identified from microscopic scale. • Composition control of composite materials was realized by regulating segregation.

Effect of Considering Wave Angles on the Motion Response of Oversized Floating Bodies in Offshore Airports under Irregular Wind and Wave Loads

Most existing studies are based on the hydroelastic response of oversized floating bodies under regular waves, ignoring the effect of wave conditions and incident wave angle on the vibration response of oversized floating bodies in real sea conditions. In this paper, the stability performance of a single module of a mega-floating body at an offshore airport was investigated by using STAR-CCM + numerical simulations based on a specific model, with the introduction of parameters under extreme random wind and wave combined sea conditions. By comparing and analyzing the distribution characteristics of the single module floating body under the action of regular waves and irregular waves, wind, and wave load, and by considering the wave angle along the flow direction, as well as the spreading direction and vertical displacement value under the action of mooring, the overall displacement amplitude of rigid displacement, elastic deformation displacement and considering the influence of both, and the distribution law of motion response along the length of the floating body, we summarize the influence of the wave angle on the dynamic response of an oversized floating body of an offshore airport. The results show that the maximum value of the hydro-elastic response tends to appear at the head and tail of the floating body, the rigid body vertical displacement dominates the role, the amplitude of all displacements of the floating body under the action of the cross wave is larger, and the stress area along the floating body is larger when the wave angle is between 15–30°. The floating body stress value is smaller with angles of 30–65°, and the ability to bear the load is stronger. The hydroelastic response under irregular wave conditions is more sensitive to the wave direction angle, and the elastic deformation has less influence.

Reinfection, recontamination and revaccination for SARS-CoV-2.

The reports on coronavirus disease 2019 (COVID-19) describe the pandemic in waves. Similar to the ocean’s waves, the frequency and amplitude of the number of new cases and the number of deaths were globally quite regular; nevertheless, they showed important regional irregularities and the direction of spread has been generally rather unpredictable for COVID-19. One of the major reasons for the repeated outbreaks is the mutating capacity of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that allows the virus to infect persons who have natural immunity or have been vaccinated. Vaccination began in vast campaigns from the second year of the pandemic that was supposed to decrease the magnitude of the waves. Although it reduced the complications, the expected attenuation of the disease expansion has not yet been met. This paper provides a short overview of the most recent data on the rate of reinfection in vaccinated and non-vaccinated individuals. It points out that testing positive for a second time for SARS-CoV-2 does not necessarily mean a reinfection; it can also be interpreted as recontamination. The symptom free outcome as well as the rapid reconversion of the polymerase chain reaction test may help to determine the difference between reinfection and recontamination. Awareness of this phenomenon may be valuable in times of human resource difficulties. The available evidence may suggest that the protective value of a prior infection could be better considered for vaccine distribution in the future.

Analytical solutions of contaminant transport in homogeneous and isotropic aquifer in three-dimensional groundwater flow.

Modeling three-dimensional contaminant transport released from arbitrary shape source geometries is useful in hydrological and environmental sciences. This article produces several analytical solutions for three-dimensional contaminant transport in a homogeneous and isotropic aquifer by using Green's function with the groundwater flow which is assumed to be in three directions. The solutions are obtained for both finite depth aquifer and semi-infinite depth aquifer. Various types of sources are discussed: point, line, plane, or cuboid sources. The continuous and instantaneous sources are also investigated. A MATLAB coding is developed to calculate the numerical integrals which occur at the solutions. Some solutions are verified with the solutions obtained in the literature. This study confirms the effect of groundwater velocities in all directions on the degree and the directions of contaminant spreading. Additionally, the results highlight the significant effect of the geometrical shape of the contaminant sources on contaminant concentrations for instantaneous and continuous sources. In particular, the cuboid source and the horizontal rectangular source provide the highest concentrations. The analytical solutions developed in this article can be applied for a wide range of contaminant transport.

Effect of the fibre length on the mechanical anisotropy of glass fibre–reinforced polymer composites printed by Multi Jet Fusion

ABSTRACT Mechanical anisotropy greatly influences the applications of materials printed by additive manufacturing techniques such as Multi Jet Fusion (MJF) and selective laser sintering. However, the mechanical anisotropy of MJF-printed fibre–reinforced polymer composites has not been well understood. In this work, the effect of the fibre length on the mechanical performance of MJF-printed glass fibre–reinforced polyamide 12 (GF/PA12) composites is systematically investigated. Both experimental and simulation results confirm that longer fibres are in favour of fibre alignment in the powder spreading direction. The composite parts with longer fibres exhibit higher porosity. When GFs with an average length of 226 μm are added, the ultimate tensile strength and tensile modulus of the composites measured in the powder bed spreading direction are remarkably improved by 51% and 326%, respectively, as compared with those of neat PA12 specimens. This work provides guidance for the printing of other high-strength fibre–reinforced polymer composites.

A combination of probabilistic and mechanistic approaches for predicting the spread of African swine fever on Merry Island

Over the last decade African swine fever virus, one of the most virulent pathogens known to affect pigs, has devastated pork industries and wild pig populations throughout the world. Despite a growing literature on specific aspects of African swine fever transmission dynamics, it remains unclear which methods and approaches are most effective for controlling the disease during a crisis. As a consequence, an international modelling challenge was organized in which teams analyzed and responded to a stream of data from an in silico outbreak in the fictive country of Merry Island. In response to this outbreak, we developed a modelling approach that aimed to predict the evolution of the epidemic and evaluate the impact of potential control measures. Two independent models were developed: a stochastic mechanistic space–time compartmental model for characterizing the dissemination of the virus among wild boar; and a deterministic probabilistic risk model for quantifying infection probabilities in domestic pig herds. The combined results of these two models provided valuable information for anticipating the main risks of dissemination and maintenance of the virus (speed and direction of African swine fever spread among wild boar populations, pig herds at greatest risk of infection, the size of the epidemic in the short and long terms), for evaluating the impact of different control measures and for providing specific recommendations concerning control interventions.

Investigation of the Impact of Powder Shape on Spreading Dense Layers Using the Spreading Tester

In Laser Beam Powder Bed Fusion (LB-PBF) technologies, spreading of powder layers as dense and as fully covered as possible is of crucial importance for a good processability of powders. Poorly covered layers or layers with undesirable features in it, such as elongated, powderless craters in the direction of spreading, might result in defective printed parts. The reason for this could be either poor powder quality or a poorly adjusted build job. To investigate the surface coverage of a single spread powder layer, a new method was developed using the Spreading Tester. With this, two powder grades differing mostly in their particle shape were used to investigate the impact of powder shape on the surface coverage.

GIS and Machine Learning for Analysing Influencing Factors of Bushfires Using 40-Year Spatio-Temporal Bushfire Data

The causes of bushfires are extremely complex, and their scale of burning and probability of occurrence are influenced by the interaction of a variety of factors such as meteorological factors, topography, human activity and vegetation type. An in-depth understanding of the combined mechanisms of factors affecting the occurrence and spread of bushfires is needed to support the development of effective fire prevention plans and fire suppression measures and aid planning for geographic, ecological maintenance and urban emergency management. This study aimed to explore how bushfires, meteorological variability and other natural factors have interacted over the past 40 years in NSW Australia and how these influencing factors synergistically drive bushfires. The CSIRO’s Spark toolkit has been used to simulate bushfire burning spread over 24 h. The study uses NSW wildfire data from 1981–2020, combined with meteorological factors (temperature, precipitation, wind speed), vegetation data (NDVI data, vegetation type) and topography (slope, soil moisture) data to analyse the relationship between bushfires and influencing factors quantitatively. Machine learning-random forest regression was then used to determine the differences in the influence of bushfire factors on the incidence and burn scale of bushfires. Finally, the data on each influence factor was imported into Spark, and the results of the random forest model were used to set different influence weights in Spark to visualise the spread of bushfires burning over 24 h in four hotspot regions of bushfire in NSW. Wind speed, air temperature and soil moisture were found to have the most significant influence on the spread of bushfires, with the combined contribution of these three factors exceeding 60%, determining the spread of bushfires and the scale of burning. Precipitation and vegetation showed a greater influence on the annual frequency of bushfires. In addition, burn simulations show that wind direction influences the main direction of fire spread, whereas the shape of the flame front is mainly due to the influence of land classification. Besides, the simulation results from Spark could predict the temporal and spatial spread of fire, which is a potential decision aid for fireproofing agencies. The results of this study can inform how fire agencies can better understand fire occurrence mechanisms and use bushfire prediction and simulation techniques to support both their operational (short-term) and strategic (long-term) fire management responses and policies.

The wetting process and crystallisation of Al2O3 substrate with molten slags: Addition of CaO‐Fe2O3

AbstractAs fluxes, CaO and Fe2O3 are widely applied to effectively improve the melting characteristics of coal ash. However, there are few studies on the effects of CaO and Fe2O3 contents in coal ash on the wetting of refractories used in entrained‐flow slagging gasifiers. This paper investigates the melting properties of ash slag and the wetting process in corundum‐based refractories in relation to the total amount of CaO and Fe2O3 and their proportions in coal ash. The rates of change of the apparent contact angle (ACA) and differential contact angle (DCA) as a function of temperature are employed to evaluate the wetting behaviour of the coal ash during the heating process. The results demonstrate that changes in the ACA result from the expansion or shrinkage of the slag. In particular, two abrupt changes in the ACA are observed at an Fe2O3/CaO ratio of .25. The wettability deteriorates after quenching at ratios ranging from .13 to .67. Differences in the crystal structure and elemental distribution along with the spreading direction are observed. X‐ray diffraction and FactSage calculations show that temperature changes the crystal composition and solid–liquid phase content, supporting the slag wetting process from the perspective of ash fusibility. A fraction of the liquid phase increases twice with increases in temperature, explaining the abrupt change in the ACAs. Overall, the wetting process of the slag can be explained by the surface tension and DCA. The wetting begins at 430 mN m−1 and becomes the most prominent at 435 mN m−1. Finally, an Fe2O3/CaO ratio of .25 is found to be more suitable for the long‐term operation of corundum‐based refractories.

Path-based multi-sources localization in multiplex networks

With the prosperity of modern technology, propagation phenomena of diverse information become universal nowadays. Nevertheless, spreading of malicious information will inevitably bring undesired harm or economic losses. These spreading phenomena are usually triggered by limited sources; therefore, it is of great significance to locate these sources to avoid further losses. With the emergence of various social platforms, social networks seem to be integrated. Hence, multiplex networks are desirable to mimic the properties of integrated social networks. Source localization problems on single-layer networks are studied by various scholars whereas less attention has been paid to corresponding problems on multiplex networks. Regarding this, we propose a source locating method in this manuscript, named path-based source localization on multiplex networks (PSLM). With the adoption of the source centrality theory, we apply a label iteration process in order to find nodes with the largest local labels which are regarded as the sources. Furthermore, high uncertainty of spreading path will be incurred by the low spreading probability. Aiming to address such uncertainty, observers are deployed in advance to record the spreading directions. Then, extensive experiments are performed on selected datasets and we find PSLM outperforms the existing ones. Moreover, we also study the effects of various factors on the locating accuracy and find that the locating accuracy improves with the increase of the inter-layer spreading rate.

Geospatial models for SARS-CoV-2 outbreak control in Cartagena and Barranquilla, Colombia, 2020Modelos geoespaciais para controle de surtos de SARS-CoV-2 em Cartagena e Barranquilla, Colômbia, 2020

RESUMENObjetivo.Determinar la estructura temporal y espacial del virus del síndrome respiratorio agudo grave (SARS-CoV-2, por su sigla en inglés), causante de la enfermedad por coronavirus (COVID-19, por su sigla en inglés) en las ciudades de Cartagena y Barranquilla para tomar acciones necesarias que apoyen el rastreo de contactos.Métodos.Estudio ecológico transversal que incluye análisis espacial basado en densidades Kernel de variables como casos, alertas desde una aplicación móvil, vulnerabilidad poblacional, índice de pobreza multidimensional, aplicación de interpolación espacial (IDW, por su sigla en inglés) de los casos activos y, por último, la aplicación de la técnica de superposición espacial como resultado final. Se utilizó la base de datos del Instituto Nacional de Salud de las ciudades de Cartagena y Barranquilla y el Departamento de Estadística Nacional.Resultados.El análisis determinó el comportamiento epidemiológico ascendente de los casos en las dos ciudades e identificó la dirección espacial de propagación de la enfermedad en los barrios, a través de la interpolación espacial. Se detectaron las zonas en las cuales intervenir en 15 barrios de Cartagena y 13 de Barranquilla, en 50 metros alrededor de los casos activos con menos de 21 días de evolución y según las capas de riesgo geográfico, como mecanismo para frenar la propagación de la COVID-19.Conclusiones.El análisis espacial permitió determinar la estructura temporal y espacial como metodología complementaria útil para el rastreo de contactos, y aportó la evidencia científica necesaria para la aplicación de medidas de intervención directa donde fuera necesario, dirigidas a reducir el contagio del SARS-CoV-2.