The accessibility of nodes in the Belgian road network

This paper presents an analysis of the accessibility of nodes in the Belgian road network. The intersection of roads are considered as the nodes and their connecting roads as the edges of a network. By means of the Dijkstra algorithm accessibility values are computed for each node by summing shortest travel times to a reference system of 158 nodes spread evenly over the Belgian territory. A comparison of the measured actual accessibility with that determined from an optimal situation provides an indication of the quality of directness of the Belgian road system. Accessibility and directness are shown cartographically. An isochronal map illustrates the access to Brussels.     

CLAST-LADEN MELT-ROCK FRAGMENT IN THE ADAMS COUNTY,COLORADO, H5 CHONDRITE

The Adams County, Colorado, H5 chondrite contains a lithic fragment, 1 cm in size, that is texturally and mineralogically quite different from the chondritic host. It is composed of: a groundmass of fine-grained euhedral to subhedral olivine (3–15 μm) and interstitial glass enclosing larger olivine and pyroxene grains (0.15-0.5 mm; about 15 vol %); an assemblage of enstatite grains (subfragment within) and an assemblage of olivine plus orthopyroxene (a second subfragment); and about 11 vol % grains of mixed troilite and nickel-iron metal. Analyses yielded these results: (i) olivine grains of the fragment groundmass have a compositional range (Fa_12–45) and most grains contain substantial CaO and Cr₂O₃ (～ 0.20 and 0.30 avg. wt%, respectively); interstitial glass has ～ 55 wt% SiO₂; (ii) larger olivine grains of the fragment are similarly high in CaO and Cr₂O₃ and also have a wide FeO/MgO range; one unusual pyroxene is an Mg-rich pigeonite; (iii) the metal is martensite in composition (11–14 wt% Ni); and (iv) major and trace element analyses by INAA indicate an H-group bulk composition for the entire 1 cm lithic fragment. On the basis of its texture and bulk and mineral compositions, the fragment is interpreted to represent unequilibrated H-group material that was partly melted by impact. The Ca- and Cr-enriched groundmass olivine and interstitial glass resulted from rapid crystallization of the chondritic melt. The Ca- and Cr-enriched larger silicate grains, including the enstatite sub-fragment and the pigeonite grain, are residual, unmelted clasts from the target material (this is supported by the presence of similar material in actual H3 chondrites). Further impact brecciation of the clast-laden melt material, and resultant impact-splashing accounts for the presence of the fragment in the H-group Adams County host and documents the coexistence of unequilibrated and equilibrated H-group material as surface regolith on one parent body.     

基于SoftGIS的土地利用地域性认同测度研究——以荷兰为例

在剖析地域性认同双重内涵及其与土地利用关系的基础上,结合SoftGIS技术,研究构建土地利用地域性认同测度方法,并以荷兰为例进行实证分析。数据分析显示,传统GIS数据可与土地利用认知数据相融合,基于核密度修正法构建的土地利用地域性认同指数可测度地域性认同的空间差异,应用于土地利用评价或规划决策。结论表明,测度平台在问卷设计和调查空间尺度上具有灵活性,数据收集快捷,通过平台的高清卫星地图定位,调查对象可反馈空间准确、情景真实的土地利用地域性认同信息。     

Geosimulation of urban growth and demographic decline in the Ruhr: a case study for 2025 using the artificial intelligence of cells and agents

The Ruhr is an “old acquaintance” in the discourse of urban decline in old industrialized cities. The agglomeration has to struggle with archetypical problems of former monofunctional manufacturing cities. Surprisingly, the image of a shrinking city has to be refuted if you shift the focus from socioeconomic wealth to its morphological extension. Thus, it is the objective of this study to meet the challenge of modeling urban sprawl and demographic decline by combining two artificial intelligent solutions: The popular urban cellular automaton SLEUTH simulates urban growth using four simple but effective growth rules. In order to improve its performance, SLEUTH has been modified among others by combining it with a robust probability map based on support vector machines. Additionally, a complex multi-agent system is developed to simulate residential mobility in a shrinking city agglomeration: residential mobility and the housing market of shrinking city systems focuses on the dynamic of interregional housing markets implying the development of potential dwelling areas. The multi-agent system comprises the simulation of population patterns, housing prices, and housing demand in shrinking city agglomerations. Both models are calibrated and validated regarding their localization and quantification performance. Subsequently, the urban landscape configuration and composition of the Ruhr 2025 are simulated. A simple spatial join is used to combine the results serving as valuable inputs for future regional planning in the context of multifarious demographic change and preceding urban growth.     

European temperature records of the past five centuries based on documentary/instrumental information compared to climate simulations

Two European temperature reconstructions for the past half-millennium, January-to-April air temperature for Stockholm (Sweden) and seasonal temperature for a Central European region, both derived from the analysis of documentary sources and long instrumental records, are compared with the output of climate simulations with the model ECHO-G. The analysis is complemented by comparisons with the long (early)-instrumental record of Central England Temperature (CET). Both approaches to study past climates (simulations and reconstructions) are burdened with uncertainties. The main objective of this comparative analysis is to identify robust features and weaknesses in each method which may help to improve models and reconstruction methods. The results indicate a general agreement between simulations obtained with temporally changing external forcings and the reconstructed Stockholm and CET records for the multi-centennial temperature trend over the recent centuries, which is not reproduced in a control simulation. This trend is likely due to the long-term change in external forcing. Additionally, the Stockholm reconstruction and the CET record also show a clear multi-decadal warm episode peaking around AD 1730, which is absent in the simulations. Neither the reconstruction uncertainties nor the model internal climate variability can easily explain this difference. Regarding the interannual variability, the Stockholm series displays, in some periods, higher amplitudes than the simulations but these differences are within the statistical uncertainty and further decrease if output from a regional model driven by the global model is used. The long-term trend of the CET series agrees less well with the simulations. The reconstructed temperature displays, for all seasons, a smaller difference between the present climate and past centuries than is seen in the simulations. Possible reasons for these differences may be related to a limitation of the traditional ‘indexing’ technique for converting documentary evidence to temperature values to capture long-term climate changes, because the documents often reflect temperatures relative to the contemporary authors’ own perception of what constituted ‘normal’ conditions. By contrast, the amplitude of the simulated and reconstructed inter-annual variability agrees rather well.     

A box model of circulation and melting in ice shelf caverns

A simple box model of the circulation into and inside the ocean cavern beneath an ice shelf is used to estimate the melt rates of Antarctic glaciers and ice shelves. The model uses simplified cavern geometries and includes a coarse parameterization of the overturning circulation and vertical mixing. The melting/freezing physics at the ice shelf/ocean interface are those usually implemented in high-resolution circulation models of ice shelf caverns. The model is driven by the thermohaline inflow conditions and coupling to the heat and freshwater exchanges at the sea surface in front of the cavern. We tune the model for Pine Island Glacier and then apply it to six other major caverns. The dependence of the melting rate on thermohaline conditions at the ice shelf front is investigated for this set of caverns, including sensitivity studies, alternative parameterizations, and warming scenarios. An analytical relation between the melting rate and the inflow temperature is derived for a particular model version, showing a quadratic dependence of basal melting on small values of the temperature of the inflow, which changes to a linear dependence for larger values. The model predicts melting at all ice shelf bases in agreement with observations, ranging from below a meter per year for Ronne Ice Shelf to about 25 m/year for the Pine Island Glacier. In a warming scenario with a one-degree increase of the inflow temperature, the latter glacier responds with a 1.4-fold increase of the melting rate. Other caverns respond by more than a tenfold increase, as, e.g., Ronne Ice Shelf. The model is suitable for use as a simple fast module izn coarse large-scale ocean models.     

An Inter-Laboratory Assessment of the Thorium Isotopic Composition of Synthetic and Rock Reference Materials

We present a concerted international effort to cross-calibrate five synthetic Th isotope reference materials (UCSC Th "A", OU Th "U", WUN, IRMM-35 and IRMM-36), and six rock reference materials (UCSC TML, Icelandic ATHO, USGS BCR-2, USGS W-2, USGS BHVO-2, LV18) using multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). We then compare our new values with a compilation of literature mass spectrometric data for these reference materials and derive recommended "consensus"²³⁰Th/²³²Th values for each. We also present isotope dilution U and Th concentration data for four rock reference materials (UCSC TML, Icelandic ATHO, USGS BCR-2, USGS W-2).     

Ultramafic inclusions from San Carlos,Arizona: Petrologic and geochemical data bearing on their petrogenesis

Ultramafic inclusions from San Carlos, Arizona, are classified into two groups. Group I inclusions are dominated by magnesian (Mg/Mg + ΣFe= 0.86 – 0.91), olivine-rich peridotites containing Cr-rich clinopyroxene and spinel. The less abundant Group I pyroxenites (containing Mg- and Cr-rich pyroxenes) occur as discrete inclusions and as portions of composite inclusions where they have a sharp, planar interface with lherzolite. Group II inclusions are dominated by clinopyroxene-rich peridotites containing Al- and Ti-rich augite and commonly abundant, Al-rich spinel. Compared to Group I inclusions, they are more Fe-rich (Mg/Mg + ΣFe= 0.62 – 0.78) and more hetereogeneous in composition and modal proportions. Similar groups occur at many ultramafic inclusion localities.Our petrographic and geochemical results lead to the following conclusions. Olivine-rich Group I inclusions are not genetically related to the host basanite, and they are formed from two components. Component A is a partial melting residue; it comprises the major portion of these inclusions and determines the modal mineralogy and major and compatible trace element composition. Component B results from a small degree (<5%) of garnet peridotite melting (probably, within the low-velocity zone). This highly LIL-element-enriched melt has migrated upwards into the overlying component A where it crystallized primarily as clinopyroxene and amphibole, and thus, introduced LIL elements into the residual component A. Subsequent cooling and subsolidus recrystallization have removed textural evidence of this mixing. This model has also been proposed for olivine-rich Group I inclusions from Victoria, Australia. At Victoria and San Carlos some relatively clinopyroxene-rich Group I lherzolites are not contaminated by component B, and they represent the best estimates of upper mantle composition prior to melting. Group I orthopyroxenites may be fragments of tectonic layers formed in lherzolite, but they could also be early cumulates (now metamorphosed) from the melt in equilibrium with component A. Group I clinopyroxenites have geochemical features of clinopyroxene in equilibrium with a magma. Thus, they could also represent early cumulates (now metamorphosed) from a magma unrelated to the host basanite. Alternatively, their geochemical characteristics could result from more complex models such as residues from partial remelting of pyroxenite dikes and veins or intradike segregation processes such as filter pressing. All Group II inclusions studied appear to be cumulates derived from a SiO₂-undersaturated magma, possibly an early magma in the same volcanic episode which culminated with eruption of the host basanite. The poikilitic texture of amphibole-rich (kaersutite) inclusions is consistent with a cumulate origin. The bulk compositions of Group II inclusions are not equivalent to typical basaltic compositions.