Professor Harold Clayton Urey, 1893–1981     

Bartholomew Nagy 《Precambrian Research》1981,14(2):183-184

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Thermal evolution of the moon     

M. Nafi Toksőz  Sean C. Solomon  John W. Minear  David H. Johnston 《Earth, Moon, and Planets》1972,4(1-2):190-213

The thermal history and current state of the lunar interior are investigated using constraints imposed by recent geological and physical data. Theoretical temperature models are computed taking into account different initial conditions, heat sources, differentiation and simulated convection. To account for the early formation of the lunar highlands, the time duration of magmatism and presentday temperatures estimated from lunar electrical conductivity profiles, it is necessary to restrict initial temperatures and abundances of radioactivie elements. Successful models require that the outer half of the Moon initially heated to melting temperatures, probably due to rapid accretion. Differentiation of radioactive heat sources toward the lunar surface occurred during the first 1.6 billion years. Temperatures in the outer 500 km are currently low, while the deep interior (radius less than 700 to 1000 km) is warmer than 1000°C, and is of primordial material. In some models there is a partially melted core. The calculated surface heat flux is between 25 and 30 erg/cm² s.Presently at the Research Triangle Institute, Research Triangle, North Carolina 27709, U.S.A.  相似文献   

Hydrocarbons in the surficial sediments of Lakes St. Clair,Erie, and Ontario     

E. Nagy  P. Mudroch  A. Mudroch  R. L. Thomas 《Environmental Geology》1984,6(1):31-37

Although the long-term effects and the fate of petroleum hydrocarbons in marine and freshwater environments are not fully understood, it is generally recognized that much of the oil released by accidental spills or by various land sources ends up in the sediment where it may remain for at least several years The present study was undertaken to collect some initial data on the hydrocarbon concentrations in surficial sediments of lakes St Clair, Erie, and Ontario The distribution of hydrocarbons in these lakes followed the general patterns found for a number of contaminants, in that the distribution tended to coincide with the outlines of the sedimentary basins The highest concentrations were found in the Western Basin of Lake Erie and in the inshore zone around the west end of the lake, suggesting major inputs from the Detroit River Apart from some spots of high concentration around known dumping grounds, the concentrations gradually diminish toward the east The distribution pattern in Lake Ontario may be more readily ascribed to water circulation patterns than to any specific source around the lake The hydrocarbon levels were found to be significantly lower than those in Lake Erie in Lake St Clair only trace quantities of hydrocarbons were found, suggesting either low inputs or low sedimentation/accumulation rates due to its shallowness Although the present survey was limited to the top 3 cm of the sediments, the resulting distribution patterns indicate the western end of Lake Erie as the area with the heaviest hydrocarbon loadings The results may also facilitate the selection of specific areas where core sampling coupled with more complete analysis of the extracts could yield significant information on the long-term accumulation of anthropogenic hydrocarbons, and on their persistence and transformations in Great Lakes sediments  相似文献   

Proposing a beneficiary-based shared responsibility approach for calculating national carbon accounts during the post-Kyoto era     

Maria Csutora  Zsófia Vetőné mózner 《Climate Policy》2013,13(5):599-616

Considerable progress has been made in Europe towards cutting GHG emissions during the last decade, but this achievement is partly due to the delocalization of manufacturing industries to emerging countries. Under the United Nations Framework Convention on Climate Change, the current emission accounting method is production-based and cannot fully capture this effect. The use of such a method is clearly unfavourable for emerging countries and could lead to difficulties in engaging them in climate policy negotiations. The consumption-based approach represents the other extreme in apportioning emission responsibilities. This article proposes the beneficiary-based shared responsibility approach, which outperforms previous methods in terms of scientific justification and political acceptability. Consumer countries benefit from enjoying the product itself, while producing countries benefit from the production process, which provides them with employment, government income, and company profit. Thus, emissions related to the material throughput used to produce exported products should be allocated to the final place of consumption. The income of production activities benefits the producer country, so emissions associated with these values should be allocated to them. The main reason for taking this accounting approach is that the responsibility for emissions and the benefits of enjoying a product should not be decoupled.  相似文献   

Numerical sensitivity test of three-electrode laterolog borehole tool     

Márk Szijártó  László Balázs  Dezső Drahos  Attila Galsa 《Acta Geophysica》2017,65(4):701-712

Finite element numerical simulation has been carried out to investigate quantitatively the response of the three-electrode laterolog borehole tool (LL3) on radial and vertical heterogeneity of the rock. In order to calculate the apparent resistivity from the electric potential and the current discharge of the measurement electrode the probe coefficient of the LL3 tool with finite electrode extent was determined. Two independent methods, a finite element modeling and a semi-analytical solution, resulted in the probe coefficient of approx. 0.15 m with a relative deviation of 2.4% due to the different geometry, resolution and electronics of the models. It was established that LL3 is only slightly sensitive to the presence of mud when the borehole diameter is d ≤ 30 cm and the ratio of the resistivity of rock and the borehole mud is 1 ≤ R _t/R _m ≤ 1000. Vertical heterogeneity test pointed out that the layer boundaries can be localized exactly even for thin bedded layer (with a thickness of 1 m) and the presence of low-resistive borehole mud. Correction factors were suggested to decrease the biasing effect of the low-resistive borehole mud and the shoulder beds on the apparent resistivity observed by LL3. Finally, it was verified that the probe has large penetration depth with excellent vertical resolution, what explains the enduring popularity of the LL3 tool in well logging.  相似文献   

Evolution of river planforms downstream of dams: Effect of dam construction or earlier human‐induced changes?          下载免费PDF全文

Marcin Słowik  József Dezső  Adam Marciniak  Gabriella Tóth  János Kovács 《地球表面变化过程与地形》2018,43(10):2045-2063

When studying the evolution of landscape, it is difficult to discriminate the influence of anthropogenic from natural causes, or recognise changes caused by different sources of human action. This is especially challenging when the influence of certain sources is overprinted. For instance, although dam closure is the most common method of altering river courses, dam construction is often preceded by hydro‐technical works such as channel straightening, embankment construction or sediment mining. Both dam construction and the hydro‐technical works that precede dam closure can result in changes in the balance between sediment supply and transport capacity, and often, changes in river planform. The main objective of this study was to verify whether the works preceding dam closure are an important driver of river planform changes on the lower Drava River (Hungary). The case study is based on geological and geophysical surveys, as well as the analysis of historical maps covering an anabranching, 23 km long valley section. We show that channel straightening conducted prior to dam closure resulted in a transition from a meandering to sinuous planform with channel bars. Dam construction itself then caused enhanced incision, exposure of bar surfaces, vegetation encroachment and the formation of an anabranching planform. Based on this study, we developed models of alluvial island and channel planform evolution downstream of dams. Dam construction enhances channel incision, narrowing, and the reduction of flow caused by earlier hydro‐technical works. Many rivers downstream of dams experience episodes of anabranching or wandering, with a multi‐thread pattern replacing sinuous, braided and meandering courses. When incision continues, river patterns evolve from anabranching to sinuous via the attachment of alluvial islands to floodplains. However, the timing and sequence of these changes depend on hydrological and sediment supply regimes, geomorphic settings and anthropogenic actions accompanying dam construction. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

Integrated geophysical survey on the ancient Deák Ferenc Sluice of Hungary     

Ali Ismet Kanli  Zsolt Pronay  Peter Tildy  Endre Toros  Boriszlav Neducza  Peter Nagy 《Acta Geophysica》2018,66(6):1397-1411

The west channel of the ancient Deák Ferenc which was constructed in 1875 in Hungary was used for controlling the water amount and the east channel was used for the shipping. In the study, four geophysical nondestructive methods were used to this old channel which needs the restoration and reinforcement works. The high-frequency seismic and acoustic measurements were carried out, the resistivity measurements were carried out to map the resistivity distribution of the slab, the seismic direct wave method was used to map the seismic velocities for understanding the stability conditions of the walls and the ground penetrating radar measurements were carried out on the slab and on the walls. The results of integrated study showed us that voids, faults and cracks were detected and the inhomogeneous construction materials were used in the slab. The obtained results emerged that the usage of nondestructive geophysical methods is essential in all stages of restoration and reinforcement works, especially for the ancient structures.  相似文献   

Weighted distances and distance transforms on the triangular tiling     

Benedek Nagy 《Transactions in GIS》2023,27(7):2042-2098

Digital geometry is a field in the intersection of discrete mathematics and geometry having various applications including geographical information systems (GIS). In digital spaces, in grids, distances can be defined based on steps in paths in somewhat similarly as in graph theory. However, the grids have more definite structures, thus one may obtain more concrete results, for example, close formulae, than on arbitrary graphs. In this article, the weighted (also called chamfer) distances, and based on them, the distance transform are investigated on the regular triangular grid. Three types of neighborhood relations are used on the grid, and therefore, three weights are used to define a distance function. Natural conditions are used on the weights such as they are positive and a larger step (in the usual and also in the Euclidean sense) cannot have a smaller weight than a smaller one. Some properties of the weighted distances are discussed; for example, they are proven to be metrics. We also give algorithms and formulae that compute the weighted distance of any point pair on a triangular grid. Algorithm for weighted distance transform is provided based on wave-front propagation. Therefore, these new distance functions are ready for further applications in GIS, in image processing tasks, in computer vision, in graphics, in networking, and also in other applied fields.  相似文献   

A digital geometry on the tetrakis square tiling—Distance and coarsening     

Benedek Nagy 《Transactions in GIS》2023,27(2):388-407

There are various tessellations of the plane, including three regular and eight semi-regular tilings. The square grid is self-dual, and the hexagonal and triangular tilings are dual to each other. The semi-regular tessellations are based on more than one type of regular tiles, while their dual tilings are based on a sole but not a regular tile. In various applications, including Geographical Information Systems, it is worth considering non-regular grids instead of the most used square grid. In this article, we are interested in the dual of the semi-regular truncated quadrille tiling, T(8,8,4), which is also known as the Khalimsky grid due to its connectedness structure. In our grid, which is called the tetrakis square or kisquadrille tiling, while it is denoted by D(8,8,4), we consider the right-angled triangle regions of the usual two-dimensional Khalimsky graph as tiles/pixels. We give an easy-to-use coordinate frame addressing the triangles of all the four different orientations. Neighbor relations are described mathematically based on this frame. Based on the shortest path algorithm, a closed formula is proven to compute the digital, that is, path-based distance on this grid. Some properties of the distance function have also been studied. Hierarchical coarsening is a frequently used technique both in Geometric and Geographical Information Systems to rescale some parts of the map. The tetrakis square grid is apt for hierarchical coarsening, and thus, it can easily be used in image compression and multigrid and other related methods.  相似文献