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Norbert I. K 《冰川冻土》2004,26(Z1):310-318
The exploration of ice sheets by melting vertical holes into the ground has some tradition in terrestrial glaciology. Such probes have been used since the 1960's to investigate the vertical structure of the ice in Greenland and Antarctica and in alpine glaciers. In this paper we look into the possibility to develop similar devices for use on extraterrestrial icy bodies, like e.g. the polar areas on Mars or the icy satellites of the outer solar system. We report on some basic experiments performed in the cryo-vacuum laboratory of the Space Research Institute of the Austrian Academy of Sciences, Graz. In these experiments the penetration of a simple melting probe into compact and porous water ice (with a snow-like texture) was monitored, both under vacuum conditions and under air pressure. The observed penetration speeds for a given power supply are compared with a simple mathematical model. We conclude that a miniature melting probe with small overall dimensions and a reasonable power demand could well be part of the payload of a future planetary mission, for example to the poles of Mars. Such missions are currently under discussion in several space agencies. Moreover such probes could also e? ectively be used in terrestrial environments. A possible design is presented at the end of the paper. 相似文献
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General purpose Computational Fluid Dynamics (CFD) solvers are frequently used in small-scale urban pollution dispersion simulations
without a large extent of ver- tical flow. Vertical flow, however, plays an important role in the formation of local breezes,
such as urban heat island induced breezes that have great significance in the ventilation of large cities. The effects of
atmospheric stratification, anelasticity and Coriolis force must be taken into account in such simulations. We introduce a
general method for adapting pressure based CFD solvers to atmospheric flow simulations in order to take advantage of their
high flexibility in geometrical modelling and meshing. Compressibility and thermal stratification effects are taken into account
by utilizing a novel system of transformations of the field variables and by adding consequential source terms to the model
equations of incompressible flow. Phenomena involving mesoscale to microscale coupled effects can be analyzed without model
nesting, applying only local grid refinement of an arbitrary level. Elements of the method are validated against an analytical
solution, results of a reference calculation, and a laboratory scale urban heat island circulation experiment. The new approach
can be applied with benefits to several areas of application. Inclusion of the moisture transport phenomena and the surface
energy balance are important further steps towards the practical application of the method. 相似文献
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Norbert I. Kömle Hui Bing Wen Jie Feng Roman Wawrzaszek Erika S. Hütter Ping He Wojciech Marczewski Borys Dabrowski Kathrin Schröer Tilman Spohn 《Acta Geotechnica》2007,2(2):127-138
A series of thermal conductivity measurements for various materials was performed in a large climate chamber. The size of
the chamber allowed the preparation of relatively large samples in a controlled thermal environment. Three types of thermal
sensors were used: (1) two needle probes; (2) a grid of temperature sensors, evenly distributed inside the sample; (3) two
additional thermal probes, which were simplified versions of an instrument originally developed for measuring thermal properties
of the ice/dust mixture expected to exist at the surface of a comet nucleus. They consist of a series of individual temperature
sensors integrated into a glass fibre rod. Each of these sensors can be operated in an active (heated) or passive (only temperature
sensing) mode. The following sample materials were used: fine-grained reddish sand, coarse-grained moist sand, gravels with
various grain size distributions from < 1 cm up to about 6 cm, and for comparison and calibration pure water (with convection
suppressed by adding agar-agar), compact ice, and compact granite. Of particular interest are the measurements with composite
samples, like stones embedded in an agar-agar matrix. We describe the evaluation methods and present the results of the thermal
conductivity measurements. 相似文献
7.
Robert S. Sommer Norbert Benecke Lembi Lõugas Oliver Nelle Ulrich Schmölcke 《第四纪科学杂志》2011,26(8):805-812
The wild horse Equus ferus was one of the most frequent species of the Late Pleistocene large ungulate fauna in Eurasia and played an important role in the subsistence of human groups, especially at the end the Late Glacial. It is frequently assumed that E. ferus became extinct in Europe at the beginning of the Holocene because of the development of woodlands and loss of open habitats. Because of its preference for open habitats and in spite of its adaptability, the appearance or disappearance of the wild horse could therefore be a suitable palaeoecological indicator for the opening of the Holocene primeval woodlands. We revised the dating and reliability of the subfossil record and dated several bones by atomic mass spectrometry 14C dating. From the beginning of the Holocene (9600 cal a BC) to the end of the Atlantic Period (3750 cal a BC) there are 207 archaeological sites with wild horse records available in Europe. E. ferus survived the Pleistocene Holocene transition in Europe, but the spatiotemporal dynamics of populations fluctuated remarkably in the early and middle Holocene. Small and sparse populations increasingly became extinct during the early Holocene, until between 7100 and 5500 cal a BC the wild horse was almost absent in central parts of the European Lowlands. Particular conditions in natural open patches in the canopy forests, chalklands and floodplains may have maintained the local survival of the horse in some regions of the Lowlands, however. In the Late Atlantic, between 5500 and 3750 cal a BC the range of the wild horse was again extended. It re‐immigrated into central and western Europe, probably as a consequence of increasing landscape opening by Neolithic peoples. The data presented here may be a valuable part of the debate on the degree of openness of the early and middle Holocene landscape. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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In the paper, a novel inversion approach is used for the solution of the problem of factor analysis. The float-encoded genetic algorithm as a global optimization method is implemented to extract factor variables using open-hole logging data. The suggested statistical workflow is used to give a reliable estimate for not only the factors but also the related petrophysical properties in hydrocarbon formations. In the first step, the factor loadings and scores are estimated by Jöreskog’s fast approximate method, which are gradually improved by the genetic algorithm. The forward problem is solved to calculate wireline logs directly from the factor scores. In each generation, the observed and calculated well logs are compared to update the factor population. During the genetic algorithm run, the average fitness of factor populations is maximized to give the best fit between the observed and theoretical data. By using the empirical relation between the first factor and formation shaliness, the shale volume is estimated along the borehole. Permeability as a derived quantity also correlates with the first factor, which allows its determination from an independent source. The estimation results agree well with those of independent deterministic modeling and core measurements. Case studies from Hungary and the USA demonstrate the feasibility of the global optimization based factor analysis, which provides a useful tool for improved reservoir characterization. 相似文献
10.
Alexander Gocht Norbert Röder 《International journal of geographical information science》2014,28(9):1744-1764
In Germany, a county-resolution data set that consists of 35 land-use and animal-stock categories has been used extensively to assess the impact of agriculture on the environment. However, because such environmental effects as emission or nutrient surplus depend on the location, even a county resolution might produce misleading results. The aim of this article is to propose a Bayesian approach which combines two sorts of information, with one being treated as defining the prior and the other the data to form a posterior, used to estimate a data set at a municipality resolution. We define the joint prior density function based on (i) remote sensing data, thus accounting for differences in county data and missing data at the municipality level, and (ii) the results of a cluster analysis that was previously applied to the micro-census, whereas the data are defined by official statistics at the county level. This approach results in a fairly accurate data set at the municipality level. The results, using the proposed method, are validated by the national research data centre by comparing the estimates to actual observations. The test statistics presented here demonstrate that the proposed approach adequately estimates the production activities. 相似文献