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1.
The rates of cosmic-ray-induced fission of U, Th, Bi, Pb, and Au in mineral samples as a function of burial depth in the lunar surface layer are calculated using the available experimental particle flux and cross section data. Theoretical correction factors are given for apparent fission track ages of extraterrestrial samples of different burial depths which were exposed to cosmic rays for various time fractions of their solidification age. Samples having typical lunar heavy element contents can yield apparent fission track ages which are too high by a factor of up to 13 due to cosmic-ray-induced fission. The interference may be neglected, if the ratio of exposure age to solidification age remains 5 × 10−3. The calculations show, that the induced fission of Bi, Pb, and Au which are known to have high meteoritic abundances may dominate spontaneous 238U-fission in long-time exposed meteorites of low U and Th contents. 相似文献
2.
Studies on the thermoluminescence depth profile produced by 600-MeV protons in artificial lunar soil
The thermoluminescence (TL) of various plagioclase feldspars embedded in a thick target of 150 kg of artificial lunar soil was measured after a 600-MeV proton irradiation. No correlation was observed between the parameters of the characteristic feldspar glow peak and the anorthite contents. The relative TL sensitivities of the individual plagioclase variants were measured and found to be practically the same for60Co-γ- and 600-MeV proton-irradiated samples.The TL intensity distribution within the target arrangement, converted to a 2π isotropic p-influx, resulted in an approximate TL depth profile of a thermally undisturbed lunar soil bomarded by galactic cosmic protons. The undisturbed TL intensity at a depth of 28 g/cm2 (? 17 cm) decreased to 39% at a depth of 106 g/cm2 (? 60 cm). For the evaluation of the temperature gradients by TL in lunar samples the experimental data at the sites of Taurus-Littrow and of Hadley-Rille yielded minimum depth intervals for sampling of ～ 20 cm and ～ 40 cm respectively, presuming an error of ± 15% in the TL determination. Certain aspects are seen by using the relation TL intensity/22Na-activity ratio versus depth (thus representing the total ionization profile) to establish22Na depth profiles. 相似文献
3.
D. Prieto Herráez L. Ferragut Canals J. M. Cascón Barbero A. Morillo Rodríguez 《International journal of geographical information science》2017,31(11):2142-2163
??This article discusses the integration of two models, namely, the Physical Forest Fire Spread (PhFFS) and the High Definition Wind Model (HDWM), into a Geographical Information System-based interface. The resulting tool automates data acquisition, preprocesses spatial data, launches the aforementioned models and displays the corresponding results in a unique environment. Our implementation uses the Python language and Esri’s ArcPy library to extend the functionality of ArcMap 10.4. The PhFFS is a simplified 2D physical wildland fire spread model based on conservation equations, with convection and radiation as heat transfer mechanisms. It also includes some 3D effects. The HDWM arises from an asymptotic approximation of the Navier–Stokes equations, and provides a 3D wind velocity field in an air layer above the terrain surface. Both models can be run in standalone or coupled mode. Finally, the simulation of a real fire in Galicia (Spain) confirms that the tool developed is efficient and fully operational. 相似文献
4.
Galileo Constellation Design 总被引：2，自引：0，他引：2
Álvaro Mozo-García Esperanza Herráiz-Monseco Ana Belén Martín-Peiró Miguel M. Romay-Merino 《GPS Solutions》2001,4(4):9-15
A significant effort has been carried out in Europe to define the European Global Navigation Satellite System (GNSS), named
Galileo Satellites flying in Medium Earth Orbits (MEO) will compose the system (according to the most recent architecture
definition baseline); a regional complement of geosynchronous satellites may be required to increase performances over Europe
and maybe also to provide some specific communication services. Nominal medium performances are envisaged, but they will be
increased by means of augmentation systems (local or wide area), or even by using simultaneously other GNSSs such as GPS.
All the involved requirements make the design process quite complex. A powerful software tool, Elcano, has been developed
for this purpose; its capabilities will be outlined, and the results of the design process will be presented. ? 2001 John
Wiley & Sons, Inc. 相似文献
5.
Longlived spallogenic 53Mn was determined in 36 individual chondrites. Combining our data with those available so far in literature (in total 91 53Mn-values of 61 individual stones) a 53Mnproduction rate of 478 ± 84dpm/kg Fe was derived. Based on this figure it was possible to calculate 53Mn-radiation ages for more than 30 stones with Trad ≤ 10 × 106 yr. A comparison of our results with the respective rare gas- and 26Al-exposure ages (so far available) shows that in general a good agreement exists between ages calculated by these three different methods. Only in the case of ‘finds’, e.g. in Bondoc and some other stones of probably high terrestrial ages. partial losses of 53Mn seem to have occurred. For well preserved objects the 53Mn method is ideal for the estimation of terrestrial residence times. 相似文献
6.
The beryllium content of 73 stony and 4 iron meteorites has been determined “non-destructively” by a newly developed sensitive low-level counting device. A fairly widespread beryllium content of stones ranging from 13 to 386 ppb was found. As expected from the lithophilic character of Be the 4 siderites contained < 8 ppb only. The resulting average chondritic abundance of 74 ppb Be is more than one order of magnitude lower than the cosmic abundance value adopted earlier by H.E. Suess and H.C. Urey (1956), but still about a factor of 2 higher than the value chosen by A.G.W. Cameron (1968). 10–15-g samples were taken in order to guarantee a rather good “mean”. For comparison the Be content of the U.S. Geological Survey basalt BCR-1 was determined in the same way to be 1.390 ± 0.006 ppm Be. 相似文献
7.
A multi-criteria approach to Great Barrier Reef catchment (Queensland, Australia) diffuse-source pollution problem 总被引：1，自引：0，他引：1
This paper presents a multi-criteria based tool for assessing the relative impact of diffuse-source pollution to the Great Barrier Reef (GBR) from the river basins draining into the GBR lagoon. The assessment integrates biophysical and ecological data of water quality and pollutant concentrations with socio-economic information pertaining to non-point source pollution and (potential) pollutant impact. The tool generates scores for each river basin against four criteria, thus profiling the basins and enabling prioritization of management alternatives between and within basins. The results support policy development for pollution control through community participation, scientific data integration and expert knowledge contributed by people from across the catchment. The results specifically provided support for the Reef Water Quality Protection Plan, released in October 2003. The aim of the plan is to provide a framework for reducing discharge of sediment, nutrient and other diffuse-source loads and (potential) impact of that discharge and for prioritising management actions both between and within river basins. 相似文献
8.
The contents of spallogenic53Mn and target elements for its production were determined in 80- to 400-mg samples from 13 different locations of the LL6 chondrite St. Severin, along the 34.8-cm drill core AIII. The53Mn content increases from the surface to the center of the stone by ≈30%. The variation with depth is satisfactorily described by several models, presuming that appropriate primary and secondary particle fluxes are chosen. The53Mn saturation activities (53Mn*) are linearly correlated with the spallogenic3He/21Ne and22Ne/21Ne ratios, which suggests the possibility to eliminate uncertainties in the determination of53Mn cosmic ray exposure ages arising from depth effects and terrestrial residence times. 相似文献
9.
Sampling acid mine drainage (AMD) or natural acid rock drainage (ARD)-impacted sediments is complex, requiring appropriate
field sampling techniques to ensure representative samples that are both repeatable and reproducible. The important factors
affecting sampling of riverine sediments are examined. These include sample site location, field observations, representative
sampling, sample collection techniques, and sample preservation. A recommended sampling and processing protocol is presented
for AMD- and ARD-impacted riverine sediments, which includes sediment sampling, Fe hydroxide floc sampling, chemical analysis,
interstitial (pore) water collection, sediment elutriates, sediment fractionation, and physical analysis. The importance of
bioassay testing is discussed, as is quality assurance and assessment approaches to define sediment quality criteria.
Received: 18 September 1995 · Accepted: 23 October 1995 相似文献
10.
The Mariner 6 and 7 infrared spectrometers provided data which, in principle, determine upper limits on the possible atmospheric abundance of every gaseous substance that was undetected but which has recognized absorptions in the accessible spectral region, 1.9 to 14.4 μ. Through supporting laboratory determinations of curves of growth under pressure broadening conditions appropriate to Mars, upper limits can be specified (expressed first in cm-atm, STP, for a vertical column and then in parts per million) for the following gases: NO2 (<0.0016, 0.23); NH3 (<0.0031, 0.44); C3O2 (<0.0032, 0.45); SO2 (?0.0037, 0.52); OCS (<0.0040, 0.56); NO (<0.0050, 0.70); O3 (<0.0061, 0.86); CH4 (<0.026, 3.7); N2O (<0.13, 18); HCl (<3.7, 520); HBr (?8.2, 1150); H2S (<27, 3800). In addition, considerations of band contours, moments of inertia, and experimental absorption coefficients permit us to place useful upper limits on twenty-seven additional substances that were not detected and for which curves of growth have not been measured: less than 1.0ppm (or, <0.0071cm-atm); SF6, NF3, Cl2CO, CF4, CHF3, Br2CO, SiF4; less than 6.0ppm (or, <0.035 cm-atm); C2F6, CO3, F2CO, C2H4, BF3, CS2, CHCl3, C2H6, H2CO, CH3F, C6H6, CH2I2; less than 50ppm (or, <0.35 cm-atm): C2H2, HCN, CH2Br2, CH2Cl2, CH3Br, PH3, CH3I, and CH3Cl. These upper limits are compared to earlier limits based upon terrestrial measurements. The present limits placed upon the possible atmospheric content of the molecules C3O2 and CO3 are of particular interest because of their relevance to the photochemistry of the Martian atmosphere. 相似文献