Circuit grinding was investigated in the Rammelsberg ore dressing plant. From short-interval sampling it was possible to make a statement about the non-stationary and stationary state of grinding. The objective of these investigations was to establish the distribution curves of the quantitative flow, of the grain sizes and of the mineralogical components in the individual streams of the circuit grinding. 相似文献
Abstract The results of this dendrogeomorphological study provide evidence of the active movement of Hilda rock glacier, a tongue‐shaped rock glacier in the Columbia Icefield region of Banff National Park. Cross‐sectional samples were cut from 44 detrital subalpine fir (Abies Iasiocarpa (Hook.) Nutt.) and Engelmann spruce (Picea engelmannii Parry) boles killed and buried by debris spilling off the steep distal slope of the rock glacier. The samples were crossdated using locally and regionally developed tree‐ring chronologies, and were shown to have been killed between 1576 and 1999. Our results show that Hilda rock glacier has advanced at an average rate of 1.6 cm/year since the late 1790s, with limited evidence of similar rates of activity extending back to the mid‐1570s. This rock glacier activity is believed to be linked to persistent periglacial processes that appear to be independent of the climatic forcing mechanisms known to influence glacier mass balances over the same interval. 相似文献
The diffusion of the dynamo-generated magnetic field into the electrically conducting inner core of the Earth may provide an explanation for several problematic aspects of long-term geomagnetic field behavior. We present a simple model which illustrates how an induced magnetization in the inner core which changes on diffusive timescales can provide a biasing field which could produce the observed anomalies in the time-averaged field and polarity reversals. The Earth's inner core exhibits an anisotropy in seismic velocities which can be explained by a preferred orientation of a polycrystalline aggregate of hexagonal close-packed (hcp) iron, an elastically anisotropic phase. Room temperature analogs of hcp iron also exhibit a strong anisotropy of magnetic susceptibility, ranging from 15 to 40% anisotropy. At inner core conditions the magnetic susceptibility of hcp iron is estimated to be between 10−4 and 10−3 SI. We speculate here that the anisotropy in magnetic susceptibility in the inner core could produce the observed anomalies in the time-averaged paleomagnetic field, polarity asymmetry, and recurring transitional virtual geomagnetic pole (VGP) positions. 相似文献
Fluxes of CO2, latent heat and sensible heat were measured above a fully-leafed deciduous forest in eastern Tennessee with the eddy correlation technique. These are among the first reported observations over such a surface. The influences of solar radiation, vapor pressure deficit and the aerodynamic and canopy resistances on these mass and energy exchanges are examined. Following a concept introduced by McNaughton and Jarvis (1983), examination of our data suggest that the water vapor exchange of a deciduous forest is not as strongly coupled with net radiation as is that of agricultural crops. The degree of decoupling is smaller than in the case of a coniferous forest. This difference may be attributable in part to the greater aerodynamic resistance to water vapor transfer in a deciduous forest. It appears that the concept of decoupling may be extended to the CO2 exchange of a deciduous forest as well.Published as Paper No. 7832, Journal Series, Nebraska Agricultural Research Division. ATDD Contribution No. 85-17. 相似文献
Knowledge of the local direction of multipath at a particular site is important for a number of reasons. For example, such
information can be used to study site selections or during monument design for GPS installations. We present a MATLAB program
for creating colorized polar maps of high-frequency multipath using TEQC report files of single-epoch data. The maps, although
not necessarily indicating the actual local direction of multipath on the ground, give the orientation with respect to the
geometry of the satellites in the sky. This information can aid the interpretation of ground multipath geometry at the site.
We give an example of short-span data with ∼0.05 Hz multipath (i.e. repeat period ≈ 20 s) although the program can be modified
for long-term measurements as well. 相似文献
The spatial distribution of different C3 and C4 grass species in tropical montane areas is commonly influenced by a number of factors that include site-specific topography. Hence, the distribution of these grasses across topographic gradients can vary significantly. In this study, we investigate the influence of topographic factors (elevation, slope and aspect) on the spatial distribution of Festuca grass species in a commonage area, comprising agro-biodiversity conservation land use. Integration of the topographic variables using GIS and binary logistic regression (LR) modelling showed that C3, Festuca grass species distribution can be predicted or mapped with an accuracy of 80% in the landscape under study. The study contributes to understanding the spatial distribution of C3 grass species and provides valuable information for designing and optimizing rangeland conservation in the subtropical montane landscapes. 相似文献
A groundwater resource characterisation and assessment model was developed for Nasia river sub-basin in the White Volta Basin, Ghana. The model is useful to policymakers for planning and sustainable management of groundwater resources in the basin for domestic and irrigation purposes. A conceptual model was constructed that characterized boundary conditions and hydrostratigraphy, and estimated recharge rates and hydraulic and storage parameters. From current understanding of the hydrogeological dynamics, three hydrostratigraphic layers were delineated. The conceptual model was converted to a three-dimensional steady-state groundwater flow model using MODFLOW. Recharge rates estimated from the base model indicate a minimum of 1.1% and maximum of 6.2% of the total rainfall. The hydraulic conductivity ranged between 0.20 and 15 m/day. Four possible scenarios were simulated: (1) increased population, (2) climate variations (reduced recharge), (3) increased abstraction for irrigation, and (4) worst-case scenario which is a combination of the first three scenarios. Results from scenarios 1 and 2 indicated that, under such conditions, the groundwater resources could be sustained and no significant effect on any of the water budget indicators was observed. For scenario 3, there was significant drop in hydraulic head in the central portions of the study area. The scenario 4 simulation indicated that there was significant reduction in groundwater levels and groundwater discharge into streams under these stressors. Such reduction can affect stream levels in the basin and, subsequently, the ecosystem. These findings are valid within the limits of uncertainty in the hydrogeological data that were used in this study.
