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11.
The strength of a frozen soil increases with decreasing temperature. Furthermore, the speed it takes to form a frozen wall increases on lowering the temperature of the freezing liquid.
With the traditional freezing systems using brine it is difficult to work with temperatures below −30°C. To go lower than this limit, it is necessary to substitute the brine by using freezing liquids that maintain good hydraulic and thermal characteristics at much lower temperatures.
Different organic liquids have been tested and good results have been obtained with some aromatic hydrocarbon mixes from the terpene family.
As a result of the research, for practical purposes a by-product ofa distilling citrus fruit skins has been selected. This liquid solidifies at −100°C approx. and maintains a low viscosity rate below −30°C.
The present paper describes the thermal and hydraulic properties of this product as a function of the temperature concerned and compares them to the same properties of classic brines of CaCl2. 相似文献
12.
J. Garcia-Guinea P. D. Townsend L. Sanchez-Muñoz J. M. Rojo 《Physics and Chemistry of Minerals》1999,26(8):658-667
Laboratory driven ionic thermal exchange of alkali feldspars from K to Na produces samples which are strongly luminescent
in the ultraviolet region near 320 nm. The sites providing this luminescence are suggested as being correlated with the motion
of Na atoms along interface-interphases of the material (i.e. with Na-O bond fracture). The thermoluminescence peaks show
multi-order kinetics. Thermal preheatings of low albite sensitize the feldspar lattice with respect to thermoluminescence
generated by exposure to UV irradiation and heating produces a strong blue luminescence spread over the range 350 nm to 500 nm
band in feldspars. The upper temperature for thermoluminescence in feldspars is ∼300 °C, which is also the point where ionic
conductivity of albite (010) begins, but the 300 °C region is also the starting point of a large second glow peak in adularia.
Whilst it seems appropriate to link the Na motion to the 350–500 nm emission, it is unclear whether these changes are the
result of the large anisotropic thermal vibration of Na atoms or the massive Na jumps that occur when the lattice reaches
300 °C. A speculative model is considered in which the UV TL emissions of natural minerals are linked to different interface-interphases
(grain boundaries, exsolution limits, twinning planes, antiphase domains). Increased interface coherency energies are related
to the kinetic order and the spectral position of luminescence emission peaks.
Received: 3 December 1998 / Revised, accepted: 17 April 1999 相似文献
13.
This study investigates the local social and fisheries impact of formal fisheries policies in Bahía de Kino, one of the most important fishing villages in terms of extraction of benthic resources in the Northern Gulf of California, Mexico. The paper focuses on cross-scale institutional interactions, describing how existing formal policies are functioning on the ground, how these policies interact with local arrangements, and how this interaction may affect the incentives of different actors towards sustainable fisheries. Besides providing lessons on how the performance of a local fishery could be improved, this paper addresses the question of whether the formal institutional structure of Mexican fishing regulations is effective in promoting responsible behavior by small-scale fishery stakeholders. It is argued that the design of the most widely used management tool to regulate access to marine resources throughout Mexico -the permit (licensing) system- provides the wrong incentives for sustainable-use. Granting secure rights to resources to those actively involved in the fishery is a necessary step for promoting sustainable fishing practices. 相似文献
14.
M. C. González-García Michele Maltoni Joan Rojo 《Astrophysics and Space Science》2007,309(1-4):447-451
The precise knowledge of the atmospheric neutrino fluxes is a key ingredient in the interpretation of the results from any
atmospheric neutrino experiment. In the standard atmospheric neutrino data analysis, these fluxes are theoretical inputs obtained
from sophisticated numerical calculations. In this work we present an alternative approach to the determination of the atmospheric
neutrino fluxes based on the direct extraction from the experimental data on neutrino event rates.
相似文献
15.
We have systematized the effects associated with climate change on urban spaces in Chile reported between 2000 and 2012. The method was based on a review of scientific articles in three databases (Scopus, Web of Knowledge and Scielo) using 32 keywords. Only 14 research papers were found related to climate change in urban spaces, most of which were case studies focused on the capital, Santiago. The main effects on urban spaces were found in four areas: (1) increase in temperature (heat islands, heat waves), (2) health problems in vulnerable populations (cardiac complications, heat stroke, and respiratory diseases), (3) increased demand for water, and (4) damage to the urban infrastructure with resulting risk to the population. In these circumstances the following measures are needed: (1) effective incorporation of the potential impacts of climate change into territorial planning instruments, (2) increased green areas to mitigate the impact of heat waves, (3) limiting of housing or public services in areas at risk, (4) encouraging the design of adaptation plans by involving the vulnerable population, and (5) implementing water conservation measures. We conclude that climate change is causing effects in urban areas that should be considered in the design and expansion of cities. 相似文献
16.
Lila Rojo Melanie A. Barnes Thomas E. Gill 《Geostandards and Geoanalytical Research》2012,36(1):83-102
Particle‐induced X‐ray emission (PIXE) and ICP‐AES can be combined to obtain a wider range of detected elements, augment previous data and/or to verify measured concentrations of heavy and trace metals in geological samples. Intercomparison of data sets generated by multiple techniques is challenging due to the differing processes and methods of each technique. Here, we compare elemental data obtained by both techniques for aeolian dust from Owens (Dry) Lake, California. Nineteen elements were detected by PIXE, sixteen by ICP‐AES and ten elements were detected by both techniques. Statistical analyses of data set groupings illustrated which parameters differed significantly between PIXE and ICP‐AES. Relative variation (%) showed that PIXE gave higher concentrations than ICP‐AES for Al, As, Cu, Fe, K, Mn, Ni, Sr, Ti and Zn in all samples. For As, Cu, Sr and Zn, relative variation was variable between the techniques. PIXE detection limits exceeded ICP‐AES concentrations for Ba, Cd, Co, Cr, Pb and Mo. Low ICP‐AES percentage recoveries of Al, Fe, K, Mn and Ti for NIST SRM 2710 indicated incomplete dissolution during digestion (EPA Method 3050B), since elements were bound in silicate structures. Variability between the two data sets is explained by differences between analytical techniques, sample preparation methods and/or variability in sample matrices. 相似文献
17.
Lila Nath Sharma Ole Reidar Vetaas Ram Prasad Chaudhary Inger Elisabeth Måren 《山地科学学报》2014,11(4):838-849
The ecotone, the spatial transition zone between two vegetation communities, is claimed to have more species than the adjoining communities. However, empirical studies do not always confirm higher richness at the ecotone. The ecotone position and structure are dynamic over time and space and it is driven by the changes in climate, land use or their interaction. In this context, we assessed the forest- grassland ecotone of temperate mountains in central Nepal by i） comparing species composition and richness across the ecotone, ii） analyzing if the forestgrassland ecotone is shifting towards the grassland center by colonizing them with trees, and iii） discussing the consequence of changed disturbance regime in the dynamics of this ecotone and the surrounding grasslands. We analyzed vegetation data sampled from belt transects laid across the forest- grassland ecotone in semi-natural grassland patches. Vegetation data consisting of species richness and composition, and size structure and regeneration of the two most dominant tree species, namely Rhododendron arboreum and Abies spectabilis, from the transects, were used to analyze the trend of the forest-grassland ecotone. Forest and grasslands were different in terms of floristic composition and diversity. Vascular plant speciesrichness linearly increased while moving from forest interior to grassland center. Spatial pattern of tree size structure and regeneration infers that forest boundary is advancing towards the grasslands at the expense of the grassland area, and tree establishment in the grasslands is part of a suceessional process. Temporally, tree establishment in grasslands started following the gradual decline in disturbance. We argue that local processes in terms of changed land use may best explain the phenomenon of ecotone shift and consequent forest expansion in these grasslands. We underpin the need for further research on the mechanism, rate and spatial extent of ecotone shift by using advaneed tools to understand the process indepth. 相似文献
18.
The Gunnedah Basin, NSW, Australia, contains more than 500 Gt of coal, and has been the subject of recent coalbed methane exploration. Large areas of the basin contain igneous intrusions and large areas of coal have been heat-affected as a consequence. A detailed study has been undertaken of coal seams intersected in a cored coalbed methane exploration drillhole in which two sill-form igneous intrusions are present. Comparisons are made between coals that are unaltered and coals that have been heat-affected, using petrographic and chemical data, coal seam gas desorption data, and gas chemical analysis data.Results demonstrate that the two igneous intrusions have had a very positive effect on coalbed methane development. The gas content in a number of heat-affected coal seams within thermal aureoles above and below the sills is substantially higher than in adjacent unaffected coal seams. In addition, the intrusions have had little effect on gas quality. The coals in the heat-affected zone were found to contain gas with approximately 95% methane. The coals in the thermal aureoles were found, under the microscope, to contain characteristic micropores and slits, which collectively may serve to enhance gas adsorption capacity, permeability, and gas desorption. Gas contents below each of the sills is substantially higher than above the sill, confirming earlier results that the sills appear to have acted as a reservoir seal, during and for some time after intrusion. The background coal rank in ACM Yannergee DDH 1 is in the high-volatile bituminous range. The igneous intrusions have resulted in an increase in rank such that large areas of coal have moved into the optimal thermogenic gas generation window. This rank increase has affected a major part of the coal-bearing sequence. 相似文献
19.
The elemental composition of the individual macerals in a suite of Australian coals has been determined in polished sections using light-element electron microprobe techniques. The analyses of the individual macerals in each coal were combined with data on maceral abundance to produce an inferred chemical composition for the organic matter of the respective whole-coal samples, and this was compared, for each sample, to the respective whole-coal ultimate analysis data, corrected to a dry, ash-free (daf) basis. Except for slightly lower values in some lower-rank coals, the inferred percentages of whole-coal C estimated from the microprobe data were found to be very close to the respective whole-coal C percentages as determined by conventional ultimate analysis. The proportion of O in the coals indicated by the microprobe study, however, appears to be as much as 2% higher than that derived from the ultimate analysis data, especially in the lower-rank coal samples. The difference it may represent errors in calculating the O percentages in ultimate analysis, errors in the microprobe analysis due to difficulties in calibration or measurement, or increased proportions of O in the coals due to factors such as take-up with storage of the polished sections. The percentages of whole-coal N calculated from the microprobe data are up to 0.5% (absolute) below the proportion of N determined directly by whole-coal ultimate analysis. This may reflect the inherent difficulty of dealing with a light element at low concentrations by the microprobe technique, or it may indicate that some of the N occurs in the coals in mineral form. The percentages of whole-coal (organic) S calculated from the microprobe study are close to the percentages of organic S determined for each sample by more conventional techniques. With the exception of (organic) O, which may be affected by other factors, and also possibly of N, the electron microprobe technique appears from the study to provide results that are consistent with ultimate analysis over a wide rank range. 相似文献
20.
Bruine de Bruin Wändi Rabinovich Lila Weber Kate Babboni Marianna Dean Monica Ignon Lance 《Climatic change》2021,167(3-4):1-21
Climatic Change - The UK, like other countries, has seen a proliferation of declarations of local climate emergencies. While these declarations have been interpreted as a demonstration of ambition,... 相似文献