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31.
32.
Cracks appeared on the northern batter at Maddingley Brown Coal Open Pit Mine, Victoria, Australia, on 8 November 2013 and a 2-day rainfall event happened 5 days later. This study models the stability of the northern batter considering the effect of the rainfall event and an emergency buttress using finite element method (FEM) encoded in Plaxis 3D. It is found that the batter tended to lead to block sliding after overburden removal. The observed vertical crack would be a combined action of the overburden removal and groundwater flow. The simulated location of cracks agrees well with the actual location, and the simulated heave of the coal seam is in good agreement with the experience in Victoria brown coal open pit mining. The rainfall accelerated the development of the cracks. With the construction of the emergency buttress, the batter became stable that is in good agreement with the monitored data. 相似文献
33.
Sean P Healey Jock A Blackard Todd A Morgan Dan Loeffler Greg Jones Jon Songster Jason P Brandt Gretchen G Moisen Larry T DeBlander 《Carbon balance and management》2009,4(1):9
Background
Although significant amounts of carbon may be stored in harvested wood products, the extraction of that carbon from the forest generally entails combustion of fossil fuels. The transport of timber from the forest to primary milling facilities may in particular create emissions that reduce the net sequestration value of product carbon storage. However, attempts to quantify the effects of transport on the net effects of forest management typically use relatively sparse survey data to determine transportation emission factors. We developed an approach for systematically determining transport emissions using: 1) -remotely sensed maps to estimate the spatial distribution of harvests, and 2) - industry data to determine landscape-level harvest volumes as well as the location and processing totals of individual mills. These data support spatial network analysis that can produce estimates of fossil carbon released in timber transport. 相似文献34.
To lay down the foundation for an underwater omni-directional optical communication system for tele-operation, we tested a point-to-point optical communication system, using laser-emitting diodes (LEDs). The LEDs used in the test emitted light in the green and blue light spectrum and were tested in a pool and in a tank filled with lake water. The primary objective of these tests was to get profiles of the behaviors of such communication systems with respect to water characteristics such as turbidity levels, prior to building the proposed omni-directional optical communication. The results of the tests indicated that turbidity level, viewing angle and separation distance plays a significant role in the behavior of blue light in water. Furthermore, it was possible to graph the profile of the behavior of light with respect to the parameters of interest. The results of the tests and related research are discussed in this paper. 相似文献
35.
Timothy J. B. Holland 《Contributions to Mineralogy and Petrology》1988,99(1):134-142
New heat capacity measurements and cell volume data are presented for a very magnesian glaucophane from a Tauern Window eclogite. These data are combined with estimated entropy, thermal expansion, and compressibility data to generate an enthalpy of formation for glaucophane from experimentally determined phase equilibria. The data are supported by preliminary experiments of the author and provide consistent calculations on the pressure of formation of the Tauern eclogites and on the position of the blueschist-greenschist transformation reaction as studied experimentally by Maruyama et al. (1986). The resulting thermodynamic data for glaucophane may be combined with the dataset of Holland and Powell (1985) to calculate phase relations for blueschists and eclogites. The stability of magnesian glaucophane lies in the pressure range between 8 and 32 kbars at 400° C and between 13 and 33 kbars at 600° C, and the unusual eclogite assemblage of glaucophane+kyanite from the Tauern Window is restricted to pressures above 20 kbars at high water activity. 相似文献
36.
An inexpensive, lightweight stream sampler is described which provides a method for continuous collection of suspended stream
sediments. The IS3* sampler collects integrated suspended stream samples, and because the sampler relies on basic sedimentation principles, it
can be deployed to collect suspended sediment stream samples for environmental studies or geochemical exploration in remote
areas. The sampler trapped from 0.45 to 1.2 g of dry sediment during 7- to 8-d field tests conducted during 1985. 相似文献
37.
38.
Measurements of rainfall, runoff and sediment export from a barren deposit of coal mine refuse in south-western Indiana were collected during three storms in the summer and autumn of 1990. Interfluve sheetwash, sediment mass flux, sediment concentration and, to a lesser extent, trunk gully discharge all responded quickly to changes in rainfall intensity. Grain-size distributions varied considerably during storms, containing exclusively fine-grained sediment at low sediment discharges but very large quantities of coarse (> 2mm) sediment at peak sediment discharges. Although data from a fairly long, multipulsed storm indicate that sediment production is limited by supply, the imbricated layer of flat chips that exists at the surface of the deposit is apparently mobilized during most high-intensity pulses of rainfall, thereby producing large volumes of coarse sediment during summer thunderstorms. 相似文献
39.
J. Stephen Hopkins Paul A. Sandifer M. Richard DeVoe A. Frederick Holland Craig L. Browdy Alvin D. Stokes 《Estuaries and Coasts》1995,18(1):25-42
Shrimp culture technology has resulted in development of a major shrimp farming industry worldwide. Without the shrimp farming industry, increasing demands for shrimp by consumers could not be met, resulting in increased pressure on wild shrimp resources. Unfortunately, there are realized and potential adverse environmental effects on estuarine ecosystems as a result of shrimp farming. The effects can be categorized as wetland destruction for construction of shrimp farms, hypernutrification of estuarine ecosystems by shrim pond effluent, “biological pollution” of native shrimp stocks through escapement of aquaculture stocks, water use and entrainment of estuarine biota, and impacts of shrimp farm chemicals on estuarine systems. While the shrimp farming industry in the United States is small, the United States is effectively addressing all the realized and potential environmental impacts through regulation and research at the federal and state levels. Areas of regulation and research include stringent prohibitions on wetland destruction, regulation of effluents and support of research to eliminate and/or reduce effluents, escapement prevention technology and development of high-health stocks, minimizing entrainment of estuarine biota through water conservation and screening technology, and regulation of chemical use in the shrimp farming industry and support of research on shrimp pathology and environmentally safe disease control. Work is still in progress and not all problems have been resolved to the complete satisfaction of shrimp farmers and estuarine conservationists. However, the situation in the United States should serve as a model of how to encourage sustainable economic development through commercial shrimp farming while abating adverse environmental impacts on estuarine systems. To further improve the situation, the development and adoption of “best management practices” for shrimp aquaculture are recommended. 相似文献
40.
Michel Guiraud Tim Holland Roger Powell 《Contributions to Mineralogy and Petrology》1990,104(1):85-98
The new, greatly expanded internally-consistent dataset of Holland and Powell includes thermodynamic data for a wide range of mineral end-members in common rock-forming minerals, in particular, including FeMg-1 substitutions in glaucophane, garnet, chloritoid and carpholite, and FeMg-1 and MgSiAl-1Al-1 substitutions in talc and chlorite. Moreover, we have the uncertainties and correlations for these data. With the data, we have calculated the full pressure-temperature phase diagram for the system Na2O–FeO–MgO–Al2O3–SiO2–H2O (NFMASH) for quartz (or coesite) and H2O in excess, in the range 300°–800°C and 5–50 kbars. By solving the set of non-linear equations formed by the equilibrium relationships for an independent set of equations between the end-members in an assemblage in NFMASH, the compositions of the minerals (and PT) can be calculated. Thus the changes in MgSiAl-1Al-1 along NMASH reactions, and FeSiAl-1Al-1 along NFASH reactions, are calculated, and the changes in FeMg-1 and MgSiAl-1Al-1 along NFMASH reactions are calculated. From this information it is straightforward to generate PT diagrams for specific rock compositions. Mineral assemblages and mineral compositional changes in the phase diagram are discussed in relation to greenschist, blueschist and eclogite facies assemblages in metapelitic rocks. It is found that the correspondence between the predictions of the phase diagrams and the observations on rocks is remarkably good. When semiquantitative extensions of the phase diagram to include Ca(MgFe)-1, NaSiCa-1Al-1, Fe3+Al-1 and KNa-1 substitutions are taken into account the agreement is essentially complete. 相似文献