938 resultados para Coal mines and mining -- Safety measures


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The fourth part has separate t.-p.: Locomotive sketches, with pen and pencil. From Philadelphia to Pittsburg. (13-192 p.)

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Title varies slightly

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Vols. -1952 issued as a supplement to division's Mineral information service; as division's Special publication.

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Mode of access: Internet.

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Thesis (Master's)--University of Washington, 2016-06

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Thesis (Master's)--University of Washington, 2016-06

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Strip samples from the Boundary Hill pit at Callide have been tested in an adiabatic oven to assess the effect of moisture on the R-70 self-heating rate of coal. The two strip samples tested had R-70 self-heating rate values of 10.23 and 8.61 degrees C/h. As the moisture content of the coal was progressively increased, from the dry state of the test, the R-70 value decreased dramatically. At approximately 40-50% of the moisture holding capacity of the coal, the self-heating rate becomes measurable. Above this critical level of moisture content, the heat produced by oxidation is dissipated by moisture evaporation and coal self-heating is significantly delayed. (c) 2005 Elsevier B.V All rights reserved.

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A concept has been developed where characteristic load cycles of longwall shields can describe most of the interaction between a longwall support and the roof. A characteristic load cycle is the change in support pressure with time from setting the support against the roof to the next release and movement of the support. The concept has been validated through the back-analysis of more than 500 000 individual load cycles in five longwall panels at four mines and seven geotechnical domains. The validation process depended upon the development of new software capable of both handling the large quantity of data emanating from a modern longwall and accurately delineating load cycles. Existing software was found not to be capable of delineating load cycles to a sufficient accuracy. Load-cycle analysis can now be used quantitatively to assess the adequacy of support capacity and the appropriateness of set pressure for the conditions under which a longwall is being operated. When linked to a description of geotechnical conditions, this has allowed the development of a database for support selection for greenfield sites. For existing sites, the load-cycle characteristic concept allows for a diagnosis of strata-support problem areas, enabling changes to be made to set pressure and mining strategies to manage better, or avoid, strata control problems. With further development of the software, there is the prospect of developing a system that is able to respond to changes in strata-support interaction in real time.

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The associations of volumetric (vBMD) and areal (aBMD) bone mineral density measures with prevalent cardiovascular disease (CVD) and subclinical peripheral arterial disease (PAD) were investigated in a cohort of older men and women enrolled in the Health, Aging, and Body Composition Study. Participants were 3,075 well-functioning white and black men and women (42% black, 51% women), aged 68-80 years. Total hip, femoral neck, and trochanter aBMD were measured using dual-energy X-ray absorptiometry. Quantitative computed tomography was used to evaluate spine trabecular, integral, and cortical vBMD measures in a subgroup (n = 1,489). Logistic regression was performed to examine associations of BMD measures with CVD and PAD. The prevalence of CVD (defined by coronary heart disease, PAD, cerebrovascular disease, or congestive heart failure) was 29.8%. Among participants without CVD, 10% had subclinical PAD (defined as ankle-arm index < 0.9). Spine vBMD measures were inversely associated with CVD in men (odds ratio of integral [ORintegral] = 1.34, 95% confidence interval [CI] 1.10-1.63; ORtrabecular = 1.25, 95% CI 1.02-1.53; ORcortical = 1.36, 95% CI 1.11-1.65). In women, for each standard deviation decrease in integral vBMD, cortical vBMD, or trochanter aBMD, the odds of CVD were significantly increased by 28%, 27%, and 22%, respectively. Total hip aBMD was associated with subclinical PAD in men (OR = 1.39, 95% CI 1.03-1.84) but not in women. All associations were independent of age and shared risk factors between BMD and CVD and were not influenced by inflammatory cytokines (interleukin-6 and tumor necrosis factors-alpha). In conclusion, our results provide further evidence for an inverse association between BMD and CVD in men and women. Future research should investigate common pathophysiological links for osteoporosis and CVD.

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The processes that take place during the development of a heating are difficult to visualise. Bulk coal self-heating tests at The University of Queensland (UQ) using a two-metre column are providing graphic evidence of the stages that occur during a heating. Data obtained from these tests, both temperature and corresponding off-gas evolution can be transformed into what is effectively a video-replay of the heating event. This is achieved by loading both sets of data into a newly developed animation package called Hotspot. The resulting animation is ideal for spontaneous combustion training purposes as the viewer can readily identify the different hot spot stages and corresponding off-gas signatures. Colour coding of the coal temperature, as the hot spot forms, highlights its location in the coal pile and shows its ability to migrate upwind. An added benefit of the package is that once a mine has been tested in the UQ two-metre column, there is a permanent record of that particular coals performance for mine personnel to view.