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- Gao, Ming-Wei
(författare)
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Optimization, scale up and simulation of tumbling mills
- 1990
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Grinding is a fundamental process in the mineral industries. Grinding mills are often very large machines. Their efficiency and energy consumption therefore are of major importance. Problems of large ball mills are discussed in this thesis. The employment of ball mills with a diameter over 5 meters in industry began only a decade ago. The abnormal behaviour of these big mills surely surprised many who had an optimistic view of them. However, the problems have to be overcome since the trend of increasing mill size is still prevailing. An optimization of the grinding process deals with a large number of co-operating parameters. Statistical approach provides a powerful tool for doing this. Its application on the simultaneous study of four important grinding parameters is described in this thesis. In the last part of the thesis a study on the population balance model is presented. Tremendous research has been carried out on this model. However, its application for designing grinding mills still requires more effort on the understanding of the selection and breakage functions. Heterogeneous materials were selected to be the experimental samples in this thesis. It is the author's opinion that the future of the population balance model depends on its ability to survive the applications on scaling-up fullscale mills for grinding those complex materials.:
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| 2. |
- Gao, Ming-Wei, et al.
(författare)
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Simulation of batch grinding of iron ore
- 1990
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Ingår i: Mineral Processing and Extractive Metallurgy. - 0371-9553 .- 1743-2855. ; 99, s. 142-146
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Tidskriftsartikel (refereegranskat)abstract
- A batch-grinding process treating a natural magnetite ore was simulated by a population-balance model. Different methods of determining selection and breakage functions for the ore were investigated. Grinding tests were performed with seven monosize fractions in a pilot-scale ball-mill. The back-calculated selection function was compared with experimentally measured values of the selection function, S, and the breakage functions so determined were checked against the results of the simulation. It appears that if the breakage functions of a material are not normalizable, it is necessary to carry out a sufficient number of monosize grinding tests to allow reliable selection and breakage functions to be estimated. Graphs. 8 ref.--AA
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| 3. |
- Gao, Ming-Wei, et al.
(författare)
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Study on the effect of parameters in stirred ball milling
- 1993
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Ingår i: International Journal of Mineral Processing. - 0301-7516 .- 1879-3525. ; 37:1, s. 45-59
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Tidskriftsartikel (refereegranskat)abstract
- Ultra-fine grinding involves a large number of parameters in its operation. In this paper, four important parameters of the Drais stirred ball mill, i.e., the bead density, slurry density, mill speed, and the effect of dispersant were selected for investigation. The experimental work was based on a factorial design and 27 milling tests were conducted. It is found that the bead density has an optimum value of 3.7 g/cc in this investigation. A lower slurry density and a smaller amount of dispersant appear to be better conditions. The mill speed should be as high as possible within the speed limit tested in this work for the best process efficiency.
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| 4. |
- Smits, A, et al.
(författare)
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Expression of platelet-derived growth factor in and around intrastriatal embryonic mesencephalic grafts
- 1993
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Ingår i: Cell Transplantation. - : SAGE Publications. - 0963-6897 .- 1555-3892. ; 2:2, s. 151-162
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Tidskriftsartikel (refereegranskat)abstract
- The expression of platelet-derived growth factor (PDGF) was investigated in the embryonic donor tissue and surrounding host brain before and after intracerebral transplantation in a rat model of Parkinson's disease (PD). Ventral mesencephalic tissue from E13-E15 rat embryos was dissociated and implanted into adult rats with unilateral lesions of the mesostriatal dopamine system. Immunohistochemical studies showed that the majority of the grafted cells were PDGF-positive at early time points after grafting. However, the immunostaining gradually decreased, and had disappeared almost completely 3 wk after transplantation. These results were in agreement with in situ hybridization data demonstrating detectable levels of mRNA for PDGF chains in graft cells after 1, but not after 6 wk. In contrast, a large number of PDGF-immunoreactive cells was observed in the host brain adjacent to the grafts from 1 wk after transplantation, and increasing with time. Increased expression of PDGF was also observed in response to a sham-operation (injection of vehicle), although the number of PDGF-positive cells seemed lower than after grafting of embryonic tissue. Double immunofluorescence labeling of these cells with an anti-glial fibrillary acidic protein (GFAP) antiserum and a monoclonal antibody against PDGF B-chain, indicated that the PDGF-positive cells were astrocytes. The dynamic expression of PDGF in and around intrastriatal embryonic mesencephalic implants has several, potentially important, implications for graft survival and function. Glial cells could utilize the elevated levels of PDGF to proliferate in a reactive gliosis, and PDGF might also augment immune responses. It is also possible that PDGF increases the survival of, and promotes neurite outgrowth from, grafted dopaminergic neurons.
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