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1.
This paper provides a preliminary examination of present and projected land use in Africa to estimate the potential availability of land in 2025 for use in producing biomass energy. Fifty countries are included in the analysis. Future cropland requirements are projected on the basis of average African cereal crop yield improvements since 1972, and minimum nutritional requirements are assumed to be met in 2025 without increasing imports above present absolute levels. Cropland, natural forests and other wilderness areas are excluded from consideration for biomass energy use. Woody biomass energy yields are estimated on the basis of nationally averaged precipitation, using a yield-precipitation correlation for commercial eucalyptus plantations in Brazil. The total African bioenergy production potential in 2025 is estimated to be about 18 EJ per year for a set of baseline assumptions that includes planting only 10% of the available non-crop, non-forest, non-wilderness area with biomass energy crops. A preliminary cost assessment suggests that much of this biomass could be produced for $1–2 GJ−1. A number of uncertainties in the modelling assumptions are examined through a sensitivity analysis. Despite limitations in the model used here, one robust conclusion is that Africa as a whole has a significant biophysical potential for producing biomass energy. This result suggests that more detailed country and sub-country level assessments would be worthwhile to understand better the practical prospects for future biomass energy production in Africa. 相似文献
2.
Tony Maillet Jacques Barbier Jr. Daniel Duprez 《Applied catalysis. B, Environmental》1996,9(1-4):251-266
A 1% Pd catalyst (38% dispersion) was prepared by impregnating a γ-alumina with palladium acetylacetonate dissolved in acetone. The behaviour of this catalyst in oxidation and steam reforming (SR) of propane was investigated. Temperature-programmed reactions of C3H8 with O2 or with O2 + H2O were carried out with different stoichiometric ratios S(S =[O2]/5[C3H8]). The conversion profiles of C3H8 for the reaction carried out in substoichiometry of O2 (S < 1) showed two discrete domains of conversion: oxidation at temperatures below 350°C and SR at temperatures above 350°C. The presence of steam in the inlet gases is not necessary for SR to occur: there is sufficient water produced in the oxidation to form H2 and carbon oxides by this reaction. Contrary to what was observed with Pt, an apparent deactivation between 310 and 385°C could be observed with Pd in oxidation. This is due to a reduction of PdOx into Pd0, which is much less active than the oxide in propane oxidation. Steam added to the reactants inhibits oxidation while it prevents the reduction of PdOx into Pd0. Compared to Pt and to Rh, Pd has a higher thermal resistance: no deactivation occurred after treatment up to 700°C and limited deactivation after treatment up to 900°C, provided that the catalyst is maintained in an oxygen-rich atmosphere during the cooling. 相似文献
3.
Tony Proctor 《Creativity & Innovation Management》1997,6(2):94-98
A new kind of computer assisted creative problem solving method is examined in which visual images are provided to support the process. Until now, much attention has been given to developing programmes which help to structure problems and ideas so that they become more meaningful to the people who are concerned with them. Emphasis has been placed almost entirely on the written word as form of expression. It is argued that a combination of pictorial imagery and written words may be more effective in helping users to gain insights into problems and to come up with ideas or solutions to problems. 相似文献
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Laney D.C. Maggio G.M. Lehmann F. Larson L. 《Selected Areas in Communications, IEEE Journal on》2002,20(9):1692-1700
Pseudochaotic time hopping (PCTH) is a previously proposed encoding/modulation scheme for ultra-wideband (UWB) impulse radio. PCTH exploits concepts from symbolic dynamics to generate aperiodic spreading sequences, resulting in a noise-like spectrum. We present a multiple-access technique suitable for the PCTH scheme. In particular, we provide an analytical expression of the bit-error rate performance as a function of the number of users and validate it by simulation. 相似文献
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Tony Fazey 《乙烯基与添加剂工艺杂志》1992,14(2):83-86
The effect of adding recycled vinyl bottle flake to virgin bottle compound has been studied. Vinyl bottles contains 10 to 50% recycled vinyl bottle flake were produced on a Bekum extrusion blow molding machine. The performance properties of the vinyl bottles were evaluated, and the optimum level of recycled flake was determined. 相似文献
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