高分子冠状聚合物对痕量铀(Ⅵ)的选择性吸附及其在分离中的应用

近年来,高分子冠醚的出现引起了人们的广泛兴趣。S.Kopolow首先合成乙烯基苯并-15-冠-5及苯并-18-冠-6的高聚物。W.H.Teigenbaum,J.M.Lehn分别合成了聚胺和主链含胺冠醚。E.Blasius还报道了酚醛型二苯并-18-冠-6和二苯并-24-冠-     

Thermal efficiency of solid electrolyte fuel cells with mixed conduction

The effect of mixed anionic and n-type electronic conduction in solid electrolytes on the thermal efficiency of a fuel cell system was analyzed quantitatively. The mixed conduction observed when electrolytes based on ceria are used in H₂/air fuel cell applications lowers the maximum attainable cell thermal efficiency to below 40%. Neither the zirconia nor the ceria based solid oxide electrolytes studied to date can be used in a low temperature (700 °C) system that meets simultaneously the requirements of power density and thermal efficiency for electric utility power plants. The material properties required for an advanced fuel cell power plant solid electrolyte were derived in terms of the ionic conductivity and the Schmalzried parameters P and P : σ_ion > 0.033 (Ω-cm)⁻¹, P > 10³ atm., P < 10⁻²³ atm. at 700 °C.     

A comparative analysis of three of ERDA''s major R & D programs

The benefits attributable to alternative energy R & D programs should be evaluated in terms of how well the technologies contribute as integral elements of the total United States energy system (rather than as isolated entities, as has typically been done in the past). Thus, the present model simulates the dynamics of the evolution of the total energy system by requiring both existing and new technologies to compete for introduction (i.e. commercialization) on a cost-competitive basis that considers the time phasing of

1. (1) retirement of energy conversion facilities,

2. (2) growth in end-use demands, and

3. (3) escalation of the costs of extracting depleting domestic energy resources.

This approach contrasts with a static model used by the Energy Research and Development Administration (ERDA), wherein assumptions must be made for each future year of interest for

1. (1) maximum capacity constraints for alternative types of conversion facilities and

2. (2) the cost of energy resources.

The present model is used to compare the relative consequences and merits of the technology products from the following three of ERDA's major energy R & D programs:

1. (1) the liquid-metal fast breeder reactor (LMFBR),

2. (2) synthetic fuels derived from coal and oil shale, and

3. (3) improved efficiencies for end-use devices (e.g. space heaters).

It is found that the development of synthetic fuels derived from coal and oil shale is the only alternative (of the three considered) that provides energy independence for the United States in the next fifty years. However, the possible collapse of the world oil cartel is shown to pose a major retardant to synfuels commercialization by the private sector until at least the end of the century. The substantial environmental impact from synfuels commercialization could be reduced significantly with the accelerated introduction of end-use utilizing devices with improved efficiencies. This latter program could result in a significant reduction in the costs of operating the United States energy ststem over the 60-yr period considered by the model. The discounted present value of this “cost reduction” (i.e. the “economic benefit”) would be two orders of magnitude greater than the R & D investment, at least one order of magnitude greater than the expected economic benefits from synfuels commercialization and two orders of magnitude greater than the economic benefits from the commercialization of the LMFBR. However, the lack of performance and cost studies of improved efficiency in end-use suggests increased funding for these technologies rather than reduced funding for the breeder.     

Hierarchical Matrices Based on a Weak Admissibility Criterion

In preceding papers [8], [11], [12], [6], a class of matrices (-matrices) has been developed which are data-sparse and allow to approximate integral and more general nonlocal operators with almost linear complexity. In the present paper, a weaker admissibility condition is described which leads to a coarser partitioning of the hierarchical -matrix format. A coarser format yields smaller constants in the work and storage estimates and thus leads to a lower complexity of the -matrix arithmetic. On the other hand, it preserves the approximation power which is known in the case of the standard admissibility criterion. Furthermore, the new weak -matrix format allows to analyse the accuracy of the -matrix inversion and multiplication.     

Two Triangulation Methods Based on Edge Refinement

In this paper two curvature adaptive methods of surface triangulation are presented. Both methods are based on edge refinement to obtain a triangulation compatible with the curvature requirements. The first method applies an incremental and constrained Delaunay triangulation and uses curvature bounds to determine if an edge of the triangulation is admissible. The second method uses this function also in the edge refinement process, i.e. in the computation of the location of a refining point, and in the re-triangulation needed after the insertion of this refining point. Results are presented, comparing both approaches.