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971.
Baker‘s yeast mediated reduction of optically active diketone is described. The two keto groups are efficiently differentiated and the ee value of the recovered material is considerably raised. It affords highly optically active key intermediates efficiently for the synthesis of natural polyhydroxylated agarofuran products. 相似文献
972.
Ming Zhao WANG Guan Liang CAI Ling XIA Jun Jian YAO Hong Yan CHEN Zhao Xing MENG Bo Li LIUDepartment of Chemistry Beijing Normal University Beijing Chemical Defense Institute PLA Beijing 《中国化学快报》2004,15(4):495-497
The crystal structures of two potential tumor imaging agents and therapeutic agents -copper(Ⅱ) complexes with salicylidene-tyrosinato Schiff base and nitrogen-donor chelating Lewis base, [Cu(sal-tyr)(bipy)] 1 and [Cu(sal-tyr)(phen)]2CH3OH 2 are presented. Our work is helpful to get deep understanding of novel 64Cu tumor imaging agents and therapeutic agents. 相似文献
973.
M. A. Diniz-Ehrhardt M. A. Gomes-Ruggiero J. M. Martínez S. A. Santos 《Journal of Optimization Theory and Applications》2004,123(3):497-517
The spectral projected gradient method SPG is an algorithm for large-scale bound-constrained optimization introduced recently by Birgin, Martínez, and Raydan. It is based on the Raydan unconstrained generalization of the Barzilai-Borwein method for quadratics. The SPG algorithm turned out to be surprisingly effective for solving many large-scale minimization problems with box constraints. Therefore, it is natural to test its perfomance for solving the sub-problems that appear in nonlinear programming methods based on augmented Lagrangians. In this work, augmented Lagrangian methods which use SPG as the underlying convex-constraint solver are introduced (ALSPG) and the methods are tested in two sets of problems. First, a meaningful subset of large-scale nonlinearly constrained problems of the CUTE collection is solved and compared with the perfomance of LANCELOT. Second, a family of location problems in the minimax formulation is solved against the package FFSQP. 相似文献
974.
G. Z. Ruan S. Y. Wang Y. Yamamoto S. S. Zhu 《Journal of Optimization Theory and Applications》2004,123(2):409-429
In this paper, a model of a linear multilevel programming problem with dominated objective functions (LMPPD(l)) is proposed, where multiple reactions of the lower levels do not lead to any uncertainty in the upper-level decision making. Under the assumption that the constrained set is nonempty and bounded, a necessary optimality condition is obtained. Two types of geometric properties of the solution sets are studied. It is demonstrated that the feasible set of LMPPD(l) is neither necessarily composed of faces of the constrained set nor necessarily connected. These properties are different from the existing theoretical results for linear multilevel programming problems. 相似文献
975.
In his curriculum vitae, John Hawkes lists his research interestsas geometric measure theory, probability (Lévy processes),and potential theory (probabilistic). In fact, he made significantcontributions to all three areas, and there are strong relationshipsbetween them. He used both geometric measure theory and potentialtheory as tools for his study of the trajectories of particularLévy processes, but in many cases he needed to developthe tool before it was ready to be used. We will summarise hisresearch later, but first we discuss what is known of his lifehistory. 相似文献
976.
Goryunov proved that the space of local invariants of Vassiliev type for generic maps from surfaces to three-space is three-dimensional.
The basic invariants were the number of pinch points, the number of triple points and one linked to a Rokhlin type invariant.
In this paper we show that, by colouring the complement of the image of the map with a chess board pattern, we can produce
a six-dimensional space of local invariants. These are essentially black and white versions of the above. Simple examples
show how these are more effective.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
977.
A note on a generalized Douglas space 总被引:1,自引:0,他引:1
Periodica Mathematica Hungarica - 相似文献
978.
Beatriz S. D'Ambrosio William J. Boone Shelly Sheats Harkness 《School science and mathematics》2004,104(1):5-15
This paper describes the mechanism used to gain insights into the state of the art of mathematics instruction in a large urban district in order to design meaningful professional development for the teachers in the district. Surveys of close to 2,000 elementary, middle school, and high school students were collected in order to assess the instructional practices used in mathematics classes across the district. Students were questioned about the frequency of use of various instructional practices that support the meaningful learning of mathematics. These included practices such as problem solving, use of calculators and computers, group work, homework, discussions, and projects, among others. Responses were analyzed and comparisons were drawn between elementary and middle school students' responses and between middle school and high school responses. Finally, fifth‐grade student responses were compared to those of their teachers. Student responses indicated that they had fewer inquiry‐based experiences, fewer student‐to‐student interactions, and fewer opportunities to defend their answers and justify their thinking as they moved from elementary to middle school to high school. In the elementary grades students reported an overemphasis on the use of memorization of facts and procedures and sparse use of calculators. Results were interpreted and specific directions for professional development, as reported in this paper, were drawn from these data. The paper illustrates how student surveys can inform the design of professional development experiences for the teachers in a district. 相似文献
979.
980.
W Y Hung S Kucherenko N J Samsatli N Shah 《The Journal of the Operational Research Society》2004,55(8):801-813
In this paper, we present a new modelling approach for realistic supply chain simulation. The model provides an experimental environment for informed comparison between different supply chain policies. A basic simulation model for a generic node, from which a supply chain network can be built, has been developed using an object-oriented approach. This generic model allows the incorporation of the information and physical systems and decision-making policies used by each node. The object-oriented approach gives the flexibility in specifying the supply chain configuration and operation decisions, and policies. Stochastic simulations are achieved by applying Latin Supercube Sampling to the uncertain variables in descending order of importance, which reduces the number of simulations required. We also present a case study to show that the model is applicable to a real-life situation for dynamic stochastic studies. 相似文献