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931.
提高低温制热量是小型家用空调器技术的一个难点,除霜带来的热量损失是低温制热量损失的一个重要方面。对小型家用空调器的除霜技术的发展进行了分析和总结,对小型家用空调器提出了一些新的除霜方式,对提高空调器的低温制热量、使用性能有重要意义。 相似文献
932.
Hong-Wei Li Yi-Bo Zhao Zhen-Qiang Yin Shuang Wang Zheng-Fu Han Wan-Su Bao Guang-Can Guo 《Optics Communications》2009,282(20):2533-0389
The number of transmitted signals in practical quantum key distribution (QKD) protocol is always finite. We discuss the security of decoy states QKD protocol with finite resources by considering the statistical fluctuation for the yield and error rate of the quantum state in different sources of pulses (signal sources and decoy sources). The number of exchanged quantum signals vs positive key generation rate is given with experiment results. 相似文献
933.
We develop a microscopic pedestrian-simulation model in which pedestrian positions are updated at discrete time steps. At each time step, each pedestrian probabilistically selects a direction of movement from a predetermined set according to a logit-type function that considers the dynamics of other pedestrians around, and then selects a step size that satisfies a certain distribution. We perform a number of field experiments on real intersecting pedestrian flows with four different angles. We then validate and calibrate the model using sample data on the deviation angles, step velocities, and velocity–density relations obtained from the experiments. 相似文献
934.
The stability number α(G) for a given graph G is the size of a maximum stable set in G. The Lovász theta number provides an upper bound on α(G) and can be computed in polynomial time as the optimal value of the Lovász semidefinite program. In this paper, we show that
restricting the matrix variable in the Lovász semidefinite program to be rank-one and rank-two, respectively, yields a pair
of continuous, nonlinear optimization problems each having the global optimal value α(G). We propose heuristics for obtaining large stable sets in G based on these new formulations and present computational results indicating the effectiveness of the heuristics.
Received: December 13, 2000 / Accepted: September 3, 2002 Published online: December 19, 2002
RID="★"
ID="★" Computational results reported in this paper were obtained on an SGI Origin2000 computer at Rice University acquired
in part with support from NSF Grant DMS-9872009.
Key Words. maximum stable set – maximum clique – minimum vertex cover – semidefinite program – semidefinite relaxation – continuous
optimization heuristics – nonlinear programming
Mathematics Subject Classification (2000): 90C06, 90C27, 90C30 相似文献
935.
By a T
*(2, k, v)-code we mean a perfect4-deletion-correcting code of length 6 over an alphabet of size v, which is capable of correcting anycombination of up to 4 deletions and/or insertions of letters that occur in transmission of codewords. Thethird author (DCC Vol. 23, No. 1) presented a combinatorial construction for such codes and prove thata T
*(2, 6, v)-code exists for all positive integers v 3 (mod 5), with 12 possible exceptions of v. In this paper, the notion of a directedgroup divisible quasidesign is introduced and used to show that a T
*(2, 6,v)-code exists for all positive integers v 3 (mod 5), except possiblyfor v {173, 178, 203, 208}. The 12 missing cases for T
*(2,6, v)-codes with v 3 (mod 5) are also provided, thereby the existenceproblem for T
*(2, 6, v)-codes is almost complete. 相似文献
936.
Bao-Li An Jian-Xin ShiWai-Kwok Wong Kok-Wai CheahRong-Hua Li Yan-Sheng YangMeng-Lian Gong 《Journal of luminescence》2002,99(2):155-160
A novel organic ligand, 6-parachloroaniline carbonyl 2-pyridine carboxylic acid, and the corresponding europium complex, tris(6-parachloroaniline carbonyl-2-pyridine carboxylate) europium (III) have been designed and synthesized. The results showed that the synthesized product was a conjugated complex, emitting remarkable strong red luminescence, and was a good red luminescence material with good thermal stability. The 5D0 lifetime of Eu3+ in the complex was examined using time-resolved spectroscopic analysis. The lifetime values for 1.0×10−5 mol/l ethanol solution of the complex and for the complex solid were 0.49±0.01 and 1.94±0.01 ms, respectively. 相似文献
937.
Concentration quenching in Yb:YAG 总被引:1,自引:0,他引:1
The concentration quenching in Yb:YAG crystals with high Yb3+ doping level was demonstrated, and studied as well. The color center and lattice distortion which originated from Yb2+ are the main reasons for producing the concentration quenching in unannealed Yb:YAG crystals, and after annealing at 1600°C in oxygen atmosphere for 24 h, Yb2+ vanished. Trace impurity ions are also responsible for this phenomenon. 相似文献
938.
Alpha-galactosyl ceramide has been identified to be a potent stimulatory agent for a novel immunological process, mediated by CD1 molecules. This paper describes a short and efficient synthesis of alpha-galactosyl ceramide. Starting from commercially available 2-deoxy galactose, a suitable sphingosine derivative was obtained in nine steps and 36% overall yield, which was subsequently glycosylated to give the target molecule. This flexible route will provide various glycolipids for further exploration of this interesting biological process. 相似文献
939.
940.
[reaction: see text] The syntheses of 4,4a-didehydrohimbacine and 4,4a-didehydrohimandravine are presented. Key steps include an intramolecular Diels-Alder reaction of a bromopentadienyl acrylate and Suzuki-Miyaura and Stille coupling reactions. 相似文献