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71.
人工神经网络研究进展及其在光谱分析中的应用 总被引:5,自引:0,他引:5
介绍最常用的人工神经网络——BP神经网络的原理、结构及其研究进展,评述了人工神经网络在光谱分析中的应用。 相似文献
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74.
Three new open-framework transition-metal borophosphates Na5(H3O){M(II)3[B3O3(OH)]3(PO4)6}.2H2O (M(II) = Mn, Co, Ni) (denoted as MBPO-CJ25) have been synthesized under mild hydrothermal conditions. Single-crystal X-ray diffraction analyses reveal that the three compounds possess isostructural three-dimensional (3D) open frameworks with one-dimensional 12-ring channels along the [001] direction. Notably, the structure can also be viewed as composed of metal phosphate layers [M(II)(PO4)2]4- with Kagomé topology, which are further connected by [B3O7(OH)] triborates, giving rise to a 3D open framework. The guest water molecules locate in the 12-ring channels. Partial Na+ ions reside in the 10-ring side pockets within the wall of the 12-ring channels, and the other Na+ ions and protonated water molecules locate in the 6-ring windows delimited by MO6 and PO4 polyhedra to compensate for the negative charges of the anionic framework. These compounds show a high thermal stability and are stable upon calcinations at ca. 500 degrees C. Ionic conductivities, due to the motion of Na+ ions, are measured for these three compounds. They have similar activation energies of 1.13-1.25 eV and conductivities of 2.7 x 10(-7)-9.9 x 10(-7) S cm(-1) at 300 degrees C. Magnetic measurements reveal that there are very weak antiferromagnetic interactions among the metal centers of the three compounds. Crystal data: MnBPO-CJ25, hexagonal, P6(3)/m (No. 176), a = 11.9683(5) A, c = 12.1303(6) A, and Z = 2; CoBPO-CJ25, hexagonal, P6(3)/m (No. 176), a = 11.7691(15) A, c = 12.112(2) A, and Z = 2; NiBPO-CJ25, hexagonal, P6(3)/m (No. 176), a = 11.7171(5) A, c = 12.0759(7) A, and Z = 2. 相似文献
75.
Using periodic structure theory, the suppression of vibration and noise radiation from an underwater vehicle due to excitation from propeller forces is investigated. The underwater vehicle is modelled in two parts (the hull and the propeller/shafting system). A model of the propeller/shafting system is constructed using a modular approach and considers the propeller, shaft, thrust bearing, isolation structure and foundation. Different forms of isolator are considered – a simple spring-damper system, a continuous rod and a periodically layered structure. The dynamic properties of the underwater vehicle and the isolation performances of various isolators are compared and analysed. The stop band properties of the periodic isolator are used to enhance the passive control performance. Furthermore, an integrated isolation device is proposed that consists of the periodic isolator and a dynamic absorber, and its isolation performance is investigated. The effects of the absorber parameters on the performance of the integrated device are also analysed. Finally, the radiated sound pressure is calculated to verify the attenuation. The numerical results show that the vibration and noise radiation are greatly attenuated in the stop bands. By optimising the design of the periodic isolators and its integrated structures, the suppression of the vibration and noise radiation can be improved effectively. 相似文献
76.
Pointing errors caused by the atmospheric turbulence will degrade the performance of free space optical (FSO) communication systems, especially the bit error rate (BER). In this paper, we innovatively analyze the relationship between BER and pointing errors by the probability density functions (PDFs) and intensity displacement in focal plane under the On-Off Keying (OOK) modulation conditions. The closed-loop experimental system is set up in laboratory, where the fast steering mirror (FSM) is real-time controlled by embedded controller with the parallel processing technology and the atmospheric turbulence is simulated by a turbulence simulation box. The results of repeated experiments show that the method of pointing errors correction we proposed is efficient under the conditions of atmospheric turbulence. By utilizing our method, the BER can decrease from nearly 10−3 to nearly or even below 10−9, thus improving the performance of FSO communication systems significantly. 相似文献
77.
Within the mean-field theory, we investigate the magnetic properties of a charged spin-1 Bose gas in two dimensions. In this system the diamagnetism competes with paramagnetism, where the Landé factor g is introduced to describe the strength of the paramagnetic effect. The system presents a crossover from diamagnetism to paramagnetism with the increasing of the Landé factor. gc denotes the critical value of the Landé factor. We get the same value of gc both in the low temperature and strong magnetic field limit. Our results also show that in very weak magnetic field no condensation happens in the two-dimensional charged spin-1 Bose gas. 相似文献
78.
Wang L Li Y Peng Y Liang Z Yu J Xu R 《Dalton transactions (Cambridge, England : 2003)》2012,41(20):6242-6246
A novel decanuclear Co(II) cluster, [Co(10)(Q)(12)(μ(6)-CO(3))(4)]·2.5DMF (1) (Q = 8-hydroxyquinoline), has been synthesized under solvothermal conditions and characterized by powder XRD, TGA and IR spectroscopy. Single-crystal X-ray diffraction analysis shows that 1 represents a new type of decanuclear cobalt cluster with an approximate supertruncated tetrahedral shape coordinated with coexisted Q ligands and in situ formed μ(6)-bridging CO(3)(2-) anions. Meanwhile, 1 is the largest aggregate in metal-Q coordination chemistry. Another distinguishing feature of 1 is the adamantane-like metallic skeleton with point symbol {6(3)}(2){6}(3), which is observed in the polynuclear metal complexes for the first time. Furthermore, it is considered that the in situ formed CO(3)(2-) anions have a crucial effect on the formation of the resultant unexpected polynuclear structures. The magnetic studies show that antiferromagnetic (AF) interactions exist within 1. 相似文献
79.
This paper studies the equilibrium behavior of customers in continuous/discrete time queueing systems under single vacation policy. In the single vacation queueing system, the server can only take exactly one vacation when no customers exist in the system. This scheme is more practical under many specific circumstances. Based on the reward–cost structure, equilibrium behavior is considered in the fully observable and almost observable cases. The threshold strategies in equilibrium are obtained and the stationary system behavior is analyzed under the corresponding strategies. Finally, we illustrate the effect of the information level as well as several parameters on the equilibrium thresholds and social benefits via numerical experiments. The research results could instruct the customers to take optimal strategies and provide the managers with reference information on the pricing problem in the queueing system. 相似文献
80.
We study existence and asymptotic stability of solutions to a n-dimensional generalized incompressible magneto-hydrodynamic system with initial value ${(u_{0},b_{0}) \in (PM^{a})^{2n}}$ , where PM a is the pseudomeasure space, and ${a \in \mathbb{R}}$ is a given parameter. Some regularizing rate estimates for the ??-th spatial derivatives of solution are also established, which particularly imply that the solution is analytic in the spatial variable. 相似文献