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51.
基于马尔可夫链的自适应性神经网络训练算法 总被引:1,自引:1,他引:0
提出一种基于马尔可夫链的自适应性神经网络训练方法,对传统的S型激励函数进行了改进,建立了自适应性的神经网络分类器。在假设样本中噪声服从于正态分布的情况下建立最大似然估计,通过后验概率建立马尔科夫链对样本进行训练,提高了神经网络训练速度。在轴承故障诊断中的测试结果表明,该算法可以迅速稳定地训练出神经网络,有效提高诊断的分类结果。 相似文献
52.
Data flow acyclic directed graphs (digraph) are widely used to describe the data dependency of mesh-based scientific computing. The parallel execution of such digraphs can approximately depict the flowchart of parallel computing. During the period of parallel execution, vertex priorities are key performance factors. This paper firstly takes the distributed digraph and its resource-constrained parallel scheduling as the vertex priorities model, and then presents a new parallel algorithm for the solution of vertex priorities using the well-known technique of forward–backward iterations. Especially, in each iteration, a more efficient vertex ranking strategy is proposed. In the case of simple digraphs, both theoretical analysis and benchmarks show that the vertex priorities produced by such an algorithm will make the digraph scheduling time converge non-increasingly with the number of iterations. In other cases of non-simple digraphs, benchmarks also show that the new algorithm is superior to many traditional approaches. Embedding the new algorithm into the heuristic framework for the parallel sweeping solution of neutron transport applications, the new vertex priorities improve the performance by 20 % or so while the number of processors scales up from 32 to 2048. 相似文献
53.
Magnetotactic bacteria (MTB) are one kind of bacteria with magnetic particles called magnetosomes in their bodies. These particles often connect together like a chain. The MTB move toward the ideal living conditions under the interaction between magnetic field produced by the magnetic particles chain and that of the earth. In the paper, a new magnetic bacteria algorithm based on power spectrum (PSMBA) for optimization is proposed. The candidate solutions are decided by power spectrum in the algorithm. It mainly includes four steps: power spectrum calculation, bacteria swimming, bacteria rotation and bacteria replacement. The effect of swimming schemes and parameter settings on the performance of PSMBA is studied. And it is compared with GA, PSO and its variants and some other optimization algorithms on 25 benchmark functions including CEC2005. The simulation results show that PSMBA has better performance on most of the problems than most of the compared algorithms. 相似文献
54.
为对远距离的直流移动负载进行供电,须考虑损耗、体积、指标等一系列的问题。要解决远距离损耗大的问题,则须采用在始端升压、负载端降压的措施;要使负载端的变换器体积小,则须提高系统频率,在变换器中采用高频变压器;要满足整个系统的指标,则须完成从部分到整体的设计过程。在此基础上,此供电电源采用AC/DC/DC变换的过程,始端变换器中采用三相PWM斩波稳压与12脉波整流相结合输出高压直流,然后经过远距离的电缆,负载端DC/DC变换器采用半桥三电平结构进行直流降压后为移动负载供电。文中分别对两个部分的拓扑以及工作原理进行了理论分析与仿真,仿真结果表明,供电电源采用这样的拓扑结构能够得到稳定的直流电压,并且不会影响始端的交流指标。 相似文献
55.
Tae Oan Ahn Chang Kee Kim Byung Kyu Kim Han Mo Jeong Jung Do Huh 《Polymer Engineering and Science》1990,30(6):341-349
Binary blends of ethylene vinyl alcohol copolymers, containing 62 (EVOH-62) and 71 (EVOH-71) mole percent vinyl alcohols, with nylons (nylon-6, nylon-6/12, and nylon-12) have been prepared from melt mixing in a twin screw compounding machine. Morphological, thermal, rheological, and mechanical properties were determined. EVOH-62/nylon-6 and EVOH-71/nylon-6 blends showed homogeneous phase morphologies in the nylon-6-rich region, and fine phase separations (c.a. 2 × 10?7 m) in the EVOH-rich region. Melting point depression, positive deviations in viscosity and flexural modulus, and negative deviation in impact strength from the simple additive rule were generally observed. And the results were possibly interpreted in terms of compatibility and increased nylon/EVOH interactions over the nylon/nylon interactions. On the contrary, clean phase separations in large domains were observed from EVOH-71/nylon-6/12 and EVOH-71 /nylon-12 blends. Fibrillation was also obtained from EVOH rich blends. Probably due to the incompatible nature of these blends, yield at low rate of shear and a mechanical property drop were also observed. 相似文献
56.
In this paper, remote information concentration is investigated which is the reverse process of the $1\rightarrow 3$ optimal asymmetric economical phase-covariant telecloning (OAEPCT). The OAEPCT is different from the reverse process of optimal universal telecloning. It is shown that the quantum information via $1\rightarrow 3$ OAEPCT procedure can be remotely concentrated back to a single qubit with a certain probability via several quantum channels. In these schemes, we adopt Bell measurement to measure the joint systems and use projected measurement and positive operator-valued measure to recover the original quantum state. The results shows non-maximally entangled quantum resource can be applied to information concentration. 相似文献
57.
粉煤灰填充PVC树脂的研究 总被引:3,自引:0,他引:3
采用WAXD、SEM和力学测试等方法对不同粒度和不同含量的粉煤灰(PFA)与聚氯乙烯(PVC)共混物的结构形态、力学性能进行了测定。结果表明,PFA粒度对PVC/PFA共混物的性能具有明显影响,当PFA粒度尺寸达到一定程度时,再降低PFA粒度尺寸对共混物的性能影响不大。随着PVC/PFA共混物中PFA含量的增加,拉伸强度和拉伸模量增大,但伸长率降低。 相似文献
58.
59.
Zunli Mo Yinxia Sun Hong Chen Ping Zhang Dandan Zuo Yanzhi Liu Hejun Li 《Polymer》2005,46(26):1046-12676
An easy process for the synthesis of poly(methyl methacrylate)/Ce(OH)3, Pr2O3/graphite nanosheet (PMMA/Ce(OH)3, Pr2O3/NanoG) composite was developed. Graphite nanosheets (NanoG) were prepared by treating the expanded graphite with sonication in aqueous alcohol solution. The PMMA/Ce(OH)3, Pr2O3/NanoG composites were prepared via in situ polymerization of MMA monomer in the presence of graphite nanosheets and Ce(OH)3, Pr2O3 through reverse micelle template, in which the methyl methacrylate was designated as the oily phase. The composites were then dispersed with chloroform and coated on glass slides to form films. Scanning and transmission electron microscopy were used to characterize the structure and dispersion of the graphite nanosheets and the composites. The results showed that the high-aspect-ratio structure of the nanosheets played an important role in forming a conducting network in the PMMA matrix. From thermogravimetric analysis, the introduction of graphite nanosheets and inorganic nanopartices exhibited a beneficial effect on the thermal stability of PMMA. 相似文献
60.
Han Mo Jeong Shang Hoon Lee Kwang Jae Cho Young Tae Jeong Kap Ku Kang Jae Kwon Oh 《应用聚合物科学杂志》2002,84(9):1709-1715
The block copolymer of poly(1‐hexadecene) (PHD) and polypropylene (PP) was effectively synthesized by the sequential polymerization of propylene and 1‐hexadecene by using highly isospecific TiCl3/Cp2Ti(CH3)2 (Cp = cyclopentadienyl). The block copolymers had two separate melting temperatures of constituent blocks. The modulus of PHD–PP block copolymer was enhanced as the content of sequentially polymerized PP block was increased. The elongation at break showed positive deviation at the intermediate compositions from the simple additive values of constituent homopolymers. Shape memory effect which utilizes the crystalline PHD block as a reversible phase and the crystalline PP block as a fixed structure was examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1709–1715, 2002; DOI 10.1002/app.10551 相似文献