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91.
92.
A new likelihood based AR approximation is given for ARMA models. The usual algorithms for the computation of the likelihood of an ARMA model require O(n) flops per function evaluation. Using our new approximation, an algorithm is developed which requires only O(1) flops in repeated likelihood evaluations. In most cases, the new algorithm gives results identical to or very close to the exact maximum likelihood estimate (MLE). This algorithm is easily implemented in high level quantitative programming environments (QPEs) such as Mathematica, MatLab and R. In order to obtain reasonable speed, previous ARMA maximum likelihood algorithms are usually implemented in C or some other machine efficient language. With our algorithm it is easy to do maximum likelihood estimation for long time series directly in the QPE of your choice. The new algorithm is extended to obtain the MLE for the mean parameter. Simulation experiments which illustrate the effectiveness of the new algorithm are discussed. Mathematica and R packages which implement the algorithm discussed in this paper are available [McLeod, A.I., Zhang, Y., 2007. Online supplements to “Faster ARMA Maximum Likelihood Estimation”, 〈http://www.stats.uwo.ca/faculty/aim/2007/faster/〉]. Based on these package implementations, it is expected that the interested researcher would be able to implement this algorithm in other QPEs. 相似文献
93.
On conditional diagnosability and reliability of the BC networks 总被引:1,自引:1,他引:0
Qiang Zhu 《The Journal of supercomputing》2008,45(2):173-184
An n-dimensional bijective connection network (in brief, BC network), denoted by X n , is an n-regular graph with 2 n nodes and n2 n?1 edges. Hypercubes, crossed cubes, twisted cubes, and Möbius cubes all belong to the class of BC networks (Fan and He in Chin. J. Comput. 26(1):84–90, [2003]). We prove that the super connectivity of X n is 2n?2 for n≥3 and the conditional diagnosability of X n is 4n?7 for n≥5. As a corollary of this result, we obtain the super connectivity and conditional diagnosability of the hypercubes, twisted cubes, crossed cubes, and Möbius cubes. 相似文献
94.
An investigation showing the performance of compact long period grating (LPG) pairs under demanding experimental conditions, making comparisons with the use of single LPGs for the simultaneous measurement of strain and temperature is presented. In this work, a LPG pair (LPGP) sensor comprising two weak (2.5 dB each) LPGs, 13 mm apart, was compared against the performance of two single LPG sensors (LPG1 & LPG2) with coupling strengths of 2.5 dB and 12.5 dB, respectively. All the LPG sensors used were subjected to extreme conditions arising from the fabrication, by choosing a high amplitude mask period with short physical length LPGs, and the high temperature annealing processes. In addition, a low resolution detection instrument was used to capture the spectra under study. Results have shown that the LPGP is 40 times better than the first single LPG used (LPG1) and three times better than the second LPG (LPG2). Using the error analysis methodology of Brady et al., the temperature and strain errors due to the uncertainty of the wavelength measurement for each of the LPG1, LPG2, and LPGP were compared with the typical performance of various fibre Bragg grating (FBG)-based sensor schemes under similar testing conditions. It was found that LPGPs offer the best performance especially when using low resolution detection instrumentation. 相似文献
95.
徐立颖 《计算机工程与设计》2008,29(10):2635-2639
传统意义下印制电路板的振动分析与设计主要是针对从电子元器件选型开展的,并不适用于商用计算机的加固技术.对商用计算机的板卡进行有效的加固设计,使其满足在振动环境下的使用要求,一直是计算机加固技术的重点.针对加固计算机板卡开展的振动分析表明,已有的加固技术并不能降低恶劣环境下板卡的振动位移,解决该问题必须采用全新的加固思路.商用计算机板卡的最新加固方案在理论分析方面和工程应用方面均表明是有效可行的,具有广泛的推广价值. 相似文献
96.
功能规模度量(FSM)方法通过量化用户功能需求(FUR)而得到软件功能规模。针对不同的功能规模度量方法都是使用不同的抽象来描述一个软件系统的问题,提出了一种通用的FSM模型。根据软件系统的抽象模型,首先对度量所涉及的数据组和事务进行了泛化,然后以IFPUG FPA为例详细说明了该通用模型和FPA之间的转换过程,最后给出了度量过程的算法描述。 相似文献
97.
高性能PCB空心线圈电流互感器为大截面结构,而理想空心线圈电流互感器要求为小截面结构。文章通过详细的理论分析和推导,解除了对截面大小的这一限制,得出大截面、高精度的PCB空心线圈电流互感器具有和理想空心线圈电流互感器相同测量原理的结论,为PCB空心线圈电流互感器的优化设计和在矿区电力系统中的应用提供了理论基础。实验研究结果表明,高性能PCB空心线圈电流互感器具有良好的测量精度、参数一致性、优异的工频暂态性能和抗电磁干扰能力,适应矿区的电力环境和电力系统进一步数字化的发展潮流。 相似文献
98.
F. Nieto S. Hernández J. Á. Jurado 《Structural and Multidisciplinary Optimization》2009,39(2):133-151
Cable supported bridges are wind prone structures. Therefore, their aerodynamic behaviour must be studied in depth in order
to guarantee their safe performance. In the last decades important achievements have been reached in the study of bridges
under wind-induced actions. On the other hand, non-conventional design techniques such as sensitivity analysis or optimum
design have not been applied although they have proved their feasibility in the automobile or aeronautic industries. The aim
of this research work is to demonstrate how non-conventional design techniques can help designers when dealing with long span
bridges considering their aeroelastic behaviour. In that respect, the comprehensive analytical optimum design problem formulation
is presented. In the application example the optimum design of the challenging Messina Strait Bridge is carried out. The chosen
initial design has been the year 2002 design proposal. Up to a 33% deck material saving has been obtained after finishing
the optimization process. 相似文献
99.
基于Web应用的全面功能点的改进 总被引:1,自引:0,他引:1
全面功能点(FFP)是一种应用广泛且使用方便的软件功能规模度量(FSM)方法,但其方法本身只能度量系统静态的方面,不能考虑到对象的交互性和对象的行为。根据COSMIC-FFP的度量元素和Web应用的结构,对COSMIC-FFP软件模型进行了改进,列出了针对Web应用的度量规则,并给出了实例说明了这些规则的使用。 相似文献
100.
Traditional data-driven energy consumption forecasting models, including machine learning and deep learning methods, showed outstanding performance in terms of forecasting accuracy and efficiency. The superior performances are based on enough training data samples. Moreover, the derived forecasting model is only applicable to the training dataset and usually is applied to specific household. In real-world smart city development, a centralized forecasting model is required to model and forecasting energy consumption patterns for multiple households, whereas the traditional data-driven forecasting approaches may become invalid. A consistent model is demanded in this scenario modeling multiple households’ energy consumption patterns. Additionally, privacy issues are also highly concerned in such scenarios. Accurate energy consumption forecasting with privacy preservations becomes a key point for the state-of-art research. In this study, we adopt an innovative privacy-preserving structure that combines deep learning and federated learning. Under the premise of guaranteeing forecasting accuracy and privacy preservation, this structure can achieve the forecasting of various household energy consumption with a consistent model that simultaneously forecast multiple household energy consumption data by transmission control protocol. 相似文献