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141.
从大学生学习成绩出发,应用广义线性回归模型研究了学生学年间成绩的相关性,揭示了大学一年级,尤其是一年级的二学期是影响学生后期学习的关键阶段.进一步应用聚类分析,得到学生成绩在大学一年级就已经埋下了两极分化的隐患,应用判别分析得出了两极分化的关键课程.该结论为教育教学和学生管理提供决策依据. 相似文献
142.
负二项分布类的条件概率封闭性 总被引:1,自引:0,他引:1
在研究只允许部分服务台进入休假状态的多服务台M/M/c排队系统时,我们发现了条件Erlang分布的一些有趣的性质,进一步研究我们发现相对应离散随机状态的负二项分布也具有很好的性质(概率封闭性.本文证明了一类负二项分布的概率封闭性.它们对导出复杂排队系统中离散状态下顾客等待时问分布及保险公司中破产概率上界的计算起着重要作用. 相似文献
143.
In high accuracy long-time integration of differential equations, round-off errors may dominate truncation errors. This article
studies the influence of round-off on the conservation of first integrals such as the total energy in Hamiltonian systems.
For implicit Runge–Kutta methods, a standard implementation shows an unexpected propagation. We propose a modification that
reduces the effect of round-off and shows a qualitative and quantitative improvement for an accurate integration over long
times.
AMS subject classification (2000) 65L06, 65G50, 65P10 相似文献
144.
A. Robledo 《Pramana》2005,64(6):947-956
We recall that at both the intermittency transitions and the Feigenbaum attractor, in unimodal maps of non-linearity of order
ζ > 1, the dynamics rigorously obeys the Tsallis statistics. We account for theq-indices and the generalized Lyapunov coefficients λq that characterize the universality classes of the pitchfork and tangent bifurcations. We identify the Mori singularities
in the Lyapunov spectrum at the onset of chaos with the appearance of a special value for the entropic indexq. The physical area of the Tsallis statistics is further probed by considering the dynamics near criticality and glass formation
in thermal systems. In both cases a close connection is made with states in unimodal maps with vanishing Lyapunov coefficients. 相似文献
145.
On social percolation and small world network 总被引:1,自引:0,他引:1
E. Ahmed H.A. Abdusalam 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(3):569-571
The social percolation model is generalized to include the propagation of two mutually exclusive competing effects on a one-dimensional
ring and a two-dimensional square lattice. It is shown that the result depends significantly on which effect propagates first
i.e. it is a non-commutative phenomenon. Then the propagation of one effect is studied on a small network. It generalizes the
work of Moore and Newman of a disease spread to the case where the susceptibility of the population is random. Three variants
of the Domany-Kinzel model are given. One of them (delayed) does not have a chaotic region for some value of the delay weight.
Received 24 February 2000 相似文献
146.
In this paper, the economic and economic-statistical design of a χ2 chart for a maintenance application is considered. The machine deterioration process is described by a three-state continuous time Markov chain. The machine state is unobservable, except for the failure state. To avoid costly failures, the system is monitored by a χ2 chart. The observation process stochastically related to the machine condition is assumed to be multivariate, normally distributed. When the chart signals, full inspection is performed to determine the actual machine condition. The system can be preventively replaced at a sampling epoch and must be replaced upon failure; preventive replacement costs less than failure replacement. The objective is to find the optimal control chart parameters that minimize the long-run average maintenance cost per unit time. For the economic-statistical design, an additional constraint guaranteeing the occurrence of the true alarm signal on the chart before failure with given probability is considered. For both designs, the objective function is derived using renewal theory. 相似文献
147.
S. Jain P. Buckley 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(1-2):133-136
Persistence is studied in a financial context by mapping the time
evolution of the values of the shares quoted on the London Financial
Times Stock Exchange 100 index (FTSE 100) onto Ising spins.
By following the time dependence
of the spins, we find evidence for power law decay of the proportion
of shares that remain either above or below their 'starting'
values. As a result, we estimate a persistence exponent for the
underlying financial market to be θf∼0.5. 相似文献
148.
The coherent potential approximation (CPA) within full counting statistics (FCS) formalism is shown to be a suitable method to investigate average electric conductance, shot noise as well as higher order cumulants in disordered systems. We develop a similar FCS-CPA formalism for phonon transport through disordered systems. As a byproduct, we derive relations among coefficients of different phonon current cumulants. We apply the FCS-CPA method to investigate phonon transport properties of graphene systems in the presence of disorders. For binary disorders as well as Anderson disorders, we calculate up to the 8-th phonon transmission moments and demonstrate that the numerical results of the FCS-CPA method agree very well with that of the brute force method. The benchmark shows that the FCS-CPA method achieves 20 times more speedup ratio. Collective features of phonon current cumulants are also revealed. 相似文献
149.
Probabilistic predictions with machine learning are important in many applications. These are commonly done with Bayesian learning algorithms. However, Bayesian learning methods are computationally expensive in comparison with non-Bayesian methods. Furthermore, the data used to train these algorithms are often distributed over a large group of end devices. Federated learning can be applied in this setting in a communication-efficient and privacy-preserving manner but does not include predictive uncertainty. To represent predictive uncertainty in federated learning, our suggestion is to introduce uncertainty in the aggregation step of the algorithm by treating the set of local weights as a posterior distribution for the weights of the global model. We compare our approach to state-of-the-art Bayesian and non-Bayesian probabilistic learning algorithms. By applying proper scoring rules to evaluate the predictive distributions, we show that our approach can achieve similar performance as the benchmark would achieve in a non-distributed setting. 相似文献
150.
WilliamJ. Griffiths Therese Koal Yuqin Wang Matthias Kohl DavidP. Enot Hans‐Peter Deigner 《Angewandte Chemie (International ed. in English)》2010,49(32):5426-5445
Metabolomics is a truly interdisciplinary field of science, which combines analytical chemistry, platform technology, mass spectrometry, and NMR spectroscopy with sophisticated data analysis. Applied to biomarker discovery, it includes aspects of pathobiochemistry, systems biology/medicine, and molecular diagnostics and requires bioinformatics and multivariate statistics. While successfully established in the screening of inborn errors in neonates, metabolomics is now widely used in the characterization and diagnostic research of an ever increasing number of diseases. In this Review we highlight important technical prerequisites as well as recent developments in metabolomics and metabolomics data analysis with special emphasis on their utility in biomarker identification and qualification, as well as targeted metabolomics by employing high‐throughput mass spectrometry. 相似文献