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81.
A generalized rule induction mechanism, immune algorithm, for knowledge bases is building an inheritance hierarchy of classes based on the content of their knowledge objects. This hierarchy facilitates group-related processing tasks such as answering set queries, discriminating between objects, finding similarities among objects, etc. Building this hierarchy is a difficult task for knowledge engineers. Conceptual induction may be used to automate or assist engineers in the creation of such a classification structure. This paper introduces a new conceptual rule induction method, which addresses the problem of clustering large amounts of structured objects. The conditions under which the method is applicable are discussed. 相似文献
82.
基于MMSE先验信噪比估计的语音增强 总被引:3,自引:0,他引:3
针对传统最小均方误差(MMSE)沿爵增强方法无法准确处理快速语音的变化问题,提出了一种堆于MMSE估计先验信噪比的语音增强方法,利用该笔法估计每帧语音俯号的每一个频率分量上的平滑系数αn,k。进行平均反馈估计,从而得到更加接近于真实情况的先验信噪比,进而使用MMSE方法进行语音的增强,提高了对于快速变化语肯的增强效果,实验结果农明,本方法比传统MMSE语青增强方法在增强性能上提高了近2dB。 相似文献
83.
陈晓云 《新疆大学学报(理工版)》2003,20(1):71-73
通过对电动机故障分析,主要研究了产生式电动机故障诊断专家系统的总体结构,知识获取,知识库建立及推理机制。 相似文献
84.
On the Asymptotic Stability of the Intrinsic and Fractional Bayes Factors for Testing Some Diffusion Models 总被引:1,自引:0,他引:1
S. Sivaganesan Rama T. Lingham 《Annals of the Institute of Statistical Mathematics》2002,54(3):500-516
Random processes, from which a single sample path data are available on a fine time scale, abound in many areas including finance and genetics. An effective way to model such data is to consider a suitable continuous-time-scale analog, X
t say, for the underlying process. We consider three diffusion models for the process X
t and address model selection under improper priors. Specifically, fractional and intrinsic Bayes factors (FBF and IBF) for model selection are considered. Here, we focus on the asymptotic stability of the IBF's and FBF's for comparing these models. Specifically, we propose to employ certain novel transformations of the data in order to ensure the asymptotic stability of the IBF's. While we use different transformations for pairwise comparisons of the models, we also show that a single common transformation can be used when simultaneously comparing all three models. We then demonstrate that, when FBF's are used to compare these models, we may have to employ different, model-specific training fractions in order to achieve asymptotic stability of the FBF's. 相似文献
85.
In this paper it will be shown that in neural systems with a recurrent architecture, the traditional concepts of knowledge representation cannot be applied any more; no stable representational relationship of reference can be found. That is why a redefinition of the relationship between the states of the environment and the internal representational states is proposed. Studying the dynamics of recurrent neural systems reveals that the goal of representation is no longer to map the environment as accurately as possible to the representation system (e.g., to symbols). It is suggested that it is more appropriate to look at neural systems as physical dynamical devices embodying the (transformation) knowledge for sensorimotor integration and for generating adequate behavior enabling the organism's survival. As an implication the representation is determined not only by the environment, but highly depends on the organization, structure, and constraints of the representation system as well as the sensory/motor systems which are embedded in a particular body structure. This leads to a system relative concept of representation. By transforming recurrent neural networks into the domain of finite automata, the dynamics as well as the epistemological implications become more clear. In recurrent neural systems a type of balance between the autonomy of the representation and the environmental dependence/influence emerges. This not only affects the traditional concept of knowledge representation, but has also implications for the understanding of semantics, language, communication, and even science. 相似文献
86.
本文研究了各总体服从多元正态分布 ,其未知参数的先验分布均为扩散先验分布时 ,如何利用待判样品的预报密度函数、构造后验概率比并据此对样品进行分类与判别 ;此方法并不需要假设各总体分布的协方差相同 ,而且在预试样本容量较小时仍然可行。 相似文献
87.
This article builds on two previous ones in which we presented the processes of construction and consolidation of one student's knowledge structures about comparisons of infinite sets, according to a recently proposed theory of abstraction. In the present article, we show that under slight variations of context, knowledge structures that have apparently been well-consolidated may become inactive and subordinate to more primitive ones. 相似文献
88.
Generalized linear mixed models (GLMMs) have been applied widely in the analysis of longitudinal data. This model confers
two important advantages, namely, the flexibility to include random effects and the ability to make inference about complex
covariances. In practice, however, the inference of variance components can be a difficult task due to the complexity of the
model itself and the dimensionality of the covariance matrix of random effects. Here we first discuss for GLMMs the relation
between Bayesian posterior estimates and penalized quasi-likelihood (PQL) estimates, based on the generalization of Harville’s
result for general linear models. Next, we perform fully Bayesian analyses for the random covariance matrix using three different
reference priors, two with Jeffreys’ priors derived from approximate likelihoods and one with the approximate uniform shrinkage
prior. Computations are carried out via the combination of asymptotic approximations and Markov chain Monte Carlo methods.
Under the criterion of the squared Euclidean norm, we compare the performances of Bayesian estimates of variance components
with that of PQL estimates when the responses are non-normal, and with that of the restricted maximum likelihood (REML) estimates
when data are assumed normal. Three applications and simulations of binary, normal, and count responses with multiple random
effects and of small sample sizes are illustrated. The analyses examine the differences in estimation performance when the
covariance structure is complex, and demonstrate the equivalence between PQL and the posterior modes when the former can be
derived. The results also show that the Bayesian approach, particularly under the approximate Jeffreys’ priors, outperforms
other procedures. 相似文献
89.
Lars Tyge Nielsen 《Mathematical Social Sciences》1984,8(1):1-14
The aim of this paper is to examine the adequacy of the so-called expected utility theory. It is concluded that the theory is inadequate when the decision-maker is decreasingly risk averse and his initial wealth is risky. 相似文献
90.
本文研究了随机线发性规划问题的几类基本模型结构.分析了随机线性规划问题对先验分布的依赖关系,给出了解除这种依赖关系的充要条件.最后用“原点距”方法与“信息熵”方法分别对先验分布作出了估计. 相似文献