MIQR Active Learning on a Continuous Function and a Discontinuous Function

Active learning balances the cost of data acquisition against its usefulness for training. We select only those data points which are the most informative about the system being modelled. The MIQR (Maximum Inter-Quartile Range) criterion is defined by computing the inter-quartile range of the outputs of an ensemble of networks, and finding the input parameter values for which this is maximal. This method ensures data selection is not unduly influenced by ‘outliers’, but is principally dependent upon the ‘mainstream’ state of the ensemble. MIQR is more effective and efficient than contending methods¹ . The algorithm automatically regulates the training threshold and the network architecture as necessary. We compare active learning methods by applying them to a continuous function and a discontinuous function. Training is more difficult for a discontinuous function than a continuous function, and the volume of data for active learning is substantially less than for passive learning.     

The stability of long action chains in XCS

 XCS [1, 2] represents a new form of learning classifier system [3] that uses accuracy as a means of guiding fitness for selection within a Genetic Algorithm. The combination of accuracy-based selection and a dynamic niche-based deletion mechanism achieve a long sought-after goal–the reliable production, maintenance, and proliferation of the sub-population of optimally general accurate classifiers that map the problem domain [4]. Wilson [2] and Lanzi [5, 6] have demonstrated the applicability of XCS to the identification of the optimal action-chain leading to the optimum trade-off between reward distance and magnitude. However, Lanzi [6] also demonstrated that XCS has difficulty in finding an optimal solution to the long action-chain environment Woods-14 [7]. Whilst these findings have shed some light on the ability of XCS to form long action-chains, they have not provided a systematic and, above all, controlled investigation of the limits of XCS learning within multiple-step environments. In this investigation a set of confounding variables in such problems are identified. These are controlled using carefully constructed FSW environments [8, 9] of increasing length. Whilst investigations demonstrate that XCS is able to establish the optimal sub-population [O] [4] when generalisation is not used, it is shown that the introduction of generalisation introduces low bounds on the length of action-chains that can be identified and chosen between to find the optimal pathway. Where these bounds are reached a form of over-generalisation caused by the formation of dominant classifiers can occur. This form is further investigated and the Domination Hypothesis introduced to explain its formation and preservation.     

Evolving Fault-Tolerant Neural Networks

In this paper, genetic algorithm is used to help improve the tolerance of feedforward neural networks against an open fault. The proposed method does not explicitly add any redundancy to the network, nor does it modify the training algorithm. Experiments show that it may profit the fault tolerance as well as the generalisation ability of neural networks.     

Normalized Gaussian Radial Basis Function networks

The performances of normalised RBF (NRBF) nets and standard RBF nets are compared in simple classification and mapping problems. In normalized RBF networks, the traditional roles of weights and activities in the hidden layer are switched. Hidden nodes perform a function similar to a Voronoi tessellation of the input space, and the output weights become the network's output over the partition defined by the hidden nodes. Consequently, NRBF nets lose the localized characteristics of standard RBF nets and exhibit excellent generalization properties, to the extent that hidden nodes need to be recruited only for training data at the boundaries of class domains. Reflecting this, a new learning rule is proposed that greatly reduces the number of hidden nodes needed in classification tasks. As for mapping applications, it is shown that NRBF nets may outperform standard RBFs nets and exhibit more uniform errors. In both applications, the width of basis functions is uncritical, which makes NRBF nets easy to use.     

Regularisation of Linear Classifiers by Adding Redundant Features

The Pseudo Fisher Linear Discriminant (PFLD) based on a pseudo-inverse technique shows a peaking behaviour of the generalisation error for training sample sizes that are about the feature size: with an increase in the training sample size, the generalisation error first decreases, reaching a minimum, then increases, reaching a maximum at the point where the training sample size is equal to the data dimensionality, and afterwards begins again to decrease. A number of ways exist to solve this problem. In this paper, it is shown that noise injection by adding redundant features to the data is similar to other regularisation techniques, and helps to improve the generalisation error of this classifier for critical training sample sizes. Received: 10 November 1998?Received in revised form: 7 January 1999?Accepted: 7 January 1999     

面向个体和敏感属性值的匿名数据发布

针对目前数据发布方法不能有效处理不同个体隐私保护需求的问题,依据个体隐私自治的原则,从面向个体和敏感属性值角度,提出一个敏感数据发布的个性化匿名发布模型和基于泛化技术的启发式算法.通过Adult数据实验,验证了算法的可行性.与Basic Incognito和Mondrian相比,信息损失少,算法性能良好.     

Strategies for improving neural net generalisation

We address the problem of training multilayer perceptrons to instantiate a target function. In particular, we explore the accuracy of the trained network on a test set of previously unseen patterns — the generalisation ability of the trained network. We systematically evaluate alternative strategies designed to improve the generalisation performance. The basic idea is to generate a diverse set of networks, each of which is designed to be an implementation of the target function. We then have a set of trained, alternative versions — a version set. The goal is to achieve useful diversity within this set, and thus generate potential for improved generalisation performance of the set as a wholewhen compared to the performance of any individual version. We define this notion of useful diversity, we define a metric for it, we explore a number of ways of generating it, and we present the results of an empirical study of a number of strategies for exploiting it to achieve maximum generalisation performance. The strategies encompass statistical measures as well as a selectornet approach which proves to be particularly promising. The selector net is a form of metanet that operates in conjunction with a version set.     

A review of state-of-the-art in Face Presentation Attack Detection: From early development to advanced deep learning and multi-modal fusion methods

Face Recognition is considered one of the most common biometric solutions these days and is widely used across a range of devices for various security purposes. The performance of FR systems has improved by orders of magnitude over the past decade. This is mainly due to the latest developments in computer vision and deep convolutional neural networks, and the availability of large training datasets. At the same time, these systems have been subject to various types of attacks. Presentation attacks are common, simple, and easy to implement. These simply involve presenting a video, photo, or mask to the camera or digital sensor and have proven capable of fooling FR systems and providing access to unauthorised users. Presentation attack detection is increasingly attracting more attention in the research community. A wide range of methods has already been developed to address this challenge. Deep learning-based methods in particular have shown very promising results. However, existing literature suggests that even with state-of-the-art methods, performance drops significantly in cross-dataset evaluation. We present a thorough, comprehensive, and technical review of existing literature on this timely and challenging problem. We first introduce and discuss the presentation attack problem and cover related and recent work in this area. In-depth technical details of existing presentation attack detection methods are then presented and critically discussed and evaluated, followed by a comprehensive discussion and evaluation of existing public datasets and commonly used evaluation metrics. Our review shows clearly that despite the recent and significant advances in this area of research, detecting unseen attacks is still considered a key problem. Machine learning methods tend to perform well, but only when test data comes from the same distribution as the training data (i.e. same dataset). New research directions are discussed in detail, including ways to improve the generalisation of machine learning methods, and move towards creating more stable presentation attack detection techniques that generalise across a wide range of unseen samples.