The field of bioacoustics is concerned with monitoring wild animals based on their vocalisations. Passive acoustic recorders are now commonly used to collect data of the soundscapes of our wild places. While the data they collect is extremely useful, the majority of the recorders use a single omnidirectional microphone, and thus cannot independently perform localisation of a calling animal. Localisation can be useful to differentiate between multiple calling animals, to improve statistical estimates of abundance, and to locate calling posts, which may be close to nests. In this paper, we consider the design of a low-cost, practical, passive directional acoustic recorder that will facilitate animal localisation, and present and evaluate a prototype system for this purpose.

BACKGROUND: In object oriented (OO) software systems, class size has been acknowledged as having an indirect effect on the relationship between certain artifact characteristics, captured via metrics, and fault-proneness, and therefore it is recommended to control for size when designing fault prediction models.

The statistical analysis of data lying on a differentiable, locally Euclidean, manifold introduces a variety of challenges because the analogous measures to standard Euclidean statistics are local, that is only defined within a neighbourhood of each datapoint. This is because the curvature of the space means that the connection of Riemannian geometry is path dependent. In this paper we transfer the problem to Weitzenbock space, which has torsion, but not curvature, meaning that parallel transport is path independent, and rather than considering geodesics, it is natural to consider autoparallels, which are `straight' in the sense that they follow the local basis vectors. We demonstrate how to generate these autoparallels in a data-driven fashion, and show that the resulting representation of the data is a useful space in which to perform further analysis.

In machine learning, one often encounters data sets where a general pattern is violated by a relatively small number of exceptions (for example, a rule that says that all birds can fly is violated by examples such as penguins). This complicates the concept learning process and may lead to the rejection of some simple and expressive rules that cover many cases. In this paper we present an approach to this problem in description logic learning by computing partial descriptions (which are not necessarily entirely complete) of both positive and negative examples and combining them. Our Symmetric Parallel Class Expression Learning approach enables the generation of general rules with exception patterns included. We demonstrate that this algorithm provides significantly better results (in terms of metrics such as accuracy, search space covered, and learning time) than standard approaches on some typical data sets. Further, the approach has the added benefit that it can be parallelised relatively simply, leading to much faster exploration of the search tree on modern computers.

Registration of images parameterized by landmarks provides a useful method of describing shape variations by computing the minimum-energy time-dependent deformation field that flows from one landmark set to the other. This is sometimes known as the geodesic interpolating spline and can be solved via a Hamiltonian boundary-value problem to give a diffeomorphic registration between images. However, small changes in the positions of the landmarks can produce large changes in the resulting diffeomorphism. We formulate a Langevin equation for looking at small random perturbations of this registration. The Langevin equation and three computationally convenient approximations are introduced and used as prior distributions. A Bayesian framework is then used to compute a posterior distribution for the registration, and also to formulate an average of multiple sets of landmarks.

ABSTRACT Variants of malware and exploits are emerging globally at an ever‐increasing rate. There is a need to automate their detection by observing their footprints over network streams, but signature‐based intrusion detection systems alone cannot cope with the dynamic nature of modern security threats. In this paper, we approach intrusion detection as a classification problem and describe a system using exemplar‐based learning to correctly classify known classes of malware and to detect, learn and classify unknown malicious streams into classes. Copyright © 2013 John Wiley & Sons, Ltd.

Emotions are dynamic. They vary continuously with regard to intensity, duration, persistence with time, and other attributes. In addition, their appearance on the face of subjects varies, and the transition in facial expressions is based on both the change in emotion and physiological constraints. In this paper, we examine the trajectories between emotions in activation-evaluation space and show that emotion trajectories are smooth and follow `common' paths between different emotions.

The recognition of basic human emotions based on facial points has been studied extensively for many years. Since complex emotions are comprised of a number of the basic emotions, in order to identify them some way to interpolate between known basic emotions must be identified. In this paper, we introduce a finite mixture model to recognise complex emotions and represent them onto the activation-evaluation space, a popular model in psychology for emotion representation. Since the activation-evaluation space is circular, the popular probability distribution models for emotion recognition are inappropriate to characterise complex emotions. The model that we propose is based on a mixture of von Mises distributions, which is an approximation to the normal distribution when wrapped onto a circle and the most common model for describing directional data. This paper describes the process of estimating the parameters of the mixture model and tests the fit of an estimated model to a set of ground truth values of emotion direction and intensity.

The predictive accuracy of a learning algorithm can be split into specificity and sensitivity, amongst other decompositions. Sensitivity, also known as completeness, is the ratio of true positives to the total number of positive examples, while specificity is the ratio of true negative to the total negative examples. In top-down learning methods of inductive logic programming, there is generally a bias towards sensitivity, since the learning starts from the most general rule (everything is positive) and specialises by excluding some of the negative examples. While this is often useful, it is not always the best choice: for example, in novelty detection, where the negative examples are rare and often varied, they may well be ignored by the learning. In this paper we introduce a method that attempts to remove the bias towards sensitivity by fortifying the model by computing and then including in the model some descriptions of the negative data even if they are considered redundant by the normal learning algorithm. We demonstrate the method on a set of standard datasets for description logic learning and show that the predictive accuracy increases.

Behaviour recognition is the process of inferring the behaviour of an individual from a series of observations acquired from sensors such as in a smart home. The majority of existing behaviour recognition systems are based on supervised learning algorithms, which means that training them requires a preprocessed, annotated dataset. Unfortunately, annotating a dataset is a rather tedious process and one that is prone to error. In this paper we suggest a way to identify structure in the data based on text compression and the edit distance between words, without any prior labelling. We demonstrate that by using this method we can automatically identify patterns and segment the data into patterns that correspond to human behaviours. To evaluate the effectiveness of our proposed method, we use a dataset from a smart home and compare the labels produced by our approach with the labels assigned by a human to the activities in the dataset. We find that the results are promising and show significant improvement in the recognition accuracy over Self-Organising Maps (SOMs).

We present a number of convergence properties of population-based Evolutionary Algorithms (EAs) on a set of test functions. Focus is on EA using k-Bit-Swap (kBS) operator. We compare our findings to past research.

Many unsupervised learning methods for recognising patterns in data streams are based on fixed length data sequences, which makes them unsuitable for applications where the data sequences are of variable length such as in speech recognition, behaviour recognition and text classification. In order to use these methods on variable length data sequences, a pre-processing step is required to manually segment the data and select the appropriate features, which is often not practical in real-world applications. In this paper we suggest an unsupervised learning method that handles variable length data sequences by identifying structure in the data stream using text compression and the edit distance between 'words'. We demonstrate that using this method we can automatically cluster unlabelled data in a data stream and perform segmentation. We evaluate the effectiveness of our proposed method using both fixed length and variable length benchmark datasets, comparing it to the Self-Organising Map in the first case. The results show a promising improvement over baseline recognition systems.

Genetic algorithms (GA) mostly commonly use three main operators: selection, crossover and mutation, although many others have been proposed in the literature. This article introduces a new operator, k-bit-swap, which swaps bits between two strings without preserving the location of those bits, changing their order of bits in the string. It can be considered as a form of crossover. We investigate the effects of this operator and demonstrate that its use improves the speed and performance on several well-known problems.

The principled non-rigid registration of groups of images requires a fully groupwise objective function. We consider the problem as one of finding the optimal dense correspondence between the images in the set, where optimality is defined using the Minimum Description Length (MDL) principle, that the transmission of a model of the data, together with the parameters of that model, should be as short as possible. We demonstrate that this approach provides a suitable objective function by applying it to the task of non-rigid registration of a set of 2D T1-weighted MR images of the human brain. Furthermore, we show that even in the case when substantial portions of the images are missing, the algorithm not only converges to the correct solution, but also allows meaningful integration of image data across the training set, allowing the original image to be reconstructed. 1

Groupwise nonrigid registrations of medical images define dense correspondences across a set of images, defined by a continuous deformation field that relates each target image in the group to some reference image. These registrations can be automatic, or based on the interpolation of a set of user-defined landmarks, but in both cases, quantifying the normal and abnormal structural variation across the group of imaged structures implies analysis of the set of deformation fields. We contend that the choice of representation of the deformation fields is an integral part of this analysis. This paper presents methods for constructing a general class of multi-dimensional diffeomorphic representations of deformations. We demonstrate, for the particular case of the polyharmonic clamped-plate splines, that these representations are suitable for the description of deformations of medical images in both two and three dimensions, using a set of two-dimensional annotated MRI brain slices and a set of three-dimensional segmented hippocampi with optimized correspondences. The class of diffeomorphic representations also defines a non-Euclidean metric on the space of patterns, and, for the case of compactly supported deformations, on the corresponding diffeomorphism group. In an experimental study, we show that this non-Euclidean metric is superior to the usual ad hoc Euclidean metrics in that it enables more accurate classification of legal and illegal variations.

This paper considers the problem of measuring the differences between deformations. It is intended to be applied in the context of applications such as the analysis of sets of non-rigidly registered medical images, where diffeomorphic warps between pairs of images establish a dense pixel-to-pixel correspondence. We introduce a new spline with explicit boundary conditions, and show how this can be used to generate general flows of bounded diffeomorphisms. Techniques are developed to describe an arbitrary continuous diffeomorphism and to invert and interpolate between such diffeomorphisms. We show how these constructions and the geodesic distance can be used in the analysis of training sets of general diffeomorphic warps.

For mobile robots, as well as other learning systems, the ability to highlight unexpected features of their environment - novelty detection - is very useful. One particularly important application for a robot equipped with novelty detection is inspection, highlighting potential problems in an environment. In this paper two novelty filters, both of which are capable of on-line and off-line novelty detection, are compared for two robot inspection tasks, one using sonar and the other camera images. The benefits and problems of using each of the filters are discussed and demonstrated.

Mobile robots require the ability to build their own maps to operate in unknown environments. A fundamental problem is that odometry-based dead reckoning cannot be used to assign accurate global position information to a map because of drift errors caused by wheel slippage. The paper introduces a fast, online method of learning globally consistent maps, using only local metric information. The approach differs from previous work in that it is computationally cheap, easy to implement and is guaranteed to find a globally optimal solution. Experiments are presented in which large, complex environments were successfully mapped by a real robot, and quantitative performance measures are used to assess the quality of the maps obtained.