The RAND Database of Worldwide Terrorism Incidents (RDWTI) seeks to index information about all terrorist incidents that occur and are mentioned in worldwide news media, providing a useful resource for policy researchers and decision makers. We examined automated classification methods that could be used to identify news articles about terrorist incidents, thus enabling analysts to read a smaller number of news articles and maintain the database with less effort and cost. The support vector machine (SVM) and Lasso methods were only modestly successful, but a classifier based on the gradient boosting method (GBM) appeared to be very successful, correctly ranking 80% of the relevant articles at the “top of the pile” for examination by a human analyst.

The need for large scale environmental monitoring to manage environmental change is well established. Ecologists have long used acoustics as a means of monitoring the environment in their field work, and so the value of an acoustic environmental observatory is evident. However, the volume of data generated by such an observatory would quickly overwhelm even the most fervent scientist using traditional methods. In this paper we present our steps towards realising a complete acoustic environmental observatory - i.e. a cohesive set of hardware sensors, management utilities, and analytical tools required for large scale environmental monitoring. Concrete examples of these elements, which are in active use by ecological scientists, are also presented.

This paper considers the stability of an object supported by several frictionless contacts in a potential field such as gravity. The bodies supporting the object induce a partition of the object's configuration space into strata corresponding to different contact arrangements. Stance stability becomes a geometric problem of determining whether the object's configuration is a local minimum of its potential energy function on the stratified configuration space. We use stratified Morse theory to develop a generic stance stability test that has the following characteristics. For a small number of contacts - less than three in 2D and less than six in 3D - stance stability depends both on surface normals and surface curvature at the contacts. Moreover, lower curvature at the contacts leads to better stability. For a larger number of contacts, stance stability depends only on surface normals at the contacts. The stance stability test is applied to quasi-static locomotion planning in two dimensions. The region of stable center-of-mass positions associated with ak-contact stance is characterized. Then, a quasi-static locomotion scheme for a three-legged robot over a piecewise linear terrain is described. Finally, friction is shown to provide robustness and enhanced stability for the frictionless locomotion plan. A full maneuver simulation illustrates the locomotion scheme.

In this demonstration, we will show how smartphones can be used as a platform for monitoring environmental change, particularly with respect to birdlife. We have researched and implemented a platform using Microsoft smartphones for remotely monitoring birds. The platform comprises smart-phones running a custom application for recording bird song. The application manages sensors in an autonomic fashion to ensure that they operate reliably for long periods of time in a power efficient manner.

Presents a trajectory planning algorithm for mobile robots which may be subject to kinodynamic constraints. Using computational methods from noncommutative harmonic analysis, the algorithm efficiently constructs an approximation to the robot's reachable-state density function. Based on a multiscale approach, the density function is then used to plan a path. One variation of the algorithm exhibits time complexity that is logarithmic in the number of steps. Simulations illustrate the method.

Considers the design of motion control algorithms for robot fish. We present modeling, control design, and experimental trajectory tracking results for an experimental planar robotic fish system that is propelled using carangiform-like locomotion. Our model for the fish's propulsion is based on quasi-steady fluid flow. Using this model, we propose gaits for forward and turning trajectories and analyze system response under such control strategies. Our models and predictions are verified by experiment.

This paper studies a form of robotic fish movement that is analogous to the carangiform style of swimming seen in nature. We propose a simple quasi-steady fluid flow model for predicting the thrust generated by the flapping tail. We then describe an experimental system, consisting of a three-link robot, that has been constructed in order to study carangiform-like swimming. Experimental results obtained with this system suggest that the simplified propulsion model is reasonably accurate. The input parameters that realize optimum thrust are experimentally determined. Finally, we consider some issues in maneuvering.

Motivated by considerations of shape changing propulsion of underwater robotic vehicles, this paper analyses the mechanics of deformable bodies operating in an ideal fluid. The application of methods from geometric mechanics results in a compact and insightful formulation of the problem. We develop an explicit formula for the fluid mechanical connection, in terms of the fluid potential function, for this class of systems. The connection can be used to analyze many issues in motion planning and control. The theory is illustrated by application to an amoeba-like device.

This paper considers the gravitational stability of a frictionless 3-dimensional object in contact with immovable objects. Arbitrarily curved objects are considered. This paper also shows how to determine the region over which the object's center of mass can move while the object maintains a given set of contacts and remains in stable equilibrium. We present symbolic solutions for up to three contacts and discuss numerical solutions for larger numbers of contacts. This analysis has application in planning the motions of quasi-statically walking robots over uneven terrain and the manipulation of heavy objects.

In both robot grasping and robot locomotion, we wish to hold objects stably in the presence of gravity. We present a derivation of second-order stability conditions for a supported heavy object, employing the tool of Stratified Morse theory. We then apply these general results to the case of objects in the plane.

A hybrid scheme for analogue-to-digital conversion (ADC) is described in which electro-optic techniques are employed to reduce the timing jitter which is a primary factor in restricting the resolution obtainable in all-electronic ADCs. The proposed system uses commercially available digitisers and optical components together with a specially designed, optically triggered sample-and-hold circuit realised in GaAs MESFET technology. A novel technique is described by means of which up to 20 parallel, interleaved ADC paths can be driven from a single mode-locked laser source. Estimated performance limits are provided.

Optically controlled sample and hold (OS/H) circuits can be used in many high-speed sampled data applications where timing jitter limits the performance. This paper presents a fully integrated OS/H which is fabricated in a commercial GaAs MESFET technology. Measured results are presented which demonstrate the operation of the circuit at sample rates approaching 500 Ms/s at 7.6-bits resolution.>

A fully tunable OTA-C second-order bandpass filter is presented which is intended for use in high precision, IF bandpass filtering applications. Detailed measured results show independent tuning of centre frequency in the range 12-50 MHz, and Q in the range 4-60. In addition, the transfer function accuracy in terms of both amplitude and group delay is of the order of 1%.>