Probabilistic models of information retrieval based on measuring the divergence from randomness

We introduce and create a framework for deriving probabilistic models of Information Retrieval. The models are nonparametric models of IR obtained in the language model approach. We derive term-weighting models by measuring the divergence of the actual term distribution from that obtained under a random process. Among the random processes we study the binomial distribution and Bose--Einstein statistics. We define two types of term frequency normalization for tuning term weights in the document--query matching process. The first normalization assumes that documents have the same length and measures the information gain with the observed term once it has been accepted as a good descriptor of the observed document. The second normalization is related to the document length and to other statistics. These two normalization methods are applied to the basic models in succession to obtain weighting formulae. Results show that our framework produces different nonparametric models forming baseline alternatives to the standard tf-idf model

On the wake of a Darrieus turbine

The theory and experimental measurements on the aerodynamic decay of a wake from high performance vertical axis wind turbine are discussed. In the initial experimental study, the wake downstream of a model Darrieus rotor, 28 cm diameter and a height of 45.5 cm, was measured in a Boundary Layer Wind Tunnel. The wind turbine was run at the design tip speed ratio of 5.5. It was found that the wake decayed at a slower rate with distance downstream of the turbine, than a wake from a screen with similar troposkein shape and drag force characteristics as the Darrieus rotor. The initial wind tunnel results indicated that the vertical axis wind turbines should be spaced at least forty diameters apart to avoid mutual power depreciation greater than ten per cent

Aircraft control system

An aircraft control system is described which is particularly suited to rotary wing aircraft. Longitudinal acceleration and course rate commands are derived from a manual control stick to control translational velocity of the aircraft along a flight path. In the collective channel the manual controls provide vertical velocity commands. In the yaw channel the manual controls provide sideslip or heading rate commands at high or low airspeeds, respectively. The control system permits pilots to fly along prescribed flight paths in a precise manner with relatively low work load

Making automation pay - cost & throughput trade-offs in the manufacture of large composite components

The automation of complex manufacturing operations can provide significant savings over manual processes, and there remains much scope for increasing automation in the production of large scale structural composites. However the relationships between driving variables are complex, and the achievable throughput rate and corresponding cost for a given design are often not apparent. The deposition rate, number of machines required and unit production rates needed are interrelated and consequently the optimum unit cost is difficult to predict. A detailed study of the costs involved for a series of composite wing cover panels with different manufacturing requirements was undertaken. Panels were sized to account for manufacturing requirements and structural load requirements allowing both manual and automated lay-up procedures to influence design. It was discovered that the introduction of automated tape lay-up can significantly reduce material unit cost, and improve material utilisation, however higher production rates are needed to see this benefit

Are there any good digraph width measures?

Several different measures for digraph width have appeared in the last few years. However, none of them shares all the "nice" properties of treewidth: First, being \emph{algorithmically useful} i.e. admitting polynomial-time algorithms for all \MS1-definable problems on digraphs of bounded width. And, second, having nice \emph{structural properties} i.e. being monotone under taking subdigraphs and some form of arc contractions. As for the former, (undirected) \MS1 seems to be the least common denominator of all reasonably expressive logical languages on digraphs that can speak about the edge/arc relation on the vertex set.The latter property is a necessary condition for a width measure to be characterizable by some version of the cops-and-robber game characterizing the ordinary treewidth. Our main result is that \emph{any reasonable} algorithmically useful and structurally nice digraph measure cannot be substantially different from the treewidth of the underlying undirected graph. Moreover, we introduce \emph{directed topological minors} and argue that they are the weakest useful notion of minors for digraphs

Older and wiser? Men’s and women’s accounts of drinking in early mid-life

Most qualitative research on alcohol focuses on younger rather than older adults. To explore older people’s relationship with alcohol, we conducted eight focus groups with 36 men and women aged 35 to 50 years in Scotland, UK. Initially, respondents suggested that older drinkers consume less alcohol, no longer drink to become drunk and are sociable drinkers more interested in the taste than the effects of alcohol. However, as discussions progressed, respondents collectively recounted recent drunken escapades, challenged accounts of moderate drinking, and suggested there was still peer pressure to drink. Some described how their drinking had increased in mid-life but worked hard discursively to emphasise that it was age and stage appropriate (i.e. they still met their responsibilities as workers and parents). Women presented themselves as staying in control of their drinking while men described going out with the intention of getting drunk (although still claiming to meet their responsibilities). While women experienced peer pressure to drink, they seemed to have more options for socialising without alcohol than did men. Choosing not to drink alcohol is a behaviour that still requires explanation in early mid-life. Harm reduction strategies should pay more attention to drinking in this age group

Numerical analysis of flow non-uniformity in the hot gas manifold of the Space Shuttle main engine

Three-dimensional viscous flow in a conceptual hot gas manifold (HGM) for the Space Shuttle Main Engine High Pressure Fuel Turbopump (SSME HPFTP) was numerically analyzed. A finite difference scheme was used to solve the Navier-Stokes equations. The exact geometry of the SSME HGM was modeled using boundary fitted curvilinear coordinates and the General Interpolants Method (GIM) code. Slight compressibility of the subsonic flow was modeled using a linearized equation of state with artificial compressibility. A time relaxation method was used to obtain a steady state solution. The feasibility and potential usefulness of computational methods in assisting the design of SSME components which involves the flow of fluids within complex geometrical shapes is demonstrated

Evidence for extended IR emission in NGC2798 and NGC6240

Extended emission at 10 and 20 microns can be used to distinguish starbursts from monsters as the underlying energy source driving the luminous infrared emission in the central regions of galaxies. The spatial extent of the mid infrared emission in the interacting galaxy NCG 2798 and the merger NGC 6240 were investigated. The 10 and 20 micron profiles of the IR source in NGC 2798 are significantly wider than beam profiles measured on a standard star, supporting a starburst interpretation of its IR luminosity. For NGC 6240 there is marginal evidence for an extended 10 micron source, suggesting that a significant fraction of its IR luminosity could be produced by a burst of star formation

Constant-degree graph expansions that preserve the treewidth

Many hard algorithmic problems dealing with graphs, circuits, formulas and constraints admit polynomial-time upper bounds if the underlying graph has small treewidth. The same problems often encourage reducing the maximal degree of vertices to simplify theoretical arguments or address practical concerns. Such degree reduction can be performed through a sequence of splittings of vertices, resulting in an _expansion_ of the original graph. We observe that the treewidth of a graph may increase dramatically if the splittings are not performed carefully. In this context we address the following natural question: is it possible to reduce the maximum degree to a constant without substantially increasing the treewidth? Our work answers the above question affirmatively. We prove that any simple undirected graph G=(V, E) admits an expansion G'=(V', E') with the maximum degree <= 3 and treewidth(G') <= treewidth(G)+1. Furthermore, such an expansion will have no more than 2|E|+|V| vertices and 3|E| edges; it can be computed efficiently from a tree-decomposition of G. We also construct a family of examples for which the increase by 1 in treewidth cannot be avoided.Comment: 12 pages, 6 figures, the main result used by quant-ph/051107