Trends in aircraft design

The improved performance of aircraft during the past decade has resulted in the need for new design and production techniques. Particular examples are integral construction and the use of sandwich panels. Although these processes are costly, especially when applied to titanium and steel construction, their use is likely to be necessary, at least to some extent. on many supersonic aircraft. The supersonic airliner is no exception to this and the paper discusses the design aspects of this type of aircraft which have a bearing on production problems. It is concluded that more research aimed at reducing the cost of sophisticated forms of construction is required

The teaching of aircraft design

Aircraft Design has been taught at the College of Aeronautics since 1946. The course is at postgraduate level and is of two years duration. In the first year the students are given three exercises in component design which aim to teach a logical approach and the fundamentals of the subject. During the second year each student works as a member of a team engaged in the design of a complete aircraft, which is chosen to be of a type currently being investigated by industry. The project aircraft invariably incorporates experimental features and the design work is therefore of the nature of research

Building Firm Foundations Sure Start Mellow Valley Evaluation Report 2005/ 2006

This report forms the Year 3 annual report. Alongside documenting findings from Year 2 evaluation activities, this report also brings together findings from previous evaluation activities and gives wider consideration to the overall progress and outcomes of the programme so far. Section two explains the evaluation approach that has been adopted and details the activities that have been conducted and the methods used. Section 3 highlights the key themes and findings to emerge from the workshops undertaken with the Sure Start teams and provides a summary of the indepth evaluation conducted of the Family Support Team. Section 4 is entitled ‘Pulling it all together’ and considers the work and achievements of Sure Start Mellow Valley with particular regard to the five outcomes of Every Child Matters. A conclusion and brief summary of findings is found in Section 5 followed by a range of further information within the Section 6 Appendices

Isolated output for class-D dc amplifiers

Transformer-coupled output stage is used with pulse-width modulated class-D dc amplifiers. Circuit is comprised of two channels corresponding to negative and positive input signals. Amplitude of secondary-current triangular pulse is function of duration of driving pulse. Therefore, circuit converts pulse-width modulated driving signal to pulse-amplitude modulated signal

Embedded Solitons in Lagrangian and Semi-Lagrangian Systems

We develop the technique of the variational approximation for solitons in two directions. First, one may have a physical model which does not admit the usual Lagrangian representation, as some terms can be discarded for various reasons. For instance, the second-harmonic-generation (SHG) model considered here, which includes the Kerr nonlinearity, lacks the usual Lagrangian representation if one ignores the Kerr nonlinearity of the second harmonic, as compared to that of the fundamental. However, we show that, with a natural modification, one may still apply the variational approximation (VA) to those seemingly flawed systems as efficiently as it applies to their fully Lagrangian counterparts. We call such models, that do not admit the usual Lagrangian representation, \textit{semi-Lagrangian} systems. Second, we show that, upon adding an infinitesimal tail that does not vanish at infinity, to a usual soliton ansatz, one can obtain an analytical criterion which (within the framework of VA) gives a condition for finding \textit{embedded solitons}, i.e., isolated truly localized solutions existing inside the continuous spectrum of the radiation modes. The criterion takes a form of orthogonality of the radiation mode in the infinite tail to the soliton core. To test the criterion, we have applied it to both the semi-Lagrangian truncated version of the SHG model and to the same model in its full form. In the former case, the criterion (combined with VA for the soliton proper) yields an \emph{exact} solution for the embedded soliton. In the latter case, the criterion selects the embedded soliton with a relative error $\approx 1$.Comment: 10 pages, 1 figur

A pattern-recognition theory of search in expert problem solving

Understanding how look-ahead search and pattern recognition interact is one of the important research questions in the study of expert problem-solving. This paper examines the implications of the template theory (Gobet & Simon, 1996a), a recent theory of expert memory, on the theory of problem solving in chess. Templates are "chunks" (Chase & Simon, 1973) that have evolved into more complex data structures and that possess slots allowing values to be encoded rapidly. Templates may facilitate search in three ways: (a) by allowing information to be stored into LTM rapidly; (b) by allowing a search in the template space in addition to a search in the move space; and (c) by compensating loss in the "mind's eye" due to interference and decay. A computer model implementing the main ideas of the theory is presented, and simulations of its search behaviour are discussed. The template theory accounts for the slight skill difference in average depth of search found in chess players, as well as for other empirical data

Simple computer method provides contours for radiological images

Computer is provided with information concerning boundaries in total image. Gradient of each point in digitized image is calculated with aid of threshold technique; then there is invoked set of algorithms designed to reduce number of gradient elements and to retain only major ones for definition of contour

Indexed Regulation

Seminal work by Weitzman (1974) revealed that prices are preferred to quantities when marginal benefits are relatively flat compared to marginal costs. We extend this comparison to indexed policies, where quantities are proportional to an index, such as output. We find that policy preferences hinge on additional parameters describing the first and second moments of the index and the ex post optimal quantity level. When the ratio of these variables’ coefficients of variation divided by their correlation is less than two, indexed quantities are preferred to fixed quantities. A slightly more complex condition determines when indexed quantities are preferred to prices. Applied to the case of climate change, we find that quantities indexed to GDP are preferred to fixed quantities for about half of the 19 largest emitters, including the United States and China, while (consistent with previous work) prices dominate for all countries.price, quantity, regulation, uncertainty, policy, environment, climate change

SAR antenna calibration techniques

Calibration of SAR antennas requires a measurement of gain, elevation and azimuth pattern shape, boresight error, cross-polarization levels, and phase vs. angle and frequency. For spaceborne SAR antennas of SEASAT size operating at C-band or higher, some of these measurements can become extremely difficult using conventional far-field antenna test ranges. Near-field scanning techniques offer an alternative approach and for C-band or X-band SARs, give much improved accuracy and precision as compared to that obtainable with a far-field approach