Aircraft flight test trajectory control

Two design techniques for linear flight test trajectory controllers (FTTCs) are described: Eigenstructure assignment and the minimum error excitation technique. The two techniques are used to design FTTCs for an F-15 aircraft model for eight different maneuvers at thirty different flight conditions. An evaluation of the FTTCs is presented

A VLBA Search for a Stimulated Recombination Line from the Accretion Region in NGC1275

The radio source 3C84, in NGC1275, has a two sided structure on parsec scales. The northern feature, presumed to be associated with a jet moving away from the Earth, shows strong evidence for free-free absorption. The ionized gas responsible for that absorption would be a source of detectable stimulated recombination line emission for a wide range of physical conditions. The VLBA has been used to search for the H65$\alpha$ hydrogen recombination line. The line is only expected to be seen against the northern feature which contains a small fraction of the total radio flux density. This spatial discrimination significantly aids the search for a weak line. No line was seen, with upper limits of roughly 15% of the continuum over a velocity range of 1486 km/s with resolutions up to 6.6 km/s. In the absence of a strong radiation field, this would imply that the free-free absorbing gas has a wide velocity width, is moving rapidly relative to the systemic velocity, or is concentrated in a thin, high density structure. All of these possibilities are reasonably likely close to an AGN. However, in the intense radiation environment of the AGN, even considering only the radiation we actually observe passing through the free-free absorbing gas, the non-detection is probably assured by a combination of saturation and radiation damping.Comment: 14 pages with 4 postscript figures. Accepted for publication in the April 2003 Astronomical Journa

Modelling the impact of referral guideline changes for mild dyskaryosis on colposcopy services in England

Objectives: This model examines the effects of changing referral strategies within the established structure of NHS cervical screening driven colposcopy practice. It considers the effects of the new strategy on colposcopy workload, patient waiting times, and associated costs and health benefits. Methods: By postal survey, the current operational strategies of colposcopy services were established by questionnaire with respect to referral practices and management protocols. After first-cut piloting, and utilising published and original research, a Markovian model was constructed, and the impact of the new strategy was determined on colposcopy workload and patient waiting times for three hypothetical clinic types. Expected costs and benefits of the new policy were assessed through the adaptation of a previous ScHARR cervical screening model. Results: Clinic workload is expected to increase by between 21% and 35% within three years of the policy change, depending on clinic efficiency in other areas; the majority of this impact would be seen within the first year. It is predicted that particularly inefficient clinics would struggle to meet the existing waiting time requirements for women referred with low-grade disease, owing to the increased level of workload seen throughout the patient pathway as a result of the implementation of the new policy. The impact of the new policy can, however, be mitigated through improving the efficiency of existing clinics, by altering policies relating to surveillance of low grade disease, post-treatment follow-up, treatment policy (whether or not treatment is performed at the initial colposcopy visit), and through adherence to national guidelines. A cost-effectiveness analysis using the ScHARR liquid-based cytology model suggests that the policy change is likely to be have a cost per quality-adjusted lifeyear gained of between £1,400 and £5,500 per quality-adjusted life-year gained (excluding the costs of follow-up), which would be deemed acceptable to organisations such as the National Institute for Health and Clinical Excellence

Nonlinear maneuver autopilot for the F-15 aircraft

A methodology is described for the development of flight test trajectory control laws based on singular perturbation methodology and nonlinear dynamic modeling. The control design methodology is applied to a detailed nonlinear six degree-of-freedom simulation of the F-15 and results for a level accelerations, pushover/pullup maneuver, zoom and pushover maneuver, excess thrust windup turn, constant thrust windup turn, and a constant dynamic pressure/constant load factor trajectory are presented

The use of the Continuously Regenerating Trap (CRT^TM) and SCRT^TM Systems to meet future emissions legislation

The progressive tightening of particulate matter (PM) legislation presents challenges to the engine development and aftertreatment communities. The Continuously Regenerating Trap (CRTTM) has been developed to enable diesel engines to meet the proposed future legislation. This passive filter system combines an oxidation catalyst with a Diesel Particulate Filter (DPF); the filter traps the PM and the oxidation catalyst generates NO2 which combusts the trapped PM at substantially lower temperatures than is possible using oxygen. This paper outlines the operating principle of the CRTTM, and describes the performance of the system. It has been shown that the very high PM conversions obtained with the CRTTM can enable even Euro 1 engines to meet the PM limits proposed for introduction in Europe in 2005. In addition, the system removes PM across the whole particle size range, including ultrafine particulates. These results will be discussed, as will in-field durability studies which have shown that the system is still capable of converting 90% of PM after very high mileage operation (up to 600,000 km). In addition to requiring very high PM conversion, the proposed future legislation requires substantial reductions in NOx emissions form heavy duty diesel vehicles. To meet these challenges the SCRTTM has been developed. This combines the CRTTM with SCR (Selective Catalytic Reduction) technology, and enables very high simultaneous conversions of CO, HC, PM and NOx to be achieved. The SCRTTM system is described, and its operating characteristics are discussed. It has been shown that the SCRTTM can potentially meet the legislative limits proposed for introduction in Europe in 2008

Diet, bowel motility, faeces composition and colonic cancer

The commonness of colonic cancer in privileged populations compared with its rarity in those pursuing a primitive manner of life suggests that environmental factors are primarily responsible. In this study, differences in diet and their ramificarions are discussed in relation to populations prone and less prone to the disease. Some possible hypotheses of causation are considered. It is concluded that in the present contexts of western populations, in so far as diet directly or indirectly is involved, there is little or no likelihood of lowering the present high preva!ence of cancer of the colon

A Direct Distance to the LMC Cepheid HV 12198 from the Infrared Surface Brightness Technique

We report on a first application of the infrared surface brightness technique on a Cepheid in the Large Magellanic Cloud, the variable HV 12198 in the young globular cluster NGC 1866. From this one star, we determine a distance modulus of 18.42 +- 0.10 (random and systematic uncertainty) to the cluster. When the results on further member Cepheids in NGC 1866 become available, we expect to derive the distance to the LMC with a +- 3-4 percent accuracy, including systematic errors, from this technique.Comment: 4 pages, 4 figures, accepted in ApJ Letter

Higher Resolution VLBI Imaging with Fast Frequency Switching

Millimetre-VLBI is an important tool in AGN astrophysics, but it is limited by short atmospheric coherence times and poor receiver and antenna performance. We demonstrate a new kind of phase referencing for the VLBA, enabling us to increase the sensitivity in mm-VLBI by an order of magnitude. If a source is observed in short cycles between the target frequency, nu_t, and a reference frequency, nu_ref, the nu_t data can be calibrated using scaled-up phase solutions from self-calibration at nu_ref. We have demonstrated the phase transfer on 3C 279, where we were able to make an 86 GHz image with 90 % coherence compared to self-calibration at nu_t. We have detected M81, our science target in this project, at 86 GHz using the same technique. We describe scheduling strategy and data reduction. The main impacts of fast frequency switching are the ability to image some of the nearest, but relatively weak AGN cores with unprecedented high angular resolution and to phase-reference the nu_t data to the nu_ref core position, enabling the detection of possible core shifts in jets due to optical depth effects. This ability will yield important constraints on jet properties and might be able to discriminate between the two competing emission models of Blandford-Konigl jets and spherical advection-dominated accretion flows (ADAFs) in low-luminosity AGNs.Comment: 4 pages, 6 figures, appears in: Proceedings of the 6th European VLBI Network Symposium held on June 25th-28th in Bonn, Germany. Edited by: E. Ros, R.W. Porcas, A.P. Lobanov, and J.A. Zensu