Thrust and wing loading requirements for short haul aircraft constrained by engine noise and field length

Propulsion system and wing loading requirements are determined for a mechanical flap and an externally blown flap aircraft for various engine noise levels and two engine cycles. Both aircraft are sized to operate from a 914m (3000 ft) runway and perform the same mission. For each aircraft concept, propulsion system sizing is demonstrated for two different engine cycles - one having a fan pressure ratio of 1.5 and a bypass ratio of 9, and the other having a fan pressure ratio of 1.25 and a bypass ratio of 17.8. The results presented include the required thrust-to-weight ratio, wing loading, resulting gross weight, and direct operating costs, as functions of the engine noise level, for each combination of engine cycle and aircraft concept

Requirements for regional short-haul air service and the definition of a flight program to determine neighborhood reactions to small transport aircraft

An evaluation of the current status and future requirements of an intraregional short haul air service is given. A brief definition of the different types of short haul air service is given. This is followed by a historical review of previous attempts to develop short haul air service in high density urban areas and an assessment of the current status. The requirements for intraregional air service, the need for economic and environmental viability and the need for a flight research program are defined. A detailed outline of a research program that would determine urban community reaction to frequent operations of small transport aircraft is also given. Both the operation of such an experiment in a specific region (San Francisco Bay area) and the necessary design modifications of an existing fixed wing aircraft which could be used in the experiment are established. An estimate is made of overall program costs

Spectral width of SuperDARN echoes: measurement, use and physical interpretation

International audienceThe Doppler velocity and spectral width are two important parameters derived from coherent scatter radar systems. The Super Dual Auroral Radar Network (SuperDARN) is capable of monitoring most of the high latitude region where different boundaries of the magnetosphere map to the ionosphere. In the past, the spectral width, calculated from SuperDARN data, has been used to identify the ionosphere footprints of various magnetosphere boundaries. In this paper we examine the way the spectral width is presently estimated from the radar data and describe several recommendations for improving the algorithm. Using the improved algorithm, we show that typical spectral width values reported in the literature are most probably overestimated. The physical interpretation of the cause of various magnitudes of the spectral width is explored in terms of the diffusion and dynamics of ionospheric plasma irregularities

New periodic orbits in the solar sail three-body problem

We identify displaced periodic orbits in the circular restricted three-body problem, wher the third (small) body is a solar sail. In particular, we consider solar sail orbits in the earth-sun system which are high above the exliptic plane. It is shown that periodic orbits about surfaces of artificial equilibria are naturally present at linear order. Using the method of Lindstedt-Poincare, we construct nth order approximations to periodic solutions of the nonlinear equations of motion. In the second part of the paper we generalize to the solar sail elliptical restricted three-body problem. A numerical continuation, with the eccentricity, e, as the varying parameter, is used to find periodic orbits above the ecliptic, starting from a known orbit at e=0 and continuing to the requied eccentricity of e=0.0167. The stability of these periodic orbits is investigated

Theory of high-energy emission from the pulsar/Be-star system PSR 1259−-63 I: radiation mechanisms and interaction geometry

We study the physical processes of the PSR B1259-63 system containing a 47 ms pulsar orbiting around a Be star in a highly eccentric orbit. Motivated by the results of a multiwavelength campaign during the January 1994 periastron passage of PSR B1259-63, we discuss several issues regarding the mechanism of high-energy emission. Unpulsed power law emission from the this system was detected near periastron in the energy range 1-200 keV. We find that the observed high energy emission from the PSR B1259-63 system is not compatible with accretion or propeller-powered emission. Shock-powered high-energy emission produced by the pulsar/outflow interaction is consistent with all high energy observations. By studying the evolution of the pulsar cavity we constrain the magnitude and geometry of the mass outflow outflow of the Be star. The pulsar/outflow interaction is most likely mediated by a collisionless shock at the internal boundary of the pulsar cavity. The system shows all the characteristics of a {\it binary plerion} being {\it diffuse} and {\it compact} near apastron and periastron, respectively. The PSR B1259-63 cavity is subject to different radiative regimes depending on whether synchrotron or inverse Compton (IC) cooling dominates the radiation of electron/positron pairs advected away from the inner boundary of the pulsar cavity. The highly non-thermal nature of the observed X-ray/gamma-ray emission near periastron establishes the existence of an efficient particle acceleration mechanism within a timescale shown to be less than $\sim 10^2-10^3$ s. A synchrotron/IC model of emission of e\pm-pairs accelerated at the inner shock front of the pulsar cavity and adiabatically expanding in the MHD flow provides an excellent explanation of the observed time variableX-ray flux and spectrum from the PSRComment: 68 pages, accepted for publication in the Astrophys. J. on Aug. 26, 199

Bovine Tuberculosis and the Establishment of an Eradication Program in the United States: Role of Veterinarians

The significance of the identification of Mycobacterium bovis as a zoonotic pathogen in 1882 was not initially recognized. After years of research by veterinarians, and other scientists, the importance of M. bovis as a pathogen and the public health ramifications, were appreciated. Veterinarians played pivotal roles in the creation of improved meat and milk inspection, diagnosis of M. bovis infected cattle, and in time, a bovine tuberculosis eradication program that would impact every cattle producer in the country. After overcoming many challenges, the 93-year-long program has decreased disease prevalence from 5% to <0.001%. Today, years of hard work by practitioners, researchers and regulatory officials alike, have yielded a program with a net benefit of almost $160 million per year

The color dependent morphology of the post-AGB star HD161796

Context. Many protoplanetary nebulae show strong asymmetries in their surrounding shell, pointing to asymmetries during the mass loss phase. Questions concerning the origin and the onset of deviations from spherical symmetry are important for our understanding of the evolution of these objects. Here we focus on the circumstellar shell of the post-AGB star HD 161796. Aims. We aim at detecting signatures of an aspherical outflow, as well as to derive the properties of it. Methods. We use the imaging polarimeter ExPo (the extreme polarimeter), a visitor instrument at the William Herschel Telescope, to accurately image the dust shell surrounding HD 161796 in various wavelength filters. Imaging polarimetry allows us to separate the faint, polarized, light from circumstellar material from the bright, unpolarized, light from the central star. Results. The shell around HD 161796 is highly aspherical. A clear signature of an equatorial density enhancement can be seen. This structure is optically thick at short wavelengths and changes its appearance to optically thin at longer wavelengths. In the classification of the two different appearances of planetary nebulae from HST images it changes from being classified as DUPLEX at short wavelengths to SOLE at longer wavelengths. This strengthens the interpretation that these two appearances are manifestations of the same physical structure. Furthermore, we find that the central star is hotter than often assumed and the relatively high observed reddening is due to circumstellar rather than interstellar extinction.Comment: Accepted for publication in A&

Inbreeding in the White Leghorn Fowl

A study, extending over a 10-year period, has been made of the effect of inbreeding in the White Leghorn breed of domestic fowl. The major object of this investigation was to study the effect of various intensities of inbreeding on the following characters: Fertility, hatchability, viability, days to first egg, egg production, egg size and body size. In the present investigation the degree of inbreeding was, in general, less intense than that from brother and sister or parent and offspring matings. One intensely inbred family, however, with the equivalent of brother and sister mating, was maintained successfully for nine generations. Six more or less distinct families, each with a somewhat different type and intensity of inbreeding but with a similar foundation ancestry, were developed. All individuals were selected primarily on the basis of high hatchability of their eggs, upon general vigor of the individual bird and of the offspring of each pair of birds. Other characters besides vigor and hatchability also were considered whenever practical. The ancestry of all the birds in the present generation of these 6 families may be traced to four males and seven females. One of the four original males (No. 823), however, has a greater degree o£ relationship to the present generation than any of the other foundation birds. This relationship still averages approximately 55 percent, with the lowest degree of relationship being 29 percent and the highest 61 percent. The relationship of the present generation to the other three foundation males does not exceed 5 percent. The relationship between brothers and sisters in the present generation chicks of the separate families ranges from 74 to 94 percent. The average inter-se relationship between the present chicks which are not sibs is above 50 percent. The inbreeding coefficients of the present birds range from 41 percent for the least inbred to 82 percent for the most intensely inbred family. There was no general decrease in percent of eggs fertile as the degree of inbreeding increased ; in fact some inbred families have shown an increase in percent of eggs fertile. There was a slow but gradual decline in the average percent hatchability of fertile eggs set for all inbreds as the inbreeding increased. The average hatchability for all inbreds, however, was in most cases well above 60 percent. In six of the families studied there was no general decrease in hatchability, which demonstrates that it is possible to maintain a reasonably safe level of hatchability under a system of intense inbreeding. There was a significant decrease in the number of days to first egg. The most intensely inbred birds on the average matured sexually 16 days earlier than the birds of the original non-inbred foundation stock. There was a general but not a consistent decrease in number of eggs laid during a given period as the inbreeding increased. An exception was observed for the 70 percent inbred group which compared favorably with the original non-inbred foundation birds in egg production. There was no marked decrease in 200-day egg production for anyone of the six separate families as a result of the inbreeding. The data on egg weight suggest no general decrease or increase in average egg weight as a result of the inbreeding. The results indicate that intensive inbreeding did not decrease materially the growth rate or adult body weight of the birds used in this experiment. With the exception of the 80 percent group, there was no increase in mortality in any of the groups up to 24 weeks of age. The pullet year mortality, however, showed a marked rise for the more intensely inbred birds with the exception of that group of birds having an inbreeding coefficient of 70 percent