Guidelines for the planning and preparation of illustrated technical talks

Guidelines are presented for the preparation of illustrated talks which are audience oriented and which are aimed at the efficient transfer of technical information. Early decisions concerning the required number of slides are helpful in initial planning for a good quality talk. Detailed considerations are: the establishment of limited objectives, selection of appropriate slide material, development of a text which is well coordinated with the slides, and accurate timing

The Economic Effect of Competition in the Air Transportation Industry

The air transportation industry has been described as a highly-competitive, regulated oligopoly or as a price-regulated cartel with blocked entry, resulting in excessive service and low load factors. The current structure of the industry has been strongly influenced by the hypotheses that increased levels of competition are desirable per se, and that more competing carriers can be economically supported in larger markets, in longer haul markets, with lower unit costs, and with higher fare levels. An elementary application of competition/game theory casts doubt on the validity of these hypotheses, but rather emphasizes the critical importance of the short-term non-variable costs in determining economic levels of competition

Sound measurements and observations of the MOD-OA wind turbine generator

Sound measurements are reported for a wind velocity of about 5 m/s and a power output of about 70 kW. Both broadband and narrowband data were obtained for a range of distances and azimuth angles from the machine. Both discrete frequency and broadband components were identified. Loading harmonics at multiples of the blade passage frequency and electrical generator harmonics at multiples of the shaft speed dominated the spectrum below 100 Hz. The 10,000 Hz peak is believed to be of mechanical origin in the nacelle and the other arises from blade aerodynamic sources. Aural detection distances of about 525 m upwind and 850 downwind were observed

Sound propagation studies for a large horizontal axis wind turbine

Systematic noise measurements in three directions with respect to the wind vector, over a range of distances to 1050 m, over a range of frequencies from 8 Hz to 2000 Hz, and for a stable wind turbine noise source (WTS-4) in windy conditions (V = 9.4 to 13.0 m/s) are presented. At frequencies above 63 Hz in the downwind and crosswind directions the sound pressure levels decay with distance according to predictions based on atmospheric absorption and spherical spreading, assuming no excess attenuation due to ground effects. In the upwind direction there is excess attenuation due to an acoustic shadow zone. The assumption of a distributed noise source leads to better noise estimates in the upwind direction. For very low frequencies 8 to 16 Hz no excess attenuation was observed in the upwind direction at distances up to 1050 m and a sound pressure level decay rate of approximately 3 dB per doubling of distance was observed in the downwind direction

Atmospheric effects on sonic-boom signatures

Atmospheric refraction, grazing incidence wave impingement, and turbulence interaction effects on sonic boom ground pressure signature

Scaling Relation for Excitation Energy Under Hyperbolic Deformation

We introduce a one-parameter deformation for one-dimensional (1D) quantum lattice models, the hyperbolic deformation, where the scale of the local energy is proportional to cosh lambda j at the j-th site. Corresponding to a 2D classical system, the deformation does not strongly modify the ground state. In this situation, the effective Hamiltonian of the quantum system shows that the quasi particle is weakly bounded around the center of the system. By analyzing this binding effect, we derive scaling relations for the mean-square width of confinement, the energy correction with respect to the excitation gap \Delta, and the deformation parameter $\lambda$. This finite-size scaling allows us to investigate excitation gap of 1D non-deformed bulk quantum systems.Comment: 9 pages, 5 figure

Multiphase modelling of vascular tumour growth in two spatial dimensions

In this paper we present a continuum mathematical model of vascular tumour growth which is based on a multiphase framework in which the tissue is decomposed into four distinct phases and the principles of conservation of mass and momentum are applied to the normal/healthy cells, tumour cells, blood vessels and extracellular material. The inclusion of a diffusible nutrient, supplied by the blood vessels, allows the vasculature to have a nonlocal influence on the other phases. Two-dimensional computational simulations are carried out on unstructured, triangular meshes to allow a natural treatment of irregular geometries, and the tumour boundary is captured as a diffuse interface on this mesh, thereby obviating the need to explicitly track the (potentially highly irregular and ill-defined) tumour boundary. A hybrid finite volume/finite element algorithm is used to discretise the continuum model: the application of a conservative, upwind, finite volume scheme to the hyperbolic mass balance equations and a finite element scheme with a stable element pair to the generalised Stokes equations derived from momentum balance, leads to a robust algorithm which does not use any form of artificial stabilisation. The use of a matrix-free Newton iteration with a finite element scheme for the nutrient reaction-diffusion equations allows full nonlinearity in the source terms of the mathematical model. Numerical simulations reveal that this four-phase model reproduces the characteristic pattern of tumour growth in which a necrotic core forms behind an expanding rim of well-vascularised proliferating tumour cells. The simulations consistently predict linear tumour growth rates. The dependence of both the speed with which the tumour grows and the irregularity of the invading tumour front on the model parameters are investigated

The Origin of Life

The origin of life is in a sense a genetic problem, for, as H. J. Muller pointed out many years ago, the essential attribute that identifies living matter is its capacity to replicate itself and its variants (1). Because this uniquely biological property has its physical basis in proteins and nucleic acids, the goal of modern work on the origin of life is to discover the manner of origin of these polymers and of the interactions between them that constitute the genetic mechanism. In attempting to review this subject in a limited space, we cannot undertake an exhaustive treatment. Rather, we summarize work published principally since 1970 in the following areas, with emphasis on those aspects that are of greatest current interest: 1. precambrian paleontology, 2. chemical evolution of genetically important monomers, 3. prebiotic dehydration-condensation reactions, 4. organic compounds in meteorites and interstellar space, and 5. biological exploration of the planets. A large number of review articles (2-5), critical and theoretical discussions (6-8), books (9-16), and conference proceedings (17-21) dealing with the origin of have appeared in recent years. In addition, a new serial, the Journal of Molecular Evolution, publishing papers on this and related subjects, appeared in 1971; the journal Space Life Sciences has been renamed "Origins of Life," and a society, the International Society for the Study of the Origin of Life, was recently founded

Reconstruction of the Part Vegetation on the Headwaters of the Piney Creek Watershed in Houston and Trinity Counties, Texas

The National Forests and Grasslands of Texas began a project in 1994 for ecosystem management involving multiple disciplines in an holistic approach to resource inventories. We first began with an intensive archival study of the forest acquisition files and the General Land Office (GLO) files in an effort to identify the western limits of the longleaf pine at the time of initial Anglo-American settlement ca. 1850. Vegetation information was gleaned from this work along with an understanding of the historical occupation of the area, aided by plotting this information onto USGS 7.5\u27 maps overlain by the historic Tobin landownership maps. We have since narrowed our focus from the mosaic of a broad area, to the headwaters of the Piney Creek watershed, an area rich in prehistory and history. Archeological survey has provided data for prehistoric occupations dating to the Early Ceramic period (ca. A.D. 500). More recent deed records, and subsequent landline surveys, have data on witness trees in the 1830s, 1860s, and 1890s, and then again after the Forest Service acquired the land in the 1930s, offering an opportunity to study specie composition over a 100 year period. This study on specie composition, tree density, and basal area, provides preliminary indications that fire suppression in the historic period significantly altered the forest composition

Vibration Responses of Test Structure No. 2 During the Edward Air Force Base Phase of the National Sonic Boom Program

In order to evaluate reaction of people to sonic booms of varying overpressures and time durations, a series of closely controlled and systematic flight tests/studies were conducted from June 3 to June 23, 1966. The dynamic responses of several building structures were measured, with emphasis on a two-story residence structure. Sample acceleration and strain recordings from F-104, B-58, and XB-70 sonic boom exposures are included, along with tabulations of the maximum acceleration and strain values measured for each one of about 140 flight tests. These data are compared with similar measurements for engine noise exposures of the building during simulated landing approaches and takeoffs of KC-135 aircraft