Future long-range transports: Prospects for improved fuel efficiency

A status report is provided on current thinking concerning potential improvements in fuel efficiency and possible alternate fuels. Topics reviewed are: (1) historical trends in airplane efficiency; (2) technological opportunities including supercritical aerodynamics, (3) vortex diffusers, (4) composite materials, (5) propulsion systems, (6) active controls, and terminal-area operations; (7) unconventional design concepts, and (8) hydrogen-fueled airplane

Breached Pairing Superfluidity at Finite Temperature and Density

A general analysis on Fermion pairing at finite temperature and density between different species with mismatched Fermi surfaces is presented. Very different from the temperature effect of BCS phase, the recently found breached pairing phase resulted from density difference of the two species lies in a region with calabash-like shape in the $T-\mu$ plane, and the most probable temperature for the new phase's creation is finite but not zero.Comment: 5 papes, 5 figures. Comments are welcome to [email protected]

Prediction of the functional properties of ceramic materials from composition using artificial neural networks

We describe the development of artificial neural networks (ANN) for the prediction of the properties of ceramic materials. The ceramics studied here include polycrystalline, inorganic, non-metallic materials and are investigated on the basis of their dielectric and ionic properties. Dielectric materials are of interest in telecommunication applications where they are used in tuning and filtering equipment. Ionic and mixed conductors are the subjects of a concerted effort in the search for new materials that can be incorporated into efficient, clean electrochemical devices of interest in energy production and greenhouse gas reduction applications. Multi-layer perceptron ANNs are trained using the back-propagation algorithm and utilise data obtained from the literature to learn composition-property relationships between the inputs and outputs of the system. The trained networks use compositional information to predict the relative permittivity and oxygen diffusion properties of ceramic materials. The results show that ANNs are able to produce accurate predictions of the properties of these ceramic materials which can be used to develop materials suitable for use in telecommunication and energy production applications

Dense quark matter in compact stars

The densest predicted state of matter is colour-superconducting quark matter, in which quarks near the Fermi surface form a condensate of Cooper pairs. This form of matter may well exist in the core of compact stars, and the search for signatures of its presence is an ongoing enterprise. Using a bag model of quark matter, I discuss the effects of colour superconductivity on the mass-radius relationship of compact stars, showing that colour superconducting quark matter can occur in compact stars at values of the bag constant where ordinary quark matter would not be allowed. The resultant ``hybrid'' stars with colour superconducting quark matter interior and nuclear matter surface have masses in the range 1.3-1.6 Msolar and radii 8-11 km. Once perturbative corrections are included, quark matter can show a mass-radius relationship very similar to that of nuclear matter, and the mass of a hybrid star can reach 1.8 \Msolar.Comment: 11 pages, for proceedings of SQM 2003 conference; references added, abstract reworde

Quark matter in compact stars?

Ozel, in a recent reanalysis of EXO 0748-676 observational data (astro-ph/0605106), concluded that quark matter probably does not exist in the center of compact stars. We show that the data is actually consistent with the presence of quark matter in compact stars.Comment: 4 pages, LaTeX; New title and overall rewrite to reflect version published in Nature. Conclusions unchange

Confining Flux Tubes in a Current Algebra Approach

We describe flux tubes and their interactions in a low energy sigma model induced by $SU({N_f}) \rightarrow SO({N_f})$ flavor symmetry breaking in $SO(N_c)$ QCD. Unlike standard QCD, this model allows gauge confinement to manifest itself in the low energy theory, which has unscreened spinor color sources and global $Z_2$ flux tubes. We construct the flux tubes and show how they mediate the confinement of spinor sources. We further examine the flux tubes' quantum stability, spectrum and interactions. We find that flux tubes are Alice strings, despite ambiguities in defining parallel transport. Furthermore, twisted loops of flux tube support skyrmion number, just as gauged Alice strings form loops that support monopole charge. This model, while phenomenologically nonviable, thus affords a perspective on both the dynamics of confinement and on subtleties which arise for global Alice strings.Comment: 29 pages (REVTEX) plus 6 figures, two corrections in the final section and added reference

Colour superconductivity in finite systems

In this paper we study the effect of finite size on the two-flavour colour superconducting state. As well as restricting the quarks to a box, we project onto states of good baryon number and onto colour singlets, these being necessary restrictions on any observable ``quark nuggets''. We find that whereas finite size alone has a significant effect for very small boxes, with the superconducting state often being destroyed, the effect of projection is to restore it again. The infinite-volume limit is a good approximation even for quite small systems.Comment: 14 pages RevTeX4, 12 eps figure

Color Magnetic Flux Tubes in Dense QCD

QCD is expected to be in the color-flavor locking phase in high baryon density, which exhibits color superconductivity. The most fundamental topological objects in the color superconductor are non-Abelian vortices which are topologically stable color magnetic flux tubes. We present numerical solutions of the color magnetic flux tube for diverse choices of the coupling constants. We also analytically study its asymptotic profiles and find that they are different from the case of usual superconductors. We propose the width of color magnetic fluxes and find that it is larger than naive expectation of the Compton wave length of the massive gluon when the gluon mass is larger than the scalar mass.Comment: 24 pages, 5 figures; v2: typos corrected, references added, minor changes; v3: published versio

An outlook for cargo aircraft of the future

An assessment is provided of the future of air cargo by analyzing air cargo statistics and trends, by noting air cargo system problems and inefficiencies, by analyzing characteristics of air-eligible commodities, and by showing the promise of new technology for future cargo aircraft with significant improvements in costs and efficiency. NASA's proposed program is reviewed which would sponsor the research needed to provide for development of advanced designs by 1985

Managing Workplace Ethics Can Generate Competitive Advantage

The many breaches of ethical conduct and violation of laws by high-profile executives which have been reported for several years have focused attention on the way firms manage business ethics and company values.  This paper identifies some of the bottom-line benefits and other benefits of actively managing the business ethics process and recommends practical approaches for developing a program for the management of that process.  It is especially important for all enterprises to review their own situations and to become active in this area.&nbsp