Classification by means of B-spline potential functions with applications to remote sensing

A method is presented for using B-splines as potential functions in the estimation of likelihood functions (probability density functions conditioned on pattern classes), or the resulting discriminant functions. The consistency of this technique is discussed. Experimental results of using the likelihood functions in the classification of remotely sensed data are given

Cryogenic thermal control technology summaries

A summarization and categorization is presented of the pertinent literature associated with cryogenic thermal control technology having potential application to in-orbit fluid transfer systems and/or associated space storage. Initially, a literature search was conducted to obtain pertinent documents for review. Reports determined to be of primary significance were summarized in detail. Each summary, where applicable, consists of; (1) report identification, (2) objective(s) of the work, (3) description of pertinent work performed, (4)major results, and (5) comments of the reviewer (GD/C). Specific areas covered are; (1) multilayer insulation of storage tanks with and without vacuum jacketing, (2) other insulation such as foams, shadow shields, microspheres, honeycomb, vent cooling and composites, (3) vacuum jacketed and composite fluid lines, and (4) low conductive tank supports and insulation penetrations. Reports which were reviewed and not summarized, along with reasons for not summarizing, are also listed

Classical Concepts in Quantum Programming

The rapid progress of computer technology has been accompanied by a corresponding evolution of software development, from hardwired components and binary machine code to high level programming languages, which allowed to master the increasing hardware complexity and fully exploit its potential. This paper investigates, how classical concepts like hardware abstraction, hierarchical programs, data types, memory management, flow of control and structured programming can be used in quantum computing. The experimental language QCL will be introduced as an example, how elements like irreversible functions, local variables and conditional branching, which have no direct quantum counterparts, can be implemented, and how non-classical features like the reversibility of unitary transformation or the non-observability of quantum states can be accounted for within the framework of a procedural programming language.Comment: 11 pages, 4 figures, software available from http://tph.tuwien.ac.at/~oemer/qcl.html, submitted for QS2002 proceeding

Evaluation of active control technology for short haul aircraft

An evaluation of the economics of short-haul aircraft designed with active controls technology and low wing-loading to achieve short field performance with good ride quality is presented. Results indicate that for such a system incorporating gust load alleviation and augmented stability the direct operating cost is better than for aircraft without active controls

COMPTEL Observations of the Gamma-Ray Blazar PKS 1622-297

We report results of observations and analyses on the gamma-ray blazar PKS 1622-297, with emphasis on the COMPTEL data (0.75 - 30 MeV) collected between April 1991 and November 1997. PKS 1622-297 was detected as a source of gamma-rays by the EGRET experiment aboard CGRO in 1995 during a gamma-ray outburst at energies above 100 MeV lasting for five weeks. In this time period the blazar was significantly (~ 5.9 sigma) detected by COMPTEL at 10-30 MeV. At lower COMPTEL energies the detection is marginal, resulting in a hard MeV spectrum. The combined COMPTEL/EGRET energy spectrum shows a break at MeV energies. The broad-band spectrum (radio - gamma-rays) shows that the gamma-ray emission dominates the overall power output. On top of the 5-week gamma-ray outburst, EGRET detected a huge flare lasting for > 1 day. Enhanced MeV emission (10 - 30 MeV) is found near the time of this flare, suggesting a possible time delay with respect to the emission above 100 MeV. Outside the 5-week flaring period in 1995, we do not detect MeV emission from PKS 1622-297.Comment: 10 pages including 9 figures, accepted for publication in A&

Quantum cryptography with squeezed states

A quantum key distribution scheme based on the use of displaced squeezed vacuum states is presented. The states are squeezed in one of two field quadrature components, and the value of the squeezed component is used to encode a character from an alphabet. The uncertainty relation between quadrature components prevents an eavesdropper from determining both with enough precision to determine the character being sent. Losses degrade the performance of this scheme, but it is possible to use phase-sensitive amplifiers to boost the signal and partially compensate for their effect.Comment: 15 pages, no figure

COMPTEL observations of the quasar PKS 0528+134 during the first 3.5 years of the CGRO mission

The COMPTEL observations of the blazar-type quasar PKS 0528+134 in the energy range 0.75 MeV to 30 MeV carried out between April 1991 and September 1994 have been analyzed. During the first two years PKS 0528+134 was most significantly detected at energies above 3 MeV. During the last year there is only evidence for the quasar at energies below 3 MeV indicating a spectral change. The time-averaged COMPTEL energy spectrum between 0.75 MeV and 30 MeV is well represented by a power-law shape. Spectra collected from different observational periods reveal different power-law shapes: a hard state during flaring observations reported by EGRET, and a soft state otherwise. The combined simultaneous EGRET and COMPTEL spectra indicate these two spectral states as well. During low intensisty gamma-ray phases no spectral break is obvious from the combined COMPTEL and EGRET measurements. For the gamma-ray flaring phases however, the combined COMPTEL and EGRET data require a spectral bending at MeV-energies. By fitting broken power-law functions the best-fit values for the break in photon index range between 0.6 and 1.7, and for the break energy between ~5 MeV and ~20 MeV. Because the flux values measured by COMPTEL below 3 MeV in both states are roughly equal, the observations would be consistent with an additional spectral component showing up during gamma-ray flaring phases of PKS 0528+134. Such a component could be introduced by e.g. a high-energy electron-positron population with a low-energy cutoff in their bulk Lorentz factor distribution. The multiwavelength spectrum of PKS 0528+134 for gamma-ray flaring phases shows that the major energy release across the entire electro-magnetic spectrum is measured at MeV-energies.Comment: 10 pages, 8 postscript figures, latex, to appear in: A&A 328, 33 (1997