Spectroscopic diagnostics applicable to the UV and EUV spectra of astrophysical sources

A bibliography is provided of the most reliable emission and absorption line ratio diagnostic calculations currently available for application to the spectra of astrophysical sources in the UV and EUV wavelength region (50–3000 Å). References are listed containing diagnostics for species in the Li through P isoelectronic sequences, as well as the iron ions Feii-Fexxiii and nickel ions Nixvii-Nixxv. Also given is the wavelength range for which diagnostic calculations are presented in each reference, along with the type of diagnostic considered. These include, for example, emission line ratios for determining electron temperatures and densities, and absorption line diagnostics for evaluating hydrogen densities.     

Certification of production-representative/productionsoftware-intensive systems for dedicated test and evaluation

Fundamental questions that arise in the certification of readiness for dedicated test and evaluation of software-intensive systems are addressed. They concern what comprises production-representative or production software, what are the software impacts on dedicated system operational test readiness, how software impacts should be considered in the certification process, and what are the retest/recertification requirements associated with software changes/modifications. A paradigm is proposed that answers these questions and outlines guidelines for implementing a solution to these issues. The paradigm is based on existing test and evaluation events and uses a combination of defense and commercial standards and definitions to propose criteria for software certification and retest or regression test     

Le silence éternel de ces espaces infinis?

During the last 40 years — the merest blip in world history — talk about Homo astronauticus has signalled a growing awareness that the passengers on planet Earth can, if they want, take off for other destinations. If the scale of past advances is a satisfactory measure of future possibilities, then the wish will be father of the achievement.     

2-D differential interferometer

A new type of differential interferometer based on holographic optical elements is developed, which allows the exact determination of a refractive index gradient field in two orthogonal directions. This interferometer will be used in TEXUS experiments to determine the temperature field in a convective liquid cell in which the temperature may be known at only one point.     

An approach to geometric reasoning in robotics

Anticipating the use of knowledge-based expert systems for robot task planning, a geometric reasoning is envisioned for the representation and manipulation of geometric information in a manner uniform with other knowledge. The general requirements for such a reasoner are outlined and a proposed architecture is described, built on four concepts: a class structure of spatial sets, features as subsets of those spatial sets, geometric abstractions as partial representations of features, and constraints as a mechanism for reasoning. An example implementation is built in an object-oriented environment and uses an underlying solids modeler, transparent to the end user     

Qualitative Reasoning methods for CELSS modeling.

Qualitative Reasoning (QR) is a branch of Artificial Intelligence that arose from research on engineering problem solving. This paper describes the major QR methods and techniques, which, we believe, are capable of addressing some of the problems that are emphasized in the literature and posed by CELSS modeling, simulation, and control at the supervisory level.     

Experimental and theoretical modeling of laser propulsion

Some schemes of laser propulsive systems are discussed. The question concerned with a body acceleration due to series of air blast waves generated by laser sparks is studied. For this purpose the numerical solutions of gasdynamic equations are found under appropriate initial conditions corresponding to the real ones. Radiative losses and spatial effects at the nozzle exit are taken into account. Theoretical results presented as coupling coefficients (equivalent to reciprocal thrust cost realizing under periodical pulse laser operation) are compared with the experiment. Using conical and parabolic nozzles irradiated by pulsed CO₂ laser the thrust cost about 2000 W/N is achieved which is close to the minimum possible one for the air blast wave-nozzle wall interaction. The main characteristics of laser propulsive jet are presented. Experimental results on recoil momentum transfered to solids under their evaporation by the pulsed CO₂-laser are presented as well. The question of plasma shielding effects on the momentum transfer under the vapour optical breakdown conditions is touched on.     

Use of satellite images to obtain accurate snowmelting runoff forecasts and to survey geothermal activity along Los Andes Range,Chile

Pilot experiments developed in Los Andes Range, Central Zone of Chile, have obtained significant snd positive preliminary results on the use of multispectral and multitemporal satellite images to prepare snowmelt runoff forecasts by measuring snowcovered area in Andean watersheds. The same information is also very useful for studying regional and semi-regional geothermal activity along Los Andes in Chile. These results will be improved with the new satellite data to be available in the next years.     

Low and medium energy gamma-ray astronomy — present status and future aspects

During the last few years quite some progress has been achieved in the field of low and medium energy gamma-ray astronomy below about 30 MeV. Gamma rays from the galactic center and anti-center region have been detected, which require a high interstellar electron flux in the 100 MeV range, if they are predominantly diffuse in nature. Though the Crab pulsar and its nebula are still the only galactic gamma-ray sources which definitely have been detected, some recently determined upper limits to the gamma-ray fluxes of other radio pulsars are close to the theoretically expected values. Active galaxies seem to have a maximum of luminosity in the range between several 100 keV and a few MeV and, therefore, are of special interest. First observational results have been reported on the Seyfert galaxies NGC 4151 and MCG 8-11-11, and the radio galaxy CenA. The nature of the diffuse cosmic gamma-ray component at low gamma-ray energies is not yet solved. Unresolved active galaxies are good candidates for its origin.Considering the present status of gamma ray astronomy the study of galactic sources like radio pulsars and the unidentified high energy gamma-ray sources, the Milky Way as a whole, active galaxies and the diffuse cosmic sky seem to be the prime targets for broad band observations below 30 MeV in the GRO area. An unexplored field like that of low energy gamma-ray astronomy, however, is always open for surprises.