Radio and infrared observations of circumstellar envelopes

This review summarizes the observational achievements at radio and infrared wavelengths since 1984 concerning the circumstellar envelopes of evolved stars. The main emphasis is on our increased knowledge of late stellar evolution, in particular during the asymptotic giant branch phase and the transition to the planetary nebula stage, and on the properties of gas/dust envelopes formed by stellar mass loss. It is not a critical review, and it is essentially free from historical references.     

Computerized Medical Devices: Trends, Problems, and Safety

Virtually all of the medical devices utilizing electronics will contain a micro or minicomputer by 1990. These devices accounted for $7 billion in U.S. sales in 1984. Their capabilities can provide the means for new or greatly improved medical procedures, and ensure greater patient safety. However, these benefits can easily be compromised if ``computer safety' is not practiced in the design, manufacturing, testing and clinical use of these devices. Along with a trend to wider usage, the number of recalls of medical devices due to computer-related problems has approximately doubled in the last five years. ``Computer-caused' problems are often not recognized or reported as such, resulting in an underestimation of the prevalence of this type of problem. Our study of technical factors causing problems in computerized devices revealed that software quality assurance (SQA), the quality of the ac power, and electromagnetic interference are primary factors. Selected design and QA techniques that are well-known in military-aerospace industries can be used to prevent the most prevalent problems occurring in computerized medical devices, without significantly affecting overall device manufacturing costs.     

Trigonometric Approximations for Bessel Functions

Bessel functions, used extensively in mathematical physics, electromagnetics, and communication-system theory, must often be approximated by appropriate formulas. The functions J?(x) and I?(x) for integer values of p are well approximated by the sum of a small number of circular and hyperbolic sines or cosines, respectively, when x is not too large, e.g., less than 10, and convenient expressions are obtained for their errors. These approximations are especially convenient for use on personal computers (PCs) and pocket calculators and in analytically evaluating integrals.     

The USSR and satellite communications : Competition and cooperation

This article examines the USSR's satellite communications provision in the international arena. The author first outlines the Intercosmos programme, collaboration between the USSR and France and India, and maritime satellite communications. He then discusses in detail the INTERSPUTNIK system, and Soviet international coverage and competitiveness in television. In conclusion, the complex interaction and overlap between cooperation and competition in space is explained.     

Organic chemistry in Titan's atmosphere: new data from laboratory simulations at low temperature.

Many experiments have already been carried out to simulate organic chemistry on Titan, the largest satellite of Saturn. They can provide fruitful information on the nature of minor organic constituents likely to be present in Titan's atmosphere, both in gas and aerosol phases. Indeed, all the organic compounds but one already detected in Titan's atmosphere have been identified in simulation experiments. The exception, C4N2, as well as other compounds expected in Titan from theoretical modeling, such as other N-organics, and polyynes, first of all C6H2, have never been detected in experimental simulation thus far. All these compounds are thermally unstable, and the temperature conditions used during the simulation experiments were not appropriate. We have recently started a new program of simulation experiments with temperature conditions close to that of Titan's environment. It also uses dedicated analytical techniques and procedures compatible with the analysis of organics only stable at low temperatures, as well solid products of low stability in the presence of O2 and H2O. Spark discharge of N2-CH4 gas mixtures was carried out at low temperature in the range 100-150 K. Products were analysed by FTIR, GC and GC-MS techniques. GC-peaks were identified by their mass spectrum, and, in most cases, by comparison of the retention time and mass spectrum with standard ones. We report here the first detection in Titan simulation experiments of C6H2 and HC5N. Their abundance is a few percent relative to C4H2 and HC3N, respectively. Preliminary data on the solid products indicate an elemental composition corresponding to (H11C11N)n. These results open new prospects in the modeling of Titan's haze making.     

An application of embedology to spatio-temporal pattern recognition

The theory of embedded time series is shown applicable for determining a reasonable lower bound on the length of test sequence required for accurate classification of moving objects. Sequentially recorded feature vectors of a moving object form a training trajectory in feature space. Each of the sequences of feature vector components is a time series, and under certain conditions, each of these time series has approximately the same fractal dimension. The embedding theorem may be applied to this fractal dimension to establish a sufficient number of observations to determine the feature space trajectory of the object. It is argued that this number is a reasonable lower bound on test sequence length for use in object classification. Experiments with data corresponding to five military vehicles (observed following a projected Lorenz trajectory on a viewing sphere) show that this bound is indeed adequate     

Space radiation quality factor investigations with “NAUSICAA”-device on board the “MIR” space station

The estimation of radiation quality factor in space flights is a serious problem of space dosimetry. The solution of this problem is based on LET-spectra measurements. The “NAUSICAA”-device installed on the “MIR” station has a detector with a large geometric factor, that gives the possibility of measuring LET-spectra with sufficient statistic in relatively short time interval and hence the corresponding Q. LET-spectra are accumulated through 24 hour periods and equivalent dose (H), absorbed dose (D), quality factor and flux (F) are measured every 10 minutes. The obtained data permit the estimate of the diurnal Q and Q in South Atlantic Anomaly. These values vary in the range of 1.4 – 2.2. The analysis of these values including their comparison with the calculated results is given in this paper.     

Temperature structure and dynamics of the middle atmosphere of Venus

The definitive data set for the mean thermal structure of the Venusian middle atmosphere is published for the first time. Some recent interim results on a modelling study to interpret the measured thermal field in terms of the global dynamics are also presented. These indicate that (a) the zonal winds on Venus fall to very low values above about 90 km, (b) there is a strong mid-latitude jet which circles the planet approximately every two days, (c) the observed solar tides are dominated by the semi-diurnal component, in agreement with theory.     

Computational intelligence and soft computing for spaceapplications

Systems using computational intelligence and soft computing have been successfully developed for many industrial and space applications. These systems seek to emulate the type of reasoning that humans perform when solving complex tasks. The field of soft computing, as defined by Zadeh-the inventor of fuzzy logic-encompasses fuzzy logic as well as other methodologies such as neural networks, genetic algorithms, and uncertainty management. It is expected that soft-computing techniques will eventually become as common and prevalent as traditional methods of computer science. This paper presents an overview of applications of fuzzy logic and soft computing to space projects. The role of fuzzy systems that can learn from experience to improve their performance is discussed. We present a report on applications of these adaptive systems to NASA space projects such as the orbital operations of the Space Shuttle, which include attitude control and rendezvous/docking operations. We also provide insights on the future of computational intelligence and soft computing and of their vast potential in industrial applications     

Batteries vs. alternatives for storing energy

Electric utilities need quickly-available sources of power for supplying expected and unexpected peak loads. Among useful sources have been the energy stored in water by pumping it to elevated storage reservoirs, in air compressed into underground chambers, and in batteries. A new power source, tBase-load nuclear and coal-fired steam plants generate off-peak energy for recharging the depleted storage facility. The aero-derived gas turbine, challenges the economics of these traditional energy-storage means. These turbines have been designed for aircraft where quick startup, rapid change in output power, and high reliability are essential. With a 1426°C (2600°F) turbine inlet temperature the available efficiencies are 42% in simple-cycle operation and 60% in a combined-cycle power plant. A recent 84-MW natural-gas-burning peak-power plant cost $204 per kW. Pacific Gas and Electric's Helmes River pumped-hydro plant had cost $656 per kW. The combined-cycle gas turbine plants, with their low manpower requirements, are producing power that costs less than power from nuclear power plants. We examine the performance and economics available from these new power sources