Flight test evaluation of a 35 GHz forward looking altimeter forterrain avoidance

Honeywell has conducted a series of flight tests of a 35 GHz digital microprocessor controlled forward looking radar altimeter. A Bell 206L Jet Ranger helicopter was used to evaluate the capability of the sensor as a detector of various types of terrain collision hazards. The sensor was composed of a covert, spread spectrum radar altimeter processor driving a 35 GHz converter and antenna assembly mounted on a steerable platform. Excellent correlation between predicted performance and observed performance was obtained     

Marangoni convection when the surface tension increases with the temperature in normal and low gravity conditions

Thermocapillary convection has been studied in n-heptanol aqueous solutions whose surface tension is increasing with the temperature.

The fluid was confined in a parallelipipedic enclosure and a thermal gradient was imposed parallel to the free liquid/gas interface. The motions induced by the thermocapillary forces have been studied under low gravity conditions during Texus sounding rocket experiments and during the Spacelab D1 mission.

The combined thermocapillary and buoyancy convection have been extensively studied during ground based experiments.

The influence of the aspect ratio and of the alcohol concentration were investigated. Detailed velocity field was determined at the steady state under normal gravity conditions by Laser Doppler Anemometry (LDA).

The aspect ratio was of 0.3 and the temperatures imposed to the lateral sides of the cell were respectively 45°C and 60°C. With these experimental conditions, two superposed contrarotative cells were observed with rapid motions in the surface from the cold to the hot side. This convective pattern was also observed during the normal and high gravity periods of parabolic flights but during the low gravity period of the parabola the motions stopped everywhere in the fluid even in the surface and reappeared immediatly at the pull out of the parabola.     

Ion composition behaviour in low and mid-latitudes during high solar activity

In the present analysis, the mass spectrometer data from the ISS-b satellite, available in the form of contour plots at an average height of 1100 km for every alternate hour, is used. This analysis showed some interesting results in terms of the diurnal variation of the transition heights; at times dominance of He⁺ over the other ions, and the seasonal variations of different constituents. In the development of ion composition models, it is suggested that this type of result should be taken into consideration.     

Noise analysis of a digital tanlock loop

The noise performance analysis of a nonuniform digital phase-locked loop (DPLL), called the digital tanlock loop (DTL), is investigated by both analytic and computer-simulation methods. The results are presented in terms of phase error probability mass function and mean time to skip cycle versus input signal-to-noise ratio (SNR). These results are compared to the ones obtained with the conventional sinusoidal DPLL loop (DPLL). It is found that, for low-to-moderate input SNR, the DTL has only a slight improvement over the DPLL. The DTL, however, has larger linear characteristics than the conventional DPLL, which makes it attractive for applications that require an increased tracking range or as a first stage in carrier tracking systems based on optimum estimation procedures such as a Kalman smoother     

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.     

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.     

Delta-electron emission in fast heavy ion atom collisions.

Biological damages such as mutations, chromosomal aberrations etc. are a consequence of biochemical changes mostly in the DNA. With ionizing radiation, these chemical changes are due to primary ionization events and secondary ionization effects caused by the primarily produced electrons. Differences in the biological response of densely ionizing radiation, like heavy charged particles, in comparison to sparsely ionizing radiation, such as X- or gamma-rays, are mainly due to the differences in the production of the so called delta-electrons. Therefore, the emission process of electrons i.e. the cross section for the primary ionization event as well as the energy and angular distribution of the emitted electrons should be understood in detail. The delta-electron emission processes occuring in fast heavy ion atom collisions are explained qualitatively. The different spectral structures of electron emission arising from either the target or the projectile are explained in terms of simple models of the kinetics of momentum transfer induced by the COULOMB forces. In collisions of very heavy ions with matter, high nuclear COULOMB forces are created. These forces lead to a strong polarization of the electronic states of the participated electrons. The effects of this polarization are discussed.     

Results from the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Observatory

The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory covers the high energy gamma ray energy range, approximately 30 MeV to 30 GeV, with a sensitivity considerably greater than earlier high energy gamma-ray satellites. Thus far, 4 pulsars have been detected and their properties measured, including in 3 cases the energy spectrum as a function of phase. The details of the galactic plane are being mapped and a spectra of the center region has been obtained in good agreement with that expected from cosmic ray interactions. The Magellanic clouds have been examined with the Large Magellanic Cloud having been detected at a level consistent with it having a cosmic ray density compatible with quasi-stable equilibrium. Sixteen Active Galactic Nuclei (AGN's) have been seen thus far with a high degree of certainty including 12 quasars and 4 BL Lac objects, but no Seyferts. Time variation has been detected in some of these AGN's.     

A multioutput LLC-type parallel resonant converter

When an LLC-type parallel resonant converter (LLC-PRC) operates above resonant frequency, the switching transistors can be turned off at zero voltage. Further study reveals that the LLC-PRC possesses the advantage of lower converter voltage gain as compared with the conventional PRC. Based on the analytic results derived, a complete set of design curves from which a systematic design procedure is developed is obtained. Experimental results from a 150-W, 150-kHz, multioutput LLC-type PRC power supply are presented