Perception and Planning Architecture for Autonomous Ground Vehicles

By combining smart sensors and traversability grids with a JAUS-based component and messaging architecture, DARPA Grand Challenge finalist team CIMAR quickly developed a robust autonomous ground vehicle (AGV), a custom-built off-road vehicle. Key components included six smart sensors for detecting environmental conditions and reporting a priori data, a smart arbiter for fusing data from multiple smart sensors, and a reactive driver for providing real-time navigation planning and obstacle avoidance     

VLSI and SPICE modeling of ALU

The Arithmetic and Logic Unit （ALU） is a combination circuit that performs a number of arithmetic and logical operations within a microprocessor. The demand for faster and compact ALUs makes it desirable to test the ALU in conjunction with pre-design parts prior to manufacture. This may be accomplished in a process using CAD and SPICE simulation software. Our purpose is to realize a method for importing a layout drawn in Tanner L-edit and simulated in T-Spice into PSpice which is referred to as software talking. To do so we use an eight-function instruction set called Complimentary Metal Oxide Semiconductor Arithmetic and Logic Unit （CMOS ALU） which is laid out in Tanner L-edit and produces an extracted net-list which is simulated in T-Spice. An ALU equivalent design is then modeled in PSpice for further testing with pre-manufactured parts of the PSpice library.     

Influence of dendritic crystallization on the structure and properties of continuous-cast pipe blanks

The influence of dendritic crystallization on the structure and properties of continuous-cast pipe blanks (diameter 150 mm) made from steel with 0.2% C is studied, in the cast and heat-treated states. Dendritic crystallization results in different chemical composition of the austenite and the boundary between the crystals, with different properties. That affects the structure of the steel. Besides the familiar factors, the improvement in the mechanical properties of cast subeutectoid steel after heat treatment is associated with the formation of impurity-rich ferrite in segregated sections of the dendritic structure.     

Electrical and mechanical characterization by instrumented indentation technique of La0.85Sr0.15Ga0.8Mg0.2O3−δ electrolyte for SOFCs

La_0.85Sr_0.15Ga_0.8Mg_0.2O_3?δ pellets obtained by the polymeric organic complex solution method, isostatic pressing and sintering at 1350 °C have been electrical and mechanically studied. Electrical measurements evidenced reasonable ionic conductivities (0.01 S cm^?1 at 800 °C), which were comparable to those reported for the La_1?xSr_xGa_1?yMg_yO_3?δ prepared by other synthesis methods. On the other hand, the mechanical properties (elastic modulus, E and hardness, H) have been determined at micro/nanometric scale using the instrumented indentation technique. While E did not vary significantly with the increasing indentation depth (h), H values strongly decreased with the indentation depth up to 500 nm. For h > 500 nm, both mechanical properties remained almost constant, thus obtaining E = 271 ± 6 GPa and H = 13.2 ± 0.4 GPa. Finally, the residual imprints and fracture mechanisms have been observed by atomic force microscopy (AFM).     

Off-axis measurements of atmospheric trace gases by use of an airborne ultraviolet-visible spectrometer

An airborne UV-visible spectrometer, the Gas Analyzer Spectrometer Correlating Optical Differences, airborne version (GASCOD/A4pi) was successfully operated during the Airborne Polar Experiment, Geophysica Aircraft in Antarctica airborne campaign from Ushuaia (54 degrees 49' S, 68 degrees 18' W), Argentina in southern spring 1999. The instrument measured scattered solar radiation through three optical windows with a narrow field of view (FOV), one from the zenith, two from the horizontal, as well as actinic fluxes through 2pi FOV radiometric heads. Only a few airborne measurements of scattered solar radiation at different angles from the zenith are available in the literature. With our configuration we attempted to obtain the average line-of-sight concentrations of detectable trace gases. The retrieval method, based on differential optical absorption spectroscopy, is described and results for ozone are shown and compared with measurements from an in situ instrument as the first method of validation.     

Some comments on models for field enhancement

To estimate the apex field-enhancement factor gamma(a)associated with a pointed protrusion on a flat planar surface, the simple physical models of a 'floating sphere at emitter-plane potential' and a 'hemisphere on a post' are often discussed. The corresponding mathematical expressions have the form: gamma(a)=m+h/rho, where rho is the sphere or hemisphere radius, h is its 'height above the emitter plane', and m is a constant variously taken as 0, 2 or 3. Recent numerical simulations for the 'hemisphere on a post' model, reported elsewhere by two of us (CJE and GV) and by Kokkaris, Modinos and Xanthakis, have shown that all of these simple formulae significantly overpredict gamma(a) if h/rho is large. This article first reexamines the basis of these simple formulae and confirms that they are less secure than is sometimes thought. The formulae reported elsewhere as fits to the numerical results are then quoted and compared with the simple formulae, and with the known exact analytical result for the 'hemi-ellipsoid on a plane' model. Discrepancies can be rationalised. Some general conclusions are drawn.     

Riemann Solvers with Runge–Kutta Discontinuous Galerkin Schemes for the 1D Shallow Water Equations

The spectrum of this survey turns on the evaluation of some eminent Riemann solvers (or the so-called solver), for the shallow water equations, when employed with high-order Runge–Kutta discontinuous Galerkin (RKDG) methods. Based on the assumption that: The higher is the accuracy order of a numerical method, the less crucial is the choice of Riemann solver; actual literature rather use the Lax-Friedrich solver as it is easy and less costly, whereas many others could be also applied such as the Godunov, Roe, Osher, HLL, HLLC, and HLLE. In practical applications, the flow can be dominated by geometry, and friction effects have to be taken into consideration. With the intention of obtaining a suitable choice of the Riemann solver function for high-order RKDG methods, a one-dimensional numerical investigation was performed. Three traditional hydraulic problems were computed by this collection of solvers cooperated with high-order RKDG methods. A comparison of the performance of the solvers was carried out discussing the issue of L1-errors magnitude, CPU time cost, discontinuity resolution and source term effects.