How should an autonomous vehicle overtake a slower moving vehicle: design and analysis of an optimal trajectory

Over the past few years, there has been much research on various aspects of control of autonomous vehicles. However, it seems that the problem of overtaking a slower moving vehicle has been somewhat neglected. This note deals with the three-phase overtaking maneuver and with designing a smooth and ergonomic optimal lane-change trajectory to be used under normal conditions. It is shown that the absolute shape, size, and time of the first-phase trajectory do not depend on the velocity of the leading, slower moving vehicle. Only the absolute point for initiating the diversion is affected. The relatively simple mathematical model for each lane-change trajectory is based on minimizing the total kinetic energy during the maneuver, superimposed on a "minimum-jerk trajectory." For high enough initial velocities, explicit formulas are obtained for the optimal distance and the optimal time of the maneuver. It is also shown that the total time is bounded from above and below, regardless of the velocity. By using the results of the suggested model, an autonomous vehicle, equipped with appropriate sensors, can estimate the best time and place to begin and end the overtaking and its total time and distance. This may help to make a decision whether to overtake or not.     

Modelling water resource systems: issues and experiences

Since their first serious introduction in the early 1 960s, systems analysis methods have held out a promise of providing information that can help improve decision making. This paper surveys a number of actual applications of optimization and simulation modelling that illustrate the variety of problems studied, the variety of approaches used to study them, and the variety of outcomes or results of such studies. Some studies have been very successful, some have not. Given the varying but generally beneficial results of such studies, it seems clear that research on, together with application of, systems analysis techniques to water resources and environmental problems should continue. The paper concludes with some suggestions for facilitating the development and effective application of this methodology.     

Nuclear magnetic resonance studies of ionomers. 6. Polyurethane-polyphosphonate blends

Blending of a poly(ether urethane) with a polyphosphonate obtained by phase transfer catalyzed polycondensation of 4,4′-biphenol and chloromethylphosphonic dichloride generates a phase-separated material. One phase contains the soft segment of the polyurethane. This has been excluded from a high-T_g phase that contains ionic species formed mainly by proton transfer and elimination reactions between the hard segment of the polyurethane and the polyphosphonate. Two glass transitions appear in the blend: one close to the T_g of the polyphosphonate and one belonging to the excluded soft segment of the polyurethane. The low temperature T_g decreases with the increasing content of the polyphosphonate, whereas the high temperature transition increases slightly, indicating an increasing purity of the soft segment and the presence of ionic interactions in the hard segment. The presence of ionic interactions is confirmed by NMR analysis of the blend. Comparison of the spectra of the blends with those of the pure components, along with two-dimensional experiments, indicate a reaction involving the chloromethyl groups of the polyphosphonate and the nitrogens of the polyurethane.     

Modeling hydrogen storage on Mg–H2 and LiNH2 under variable temperature using multiple regression analysis with respect to ANOVA

The world is facing a major problem due to the depletion of conventional energy sources. Hydrogen is considered one of the most promising sources of energy. Recently, one of the problems facing utilization of hydrogen energy is the storage. Therefore, finding materials to store hydrogen based on the adsorption/desorption methodology (i.e. metal hydrides) is considered extremely vital issue. During this work two candidate materials (i.e. Mg–H₂ and LiNH₂) were investigated at different temperatures (25–45 °C). The results revealed that both candidate materials possessed long cycle life and cyclibility which opens the wide door to use these materials in vehicular applications. On the other hand the generated mathematical models based on the multiple regression analysis with respect to ANOVA showed that increasing temperature will increase the weight of hydrogen adsorption for both candidate materials.     

Propagation-invariant wave fields with finite energy

Propagation invariance is extended in the paraxial regime, leading to a generalized self-imaging effect. These wave fields are characterized by a finite number of transverse self-images that appear, in general, at different orientations and scales. They possess finite energy and thus can be accurately generated. Necessary and sufficient conditions are derived, and they are appropriately represented in the Gauss-Laguerre modal plane. Relations with the following phenomena are investigated: classical self-imaging, rotating beams, eigen-Fourier functions, and the recently introduced generalized propagation-invariant wave fields. In the paraxial regime they are all included within the generalized self-imaging effect that is presented. In this context we show an important relation between paraxial Bessel beams and Gauss-Laguerre beams.     

Operation of TEA CO2lasers with rough surface electrodes

In contrast with the normally accepted concepts in the construction of transversely excited atmospheric (TEA) CO2lasers it is found that homogeneously roughened electrodes perform better then polished ones.