Trajectory generation for road vehicle obstacle avoidance using convex optimization

This paper presents a method for trajectory generation using convex optimization to find a feasible, obstacle-free path for a road vehicle. Consideration of vehicle rotation is shown to be necessary if the trajectory is to avoid obstacles specified in a fixed Earth axis system. The paper establishes that, despite the presence of significant non-linearities, it is possible to articulate the obstacle avoidance problem in a tractable convex form using multiple optimization passes. Finally, it is shown by simulation that an optimal trajectory that accounts for the vehicle’s changing velocity throughout the manoeuvre is superior to a previous analytical method that assumes constant speed

Nonuniversal behavior of scattering between fractional quantum Hall edges

Among the predicted properties of fractional quantum Hall states are fractionally charged quasiparticles and conducting edge-states described as chiral Luttinger liquids. In a system with a narrow constriction, tunneling of quasi-particles between states at different edges can lead to resistance and to shot noise. The ratio of the shot noise to the backscattered current, in the weak scattering regime, measures the fractional charge of the quasi-particle, which has been confirmed in several experiments. However, the non-linearity of the resistance predicted by the chiral Luttinger liquid theory was apparently not observed in some of these cases. As a possible explanation for these discrepancies, we consider a model where a smooth edge profile leads to formation of additional edge states. Coupling between the current carrying edge mode and the additional phonon like mode can lead to {\it nonuniversal} exponents in the current-voltage characteristic, while preserving the ratio between shot noise and the back-scattered current, for weak backscattering. For special values of the coupling, one may obtain a linear I-V behavior.Comment: 10 pages, 3 figure

BIOTIGER, A NATURAL MICROBIAL PRODUCT FOR ENHANCED HYDROCARBON RECOVERY FROM OIL SANDS.

BioTiger{trademark} is a unique microbial consortia that resulted from over 8 years of extensive microbiology screening and characterization of samples collected from a century-old Polish waste lagoon. BioTiger{trademark} shows rapid and complete degradation of aliphatic and aromatic hydrocarbons, produces novel surfactants, is tolerant of both chemical and metal toxicity and shows good activity at temperature and pH extremes. Although originally developed and used by the U.S. Department of Energy for bioremediation of oil-contaminated soils, recent efforts have proven that BioTiger{trademark} can also be used to increase hydrocarbon recovery from oil sands. This enhanced ex situ oil recovery process utilizes BioTiger{trademark} to optimize bitumen separation. A floatation test protocol with oil sands from Ft. McMurray, Canada was used for the BioTiger{trademark} evaluation. A comparison of hot water extraction/floatation test of the oil sands performed with BioTiger{trademark} demonstrated a 50% improvement in separation as measured by gravimetric analysis in 4 h and a five-fold increase at 25 hr. Since BioTiger{trademark} performs well at high temperatures and process engineering can enhance and sustain metabolic activity, it can be applied to enhance recovery of hydrocarbons from oil sands or other complex recalcitrant matrices

The Evolution of Quasiparticle Charge in the Fractional Quantum Hall Regime

The charge of quasiparticles in a fractional quantum Hall (FQH) liquid, tunneling through a partly reflecting constriction with transmission t, was determined via shot noise measurements. In the nu=1/3 FQH state, a charge smoothly evolving from e*=e/3 for t=1 to e*=e for t<<1 was determined, agreeing with chiral Luttinger liquid theory. In the nu=2/5 FQH state the quasiparticle charge evolves smoothly from e*=e/5 at t=1 to a maximum charge less than e*=e/3 at t<<1. Thus it appears that quasiparticles with an approximate charge e/5 pass a barrier they see as almost opaque.Comment: 4 pages, Correct figure 3 and caption include

Movement patterns of forest elephants (Loxodonta cyclotis Matschie, 1900) in the Odzala-Kokoua National Park, Republic of Congo

[Otros] Les éléphants de forêt d'Afrique (Loxodonta cyclotis Matschie, 1900) sont des ingénieurs en écologie qui jouent un rôle fondamental dans la dynamique de la végétation. L'espèce constitue une préoccupation immédiate pour la conservation, mais elle est relativement peu étudiée. Pour combler cette lacune de connaissances, nous avons étudié les facteurs de déplacements quotidiens (déplacements linéaires) des éléphants de forêt ¿ caractérisés par un ensemble de variables géographiques, météorologiques et anthropiques ¿ dans le Parc National d'Odzala¿Kokoua, en République du Congo. Concrètement, nous avons utilisé la forêt d'arbres décisionnels pour modéliser et démêler les principaux facteurs environnementaux régissant les déplacements de six éléphants de forêt, équipés de colliers GPS et suivis pendant 16 mois. Les résultats ont montré que les femelles se déplaçaient plus loin que les mâles, tandis que la présence de routes ou d¿établissements humains perturbait le comportement des éléphants, ce qui accélérait les déplacements. Les éléphants de forêt se déplaçaient plus rapidement dans les cours d¿eau et dans les forêts dont le sous¿bois était dominé par les forêts de Marantaceae et les bais, mais se déplaçait plus lentement dans les savanes. Enfin, les zones inondables ¿ characterisées par l¿altitude et les précipitations accumulées ¿ et les températures plus élevées empêchaient des déplacements plus longs. Nous espérons que ces résultats amélioreront les connaissances sur les mouvements des espèces à travers différents habitats, ce qui serait bénéfique pour la gestion de leur conservation.[EN] African forest elephants (Loxodonta cyclotis Matschie, 1900) are ecological engineers that play a fundamental role in vegetation dynamics. The species is of immediate conservation concern, yet it is relatively understudied. To narrow this knowledge gap, we studied the drivers of daily movement patterns (linear displacements) of forest elephants¿characterised by a set of geographical, meteorological and anthropogenic variables¿in the Odzala¿Kokoua National Park, Republic of Congo. Explicitly, we used conditional random forest to model and disentangle the main environmental factors governing the displacements of six forest elephants,fitted with GPS collars and tracked over 16 months. Results indicated that females moved further distances than males, while the presence of roads or human settlements disrupted elephant behaviour resulting in faster displacements. Forest elephants moved faster along watercourses and through forest with understory dominated by Marantaceae forests and bais, but moved slower in savannahs. Finally, flood¿prone areas¿described by elevation and accumulated precipitation¿and higher temperatures prevented longer displacements. We expect these results to improve the knowledge on the species movements through different habitats, which would benefit its conservation management.The fieldwork was financed by African Parks. We are grateful to the Congolese wildlife authorities (Ministère de l'Économie Forestière et de l'Environnement) for the permission to carry out this study, and we are deeply indebted to the director of the OKNP and to the conservation, wildlife monitoring and research manager, Erik Marav, respectively, for their continued support during our study. We are particularly grateful to Dr. Mike Kock, veterinarian, for collaring the elephants and to the field tracking team. We are also grateful to Séan Cahill for the useful comments and English correction that helped improve this manuscript. 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Boundary interactions changing operators and dynamical correlations in quantum impurity problems

Recent developments have made possible the computation of equilibrium dynamical correlators in quantum impurity problems. In many situations however, one is rather interested in correlators subject to a non equilibrium initial preparation; this is the case for instance for the occupation probability $P(t)$ in the double well problem of dissipative quantum mechanics (DQM). We show in this paper how to handle this situation in the framework of integrable quantum field theories by introducing ``boundary interactions changing operators''. We determine the properties of these operators by using an axiomatic approach similar in spirit to what is done for form-factors. This allows us to obtain new exact results for $P(t)$; for instance, we find that that at large times (or small $g$), the leading behaviour for g < 1/2} is $P(t)\propto e^{-\Gamma t}\cos\Omega t$, with the universal ratio. $\Omega/\Gamma = \cot {\pi g}/{2(1-g)}$.Comment: 4 pages, revte

Role of soil texture, clay mineralogy, location, and temperature in coarse wood decomposition—a mesocosm experiment

Of all the major pools of terrestrial carbon (C), the dynamics of coarse woody debris (CWD) are the least understood. In contrast to soils and living vegetation, the study of CWD has rarely relied on ex situ methods for elaborating controls on decomposition rates. In this study, we report on a mesocosm incubation experiment examining how clay amount (8%, 16%, and 24% clay), clay type (soil reconstructed with kaolinite vs. montmorillonite), wood placement (on litter layer surface, at the litter layer–soil interface, buried in the mineral soil), and laboratory incubation temperature (10°, 20°, or 30°C) control decomposition rates of highly standardized stakes and blocks of coarse aspen wood. Clay type effect was pronounced, with wood decomposing more quickly in kaolinite- than in montmorillonite-amended soils, perhaps due to a combined effect of moisture and microbial access to the substrate. Clay amount had only very limited effect on wood decomposition, which was a function of contact with the mineral soil (Surface \u3c Interface \u3c Mineral), perhaps due to greater contact with the decomposer community. Temperature effects were significant and dependent on interactions with clay type and wood placement. Effects of temperature on wood decomposition declined as the effects of soil variables increased, suggesting a hierarchy of controls on wood decomposition rates. Both water content and temperature had a strong effect on wood decomposition. Our results highlight that multiple interacting factors likely regulate wood decomposition processes. Multifactorial field experiments are needed to examine the physical, chemical, and biological factors controlling wood decompositio

Strong quasi-particle tunneling study in the paired quantum Hall states

The quasi-particle tunneling phenomena in the paired fractional quantum Hall states are studied. A single point-contact system is first considered. Because of relevancy of the quasi-particle tunneling term, the strong tunneling regime should be investigated. Using the instanton method it is shown that the strong quasi-particle tunneling regime is described as the weak electron tunneling regime effectively. Expanding to the network model the paired quantum Hall liquid to insulator transition is discussed

Flow Phase Diagram for the Helium Superfluids

The flow phase diagram for He II and $^3$He-B is established and discussed based on available experimental data and the theory of Volovik [JETP Letters {\bf{78}} (2003) 553]. The effective temperature - dependent but scale - independent Reynolds number $Re_{eff}=1/q=(1+\alpha')/\alpha$, where $\alpha$ and $\alpha'$ are the mutual friction parameters and the superfluid Reynolds number characterizing the circulation of the superfluid component in units of the circulation quantum are used as the dynamic parameters. In particular, the flow diagram allows identification of experimentally observed turbulent states I and II in counterflowing He II with the turbulent regimes suggested by Volovik.Comment: 2 figure