Performance Evaluation of Vision-Based Algorithms for MAVs

An important focus of current research in the field of Micro Aerial Vehicles (MAVs) is to increase the safety of their operation in general unstructured environments. Especially indoors, where GPS cannot be used for localization, reliable algorithms for localization and mapping of the environment are necessary in order to keep an MAV airborne safely. In this paper, we compare vision-based real-time capable methods for localization and mapping and point out their strengths and weaknesses. Additionally, we describe algorithms for state estimation, control and navigation, which use the localization and mapping results of our vision-based algorithms as input.Comment: Presented at OAGM Workshop, 2015 (arXiv:1505.01065

Imaging nonequilibrium atomic vibrations with x-ray diffuse scattering

For over a century, x-ray scattering has been the most powerful tool for determining the equilibrium structure of crystalline materials. Deviations from perfect periodicity, for example due to thermal motion of the atoms, reduces the intensity of the Bragg peaks as well as produces structure in the diffuse scattering background. Analysis of the thermal diffuse scattering (TDS) had been used to determine interatomic force constants and phonon dispersion in relatively simple cases before inelastic neutron scattering became the preferred technique to study lattice dynamics. With the advent of intense synchrotron x-ray sources, there was a renewed interest in TDS for measuring phonon dispersion. The relatively short x-ray pulses emanating from these sources also enables the measurement of phonon dynamics in the time domain. Prior experiments on nonequilibrium phonons were either limited by time-resolution and/or to relatively long wavelength excitations. Here we present the first images of nonequilibrium phonons throughout the Brillouin zone in photoexcited III-V semiconductors, indium-phosphide and indium-antimonide, using picosecond time-resolved diffuse scattering. In each case, we find that the lattice remain out of equilibrium for several hundred picoseconds up to nanoseconds after laser excitation. The non-equilibrium population is dominated by transverse acoustic phonons which in InP are directed along high-symmetry directions. The results have wide implications for the detailed study of electron-phonon and phonon-phonon coupling in solids.Comment: 10 pages, 3 figure

Enquêtes sur les helminthes du dromadaire tchadien. Etude des strongyloses gastro-intestinales et de l'haemoncose à Haemoncus longistipes

Les auteurs ont procédé dans les zones Nord de la République du Tchad, au-delà du 13e parallèle, à l'autopsie de 132 dromadaires et à de nombreux examens hématologiques et coproscopiques. Les parasites rencontrés comprennent 22 espèces appartenant à 17 genres différents. Les plus fréquentes sont, dans l'ordre décroissant: Cephalopina titillator (72,6 p. 100), Haemonchus longistipes (72 p. 100), divers Anoplocephalidae agents du téniasis (47,1 p. 100), les Kystes d'Echinococcus granulosus (35,6 p. 100), Buckleyuris globulosa (34,8 p. 100), Oesophagostomum columbianum (28 p. 100), Strongyloides papillosus (22,7 p. 100) et de nombreux Trichostrongylidae et Heligmosomatidae (14,4 p. 100) Trichostrongylus vitrinus; Trichostrongylus probolurus; Impalaia nudicollis). Ces parasites sont associés dans 85 p. 100 des cas notamment avec Nématodes gastro-intestinaux. Ils agissent: - en prélevant du sang; - en modifiant certains métabolismes; - en irritant la muqueuse intestinale. Bien souvent helminthes et trypanosomes sont associés. Le taux de morbidité oscille autour de 90-100 p. 100. La mortalité annuelle est estimée à 4 p. 100 dans certaines zones du Nord-Est de la Républiqu

Activité du tétrochlorodifluoroéthone sur divers Trématodes et sa toxicité à l’égard des Ovins

Guilhon Jean, Graber M., Barnabé R. Activité du tétrachlorodifluoroéthane sur divers Trématodes et sa toxicité à l’égard des Ovins. In: Bulletin de l'Académie Vétérinaire de France tome 124 n°2, 1971. pp. 79-86

Birational cobordism invariance of uniruled symplectic manifolds

A symplectic manifold $(M,\omega)$ is called {\em (symplectically) uniruled} if there is a nonzero genus zero GW invariant involving a point constraint. We prove that symplectic uniruledness is invariant under symplectic blow-up and blow-down. This theorem follows from a general Relative/Absolute correspondence for a symplectic manifold together with a symplectic submanifold. A direct consequence is that symplectic uniruledness is a symplectic birational invariant. Here we use Guillemin and Sternberg's notion of cobordism as the symplectic analogue of the birational equivalence.Comment: To appear in Invent. Mat

Depinning transition of a directed polymer by a periodic potential: a d-dimensional solution

We study the depinning phase transition of a directed polymer in a $d$-dimensional space by a periodic potential localized on a straight line. We give exact formulas in all dimensions for the critical pinning we need to localize the polymer. We show that a bounded state can still arise even if, in average, the potential layer is not attractive and for diverging values of the potential on the repulsive sites. The phase transition is of second order.Comment: 11 Pages in LaTeX. Figures available from the authors. [email protected] (e-mail address

Curve counting via stable pairs in the derived category

For a nonsingular projective 3-fold $X$, we define integer invariants virtually enumerating pairs $(C,D)$ where $C\subset X$ is an embedded curve and $D\subset C$ is a divisor. A virtual class is constructed on the associated moduli space by viewing a pair as an object in the derived category of $X$. The resulting invariants are conjecturally equivalent, after universal transformations, to both the Gromov-Witten and DT theories of $X$. For Calabi-Yau 3-folds, the latter equivalence should be viewed as a wall-crossing formula in the derived category. Several calculations of the new invariants are carried out. In the Fano case, the local contributions of nonsingular embedded curves are found. In the local toric Calabi-Yau case, a completely new form of the topological vertex is described. The virtual enumeration of pairs is closely related to the geometry underlying the BPS state counts of Gopakumar and Vafa. We prove that our integrality predictions for Gromov-Witten invariants agree with the BPS integrality. Conversely, the BPS geometry imposes strong conditions on the enumeration of pairs.Comment: Corrected typos and duality error in Proposition 4.6. 47 page

Gate-defined graphene double quantum dot and excited state spectroscopy

A double quantum dot is formed in a graphene nanoribbon device using three top gates. These gates independently change the number of electrons on each dot and tune the inter-dot coupling. Transport through excited states is observed in the weakly coupled double dot regime. We extract from the measurements all relevant capacitances of the double dot system, as well as the quantized level spacing

Holomorphic anomaly equations and the Igusa cusp form conjecture

Let $S$ be a K3 surface and let $E$ be an elliptic curve. We solve the reduced Gromov-Witten theory of the Calabi-Yau threefold $S \times E$ for all curve classes which are primitive in the K3 factor. In particular, we deduce the Igusa cusp form conjecture. The proof relies on new results in the Gromov-Witten theory of elliptic curves and K3 surfaces. We show the generating series of Gromov-Witten classes of an elliptic curve are cycle-valued quasimodular forms and satisfy a holomorphic anomaly equation. The quasimodularity generalizes a result by Okounkov and Pandharipande, and the holomorphic anomaly equation proves a conjecture of Milanov, Ruan and Shen. We further conjecture quasimodularity and holomorphic anomaly equations for the cycle-valued Gromov-Witten theory of every elliptic fibration with section. The conjecture generalizes the holomorphic anomaly equations for ellliptic Calabi-Yau threefolds predicted by Bershadsky, Cecotti, Ooguri, and Vafa. We show a modified conjecture holds numerically for the reduced Gromov-Witten theory of K3 surfaces in primitive classes.Comment: 68 page