Alcatel-Lucent

About: Alcatel-Lucent is a based out in Stuttgart, Germany. It is known for research contribution in the topics: Signal & Network packet. The organization has 37003 authors who have published 53332 publications receiving 1430547 citations. The organization is also known as: Alcatel-Lucent S.A. & Alcatel.

Magnetoelectric phase diagrams of orthorhombic R MnO 3 ( R = Gd , Tb, and Dy)

Abstract: Magnetoelectric phase diagrams have been investigated for rare-earth manganites with orthorhombically distorted perovskite structure, $R{\mathrm{MnO}}_{3}$ ($R=\mathrm{Gd}$, Tb, and Dy). A variety of magnetic and electric phases emerge with varying $R$-site ion, temperature, and magnetic field in these systems. The magnetoelectric phase diagram varies sensitively with the direction of a magnetic field relative to the crystallographic axes. Although the ground state of ${\mathrm{GdMnO}}_{3}$ with the largest ionic radius of $R({r}_{R})$ is not ferroelectric in zero magnetic fields $(H=0)$, a ferroelectric phase with electric polarization $(P)$ along the $a$ axis appears by applying $H(g\ensuremath{\sim}1\phantom{\rule{0.3em}{0ex}}\mathrm{T})$ along the $b$ axis. Both ${\mathrm{TbMnO}}_{3}$ and ${\mathrm{DyMnO}}_{3}$ show a ferroelectric order with $P$ along the $c$ axis even at $H=0$ below a lock-in transition temperature where nonzero wave vectors for magnetic and lattice modulations become nearly constant. These systems also exhibit a flop of the ferroelectric polarization ($P\ensuremath{\Vert}c$ to $P\ensuremath{\Vert}a$) when $H$ is applied along the $a$ or $b$ axis. By contrast, the application of $H$ above $\ensuremath{\sim}10\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ along the $c$ axis completely suppresses the ferroelectricity in ${\mathrm{TbMnO}}_{3}$. Possible origins of the observed evolution of magnetoelectric phases are discussed in consideration of magnetism and lattice distortion in the perovskite rare-earth manganites.

Scaling and related techniques for geometry problems

Abstract: Three techniques in computational geometry are explored: Scaling solves a problem by viewing it at increasing levels of numerical precision; activation is a restricted type of update operation, useful in sweep algorithms; the Cartesian tree is a data structure for problems involving maximums and minimums. These techniques solve the minimum spanning tree problem in Rk1 and Rk

Large magnetoresistance in non-magnetic silver chalcogenides

Abstract: Several materials have been identified over the past few years as promising candidates for the development of new generations of magnetoresistive devices. These range from artificially engineered magnetic multilayers' and granular alloys, in which the magnetic-field response of interfacial spins modulates electron transport to give rise to 'giant' magnetoresistance, to the manganite peravskites, in which metal-insulator transitions driven by a magnetic field give rise to a `colossal' magnetoresistive response (albeit at very high fields). Here we describe a hitherto unexplored class of magnetoresistive compounds, the silver chalcogenides. At high temperatures, the compounds Ag_2S, Ag_2Se and Ag_2Te are superionic conductors; below similar to 400 K, ion migration is effectively frozen and the compounds are non-magnetic semiconductors that exhibit no appreciable magnetoresistance. We show that slightly altering the stoichiometry can lead to a marked increase in the magnetic response. At room temperature and in a magnetic field of similar to 55 kOe, Ag_(2+δ)Se and Ag_(2+δ)Te show resistance increases of up to 200%, which are comparable with the colossal-magnetoresistance materials. Moreover, the resistance of our most responsive samples exhibits an unusual linear dependence on magnetic field, indicating both a potentially useful response down to fields of practical importance and a peculiarly long length scale associated with the underlying mechanism.

Atomic-scale imaging of nanoengineered oxygen vacancy profiles in SrTiO3

Abstract: At the heart of modern oxide chemistry lies the recognition that beneficial (as well as deleterious) materials properties can be obtained by deliberate deviations of oxygen atom occupancy from the ideal stoichiometry. Conversely, the capability to control and confine oxygen vacancies will be important to realize the full potential of perovskite ferroelectric materials, varistors and field-effect devices. In transition metal oxides, oxygen vacancies are generally electron donors, and in strontium titanate (SrTiO3) thin films, oxygen vacancies (unlike impurity dopants) are particularly important because they tend to retain high carrier mobilities, even at high carrier densities. Here we report the successful fabrication, using a pulsed laser deposition technique, of SrTiO3 superlattice films with oxygen doping profiles that exhibit subnanometre abruptness. We profile the vacancy concentrations on an atomic scale using annular-dark-field electron microscopy and core-level spectroscopy, and demonstrate absolute detection sensitivities of one to four oxygen vacancies. Our findings open a pathway to the microscopic study of individual vacancies and their clustering, not only in oxides, but in crystalline materials more generally.

Interference aware routing in multi-radio wireless mesh networks

Abstract: We address the problem of interference aware routing in multi-radio infrastructure mesh networks wherein each mesh node is equipped with multiple radio interfaces and a subset of nodes serve as Internet gateways. We present a new interference aware routing metric - iAWARE that aids in finding paths that are better in terms of reduced interflow and intra-flow interference. We incorporate this metric and new support for multi-radio networks in the well known AODV routing protocol to design an enhanced AODV-MR routing protocol. We study the performance of our new routing metric by implementing it in our wireless testbed consisting of 12 mesh nodes. We show that iAWARE tracks changes in interfering traffic far better than existing well known link metrics such as ETT and IRU. We also demonstrate that our AODV-MR protocol delivers increased throughput in single radio and two radio mesh networks compared to similar protocol with WCETT and MIC routing metrics. We also show that in the case of two radio mesh networks, our metric achieves good intra-path channel diversity.