10,000 publications from this institution
A localization technique using reliable, highly accurate, robust, inexpensive light beam sensors designed for mechanical assembly and manufacturing is presented. The technique involves passing polyhedral objects through a set of crossed beams and storing the positions when any beam is broken or reconnects. The geometrical constraints simplify the correspondence problem, so that it is solvable in linear time or can be solved using a precomputed hash table. The global minimum least-squared error pose is computed exactly using methods from algebra and numerical analysis. The limitations of this technique result from the beam sensor's limitations.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
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Entanglement properties of excited eigenstates (or of thermal mixed states) are difficult to study with conventional analytical methods. We approach this problem for random spin chains using a recently developed real-space renormalization group technique for excited states ("RSRG-X"). For the random $XX$ and quantum Ising chains, which have logarithmic divergences in the entanglement entropy of their (infinite-randomness) critical ground states, we show that the entanglement entropy of excited eigenstates retains a logarithmic divergence while the mutual information of thermal mixed states does not. However, in the $XX$ case the coefficient of the logarithmic divergence extends from the universal ground-state value to a universal interval due to the degeneracy of excited eigenstates. These models are noninteracting in the sense of having free-fermion representations, allowing strong numerical checks of our analytical predictions.
Abstract Die Insertion ungesättigter Liganden in M‐C‐ oder M‐H‐Bindungen verläuft über eine migratorische Insertion, die eine fundamentale metallorganische Reaktion ist. Jüngste Berichte bestätigen migratorische Insertionen von Alkenen in M‐O‐ und M‐N‐Bindungen im Verlauf von Alkenalkoxylierungen bzw. Alkenaminierungen. Wir geben hier einen Überblick über den Stand der Literatur und wollen außerdem betrachten, wie diese jüngsten Studien mit klassischen Experimenten der Bildung von C‐O‐ und C‐N‐Bindungen mit Alkenkomplexen später Übergangsmetalle zusammenhängen.
Abstract Polystyrol (Ia) kann zu (Ib) bromiert und dann nach Metallierung zu (Ic) mit Disulfiden (II) in die Thioether (III) übergeführt werden.
Abstract California is expected to experience great spatial/temporal variations evaporation. These variations arise from strong north‐south, east‐west gradients in rainfall and vegetation, strong interannual variability in rainfall (±30%) and strong seasonal variability in the supply and demand for moisture. We used the Breathing Earth System Simulator to evaluate the rates and sums of evaporation across California, over the 2001–2017 period. Breathing Earth System Simulator is a bottom‐up, biophysical model that couples subroutines that calculate the surface energy balance, photosynthesis, and stomatal conductance. The model is forced with high‐resolution remote sensing data (1 km).The questions we address are as follows: How much water is evaporated across the natural and managed ecosystems of California? How much does evaporation vary during the booms and busts in annual rainfall? and Is evaporation increasing with time due to a warming climate? Mean annual evaporation, averaged over the 2001–2017 period, was relatively steady (393 ± 21 mm/year) given the high interannual variation in precipitation (519 ± 140 mm/year). No significant trend in evaporation at the statewide level was detected over this time period, despite a background of a warming climate. Irrigated agricultural crops and orchards, at 1‐km scale, use less water than inferred estimates for individual fields. This leaves the potential for sharing water, a scarce resource, more equitably among competing stakeholders, for example, farms, fish, people, and ecosystems.
Este articulo relata como asumi el oficio etnografico, tropezando con el gimnasio de boxeo en Chicago, que es el escenario y el caracter central de mi estudio del boxeador profesional en el gueto negro norteamericano, y como disene el libro Entre las cuerdas tanto para desarrollar metodologicamente como para elaborar empiricamente el concepto clave de habitus de Pierre Bourdieu. Habitus es el topico de investigacion: el libro hace la diseccion de la forja de las disposiciones corporales y mentales que componen al pugilista competitivo en el crisol del gimnasio. Pero tambien es la herramienta de investigacion: la adquisicion practica de aquellas disposiciones por parte del analista tiene la funcion de vehiculo tecnico para penetrar mejor en su produccion social y su ensamblaje. El aprendizaje del sociologo es un espejo metodologico del aprendizaje experimentado por los sujetos empiricos del estudio; el primero es extraido para excavar mas profundamente en el ultimo y desenterrar su logica interna y sus propiedades subterraneas, y ambos a su vez prueban la robustez y fecundidad del habitus como guia para sondear las fuentes de la conducta social. Apropiadamente utilizado, el habitus no solo ilumina la abigarrada logica de la accion social, tambien fundamenta las variadas virtudes de la profunda inmersion en, y el entreveramiento carnal con, el objeto de la investigacion etnografica
Abstract Hydrodynamic pressures and structural response of concrete gravity dams, including dam‐reservoir interaction, due to the vertical component of earthquake ground motions are investigated. The response of the dam is approximated by the deformations in the fundamental mode of vibration, and the effects of deformability of bed rock on hydrodynamic pressures are recognized in the analysis. Expressions for the complex frequency response functions for the dam displacement, dam acceleration and lateral hydrodynamic force are derived. These results along with the Fast Fourier Transform algorithm are utilized to compute the time‐history of responses of dams of 100, 300 and 600 ft height, with full reservoir, for different values of elastic modulus of mass concrete: 3.0, 3.5, 4.0, 4.5 and 5.0 million psi, to the vertical component of El Centro, 1940, and Taft, 1952, ground motions. It is concluded that the hydrodynamic forces caused by vertical ground motion are affected substantially by damreservoir interaction and depend strongly on the modulus of elasticity of the dam. The dam response to the vertical component of ground motion is compared with that due to the horizontal component. It is concluded that because the vertical component of ground motion causes significant hydrodynamic forces in the horizontal direction on a vertical upstream face, responses to the vertical component of ground motion are of special importance in analysis of concrete gravity dams subjected to earthquakes.
