86,868 research outputs found
Criteri di intervento distribuito per la difesa idraulica. Un caso di studio
No full textViene illustrata l'efficacia, in termini di attenuazione del rischio idraulico, delle opere di sistemazione idraulica distribuite lungo l'asta principale di un corso d'acqua. La nota trae spunto dallo studio per la sistemazione dell'asta principale del fiume Pesa, affluente sinistro del fiume Arno, proposta con il Piano di Bonifica e Tutela del Territorio della Val di Pesa. Gli interventi studiati riguardano la realizzazione di casse di espansione attrezzate, il condiziona-mento semi-strutturale di aree soggette ad inondazione naturale, interventi vincolistici di tipo normativo e relativa rinaturazione delle aree di pertinenza fluviale. Gli effetti di tali interventi hanno mostrato una attenuazione media dei colmi di piena (TR=100 anni) lungo l’asta principale del 16 %, a fronte di opere a limitato impatto ambientale, eseguibili in modo progressivo nel tempo, con un impegno economico relativamente contenuto
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
[Newspaper Clipping: Author Claims Evidence of Second JFK Assassin #1]
No full textNewspaper article titled "Author Claims Evidence of Second JFK Assassin." The article states that author Richard J. Whalen concluded "that there is circumstantial evidence to support the theory of a second assassin in the shooting of President John F. Kennedy.
Reduced-order particle-in-cell simulations of a high-power magnetically shielded Hall thruster
No full textHigh-power magnetically shielded Hall thrusters have emerged in recent years to meet the needs of the next-generation on-orbit servicing and exploration missions. Even though a few such thrusters are currently undergoing their late-stage development and qualification campaigns, many unanswered questions yet exist concerning the behavior and evolution of the plasma in these large-size thrusters that feature an unconventional magnetic field topology. Noting the complex, multi-dimensional nature of plasma processes in Hall thrusters, high-fidelity particle-in-cell (PIC) simulations are optimal tools to study the intricate plasma behavior. Nonetheless, the significant computational cost of traditional multi-dimensional PIC schemes renders simulating the high-power thrusters without any physics-altering speed-up factors unfeasible. The novel reduced-order ‘quasi-2D’ PIC scheme enables a significant reduction in the computational cost requirement of the PIC simulations. Thus, in this article, we demonstrate the applicability of the reduced-order PIC for a cost-efficient, self-consistent study of the physics in high-power Hall thrusters by performing simulations of a 20 kW-class magnetically shielded Hall thruster along the axial-azimuthal and radial-azimuthal coordinates. The axial-azimuthal quasi-2D simulations are performed for three operating conditions in a rather simplified representation of the thruster’s inherently 3D configuration. Nevertheless, we have resolved self-consistently an unprecedented 650 μs of the discharge evolution without any ad-hoc electron mobility model, capturing several breathing cycles and approximating the experimental performance parameters with an accuracy of 70%-80% across the operating conditions. The radial-azimuthal simulations, carried out at three cross-sections corresponding to different axial locations within the discharge channel, have casted further light on the evolution of the azimuthal instabilities and the resulting variations in the electrons’ cross-field mobility and the plasma-wall interactions. Particularly, we observed the development of a long-wavelength, relatively low-frequency wave mode near the exit plane of the thruster’s channel that induces a notable electron transport and a significant ion heating
Also By The Same Author: AKTiveAuthor, a Citation Graph Approach to Name Disambiguation
No full textThe desire for definitive data and the semantic web drive for inference over heterogeneous data sources requires co-reference resolution to be performed on those data. In particular, name disambiguation is required to allow accurate publication lists, citation counts and impact measures to be determined. This paper describes a graph-based approach to author disambiguation on large-scale citation networks. Using self-citation, co-authorship and document source analyses, AKTiveAuthor clusters papers, achieving precision of 0.997 and recall of 0.818 over a test group of eight surname clusters
John F. Kennedy telegram to Roosevelt
No full textJersey Homesteads (later the Borough of Roosevelt) was established in the 1930s as an agro-industrial cooperative community. It was established specifically for urban Jewish garment workers, many of whom had emigrated from Europe. President John F. Kennedy sent a telegram to the citizens of Roosevelt, New Jersey, apologizing for not being able to attend the memorial dedication in honor of former President Franklin Delano Roosevelt. (Jersey Homesteads became Roosevelt in 1945 in honor of the president.) President Kennedy expressed his gratitude to the people of Roosevelt for constructing the memorial, and commented that it will serve as a constant reminder of Roosevelt's good works
Development status of the HT5k high voltage model
No full textSince 2013, SITAEL has been developing its 5kW-class Hall thruster unit, the HT5k-TU, comprising the HT5k thruster and the HC20 hollow cathode. Through several supporting projects, the thruster unit has undergone three design iterations and is now in the Engineering Model definition phase. As the design of the thruster unit evolved towards higher levels of maturity, multiple test campaigns were performed including several characterization tests, magnetic field topology optimization for life extension, tests with alternative propellants, assessment of operation in direct-drive mode, facility background pressure effects tests at two different pressure levels, thermal cycling and endurance test. As a result, the HT5k-TU thruster family cumulated more than 700 hrs of firing, demonstrating stable and efficient thruster operation in the power range of 3 to 7 kW. One important modification in the design of the HT5k thruster was the implementation of magnetic shielding of the discharge channel walls, eliminating in this way one main failure mode of the thruster. This improvement results in increasing the thruster lifetime by at least two orders of magnitude, making the thruster design further apt for station-keeping and deep-space robotic exploration missions of long lifetime. These scenarios typically necessitate operating the thruster at relatively-high specific impulses. However, operation of the thruster unit in the high-voltage range (500-800 V) require updating several design solutions, particularly from the perspective of voltage isolation and heat management. In this respect, to better understand the implications and requirements of high-voltage Hall thruster operation, the HT5k-TU models, both unshielded and shielded, were tested in this voltage range. The aim was to investigate the performance and stability of the thruster, in addition to better understanding the impacts from the design compatibility point of view. This paper presents an overview of the development activities performed on the various models of the HT5k-TU, focusing on the characterization results in the high-voltage regime. Furthermore, we also discuss the solutions devised for addressing the technological requirements of high-voltage Hall thruster's operation
Logarithmic variance profiles and the corresponding f-1 spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection
No full textWe report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014 and Pr ' 0:8. For Ra = 1:35x1014, 2(z) could be described well by a logarithmic dependence on the vertical position z in a range of z 1 < z < z 2 with z 1 ' 70 and z 2 = 0:1L. Here L=(2Nu) is the thickness of a thin thermal sublayer adjacent to the horizontal plate where the heat flux (denoted by the Nusselt number Nu) is carried mostly by thermal diffusion. In the log layer, we found that the temperature spectra had a significant frequency range over which P(f) f with close to 1. As Ra decreased, increased so that the log layer became thinner. At Ra = 2:05 1011, z 2 < z 1 and therefore there was no range for a log layer. Correspondingly, the temperature spectrum near the horizontal plate did not have the f1 scaling form either
Maine author Franklin F. Gould recalls his first glimpse of the outside world
No full textMaine author Franklin F. Gould recalls his first glimpse of the outside world as he relates how, as a young farm boy in the late 1800\u27s, he drove his father\u27s horses on an errand to an icebound river
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