4,199 research outputs found

    Quantitative Kinetic Energy Estimated from Disdrometer Signal

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    The kinetic energy of the rain drops was predicted in a relation between the rain rate and rain quantity, derived directly from the rain drop size distribution (DSD), which had been measured by a disdrometer located in the eastern state of Alagoas-Brazil. The equation in the form of exponential form suppressed the effects of large drops at low rainfall intensity observed at the beginning and end of the rainfall. The kinetic energy of the raindrop was underestimated in almost rain intensity ranges and was considered acceptable by the performance indicators such as coefficient of determination, average absolute error, percent relative error, mean absolute error, root mean square error, Willmott's concordance index and confidence index

    Hubbard-model description of the high-energy spin-spectral-weight distribution in La(2)CuO(4)

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    The spectral-weight distribution in recent neutron scattering experiments on the parent compound La2_2CuO4_4 (LCO), which are limited in energy range to about 450\,meV, is studied in the framework of the Hubbard model on the square lattice with effective nearest-neighbor transfer integral tt and on-site repulsion UU. Our study combines a number of numerical and theoretical approaches, including, in addition to standard treatments, density matrix renormalization group calculations for Hubbard cylinders and a suitable spinon approach for the spin excitations. Our results confirm that the U/8tU/8t magnitude suitable to LCO corresponds to intermediate UU values smaller than the bandwidth 8t8t, which we estimate to be 8t2.368t \approx 2.36 eV for U/8t0.76U/8t\approx 0.76. This confirms the unsuitability of the conventional linear spin-wave theory. Our theoretical studies provide evidence for the occurrence of ground-state d-wave spinon pairing in the half-filled Hubbard model on the square lattice. This pairing applies only to the rotated-electron spin degrees of freedom, but it could play a role in a possible electron d-wave pairing formation upon hole doping. We find that the higher-energy spin spectral weight extends to about 566 meV and is located at and near the momentum [π,π][\pi,\pi]. The continuum weight energy-integrated intensity vanishes or is extremely small at momentum [π,0][\pi,0]. This behavior of this intensity is consistent with that of the spin waves observed in recent high-energy neutron scattering experiments, which are damped at the momentum [π,0][\pi,0]. We suggest that future LCO neutron scattering experiments scan the energies between 450 meV and 566 meV and momenta around [π,π][\pi,\pi].Comment: 23 pages, 5 figure

    Charge Influence On Mini Black Hole's Cross Section

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    In this work we study the electric charge effect on the cross section production of charged mini black holes (MBH) in accelerators. We analyze the charged MBH solution using the {\it fat brane} approximation in the context of the ADD model. The maximum charge-mass ratio condition for the existence of a horizon radius is discussed. We show that the electric charge causes a decrease in this radius and, consequently, in the cross section. This reduction is negligible for protons and light ions but can be important for heavy ions.Comment: 4 pages, 0 figure. To be published in Int. J. Mod. Phys. D

    Water Law in the United States and Brazil - Climate Change and Two Approaches to Emerging Water Poverty

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    This article examines two of the major water legal regimes in theAmericas—that of Brazil and the United States. Both countries haveextensive wet and dry regions and both hydro-regimes face a significantthreat from global warming. Brazil, for instance, is home to betweeneight and fifteen percent of the world’s fresh water, and its fast-growingeconomy and population present major challenges in management andallocation. The U.S. also faces major water allocation problems resultingfrom past settlement policies; unsustainable reclamation projects; andalso fast-growing domestic, industrial and agricultural demand. In the United States, water has traditionally been perceived as arenewable and limitless resource, a cultural legacy that has exerted apowerful influence on the nation’s common law. Similarly, in Brazil, thenotion of water as infinitely abundant drove water policies until theenactment of the Constitution in 1988. In both countries, however,hydrological realities have become impossible to ignore. Their respectivelaws and jurisprudence have begun shifting toward management andallocation systems that acknowledge the limited nature of the resource. This article surveys the two countries’ water regimes, offering abrief history of their evolution and then focusing on the challenges of thepresent. It examines how the notion of a strong private property rightin water is slowly (in the North-American case) and more abruptly (in the Brazilian case) evolving in the face of increased governmentalintervention. The article then turns to the challenges of climate change. InBrazil, policies that fail to take desertification into account may threatenthe country’s energy supply as well as the availability of potable water.In the United States, ignoring climate change in water management andallocation policies could significantly increase the existing water scarcityin the West and exacerbate the growing and already serious watershortage in the traditionally humid East

    A novel topology optimisation methodology for robust design of structural components considering material defects

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    This work outlines a new Topology Optimisation methodology whereby material defects are introduced at the earliest stage of the structural design process, leading to more robust final design solutions. We couple the Levelset Method and the Floating Node Method to capture a moving material boundary explicitly on the Finite Element mesh. A continuum design sensitivity analysis scheme based on a measure of the energy release rate is used to quantify the impact of the defect. We show how the structure is optimised to reduce this measure and mitigate the impact of the material defect on the overall response

    Space Shuttle program communication and tracking systems interface analysis

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    The Space Shuttle Program Communications and Tracking Systems Interface Analysis began April 18, 1983. During this time, the shuttle communication and tracking systems began flight testing. Two areas of analysis documented were a result of observations made during flight tests. These analyses involved the Ku-band communication system. First, there was a detailed analysis of the interface between the solar max data format and the Ku-band communication system including the TDRSS ground station. The second analysis involving the Ku-band communication system was an analysis of the frequency lock loop of the Gunn oscillator used to generate the transmit frequency. The stability of the frequency lock loop was investigated and changes to the design were reviewed to alleviate the potential loss of data due the loop losing lock and entering the reacquisition mode. Other areas of investigation were the S-band antenna analysis and RF coverage analysis
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