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Sequential, adaptive, and gradient diffusion filters are implemented into spatial multiscale three-dimensional variational data assimilation (3DVAR) as alternative schemes to model background error covariance matrix for the common...
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Sequential, adaptive, and gradient diffusion filters are implemented into spatial multiscale three-dimensional variational data assimilation (3DVAR) as alternative schemes to model background error covariance matrix for the commonly used correction scale method, recursive filter method, and sequential 3DVAR. The gradient diffusion filter (GDF) is verified by a two-dimensional sea surface temperature (SST) assimilation experiment. Compared to the existing DF, the new GDF scheme shows a superior performance in the assimilation experiment due to its success in extracting the spatialmultiscale information. The GDF can retrieve successfully the longwave information over the whole analysis domain and the shortwave information over data-dense regions. After that, a perfect twin data assimilation experiment framework is designed to study the effect of the GDF on the state estimation based on an intermediate coupled model. In this framework, the assimilation model is subject to "biased" initial fields from the "truth" model. While the GDF reduces the model bias in general, it can enhance the accuracy of the state estimation in the region that the observations are removed, especially in the South Ocean. In addition, the higher forecast skill can be obtained through the better initial state fields produced by the GDF.
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NIST produces large-format, dual-polarization-sensitive detector arrays for a broad range of frequencies (30-1400 GHz). Such arrays enable a host of astrophysical measurements. Detectors optimized for cosmic microwave background o...
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NIST produces large-format, dual-polarization-sensitive detector arrays for a broad range of frequencies (30-1400 GHz). Such arrays enable a host of astrophysical measurements. Detectors optimized for cosmic microwave background observations are monolithic, polarization-sensitive arrays based on feedhorn and planar Nb antenna-coupled transition-edge superconducting (TES) bolometers. Recent designs achieve multiband, polarimetric sensing within each spatial pixel. In this proceeding, we describe our multichroic, feedhorn-coupled design; demonstrate performance at 70-380 GHz; and comment on current developments for implementation of these detector arrays in the advanced Atacama Cosmology Telescope receiver
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This report describes a project to improve photovoltaic fabrics. It had four objectives: 1) Efficiency - make PV wires on a continuous basis that exhibit 7% efficiency; 2) Automated Welding - demonstrate an automated means of inte...
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This report describes a project to improve photovoltaic fabrics. It had four objectives: 1) Efficiency - make PV wires on a continuous basis that exhibit 7% efficiency; 2) Automated Welding - demonstrate an automated means of interconnecting the electrodes of one wire to the electrodes of a neighboring wire; 3) Weaving - fabric to determine the optimum wire density, relative to the co-woven inert yarn, for power production, flexibility, and wearability; 4) Battery Charging - produce fabrics that are able to charge 4AA batteries within 4 hours of exposure to direct sunlight (AM1.5). Over the duration of the project we demonstrated PV efficiency ranging from 5.04% (wire on a black background) to >8% efficiency on a white cloth background. A bare primary electrode on a nano-silver coating exhibited an efficiency of 6.45%. This high level of performance was accomplished by means of high performance active layer polymers, stainless steel electrodes with lower resistivity, optimized coating formulations for all layers, a new cladding formulation, and process optimization. We supplied several thousand feet of high performance PV wire for weaving trials and fabric delivery.
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ACTPol is the polarization-sensitive receiver on the Atacama Cosmology Telescope. ACTPol enables sensitive millimeter wavelength measurements of the temperature and polarization anisotropies of the Cosmic Microwave Background (CMB...
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ACTPol is the polarization-sensitive receiver on the Atacama Cosmology Telescope. ACTPol enables sensitive millimeter wavelength measurements of the temperature and polarization anisotropies of the Cosmic Microwave Background (CMB) at arcminute angular scales. These measurements are designed to explore the process of cosmic structure formation, constrain or determine the sum of the neutrino masses, probe dark energy, and provide a foundation for a host of other cosmological tests. We present an overview of the first season of ACTPol observations focusing on the optimization and calibration of the first detector array as well as detailing the on-sky performance.
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The international Muon Ionization Cooling Experiment (MICE) aims at demonstrating transverse cooling of muon beams by ionization. The ionization cooling channel of MICE requires eight 201 MHz normal conducting RF cavities to compe...
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The international Muon Ionization Cooling Experiment (MICE) aims at demonstrating transverse cooling of muon beams by ionization. The ionization cooling channel of MICE requires eight 201 MHz normal conducting RF cavities to compensate the longitudinal beam energy loss in the cooling channel. In this paper, we present the recent progress on the electropolishing work on MICE RF cavity at LBNL, which is intended to improve the cavity performance in the presence of strong external magnetic field, and the RF simulation with SLAC’s ACE3P code to study the multipacting effects in the cavity and at the coupler regions with the influence from the external magnetic field.
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University of Chinese Academy of Sciences (UCAS) participated in the first task, namely temporally-anchored ad hoc retrieval in Microblog track, aiming to efficiently and effectively retrieve tweets. Based on the conventional appl...
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University of Chinese Academy of Sciences (UCAS) participated in the first task, namely temporally-anchored ad hoc retrieval in Microblog track, aiming to efficiently and effectively retrieve tweets. Based on the conventional application of learning to rank, we incorporated a machine learning approach, such as logistic regression for selecting high-quality training data for improving the effectiveness. Except for the tweets' content features, we also used the features of the web information, external evidence, which is related with the URLS to improve the effectiveness.
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A variational method is used to estimate wave-affected parameters in a two-equation turbulence model with assimilating the temperature data into an ocean boundary layer model. Enhancement of turbulent kinetic energy dissipation du...
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A variational method is used to estimate wave-affected parameters in a two-equation turbulence model with assimilating the temperature data into an ocean boundary layer model. Enhancement of turbulent kinetic energy dissipation due to breaking waves is considered. The Mellor-Yamada 2.5 turbulence closure scheme (MY-2.5) with the two uncertain wave-affected parameters (wave energy factor alpha and Charnock coefficient Beta) is selected as the two-equation turbulence model for this study. Two types of experiments are conducted. First, within an identical synthetic experiment framework, the upper layer temperature "observations" in summer generated by a "truth" model are assimilated into a biased simulation model to investigate if (alpha, Beta) can be successfully estimated using the variational method. Second, real temperature profiles from the Ocean Weather Station Papa are assimilated into the biased simulation model to obtain the optimal wave-affected parameters. With the optimally-estimated parameters, the upper layer temperature can be well predicted. Furthermore, the horizontal distribution of the wave-affected parameters employed in a high order turbulence closure scheme can be estimated optimally by using the four-dimensional variational method that assimilates the upper layer available temperature data into an ocean general circulation model.
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Today's scientific challenges such as routes to a sustainable energy future, materials by design or biological and chemical environmental remediation methods, are complex problems that require the integration of a wide range of co...
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Today's scientific challenges such as routes to a sustainable energy future, materials by design or biological and chemical environmental remediation methods, are complex problems that require the integration of a wide range of complementary expertise to
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This paper reports on the research effort to improve the thermal conductivity of the copper-based alloy NARloy-Z (Cu-3 wt.%Ag-0.5 wt.% Zr), the state-of-the-art alloy used to make combustion chamber liners in regeneratively-cooled...
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This paper reports on the research effort to improve the thermal conductivity of the copper-based alloy NARloy-Z (Cu-3 wt.%Ag-0.5 wt.% Zr), the state-of-the-art alloy used to make combustion chamber liners in regeneratively-cooled liquid rocket engines, using nanotechnology. The approach was to embed high thermal conductivity multiwall carbon nanotubes (MWCNTs) and diamond (D) particles in the NARloy-Z matrix using powder metallurgy techniques. The thermal conductivity of MWCNTs and D have been reported to be 5 to 10 times that of NARloy-Z. Hence, 10 to 20 vol. % MWCNT finely dispersed in NARloy-Z matrix could nearly double the thermal conductivity, provided there is a good thermal bond between MWCNTs and copper matrix. Quantum mechanics-based modeling showed that zirconium (Zr) in NARloy-Z should form ZrC at the MWCNT-Cu interface and provide a good thermal bond. In this study, NARloy-Z powder was blended with MWCNTs in a ball mill, and the resulting mixture was consolidated under high pressure and temperature using Field Assisted Sintering Technology (FAST). Microstructural analysis showed that the MWCNTs, which were provided as tangles of MWCNTs by the manufacturer, did not detangle well during blending and formed clumps at the prior particle boundaries. The composites made form these powders showed lower thermal conductivity than the base NARloy-Z. To eliminate the observed physical agglomeration, tangled multiwall MWCNTs were separated by acid treatment and electroless plated with a thin layer of chromium to keep them separated during further processing. Separately, the thermal conductivities of MWCNTs used in this work were measured, and the results showed very low values, a major factor in the low thermal conductivity of the composite. On the other hand, D particles embedded in NARloy-Z matrix showed much improved thermal conductivity. Elemental analysis showed migration of Zr to the NARloy-Z-D interface to form ZrC, which appeared to provide a low contact thermal resistance.
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摘要 :
This paper reports on the research effort to improve the thermal conductivity of the copper-based alloy NARloy-Z (Cu-3 wt.%Ag-0.5 wt.% Zr), the state-of-the-art alloy used to make combustion chamber liners in regeneratively-cooled...
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This paper reports on the research effort to improve the thermal conductivity of the copper-based alloy NARloy-Z (Cu-3 wt.%Ag-0.5 wt.% Zr), the state-of-the-art alloy used to make combustion chamber liners in regeneratively-cooled liquid rocket engines, using nanotechnology. The approach was to embed high thermal conductivity multiwall carbon nanotubes (MWCNTs) and diamond (D) particles in the NARloy-Z matrix using powder metallurgy techniques. The thermal conductivity of MWCNTs and D have been reported to be 5 to 10 times that of NARloy-Z. Hence, 10 to 20 vol. % MWCNT finely dispersed in NARloy-Z matrix could nearly double the thermal conductivity, provided there is a good thermal bond between MWCNTs and copper matrix. Quantum mechanics-based modeling showed that zirconium (Zr) in NARloy-Z should form ZrC at the MWCNT-Cu interface and provide a good thermal bond. In this study, NARloy-Z powder was blended with MWCNTs in a ball mill, and the resulting mixture was consolidated under high pressure and temperature using Field Assisted Sintering Technology (FAST). Microstructural analysis showed that the MWCNTs, which were provided as tangles of MWCNTs by the manufacturer, did not detangle well during blending and formed clumps at the prior particle boundaries. The composites made form these powders showed lower thermal conductivity than the base NARloy-Z. To eliminate the observed physical agglomeration, tangled multiwall MWCNTs were separated by acid treatment and electroless plated with a thin layer of chromium to keep them separated during further processing. Separately, the thermal conductivities of MWCNTs used in this work were measured, and the results showed very low values, a major factor in the low thermal conductivity of the composite. On the other hand, D particles embedded in NARloy-Z matrix showed much improved thermal conductivity. Elemental analysis showed migration of Zr to the NARloy-Z-D interface to form ZrC, which appeared to provide a low contact thermal resistance. These results are consistent with the quantum mechanics-based model predictions. NARloy-Z-D composites have relatively high thermal conductivities and are promising for further development.
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