Microwave-specific heating of crystalline species in nuclear waste glass

The microwave heating of a crystal-free and a partially trevorite-crystallized nuclear waste glass simulant was evaluated. Our results show that a 500-mg monolith of partially crystallized waste glass can be heated from room temperature to above 1600°C within 2 minutes using a single-mode, highly focused, 2.45-GHz microwave, operating at 300 W. Using X-ray diffraction measurements, we show that trevorite is no longer detectable after irradiation and thermal quenching. When a crystal-free analog of the same waste glass simulant composition was exposed to the same microwave radiation, it could not be heated above 450°C regardless of the heating time. The reduction in crystalline content achieved by selectively heating spinels in the presence of glass suggests that microwave-specific heating should be further explored as a technique for remediating crystal accumulation in a glass melt.     

BUBBLE MEASUREMENTS IN A GAS-LIQUID JET

Measurements have been carried out in the developing and fully developed regions of a free, axisymmetric, isothermal, air-water, bubbly jet. Three experiments have been conducted at a fixed jet-exit Reynolds number and gas superficial velocity using three different bubble injector assemblies producing bubbles of moderately different average sizes and size distributions. The volume fraction of the bubbly jet flow examined in this study is low and the resulting dispersed flow is dilute. A one-component Phase-Doppler Velocimetry system has been employed to measure bubble size and velocity non-intrusively. Visual data collected simultaneously with the light-scattering measurements were analyzed with the aid of image processing and used to verify the trends portrayed by the light-scattering measurements and to determine average bubble size. Our measurements show that, even in the dilute flow examined here, differences in initial bubble-size and size distribution can influence the RMS velocity fluctuations of the bubbles, particularly in the jet development region. The average bubble velocities are less sensitive. Evidence that the development pattern of the jet near the exit is affected by the presence of the bubbles is also presented. Near the exit of the jet, bubbles are shown to be ejected laterally outside the jet due to the significant lift force caused by the high velocity gradient in the axisymmetric shear layer. The observed sensitivity of the bubble flow to size-related parameters and initial conditions in this dilute case, indicates that discrepancies in previous measurements of dispersed, bubbly flows could be attributed to different size characteristics and/or initial conditions.     

采用DGS降低相位噪声和提高输出功率的倒扣集成振荡器

设计了一种新型的缺陷接地结构(DGS)并将之应用到倒扣集成毫米波振荡器中.分析并比较了具有DGS结构和没有DGS结构的两种振荡器性能.测试数据显示具有DGS结构的振荡器与没有DGS结构的振荡器相比,相位噪声降低4～6dB,输出功率增加0.8dBm.研究结果表明DGS结构嵌入到振荡器的谐振电路和输出端时,振荡器的相位噪声降低且输出功率增大.     

A concept for the generation of out-of-plane distortion from tailored FRP laminates

The phenomenon of thermally induced distortions in unsymmetrical laminates is well understood, and it may be shown that a square, unsymmetrical 0.90 laminate will tend to form two stable geometries with a snap-through phenomenon between them. This paper discusses laminates in which at each point the lay-up is symmetrical across the laminate mid-plane, but which still exhibit multiple stable geometries. The number of stable geometries can be controlled by the details of the lay-up from the minimum of two to, in principle, an unlimited number. In addition it will be shown how a similar process can be used to generate multiple stable stress states and geometries in unidirectional laminates. This paper represents a very preliminary experimental investigation of the design space available for such composite laminates. Possible applications of composites with multiple stable geometries are noted.     

Use of pooled time series in the study of naturally occurring clinical events and problem behavior in a foster care setting.

Pooled time series is an underused analytic technique with the potential to increase researchers' ability to exploit clinical data. This article demonstrates the value of pooled time series by analyzing the behavior of youths in a specialized foster care treatment setting in response to a naturally occurring clinical event: changes in the number of youths living together in a treatment foster care setting. Pooled time series moves beyond typical clinical analyses with an increased capability of controlling statistically for complex within-S effects and with a clinically useful measure of effect size. The complexity of the intra-S data made it virtually impossible to determine the relevant significance (i.e., clinical meaning) of the clinical event by the use of standard n?=?1 visual analysis procedures or standard statistical methods (e.g., chi square). After things such as autocorrelation and individual time trends were statistically controlled, each additional youth increased the number of problematic behaviors by one behavior per youth per day on the Parent Daily Report. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A quasi-two-dimensional electrochemistry modeling tool for planar solid oxide fuel cell stacks

A quasi-two-dimensional numerical model is presented for the efficient computation of the steady-state current density, species concentration, and temperature distributions in planar solid oxide fuel cell stacks. The model reduction techniques, engineering approximations, and numerical procedures used to simulate the stack physics while maintaining adequate computational speed are discussed. The results of the model for benchmark cases with and without on-cell methane reformation are presented with comparisons to results from other research described in the literature. Simulations results for a multi-cell stack have also been demonstrated to show capability of the model on simulating cell to cell variation. The capabilities, performance, and scalability of the model for the study of large multi-cell stacks are then demonstrated.     

xLi2MnO3·(1 − x)LiMO2 blended with LiFePO4 to achieve high energy density and pulse power capability

A lithium-ion positive electrode is proposed that contains both high energy density and efficient pulse power capability, even at low state-of-charge (SOC). The pulse power capability at low SOC is attractive for applications, such as plug-in hybrid electric vehicles (PHEVs), which require pulse power operation over the entire useable SOC window. A lithium- and manganese-rich transition-metal layered-oxide (LMR-NMC), also classified as a layered-layered oxide material, is blended with a lithium iron phosphate (LFP) to achieve a potentially low-cost, high-performance electrode. The LMR-NMC material provides high energy by delivering cathode material gravimetric energy densities greater than 890 Wh kg⁻¹. The pulse power capability of this material at low SOC is greatly improved by incorporating a modest quantity of LFP. The LFP serves as an internal redox couple to charge and discharge the more rate-limited LMR-NMC material at moderate to low SOCs.     

Simplified calculation of the area specific impedance for battery design

Battery design is a critical aspect of material and system development that leads to the commercialization of effective electrochemical energy storage systems. Successful modeling of battery designs relies upon accurate calculation of the area specific impedance (ASI). A simplified calculation of the ASI is presented that accounts for physical limitations without performing computationally expensive calculations. The limiting currents for transport within the electrolyte and within the intercalation materials are implemented into a linear form of the Butler-Volmer equation to calculate the interfacial impedance. Lithium-ion batteries are then designed to examine the effect of power to energy ratio on battery dimensions. A large ASI is shown to be detrimental to battery design regardless if the increase in impedance results from mass transport limitations or a reduction in electrochemical active area due to small electrode loadings. The smaller electrochemical active area does not increase the voltage losses of a battery when a constant C-rate is maintained. However, the higher ASI values from low electrode loadings require a larger separator and current collector area resulting in a greater battery volume and weight to achieve similar energy and power requirements when compared to a system with a lower ASI.     

Mapping the thermal distribution within a silica preform tube using regenerated fibre Bragg gratings

The temperature profile of the reaction zone inside the silica substrate tube during thermal heating with a H₂/O₂ flame under conditions identical to those used in the fabrication of optical fibre preforms using a modified chemical vapour deposition lathe has been characterised with ultra-high temperature stable regenerated optical fibre Bragg gratings. Experimental and theoretical results indicate a significant drop in temperature – up to several hundred degrees – across the tube wall from outside to inside. These results are in contradiction with the broadly accepted assumption that there is no significant thermal gradient across the tube itself. An array of regenerated gratings demonstrates that optical fibre grating based sensing can achieve distributed ultra-high temperature mapping and monitoring in harsh environments.     

National geodatabase of tidal stream power resource in USA

A geodatabase of tidal constituents is developed to present the regional assessment of tidal stream power resource in the USA. Tidal currents are numerically modeled with the Regional Ocean Modeling System (ROMS) and calibrated with the available measurements of tidal current speeds and water level surfaces. The performance of the numerical model in predicting the tidal currents and water levels is assessed by an independent validation. The geodatabase is published on a public domain via a spatial database engine with interactive tools to select, query and download the data. Regions with the maximum average kinetic power density exceeding 500 W/m² (corresponding to a current speed of ～1 m/s), total surface area larger than 0.5 km² and depth greater than 5 m are defined as hotspots and documented. The regional assessment indicates that the state of Alaska (AK) has the largest number of locations with considerably high kinetic power density, followed by, Maine (ME), Washington (WA), Oregon (OR), California (CA), New Hampshire (NH), Massachusetts (MA), New York (NY), New Jersey (NJ), North and South Carolina (NC, SC), Georgia (GA), and Florida (FL).