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101.
Field measurement of albedo for limited extent test surfaces 总被引:3,自引:0,他引:3
A new method is introduced for field measurement of surface albedo. This method consists of the use of a cylindrical shade ring made of opaque fabric with a known (low) albedo placed over a test surface. The albedo measurement is accomplished using two small pyranometers situated so that the downward-facing pyranometer receives radiation only from the test surface and the shade ring. The upward-facing pyranometer simultaneously records the incoming solar radiation. The radiation received by the downward-facing pyramometer is a combination of reflected radiation from shaded and unshaded portions of these two surfaces, requiring detailed accounting of the resulting view factor geometries. The method presented here improves upon past approaches by allowing for smaller sample sizes, minimizing errors associated with reflective properties of the surroundings, and allowing for accurate measurements even under partially cloudy skies. In addition to these methodological improvements we introduce an approach for estimating the uncertainty in the resulting albedo measurements. Results from field measurements are presented to validate the measurement protocol, and to compare its accuracy with the accuracy of a published standard. 相似文献
102.
Conversion coefficients were calculated for fluence-to-absorbed dose, fluence-to-equivalent dose, fluence-to-effective dose and fluence-to-gray equivalent for isotropic exposure of an adult female and an adult male to deuterons ((2)H(+)) in the energy range 10 MeV-1 TeV (0.01-1000 GeV). Coefficients were calculated using the Monte Carlo transport code MCNPX 2.7.C and BodyBuilder? 1.3 anthropomorphic phantoms. Phantoms were modified to allow calculation of the effective dose to a Reference Person using tissues and tissue weighting factors from 1990 and 2007 recommendations of the International Commission on Radiological Protection (ICRP) and gray equivalent to selected tissues as recommended by the National Council on Radiation Protection and Measurements. Coefficients for the equivalent and effective dose incorporated a radiation weighting factor of 2. At 15 of 19 energies for which coefficients for the effective dose were calculated, coefficients based on ICRP 1990 and 2007 recommendations differed by <3%. The greatest difference, 47%, occurred at 30 MeV. 相似文献
103.
Satadru Kashyap Kyle Griep John A. Nychka 《Materials science & engineering. C, Materials for biological applications》2011,31(4):762-769
Thermal treatment of bioactive glass ceramics dictates many important features such as microstructure, degree of crystallinity, mechanical properties, and biological response. This report investigates the heat treating conditions and the Avrami crystallization kinetics of melt cast bioactive glass 45S5 at 680 °C. Glass discs were found to follow three dimensional bulk crystallization kinetics (Avrami exponent n = 3). Partially crystallized bioactive glass samples were subjected to in vitro immersion testing to assist a comparative study of the adhesion capabilities of the mineralized layer formed on crystalline and amorphous regions. Higher adhesion of the mineralized layer to the amorphous region was observed as compared to its crystalline counterpart. Furthermore, Palmqvist crack propagation in amorphous and partially crystallized bioactive glass was studied. The crack paths in amorphous bioactive glass were straight, yet crack deflections were observed in the crystalline regions, likely attributed to different crystallographic orientations of crystals or residual thermal mismatch strains present in the bioglass ceramic. Hence, the mineralized layer interfacial fracture toughness and bulk fracture toughness of bioglass ceramics are different from their amorphous counterpart. 相似文献
104.
Relaxor/Ferroelectric Composites: A Solution in the Quest for Practically Viable Lead‐Free Incipient Piezoceramics
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Claudia Groh Daniel J. Franzbach Wook Jo Kyle G. Webber Jens Kling Ljubomira A. Schmitt Hans‐Joachim Kleebe Soon‐Jong Jeong Jae‐Shin Lee Jürgen Rödel 《Advanced functional materials》2014,24(3):356-362
Recently developed lead‐free incipient piezoceramics are promising candidates for off‐resonance actuator applications with their exceptionally large electromechanical strains. Their commercialization currently faces two major challenges: high electric field required for activating the large strains and large strain hysteresis. It is demonstrated that design of a relaxor/ferroelectric composite provides a highly effective way to resolve both challenges. Experimental results in conjunction with numerical simulations provide key parameters for the development of viable incipient piezoceramics. 相似文献
105.
Rebecca S. Hayden Jean‐Philippe Fortin Benjamin Harwood Balajikarthick Subramanian Kyle P. Quinn Irene Georgakoudi Alan S. Kopin David L. Kaplan 《Advanced functional materials》2014,24(4):472-479
The goals of the present study are to establish an in vitro co‐culture model of osteoblast and osteoclast function and to quantify the resulting bone remodeling. The bone is tissue engineered using well‐defined silk protein biomaterials in 2D and 3D formats in combination with human cells. Parathyroid hormone (PTH) and glucose‐dependent insulinotropic peptide (GIP) are selected because of their roles in bone remodeling for expression in tethered format on human mesenchymal stem cells (hMSCs). The cell‐modified biomaterial surfaces are reconstructed from scanning electron microscopy images into 3D models for quantitative measurement of surface characteristics. Increased calcium deposition and surface roughness are found in 3D surface models of silk protein films remodeled by co‐cultures containing tethered PTH, and decreased surface roughness is found for the films remodeled by tethered GIP co‐cultures. Increased surface roughness is not found in monocultures of hMSCs expressing tethered PTH, suggesting that osteoclast‐osteoblast interactions in the presence of PTH signaling are responsible for the increased mineralization. These data point towards the design of in vitro bone models in which osteoblast‐osteoclast interactions are mimicked for a better understanding of bone remodeling. 相似文献
106.
Studies of anxiety suggest that threat stimuli can be identified preattentively, but this conclusion is questionable because of possible low-level perceptual confounds. Two experiments used visual search tasks in which abstract shapes were conditioned to carry neutral or negative valence. Experiment 1 found generally faster responses to threat-associated abstract stimuli but no evidence that they were detected preattentively, irrespective of trait anxiety level. A similar pattern was found in Experiment 2, in which individuals high in snake or spider fear showed no evidence of preattentive detection of abstract stimuli associated with their feared object. In contrast, implicit behavioral measures showed significant effects of conditioning, demonstrating that targets associated with threat were negatively evaluated in these experiments. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
107.
JR Petrie AD Morris K Minamisawa TE Hilditch HL Elliott M Small J McConnell 《Canadian Metallurgical Quarterly》1998,83(5):1552-1557
Dietary sodium restriction has a variety of effects on metabolism, including activation of the renin-angiotensin system. Angiotensin II has complex metabolic and cardiovascular effects, and these may be relevant to the effects of both nonpharmacological and pharmacological interventions in noninsulin-dependent diabetes mellitus (NIDDM). We have assessed the effect of dietary sodium restriction on insulin sensitivity and endogenous glucose production in eight normotensive patients with diet-controlled NIDDM who underwent hyperinsulinemic clamp studies in a randomized, double-blind, placebo-controlled cross-over protocol after two 4-day periods on sodium replete (160 mmol/day) and sodium deplete (40 mmol/day) diets. Mean +/- SD 24-h urinary sodium was 197 +/- 76.0 mmol (replete) and 67 +/- 19.5 mmol (deplete), P = 0.03. Insulin sensitivity was 42.0 +/- 11.3 mumol/kg.min (replete) and 37.0 +/- 11.6 mumol/kg.min (deplete), P = 0.04 (a reduction of 12%). Blood pressure was 130 +/- 21/78 +/- 11 mmHg (replete) and 128 +/- 12/73 +/- 10 mmHg (deplete). Dietary sodium restriction may result in a decrease in peripheral insulin sensitivity in normotensive patients with NIDDM, possibly via an elevation in prevailing angiotensin II concentrations. 相似文献
108.
Fatty acid carbons are well-resolved in13C nuclear magnetic resonance (NMR) spectra of lipid extracts, but application of this methodology to the metabolism of13C-labelled fatty acids has not yet been reported. In the present study,13C NMR was used to monitor the presence of 98% [U-13C]eicosapentaenoic acid (EPA) in liver and carcass lipids 24 h after it had been injected into the stomach of a rat. Natural
abundance13C NMR spectra of liver total fatty acid extracts were obtained from four control rats for comparison. At 24 h post-injection,
quantitative high resolution13C NMR showed13C enrichment in liver fatty acid extracts was present mainly at olefinic and at the n−1 to n−4 carbons, but13C signal intensities for C−1 to C−4 of [U-13C]EPA were markedly reduced or absent. Small13C resonances, possibly indicative of some13C incorporation into docosahexaenoic acid and saturated or monounsaturated fatty acids, were present in spectra of liver fatty
acids. Liver and carcass fatty acid composition was similar in both the controls and the EPA-injected rat, suggesting little
accumulation of the injected [U-13C]EPA after 24 h. We conclude that the carbon-specific data provided by13C NMR of lipid extracts may be useful in monitoring the fate of individual carbons during tracer studies using13C-labelled fatty acids. 相似文献
109.
Lateral Resistance of Full-Scale Pile Cap with Gravel Backfill 总被引:1,自引:0,他引:1
A static lateral load test was performed on a full-scale 3×3 pile group driven in saturated low-plasticity silts and clays. The steel pipe piles were attached to a concrete pile cap which created a “fixed-head” end constraint. A gravel backfill was compacted in place on the backside of the cap. Lateral resistance was therefore provided by pile–soil–pile interaction, as well as base friction and passive pressure on the cap. In this case, passive resistance contributed about 40% of the total resistance. The log–spiral method provided the best agreement with measured resistance. Estimates of passive pressure computed using the Rankine method significantly underestimated the resistance while the Coulomb method overestimated resistance. The cap movement required to fully mobilize passive resistance in the gravel backfill was about 6% of the cap height. This is somewhat larger than reported in other studies likely due to the underlying clay layer. The p-multipliers developed for the free-head pile group provided reasonable estimates of the pile–soil–pile resistance for the fixed-head pile group once gaps adjacent to the pile were considered. 相似文献
110.
Adhesive Bonding of Aluminum Alloys 总被引:1,自引:0,他引:1
Edward M. Petrie Author Vitae 《Metal Finishing》2007,105(9):49-56