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81.
Srinivasan Raghavan Hsin Wang Ralph B. Dinwiddie Wallace D. Porter Robert Vaen Detlev Stöver Merrilea J. Mayo 《Journal of the American Ceramic Society》2004,87(3):431-437
Zirconia doped with 3.2–4.2 mol% (6–8 wt%) yttria (3–4YSZ) is currently the material of choice for thermal barrier coating topcoats. The present study examines the ZrO2 -Y2 O3 -Ta2 O5 /Nb2 O5 systems for potential alternative chemistries that would overcome the limitations of the 3–4YSZ. A rationale for choosing specific compositions based on the effect of defect chemistry on the thermal conductivity and phase stability in zirconia-based systems is presented. The results show that it is possible to produce stable (for up to 200 h at 1000°–1500°C), single (tetragonal) or dual (tetragonal + cubic) phase chemistries that have thermal conductivity that is as low (1.8–2.8W/m K) as the 3–4YSZ, a wide range of elastic moduli (150–232 GPa), and a similar mean coefficient of thermal expansion at 1000°C. The chemistries can be plasma sprayed without change in composition or deleterious effects to phase stability. Preliminary burner rig testing results on one of the compositions are also presented. 相似文献
82.
A series of templated carbons with various high surface areas (2033–3798 m2/g) have been prepared using various microporous zeolites as hard templates. Molecular hydrogen storage and spiltover hydrogen storage on these templated carbons were investigated and compared with superactivated carbon AX-21 and other reported porous carbon sorbents at 298 K and 100 atm. Two relationships between the surface areas of these carbons and their hydrogen capacities were obtained. The relationship between molecular hydrogen capacity and surface area showed a 0.23 wt.% H2/1000 m2/g of carbon sorbent at 298 K and 100 atm, indicating that merely increasing surface areas of the carbon sorbents cannot achieve a significant molecular hydrogen capacity at ambient temperature. Spiltover hydrogen storage was achieved by doping Pt nanoparticles (as dissociative hydrogen source) on these carbons (spiltover hydrogen receptor). Our first result on the relationship between the spiltover hydrogen capacity and surface area showed 0.4 wt.% H2/1000 m2/g of carbon sorbent at 298 K and 100 atm, which indicated that storage via spillover can lead to an average of 70% enhancement compared to molecular hydrogen storage. 相似文献
83.
Fluorescent protein tomography scanner for small animal imaging 总被引:2,自引:0,他引:2
Zacharakis G Ripoll J Weissleder R Ntziachristos V 《IEEE transactions on medical imaging》2005,24(7):878-885
Microscopy of fluorescent proteins has enabled unprecedented insights into visualizing gene expression in living systems. Imaging deeper into animals, however, has been limited due to the lack of accurate imaging methods for the visible. We present a novel system designed to perform tomographic imaging of fluorescent proteins through whole animals. The tomographic method employed a multiangle, multiprojection illumination scheme, while detection was achieved using a highly sensitive charge-coupled device camera with appropriate filters. Light propagation was modeled using a modified solution to the diffusion equation to account for the high absorption and high scattering of tissue at the visible wavelengths. We show that the technique can quantitatively detect fluorescence with sub millimeter spatial resolution both in phantoms and in tissues. We conclude that the method could be applied in tomographic imaging of fluorescent proteins for in vivo targeting of different diseases and abnormalities. 相似文献
84.
Ralph Skomski Priyanka Manchanda Ichiro Takeuchi Jun Cui 《JOM Journal of the Minerals, Metals and Materials Society》2014,66(7):1144-1150
The geometrical optimization of aligned hard-soft permanent-magnet nanocomposites is investigated by model calculations. Considered criteria are the shapes of the soft and c-axis-aligned hard phases, the packing fraction of the soft phase, and magnetostatic interactions. Taking into account that the energy product is enhanced via the volume fraction of the soft phase, subject to maintaining coercivity, we find that the best structures are soft-magnetic cubes as well as long rods with a square cross section. Comparing embedded soft cubes with embedded soft spheres of the same size, our nucleation-field analysis shows that the volume fraction of the soft phase is enhanced by 91%, with a coercivity reduction of only 25%. Magnetostatic interactions often but not always deteriorate the permanent-magnet performance, as exemplified by the example of MnBi:FeCo bilayers and multilayers. 相似文献
85.
Biography of Brigadier John Tiltman, who worked as a cryptologist for the British and American governments from 1920 to 1980. 相似文献
86.
Ralph F. Bogardus 《History of Photography》2013,37(3):179-196
Abstract It is little disputed that the invention of photography had a pervasive, jarring impact on society and culture during the years following its introduction to the world. The influence of the medium on visual artists has already been widely discussed, but study of its literary consequences has only recently begun. Photography did not go unnoticed by writers; commentary on the revolutionary medium appears frequently in journal entries, letters, essays, and fiction. Writers such as Emerson, Thoreau, Poe, Holmes, and Baudelaire responded to it with both delight and anger, lucidity and confusion. Occasionally, even, a writer such as Emile Zola took up the camera himself and made pictures, but the closest that most writers came to photographing was through their mode of writing - their journalism, travel literature, and realist fiction1. 相似文献
87.
Efficient real-time trajectory tracking 总被引:1,自引:0,他引:1
Ralph Lange Frank Dürr Kurt Rothermel 《The VLDB Journal The International Journal on Very Large Data Bases》2011,20(5):671-694
Moving objects databases (MOD) manage trajectory information of vehicles, animals, and other mobile objects. A crucial problem
is how to efficiently track an object’s trajectory in real-time, in particular if the trajectory data is sensed at the mobile
object and thus has to be communicated over a wireless network. We propose a family of tracking protocols that allow trading
the communication cost and the amount of trajectory data stored at a MOD off against the spatial accuracy. With each of these
protocols, the MOD manages a simplified trajectory that does not deviate by more than a certain accuracy bound from the actual
movement. Moreover, the different protocols enable several trade-offs between computational costs, communication cost, and
the reduction in the trajectory data: Connection-Preserving Dead Reckoning minimizes the communication cost using dead reckoning, a technique originally designed for tracking an object’s current position.
Generic Remote Trajectory Simplification (GRTS) further separates between tracking of the current position and simplification of the past trajectory and can be realized
with different line simplification algorithms. For both protocols, we discuss how to bound the space consumption and computing
time at the moving object and thereby present an effective compression technique to optimize the reduction performance of
real-time line simplification in general. Our evaluations with hundreds of real GPS traces show that a realization of GRTS
with a simple simplification heuristic reaches 85–90% of the best possible reduction rate, given by retrospective offline
simplification. A realization with the optimal line simplification algorithm by Imai and Iri even reaches more than 97% of
the best possible reduction rate. 相似文献
88.
89.
A method is described for the determination of tributyltin (TBT) in NRCC sediment CRM PACS-2 by isotope dilution (ID) analysis using HPLC-ICPMS. Reverse spike ID analysis was performed to determine the accurate concentration of a 117Sn-enriched TBT spike using a well-characterized natural abundance TBT standard. The accuracy of the latter is critical for obtaining reliable results. A unique approach, using hydride generation GC/MS, was developed to quantify the inorganic Sn and dibutyltin impurities in the natural abundance TBT standard. The true natural abundance TBT standard concentration was obtained following correction for these impurities. The total Sn concentration in the natural abundance TBT standard was determined by ID analysis using an enriched inorganic 117Sn following closed vessel mixed-acid digestion. Calibration of the enriched inorganic 117Sn standard was achieved by reverse ID analysis against a natural abundance inorganic tin standard prepared from the high-purity metal. An overall uncertainty associated with the present method was estimated, to which the uncertainties arising from measurement of the natural abundance TBT concentration, from the measurement of the isotope ratio in the spiked sample and in the reverse ID calibration solutions, and from estimation of the extraction efficiency were the main contributors. A concentration of 1.018 +/- 0.054 mg kg(-1) (expanded uncertainty, k = 2) as tin was obtained for TBT in PACS-2 using the present method, in excellent agreement with the certified value of 0.98 +/- 0.13 mg kg(-1) (95% confidence interval). A TBT concentration of 0.97 +/- 0.11 mg kg(-1) (expanded uncertainty, k = 2) as tin in PACS-2 was determined using the standard additions technique. Much smaller expanded uncertainty was obtained with ID, clearly demonstrating its superiority in providing more accurate and precise results over the method of additions. A detection limit (3sigma) of 0.02 mg kg(-1) for TBT, based on a 0.5-g subsample, was obtained. 相似文献
90.
Addicks E Mazitschek R Giannis A 《Chembiochem : a European journal of chemical biology》2002,3(11):1078-1088
Integrins, a widely expressed family of heterodimeric cell surface adhesion proteins, are expressed in a variety of cell types. They play a decisive role in cell-cell adhesion or cell to extracellular matrix adhesion events. Antagonists of alpha(v)beta(3) or alpha(IIb)beta(3) integrin may have a potential use in suppression of pathological processes. We present the synthesis of novel tricyclic benzodiazepinedione-based RGD analogues, which were subsequently tested in a solid-phase receptor assay in order to investigate their binding affinities towards alpha(v)beta(3) and alpha(IIb)beta(3) integrin. 相似文献