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91.
John J. A. Barry Marta M. C. G. Silva Sarah H. Cartmell Robert E. Guldberg Colin A. Scotchford Steven M. Howdle 《Journal of Materials Science》2006,41(13):4197-4204
Porous scaffold structures are used in tissue engineering to provide structural guidance for regenerating tissues. The use
of carbon dioxide (CO2) to create such scaffolds has received some attention in the past but many researchers believe that although CO2 processing of polymers can lead to porous scaffolds there is limited interconnectivity between the pores. In this study,
highly porous (greater than 85%) and well interconnected scaffolds were obtained in which the size, distribution and number
of pores could be controlled. This control was achieved by altering the rate of venting from polymer discs saturated with
CO2 under modest temperature and pressure. The polymer used is a blend of poly (ethyl methacrylate) and tetrahydrofurfuryl methacrylate
(PEMA/THFMA). This polymer system has shown promise for potential applications in cartilage repair. 相似文献
92.
Jae Hong Park Tae Yun Kwon Hyung Joon Kim Seung Rae Kim Dae Sung Yoon Chae-Il Cheon Hwan Kim Tae Song Kim 《Journal of Electroceramics》2006,17(2-4):565-572
The PZT thick film cantilever devices fabricated via MEMS process have much attraction because they are appropriate for biological
transducer or sensor, resulting from their large actuating force and relatively high sensitivity especially in liquid. By
means of resonance behavior, theoretical calculation and experimental verification of the PZT thick film cantilever devices
have not been studied before. Accordingly, we focused on the sensitivity analysis and interpretation of the PZT thick film
cantilevers in this study. Especially, the investigation for mass sensitivity of the PZT thick film cantilever is of importance
for physical, chemical and biological sensing application. The PZT thick film cantilever devices were constructed on Pt/TiO2/SiN
X
/Si substrates using screen printing method and MEMS process. The harmonic oscillation response (resonance frequency) was
measured using an optical laser interferometric vibrometer. The effect of cantilever geometry on the resonance frequency change
was investigated. Compared with the theoretical resonant frequency change by mass loading, the experimental resonant frequency
change of the PZT micromechanical thick film cantilever shows a variation of less than 2%. Mass sensitivities are estimated
to be 30.7, 57.1 and 152.0 pg/Hz for the 400 × 380 μm, 400 × 480 μm and 400 × 580 μm cantilever, respectively. 相似文献
93.
van den Brink Dani?lle; Brown Colin M.; Hagoort Peter 《Canadian Metallurgical Quarterly》2006,32(2):364
An event-related brain potential experiment was carried out to investigate the temporal relationship between lexical selection and the semantic integration in auditory sentence processing. Participants were presented with spoken sentences that ended with a word that was either semantically congruent or anomalous. Information about the moment in which a sentence-final word could uniquely be identified, its isolation point (IP), was compared with the onset of the elicited N400 congruity effect, reflecting semantic integration processing. The results revealed that the onset of the N400 effect occurred prior to the IP of the sentence-final words. Moreover, the factor early or late IP did not affect the onset of the N400. These findings indicate that lexical selection and semantic integration are cascading processes, in that semantic integration processing can start before the acoustic information allows the selection of a unique candidate and seems to be attempted in parallel for multiple candidates that are still compatible with the bottom-up acoustic input. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
94.
A castability model based on elemental solid-liquid partitioning in advanced nickel-base single-crystal superalloys 总被引:1,自引:0,他引:1
A castability model that accounts for the characteristic segregation behavior of constituent elements in Ni-base superalloys
has been developed and experimentally verified in production scale casting trials. The model ranks alloy compositions with
respect to their susceptibility to freckle formation during directional solidification. Thirty-nine distinct Ni-base single-crystal
superalloys encompassing a broad range of compositions were investigated to assess the influence of the constituent elements
on their solidification characteristics. Linear regression was applied to the fitted solid-liquid partition coefficients of
the major constituent elements to develop formulas capable of describing elemental interactions. The high-density refractory
elements Ta, W, and Re were found to segregate most severely during solidification. Increasing the amount of Cr and Mo in
high-refractory single-crystal alloys reduced the extent of W and Re microsegregation during solidification. This effect was
found to minimize the occurrence of freckle defects due to the corresponding decrease in the density inversion term, which
is effectively the driving force for thermosolutal convective instabilities known to cause macroscopic grain defects during
single-crystal solidification. Model predictions were validated using production scale casting trials where additions of 1.5
wt pct (1.9 at. pct) Cr and 3.0 wt pct (2.0 at. pct) Mo to a high-refractory superalloy more than halved the number of solidification-related
grain defects formed. These findings suggest that elemental interactions between Cr, Mo, W, and Re need to be considered when
optimizing alloys for high-temperature creep properties. 相似文献
95.
This paper reports on research carried out in 1999–2001 on the use of e-business applications in enterprise resource planning (ERP)-based organisations. Multiple structured interviews were used to collect data on 11 established organisations from a diverse range of industries. The findings are analysed according to the level of sophistication of e-business models and their transformational impact on the organisation. Early adopters of e-business show a trend towards cost reductions and administrative efficiencies from e-procurement and self-service applications used by customers and employees. More mature users focus on strategic advantage and generate this through an evolutionary model of organisational change. Two complex case studies of e-business integration with global suppliers and their corporate customers are analysed to identify specific stages of benefits accrual through the e-business transformation process. Collectively, the set of case studies is used to demonstrate the increased benefits derived from an e-business architecture based on a network of ERP-enabled organisations. 相似文献
96.
Hakan Civi Colin Christopher Aytul Ercil 《Journal of Mathematical Imaging and Vision》2003,19(3):237-253
Combining implicit polynomials and algebraic invariants for representing and recognizing complicated objects proves to be a powerful technique. In this paper, we explore the findings of the classical theory of invariants for the calculation of algebraic invariants of implicit curves and surfaces, a theory largely disregarded in the computer vision community by a shadow of skepticism. Here, the symbolic method of the classical theory is described, and its results are extended and implemented as an algorithm for computing algebraic invariants of projective, affine, and Euclidean transformations. A list of some affine invariants of 4th degree implicit polynomials generated by the proposed algorithm is presented along with the corresponding symbolic representations, and their use in recognizing objects represented by implicit polynomials is illustrated through experiments. An affine invariant fitting algorithm is also proposed and the performance is studied. 相似文献
97.
In this paper, we review an extension of the learning rules in a Principal Component Analysis network which has been derived to be optimal for a specific probability density function. We note that this probability density function is one of a family of pdfs and investigate the learning rules formed in order to be optimal for several members of this family. We show that, whereas we have previously (Lai et al., 2000; Fyfe and MacDonald, 2002) viewed the single member of the family as an extension of PCA, it is more appropriate to view the whole family of learning rules as methods of performing Exploratory Projection Pursuit. We illustrate this on both artificial and real data sets. 相似文献
98.
Leonard J. Borucki Thomas Witelski Colin Please Peter R. Kramer Donald Schwendeman 《Journal of Engineering Mathematics》2004,50(1):1-24
Statistical models are presented to describe the evolution of the surface roughness of polishing pads during the pad-conditioning process in chemical-mechanical polishing. The models describe the evolution of the surface-height probability-density function of solid pads during fixed height or fixed cut-rate conditioning. An integral equation is derived for the effect of conditioning on a foamed pad in terms of a model for a solid pad. The models that combine wear and conditioning are then discussed for both solid and foamed pads. Models include the dependence of the surface roughness on the shape and density of the cutting tips used in the conditioner and on other operating parameters. Good agreement is found between the model, Monte Carlo simulations and with experimental data. 相似文献
99.
The utilisation of oligosaccharides by oral microorganisms and intestinal enzymes are important factors in determining their effectiveness as alternative sweeteners. In this study, classes of naturally occurring sugars were assessed using in vitro models for oral and intestinal digestibility, in order to test the influence of chemical structure on functional properties. Amongst the classes of sucrose isomers, α-glucobioses, β-glucobioses and sucrose-based oligosaccharides, structures were identified that were not utilised by the common oral bacterium Streptococcus mutans, and would therefore contribute to the non-cariogenic potential of a sweetener. Analysis of the rate and products of digestion by a rat glucosidase mixture was used to determine the relative intestinal digestibility. The results showed that oligosaccharides containing a (1 → 6)-β-Glc group, including gentiobiose and gentiobiitol, together with melezitose, a sucrose-derived oligosaccharide containing a α-Glc-(1 → 3)-Fru moiety were resistant to digestion by both S. mutans and mammalian intestinal enzymes, highlighting their potential as dietary sugar substitutes. 相似文献
100.