6,043 research outputs found
Organizational culture and knowledge management success at project and organizational levels in contracting firms
Author name used in this publication: Patrick S. W. Fong2009-2010 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe
Preparation of bioactive surface via gel oxidation on titanium for biomedical application (hip joint replacement)
Titanium and its alloys are widely used as implant in biomedical applications. They
have good mechanical and chemical properties, biocompatibility and biointegration
with human body, but they have no ability to bond directly to natural bone. Therefore,
alkali and heat treatments (gel oxidation) were introduced to improve the bioactivity
of titanium by forming a mixture of sodium titanate and rutile on the surface of
titanium. This method enables titanium to possess a bioactive surface which is
essential to induce the apatite formation. This study aims to investigate the effects of
alkali, sodium removal and heat treatments on in vitro bioactivity of titanium. UV light
irradiation was used to study the effect on in vitro bioactivity of titanium. Alkalitreated
titanium subjected to heat treatment in air have shown better overall in vitro
performance than those treated in argon atmosphere. Therefore, the sodium removal
treatment (dilute hydrochloric acid (HCl) treatment) was introduced to convert sodium
titanate into anatase to improve the bioactivity of titanium treated in argon atmosphere.
Thus, four samples (AT-0.5-HT500R, AT-0.5-HT600R, AT-5-HT500R and AT-5-
HT600R) with different ratios of anatase to rutile were produced by varying the
concentration of HCl acid treatment and heating temperature in argon atmosphere. It
was found that the incorporation of sodium removal treatment has reduced two times
the duration of apatite formation as compared with the conventional alkali and heat
treatments. In order to further enhance the bioactivity, these samples were subjected
to six different conditions of ultraviolet light irradiation and followed by in vitro
bioactivity test. As a result, AT-5-HT500R (82.2% anatase and 17.8% rutile) was
proven to deliver the best performance. It was confirmed that UV light irradiation
enhances the bioactivity by removing hydrocarbon, inducing superhydrophilicity and
forming OH groups. It was discovered that the duration of apatite formation was
shortened to 7 days. Furthermore, the continuous UVA irradiation during in vitro test
resulted in the acceleration of bonelike apatite formation in 3 days. It can be concluded
that the sodium removal treatment and UV light irradiation give very significant impact to the formation of bonelike apatite on the titanium surfaces for biomedical
applications
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Numerical simulation of microflow over superhydrophobic surfaces by lattice Boltmann method
This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.The superhydrophobicity of a microchannel is determined by not only the wettability of channel wall but also the surface topography. Recent experiments have found that superhrydrophobic surfaces can be achieved by pattering roughness on hydrophobic surfaces. In this paper, the dynamics of two-phase flow in microchannel with different wettability and topography is studied numerically by the lattice Boltzmann method (LBM). The mechanism of drag reduction resulted from the superhydrophobicity is investigated. In
particular, the effect of different rough surfaces on superhydrophobicity is analyzed. It is found that flow behaviours are strongly affected by the wall wettability and topography. The results show that the LBM has a good application prospect in the study of drag reduction in microchannels.The UK Royal Society-NSFC (China) International Joint Project (2009-2011), China NSFC under grant (50920105504), and China Scholarship Council (CSC)
Peak effect in twinned superconductors
A sharp maximum in the critical current as a function of temperature
just below the melting point of the Abrikosov flux lattice has recently been
observed in both low and high temperature superconductors. This peak effect is
strongest in twinned crystals for fields aligned with the twin planes. We
propose that this peak signals the breakdown of the collective pinning regime
and the crossover to strong pinning of single vortices on the twin boundaries.
This crossover is very sharp and can account for the steep drop of the
differential resistivity observed in experiments.Comment: 4 pages, revtex 3.0, no figure
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AQUA: an ontology driven question answering system
This paper describes AQUA our question answering over the Web. AQUA was designed to work over heterogeneous sources. This means that AQUA is equipped to work as closed domain and in addition to open-domain question answering. As a first instance, AQUA tries to answer a question using a Knowledge base. If a query cannot be satisfied over a knowledge base/database. Then, AQUA tries to find an answer on web pages (i.e. it uses as corpus the internet as resource). Our system uses NLP (Natural Language Processing), First order logic and Information Extraction technologies. AQUA has been tested using an ontology which describes academic life. Keywords Ontologies, Information Extraction, Machine Learnin
Everyone loses when the values of employees clash with those of the firm
When employees suppress their values they risk burnout and firms' productivity falls, writes Chia-Huei W
Reconstructing ice-sheet accumulation rates at ridge B, East Antarctica
Understanding how ice sheets responded to past climate change is fundamental to forecasting how they will respond in the future. Numerical models calculating the evolution of ice sheets depend upon accumulation data, which are principally available from ice cores. Here, we calculate past rates of ice accumulation using internal layering. The englacial structure of the East Antarctic ice divide at ridge B is extracted from airborne ice-penetrating radar. The isochronous surfaces are dated at their intersection with the Vostok ice-core site, where the depth–age relationship is known. The dated isochrons are used as input to a one-dimensional ice-flow model to investigate the spatial accumulation distribution. The calculations show that ice-accumulation rates generally increase from Vostok lake towards ridge B. The western flank of the ice divide experiences markedly more accumulation than in the east. Further, ice accumulation increases northwards along the ice divide. The results also show the variability of accumulation in time and space around the ridge B ice divide over the last 124 000 years
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