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1.
Young-Sun Heo Jay G. Sanjayan Cheon-Goo Han Min-Cheol Han 《Construction and Building Materials》2011,25(6):2928-2938
In this paper, a construction application of a technique to improve the fire resistance of high strength concrete is presented. Before the construction application, fire tests of three hours duration were carried out in accordance with ISO-834. Three types of mitigating methods, namely, a specimen with no protection (control), with fireproof panel protection and with the combination of polypropylene fibre reinforcement and metal mesh confinement (Fibre/Mesh), were applied to full sized columns for comparison purposes. The fire resistance performance of all columns was tested under loads. After the fire tests, the severity of spalling of specimens was assessed, and the best performing technique, Fibre/Mesh, for spalling protection was selected for an application in practice. The process of the construction application is described in detail, including pumping, pouring and compacting of the concrete. The concrete quality was examined and the behaviour of the concrete was observed. Consequently, it was verified that this new spalling resistance technique is feasible in practice. 相似文献
2.
When fly ash-based geopolymer mortars were exposed to a temperature of 800 °C, it was found that the strength after the exposure
sometimes decreased, but at other times increased. This paper shows that ductility of the mortars has a major correlation
to this strength gain/loss behaviour. Specimens prepared with two different fly ashes, with strengths ranging from 5 to 60 MPa,
were investigated. Results indicate that the strength losses decrease with increasing ductility, with even strength gains
at high levels of ductility. This correlation is attributed to the fact that mortars with high ductility have high capacity
to accommodate thermal incompatibilities. It is believed that the two opposing processes occur in mortars: (1) further geopolymerisation
and/or sintering at elevated temperatures leading to strength gain; (2) the damage to the mortar because of thermal incompatibility
arising from non-uniform temperature distribution. The strength gain or loss occurs depending on the dominant process. 相似文献
3.
Walker PS Sathasivam S 《Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine》2000,214(1):101-119
The starting point of this article is a general design criterion applicable to all types of total knee replacement. This criterion is then expanded upon to provide more specifics of the required kinematics, and the forces which the total knee must sustain. A characteristic which differentiates total knees is the amount of constraint which is required, and whether the constraint is translational or rotational. The different forms of total knee replacement are described in terms of these constraints, starting with the least constrained unicompartments to the almost fully constrained fixed and rotating hinges. Much attention is given to the range of designs in between these two extreme types, because they constitute by far the largest in usage. This category includes condylar replacements where the cruciate ligaments are preserved or resected, posterior cruciate substituting designs and mobile bearing knees. A new term, 'guided motion knees', is applied to the growing number of designs which control the kinematics by the use of intercondylar cams or specially shaped and even additional bearing surfaces. The final section deals with the selection of an appropriate design of total knee for specific indications based on the design characteristics. 相似文献
4.
A. Castel S. J. Foster T. Ng J. G. Sanjayan R. I. Gilbert 《Materials and Structures》2016,49(5):1619-1628
The main purpose of this research is to study the time dependent behaviour of a geopolymer concrete. The geopolymer binder is composed of 85.2 % of low calcium fly ash and only 14.8 % of ground granulated blast furnace slag. Both drying shrinkage and creep are studied. In addition, different curing conditions at elevated temperature were used. All experimental results were compared to predictions made using the Eurocode 2. The curing regime plays an important role in the magnitude and development of both creep and drying shrinkage of class F fly ash based geopolymer concrete. A minimum of 3 days at 40 °C or 1 day at 80 °C is required to obtain final drying shrinkage strains similar to or less than those adopted by Eurocode 2 for ordinary Portland cement (OPC) concrete. Creep strains were similar or less than those predicted by Eurocode 2 for OPC concrete when the geopolymer concrete was cured for 3 days at 40 °C. After 7 days at 80 °C, creep strains became negligible. 相似文献
5.
Factors contributing to early age shrinkage cracking of slag concretes subjected to 7-days moist curing 总被引:1,自引:1,他引:0
The objective of this study was to investigate all the factors contributing to early age shrinkage cracking in concrete, namely,
shrinkage, tensile creep, tensile elastic modulus, tensile strength of concretes, and to study the effect of slag as a binder
on these factors. The above-mentioned factors were measured in early age concretes made with 0, 35, 50 and 65% level replacement
of ordinary Portland cement by slag. All the concretes studied were moist cured for 7-days. It was found that, at lower slag
replacement levels (0, 35 and 50%), the tensile strength decreased with increasing slag replacement. However, this is more
than compensated by decreasing tensile elastic modulus and shrinkage. There was no significant change found in tensile creep
with the changing slag levels. The study shows that the influence of the tensile elastic modulus is a major consideration
for early age cracking of slag concretes. 相似文献
6.
7.
Solution Processing Route to Multifunctional Titania Thin Films: Highly Conductive and Photcatalytically Active Nb:TiO2
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Davinder S. Bhachu Sanjayan Sathasivam Gopinathan Sankar David O. Scanlon Giannantonio Cibin Claire J. Carmalt Ivan P. Parkin Graeme W. Watson Salem M. Bawaked Abdullah Y. Obaid Shaeel Al‐Thabaiti Sulaiman N. Basahel 《Advanced functional materials》2014,24(32):5075-5085
This paper reports the synthesis of highly conductive niobium doped titanium dioxide (Nb:TiO2) films from the decomposition of Ti(OEt)4 with dopant quantities of Nb(OEt)5 by aerosol‐assisted chemical vapor deposition (AACVD). Doping Nb into the Ti sites results in n‐type conductivity, as determined by Hall effect measurements. The doped films display significantly improved electrical properties compared to pristine TiO2 films. For 5 at.% Nb in the films, the charge carrier concentration was 2 × 1021 cm?3 with a mobility of 2 cm2 V–1 s–1 . The corresponding sheet resistance is as low as 6.5 Ω sq–1 making the films suitable candidates for transparent conducting oxide (TCO) materials. This is, to the best of our knowledge, the lowest reported sheet resistance for Nb:TiO2 films synthesized by vapour deposition. The doped films are also blue in colour, with the intensity dependent on the Nb concentration in the films. A combination of synchrotron, laboratory and theoretical techniques confirmed niobium doping into the anatase TiO2 lattice. Computational methods also confirmed experimental results of both delocalized (Ti4+) and localized polaronic states (Ti3+) states. Additionally, the doped films also functioned as photocatalysts. Thus, Nb:TiO2 combines four functional properties (photocatalysis, electrical conductivity, optical transparency and blue colouration) within the same layer, making it a promising alternative to conventional TCO materials. 相似文献
8.
The effect of gypsum in slag-blended cement on free and restrained shrinkage of concrete subjected to various curing conditions
is presented in this paper. Added gypsum in slag-blended cements was found to increase the autogenous shrinkage of concrete
up to 56 days. However, added gypsum caused small reduction in the long-term shrinkage when the concrete was exposed to drying.
Slag concretes with 3% added gypsum content, when exposed to drying at the age of 24 h, exhibited more cracking tendency than
comparable concrete with 0% added gypsum. This is attributed to the increased shrinkage evolution of slag concrete with 3%
gypsum content at early ages. However, if moist cured for 7 days, increasing the amount of gypsum from 3 to 5% in slag-blended
cement reduced the cracking tendency. It is concluded that the beneficial effect of increasing gypsum in reducing cracking
tendency in slag concrete is only favourable if moist cured for 7 days. 相似文献
9.
Caffeine (Caf) ingestion increases plasma epinephrine (Epi) and exercise endurance; these results are frequently transferred to coffee (Cof) consumption. We examined the impact of ingestion of the same dose of Caf in Cof or in water. Nine healthy, fit, young adults performed five trials after ingesting (double blind) either a capsule (Caf or placebo) with water or Cof (decaffeinated Cof, decaffeinated with Caf added, or regular Cof). In all three Caf trials, the Caf dose was 4.45 mg/kg body wt and the volume of liquid was 7.15 ml/kg. After 1 h of rest, the subject ran at 85% of maximal O2 consumption until voluntary exhaustion (approximately 32 min in the placebo and decaffeinated Cof tests). In the three Caf trials, the plasma Caf and paraxanthine concentrations were very similar. After 1 h of rest, the plasma Epi was increased (P < 0.05) by Caf ingestion, but the increase was greater (P < 0.05) with Caf capsules than with Cof. During the exercise there were no differences in Epi among the three Caf trials, and the Epi values were all greater (P < 0.05) than in the other tests. Endurance was only increased (P < 0. 05) in the Caf capsule trial; there were no differences among the other four tests. One cannot extrapolate the effects of Caf to Cof; there must be a component(s) of Cof that moderates the actions of Caf. 相似文献
10.
Pavement roughness is a common measure of pavement distress and one regularly measured by road authorities. While permanent pavement deterioration that equates to increased roughness is commonly modeled, cyclical or seasonal variations are often not included. While these variations may be small, they may be important when alternate pavements are compared directly for performance. We propose that seasonal variation may be described by partitioning the data into groups that are modeled as a segmentation problem. We developed a minimum message length (MML) segmentation tree (MMLST) criterion for partitioning and segmentation of the data. We performed simulated comparisons comparing common segmentation criterion (MMLST, maximum likelihood, Akaike information criterion, and Bayesian information criterion) and conclude that MMLST is the preferred criterion. MMLST assists in answering the following questions. First, is the observed segmentation pattern due to seasonal variation or merely random scatter? Second, given evidence of seasonal variation, what type of segmentation pattern should model these trends? Furthermore, does the interaction of climatic and soil conditions appear to affect this variation? 相似文献