8,913 research outputs found
Strong decays of the newly observed , , , and
The strong decay properties of the newly observed , ,
and are studied in a constituent quark model. It is
predicted that the and seem to be two overlapping
resonances. The could be identified as the with ,
while the is most likely to be the high-mass mixed state
() via the - mixing. The
favors the low-mass mixed state via the
- mixing. The as the assignment bears
controversies for its too broad width given in experiments.Comment: 8 pages, 5 figures; The review of the model is added. Some discussion
of the is include
The reaction at low energies in a chiral quark model
A chiral quark-model approach is extended to the study of the
scattering at low energies. The process of at
MeV/c (i.e. the center mass energy GeV) is
investigated. This approach is successful in describing the differential cross
sections and total cross section with the roles of the low-lying
resonances in shells clarified. The dominates the
reactions over the energy region considered here. Around MeV/c,
the is responsible for a strong resonant peak in the
cross section. The has obvious contributions around
MeV/c, while the contribution of is less
important in this energy region. The non-resonant background contributions,
i.e. -channel and -channel, also play important roles in the explanation
of the angular distributions due to amplitude interferences.Comment: 18 pages and 7 figure
Static and Dynamic Mechanical Properties of Sustainable Engineered Geopolymer Composites
Engineered geopolymer composites (EGCs) exhibiting superior tensile strain-hardening and multiple cracking behaviour are sustainable alternatives to traditional ductile cementitious composites whereas the extremely high cost and potential environmental impact of the widely used oil-coated polyvinyl alcohol (PVA) or polyethylene fibres in EGCs would limit their large-scale application. Partial replacement of these fibres with recycled fibres can reduce the material cost and improve the sustainability of EGCs. In recent years, the fresh properties and static mechanical properties of EGCs made from different precursors including fly ash and ground granulated blast-furnace slag have been increasingly studied, while the dynamic mechanical properties of EGCs cured at ambient temperature have been rarely explored.
This thesis aims to develop a novel sustainable fly ash-slag based EGC with recycled tyre polymer (RTP) fibre as partial substitute for PVA fibre based on micromechanics design theory and systematically investigate the effect of hybrid PVA and RTP fibre content on the quasi-static and dynamic mechanical properties of EGCs. Firstly, a series of tests were conducted to study the engineering properties of EGCs with different PVA and RTP fibre dosages including workability, setting time, drying shrinkage, compressive strength, elastic modulus, splitting tensile strength, uniaxial tensile behaviour as well as the micromechanical characteristics in terms of fibre bridging stress-crack opening and strain-hardening indices. Afterwards, the dynamic compressive and splitting tensile behaviour were explored using the split Hopkinson pressure bar apparatus in terms of failure pattern, stress-strain (or displacement) response, dynamic compressive and splitting tensile strengths, dynamic increase factor (DIF) and energy absorption capacity. Some empirical equations were proposed to estimate the relationships between DIF and strain rate. Afterwards, the microstructural characterisation using scanning electron microscopy (SEM), backscattered electron microscopy (BSE) and X-ray computed tomography (XCT) techniques was carried out to understand the fibre bridging mechanism of the hybrid PVA-RTP fibre reinforced EGC. Lastly, the optimal mixtures of EGC were proposed considering the material cost, environmental impact, and acceptable engineering properties for civil infrastructure applications.
Results indicate that the developed EGCs can meet the strength-based and energy-based criteria for robust tensile strain-hardening behaviour. Replacing a small amount of PVA fibre with RTP fibre can lead to better dynamic mechanical properties and drying shrinkage resistance, lower material cost and higher sustainability as well as retaining acceptable static mechanical properties. This thesis can provide new insights into the effect of hybrid fibre reinforcement on the dynamic mechanical behaviour of EGCs under a wide range of strain rates (10β° sΒ―ΒΉ to 10Β³ sΒ―ΒΉ) as well as promote the development and application of low-carbon construction materials in the future
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