Numerical study on the flexural performance of precast segmental concrete beams with unbonded internal steel tendons

This study presents a numerical investigation of the flexural performance of precast segmental concrete beams (PSBs) with unbonded internal steel tendons. Numerical models developed in this study using Abaqus software capture well the responses of the PSBs reported in previous studies. This is the first time a three-dimensional numerical model is built and successfully validated against experimental results of PSBs in literature. Based on the verified numerical model, intensive simulations of performances of segmental beams with different parameters and various conditions, i.e. tension-controlled, compression-controlled and balanced sections, are carried out. Based on the numerical results, the flexural behaviour of PSBs under four-point loading is extensively discussed regarding the failure modes, joint opening, stress increment in the tendon and the stress transfer mechanism. A parametric study is also conducted and the results show that the effective prestress, prestressing steel reinforcement ratio, and span length-to-tendon depth ratio strongly affect the load-carrying capacity, ductility, tendon stress increment, joint opening and failure modes of PSBs with unbonded tendons, while the loading type, concrete strength and the number of joints show insignificant effects on the flexural performance of the structure

A protocol to determine seed storage behaviour

This publications provides an approach by which conservationists can determine whether or not long-term seed storage is feasible for a particular species, i.e. whether or not that species shows orthodox seed storage behaviour. It provides advice on the implementation of the protocol, examples of ways in which the results from seed storage studies could be misinterpreted due to confounding factors, as well as several alternative approaches for estimating seed storage behaviour prior to carrying out actual investigations with the seeds. In particular, the latter section introduces the concept of a multicriteria approach for estimating seed storage behaviour. It is intended to be used along with the Compendium (see IPGRI Handbooks for Genebanks No.4 - Seed Storage behaviour: a Compendium); these two publications are essentially complementary. The overall aim of the protocol is to guide and encourage further work in this area of seed physiology (particularly for species on which relatively less work has been done to date)m with the objective to expanding on/up-dating the type of species-specific data compiled in the compendium

Seed storage behavior: a compendium

This handbook provides an introduction to seed storage physiology for those responsible for plant genetic conservation and a selective summary of the literature on seed survival in storage, and thus on seed storage behaviour, for over 7000 species from 251 families. Part IA summarizes progress in our understanding of seed physiology in relation to seed storage for genetic conservation in the past 17 years since the publication of The Storage of Recalcitrant Seeds: Achievements and Possible Approaches by King and Roberts (1979), and particularly the various problems that may result in the misclassification of seed storage behaviour. Part IB provides a compendium of information on seed survival during storage and attempts to classify plant species into the several categories of seed storage behaviour. You can search the data on seed storage behavio

A Model Behind the Standard Model

In spite of its many successes, the Standard Model makes many empirical assumptions in the Higgs and fermion sectors for which a deeper theoretical basis is sought. Starting from the usual gauge symmetry $u(1) \times su(2) \times su(3)$ plus the 3 assumptions: (A) scalar fields as vielbeins in internal symmetry space \cite{framevec}, (B) the ``confinement picture'' of symmetry breaking \cite{tHooft,Banovici}, (C) generations as ``dual'' to colour \cite{genmixdsm}, we are led to a scheme which offers: (I) a geometrical significance to scalar fields, (II) a theoretical criterion on what scalar fields are to be introduced, (III) a partial explanation of why $su(2)$ appears broken while $su(3)$ confines, (IV) baryon-lepton number (B - L) conservation, (V) the standard electroweak structure, (VI) a 3-valued generation index for leptons and quarks, and (VII) a dynamical system with all the essential features of an earlier phenomenological model \cite{genmixdsm} which gave a good description of the known mass and mixing patterns of quarks and leptons including neutrino oscillations. There are other implications the consistency of which with experiment, however, has not yet been systematically explored. A possible outcome is a whole new branch of particle spectroscopy from $su(2)$ confinement, potentially as rich in details as that of hadrons from colour confinement, which will be accessible to experiment at high energy.Comment: 66 pages, added new material on phenomenology, and some new reference

New Higgs signals induced by mirror fermion mixing effects

We study the conditions under which flavor violation arises in scalar-fermion interactions, as a result of the mixing phenomena between the standard model and exotic fermions. Phenomenological consequences are discussed within the specific context of a left-right model where these additional fermions have mirror properties under the new SU(2)_R gauge group. Bounds on the parameters of the model are obtained from LFV processes; these results are then used to study the LFV Higgs decays (H --> tau l_j, l_j = e, mu), which reach branching ratios that could be detected at future colliders.Comment: 12 pages, 2 figures, ReVTex4, graphicx, to be published in Phys. Rev.

Near-infrared and mid-infrared semiconductor broadband light emitters

Semiconductor broadband light emitters have emerged as ideal and vital light sources for a range of biomedical sensing/imaging applications, especially for optical coherence tomography systems. Although near-infrared broadband light emitters have found increasingly wide utilization in these imaging applications, the requirement to simultaneously achieve both a high spectral bandwidth and output power is still challenging for such devices. Owing to the relatively weak amplified spontaneous emission, as a consequence of the very short non-radiative carrier lifetime of the inter-subband transitions in quantum cascade structures, it is even more challenging to obtain desirable mid-infrared broadband light emitters. There have been great efforts in the past 20 years to pursue high-efficiency broadband optical gain and very low reflectivity in waveguide structures, which are two key factors determining the performance of broadband light emitters. Here we describe the realization of a high continuous wave light power of >20 mW and broadband width of >130 nm with near-infrared broadband light emitters and the first mid-infrared broadband light emitters operating under continuous wave mode at room temperature by employing a modulation p-doped InGaAs/GaAs quantum dot active region with a ‘J’-shape ridge waveguide structure and a quantum cascade active region with a dual-end analogous monolithic integrated tapered waveguide structure, respectively. This work is of great importance to improve the performance of existing near-infrared optical coherence tomography systems and describes a major advance toward reliable and cost-effective mid-infrared imaging and sensing systems, which do not presently exist due to the lack of appropriate low-coherence mid-infrared semiconductor broadband light sources

Strange nucleon form factors in the perturbative chiral quark model

We apply the perturbative chiral quark model at one loop to calculate the strange form factors of the nucleon. A detailed numerical analysis of the strange magnetic moments and radii of the nucleon, and also the momentum dependence of the form factors is presented.Comment: 18 pages, 6 figure