1,641 research outputs found
Diquark mass differences from unquenched lattice QCD
We calculate diquark correlation functions in the Landau gauge on the lattice
using overlap valence quarks and 2+1-flavor domain wall fermion configurations.
Quark masses are extracted from the scalar part of quark propagators in the
Landau gauge. Scalar diquark quark mass difference and axial vector scalar
diquark mass difference are obtained for diquarks composed of two light quarks
and of a strange and a light quark. Light sea quark mass dependence of the
results is examined. Two lattice spacings are used to check the discretization
effects. The coarse and fine lattices are of sizes and
with inverse spacings and , respectively.Comment: 9 figure
Mitigation mechanism of longitudinal ribs on rain-wind induced vibrations of stay cables
For cable stayed bridges rain-wind induced vibrations of stay cables are probably the most widespread and controversial phenomenon. Aerodynamic countermeasures have been implemented to tackle such vibrations, but there is still not sufficient insight on the inherent mitigation mechanisms. To this goal, a numerical model, based on lubrication theory, was employed in order to study the coupled cable vibration response, aerodynamic forces, and formation and oscillation of rivulets for stay cables equipped with longitudinal ribs. Coupled equations governing the synchronous cable motion and water film evolution were established in order to understand the effects of several key parameters associated with the vibration mitigation performance of the ribs. Such parameters include the cable inclination angle, the wind yaw angle, the number and the height of the ribs. Computed results were successfully validated against experimental data. For the various studied cases, it was apparent that the ribs did not stop the formation of rivulets, but they could affect both their position and oscillation ranges. Through such a control action they could further affect the oscillation range and frequency content of aerodynamic forces, mitigating or not cable vibrations
Nearby SNR: a possible common origin to multi-messenger anomalies in spectra, ratios and anisotropy of cosmic rays
The multi-messenger anomalies, including spectral hardening or excess for
nuclei, leptons, ratios of and B/C, and anisotropic reversal, were
observed in past years. AMS-02 experiment also revealed different spectral
break for positron and electron at 284 GeV and beyond TeV respectively. It is
natural to ask whether all those anomalies originate from one unified physical
scenario. In this work, the spatially-dependent propagation (SDP) with a nearby
SNR source is adopted to reproduce above mentioned anomalies. There possibly
exists dense molecular cloud(DMC) around SNRs and the secondary particles can
be produced by pp-collision or fragmentation between the accelerated primary
cosmic rays and DMC. As a result, the spectral hardening for primary, secondary
particles and ratios of and can be well reproduced. Due to the
energy loss at source age of 330 kyrs, the characteristic spectral break-off
for primary electron is at about 1 TeV hinted from the measurements. The
secondary positron and electron from charged pion take up energy from
their mother particles, so the positron spectrum has a cut-off at 250
GeV. Therefore, the different spectral break for positron and electron together
with other anomalies can be fulfilled in this unified physical scenario. More
interesting is that we also obtain the featured structures as spectral
break-off at 5 TV for secondary particles of Li, Be, B, which can be served to
verify our model. We hope that those tagged structures can be observed by the
new generation of space-borne experiment HERD in future.Comment: 16 pages, 12 figure
State-of-the-art review of 3DPV technology: structures and models
© 2019 Elsevier Ltd Increasing energy conversion efficiency from sunlight to power is one of the key solutions for the world's energy shortage and greenhouse gas reduction, but the conventional flat photovoltaic module without sun tracking mechanism has the low sunlight energy collection ability. This paper presents the state-of-the-art three-dimensional photovoltaic (3DPV) technology with high photovoltaic energy conversion efficiency, which is able to absorb off-peak sunlight and reflected light more effectively, thereby it can generate more power. At first, this paper is to catalogue and critique different 3DPV structures and models, as well as assess their characteristics. Afterwards, the main influence factors on the 3DPV structures and models including shape, height and spacing of the solar cells, latitude of the installation, optimal device design and shadow cast, are reviewed. Finally, the challenges and future technological developments of 3DPV structures and models are highlighted. This study demonstrated that the 3DPV technology can increase the captured sunlight approximately 15–30% in comparison with the conventional flat PV technology
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