12,800 research outputs found
Model B4 : multi-decade creep and shrinkage prediction of traditional and modern concretes
To improve the sustainability of concrete infrastructure, engineers face the challenge of incorporating new concrete materials while pushing the expected design life beyond 100 years. The time-dependent creep and shrinkage response of concrete governs the serviceability and durability in this multi-decade time frame. It has been shown that current prediction equations for creep and shrinkage underestimate material deformations observed in structures outside of a laboratory environment. A new prediction model for creep and shrinkage is presented that can overcome some of the shortcomings of the current equations. The model represents an extension and systematic recalibration of model B3, a 1995 RILEM Recommendation, which derives its functional form from the phenomena of diffusion, chemical hydration, moisture sorption, and the evolution of micro-stresses in the cement structure. The model is calibrated through a joint optimization of a new enlarged laboratory test database and a new database of bridge deflection records to overcome the bias towards short-term behavior. A framework for considering effects of aggregates, admixtures, additives, and higher temperatures is also incorporated
Geoarchaeological evidence of the AD 1642 Yellow River flood that destroyed Kaifeng, a former capital of dynastic China
Rising global temperatures will increase the number of extreme weather events, creating new challenges for cities around the world. Archaeological research on the destruction and subsequent reoccupation of ancient cities has the potential to reveal geological and social dynamics that have historically contributed to making urban settings resilient to these extreme weather events. Using a combination of archaeological and geological methods, we examine how extreme flood events at Kaifeng, a former capital of dynastic China, have shaped the city’s urban resilience. Specifically, we focus on an extreme Yellow River flood event in AD 1642 that historical records suggest killed around 300,000 people living in Kaifeng. Our recent archaeological excavations have discovered compelling geological and archaeological evidence that corroborates these documents, revealing that the AD 1642 Yellow River flood destroyed Kaifeng’s inner city, entombing the city and its inhabitants within meters of silt and clay. We argue that the AD 1642 flood was extraordinarily catastrophic because Kaifeng’s city walls only partly collapsed, entrapping most of the flood waters within the city. Both the geology of the Yellow River floods as well as the socio-political context of Kaifeng shaped the city’s resilience to extreme flood events
A New Non-Abelian Topological Phase of Cold Fermi Gases in Anisotropic and Spin-Dependent Optical Lattices
To realize non-Abelian s-wave topological superfluid (TS) of cold Fermi
gases, generally a Zeeman magnetic field larger than superfluid pairing gap is
necessary. In this paper we find that using an anisotropic and spin-dependent
optical lattice (ASDOL) to trap gases, a new non-Abelian TS phase appears, in
contrast to an isotropic and spin-independent optical lattice. A characteristic
of this new non-Abelian TS is that Zeeman magnetic field can be smaller than
the superfluid pairing gap. By self-consistently solving pairing gap equation
and considering the competition against normal state and phase separation, this
new phase is also stable. Thus an ASDOL supplies a convenient route to realize
TS. We also investigate edge states and the effects of a harmonic trap
potential
Implications on SUSY breaking mediation mechanisms from observing and the muon
We consider and the muon in various SUSY
breaking mediation mechanisms. If the decay is observed
at Tevatron Run II with a branching ratio larger than ,
the noscale supergravity (including the gaugino mediation), the gauge mediation
scenario with small number of messenger fields and low messenger scale, and a
class of anomaly mediation scenarios will be excluded, even if they can
accommodate a large muon . On the other hand, the minimal
supergravity scenario and similar mechanisms derived from string models can
accommodate this observation.Comment: 4 pages, 3 figure
Theory for superconductivity in (Tl,K)FeSe as a doped Mott insulator
Possible superconductivity in recently discovered (Tl,K)FeSe
compounds is studied from the viewpoint of doped Mott insulator. The Mott
insulating phase is examined to be preferred in the parent compound at
due to the presence of Fe vacancies. Partial filling of vacancies at the
Fe-sites introduces electron carriers and leads to electron doped
superconductivity. By using a two-orbital Hubbard model in the strong coupling
limit, we find that the s-wave pairing is more favorable at small Hund's
coupling, and d wave pairing is more favorable at large Hund's
coupling.Comment: 4+ pages, 3 figures, to appear in EP
Topological superfluid of spinless Fermi gases in p-band honeycomb optical lattices with on-site rotation
In this paper, we put forward to another route realizing topological
superfluid (TS). In contrast to conventional method, spin-orbit coupling and
external magnetic field are not requisite. Introducing an experimentally
feasible technique called on-site rotation (OSR) into p-band honeycomb optical
lattices for spinless Fermi gases and considering CDW and pairing on the same
footing, we investigate the effects of OSR on superfluidity. The results
suggest that when OSR is beyond a critical value, where CDW vanishes, the
system transits from a normal superfluid (NS) with zero TKNN number to TS
labeled by a non-zero TKNN number. In addition, phase transitions between
different TS are also possible
Identification and quantification of atmospheric pollutants in natural and man-made ecosystems
Target localization based on distributed array networks with magnitude-only measurements
The source localization problem based on distributed array networks is formulated into a group sparsity-based phase retrieval problem where only the magnitude of received signals is available. Under such a framework, a 2-D localization method is proposed, where unlike traditional methods, random phase errors at array sensors will not affect estimation results. In addition, to deal with the off-grid problem for sparsity-based solutions, a model for off-grid bias is proposed and an efficient two-step method is developed accordingly to solve the 2-D off-grid problem. Simulation results show that the proposed solutions can solve the problem effectively
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