24,102 research outputs found
FE modelling of bond interaction of FRP bars to concrete
In this paper a computational modelling approach is used to investigate the bond behaviour of fibre-reinforced plastic (FRP) bars in concrete. Two finite element packages (ANSYS and ABAQUS) are used to model the bond interaction of FRP reinforcing bars in cubes and beams. The main purpose of this work is to develop additional understanding of how FRP bars ‘cooperate’ with concrete to sustain the pullout load. Two modelling approaches are presented. In the first approach, a spring describing the behaviour of short embedment lengths in pullout tests was used for predicting the behaviour of longer embedment lengths. In the second approach, spring characteristics obtained from an experimentally determined bond stress against anchorage length envelope are used in FE modelling of beams. Both approaches showed good agreement between analytical and experimental results. However, further development on the analytical modelling of the bond interaction is required, in order to consider the effect of all parameters that influence bond
Numerical simulation of two-phase cross flow in the gas diffusion layer microstructure of proton exchange membrane fuel cells
The cross flow in the under-land gas diffusion layer (GDL) between 2 adjacent channels plays an important role on water transport in proton exchange membrane fuel cell. A 3-dimensional (3D) two-phase model that is based on volume of fluid is developed to study the liquid water-air cross flow within the GDL between 2 adjacent channels. By considering the detailed GDL microstructures, various types of air-water cross flows are investigated by 3D numerical simulation. Liquid water at 4 locations is studied, including droplets at the GDL surface and liquid at the GDL-catalyst layer interface. It is found that the water droplet at the higher-pressure channel corner is easier to be removed by cross flow compared with droplets at other locations. Large pressure difference Δp facilitates the faster water removal from the higher-pressure channel. The contact angle of the GDL fiber is the key parameter that determines the cross flow of the droplet in the higher-pressure channel. It is observed that the droplet in the higher-pressure channel is difficult to flow through the hydrophobic GDL. Numerical simulations are also performed to investigate the water emerging process from different pores of the GDL bottom. It is found that the amount of liquid water removed by cross flow mainly depends on the pore's location, and the water under the land is removed entirely into the lower-pressure channel by cross flow
General covariant geometric momentum, gauge potential and a Dirac fermion on a two-dimensional sphere
For a particle that is constrained on an ()-dimensional ()
curved surface, the Cartesian components of its momentum in -dimensional
flat space is believed to offer a proper form of momentum for the particle on
the surface, which is called the geometric momentum as it depends on the mean
curvature. Once the momentum is made general covariance, the spin connection
part can be interpreted as a gauge potential. The present study consists in two
parts, the first is a discussion of the general framework for the general
covariant geometric momentum. The second is devoted to a study of a Dirac
fermion on a two-dimensional sphere and we show that there is the generalized
total angular momentum whose three cartesian components form the
algebra, obtained before by consideration of dynamics of the particle, and we
demonstrate that there is no curvature-induced geometric potential for the
fermion.Comment: 8 pages, no figure. Presentation improve
Experimental implementation of high-fidelity unconventional geometric quantum gates using NMR interferometer
Following a key idea of unconventional geometric quantum computation
developed earlier [Phys. Rev. Lett. 91, 197902 (2003)], here we propose a more
general scheme in such an intriguing way: , where and are respectively the dynamic and
geometric phases accumulated in the quantum gate operation, with as a
constant and being dependent only on the geometric feature of the
operation. More arrestingly, we demonstrate the first experiment to implement a
universal set of such kind of generalized unconventional geometric quantum
gates with high fidelity in an NMR system.Comment: 4 pages, 3 figure
Photovoltaic Oscillations Due to Edge-Magnetoplasmon Modes in a Very-High Mobility 2D Electron Gas
Using very-high mobility GaAs/AlGaAs 2D electron Hall bar samples, we have
experimentally studied the photoresistance/photovoltaic oscillations induced by
microwave irradiation in the regime where both 1/B and B-periodic oscillations
can be observed. In the frequency range between 27 and 130 GHz we found that
these two types of oscillations are decoupled from each other, consistent with
the respective models that 1/B oscillations occur in bulk while the
B-oscillations occur along the edges of the Hall bars. In contrast to the
original report of this phenomenon (Ref. 1) the periodicity of the
B-oscillations in our samples are found to be independent of L, the length of
the Hall bar section between voltage measuring leads.Comment: 4 pages, 4 figure
Crossover of magnetoresistance in the zerogap half-metallic Heusler alloy Fe2CoSi
This work reports on the band structure and magneto-transport investigations
of the inverse Heusler compound Fe2CoSi. The first-principles calculations
reveal that Fe2CoSi has a very peculiar band structure with a conducting
property in the majority spin channel and a nearly zero bandgap in the minority
spin channel. The synthesized Fe2CoSi sample shows a high-ordered inverse
Heusler structure with a magnetic moment of 4.88 {\mu}B at 5 K and a high Curie
temperature of 1038 K. With increasing temperature, a crossover from positive
to negative magnetoresistance (MR) is observed. Complemented with the Hall
effect measurements, we suggest the intriguing crossover of MR can be ascribed
to the dominant spin carriers changing from the gapless minority spin channel
to the majority spin channel at Fermi level.Comment: 16 pages, 5 figures, submitted for publicatio
Microwave photoresistance of a high-mobility two-dimensional electron gas in a triangular antidot lattice
The microwave (MW) photoresistance has been measured on a high-mobility
two-dimensional electron gas patterned with a shallow triangular antidot
lattice, where both the MW-induced resistance oscillations (MIRO) and
magnetoplasmon (MP) resonance are observed superposing on sharp commensurate
geometrical resonance (GR). Analysis shows that the MIRO, MP, and GR are
decoupled from each other in these experiments.Comment: 5 pages, 4 figures, paper accepted by PR
Design and experiment of an embedded multi-function wireless sensor for multi-service agricultural information acquisition
Multi-service agricultural information has several data forms including text, audio, image and video. How to rapidly acquire and wirelessly transmit multi-service agricultural information is an essential prerequisite for sustainable development of precision agriculture. Devices for agricultural information acquisition in precision agriculture have different varieties and various input/output interfaces; however, these devices have only one single function and are lack of extensibility. To meet the demand of multi-service agricultural information acquisition in precision agriculture, a multi-service agricultural information acquisition sensor node (MAIAS) with multi-function integration was developed based on Android. A SC7731 chip is used as microcontroller chip of the node. Combined with ADC interface, microphone, image sensor, WiFi and 3G mobile communication module, the node was designed for rapid acquisition and wireless transmission of multi-service agricultural information in form of text, audio, image and video. To verify the performance of agricultural information acquisition and wireless data transmission of the node, experiments were conducted to acquire data of soil moisture content, audio, image and video in laboratory conditions. Audio data were transmitted by
3G mobile communication networks; the average transmission rate was about 21KB/s. Considering of large data volume, image and video data was transmitted using WiFi network, with the average rate of 2.63MB/s. The results show that the node could be connected with sensors for text information acquisition by ADC interface, and could satisfy the requirement on data acquisition of audio, image and video. The results also indicate that the node was feasible for rapid acquisition and wireless transmission of multi-service agricultural information in precision agriculture
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