11,405 research outputs found
Dynamic simulation of a peristaltic micropump considering coupled fluid flow and structural motion
This paper presents lumped-parameter simulation of dynamic characteristics of peristaltic micropumps. The pump consists of three pumping cells connected in series, each of which is equipped with a compliant diaphragm that is electrostatically actuated in a peristaltic sequence to mobilize the fluid. Diaphragm motion in each pumping cell is first represented by an effective spring subjected to hydrodynamic and electrostatic forces. These cell representations are then used to construct a system-level model for the entire pump, which accounts for both cell- and pump-level interactions of fluid flow and diaphragm vibration. As the model is based on first principles, it can be evaluated directly from the device's geometry, material properties and operating parameters without using any experimentally identified parameters. Applied to an existing pump, the model correctly predicts trends observed in experiments. The model is then used to perform a systematic analysis of the impact of geometry, materials and pump loading on device performance, demonstrating its utility as an efficient tool for peristaltic micropump design
Search for anomalous top quark production at the early LHC
We present a detailed study of the anomalous top quark production with
subsequent decay at the LHC induced by model-independent flavor-changing
neutral-current couplings, incorporating the complete next-to-leading order QCD
effects. Our results show that, taking into account the current limits from the
Tevatron, the LHC with TeV may discover the anomalous coupling at
5 level for a very low integrated luminosity of 61 pb. The
discovery potentials for the anomalous couplings at the LHC are examined in
detail. We also discuss the possibility of using the charge ratio to
distinguish the and couplings.Comment: 4 pages, 3 figures, version appears in Phys. Rev. Let
Thrust distribution in Higgs decays at the next-to-leading order and beyond
We present predictions for the thrust distribution in hadronic decays of the
Higgs boson at the next-to-leading order and the approximate
next-to-next-to-leading order. The approximate NNLO corrections are derived
from a factorization formula in the soft/collinear phase-space regions. We find
large corrections, especially for the gluon channel. The scale variations at
the lowest orders tend to underestimate the genuine higher order contributions.
The results of this paper is therefore necessary to control the perturbative
uncertainties of the theoretical predictions. We also discuss on possible
improvements to our results, such as a soft-gluon resummation for the 2-jets
limit, and an exact next-to-next-to-leading order calculation for the
multi-jets region
Surface micromachined electrostatically actuated micro peristaltic pump
An electrostatically actuated micro peristaltic pump is reported. The micro pump is entirely surface micromachined using a multilayer parylene technology. Taking advantage of the multilayer technology, the micro pump design enables the pumped fluid to be isolated from the electric field. Electrostatic actuation of the parylene membrane using both DC and AC voltages was demonstrated and applied to fluid pumping based on a 3-phase peristaltic sequence. A maximum flow rate of 1.7 nL min^–1 and an estimated pumping pressure of 1.6 kPa were achieved at 20 Hz phase frequency. A dynamic analysis was also performed with a lumped-parameter model for the peristaltic pump. The analysis results allow a quantitative understanding of the peristaltic pumping operation, and correctly predict the trends exhibited by the experimental data. The small footprint of the micro pump is well suited for large-scale integration of microfluidics. Moreover, because the same platform technology has also been used to fabricate other devices (e.g. valves, electrospray ionization nozzles, filters and flow sensors), the integration of these different devices can potentially lead to versatile and functional micro total analysis systems (µTAS)
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