1,478 research outputs found
Exploding wire initiation and electrical operation of a 40-kV system for arc-heated drivers up to 10 feet long
Exploding wire initiation and electrical operation of 40 kV system for arc heated drivers up to 10 feet lon
Arc driver operation for either efficient energy transfer or high-current generator
An investigation is made to establish predictable electric arcs along triggered paths for research purposes, the intended application being the heating of the driver gas of a 1 MJ electrically driven shock tube. Trigger conductors consisting of wires, open tubes, and tubes pressurized with different gases were investigated either on the axis of the arc chamber or spiraled along the chamber walls. Design criteria are presented for successful arc initiation with reproducible voltage-current characteristics. Results are compared with other facilities and several application areas are discussed
Shortcut to a Fermi-Degenerate Gas of Molecules via Cooperative Association
We theoretically examine the creation of a Fermi-degenerate gas of molecules
via a photoassociation or Feshbach resonance applied to a degenerate Bose-Fermi
mixture of atoms. This problem raises an interest because, unlike bosons,
fermions in general do not behave cooperatively, so that the collective
conversion of, say, two million atoms into one million molecules is not to be
expected. Nevertheless, we find that the coupled Fermi system displays
collective Rabi-like oscillations and adiabatic passage between atoms and
molecules, thereby mimicking Bose-Einstein statistics. Cooperative association
of a degenerate mixture of Bose and Fermi gases could therefore serve as a
shortcut to a degenerate gas of Fermi molecules.Comment: 4 pages, 2 figures, submitted to PRL; v2: expanded intro, added
discussion on neglect of collisions and when mimicking should occu
A study of the effects of micro-gravity on seed germination
This study will identify characteristics of seed germination dependent upon gravity. To accomplish this objective, four different seed types will be germinated in space and then be compared to a control group germinated on Earth. Both the experimental and control groups will be analyzed on the cellular level for the size of cells, structural anomalies, and gravitational effects. The experiment will be conducted in a Get Away Special Canister (GAS Can no. 608) owned by the U.S. Space and Rocket Center and designed for students. The GAS Can will remain in the cargo bay of the Space Shuttle with minimal astronaut interaction
Exploratory Investigation of an Airfoil with Area Suction Applied to a Porous, Round Trailing Edge Fitted with a Lift-control Vane
Section Characteristics of a 10.5-percent-thick Airfoil with Area Suction as Affected by Chordwise Distribution of Permeability
An implicit and explicit solver for contact problems
The interaction of rolling tyres with road surfaces is one of the major contributions to road traffic noise. The generation mechanisms of tyre/road noise are usually separated in structure borne and airborne noise. In both mechanisms the contact zone is important. In order to reduce tyre/road noise at the source, accurate (numerical) prediction models are needed. For accurate results, the tyre has to be modelled by a threedimensional finite element model, accounting for complex rubber material behaviour, tread profiles and a detailed tyre construction. A dynamic analysis of a tyre in contact can then be carried out in the time domain. The Structural Dynamics and Acoustics group of the University of Twente has developed an alternative contact solver. The solver, in which the contact condition is always satisfied, is successfully applied to an implicit and explicit three-dimensional finite element model. As a consequence there is no need for contact\ud
elements or contact parameters. The finite element model is valid for large translations and rotations, in which different material models and friction models can be added. This paper explains the solver for an implicit and explicit scheme and presents some examples. In one of the examples a deformable rubber ring is modelled, which is rolling on a rigid surface at a slip angle. The results are compared to the finite element package Abaqus. The examples show the robustness and potential of the algorithm
Synthesis and use of a lysolecithin analog for the purification of UDP-glucuronosyltransferase.
Can the Renormalization Group Improved Effective Potential be used to estimate the Higgs Mass in the Conformal Limit of the Standard Model?
We consider the effective potential in the standard model with a single
Higgs doublet in the limit that the only mass scale present is
radiatively generated. Using a technique that has been shown to determine
completely in terms of the renormalization group (RG) functions when using the
Coleman-Weinberg (CW) renormalization scheme, we first sum leading-log (LL)
contributions to using the one loop RG functions, associated with five
couplings (the top quark Yukawa coupling , the quartic coupling of the Higgs
field , the SU(3) gauge coupling , and the couplings
and ). We then employ the two loop RG functions with the three couplings
, , to sum the next-to-leading-log (NLL) contributions to and
then the three to five loop RG functions with one coupling to sum all the
contributions to . In order to compute these sums, it is
necessary to convert those RG functions that have been originally computed
explicitly in the minimal subtraction (MS) scheme to their form in the CW
scheme. The Higgs mass can then be determined from the effective potential: the
result is decreases to at
order and at order. No reasonable
estimate of can be made at orders or . This is taken
to be an indication that this mechanism for spontaneous symmetry breaking is in
fact viable, though one in which there is slow convergence towards the actual
value of . The mass is argued to be an upper bound on
.Comment: 24 pages, 5 figures. Updated version contains new discussion,
references, figures, and corrects errors in reference
- …