925 research outputs found
Surface activation of Concorde by Be-7
Activation analysis of two airframe components from the Concorde aircraft has identified the presence of Be-7, a nuclide found by other investigators that was deposited on the forward edge of the Long Duration Exposure Facility (LDEF) structure. The results of the Concorde analysis indicate that this phenomenon is very much a surface effect, and that the areal densities of the Be-7 are comparable to those found for LDEF. The collection of Be-7 by the aircraft must be greater than in the case of LDEF (since duration for which Concorde is accumulating the nuclide is shorter) and is of the order of 1.2 to 41 nuclei/sq cm(-)s(exp -1) depending upon assumptions made regarding the altitude at which collection becomes appreciable, and the efficiency of the process which removes the radionuclide
Determination of Stark parameters by cross-calibration in a multi-element laser-induced plasma
We illustrate a Stark broadening analysis of the electron density N(e) and temperature T(e) in a laser-induced plasma (LIP), using a model free of assumptions regarding local thermodynamic equilibrium (LTE). The method relies on Stark parameters determined also without assuming LTE, which are often unknown and unavailable in the literature. Here, we demonstrate that the necessary values can be obtained in situ by cross-calibration between the spectral lines of different charge states, and even different elements, given determinations of N(e) and T(e) based on appropriate parameters for at least one observed transition. This approach enables essentially free choice between species on which to base the analysis, extending the range over which these properties can be measured and giving improved access to low-density plasmas out of LTE. Because of the availability of suitable tabulated values for several charge states of both Si and C, the example of a SiC LIP is taken to illustrate the consistency and accuracy of the procedure. The cross-calibrated Stark parameters are at least as reliable as values obtained by other means, offering a straightforward route to extending the literature in this area
Approaching the adiabatic timescale with machine-learning
The control and manipulation of quantum systems without excitation is
challenging, due to the complexities in fully modeling such systems accurately
and the difficulties in controlling these inherently fragile systems
experimentally. For example, while protocols to decompress Bose-Einstein
condensates (BEC) faster than the adiabatic timescale (without excitation or
loss) have been well developed theoretically, experimental implementations of
these protocols have yet to reach speeds faster than the adiabatic timescale.
In this work, we experimentally demonstrate an alternative approach based on a
machine learning algorithm which makes progress towards this goal. The
algorithm is given control of the coupled decompression and transport of a
metastable helium condensate, with its performance determined after each
experimental iteration by measuring the excitations of the resultant BEC. After
each iteration the algorithm adjusts its internal model of the system to create
an improved control output for the next iteration. Given sufficient control
over the decompression, the algorithm converges to a novel solution that sets
the current speed record in relation to the adiabatic timescale, beating out
other experimental realizations based on theoretical approaches. This method
presents a feasible approach for implementing fast state preparations or
transformations in other quantum systems, without requiring a solution to a
theoretical model of the system. Implications for fundamental physics and
cooling are discussed.Comment: 7 pages main text, 2 pages supporting informatio
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Economic evaluation of smoking cessation in Ontario's regional cancer programs.
Quitting smoking after a diagnosis of cancer results in greater response to treatment and decreased risk of disease recurrence and second primary cancers. The objective of this study was to evaluate the potential cost-effectiveness of two smoking cessation approaches: the current basic smoking cessation program consisting of screening for tobacco use, advice, and referral; and a best practice smoking cessation program that includes the current basic program with the addition of pharmacological therapy, counseling, and follow-up. A Markov model was constructed that followed 65-year-old smokers with cancer over a lifetime horizon. Transition probabilities and mortality estimates were obtained from the published literature. Costs were obtained from standard costing sources in Ontario and reports. Probabilistic and deterministic sensitivity analyses were conducted to address parameter uncertainties. For smokers with cancer, the best practice smoking cessation program was more effective and more costly than the basic smoking cessation program. The incremental cost-effectiveness ratio of the best practice smoking cessation program compared to the basic smoking cessation program was 5050 per LY gained for males, and 4100 per LY gained for females. Results were most sensitive to the hazard ratio of mortality for former and current smokers, the probability of quitting smoking through participation in the program and smoking-attributable costs. The study results suggested that a best practice smoking cessation program could be a cost-effective option. These findings can support and guide implementation of smoking cessation programs
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Simultaneous removal of oil and gases from liquid sources using a hollow fiber membrane
The present invention includes an apparatus and method for removing oil from a oil-containing liquid comprising oil and gas comprising: a source of oil-containing liquid; and a membrane contactor system in fluid communication with the source of oil-containing liquid, the membrane contactor system comprising one or more membrane contactors having a first and a second surface, wherein the first surface coalesces oil and removes gas from the oil-containing liquid, and the oil and gas are collected on the second surface from the oil-containing liquid.Board of Regents, University of Texas Syste
Synthesis of mechanical error in rapid prototyping processes using stochastic 1 approach
Published ArticleA synthesis procedure for allocating tolerances and clearances in rapid prototyping (RP) processes has been developed, using a unified method based on stochastic approach, as developed by the authors, to study the mechanical error in RP processes. The tolerances and clearances that cause mechanical error have been assumed to be random variables, and are optimally allocated so as to restrict the mechanical error within the specified limits. Using the synthesis procedure, the allocation is done for the Fused Deposition Modeling (FDM) and the Stereolithography (SL) processes
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