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排序方式: 共有45条查询结果,搜索用时 112 毫秒
1.
Polyethyleneimine (PEIM) samples crosslinked by a commercial epoxy resin (Epon 828) were prepared, and their adsorption capacity for acidic gases was studied. The swelling and deswelling characteristics of the crosslinked samples were also examined as part of this program. Reactivation of these adsorbents could be carried out by heat, or by a combination of heat and treatment in dilute alkalies. 相似文献
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A new approach for design of improved interfacial bonding between carbon fibers and polymeric matrices is described. In this method the affinity of surface-treated carbon fibers to various polymer matrices is simulated by analyzing the adsorption characteristics of model compounds, typical of the polymer units, onto very high surface area carbon fibers. The affinity can be evaluated by the use of Thermogravimetric Analysis (TGA) to measure adsorption–desorption characteristics. Since high surface area, activated carbon fibers (ACF) can be chemically treated to obtain acidic, basic, nonpolar or highly polar surfaces, it should be possible to assess the interactions of chemically modified surfaces with model compounds such as methanol (MeOH), acetone, dimethylformamide (DMF), dimethylether, tetrahydrofuran (THF) and water. Some preliminary results are presented, indicating that surface treatments for carbon fibers other than oxidation may lead to enhanced bonding with polymeric matrices. 相似文献
4.
Numerical simulations and laboratory measurements have been used to illuminate the interaction of a moving shock wave impacting
on metallic grids at various shock strengths and grid solidities. The experimental work was carried out in a large scale shock
tube facility while computational work simulated the flow field with a time-dependent inviscid and a time-dependent viscous
model. The pressure drop measured across the grids is a result of two phenomena which are associated with the impact of the
shock on the metallic grids. First are the reflection and refraction of the incoming shock on the grid itself. This appears
to be the main inviscid mechanism associated with the reduction of the strength of the transmitted shock. Second, viscous
phenomena are present during the reflection and refraction of the wave as well as during the passage of the induced flow of
the air through the grid. The experimental data of pressure drop across the grid obtained in the present investigation are
compared with those obtained from computations. The numerical results slightly overpredict the experimental data of relative
pressure drop which increases substantially with grid solidity at fixed flow Mach numbers. The processes of shock reflection
and refraction are continuous and they can be extended in duration by using thicker grids that will result in lower compression
rates of the structural loading and increase the viscous losses associated with these phenomena which will further attenuate
the impacting shock. Preliminary theoretical analysis suggests that the use of a graded porosity/solidity material will result
in higher pressure drop than a constant porosity/solidity material and thus provide effective blast mitigation.
相似文献
5.
Adamson P Andreopoulos C Armstrong R Auty DJ Ayres DS Backhouse C Barr G Bishai M Blake A Bock GJ Boehnlein DJ Bogert D Cavanaugh S Cherdack D Childress S Choudhary BC Coelho JA Coleman SJ Corwin L Cronin-Hennessy D Danko IZ de Jong JK Devenish NE Diwan MV Dorman M Escobar CO Evans JJ Falk E Feldman GJ Frohne MV Gallagher HR Gomes RA Goodman MC Gouffon P Graf N Gran R Grant N Grzelak K Habig A Harris D Hartnell J Hatcher R Himmel A Holin A Huang X Hylen J Ilic J Irwin GM Isvan Z Jaffe DE 《Physical review letters》2011,106(18):181801
Measurements of neutrino oscillations using the disappearance of muon neutrinos from the Fermilab NuMI neutrino beam as observed by the two MINOS detectors are reported. New analysis methods have been applied to an enlarged data sample from an exposure of 7.25×10(20) protons on target. A fit to neutrino oscillations yields values of |Δm(2)|=(2.32(-0.08)(+0.12))×10(-3) eV(2) for the atmospheric mass splitting and sin(2)(2θ)>0.90 (90% C.L.) for the mixing angle. Pure neutrino decay and quantum decoherence hypotheses are excluded at 7 and 9 standard deviations, respectively. 相似文献
6.
Y. Andreopoulos 《Russian Journal of Electrochemistry》2008,44(4):390-396
A nearly homogeneous and isotropic decaying compressible turbulence and a vortex flow have been investigated experimentally
in a large-scale shock tube facility. Rectangular grids of various mesh sizes were used to generate turbulence with Reynolds
numbers based on Taylor’s microscale ranging from 260 to 1300. Measurements of the three-dimensional velocity and vorticity
vectors, the full velocity gradient and rate-of-strain tensors with instrumentation of high temporal and spatial resolution
have been carried out. This allowed estimates of dilatation, compressible dissipation and dilatational stretching to be obtained.
The time-dependent signals of enstrophy, vortex stretching/tilting vector and helicity were found to exhibit a rather strong
intermittent behavior which is characterized by high amplitude bursts with values up to 8 times their r.m.s. within periods
of less violent and longer lived events. Several of these bursts are evident in all the signals suggesting the existence of
a dynamical flow phenomenon as a common cause. Further interpretation of the results was obtained by considering the decomposition
of the velocity field into a solenoidal contribution and a potential part. The effect of the Mach number is to increase the
influence of the solenoidal part of the contribution and therefore make the flow more “vortex-dominated”.
Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 4, pp. 422–428.
The text was submitted by the authors in English. 相似文献
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Summary A method of calculating the separated flow of a viscous fluid is proposed, which allows to split up properly the boundary condition problem from the viscous phenomena. The theory is developed for the flow past a plate and yields wakes of finite extension having an underpressure which depends directly on the amount of vorticity diffusion and dissipation occurring in the fluid. Application of the method to real flows shows good agreement between the calculated and the measured velocity distributions in front of the plate and in the wake.
Résumé Une méthode de calcul de l'écoulement décollé d'un fluide visqueux est proposée qui permet de séparer clairement le problème aux limites des phénomènes visqueux. La théorie est développée pour l'écoulement autour d'une plaque et donne des sillages de longueur finie ayant une dépression de culot directement dépendante de l'intensité de la diffusion et dissipation de la vorticité se produisant dans le fluide. L'application de la méthode à des écoulements réels montre une bonne concordance entre les répartitions de vitesse calculées et mesurées sur le devant de la plaque et dans le sillage.相似文献
9.
Michael DG Adamson P Alexopoulos T Allison WW Alner GJ Anderson K Andreopoulos C Andrews M Andrews R Arms KE Armstrong R Arroyo C Auty DJ Avvakumov S Ayres DS Baller B Barish B Barker MA Barnes PD Barr G Barrett WL Beall E Becker BR Belias A Bergfeld T Bernstein RH Bhattacharya D Bishai M Blake A Bocean V Bock B Bock GJ Boehm J Boehnlein DJ Bogert D Border PM Bower C Boyd S Buckley-Geer E Bungau C Byon-Wagner A Cabrera A Chapman JD Chase TR Cherdack D Chernichenko SK Childress S Choudhary BC 《Physical review letters》2006,97(19):191801
This Letter reports results from the MINOS experiment based on its initial exposure to neutrinos from the Fermilab NuMI beam. The rates and energy spectra of charged current nu(mu) interactions are compared in two detectors located along the beam axis at distances of 1 and 735 km. With 1.27 x 10(20) 120 GeV protons incident on the NuMI target, 215 events with energies below 30 GeV are observed at the Far Detector, compared to an expectation of 336+/-14 events. The data are consistent with nu(mu) disappearance via oscillations with |Delta(m)2/32|=2.74 +0.44/-0.26 x10(-3)eV(2) and sin(2)(2theta(23))>0.87 (68% C.L.). 相似文献
10.
Adamson P Andreopoulos C Arms KE Armstrong R Auty DJ Ayres DS Baller B Barr G Barrett WL Becker BR Belias A Bernstein RH Bhattacharya D Bishai M Blake A Bock GJ Boehm J Boehnlein DJ Bogert D Bower C Buckley-Geer E Cavanaugh S Chapman JD Cherdack D Childress S Choudhary BC Coleman SJ Culling AJ de Jong JK Diwan MV Dorman M Dytman SA Escobar CO Evans JJ Falk Harris E Feldman GJ Frohne MV Gallagher HR Goodman MC Gouffon P Gran R Grashorn EW Grossman N Grzelak K Habig A Harris D Harris PG 《Physical review letters》2008,101(15):151601
A search for a sidereal modulation in the MINOS near detector neutrino data was performed. If present, this signature could be a consequence of Lorentz and CPT violation as predicted by the effective field theory called the standard-model extension. No evidence for a sidereal signal in the data set was found, implying that there is no significant change in neutrino propagation that depends on the direction of the neutrino beam in a sun-centered inertial frame. Upper limits on the magnitudes of the Lorentz and CPT violating terms in the standard-model extension lie between 10(-4) and 10(-2) of the maximum expected, assuming a suppression of these signatures by a factor of 10(-17). 相似文献