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A two-dimensional steady-sate analysis of semi-infinite brittlecrack growth at a constant subcritical rate in an unboundedfully-coupled thermoelastic solid under mixed-mode thermomechanicalloading is made. The loading consists of normal and shear tractionsand heat fluxes applied as point sources (line loads in theout-of-plane direction). A related problem is solved exactly in an integral transformspace, and robust asymptotic forms used to reduce the originalproblem to a set of integral equations. The equations are partiallycoupled and exhibit operators of both Cauchy and Abel types,yet can be solved analytically. The temperature change field at a distance from the moving crackedge is then constructed, and its dominant term is found tobe controlled by the imposed heat fluxes. The role of this termis, indeed, enhanced if the heat fluxes serve to render thecrack as a net heat source/sink for the solid, as opposed tobeing a transmitter of heat across its plane. More generally,the influence of the thermoelastic coupling on this field, aswell as other functions, is found to increase with crack speed. 相似文献
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Amundson LM Owen BC Gallardo VA Habicht SC Fu M Shea RC Mossman AB Kenttämaa HI 《Journal of the American Society for Mass Spectrometry》2011,22(4):670-682
Positive-mode atmospheric pressure chemical ionization tandem mass spectrometry (APCI-MS
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) was tested for the differentiation of regioisomeric aromatic ketocarboxylic acids. Each analyte forms exclusively an abundant
protonated molecule upon ionization via positive-mode APCI in a commercial linear quadrupole ion trap (LQIT) mass spectrometer.
Energy-resolved collision-activated dissociation (CAD) experiments carried out on the protonated analytes revealed fragmentation
patterns that varied based on the location of the functional groups. Unambiguous differentiation between the regioisomers
was achieved in each case by observing different fragmentation patterns, different relative abundances of ion-molecule reaction
products, or different relative abundances of fragment ions formed at different collision energies. The mechanisms of some
of the reactions were examined by H/D exchange reactions and molecular orbital calculations. 相似文献
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The binding dynamics of the guests acenaphthene, phenanthrene, fluorene, and acenaphthenol with sodium cholate aggregates were studied using laser flash photolysis and fluorescence. The location of the guests in the bile salt aggregate is determined by the guest's hydrophobicity, where acenaphthene, phenanthrene, and fluorene bind to the primary aggregates, while acenaphthenol binds to the secondary bile salt aggregates. The residence time of the guests in the primary aggregates and the access of ionic species from the aqueous phase to the guest in the aggregate depend on the size and the shape of the guest. These results show that bile salt aggregates are adaptable supramolecular host systems. 相似文献
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Amita Gupta Alexei Yu Ganin Parmanand Sharma Vikrant Agnihotri LM Belova KV Rao Mikhail E Kozlov AA Zakhidov RH Baughman 《Pramana》2002,58(5-6):1051-1059
We present studies of novel nanocomposites of BiNi impregnated into the structure of opals as well as inverse opals. Atomic force microscopy and high resolution elemental analyses show
a highly ordered structure and uniform distribution of the BiNi filler in the matrix. These BiNi-based nanocomposites are
found to exhibit distinct ferromagnetic-like ordering with transition temperature of about 675 K. As far as we know there
exists no report in literature on any BiNi compound which is magnetic. 相似文献
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Somuramasami J Duan P Amundson LM Archibold E Winger BE Kenttämaa HI 《Journal of the American Society for Mass Spectrometry》2011,22(6):1040-1051
Several lignin model compounds were examined to test whether gas-phase ion–molecule reactions of trimethylborate (TMB) in
a FTICR can be used to differentiate the ortho-, meta-, and para-isomers of protonated aromatic compounds, such as those formed during degradation of lignin. All three regioisomers could
be differentiated for methoxyphenols and hydroxyphenols. However, only the differentiation of the ortho-isomer from the meta- and para-isomers was possible for hydroxyacetophenones and hydroxybenzoic acids. Consideration of the previously reported proton affinities
at all basic sites in the isomeric hydroxyphenols, and the calculated proton affinities at all basic sites in the three methoxyphenol
isomers, revealed that the proton affinities of the analytes relative to that of TMB play an important role in determining
whether and how they react with TMB. The loss of two methanol molecules (instead of one) from the adducts formed with TMB
either during ion–molecule reactions, or during sustained-off resonance irradiated collision-activated dissociation of the
ion–molecule reaction products, revealed the presence of two functionalities in almost all the isomers. This finding supports
earlier results suggesting that TMB can be used to count the functionalities in unknown oxygen-containing analytes. 相似文献
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Habicht SC Vinueza NR Amundson LM Kenttämaa HI 《Journal of the American Society for Mass Spectrometry》2011,22(3):520-530
We report here a comparison of the use of diagnostic ion–molecule reactions for the identification of oxygen-containing functional
groups in Fourier-transform ion cyclotron resonance (FTICR) and linear quadrupole ion trap (LQIT) mass spectrometers. The
ultimate goal of this research is to be able to identify functionalities in previously unknown analytes by using many different
types of mass spectrometers. Previous work has focused on the reactions of various boron reagents with protonated oxygen-containing
analytes in FTICR mass spectrometers. By using a LQIT modified to allow the introduction of neutral reagents into the helium
buffer gas, this methodology has been successfully implemented to this type of an ion trap instrument. The products obtained
from the reactions of trimethyl borate (TMB) with various protonated analytes are compared for the two instruments. Finally,
the ability to integrate these reactions into LC-MS experiments on the LQIT is demonstrated. 相似文献
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The purpose of this work is to investigate acoustic source localization algorithms suitable for use with distributed sensor networks. Traditional sensor networks employ a central controller; however centralized data processing in large-scale sensor networks is not always desirable because of the excessive communication and computational complexity it requires. Therefore, fully distributed localization algorithms are considered. The most important aspect of these algorithms is that they be scalable for use in large sensor networks. The scalability is achieved by forming sensor nodes into groups which collaborate to locate sources. Source locations are determined from time of arrival (TOA) information of the acoustic wave front. Two source location solution methods are used: least squares (LS) and Tikhonov regularized inversion (RI). Experimental results validate the accuracy of a distributed localization approach, and the effectiveness of the LS and RI methods are compared. Additionally, important parameters of the distributed localization algorithm are considered. 相似文献
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Bakken Andrew P. Hill Charles G. Amundson Clyde H. 《Applied biochemistry and biotechnology》1991,(1):741-756
A novel chemical reactor, consisting of β-galactosidase fromAspergillus oryzae immobilized on a ribbed membrane made from polyvinyl-chloride and silica, was used to hydrolyze the lactose constituent of
skim milk. Multiresponse nonlinear regression methods were employed to determine the kinetic parameters of rate expressions
based on a proposed enzymatic mechanism that includes the formation of oligosaccharides. HPLC methods were employed to monitor
the concentrations of all species present in the effluent stream. For the experimental conditions used in this research, a
rate expression that includes the inhibition effect of α-galactose is sufficient to model the reaction network. 相似文献