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91.
92.
An experimental technique is presented for measuring the heat dissipation and localization during cyclic loading of materials.
The temperature field is measured by a number of thermistors and an infrared camera, which scans the specimen surface continuously.
The specimen is mounted inside an isothermal chamber. The measured whole-field temperature can be used for detection of damage
propagation and localization. The resolution of the technique under various boundary conditions is discussed using a onedimensional
model for the heat loss under steady-state conditions. Applications of the technique are demonstrated for specimens made of
fiber-reinforced ceramic and polymer matrix composites (PMCs). A methodology is proposed for measuring changes in damping
and stiffness properties of viscoelastic polymer matrix composites using the temperature rise of a cyclic loaded specimen.
It is demonstrated that for a ceramic matrix composite, where interfacial frictional sliding gives rise to heat dissipation,
the temperature resolution can be used for detection of stress-strain hysteresis with an accuracy better than that of the
stress-strain data. 相似文献
93.
Birrell JA Desrosiers JN Jacobsen EN 《Journal of the American Chemical Society》2011,133(35):13872-13875
A highly enantioselective acylation of silyl ketene acetals with acyl fluorides has been developed to generate useful α,α-disubstituted butyrolactone products. This transformation is promoted by a new thiourea catalyst and 4-pyrrolidinopyridine and represents the first example of enantioselective thiourea anion-binding catalysis with fluoride. 相似文献
94.
Hansen M Jacobsen NW Nielsen FK Björklund E Styrishave B Halling-Sørensen B 《Analytical and bioanalytical chemistry》2011,400(10):3409-3417
This paper presents the development, optimization and validation of a methodology to determine nine key steroid hormones (viz.
pregnenolone, progesterone, dehydroepiandrosterone, androstenedione, testosterone, dihydrotestosterone, estrone, 17α-estradiol
and 17β-estradiol) expressed in the steroidogenesis in biological fluids. The analytical method allows for the determination
of steroid hormones in blood plasma and serum down to 0.08–0.16 ng/mL for estrogens, 0.20–0.36 ng/mL for androgens and 0.36–0.43 ng/mL
for progestagens. These limits of detection were obtainable using a two-step solid-phase clean-up for fractionation and elimination
of interfering lipids (fatty acids, phospholipids, glycerides and sterols) from the steroid hormones. The accuracy of the
method was 50–112% in the range 0.10 to 2.00 ng/mL. 相似文献
95.
Fortman GC Jacobsen H Cavallo L Nolan SP 《Chemical communications (Cambridge, England)》2011,47(34):9723-9725
The catalytic activity of a series of coordinatively unsaturated NHC-M(III) (M = Rh, Ir; NHC = N-heterocyclic carbene) complexes was tested in the deuteration of secondary and tertiary silanes. Among these, [IrCl(I(t)Bu')(2)] provides the highest conversions to the deuterated species. Mechanistic studies highlight the reversible nature of the ortho-metalation reaction. 相似文献
96.
97.
98.
99.
The metal-insulator transition in TTF-MTCNQ is broadened and shifted to a higher temperature compared to the transition in TTF-TCNQ. Tetramethyl-TTF-MTCNQ is found to display a similar behaviour, while tetramethyl-TSF-MTCNQ is insulating. The paramagnetic susceptibility of TTF-MTCNQ is comparable to that of TTF-TCNQ above the transition. 相似文献
100.
The effect of a transverse magnetic field on the chain axis resistivity of the new organic conductor (TMTSF)2PF6 is found to be substantial near the transition point. δρ/ρ0 is + 20% at B=6Vsm-2 just above the transition. An interpretation based on curvature in the Fermi surface is proposed. 相似文献