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911.
Martin D. Griffith Justin Leontini Mark C. Thompson Kerry Hourigan 《Journal of Fluids and Structures》2011,27(5-6):855-860
A numerical investigation of the flow past a circular cylinder centred in a two-dimensional channel of varying width is presented. For low Reynolds numbers, the flow is steady. For higher Reynolds numbers, vortices begin to shed periodically from the cylinder. In general, the Strouhal frequency of the shedding vortices increases with blockage ratio. In addition, a two-dimensional instability of the periodic vortex shedding is found, both empirically and by means of a Floquet stability analysis. The instability leads to a beating behaviour in the lift and drag coefficients of the cylinder, which occurs at a Reynolds number higher than the critical Reynolds number for the three-dimensional mode A-type instability, but lower than a Reynolds number for any mode B-type instability. 相似文献
912.
Piotr T. Chruściel Justin Corvino James Isenberg 《Communications in Mathematical Physics》2011,304(3):637-647
Given a collection of N solutions of the (3 + 1) Einstein constraint equations which are asymptotically Euclidean and vacuum near infinity, we show
how to construct a new solution of the constraints which is itself asymptotically Euclidean, and which contains specified
sub-regions of each of the N given solutions. This generalizes earlier work which handled the time-symmetric case, thus providing a construction of large
classes of initial data for the many body problem in general relativity. 相似文献
913.
Sivels Ciara B. McIntyre Justin I. Bowyer Theodore W. Kalinowski Martin B. Pozzi Sara A. 《Journal of Radioanalytical and Nuclear Chemistry》2017,314(2):829-841
Journal of Radioanalytical and Nuclear Chemistry - Developments in radioxenon monitoring since the implementation of the International Monitoring System are reviewed with emphasis on the most... 相似文献
914.
Sheaves and sheaf cohomology are powerful tools in computational topology, greatly generalizing persistent homology. We develop an algorithm for simplifying the computation of cellular sheaf cohomology via (discrete) Morse theoretic techniques. As a consequence, we derive efficient techniques for distributed computation of (ordinary) cohomology of a cell complex. 相似文献
915.
916.
Identification of six new Alternaria sulfoconjugated metabolites by high‐resolution neutral loss filtering
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917.
Justin M. Delancey Matthew D. Cavazza Matthew G. Rendos Cory J. Ulisse Susan G. Palumbo Robert T. Mathers 《Journal of polymer science. Part A, Polymer chemistry》2011,49(17):3719-3727
Renewable resources have been utilized to control the degree of crosslinking during ring‐opening metathesis polymerizations (ROMP). In this regard, the addition of monoterpenes to thermosets created a sustainable method for adjusting the physical properties and thermal stability. A number of monoterpenes with alkenes were examined as monofunctional reactants. The presence of these monoterpenes, such as β‐pinene, during the ROMP of dicyclopentadiene altered the degree of crosslinking and plasticized the thermoset. The resulting physical properties were tailored to obtain desired modulus and glass transition (Tg) temperatures. The influence of time, temperature, weight percent β‐pinene, and different metathesis catalysts was examined by dynamic mechanical analysis, thermogravimetric analysis, and FTIR spectroscopy. A comparison of β‐pinene with other monoterpenes, such as carvone, limonene oxide, myrcene, and d‐limonene, resulted in a reactivity profile for this general method. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
918.
This Letter reveals an innovative and facile procedure to prepare quinoxalines in two synthetic steps. The microwave assisted Petasis reaction is followed by the acid mediated unmasking of an internal amino nucleophile, cyclodehydration and oxidation to give collections of quinoxalines in good to excellent yields. 相似文献
919.
Kai Sun Ritobrata Sur Jay B. Jeffries Ronald K. Hanson Tommy Clark Justin Anthony Scott Machovec John Northington 《Applied physics. B, Lasers and optics》2014,117(1):411-421
A real-time, in situ water vapor (H2O) sensor using a tunable diode laser near 1,352 nm was developed to continuously monitor water vapor in the synthesis gas of an engineering-scale high-pressure coal gasifier. Wavelength-scanned wavelength-modulation spectroscopy with second harmonic detection (WMS-2f) was used to determine the absorption magnitude. The 1f-normalized, WMS-2f signal (WMS-2f/1f) was insensitive to non-absorption transmission losses including beam steering and light scattering by the particulate in the synthesis gas. A fitting strategy was used to simultaneously determine the water vapor mole fraction and the collisional-broadening width of the transition from the scanned 1f-normalized WMS-2f waveform at pressures up to 15 atm, which can be used for large absorbance values. This strategy is analogous to the fitting strategy for wavelength-scanned direct absorption measurements. In a test campaign at the US National Carbon Capture Center, the sensor demonstrated a water vapor detection limit of ~800 ppm (25 Hz bandwidth) at conditions with more than 99.99 % non-absorption transmission losses. Successful unattended monitoring was demonstrated over a 435 h period. Strong correlations between the sensor measurements and transient gasifier operation conditions were observed, demonstrating the capability of laser absorption to monitor the gasification process. 相似文献
920.
Epitaxial (001)-oriented PbSc0.5Ta0.5O3 (PST) thin films were deposited by pulsed laser deposition. Local piezoelectric investigations performed by piezoelectric force microscopy show a dual slope for the piezoelectric coefficient. A piezoelectric coefficient of 3 pm/V was observed at voltages up to 0.8 V. However, at voltages above 0.8 V, there is a steep increase in piezoelectric coefficient mounting to 23.2 pm/V. This nonlinear piezoelectric response was observed to be irreversible in nature. In order to better understand this nonlinear behavior, voltage dependent dielectric constant measurements were performed. These confirmed that the piezoelectric non-linearity is indeed a manifestation of a dielectric non-linearity. In contrast to classical ferroelectric systems, the observed dielectric non-linearity in this relaxor material cannot be explained by the Rayleigh model. Thus the dielectric non-linearity in the PST films is tentatively explained as a manifestation of a percolation of the polar nano regions. 相似文献