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991.
Computational fluid dynamics simulations were employed to compare performance of various designs of a pretreatment screw conveyor
reactor. The reactor consisted of a vertical screw used to create cross flow between the upward conveying solids and the downward
flow of acid. Simulations were performed with the original screw design and a modified design in which the upper flights of
the screw were removed. Results of the simulations show visually that the modified design provided favorable plug flow behavior
within the reactor. Pressure drop across the length of the reactor without the upper screws in place was predicted by the
simulations to be 5 vs 40 kPa for the original design. 相似文献
992.
Spatiotemporal chaos in parametrically excited surface waves is compared to fully developed turbulence. Measured correlation functions decay in both space and time. In contrast to turbulence, the inertial range is absent in the Faraday experiment and intermittency is concentrated at a few preferred wavelengths. 相似文献
993.
994.
995.
Optimal hypercontractivity bounds for the fermion oscillator semigroup are obtained. These are the fermion analogs of the optimal hypercontractivity bounds for the boson oscillator semigroup obtained by Nelson. In the process, several results of independent interest in the theory of non-commutative integration are established.Work supported by U.S. National Science Foundation grant no. PHY90-19433-A01. 相似文献
996.
Yanmin Wang Eric Forssberg Peng Lin 《Particle & Particle Systems Characterization》2005,22(5):336-344
This paper presents the experimental results on the wet grinding of a moist calcium carbonate material in a hybrid comminution system, which consists of a high pressure roller mill (HPRM) and a subsequent stirred bead mill. The results show that the pre‐treatment of the material with the HPRM could result in energy saving and efficient size reduction during the subsequent wet ultra‐fine grinding in the stirred bead mill. It was found that the level of fineness of the ground product is dramatically influenced by the number of repeat passes of pre‐grinding in the HRPM. The formation of micro‐cracks in the particles under compressive loads was discussed in order to elucidate the role of the HRPM as a pre‐grinder in the hybrid comminution system. The simulated breakage behaviors of various irregular shaped particles indicate that the tortuous micro‐crack propagation paths and the crack branching behavior are related to the heterogeneity of the particle and the stress distributions. 相似文献
997.
Frequency and intensity ranges (in true decibel sound pressure level, 20 microPa at 1 m) of voice production in trained and untrained vocalists were compared with the perceived dynamic range (phons) and units of loudness (sones) of the ear. Results were reported in terms of standard voice range profiles (VRPs), perceived VRPs (as predicted by accepted measures of auditory sensitivities), and a new metric labeled as an overall perceptual level construct. Trained classical singers made use of the most sensitive part of the hearing range (around 3-4 kHz) through the use of the singer's formant. When mapped onto the contours of equal loudness (depicting nonuniform spectral and dynamic sensitivities of the auditory system), the formant is perceived at an even higher sound level, as measured in phons, than a flat or A-weighted spectrum would indicate. The contributions of effects like the singer's formant and the sensitivities of the auditory system helped the trained singers produce 20% to 40% more units of loudness, as measured in sones, than the untrained singers. Trained male vocalists had a maximum overall perceptual level construct that was 40% higher than the untrained male vocalists. Although the A-weighted spectrum (commonly used in VRP measurement) is a reasonable first-order approximation of auditory sensitivities, it misrepresents the most salient part of the sensitivities (where the singer's formant is found) by nearly 10 dB. 相似文献
998.
999.
Zbigniew Kisiel Lech Pszczó?kowski Manfred Winnewisser Eric Herbst 《Journal of Molecular Spectroscopy》2005,233(2):231-243
We report the results of a comprehensive reinvestigation of the rotational spectrum of diethyl ether based on broadband millimetre-wave spectra recently recorded at The Ohio State University and in Warsaw, covering the frequency region 108-366 GHz. The data set for the ground vibrational state of trans-trans diethyl ether has been extended to over 2000 lines and improved spectroscopic constants have been determined. Rotational spectra in the first excited vibrational states of the three lowest vibrational modes of trans-trans-diethyl ether, ν20, ν39, and ν12 have been assigned. The v20 = 1 and v39 = 1 states are near 100 cm−1 in vibrational term value and are coupled by a strong c-axis Coriolis interaction, which gives rise to many spectacular manifestations in the rotational spectrum. All of these effects have been successfully fitted for a dataset comprising over 3000 transitions, leading to precise determination of the energy difference between these states, (ΔE/hc)=10.400222(5) cm−1. A newly developed software package for assignment and analysis of broadband spectra is described and made available. 相似文献
1000.
The first successful preparation of 14,36-didehydro pristinamycins IIA and IIB is reported via different strategies. 相似文献