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71.
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73.
We introduce a sort of semilinear structure on subsets of the family of semigroups
defined on a metric space. The key step is the definition of the sum of two
semigroups, which is here achieved by means of the classical operator splitting
technique. No linearity assumption is required, since the whole construction is
in a metric space. 相似文献
74.
International safety standards recommend a limit below 30% variation in acoustic intensity for ultrasound therapy (UST) equipment. In view of this question, the purpose of this work was to evaluate the intensity of new UST equipment in the Brazilian market. An evaluation was performed of eight models manufactured by six different national manufacturers; under continuous and pulsed conditions, at frequencies of 1.0-3.0 MHz, for a total of 48 items of equipment. The intensities were analysed according to the technical standards IEC 601-2-5, in the range 0.01-3.0 Wcm(-2), using a radiation pressure scale UPM-DT-10 (Ohmic Instruments), previously calibrated. The results demonstrated that the models Sonacel, Sonacel plus, Sonacel III, Avatar I, and Sonamed I, although they were new (unused) presented calibration errors of over 30% in more than one intensity checked, and the models SONOPULSE, PRO-SEVEN and SONOMASTER ST. are within the standards proposed. The results show that industry must improve quality control on their production lines, as well as that there is a need for a supervising body at national level. Published by Elsevier Science B.V. 相似文献
75.
Hui Wang Lorenzo Vendrame Dr. Christophe Fliedel Dr. Si Chen Dr. Florence Gayet Dr. Franck D'Agosto Dr. Muriel Lansalot Dr. Eric Manoury Prof. Rinaldo Poli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(16):5205-5214
Unimolecular amphiphilic nanoreactors with a poly(4-vinyl-N-methylpyridinium iodide) (P4VPMe+I−) polycationic outer shell and two different architectures (core-cross-linked micelles, CCM, and nanogels, NG), with narrow size distributions around 130–150 nm in diameter, were synthesized by RAFT polymerization from an R0-4VPMe+I−140-b-S50-SC(S)SPr macroRAFT agent by either chain extension with a long (300 monomer units) hydrophobic polystyrene-based block followed by cross-linking with diethylene glycol dimethacrylate (DEGDMA) for the CCM particles, or by simultaneous chain extension and cross-linking for the NG particles. A core-anchored triphenylphosphine (TPP) ligand functionality was introduced by using 4-diphenylphosphinostyrene (DPPS) as a comonomer (5–20 % mol mol−1) in the chain extension (for CCM) or chain extension/cross-linking (for NG) step. The products were directly obtained as stable colloidal dispersions in water (latexes). After loading with [RhCl(COD)]2 to yield [RhCl(COD)(TPP@CCM)] or [RhCl(COD)(TPP@NG)], respectively, the polymers were used as polymeric nanoreactors in Rh-catalyzed aqueous biphasic hydrogenation of the model substrates styrene and 1-octene, either neat (for styrene) or in an organic solvent (toluene or 1-nonanol). All hydrogenations were rapid (TOF up to 300 h−1) at 25 °C and 20 bar of H2 pressure, the biphasic mixture rapidly decanted at the end of the reaction (<2 min), the Rh loss was negligible (<0.1 ppm in the recovered organic phase), and the catalyst phase could be recycled 10 times without significant loss of catalytic activity. 相似文献
76.
Rinaldo M. Colombo Veronika Schleper 《Nonlinear Analysis: Real World Applications》2012,13(5):2195-2213
This paper presents a model for 2 inviscid, immiscible, compressible and isentropic fluids in 1 space dimension. Its well posedness is proved, globally in time, for data having small total variation. In a sample non-smooth case, the limit in which one of the fluids becomes incompressible is characterized. 相似文献
77.
Thiago Manha Gasparini Rosário Elida Suman Bretas Aline Bruna da Silva Rinaldo Gregorio Jr. 《Journal of Polymer Science.Polymer Physics》2012,50(18):1304-1311
Mats of highly oriented poly(vinylidene fluoride) nanofibers were electrospun by means of a conventional electrospinning equipment; the orientation, however, was obtained using a disk collector rotating at a speed of 4000 rpm and a device that reduced the influence of air displacement during nanofiber orientation. Thermal transitions of the mats were determined by differential scanning calorimetry, the predominant crystalline phase by Fourier transform infrared spectroscopy and wide‐angle X‐ray scattering and the nanofiber orientation and morphology by scanning electron microscopy. Relative permittivity, loss index, stable remnant polarization, and coercive field of the mats were also determined and compared with those obtained for a mat electrospun at 2000 rpm and an oriented commercial film. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 000: 000–000, 2012 相似文献
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79.
Summary Over the past few years many mathematical models have been proposed for the analysis of externally pressurized bearings. But the gaps between experimental observations and the results of model analysis are still wide. These gaps are due to the simplifying hypothesis, that underlie the methods.A mathematical model for designing bearings that takes account of the effects of journal rotation has recently been devised at the Institute of Applied Mechanics of Genoa University. A test stand has also been designed and built, fitted with up-to-date instruments for the experimental analysis of bearings for several journal rotation speeds or for different load conditions.This paper presents a summary of the big program of experimental tests conducted with Italian CNR support and compares these experimental results with the theoretical results obtained by recasting the mathematical model to allow for the principal effects evidenced by the tests.
Sommario Negli ultimi anni sono stati proposti molti modelli matematici atti all'analisi dei cuscinetti pressurizzati dall'esterno. Tuttavia nella letteratura si notano ancora notevoli discordanze fra le osservazioni sperimentali ed i risultati dell'analisi su modello. Tali differenze sono imputabili alle ipotesi semplificative adottate nell'impostazione dei metodi proposti.Presso l'Istituto di Meccanica Applicata di Genova è stato elaborato, negli anni scorsi, un modello matematico per la progettazione dei cuscinetti che tiene conto anche degli effetti dovuti alla rotazione del perno. E stato inoltre progettato e costruito un hanco di prova, dotato di moderne strumentazioni atte all'analisi sperimentale dei cuscinetti per varie velocità di rotazione del perno o per diverse condizioni di carcio.Il presente articolo presenta la sintesi del vasto programma di prove sperimentali condotte con il finanziamento del C.N.R. e confronta tali risultati sperimentali con quelli teorici ottenuti rielaborando il modello matematico per tener conto dei principali effetti messi in evidenza dalle prove.相似文献
80.
On the Control of the Friction Force 总被引:1,自引:1,他引:1
This paper tackles the problem of controlling the Coulomb friction force in order to achieve damping characteristics which can be advantageous in engineering applications, particularly in the area of vibration control, for example, vehicle suspensions, rotating machinery foundations or earthquake protection systems. The control schemes employed belong to the family of variable structure controllers (VSC), a class of robust control algorithms, namely sliding mode control (SMC) and switched state feedback (SSF). The schemes perform force tracking control, aiming at making the friction force track a reference force in order to reduce the acceleration experienced by a suspended mass. The plant investigated is a 2-degree of freedom system and in this study represents a quarter car. The controller performances are investigated both numerically and experimentally. 相似文献