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81.
The aim of this study is the evaluation by mechanical testing of the durability of rigid PVC. The prediction of mechanical durability is made by following the change in the brittle temperature TB at a constant speed by an indentation test after artificial and natural weathering. TB is presented as a possible durability index for thin, extruded rigid PVC profiles. 相似文献
82.
A study by convergent beam electron diffraction has been performed in order to clarify the symmetry of the phase III of Pb2CoWO6. Microdiffractions with higher-order Laue zone on monodomain areas have confirmed the cell proposed in our preceding study. In addition, an ‘axial’ glide plane (c) has been found normal to the b axis. In the conditions of observation, the convergent beam electron diffraction patterns lead to an apparent point group mmm. No breakdown of a mirror symmetry could be found. The discrepancy between this result and the existence of a spontaneous polarisation is discussed. 相似文献
83.
Grignard condensation routes to 1,3‐disilacyclobutane‐containing cyclolinear polycarbosilanes 下载免费PDF全文
Xinxing Liu Jitendra S. Rathore Geraud Dubois Leonard V. Interrante 《Journal of polymer science. Part A, Polymer chemistry》2017,55(9):1547-1557
Alkylene‐ and arylene‐bridged cyclolinear polycarbosilanes (CLPCS) with 1,3‐disilacyclobutane (DSCB) rings incorporated in the main chain of the polymer were prepared by polycondensation between corresponding di‐functional DSCB derivatives and di‐Grignard reagents. Well‐defined, low molecular weight (Mn = 3–5K; DP = 17–26), hexylene‐ and phenylene‐bridged CLPCS polymers were obtained without appreciable ring opening of the DSCB rings. Large exothermic peaks were observed in the DSC for these CLPCSs, which indicated, along with the IR spectra, that crosslinking occurred on heating to about 250 °C via the ring opening of the embedded, alternating, DSCB rings. Moreover, PB‐CLPCS undergoes photochemically induced crosslinking on UV irradiation to form crosslinked polycarbosilane network films. The spin‐cast, cured, films of these CLPCSs exhibit relatively low dielectric constants and promising thermal and mechanical properties for applications in electronics, for example, directly UV‐photoimprinted low‐k dielectrics. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1547–1557 相似文献
84.
Ph. Savignac E. Elia Aboujaoude N. Collignon M. P. Teulade 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):491-494
Abstract Phosphoryl and silyl chlorides phosphonoalkylation lead to the direct generation of phosphonyl-phosphonyl and phosphonyl-silyl carbanions the properties of which are discussed. 相似文献
85.
V. Ph. Zhuravlev 《Doklady Physics》2017,62(5):271-272
By the example of a brake pad, a typical error is illustrated, i.e., the fact that the initial conditions should be reconsidered upon finding that there is no solution of the static problem in a certain region of parameters (incorrect in the sense of Hadamard). For example, it turns out that the conditions of disk rotation in the positive direction cannot be implemented in the domain of parameters leading to a “paradox.” In this region, the “brake-pad” mechanism is transformed into the “wedge stopper” mechanism. 相似文献
86.
Fouad Laoutid Marion Lorgouilloux Didier Lesueur Leila Bonnaud Philippe Dubois 《Polymer Degradation and Stability》2013
In this study, we evaluated the potential flame retardant effect of calcium-based hydrated minerals, such as hydrated lime, partially and completely hydrated dolomitic limes in polyethylene (MDPE) and ethylene vinyl acetate copolymers (EVA) and compared to that obtained with magnesium di-hydroxide (MDH). The most significant flame retardant effects, observed using the mass loss calorimeter test, indicated that Ca-based MDPE composites showed similar peak Heat Release Rate (pHRR) level to that obtained with MDH composite while the pHRR was lower for Ca-based fillers in EVA compositions. X-ray Diffraction (XRD) data, combined with thermal analysis results, indicated that the calcium di-hydroxide plays a role in the formation of an intumescent cohesive residue during the combustion. Indeed, Ca(OH)2 reacts with CO2 formed during the thermal degradation of the polymer to generate CaCO3 (calcium carbonate) that contributes to the enhancement of the mechanical resistance of the residue. 相似文献
87.
Vladimir Dolgovskiy Stéphane Schilt Nikola Bucalovic Gianni Di Domenico Serge Grop Benoît Dubois Vincent Giordano Thomas Südmeyer 《Applied physics. B, Lasers and optics》2014,116(3):593-601
We demonstrate the first ultra-stable microwave generation based on a 1.5-μm diode-pumped solid-state laser (DPSSL) frequency comb. Our system relies on optical-to-microwave frequency division from a planar-waveguide external cavity laser referenced to an ultra-stable Fabry–Perot cavity. The evaluation of the microwave signal at ~10 GHz uses the transportable ultra-low-instability signal source ULISS®, which employs a cryo-cooled sapphire oscillator. With the DPSSL comb, we measured ?125 dBc/Hz phase noise at 1 kHz offset frequency, likely limited by the photo-detection shot-noise or by the noise floor of the reference cryo-cooled sapphire oscillator. For comparison, we also generated low-noise microwave using a commercial Er:fiber comb stabilized in similar conditions and observed >20 dB lower phase noise in the microwave generated from the DPSSL comb. Our results confirm the high potential of the DPSSL technology for low-noise comb applications. 相似文献
88.
We study a model for a massive test particle in a microscopic periodic potential and interacting with a reservoir of light particles. In the regime considered, the fluctuations in the test particle’s momentum resulting from collisions typically outweigh the shifts in momentum generated by the periodic force, so the force is effectively a perturbative contribution. The mathematical starting point is an idealized reduced dynamics for the test particle given by a linear Boltzmann equation. In the limit that the mass ratio of a single reservoir particle to the test particle tends to zero, we show that there is convergence to the Ornstein–Uhlenbeck process under the standard normalizations for the test particle variables. Our analysis is primarily directed towards bounding the perturbative effect of the periodic potential on the particle’s momentum. 相似文献
89.
D. Kocheva G. Rainovski J. Jolie N. Pietralla A. Blazhev A. Astier R. Altenkirch S. Ansari Th. Braunroth M. L. Cortés A. Dewald F. Diel M. Djongolov C. Fransen K. Gladnishki A. Hennig V. Karayonchev J. M. Keatings E. Kluge J. Litzinger C. Müller-Gatermann P. Petkov M. Rudigier M. Scheck Ph. Scholz P. Spagnoletti M. Spieker C. Stahl R. Stegmann M. Stoyanova P. Thöle N. Warr V. Werner W. Witt D. Wölk K. O. Zell P. Van Isacker V. Yu. Ponomarev 《The European Physical Journal A - Hadrons and Nuclei》2017,53(9):175
90.
Ph. Vermeulen J. A. Fernández Pierna H. P. van Egmond J. Zegers P. Dardenne V. Baeten 《Analytical and bioanalytical chemistry》2013,405(24):7765-7772
In recent years, near-infrared (NIR) hyperspectral imaging has proved its suitability for quality and safety control in the cereal sector by allowing spectroscopic images to be collected at single-kernel level, which is of great interest to cereal control laboratories. Contaminants in cereals include, inter alia, impurities such as straw, grains from other crops, and insects, as well as undesirable substances such as ergot (sclerotium of Claviceps purpurea). For the cereal sector, the presence of ergot creates a high toxicity risk for animals and humans because of its alkaloid content. A study was undertaken, in which a complete procedure for detecting ergot bodies in cereals was developed, based on their NIR spectral characteristics. These were used to build relevant decision rules based on chemometric tools and on the morphological information obtained from the NIR images. The study sought to transfer this procedure from a pilot online NIR hyperspectral imaging system at laboratory level to a NIR hyperspectral imaging system at industrial level and to validate the latter. All the analyses performed showed that the results obtained using both NIR hyperspectral imaging cameras were quite stable and repeatable. In addition, a correlation higher than 0.94 was obtained between the predicted values obtained by NIR hyperspectral imaging and those supplied by the stereo-microscopic method which is the reference method. The validation of the transferred protocol on blind samples showed that the method could identify and quantify ergot contamination, demonstrating the transferability of the method. These results were obtained on samples with an ergot concentration of 0.02 % which is less than the EC limit for cereals (intervention grains) destined for humans fixed at 0.05 %. Online Abstract Figure
Pictures showing a the manual removal of ergot bodies and b the observation by the stereo-microscopic method (official method); c the metallic holder with the reference material, and d the NIR hyperspectral SisuCHEMA instrument 相似文献