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排序方式: 共有295条查询结果,搜索用时 31 毫秒
41.
O. Yavas P. Leiderer H. K. Park C. P. Grigoropoulos C. C. Poon W. P. Leung N. Do A. C. Tam 《Applied Physics A: Materials Science & Processing》1994,58(4):407-415
The dynamics of liquid-vapor phase-change in the nanosecond time-scale induced by pulsed-laser heating of a liquid on a solid sample is studied by means of optical reflectance and scattering measurements, and the piezoelectric detection technique. The liquids studied include water, ethanol, methanol, IsoproPropyl Alcohol (IPA), and mixtures of water and IPA. The threshold fluence for nucleation is determined with high accuracy using the optical and acoustic signals. Heat diffusion calculations performed for the threshold fluences indicate that the liquids are sufficiently superheated before nucleation sets on. The transient optical reflectance signal is analyzed by an effective-medium theory to provide bubble-growth kinetics, so that the bubble-growth velocity for the test liquids could be estimated. In addition, it is observed that, following the thermally induced nucleation, repetitive acoustic cavitation at the surface of the solid sample occurs, with a time interval related to the speed of sound in the liquid. 相似文献
42.
Mathematical Programming - Non-smooth optimization is a core ingredient of many imaging or machine learning pipelines. Non-smoothness encodes structural constraints on the solutions, such as... 相似文献
43.
The theory of an automated fringe-pattern analysis using temporal phase stepping method for moiré interferometry is presented.
The automated method provides a fast and accurate strain measurement for moiré interferometry. Measurements on a tapered composite
specimen with a dropped ply are shown to highlight the capability of this technique to obtain the strain distribution, particularly
around the region with a dropped ply. 相似文献
44.
Clarice Poon 《Applied and Computational Harmonic Analysis》2017,42(3):402-451
Many of the applications of compressed sensing have been based on variable density sampling, where certain sections of the sampling coefficients are sampled more densely. Furthermore, it has been observed that these sampling schemes are dependent not only on sparsity but also on the sparsity structure of the underlying signal. This paper extends the result of Adcock, Hansen, Poon and Roman (arXiv:1302.0561, 2013) [2] to the case where the sparsifying system forms a tight frame. By dividing the sampling coefficients into levels, our main result will describe how the amount of subsampling in each level is determined by the local coherences between the sampling and sparsifying operators and the localized level sparsities – the sparsity in each level under the sparsifying operator. 相似文献
45.
Shi C Guo T Poon KC Lin Z Jia G 《Dalton transactions (Cambridge, England : 2003)》2011,40(42):11315-11320
The thermodynamic and kinetic aspects of the rearrangement reactions of a series of metallabenzenes to cyclopentadienyl complexes have been investigated by DFT computational study in order to reveal how substituents on the metallacycle, ligands around the metal center, and metals affect the transformation. We found that substitutents and their locations on the metallacycle have a significant effect on the thermodynamics and kinetics of the rearrangement reactions. 相似文献
46.
We introduce active, probe-based microrheological techniques for measuring the flow and deformation of complex fluids. These techniques are ideal for mechanical characterization either when little sample is available, or when samples show significant spatial heterogeneity. We review recent results, paying particular attention to comparing and contrasting rheological parameters obtained from micro- and macro-rheological techniques. 相似文献
47.
B. Poon L. Ponson J. Zhao G. Ravichandran 《Journal of the mechanics and physics of solids》2011,59(10):2238-2257
The compressive response of fully dense and 10 vol% porous Ti2AlC MAX phase materials subjected to quasi-static uniaxial and cyclic loading including their repeatable hysteretic behavior is presented. Damage accumulation in the form of kink bands and microcracking is characterized using ultrasonics and scanning electron microscopy under different levels of compressive loading. The observations and measurements are correlated quantitatively using a model based on friction between the crack faces, which is the main dissipation process. The model is shown to capture the hysteretic behavior of Ti2AlC MAX phase and quantitatively reproduce the experimentally measured stress–strain curves. 相似文献
48.
Wai‐Yeung Wong Suk‐Yue Poon Jian‐Xin Shi Kok‐Wai Cheah 《Journal of polymer science. Part A, Polymer chemistry》2006,44(16):4804-4824
A series of blue‐light‐emitting oligo(fluorenyleneethynylenesilylene)s (OFESs) of the general formula HC?CRC?C(EC?CRC?C)mEC?CRC?CH (E = SiPh2, SiMe2, or SiMe2? SiMe2; m = 0–2; R = 9,9‐dihexylfluorene‐2,7‐diyl) and their phosphorescent platinum‐containing oligoynes and polyynes were synthesized and characterized. The solution properties and regiochemical structures of this new structural class of organosilicon‐based polyplatinayne polymers {trans‐[? Pt(PBu3)2C ?CRC?C(EC?CRC?C)mEC?CRC?C? ]n} were studied with IR and NMR (1H, 13C, 29Si, and 31P) spectroscopy. The optical absorption and photoluminescence spectra of these metallopolymers were examined and compared with their discrete oligomeric model complexes. Our studies led to a novel approach of using the sp3‐silyl moiety as a conjugation interrupter to limit the effective conjugation length in metal polyynes, which could boost the phosphorescence decay rates essential for light‐energy harvesting from the triplet excited state. The influence of the heavy platinum atom and the group 14 silyl unit possessing different side‐group substituents on the thermal and phosphorescence properties was investigated in detail. We also established the goal of studying the evolution of the lowest singlet and triplet excited states with chain length m of OFESs and the nature of E in these metallopolymers. This work indicated that the phosphorescence emission efficiency harnessed through the heavy‐atom effect of platinum in the main chain did not change very much with oligomer chain length m but generally decreased with the E group in the order SiMe2 > SiMe2? SiMe2 > SiPh2. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4804–4824, 2006 相似文献
49.
50.
The Ruderman-Kittel-Kasuya-Yosida interaction in amorphous La80Au20 alloys with dilute Gd impurities
From magnetization measurements on some amorphous dilute La80?xGdxAu20 alloys with x ? 1 we have shown that the magnetic behavior follows the scaling laws of a spin-glass system, characteristic of the 1/r3 dependence of the pairwise interaction. We have also determined the strength of the Ruderman-Kittel-Kasuya-Yosida interaction V(r) = (V0cos 2kFr)/r3, to be V0 = 0.20 × 10?37 ergcm3. The corresponding value of the s-f exchange integral is |Jsf| = 0.14 eV, which is compared with values determined from other experiments. 相似文献