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61.
Niels M. B. Smeets Johan P. A. Heuts Jan Meuldijk Michael F. Cunningham Alex M. Van Herk 《Journal of polymer science. Part A, Polymer chemistry》2009,47(19):5078-5089
The effect the catalytic chain transfer agent, bis[(difluoroboryl) dimethylglyoximato] cobalt(II) (COBF), on the course of the ab initio emulsion polymerization of methyl methacrylate, and the product properties in terms of the molecular weight distribution were investigated. The emulsion polymerization kinetics have been studied with varying surfactant, initiator, and COBF concentrations. The experimentally determined average number of radicals per particle strongly depends on the concentration of COBF and proves to be in good agreement with the results of model calculations. The apparent chain transfer constant, determined up to high conversion, is in excellent agreement with the predicted value based on a mathematical model based on COBF partitioning and the Mayo equation. The results of this work enhance the fundamental understanding of the influence a catalytic chain transfer agent has on the course of the emulsion polymerization and the control of the molecular weight distribution. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5078–5089, 2009 相似文献
62.
Neher T Laugesen S Jensen NS Kragelund L 《The Journal of the Acoustical Society of America》2011,130(3):1542-1558
This study aimed to clarify the basic auditory and cognitive processes that affect listeners' performance on two spatial listening tasks: sound localization and speech recognition in spatially complex, multi-talker situations. Twenty-three elderly listeners with mild-to-moderate sensorineural hearing impairments were tested on the two spatial listening tasks, a measure of monaural spectral ripple discrimination, a measure of binaural temporal fine structure (TFS) sensitivity, and two (visual) cognitive measures indexing working memory and attention. All auditory test stimuli were spectrally shaped to restore (partial) audibility for each listener on each listening task. Eight younger normal-hearing listeners served as a control group. Data analyses revealed that the chosen auditory and cognitive measures could predict neither sound localization accuracy nor speech recognition when the target and maskers were separated along the front-back dimension. When the competing talkers were separated along the left-right dimension, however, speech recognition performance was significantly correlated with the attentional measure. Furthermore, supplementary analyses indicated additional effects of binaural TFS sensitivity and average low-frequency hearing thresholds. Altogether, these results are in support of the notion that both bottom-up and top-down deficits are responsible for the impaired functioning of elderly hearing-impaired listeners in cocktail party-like situations. 相似文献
63.
Ruijgrok PV Verhart NR Zijlstra P Tchebotareva AL Orrit M 《Physical review letters》2011,107(3):037401
We present the first quantitative measurements of the torque exerted on a single gold nanorod in a polarized three-dimensional optical trap. We determined the torque both by observing the time-averaged orientation distribution and by measuring the dynamics of the rotational brownian fluctuations. The measurements are in good agreement with calculations, where the temperature profile around the hot nanorod gives rise to a reduced, effective viscosity. The maximum torque on a 60 nm×25 nm nanorod was 100 pN·nm, large enough to address single-molecule processes in soft and biological matter. 相似文献
64.
65.
Optimization of bolt thread stress concentrations 总被引:2,自引:0,他引:2
Designs of threaded fasteners are controlled by different standards, and the number of different thread definitions is large. The most commonly used thread is probably the metric ISO thread, and this design is therefore used in the present paper. Thread root design controls the stress concentration factor of threads and therefore indirectly the bolt fatigue life. The root shape is circular, and from shape optimization for minimum stress concentration it is well known that the circular shape is seldom optimal. An axisymmetric Finite Element formulation is used to analyze the bolted connection, and a study is performed to establish the need for contact modeling with regard to finding the correct stress concentration factor. Optimization is performed with a simple parameterization with two design variables. Stress reduction of up to 9% is found in the optimization process, and some similarities are found in the optimized designs leading to the proposal of a new standard. The reductions in the stress are achieved by rather simple changes made to the cutting tool. 相似文献
66.
We investigate connections between arithmetic properties of rings and topological properties of their prime spectrum. Any property that the prime spectrum of a ring may or may not have, defines the class of rings whose prime spectrum has the given property. We ask whether a class of rings defined in this way is axiomatizable in the model theoretic sense. Answers are provided for a variety of different properties of prime spectra, e.g., normality or complete normality, Hausdorffness of the space of maximal points, compactness of the space of minimal points. 相似文献
67.
Niels Vigand Pedersen 《Aequationes Mathematicae》1994,48(2-3):228-253
Summary For a simply connected solvable Lie group we specify the structure of the product, the inverse and the exponential map expressed in suitable coordinates (canonical coordinates of the second kind), and point out that in these coordinates the product and inverse are expressed entirely in terms of polynomials, exponential functions and trigonometric functions. We devise algorithms for computing the product, the inverse and the exponential map. 相似文献
68.
69.
Consider a Hilbert space
equipped with a time-structure, i.e., a resolution E of the identity on
defined on subsets of some linearly ordered set Λ. For which x and y in
is it possible to find a causal (time respecting) compact operator T, so that Tx = y? When T is required to be a Hilbert-Schmidt operator and (Λ, E) is sufficiently regular, this question is answered in terms of the “time-densities” of x and y. The condition is that the integral ∝gLμx({s t})−1 dμy(t) should be finite, where μx and μy are the measures on Λ given by μx(Ω) = ¦|E(Ω)x¦|2 and μy(Ω) = ¦|E(Ω)y¦|2. Further a solution is given for the related problem of minimizing the sum of ¦|Tx − y¦|2 and the squared Hilbert-Schmidt norm ¦|R¦|22 of T. 相似文献
70.
The effective heat conduction of short fibre reinforced materials considering the fibre distribution
This contribution focuses on the effective heat conductivity of short fibre reinforced materials. For this purpose, a representative volume element (RVE), which is able to represent all possible fibre orientation distributions, is introduced and modelled in ABAQUS. Subsequently, the effective heat conductivity of the RVE is derived, employing a numerical homogenisation scheme, and a phenomenological material model is fitted to those results. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献