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841.
José Luis Sánchez Bote Antonio Pedrero González Juan José Gómez Alfageme 《Applied Acoustics》2012,73(9):977-985
This paper presents a new verification procedure for sound source coverage according to ISO 140–5 requirements. The ISO 140–5 standard applies to the measurement of façade insulation and requires a sound source able to achieve a sufficiently uniform sound field in free field conditions on the façade under study. The proposed method involves the electroacoustic characterisation of the sound source in laboratory free field conditions (anechoic room) and the subsequent prediction by computer simulation of the sound free field radiated on a rectangular surface equal in size to the façade being measured. The loudspeaker is characterised in an anechoic room under laboratory controlled conditions, carefully measuring directivity, and then a computer model is designed to calculate the acoustic free field coverage for different loudspeaker positions and façade sizes. For each sound source position, the method provides the maximum direct acoustic level differences on a façade specimen and therefore determines whether the loudspeaker verifies the maximum allowed level difference of 5 dB (or 10 dB for façade dimensions greater than 5 m) required by the ISO standard. Additionally, the maximum horizontal dimension of the façade meeting the standard is calculated and provided for each sound source position, both with the 5 dB and 10 dB criteria. In the last section of the paper, the proposed procedure is compared with another method used by the authors in the past to achieve the same purpose: in situ outdoor measurements attempting to recreate free field conditions. From this comparison, it is concluded that the proposed method is able to reproduce the actual measurements with high accuracy, for example, the ground reflection effect, at least at low frequencies, which is difficult to avoid in the outdoor measurement method, and it is fully eliminated with the proposed method to achieve the free field requisite. 相似文献
842.
We give a -approximation algorithm for minimizing total weighted completion time on a single machine under release time and precedence constraints. This settles a recent conjecture on the approximability of this scheduling problem (Skutella, 2016). 相似文献
843.
844.
The interaction between electric and magnetic fields enables smart devices which can find applications in sensor technology and data storage. Materials showing magneto-electric (ME) coupling combine different ferroic characteristics. In the present contribution we focus on composites, which combine ferroelectric and ferromagnetic phases due to strain couplings, such that they generate a strain-induced ME coupling. We derive a two-scale homogenization approach for the determination of effective properties in consideration of microscopic morphologies. Furthermore, we demonstrate the strong influence of ferroelectric polarization states on the ME-coefficient by modeling the switching of remanent polarizations on the microscale. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
845.
Prof. Dr. B. F. Arnold 《Mathematical Methods of Operations Research》1990,34(1):59-74
Summary In controlling the mean of a multivariate normally distributed quality characteristic the main disadvantage of the globalT
2-control charts is that they don't indicate the component of the quality characteristic which gives rise to an alarm. To avoid this disadvantage the joint use of¯x-charts is proposed in this paper, where — for the sake of simplicity — the investigations are restricted to the case of independent components and to one-sided¯x-charts. On the basis of an economic objective function an approximation to the optimal design of the¯x-charts procedure is derived and discussed. It turns out that at least in the bivariate case the nearly optimal economic design is very close to the exact solution.Supported by the Deutsche Forschungsgemeinschaft (DFG). 相似文献
846.
José Luiz Boldrini Luís H. de Miranda Gabriela Planas 《Journal of Evolution Equations》2013,13(3):535-560
This article considers the issues of existence and regularity of solutions to the following doubly nonlinear differential inclusion $$\omega_t+\alpha (\omega_t)-\Delta \omega-\Delta_p{\omega} \ni f$$ where α is a maximal monotone operator in ${\mathbb{R}^2}$ and Δ p denotes the p-Laplacian with p > 2. The investigation on fractional regularity is based on the Galerkin method combined with a suitable basis for W 1,p , which we exhibit as a preliminary result. This approach also allows the obtaining of estimates in the so-called Nikolskii spaces, since it balances the interplay between the maximal monotone operator with the appearing higher order nonlinear terms. 相似文献
847.
Christopher M. Tollan Jon Echeberria Rebeca Marcilla José A. Pomposo David Mecerreyes 《Journal of nanoparticle research》2009,11(5):1241-1245
The synthesis and characterisation of gold nanorods have been carried out by reduction of the gold salt HAuCl4. This has been done using a single reducing agent, acetylacetone, rather than the two reducing agents, sodium borohydride
and ascorbic acid, normally required by standard wet chemistry methods of gold nanorod formation. Using this novel method,
the nanorods were synthesised at several different pH values which were found to greatly affect both the rate at which the
nanorods form and their physical dimensions. The concentrations of acetylacetone and silver nitrate used relative to the gold
salt were found to alter the aspect ratio of the nanorods formed. Rods with an average length of 42 nm and an aspect ratio
of 4.6 can be easily and reproducibly formed at pH 10 using this method. Nanorods formed under optimum conditions were investigated
using TEM.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
848.
Oswin Aichholzer Thomas Hackl David Orden Pedro Ramos Günter Rote André Schulz Bettina Speckmann 《Graphs and Combinatorics》2013,29(6):1577-1593
We study flip graphs of triangulations whose maximum vertex degree is bounded by a constant k. In particular, we consider triangulations of sets of n points in convex position in the plane and prove that their flip graph is connected if and only if k > 6; the diameter of the flip graph is O(n 2). We also show that, for general point sets, flip graphs of pointed pseudo-triangulations can be disconnected for k ≤ 9, and flip graphs of triangulations can be disconnected for any k. Additionally, we consider a relaxed version of the original problem. We allow the violation of the degree bound k by a small constant. Any two triangulations with maximum degree at most k of a convex point set are connected in the flip graph by a path of length O(n log n), where every intermediate triangulation has maximum degree at most k + 4. 相似文献
849.
Background
The tactile sense is being used in a variety of applications involving tactile human-machine interfaces. In a significant number of publications the classical threshold concept plays a central role in modelling and explaining psychophysical experimental results such as in stochastic resonance (SR) phenomena. In SR, noise enhances detection of sub-threshold stimuli and the phenomenon is explained stating that the required amplitude to exceed the sensory threshold barrier can be reached by adding noise to a sub-threshold stimulus. We designed an experiment to test the validity of the classical vibrotactile threshold. Using a second choice experiment, we show that individuals can order sensorial events below the level known as the classical threshold. If the observer's sensorial system is not activated by stimuli below the threshold, then a second choice could not be above the chance level. Nevertheless, our experimental results are above that chance level contradicting the definition of the classical tactile threshold. 相似文献850.
M. F. Haroun P. S. Moussounda P. Légaré J.-C. Parlebas 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,78(3):353-358
We use a periodic density functional theory (DFT) code to study the
adsorption of CH3 and H, as well as their co-adsorption on a Ni(111)
surface with and without Ni ad-atom, at a surface coverage of 0.25 monolayer
(ML). We systematically investigate the site preference for CH3 and H.
Then we combine CH3 and H in many co-adsorbed configurations on both
surfaces. Methyl and hydrogen adsorption on a flat Ni(111) surface favours
the hollow site over the top site. The presence of a Ni ad-atom stabilizes
the adsorption of CH3 better than a flat surface, while hydrogen is
more stable on a flat Ni(111) surface. When H and CH3 are co-adsorbed
at nearest Ni neighbours on the (111) surface, their interaction is always
repulsive. However, the dissociative adsorption of CH4 is stabilised
when the fragments are infinitely separated. For the co-adsorbed fragments
CH3 and H, in the presence of an ad-atom, the repulsive interaction is
lowered, so that the dissociative form of CH4 is locally stable. 相似文献