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41.
We propose and study quantitative measures of smoothness f ? A(f) which are adapted to anisotropic features such as edges in images or shocks in PDE’s. These quantities govern the rate of approximation by adaptive finite elements, when no constraint is imposed on the aspect ratio of the triangles, the simplest example being \(A_{p}(f)=\|\sqrt{|\mathrm{det}(d^{2}f)|}\|_{L^{\tau}}\) which appears when approximating in the L p norm by piecewise linear elements when \(\frac{1}{\tau}=\frac{1}{p}+1\). The quantities A(f) are not semi-norms, and therefore cannot be used to define linear function spaces. We show that these quantities can be well defined by mollification when f has jump discontinuities along piecewise smooth curves. This motivates for using them in image processing as an alternative to the frequently used total variation semi-norm which does not account for the smoothness of the edges. 相似文献
42.
43.
Albert A. Groenwold L. F. P. Etman Derren W. Wood 《Structural and Multidisciplinary Optimization》2010,41(1):39-56
We propose to replace a number of popular approximations by their diagonal quadratic Taylor series expansions. The resulting
separable quadratic approximations are easily convexified, and are well suited for use in dual sequential approximate optimization
(SAO) algorithms. Global convergence of the resulting SAO algorithms may be enforced in a natural way using conservatism.
The approximated approximation approach is explicitly illustrated for (i) reciprocal and exponential intervening variables,
(ii) the intervening variables used in the method of moving asymptotes (MMA), (iii) the intervening variables used in CONLIN,
and (iv) the TANA-3 approximations. The use of intermediate responses for use in, for example, truss and frame-like structures,
is also discussed. Key advantages of replacing nonlinear approximations by their diagonal quadratic approximations are that
these approximated approximations can all be used simultaneously in a single dual statement; the dual does not depend on the form of the original approximations. In addition, in a dual setting, the resulting subproblems
yield simple analytical relationships between the primal and dual variables, which is often not the case with the original
nonlinear approximations. An important example hereof is the exponential approximation. Although the diagonal quadratic approximations
may differ notably from their original counterparts, they typically are quite similar in a sufficiently small search subregion,
which relates to the move limits commonly used in SAO anyway. 相似文献
44.
Antonio de la Oliva Ignacio Soto Albert Banchs Johannes Lessmann Christian Niephaus Telemaco MeliaAuthor vitae 《Computer Standards & Interfaces》2011,33(6):556-564
The IEEE 802.21 standard facilitates media independent handovers by providing higher layer mobility management functions with common service primitives for all technologies. Right after the base specification was published, several voices rose up in the working group advocating to broaden the scope of IEEE 802.21 beyond handovers. This paper aims at updating the reader with the main challenges and functionalities required to create a Media Independence Service Layer, through the analysis of scenarios which are being discussed within the working group: 1) Wireless Coexistence, and 2) Heterogeneous Wireless Multihop Backhaul Networks. 相似文献
45.
The separation of mixed auditory signals into their sources is an eminent neuroscience and engineering challenge. We reveal the principles underlying a deterministic, neural network-like solution to this problem. This approach is orthogonal to ICA/PCA that views the signal constituents as independent realizations of random processes. We demonstrate exemplarily that in the absence of salient frequency modulations, the decomposition of speech signals into local cosine packets allows for a sparse, noise-robust speaker separation. As the main result, we present analytical limitations inherent in the approach, where we propose strategies of how to deal with this situation. Our results offer new perspectives toward efficient noise cleaning and auditory signal separation and provide a new perspective of how the brain might achieve these tasks. 相似文献
46.
47.
Most empirical investigations of the business cycles in the United States have excluded the dimension of asymmetric conditional volatility. This paper analyses the volatility dynamics of the US business cycle by comparing the performance of various multivariate generalised autoregressive conditional heteroskedasticity (GARCH) models. In particular, we propose two bivariate GARCH models to examine the evidence of volatility asymmetry and time-varying correlations concurrently, and then apply the proposed models to five sectors of Industrial Production of the United States. Our findings provide strong evidence of asymmetric conditional volatility in all sectors, and some support of time-varying correlations in various sectoral pairs. This has important policy implications for government to consider the effective countercyclical measures during recessions. 相似文献
48.
Health Outcomes and Socio-economic Status Among the Elderly in China: Evidence from the CHARLS Pilot
John Strauss Xiaoyan Lei Albert Park Yan Shen James P. Smith Zhe Yang Yaohui Zhao 《Journal of population ageing》2010,3(3-4):111-142
We are concerned in this paper with measuring health outcomes among the elderly in Zhejiang and Gansu provinces, China, and examining the relationships between different dimensions of health status and measures of socio-economic status (SES). We are CHARLS pilot data to document health conditions, using a very rich set of health indicators that include both self-reported measures and biomarkers. We also examine correlations between these health outcomes and two important indicators of socio-economic status (SES): education and log of per capita expenditure (log pce), our preferred measure of household resources. In general education tends to be positively correlated with better health outcomes, as it is in other countries. However, unmeasured community influences turn out to be highly important, much more so than one usually finds in other countries. While it is not yet clear which aspects of communities matter and why they matter, we set up an agenda for future research on this topic. We also find a large degree of under-diagnosis of hypertension, a major health problems that afflicts the aged. This implies that the current health system is not well prepared to address the rapid aging of the Chinese population, at least not in Gansu and Zhejiang. 相似文献
49.
A physical model describing the I(V) characteristics of planar limiting current oxygen sensors based in an ion-conducting electrolyte is presented. The model focuses on the minimization of the electrochemical potential and the diffusion across a porous layer covering the measuring electrode. The proposed model describes three key phenomena in the response of the sensors: the influence of the polarization resistance on the slope of I(V), the linearity between the limiting current and the diffusivity of the porous layer and a low non-zero current at zero polarization. 相似文献
50.
A survey and taxonomy on energy efficient resource allocation techniques for cloud computing systems
Abdul Hameed Alireza Khoshkbarforoushha Rajiv Ranjan Prem Prakash Jayaraman Joanna Kolodziej Pavan Balaji Sherali Zeadally Qutaibah Marwan Malluhi Nikos Tziritas Abhinav Vishnu Samee U. Khan Albert Zomaya 《Computing》2016,98(7):751-774
In a cloud computing paradigm, energy efficient allocation of different virtualized ICT resources (servers, storage disks, and networks, and the like) is a complex problem due to the presence of heterogeneous application (e.g., content delivery networks, MapReduce, web applications, and the like) workloads having contentious allocation requirements in terms of ICT resource capacities (e.g., network bandwidth, processing speed, response time, etc.). Several recent papers have tried to address the issue of improving energy efficiency in allocating cloud resources to applications with varying degree of success. However, to the best of our knowledge there is no published literature on this subject that clearly articulates the research problem and provides research taxonomy for succinct classification of existing techniques. Hence, the main aim of this paper is to identify open challenges associated with energy efficient resource allocation. In this regard, the study, first, outlines the problem and existing hardware and software-based techniques available for this purpose. Furthermore, available techniques already presented in the literature are summarized based on the energy-efficient research dimension taxonomy. The advantages and disadvantages of the existing techniques are comprehensively analyzed against the proposed research dimension taxonomy namely: resource adaption policy, objective function, allocation method, allocation operation, and interoperability. 相似文献