Aeroelastic energy harvesting can be used to power wireless sensors embedded into bridges, ducts, high-altitude buildings, etc. One challenging issue is that the wind speed in some application environments is low, which leads to an inefficiency of aeroelastic energy harvesters. This paper presents a novel nonlinear magnetic-coupled flutter-based aeroelastic energy harvester to enhance energy harvesting at low wind speeds.The presented harvester mainly consists of a piezoelectric beam, a two-dimensional airfoil, two tip magnets and two external magnets. The function of magnets is to reduce the cut-in wind speed of the flutter-based aeroelastic energy harvester and enhance energy harvesting performance at low wind speeds. A theoretical model is deduced based on Hamilton's principle, theory of aeroelasticity, Kirchhoff's laws and experimental measurements, etc. A good agreement is found between numerical simulation and experimental results, which verifies the accuracy of the theoretical model. Stability analysis is provided to determine the characteristics of the presented harvester. More importantly, it is numerically and experimentally verified that the presented harvester has a much lower cut-in wind speed (about 1.0 m/s) and has a better energy harvesting performance at a low wind speed range from 1.0 m/s to 2.9 m/s, when compared with traditional flutter-based aeroelastic energy harvesters.
Genome-wide association studies (GWAS) have identified many genetic factors underlying complex human traits. However, these factors have explained only a small fraction of these traits' genetic heritability. It is argued that many more genetic factors remain undiscovered. These genetic factors likely are weakly associated at the population level and sparsely distributed across the genome. In this paper, we adapt the recent innovations on Tukey's Higher Criticism (Tukey [The Higher Criticism (1976) Princeton Univ.]; Donoho and Jin [Ann.Statist. 32 (2004) 962-994]) to SNP-set analysis of GWAS, and develop a new theoretical framework in large-scale inference to assess the joint significance of such rare and weak effects for a quantitative trait. In the core of our theory is the so-called detection boundary, a curve in the two-dimensional phase space that quantifies the rarity and strength of genetic effects. Above the detection boundary, the overall effects of genetic factors are strong enough for reliable detection. Below the detection boundary, the genetic factors are simply too rare and too weak for reliable detection. We show that the HC-type methods are optimal in that they reliably yield detection once the parameters of the genetic effects fall above the detection boundary and that many commonly used SNP-set methods are suboptimal. The superior performance of the HC-type approach is demonstrated through simulations and the analysis of a GWAS data set of Crohn's disease.
Abstract-In this paper, a novel technique is proposed to solve the electromagnetic scattering by large finite arrays by combining the tangential equivalence principle algorithm (T-EPA) with multilevel fast multipole algorithm (MLFMA). The equivalence principle algorithm (EPA) is a kind of domain decomposition scheme for the electromagnetic scattering and radiation problems based on integral equation (IE). For the array with same elements, only one scattering matrix needs to be constructed and stored. T-EPA has better accuracy than the original EPA. But the calculation for the impedance matrix in T-EPA is still time consuming. MLFMA is proposed to speed up the matrix-vector multiplication in T-EPA. Numerical results are shown to demonstrate the accuracy and efficiency of the proposed technique.
Abstract-A basis function with the traveling wave phase factor, called as the phase extracted (PE) basis functions in this paper, has been applied for efficient solution of scattering from 3 dimensional (3-D) electrically large objects. In this paper, a rigorous derivation is given as a physical insight of this basis function. Defined on large patches and containing propagating wave phase dependence, this kind of bases exhibits very strong directivity, leading to a highly sparsed impedance matrix. Based on such observation, a matrix sparsification technique and an impedance prediction technique have been developed in this paper. The total memory requirement and computational time could be reduced significantly with methods proposed in this paper. The basic requirements of basis functions, i.e., current continuity and absence of charge accumulation are demonstrated, and the excellent behavior of PE basis functions in wideband applications has been summarized briefly. Several numerical examples have been given to show its good accuracy and high efficiency in solving scattering from electrically large complex objects.
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