In a number of his recent papers Karl Gustafson has outlined the similarities between the Antieigenvalue Theory he founded and several finite dimensional matrix optimization theorems for positive matrices arising in statistics. In this paper, we will show how the techniques that the author and Karl Gustafson have used for computation of Antieigenvalues can also be applied to prove and generalize these matrix optimization theorems in statistics. We will primarily focus on two techniques which we have used in Antieigenvalue computations in recent years. These two techniques are a two nonzero component property for certain class of functionals, and converting the matrix optimization problems in statistics to a convex programing problem. Indeed, these two techniques allow us to generalize some of the matrix optimization problems arising in statistics to strongly accretive operators on finite or infinite dimensional Hilbert spaces. 相似文献
In this paper, we combine two types of local search algorithms for global optimization of continuous functions. In the literature, most of the hybrid algorithms are produced by combination of a global optimization algorithm with a local search algorithm and the local search is used to improve the solution quality, not to explore the search space to find independently the global optimum. The focus of this research is on some simple and efficient hybrid algorithms by combining the Nelder–Mead simplex (NM) variants and the bidirectional random optimization (BRO) methods for optimization of continuous functions. The NM explores the whole search space to find some promising areas and then the BRO local search is entered to exploit optimal solution as accurately as possible. Also a new strategy for shrinkage stage borrowed from differential evolution (DE) is incorporated in the NM variants. To examine the efficiency of proposed algorithms, those are evaluated by 25 benchmark functions designed for the special session on real-parameter optimization of CEC2005. A comparison study between the hybrid algorithms and some DE algorithms and non-parametric analysis of obtained results demonstrate that the proposed algorithms outperform most of other algorithms and their difference in most cases is statistically considerable. In a later part of the comparative experiments, a comparison of the proposed algorithms with some other evolutionary algorithms reported in the CEC2005 confirms a better performance of our proposed algorithms. 相似文献
The physiopathological mechanism underlying the tinnitus phenomenon is still the subject of an ongoing debate. Since oscillatory EEG activity is increasingly recognized as a fundamental hallmark of cortical integrative functions, this study investigates deviations from the norm of different resting EEG parameters in patients suffering from chronic tinnitus. 相似文献
Surface phonon cavities that are homogenous in both mechanical and dielectric properties are reported. The cavities are formed by the placement of a defect of a single domain within periodic domain inversion of single crystal piezoelectric lithium niobate that exhibits surface phononic bandgap through the phonon‐polariton coupling. Surface cavity resonances are observed within the bandgap, which manifest in entrapment of phonon‐polariton within the defect. In addition to demonstrating that the observed resonances are non‐radiative and decoupled to bulk radiation, which is critical for high Q cavities, it is also shown the possibility to tune the surface cavity resonance spectra simply by varying the defect width. Such an ability to excite surface cavity resonance that is non‐radiative with simultaneous localization of the electric field together with the advantage of a cavity that is physically formed from a completely monolithic and uniform material offers unique opportunities for widespread applications for example in actuation, detection, and phonon lasing that can be fully integrated with other physical systems such as quantum acoustics, photonics, and microfluidics.
The silicon-on-insulator (SOI) power devices show good electrical performance but they suffer from inherent self-heating effect (SHE), which limits their operation at high current levels. The SHE effect is because of low thermal conductivity of the buried oxide layer. In this paper we propose a novel silicon on insulator lateral double diffused MOSFET (SOI-LDMOSFET) where the buried insulator layer under the active region consists of two materials in order to decrease the SHE. The proposed structure is called dual material buried insulator SOI-LDMOSFET (DM-SOI). Using two-dimensional and two-carrier device simulation, we demonstrate that the heat dissipation and the SHE can be improved in a conventional SOI-LDMOSFET by replacement of the buried oxide with dual material buried insulator (silicon nitride and silicon oxide) beneath the active region. The heat generated in the active silicon layer can be flowed through the buried silicon nitride layer to the silicon substrate easily due to high thermal conductivity of silicon nitride. Furthermore, the channel temperature is reduced, negative drain current slope is mitigated and electron and hole mobility is increased during high-temperature operation. The simulated results show that silicon nitride is a suitable alternative to silicon dioxide as a buried insulator in SOI structures, and has better performance in high temperature. 相似文献
The use of conductive coating on interconnect ferritic stainless steel can reduce electrical resistivity. In this study, an AISI 430 ferritic stainless steel interconnect was coated with a manganese base pack mixture by pack cementation. The effect of oxide scale thickness on electrical conductivity was evaluated by applying isothermal oxidation at 750?°C. This effect was also investigated at different temperatures (400?C900?°C). The formation of manganese spinels during annealing improved the oxidation resistance and electrical conductivity. Results showed that the increase in isothermal oxidation time and temperature increased the oxide thickness, and this resulted in the relatively low values of electrical conductivity. Manganese spinels enhanced the electrical conductivity and oxidation resistance of coated substrates as compared to uncoated substrates. 相似文献
The well-known Levenberg–Marquardt method is used extensively to solve systems of nonlinear equations. An extension of the Levenberg–Marquardt method based on new nonmonotone technique is described. To decrease the total number of iterations, this method allows the sequence of objective function values to be nonmonotone, especially in the case where the objective function is ill-conditioned. Moreover, the parameter of Levenberg–Marquardt is produced according to the new nonmonotone strategy to use the advantages of the faster convergence of the Gauss–Newton method whenever iterates are near the optimizer, and the robustness of the steepest descent method in the case in which iterates are far away from the optimizer. The global and quadratic convergence of the proposed method is established. The results of numerical experiments are reported. 相似文献
Aspects of the red thermoluminescence (RTL) and IR (833±5 nm) stimulated red (λemission=600–750 nm) luminescence (orange-red IRSL) of potassium feldspar from different origins are described. Anomalous fading of RTL (300–500°C) from a selection of potassium feldspar samples was tested. High temperature RTL (300–450°C) exhibits less anomalous fading in comparison to UV luminescence, for the samples under study. The result supports the contention of Zink and Visocekas (1997) that the red TL emission from feldspar does not fade. It was found that RTL is bleachable due to IR exposure, and the relationship between RTL lost and orange-red IRSL produced is linear. It is shown that around one third of the trapped charge responsible for the orange-red IRSL signal gives rise to an RTL signal, indicating that some traps and luminescence centres are shared for RTL and orange-red IRSL.
Specific characteristics of orange-red IRSL from feldspar were identified. It was found that the orange-red IRSL decay curve is bleachable by IR and daylight and can be described by the sum of three exponential components. Orange-red IRSL fading was tested. Short-term storage tests (up to 2 weeks) showed no fading. Longer-term (ca. months) storage of orange-red IRSL do in fact indicate fading, though at levels considerably lower than for the UV emission. The contradictory result is possibly due to the detection wavelength. As such, it is highly likely that the long-term fading experiment is strongly influenced by the feldspar emission centred at ca. 570 nm, which exhibits anomalous fading, while the short-term fading experiment is more greatly influenced by the far red emission centred at ca. 710 nm that in comparison to UV emission shows no or less fading. 相似文献
In this letter,we are going to use a geometrical approach to describe the free energy of DNA structures.The exact solutions of the equilibrium shape equations in a general WLC model for DNA forms by using the Feoli's formalism [A.Feoli,et al.,Nucl.Phys.B 705(2005) 577] are studied.Then,the free energy of transition between Band Z-DNA is calculated in this formalism. 相似文献