Self-regulation in infinite populations with fission-death dynamics

The evolution of an infinite population of interacting point entities placed in ${\mathbb{R}}^d$ is studied. The elementary evolutionary acts are death of an entity with rate that includes a competition term and independent fission into two entities. The population states are probability measures on the corresponding configuration space and the result is the construction of the evolution of states in the class of sub-Poissonian measures, that corresponds to the lack of clusters in such states. This is considered as a self-regulation in the population due to competition.     

基于石墨烯的光学控制窄带太赫兹开关

本文提出了一种光控太赫兹开关,该开关采用覆盖单层石墨烯的十字金属谐振器超表面。利用石墨烯表面电导率模型和有限元法计算了这种复合结构的光谱特性。模拟结果表明,在0.2 W/mm²的光泵浦后,传输谱（调制深度为36.8%,Q-因子为250）出现了窄带共振衰减现象。另外,这种衰减的调制深度可以通过改变泵浦强度微调节。因此,光学可调谐太赫兹开关的设计将有助于太赫兹通信应用的功能组件开发。     

Resistive switching behaviors of Cu/TaOx/TiN device with combined oxygen vacancy/copper conductive filaments

Forming-free and self-compliant bipolar resistive switching is observed in Cu/TaO_x/TiN conductive bridge random access memory. Generally, Pt has been investigated as an inert electrode. However, Pt is not desirable material in current semiconductor industry for mass production. In this study, all electrodes are adapted to complementary metal-oxide-semiconductor compatible materials. The self-compliant resistive switching is achieved via usage of TiN bottom electrode. Also, dissolved Cu ions in TaO_x lead to forming-free resistive switching behavior. The resistive switching mechanism is formation and rupture of combined oxygen vacancy/metallic copper conductive filament. We propose that Cu/TaO_x/TiN is a promising candidate for a conductive bridge random access memory structure.     

Scaling spectra and return times of dynamical systems

The grand canonical version of the spectrum of singularities formalism is presented, relying naturally upon certain Markov transition graphs. The structure of a graph is simply determined by the close return times of the dynamical system described. Thus, an intimate connection exists between the shape of the singularity curve and a small but interesting set of dynamical properties.     

Oxygen deficiency effect on resistive switching characteristics of copper oxide thin films

In this Letter, bilayered Cu₂O/CuO thin films were grown on Nb doped SrTiO₃ (Nb:STO) substrates by plasma assisted molecular beam epitaxy. The current-voltage characteristics of Pt/Cu₂O/CuO/Nb:STO devices show reproducible and pronounced current-voltage hysteresis which was induced by the CuO/Nb:STO junctions. By comparing the current-voltage curves of the bilayered and single-layered CuO thin films, we attribute the prominent switching behavior to the oxygen-vacancies-mediated-carriers-trapped-detrapped process with the aid of the applied forward (reversed) bias voltage.     

Image segmentation using adaptive loopy belief propagation

Loopy belief propagation (LBP) algorithm over pairwise-connected Markov random fields (MRFs) has become widely used for low-level vision problems. However, Pairwise MRF is often insufficient to capture the statistics of natural images well, and LBP is still extremely slow for application on an MRF with large discrete label space. To solve these problems, the present study proposes a new segmentation algorithm based on adaptive LBP. The proposed algorithm utilizes local region information to construct a local region model, as well as a local interaction region MRF model for image segmentation. The adaptive LBP algorithm maximizes the global probability of the proposed MRF model, which employs two very important strategies, namely, “message self-convergence” and “adaptive label pruning”. Message self-convergence can improve the reliability of a pixel in choosing a label in local region, and label pruning can dismiss impossible labels for every pixel. Thus, the most reliable information messages transfer through the LBP algorithm. The experimental results show that the proposed algorithm not only obtains more accurate segmentation results but also greater speed.     

聚变等离子体中高能量粒子驱动的鱼骨模不稳定性研究

在考虑高能量粒子密度的空间分布及箍缩角分布的条件下,建立了研究鱼骨模的色散关系,并作了数值研究。结果表明：当高能量粒子的密度高于某个阈值时,鱼骨模会在高能量粒子密度梯度最大处被激发,其频率与高能量粒子的环向进动频率一致。在高β_h 区间,高能量勉强通行粒子将驱动鱼骨模进入第二稳定区。高能量捕获粒子能激发非共振鱼骨模,与勉强通行粒子激发的鱼骨模类似,在高β_h 区存在第二稳定区。     

Recurrence time statistics in chaotic dynamics. I. Discrete time maps

The dynamics of transitions between the cells of a finite-phase-space partition in a variety of systems giving rise to chaotic behavior is analyzed, with special emphasis on the statistics of recurrence times. In the case of one-dimensional piecewise Markow maps the recurrence problem is cast into a-renewal process. In the presence of intermittency, transitions between cells define a non-Markovian, non-renewal process reflected in the presence of power-law probability distributions and of divergent variances and mean values.     

Relaxation time for a dimer covering with height representation

This paper considers the Monte Carlo dynamics of random dimer coverings of the square lattice, which can be mapped to a rough interface model. Two kinds of slow modes are identified, associated respectively with long-wavelength fluctuations of the interface height, and with slow drift (in time) of the system-wide mean height. Within a continuum theory, the longest relaxation time for either kind of mode scales as the system sizeN. For the real, discrete model, an exactlower bound ofO(N) is placed on the relaxation time, using variational eigenfunctions corresponding to the two kinds of continuum modes