Coupled caloric effects in multiferroics

We propose a conception – coupled caloric effect   where the enhanced caloric effects originate from the coupling among magnetic, ferroelectric, and structural degrees of freedom. Specifically, as the magneto-electric case, the magnitude of the coupled caloric effect was evaluated for a ferromagnetic–ferroelectric system using a phenomenological calculation based on Landau phase transition theory. The isothermal entropy change is greatly enhanced by increasing the magneto-electric coupling strength. This work indicates that the caloric effect in a ferromagnetic–ferroelectric coupled system consists of pure magnetic entropy change (Δ_SM$\mathrm{\Delta }{S}_M$), pure ferroelectric one (Δ_SE$\mathrm{\Delta }{S}_E$), and coupled one (Δ_SME$\mathrm{\Delta }{S}_{\mathit{ME}}$) that plays a significant part. The counterpart of the last one in magneto-structural coupled system was usually neglected. Our study provides a route to energy-efficient refrigeration via realization of coupling among various ferroic orders.     

The risks and returns of stock investment in a financial market

The risks and returns of stock investment are discussed via numerically simulating the mean escape time and the probability density function of stock price returns in the modified Heston model with time delay. Through analyzing the effects of delay time and initial position on the risks and returns of stock investment, the results indicate that: (i) There is an optimal delay time matching minimal risks of stock investment, maximal average stock price returns and strongest stability of stock price returns for strong elasticity of demand of stocks (EDS), but the opposite results for weak EDS; (ii) The increment of initial position recedes the risks of stock investment, strengthens the average stock price returns and enhances stability of stock price returns. Finally, the probability density function of stock price returns and the probability density function of volatility and the correlation function of stock price returns are compared with other literatures. In addition, good agreements are found between them.     

Impulsive generalized function synchronization of complex dynamical networks

This Letter investigates generalized function synchronization of continuous and discrete complex networks by impulsive control. By constructing the reasonable corresponding impulsively controlled response networks, some criteria and corollaries are derived for the generalized function synchronization between the impulsively controlled complex networks, continuous and discrete networks are both included. Furthermore, the generalized linear synchronization and nonlinear synchronization are respectively illustrated by several examples. All the numerical simulations demonstrate the correctness of the theoretical results.     

A novel evacuation passageway formed by a breathing air supply zone combined with upward ventilation

With the development of transportation, the tunnel has become one of the important facilities of railway, highway and subway transportation. However, fire hazards occurring inside the tunnel may incur huge numbers of casualties and property losses. In this paper, a breathing air supply zone combined with an upward ventilation assisted tunnel evacuation system (BTES) is introduced. It can be used to create a safe, smoke-free evacuation passageway out of the tunnel. The BTES is optimized to achieve high-performance. The impacts of heat release rates, fire source locations and fire detection times are also discussed.     

High-order rogue waves for the Hirota equation

The Hirota equation is better than the nonlinear Schrödinger equation when approximating deep ocean waves. In this paper, high-order rational solutions for the Hirota equation are constructed based on the parameterized Darboux transformation. Several types of this kind of solutions are classified by their structures.     

Structure and detonation performance of a novel HMX/LLM‐105 cocrystal explosive

Intermolecular interactions and properties of octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐ tetrazocine (HMX) / 2,6‐diamino‐3,5‐dinitropyrazine‐1‐oxide (LLM‐105) cocrystal were studied by using the dispersion‐corrected density functionals (ωB97XD, B97D) and meta‐hybrid functional (M062x) methods. Binding energies, heats of formation, thermodynamic properties, atoms in molecules, and natural bond orbital analysis were performed to investigate HMX/LLM‐105 complexes. Results show that the main intermolecular interactions between HMX and LLM‐105 are CH…O, NH…O, N…O, and O…O interactions. In addition, Monte Carlo simulation was employed to predict the crystal structure of HMX/LLM‐105 cocrystal. The HMX/LLM‐105 cocrystal is most likely to crystallize in C2/c space group, and its corresponding cell parameters are Z = 8, a = 41.63 Å, b = 6.77 Å, c = 45.63 Å, ß = 164.55°, and ρ = 1.99 g/cm³. Detonation velocity and pressure of HMX/LLM‐105 cocrystal are 8.95 km/s, 37.69GPa, a little lower than those of HMX (9.10 km/s, 37.76GPa). However, according to the net charges of nitro group, HMX/LLM‐105 cocrystal exhibits less sensitive than HMX. Finally, bond dissociation energy calculation shows that HMX/LLM‐105 complexes are thermally stable. Considering thermal stability, sensitivity, and detonation performance, HMX/LLM‐105 cocrystal meets the requirements of insensitive high energy density materials. Copyright © 2013 John Wiley & Sons, Ltd.     

基于符号分析的极大联合熵延迟时间求取方法

本文通过符号分析法求取联合熵的极大值点, 进而得到相空间重构的最佳延迟时间, 通过对几个典型的混沌系统进行数值仿真试验, 结果表明, 该方法简化了计算, 提高了效率, 能够准确快速地获得最佳延迟时间, 从而有效地重构原系统的相空间, 为混沌信号识别提供一种快速有效的途径. 关键词： 相空间重构 延迟时间 联合熵 符号分析     

过模波导器件的迭代设计方法

从模式保留和转换的角度, 过模波导器件可分为模式转换器、模式保留器和模式综合器. 传统方法只解决其中一种器件的设计或者对器件的某个指标进行改进. 本文在深入分析耦合波理论之后, 提出了过模波导器件的迭代设计方法, 从原理上解决了过模波导器件的设计问题. 该方法能够统一设计三类过模波导器件, 通过添加不同的结构控制方法, 可得到转换效率更高、带宽更宽、结构更紧凑、满足不同工程需求的器件, 而且还能有效设计一些新型器件. 给出了两个设计实例: 双频TM₀₁–TE₁₁模式变换器和光壁馈源喇叭. 双频TM₀₁–TE₁₁模式变换器的两个工作频点为8.75 GHz和10.3 GHz, 波导半径为16 mm, 在两个频点转换效率为99%以上. 光壁馈源喇叭实现TE₁₁模式向高斯束的转换. CST仿真结果验证了这两个器件设计的正确性和有效性. 关键词： 耦合波理论 模式转换器 模式过渡器 迭代法     

环境卫星HJlA超光谱成像仪在轨辐射定标及光谱响应函数敏感性分析

环境卫星HJIA搭载的超光谱成像仪HSI是我国第一个对地观测的星载高光谱传感器,针对超光谱成像仪缺乏各通道光谱响应函数这一问题,对传统的反射率基法予以改进,提出一种不使用光谱响应函数的场地定标方法.利用敦煌场地2009年8月定标实验数据,实现超光谱成像仪在轨辐射定标.通过构建不同形状的光谱响应函数,分析光谱响应函数形状对最终辐射定标结果产生的误差.结果表明,利用新提出的场地定标方法可以实现超光谱成像仪绝对辐射定标,除水汽和氧气吸收通道外,光谱响应函数对定标结果的影响小于3%,采用新定标方法得到的定标系数可以满足应用的需求.     

Phenomenological gravitational radiation from rotating stellar collapse to an intermediate mass Kerr black hole

Intermediate mass black holes may be formed through repeated coalescences of compact objects or through the direct collapse of a hypermassive star formed through runaway collisions of main sequence stars. The gravitational wave signature of these two formation scenarios will be different. Here we present an initial study of the waveform generated during the direct axisymmetric collapse of a hypermassive star in order to facilitate searches for this source. We approximate the collapse of the core as an axisymmetric Newtonian free-fall of a rotating relativistic degenerate iron core. The collapse waveform can be reasonably well modeled by an exponential growth.