Existence and global exponential stability of almost periodic solutions for BAM neural networks with distributed leakage delays on time scales

In this paper, we deal with a class of BAM neural networks with distributed leakage delays on time scales. Some sufficient conditions which ensure the existence and exponential stability of almost periodic solutions for such class of BAM neural networks are obtained by applying the exponential dichotomy of linear differential equations, Lapunov functional method and contraction mapping principle. An example is given to illustrate the effectiveness of the theoretical predictions. The obtained results in this paper are completely new and complement the previously known publications.     

水稻种子吸涨时渗漏的变化及其与愈伤组织诱导的关系

以吸涨或不经吸涨处理的水稻种子诱导愈伤组织,结果表明,经吸涨24小时的种子,其愈伤组织的诱导率下降.试验进一步指出,种子吸涨期间,外界介质电导率不断上升,氨基酸也在不断外渗,说明种子内的电解质与非电解质在逐渐外渗,且其渗漏量随吸涨时间的延长而增长.并且种子吸涨期间物质的外渗呈现一定的规律变化.因此,吸涨种子愈伤组织诱导下降,是与种子内物质的渗漏有关.     

热漏对换热器(火积)耗散最小化的影响

建立了存在热漏的换热器的传热过程模型.假定热流体与冷流体间的传热以及冷流体与外界环境间的热漏均服从牛顿传热定律,在冷流体净传热量一定的条件下,应用最优控制理论导出了换热过程(火积)耗散最小时热流体温度和冷流体温度的最优构型,并将最优路径分别与热流体温度一定和热流率一定的传统传热策略进行了比较.研究结果对于实际换热器的优化设计和最优运行具有一定的理论指导意义.     

炉内管道泄漏声检测与定位系统的研究现状

电站锅炉管道泄漏的声检测与定位系统,已经越来越广泛地应用于电站锅炉。该系统主要利用声学技术检测炉内管道的泄漏状态,并利用多传声器定位机理对泄漏点进行定位,有效地减少了由管道泄漏引起的非计划停炉,这对电站锅炉来说意义尤为重要。本文分析了炉内管道泄漏声检测与定位系统的关键技术,介绍了该系统的发展概况及应用现状,并提出了改进方向。     

Leakage current reduction by thermal oxidation in Ni/Au Schottky contacts on lattice-matched Ino.18Al0.82N/GaN heterostructures

By using temperature-dependent current-voltage, variable-frequency capacitance-voltage, and Hall measurements, the effects of the thermal oxidation on the electrical properties of Ni/Au Schottky contacts on lattice-matched Ino.18Alo.82N/GaN heterostructures are investigated. Decrease of the reverse leakage current down to six orders of magni- tude is observed after the thermal oxidation of the Ino.18Alo.82N/GaN heterostructures at 700 ℃. It is confirmed that the reverse leakage current is dominated by the Frenkel-Poole emission, and the main origin of the leakage current is the emis- sion of electrons from a trap state near the metal/semiconductor interface into a continuum of electronic states associated with the conductive dislocations in the InxAll-xN barrier. It is believed that the thermal oxidation results in the formation of a thin oxide layer on the InxAll-xN surface, which increases the electron emission barrier height.     

采空区流场非达西渗流一种新的迭代算法

对Bachmat非线性渗流方程求解问题，结合采空区问题的力学特点，提出基于变渗透率达西 (Darcy)渗流求解非线性渗流的迭代算法. 建立了冒落采空区非线性漏风流态的有限元数 值模型，通过对复杂边界采空区的漏风渗流的计算，得到与实际流态更接近的流动规律(风 压等值线和流函数线)和采空区漏风强度分布(速度场). 结果表明，迭代算法是振荡性收 敛的，收敛速度快；与Darcy渗流相比，采空区非线性渗流速度场趋向于平缓，在工作面附 近30\,m范围内最大风速降低到原来的0.61倍，其余大部分区域速度略有增加. 迭代方法满 足工程要求.     

Study on the radiation problem caused by electron beam loss in accelerator tubes

The beam dynamic code PARMELA was used to simulate the transportation process of accelerating electrons in S-band SW linacs with different energies of 2.5, 6 and 20 MeV. The results indicated that in the ideal condition, the percentage of electron beam loss was 50% in accelerator tubes. Also we calculated the spectrum, the location and angular distribution of the lost electrons. Calculation performed by Monte Carlo code MCNP demonstrated that the radiation distribution of lost electrons was nearly uniform along the tube axis, the angular distributions of the radiation dose rates of the three tubes were similar, and the highest leaking dose was at the angle of 160° with respect to the axis. The lower the energy of the accelerator, the higher the radiation relative leakage. For the 2.5 MeV accelerator, the maximum dose rate reached 5% of the main dose and the one on the head of the electron gun was 1%, both of which did not meet the eligible protection requirement for accelerators. We adopted different shielding designs for different accelerators. The simulated result showed that the shielded radiation leaking dose rates fulfilled the requirement.     

螺旋线型倍压器传输线损耗参数

 通过介绍螺旋线型倍压器的结构参数和工作原理,分析了影响螺旋线型倍压器输出特性的3个损耗参数：开关电阻损耗因子。螺旋线型倍压器传输线电阻损耗因子和传输线相邻同轴电容之间漏感损耗因子;螺旋线型倍压器的损耗参数主要由其结构参数所决定,通过实验研究,给出了各结构参数对螺旋线型倍压器输出特性的影响关系,并且给出了传输线电阻损耗因子和相邻同轴电容间漏感损耗因子与传输线结构参数间的经验公式,为螺旋线倍压器的电路模型构建提供参考数据。     

Existence and global stability of almost automorphic solutions for shunting inhibitory cellular neural networks with time-varying delays in leakage terms on time scales

In this paper, shunting inhibitory cellular neural networks(SICNNs) with time-varying delays in leakage terms on time scales are investigated. With the aid of the existence of the exponential dichotomy of linear dynamic equations on time scales, fixed point theorem and the theory of calculus on time scales, we establish some sufficient conditions to ensure the existence and exponential stability of almost automorphic solutions for the model. An example with its numerical simulations is given to illustrate the feasibility and effectiveness of the theoretical findings.     

Numerical Study on the Waveguiding Properties of Photonic Crystal Fibers

The photonic band structure, mode field distribution, and leakage loss of different photonic crystal fibers are studied by the full vectorial plane wave expansion method and an extended beam propagation method. A comparison on the waveguiding mechanism is conducted among solid-core triangular-lattice PCF, air-core honeycomb PCF, and solid-core honeycomb PCF. For the latter two structures, which conduct light by the photonic bandgap effect, the advantages of down-doped solid-core honeycomb structure are demonstrated for its Gaussian-like mode field distribution and low leakage loss. A combined study on the leakage loss and band structure of solid-core honeycomb PCF has revealed the distinctive properties of photonic bandgap effect.