Analytical modeling of loss characteristics of a polymer arrayed waveguide grating multiplexer

Theoretical analysis is performed for the loss characteristics of a polymer arrayed waveguide grating (AWG) multiplexer around the central wavelength of 1.55 μm with the wavelength spacing of 1.6 nm. The total loss of the device includes the diffraction loss in the input and output (I/O) slab waveguides, bent loss caused by the AWG and I/O channels, leakage loss resulted from the high refractive index substrate, and propagation loss due to the absorption and scattering of the materials of the device. The effects of some structural parameters on the loss characteristics are investigated and discussed. The computed results show that when we select the core thickness as 4 μm, core width as 6 μm, pitch of adjacent waveguides as 15.5 μm, diffraction order as 50, the number of the arrayed waveguides as 91, that of the I/O channels as 17, confined layer thickness between the core and the substrate as 10 μm, distance between the focal point and the origin as 5500 μm, and central angle between the central waveguide and the x-axis (i.e. the vertical of the symmetrical line of the device) as 60°, the total loss of the device can be dropped to the range 3.79–7.93 dB.     

闪速存储器中应力诱生漏电流的产生机理

通过实验研究了闪速存储器存储单元中应力诱生漏电流(SILC)的产生机理. 研究结果表明，在低电场应力下，其可靠性问题主要是由载流子在氧化层里充放电引起，而在高电场下，陷阱和正电荷辅助的隧穿效应导致浮栅电荷变化是引起闪速存储器失效的主要原因. 分别计算了高场应力和低场应力两种情况下SILC中的稳态电流和瞬态电流的大小. 关键词： 闪速存储器 应力诱生漏电流 电容耦合效应 可靠性     

轴流压气机时尖泄漏涡的时均流动

用三维激光多普勒测速系统测量研究低速大尺寸单级压气机设计状态转子内尖区流场．结果表明，泄漏流在气流一进入转子叶片通道就开始发生，发生于前半弦长，其诱导形成的泄漏涡约在30％弦长处达到最强，随后逐渐衰减，其涡核顺下游慢慢向压力面方向和低时高方向移动，涡核在转子出口移至通道中部．泄漏涡影响区域沿流向逐渐扩大，并向压力面方向和低叶高方向移动．设计状态叶尖泄漏涡在转子尖区流动中起主要作用，是造成尖部流动阻塞的主要因素．     

房屋建筑渗漏水的问题与对策

通过对一住宅小区房屋渗漏水情况的调查研究，分析了房屋建筑渗漏水的原因。从而探讨防止房屋渗漏水的有效措施。     

Saltwater transport in a heterogeneous formation: A case study

Historical information of the hydraulic and salinity aspect, detailed geological information, and information on the physical characteristics of the different layers comprising the formation, are needed for simulating the saltwater transport process in aquifers. In most simulation studies of field situations, there is an inadequacy of data and the modeller has to make justifiable assumptions to analyze a particular situation in order to provide an insight into the problem.A quasi-three-dimensional solute transport model is used to analyze the saltwater encroachment phenomena in aquifers underlying the City of Bangkok; first by calibrating the model's performance with available historical data and then by assessing the extent of future saltwater encroachment with the implementation of the regulatory pumpage to be followed in order to restrict the alarming rate of land subsidence. Model simulation indicates a substantial reduction in the rate of encroachment of the saltwater front with a reduction of pumpage after 1987.     

A Protocol for Bidirectional Quantum Secure Communication Based on Genuine Four-Particle Entangled States

By swapping the entanglement of genuine four-particle entangled states, we propose a bidirectional quantum secure communication protocol. The biggest merit of this protocol is that the information leakage does not exist. In addition, the ideas of the ＂two-step＂ transmission and the block transmission are employed in this protocol. In order to analyze the security of the second sequence transmission, decoy states are used.     

金属磁记忆效应的第一性原理计算与实验研究

为研究铁磁材料应力集中区域金属磁记忆信号的产生机理及其变化规律, 采用基于密度泛函理论的第一性原理平面波赝势法, 建立了磁记忆效应的磁力学模型; 计算分析了力与磁记忆自发漏磁信号的定量变化关系. 研究结果表明:力作用导致晶格畸变是磁记忆自发漏磁信号产生的根本原因; 常温下, 磁记忆信号随应力近似线性变化的规律与X70钢管水压爆破实验结果具有很好的一致性. 研究结果有助于金属磁记忆检测机理的研究. 关键词： 金属磁记忆 第一性原理 漏磁信号     

Leakage currents in ferroelectric thin films

The main mechanisms of leakage currents in thin lead zirconate titanate (PZT) ferroelectric films prepared by the sol–gel method are discussed. Four specific regions are determined in I–V dependencies. At very weak fields (10–20 kV/cm), the current falls with the voltage increase as a result of depolarization. In the low fields region (about 70–100 kV/cm), the leakage current decreases with the decrease of voltage ramp speed and its components are the ohmic and displacement currents. In the high fields region (≥130 kV/cm), the leakage current increases with the decrease of step voltage ramp in contrast to the previous case. Possible conductivity mechanisms are the Poole– Frenkel emission and hopping conduction. In the transition region between above-mentioned ones (from 80–90 to ～130 kV/cm), an abrupt unstable increase of current is observed caused by breakdown of reverse bias Schottky barrier. Depolarization currents are studied for sol–gel PZT films prepared at different preparation conditions.     

跨音速轴流风扇转子叶顶泄漏流的数值研究

采用数值模拟方法研究了不同间隙,不同流量工况下叶顶泄漏流非定常流动特征,发现在研究的三个间隙中,只有当间隙大于或等于设计间隙时,流动才会出现非定常性.随着流量的减小,泄漏涡轨迹前移,当泄漏涡轨迹到达相邻叶片压力面时,影响压力面压力分布,打破流场静态平衡,引起叶顶流场及激波位置、强度发生非定常波动.     

Cavity loss induced generation of W states

The existence of decoherence-free subspace (DFS) has been discussed widely. In this paper, we propose an alternative scheme for generating the four-atom $W$ states by manipulating DF qubits. The atoms are divided into two pairs and trapped in two separate optical cavities. Manipulation of atoms within DFS may generate a two-atom maximally entangled state in an individual cavity, which is a stable state. After driving the system out of DFS, the atoms will interact resonantly with the cavity field. The photons leaking from the cavities interfere at the beamsplitter, which destroys which-path information, and are finally detected by one of the detectors, leading to the generation of a $W$ state. In addition, the numerical simulation indicates that the fidelity of the prepared state can, for a very wide parameter regime, be very close to unity.