Some basic principles in dynamic theory of viscoelastic materials with voids

According to the basic idea of classical yin-yang complementarity and modern dual-complementarity, in a simple and unified way proposed by Luo, some basic principles in the dynamic theory of viscoelastic materials with voids can be estab- lished systematically. In this paper, an important integral relation in terms of con- volutions is given, which can be considered as the generalized principle of virtual work in mechanics. Based on this relation, it is possible not only to obtain the principle of virtual work and the reciprocal theorem, but also to derive systemati- cally the complementary functionals for the eight-field, six-field, four-field simpli- fied Gurtin-type variational principles and the potential energy-functional for the two-field one in the dynamic theory of viscoelastic materials with voids by the generalized Legendre transformations given in this paper. Furthermore, with this approach, the intrinsic relationship among various principles can be explained clearly.     

一种简便的计算层析系统X射线硬化校正方法

以实物拍摄为依据,用一种最简便的修正方法解决计算机X射线层析术成像时由于硬化效应引起的切片图灰度失真问题。用高性能数字X射线机FAXITRON MX-20(射线管焦点20μm,探测板灰度等级16位)对不同厚度的物体进行透射成像,测得对应的透射光强度,并利用新创的指数拟合法得到理想的拟合曲线,由此推导硬化效应的指数校正公式;最后利用实验室的微型计算机层析设备进行扇形束扫描,并逆投影重建生成计算层析断层图像,验证了该校正方法的实用性。该指数拟合法的误差不到常用的二阶多项式拟合法的1/3,对物体计算层析重构,硬化校正以前有明显的“杯状”伪迹,切片灰度不均匀,用指数法修正以后该伪迹消失,切片灰度均匀。     

Investigation of all-solid photonic bandgap fiber with low losses in low-order bandgaps

We report synoptically an investigation of design, fabrication and characterization of a new all-solid photonic bandgap fiber. By introducing an index depressed layer around a high index core in every unit cell of photonic crystal cladding, a novel all-solid bandgap fiber is predicted to obtain low confinement and bend losses within low-order bandgaps. After optimizing the structure parameters, we fabricate a batch of rods used for cladding cells, select a pure-silica rod for core cell and an inner-hexagonal jacket tube. We demonstrate an all-solid bandgap fiber with the transmission loss as low as 2 dB/km at 1,310 nm and a bandwidth of over 700 nm within the first bandgap. The guiding properties are also measured, respectively, such as transmission spectrum, attenuation spectrum, bend loss, mode field intensity profile, and chromatic dispersion.     

The freeze of intrapulse Raman scattering effect of ultrashort solitons in optical fiber

The effect of intrapulse Raman scattering (IRS) for the propagation of the femtosecond solitons in an optical fiber is investigated. To factually simulate its influence, a combination of 27 Lorentian lines to fit experimental Raman gain profile is adopted. By using nonlinear Schrödinger equation and finite-difference time domain method, the propagations of femtosecond fundamental solitons in an optical fiber are numerically calculated. When the initial power is suitably enhanced, it is found that the pulse shape is almost the same as initial pulse and the delay Raman response only makes small pulse shift. In other words, when ultrashort soliton is considered, the IRS effect is similarly frozen under the enhanced initial power.     

Notes on Superadditivity of Wigner–Yanase–Dyson Information

The classical Fisher information is superadditive in the sense that the Fisher information of a bivariate probability density is always not less than the sum of those of the marginals. The longstanding conjecture concerning the superadditivity of the Wigner–Yanase–Dyson information is a quantum analogue of this property. It is remarkable that Hansen constructed a numerical counterexample to the quantum case (J. Stat. Phys. 126: 643–648, 2007). However, the requirement of superadditivity of an information-theoretic quantity such as the Wigner–Yanase–Dyson information seems so intuitive, it is desirable to identify conditions as general as possible such that the superadditivity holds. In this paper, we establish the superadditivity in several physically significant cases.     

Jackiw-Pi模型的新涡旋解

运用φ映射拓扑流理论研究了Jackiw-Pi模型中的自对偶方程，得到一个静态的自对偶解满足带有δ函数项的刘维尔方程, 从而得到了一个完整的带有拓扑信息的涡旋解,自然给出了磁通量子化.     

250步混沌强度解析混沌特征及其在心率研究中的应用

应用250步混沌强度分析Lorenz系统，分别对3维和x分量进行了计算表明，250步混沌强度与Lorenz系统的参数有明显关系.计算了正常人的窦性心率的250步混沌强度，得到了它与年龄的关系：y=6.4623-0.0496x，相关系数为-0.669，这一结果支持了Goldberger的观点，如果人的250步混沌强度照此规律衰减，将在130岁降到0.     

Synthesis and luminescent properties of Y6W2O15:Eu phosphors

In this paper, a novel phosphor, Y₆W₂O₁₅:Eu³⁺ was synthesized by thermal decomposition and phase transition of its decatungstate gel precursor. With stepwise increase of temperature to 750 °C, a crystalline phase of Y₆W₂O₁₅:Eu³⁺forms that gives intense red emission when excited at 466 nm, the emission is attributed to the Eu³⁺ ions transitions from ⁵D₀ excited states to ⁷F_J (J=0-4) ground states. The long excitation wavelength proves the Eu³⁺ transition follows the photoexcitation of the oxygen-metal (O→W lmct) charge transfer bands in yttrium tungstate. Some structural information regarding Y₆W₂O₁₅ provided by luminescence is in accord with that characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The long-wavelength excitation properties of this material may find application in the production of red phosphors for white light-emitting diodes (LEDs).     

Photosensitivity-enabled dispersion controllability for quasi-phase-matching in photonic crystal fibers

A novel photonic crystal fiber featured by concentric cores is proposed to induce dispersion controllability by photosensitivity. Chromatic dispersion can be changed from -1827 to 72 ps/nm/km with refractive index modulation of 4 x 10(-4) produced in Ge-doped regions in the fiber. Effective mode area of inner mode is as small as 6.4 mum(2). The proposed fiber enables to achieve quasi-phase-matched nonlinear parametric interaction in a single piece of photonic crystal fiber, by periodically alternating dispersion and compensating for phase mismatching caused by the dispersion.     

强流离子束离子径向密度分布的模拟研究

对初始分布为K-V分布的离子束进行模拟研究.除观察到存在束晕现象外，还发现离子束在通 道内运行过程中，离子沿径向密度分布发生了变化. 通过延迟反馈控制，不仅可以消除束晕 ，而且只要控制参数适当，也可以使束中心部分呈均匀分布状态. 关键词： 强流离子束 束晕 填充因子 离子密度分布