Jet formation in shock-heavy gas bubble interaction

The influences of the acoustic impedance and shock strength on the jet formation in shock-heavy gas bubble interaction are numerically studied in this work. The process of a shock interacting with a krypton or a SF 6 bubble is studied by the numerical method VAS2D. As a validation, the experiments of a SF 6 bubble accelerated by a planar shock were performed. The results indicate that, due to the mismatch of acoustic impedance, the way of jet formation in heavy gas bubble with different species is diversified under the same initial condition. With respect to the same bubble, the manner of jet formation is also distinctly different under different shock strengths. The disparities of the acoustic impedance result in different effects of shock focusing in the bubble, and different behaviors of shock wave inside and outside the bubble. The analyses of the wave pattern and the pressure variation indicate that the jet formation is closely associated with the pressure perturbation. Moreover, the analysis of the vorticity deposition, and comparisons of circulation and baroclinic torque show that the baroclinic vorticity also contributes to the jet formation. It is concluded that the pressure perturbation and baroclinic vorticity deposition are the two dominant factors for the jet formation in shock-heavy gas bubble interaction.     

On Dirichlet Problem for a Class of Delayed Reaction–Diffusion Equations with Spatial Non-locality

We consider a very general class of delayed reaction–diffusion equations in which the reaction term can be non-monotone as well as spatially non-local. By employing comparison technique and a dynamical system approach, we study the global asymptotic behavior of solutions to the equation subject to the homogeneous Dirichlet condition. Established are threshold results and global attractiveness of the trivial steady state, as well as the existence, uniqueness and global attractiveness of a positive steady state solution to the problem. As illustrations, we apply our main results to the local delayed diffusive Mackey–Glass equation and the nonlocal delayed diffusive Nicholson blowfly equation, leading to some very sharp results for these two particular models.     

一种新型酶生物燃料电池阳极构建及性能研究

通过酸化碳纳米管(CNTs)和β-环糊精(β-CD)之间的范德华力作用, 实现CNTs的β-CD功能化. β-CD具有内腔疏水、外壁亲水的环状结构, 其内腔容易与二茂铁(Fc)形成稳定的主客体包合结构, 实现Fc在碳纳米管上的高效固载; 再将CNTs-β-CD-Fc复合物与葡萄糖氧化酶(GOD)混合, 采用戊二醛实现酶分子间的交联, 形成GOD/CNTs-β-CD-Fc复合物, 然后将其涂覆到玻碳电极(GC)上, 得到一种新型的酶生物燃料电池阳极(GOD/CNTs-β-CD-Fc/GC). 采用同步热分析法、傅里叶变换红外光谱和透射电子显微镜对所制备的CNTs-β-CD-Fc复合物进行了表征, 采用循环伏安法研究了GOD/CNTs-β-CD-Fc/GC电极对葡萄糖氧化的催化性能. 结果表明: 在同等实验条件下, 没有固载Fc的GOD/CNTs- β-CD/GC电极基本无催化电流, 而GOD/CNTs-β-CD-Fc/GC电极表现出比GOD/CNTs-Fc/GC电极更为优越的电催化性能. 进一步以GOD/CNTs-β-CD-Fc/GC电极或GOD/CNTs-Fc/GC电极为酶阳极, 商用催化剂E-TEK Pt/C电极(E-TEK Pt/C/GC)为阴极, 构建葡萄糖/氧气生物燃料电池(EBFC), 结果表明前者的最大功率密度(33 μW·cm^-2, 0.18 V)几乎是后者的三倍(11.7 μW·cm^-2, 0.16 V). 通过记录开路电位随时间的变化研究了EBFC的稳定性, 以GOD/CNTs-β-CD-Fc/GC电极为阳极的EBFC在连续工作9 h后仍保留了92%的开路电位, 表明该电池具有良好的连续工作稳定性. 我们提出的这种新型生物燃料电池阳极的构造方法, 为构建高性能、高稳定性的葡萄糖/氧气EBFC提供了新的思路.     

Direct Synthesis of High Purity Silicon Wires by Electrorefining in Molten KF-NaF Eutectic

The electrochemical synthesis silicon wires by electrorefining metallurgical grade silicon in thermally dried and pre-electrolyzed molten KF-NaF eutectic were studied at temperatures 800-900 oC using cyclic voltammetry and ac impedance. One oxidation peak at -0.14 V could be attributed to the reaction of Si to Si⁴⁺. A cathodic peak occurred at -0.56 V in the cyclic voltammogram and one response semicircle in the ac impedance spectrum was observed, supporting a one-step electrochemical reduction process of Si⁴⁺→Si. The electrochemical reaction of silicon was controlled by the diffusion process. The purity of electrorefined silicon wires was up to 99.999% by ICP-MS analysis.     

Formation and Characteristics of Acrylonitrile/Urea Inclusion Compound

The formation process and composition of the acrylonitrile/urea inclusion compounds (AN/UIC) with different aging times and AN/urea molar feed ratios are studied by differen-tial scanning calorimetry (DSC) and X-ray diffraction (XRD). It is suggested that DSC candetermine the guest/host ratio and the heat of decomposition. Meanwhile, the guest/host ratio and heat of decomposition are obtained, which are 1.17 and 5361.53 J/mol, respec-tively. It is suggested AN molecules included in urea canal lattice may be packed flat against each other. It is found that the formation of AN/UIC depends on the aging time. XRD results reveal that once AN molecules enter urea lattice, AN/UIC are formed, which possess the final structure. When AN molecules are sufficient, the length of AN molecular arrays in urea canals increases as aging time prolonging until urea tunnels are saturated by AN.     

混合模式色谱材料Click TE-GSH高效富集多磷酸化肽

多磷酸蛋白对于生物体适应内外环境具有重要意义,而明确多磷酸蛋白的磷酸位点功能及其信号转导机制尤为关键. 复杂生物样品中多磷酸化肽的低丰度、低电离的特性,以及非磷酸化肽的抑制作用,决定了质谱分析前进行多磷酸化肽富集是非常必要的步骤. 本工作采用基于巯基-烯烃点击化学法合成的混合模式材料Click TE-GSH进行单磷酸化肽和多磷酸化肽的选择性富集. 我们建立了单磷酸化肽、双磷酸化肽和多磷酸化肽的顺序分段富集方法. 该优化方法能抗干扰,应用于脱脂牛奶时富集到11条多磷酸化肽. 与商品化固化金属亲和色谱(IMAC)材料相比,Click TE-GSH富集多磷酸化肽的选择性更好. 本工作所建立的富集方法为高效富集多磷酸化肽提供新方法和新技术.     

Propagation of high-power partially coherent fibre laser beams in a real environment

The propagation performance of high-power partially coherent fibre laser beams in a real environment is investigated and the theoretical model of a high-power fibre laser propagating in a real environment is established. The influence of a collimating system and thermal blooming is considered together with atmospheric turbulence and mechanical jitter. The laser energy concentration of partially coherent beams in the far field is calculated and analysed based on the theoretical model. It is shown that the propagation performance of partially coherent beams depends on the collimating system, atmospheric turbulence, mechanical jitter and thermal blooming. The propagation performance of partially coherent beams and fully coherent beams is studied and the results show that partially coherent beams are less sensitive to the influence of thermal blooming, which results in that the energy degeneration for partially coherent beams is only 50% of that for fully coherent beams. Both partially coherent beams and fully coherent beams become less sensitive to thermal blooming when the average structural constant of the refraction index fluctuations increases to 1.7 × 10^-14 m^-2/3. The investigation presents a reference for applications of a high-power fibre laser system.     

Multiferroic tunnel junctions

Magnetic tunnel junctions with ferroelectric barriers, often referred to as multiferroic tunnel junctions, have been proposed recently to display new functionalities and new device concepts. One of the notable predictions is that the combination of two charge polarizing states and the parallel and antiparallel magnetic states could make it a four resistance state device. We have recently studied the ferroelectric tunneling using a scanning probe technique and multiferroic tunnel junctions using ferromagnetic La_0.7Ca_0.3MnO₃ and La_0.7Sr_0.3MnO₃ as the electrodes and ferroelectric (Ba, Sr)TiO₃ as the barrier in trilayer planner junctions. We show that very thin (Ba, Sr)TiO₃ films can sustain ferroelectricity up till room temperature. The multiferroic tunnel junctions show four resistance states as predicted and can operate at room temperatures.     

Properties of a dielectric plate using entangled two-photon states

We theoretically study the properties of a dielectric plate with a modified Hong-Ou-Mandel interferometer. The fourth-order correlation functions are calculated in two regimes, which are divided depending on the relative size between the thickness of the dielectric plate and the one-photon coherence length. When the thickness of the dielectric plate is less than the one-photon coherence length, a novel modulation behavior of the coincidence rate is observed, which has not been discussed before. If the thickness of the dielectric plate is larger than the one-photon coherence length, coalescence and anti-coalescence are observed. The obtained results highlight the effects of a linear optical element on fourth-order interference.     

Eshelby’s problem in an anisotropic multiferroic bimaterial plane

We solve analytically the Eshelby’s problem in an anisotropic multiferroic bimaterial plane. The solution is based on the extended Stroh formalism of complex variables, and is valid for the inclusion of arbitrary shapes, described by a Laurent polynomial, a polygon, or the one bounded by a Jordan curve. Furthermore, the results in the corresponding half plane and full plane can be reduced directly from the bimaterial-plane solution. As such, the solution unifies the complex variable method and the Green’s function method, extending further to the multiferroic bimaterial plane of general anisotropy. The essential eigenfunctions are also identified by which the induced fields can be simply determined. Numerical results are presented to investigate the features of these eigenfunctions as well as the strain, electric and magnetic fields (components of the extended Eshelby tensor). Particularly, we present the values of these fields at the center of the N-side regular polygonal inclusion and also the average values of these fields over the inclusion area. The effect of the half-plane traction-free surface condition as well as the effect of various couplings on the induced fields is discussed in detail. For the N-side regular polygonal inclusion, it is found that, when the inclusion is in the full plane, both the center and average values of the Eshelby tensor are independent of the side number N, except for N = 4. We further show that the piezoelectric and piezomagnetic coupling coefficients could significantly affect the Eshelby tensor. These features should be useful in controlling the Eshelby tensor for the design of better multiferroic composites. Typical contours of the field quantities in and around the inclusion bounded by both straight and curved line segments in a multiferroic bimaterial plane are also presented.