Multistrain edge‐based compartmental model on networks

Multistrain diseases, which are infected through individual contacts, pose severe public health threat nowadays. In this paper, we build competitive and mutative two‐strain edge‐based compartmental models using probability generation function (PGF) and pair approximation (PA). Both of them are ordinary differential equations. Their basic reproduction numbers and final size formulas are explicitly derived. We show that the formula gives a unique positive final epidemic size when the reproduction number is larger than unity. We further consider competitive and mutative multistrain diseases spreading models and compute their basic reproduction numbers. We perform numerical simulations that show some dynamical properties of the competitive and mutative two‐strain models.     

Structural,magnetic and optical properties of two concomitant molecular crystals

A new 1D complex has been prepared and characterized. X-ray single crystal structure confirms that the Cu(II) ions assemble in alternating chains with Cu … Cu distances of 2.5685(4) and 3.1760(4) Å. The temperature dependence of the magnetic susceptibility reveals an antiferromagnetic interaction between the paddle-wheel copper centers with an exchange of −300 cm⁻¹. The exchange integral was also determined by quantum chemical ab-initio calculations, using polarised and unpolarised basis sets reproducing well the experimental value. The second harmonic generation efficiency of a concomitantly crystallized material was evaluated and was found to be comparable to urea.     

A computational method for geometric optimization of enhanced heat transfer devices based upon entropy generation minimization

A computational fluid dynamics‐based optimization methodology is developed, appropriate for the geometric optimization of enhanced heat transfer devices based upon the principle of entropy generation minimization, in which the objective function is evaluated from a flow field obtained by computational simulation. A quasi‐Newton optimization procedure is employed, with computation of the objective function gradients based upon a finite difference approach. The optimization procedure is developed to be general with regard to the choice of objective function, the details of the problem under consideration, and the computational methodology employed in solving the fluid flow and heat transfer problems. A novel implementation of a Taylor series‐based procedure for the fast solution of nearby problems is presented, which is found to greatly benefit the efficiency of the present methodology. Finally, a numerical experiment is presented, illustrating the use of the present method in the geometric optimization of a practical enhanced heat transfer device on the basis of the criterion of entropy generation minimization. The optimization of the fin spacing of a simple plate fin heat sink is considered, and a comparison of the computational results with results obtained by analytical optimization based upon empirical friction factor and Nusselt number correlations is given. Copyright © 2012 John Wiley & Sons, Ltd.     

A Microcell for Stripping Analysis with Glassy Carbon and Mercury-Plated Glassy Carbon Electrodes

Abstract

A microcell has been constructed for stripping analysis in solution volumes as low as 5 μl, employing a glassy carbon or mercury-plated glassy carbon working electrodes and a three electrode system. Using normal d.c. stripping techniques, as little as 100 picograms of mercury and 10 picograms of lead can be determined. With the more sensitive second harmonic a.c. voltammetric technique, this limit is lowered to 10 picograms of mercury and 1 picogram of lead.     

不均匀场中氢分子离子高次谐波产生的理论研究

在非Born-Oppenheimer近似下，通过求解含时薛定谔方程的方法，对氢分子离子在不均匀场中高次谐波的产生进行了理论研究.计算结果显示，同均匀场相比，电离的电子在不均匀场中加速会获得更多的能量，从而更有利于得到宽频谱.此外,通过优化不均匀场中的空间不均匀度，长量子路径被明显的抑制，最终通过叠加110阶到150阶谐波，获得一个60as的孤立阿秒脉冲.同时，通过库仑势和激光场的相互作用势以及时频分布图解释了其中的物理机制.     

Optical pulse shaper with integrated slab waveguide for arbitrary waveform generation using optical gradient force

Integrated optical pulse shaper opens up possibilities for realizing the ultra high-speed and ultra wide-band linear signal processing with compact size and low power consumption. We propose a silicon monolithic integrated optical pulse shaper using optical gradient force, which is based on the eight-path finite impulse response. A cantilever structure is fabricated in one arm of the Mach–Zehnder interferometer（MZI） to act as an amplitude modulator. The phase shift feature of waveguide is analyzed with the optical pump power, and five typical waveforms are demonstrated with the manipulation of optical force. Unlike other pulse shaper schemes based on thermo–optic effect or electro–optic effect, our scheme is based on a new degree of freedom manipulation, i.e., optical force, so no microelectrodes are required on the silicon chip,which can reduce the complexity of fabrication. Besides, the chip structure is suitable for commercial silicon on an insulator（SOI） wafer, which has a top silicon layer of about 220 nm in thickness.     

On a hidden symmetry of quantum harmonic oscillators

We consider a six-parameter family of the square integrable wave functions for the simple harmonic oscillator, which cannot be obtained by the standard separation of variables. They are given by the action of the corresponding maximal kinematical invariance group on the standard solutions. In addition, the phase space oscillations of the electron position and linear momentum probability distributions are computer animated and some possible applications are briefly discussed. A visualization of the Heisenberg uncertainty principle is presented.     

刮片式制冰蓄冷性能的实验研究

对刮片式动态冰浆制取系统进行实验研究,分析系统的能效比和蒸发器进出口温度、冷凝器进出口温度以及冷凝水和盐溶液流量曲线变化。研究结果表明:对制冷量为20kW的刮片式制冰装置,盐溶液有1.5℃的过冷度,随着盐溶液浓度越高其冰点越低,系统的能效系数最高达到1.9,有利于制冰蓄冷节能。     

Exact pressure integrations on submerged bodies in waves using a quadtree adaptive mesh algorithm

The development of an adaptive free surface, mesh cutting, methodology, in order to analytically integrate pressures on varying wet parts of partially submerged surfaces in the presence of waves, is presented. Given a function of free‐surface elevation, the algorithm checks for the intersection of the body with the free surface and, based on user‐defined parameters, modifies the initial mesh, by subdividing the elements where necessary and eliminating others, via a quadtree approach. Redundant sub‐divisions, generated in the quad‐division process, are partially eliminated, but the quadrilateral nature of the elements is always kept. The free‐surface function must be single‐valued and its definition domain simply connected. Hydrostatic and Froude–Krylov forces are computed exactly on each panel by means of analytical formulations, which are derived and presented, based on the theory of linear gravity waves and from applying Green's theorem. Copyright © 2014 John Wiley & Sons, Ltd.     

Stuffed Tridymite Structures: Synthesis,Structure, Second Harmonic Generation,Optical, and Multiferroic Properties

The stuffed tridymite structure Ba(Zn/Co)_1−xSi_1−xM_2xO₄ (M=Al³⁺ and Fe³⁺) is explored for the possible multiferroic behavior and to develop new inorganic colored materials. The compounds were synthesized by employing conventional solid-state chemistry methods in the temperature range 1100–1175 °C for 24 h. The powder X-ray diffraction (PXRD) and Rietveld refinement studies indicate that the compounds stabilize in the P63 space group (no. 173). The refinement results were also rationalized by employing Raman spectroscopic studies. The compounds were found to be second harmonic generation (SHG) active and show weak ferroelectric behavior. The co-substitution of Co²⁺ and Fe³⁺ in the structure gives rise to a weak ferromagnetic behavior to the compound, BaCo_0.75Si_0.75Fe_0.5O₄, making it a multiferroic material. The optical studies on the prepared compounds exhibited blue color (Co²⁺ in T_d geometry), purple color (Ni²⁺ in T_d geometry), and simultaneous substitution of Co²⁺ and Fe³⁺ gives rise to blue-green color owing to metal-to-metal charge transfer (MMCT) effect.