呼图壁种牛场草原生态站鼠类群落初步研究

本文根据１９９５年７￣８月的调查资料并采用聚类分析方法对呼图壁种牛场草原生态站鼠类群落及其演替进行了分析研究。结果表明：该地区的鼠类可划分为２种群落，灰仓鼠＋小家鼠为主的农田居民点鼠类群落，五趾跳鼠＋根田鼠为主的荒漠草原鼠类群落，种的多样性和生态环境的差异有关，随着人类经济活动的增加，经营时间的不同，鼠类群落受到的影响程度也不一样，在荒漠向人工环境转化过程中存在于其中的鼠类也呈现有规律的演替现象。     

A new coupled model for alloy solidification

A new coupled model in the binary alloy solidification has been developed. The model is based on the cellular automaton (CA) technique to calculate the evolution of the interface governed by temperature, solute diffusion and Gibbs-Thomson effect. The diffusion equation of temperature with the release of latent heat on the solid/liquid (S/L) interface is valid in the entire domain. The temperature diffusion without the release of latent heat and solute diffusion are solved in the entire domain. In the interface cells, the energy and solute conservation, thermodynamic and chemical potential equilibrium are adopted to calculate the temperature, solid concentration, liquid concentration and the increment of solid fraction. Compared with other models where the release of latent heat is solved in implicit or explicit form according to the solid/liquid (S/L) interface velocity, the energy diffusion and the release of latent heat in this model are solved at different scales, i.e. the macro-scale and micro-scale. The variation of solid fraction in this model is solved using several algebraic relations coming from the chemical potential equilibrium and thermodynamic equilibrium which can be cheaply solved instead of the calculation of S/L interface velocity. With the assumption of the solute conservation and energy conservation, the solid fraction can be directly obtained according to the thermodynamic data. This model is natural to be applied to multiple (< 2) spatial dimension case and multiple (< 2) component alloy. The morphologies of equiaxed dendrite are obtained in numerical experiments.     

一种小家电设计的教学实践

为了使物理教学贴近生活实际，拉近物理学与实际问题的距离，我们进行了小家电（电吹风）设计的教学实践．实践方案如下．     

Phase field model simulations of hydrogel dynamics under chemical stimulation

Two decades ago, it has been observed experimentally that hydrogels immersed in a bath solution swells or shrinks under external stimulations (Ric?ka et al., Macromolecules 17:2916?C2921, 1984). Recently, this fact has received renewed interest, since understanding the precise mechanisms underlying that kind of behavior has the potential to tailor most sensitive drug delivery systems based on hydrogels (Segalman and Witkowski, Mater Sci Eng C 2:243?C249, 1995). Here we contribute to a precise understanding of the mechanisms responsible for the hydrogels?? swelling kinetics as well as dynamics by proposing for the first time a model approach that can resolve the inherent short-range correlation effects along the hydrogel?Csolution interface jointly with the long-range ionic transport fields. To that end, we investigate the swelling dynamics of hydrogels, which is a moving boundary problem, by a phase field model, which couples the Nernst?CPlanck equation for the concentration of mobile ions, Poisson equation for the electric potential, mechanical equation for the displacement, and an equation for the phase field variable. Simulation for two-dimensional case reveals that under the chemical stimulation, the hydrogel will swell or shrink if the concentration of mobile ions inside bath solution decreases or increases. This is in agreement with the experimental results qualitatively and validates our new model approach.     

Native biofilm cultured under controllable condition and used in mediated method for BOD measurement

In this article, we developed a native biofilm (NBF) bioreactor used for biochemical oxygen demand mediated method (BOD_Med). There were two innovations differed from previous BOD_Med assay. Firstly, the immobilization of microorganisms was adopted in BOD_Med. Secondly, the NBF was introduced for BOD measurement. The NBF bioreactor has been characterized by optical microscopy. A culture condition of NBF with 24 h, 35 °C and pH 7 was optimized. Furthermore, a measuring condition with 35 °C, pH 7 and 55 mM ferricyanide in 1 h incubation were optimized. Based on the optimized condition, the real wastewater samples from local sewage treatment plant had been measured. Performances of the NBFs proposed at different culture conditions were recorded for 110 d, and the results indicated that long-term storage stability was obtained. With the proposed method, an uncontaminated native microbial source solution can be obtained from a wastewater treatment plant. In this way, we can ensure that the microbial species of all in the NBF are same as that in the target to be measured.     

Arrayed waveguide grating multiplexer with high thermal stability on silicon

In this paper, certain important parameters are optimized for a polymer/Si arrayed waveguide grating (AWG) multiplexer by using grating theory. A 32-channel multiplexer is designed and fabricated using newly synthesized fluorinated poly (ether ether ketone) with a high thermal stability. The measured wavelength channel spacing is 0.796 nm, and center wavelength and 3-dB bandwidth are 1548 nm and 0.3 nm, respectively.     

Solid state reactions of nitrogenous heterocyclic compounds (I) —Solid state reactions of 3-methyl-1-phenyl-5-pyrazolone with carbonyl compounds

The solid state reaction of 3-methyl-1-phenyl-5-pyrazolon(eM PP) with aromatic aldehydes and ketones, benzil derivatives and imides, and the solid state Michael addition reaction of MPP with 4-arylidene-3-methyl-lphenyl-5-pyrazolone2 were investigated. Some new solid state reactions between the reactants were found, from which a series of new compounds were obtained. The structures of the products were identified by IR,¹H NMR, MS, elemental analyses and also by X-ray crystal analysis, and the reaction mechanism of MPP with aromatic aldehydes and ketones was proposed. Project supported by the National Natural Science Foundation of China.     

Evaluation of liquid junction potentials and determination of pH values of strong acids at moderate ionic strengths

A new experimental approach is proposed for the evaluation of liquid junction potentials and single ion activities. Neither of these quantities can be experimentally measured without assumption. Furthermore, they are concentration dependent but without clearly defined functional relationships. Thus, a given assumption may be satisfactory to obtain these quantities at a given concentration, but will fail at another concentration. It is the intent of this paper to establish a functional relationship between the ratio of activity coefficients and the ionic strength, through which the liquid junction potentials may be computed, as well as the pH values at moderate ionic strengths (<1.0 m). Experimental results are presented and uncertainties are discussed.     

基于DeltaE的驻波型热声发动机设计方法

在消化和吸收目前普遍接受的热声系统计算软件DeltaE(Design Environment for Low Amplitude Thermoacoustic Engines)的基础上,发展了驻波型热声发动机的结构设计方法;提出引入双参数评估法对发动机性能进行评估,以获取较高的热声转化效率。     

Optimal design and analysis of a high-speed, low-voltage polymer Mach-Zehnder interferometer electro-optic switch

Detailed model, analysis and design technique are presented for simulating a high-speed polymer Mach-Zehnder interferometer (MZI) electro-optic switch with push-pull dual driving electrodes and rib waveguides. The novel formulas of the time-domain response are derived. Thorough optimization and simulation for the designed device are performed. The total length of the basic function unit of the switch is about 5049 μm, the push-pull switching voltage is 2.23 V, the switching time is 18.1 ps, and the insertion loss and crosstalk are less than 2.64 and −30 dB, respectively, within the range of the operation wavelength from 1534 to 1566 nm. These results are in good agreement with those obtained from the beam propagation method (BPM).