Tunable acoustic metamaterial with negative modulus

A tunable negative modulus metamaterial is presented, and it is achieved by adjusting the medium density and an effective volume of a split hollow sphere (SHS). This work comprises experimental and numerical studies. The effects of water/air component and the steel ball on the transmission properties were investigated in the impedance tube system. The experimental results show that the transmission dip has a significant blue-shift with increasing water content, whereas the steel ball has a relatively small influence on the resonant frequency. The simulated results by the finite-element method (FEM) are in agreement with the experimental results. Based on medium parameters among the SHS, acoustic metamaterial (AM) with negative modulus can easily be designed in the expected frequency domain, and it provides a convenient route to tune AMs.     

二维流场、热结构松耦合模拟研究

本文针对轴对称型飞行器前缘部位,采用松耦合方法,开展了二维高超声速流固界面的热耦合计算。满足非稳态N-S方程的外部流场和内部非稳态热传导均采用商用软件FLUENT进行计算。通过对相同时刻,不同松耦合推进时间步长引起的壁面热流密度、壁面温度、表面传热系数的差异对比,得出了松耦合推进时间对以上参数的影响规律,这对有效实施松耦合方法进行高超声速飞行器模拟具有积极意义。     

基于小波包能量谱爆炸参量对爆破振动信号能量分布的影响

基于现场实测爆破振动数据,根据爆破振动信号具有短时非平稳的特点,采用小波包分析技术对不同爆炸参量(爆心距、最大段药量和微差雷管段数)下产生的爆破振动信号进行小波包能量谱分析,获得了爆破振动信号不同频带的能量分布,研究了不同爆炸参量下的爆破振动信号能量分布特征,从爆破振动信号能量角度探讨了不同爆炸参量下爆破地震波的衰减规律,为研究爆破地震效应提供了一种新的分析技术。     

超声雾化进样技术在ICP-AES中的应用研究

研究了超声雾化进样系统在电感耦合等离子体原子发射光谱(ICP-AES)中的应用,考察了测定的影响因素。结果表明,超声雾化进样条件下,影响谱线强度和测量精密度的因素较多。其中影响较大的因素主要有:载气流量、进样速度、进样时间、冲洗条件及溶液的介质条件。载气的最大允许量远小于气动雾化中的常规用量。同时,进样时间对测量精密度的影响较大,而积分时间对测定的影响较小。此外,冲洗条件对记忆时间的影响较大, 辅助冲洗水流的方式有助于减小记忆效应的影响。实验表明:超声雾化进样条件下,As,Pb,Se,Bi,Ge,Mo,Cd,Cu等八种元素的检出限低于气动雾化进样的检出限10～25倍,超声雾化进样技术在ICP-AES中的应用有助于改善ICP-AES测定的灵敏度。     

Dispersion characteristics of two-dimensional unmagnetized dielectric plasma photonic crystal

This paper studies dispersion characteristics of the transverse magnetic (TM) mode for two-dimensional unmagnetized dielectric plasma photonic crystal by a modified plane wave method. First, the cutoff behaviour is made clear by using the Maxwell--Garnett effective medium theory, and the influences of dielectric filling factor and dielectric constant on effective plasma frequency are analysed. Moreover, the occurence of large gaps in dielectric plasma photonic crystal is demonstrated by comparing the skin depth with the lattice constant, and the influence of plasma frequency on the first three gaps is also studied. Finally, by using the particle-in-cell simulation method, a transmission curve in the \Gamma -X direction is obtained in dielectric plasma photonic crystal, which is in accordance with the dispersion curves calculated by the modified plane wave method, and the large gap between the transmission points of 27~GHz and 47~GHz is explained by comparing the electric field patterns in particle-in-cell simulation.     

Dissipation-Managed Bright Soliton in a 1D Bose-Einstein Condensate in an Optical-Lattice Potential

We study the formation of a dynamically-stabilized dissipation-managed bright soliton in a quasi-one-dimensional Bose-Einstein condensate by including an imaginary three-body recombination loss term and an imaginary linear feeding one in the Gross-Pitaevskii equation, trapped in a shallow optical-latticepotential. Based on the direct approach of perturbation theory for the nonlinear Schrödinger equation, we demonstrate that the height (as well as width) of bright soliton may have little change through selecting experimental parameters.     

稀土在烤烟植株中的分布及其对烟叶化学成份影响的研究

作为一种生理活性物质,稀土施用在烟草上平均增产11％,上中等烟比例提高7．53％左右,稀土应用于烤烟大部分限于田间试验,缺深入的机理研究^[2-4]。本试验用低浓度混合硝酸稀土喷施烤烟叶面,研究了稀土在烤烟植株中的含量,分布及土壤中可溶态稀土的变化情况及稀土对烟叶化学成份的影响,旨在为烤烟施用稀土提供科学依据。     

酶促合成油酸香茅醇酯的超临界连续反应-分离过程

将固定床动态酶促反应过程和超临界二氧化碳萃取分离过程相耦合,设计并建立了一套超临界相反应分离一体化的实验装置。在该装置上初步考察了反应压力和温度对脂肪酶催化油酸甲酯和外消旋香茅醇酯交换反应的影响。结果表明,我们所建立的反应装置能有效地实现反应分离一体化过程;当体系压力接近二氧化碳的临界压力时反应速率最高;9MPa压力下反应温度为328K时反应转化率最高,而在14MPa压力下反应转化率在308K～328K之间随着温度的升高而增大。     

电沉积方式对Ni-nanoAl2O3复合镀层组织结构和耐蚀性能的影响

双脉冲;Ni-nanoAl2O3复合镀层;耐蚀性     

Effect on Intensity Correlation Time by Input Signal in a Single-Mode Laser with Bias Signal Modulation

The effect on intensity correlation time T by input signal is studied for gain-noise model of a single-mode laser driven by colored pump noise and colored quantum noise with colored cross-correlation with a bias signal modulation in this paper. By using the linear approximation method, we detect that there exists maximum （i.e., resonance） in the curve of the intensity correlation time T upon bias current io when the noise correlation coefficient λ is positive; and there exists minimum （i.e., suppression） in the T-io curve when λ is negative. And whenλ is zero, T increases monotonously with increasing io. Furthermore, the curve of T upon the signal frequency Ω is also studied. Our study shows that no matter what the value of λ is, there exists minimum （i.e., suppression） in the T-Ω curve.