Hot-wire amperometric monitoring of flowing streams

This paper describes the design of a hot-wire electrochemical flow detector, and the advantages accrued from the effects of locally increased temperature, mainly thermally induced convection, upon the amperometric monitoring of flowing streams. A new hydrodynamic modulation voltammetric approach is presented, in which the solution flow rate remains constant while the temperature of the working electrode is modulated. Factors influencing the response, including the flow rate, temperature pulse, or applied potential, have been investigated. The hot-wire operation results also in a significant enhancement of the flow injection amperometric response. The minimal flow rate dependence observed with the heated electrode should benefit the on-line monitoring of streams with fluctuated natural convection, as well as various in-situ remote sensing applications.     

金属丝力学性能测试的设计性实验

将金属丝力学性能测试实验引入设计性物理实验,自组手工加载机构,再配以力传感器和位移传感器,构成手工测量应力和应变及其关系的仪器.利用该试验装置对金属丝进行了测试,得到了应力-应变曲线和屈服强度、强度极限、延伸率等力学指标.     

谐振频率可调的环状开口谐振器结构及其效应

理论和实验研究表明，开口谐振环(SRRs)中可以激励磁谐振从而实现负磁导率.通过在SRRs结构中引入与其开口边平行的金属短杆设计并制备了新的磁谐振单元，采用波导法系统研究了短杆对SRRs和左手材料的微波透射特性以及左手效应的影响.实验和数值模拟表明：金属短杆和SRRs开口边形成附加电容，导致SRRs开口电容增大从而引起谐振频率降低.随短杆长度l和短杆与SRRs间距d的增大，SRRs谐振频率也随之减小和增加.短杆的加入不影响SRRs的负磁导率特性，改变短杆与SRRs间距d< 关键词： 开口谐振环 金属短杆 调控 左手材料     

螺旋型爆磁压缩脉冲功率源模拟计算

 以间接馈电的两级螺旋型爆磁压缩发生器为初始功率源，基于等效电路模型，编制了一个螺旋型爆磁压缩脉冲功率源计算程序BCYSSYS。利用该程序对04型爆磁压缩发生器驱动电感负载进行了计算，并将计算结果与实验结果进行比较，两者基本吻合；对该发生器驱动电容负载进行了计算。同时利用铜金属丝电爆炸过程中电阻率与比作用量的关系数据表，对爆磁压缩发生器驱动含电爆炸丝断路开关的电感储能脉冲功率调节系统进行了数值计算。     

Optical and continuous-wave characteristics of V-grooved quantum well wire lasers confined by a p-n junction array

Role of the side-wall quantum wells in a V-grooved quantum well wire (QWW) is briefly reviewed by temperature-dependent photoluminescence, and then continuous-wave (cw) characteristics of QWW lasers confined by a p-n junction array are reported. In terms of the effectiveness in current confinement, very high power operation (over 11 mW) and a single longitudinal mode operation up to 8mW are achieved. Room-temperature threshold currents are measured to be 32.5 mA (pulsed) and 47.8 mA (cw) for a 200 m long uncoated cavity. The current- and temperature-tuning rates of the oscillation wavelength are as low as 0.038 nm/mA and 0.17 nm/°C, respectively.     

探究红热铜丝伸入稀硫酸时产生的“意外”现象

对红热铜丝伸入稀硫酸时产生的“意外”现象进行了实验探究,研究后得出的结论为:稀硫酸局部受高热使硫酸分子逸出形成白雾。铜在高温加热时产生氧化铜和氧化亚铜,氧化铜迅速溶于稀硫酸生成硫酸铜,由于硫酸铜的量少,所得的混浊液在短时内不易观察到蓝色;氧化亚铜则脱落在溶液中,但由于硫酸分子逸出、氧化铜消耗硫酸等因素导致硫酸浓度下降,从而使氧化亚铜的溶解速率减慢,所以砖红色的混浊物为氧化亚铜且能暂时存在。     

温度补偿法解决二元气液平衡系统相图绘制实验中的分馏效应

通过改装二元气液平衡系统相图绘制实验的装置,同时测定了环己烷-乙醇气液系统建立平衡时的沸点和露点温度,绘制并对比未保温、保温和温度补偿条件下的环己烷-乙醇气液相图。研究发现,由于分馏效应的存在,未保温和简易保温情况下,测得的溶液的沸点与露点两者温度均存在较大的差异,利用沸点温度绘制的气相线存在严重失真;对系统进行了温度补偿后根据沸点和露点温度绘制的两条气相线能吻合较好,即气相分馏效应得到了解决。     

Different effect of evanescent modes on acoustic phonon transport in different types of a three-dimensional quantum wire

By the use of the scattering matrix method, we investigate the effect of evanescent modes on acoustic phonon transport and thermal conductance in both convex and concave type three-dimensional quantum wire. Our results show that the evanescent modes can enhance the transmission coefficient and the thermal conductance in the concave type three-dimensional quantum wire. However, for the convex type three-dimensional quantum wire, the evanescent modes can play adverse effect on the phonon transport. When the length of scattering region is large enough, for all types of three-dimensional quantum wire, the influence of evanescent modes on phonon transport becomes very weak.     

An effective screened Coulomb interaction in a quasi-one-dimensional system

In this paper, we derive an analytical expression for the screened Coulomb potential between charge carriers in quasi-one-dimensional (Q1D) semiconductor structures. As an application, this potential has been used to investigate the screening effect on the binding energy of a neutral donor (D⁰$D^0$) in quantum wires (QWRs). It is found that the screening effect decreases the neutral donor binding energy, and the screening effects are more obvious in wide QWRs than that in narrow ones. Dependence of screening length on temperature and carrier concentration has also been discussed.     

Anisotropic optical absorption in quantum well wires induced by high-frequency laser fields

The subband structure and optical properties of a cylindrical quantum well wire under intense non-resonant laser field are investigated by taking into account the correct dressing effect for the confinement potential. The energy levels and wave functions are calculated within the effective mass- approximation using a finite element method. It is found that the absorption coefficient and the saturation intensity are strongly affected by the laser amplitude and frequency as well as by the incident light polarization. As a key result, a large anisotropy in the linear and nonlinear optical absorptions for very intense laser field is predicted. These effects can be useful for the design of polarization sensitive devices.