Anodic Stripping Voltammetry Using a Vibrating Electrode

This work proposes a vibrating microwire electrode as working electrode in stripping voltammetry. The vibration was found to maintain a constant and thin (1–2 μm) diffusion layer during the deposition step. The electrode vibration eliminated the need for external stirring of the solution, thus facilitating in situ detection in the environment. The vibration was effected by fixing a low‐voltage (3 V), asymmetric, electrical rotor to the working electrode (a gold microwire of either 5 or 25 μm). The sensitivity of the vibrated electrode was ca. 22×greater than stationary. Measurements of copper (4 nM) by anodic stripping voltammetry using the vibrating electrode had a low standard deviation (1% for n=6) indicating that the diffusion layer had only minor variability. The agitation mechanism was unaffected by water moving at >2 m s^?1 and by water pressure equivalent to a depth of >40 m, indicating its suitability for in situ measurements. The vibrating probe was used for in situ detection of copper by anodic stripping voltammetry to a depth of 6 m. Using a 5 min deposition time, the limit of detection for labile copper was 38 pM.     

Viscosity measurements of hydrogen at high temperatures up to 573 K by a curved vibrating wire method

The viscosities of hydrogen were measured at temperatures of (296 to 573) K and at pressures up to 0.7 MPa by the vibrating wire method. In this study, a tungsten wire 50 μm in diameter and 24 mm in length is bent into semicircular form. The direction of the vibrating motion is fixed using the curved wire, and a more compact sample vessel can be used than in a traditional straight vibrating wire method requiring weight for the tension in the wire. Alternating voltages with different frequencies were supplied to the curved wire, which was set between samarium cobalt magnets. The generated induced voltages depending on the supplied frequencies were measured by a lock-in amplifier, and the resonant curve was obtained. The resonant frequency and half-width of the resonant curve were determined by curve fitting. The wire’s effective diameter and internal friction coefficient, which represents the damping from the wire material and the magnetic force, are very important parameters for evaluating the viscosities, and they were precisely calibrated by measuring helium and nitrogen as reference fluids. Finally, the viscosities of hydrogen were obtained with an uncertainty of 1.4% (k = 2).     

Effect of random longitudinal vibrations on the Poiseuille flow of a complex liquid

In this work, the rectilinear Poiseuille flow of a complex liquid flowing in a vibrating pipe is analyzed. The pipe wall performs oscillations of small amplitude that can be adequately represented by a weakly stochastic process, for which a quasi-static perturbation solution scheme is suggested. The flow is analyzed using the Bautista–Manero–Puig constitutive equation, consisting on the upper-convected Maxwell equation coupled to a kinetic equation to account for the breakdown and reformation of the fluid structure. A drastic enhancement of the volumetric flow is predicted in the region where the fluid experiences pronounced shear-thinning. Finally, flow enhancement is predicted using experimental data reported elsewhere for wormlike micellar solutions of cetyl trimethyl ammonium tosilate.     

Transient analytical solution for the motion of a vibrating cylinder in the Stokes regime using Laplace transforms

A new analytical solution for the motion of an elastic cylinder in a viscous fluid is derived using Laplace transforms. Unlike previously available solutions, full expressions for transient terms are given. The solution is compared with conventional treatments of this problem. It is expected to have particular value for applications related to viscosity measurement using vibrating-wire viscometers applied to higher viscosity fluids.     

Liquid density of HFE-7200 and HFE-7500 from T = (283 to 363) K at pressures up to 100 MPa

The liquid densities of HFE-7200 (1-ethoxy-1,1,2,2,3,3,4,4,4-nonafluorobutane, CAS Registry Number: 163702-05-4) and HFE-7500 (3-ethoxyperfluoro(2-methylhexane), CAS Registry Number: 297730-93-9) have been measured over the temperature range from (283 to 363) K and pressures up to 100 MPa by using a high pressure vibrating-tube densimeter. R134a has been used as a reference fluid to validate the densimeter. The uncertainty of each obtained datum was estimated, and the maximum expanded uncertainty with a level of confidence of 0.95 (k = 2) of density measurement for HFE-7200 and HFE-7500 were 0.04% and 0.03%, respectively. The measured liquid densities were correlated with the modified Tait equation and the maximum deviation is less than 0.03%. The isothermal compressibility and isobaric thermal expansivity were also calculated.     

Synthesis and magnetic characterization of Zn0.7Ni0.3Fe2O4 nanoparticles via microwave-assisted combustion route

We report on the synthesis of Zn_0.7Ni_0.3Fe₂O₄ nanoparticles via microwave assisted combustion route by using urea as fuel. XRD and FT-IR analyses confirm the composition and structure as spinel ferrite. The crystallite size estimated from XRD (16.4 nm) and the magnetic core size (15.04 nm) estimated from VSM agree well, while a slightly smaller magnetic diameter reflects a very thin magnetically dead layer on the surface of the nanoparticles. Morphological investigation of the products was done by TEM which revealed the existence of irregular shapes such spherical, spherodial and polygon. Magnetization measurements performed on Zn_0.7Ni_0.3Fe₂O₄ nanoparticles showed that saturation was not attained at even in the high magnetic field. The sample shows superparamagnetic behavior at around the room temperature and ferromagnetic behavior below the blocking temperature which is measured as 284 K.     

全固态激励小型TEA CO_2激光器的研制

基于国产非晶态合金磁芯,研制了采用可控硅开关、脉冲升压变压器、以及两级磁脉冲压缩网络的全固态激励电路系统,并且应用于放电体积为29 cm3,工作气压为100 kPa的电晕预电离小型TEA CO2激光器。讨论了提高系统能量传输效率和减小系统体积的设计方法,并且测量了系统的工作性能以及各部分的能量损失。实验结果表明:磁脉冲压缩网络的能量传输效率大于83%,全固态激励系统的总效率大于75%;连接激光器负载时,输出脉冲的电压峰值约为22 kV,电流上升时间约为100 ns;得到了脉冲能量109 mJ,宽度70ns的激光输出,激光器整体效率约为3.3%。在目前的封离体积与气体循环方式限制下,激光器最大重复频率约为100 Hz,而激励电路部分可以达到400 Hz的工作频率。     

Measurement of surface profile in vibrating environment with instantaneous phase shifting interferometry

In-process measurement has been the requirement of the precision industries, but due to vibrations while manufacturing, in-process measurement has been difficult to achieve. There is little work on in-process measurement using phase shifting interferometry, as phase shifting is extremely sensitive to vibrations. In this work, the advantage of the developed non-mechanical and instantaneous phase shifting interferometry is felt while measuring surface profile of large flat surfaces under vibrating conditions which can be extended for in-process measurement of surface profile. A near common path optical configuration is achieved and the effect of the environment is reduced. Moreover, the measurement of phase is instantaneous which increases the versatility of this technique for measuring vibrating objects. Profile measurements were carried out on a smooth mirror surface excited with vibrations of different frequencies and the technique was found to be immune to vibrations of up to 1000 Hz.     

On the nonlinear interpretation of a vibrating wire viscometer operated at large amplitude

A non-linear interpretation is proposed for the vibrating wire (VW) viscometer operated with the transient or ringdown method. This new interpretation is motivated by the necessity of having an acceptable signal to noise ratio (SNR) such that a measurement can be performed in 1 s. A large SNR is achieved by a large oscillation amplitude such that the requisite conditions for the linear interpretation are no longer met. We demonstrate the applicability of a new non-linear interpretation with wires of length 40 mm and 50 mm over a viscosity range from 0.3 to 159 mPa s where the maximum amplitude of motion is approximately two thirds of the radius.