An anomalous magnetoelastic effect in nickel

A new magnetoelastic effect in nickel has been found that led us to modify some current theories about magnetization processes in weak fields. A longitudinal compression in Ni decreases its magnetization instead of increasing it. This behavior can be explained by a weak field spin rotation model, as opposed to the usual domain-wall motion theory. The important role played by residual stresses has also been taken into account, and a method for evaluating them is suggested.     

Instrument transducers based on magnetoelastic interaction in amorphous ferromagnets

Translated from Izmeritel'naya Tekhnika, No. 1, pp. 35–37, January, 1991.     

Calculation of piezoelectric transducers based on MIM structures

The conditions for optimal excitation of piezoceramic transducers are determined from the equality of the bias and conduction currents in a metal-polar insulator-metal (MIM) structure under an external electric field. Charge-carrier injection from the cathode is shown to affect the electric field strength distribution along the thickness of the insulator and the integral characteristic, i.e., the capacitance of thin-layer structures. Numerical computation indicates that in the case of piezoceramic plates 0.4–0.5 mm thick electron emission from the cathode is possible at voltages of 5–8 V.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 50–54, February, 1995.     

Investigation of pressure transducers based on w-fiber waveguides

Translated from Izmeritel'naya Tekhnika, No. 5, pp. 17–19, May, 1991.     

Elimination of the effect of winding resistance in transformer-coupled ac bridges

Determination of the additive component of measurement error at the higher ranges of ac bridges is discussed. It is shown that this component contributes significantly to the total instrument error can be found and eliminated from the result of measurement without a reference measure. Translated from Izmeritel'naya Tekhnika, No. 7, pp. 44–47, July, 1996.     

Broadband tonpilz underwater acoustic transducers based onmultimode optimization

Head flapping has often been considered to be deleterious for obtaining a tonpilz transducer with broadband, high power performance. In the present work, broadband, high power tonpilz transducers have been designed using the finite element (FE) method. Optimized vibrational modes including the flapping mode of the head are effectively used to achieve the broadband performance. The behavior of the transducer in its longitudinal piston mode and in its flapping mode is analysed for in-air and in-water situations. For the 37.8% bandwidth of the center frequency from 28.5 to 41.8 kHz, the amplitude variation of the transmitting voltage response (TVR) does not exceed ±2 dB and a maximum TVR of 146.8 dB (ref. 1 μPa/volt at 1 meter) is obtained. Reasonable agreement between the experimental results and the numerical results is achieved. A maximum sound pressure level of 214.8 dB can be expected. Further numerical calculation indicates that there is potential for increasing the bandwidth by varying other parameters in the design     

Heat-flux transducers based on artificially anisotropic thermoelectric materials

The use of artificially anisotropic thermoelectric material as a heat-flux transducer, the method of selecting its components, and optimization of the parameters are discussed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 35, No. 2, pp. 229–233, August, 1978.     

A scenario to the anomalous Hall effect in the mixed state of superconductors

We argue that the motion of vacancies in a pinned vortex lattice may dominate the contribution to the Hall effect in an appropriate parameter regime for a superconductor. Based on this consideration a model is constructed to explain the anomalous Hall effect without any modification of the basic vortex dynamic equation. Quantitative predictions are obtained. Present model can be directly tested by an observation of the vacancy motion.     

基于压电传感器的树脂基复合材料固化过程监测

复合材料固化成型工艺是影响树脂基复合材料结构性能的关键之一,因此需要针对其固化过程进行有效在线监测。本文基于压电传感器提出一种超声导波技术和机电阻抗技术相结合的树脂基复合材料固化过程监测方法,研究了超声导波能量与固化时间的关系及机电阻抗共振峰随固化时间的变化规律。研究表明,固化过程中树脂基复合材料结构的超声导波信号幅值和机电阻抗信号共振峰频率均出现先减小后增大并逐渐平稳的趋势,可以体现树脂基复合材料固化过程中的一系列变化。以监测单向碳纤维(T300)/热固性环氧树脂预浸料固化为例,验证压电传感器对复合材料固化的监测方法。T300/热固性环氧树脂复合材料在真空袋压、固化温度为120℃条件下,20 min为凝胶时间点,65 min为固化完成时间点。本研究基于压电固化过程在线监测方法为树脂基复合材料成型工艺的设计和优化提供了基础数据和技术支撑。      

The effect of temperature and humidity on electrospinning

Electrospinning is a process that generates nanofibres. Temperature and humidity affect this process. In this article the influence of humidity and temperature on the formation and the properties of nanofibres are studied using cellulose acetate (CA) and poly(vinylpyrrolidone) (PVP) as target materials. The experiments indicate that two major parameters are dependent of temperature and have their influence on the average fibre diameter. A first parameter is the solvent evaporation rate that increases with increasing temperature. The second parameter is the viscosity of the polymer solution that decreases with increasing temperature. The trend in variation of the average nanofibre diameter as a function of humidity is different for CA and PVP, which can be explained by variations in chemical and molecular interaction and its influence on the solvent evaporation rate. As the humidity increases, the average fibre diameter of the CA nanofibres increases, whilst for PVP the average diameter decreases. The average diameter of nanofibres made by electrospinning change significantly through variation of temperature and humidity.