An SVM approach with electromagnetic methods to assess metal plate thickness

Eddy current testing (ECT) is a non-destructive technique that can be used in the measurement of conductive material thickness. In this work ECT and a machine learning algorithm (support vector machine – SVM) are used to determine accurately the thickness of metallic plates. The study has been made with ECT measurements on real specimens. At a first stage, a few number of plates is considered and SVM is used for a multi-class classification of the conductive plate thicknesses within a finite number of categories. Several figures of merit were tested to investigate the features that lead to “good” separating hyperplanes. Then, based on a SVM regressor, a reliable estimation of the thickness of a large quantity of plates is tested.Eddy currents are induced by imposing a voltage step in an excitation coil (transient eddy currents – TEC), while a giant magnetoresistance (GMR) is the magnetic sensor that measures the transient magnetic field intensity in the sample vicinity. An experimental validation procedure, including machine training with linear and exponential kernels and classification errors, is presented with sets of samples with thicknesses up to 7.5 mm.     

Modulations in line shapes of magnetoconductance curves for diodes of pentacene:fullerene charge transfer complexes

This work investigates that the applied electric field modulates the line shapes of magnetoconductance (MC) responses in pentacene:fullerene diodes under illumination. We attribute the line shape of MC curves herein is correlated with the strength of the exchange interaction in pentacene:fullerene charge transfer (CT) complex states. Applying the reversed bias increases the built-in electric field (E_built-in) of the diodes to offset the exchange interaction of CT complex states and narrows the line shapes of MC responses. The saturation field of MC curves in the pentacene:fullerene bulk heterojunction device is 752 Oe when the device is biased at 0.4 V and decreases to 212 Oe at a reversed bias of −1.0 V. The line shape of MC curves for the diode made of pristine pentacene or fullerene as the active layer does not change with the applied bias voltage. Our results indicate the correlations of MC responses with the exchange interaction of CT complexes as modulated by the applied electric field.     

Theoretical investigation of voltage effect on magnetoresistance in an organic small molecule device

We theoretically study the voltage effect on organic magnetoresistance (OMAR) in a weak disordered small molecule device on the basis of the quantum dynamics. It is found that with the increase of the voltage, the OMAR effect is reduced. The results show a good agreement with the experimental data. In addition, the carrier density effect on OMAR has also been discussed.     

基于巨磁阻传感器的无损检测系统研究与设计

针对现代工业与安全检测中对非铁磁性工件的表面及近表面缺陷检测需要,基于涡流无损检测原理,采用灵敏度高、体积小、工作频率范围宽(0Hz到MHz)的GMR传感器,结合基于单片机STM32的直接数字频率合成(DDS)信号产生方法及锁相技术研制了一套涡流无损检测系统。实验结果表明该基于 GMR传感器的无损检测系统能够较好的检测出铝板试件表面及表面下2 mm处缺陷的存在,多道扫描结果可清晰判别出缺陷的位置和大小,该系统可以准确完成对导电材料表面及近表面的无损检测。     

A new application of giant reed waste material for ammonium removal

Excess nitrogen is one of the main causes of eutrophication in water bodies. In this study, the undesirable agricultural lignocellulosic material giant reed was used to remove ammonium ions from aqueous solutions. Batch experiments were conducted to investigate the effect of various parameters such as contact time, initial ammonium concentration, adsorbent dosage, pH, particle size, agitation rate and phosphate coexisting during the ammonium adsorption process. The ammonium sorption capacity of fibrous giant reed (FGR) at equilibrium was 12.49?mg?N/g with a maximum removal efficiency of 76% observed within 30?min at pH range of 6.5–9.5. Results revealed that the Freundlich isotherm model fitted better with the sorption process than the Langmuir model, and the adsorption process was well described by pseudo-second-order kinetic model. FT-IR analyses indicated that complexation and ion exchange could be the main mechanisms for the ammonium removal by FGR. Results revealed that FGR has a sorption capacity comparable to that of other natural sorbents with the advantage of greater availability with no cost.     

La0．67Sr0．33MnO3／SrFe12O19纳米复合体系的电性、磁性及磁电阻效应

La0．67Sr0．33MnO3／SrFe12O19复合体系的磁滞回线形状特征以及体系的剩磁增强，表明La0．67Sr0．33MnO3与SrFe12O19两相之间存在铁磁交换耦合作用．随SrFe12O19复合量的增加，体系的电阻率增大、低场磁电阻减小，并且出现了金属一半导体的转变，该转变温度低于La0．67Sr0．33MnO3的居里温度．     

VCR412在OTR轮胎胎侧胶中的应用

试验研究高顺式聚丁二烯复合橡胶VCR412在全钢巨型工程机械子午线轮胎胎侧胶中的应用。结果表明：配方中在相同的炭黑用量情况下与镍系顺丁橡胶相比高顺式聚丁二烯复合橡胶定伸更高,且具有较好综合物理性能及较低的压缩生热;在同等300%定伸VCR412配方炭黑减量相比镍系顺丁橡胶炭黑量不变情况下,综合物理性能更好且具有优异的抗屈挠裂口增长性能及更低压缩生热。     

非正分钙钛矿化合物(La0.8Sr0.2)0.7MnO3的磁电阻效应

采用固相反应法制备了名义成分为(La0.8Sr0.2)0.7MnO3的多晶钙钛矿锰氧化物,通过电阻率、磁化曲线和居里温度的测量,对其磁性与磁电阻效应进行了研究。样品近似呈La0.8Sr0.2MnO3/Mn3O4两相复合结构。其电阻率随温度的变化曲线具有双峰特征,特别是其磁电阻比在一个较宽的温区内(220~320K)基本上保持不变,相对正分样品La0.8Sr0.2MnO3而言,非正分样品磁电阻比的温度稳定性大大提高,这一特性也表明了其作为磁电阻传感器材料的可行性。