基于磁阻原理非接触式位移测量的非线性方法

针对低功耗和非接触式位移测量的应用需求，利用磁阻传感器，本文在传统的线性测量方法的基础上，提出了一种非线性的测量方法。设计了一个测量系统，实测结果表明该方法测量精度高、测量范围广、简单易用，也节省了成本。     

五相步进电机在平流泵中的应用

较详细介绍了五相步进电机在平流泵中的应用,给出了一种基于斩波恒流方式的步进电机驱动电路和驱动方案,详细说明了其原理;对平流泵应用过程中的高频出力、低频振荡及平流泵的控制精度等给出了较详细的解决方法.     

Preparation of LaNiO3/SrTiO3/LaNiO3 capacitor structure through sol–gel process

In this paper, SrTiO₃/LaNiO₃ (STO/LNO) bilayer films were prepared on lanthanum aluminate (LAO) substrates by use of the sol–gel technique. An array of LNO electrodes with diameters of 200 μm was prepared on the surface of STO/LNO bilayer films. Therefore, LaNiO₃/SrTiO₃/LaNiO₃ (LNO/STO/LNO), a capacitor structure with symmetrical top and bottom electrodes, was obtained. The XRD analysis showed that the obtained capacitor structure has a biaxial texture. The dielectric test suggested that the relative dielectric constant of the LNO/STO/LNO structure is symmetric, has a high tunability, and has a low dielectric dissipation factor (tan δ) in response to varying electric field bias. As the temperature decreased, the relative dielectric constant of the STO film increased, the tunability increased, and the tan δ decreased. At test conditions of 80 K and 100 kH, the tunability and the figure of merit (FOM) reached 56% and 107, respectively.     

High‐performance electromagnetic interference shielding material based on an effective mixing protocol

A facile and economic method is developed for the fabrication of new lightweight materials with high electromagnetic interference (EMI) shielding performance, good mechanical properties and low electrical percolation threshold through melt mixing. Electrical properties, DC conductivity, EMI shielding performance and mechanical properties of poly(trimethylene terephthalate) (PTT)/multiwalled carbon nanotube (MWCNT) nanocomposites with varying filler loading of MWCNTs were investigated. High‐resolution transmission electron microscopy was used to determine the distribution of MWCNTs in the PTT matrix. The newly developed nanocomposites show excellent dielectric and EMI shielding properties. Theoretical electrical percolation threshold was achieved at 0.21 wt% loading of MWCNTs, due to the high aspect ratio and the three‐dimensional network formation of MWCNTs. Experimental DC conductivity values were compared with those of theoretical models such as the Voet, Bueche and Scarisbrick models, which showed good agreement. The PTT/3% MWCNT composite showed an EMI shielding value of ～38 dB (99.99% attenuation) with a sample thickness of 2 mm. Power balance was used to determine the actual contribution of reflection, absorption and transmission loss to the total EMI shielding value. The nanocomposites showed good tensile and impact properties and the composite with 2% MWCNTs exhibited an improvement in tensile strength of as much as 96%. © 2018 Society of Chemical Industry     

Investigation of non-isothermal crystallization,dynamic mechanical and dielectric properties of poly(ether-ketone) matrix composites

ABSTRACT

Poly(ether-ketone)/hexagonal boron nitride (h-BN) composites reinforced with micrometer-sized h-BN particles were investigated. The composites exhibited glass transition temperature (T_g) and thermal stability over 160°C and 560°C, respectively. The melting point and peak crystallization temperatures of the composites decreased up to 17°C and 12°C, respectively. The linear CTE of the composites decreased both below and above the T_g. The storage modulus increased with increasing h-BN content at all temperatures (50–250°C). The composites possessed excellent dielectric properties with insignificant dispersion with increasing frequency. Thus, resultant composites are promising candidates for the printed circuit boards/electronic substrates.     

基于故障统一模型的故障检测策略

随着集成电路制造工艺持续向纳米尺度的推进,数字电路受老化、工艺误差、软错误等故障所造成的时序偏差越发突出,严重威胁了电路的“时序安全”。文中通过分析故障影响信号稳定性侵犯模型,提出了一种新的故障检测模型。该模型扩展了现有的故障检测能力,通过使用C单元作为稳定性检测器输出单元,提高了其对高速的适应性。仿真结果显示,与已有结果相比其具有明显的速度优势和较小的硬件开销。     

Accurate rotor flux orientation technique for indirect rotor flux oriented control of induction motor drives

Abstract

In this paper, a novel detuning index is first proposed for indicating the proper timing required to correct the rotor time constant of indirect rotor flux oriented controlled single‐cage induction motor drives. This index can faithfully reflect the influence of rotor resistance changes as well as rotor flux changes. It also reduces greatly the number of rotor time constant estimations in practical applications. The theoretical basis of the index and the physical meaning are described in the paper in detail. Based on the proposed index, an on‐line rotor time constant estimator is also proposed to make corrections. Only existing available quantities of the closed loop controller are used for calculating the estimated rotor time constant accurately. Both simulation and experimental results verify the effectiveness of the proposed rotor flux orientation technique. It is seen that the proposed rotor flux orientation technique is suitable for practical applications.     

Determination of bone mineral volume fraction using impedance analysis and Bruggeman model

Measurements by impedance spectroscopy and Bruggeman effective medium approximation model were employed in order to determine the mineral volume fraction of dry bone. This approach assumes that two or more phases are present into the composite: the matrix (environment) and the other ones are inclusion phases. A fragment of femur diaphysis dense bone from a young pig was investigated in its dehydrated state. Measuring the dielectric properties of bone and its main components (hydroxyapatite and collagen) and using the Bruggeman approach, the mineral volume filling factor was determined. The computed volume fraction of the mineral volume fraction was confirmed by a histogram test analysis based on the SEM microstructures. In spite of its simplicity, the method provides a good approximation for the bone mineral volume fraction. The method which uses impedance spectroscopy and EMA modeling can be further developed by considering the conductive components of the bone tissue as a non-invasive in situ impedance technique for bone composition evaluation and monitoring.     

Effect of CuO on the sintering and cryogenic microwave characteristics of (Zr0.8Sn0.2)TiO4 ceramics

The effect of CuO on the sintering temperature, microstructure and microwave dielectric properties of (Zr_0.8Sn_0.2)TiO₄ (ZST) modified with 1 wt% of ZnO has been investigated. Microwave dielectric properties of ZST ceramics are measured from cryogenic to room temperatures (15–290 K). Crystallite sizes of sintered ZST ceramics as derived from XRD are in the 30–50 nm range. The addition of CuO effectively reduced the sintering temperature to 1300 1C, possibly due to liquid-phase effects. Addition of CuO did not cause any secondary phases up to 1.5 wt% of CuO. The dielectric constant (ε_r) and temperature coefficient of resonant frequency (ε_f) of ZST ceramics do not significantly vary with temperature, whereas the unloaded quality factor (Q_u) changes noticeably. It is found that the Q_u factor of the sample without CuO decreased with increase in temperature, whereas the samples with addition of CuO up to 1.0 wt% showed less dependence on temperature. The Q_u factor of CuO-free ZST is 15,000 and that of ZST with 0.5 wt% of CuO is 11,800 at 15 K. The Q_u factor while measured at room temperature ranged between 2900 and 7000. Efforts were made to understand whether the increase in Q_u factor at both cryogenic and room temperatures is the result of intrinsic or extrinsic factors.     

Terahertz characterisation of UV offset lithographically printed electronic-ink

Inkjet-printed electronics are showing promising potential in practical applications, but methods for real-time, non-contact monitoring of printing quality are lacking. This work explores Terahertz (THz) sensing as an approach for such monitoring. It is demonstrated that alterations in the localised dielectric characteristics of inkjet-printed electronics can be qualitatively distinguished using quasi-optically-based, sub-THz reflection spectroscopy. Decreased reflection coefficients caused by the sintering process are observed and quantified. Using THz near-field scanning imaging, it is shown that sintering produces a more uniform spatial distribution of permittivity in the printed carbon patterns. Images generated using THz-TDS based imaging are presented, demonstrating the combination of high resolution imaging with quantification of complex permittivities. This work, for the first time, demonstrates the feasibility of quality control in printed electronic-ink with THz sensing, and is of practical significance to the development of in-situ and non-contact commercial-quality characterisation methods for inkjet-printed electronics.