DC SQUID Spectrometers for NMR

We report experiments in which we have used DC SQUIDs in pulsed NMR spectrometers to observe directly the free precession of nuclear spins. A broadband spectrometer, which operates in flux-locked loop mode with a bandwidth of 3.4 MHz using a SQUID with additional positive feedback and an untuned superconducting input circuit, has been used to observe NMR signals from platinum powder at frequencies of 38, 65, 85, 240 and 513 kHz. The performance is compared with a second system in which a DC SQUID is operated open loop as a small signal rf amplifier with a series tank input circuit tuned at 1 MHz.     

基于SQUID的直流电阻电桥指零仪设计

设计了一款基于超导量子干涉仪(SQUID)的直流电阻电桥指零仪电路,该电路可用作高精度电阻电桥中低值电阻(0.1~100Ω)测量的指零仪电路。通过自制SQUID外围电路并优化电路其输入耦合线圈的互感值,实现微弱电桥不平衡电流的精密测量。与传统电阻电桥基于测量不平衡电压的纳伏计指零仪相比,其检测灵敏度在中低值电阻测量范围有数量级的提升。设计的作为指零仪的SQUID磁通锁定环1/f转折频率在2Hz左右,磁通白噪声水平在3.5μΦ₀/左右,并且输入线圈与SQUID互感系数高达10nH,其等效的电流白噪声密度0.7pA/。将其用作电阻电桥指零仪测量100Ω标准电阻(工作电流为10mA)的分辨率可达到10^-11量级。     

基于PSoC的汽车前照灯智能控制系统研究

阐述了智能控制系统能够在不同路面状况下,对前照灯的照射角和亮度实施全自动实时调整,更好的实现汽车前照灯的智能化控制。由于PSoC（Programmable Systemon Chip）具有集成度高,低功耗,本文设计了一套基于PSoC的汽车前照灯智能控制系统。     

多通道微注灌装控制系统设计

目的研究一种卡式多通道微注灌装机系统,实现从液体及粉末的微量灌装到卡式对象的自动封装。方法设计系统机械结构,包括自动送卡环节、微注灌液环节、微量灌粉环节、封装环节,同时设备基于可编程控制器、人机界面监控,采用闭环控制并结合接近开关、行程开关实现对整个系统的精确控制。结果该设备能够完成卡式对象的微量灌装及自动封膜。结论该系统自动化程度高,整个生产过程稳定,产品规格性能优异,能够解决微量灌注、高效封膜的难题。     

Broadband DC SQUID NMR Spectrometry on Bulk Metals

We report on experiments in which we have used a DC SQUID with additional positive feedback (APF) in a broadband pulsed NMR spectrometer, of bandwidth 3.4 MHz, to observe directly the free precession of nuclear spins in bulk metallic samples. The sample is located inside a superconducting receiver coil, which forms a flux transformer with the input coil of the SQUID. The broadband response of the flux transformer, combined with the relatively large bandwidth of the APF SQUID when operated in flux-locked-loop mode, results in a short recovery time. This enables the study of solid-state samples with a short spin-spin relaxation time at frequencies below 1MHz, appropriate at millikelvin temperatures. A further advantage of this scheme is that the NMR frequency can be varied without changes in the detection electronics being necessary. The sensitivity of the DC SQUID detection system, compared with conventional NMR, allows the study of small single crystal samples. The decay of eddy currents following the transmitter pulse is governed by sample size, geometry and resistivity. Typical decay times of less than 10 us are expected on 0.5 mm diameter cylindrical samples. We discuss progress on experiments with aluminium wires at a temperature of 20 mK.     

Improving the Sensitivity of Superconductor-Based DC Magnetometer

In this study we report on some critical factors affecting the sensitivity of a magnetic field sensor whose working principle is based on a linear DC field dependence of the second harmonic of the AC response in polycrystalline type-II superconductors. DC-fields down to 2?nT in magnitude could be detected by finding optimal conditions. The optimal sensor design was determined by studying superconductor cores having different geometries and coil configurations. The optimal AC-field frequency, which is required for excitation of the specimen, was found to be 50?kHz. The second harmonic signal changes quite linearly with the DC-field up to 0.1?Oe.     

智能化医用X射线机质控软件的研究

为提高医用X射线机质量控制的工作效率和准确度,在研究X射线辐射源的基础上,参照WS 76-2017和JJG 744-2004标准,对医用X射线设备智能化检测进行了系统构建,并应用MATLAB实现了智能质量控制软件.对智能化系统的设计、功能和实现方法进行了介绍.软件经验证具备一定的可行性,可以为医用X射线设备的智能化管理和远程质量控制及全自动检测提供借鉴.     

多管微型姿态控制发动机的点火控制系统

为了对多管微型姿态控制发动机在旋转状态的工作状况和动力特性进行测试,需要设计相应的点火控制系统对姿态控制发动机点火的数量和方位角进行控制.控制系统由控制程序和控制电路两部分组成.控制程序采用C++语言编写,通过RS-232通讯接口向控制电路发送控制指令;控制电路在MAX-plus Ⅱ软件平台上采用CPLD方式设计,由接口电路模块、控制电路模块、延时电路模块和译码电路模块四个模块组成,通过对控制指令解码并结合相位信号控制点火发动机的数量和点火方位.     

Integrated niobium DC SQUID gradiometers for non-destructive evaluation and biomagnetism

We describe the design and fabrication of thin-film Nb gradiometers with integrated DC SQUIDs for use in non-destructive evaluation (NDE) and biomagnetism. Issues of sensitivity, imbalance and field response are considered. Results are presented from eddy-current NDE in an unshielded environment of aluminium plates with sub-surface flaws, and from biomagnetic measurements of spinal and peripheral nerve evoked fields.     

智能过流保护器测试仪温度控制系统研究

文章从系统结构、硬件、软件等方面对智能过流保护测试仪温度控制系统设计进行阐述,并对各部分功能进行了分析。基于单片机的温控系统具有节能环保、结构简单、操作方便、显示直观及精度高等优点,为进一步提高过流保护测试仪器的测试信号精度提供了科学的参考和依据。     

Effects on DC SQUID characteristics of damping of input coil resonances

The possibility of improving dc SQUID performance by damping the input circuit resonances caused by parasitic capacitances is studied experimentally. A high-quality dc SQUID was coupled to a first-order axial gradiometer built for neuromagnetic research, and a resistor-capacitor shunt was connected in parallel with the input coil of the SQUID. Ten differentRC shunts were studied with the SQUID operating in a flux-locked loop, carefully shielded against external disturbances. It was found that increasing the shunt resistance resulted in smoother flux-voltage characteristics and smaller noise. At best, the minimum obtainable equivalent flux noise level was one-fourth that for the unshunted SQUID. The noise level is a function of the shunt resistanceR _s only, except for shunt capacitance values bringing the low-frequency resonance of the input coil close to the flux modulation frequency. At a constant bias current level, where the amplitude of the flux-voltage characteristics is at maximum, the equivalent flux noise varies asR _s ^/–0.7 . The results agree reasonably well with recently published predictions based on numerical simulations where the whole input circuit with parasitic capacitances was taken into account.     

SQUID Amplifier System for Vibrating Wire Resonators

We describe a simple coupling scheme of superconducting vibrating wire resonators to a SQUID amplifier for achieving supreme signal to noise characteristics. Our construction resulted in a gain factor near 10 ⁸ ₀ /V at 1 kHz with an amplifier noise level of about 20 ₀ / . Extremely small movements of the wires in very small magnetic fields can thus be detected.     

高龄用户智能产品多通道交互映射路径研究

目的 在老龄化与智能化的融合发展趋势下,通过探索多通道交互映射模式,提升高龄用户与智能产品交互过程的自然性、适配性和人性化。方法 以高龄用户智能产品人机交互系统为中心,从机能水平、行为习惯、语义表达、活动范围四个部分构建高龄用户特征模型,从通道、产品、交互不同属性层面构建智能产品多通道交互特征模型,并进一步研究两者间的映射关系。基于直觉模式-感官层、自然方式-行为层、逻辑关系-语义层、数字形式-空间层四种映射模式,提出以高龄用户为中心的智能产品多通道交互映射路径。结论 从“人-产品-环境”的系统视角,构建了高龄用户智能产品多通道交互映射关系模型,为高龄用户多通道交互设计研究提供思路借鉴,为智能产品适老化设计提供理论指导。     

智能控制四元结构的研究

在智能控制二元和三元结构的基础上，结合相关学科特点与关系，提出了智能控制的四元交集结构理论，认为智能控制是自动控制、人工智能、信息论和运筹学的交集。给出了把信息论作为智能控制结构一个子集的理由，并提出构成四元的交换关系。     

基于ARM7的表贴元件包装机智能控制系统

根据我国当前表帖元件包装机温度控制精度及封装效率都较低的现状,设计了基于ARM7处理器S3C44B0X的智能控制系统.介绍了该控制系统的硬件电路组成并给出了主程序流程,针对温度控制提出了带有加权因子的模糊控制算法.实际应用表明,该智能系统的控制效果优于常规控制系统.     

热封切制袋机中多通道温控系统的设计

阐述了一种高精度多通道温度控制器的设计方案。通过高速转换输出的16 位AD 芯片AD7705 以及ARM 处理器,可以实现快速轮番采集多路温度信号。采用积分分离的PID 算法,计算并输出PWM 控制信号,通过固态继电器控制加热器件通断时间,使得各通道温度达到预设温度并在控制精度允许范围内小幅度波动。通过Modbus 通信协议与上位机进行通信,可以实现单台上位机同时监控多个温度控制器。     

汽油机控制参数的电控与测试研究

以MCS－8098单片机作为中央控制器,设计了一种电控发动机基本控制参数测试装置,利用该装置对汽油机的空燃比和点火提前角等控制参数进行了实际测试。应用测试获得的数据对发动机进行实际控制时,取得了比较满意的效果。     

我国生猪养殖环境智能控制标准体系建设研究

本文分析研究我国生猪养殖环境智能控制标准化的现状,基于智能控制的设施设备以及运行维护需求,提出了生猪养殖环境智能控制标准体系框架及内容,以期运用标准化手段提升我国生猪养殖环境智能化控制水平.