电子组装中元器件的选择与应用(续一)

电子元器件的质量可靠性直接影响到产品整机可靠性。主要总结了常见无源元件及有源器件的分类、结构特点及应用领域。对元器件的选择和使用给出了经验指导,而且对其组装工艺进行了简要阐述。     

基于半有源RFID技术的人员跟踪定位系统

针对人们对特殊复杂环境下信息安全和人员管理的实际需求,而传统GPS定位技术在无法满足实时、高精度定位的问题,提出了一种基于半有源RFID技术的人员跟踪定位方法。设计并开发出的125 kHz低频激励器,激励半径1¹0 m可调,激励区域边沿控制达到分米级。采用低频激励器、RFID阅读器和双频标签搭建的实验系统经过测试,系统稳定可靠,人员定位跟踪信息实时、准确。     

仪器分辨率对氧气A带被动测距的影响分析

透过率的计算是红外目标被动测距技术的核心,其精度直接影响到被测距离的精度,而仪器分辨率又直接影响到光谱信号的精度。为了研究光谱仪器分辨率对带平均透过率的影响,选用氧气A带为研究对象,采用基线拟合方式计算被测目标的带平均透过率,利用随机Malkmus模型计算被测目标距离,从而获得仪器分辨率对被动测距的影响。为此,搭建了被动测距实验系统,通过对卤素灯光源在不同距离的光谱测量,验证仪器分辨率对带平均模式被动测距的影响。首先,介绍氧气A带透过率的计算方法,计算理论值;以卤素灯为光源,利用光谱仪分别测量相同距离不同分辨率的光谱曲线,计算实测大气透过率,分析光谱分辨率对单谱线的影响;然后,在分析比较透过率模型和实测透过率谱线的基础上,对透过率计算模型进行拟合、校正,验证光谱分辨率对带模型的影响。对于单条谱线,仪器的不同分辨率可测得的谱线区别较大,而对带平均谱线,相同波数点的光谱信号取平均,获得平均效应,使得被测谱线几乎没有变化;分辨率的模型选择需根据不同的应用场合、不同的精度要求选择合适的分辨率。实验结果表明：分辨率对单谱线的透过率影响较大,随着分辨率的降低,被捕获的光谱信息点取值越少,被测目标距离相关系数越小;分辨率对带平均透过率的计算影响较小,不同分辨率下测得的目标距离,几乎重合;而仪器分辨率越高则测量时间越长,当使用带平均透过率计算被测目标距离,在精度要求范围内,可以适当降低仪器分辨率,从而极大地提高测量速度,并达到测量实时性,同时降低系统搭建的成本。该结论可为透过率测量的应用提供依据。     

Chemical synthesis of an RNA sequence containing 2-thiocytidine (sC): the DY647 labelled anticodon stem and loop sequence of Staphylococcus aureus tRNA (sC32, mnmU34, tA37)

Incorporation of 2-thiocytidine (s²C) into a DY647 labelled 17-mer RNA sequence corresponding to the anticodon stem loop of Staphylococcus aureus tRNA^Arg has been achieved by phosphoramidite chemistry. Key to the success was the use of dilute iodine for the P(III) to P(V) oxidation step plus the choice of the trimethylsilylethyl (tse) ester as protection for the threonyl carboxyl group of t⁶A. In trial experiments with N⁴-benzoyl-2-thiocytidine, the use of dilute t-BuOOH in toluene as an alternative oxidising agent caused substantial desulfurization.     

Passive sampling techniques for sensing freely dissolved hydrophobic organic chemicals in sediment porewater

With compiled and analyzed information about recent advances in passive sampling techniques for sediment porewater, we discuss common quantitation methods (equilibrium and kinetic diffusion-controlled sampling), effects of temperature and salinity on passive sampling, and benefits and drawbacks of currently available passive samplers based on the principles of solid-phase microextraction.The results show that the in-fiber standardization technique, which is kinetic diffusion-controlled, could shorten sampling time and obtain accurate results using isotopically-labeled reference compounds. Another quantitative method, time-weighted average sampling, may be viable for simultaneously measuring all analytes in sediment porewater, as it is more effective with respect to cost and time. In addition, the effects of temperature and salinity on passive sampling should be quantified in field applications.Currently available passive samplers (e.g., employing polymer-coated fibers and low-density polyethylene sheets) can sense hydrophobic organic chemicals (HOCs) in sediment porewater, but the small capacity and the inflexibility of polymer-coated fibers need to be further improved, while better physical protection of polyethylene devices, particularly when they are deployed under rough conditions, should be carefully considered.In conclusion, passive samplers for in-situ measurement of dissolved HOCs in sediment porewater should be combined with a suitable quantitative method and calibration for the effects of temperature and salinity.     

Spectrally Combined Encoding for Profiling Heterogeneous Circulating Tumor Cells Using a Multifunctional Nanosphere‐Mediated Microfluidic Platform

Comprehensive phenotypic profiling of heterogeneous circulating tumor cells (CTCs) at single‐cell resolution has great importance for cancer management. Herein, a novel spectrally combined encoding (SCE) strategy was proposed for multiplex biomarker profiling of single CTCs using a multifunctional nanosphere‐mediated microfluidic platform. Different cellular biomarkers uniquely labeled by multifunctional nanosphere barcodes, possessing identical magnetic tags and distinct optical signatures, enabled isolation of heterogeneous CTCs with over 91.6 % efficiency and in situ SCE of phenotypes. By further trapping individual CTCs in ordered microstructures on chip, composite single‐cell spectral signatures were conveniently and efficiently obtained, allowing reliable spectral‐readout for multiplex biomarker profiling. This SCE strategy exhibited great potential in multiplex profiling of heterogeneous CTC phenotypes, offering new avenues for cancer study and precise medicine.     

高灵敏度全集成UHF RFID标签的设计与实现

本文给出了一款基于ISO1800-6B协议的全集成的无源UHF RFID标签,这款芯片由模拟前端、基带处理器和EEPROM 存储器组成。在设计过程中,我们采用了具有高效率的差分驱动CMOS整流器使得通信范围得到扩展。我们采用新颖的高性能的电压限制器为芯片提供稳定的电压,这款限压器的在不同温度和工艺变化下的电压漂移只有172mV。在稳压器的设计中,我们采用动态带宽增强技术提高其稳压能力。对已解调器,我们采用了一款轨到轨的比较器实现在任何通信范围下对输入信号的正确解调。标签芯片采用TSMS 0.18um CMOS 工艺,芯片面积为900×800 um2。测试结果显示,芯片功耗为6.8uW,灵敏度达到-13.5dBm。     

RFID在电子标签中的应用

基于RFID技术,分析RFID电子标签系统的基本组成,对RFID中的编码调制、基带编码、数字调制法、双工方式、检错纠错等重要技术点进行了描述。根据不同频率说明了RFID在不同波段的优缺点。最后,提出RFID在电子标签几个重要领域的应用特点,最后详细描述了RFID在电子标签中应用的几个典型方面,包括身份识别、商品防伪、智能交通、商品供应链以及图书馆电子标签等,并给出应用方法和意义。     

A Time‐Optimal Anti‐collision Algorithm for FSA‐Based RFID Systems

With the introduction of the new generation RFID technology, EPCglobal Class‐1 Generation‐2, there is considerable interest in improving the performance of the framed slotted Aloha (FSA)‐based tag collision arbitration protocol. We suggest a novel time‐optimal anti‐collision algorithm for the FSA protocol. Our performance evaluation demonstrates that our algorithm outperforms other tag collision arbitration schemes.     

扩展卡尔曼滤波在无源定位中的应用研究

阐述了卡尔曼滤波(KF)和扩展卡尔曼滤波(EKF)的原理和方法,建立了无源定位系统的状态模型和观测模型,推导了将非线性观测模型线性化,并利用EKF进行递推滤波估计的步骤和公式。通过计算机仿真,验证了运用EKF算法解决基于方位角及其变化率测量信息的无源定位方法,结果表明,运用EKF滤波算法,可以实现单观测站对运动目标的无源定位,初始状态估计误差对定位收敛的性能有较大影响。