Pressure-enforced plasticity in MAX phases: from single grain to polycrystal investigation

Ti₄AlN₃, Ti₃AlC₂ and Ti₃Al_0.8Sn_0.2C₂ MAX phases were plastically deformed at room temperature (RT) under gaseous confining pressure. Microstructures of as-grown and deformed samples are carefully analysed using scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM). It is demonstrated that high level of plastic deformation can be reached under confining gas pressure; the later suppresses the brittle failure at RT to the profit of plasticity. Multiscale characterization techniques are shown to provide a unique insight into all the scales of the plastic deformation; in particular, the effect of the mesoscale. Indeed, grain shape and orientation relative to the compression axis are shown to play a key role in the deformation process, intergranular stresses leading to a complex stress field in the polycrystalline samples. The TEM results show that dislocation activity highly depends on the grain orientation. The observation of dislocation entanglements unambiguously demonstrates that dislocations may be organized in such a configuration so that their glide in the basal plane can be hindered when deep plastic regime is reached.     

Physical insight of superconductivity of Nb2AlC: in situ Raman spectrometry investigation

Superconductivity of Nb₂AlC has been previously reported, but the origin is not clear. In this paper, in situ Raman spectra of Nb₂AlC are measured in the temperature range from 80 to 380 K at ambient pressure. The line‐width of E_2g (ω₁) mode increases with temperature which originates from the anharmonic phonon–phonon scattering. On the contrary the line‐widths of E_2g (ω₂) and A_1g (ω₄) modes decrease continuously at elevated temperature. The phenomenon is explained by the electron–phonon coupling. The origin of superconductivity is therefore interpreted by the coupling of Nb 4d electrons with E_2g (ω₂) and A_1g (ω₄) phonon modes. Copyright © 2013 John Wiley & Sons, Ltd.     

数据采集系统中的DSP控制回路

在某些信号采集系统中,传感器的工作电压随着环境的变化而变化,这时高速的数据处理能力以及高精度的反馈控制能力就显得至关重要。介绍由TMS320VC5416和MAX5633所架构的生物信号传感器控制系统,给出高精度多通道D/A在数据采集系统中的应用方法,着重讨论TMS320VC5416与MAX5633的一种串行接口连接方法以及相关的软件实现方法。该系统能成功地解决工作电压变化所带来的问题,对数据采集系统的设计具有指导作用。     

基于MAX260的自动跟踪滤波器的工程设计与应用

为实现自动跟踪信号频率变化并除去噪声及不需要的频率信号输出,根据工程项目的实际需要设计了一种能自动跟踪信号频率变化的极窄带通的滤波器,滤波器主要由开关电容滤波器MAX260BCNG和锁相芯片CD4046结合实现,其中心频率在1 Hz~7.5 MHz之间调控方便。经实际应用,该滤波器性能可靠,可以满足工程项目的性能指标。     

MAX5481在夫兰克-赫兹实验仪中的应用

提出了一种基于数字电位器MAX5481的夫兰克-赫兹实验仪设计方案;介绍了数字电位器MAX5481的接口、控制方式及应用方案.该方案为数字电位器在模拟电路中替代机械电位器提供了借鉴.     

带有诊断监视器的激光驱动器MAX3740及其应用

MAX3740A是带有诊断监视器的高速VCSEL驱动器,可输出15mA激光调制电流和15mA偏置电流,并可在温度和激光器特性发生变化时通过自动功率控制（APC）来调整激光偏置电流以保持恒定的平均光功率。     

Design and investigations on a compact,UWB, monopole antenna with reconfigurable band notches for 5.2/5.8 GHz WLAN and 5.5 GHz Wi‐MAX bands

This article represents a microstrip line–fed novel circular monopole antenna with ultra‐wideband (UWB) characteristics. The compact antenna provides reconfigurable notches at WLAN (5.2/5.8 GHz) and Wi‐MAX (5.5 GHz) frequency bands. The band rejection is achieved by etching an open‐ended L‐shaped slot in the ground plane, which effectively mitigates the interference between WLAN, Wi‐MAX, and UWB systems with an effective patch area of 36.26%. The proposed antenna operates from 3.05 to 12.11 GHz with VSWR 2 except at stopband (3.89‐5.93 GHz) to filter the WLAN and Wi‐MAX signals. The simulated return loss, gain, and radiation pattern of the proposed antenna has been experimentally verified with the fabricated one which holds a good agreement.     

全景视觉态势感知系统的多通道串口通信

串口通信作为传统的通信方式仍然受到广泛应用,本文介绍了基于PIC16F877A单片机、TL16C754异步通信芯片和MAX485芯片实现异步通信串口扩展的整体方案。方案实现了十四个串口同时进行长时间稳定可靠的双向数据通信。通过开展相应的试验,证明了该处理方案的有效性,并在某工程项目中得到应用。     

低功耗高精度温度多路采集测温系统研究

针对旋转物体、移动部件或物体内部温度分布采集的问题,文中设计了一种小体积、精度高、低功耗的温度测量系统。该系统能无线传输数据并能温度数据多通道采集。系统采用PT100作为温度传感器,利用高一致性和低导通阻抗的多路模拟开关ADG888实现多路测量控制。软件上,通过建立铂阻值与ADC转换结果的修正函数,对PT100的整个信号链进行系统校准,获得准确的PT100阻值。在比较多种非线性处理方法并进行误差分析后,采用PT100的传递函数校正非线性误差,以获得高精度的测量值。经测试,温度多路采集系统在0~300 ℃的设计温度范围内可达到0.5 ℃的精度。     

大豆糖蛋白的结构研究

应用NaClO2-HOAc提取结合层析柱提纯, 从大豆细胞壁物质(膳食纤维)中分离出PRF3纯组分。这是一种富含羟脯氨酸的糖蛋白, 本文对其结构特征作详尽剖析。结果表明, PRF3多糖部分的主链结构是由β(1→4)糖苷键连接的半乳聚糖,主链通过3-C分支点连接由α(1→3)键连的低聚阿拉伯糖侧链, 多糖与多肽之间通过HPr-Ara和Ser-Gal糖苷键连接在一起。