可编程单次脉冲发生器的教学实验

介绍了一个数字系统综合设计实验：可编程单次脉冲发生器的设计与实现。该脉冲发生器可在输入按键的控制下,产生单次的脉冲,脉冲的宽度可由8位的输入数据控制。实验以FPGA为硬件基础,以MAX＋plusⅡ为软件工具开发完成。实验不仅体现了数字系统设计实验课程的综合训练目标,要求学生能综合、灵活应用VerilogHDL语言,掌握多层次结构系统设计方法、Top_down设计思想和FPGA开发方法等理论知识,并且与工程实际结合紧密。所开发的系统具有很大的实用价值,是一个值得推广的典型教学实验。     

Density Functional Theory Study of Mn+1AXn Phases: A Review

M_n+1AX_n phases (MAX phases for short with M: transition metal, A: A group elements, X: C or N, and n = 1–3) have attracted considerable attention due to the unique combination of the ceramic- and metal-like properties. The density functional theory (DFT) has emerged as a powerful theoretical approach that complements experimental testing and serves as a predictive tool in the identification and characterization of MAX phases. After the beginning with a brief introduction of the MAX phase and DFT, we review the DFT study on this class of materials, including crystal structure, electronic structure, point defects, lattice dynamics, and related properties, phase stability, compressibility, and elastic properties. Comparison between the theoretical values and available experimental ones shows that they are in decent agreement for most part, especially in the lattice constants, elastic properties, and compressibility. This article is concluded with an outlook of future research on DFT study of MAX phases, major challenges to be met and possible solutions in some cases.     

固溶体MAX相(Ti0.5V0.5)3AlC2的制备及其对MgH2储氢性能的催化影响

通过无压烧结法制备了固溶体MAX相(Ti_(0.5)V_(0.5))_3AlC_2,研究了其添加对MgH_2储氢性能的影响。结果发现,固溶体MAX相(Ti_(0.5)V_(0.5))_3AlC_2中的Ti和V元素通过协同作用,呈现出更高的催化活性。添加质量分数10%(Ti_(0.5)V_(0.5))_3AlC_2的MgH_2样品的起始放氢温度为230℃,较原始MgH_2降低了60℃。在275℃下等温放氢,(Ti_(0.5)V_(0.5))_3AlC_2添加样品的放氢速率可达0.35%·min~(-1),是原始MgH_2样品的4倍左右。此外,完全放氢后的MgH_2-10%(Ti_(0.5)V_(0.5))_3AlC_2样品在150℃、5 MPa氢压下,可在60 s内吸收4.7%的氢。计算显示,MgH_2-10%(Ti_(0.5)V_(0.5))_3AlC_2样品的表观活化能为79.6 kJ·mol~(-1),较原始MgH_2(153.8 kJ·mol~(-1))降低了48%,这是MgH_2放氢性能得到改善的主要原因。     

A/D转换器MAX194与单片机的接口技术

介绍一种14位串行模数转换器MAX194,它不仅速度快、精度高、功耗低,而且与单片机连接方便,编程简单。它在高精度的以单片机为核心的应用系统中是很好的选择。     

基于VHDL的数字频率计的设计

本文的数字频率计设计,采用自上向下的设计方法,实现整个电路的测试信号控制、数据运算处理和控制数码管的显示输出。一块复杂可编程逻辑器件CPLD芯片EPM7128SLC84-15完成各种时序逻辑控制、计数功能。在MAX+PLUS II平台上,用VHDL语言编程完成了CPLD的软件设计、编译、调试、仿真。本文详细论述了系统自上而下的设计方法及CPLD的软件编程设计。     

无人机虚拟仿真三维交互控制模型的设计与实现

介绍了如何利用Pro/E、3DS MAX及Cult 3D软件设计制作无人机虚拟仿真三维交互控制模型,实现无人机的精确建模、动态模拟和交互控制.     

Microstructure and phase transformation of Ti3AC2 (A = Al,Si) in hydrofluoric acid solution

In this paper, Ti₃AC₂ (A = Al, Si) were prepared by pressureless argon shielding synthesis technique. The microstructure and phase transformation of as‐prepared Ti₃AC₂ (A = Al, Si) in hydrothermal hydrofluoric acid (HF) solution were investigated systematically. Results showed that the obtained Ti₃AlC₂ and Ti₃SiC₂ were closely aligned layered structure. In hydrothermal HF solution, Al or Si element was preferentially etched from the layered structure, inducing obvious transformation of microstructure and phase composition. For Ti₃AlC₂, Al atoms diffused out of the structure and reacted with HF to form AlF₃•H₂O, which induced the rearrangement of the Ti and C atoms, and finally resulted in the formation of TiC_x cubic phase. With the hydrothermal temperature and reaction time increasing, the TiC_x phase gradually disappeared and the grain size of AlF₃•H₂O gradually increased. When Ti₃SiC₂ was immersed in hydrothermal HF solution, the main products were TiC and SiC. Interestingly, with the hydrothermal treatment temperature and reaction time increasing, TiC gradually disappeared, while SiC nearly kept unchanged. This can be explained that SiC was covalently bonded carbide, while TiC was metallically bonded, having relatively weak bond energy and consequently being unstable in hydrothermal HF solution.     

采用MAX813L芯片对复位电路可靠性提高的讨论

文中对五种单片机复位电路进行了分析并作比较．结合几种不同复位电路在实际产品上的应用结果,表明采用MAX813L专用复位芯片可以大大提高产品的稳定性和可靠性．     

一种调幅红外无线耳机的设计

采用MAX1726与MAX9722器件,通过幅度调制方式,实现一款红外无线耳机.该红外无线耳机具有供电方式多样、方向性好、音量可调节等功能.给出了详细设计原理与硬件实现.