基于声学特性的灯泡贯流式水轮发电机组噪声信号采集系统设计

大量程、高精度的噪声信号采集是基于声学特性的灯泡贯流式水轮发电机组故障诊断的前提。为此,该文设计一种灯泡贯流式水轮发电机组噪声信号采集系统,介绍噪声信号采集系统原理,完成基于两级分段组合的放大电路设计,解决传统单级调理电路不易实现全量程、大动态范围信号放大的问题,给出详细的信号放大电路、滤波电路等参数设计方法和采集卡A/D转换器分辨率计算方法。仿真和现场测试表明:该发电机组噪声采集系统的测量范围为20-140 dB,最大级线性误差为0.3 dB,可为后续基于声学谱分析的故障诊断提供可靠的数据。     

基于高速A／D卡的全波形采集超声自动检测系统

设计了一种全波形采集超声自动检测系统,实现了A,B,C 3种扫描方式且具有记录被检材料上所有检测点超声A扫描波形的功能,支持材料超声检测、评价技术研究.该系统由高速A/D卡、超声检测仪、自动扫描器、运动控制系统和CSCAN软件等组成,作为核心部件的高速A/D卡选用PCI-9820型,负责从超声检测仪采集A扫描波形信号.自动扫描过程中,A/D卡与超声检测仪、运动控制系统之间通过硬件信号实现同步,使A扫描波形数据的采集与被检材料上声传播的渡越时间、预定测量点位置相对应,采集得到的A扫描波形数据通过A/D卡的板载SDRAM及DMA功能异步传输至计算机内存,并由CSCAN软件进一步实现数据压缩、滤波、存储以及不同方式成像等处理.测试结果证明,该系统运行速度快,成像精度高且性能稳定. 更多还原     

应用于雷达系统的双路高速数据采集存储系统设计

介绍了一种用于对雷达回波I/Q信号进行双路高速采集与数据存储的系统,采样速率为200MHz,分辨率为12位,存储深度为4GB.该系统采用FPGA作为主控制器,ADS62P29作为高速数据转换器,K9K8G08U0M作为大容量数据存储器,通过USB实现系统与计算机之间的通信.利用Cadence软件和VHDL语言完成了系统设计、软件仿真及关键信号的完整性仿真.测试结果表明,ADC的有效位数可达10.69,输入信号为80 MHz的正弦信号时,两路ADC信号之间的相干系数达到0.998 4,可满足雷达系统对回波信号进行高精度相位测量的要求.     

一种基于高速A/D的刻线瞄准信号处理方法

介绍了基于高速A/D信号处理方法的系统组成和工作原理,包括对瞄准信号的模拟信号调理、A/D采样、数字信号处理等环节,能够实现2 nm的瞄准分辨率,可用于激光干涉比长仪的动态显微瞄准系统.通过实验验证了方法的可行性,即使在干扰较大的非理想波形信号的情况下也能得到对刻线瞄准的较高的重复性.     

四通道高精度USB型数据采集系统设计

阐述了一种系统基于USB协议高速高精度数据采集设计,系统采用一种新型音频A/D芯片AKM5394,利用差分方式进行数据采集,由CPLD芯片及高速、高精度的AKM5394芯片、FIFO,开发高精度高速数据采集系统,并使用USB接口在主机中实现数据存储与图形显示。该系统在Windows 2000或Windows XP环境下的驱动程序及用户应用程序采用的是Visual C 语言实现的,而固件代码则是用C语言实现的。系统具有低成本、高性能的特点,能够广泛应用于精度、速度各方面性能要求比较高的测控、信号分析等多个领域。实验室环境下测量的精度达到22位以上,效果良好。     

数据采集系统中A/D转换器的正确选择

A/D转换器是数据采集系统的核心器件,它的技术指标直接影响整个采集系统的精度.本文详细地介绍了A/D转换器的采样率、分辨率和精度三个技术指标,为用户正确选择A/转换器并建立数据采集系统提供参考.     

一种小型医院影像数字化管理系统的设计与实施探讨

医学图像信息数字化及其计算机处理技术从根本上改变了传统的医学图像采集、显示、存储和传输的模式,为医学诊断、临床治疗以及医学研究提供了精确的医学图像信息.探讨一种可以实现医学图像的自动获取、存储、显示、分析、传输和管理的小型超声工作站系统.讨论通过A/D转换和信号滤波将模拟信号数字化,通过Windows操作系统的API调用,实现超声诊断的图文数字化管理.     

用低速采样A/D板分析稳态高频信号

数字信号分析技术中,一般在时域采集一系列离散的样本信号来逼近连续的实际信号,对采样有一定的技术要求,这在有关信号处理的著作中有详细论述。[1,2]对于稳态的谐频信号,通常要求在一个周期内采集到两个以上的样本,即要求采样率不低于信号频率的两倍,为此,在分析高频信号时,一般必须采用相应的高频采样的A/D板。 从实际情况考虑,A/D板的采样率除了受到它本身瞬态响应特性的限制外,还受到计算机运算速率及数据贮存量等方面客观条件的制约,并不能任意加以提高。因此,如果采取适当措施,能用低速采样的A/D板来分析高频信号,则将具有重要的理…     

USB多路数据采集器

针对目前大多数采集系统无法实现多通道高分辨率采样及携带不方便等情况,提出了一种基于USB的多路数据采集系统的设计方法。系统利用ARM+FPGA+AD7656的系统组合实现16路通道同步信号采样,FPGA用于实现对A/D转换的逻辑控制,通过ARM7处理器对A/D转换数据进行处理,再由USB接口与计算机进行数据通信。测试结果表明,基于FPGA与ARM的多通道数据采集系统结构简单、控制方便、设计成本较低,能够准确快速地对16路信号同时进行采集。     

海底管道缺陷漏磁检测器数据采集系统研发

针对海底管道内可利用空间小、运行工况恶劣的实际情况,研发一款海底管道缺陷漏磁检测器数据采集系统.该系统选用ARM实现对各功能单元的控制,并以FPGA结合A/D采样芯片进行多路漏磁检测信号的并行采集;通过对各功能单元的一体化和集成设计,在确保能准确有效采集和存储缺陷漏磁信号数据的前提下,实现系统结构的整合及简化.牵拉试验和检测工程应用结果表明:该数据采集系统运行稳定,采集、处理缺陷漏磁检测数据质量高,达到设计要求,完全满足海底油气管道缺陷漏磁检测工程应用的技术要求.     

检定和校准证书的异同与应用

本文介绍了检定和校准以及证书的两点相同、五点不同之处,说明了对检定证书和校准证书的正确应用。     

Heat and Mass Transfer and Modeling and Prediction of Environmental Catastrophes

Basic definitions and concepts of the physicomathematical theory of natural catastrophes are given. Possibilities of mathematical modeling of natural and technogenic catastrophes are discussed in the context of the theory of heat and mass transfer and the mechanics of reacting media. The importance of taking into account conjugate heat and mass exchange in modeling catastrophes is emphasized. A formula for evaluating the probability of a collisional catastrophe is given.     

凝固科学技术与材料

从凝固科学与实践发展的角度介绍了当前凝固材料体系的基本框架和凝固科学主要发展阶段的基本理论。作为材料科学与工程的基本组成，凝固科学技术正在现代科学理论的基础上针对传统材料的改性提高和新材料的发展需求，以控形、控构、控性为目标开展优质铸件的定向、晶体生长、快凝、深过冷及各种新型和超常领域凝固过程的研究，并介绍了其中某些方面和展望了可能的发展趋势。     

Multi-ferroic and magnetoelectric materials and interfaces

The existence of multiple ferroic orders in the same material and the coupling between them have been known for decades. However, these phenomena have mostly remained the theoretical domain owing to the fact that in single-phase materials such couplings are rare and weak. This situation has changed dramatically recently for at least two reasons: first, advances in materials fabrication have made it possible to manufacture these materials in structures of lower dimensionality, such as thin films or wires, or in compound structures such as laminates and epitaxial-layered heterostructures. In these designed materials, new degrees of freedom are accessible in which the coupling between ferroic orders can be greatly enhanced. Second, the miniaturization trend in conventional electronics is approaching the limits beyond which the reduction of the electronic element is becoming more and more difficult. One way to continue the current trends in computer power and storage increase, without further size reduction, is to use multi-functional materials that would enable new device capabilities. Here, we review the field of multi-ferroic (MF) and magnetoelectric (ME) materials, putting the emphasis on electronic effects at ME interfaces and MF tunnel junctions.     

CellML and associated tools and techniques

We have, in the last few years, witnessed the development and availability of an ever increasing number of computer models that describe complex biological structures and processes. The multi-scale and multi-physics nature of these models makes their development particularly challenging, not only from a biological or biophysical viewpoint but also from a mathematical and computational perspective. In addition, the issue of sharing and reusing such models has proved to be particularly problematic, with the published models often lacking information that is required to accurately reproduce the published results. The International Union of Physiological Sciences Physiome Project was launched in 1997 with the aim of tackling the aforementioned issues by providing a framework for the modelling of the human body. As part of this initiative, the specifications of the CellML mark-up language were released in 2001. Now, more than 7 years later, the time has come to assess the situation, in particular with regard to the tools and techniques that are now available to the modelling community. Thus, after introducing CellML, we review and discuss existing editors, validators, online repository, code generators and simulation environments, as well as the CellML Application Program Interface. We also address possible future directions including the need for additional mark-up languages.     

Synthesis and luminescent properties of alkali-metal and ammonium fluorosulfatozirconates and fluorosulfatohafnates

We have synthesized a variety of alkali-metal and ammonium fluorosulfatometallates (titanates, zirconates, and hafnates). The alkali fluorosulfatozirconates and fluorosulfatohafnates have been shown to exhibit efficient roentgenoluminescence (RL) in the UV through visible spectral region, with a maximum at 390–440 nm. Their RL spectra depend significantly on their composition (cation, anion, and water content), coordination of KF and K₂SO₄, and relative amounts of fluorine and SO₄ groups. We have examined the effect of heat treatment on the RL of these compounds. The rubidium and cesium fluorosulfatozirconates Rb₃Zr₂F₉SO₄ · 2H₂O, Cs₂ZrF₂(SO₄)₂ · 2H₂O, Cs₈Zr₄F₂(SO₄)₁₁ · 16H₂O, and Cs₂ZrF₄SO₄ offer the most efficient RL.     

热交换器的分类及优缺点分析

热交换器是将不同温度介质之间的热量通过热传导的形式,由高温介质传递给低温介质,使介质达到生产所需温度的工艺设备,也可作为一种节能设备使用.通过对不同热交换器的结构分析,总结不同热交换器的优缺点、适用环境,为生产工艺设计人员及设备制造单位在选择可降低能耗、提高效率的设备上提供参考.