脉冲超声波的发射与接收电路设计

设计了一种应用于超声波液体流量计中的脉冲超声波的发射与接收电路。发射电路由光电隔离电路、场效应管驱动电路及尖脉冲激励电路组成;接收电路由前置放大电路、巴特沃思带通滤波器及自动增益控制电路组成。试验结果显示,此电路性能良好,保证了超声流量测量的精度。     

高声衰减树脂基复合材料超声检测方法

根据高声衰减树脂基复合材料的特点,采用高能超声激励技术和接收端信号增强技术结合的穿透法对该种材料进行检测。分析了影响超声波幅值的激励电压、超声仪阻尼电阻、激励电信号波形等因素,提出了双极性方波脉冲串的激励方式,设计了接收端的放大电路,确定了检测参数。结果表明:在小于击穿电压的前提下,激励电压与超声波幅值成正比;其他条件不变,超声仪阻尼电阻调至最大时,可激励最大幅值的超声波信号;在同一条件下,不同激励电信号波形激励的超声波幅值大小关系为双极性方波脉冲串单方波尖脉冲;提出的方法实现了高声衰减树脂基复合材料的超声检测,且可检测不大于5mm的缺陷。     

印刷电路板双向脉冲镀铜可编程开关电源研制

为降低开关损耗对双向脉冲镀铜质量的影响,输出满足印刷电路板封孔镀铜需求的脉冲波形,通过研究封孔镀铜工艺及其技术指标,应用软开关与DSP2812详细设计了支持电镀参数设置和脉冲波形可编程控制的大容量双向脉冲电源。主电路利用软开关降低高频镀铜的开关损耗,由控制电路的DSP2812为封孔镀铜提供触发信号,控制主电路周期性输出15 V/800 A正向、24 V/2000 A反向可调的脉冲镀铜激励。利用研制的双向脉冲电源对φ20μm×80μm盲孔进行封孔镀铜试验,镀铜凹陷均值为11.34～13.28μm,双向脉冲输出稳定,盲孔均镀性良好。     

MD—1型脉冲电镀专用调制器

只需将新型的MD-1脉冲电镀专用调制器与常用的直流电源连接,便可形成脉冲电源,使应用脉冲电渡技术所需设备费用大幅度下降.专用调制器由集成电路与大功率场效应管等新型器件组成,性能稳之、易于调控.     

核磁共振技术在煤化学研究中的应用

本文介绍了不同核磁共振方法和技术在煤化学研究中的应用。主要论及液体核磁共振的常规氢谱、碳谱、多脉冲技术和二维谱，以及固体核磁共振谱和核磁共振成象技术。     

激光传感器窄脉冲峰值保持电路的设计

针对激光传感器窄脉冲信号在窄到一定程度时激光脉冲峰值功率明显下降的问题,从理论上对电路进行分析,介绍峰值保持电路的工作原理,设计了具有自动放电功能、脉冲保持时间可调的窄脉冲峰值保持电路。     

脉冲阵列式套管消磁仪设计

阐述了脉冲阵列式套管消磁仪的工作原理及主体结构,选用了电磁退磁作为套管消磁的方法,重点介绍了消磁线圈的结构设计和电路控制的工作原理。激励线圈使用阵列式组合,通过改变线圈的电流方向和大小来实现套管退磁。     

用于产生电解金属电镀电流脉冲的方法及电路结构

公开号　ＣＮ１２０５７４５Ａ　　申请人　阿托特德国有限公司　　地址　联邦德国柏林　　本发明涉及产生用于电镀的、周期性重复的短暂单极性或双极性脉冲状电流ＩＧ、Ｉε的方法及用于电镀的电路结构，通过它可产生这种脉冲状电流ＩＧ、Ｉε。这种电镀方法被称为脉冲电镀法。根据本发明，在由电解槽直流电流源２及由电镀槽４形成的槽电阻ＲＢ组成的电镀直流电流电路５中串联了一个电流互感器１的次级线圈６。互感器的初级线圈７具有的圈数多于次级线圈的圈数。对初级线圈供给高电压及相对低电流的脉冲。次级的大脉冲电流暂时地补偿了电镀…     

应力波时间仪的研制和应用

应力波时间间隔仪主要由加速度传感器、应力波脉冲转换器、计数、译码和显示单元电路组成。它可以测量出应力波通过材料两端的时间。从而得到应力波的传播速率。本文给出了应力波信号放大 ,变换及门信号产生、计数电路的设计原理     

板状炸药在高锰钢表面产生的爆炸载荷的测量

本文介绍了对爆炸硬化所用板状炸药在高锰钢表面产生的爆炸载荷进行的估算和用锰铜传感器、脉冲恒流源供电电路进行了测量。     

核磁共振测井渗透率模型及其应用

渗透率是储层评价的重要参数之一,利用测井方法求取渗透率是最经济的。常规测井已经发展了多种计算渗透率的方法,但是这些方法在精度和通用性方面尚不能满足储层评价的需要。核磁共振测井得到的回波串中包含了孔径大小及流体赋存状态等十分丰富的信息,用核磁共振测井来确定地层渗透率有独特的优势。本文综述了目前国内外常用的三种核磁共振测井渗透率模型,Coates模型、SDR模型以及回波串的和计算公式,介绍了这三种模型的基本形式,各自的特点及适用范围。     

核磁测井影响因素分析

文章主要介绍了核磁共振测井技术在应用过程中的影响因素,研究了核磁共振技术的影响因素如矿化度、温度、等待时间、回波间隔等。该项研究可以为分析孔隙度、渗透率、饱和度和储层流体性质等参数提供帮助,从而更好地推进核磁测井技术的应用。     

核磁共振束缚水饱和度模型研究

岩心最佳饱和度模型的确定是核磁共振测井实验研究工作的重要方面,有助于现场测井中有关参数的合理选择,用以更好地评价油、气储层。分析岩心核磁共振实验资料,采用频谱法（SBVI）计算束缚水饱和度模型参数,选定适合区块的模型参数。     

普光气田碳酸盐岩储层测井解释方法

普光气田目的层段飞仙关组-长兴组海相碳酸盐岩地层发育气层,储层类型以孔隙-孔洞型为主,局部发育裂缝。针对这些储层特征,参考地质资料、微电阻率扫描成像资料,总结出了利用常规测井资料识别储层储集空间类型的方法;并在碳酸盐岩储层孔隙度参数求取中,采用光电吸收截面指数(Pe值),准确确定储层中岩性成分,为求取孔隙度参数提供了保障;在识别储层流体性质方面,通过实践经验总结出了交会图法、纵横波速度比值法等多种识别流体的方法,同时在核磁共振资料识别流体性质方面也做了大量的工作,在实际生产中显示出了很好的应用效果。     

基于FPGA与AD7985的脉冲电源数据采集设计

为了满足精密电镀的控制需求,设计了一种基于FPGA和AD7985的高速高精度的数据采集系统,该数据采集系统可应用于高精度的脉冲电镀电源中,用于采集输出脉冲的电流和电压参数并用于电流调控.首先设计分析了采集系统的主要硬件电路,包括隔离放大电路、电压跟随电路和AD转换电路;然后对AD7985的控制时序进行了研究,给出了控制...     

Simultaneous determination of oil and water contents in different oilseeds by pulsed nuclear magnetic resonance

Routine analysis of oil and water contents in different oilseeds with the Bruker Minispec pulsed nuclear magnetic resonance (NMR) analyzer (Bruker Analytische Mestechnik, Rheinstetten, Germany) is rapid (16 s measurements), precise, accurate and nondestructive. In 1991, subcommittee SC2 (oil seeds) of the Technical Committee Number 34 [organized by the International Standards Organization (ISO), Geneva, Switzerland] organized an international collaborative study for pulsed NMR analysis of oil content in whole rapessed. An additional study was performed in 1993 to extend the method to sunflower, linseed and soy seeds. The Draft International Standard ISO DIS/10565 (Draft International Standards, International Standards Organization, Geneva, 1993) describes the procedure of the pulsed NMR method for determination of oil content in rapeseed and presents the interlaboratory comparison results based on the calculations described in the Normative ISO 5725 (Draft International Standards, International Standards Organization, Geneva, 1993). The standard was approved in 1992 and will be published in 1993. The interlaboratory collaborative studies showed that the analyses of oil and moisture by pulsed NMR were either comparable or more repeatable than measurements done by the traditional methods. No statistical differences between determinations by the traditional and pulsed NMR methods were found. Simultaneous determination of percent moisture and percent oil content in whole seeds is possible with pulsed NMR by the spin-echo method. In addition, multiple components of the oil can be detected and quantitated by T2 analysis from the Carr-Purcell-Meiboom-Gill pulse sequence. The instrument is easy to calibrate with whole oilseeds, and the calibration can be checked periodically with the same seeds because the measurement is nondestructive. Pulsed NMR provides a rapid alternative to the long, laborious, traditional methods of analysis and offers substantial long-term savings of both time and money. Minimal operator training is required once the technique has been established for routine use. Presented at the 84th AOCS Annual Meeting & Expo, April 27, 1993, Anaheim, California.     

Petrophysical characterization of coals by low-field nuclear magnetic resonance (NMR)

Nuclear magnetic resonance (NMR) has been widely used in petrophysical characterization of sandstones and carbonates, but little attention has been paid in the use of this technique to study petrophysical properties of coals, which is essential for evaluating coalbed methane reservoir. In this study, two sets of NMR experiments were designed to study the pore types, pore structures, porosity and permeability of coals. Results show that NMR transverse relaxation (T₂) distributions strongly relate to the coal pore structure and coal rank. Three T₂ spectrum peaks identified by the relaxation time at 0.5-2.5 ms, 20-50 ms and >100 ms correspond to pores of <0.1 μm, >0.1 μm and cleats, respectively, which is consistent with results from computed tomography scan and mercury intrusion porosimetry. Based on calculated producible and irreducible porosities through a T₂ cutoff time method, we propose a new NMR-based permeability model that better estimates the permeability of coals. In combination with mercury intrusion porosimetry, we also propose a NMR-based pore structure model that efficiently estimates the pore size distribution of coals. The new experiments and modeling prove the applicability of NMR in petrophysical characterization of intact coal samples, which has potential applications for NMR well logging in coalbed methane exploration.     

Selective multi-component diffusion measurement in zeolites by pulsed field gradient NMR

The potential of pulsed field gradient (PFG) NMR for selective diffusion measurement in multi-component liquids is far from being fulfilled in multi-component diffusion studies with zeolites. We present two recent developments in PFG NMR instrumentation, which will significantly improve the measuring conditions for multi-component diffusion in zeolites and other nanoporous materials. They include options for an enhancement of the sensitivity with respect to smaller displacements by a novel principle of field gradient pulse matching and with respect to selectivity between different components by combining PFG NMR with magic angle spinning (MAS) NMR with a microimaging gradient system. The potentials and limitations of the two options are demonstrated by the first results of selective PFG NMR self-diffusion measurements with zeolitic adsorbate–adsorbent systems containing as much as four different species of guest molecules.     

High-Resolution 1H Solid-State NMR Spectroscopy Using Windowed LG4 Homonuclear Dipolar Decoupling

We investigate the optimal implementation of windowed LG4 decoupling for the direct acquisition of high-resolution ¹H solid-state NMR spectra in the moderate magic-angle spinning regime (ω_r<2π × 35 kHz). We determine how the optimal value of the azimuth of the LG rotation axis, α, is affected by the choice of windowing parameters. We find that for both the windowless and windowed implementation of LG4, the optimal value of α is that for which the chemical-shift scaling factor is approximately 0.43. We then provide an analytical expression for estimating the chemical-shift scaling factor as a function of both α and the windowed decoupling parameters, which allows the optimal value of α to be easily determined for any implementation of LG4. We also introduce a simple and general method for improving the performance of any phase-modulated homonuclear dipolar decoupling sequence by compensating for pulse imperfection errors that accumulate in windowed spectra due to the repeated switching of the RF irradiation. This method involves the introduction of short (<0.5 µs) compensation pulses at the start and end of each decoupling pulse, the duration and phase of which are chosen to cancel the effects of the amplitude and phase transients that arise as a result of the RF switching. We demonstrate how this method can be implemented for homonuclear dipolar decoupling sequences such as wPMLG and wLG4 to reduce the chemical-shift scaling factor distortions generated by phase transients such that high-quality, high-resolution ¹H NMR spectra can be acquired at arbitrary RF offsets.