星载感应式空心磁芯磁传感器的研究

优化设计了频率带宽为1 Hz~10 k Hz的空心磁芯感应式磁传感器。首先提出空心结构的磁芯,分析空心磁芯的退磁因数和有效磁导率,并仿真、实测空心磁芯感应线圈的磁通,得出一定壁厚的空心磁芯感应线圈的磁通可以等于相同长径比棒状磁芯感应线圈的磁通。然后分析空心磁芯感应式磁传感器的灵敏度与噪声,通过数学算法优化噪声公式达到要求的噪声指标和较低的重量。为验证理论分析,设计空心磁芯感应式磁传感器,在屏蔽室对空心磁芯感应式磁传感器的性能进行测试,频率高于400 Hz时灵敏度为0.73 V/n T。100 Hz时噪声为0.06 p T/Hz1/2,总重量为80 g。实测的空心磁芯感应式磁传感器的灵敏度与噪声和理论分析一致。空心磁芯感应式磁传感器与THEMIS相比具有噪声低、重量轻的优点,能够满足空间电磁探测的实用条件。     

适用于瞬变电磁勘探的低温超导磁传感器

低温超导量子干涉器件(SQUID)直接测量磁场,噪声低(fT,10-15T,量级)、带宽大、低频响应特性好,可提升瞬变电磁法(TEM)晚期接收信号质量,实现大深度探测。基于欠阻尼低温SQUID和单片读出技术构建了高性能低温SQUID传感器,研究了SQUID和读出电路的噪声匹配技术,传感器本底噪声水平7 fT/√Hz@1kH z,带宽2 MHz,摆率1.5 nT·μs-1。在长春市烧锅镇和上海市横沙岛分别开展了低温SQUID瞬变电磁系统与空心线圈瞬变电磁系统的对比验证,在烧锅镇,低温SQUID成功记录了80 ms衰减曲线(空心线圈20 ms),计算的视电阻率与已有地质资料一致。横沙岛实验中,SQUID衰减曲线可达300 ms(空心线圈:100 ms),进一步验证了SQUID对地球深部信息的探测能力。     

用于闪电磁场测量的感应式传感器

针对闪电电磁脉冲频谱较宽的特点,设计一种用于闪电磁场测量的宽频带感应式传感器。采用空心线圈作为接收传感器,提高传感器工作带宽;建立传感器等效噪声模型,对传感器灵敏度和噪声水平进行了理论分析和仿真,研制了低噪声检测电路,设计制作了一款低噪声、宽频带、感应式磁场传感器。采用亥姆赫兹线圈对传感器进行了标定,并在磁屏蔽室内进行了噪声水平测试,测试结果表明,传感器带宽为1～100 kHz,在10 kHz处噪声为20 f T/(Hz)~(1/2),在100 kHz处噪声为4 f T/(Hz)~(1/2),测试性能与理论分析一致。     

用于感应式磁传感器低噪声前置放大器的研制

感应式磁传感器是频率域电磁法(FEM)中使用最广泛的磁传感器,通常由感应线圈和前置放大器组成,其中前置放大电路是影响磁感应式磁传感器性能指标的核心因素。为了增加感应式磁传感器探测深度和微弱磁场信号的能力,要求前置放大电路具有宽频带和低噪声等性能。基于磁通负反馈的原理设计并研制了斩波前置放大器,有效抑制了感应线圈的输出噪声,使感应线圈谐振频率两侧具有平坦的幅频特性曲线,拓宽了感应式传感器的响应频带。在屏蔽室内对斩波前置放大器的性能指标进行了测试,其频带范围为0.001Hz~10 k Hz,输入噪声为槡3.75 n V/Hz,为感应式磁传感器在实际中的应用提供了性能保障。     

典型反馈电路的噪声特性分析

实际放大电路中,常常采用反馈来展宽带宽,稳定工作点,减小非线性失真,提高或降低输入阻抗等。但是,采用了反馈会使放大器系统的噪声系数变坏,如果设计合理,能使变坏的程度减小到忽略不计。现重点研究电压并联负反馈电路、电流串联负反馈电路、电流并联负反馈电路的噪声特性。针对各个反馈电路,先推导电路总增益Kv,接着计算各噪声源对输出噪声的贡献,得到总输出噪声E2no,然后转化成等效输入噪声E2ni,最后根据等效噪声模型求得最佳源电阻Ro和最佳噪声系数Fo。通过对推导出的公式进行分析可得,对于典型反馈电路,当满足一定条件时,最佳源电阻、最佳噪声系数和没有反馈的情况相同,即反馈对噪声的影响可忽略不计。     

地空频率域电磁系统空心线圈传感器优化设计

针对地空频率域电磁法(GAFEM)的大范围、快速探测需求,研制了一种适用于GAFEM的高灵敏度、低噪声、低质量的空心线圈传感器(ACS)。首先,根据一维正演计算了收发距10 km处的等效面积归一化响应电压,进而确定传感器灵敏度和噪声水平的指标需求;然后,建立ACS的电路等效模型,并对电路噪声进行分析计算,引进拉格朗日乘子法来优化ACS的设计参数以达到灵敏度、噪声和质量指标要求;最后,根据优化参数设计空心线圈传感器,在电磁屏蔽室对其进行测试,结果显示在噪声参考频率(100 Hz)处,优化传感器噪声为0.09 pT/Hz~(1/2),灵敏度为14.7 mV/nT,总质量为1.25 kg。野外实验表明,地面同一测点处,本文优化ACS测量的磁场幅度与AMTC-30磁棒的测量值一致;且在空中飞行中,该ACS能获得有效磁场信号。     

电流参数对基波正交磁通门传感器灵敏度的影响

为了研究激励电流参数对基波正交磁通门灵敏度的影响,利用钴基合金磁芯和单线圈构建基波正交磁通门。实验结果表明,增加激励电流振幅(Iac),会改善基波正交磁通门的灵敏度;然而,随着激励电流偏置(Idc)增加,基波正交磁通门灵敏度下降;激励频率对灵敏度影响相对复杂。随着频率的增加,灵敏度呈现先增加后降低的趋势,存在一个最佳频率。该频率大小近似等于基波正交磁通门线圈等效LC电路的谐振频率(fo)。基于旋转磁化理论和等效电路模型对上述实验结果进行了分析。该项研究对优化传感器灵敏度,提高正交磁通门信噪比具有指导作用。     

地空瞬变电磁三分量空芯线圈传感器设计

瞬变电磁法(TEM)作为地球物理非地震探勘的主要电磁方法之一,广泛应用于油气、矿产等地下资源探测,采集数据时一般使用线圈传感器。针对现有的TEM单分量线圈传感器存在的反应异常体信息不全面和数据易丢失的问题,本文设计了一个三分量TEM线圈传感器。通过分析传感器灵敏度与线圈结构参数的关系,对线圈结构、匝数等进行了设计;通过分析TEM磁场传感器频率响应特点,采用欠阻尼匹配模式减小信号失真;通过分析磁传感器各类噪声源分布,选定了适宜的放大器,降低了本底噪声。所研制的三分量TEM感应式磁场传感器重量控制在3.2 kg,工作频段为10 mHz-10 kHz,X分量和Y分量的本底噪声保持在■,灵敏度分别为8.4 nT/s和9.8 nT/s,垂直分量的本底噪声达到■,灵敏度为18.5 nT/s。与现有的单分量TEM接收磁场传感器相比,本设计实现了三个分量的信号采集,且在体积和总重量增大不多的基础上,降低了传感器的灵敏度和本底噪声,提高了信号的信噪比。     

基于低噪声运放的传感器前置放大器设计

随着低噪声运放技术的发展，基于低噪声运放的传感器前置放大器将得到越来越广泛的应用。与分立元件的传感器前置放大器设计相比，基于低噪声运放的传感器前置放大器设计面临一些新的挑战。探讨了基于低噪声运放的传感器前置放大器设计中的若干技术问题，包括低噪声运放的选择、同相放大与反相放大的选择、负反馈对噪声性能的影响、噪声匹配、外围电阻选择及合理布局布线。     

一种时域电磁法剩余油探测装置的参数研究

提出了一种非接触式剩余油探测装置的参数设计方法.通过两种观测装置在均匀介质中时域电磁响应特性的对比,确定了最佳观测装置结构.分析了发射信号脉冲宽度和关断时间对响应信号的影响.研究了发射线圈电性与实际发射波形关断时间的关系,提出了发射线圈参数的选择原则.讨论了斜阶跃波激励下接收线圈的过渡过程,并给出了匹配电阻和接收线圈分布电容的估算方法.根据分析结果最终设计了装置参数并进行了室内实验.结果表明,不论从响应信号幅度还是延迟时间,均可对不同电导率的介质进行有效识别,为今后时间域电磁法剩余油探测的井下实验奠定了基础.     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.