细管道内表面光电检测方法研究

管道是气体和液体传输的重要手段,管道内表面的检测对于工业和国防中管道泄漏事故的预防,减少环境污染和经济损失非常重要。随着电子和半导体技术的发展,光电器件逐步趋于小型化。介绍了基于激光阵列、PSD光电检测、光环截面以及结构光检测等光电检测方法的测量原理和系统构成,并在此基础上对不同光电检测方法的优缺点进行了分析和比较。分析结果表明：光电检测技术适用于管道内表面检测;并朝着快速识别缺陷、管道内表面瑕疵的精确三维测量以及三维图像直观显示管壁缺陷的方向发展。     

小型绝对式光电编码器误码自动检测系统

在批量生产光电编码器时,对光电编码器是否存在误码进行检测是一个重要的环节。现有的检测方法采用二进制灯排手动转动编码器用肉眼进行观测,存在手动检测慢、肉眼观测误差较大、检测结果受转动速度影响等缺点。在大批量生产的光电编码器,采用传统方法进行误码检测费时费力。为解决编码器生产及使用过程中对光电编码器的自动误差检测,本文设计了小型光电编码器误码自动检测系统。首先,在参照大量光电编码器生产经验的基础上,分析了编码器误码产生的主要原因;然后,提出了基于微分算法实现对光电编码器是否存在误码进行判断的误码自动检测方法;最后,以FPGA为主控芯片,设计了小型光电编码器自动误码检测系统。该系统能够实现对光电编码器的高速数据采集、数据处理与误码判断,并将误码判断结果通过LCD液晶显示。同时,可以根据需要将数据传输到计算机中作进一步分析。检测实验表明:本文所设计的误码检测系统成功实现了对15位串/并口光电编码器在高速和低速下进行数据采集及误码判断。系统可用于批量生产下光电编码器的误码自动检测,减少了人工操作,提高了自动化程度。系统具有智能便捷,移动性强,适用于实验室及各种工作场合下的误码检测等优点,检测速度较以往检测方法提高了3~5倍。     

线偏振光旋光角检测定位准确度的研究

在线偏振光旋光实验中,对视觉检测定位进行了理论分析和实验研究,通过对各种条件下检测准确度的分析和实验验证,得出了最优准确度检测方法.同时,对使用光电技术进行检测定位与视觉检测差异进行了分析研究,指出了提高检测准确度的方法和途径.     

新型动态多光学目标模拟装置研究

介绍了多光学系统观测平台的检测方法现状,列举了现有检测用光电靶标的局限性。叙述了动态光学靶标的功能原理,提出一种新的检测设备,即双光源动态光电目标模拟装置的设计方案。并对其进行了理论分析和可行性论证。着重对坐标变换过程进行了演算,证明基准转换的正确性。结合理论基础和现有的工程设计经验,论述了该新型双光源动态光电目标模拟装置的工程化设计方案。最后对该设计方案的最终精度进行了分析,验证了该设计方案可以满足多光学系统观测平台的综合检测和标定需求。     

基于运动控制技术的编码器自动检测系统

为了改进编码器误差检测方法,提高检测效率,基于对光电轴角编码器误差检测现状的分析,设计了一种编码器误差自动检测系统。介绍了自动检测系统的工作原理,系统的硬件设计和软件设计。利用运动和全闭环控制技术,以24位高精度增量式光电轴角编码器为反馈元件,该自动检测系统可自动完成对编码器测试点的定位、数据获取和误差数据分析,定位精度为2″,可以检测18位以下各类光电轴角编码器的误差,检测效率是标准检测装置的6倍。该实验结果验证了方案的可行性。     

光电经纬仪作用距离的室内检测模型

针对光电经纬仪室内检测作用距离问题,提出光电经纬仪作用距离指标的室内检测模型。从对目标进行跟踪捕获的实际工作过程中的4个边界点出发,检测光电经纬仪的目标对比度指标,并在此基础上结合天气条件参数对作用距离进行估算。由实验结果可知,该光电经纬仪目标对比度范围为5%~13%;在北纬45,7月,白天的无云无雨天气条件下,作用距离为30.105 km,与实际外场跟飞结果相比,误差约为1 km。该方法适用于跟踪天空背景下的目标时的作用距离估算。     

光电编码器故障诊断技术研究现状与展望

光电编码器是以高精度计量光栅为检测元件的高精度数字化测角设备,在当代自动化领域应用广泛。为深入研究光电编码器故障诊断方法,提高诊断效率,本文首先介绍了光电编码器分类、工作原理;其次,介绍了国内外光电编码器故障诊断关键技术现状,对具有代表性的故障诊断技术进行了分析与比较,总结了各诊断方法的优缺点;最后,对光电编码器诊断技术进行了展望,揭示了其诊断方法向自动化、便携化、动态检测、多技术融合和故障预测方向发展的趋势。     

基于小波双尺度分析的光电小目标检测

 空间光电图像中的小目标检测可视为对目标信号的奇异值检测问题,而基于小波变换的多尺度分析是信号奇异值检测的重要方法。文中阐述了现有小波多尺度分析方法进行小目标检测的原理,并针对其运用中存在的模极大值线难以搜索以及目标定位精度不高的问题,利用小波函数的对称性及空间小目标信号近似对称的特点,提出了一种通过分析小波大小两个尺度来直接对光电小目标进行检测的方法,并对该方法进行了实现与仿真。仿真结果表明,该方法可以有效提高小目标的检测速度和定位精度。     

高精度表面等离子体共振传感中的信号处理方法

表面等离子体共振传感技术是一种简单可行并广为应用的光学高精度表面检测方法,能够对折射率的变化(10-8)进行检测。若要实现高灵敏度、高稳定性、高可靠性的检测,除了光电系统硬件外,信号的数据处理方法也是关键技术之一。运用合适的数据处理方法可有效地降低实验中的随机噪声以及系统不理想性所带来的影响,可大大提高测量精度、准确性和测量范围。从信号处理方法的角度,根据国内外近年来的研究成果,利用表面等离子体共振实现了在微量检测和薄膜分析时进行数据处理的算法。     

散射式能见度测量仪的动态特性研究

通过半导体激光照射采样气体,利用光电检测电路检测前向散射光强,并通过滤波电路、真值转换电路以及后置放大电路,最终将信号进行采样送入微处理器中处理。通过对信号处理电路的各个模块进行动态特性分析,从而找出对系统影响最大的模块部分并提出改进。结果表明,光电检测电路的动态特性对系统的影响最为显著,通过适当减小负载电阻,可有效改善电路的线性动态范围。     

合成双射流激励器振动噪声特性

合成双射流激励器工作噪声远低于合成射流激励器工作噪声, 但其噪声特性仍然限制了其应用于笔记本电脑、空调、冰箱等室内电子设备散热. 为降低合成双射流激励器整体噪声, 采用数值模拟的手段探究合成双射流激励器在不同边界条件下的振动噪声特性, 为合成双射流激励器降噪设计提供指导. 结果表明: 压电振子与壳体的振动共同影响着激励器振动噪声声压级大小; 夹持条件对振动噪声影响很大, 压电振子处于夹支条件时, 激励器的振动噪声声压级比压电振子处于简支时的激励器最大声压级低10 dB.      

骨导振子佩戴位置对重放声的影响*

骨导振子佩戴位置会影响骨传导声重放的性能,但已有研究还不够全面和完善。针对11名双耳听力正常的受试者,采取不同的骨导振子佩戴位置,对骨传导声重放在听力阈值、主观音质评价和语言清晰度3个方面进行了研究。实验结果表明不同的佩戴位置会影响骨传导声重放性能,髁骨位置在3个实验都表现最好,髁骨的听力阈值比乳突位置平均低8.7 dB,主观音质评价得分平均高乳突38.4分。该文的研究可为骨导振子佩戴位置的选择提供依据,并为声重放质量的改进提供参考。     

双层弹性支撑板的水下宽带隔声

为实现水下宽带隔声,提出了一种由弹性元件支撑两块刚性端板构成的双层弹性支撑板结构。采用弹簧振子振动分析法和声传播理论,建立了平面波入射的水下隔声理论模型,分析了结构参数对隔声量的影响规律,结果表明足够小的弹性元件单位面积弹性系数或足够大的端板单位面积质量都可以连续一致地提高隔声量.仿真分析了双层弹性支撑板的振动位移和声输入阻抗,比较了双层弹性支撑板与连续介质层的隔声特性,结果表明,降低弹性元件质量,有助于在低频段消除半波全透射现象.在同厚度、同质量、同静态压缩率条件下,双层弹性支撑板能更好的降低两侧流体的振动及声耦合,隔声频带更宽,带内一致性更好,隔声量更大.      

Responses of pigeon vestibular nerve fibers to sound and vibration with audiofrequencies

Single unit recordings were made from the nerve branch innervating the crista in the horizontal semicircular canal of a pigeon. The vestibular organ was either stimulated with sound through the ear canal or with a vibrator in contact with the membraneous ampulla roof. Units responding to sound or vibration showed tuning with a best frequency of approximately 0.7 kHz. The average low-frequency slope of the tuning curves is--16 dB/oct; the average high-frequency slope 20 dB/oct. The threshold amplitude for vibrator stimulation is 30 nm. This value comes close to the calculated threshold value for cupula deflection in the human semicircular canal.     

Diffraction of electromagnetic waves of optical range on a metallic nanovibrator

A solution of the two-dimensional integro-differential equation describing diffraction of electromagnetic waves on metallic nanovibrators and on nanocrystals coated by a metallic film was obtained. Copper and gold nanoantenna characteristics were studied theoretically in the optical range. It was noted that the dependence of the scattered field on frequency is of a resonant character and the resonant wavelengths of nanovibrators are larger than those of an ideally conducting vibrator of the same size.     

Induced field of an electromagnetic vibrator above a conducting screen placed in a microwave beam

The induced field of a cylindrical electromagnetic vibrator with spherically rounded ends is calculated. The vibrator is above a flat screen placed in a linearly polarized quasi-optical microwave beam. The plane of the screen is perpendicular to the Poynting vector of the radiation. The axis of the vibrator is aligned with the vector of the exciting field electrical component. In calculation, the length of the vibrator and the vibrator-screen distance were varied, while its diameter and the initial field were kept constant. It is found that the induced field of the vibrator with a length close to the half-wavelength of the field is maximal at the ends of the vibrator and the field strength resonantly depends on the length of the vibrator. The shortening of the “half-wavelength” vibrator that provides a maximal induced field is determined. The result of numerical simulation is to an extent intriguing. It is revealed that the induced field of a resonance half-wavelength vibrator rises considerably when the vibrator-screen distance becomes shorter than the quarter-wavelength of the field. The Q factor of an equivalent electromagnetic oscillating circuit characterizing the vibrator also grows, and the induced field more and more concentrates between the screen and the surface of the vibrator’s ends facing the screen. Full-scale experiments qualitatively support theoretical predictions. The results allow researchers to considerably extend the application area of vibrators as initiators of breakdown in high-pressure gases to ignite microwave discharges in quasi-optical beams with a low initial field.     

微穿孔介电弹性体薄膜的吸声性能试验分析*

针对普通薄膜型降噪结构的吸声性能较差和吸声带宽较窄的问题,本文设计了一种微穿孔的介电弹性体薄膜吸声结构。该结构由穿孔的介电弹性体薄膜与背腔组合而成,目的是拓宽介电弹性体薄膜低频率段的吸声带宽。针对微穿孔的介电弹性体薄膜吸声结构,从试验角度分析穿孔薄膜初始厚度、穿孔孔径及穿孔间距对结构吸声性能的影响。分析结果可知：通过适当增加薄膜的初始厚度,薄膜的整体吸声性能得到有效提升,最大可将319Hz吸声频带的吸声系数从0.2提升至0.7;减小薄膜的穿孔孔径能够有效拓宽穿孔薄膜的吸声频带,可使吸声系数0.4以上的吸声带宽由304Hz拓宽至432Hz;适当控制穿孔间距能够达到更好的吸声效果。     

Acoustoseismic wave fields generated by surface seismic vibrators

Results of experimental and theoretical studies of acoustoseismic wave fields generated by surface seismic vibrators are presented. In experiments with high-power seismic vibrators operating in a frequency range of 5–10 Hz, acoustic waves were recorded at distances up to 50 km from the source. The long-range sound propagation from seismic vibration sources was observed in a near-surface waveguide arising due to temperature inversion. The effect of the acoustoseismic induction, i.e., excitation of surface seismic waves by the acoustic wave arriving from the vibrator, was also detected. The results of mathematical modeling of the acoustoseismic field generation by an operating seismic vibrator are presented. They include the modeling of the radiation of a harmonic acoustic wave’s by the vibrator, its trapping by the near-surface waveguide, the long-range low-frequency acoustic wave propagation in the presence of the waveguide, and the induction of a surface seismic wave by the arriving harmonic acoustic wave. It is shown that a seismoacoustic wave propagating at the boundary between the elastic earth and the atmosphere is an analog of the Stonely wave that appears in the presence of a near-surface low-temperature layer in the atmosphere.     

氧化铟锡薄膜的磁感应热声分析

基于优良导体在磁场下的涡流效应理论和固体的热声效应理论,建立了氧化铟锡(ITO)导电薄膜磁-热-声效应的理论模型,推导了导电薄膜热致发声的温度振荡和输出声压表达式。对有基底的ITO导电膜进行了磁场下的热声理论计算和实验测试,结果表明：薄膜的温度振荡值随频率呈上升趋势,与电-热-声模型相比趋势相反;薄膜声压的理论值与实验值在频域内的变化趋势基本吻合,验证了理论模型的正确性。进而,根据磁-热-声的理论模型,分析了线圈相关参数对薄膜声压级的影响,结果表明：薄膜声压级随着线圈匝数的增加而增大,随着薄膜与线圈中心距离的增加而减小,随着线圈半径的增加而减小。文中的研究结果拓展了导电薄膜在扬声器等领域的应用。     

Estimation of absolute sound pressure in a small-sized sonochemical reactor

A small-sized sonochemical reactor in which the absolute value of the sound pressure amplitude can be estimated from the vibration velocity of the transducer was investigated. The sound pressure distribution in the reactor and the relationship between the vibration velocity and the sound pressure amplitude were derived through Helmholtz wave equation. The reactor consists of a bolt-clamped Langevin transducer and a rectangular cell with a tungsten reflector. A 3λ/4-standing-wave-field was generated in the reactor to simplify the sound pressure distribution. The sound pressure distribution was measured from the optical refractive index change of water using a laser interferometer. The experimental and theoretical results showed a good agreement in the absolute value of the sound pressure amplitude, and it was confirmed that the sound pressure in the sonochemical reactor can be estimated from the input current of the vibrator.