共查询到20条相似文献,搜索用时 93 毫秒
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为实现低频、小尺寸水下声源,利用具有大应变、快速响应和高能量密度等优势的NiMnGa合金为驱动元件设计了水声换能器。基于NiMnGa合金变形原理,建立了NiMnGa纵振式换能器物理模型,推导了等效电路。通过有限元法,实现了NiMnGa纵振式换能器电磁-机械-声的多物理场耦合仿真,用于预测换能器的水下声学性能。制作了小型NiMnGa纵振式换能器样机,并在水中测试了500~800 Hz频带内的声源级。实验结果表明,换能器样机辐射面直径为8 mm,水中谐振频率为700 Hz,最大声源级为115.5 dB。 相似文献
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针对深水、低频、宽带换能器的技术需求,结合Janus-Helmholtz换能器的结构特点和铁镓单晶材料低场应变大及机械强度高的特性,提出了铁镓单晶Janus-Helmholtz换能器设计方案。采用永磁偏磁场和环形闭合磁路,建立了一系列铁镓单晶磁致伸缩换能器理论分析模型,包括对磁致伸缩材料参数进行线性化处理,设计了换能器最佳工作点,结合静态磁场和动态磁场分布情况分段细化换能器驱动等效参数,以及利用全阻抗模型通过电感损耗等效计算换能器静态阻抗,然后通过二维有限元分析等效模型,优化分析了换能器的结构参数与电声性能。最后制作了换能器样机,并进行了测试与分析。对比仿真和测试结果表明:全阻抗模型得到的阻抗曲线与样机测试结果相一致,有限元等效模型计算的发送电流响应与样机测试结果良好吻合。换能器样机水中谐振基频为1000 Hz,谐振频率下发送电流响应176.4 dB;在875~2300 Hz频率范围内,发送电流响应起伏不大于6 dB;增加驱动电流有效值到16.2 A,最大声源级可以达到196.2 dB。 相似文献
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研究了一种将多个椭圆弯张壳体在短轴方向进行机械叠合的超低频弯张换能器,每个弯张壳体采用超磁致伸缩材料进行驱动。推导了多个叠合壳体的等效电路,利用支路阻抗方法得到了换能器频率和阻抗的方程表达式。针对多个壳体叠合的结构复杂性,采用有限元方法计算并分析了叠合壳体换能器的多个结构点的振动位移分布,通过平动位移分布设计了活塞辐射面的结构参数。将有限元方法计算的换能器在空气中和水中的谐振频率与等效电路法计算的结果进行了对比,符合较好。研制了6个壳体叠合的超低频弯张换能器样机,换能器外形尺寸为Φ230×630 mm,重量为39 kg。换能器经湖上试验,水中谐振频率130 Hz,最大发送电流响应161.1 dB,最大发射声源级为180.4 dB,实现了超低频、小尺寸的发射能力。 相似文献
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高性能环境友好型无铅压电陶瓷及其应用是当前压电材料研究的热点之一,为了探究其在水声换能器领域的应用潜力,该文对铌酸钾钠基无铅压电陶瓷和锆钛酸铅压电陶瓷纵振式换能器进行了对比研究。依据仿真结果优化结构尺寸,制作了两种换能器样机并测试了其在空气中和水中的电声性能。测试结果表明,铌酸钾钠基无铅压电陶瓷换能器的谐振频率为35kHz,最大发送电压响应为 151dB,声源级可达 190dB,在 26kHz~67kHz 的频率范围内发送电压响应的起伏不超过±4.5dB,谐振频率处-3dB 的指向性开角约为 76°。该无铅压电陶瓷换能器具有和锆钛酸铅压电陶瓷换能器相当的发射性能,有望推动无铅压电材料在水声换能器领域的应用进程。 相似文献
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多谐振宽带Janus-Ring换能器 总被引:1,自引:0,他引:1
提出了一种多谐振宽带Janus-Ring换能器,两个一定距离的压电圆环换能器(Ring换能器)嵌套在双面纵振Janus换能器的两端,Ring换能器的径向振动、Janus换能器的纵振动与它们中间形成的Helmholtz液腔振动相耦合,可大大拓展换能器的工作带宽。使用有限元方法设计并研制了Janus-Ring换能器样机,经测试在1.8~8.0 kHz范围内,样机最大发射电压响应144 dB,起伏小于6 dB。相比传统的Janus-Helmholtz换能器,Janus-Ring换能器有效拓展了工作频带,增大了发射电压响应,减小了频带内的发射电压响应起伏。 相似文献
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建立了弯曲圆盘换能器镜像虚源等效模型,利用脉动球源互作用原理对弯曲圆盘与其镜像虚源的互辐射作用进行理论分析,给出了互辐射阻抗及系统谐振频率的数学表达。提出了虚源互作用的低频换能器设计思想,将刚性反射板引入弯曲圆盘换能器临近辐射面的声场中,通过理论分析、有限元模拟和样机实验研究了低频换能器谐振频率与主要结构参数之间的关系。结果表明,弯曲圆盘与镜像虚源间的互辐射作用可以有效降低换能器的谐振频率,当反射板直径与弯曲圆盘辐射面直径相当时,谐振频率可降低至其自身谐振频率的50%以下;当反射板直径为弯曲圆盘辐射面直径2倍时,谐振频率可降低至37%。 相似文献
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A multi-conjugate adaptive optics (MCAO) can offer a possibility of widening field of view (FOV) characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle's expressions of two deformable mirrors (DMs) MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance. 相似文献
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Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use. 相似文献
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A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands. 相似文献
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40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm. 相似文献
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Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser. 相似文献
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Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored. 相似文献
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Xin Kang 《中国光学快报(英文版)》2008,6(2)
An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography. 相似文献
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The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films. 相似文献
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References: 《声学学报:英文版》2008,27(1):85-96
Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation. 相似文献