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用甲苯-2,4-二异氰酸酯(2,4-TDI)、聚醚二醇(PPO)和3,3’-二氯-4,4’-二氨基二苯基甲烷(MOCA)等原料合成了聚氨酯弹性体,在脉冲声管中测试了合成试样的声压反射系数和吸声系数,研究了合成工艺参数对其水下声学性能的影响。测试结果表明,TDI-PPO-MOCA合成型聚氨酯弹性体是一种良好的水下吸声材料,其吸声性能受到固化温度,扩链剂含量等参数的影响。加入填料和改变其结构可以进一步改善聚氨酯弹性体的水下声学性能,因此合理地设计实验工艺参数,可以得到水下声学性能更佳的聚氨酯弹性体。为工业生产提供了理论参考。 相似文献
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混浊海水的声吸收和声散射特性对水声探测设备工作性能的影响较大。通过经验公式仿真分析了温度、盐度和压强对低频段、低悬浮泥沙颗粒浓度混浊海水声吸收的影响。结果表明:温度和盐度对混浊海水声吸收的影响较大,而压强对混浊海水声吸收的影响可以忽略。构建并研制了一套混浊海水声吸收特性测量系统,实验研究了温度对混浊海水声吸收的影响,声吸收系数随温度的变化规律与仿真结果吻合较好。此研究成果可对混浊海水中的声传播建模、声纳探测系统设计及声纳性能的评估等提供一定参考。 相似文献
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声波导管的设计是影响声学信号信噪比的关键因素,导管内径越大、长度越短,越利于声波传输,但同时对声学共鸣腔产生更大的扰动。提出了采用变径声波导管降低声波的能量损耗和扰动方法,建立了变径声波导管的衰减和扰动模型,对比分析声学信号在不同尺寸声波导管内的能量衰减和导管对圆柱轴向非缔合声学共振频率和半宽的扰动,获得了优化的导管尺寸,在声波传输能量损失较小的情况下对内长为80 mm圆柱腔体首个轴向非缔合声学共振频率产生的相对扰动在3×10-5以内,该声波导管的优化设计可为高温气体声学温度计的深入研究提供理论支持。 相似文献
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为更好地指导黄麻纤维毡的产品设计与应用,开展基于JCA吸声模型的黄麻纤维毡声学有限元模型构建与验证研究。利用阻抗管测取黄麻纤维毡吸声系数,并辨识出用JCA吸声模型表征的黄麻纤维毡相关物理特征参数,基于所建立黄麻纤维毡声学有限元模型获取其吸声系数和声压、声能分布。研究表明,黄麻纤维毡在高频率范围内具有较好吸声性能,其在中、低频范围内的吸声系数随频率的增加近似呈线性增加;JCA吸声模型能较好描述黄麻纤维毡吸声性能;基于COMSOL软件所建立黄麻纤维毡声学有限元模型是可靠的,可用于植物纤维材料吸声性能的仿真分析。 相似文献
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Dynamic light scattering (photon correlation spectroscopy) has been applied to the determination of sound velocity and sound attenuation from the Brillouin component of the frequency spectrum scattered from a fluid sample transversed by a laser beam. In this paper the time-resolved determination of the Brillouin component is described. The measurement of the linewidth allows an accurate determination of the sound attenuation, while the central frequency is connected to the adiabatic sound velocity. Sound attenuation and sound velocity measurements are presented for the new refrigerant pentafluorethane (R125). The accuracy and possible systematic errors of this technique are discussed and compared to those obtained from other spectroscopic and acoustic techniques.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado. U.S.A. 相似文献
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以描述高分子材料粘弹行为的三元模型为出发点,以声波在高分子介质中的传播理论为依据,推导出了材料的水声声衰减能力与材料的动态力学性能参数包括损耗因子、松弛前的剪切模量、松弛后的剪切模量以及材料的密度和厚度之间的关系式。为实验验证所推导的关系式,设计合成了一系列阻尼性能不同的聚合物,分别测试了它们的动态力学性能和声衰减能力。用材料的动态力学性能参数计算得到的水声声衰减系数与实验测得的声衰减能力相符合。该数学模型为找出吸声系数与材料的动态力学性能之间的关系、指导水声材料设计奠定了基础。 相似文献
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The spectra and optical quantum state of guided acoustic wave Brillouin scattering in optical fibers are measured. Spectra from 0.95 to 2?GHz are obtained with amplitude resolution as sensitive as 0.01 shot noise unit. Quantum homodyne tomography measurements confirm the thermal quantum statistics of guided acoustic wave Brillouin scattering, which is useful knowledge in the context of experimental continuous-variable quantum key distribution. 相似文献
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Accuracy limitations on Brillouin lidar measurements of temperature and sound speed in the ocean 总被引:5,自引:0,他引:5
There are five mutually dependent variables relevant to Brillouin lidar measurements of temperature and sound speed in the ocean; they are (1) the Brillouin shift, (2) the sound speed, (3) the index of refraction, (4) the temperature, and (5) the salinity. We use three well-known relations to analyze rigorously the interdependence of these five variables. Clearly, a Brillouin shift measurement does not provide a stand-alone determination of temperature or sound speed; one more variable or one more relation must be known. The use of mean values of salinity that have been obtained by an analysis of a large set of historical in situ data is considered for this additional relation. 相似文献
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提出了一种利用有源控制改善吸声尖劈低频声吸收的方法。实验研究了正入射下,有源控制系统对吸声尖劈低频段吸声性能的补偿效果;比较了用有源控制分别对吸声尖劈正面和背面声阻抗与空气阻抗进行匹配两种误差策略,发现将误差传声器放置在尖劈前更合理,既能保证较好的低频吸声效果,又能占用较少的空间。实验结果表明,有源控制系统与20cm长的传统尖劈相结合所构成的总长约40cm的有源吸声尖劈,在100-1000Hz频率段,吸声系数可以达到0.98-1.00,和80cm长的传统尖劈的吸声性能相当。 相似文献
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敷设粘弹性材料的多层吸声模型阻抗匹配 总被引:1,自引:0,他引:1
研究敷设粘弹性材料多层结构的阻抗匹配方法对水下目标隐身具有重要意义。文中利用多层介质声传播理论,推导了简洁的任意多层结构模型声场特性计算公式,并结合粘弹性材料的动态特性,应用所推公式计算了水下敷设吸声材料多层模型的声场特性。借助数值分析方法,对多层结构模型各层材料特性阻抗与模型声学性能间的关系进行了仿真,探索利用模型各层特性阻抗设计模型阻抗匹配的方法。通过分析模型各层特性阻抗比例关系对模型声场特性的影响,得出其实现阻抗匹配的最优取值范围。研究结果对设计、选取吸声材料具有重要意义。 相似文献
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It is investigated how nuclear degrees of freedom of tunneling system (TS) inherent in amorphous solids influence its acoustic properties. It was shown in our previous papers that below 10 mK nuclear quadrupole interaction breaks down the coherent tunneling. This phenomenon results in appearance of the quasi-gap in the distribution function for the tunneling amplitude splitting. The quasi-gap is responsible for the plateau in the temperature dependence of the real part of a dielectric permittivity or speed of sound. In this paper we are interested in ultrasonic absorption and thermal conductivity which are intimately connected. We demonstrate that there exists a temperature interval in a millikelvin region where the sound absorption behavior changes drastically from the behavior predicted by the standard tunneling model (STM). In particular, the sound absorption increases approximately by an order of magnitude. Since in the millikelvin region the heat transport is due to acoustic phonons, the thermal conductivity also should demonstrate a strong increase as compared to standard tunneling model. The application of a strong magnetic field is known to restore the coherent tunneling and the standard distribution for the tunneling splitting amplitude. Thus, one can expect that in a strong magnetic field the thermal conductivity should drop in the temperature interval where the coherent tunneling was initially destroyed. 相似文献
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Chuanyin Yang Jingcheng Shang Xinyi Zhang Rongjing Hu XingDao He 《Journal of Modern Optics》2018,65(8):970-977
In order to study the effect of gas pressure on spontaneous Rayleigh–Brillouin scattering spectrum and verify the validity of Tenti S6 model at pressures up to 8 atm, the spontaneous Rayleigh–Brillouin scattering experiment in nitrogen was performed for a wavelength of 532 nm at the constant room temperature of 296 K and a 90° scattering angle. By comparing the experimental spectrum with the theoretical spectrum, the normalized root mean square deviation was calculated and found less than 2.2%. It is verified that Tenti S6 model can be applied to the spontaneous Rayleigh–Brillion scattering of nitrogen under higher pressures. The results of the experimental data analysis demonstrate that pressure has more effect on Brillouin peak intensity and has negligible effect on Brillouin frequency shift, and pressure retrieval based on spontaneous Rayleigh–Brillouin scattering profile is a promising method for remote of pressure, such as harsh environment applications. Some factors that caused experiment deviations are also discussed. 相似文献
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对高温气冷堆堆芯温度的可靠测量是目前的技术难题之一。传统温度计依靠实验室标定的材料特性与温度的关系进行测温,然而,长期暴露在高温、高辐照环境中,其测温材料的性质会发生改变且得不到及时校准,温度传感器易发生漂移甚至失效。气体声学温度计通过测量单原子气体的声速可以直接获得热力学温度;由于气冷堆内氦气介质相对稳定,利用氦气声速获得温度具有较高的可靠性。针对实用氦气声学温度计开展了初步研究,基于圆柱声学共鸣法设计了实用声学温度计测试系统,采用声波导管声学传感器测量了488K至806K圆柱共鸣腔内氦气的声学共振频率,修正了热边界层和粘性边界层的影响;基于量子力学从头算得到的氦气声学维里状态方程,获得了热力学温度。对氦气共振频率的测量相对标准偏差小于0.07%,温度测量的信噪比可满足需求,声学温度计与热电偶测温结果差异小于1%。研究结果为未来持续开展极端环境下气体声学温度计的应用研究提供了支持。 相似文献
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