共查询到20条相似文献,搜索用时 109 毫秒
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有限大含多孔材料和空气层复合板结构隔声特性的研究尚不充分。该文旨在研究四边简支边界条件下复合板结构隔声特性。首先基于流体饱和多孔弹性介质的声传播理论计算了声波在多孔介质中的传播波数;继而采用四边简支边界条件下板结构的模态函数,利用模态叠加法和伽辽金法推导了复合板结构隔声系数理论模型,并数值求解复合板隔声量。将理论模型得到的四边简支复合板隔声量与实验结果对比,验证了理论模型的正确性。最后,详细讨论了边界条件、板结构尺寸和多孔材料厚度等主要参数对隔声特性的影响。结果表明:四边简支复合结构隔声特性曲线上“谷值”出现得较少,并且简支复合板隔声特性的第一个“吻合频率”比固支支撑复合板更靠近低频,当频率超过3000 Hz以后,简支和固支边界条件复合板结构隔声特性趋于一致。 相似文献
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基于高速列车减振降噪需求,本文应用Biot提出的多孔弹性介质声传播理论,采用传递矩阵法理论推导了典型分层结构的隔声量计算公式,给出了空气层与多孔材料对分层复合结构隔声特性的影响。将传递矩阵与遗传算法相结合,对特定中低频段内的复合结构隔声特性进行了优化。研究结果表明:空气层和多孔材料有助于分层复合结构隔声量的提高,特别是空气层对低频隔声有很好的促进作用,另外空气层与多孔材料的分配情况也影响着隔声效果。含有空气层的复合结构在提高隔声量的同时降低了结构的总体重量,实现了高速列车隔声材料低能耗和轻量化的设计目标。 相似文献
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为使用混响法快捷地测量水下结构物的辐射噪声,需基于港口或海岸建造海上混响水池。针对内外都是水情况下的海上混响水池壁面隔声问题,设计了一种带梁空气夹层板水下隔声结构,通过仿真比较了不同参数的空气夹层板的隔声性能。为评价声波无规入射情况下水下大尺寸隔声结构隔声性能,提出了一种混响评价方法,通过隔声实验比较了混响法与脉冲法的不同。结果表明:带梁空气夹层板的水下隔声性能优异,声波无规入射情况下,面板厚度0.015 m、空气层厚度0.020 m的带梁空气夹层板在2~10 kHz频段插入损失大于20 dB;混响法可以有效评价大尺寸水下隔声结构的平均隔声性能,其反映的声波无规入射的平均隔声性能更接近于实际应用情况。 相似文献
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《应用声学》1986,5(4):44-46,33
19 GBJ 75-84建筑隔声测量规范 本规范为了统一实验室和现场对建筑物和建筑构件的空气声和撞击声隔声测匿,规定了测量方法和测量条件,使所测得的同一建筑物或建筑构件(包括墙、楼板、门和窗等)的隔声性能尽可能地接近,具备相互可比的统一基础,以便于建筑隔声的设计.编制中参考了国际标准ISO 140/1-8-1978 《声学——建筑物和建筑构件的隔声测量》。本规范共分六章为:总则、建筑构件空气声隔声的实验室测量、建筑物内两室之间空气声隔声的观场测量、外墙和外墙构件空气声隔声的现场测量、楼板撞击声隔声的实验室测量和楼板撞击声隔声的现场测量,及七个附录为:名词解释、测 相似文献
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Surface thermal lens (STL) signal produced by a cw
modulated top-hat beam excitation is detected by an obliquely-incident probe
beam. The dependence of the STL amplitude on the incident angle θ of the
probe beam is experimentally investigated. The STL amplitude as a function
of the detection distance is measured at different angles of incidence. The
results show that the maximum STL amplitude and the optimum detection
distance, where the maximum STL amplitude is obtained, decrease by
cosθ as the incident angle increases. These experimental dependences are well
explained by a simple theoretical model. 相似文献
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Kaoru Ikeda 《Letters in Mathematical Physics》1987,14(4):321-328
A supersymmetric extension of the Toda lattice (STL) hierarchy is introduced. Explicit representation of solutions of the STL hierarchy is given by means of the Riemann-Hilbert decomposition. The STL hierarchy connected with the infinite-dimensional Lie super algebra osp (/) is studied. 相似文献
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Rohollah Fallah Madvari Mohammad Reza Monazzam Mohsen Niknam Sharak Mohsen Mosa Farkhani 《声与振动》2020,54(2):127-137
Honeycomb structures have recently, replaced with conventional homogeneous materials. Given the fact that sandwich panels containing a honeycomb
core are able to adjust geometric parameters, including internal angles, they are
suitable for acoustic control applications. The main objective of this study was
to obtain a transmission loss curve in a specific honeycomb frequency range along
with same overall dimensions and weight. In this study, a finite element model
(FEM) in ABAQUS software was used to simulate honeycomb panels, evaluate
resonant frequencies, and for acoustic analysis. This model was used to obtain
acoustic pressure and then to calculate the sound transmission loss (STL) in
MATLAB software. Vibration and acoustic analysis of panels were performed
in the frequency range of 1 to 1000 Hz. The models analyzed in this design
includes 14-single row-honeycomb designs with angles of −45°, −30°, −15°,
0°, +15°, +30°, +45°. The results showed that a-single row and −45°cell angle
honeycomb panel in the frequency range of 1 to 1000 Hz had the highest STL
as well as the highest number of frequency modes (90 mods). Furthermore, the
panel had the highest STL regarding the area under the STL curve (dB∙Hz).
The panels containing more frequency mods, have a higher transmission loss.
Moreover, the sound transmission loss is more sensitive to the cell angle variable
(θ). In other studies, the STL was more sensitive to the number of honeycomb
cells in the horizontal and vertical directions, as well as the angle of cells. 相似文献
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In this study, a new prediction method is suggested for sound transmission loss (STL) of multilayered panels of infinite extent. Conventional methods such as random or field incidence approach often given significant discrepancies in predicting STL of multilayered panels when compared with the experiments. In this paper, appropriate directional distributions of incident energy to predict the STL of multilayered panels are proposed. In order to find a weighting function to represent the directional distribution of incident energy on the wall in a reverberation chamber, numerical simulations by using a ray-tracing technique are carried out. Simulation results reveal that the directional distribution can be approximately expressed by the Gaussian distribution function in terms of the angle of incidence. The Gaussian function is applied to predict the STL of various multilayered panel configurations as well as single panels. The compared results between the measurement and the prediction show good agreements, which validate the proposed Gaussian function approach. 相似文献
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Influence of Surface Transition Layers on Phase Transformation and Pyroelectric Properties of Ferroelectric Thin Film 下载免费PDF全文
Taking into account surface transition layers (STLs), we study the phase transformation and pyroelectric properties of ferroelectric thin films by employing the transverse Ising model (TIM) in the framework of the mean field approximation. The distribution functions representing the intra-layer and inter-layer couplings between the two nearest neighbour pseudo-spins are introduced to characterize STLs. Compared with the results obtained by the traditional treatments for the thin films using only the single surface transition layer (SSL), it is shown that the STL model reflects a more realistic and comprehensive situation of films. The effects of various parameters on the phase transformation properties have shown that STL can make the Curie temperature of the film higher or lower than that of the corresponding Sulk material, and the thickness of STL is a key factor influencing the film properties. For a film with definite thickness, there exists a critical STL thickness at which ferroelectricity will disappear when the intra-layer and inter-layer interactions are weak. 相似文献
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A combined laser calorimetry (LC) and surface thermal lens (STL) technique with a continuous-wave (cw) modulated excitation
is developed for characterizing the absorption properties of optical coatings. LC and STL signals are simultaneously obtained
with highly reflective coating samples irradiated at 1064 nm. With a modulated irradiation power of 2.6 W, the limits of absorptance
detection for the LC and STL signals are approximately 1.2×10-6 and 0.5×10-6, respectively. The influences of different excitation parameters (modulation frequency, excitation-beam power and irradiation
time) on the absorptance measurements are experimentally analyzed. The applicability of the combined LC and STL technique
to the investigation of the laser-induced absorption changes of optical coatings in an absolute absorptance scale is demonstrated.
PACS 42.87.-d; 78.20.-e 相似文献
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Several prediction methods have recently been developed for systematically studying the effects of general boundary conditions on the sound transmission loss (STL) of plate-like structures. But corresponding experimental validation studies remain scarce owing to the difficulty of obtaining accurate boundary conditions for practical structures. This paper presents a convincing experiment conducted on a baffled plate system to validate the STL prediction model in a previous paper by Yu et al. [Noise Control Eng. J. 58(2), 187-200, 2010]. A method is proposed to determine the boundary conditions of this system, and experimental STL compares well with the predictions based on the identified boundary condition. 相似文献
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给出了连续调制激励光照射下光学薄膜样品表面热变形场的理论分布,并由此定义了表面热透镜(STL)信号。根据表面热透镜理论实验测量了一个BK7基底高反膜样品的形变,给出了表面热透镜信号随调制频率的变化曲线。实验结果表明:在采用的STL实验构型中,探测了最小1.985 nm的直流形变,对应不调制时的形变为3.97 nm,相应的形变探测灵敏度达到了10 pm量级;直流形变与功率成线性关系;交流表面热透镜信号随着频率增大而减小,在高频端近似成线性减小。 相似文献