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71.
Single-crystal elasticity of the rhodochrosite at high pressure by Brillouin scattering spectroscopy
ABSTRACTThe sound velocity properties of single-crystal rhodochrosite (MnCO3) were determined up to 9.7?GPa at ambient temperature by Brillouin scattering spectroscopy. Six elastic constants were calculated by a genetic algorithm method using the Christoffel's equations at each pressure. The elastic constants increased linearly as a function of pressure and its pressure derivatives ?Cij/?P for C11, C33, C44, C12, C13, C14 were 5.86 (±0.36), 3.82 (±0.44), 2.06 (±0.39), 5.07 (±0.27), 5.34 (±0.44), 1.52 (±0.24), respectively. Based on the derived elastic constants of rhodochrosite, the aggregate adiabatic bulk and shear moduli (Ks and G) were calculated using the Voigt-Reuss-Hill averages and the linear fitting coefficients (?Ks/?P)T and (?G/?P)T were 5.05(±0.26) and 0.73(±0.05), respectively. The aggregate Vp of rhodochrosite increased clearly as a function of pressure and its pressure derivative ?Vp/?P was 7.99(±0.53)?×?10?2?km/(s?GPa), while the aggregate Vs increased slowly and ?Vs/?P was only 1.19(±0.12)?×?10?2?km/(s?GPa). The anisotropy factor for As of rhodochrosite increased from ~40% at 0.8?GPa to ~48% at 9.7?GPa, while Ap decreased from ~19% to ~16% at the corresponding pressure. 相似文献
72.
73.
基于可压缩流体力学基本理论, 通过边界积分方程, 采用不同表面压力模型, 求解空泡在计及可压缩性的涡流场中的运动规律; 通过表面离散及坐标变换, 采用Kirchhoff动边界积分方程, 将空泡表面视为运动变形边界, 作为直接噪声源, 获得涡流场中空泡运动产生的时域声压分布; 分析了涡流场参数对空泡运动规律及声辐射特性的影响. 研究结果表明: 计及流场可压缩性, 空泡的脉动幅度会随时间减弱, 辐射声压幅值随之减小; 空泡在涡流场中会发生延展、 颈缩、 撕裂, 并在撕裂后子空泡中形成射流; 当流场中的压力减小时, 空泡运动过程中的最大半径与撕裂前的最大长度逐渐增加, 且当流场中压力较小时, 空泡撕裂时形成的子空泡增多; 空泡辐射声压的指向性较弱, 撕裂会使辐射声压产生突变, 形成极大峰值; 随着涡通量的增大或空泡数的减小, 空泡脉动周期及其诱导的辐射声压波动周期随之延长, 辐射声压峰值逐渐滞后并减小. 本文结果旨在为涡流场中空泡运动规律及声辐射特性的相关研究提供参考.
关键词:
可压缩
涡流场
空泡
声辐射 相似文献
74.
I.IntroductionInordertocontroltheemissionofthestructurebornenoise,itisnecessarytostudythedifferentphysicalcharacteristicqualltitiesonrotationaldegreesoffreedombesidesthoseontranslationaldegreesoffreedom,duetothemulti-degreesoffreedomoftheemission.Amongthemthemomentmobilityisthemostimportalltone.Inrecentyears,adirectexcitationtechniqueforthemomenthasbeendevelopedbyacollaborattheresearchprojectbetweenShalltouUniversityandLiverpoolUniversity.Thernome11tmobilityisobtainedbyusingamomentactuatorwh… 相似文献
75.
I.IntroductionAerodyntalcnoiseofturbomaChinrynotoalythectstheenvironmentbutalsosometimesresultsinstructuredamage.Aeroacoustics,asaintewhsciPlineofacousticsandaerodynamics,isattractingmorandmoreatteDtionandresearch.TherearetwoimportalltcontentsonthenoiseproducingmechAnsmsinaeroacousticproblem.OneisaboutthesourcesofnoiseinturbomachinryGenetallytherearethreetyPesofsources:thickness,forceandturbulencestress,correspondingrespectivelyTomonopole,dipoleandquadruplesourcesThelatertwokindsofsourcesh… 相似文献
76.
In this paper, a novel method for Three dimensional active sound field cancellation is proposed. The optimum sound cancellations in different situations may be obtained. An array whose elements lie on a set of rings placed on the surface of a scattering object is considered as the device. It is quite possible to cancel the scattered sound field to any arbitrary level over either the whole space or a partial area of interest, as long as the number of the array elements is sufficient. 相似文献
77.
TIAN Jing 《声学学报:英文版》1996,(4)
I.IntroductionInlate198()'s,thestudiesonactivenoisecontrolhavebeengraduallyturnedfromtheductsandopenspacestothemorepracticaIenclosedsoundfields.SomespeciaIworkinaccordancewiththeactiveattenuationofcabinnoisehasstartedwiththeoreticalmechanisms,systemdesignandtransducerdevelopmellt.Intensivereflectionsandtheformedstandingwavedistributioni11al1enclosedsoundfieldarealwaysthemaindifficultiesforactivenoisecontrolinthesecases.Ontheotherhand,normalmoderesponseofthefieldalsoimplementsanewmethod,theap… 相似文献
78.
G. A. Martynov 《Theoretical and Mathematical Physics》2006,146(2):285-294
We study the propagation of small-amplitude acoustic waves in liquids and gases and use the hydrodynamic equations to obtain
an exact dispersion equation. This equation in dimensionless variables contains only two material constants p and q. We solve
the dispersion equation, obtaining an exact solution that holds for all values of the parameters and all frequencies up to
hypersonic, and thus analytically establish exactly how the speed of sound c, the wave vector k, and the damping factor x
depend on the frequency ω and the dimensionless material constants p and q. Studying the behavior of the solution in the sonic
and ultrasonic frequency bands for ω < 107 sec-1 results in an expression for the damping factor, which differs from the Kirchhoff formula. The speed of sound c and the wave
vector k are shown to have finite nonzero values for all hypersonic frequencies. At the same time, there exists a certain
maximum frequency value, ωmax ≈ 1011-1012 sec-1, at which the damping factor x is zero. This frequency determines the boundary of the applicability domain for the hydrodynamic
equations.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 146, No. 2, pp. 340–352, February, 2006. 相似文献
79.
80.
电子琴频谱的实验研究 总被引:1,自引:1,他引:0
介绍一个学生实验,用最基本的频谱分析方法,以CASIO MT-18电子琴作声源,对其中四种模拟乐器乐音信号的频谱进行测量及分析。 相似文献