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851.
A review of otoacoustic emissions 总被引:32,自引:0,他引:32
R Probst B L Lonsbury-Martin G K Martin 《The Journal of the Acoustical Society of America》1991,89(5):2027-2067
Otoacoustic emissions measured in the external ear canal describe responses that the cochlea generates in the form of acoustic energy. For the convenience of discussing their principal features, emitted responses can be classified into several categories according to the type of stimulation used to evoke them. On this basis, four distinct but interrelated classes can be distinguished including spontaneous, transiently evoked, stimulus-frequency, and distortion-product otoacoustic emissions. The present review details the findings that have been described for each emission type according to this classification schema. Additionally, the known features of emitted responses are discussed for both normally hearing and hearing-impaired humans and experimental animals, and with respect to their potential clinical applications. The findings reviewed here clearly indicate that future studies of otoacoustic emissions will significantly increase our understanding of the basic mechanisms of cochlear function while, at the same time, provide a new and important clinical tool. 相似文献
852.
853.
A numerical model for simulating nonlinear pulsed beams radiated by rectangular focused transducers, which are typical of
diagnostic ultrasound systems, is presented. The model is based on a KZK-type nonlinear evolution equation generalized to
an arbitrary frequency-dependent absorption. The method of fractional steps with an operator-splitting procedure is employed
in the combined frequency-time domain algorithm. The diffraction is described using the implicit backward finite-difference
scheme and the alternate direction implicit method. An analytic solution in the time domain is employed for the nonlinearity
operator. The absorption and dispersion of the sound speed are also described using an analytic solution but in the frequency
domain. Numerical solutions are obtained for the nonlinear acoustic field in a homogeneous tissue-like medium obeying a linear
frequency law of absorption and in a thermoviscous fluid with a quadratic frequency law of absorption. The model is applied
to study the spatial distributions of the fundamental and second harmonics for a typical diagnostic ultrasound source. The
nonlinear distortion of pulses and their spectra due to the propagation in tissues are presented. A better understanding of
nonlinear propagation in tissue may lead to improvements in nonlinear imaging and in specific tissue harmonic imaging.
Published in Russian in Akusticheskiĭ Zhurnal, 2006, Vol. 52, No. 4, pp. 560–570.
This article was translated by the authors. 相似文献
854.
We have used electronic spectroscopy in the 160–1100 nm range to study the polyvinyl alcohol-nickel(II) chloride system. Based
on the results obtained, we hypothesize formation of mixed-ligand complexes of the type [Ni(H2O)6-nCln]2-n (n = 0, 1,..., 5) in the polyvinyl alcohol matrix. Transformation of the coordination sphere as the NiCl2 concentration changes is apparent both in the region of the d-d transition bands (350–1100 nm) and in the region of the charge
transfer bands (160–250 nm). We propose assigning the absorption bands separated by mathematical treatment to complexes of
specific compositions.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 136–138, January–February, 2006. 相似文献
855.
856.
We construct a probability model seemingly unrelated to the considered stochastic process of coagulation and fragmentation.
By proving for this model the local limit theorem, we establish the asymptotic formula for the partition function of the equilibrium
measure for a wide class of parameter functions of the process. This formula proves the conjecture stated in [5] for the above
class of processes. The method used goes back to A. Khintchine. 相似文献
857.
In this work we present a first-order partial differential equationwhich defines the topology of single atomic entitiesin multiatomic systems. Such an equation, obtained by R. F.W. Bader, is here analysed and discussed from a general mathematicalpoint of view; a method is then proposed for defining the initialor boundary condition. With this contribution we would liketo promote and stimulate a more detailed analysis which goesbeyond practical purposes and basic mathematical analysis inorder to have a deeper understanding of the theory behind theequation and its consequences for practical applications. 相似文献
858.
Ivonin I. V. Lavrent'eva L. G. Aleksandrova G. A. Devyat'yarova L. L. 《Russian Physics Journal》2002,45(10):997-1000
The effect of the arsenic concentration in the vapor phase on the growth step distribution over the surface of GaAs epitaxial layers grown in a chlorine-hydride vapor-transport system on substrates with 4° (111)A and (113)A orientations is studied. It is demonstrated that the average distance between steps in the echelon depends on the arsenic concentration and increases with it up to a certain constant value. It is assumed that this is connected with the change in the kink density at the steps. 相似文献
859.
H.O.U. Fynbo Y. Prezado J. Äystö U.C. Bergmann M.J.G. Borge P. Dendooven W. Huang J. Huikari H. Jeppesen P. Jones B. Jonson M. Meister G. Nyman M. Oinonen K. Riisager O. Tengblad I.S. Vogelius Y. Wang L. Weissman K.W. Rolander 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):135-138
860.
Field equations of the S2 sigma model (“the A3 model”) with spontaneously broken Z(2) symmetry are presented for (D+1)-dimensional space–time. The A3 model is an extension of the sine-Gordon equation (SGE) and supports kink-like U(1) charged solitons which are a generalization of neutral solitons of the SGE. The natural question arises — is the A3 model completely integrable in (1+1)-dimensional space–time? The Lorentz-invariant scalar A3 field can be viewed as a promising alternative to the Higgs field. 相似文献