现代嗓声科学系列讲座选讲之二——嗓声的产生

现代言语声学理论与实验已大体上说明了正常(normal)语音产生的原理。这指的是,我们对语音产生(除神经外的)的生理过程、声道内(以下在许多词组中声与音二字沿习惯用,具有同意;除声明外,声源均指经喉部声带调制气流转化成声的声源;“声道”包括声带;“声道内”指声门以上,不包括声带)声源和声道滤波的物理过程已基本搞清。但是对噪声在不同声区时的声源情况还了解较少;声源与声门上/下的作用还颇待研究;对于控制嗓声系统各部统     

六角结构金属中特殊位错组态的分析

本文从稳定的位错组态的能量最低原理出发,分析了六角结构金属中能够出现的特殊位错组态,这些位错组态由两组分别位于间距很小的两个滑移面上的位错列阵组成,用透射电子显微镜观察时,它们呈现为有规则的位错“网络”。 关键词：     

间歇性排气嗓声辐射特性的研究

将排气噪声分为三类,研究了间歇性排气过程中的空气动力学和噪声特性,建立了间歇性排气噪声中的单极子源和四极子源所产生噪声的声压级表达式。对气路系统中各参数对噪声的影响进行了全面深入的研究。     

纳米多晶铜微观结构的分子动力学模拟

基于EAM镶嵌原子势函数,采用分子动力学模拟了零温下纳米多晶铜的微观结构.首先用Voronoi几何方法构造了5个纳米多晶铜数值模型,在300K弛豫50ps并退火至0K.然后分析零温下弛豫模型的径向分布函数、原子能量、配位数、原子Voronoi体积、以及本征应力分布 关键词： 纳米多晶铜 微观结构 分子动力学     

金属中空位的形成能

从固体的表面张力出发,求得空位的形成能。发现由这理论计算得到的空位形成能的数值与实验值符合,金属的空位形成能与自扩散激活能以及熔化温度各成正比关系,这些关系中之一表明,空位形成能与自扩散激活能的比值为0.43。另外,空位形成能也是原子序数的周期性函数。     

FeS2多晶薄膜电子结构的实验研究

用磁控溅射方法制各纯Fe薄膜,并硫化合成FeS2.采用同步辐射X射线近边吸收谱与X射线光电子能谱研究了薄膜的电子结构.结果表明,合成的FeS2薄膜,在费米能级附近,有较强的Fe 3d态密度存在,同时,在价带谱中2-10eV处有强度较大的S 3p态密度存在;Fe的3d轨道在八面体配位场作用下分别为t2g和eg轨道,实验中由Fe的吸收谱计算得到两分裂能级之差为2.1eV;实验测得FeS2价带结构中导带宽度约为2.4eV,导带上方仍存在第二能隙,其宽度约为2.8eV.     

现代嗓声科学系列讲座之一——现代嗓声研究的范围、意义、方法、特点和分类

“现代嗓声科学系列讲座”是王土谦同志1988年初为北京嗓声学界举办的系列讲座。该讲座包括:现代嗓声研究的范围、意义、方法、特点和分类;声乐和言语的声学关系;嗓声——听觉链;嗓声的产生;嗓声产生中喉腔、喉室、喉管、咽管的问题;一些有关的心理声学;声乐声感知研究的进展;关于掩盖音与开放音的问题;嗓声的计算机分析与合成;歌手共振峰概念的发展及其与声源机制的关系;近来国际上对嗓声源及其与声门上、下系统交互作用的研究等专题。本刊将陆续选登部分内容。参考文献及图表由编辑部删留。     

蒸发条件对碘化铅多晶薄膜结构的影响

采用真空蒸发法在普通玻璃上制备了PbI₂多晶薄膜.研究了蒸发速率、蒸发源与衬底距离、薄膜厚度以及衬底温度等实验条件对所制备PbI₂多晶薄膜结构的影响.利用X射线衍射仪和扫描电子显微镜对样品进行了测试.结果表明，在衬底温度为室温时得到(001)择优取向的多晶PbI₂薄膜，即沿c轴垂直衬底方向取向生长的薄膜.当衬底温度升高时，薄膜的择优取向逐渐由(001)转向(003)，且晶体颗粒变大.薄膜中的内应力随衬底温度的升高而降低.     

多晶的离子注入

§1 前言 电致发光元件的研究,直到现在还没有达到当初所期望的较大的进展,特别是对于Ⅱ—Ⅳ族化合场ZnS的EL进行了深入的研究,但在应用上还存在亮度,寿命等问题。ZnS系半导体作为可见发光材料,具有很多物理和化学特征,并且容易偏离化学比,所以不用说发光的理论研究,就是在说明是否发光的单纯现象方面,也是非常困难的。电致发光元件的分类有几种,按电压可分为直流EL和交流EL。交流EL本质是激发和发光过程间有半周期的延迟,更确切地说是指steinberger等人的学说所表示的现象,为方便起见,我们认为它是指加交流电压时发光的场合。     

退火对多晶ZnO薄膜结构与发光特性的影响

用射频反应溅射法在Si（111）衬底上制备了C轴取向的多晶ZnO薄膜，通过不同温度的退火处理，研究了退火对多晶ZnO薄膜结构和发光特性的影响.由x射线衍射得知，随退火温度的升高，晶粒逐渐变大，薄膜中压应力由大变小至出现张应力.光致发光测量发现，样品在430nm附近有一光致发光峰, 峰的强度随退火温度升高而减弱，联合样品电阻率随退火温度升高而逐渐变大的测量及能级图，推测出ZnO薄膜中的蓝光发射主要来源于锌填隙原子缺陷能级与价带顶能级间的跃迁. 关键词： ZnO薄膜 退火 光致发光 射频反应溅射     

On the velocity of propagation of a signal in nonlinear optical media

The maximum velocity of propagation of a signal, which is defined as the velocity of propagation of the wave front, is considered for electromagnetic waves in nonlinear media. It is shown that the magnitude of velocity is determined to a considerable extent on the form of the constitutive equation defining the relation between the polarization of the medium with the radiation field strength. In the noninertial nonlinearity model, this velocity may be smaller (in media with self-focusing nonlinearity) or larger (defocusing nonlinearity) than the velocity of light in vacuum. For real nonlinear media, for which the inertia of their response is taken into account, the wave front velocity coincides with the velocity of light in vacuum.     

On the theory of scattering of electromagnetic waves in media with space-time velocity fluctuations

We express the effective permittivity tensor for a medium that is, on the average, motionless and nonstationary. It is shown that fast time pulsations of velocity lead to an increase in the average wave field and in the propagation velocity of an electromagnetic wave. Using a computer, we compare the surfaces of the frequency spectra of the strength of the scattered field for the Gaussian and diffusion components of the solenoidal velocity field. Dips are shown to emerge in the frequency spectrum that corresponds to the diffusion correlation function as the velocity pulsation increases.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 9, pp. 1091–1095, September, 1996.     

On the specifics of measuring attenuation and velocity of ultrasound in media with microstructure

We examine specific problems of measuring attenuation and velocity of ultrasound in engineering materials using the pulse method of exciting and receiving elastic oscillations. These problems are related to the influence of the internal structure of metals and alloys on the propagation in them of elastic longitudinal and shear waves in the megahertz frequency range. Using the example of a probing signal in the form of a radio pulse with a smooth envelope of Gaussian shape, additional sources of measurement error of the echo method of evaluation of the main acoustic characteristics used in problems of nondestructive testing and ultrasonic diagnostics of materials with microstructure were revealed.     

Boson peak, flickering noise, backscattering processes and radiative transfer in random media

The method of matrix Green’s functions in the classical theory of electromagnetic waves is stated. This method allows to obtain a closed equation system in the presence of the random media for the calculation both coherent, and incoherent (fluctuating) components of radiation. The density and heterogeneity of scattering media can be arbitrary. The coherent channel is calculated independently. The fluctuating radiation distribution in the medium is developed initially by an interference pattern generated by the coherent channel. The limitations of the processes speed are absent. The theory embraces such phenomena as the boson peak, flickering noise, memory effect, backscattering processes and also conventional radiative transfer equation and Fresnel’s formulae.     

On the statistical theory of spatial structure formation in random media

It is shown that, in parametrically excited stochastic dynamic systems described by partial differential equations, space structures (clustering) can be formed with probability 1 due to rare events occurring with probability tending to zero. Such problems arise in hydrodynamics, magnetohydrodynamics, plasma physics, astrophysics, and radiophysics. … Chaos is the place which serves to contain all things; for if this had not subsisted neither earth nor water nor the rest of the elements, nor the Universe a whole, could have been constructed… Sextus Empiricus, Against the Physics, against the Ethicists, R. G. Bury, p. 217, Harvard University Press, 1997.     

Ultrasonic wave velocity in the restructuring of disperse media

The ultrasonic wave velocities in the restructuring of disperse media were measured using interference and pulsed techniques and the coefficient of reflection in suspensions of starch, Al₂O₃, and SiO₂ particles, glass bulbs, their porous sediments, and composites of Fe₃O₄ particles in 10% gelatin aqueous solution at a frequency of 3 MHz. The experiments showed alternating variation in the concentration velocity coefficient during the transition of the dispersed phase concentration from the subpercolation to percolation region. The minimum ultrasonic wave velocity in the region of discrete clusters correlates with the ratio between the particle and matrix densities. The results obtained are explained using the Isakovich, Chaban, Rytov, Biot, Hausdorff, and other theories.     

On the steady-state structure of shock waves in elastic media and dielectrics

A simplified system of equations describing small-amplitude nonlinear quasi-transverse waves in an elastic weakly anisotropic medium with complicated dissipation and dispersion is considered. A simplified system of equations derived for describing the propagation and evolution of one-dimensional weakly nonlinear electromagnetic waves in a weakly anisotropic dielectric is found to be of the same type as the system of equations for quasi-transverse waves in an elastic medium. The steady-state structure of small-amplitude quasi-transverse discontinuities and a large number of admissible discontinuity types is studied using this system of equations. Viscous dissipation is traditionally assumed to be described in terms of the next differentiation order as compared to those constituting the hyperbolic system describing long waves, while the terms responsible for dispersion have an even higher differentiation order.     

Conductivity of 2D polycrystalline media in a magnetic field

The effective conductivity of 2D polycrystalline media in a magnetic field is considered. A current trap model constructed for strongly anisotropic polycrystalline media makes it possible to determine the distribution of the Joule heat liberated in such media.     

On the possibility of using the velocity of recorded signal for tomographic study of excited media

In this paper, by the example of optical and acoustic study of nonlinear crystals, we solve the problem of dynamic reconstruction of the internal structure of an object using a set of linear integrals, which depend parametrically on the time and velocity of integrated signals. Possible practical reconstruction algorithms are discussed. The results of model experiments with one of the above algorithms are given. State University, Makhachkala, Dagestan, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 6, pp. 761–768, June, 1997.