摘要:

Techniques are described for the theoretical prediction of acoustic surface wave orientations on anisotropic crystalline substrates having minimal diffraction spreading. These techniques are illustrated by the theoretical and experimental discovery of a minimal diffraction cut on Bi12GeO20having diffraction retarded by at least two orders of magnitude over isotropic materials. Euler angles for this orientation are 45°, 40.04°, and 90°, while the surface wave velocity and the &Dgr;v/vparameter are 1827 m/sec and 0.0031, respectively.

ISSN:0021-8979    

DOI:10.1063/1.1662686

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Conductance and signal measurements are presented for interdigital transducers on rotatedZ‐cutX‐propagating lithium niobate. The +41.5° rotated cut is shown to be a superior one for Rayleigh wave generation compared to the conventionalY‐cutZ‐propagating material. It has a higher electromechanical coupling constant and noticeably greater freedom from bulk wave generation at least up to the third harmonic Rayleigh wave frequency.

ISSN:0021-8979    

DOI:10.1063/1.1662687

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A substance is considered to diffuse into a finite cylinder through its entire surface from a finite amount of well‐mixed gas which is at concentration equilibrium with the surface. Equations are derived for the time dependence of the amount of substance in the cylinder and its concentration at a point. The results are developed mainly in terms of isotopic self‐diffusion (as in the diffusion‐controlled exchange of isotopic oxygen with an oxide), but may also be applied to the diffusion of an inert substance or to a heat conduction situation.

ISSN:0021-8979    

DOI:10.1063/1.1662688

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Profiles of channeled and dechanneled31P ions in the energy range 30–900 keV have been measured in ⟨100⟩, ⟨111⟩, ⟨112⟩, and ⟨110⟩ Si. The maximum range,Rmax, of the channeled ions has been determined and used to calculate values of electronic stopping power. The variation of these values with substrate orientation agrees qualitatively with that predicted by the Firsov theory, although the actual values are 2–3 times the Firsov prediction. Dechanneled profiles (450 keV) were measured in 0.3° steps up to 1.2° for all four orientations and in 2° steps up to 10° for the ⟨100⟩ and ⟨111⟩ orientations. The effect of tilt direction on the dechanneling was studied. Dechanneling from the ⟨111⟩, ⟨112⟩, and ⟨110⟩ orientations exhibited a marked sensitivity to the direction of tilt. By tilting in an appropriate maximum‐dechanneling direction, dechanneling from the ⟨100⟩ and ⟨111⟩ orientations was found to be continuous, starting with the 0.3° tilt and saturating for tilts above 4.2°. The projected range,Rp, determined from the fully dechanneled or random distributions, was found to vary almost linearly with energy and has a slope of ∼1.1 &mgr;m/MeV.

ISSN:0021-8979    

DOI:10.1063/1.1662689

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The theory of dark field imaging technique as applied to acousto‐optic interactions has been developed and then used in studies of linear and nonlinear surface acoustic waves and volume acoustic waves. The theory is consistently expressed in terms of phase transmittance function. Experimental results show how the technique can be applied in the case of multimode propagation to unfold the complex frequency spectra of spurious modes in surface wave devices, and how to discriminate between different harmonics in the case of nonlinear acoustic propagation.

ISSN:0021-8979    

DOI:10.1063/1.1662690

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The Kerr response of seven nematic substances has been measured just above their nematic‐isotropic transition temperature, in their isotropic state. If the reciprocal of the Kerr constantBis plotted against temperature, a linear relationship analogous to the Curie‐Weiss dielectric relationship in ferroelectrics is found in all cases. The transient Kerr response—that is, the variation of induced birefringence with time in response to a field step—was also measured in three of the compounds. Inp‐(p‐ethoxybenzylidene) amino benzonitrile (EBAB), a maximum Kerr constant of 175×10−10cm2V−1was observed, together with a response time of 13 nsec. The extremely short response time indicates that molecular association does not take place. On the other hand,n‐(p‐methoxybenzylidene)‐p‐butylaniline (MBBA) under similar conditions showed a response time of 3 &mgr;sec, indicating that a high degree of association does take place in the isotropic phase.

ISSN:0021-8979    

DOI:10.1063/1.1662691

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Metal migration induced by electric field and temperature gradients has been studied in aluminum‐silicon and gold‐silicon interdigitized test structures. At current densities of 2×106A/cm2and temperature gradients of 75 °C/cm migration occurred across the Si&sngbnd;SiO2interface. Calculated diffusion profiles show that below 350 °C, mass transport is more rapid with aluminum. At temperatures between 350 and 550 °C, metal migration is more rapid with gold metallization. Metal migration was shown to be a multistaged process without the existence of a unique activation energy.

ISSN:0021-8979    

DOI:10.1063/1.1662692

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Using the theory of elasticity for large deformations and a strain energy function of the formW=½&PHgr;(I1−3)+½&PSgr;(I2−3), where &PHgr; and &PSgr; are constants, formulas for the phase velocity and damping of torsional waves of small amplitude in stretched viscoelastic isotropic vessels of arbitrary wall thickness and filled with a viscous fluid under pressure have been derived and experimentally tested (frequency range 0.3–33 Hz; viscosity of the fluids between 0.01 and 13 P; pressure between 0 and 4×105dyn cm−2; stretches up to twice the original length) in vertically or horizontally suspended latex tubes and in such tubes floating on a pillow of pressurized air. The agreement between theory and experiment is satisfactory. The phase velocity increases with the stretch, but decreases with an increase of the fluid viscosity. The damping decreases with an increase of the stretch. At the higher frequencies the damping increases with an increase of the viscosity of the fluid, but at the lower frequencies the opposite is the case. The influence of pressure both on phase velocity and damping proved small in the pressure range that was considered (0–4×105dyn cm−2).

ISSN:0021-8979    

DOI:10.1063/1.1662693

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Radiative heat transfer in inhomogeneous materials is governed by the photon mean free path. For long‐wave photons, the mean free path depends on the size and shape of the individual grains and, where applicable, of the voids. Long‐wave photons have long mean free paths and play an important role in the heat transfer. In some cases they cause the radiative thermal conductivity at moderately high temperatures to be larger than one would expect by extrapolating from highest temperatures (above 2000 °K) according to aT3law. Some special cases are treated including polycrystalline solids, densely packed powders, foams, and fibrous aggregates.

ISSN:0021-8979    

DOI:10.1063/1.1662694

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The reaction of iodine with silver at temperatures from 25 to 150 °C has been studied with a quartz crystal microbalance and by x‐ray diffraction. The reaction approximately obeys the parabolic law and the reaction rate decreases with increasing temperature up to 146 °C, the transformation temperature of AgI. Crystals of &bgr;‐AgI grow with various orientations on the silver surface at 25 °C, but gradually grow with the basal planes parallel to the film surface with increasing temperature. It is concluded that the diffusion of iodine atoms through the iodide films is rate determining, and that the adsorption of iodine gas and the oriented growth of the AgI film influence the diffusion and lead to the observed temperature dependence of the reaction.

ISSN:0021-8979    

DOI:10.1063/1.1662695

出版商:AIP    

年代:1973

数据来源: AIP