摘要:

Two new variable color display device arrangements are described. These arrangements combine the unique polarization switching capabilities of the twisted nematic liquid crystal electro‐optical cell with the anisotropic optical properties of separate passive optical elements. In one scheme, the passive element is a birefringent film in combination with a neutral polarizer, and colors are transmitted by the selective interference of white light. In another design, where the passive element is a pleochroic filter, the transmitted colors result from the selective absorption of white light. These arrangements make possible large area displays, since the colors transmitted do not depend on the temperature or thickness of the nematic layer. Transmission curves and other color information are given for a number of examples.

ISSN:0021-8979    

DOI:10.1063/1.1662046

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A regenerative mechanism is proposed which can lead to unlimited multiplication of disclinations. This mechanism consists of a glissile segment of a disclination pinned by two sessile ``jogs'', and therefore is similar to a Frank‐Read source for dislocations. It is also possible to have a U‐mill, Z‐mill, and L‐mill for disclination multiplication. It is further shown that a single source can give rise to disclinations of opposite signs (and this allows rotation in both directions of that part of the crystal above the source, relative to the part below), depending upon the direction in which the source operates.

ISSN:0021-8979    

DOI:10.1063/1.1662047

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Experiments on frequency mixing show that up and down conversion is enhanced over results reported for lithium niobate alone. Convolution experiments with a transverse electrode configuration show a similar enhancement. In addition, it is shown that one may represent the convolver with a load‐independant voltage element in the linear response region; but when saturation begins, this source becomes dependent on load current. Experiments are reported which demonstrate how one signal may be used to vary the attenuation of another.

ISSN:0021-8979    

DOI:10.1063/1.1662048

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A variational analysis is presented for the phase velocity of an acoustic wave guided by the apex of an infinitely tall wedge. The lowest‐order antisymmetric flexural mode is considered. It is demonstrated that rather simple approximations to the particle displacements lead to an accurate prediction of the mode phase velocity as a function of the apex angle. An analytic expression is obtained for phase velocity in the limit of small apex angles.

ISSN:0021-8979    

DOI:10.1063/1.1662049

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A method of calculating the angle between the propagation direction and the direction of energy flow of a plane wave is developed. The method is suitable for any crystal symmetry, and the necessary transformations are given in the Appendix. Calculations are carried out for calcium sulfate which is an orthorhombic crystal that shows the full number of pure vibration directions.

ISSN:0021-8979    

DOI:10.1063/1.1662050

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An experimental study has been made of magnetic hysteresis in plastically deformed and annealed gadolinium (Gd) metal as a function of annealing temperature. Seven plastically deformed samples were annealed at temperatures ranging from 155° to 916°C; major and minor magnetic hysteresis loops of these seven samples plus one as‐deformed sample were examined. The results are discussed in terms of the recovery and recrystallization processes. The measurements of magnetic parameters clearly show three distinct regions of behavior, viz., the regions of annealing temperatureTa<300°C, 300<Ta<500°C, andTa<500°C. These regions are identified as regions of recovery, recrystallization, and completed recrystallization plus additional grain growth, respectively. Two distinct advantages of the magnetic measurements are (i) using the magnetic measurements, it was found possible to distinguish between metallurgical processes which are not easily detectable using traditional measuring techniques, and (ii) the weak‐field magnetic parameters were found to be extremely sensitive to changes in microstructure resulting from the isochronal anneals. The weak‐field (or Rayleigh) hysteresis‐loop data are analyzed in terms of a spring model of domain‐wall pinning by defects. Good qualitative agreement is found between experimental results and predictions based upon this model.

ISSN:0021-8979    

DOI:10.1063/1.1662051

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A system of approximate two‐dimensional surface‐wave equations and edge conditions in one scalar variable is derived from Hamilton's principle for linear piezoelectric media by assuming suitable depth behavior and integrating with respect to depth. The assumed behavior with depth is determined from the known straight‐crested surface‐wave solutions of the three‐dimensional equations for the plated and unplated substrate in connection with the known variable‐crested solutions for the isotropic substrate. The influence of the inertia, stiffness, and electrical shorting of the film is included in the analysis. The application of the derived equations to the problems for isotropic substrates treated earlier by anad hoctechnique indicates that the derived equations are extremely accurate. Among other things, the analysis reveals that a slot in an aluminum‐oxide film on a T‐40 glass substrate exhibits guiding characteristics twice as good as the combination of aluminum on T‐40 glass in the essentially nondispersive range. The derived equations are used in the determination of the dispersion curves for piezoelectric surface waves guided by gold strips ony‐cut lithium niobate for propagation in thexandzdirections, respectively. Although the dispersion curves forzpropagation turn out as expected, the dispersion curves forxpropagation have an interesting and unusual shape indicating two ranges of essentially nondispersive propagation. The unusual shape is a consequence of the fact that two straight‐crested surface waves couple strongly in the propagation range of interest.

ISSN:0021-8979    

DOI:10.1063/1.1662052

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The dislocation contribution to the ultrasonic attenuation of high‐purity copper single crystals has been quantitatively determined by forming the difference between the measured attenuation and the nondislocation part of attenuation as measured after heavy irradiation. In this way mainly, the influence of temperature, deformation, &ggr; irradiation, and heat treatment on the dislocation damping has been studied. The measurements were evaluated according to the Granato‐Lu¨cke theory of dislocation resonance. One of the main objectives of the work was to test the applicability of various experimental and theoretical methods for gaining quantitative information on dislocations from ultrasonic attenuation measurements.

ISSN:0021-8979    

DOI:10.1063/1.1662053

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A wave equation has been formulated for the propagation of sound in suspensions and emulsions, taking into consideration the different viscosities and thermodynamic properties of the suspension components. The suspension has been assumed to be homogeneous in the sound field for the particle size to be much smaller than the incident wavelength and to be a continuous fluid which enters and leaves the control volume element at volume‐averaged values of velocity and momentum. This equivalent continuous fluid has been assumed to possess a density equal to the volume‐averaged density and a compressibility equal to the effective compressibility of the suspension or emulsion (calculated from the scattering theory). The formulated wave equation immediately yields the acoustical properties of suspensions or emulsions, such as sound velocity and viscous and thermal attenuation coefficients.

ISSN:0021-8979    

DOI:10.1063/1.1662054

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An homeotropic cell is built with a thin layer (5–25 &mgr;m) of nematic liquid crystal such as MBBA sandwiched between two indium oxide coated glass plates. The transient behavior of the cooperative angular variation of molecules submitted to an electric field step is studied theoretically. Experimental results are obtained by optical detection of the birefringence variations in the cell. Comparison of these studies allows one to determine the viscosity coefficient &ggr;1(−&lgr;1in Leslie's notation).

ISSN:0021-8979    

DOI:10.1063/1.1662055

出版商:AIP    

年代:1973

数据来源: AIP