摘要:

Folded‐path guided surface wave delay lines offer a significant potential advantage over single‐propagation path delay lines for obtaining very long delay times. Measurements are reported here for a spiral folded‐path delay line employing a gold strip on fused quartz as the guidance structure. A 260 &mgr;sec delay was obtained at 20 MHz. The spurious signal was ≥35 dB down and the differential propagation loss was 0.03 dB/&mgr;sec. These favorable results indicate that practical long delay lines based on surface acoustic wave guidance techniques are quite feasible and that delay times into the millisecond range are attainable at higher frequencies.

ISSN:0021-8979    

DOI:10.1063/1.1660449

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A centrifugal field can cause migration of solvent inclusions in crystals, both by the preferential sedimentation of the denser solute ions and by diffusion across the concentration gradient caused by the variation of solubility with pressure. The two mechanisms can act either in the same or in opposite directions so that both centripetal and centrifugal migration are possible. Aqueous inclusions in KI were observed to move centripetally at about 0.05 mm/h at room temperature in centrifugal fields of 210 000 G; at higher temperatures the direction of migration was reversed. Inclusion movement was also observed in KCl and Pb(NO3)2. Plastic deformation, cracking, and changes in inclusion shape were also encountered.

ISSN:0021-8979    

DOI:10.1063/1.1660450

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Elements of the anisotropic resistivity tensorRof silver were measured for a large range of field directions. Helicon standing‐wave resonances in flat plate samples were used to measure the tensor elementsRij. Samples were tipped in the magnetic field. Data were taken for crystallographic directions ofB0which completely outlined the unit stereographic triangle. Measurements were also made for many directions in the interior of the unit triangle. Hall effect and transverse‐even voltage terms were measured, as well as the transverse magnetoresistance. Results are presented which can be compared to the predictions provided by Fermi surface shape.

ISSN:0021-8979    

DOI:10.1063/1.1660451

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A double crystal x‐ray spectrometer was used to determine the crystallographic polarity of the structure of gel‐grown &bgr;‐AgI single crystals showing that the Ag+plane is the (00.1) and the I−plane is the (00.1¯). This result is consistent with chemical etching studies, polarizability, and electronegativity of the ions.

ISSN:0021-8979    

DOI:10.1063/1.1660452

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Attenuation measurements have been made of the body‐centered crystal niobium for three waves along the ⟨110⟩ direction. The room‐temperature measurements are consistent with dislocations lying in the (110) planes with glide directions along the ⟨100⟩ axes. The fast shear has the largest attenuation and it has been measured over a temperature range from 30° to 300°K with frequencies from 10 to 150 MHz. The attenuation can be divided into a square‐law attenuation and a dislocation component. The dislocation component can be used to evaluate a drag coefficient which is nearly constant down to 78°K. It rises at low temperatures indicating an electron drag effect. The constant region is consistent with a phonon viscosity damping with a crystal having a peak in the thermal conductivity. The electron drag confirms a theoretical calculation giving a drag inversely proportional to the electrical resistivity.

ISSN:0021-8979    

DOI:10.1063/1.1660453

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Tests have shown that it is possible to switch a ferroelectric/photoconductor memory device between its ``1'' and ``0'' memory states in 10 &mgr;sec with 10 W/cm2irradiance. Both a He&sngbnd;Ne laser and a CRT have been used to address the device which stores the bits of information as close as 25 &mgr; apart. The device can retain stored information for more than 60 h with power off, and withstand 107disturb pulses in the dark.

ISSN:0021-8979    

DOI:10.1063/1.1660454

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Deviations from stoichiometry occurring during the crystal growth of lithium niobate have been studied by93Nb NMR and by shifts in the ferroelectric transition temperature. The high‐temperature phase equilibria of nonstoichiometric lithium niobate were accurately determined by these techniques together with DTA and crystal‐growth experiments. The congruently melting composition is located at 48.6 mole% Li2O and the solid‐solution region at room temperature extends from 48% to 50% Li2O. The implications of growth at noncongruently melting compositions on the compositional uniformity of lithium niobate are discussed in detail.

ISSN:0021-8979    

DOI:10.1063/1.1660455

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Samples ofn‐type AlxGa1−xAs were prepared by liquid phase epitaxy on a GaAs substrate. Whenx≳0.4the material has the indirect band structure characteristic of AlAs. Longitudinal piezoresistance measurements were performed on this material with stress along the⟨100⟩and⟨111⟩crystallographic directions. The results indicate that the lowest conduction‐band minima in the alloy, and by inference in pure AlAs, lie along the⟨100⟩directions inkspace as in silicon.

ISSN:0021-8979    

DOI:10.1063/1.1660456

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Series form solutions are given for both the TEl0and the LSM mode in a rectangular waveguide partially and completely filled with an isotropic inhomogeneous plasma. The inhomogeneity of the plasma is represented by a polynomial profile and assumed to occur in the direction transverse to the direction of propagation in the waveguide. Numerical calculations showing the variations of cutoff frequency vs the thickness of the plasma are given.

ISSN:0021-8979    

DOI:10.1063/1.1660457

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Measurements of an rf Gaussian pulse propagating along a coaxial gas discharge indicate that the dispersion suffered by the pulse can be attributed to the anode glow region of the discharge. The signal's group velocity agrees with an approximate theory in which the region between the two conductors is filled with a homogeneous plasma. Large amounts of signal spreading and attenuation are observed near the average electron plasma frequency and are ascribed to collision and intermode coupling losses in the system.

ISSN:0021-8979    

DOI:10.1063/1.1660458

出版商:AIP    

年代:1971

数据来源: AIP