摘要:

The characteristics of one‐dimensional electron diode with low‐pressure argon scattering gas are analyzed by a Monte Carlo method. Experimentally determined differential elastic scattering cross sections, extra‐polated to zero energy, are employed. Current‐voltage characteristics are compared with those obtained from a hard‐sphere collision model. Negative resistance is found for low emission current densities and low pressure as a result of the Ramsauer cross section. The randomization of energy between velocity components is found to be quite large for accelerating potentials and pressure‐electrode separation values as low as ½ Torr·cm. The energy dependence of total cross section has a more pronounced effect on the current‐voltage curves than nonisotropic scattering.

ISSN:0021-8979    

DOI:10.1063/1.1710036

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The sound velocities, bulk modulus, and their pressure and temperature derivatives have been measured on a polycrystalline ZnO by means of a pulse‐superposition method. The pressure derivatives found from the experiments up to 3 kbar at 25°C are: (dv1/dP)=3.643×10−3km/sec·kbar, (dvt/dP)=−3.193×10−3km/sec·kbar, and (dBs/dP)=4.78. The negative value of (dvt/dP) for ZnO is anomalous for crystalline solids. No anomalous behavior was observed in the temperature derivatives near 25°C. They are (dv1/dT)=−1.871×10−4km/sec·deg, (dvt/dT)=−0.392×10−4km/sec·deg, and (dBs/dT)=−0.129 kbar/deg. The Gru¨neisen constant was calculated from the present pressure derivatives of elastic constants and was found to be negative, whereas the value calculated from the thermal‐expansion data at 25°C is positive. This result seems to indicate that the thermal expansivity of ZnO may be negative at very low temperatures.

ISSN:0021-8979    

DOI:10.1063/1.1710037

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The problems considered are whether the breakdown that occurs between two parallel‐plane electrodes in a vacuum is an anode‐induced or cathode‐induced breakdown and what conditions determine which type of breakdown is dominant. The critical anode power density for an anode‐induced breakdown and the critical cathode current density for a cathode‐induced breakdown were measured and the experimental results were compared with predictions from theory of heat conduction. An analysis of these experimental results led to a criterion for determining the type of breakdown that predominates as a function of separation between electrodes and of the thermal and electrical conductivities of the material of the electrodes. It was shown that there were four distinct regions of separation: two anode‐induced regions, one cathode‐induced region, and one transition region of both types.

ISSN:0021-8979    

DOI:10.1063/1.1710038

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A simple form of the strain‐energy function of natural rubber results if the latter is expressed an an analytic function of the extension ratios rather than the invariants. For incompressible isotropic materials it is postulated that this is a separable symmetric function of the extension ratios, i.e.,W = w(&lgr;1) +w(&lgr;2) +w(&lgr;3). This form has been substantiated by critical plots using uniaxial and biaxial data reported in the literature by several investigators. The above form appears to be valid over a wide range of deformations (0.2≤&lgr;≤3.5). An explicit representation ofWfor this range is given in graphical form. In the more limited range (0.6≤&lgr;≤2.5)w(&lgr;) has the analytic formw=2 &mgr;&lgr; (ln&lgr;−1).

ISSN:0021-8979    

DOI:10.1063/1.1710039

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The electrostatic wave in a plasma may be amplified parametrically by applying a pump power at microwave frequencies. The theory of the parametric interaction between the electrostatic wave and a guided electromagnetic wave is presented, and the gain parameter is derived in terms of the pump power. The pump power required to observe the effect of the pumping at microwave frequencies is calculated to be orders of magnitude less than the optical power required to produce the Raman effect in plasmas.

ISSN:0021-8979    

DOI:10.1063/1.1710040

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Samples of Mn‐, Cd‐, and Zn‐doped GaAs were diffused to near compensation with Li. A number of Li‐localized vibrational‐mode absorption peaks have been observed. Three bands are present in Mn‐ and Cd‐doped material. A simple model is proposed which is based upon interstitial Li paired with Mn or Cd, where the ion pairs are oriented along a ⟨100⟩ direction. In Zn‐doped material four Li bands associated with Li‐Zn complexes are observed. In this case the authors are unable to present a model consistent with existing experimental data.

ISSN:0021-8979    

DOI:10.1063/1.1710041

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Propagation modes for electromagnetic waves in circular ferrite rods magnetized along the axis can be computed exactly by well‐known and straightforward procedures; however, three parameters must be specified to define a mode family in the normalized frequency vs axial wavenumber (&ohgr; — &bgr;) plane. The magnetostatic approximation requires but one parameter, the saturation magnetization normalized with respect to the dc magnetizing field, 4&pgr;M0/H0, and thus allows the whole range of solutions to be readily visualized and simply portrayed. The transition from the exact solution to the magnetostatic limit has not been previously studied and is the primary object of these investigations. At the same time it has been found helpful to classify the exact solutions and to suggest an appropriate terminology. Numerical computations have been made and compared with magnetostatic calculations and with other results.

ISSN:0021-8979    

DOI:10.1063/1.1710042

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1710044

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1710045

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1710047

出版商:AIP    

年代:1967

数据来源: AIP