摘要:

The initial‐boundary‐value problem for the transient temperature fields in oil shale, which is heated by a propagating combustion flame in aninsituretort chimney, is formulated and solved analytically. The heat source of the flame is represented by a Gaussian distribution, which models the average statistical variations in radial and axial flame extensions, and is assumed to build up to maximum strength in accordance with a temporal relaxation process. The transient temperature fields in the oil shale surrounding the retort are calculated and discussed with respect to their spatial variations and dependence on the flame relaxation time. The theoretical temperature distributions are shown to be consistent with those observed experimentally. The high‐temperature core extends less than a retort radius into the surrounding shale bed. This result has implications for (i) theinsituretort design and (ii) the environmental impact ofinsituretorts. It appears that the spacing between neighboring retorts can be reduced and that the thermal effects of retorts on the environment are less severe than previously anticipated.

ISSN:0021-8979    

DOI:10.1063/1.324580

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Estimates of the stresses generated in a silicon wafer by thermomigration processing indicate the potential presence of stresses ranging from 1.7×10−1to 7×103MPa. The causes of these stresses include the heating and cooling of the wafer, the partial infrared transparency of silicon, thermal edge losses from the periphery of the wafer, the increasing solubility of silicon in the inclusion with increasing temperature, the difference in thermal conductivity between the liquid inclusion and the silicon matrix, the lattice expansion induced by impurity atoms in the dopant trials, the mismatch in thermal expansion coefficients in the Al‐Si sandwich at the completion of processing, and inclusions frozen in the wafer. Various ways of decreasing or eliminating these stresses are suggested so that the performance and yield of devices made by thermomigration will be optimized.

ISSN:0021-8979    

DOI:10.1063/1.324581

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A Lorentz‐like transformation (LLT) is introduced in the supersonic regime which keeps the wave equation invariant and simultaneously fixes the coordinate system to the body, producing small disturbances. Its implications, which appear to be far reaching, are briefly discussed.

ISSN:0021-8979    

DOI:10.1063/1.324582

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The rate of metal evaporation from the cathode spot in a vacuum arc is calculated and expressed in approximate formulas as a function of arc current by use of estimated values of its radius and temperature on the basis of the cathode mechanism theory proposed recently. As the evaporation rate is in good agreement with the experimental erosion rate, these formulas for the radius, temperature, and rate of evaporation on the cathode spot as a function of arc current are very useful in the industrial field.

ISSN:0021-8979    

DOI:10.1063/1.324583

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

This paper presents an investigation of the generation of a plasma wave and a second‐harmonic electromagnetic wave in a collilsionless hot magnetoplasma by a Gaussian EM beam (pump wave) propagating perpendicular to a static magnetic field in the ordinary mode. Because of the Gaussian intensity distribution of the EM wave, the ponderomotive force becomes finite and the electrons become redistributed; the electron density gradient (so created) and the intensity gradient of the EM wave lead to the generation of a plasma wave at the pump‐wave frequency. The intensity of the magnetic field significantly affects the plasma‐wave generation. When the pump‐wave frequency is equal to the upper‐hybrid frequency, resonant excitation of the plasma wave occurs. The plasma wave interacting with the pump wave leads to the generation of a second‐harmonic electromagnetic wave. Moreover, as the pump wave propagates in the plasma, its self‐focusing occurs; consequently, the plasma‐wave and the second‐harmonic generation become drastically affected.

ISSN:0021-8979    

DOI:10.1063/1.324584

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

In common laser fluorescence spectroscopy a quasi‐instantaneous distribution of the laser‐coupled levels according to their statistical weights is assumed. This saturation case can only be achieved by a fast rising laser pulse of sufficient intensity. Otherwise, losses from the laser‐pumped levels and the time dependence of the laser pulse have to be taken into account. In this paper a model including losses is investigated. Normalized fluorescence curves result which are characterized by one fit parameter. Into this parameter the rise time of the laser pulse, the overlap of the laser line and of the corresponding atomic line and its oscillator strength enter. The influence of the loss processes on the peak of the fluorescence curve can be shown. The model is applied to measurements at a nonthermal neon plasma of a microwave discharge. Transitions from the levels 2p5 3s 3P0,3P1,3P2to a common upper level 2p5 3p 3P1have been pumped. Evaluation of the fluorescence signal (2p5 3p 3P1→2p5 3s 1P1) leads to relative populations of the lower levels. The agreement between the theoretical and the experimental fluorescence curve proves the applicability of our model. By this method the range of applicability of laser fluorescence spectroscopy can be extended to nonsaturation cases.

ISSN:0021-8979    

DOI:10.1063/1.324585

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Plasmas heated uniformly by inverse bremsstrahlung are found to approach a constant electron‐ion temperature difference as a function of only the laser intensity and wavelength. A quasistatic model is employed to account for the radial expansion of plasmas. Analytic solutions up to the first order in &bgr; are obtained for the electron and ion temperatures.

ISSN:0021-8979    

DOI:10.1063/1.324595

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A general dispersion relation for the rotationally symmetric (m=0) and asymmetric (m≠0) low‐frequency waves has been delineated, utilizing a dimensional treatment as done by Hoh, for a high‐pressure (p∼10−2Torr) Penning discharge having gradients (radial) of ion density, plasma potential, and electron temperature. The present analysis is found to be very helpful for investigating the role of the temperature gradient in exciting various modes; here, a positive temperature gradient has been found to have a destabilizing influence in general. The theoretical predictions of the growth condition and the frequency of the instability have been found to agree well with the present experimental observation of anm=0 mode. Further, an experiment on the suppression of this instability has been carried out for understanding the excitation mechanism.

ISSN:0021-8979    

DOI:10.1063/1.324596

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Crystalline properties of Ne+‐implanted garnet films with varying implantation energies and dosages have been studied by means of the double‐crystal x‐ray‐diffraction method, and it was found that when implantation‐induced damage was low, Pendello¨sung interference was observed which is directly related to crystal perfection, and a layer with large microscopic strain was found to become amorphous. The damage profiles were determined by measuring changes in x‐ray rocking curves after etching the implanted layers. Based on these experimental results, an implanted layer model was derived. The influences of the crystalline properties on the magnetic properties were also investigated from the viewpoints of the flux keeper and hard‐bubble‐suppression effects. For high implantation dosage the amorphous layer becomes magnetically inactive. This phenomenon is ascribed to randomly oriented micro‐magnetic‐domains with zero net magnetization caused by large microscopic strain in the amorphous layer. The effect of annealing is also discussed.

ISSN:0021-8979    

DOI:10.1063/1.324597

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Crystal structures and lattice constants have been determined for ruby at hydrostatic pressures up to 46 kbar using a gasketed opposed‐anvil diamond cell on a four‐circle diffractometer. The measured compressibility is slightly anisotropic, having a value of 1.36±0.03×10−4kbar−1parallel tocand 1.22±0.03×10−4kbar−1perpendicular toc. If a Birch‐Murnaghan equation of state is used andK′0is assumed to be 4, the isothermal bulk modulus is 2.57±0.06 Mbar. Refined atomic coordinates do not change with pressure; therefore, the structure compresses in a uniform manner. This study demonstrates that crystal structures may be determined at high pressure on single crystals with a precision approaching that of room‐pressure results.

ISSN:0021-8979    

DOI:10.1063/1.324598

出版商:AIP    

年代:1978

数据来源: AIP