摘要:

The progress of an isothermal chemical reaction on a catalytic surface, which is located in a laminar hydrodynamic flow field of large Reynolds number, is analyzed. Past analytical investigations have been restricted primarily to chemical reactions in fully velocity developed flow fields subject frequently to one or both of the following approximations. (i) The actual velocity distribution is replaced by a flow of uniform velocity. (ii) The concentrations of the reactants on the catalytic surface are prescribed subject to certain hypotheses concerning the rate controlling mechanism.In this investigation the principal aim has been to calculate the actual surface concentration in a laminar boundary layer flow without unduly sacrificing the hydrodynamic features or introducing unnecessary assumptions about the effective over‐all reaction mechanism. The method presented, which is related to an analysis of convective heat transfer from a nonisothermal surface, is applicable to arbitrary catalytic reaction mechanisms in a certain class of laminar boundary layer type flow fields.

ISSN:0021-8979    

DOI:10.1063/1.1722258

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

A thin circular ferrite post magnetized lengthwise is placed in a rectangular wave guide with its axis normal to the direction of propagation of the incident waves. The polarization is such that the electric vector is parallel to the post. The reflected and transmitted waves are calculated both with respect to their intensities and phases. The results are also applied to find the influence of a thin ferrite post upon the resonant frequency of a rectangular cavity.

ISSN:0021-8979    

DOI:10.1063/1.1722259

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

The application of a method combining x‐ray microscopy and diffraction analysis to the study of the substructure of nickel and nickel alloys disclosed the coexistence of three orders of magnitude of substructural entities. These three orders are structurally interrelated and distinguished by different ranges of size, disorientation angle, and lattice misalignment. The statistical analysis of the data disclosed that for the two largest orders of substructural entities increasing amounts of room temperature deformation cause (1) a decrease in the mean size and a decrease in the spread of the size distribution, (2) an increase in the mean disorientation angle between substructural entities of the same order and an increase in the spread of the distribution of angles, and (3) an increase in the mean lattice misalignment and spread in the distribution of misalignment. Progressive room temperature deformation causes the low‐angle boundaries to become increasingly unsymmetrical and greatly increases the number of the smallest substructural entities. The rise of flow stress as a function of room temperature deformation was correlated to the systematic modification of substructure characteristics.

ISSN:0021-8979    

DOI:10.1063/1.1722260

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

The numerical solution for a spherical shock in water produced by spherical piston of known expanding motion and initial nonzero radius is described. This solution is of interest during the time when the radius of the shock and that of the piston are of the same order of magnitude, that is, when point source solutions do not hold. Calculations are carried out for a constant velocity piston and for a piston with decreasing velocity.

ISSN:0021-8979    

DOI:10.1063/1.1722261

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

A modified Landau‐Lifshitz equation is solved for a single‐domain sphere and an infinitely‐wide thin single‐domain sheet of ferromagnetic material neglecting anisotropy. The external magnetic field is switched from one direction to its opposite instantaneously at the initial time and the behavior of the magnetization vector is investigated thereafter. It is shown that there is a critical value of the damping constant corresponding to the minimum value of the (repetitive) magnetization reversal time. If the damping constant is larger than the critical value, the magnetization vector moves slower; if it is smaller, the magnetization vector moves faster but oscillates so that it takes longer time until it comes to a rest at the final position. The critical values of the Landau‐Lifshitz damping constant &lgr; are &ggr;Mfor the sphere and 0.013&ggr;Mfor the thin sheet, where &ggr; andMare the gyromagnetic ratio and the magnetization, respectively. The computed minimum switching time for the thin sheet of 4–79 molybdenum Permalloy is of the order of 10−9sec.

ISSN:0021-8979    

DOI:10.1063/1.1722262

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

The resistance of the semitransparent photoemissive films Sb&sngbnd;Cs, Sb&sngbnd;Rb, Bi&sngbnd;Cs, Bi&sngbnd;Rb, Te&sngbnd;Cs, Te&sngbnd;Rb, and Ag&sngbnd;O&sngbnd;Cs was measured as a function of temperature. A thermal activation energy associated with conductivity was determined for each of the materials.

ISSN:0021-8979    

DOI:10.1063/1.1722263

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

A new mathematical approach for the analysis of radioactive tracer experiments on compartmentalized systems in steady states is presented. The experimental measurements of the amounts of tracer in one or more compartments are approximated by a sum of exponential functions of time. The coefficients and exponential factors of these functions are shown to represent a set of invariants of the data. These are then related in a concise matrix equation to the compartmental model parameters, which are defined as the transition probabilities per unit time per unit quantity (turn‐over rates) of molecules from one compartment (or state) into another.When measurements are incomplete, the freedom in choosing a model is expressed in turns of a minimum number of variables equal to the difference between the number of model parameters and the number of invariants found in the data. It is shown how other information regarding the model parameters or the amounts of material in steady state may be combined with the tracer data to reduce the degrees of freedom of a proposed model.Matrix transformations are worked out to allow the mapping of all mathematically consistent models in the configuration space of the minimum variables. The boundaries in this space corresponding to the limits for physically realizable models are found. Thus, a model is expressed by a set of coordinates and the values of all the parameters are obtained by substituting the values of the coordinates. Investigation of the range of variation of each parameter over the bounded region is also possible.

ISSN:0021-8979    

DOI:10.1063/1.1722264

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

By observation of rolling friction effects, the rate of drying of paints, varnishes, and other surface coatings can be evaluated more precisely than by previous methods. The time of descent of a ball rolling down a coated incline has been proposed as an index of surface condition. The basic physical phenomenon involved, however, is rolling friction, so the coefficient of rolling friction would be preferable for use as a standard. A metric analogous to Brinell hardness can be defined from the coefficient of rolling friction. The ratio between the coefficient of rolling friction and the radius of the test ball is proposed as an index of surface condition.

ISSN:0021-8979    

DOI:10.1063/1.1722265

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

The generation of an even‐order subharmonic, or harmonic, oscillation in a driven nonlinear resonant system described by just a cubic nonlinear term requires the simultaneous appearance of a zero‐frequency component. This component effectively introduces a squared nonlinear term. A simple experiment with an electrical circuit is described, showing the presence of the zero‐frequency component.

ISSN:0021-8979    

DOI:10.1063/1.1722266

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

Various kinds of silica glass and natural and synthetic crystals have been irradiated with fast neutrons at temperatures of ∼250°C and above 300°C. In the glasses, asymmetric paramagnetic resonance lines resulting from the irradiation have been observed with apparentgvalues of 2.0013±0.0006 and 2.0090±0.0007, and half‐widths of ≈1.7 gauss and ≈40 gauss, respectively. Two groups of lines were found in the natural crystals and have been associated with the two lines in the glasses, the two lines in the glasses being the envelope of the lines in the crystals when they are summed over random orientations with respect to the magnetic field. On the basis ofgvalues, absence of common impurity and of hyperfine splitting, and the thermal stability of the lines, it is concluded that the observed resonances in the silica glasses and crystals have their origin in defects in the basic SiO4tetrahedra generated by fast neutrons and primary and secondary knockons. From preliminary optical bleaching data in neutron irradiated Corning silica it is tentatively concluded that the resonance withg=2.0013 is associated with the defect which gives rise to an optical absorption band at 2120 A. Thegvalues of the two lines in the silica glasses suggest that one center is an electron and the other a hole.

ISSN:0021-8979    

DOI:10.1063/1.1722267

出版商:AIP    

年代:1956

数据来源: AIP