摘要:

The tensile strengths of several liquids at low temperature were measured by a linear deceleration method. The values found were as follows (expressed in atoms): argon −12, nitrogen −10, oxygen −15, and helium −0.16. The values are somewhat lower than those calculated from the theory.

ISSN:0031-9171    

DOI:10.1063/1.1724385

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The reflection coefficient for a small‐amplitude second sound wave reflected by a large‐amplitude first sound wave front is derived. This type of reflection is unique in that the discontinuity (the first sound wave) travels faster than the wave being reflected. Hence, the discontinuity can overtake the second sound wave from behind. It is shown that the principal term in the reflection coefficient is due to the particle velocity associated with a pressure wave. This reflection coefficient is positive when the discontinuity overtakes the second sound wave from behind and negative when the discontinuity and the second sound wave are approaching one another head‐on. The reflection coefficient for a small‐amplitude first sound wave reflected by a large‐amplitude second sound wave front is also derived.

ISSN:0031-9171    

DOI:10.1063/1.1724393

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A method is presented for calculating the grand‐partition function of a one‐dimensional gas with the potentialV(x) = + ∞ for 0 ≤x< &dgr; andV(x) = −&agr;e−&ggr;xforx≥ &dgr;.

ISSN:0031-9171    

DOI:10.1063/1.1724399

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The classical theory of Brownian motion of a periodic system is generalized to include the case where the period of the system is very short compared with times characteristic of its interaction with the environment. The system is described in terms of action and phase variables, which are constants of the motion in the absence of interactions. The probability density of the system, averaged over a time which is very long compared with a period of the motion, and long enough to include many interactions, is shown to be a solution of a Fokker‐Planck equation in action‐phase variables. Conditions for this are that the interaction is sufficiently weak and that the environment remains in thermal equilibrium. Explicit expressions for the friction coefficients are obtained. When the probability density of the system is independent of its phase, its irreversible behavior can be described as a random walk in action space. This is a reasonable classical analog to the quantum‐statistical description by means of the Pauli equation. The properties of a harmonic oscillator with a special interaction are considered in detail; it is shown that the friction coefficients are proportional to the spectral density of a fluctuating force associated with the interaction, evaluated at the frequency of the oscillator.

ISSN:0031-9171    

DOI:10.1063/1.1724384

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A closed expression is given for the distribution functions in the classical theory of statistical equilibrium. This expression, when suitably expanded, permits one to obtain rather simply the general term in the virial expansion of the distribution functions and of the equation of state.

ISSN:0031-9171    

DOI:10.1063/1.1724386

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

In high‐temperature plasmas, collisions are very infrequent. Thus the charged particles travel on independent orbits determined by the electromagnetic field. At first sight this would seem completely different from a conventional fluid where particles are closely hemmed in by their neighbors. However, there can exist collective modes of motion in which the particles interact with each other by altering the fields.In this paper a new method is developed for the solution of the linearized transport equation. By facilitating direct use of the properties of particle orbits, a considerable simplification is achieved. In particular, a variational expression is derived for determining stability which is rigorous in the limit of small Larmor radius.

ISSN:0031-9171    

DOI:10.1063/1.1724387

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A method is developed for investigating the propagation of disturbances at small amplitude in fluids from the molecular or ionic standpoint. Adopting as variables the displacements of the particles from a configuration of thermal equilibrium, the equations of motion are derived, in statistical form, for both classical and quantum mechanics.It is shown how to apply this theory in the high‐frequency region by neglecting the correlation between the displacements of neighboring particles. Relaxation frequencies are defined, and it is shown that anomalous absorption and dispersion will be found in their neighborhood. Beyond the relaxation frequency, the medium will show elastic or dispersive properties, according to whether the thermal velocities are below or exceed the velocity of propagation. A completely ionized system will have no relaxation frequencies.

ISSN:0031-9171    

DOI:10.1063/1.1724388

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

In the classical Chapman‐Enskog theory of a fully ionized gas, the transport coefficients evolve as functionals of certain weighted total scattering cross sections. If a Coulomb potential is assumed between scattering particles, these scattering integrals diverge. A common procedure to circumvent this difficulty is to integrate the Coulomb results up to the Debye cutoff. A more appropriate procedure involves the use of the shielded Coulomb potential, in which case the scattering integrals converge, and there is no need to introduce a cutoff. These integrals are calculated using the shielded Coulomb potential and the resultant transport coefficients are compared with those of the standard ``Coulomb plus Debye cutoff'' calculations. To the ``dominant log term'' the two procedures give identical results. To terms of the next order of accuracy for the viscosity and thermal conductivity the difference between the two formulations is of the order of 0.5%, and for the diffusion and electrical conductivity the difference is of the order of 2%. The major calculation is that of the classical cross section for the screened Coulomb potential.

ISSN:0031-9171    

DOI:10.1063/1.1724389

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A regular hydromagnetic oscillation was excited in a linear discharge tube with metal walls. An externally applied axial magnetic field and discharge currents less than 104amperes were essential to the production of the oscillation. Complete spatial current distributions derived from measurements of the radial and time dependence of the three components of magnetic field showed a helical notch (screw thread) of reduced current density which rotated with uniform angular velocity. The pitch and apparent rotational frequency of the oscillation depended on the gas density, discharge current, and applied axial magnetic field; the right‐ or left‐handedness and rotational sense depended on the relative orientation of the applied axial magnetic field and the self field of the discharge current. The helical regularity could be described as a superposition of hydromagnetic waves traveling in the axial and circumferential directions.

ISSN:0031-9171    

DOI:10.1063/1.1724390

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The plasma is treated as an assembly of classical particles having massesm+andm−and charges ±e. It is shown that if such a plasma is in thermodynamic equilibrium it is unaffected by a magnetostatic field. In particular, it cannot be confined by a magnetostatic field and at the same time be in equilibrium. In absence of collisions there exist stationary solutions for the magnetic field and the particle distribution in phase space such that the gas is confined. The solutions are self‐consistent, meaning that the particle motions generate the field, which in turn maintains the particle distribution. However, this distribution may not be Maxwellian. As an example the linear pinch is treated. The fields, the particle number densities, and the current density are calculated for one particular case.

ISSN:0031-9171    

DOI:10.1063/1.1724391

出版商:AIP    

年代:1959

数据来源: AIP