摘要:

In this paper, we consider gas dynamical models of spiral galaxies in which there is a rigidly rotating, weakly barlike structure in the central regions. It is found that, in the neighborhood of the corotation circle, this barlike structure forces atrailing spiral wave. Such a driven wave could then propagate inwards to the bar and complete a feedback loop to maintain the spiral structure. For basic distributions typical of our Galaxy, if a ten‐per‐cent oval distortion is assumed, the strength of the induced spiral field is found to be of the order of a few per cent of the axisymmetric field, in agreement with observational d

ISSN:0022-2526    

DOI:10.1002/sapm19735211

年代:1973

数据来源: WILEY

ISSN:0022-2526    

DOI:10.1002/sapm197352121

年代:1973

数据来源: WILEY

摘要:

The linear stability to axisymmetric perturbations of compressible non‐dissipative swirling flow is shown to be insured if a suitably defined “Richardson number” depending on the basic velocity, temperature and density fields everywhere exceeds 1/4. This result combines and generalizes in a natural way some known results for incompressible swirling flow and stratified parallel

ISSN:0022-2526    

DOI:10.1002/sapm197352139

年代:1973

数据来源: WILEY

摘要:

This paper is concerned with certain mathematical aspects of long nonlinear wave propagation on a free surface. Some special solutions are noted and the equations are shown to have an infinite number of conservation laws.

ISSN:0022-2526    

DOI:10.1002/sapm197352145

年代:1973

数据来源: WILEY

摘要:

A theory describing the behavior of a system as it evolves slowly through internal nonlinear resonances is presented. The energy sharing process is seen to be quite complex as it depends crucially on both nonlinear and frequency detuning effects. Two phenomena are discussed in detail although the general ideas are applicable to many situations. Firstly we examine the interaction between the quadratically coupled oscillators whose natural frequencies are in the ratio 2:1 for a limited period of time. Such a system is shown to be an extremely useful switching device. Secondly we examine the time dependent Duffing equation and find that smooth forward and reverse transitions occur without the presence of dissipation.

ISSN:0022-2526    

DOI:10.1002/sapm197352151

年代:1973

数据来源: WILEY

摘要:

A transportation system is operated with one vehicle andNservice points. At one terminal of the system passengers arrive in groups only at discrete points in time; at the other service points, riders enter steadily at constant rates. Vehicle travel times between adjacent service points are random variables. The problem addressed in this paper is that of devising the operating strategy which minimizes average waiting time for passengers of the system. Using different kinds of probabilistic analysis, we obtain optimal policy statements both when the discrete‐time arrivals occur at fixed instants of equal spacing, and when these arrivals occur in Poisson fashion. Some specific applications are discusse

ISSN:0022-2526    

DOI:10.1002/sapm197352175

年代:1973

数据来源: WILEY