Variable-volume atomic storage vessel for hydrogen masers

Vessel, located in maser cavity, is made from cylindrical, convoluted flexible bellows which can be expanded or contracted along the cylinder axis vertically. Inner surface area remains constant with changing volume, permitting measurement of frequency deviations of excited atoms

An iterative procedure for obtaining maximum-likelihood estimates of the parameters for a mixture of normal distributions

A general iterative procedure is given for determining the consistent maximum likelihood estimates of normal distributions. In addition, a local maximum of the log-likelihood function, Newtons's method, a method of scoring, and modifications of these procedures are discussed

The numerical evaluation of the maximum-likelihood estimate of a subset of mixture proportions

Necessary and sufficient conditions are given for a maximum likelihood estimate of a subset of mixture proportions. From these conditions, likelihood equations are derived satisfied by the maximum-likelihood estimate and a successive-approximations procedure is discussed as suggested by equations for numerically evaluating the maximum-likelihood estimate. It is shown that, with probability one for large samples, this procedure converges locally to the maximum-likelihood estimate whenever a certain step-size lies between zero and two. Furthermore, optimal rates of local convergence are obtained for a step-size which is bounded below by a number between one and two

An iterative procedure for obtaining maximum-likelihood estimates of the parameters for a mixture of normal distributions, Addendum

New results and insights concerning a previously published iterative procedure for obtaining maximum-likelihood estimates of the parameters for a mixture of normal distributions were discussed. It was shown that the procedure converges locally to the consistent maximum likelihood estimate as long as a specified parameter is bounded between two limits. Bound values were given to yield optimal local convergence

Nietzsche und Seine Schwester: Eine Fussnote

Paper by H. F. Peters, Portland State University

Recurrent shell infall events in a B0.5e star: HD 58978 1979-1988

Infall from the circumstellar envelope onto the bright B0.5 IVe star, HD 58978 was studied. The IUE data indicate that the star was surrounded by a low and moderately ionized circumstellar shell at least 12 times between 1979 and 1988. During 6 of these episodes, the signatures of cool circumstellar material were redshifted with respect to the photosphere by 20 to 80 km/sec. The data indicate that the transition from infall to minimal shell absorption can occur in under 10 days, and are consistent either with infall phases lasting up to 6 months, or with infall episodes shorter than 10 to 15 days. The long term behavior of the shell episodes is compared with variability in the stellar wind

Influence of diesel surrogates on the behavior of simplified spray models

Numerous experimental investigations make use of diesel surrogates to make the computational time reasonable. In the few studies where measured (surrogate and real diesel) and computed (surrogate only) results have been compared, the selection methodology for the surrogate constituent compounds and the measures taken to validate the chemical kinetic models are not discussed, and the range of operating conditions used is often small. Additionally, most simplified models use tuning variables to fit model results to measurements. This work makes the comparison between some frequently used diesel surrogates using a simple 1D vaporizing spray model, with the spray cone angle as the tuning parameter. Results show that liquid length and fuel fraction strongly depend on the physical properties of the used fuel for a fixed spray angle. These parameters are important for modeling auto-ignition and pollutant formation. The spray angle is varied till the spray length is the same for each surrogate. Results show important differences between other spray parameters such as local mixture fraction and axial velocity

Development of mathematical techniques for the analysis of remote sensing data

There are no author-identified significant results in this report

Dynamical aspects of inextensible chains

In the present work the dynamics of a continuous inextensible chain is studied. The chain is regarded as a system of small particles subjected to constraints on their reciprocal distances. It is proposed a treatment of systems of this kind based on a set Langevin equations in which the noise is characterized by a non-gaussian probability distribution. The method is explained in the case of a freely hinged chain. In particular, the generating functional of the correlation functions of the relevant degrees of freedom which describe the conformations of this chain is derived. It is shown that in the continuous limit this generating functional coincides with a model of an inextensible chain previously discussed by one of the authors of this work. Next, the approach developed here is applied to a inextensible chain, called the freely jointed bar chain, in which the basic units are small extended objects. The generating functional of the freely jointed bar chain is constructed. It is shown that it differs profoundly from that of the freely hinged chain. Despite the differences, it is verified that in the continuous limit both generating functionals coincide as it is expected.Comment: 15 pages, LaTeX 2e + various packages, 3 figures. The title has been changed and three references have been added. A large part of the manuscript has been rewritten to improve readability. Chapter 4 has been added. It contains the construction of the generating functional without the shish-kebab approximation and a new derivation of the continuous limit of the freely jointed bar chai