An observational test of common-envelope evolution

By analysing and modelling the change in the abundance ratio of $^{12}$C/$^{13}$C and $^{16}$O/$^{17}$O on the surface of the lower mass star of a binary during the common-envelope (CE) phase of evolution, we propose a simple observational test of the CE scenario. The test is based on the infrared measurement of either the $^{12}$C/$^{13}$C or $^{16}$O/$^{17}$O ratio of red dwarfs in post-common envelope binaries (PCEB's). In certain cases (main-sequence red dwarf secondaries in PCEB's without planetary nebulae), as well as determining whether or not accretion has occurred during the CE phase, we can determine the amount of mass accreted during the CE phase and hence the initial mass of the red dwarf component prior to the CE phase. In the other cases considered (low-mass red dwarfs in PCEB's and red dwarf's in PCEB's with planetary nebulae) we can only say whether or not accretion has occurred during the CE phase.Comment: uuencoded compressed postscript. The preprint are also available at URL http://www.ast.cam.ac.uk/preprint/PrePrint.htm

Multi-frequency fine resolution imaging radar instrumentation and data acquisition

Development of a dual polarized L-band radar imaging system to be used in conjunction with the present dual polarized X-band radar is described. The technique used called for heterodyning the transmitted frequency from X-band to L-band and again heterodyning the received L-band signals back to X-band for amplification, detection, and recording

NASA Workshop on Distributed Parameter Modeling and Control of Flexible Aerospace Systems

Although significant advances have been made in modeling and controlling flexible systems, there remains a need for improvements in model accuracy and in control performance. The finite element models of flexible systems are unduly complex and are almost intractable to optimum parameter estimation for refinement using experimental data. Distributed parameter or continuum modeling offers some advantages and some challenges in both modeling and control. Continuum models often result in a significantly reduced number of model parameters, thereby enabling optimum parameter estimation. The dynamic equations of motion of continuum models provide the advantage of allowing the embedding of the control system dynamics, thus forming a complete set of system dynamics. There is also increased insight provided by the continuum model approach

Replacement of a Major Ventilation Raise at the Homestake Gold Mine

Few tasks are more important to the Ventilation Engineer than planning major airways. This paper presents a case study of the inception, design, installation, cost and performance of a 253 m long, 4.27 m diameter subsurface replacement exhaust raise and its connecting drifts. The original raise served as a component of the primary exhaustway (140 m3/s) and heat rejection sink (8MW) for the deepest production district, responsible for 45% of the mine\u27s total ounce production. The chronology of ground control problems with the original raise and attempts to halt the unraveling are described. Planning for a replacement raise commenced once it was realized that the original raise could not be saved. Computer simulation helped size the new raise and connecting drifts. Selection of the raise location was based on a careful rock mechanics assessment. A temporary ventilation bypass system was designed to minimize production loss in event of a catastrophic failure of the old raise while the new raise was being bored. This failure occurred shortly after the temporary bypass was ready. The new raise system was completed in February 1995 at a cost of $US 1.475 million. The troubles encountered, resistance measurements, and final costs are given, and a comparison of planned and actual performance is made

The influence of gas expulsion and initial mass-segregation on the stellar mass-function of globular star clusters

Recently de Marchi, Paresce & Pulone (2007) studied a sample of twenty globular clusters and found that all clusters with high concentrations have steep stellar mass-functions while clusters with low concentration have comparatively shallow mass-functions. No globular clusters were found with a flat mass-function and high concentration. This seems curious since more concentrated star clusters are believed to be dynamically more evolved and should have lost more low-mass stars via evaporation, which would result in a shallower mass-function in the low-mass part. We show that this effect can be explained by residual-gas expulsion from initially mass-segregated star clusters, and is enhanced further through unresolved binaries. If gas expulsion is the correct mechanism to produce the observed trend, then observation of these parameters would allow to constrain cluster starting conditions such as star formation efficiency and the time-scale of gas expulsion.Comment: accepted for publication in MNRAS, 10 pages, 6 figure

Online Music Piracy: Are Lawsuits The Best Approach?

In the age of digital technology, perfect copies of sound recordings may be easily made and shared in violation of copyright law.  Music piracy in the form of illegal downloading is a worldwide phenomenon that has a significant impact on the music industry.   In response to the perceived threat to the music industry, lawsuits have been filed in the United States and abroad based on copyright infringement for illegally downloading music. This paper examines copyright law, case law, and recent litigation.  In the wake of legal efforts to curtail illegal downloading, a survey of 112 undergraduate students was conducted in an effort to determine whether the lawsuits filed by the music industry are a deterrent to downloading music.  Potential solutions are proposed and economic consequences discussed

Knot undulator to generate linearly polarized photons with low on-axis power density

Heat load on beamline optics is a serious problem to generate pure linearly polarized photons in the third generation synchrotron radiation facilities. For permanent magnet undulators, this problem can be overcome by a figure-8 operating mode. But there is still no good method to tackle this problem for electromagnetic elliptical undulators. Here, a novel operating mode is suggested, which can generate pure linearly polarized photons with very low on-axis heat load. Also the available minimum photon energy of linearly polarized photons can be extended much by this method