Fluidic packaging of microengine and microrocket devices for high pressure and high temperature operation

The fluidic packaging of Power MEMS devices such as the MIT microengine and microrocket requires the fabrication of hermetic seals capable of withstanding temperature in the range 20-600/spl deg/C and pressures in the range 100-300 atm. We describe an approach to such packaging by attaching Kovar metal tubes to a silicon device using glass seal technology. Failure due to fracture of the seals is a significant reliability concern in the baseline process: microscopy revealed a large number of voids in the glass, pre-cracks in the glass and silicon, and poor wetting of the glass to silicon. The effects of various processing and materials parameters on these phenomena were examined. A robust procedure, based on the use of metal-coated silicon substrates, was developed to ensure good wetting. The bending strength of single-tube specimens was determined at several temperatures. The dominant failure mode changed from fracture at room temperature to yielding of the glass and Kovar at 600/spl deg/C. The strength in tension at room temperature was analyzed using Weibull statistics; these results indicate a probability of survival of 0.99 at an operational pressure of 125 atm at room temperature for single tubes and a corresponding probability of 0.9 for a packaged device with 11 joints. The residual stresses were analyzed using the method of finite elements and recommendations for the improvement of packaging reliability are suggested

Possible tests of neutrino maximal mixing and comments on matter effects

We show in a simple and general way that matter effects do not contribute to the averaged value of the probabilities of transition of solar $\nu_e$'s into other states in the case of maximal mixing of any number of massive neutrinos. We also show that future solar neutrino experiments (Super-Kamiokande and SNO) will allow to test the model with maximal mixing of three massive neutrinos in a way that does not depend on the initial solar neutrino flux.Comment: RevTeX file, 11 pages including 1 figure. The postscript file is available at http://www.to.infn.it/teorici/giunti/papers.htm

Sum Rules of Neutrino Masses and CP Violation in the Four-Neutrino Mixing Scheme

We show that the commutator of lepton mass matrices is invariant under terrestial matter effects in the four-neutrino mixing scheme. A set of model-independent sum rules for neutrino masses, which may be generalized to hold for an arbitrary number of neutrino families, are for the first time uncovered. Useful sum rules for the rephasing-invariant measures of leptonic CP violation have also been found. Finally we present a generic formula of T-violating asymmetries and expect it to be applicable to the future long-baseline neutrino oscillation experiments.Comment: RevTex 8 pages. 3 references added. Phys. Rev. D (in printing

Tangible and virtual digital sound programming and manipulation for children

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2005.Includes bibliographical references (p. 136-139).Creative Digital sound manipulation is a powerful means of personal expression. However, it remains explored by only a small number of engineers, mathematicians, and avant-garde musicians and composers. Others find the interfaces both obtuse and focused more on how the sounds are manipulated than what expressivity the manipulations offer. Yet digital sound manipulation can be accessible to everybody. It can even be a powerful way for people to explore, design, and create while learning about mathematics, dataflow, networks, and computer programming. SoundBlocks and SoundScratch are two different environments in which children can manipulate digital sound. SoundBlocks is a tangible programming language for describing dataflow with adaptive, context-aware primitives and real-time sensing. SoundScratch is a set of sound primitives that extend the media-rich capabilities of the children's programming language called Scratch. Both environments have been created and developed as a way to explore how it might be possible to construct an environment in which youth design their own sounds. Children ages 10-15 years old have explored the environments and participated n user studies. Music educators have observed these studies, and their observations are summarized.by John Harrison.S.M

A quantum mechanical relation connecting time, temperature, and cosmological constant of the universe: Gamow's relation revisited as a special case

Considering our expanding universe as made up of gravitationally interacting particles which describe particles of luminous matter and dark matter and dark energy which is described by a repulsive harmonic potential among the points in the flat 3-space, we derive a quantum mechanical relation connecting, temperature of the cosmic microwave background radiation, age, and cosmological constant of the universe. When the cosmological constant is zero, we get back the Gamow's relation with a much better coefficient. Otherwise, our theory predicts a value of the cosmological constant $2.0 10^{-56} {\rm {cm^{-2}}}$ when the present values of cosmic microwave background temperature of 2.728 K and age of the universe 14 billion years are taken as input.Comment: 4 pages, 1 figure, Study of the Universe from a condensed matter point of view, section III corrected with a single body potentia