32,694 research outputs found
Q-Exact Actions for BF Theories
The actions for all classical (and consequently quantum) theories on
-manifolds is proven to be given by anti-commutators of hermitian,
nilpotent, scalar fermionic charges with Grassmann-odd functionals. In order to
show this, the space of fields in the theory must be enlarged to include ``mass
terms'' for new, non-dynamical, Grassmann-odd fields. The implications of this
result on observables are examined.Comment: 12 pgs., LaTeX, MIT-CTP-227
Applicability of satellite remote sensing for detection and monitoring of coal strip mining activities
The author has identified the following significant results. Large areas covered by orbital photography allows the user to estimate the acreage of strip mining activity from a few frames. Infrared photography both in color and in black and white transparencies was found to be the best suited for this purpose
A streamline curvature method for design of supercritical and subcritical airfoils
An airfoil design procedure, applicable to both subcritical and supercritical airfoils, is described. The method is based on the streamline curvature velocity equation. Several examples illustrating this method are presented and discussed
Low-temperture electrostatic silicon-to-silicon seals using sputtered borosilicate glass
Silicon members are hermetically sealed to each other. Process produces no measurable deformation of silicon surfaces and is compatible with package designs of tight tolerance. Seals have been made with glass coatings in 10-mm to 20-mm thickness range without any prior annealing of coated silicon substrates
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Rapid Design and Manufacture of Ultralight Cellular Materials
This paper details the design, manufacture and testing of regular metallic lattice structures
with unit cell sizes in the range 0.8mm to 5mm and truss elements of 100-500 µm in diameter [1].
The structures were manufactured using Selective Laser Melting (SLM) technology from 316L
stainless steel. Compression tests have shown yield loadings of over 3.5kN despite being only
18mm by 18mm by 10mm in height, the results are favourably comparable to current
commercially available metallic foams. Software has been developed that creates slice files
without the use of CAD software or STL files and is capable of producing lattices within a
volume defined by a STL file.Mechanical Engineerin
The Apollo spacecraft: A chronology volume 4, 21 January 1966 - 13 July 1974
This final volume of the chronology is divided into three parts: (1) preparation for flight, the accident, and investigation; (2) recovery, spacecraft redefinition, and the first manned flight; and (3) man circles the moon, the Eagle lands, and manned space exploration. Congressional documents, official correspondence, government and contractor reports, memoranda, working papers, and minutes of meetings were used as primary sources. A relatively few entries are based on press releases and newspaper and magazine articles
Phenomenological Constraints on Axion Models of Dynamical Dark Matter
In two recent papers (arXiv:1106.4546, arXiv:1107.0721), we introduced
"dynamical dark matter" (DDM), a new framework for dark-matter physics in which
the requirement of stability is replaced by a delicate balancing between
lifetimes and cosmological abundances across a vast ensemble of individual
dark-matter components whose collective behavior transcends that normally
associated with traditional dark-matter candidates. We also presented an
explicit model involving axions in large extra spacetime dimensions, and
demonstrated that this model has all of the features necessary to constitute a
viable realization of the general DDM framework. In this paper, we complete our
study by performing a general analysis of all phenomenological constraints
which are relevant to this bulk-axion DDM model. Although the analysis in this
paper is primarily aimed at our specific DDM model, many of our findings have
important implications for bulk axion theories in general. Our analysis can
also serve as a prototype for phenomenological studies of theories in which
there exist large numbers of interacting and decaying particles.Comment: 48 pages, LaTeX, 13 figures, 1 tabl
Ring-opening copolymerization (ROCOP): synthesis and properties of polyesters and polycarbonates
Controlled routes to prepare polyesters and polycarbonates are of interest due to the widespread application of these materials and the opportunities provided to prepare new copolymers. Furthermore, ring-opening copolymerization may enable new poly(ester–carbonate) materials to be prepared which are inaccessible using alternative polymerizations. This review highlights recent advances in the ring-opening copolymerization catalysis, using epoxides coupled with anhydrides or CO2, to produce polyesters and polycarbonates. In particular, the structures and performances of various homogeneous catalysts are presented for the epoxide–anhydride copolymerization. The properties of the resultant polyesters and polycarbonates are presented and future opportunities highlighted for developments of both the materials and catalysts
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The rocks from space initiative and the space safari
This paper reports the successes of a new initiative in the UK using electronic resources, such as virtual learning environments and e-classrooms, for planetary and space science public engagement activities
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