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Andrews L.C.,Micro Encoder Inc. | Bernstein H.J.,Dowling College
Journal of Applied Crystallography | Year: 2014

Niggli reduction can be viewed as a series of operations in a six-dimensional space derived from the metric tensor. An implicit embedding of the space of Niggli-reduced cells in a higher-dimensional space to facilitate calculation of distances between cells is described. This distance metric is used to create a program, BGAOL, for Bravais lattice determination. Results from BGAOL are compared with results from other metric based Bravais lattice determination algorithms. This embedding depends on understanding the boundary polytopes of the Niggli-reduced cone N in the six-dimensional space G 6. This article describes an investigation of the boundary polytopes of the Niggli-reduced cone N in the six-dimensional space G 6 by algebraic analysis and organized random probing of regions near one-, two-, three-, four-, five-, six-, seven- and eightfold boundary polytope intersections. The discussion of valid boundary polytopes is limited to those avoiding the mathematically interesting but crystallographically impossible cases of zero-length cell edges. Combinations of boundary polytopes without a valid intersection in the closure of the Niggli cone or with an intersection that would force a cell edge to zero or without neighboring probe points are eliminated. In all, 216 boundary polytopes are found. There are 15 five-dimensional boundary polytopes of the full G 6 Niggli cone N. © 2014 International Union of Crystallography.

McGill K.J.,Dowling College | Asadi M.,Dowling College | Karakasheva M.T.,Dowling College | Andrews L.C.,Micro Encoder Inc. | Bernstein H.J.,Dowling College
Journal of Applied Crystallography | Year: 2014

A database of lattices using the G 6 representation of the Niggli-reduced cell as the search key provides a more robust and complete search than older techniques. Searching is implemented by finding the distance from the probe cell to other cells using a topological embedding of the Niggli reduction in G 6, so that all cells representing similar lattices will be found. The embedding provides the first fully linear measure of distances between unit cells. Comparison of results with those from older cell-based search algorithms suggests significant value in the new approach. © 2014 International Union of Crystallography.

McNamara J.,Micro Encoder Inc.
International Conference on Software Engineering Theory and Practice 2010, SETP 2010 | Year: 2010

Multithreaded applications present new challenges to software testing. Testing must take into account not only the different inputs to a process, but the interaction of such processes with each other. These interactions cause race conditions that do not appear when considering each operation in the process as independent. The resulting parameter space quickly becomes large. We investigate how stochastic testing, having success in testing large parameter spaces, can be applied to the testing of multithreaded applications. This paper is a case study of how stochastic testing can be used as an effective black-box approach. The results of such testing can be analyzed to formulate future regressions.


Micro Encoder Inc. | Date: 2007-01-17

Electronic surface displacement sensors.

Bischoff C.,University of Chicago | Bischoff C.,Harvard - Smithsonian Center for Astrophysics | Brizius A.,University of Chicago | Brizius A.,Max Planck Institute for Radio Astronomy | And 68 more authors.
Astrophysical Journal | Year: 2013

The Q/U Imaging ExperimenT (QUIET) is designed to measure polarization in the cosmic microwave background, targeting the imprint of inflationary gravitational waves at large angular scales(∼1°). Between 2008 October and 2010 December, two independent receiver arrays were deployed sequentially on a 1.4 m side-fed Dragonian telescope. The polarimeters that form the focal planes use a compact design based on high electron mobility transistors (HEMTs) that provides simultaneous measurements of the Stokes parameters Q, U, and I in a single module. The 17-element Q-band polarimeter array, with a central frequency of 43.1 GHz, has the best sensitivity (69 μKs1/2) and the lowest instrumental systematic errors ever achieved in this band, contributing to the tensor-to-scalar ratio at r < 0.1. The 84-element W-band polarimeter array has a sensitivity of 87 μKs1/2 at a central frequency of 94.5 GHz. It has the lowest systematic errors to date, contributing at r < 0.01. The two arrays together cover multipoles in the range ℓ ∼ 25-975. These are the largest HEMT-based arrays deployed to date. This article describes the design, calibration, performance, and sources of systematic error of the instrument. © 2013. The American Astronomical Society. All rights reserved.

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