3,367 research outputs found
The materials processing research base of the Materials Processing Center
The goals and activities of the center are discussed. The center activities encompass all engineering materials including metals, ceramics, polymers, electronic materials, composites, superconductors, and thin films. Processes include crystallization, solidification, nucleation, and polymer synthesis
Scattering a pulse from a chaotic cavity: Transitioning from algebraic to exponential decay
The ensemble averaged power scattered in and out of lossless chaotic cavities
decays as a power law in time for large times. In the case of a pulse with a
finite duration, the power scattered from a single realization of a cavity
closely tracks the power law ensemble decay initially, but eventually
transitions to an exponential decay. In this paper, we explore the nature of
this transition in the case of coupling to a single port. We find that for a
given pulse shape, the properties of the transition are universal if time is
properly normalized. We define the crossover time to be the time at which the
deviations from the mean of the reflected power in individual realizations
become comparable to the mean reflected power. We demonstrate numerically that,
for randomly chosen cavity realizations and given pulse shapes, the probability
distribution function of reflected power depends only on time, normalized to
this crossover time.Comment: 23 pages, 5 figure
Density Matrix Perturbation Theory
An expansion method for perturbation of the zero temperature grand canonical
density matrix is introduced. The method achieves quadratically convergent
recursions that yield the response of the zero temperature density matrix upon
variation of the Hamiltonian. The technique allows treatment of embedded
quantum subsystems with a computational cost scaling linearly with the size of
the perturbed region, O(N_pert.), and as O(1) with the total system size. It
also allows direct computation of the density matrix response functions to any
order with linear scaling effort. Energy expressions to 4th order based on only
first and second order density matrix response are given.Comment: 4 pages, 2 figure
Test beam Characterizations of 3D Silicon Pixel detectors
3D silicon detectors are characterized by cylindrical electrodes
perpendicular to the surface and penetrating into the bulk material in contrast
to standard Si detectors with planar electrodes on its top and bottom. This
geometry renders them particularly interesting to be used in environments where
standard silicon detectors have limitations, such as for example the radiation
environment expected in an LHC upgrade. For the first time, several 3D sensors
were assembled as hybrid pixel detectors using the ATLAS-pixel front-end chip
and readout electronics. Devices with different electrode configurations have
been characterized in a 100 GeV pion beam at the CERN SPS. Here we report
results on unirradiated devices with three 3D electrodes per 50 x 400 um2 pixel
area. Full charge collection is obtained already with comparatively low bias
voltages around 10 V. Spatial resolution with binary readout is obtained as
expected from the cell dimensions. Efficiencies of 95.9% +- 0.1 % for tracks
parallel to the electrodes and of 99.9% +- 0.1 % at 15 degrees are measured.
The homogeneity of the efficiency over the pixel area and charge sharing are
characterized.Comment: 5 pages, 7 figure
Hammerhead, an ultrahigh resolution ePix camera for wavelength-dispersive spectrometers
Wavelength-dispersive spectrometers (WDS) are often used in synchrotron and
FEL applications where high energy resolution (in the order of eV) is
important. Increasing WDS energy resolution requires increasing spatial
resolution of the detectors in the dispersion direction. The common approaches
with strip detectors or small pixel detectors are not ideal. We present a novel
approach, with a sensor using rectangular pixels with a high aspect ratio
(between strips and pixels, further called "strixels"), and strixel
redistribution to match the square pixel arrays of typical ASICs while avoiding
the considerable effort of redesigning ASICs. This results in a sensor area of
17.4 mm x 77 mm, with a fine pitch of 25 m in the horizontal direction
resulting in 3072 columns and 176 rows. The sensors use ePix100 readout ASICs,
leveraging their low noise (43 e, or 180 eV rms). We present results
obtained with a Hammerhead ePix100 camera, showing that the small pitch (25
m) in the dispersion direction maximizes performance for both high and low
photon occupancies, resulting in optimal WDS energy resolution. The low noise
level at high photon occupancy allows precise photon counting, while at low
occupancy, both the energy and the subpixel position can be reconstructed for
every photon, allowing an ultrahigh resolution (in the order of 1 m) in
the dispersion direction and rejection of scattered beam and harmonics. Using
strixel sensors with redistribution and flip-chip bonding to standard ePix
readout ASICs results in ultrahigh position resolution (1 m) and low
noise in WDS applications, leveraging the advantages of hybrid pixel detectors
(high production yield, good availability, relatively inexpensive) while
minimizing development complexity through sharing the ASIC, hardware, software
and DAQ development with existing versions of ePix cameras.Comment: 8 pages, 6 figure
Justice and Natural Resources: Concepts, Strategies, and Applications
This digital resource contains only an abstract, cover image and table of contents information from the published book.
Print copy of book is available in the University of Colorado\u27s Wise Law Library: http://128.138.161.92/record=b257401
Contents: PART ONE : FRAMEWORKS: Beyond traditional environmental justice / David H. Getches, David N. Pellow -- Assessing claims of environmental justice : conceptual frameworks / Gary C. Bryner -- Water, poverty, equity, and justice in Colorado : a pragmatic approach / James l. Wescoat Jr., Sarah Halvorson, Lisa Headington, Jill Replogle -- International environmental protection : human rights and North-South divide / Tseming Yang -- PART TWO : CONCEPTS: The coincidental order of environmental injustice / Jeff Romm -- Environmental justice in an era of devolved collaboration / Sheila Foster -- Tribal sovereignty and environmental justice / Sarah Krakoff -- PART THREE : STRATEGIES AND APPLICATIONS: Expanding civil rights protections in contested terrain : using Title VI of the Civil Rights Act of 1964 / Luke W. Cole -- Forest management and environmental justice in northern New Mexico / Henry H. Carey -- NEPA in Indian Country : compliance requirement to decision-making tool / Dean B. Suagee -- A framework to assess environmental justice concerns for proposed federal projects / Jan Buhrmann -- Protecting natural resources and the issue of environmental justice / Barry E. Hill, Nicholas Targ -- Mineral development : protecting the land and communities / Kathryn M. Mutz -- CONCLUSION: Hoping against history : environmental justice in the twenty-first century / Patricia Nelson Limerickhttps://scholar.law.colorado.edu/books_reports_studies/1133/thumbnail.jp
Spectacular X-ray tails, intracluster star formation and ULXs in A3627
We present the discovery of spectacular double X-ray tails associated with
ESO137-001 and a possibly heated X-ray tail associated with ESO137-002, both
late-type galaxies in the closest rich cluster Abell 3627. A deep Chandra
observation of ESO137-001 allows us for the first time to examine the spatial
and spectral properties of such X-ray tails in detail. Besides the known bright
tail that extends to ~ 80 kpc from ESO137-001, a fainter and narrower secondary
tail with a similar length was surprisingly revealed. There is little
temperature variation along both tails. We also identified six X-ray point
sources as candidates of intracluster ULXs with L(0.3-10 keV) of up to
2.5x10^40 erg s^-1. Gemini spectra of intracluster HII regions downstream of
ESO137-001 are also presented, as well as the velocity map of these HII regions
that shows the imprint of ESO137-001's disk rotation. For the first time, we
unambiguously know that active star formation can happen in the cold ISM
stripped by ICM ram pressure and it may contribute a significant amount of the
intracluster light. We also report the discovery of a 40 kpc X-ray tail of
another late-type galaxy in A3627, ESO137-002. Its X-ray tail seems hot, ~ 2
keV (compared to ~ 0.8 keV for ESO137-001's tails). We conclude that the high
pressure environment around these two galaxies is important for their bright
X-ray tails and the intracluster star formation.Comment: ApJ in press, January 2010, v708, only several minor word changes,
emulateapj5.sty, 24 pages, 11 color + 5 B/W figures (figure quality degraded)
and 4 tables. The abstract has been abbreviated. A high-resolution PDF is
available at: http://www.astro.virginia.edu/~ms4ar/eso137_p3.pd
Invest to Save: Report and Recommendations of the NSF-DELOS Working Group on Digital Archiving and Preservation
Digital archiving and preservation are important areas for research and development, but there is no agreed upon set of priorities or coherent plan for research in this area. Research projects in this area tend to be small and driven by particular institutional problems or concerns. As a consequence, proposed solutions from experimental projects and prototypes tend not to scale to millions of digital objects, nor do the results from disparate projects readily build on each other. It is also unclear whether it is worthwhile to seek general solutions or whether different strategies are needed for different types of digital objects and collections. The lack of coordination in both research and development means that there are some areas where researchers are reinventing the wheel while other areas are neglected.
Digital archiving and preservation is an area that will benefit from an exercise in analysis, priority setting, and planning for future research. The WG aims to survey current research activities, identify gaps, and develop a white paper proposing future research directions in the area of digital preservation. Some of the potential areas for research include repository architectures and inter-operability among digital archives; automated tools for capture, ingest, and normalization of digital objects; and harmonization of preservation formats and metadata. There can also be opportunities for development of commercial products in the areas of mass storage systems, repositories and repository management systems, and data management software and tools.
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