3,175 research outputs found
Process for making diamonds
A description is given of a device and process for making industrial diamonds. The device is composed of an exponential horn tapering from a large end to a small end, with a copper plate against the large end. A magnetic hammer abuts the copper plate. The copper plate and magnetic hammer function together to create a shock wave at the large end of the horn. As the wave propagates to the small end, the extreme pressure and temperature caused by the wave transforms the graphite, present in an anvil pocket at the small end, into diamonds
Synthesis of diamonds
Shock wave transmitted through a solid exponential horn generates heat and pressure to convert part of a charge of graphite to diamonds. The shock wave is generated in the apparatus by a complex of magnetic fields and eddy currents
Moduli stabilisation in early superstring cosmology
We study moduli stabilization by thermal effects in the cosmological context.
The implementation of finite temperature, which spontaneously breaks
supersymmetry, induces an effective potential at one loop level. At the points
where extra massless states appear in the string spectrum, the potential
develops local minima whose depth depends on the temperature. Moduli attracted
to these points acquire dynamical masses which decrease with cosmological
evolution. This makes the coherent scalar oscillations dilute before
nucleosynthesis, and the cosmological moduli problem is avoided. In particular,
we study the effective potential induced by a maximally supersymmetric
heterotic string gas for spacetime dimension D>=4, and a gas of type II strings
compactified on Calabi-Yau three-folds (D=4). In the former case, the local
minima of the potential arise at enhanced gauge symmetry points, which can
stabilize all moduli but the dilaton. In the latter case, the local minima are
reached at the loci where 2-cycles or 3-cycles in the Calabi-Yau space shrink
to zero size, accompanied with either conifold transitions or non Abelian gauge
symmetries. This stabilizes the type II moduli which characterize the
deformation of these shrinking cycles. Moduli stabilization in the dual string
models is also investigated by heterotic/type I S-dualities and type
II/heterotic dualities.Comment: 13+1 pages. Based on a talk given at the "The Seventh International
Conference Quantum Theory and Symmetries", Prague, Czech Republic, on August
7-13, 201
Language Style as Identity Construction: A Footing and Framing Approach
Despite the prevalence of conceptualizations of style shifting as a reactive phenomenon, conditioned by contextual factors such as formality and audience, style shifting increasingly has come to be viewed as a proactive phenomenon which speakers freely use to shape and re-shape context, as well as their personal and interpersonal identities (e.g. California Style Collective 1993, Coupland forthcoming). In this presentation, we suggest that an explanation for style shifting based on the interactional sociolinguistic notions of footing and frame indexing (e.g. Goffman 1981, Tannen and Wallat 1993) provides a neat encapsulation of some of the central tenets of these more proactive approaches, while at the same time addressing their limitations
Non Radiation Hardened Microprocessors in Spaced Based Remote Sensing Systems
The CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) mission is a comprehensive suite of active and passive sensors including a 20Hz 230mj Nd:YAG lidar, a visible wavelength Earth-looking camera and an imaging infrared radiometer. CALIPSO flies in formation with the Earth Observing System Post-Meridian (EOS PM) train, provides continuous, near-simultaneous measurements and is a planned 3 year mission. CALIPSO was launched into a 98 degree sun synchronous Earth orbit in April of 2006 to study clouds and aerosols and acquires over 5 gigabytes of data every 24 hours. The ground track of one CALIPSO orbit as well as high and low intensity South Atlantic Anomaly outlines is shown. CALIPSO passes through the SAA several times each day. Spaced based remote sensing systems that include multiple instruments and/or instruments such as lidar generate large volumes of data and require robust real-time hardware and software mechanisms and high throughput processors. Due to onboard storage restrictions and telemetry downlink limitations these systems must pre-process and reduce the data before sending it to the ground. This onboard processing and realtime requirement load may mean that newer more powerful processors are needed even though acceptable radiation-hardened versions have not yet been released. CALIPSO's single board computer payload controller processor is actually a set of four (4) voting non-radiation hardened COTS Power PC 603r's built on a single width VME card by General Dynamics Advanced Information Systems (GDAIS). Significant radiation concerns for CALIPSO and other Low Earth Orbit (LEO) satellites include the South Atlantic Anomaly (SAA), the north and south poles and strong solar events. Over much of South America and extending into the South Atlantic Ocean the Van Allen radiation belts dip to just 200-800km and spacecraft entering this area are subjected to high energy protons and experience higher than normal Single Event Upset (SEU) and Single Event Latch-up (SEL) rates. Although less significant, spacecraft flying in the area around the poles experience similar upsets. Finally, powerful solar proton events in the range of 10MeV/10pfu to 100MeV/1pfu as are forecasted and tracked by NOAA's Space Environment Center in Colorado can result in Single Event Upset (SEU), Single Event Latch-up (SEL) and permanent failures such as Single Event Gate Rupture (SEGR) in some technologies. (Galactic Cosmic Rays (GCRs) are another source, especially for gate rupture) CALIPSO mitigates common radiation concerns in its data handling through the use of redundant processors, radiation-hardened Application Specific Integrated Circuits (ASIC), hardware-based Error Detection and Correction (EDAC), processor and memory scrubbing, redundant boot code and mirrored files. After presenting a system overview this paper will expand on each of these strategies. Where applicable, related on-orbit data collected since the CALIPSO initial boot on May 4, 2006 will be noted
Civil engineering program evaluator reflections: The most recent lessons learned
For the 2011-2012 ABET accreditation cycle, a number of changes across the criteria have impacted the way in which programs must approach their accreditation efforts.1 The most significant change is related to the reporting of assessment activities and their use for program improvement. For the first time this year, assessment results of program educational objectives and student outcomes are reported in Criterion 4, Continuous Improvement. Additionally, there have been changes to the former Criterion 9, Program Criteria. The Program Criteria is no longer numbered, but more importantly, contains some fairly significant changes impacting the assessment of student performance. The changes include no longer requiring programs to specifically incorporate the program criteria in their student outcomes and no longer requiring programs to assess the degree to which students are achieving the program criteria. The purpose of this paper is to capture the experiences of three Civil Engineering Program Evaluators who have visited programs with differing characteristics during this accreditation cycle. It takes the reader from initial contact with the program chair through review of the self study and student transcripts to the on-site visit and offers lessons learned on how to best meet the current ABET Criteria and prepare for an ABET visit
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A protocol paper on the preservation of identity: understanding the technology adoption patterns of older adults with age-related vision loss (ARVL)
There are a growing number of older adults with age-related vision loss (ARVL) for whom technology holds promise in supporting their engagement in daily activities. Despite the growing presence of technologies intended to support older adults with ARVL, there remains high rates of abandonment. This phenomenon of technology abandonment may be partly explained by the concept of self-image, meaning that older adults with ARVL avoid the use of particular technologies due to an underlying fear that use of such technologies may mark them as objects of pity, ridicule, and/or stigmatization. In response to this, the proposed study aims to understand how the decision-making processes of older adults with ARVL, as it relates to technology adoption, is influenced by the negotiation of identity. The study protocol will justify the need for this critical ethnographic study, unpack the theoretical underpinnings of this work, detail the sampling/recruitment strategy, describe the methods which included a home tour, go-along, and semi-structured in-depth interview, as well as the collective approach taken to analyze the data. The protocol concludes by examining the ethical tensions associated with this study, including a focus on the methods adopted as well as the ethical challenges inherent when working with an older adult population experiencing vision loss
G3-homogeneous gravitational instantons
We provide an exhaustive classification of self-dual four-dimensional
gravitational instantons foliated with three-dimensional homogeneous spaces,
i.e. homogeneous self-dual metrics on four-dimensional Euclidean spaces
admitting a Bianchi simply transitive isometry group. The classification
pattern is based on the algebra homomorphisms relating the Bianchi group and
the duality group SO(3). New and general solutions are found for Bianchi III.Comment: 24 pages, few correction
Private Rainbows
I make art that refers to how the self is mediated through structures, objects, and images — a kind of self-portraiture that circles around its subject, reflecting a state of simultaneous formation and disintegration. Over the past few years, I have used my iPhone as a tool to make images of everyday life. As the user of this device, I am defined by both my presence and absence. I am interested in the process of locating the self within the scattered yet ordered space of the screen
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