14,932 research outputs found
Spin squeezing: transforming one-axis-twisting into two-axis-twisting
Squeezed spin states possess unique quantum correlation or entanglement that
are of significant promises for advancing quantum information processing and
quantum metrology. In recent back to back publications [C. Gross \textit{et al,
Nature} \textbf{464}, 1165 (2010) and Max F. Riedel \textit{et al, Nature}
\textbf{464}, 1170 (2010)], reduced spin fluctuations are observed leading to
spin squeezing at -8.2dB and -2.5dB respectively in two-component atomic
condensates exhibiting one-axis-twisting interactions (OAT). The noise
reduction limit for the OAT interaction scales as , which
for a condensate with atoms, is about 100 times below standard
quantum limit. We present a scheme using repeated Rabi pulses capable of
transforming the OAT spin squeezing into the two-axis-twisting type, leading to
Heisenberg limited noise reduction , or an extra 10-fold
improvement for .Comment: 4 pages, 3 figure
The effects of surface finish and grain size on the strength of sintered silicon carbide
The effects of surface treatment and microstructure, especially abnormal grain growth, on the strength of sintered SiC were studied. The surfaces of sintered SiC were treated with 400, 800 and 1200 grit diamond wheels. Grain growth was induced by increasing the sintering times at 2050 C. The beta to alpha transformation occurred during the sintering of beta-phase starting materials and was often accompanied by abnormal grain growth. The overall strength distributions were established using Weibull statistics. The strength of the sintered SiC is limited by extrinsic surface flaws in normal-sintered specimens. The finer the surface finish and grain size, the higher the strength. But the strength of abnormal sintering specimens is limited by the abnormally grown large tabular grains. The Weibull modulus increases with decreasing grain size and decreasing grit size for grinding
Fault diagnostic instrumentation design for environmental control and life support systems
As a development phase moves toward flight hardware, the system availability becomes an important design aspect which requires high reliability and maintainability. As part of continous development efforts, a program to evaluate, design, and demonstrate advanced instrumentation fault diagnostics was successfully completed. Fault tolerance designs for reliability and other instrumenation capabilities to increase maintainability were evaluated and studied
Business Ecosystem and Stakeholders’ Role Transformation: Evidence from China’s Emerging Electric Vehicle Industry
Nurturing an emerging industry’s business ecosystem always requires stakeholders’ efforts and role transformation. By systematically reviewing and studying the evolution of the Chinese electric vehicle industry, this paper constructs a three-dimensional theoretical framework including stages of business ecosystem lifecycle, stakeholder classification and functional roles, to analyse the transformation both of different stakeholders and their functional roles. The findings show that business ecosystem stakeholders have experienced role transformation following a mechanism defined as the ‘Triple Oscillation’ Model during the evolution of the emerging industry. These findings also help develop a conceptual model of agent-based system for business ecosystem evolution, which could be a starting point for further emerging industry study
Cerenkov Line Emission as a Possible Mechanism of X-ray Lines in Gamma-ray Bursts
The recent discoveries of X-ray lines in the afterglows of gamma-ray bursts
(GRBs) provide significant clues to the nature of GRB progenitors and central
environments. However, the iron line interpretation by fluorescence or
recombination mechanism requires a large amount of iron material. We argue that
the very strong iron line could be attributed to an alternative mechanism:
Cerenkov line emission since relativistic electrons and dense medium exist near
GRB sites. Therefore, the broad iron lines are expected, and line intensity
will be nearly independent of the iron abundance, the medium with the
anomalously high Fe abundance is not required.Comment: 4 pages, revised version accepted for the publication in ApJ
Brushing Element Fields
Aggregate elements following certain directions have a variety
of applications in graphics, design, and visualization. However,
authoring oriented elements in various output domains, especially
in 3D, remains challenging. We propose a novel brushing system to
facilitate interactive authoring of aggregate elements with diverse
properties over given output domains via an element synthesis
approach. To increase output quality and reduce input workload,
we further propose element fields that can automatically orient
the entire elements in better alignments over the output domains
according to partially user-specified strokes. The proposed system
can effectively synthesize distinct types of elements within various
output domains in higher quality and efficiency and offer more user
friendliness than existing practices. Our method can be applied to
practical applications such as graphic design, artistic collage, and
aggregate modelin
A Critical Examination of Hypernova Remnant Candidates in M101. II. NGC 5471B
NGC 5471B has been suggested to contain a hypernova remnant because of its
extraordinarily bright X-ray emission. To assess its true nature, we have
obtained high-resolution images in continuum bands and nebular lines with the
Hubble Space Telescope, and high-dispersion long-slit spectra with the Kitt
Peak National Observatory 4-m echelle spectrograph. The images reveal three
supernova remnant (SNR) candidates in the giant HII region NGC 5471, with the
brightest one being the 77x60 pc shell in NGC 5471B. The Ha velocity profile of
NGC 5471B can be decomposed into a narrow component (FWHM = 41 km/s) from the
background HII region and a broad component (FWHM = 148 km/s) from the SNR
shell. Using the brightness ratio of the broad to narrow components and the Ha
flux measured from the WFPC2 Ha image, we derive an Ha luminosity of
(1.4+-0.1)x10^39 ergs/s for the SNR shell. The [SII]6716,6731 doublet ratio of
the broad velocity component is used to derive an electron density of ~700
cm^-3 in the SNR shell. The mass of the SNR shell is thus 4600+-500 Mo. With a
\~330 km/s expansion velocity implied by the extreme velocity extent of the
broad component, the kinetic energy of the SNR shell is determined to be
5x10^51 ergs. This requires an explosion energy greater than 10^52 ergs, which
can be provided by one hypernova or multiple supernovae. Comparing to SNRs in
nearby active star formation regions, the SNR shell in NGC 5471B appears truly
unique and energetic. We conclude that the optical observations support the
existence of a hypernova remnant in NGC 5471B.Comment: 27 pages, 9 figures, to appear in May 2002 issue of The Astronomical
Journa
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