59,495 research outputs found
Precision capacitor has improved temperature and operational stability
Vacuum dielectric capacitor is fabricated from materials with very low temperature coefficients of expansion. This precision capacitor in the 1000-2000 picofarad range has a near-zero temperature coefficient of capacitance, eliminates ion chamber action caused by air ionization in the dielectric, and minimizes electromagnetic field charging effects
Proposal for demonstrating the Hong-Ou-Mandel effect with matter waves
The Hong-Ou-Mandel (HOM) effect is a striking demonstration of destructive
quantum interference between pairs of indistinguishable bosons, realised so far
only with massless photons. Here we propose an experiment which can realise
this effect in the matter-wave regime using pair-correlated atoms produced via
a collision of two Bose-Einstein condensates and subjected to two laser induced
Bragg pulses. We formulate a novel measurement protocol appropriate for the
multimode matter-wave field, which---unlike the typical two-mode optical
case---bypasses the need for repeated measurements under different displacement
settings of the beam-splitter, thus dramatically reducing the number of
experimental runs required to map out the interference visibility. The protocol
can be utilised in related matter-wave schemes; here we focus on condensate
collisions and by simulating the entire experiment we predict a HOM-dip
visibility of ~69%. By being larger than 50%, such a visibility highlights
strong quantum correlations between the atoms and paves the way for a possible
demonstration of a Bell inequality violation with massive particles in a
related Rarity-Tapster setup.Comment: Essentially the same version as v2, except in Nature Communications
style; for Supplementary Information see the source fil
Properties of non-stoichiometric metallic carbides final report
Nonstoichiometric transition metal carbide propertie
Office quality classification theoretical and empirical issues
Office quality classification literature recognises identification of office classes through division of office market rent distribution into intervals but failed to provide sound theoretical framework and comprehensive empirical approach to this method. This paper theorised that as office rental levels are a function of office quality; high quality office classes should have their mean rents greater than average market rent and mean rents of low quality classes. Also that heterogeneous nature of property coupled with lack of perfect information to market participants could result into differential evaluation of rent and quality of the same property by different market participants. The behaviour of participants normally reflects in distribution of market rent by depicting natural breaks in the distribution that could be captured by univariate data exploration. Frequency and histograms of rent distributions that were assumed to depict the behaviour of market participants were used to divide rent distribution to intervals to identify office quality classes. The results of this classification were validated by discriminant analysis. 67% and 59% accuracies were achieved for estimation and holdout subsamples respectively. This paper extended theoretical and empirical approaches in office quality classification. The proposed empirical approach could be used in future classification research
Constraining Primordial Magnetism
Primordial magnetic fields could provide an explanation for the galactic
magnetic fields observed today, in which case they may also leave interesting
signals in the CMB and the small-scale matter power spectrum. We discuss how to
approximately calculate the important non-linear magnetic effects within the
guise of linear perturbation theory, and calculate the matter and CMB power
spectra including the SZ contribution. We then use various cosmological
datasets to constrain the form of the magnetic field power spectrum. Using
solely large-scale CMB data (WMAP7, QUaD and ACBAR) we find a 95% CL on the
variance of the magnetic field at 1 Mpc of B_\lambda < 6.4 nG. When we include
SPT data to constrain the SZ effect, we find a revised limit of B_\lambda < 4.1
nG. The addition of SDSS Lyman-alpha data lowers this limit even further,
roughly constraining the magnetic field to B_\lambda < 1.3 nG.Comment: 12 pages, 9 figure
Spontaneous symmetry breaking in a two-doublet lattice Higgs model
An SU(2) lattice gauge theory with two doublets of complex scalar fields is
considered. All continuous symmetries are identified and, using the
nonperturbative methods of lattice field theory, the phase diagram is mapped
out by direct numerical simulation. Two-doublet models contain phase
transitions that separate qualitatively distinct regions of the parameter
space. In some regions global symmetries are spontaneously broken. For some
special choices of the model parameters, the symmetry-breaking order parameter
is calculated. The pattern of symmetry breaking is verified further through
observation of Goldstone bosons.Comment: 24 pages, 13 figures, references added, published versio
The Low Adhesion Problem due to Leaf Contamination in the Wheel/Rail Contact: Bonding and Low Adhesion Mechanisms
Autumn leaves often cause low adhesion problems for train operations, leading to station overruns and signals passed at danger (SPADS). The aim of this paper was to review operational data and research methods to assess the current understanding of the problem and formulate hypotheses for the causes. Incident analysis showed the relatively high possibility of incidents between the hours of 05:00 – 10:00 and 20:00 – 24:00, suggesting the dew effect was important. This result corresponds to the knowledge that wet leaves in the contact area produce very low friction coefficients, below 0.1. Current mitigation methods, such as sanding, seem inadequate to remove the leaf films completely. To explain the bonding mechanism between the leaf film and the rail, a laboratory-based model and a field-based model were developed based on previous studies. Moreover, key parameters for a strong bond formation were identified, which are iron oxide, temperature, pressure and leaf material. The research gaps were identified by a paper grading method, and several hypotheses for bonding mechanisms and low adhesion mechanisms were proposed, such as sub- or super critical water and pectin gel
Getting on the E List: E-Mail Use in a Community of Service Provider
This case examines how a community of organizations providing service to people experiencing homelessness made use of an electronic mail list. Current economic conditions have encouraged organizations in various sectors—including nonprofits—that might normally compete for scarce resources to collaborate with one another to increase their chances of survival. One set of tools likely to be of value in such relationships includes various online discussion technologies. An examination of this community’s email list use over a three-year period suggests a somewhat complex picture regarding technology use. More specifically, some issues both constrain and enable use. Additionally, seemingly basic and minimal uses of the list provided not only the greatest functionality for the users, but also led to several unanticipated consequences for those involved
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