23,247 research outputs found

    On the integrability of a new lattice equation found by multiple scale analysis

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    In this paper we discuss the integrability properties of a nonlinear partial difference equation on the square obtained by the multiple scale integrability test from a class of multilinear dispersive equations defined on a four points lattice

    Gas Detection for Experiments

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    Flammable gases are often used in detectors for physics experiments. The storage, distribution and manipulation of such flammable gases present several safety hazards. As most flammable gases cannot be detected by human senses, specific well-placed gas detection systems must be installed. Following a request from the user group and in collaboration with CERN safety officers, risk analyses are performed. An external contractor, who needs to receive detailed user requirements from CERN, performs the installations. The contract is passed on a guaranteed results basis. Co-ordination between all the CERN groups and verification of the technical installation is done by ST/AA/AS. This paper describes and focuses on the structured methodology applied to implement such installations based on goal directed project management techniques (GDPM). This useful supervision tool suited to small to medium sized projects facilitates the task of co-ordinating numerous activities to achieve a completely functional system

    Batch Nonlinear Continuous-Time Trajectory Estimation as Exactly Sparse Gaussian Process Regression

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    In this paper, we revisit batch state estimation through the lens of Gaussian process (GP) regression. We consider continuous-discrete estimation problems wherein a trajectory is viewed as a one-dimensional GP, with time as the independent variable. Our continuous-time prior can be defined by any nonlinear, time-varying stochastic differential equation driven by white noise; this allows the possibility of smoothing our trajectory estimates using a variety of vehicle dynamics models (e.g., `constant-velocity'). We show that this class of prior results in an inverse kernel matrix (i.e., covariance matrix between all pairs of measurement times) that is exactly sparse (block-tridiagonal) and that this can be exploited to carry out GP regression (and interpolation) very efficiently. When the prior is based on a linear, time-varying stochastic differential equation and the measurement model is also linear, this GP approach is equivalent to classical, discrete-time smoothing (at the measurement times); when a nonlinearity is present, we iterate over the whole trajectory to maximize accuracy. We test the approach experimentally on a simultaneous trajectory estimation and mapping problem using a mobile robot dataset.Comment: Submitted to Autonomous Robots on 20 November 2014, manuscript # AURO-D-14-00185, 16 pages, 7 figure

    Lax forms of the qq-Painlev\'e equations

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    All qq-Painlev\'e equations which are obtained from the qq-analog of the sixth Painlev\'e equation are expressed in a Lax formalism. They are characterized by the data of the associated linear qq-difference equations. The degeneration pattern from the qq-Painlev\'e equation of type A2A_2 is also presented.Comment: 24 page

    Local elastic response measured near the colloidal glass transition

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    We examine the response of a dense colloidal suspension to a local force applied by a small magnetic bead. For small forces, we find a linear relationship between the force and the displacement, suggesting the medium is elastic, even though our colloidal samples macroscopically behave as fluids. We interpret this as a measure of the strength of colloidal caging, reflecting the proximity of the samples' volume fractions to the colloidal glass transition. The strain field of the colloidal particles surrounding the magnetic probe appears similar to that of an isotropic homogeneous elastic medium. When the applied force is removed, the strain relaxes as a stretched exponential in time. We introduce a model that suggests this behavior is due to the diffusive relaxation of strain in the colloidal sample.Comment: long-delayed followup paper to Habdas et al., EPL 67, 477-483 (2004

    Economics and the marriage wars

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    We critique the economic analysis of marriage and divorce descending from Becker (1981): we call this the "economic" approach. Marriage is based on the "productive" gains available from specialization in market production and household production, and on the production of children. ln the more recent development of the theory, the husband and wife bargain over the gains. This analysis contrasts with the "covenant" view of marriage which is based on the Judea-Christian tradition. The ethical focus of the covenant view is self-giving love, which is not dependent on economic efficiency. We suggest that the changing attitudes to marriage and divorce in the West may reflect "motivation crowding out," as the economic approach erodes the values underpinning the covenant view. Marriage, like the monarchy over the last three centuries, remains popular in many quarters. But the mere existence of an institution can mask its wholesale transformation
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