3,435 research outputs found
Evaluation of Upper Extremity Movement Characteristics during Standardized Pediatric Functional Assessment with a Kinect®-based Markerless Motion Analysis System
A recently developed and evaluated upper extremity (UE) markerless motion analysis system based on the Microsoft® Kinect® has potential for improving functional assessment of patients with hemiplegic cerebral palsy. 12 typically-developing adolescents ages 12-17 were evaluated using both the Kinect-based system and the Shriners Hospitals for Children Upper Extremity Evaluation (SHUEE), a validated measure of UE motion. The study established population means of UE kinematic parameters for each activity. Statistical correlation analysis was used to identify key kinematic metrics used to develop automatic scoring algorithms. The Kinect motion analysis platform is technically sound and can be applied to standardized task-based UE evaluation while providing enhanced sensitivity in clinical analysis and automation through scoring algorithms
Mode mixing and losses in misaligned microcavities
We present a study on the optical losses of Fabry-P\'erot cavities subject to
realistic transverse mirror misalignment. We consider mirrors of the two most
prevalent surface forms: idealised spherical depressions, and Gaussian profiles
generated by laser ablation. We first describe the mode mixing phenomena seen
in the spherical mirror case and compare to the frequently-used clipping model,
observing close agreement in the predicted diffraction loss, but with the
addition of protective mode mixing at transverse degeneracies. We then discuss
the Gaussian mirror case, detailing how the varying surface curvature across
the mirror leads to complex variations in round trip loss and mode profile. In
light of the severe mode distortion and strongly elevated loss predicted for
many cavity lengths and transverse alignments when using Gaussian mirrors, we
suggest that the consequences of mirror surface profile are carefully
considered when designing cavity experiments.Comment: 16 pages, 12 figure
Efficient operator method for modelling mode mixing in misaligned optical cavities
The transverse field structure and diffraction loss of the resonant modes of
Fabry-P\'erot optical cavities are acutely sensitive to the alignment and shape
of the mirror substrates. We develop extensions to the `mode mixing' method
applicable to arbitrary mirror shapes, which both facilitate fast calculation
of the modes of cavities with transversely misaligned mirrors and enable the
determination and transformation of the geometric properties of these modes. We
show how these methods extend previous capabilities by including the
practically-motivated case of transverse mirror misalignment, unveiling rich
and complex structure of the resonant modes.Comment: 17 pages, 7 figure
Optimisation of Scalable Ion-Cavity Interfaces for Quantum Photonic Networks
In the design optimisation of ion-cavity interfaces for quantum networking
applications, difficulties occur due to the many competing figures of merit and
highly interdependent design constraints, many of which present `soft-limits',
amenable to improvement at the cost of engineering time. In this work we
present a systematic approach to this problem which offers a means to identify
efficient and robust operating regimes, and to elucidate the trade-offs
involved in the design process, allowing engineering efforts to be focused on
the most sensitive and critical parameters. We show that in many relevant cases
it is possible to approximately separate the geometric aspects of the
cooperativity from those associated with the atomic system and the mirror
surfaces themselves, greatly simplifying the optimisation procedure. Although
our approach to optimisation can be applied to most operating regimes, here we
consider cavities suitable for typical ion trapping experiments, and with
substantial transverse misalignment of the mirrors. We find that cavities with
mirror misalignments of many micrometres can still offer very high photon
extraction efficiencies, offering an appealing route to the scalable production
of ion-cavity interfaces for large scale quantum networks
A Hybrid Lagrangian Variation Method for Bose-Einstein Condensates in Optical Lattices
Solving the Gross--Pitaevskii (GP) equation describing a Bose--Einstein
condensate (BEC) immersed in an optical lattice potential can be a numerically
demanding task. We present a variational technique for providing fast, accurate
solutions of the GP equation for systems where the external potential exhibits
rapid varation along one spatial direction. Examples of such systems include a
BEC subjected to a one--dimensional optical lattice or a Bragg pulse. This
variational method is a hybrid form of the Lagrangian Variational Method for
the GP equation in which a hybrid trial wavefunction assumes a gaussian form in
two coordinates while being totally unspecified in the third coordinate. The
resulting equations of motion consist of a quasi--one--dimensional GP equation
coupled to ordinary differential equations for the widths of the transverse
gaussians. We use this method to investigate how an optical lattice can be used
to move a condensate non--adiabatically.Comment: 16 pages and 1 figur
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