18,310 research outputs found
Micro-displacement sensors based on plastic photonic bandgap Bragg fibers
We demonstrate an amplitude-based micro-displacement sensor that uses a
plastic photonic bandgap Bragg fiber with one end coated with a silver layer.
The reflection intensity of the Bragg fiber is characterized in response to
different displacements (or bending curvatures). We note that the Bragg
reflector of the fiber acts as an efficient mode stripper for the wavelengths
near the edge of the fiber bandgap, which makes the sensor extremely sensitive
to bending or displacements at these wavelengths. Besides, by comparison of the
Bragg fiber sensor to a sensor based on a regular multimode fiber with similar
outer diameter and length, we find that the Bragg fiber sensor is more
sensitive to bending due to presence of mode stripper in the form of the
multilayer reflector. Experimental results show that the minimum detection
limit of the Bragg fiber sensor can be smaller than 5 um for displacement
sensing
Self-organized criticality in the intermediate phase of rigidity percolation
Experimental results for covalent glasses have highlighted the existence of a
new self-organized phase due to the tendency of glass networks to minimize
internal stress. Recently, we have shown that an equilibrated self-organized
two-dimensional lattice-based model also possesses an intermediate phase in
which a percolating rigid cluster exists with a probability between zero and
one, depending on the average coordination of the network. In this paper, we
study the properties of this intermediate phase in more detail. We find that
microscopic perturbations, such as the addition or removal of a single bond,
can affect the rigidity of macroscopic regions of the network, in particular,
creating or destroying percolation. This, together with a power-law
distribution of rigid cluster sizes, suggests that the system is maintained in
a critical state on the rigid/floppy boundary throughout the intermediate
phase, a behavior similar to self-organized criticality, but, remarkably, in a
thermodynamically equilibrated state. The distinction between percolating and
non-percolating networks appears physically meaningless, even though the
percolating cluster, when it exists, takes up a finite fraction of the network.
We point out both similarities and differences between the intermediate phase
and the critical point of ordinary percolation models without
self-organization. Our results are consistent with an interpretation of recent
experiments on the pressure dependence of Raman frequencies in chalcogenide
glasses in terms of network homogeneity.Comment: 20 pages, 18 figure
Modelling the Home Health Care Nurse Scheduling Problem for Patients with Long-Term Conditions in the UK
In this work, using a Behavioural Operational Research (BOR) perspective, we develop a model for the Home Health Care Nurse Scheduling Problem (HHCNSP) with application to renal patients taking Peritoneal Dialysis (PD) at their own homes as treatment for their Chronic Kidney Disease (CKD) in the UK. The modelling framework presented in this paper can be extended to much wider spectra of scheduling problems concerning patients with different long-term conditions in future work
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