Practical statistical methods for call centres with a case study addressing urgent medical care delivery

Our interest is in forecasting for call centres, and in particular out-of-hours call centres (OOHCC) which deal with patient requests for medical advice outside normal working hours. Planning needs accurate forecasts of incoming call volumes. These vary by hour, day, and season, and must account for calendar effects such as Christmas. Using historical data, we explain how to use simple regression models to forecast call volumes arriving on specified days, taking into account calendar effects. We then show how we forecast the pattern of arrivals of calls during a specified day. These result in predictions for volumes of calls arriving for each day of the year, and their pattern of arrival during the day. We show how simulation models may then be used for resource allocation, uncertainty analysis, and staff scheduling. The data are details of call numbers and queue lengths from all parts of the patient-advice process for around five years, for a call centre based in Newcastle-upon-Tyne. There are around 350,000 complete cases in total. The methods are easily extended to other kinds of call centre. We describe the impact Swine flu had on call volumes in the summer of 2009, and our reactions to amend models in order to maintain forecast quality

Polarimetric Observations of 15 AGNs at High Frequencies

Original paper can be found at: http://www.astrosociety.org/pubs/cs/328.html--Copyright Astronomical Society of the PacificWe have obtained total and polarized intensity images of 15 AGNs with the VLBA at 7 mm at 17 epochs from 25/26 March 1998 to 14 April 2001. The VLBA observations are accompanied at many epochs by simultaneous mea- surements of polarization at 1.35/0.85 mm as well as less frequent simultaneous optical polarization measurements. We discuss the similarities and complexities of polarization behavior at different frequencies along with the VLBI properties

Integral Equations

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Multi-frequency Polarization Properties of Blazars

Original paper can be found at: http://www.astrosociety.org/pubs/cs/328.html--Copyright Astronomical Society of the PacificWe have obtained total and polarized intensity images of 15 AGNs with the VLBA at 7 mm at 17 epochs, accompanied at many epochs by nearly simultaneous measurements of polarization at 1.35/0.85 mm and at optical wavelengths. Analysis of the data shows an obvious connection between the polarized emission at high frequencies and the most strongly polarized features in parsecscale jets. The largest deviations between polarization parameters at different frequencies are detected when a new compact knot emerges from the core, and are likely caused by very short time-scale (<1 week) polarization variability during the events

Jet Kinematics of AGNs at High Radio Frequencies

Original paper can be found at: http://www.astrosociety.org/pubs/cs/348.html--Copyright Astronomical Society of the PacificWe have completed a 3 yr program of polarization monitoring of 15 active galactic nuclei with the Very Long Baseline Array at 7 mm wavelength. At some epochs the images are accompanied by nearly simultaneous polarization measurements at 3 mm, 1.35/0.85 mm, and optical wavelengths. We determine apparent velocities in the jets of all sources in the sample. We suggest a new method to estimate Doppler factor of the jet components based on their VLBI properties. This allows us to derive the Lorentz factors and viewing angles of superluminal knots and opening angles of the jets