Office of the Children’s Commissioner: 'Don't make assumptions': Children's and young people's views of the child protection system and messages for change

"The aim of this research, commissioned by the Office of the Children’s Commissioner and carried out by a team from the University of East Anglia, was to seek children and young people’s views of the child protection system and to consider how those views might contribute to improving responses to abuse and neglect. It aimed to gather the views of children and young people living with their parents, who all had a child protection plan in place. The research is timely as it comes during a period when the child protection system in England is being reviewed. We hope that the findings will be of interest to children and families involved in child protection, as well as to professionals working with children and to policy makers." - Page 7

A Practical Model and an Optimal Controller for Variable Speed Wind Turbine Permanent Magnet Synchronous Generator

The aim of this paper is the complete modeling and simulation of an optimal control system using practical setup parameters for a wind energy conversion system (WECS) through a direct driven permanent magnet synchronous generator (D-PMSG) feeding ac power to the utility grid. The generator is connected to the grid through a back-to-back PWM converter with a switching frequency of 10 KHz. A maximum power point tracking (MPPT) control is proposed to ensure the maximum power capture from wind turbine, and a PI controller designed for the wind turbine to generate optimum speed for the generator via an aerodynamic model. MATLAB/Simulink results demonstrate the accuracy of the developed control scheme

Five-level selective harmonic elimination PWM strategies and multicarrier phase-shifted sinusoidal PWM: A comparison

The multicarrier phase-shifted sinusoidal pulse-width modulation (MPS-SPWM) technique is well-known for its important advantage of offering an increased overall bandwidth as the number of carriers multiplied with their equal frequency directly controls the location of the dominant harmonics. In this paper, a five-level (line-to-neutral) multilevel selective harmonic elimination PWM (MSHE-PWM) strategy based on an equal number of switching transitions when compared against the previously mentioned technique is proposed. It is assumed that the four triangular carriers of the MPS-SPWM method have nine per unit frequency resulting in seventeen switching transitions for every quarter period. Requesting the same number of transitions from the MSHE-PWM allows the control of sixteen non-triplen harmonics. It is confirmed that the proposed MSHE-PWM offers significantly higher converter bandwidth along with higher modulation operating range. Selected results are presented to confirm the effectiveness of the proposed technique

Calculating the interior permanent-magnet motor

This paper describes the calculation of torque in a brushless permanent-magnet line-start AC motor by means of the flux-MMF diagram in combination with the finite-element method. Results are compared with measured flux-MMF diagrams, with shaft torque measurements, and with torque calculated using the classical phasor diagram

Performance estimation of interior permanent-magnet brushless motors using the voltage-driven flux-MMF diagram

The flux-magnetomotive force (flux-MMF) diagram, or "energy conversion loop," is a powerful tool for computing the parameters of saturated interior permanent-magnet brushless motors, especially when the assumptions underlying classical dq theory are not valid, as is often the case in modern practice. Efficient finite-element computation of the flux-MMF diagram is possible when the motor current is known a priori, but in high-speed operation the current regulator can lose control of the current waveform and the computation becomes "voltage-driven" rather than "current-driven." This paper describes an efficient method for estimating the motor performance-average torque, inductances-by solving the voltage-driven problem. It presents experimental validation for a two-pole brushless interior permanent-magnet motor. The paper also discusses the general conditions under which this method is appropriate, and compares the method with alternative approaches

Line-start permanent-magnet motor single-phase steady-state performance analysis

This paper describes an efficient calculating procedure for the steady-state operation of a single-phase line-start capacitor-run permanent-magnet motor. This class of motor is beginning to be applied in hermetic refrigerator compressors as a high-efficiency alternative to either a plain induction motor or a full inverter-fed drive. The calculation relies on a combination of reference-frame transformations including symmetrical components to cope with imbalance, and dq axes to cope with saliency. Computed results are compared with test data. The agreement is generally good, especially in describing the general properties of the motor. However, it is shown that certain important effects are beyond the limit of simple circuit analysis and require a more complex numerical analysis method

A general magnetic-energy-based torque estimator: validation via a permanent-magnet motor drive

This paper describes the use of the current–flux-linkage ($i{-}psi$ ) diagram to validate the performance of a general magnetic-energy-based torque estimator. An early step in the torque estimation is the use of controller duty cycles to reconstruct the average phase-voltage waveform during each pulsewidth-modulation (PWM) switching period. Samples over the fundamental period are recorded for the estimation of the average torque. The fundamental period may not be an exact multiple of the sample time. For low speed, the reconstructed voltage requires additional compensation for inverter-device losses. Experimental validation of this reconstructed waveform with the actual PWM phase-voltage waveform is impossible due to the fact that one is PWM in nature and the other is the average value during the PWM period. A solution to this is to determine the phase flux-linkage using each waveform and then plot the resultant $i{-}psi$ loops. The torque estimation is based on instantaneous measurements and can therefore be applied to any electrical machine. This paper includes test results for a three-phase interior permanent-magnet brushless ac motor operating with both sinusoidal and nonsinusoidal current waveforms

Rethinking clinical trials of transcranial direct current stimulation: Participant and assessor blinding is inadequate at intensities of 2mA

Copyright @ 2012 The Authors. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and 85 reproduction in any medium, provided the original author and source are credited. The article was made available through the Brunel University Open Access Publishing Fund.Background: Many double-blind clinical trials of transcranial direct current stimulation (tDCS) use stimulus intensities of 2 mA despite the fact that blinding has not been formally validated under these conditions. The aim of this study was to test the assumption that sham 2 mA tDCS achieves effective blinding. Methods: A randomised double blind crossover trial. 100 tDCS-naïve healthy volunteers were incorrectly advised that they there were taking part in a trial of tDCS on word memory. Participants attended for two separate sessions. In each session, they completed a word memory task, then received active or sham tDCS (order randomised) at 2 mA stimulation intensity for 20 minutes and then repeated the word memory task. They then judged whether they believed they had received active stimulation and rated their confidence in that judgement. The blinded assessor noted when red marks were observed at the electrode sites post-stimulation. Results: tDCS at 2 mA was not effectively blinded. That is, participants correctly judged the stimulation condition greater than would be expected to by chance at both the first session (kappa level of agreement (κ) 0.28, 95% confidence interval (CI) 0.09 to 0.47 p = 0.005) and the second session (κ = 0.77, 95%CI 0.64 to 0.90), p = <0.001) indicating inadequate participant blinding. Redness at the reference electrode site was noticeable following active stimulation more than sham stimulation (session one, κ = 0.512, 95%CI 0.363 to 0.66, p<0.001; session two, κ = 0.677, 95%CI 0.534 to 0.82) indicating inadequate assessor blinding. Conclusions: Our results suggest that blinding in studies using tDCS at intensities of 2 mA is inadequate. Positive results from such studies should be interpreted with caution.GLM is supported by the National Health & Medical Research Council of Australia ID 571090

Embedded finite-element solver for computation of brushless permanent-magnet motors

This paper describes the theory underlying the formulation of a “minimum set” of finite-element solutions to be used in the design and analysis of saturated brushless permanent-magnet motors. The choice of finite-element solutions is described in terms of key points on the flux–MMF diagram. When the diagram has a regular shape, a huge reduction in finite-element analysis is possible with no loss of accuracy. If the loop is irregular, many more solutions are needed. This paper describes an efficient technique in which a finite-element solver is associated with a classical $d$– $q$-axis circuit model in such a way that the number of finite-element solutions in one electrical half-cycle can be varied between 1 and 360. The finite-element process is used to determine not only the average torque but also the saturated inductances as the rotor rotates