Structural-acoustic coupling and psychophysical effects in the active control of noise in vehicles

Active noise control systems offer a potential method of reducing the weight of passive acoustic treatment and, therefore, increasing vehicles' fuel efficiency. These can be particularly cost-efficient if integrated with the entertainment system. A combined system is presented employing feedforward control of engine noise and feedback control of road noise, using a `modal' error signal. Due to the dependence of the feedback system on the modal response of the vehicle cabin, the influence of structural-acoustic coupling on this response and the consequent effects on the control performance are investigated. Simulations of the performance of the control systems in rigid and non-rigid enclosures show that the feedforward component is largely unaffected by structural-acoustic coupling, whilst the modal feedback performance is reduced by 3 dB due to the shift in the frequency of the targeted acoustic mode. The simulation results are confirmed through experiments conducted in a structural-acoustic coupled enclosure

Coherent rotations of a single spin-based qubit in a single quantum dot at fixed Zeeman energy

Coherent rotations of single spin-based qubits may be accomplished electrically at fixed Zeeman energy with a qubit defined solely within a single electrostatically-defined quantum dot; the $g$-factor and the external magnetic field are kept constant. All that is required to be varied are the voltages on metallic gates which effectively change the shape of the elliptic quantum dot. The pseudospin-1/2 qubit is constructed from the two-dimensional $S=1/2$, $S_z=-1/2$ subspace of three interacting electrons in a two-dimensional potential well. Rotations are created by altering the direction of the pseudomagnetic field through changes in the shape of the confinement potential. By deriving an exact analytic solution to the long-range Coulomb interaction matrix elements, we calculate explicitly the range of magnitudes and directions the pseudomagnetic field can take. Numerical estimates are given for {GaAs}.Comment: Restructured manuscript, more details shown (results unchanged); Six pages, revtex4; More info at http://soliton.phys.dal.c

Multichannel control systems for the attenuation of interior road noise in vehicles

This paper considers the active control of road noise in vehicles, using either multichannel feedback control, with both headrest and floor positioned microphones providing feedback error signals, or multichannel feedforward control, in which reference signals are provided by the microphones on the vehicle floor and error signals are provided by the microphones mounted on the headrests. The formulation of these control problems is shown to be similar if the constraints of robust stability, limited disturbance enhancement and open-loop stability are imposed. A novel formulation is presented for disturbance enhancement in multichannel systems, which limits the maximum enhancement of each individual error signal. The performance of these two systems is predicted using plant responses and disturbance signals measured in a small city car. The reduction in the sum of the squared pressure signals at the four error microphones for both systems is found to be up to 8 dB at low frequencies and 3 dB on average, where the sound level is particularly high from 80 to 180 Hz. The performance of both systems is found to be robust to measured variations in the plant responses. The enhancements in the disturbance at higher frequencies are smaller for the feedback controller than for the feedforward controller, although the performance of the feedback controller is more significantly reduced by the introduction of additional delay in the plant response.<br/

Psychiatric genetics and the structure of psychopathology

For over a century, psychiatric disorders have been defined by expert opinion and clinical observation. The modern DSM has relied on a consensus of experts to define categorical syndromes based on clusters of symptoms and signs, and, to some extent, external validators, such as longitudinal course and response to treatment. In the absence of an established etiology, psychiatry has struggled to validate these descriptive syndromes, and to define the boundaries between disorders and between normal and pathologic variation. Recent advances in genomic research, coupled with large-scale collaborative efforts like the Psychiatric Genomics Consortium, have identified hundreds of common and rare genetic variations that contribute to a range of neuropsychiatric disorders. At the same time, they have begun to address deeper questions about the structure and classification of mental disorders: To what extent do genetic findings support or challenge our clinical nosology? Are there genetic boundaries between psychiatric and neurologic illness? Do the data support a boundary between disorder and normal variation? Is it possible to envision a nosology based on genetically informed disease mechanisms? This review provides an overview of conceptual issues and genetic findings that bear on the relationships among and boundaries between psychiatric disorders and other conditions. We highlight implications for the evolving classification of psychopathology and the challenges for clinical translation

Design and implementation of a personal audio system in a car cabin

The generation of personal listening zones in a car cabin would allow the different occupants to listen to different audio programmes without the use of headphones. This would allow, for example, the driver to listen to a navigation system whilst the rear passengers watched a film. Personal audio systems have previously been implemented in mobile devices and monitors, for example, however, the investigation of the effects of an enclosure on the generation of personal listening zones has been limited. This paper presents an investigation of the effects of a car cabin sized enclosure on the generation of independent listening zones in the front and rear seats. The standard car audio loudspeaker array is used to produce independent listening zones at low frequencies, while a second array of small loudspeakers positioned at the four headrest positions is used to provide control over the rest of the audio bandwidth. The proposed arrays are implemented in a real car and the results of a real-time implementation are presented.<br/

Risk information services for Disaster Risk Management (DRM) in the Caribbean : service readiness document

This document specifies the EO information products / services to be delivered in support of the World Bank project (Handbook for the Assessment of Landslide and Flood Hazards and Risks to Support Development Processes, led by ITC Netherlands), and describes the scope and extent of assessment that will be carried out following production and delivery. It is to be reviewed and agreed by the WB TTL for the project (and local users, if applicable), and will form the basis of subsequent activities to be carried out in the service assessment phase

Risk information services for Disaster Risk Management (DRM) in the Caribbean : mainstreaming opportunities

This document describes the assessment of opportunities for mainstreaming the satellite Earth Observation (EO) information products / services delivered by the British Geological Survey (BGS) via the framework of the European Space Agency (ESA) eoworld2 initiative. The products /services were delivered to the Caribbean region and the World Bank (WB) primarily via the ‘Caribbean Handbook on Risk Information Management’ project (CHARIM) which is financed by the EU-funded ACP-EU Natural Disaster Risk Reduction Program, managed by the Global Facility for Disaster Reduction and Recovery, led by the WB team, and implemented with the University of Twente, ITC and the local users from various Government Ministries in the Caribbean region. The prospect of increased exploitation and additional opportunities in further WB operations, programmes and initiatives is briefly addressed, as is an evaluation of further actions to be taken to further grow uptake of EO products / services across the WB in future