Improving the applicability of radar rainfall estimates for urban pluvial flood modelling and forecasting

This work explores the possibility of improving the applicability of radar rainfall estimates (whose accuracy is generally insufficient) to the verification and operation of urban storm-water drainage models by employing a number of local gauge-based radar rainfall adjustment techniques. The adjustment techniques tested in this work include a simple mean-field bias (MFB) adjustment, as well as a more complex Bayesian radar-raingauge data merging method which aims at better preserving the spatial structure of rainfall fields. In addition, a novel technique (namely, local singularity analysis) is introduced and shown to improve the Bayesian method by better capturing and reproducing storm patterns and peaks. Two urban catchments were used as case studies in this work: the Cranbrook catchment (9 km2) in North-East London, and the Portobello catchment (53 km2) in the East of Edinburgh. In the former, the potential benefits of gauge-based adjusted radar rainfall estimates in an operational context were analysed, whereas in the latter the potential benefits of adjusted estimates for model verification purposes were explored. Different rainfall inputs, including raingauge, original radar and the aforementioned merged estimates were fed into the urban drainage models of the two catchments. The hydraulic outputs were compared against available flow and depth records. On the whole, the tested adjustment techniques proved to improve the applicability of radar rainfall estimates to urban hydrological applications, with the Bayesian-based methods, in particular the singularity sensitive one, providing more realistic and accurate rainfall fields which result in better reproduction of the urban drainage system’s dynamics. Further testing is still necessary in order to better assess the benefits of these adjustment methods, identify their shortcomings and improve them accordingly

Predicting neural recording performance of implantable electrodes

Recordings of neural activity can be used to aid communication, control prosthetic devices or alleviatedisease symptoms. Chronic recordings require a high signal-to-noise ratio that is stable for years. Currentcortical devices generally fail within months to years after implantation. Development of novel devices toincrease lifetime requires valid testing protocols and a knowledge of the critical parameters controllingelectrophysiological performance. Here we present electrochemical and electrophysiological protocolsfor assessing implantable electrodes. Biological noise from neural recording has significant impact on signal-to-noise ratio. A recently developed surgical approach was utilised to reduce biological noise. This allowed correlation of electrochemical and electrophysiological behaviour. The impedance versus frequency of modified electrodes was non-linear. It was found that impedance at low frequencies was astronger predictor of electrophysiological performance than the typically reported impedance at 1 kHz.Low frequency impedance is a function of electrode area, and a strong correlation of electrode area with electrophysiological response was also seen. Use of these standardised testing protocols will allow future devices to be compared before transfer to preclinical and clinical trials

Development of Superconducting Tuning Quadrupole Corrector (MQT) Prototypes for the LHC

The main quadrupoles of the Large Hadron Collider (LHC) are connected in families of focusing and defocusing magnets. In order to make tuning corrections in the machine a number of quadrupole corrector magnets (designated MQT) are necessary. These 56 mm diameter aperture magnets have to be compact, with a maximum length of 395 mm and a coil radial thickness of 5 to 7.5 mm, while generating a minimum field gradient of 110 T/m. Two design options have been explored, both using the "counter-winding" system developed at CERN for the fabrication of low cost corrector coils. The first design, with the poles composed of two double-pancake coils, each counter-wound using a single wire, superposed to create 4-layer coils, was developed and built by ACCEL Instruments GmbH. A second design where single coils were counter-wound using a 3-wire ribbon to obtain 6-layer coils was developed at CERN. This paper describes the two designs and reports on the performance of the prototypes during testing

Measuring active volume using electrical resistance tomography in a gas-sparged model anaerobic digester

Inadequate mixing in anaerobic digesters fitted with gas sparging systems is caused by many factors, and leads to dead zones where sludge remains stagnant. The present study explores a range of gas sparging configurations that can be implemented to maximize active volume, and validates electrical resistance tomography (ERT) as an effective measurement tool for analysing mixing conditions without the need for visual access to the liquid volume. Air was used as the gas phase, and xanthan gum Keltrol-T (XGKT) solutions at concentrations of 0.15 and 0.4 wt% were selected as transparent simulant fluids for their rheological similarity to digested sludge. Gas flow rate, sparger nozzle orientation (upward-facing vs. downward-facing), and nozzle height were varied, and mixing performance was assessed using flow visualisation experiments. Results were then replicated with ERT for comparison. It was found that the 0.15 wt% XGKT solution achieved almost complete mixing for all configurations, while the 0.4 wt% XGKT solution developed stable, unmixed regions. Gas flow rate made little difference to the final mixed volume suggesting lower power input does not sacrifice steady-state active volume in the reactor. Positioning the nozzle closer to the bottom of the vessel and sparging gas downward both reduced inactive volume. ERT measurements matched flow visualisation results closely, and were able to capture details that flow visualisation ignores. It has been shown that there is great potential for implementing ERT as a method for researching flow behaviours in complex opaque materials, especially the formation and progression of active volume

Status of the Production of the LHC Superconducting Corrector Magnets

The Large Hadron Collider (LHC) will be equipped with a large number (6400) of superconducting corrector magnets. These magnets are powerful, with typical peak fields of 3-4 T on the coils, but at the same time compact and of low cost. There are many types: sextupoles, octupoles and decapoles to correct the main dipole field, dipoles, quadrupoles, sextupoles and octupoles to condition the proton beams and several nested correctors from dipole to dodecapole in the inner triplets. The sizes vary from 6 kg, 110 mm long, nested decapole-octupole spool pieces to 1800 kg, 1.4m long, trim quadrupoles. The fabrication of the 11 different types of magnets is assured by 10 contracts placed at 6 firms, two of which are in India. A number of magnets are now in series production, others in their pre-series production. The paper describes the present state of the fabrication and the testing of these magnets

Evolution of flow regimes in non-Newtonian liquids under gas sparging

This paper provides experimental evidence supporting the idea that the transition to turbulent flow is governed by the ratio of the specific power input (SPI) and the term G/λ, where G is the viscoelastic modulus of the liquid and λ is the relaxation time, in a vessel containing a fluid agitated by sparged gas (air) at low superficial gas velocities. This finding provides a method for judging the flow regime within a vessel a priori using a nondimensional quantity and can be used as a scale for decision-making in cases where real-time visual analysis is not possible. While the work reported below is motivated by anaerobic digestion of wastewater sludge, the results are obtained using model liquids and should, therefore, have wide application in chemical process engineering, such as CFD simulation of mixing in viscoelastic fluids and mixing in fermentation processes