A Comparison of Two Actuators for a Semi-Active Helmholtz Resonator

Two electro-mechanical actuators are examined for a semi-active Helmholtz resonator acoustic device. The device is used to reflect narrow band noise back to the source in an acoustic duct. The controller and actuator are used to tune the system on-line allowing optimum performance over a range of operating conditions. Actuator. dynamics play an important role in the controller design and the operation of the device. Two variations of an electro-mechanical actuator are considered here. The first uses a dual voice coil speaker with local feedback compensation and the second uses the same speaker without the compensation. It is shown that both arrangements are effective but with competing advantages. The compensated actuator provides more control authority but adds considerable background noise while the uncompensated actuator provides less control authority but adds no background noise. The choice of actuator depends on the noise control objectives of the particular application

Efficient generation of transgenic pigs using equine infectious anaemia virus (EIAV) derived vector

AbstractTraditional methods of transgene delivery in livestock are inefficient. Recently, human immunodeficiency virus (HIV-1) based lentiviral vectors have been shown to offer an efficient transgene delivery system. We now extend this method by demonstrating efficient generation of transgenic pigs using an equine infectious anaemia virus derived vector. We used this vector to deliver a green fluorescent protein expressing transgene; 31% of injected/transferred eggs resulted in a transgenic founder animal and 95% of founder animals displayed green fluorescence. This compares favourably with results using HIV-1 based vectors, and is substantially more efficient than the standard pronuclear microinjection method, indicating that lentiviral transgene delivery may be a general tool with which to efficiently generate transgenic mammals

Are current dynamic water quality models too complex? A comparison of a new parsimonious phosphorus model, SimplyP, and INCA-P

Catchment-scale water quality models are becoming increasingly popular tools for exploring the potential effects of land management, land use change and climate change on water quality. However, the dynamic, catchment-scale nutrient models in common usage are complex, with many uncertain parameters requiring calibration, limiting their usability and robustness. A key question is whether this complexity is justified. To explore this, we have developed a parsimonious P model, SimplyP, incorporating a coupled rainfall-runoff model and a biogeochemical model able to simulate streamflow, suspended sediment, particulate and dissolved P dynamics. The model’s complexity is compared in a small rural catchment in northeast Scotland. For three land use classes, less than six SimplyP model parameters must be determined through calibration alone, the rest may be based on measurements; INCA-P has around 40 unmeasurable parameters. Despite simpler process-representation, SimplyP produced a slightly better dissolved P simulation during both calibration and validation, and produced similar long-term projections in response to changes in land management. Results support the hypothesis that INCA-P is overly complex for the study catchment. We hope our findings will help prompt wider model comparison exercises, as well as debate amongst the water quality modelling community as to whether today's models are fit for purpose. Simpler models such as SimplyP have the potential to be useful management and research tools, building blocks for future model development (prototype code is freely available), or benchmarks against which more complex models could be evaluated

Why so serious? Theorising playful model-driven group decision support with situated affectivity

This is the author accepted manuscript. The final version is available from Springer via the DOI in this record.An integrative approach to theorising behavioural, affective and cognitive processes in modeldriven group decision support (GDS) interventions is needed to gain insight into the (micro-)processes by which outcomes are accomplished. This paper proposes that the theoretical lens of situated affectivity, grounded in recent extensions of scaffolded mind models, is suitable to understand the performativity of affective micro-processes in model-driven GDS interventions. An illustrative vignette of a humorous micro-moment in a group decision workshop is presented to reveal the performativity of extended affective scaffolding processes for group decision development. The lens of situated affectivity constitutes a novel approach for the study of interventionist practice in the context of group decision making (and negotiation). An outlook with opportunities for future research is offered to facilitate an integrated approach to the study of cognitive-affective and behavioural micro-processes in model-driven GDS interventions.This work was supported in part by the EU FP7-ENERGY- SMARTCITIES-2012 (314277) project STEEP (Systems Thinking for Comprehensive City Efficient Energy Planning

A Compensated Acoustic Actuator for Systems with Strong Dynamic Pressure Coupling

This study improves the performance of a previously developed acoustic actuator in the presence of an acoustic duct system with strong pressure coupling. The speaker dynamics and the acoustic duct dynamics are first modeled separately. The two systems are then coupled, and the resulting system is modeled. A velocity sensor is developed and used in feedback compensation. The resulting speaker system has minimal magnitude and phase variation over a 20–200 Hz bandwidth. These conclusions are verified through experimental results

An Electronically Tunable Resonator for Noise Control

Many engineering systems create unwanted noise that can be reduced by the careful application of engineering noise controls. When this noise travels down tubes and pipes, a tuned resonator can be used to muffle noise escaping from the tube. The classical examples are automobile exhaust and ventilation system noise. In these cases where a narrow frequency band of noise exists, a traditional engineering control consists of adding a tuned Helmholtz resonator to reduce unwanted tonal noise by reflecting it back to the source (Temkin, 1981). As long as the frequency of the unwanted noise falls within the tuned resonator frequency range, the device is effective. However, if the frequency of the unwanted sound changes to a frequency that does not match the tuned resonator frequency, the device is no longer effective. Conventional resonators have fixed tuning and cannot effectively muffle tonal noise with time-varying frequency

Radiation Heat Transfer Modeling in Electrorheological Fluids: The Effect of Field-Induced Chaining

Absorption is the dominant mode of attenuation of incident radiation energy through an electrorheological (ER) fluid made of Zeolite particles. A simple mathematical model of ER fluids with fully dispersed particles for predicting transmittance has previously been developed and proven to be experimentally sound. The present work develops a model which includes the influence of electric field-induced particle chaining on transmittance through ER fluids. The resulting model successfully predicts the enhanced levels of energy transport in the chained-particle state as a function of applied field strength and particle/fluid properties. The validity of the model is confirmed with experimental transmittance data and excellent agreement is observed. This model combined with data from previous studies will provide more complete models for radiative heat transfer in ER fluids and will provide a basis for optical chaining ER fluid state sensor development for use in the dynamic active control of ER fluid transport properties