Smart double panel with decentralised active dampers for control of sound transmission

This report presents the results of a theoretical study of active sound transmission control through a double panel. The double panel material and geometrical properties have been chosen so as to emulate section of an aircraft fuselage, or bodywork of a vehicle. It consists of two plates: an aluminium plate simply supported along all the edges and a honeycomb plate with all the edges free. The two plates, having the same length and width, are connected using elastic mounts, so that a double panel with a thin rectangular cavity between the plates is formed. Since the two plates are linked by the mounting system, and since the air is confined in the cavity between them, they form a structurally and acoustically coupled system. The sound transmission properties of the system are studied in such a way that the aluminium plate (“source panel”) is excited using a plane acoustic wave, while the honeycomb plate (“radiating panel”) radiates sound into free field.The aim of the active control is to reduce the sound transmitted in a broad frequency band, but with a particular focus on the reduction of the sound transmission at lower frequencies of the band. Decentralised velocity feedback control systems (applying active damping) are implemented, with purpose of reducing sound transmission at resonance frequencies. Control sensors and actuators are embedded into the double plate system as a regular array, so that a smart double panel is created. The theoretical study includes analysis of the passive sound transmission in terms of a parametric study, implementation of the active control using skyhook velocity sensors and skyhook force actuators, and the performance/stability analysis in case when reactive actuators and skyhook velocity sensors are used. In the latter case the actuating force is obtained using actuators located in the air cavity which can react off the two plate

SARS-CoV-2 lineage B.1.1.7 is associated with greater disease severity among hospitalised women but not men: multicentre cohort study.

BACKGROUND: SARS-CoV-2 lineage B.1.1.7 has been associated with an increased rate of transmission and disease severity among subjects testing positive in the community. Its impact on hospitalised patients is less well documented. METHODS: We collected viral sequences and clinical data of patients admitted with SARS-CoV-2 and hospital-onset COVID-19 infections (HOCIs), sampled 16 November 2020 to 10 January 2021, from eight hospitals participating in the COG-UK-HOCI study. Associations between the variant and the outcomes of all-cause mortality and intensive therapy unit (ITU) admission were evaluated using mixed effects Cox models adjusted by age, sex, comorbidities, care home residence, pregnancy and ethnicity. FINDINGS: Sequences were obtained from 2341 inpatients (HOCI cases=786) and analysis of clinical outcomes was carried out in 2147 inpatients with all data available. The HR for mortality of B.1.1.7 compared with other lineages was 1.01 (95% CI 0.79 to 1.28, p=0.94) and for ITU admission was 1.01 (95% CI 0.75 to 1.37, p=0.96). Analysis of sex-specific effects of B.1.1.7 identified increased risk of mortality (HR 1.30, 95% CI 0.95 to 1.78, p=0.096) and ITU admission (HR 1.82, 95% CI 1.15 to 2.90, p=0.011) in females infected with the variant but not males (mortality HR 0.82, 95% CI 0.61 to 1.10, p=0.177; ITU HR 0.74, 95% CI 0.52 to 1.04, p=0.086). INTERPRETATION: In common with smaller studies of patients hospitalised with SARS-CoV-2, we did not find an overall increase in mortality or ITU admission associated with B.1.1.7 compared with other lineages. However, women with B.1.1.7 may be at an increased risk of admission to intensive care and at modestly increased risk of mortality.This report was produced by members of the COG-UK-HOCI Variant substudy consortium. COG-UK-HOCI is part of COG-UK. COG-UK is supported by funding from the Medical Research Council (MRC) part of UK Research & Innovation (UKRI), the National Institute of Health Research (NIHR) and Genome Research Limited, operating as the Wellcome Sanger Institute

SARS-CoV-2 Omicron is an immune escape variant with an altered cell entry pathway

Vaccines based on the spike protein of SARS-CoV-2 are a cornerstone of the public health response to COVID-19. The emergence of hypermutated, increasingly transmissible variants of concern (VOCs) threaten this strategy. Omicron (B.1.1.529), the fifth VOC to be described, harbours multiple amino acid mutations in spike, half of which lie within the receptor-binding domain. Here we demonstrate substantial evasion of neutralization by Omicron BA.1 and BA.2 variants in vitro using sera from individuals vaccinated with ChAdOx1, BNT162b2 and mRNA-1273. These data were mirrored by a substantial reduction in real-world vaccine effectiveness that was partially restored by booster vaccination. The Omicron variants BA.1 and BA.2 did not induce cell syncytia in vitro and favoured a TMPRSS2-independent endosomal entry pathway, these phenotypes mapping to distinct regions of the spike protein. Impaired cell fusion was determined by the receptor-binding domain, while endosomal entry mapped to the S2 domain. Such marked changes in antigenicity and replicative biology may underlie the rapid global spread and altered pathogenicity of the Omicron variant

Investigation of hospital discharge cases and SARS-CoV-2 introduction into Lothian care homes

Background The first epidemic wave of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) in Scotland resulted in high case numbers and mortality in care homes. In Lothian, over one-third of care homes reported an outbreak, while there was limited testing of hospital patients discharged to care homes. Aim To investigate patients discharged from hospitals as a source of SARS-CoV-2 introduction into care homes during the first epidemic wave. Methods A clinical review was performed for all patients discharges from hospitals to care homes from 1st March 2020 to 31st May 2020. Episodes were ruled out based on coronavirus disease 2019 (COVID-19) test history, clinical assessment at discharge, whole-genome sequencing (WGS) data and an infectious period of 14 days. Clinical samples were processed for WGS, and consensus genomes generated were used for analysis using Cluster Investigation and Virus Epidemiological Tool software. Patient timelines were obtained using electronic hospital records. Findings In total, 787 patients discharged from hospitals to care homes were identified. Of these, 776 (99%) were ruled out for subsequent introduction of SARS-CoV-2 into care homes. However, for 10 episodes, the results were inconclusive as there was low genomic diversity in consensus genomes or no sequencing data were available. Only one discharge episode had a genomic, time and location link to positive cases during hospital admission, leading to 10 positive cases in their care home. Conclusion The majority of patients discharged from hospitals were ruled out for introduction of SARS-CoV-2 into care homes, highlighting the importance of screening all new admissions when faced with a novel emerging virus and no available vaccine

Decentralized vibration control in a launch vehicle payload fairing

The development of smart structures and active noise and vibration control technologies promised to revolutionize the design, construction and, most importantly, the performance of many complex engineering. However, the early promise of these technologies has not been realized in large-scale systems primarily because of the excessive complexity, cost, and weight associated with centralized control systems. Now, recent developments in MEMS sensors and actuators, along with networked embedded processor technology, have opened new research avenues in decentralized controls. Such a control system consists of numerous nodes, possessing limited computational capability, sensors, and actuators. Each of these nodes is also capable of communicating with other nodes via a wired or wireless network. This results in a dramatic shift in the control system paradigm from that of a single, centralized computer to that of numerous decentralized, networked processors. This work describes the application of such a control system to the reduction of structural acoustic radiation in a launch vehicle payload fairing. A JAVA-based simulation tool is employed to simulate the interactions of the physical system with the networked embedded controllers. Results will indicate the potential for such a control system as well as the limitations imposed by the networked embedded processor hardware

Distributed group-based vibration control with a networked embedded system

The purpose of this work is to demonstrate the performance of a distributed vibration control system based on a networked embedded system. The platform from which control is affected consists of a network of computational elements called nodes. Each node possesses its own computational capability, sensor, actuator and the ability to communicate with other nodes via a wired or wireless network. The primary focus of this work is to demonstrate the use of existing group management middleware concepts to enable vibration control with such a distributed network. Group management middleware is distributed software that provides for the establishment and maintenance of groups of distributed nodes and that provides for the network communication within such groups. The reason for developing distributed control based on group concepts is that communication of real-time sensor and actuator data among all system nodes would not be possible due to bandwidth constraints. Group management middleware provides for inter-node communications among subsets of nodes in an efficient and scalable manner. The objective of demonstrating the effectiveness of such grouping for distributed control is met by designing distributed feedback compensators that take advantage of node groups in order to affect their control. Two types of node groups are considered: groups based on physical proximity and groups based on modal sensitivity. The global control objective is to minimize the vibrational response of a rectangular plate in specific modes while minimizing spillover to out-of-bandwidth modes. Results of this investigation demonstrate that such a distributed control system can achieve vibration attenuations comparable to that of a centralized controller. The importance of efficient use of network communications bandwidth is also discussed with regard to the control architectures considered

The effect of flow-induced coupling on sound radiation from convected fluid loaded plates.

Recent investigations concerning the effects of fluid convection on structural acoustic radiation have noted that radiation efficiency increases with increasing flow speeds. However, most of these studies based this conclusion on simulations that neglected flow-induced structural mode coupling. Yet, flow-induced coupling is know to have dramatic effects on structural dynamics including static and dynamic instabilities, and should therefore be expected to significantly affect sound radiation. The purpose of this investigation is to quantify the effects that fluid flow has on the sound radiated from rectangular vibrating plates when flow-induced structural modal coupling is considered. The discussion includes a description of the fundamental physics associated with a simply supported, vibrating, rectangular plate imbedded in an infinite baffle and radiating into a semi-infinite, convected fluid. This is followed by a discussion of the effect that flow-induced coupling has on the structural dynamic behavior. Finally, numerical results are presented that demonstrate the effect that such coupling has on the sound power radiated from a plate

Vibro-acoustic control with a distributed sensor network.

The purpose of this work is to demonstrate the ability of a distributed control system, based on a smart sensor network, to reduce acoustic radiation from a vibrating structure. The platform from which control is effected consists of a network of smart sensors, each referred to as a node. Each node possesses its own computational capability, sensor, actuator and the ability to communicate with other nodes via a wired or wireless network. The primary focus of this work is to employ existing group management middleware concepts to enable vibro-acoustic control with such a distributed network. Group management middleware is distributed software that provides for the establishment and maintenance of groups of distributed nodes and that provides for the network communication among such groups. The control objective is met by designing distributed feedback compensators that take advantage of node groups in order to effect their control. The node groups are formed based on physical proximity. The global control objective is to minimize the radiated sound power from a rectangular plate. Results of this investigation demonstrate that such a distributed control system can achieve attenuations comparable to those achieved by a centralized controller

Decentralized structural acoustic control of a launch vehicle payload fairing

The development of smart structures and active noise and vibration control technologies promised to revolutionize the design, construction and, most importantly, the performance of many complex engineering. However, the early promise of these technologies has not been realized in large-scale systems primarily because of the excessive complexity, cost, and weight associated with centralized control systems. Now, recent developments in MEMS sensors and actuators, along with networked embedded processor technology, have opened new research avenues in decentralized controls. Such a control system consists of numerous nodes, possessing limited computational capability, sensors, and actuators. Each of these nodes is also capable of communicating with other nodes via a wired or wireless network. This results in a dramatic shift in the control system paradigm from that of a single, centralized computer to that of numerous decentralized, networked processors. This work describes the application of such a control system to the reduction of structural acoustic radiation in a launch vehicle payload fairing. A JAVA-based simulation tool is employed to simulate the interactions of the physical system with the networked embedded controllers. Results will indicate the potential for such a control system as well as the limitations imposed by the networked embedded processor hardware

IMECE2005-81605 SIMULATIONS OF FAULT-ADAPTIVE CONTROL

ABSTRACT The objective of this work is to detect failures in a vibration control system and adapt the control system in order to maintain optimal performance. Fault detection and isolation (FDI) filters, which are a subset of state observers specifically designed to detect and identify known types of system failures, are used to detect sensor and actuator malfunctions. The output of such filters is used to reconfigure feedback compensators in order to maintain closed loop objectives. Such reconfiguration allows the system to continue operating optimally under certain system failures. Simulations have been performed for vibration control of a simply supported beam. The simulation is allowed to "fail" in certain pre-defined ways. FDI filters designed to detect these failures operate in parallel with the compensator. When a failure occurs the FDI filter output is used to switch to a new compensator that is appropriate for the new system condition. There are several challenges inherent in this effort but the most important is the management of compensator switching. Since switching involves system discontinuity, therefore stability of the system is very difficult to guarantee. Even if the plant and compensator are dissipative, stability cannot necessarily be proven. Simulation results will demonstrate some of these challenges and the effectiveness of this approach for maintaining suitable closed loop performance in the presence of system failures