Laser Doppler velocimeter system simulation for sensing aircraft wake vortices. Part 2: Processing and analysis of LDV data (for runs 1023 and 2023)

A data analysis program constructed to assess LDV system performance, to validate the simulation model, and to test various vortex location algorithms is presented. Real or simulated Doppler spectra versus range and elevation is used and the spatial distributions of various spectral moments or other spectral characteristics are calculated and displayed. Each of the real or simulated scans can be processed by one of three different procedures: simple frequency or wavenumber filtering, matched filtering, and deconvolution filtering. The final output is displayed as contour plots in an x-y coordinate system, as well as in the form of vortex tracks deduced from the maxima of the processed data. A detailed analysis of run number 1023 and run number 2023 is presented to demonstrate the data analysis procedure. Vortex tracks and system range resolutions are compared with theoretical predictions

A feasibility study for the detection of upper atmospheric winds using a ground based laser Doppler velocimeter

A possible measurement program designed to obtain the information requisite to determining the feasibility of airborne and/or satellite-borne LDV (Laser Doppler Velocimeter) systems is discussed. Measurements made from the ground are favored over an airborne measurement as far as for the purpose of determining feasibility is concerned. The expected signal strengths for scattering at various altitude and elevation angles are examined; it appears that both molecular absorption and ambient turbulence degrade the signal at low elevation angles and effectively constrain the ground based measurement of elevation angles exceeding a critical value. The nature of the wind shear and turbulence to be expected are treated from a linear hydrodynamic model - a mountain lee wave model. The spatial and temporal correlation distances establish requirements on the range resolution, the maximum detectable range and the allowable integration time

Laser Doppler velocimeter system simulation for sensing aircraft wake vortices

A hydrodynamic model of aircraft vortex wakes in an irregular wind shear field near the ground is developed and used as a basis for modeling the characteristics of a laser Doppler detection and vortex location system. The trailing vortex sheet and the wind shear are represented by discrete free vortices distributed over a two-dimensional grid. The time dependent hydrodynamic equations are solved by direct numerical integration in the Boussinesq approximation. The ground boundary is simulated by images, and fast Fourier Transform techniques are used to evaluate the vorticity stream function. The atmospheric turbulence was simulated by constructing specific realizations at time equal to zero, assuming that Kolmogoroff's law applies, and that the dissipation rate is constant throughout the flow field. The response of a simulated laser Doppler velocimeter is analyzed by simulating the signal return from the flow field as sensed by a simulation of the optical/electronic system

Development of a Degradation Model for the Collapse Analysis of Composite Aerospace Structures

For stiffened structures in compression the most critical damage mechanism leading to structural collapse is delamination or adhesive disbonding between the skin and stiffener. This paper presents the development of a numerical approach capable of simulating interlaminar crack growth in composite structures as a representation of this damage mecha-nism. A degradation methodology was proposed using shell layers connected at the nodes by user-defined multiple point constraints (MPCs), and then controlling the properties of these MPCs to simulate the initiation and propagation of delamination and disbonding. A fracture mechanics approach based on the Virtual Crack Closure Technique (VCCT) is used to detect growth at the delamination front. Numerical predictions using the degradation methodology were compared to experimental results for double cantilever beam (DCB) specimens to dem-onstrate the effectiveness of the current approach. Future development will focus on address-ing the apparent conservatism of the VCCT approach, and extending the application of the method to other specimen types and stiffened structures representative of composite fuselage designs. This work is part of the European Commission Project COCOMAT (Improved MA-Terial Exploitation at Safe Design of COmposite Airframe Structures by Accurate Simulation of COllapse), an ongoing four-year project that aims to exploit the large strength reserves of composite aerospace structures through more accurate prediction of collapse

Resonant Processes in a Frozen Gas

We present a theory of resonant processes in a frozen gas of atoms interacting via dipole-dipole potentials that vary as $r^{-3}$, where $r$ is the interatomic separation. We supply an exact result for a single atom in a given state interacting resonantly with a random gas of atoms in a different state. The time development of the transition process is calculated both on- and off-resonance, and the linewidth with respect to detuning is obtained as a function of time $t$. We introduce a random spin Hamiltonian to model a dense system of resonators and show how it reduces to the previous model in the limit of a sparse system. We derive approximate equations for the average effective spin, and we use them to model the behavior seen in the experiments of Anderson et al. and Lowell et al. The approach to equilibrium is found to be proportional to $\exp (-\sqrt{\gamma_{eq}t}$), where the constant $\gamma _{eq}$ is explicitly related to the system's parameters.Comment: 30 pages, 6 figure

Prevalence of mixed genotype hepatitis C virus infections in the UK as determined by genotype‐specific PCR and deep sequencing

The incidence of mixed genotype hepatitis C virus infections in the UK is largely unknown. As the efficacy of direct acting antivirals is variable across different genotypes, treatment regimens are tailored to the infecting genotype, which may pose issues for the treatment of underlying genotypes within undiagnosed mixed genotype HCV infections. There is therefore a need to accurately diagnose mixed genotype infections prior to treatment. PCR-based diagnostic tools were developed to screen for the occurrence of mixed genotype infections caused by the most common UK genotypes, 1a and 3, in a cohort of 506 individuals diagnosed with either of these genotypes. The overall prevalence rate of mixed infection was 3.8% however this rate was unevenly distributed, with 6.7% of individuals diagnosed with genotype 3 harbouring genotype 1a strains and only 0.8% of samples from genotype 1a patients harbouring genotype 3 (p<0.05). Mixed infection samples consisted of a major and a minor genotype, with the latter constituting less than 21% of the total viral load and, in 67% of cases, less than 1% of the viral load. Analysis of a subset of the cohort by Illumina PCR-next generation sequencing resulted in a much greater incidence rate than obtained by PCR. This may have occurred due to the non-quantitative nature of the technique and despite the designation of false positive thresholds based on negative controls

Evaluation of an explicit vocabulary teaching intervention for children learning English as an additional language in primary school

Many children learning English as an Additional Language (EAL) possess lower levels of English vocabulary knowledge relative to their non-EAL English-speaking peers. Longitudinal work suggests that this group discrepancy does not decrease markedly over time as a result of regular classroom teaching. Twelve EAL learners with English vocabulary weaknesses took part in a low-intensity, 10-week vocabulary intervention. Working one-to-one with speech and language therapy students, children took part in weekly activities designed to promote receptive and productive knowledge of 20 target words within the Tier-2 vocabulary category. When assessed on a bespoke word knowledge assessment, children made statistically significant gains between pretest and posttest in both receptive and productive knowledge of taught words, and maintained this knowledge six months later. Multi-component explicit vocabulary instruction offering opportunities for active engagement and discussion is thus presented as one potentially effective means of promoting the Tier-2 vocabulary knowledge of EAL learners in primary school in England

A randomized trial of an Asthma Internet Self-management Intervention (RAISIN): study protocol for a randomized controlled trial

<b>Background</b><p></p> The financial costs associated with asthma care continue to increase while care remains suboptimal. Promoting optimal self-management, including the use of asthma action plans, along with regular health professional review has been shown to be an effective strategy and is recommended in asthma guidelines internationally. Despite evidence of benefit, guided self-management remains underused, however the potential for online resources to promote self-management behaviors is gaining increasing recognition. The aim of this paper is to describe the protocol for a pilot evaluation of a website 'Living well with asthma' which has been developed with the aim of promoting self-management behaviors shown to improve outcomes.<p></p> <b>Methods</b><p></p> The study is a parallel randomized controlled trial, where adults with asthma are randomly assigned to either access to the website for 12 weeks, or usual asthma care for 12 weeks (followed by access to the website if desired). Individuals are included if they are over 16-years-old, have a diagnosis of asthma with an Asthma Control Questionnaire (ACQ) score of greater than, or equal to 1, and have access to the internet. Primary outcomes for this evaluation include recruitment and retention rates, changes at 12 weeks from baseline for both ACQ and Asthma Quality of Life Questionnaire (AQLQ) scores, and quantitative data describing website usage (number of times logged on, length of time logged on, number of times individual pages looked at, and for how long). Secondary outcomes include clinical outcomes (medication use, health services use, lung function) and patient reported outcomes (including adherence, patient activation measures, and health status).<p></p> <b>Discussion</b><p></p> Piloting of complex interventions is considered best practice and will maximise the potential of any future large-scale randomized controlled trial to successfully recruit and be able to report on necessary outcomes. Here we will provide results across a range of outcomes which will provide estimates of efficacy to inform the design of a future full-scale randomized controlled trial of the 'Living well with asthma' website