The nature of a primary jet within a circumbinary disc outflow in a young stellar system

Most stars form in binaries, and both stars may grow by accreting material from a circumbinary disc onto their own discs. We suspect that in many cases a wide molecular wind will envelope a collimated atomic jet emanating from close to an orbiting young star. This so-called Circumbinary Scenario is explored here in order to find common identifiable properties. The dynamical set up is studied with three dimensional simulations with chemistry and cooling included. We extract the properties on scales of order 100 AU and compare to the Co-Orbital Scenario in which the wind and jet sources are in orbit. We find that the rapid orbital motion generates a wide ionised sheath around the jet core with a large opening angle at the base. This is independent of the presence of the surrounding molecular outflow. However, the atomic jet is recollimated beyond ∼ 55 AU when the molecular outflow restricts the motion of the ambient medium which, in turn, confines the jet. These physical properties are related to the optical Hα imaging, providing a means of distinguishing between models. The high excitation sheath and recollimation region can be explored on these scales through the next generation of instruments. However, in general, the amount and location of the ionised material, whether in the knots or the sheath, will depend on several parameters including the orbital period, axis alignment and pulse amplitude

Final Report - Regulatory Considerations for Adaptive Systems

This report documents the findings of a preliminary research study into new approaches to the software design assurance of adaptive systems. We suggest a methodology to overcome the software validation and verification difficulties posed by the underlying assumption of non-adaptive software in the requirementsbased- testing verification methods in RTCA/DO-178B and C. An analysis of the relevant RTCA/DO-178B and C objectives is presented showing the reasons for the difficulties that arise in showing satisfaction of the objectives and suggested additional means by which they could be satisfied. We suggest that the software design assurance problem for adaptive systems is principally one of developing correct and complete high level requirements and system level constraints that define the necessary system functional and safety properties to assure the safe use of adaptive systems. We show how analytical techniques such as model based design, mathematical modeling and formal or formal-like methods can be used to both validate the high level functional and safety requirements, establish necessary constraints and provide the verification evidence for the satisfaction of requirements and constraints that supplements conventional testing. Finally the report identifies the follow-on research topics needed to implement this methodology

New Atheism and Religious Language

A critical discussion

Towards extracting 3-D structural representations of AGR core fuel channels from 2-D in-core inspection videos

Remote Visual Inspection (RVI) of Advanced Gas-cooled Reactor (AGR) nuclear power stations allows engineers to gain an understanding of the AGR graphite core health by investigating the incorporated fuel channels. During planned, periodic outages, video footage of the pre-selected fuel channels is acquired using specialist inspection tools and is subsequently taken offline for further analysis using visualization techniques. Current methods of visualization however provide limited structural information due to the loss of depth information as a direct result of the image acquisition process. This paper introduces a new bespoke 3-D reconstruction framework to recover lost depth information to produce 3-D point cloud reconstructions of fuel channels from inspection videos. We also present here a new, lab based, experimental rig setup with which we effectively captured data under lab controlled conditions to verify our 3-D reconstruction algorithms. Our proposed method is tested on 2-D in core inspection videos in addition to the footage captured within laboratory conditions and outperforms state-of-the-art incremental reconstruction frameworks whilst producing a more representative 3-D point cloud for improved in-core visualization

3-D advanced gas-cooled nuclear reactor fuel channel reconstruction using structure-from-motion

During planned, periodic outages, a selection of fuel channels within the UK fleet of Advanced Gas-cooled Reactor (AGR) cores are inspected using specialist tools which record video footage and other sensory data for each channel which undergoes inspection. Current visualization techniques comprise of manually produced montages by inspection engineers of points of interest (i.e. structural defects) and 2-D panoramic images of the fuel channels automatically produced using bespoke image stitching software. Both techniques however provide limited structural information due to the loss of depth data as a result of the image formation process. By recovering the depth information from the footage, a 3-D model could be constructed and subsequently, allow for more accurate profiling of specific defects observed during inspection in addition to obtaining the fuel channels structure using existing footage. This work explores the preliminary application of a 3-D visualization technique known as Structure-from-Motion (SfM) which aims to obtain 3-D information by exploiting image correspondences across multiple viewpoints of the same scene in the RVI footage. This paper investigates the difficulties of applying state-of-the-art SfM to RVI footage and we present new techniques to improve feature correspondence searching in repetitive, non-descript environments

What do the terms resistance, tolerance, and resilience mean in the case of Ostrea edulis infected by the haplosporidian parasite Bonamia ostreae

The decline of the European flat oyster Ostrea edulis represents a loss to European coastal economies both in terms of food security and by affecting the Good Environmental Status of the marine environment as set out by the European Council's Marine Strategy Framework Directive (2008/56/EC). Restoration of O. edulis habitat is being widely discussed across Europe, addressing key challenges such as the devastating impact of the haplosporidian parasite Bonamia ostreae. The use of resistant, tolerant, or resilient oysters as restoration broodstock has been proposed by restoration practitioners, but the definitions and implications of these superficially familiar terms have yet to be defined and agreed by all stakeholders. This opinion piece considers the challenges of differentiating Bonamia resistance, tolerance, and resilience; challenges which impede the adoption of robust definitions. We argue that, disease-resistance is reduced susceptibility to infection by the parasite, or active suppression of the parasites ability to multiply and proliferate. Disease-tolerance is the retention of fitness and an ability to neutralise the virulence of the parasite. Disease-resilience is the ability to recover from illness and, at population level, tolerance could be interpreted as resilience. We concede that further work is required to resolve practical uncertainty in applying these definitions, and argue for a collaboration of experts to achieve consensus. Failure to act now might result in the future dispersal of this disease into new locations and populations, because robust definitions are important components of regulatory mechanisms that underpin marine management.</p

The Numerical Modelling Of Scenarios For The Herbig-Haro Object HH30

The classical T-Tauri star HH30 in Taurus-Auriga exhibits a well-collimated plume of hot, optically-emitting atomic and partially ionised Hydrogen, and also a colder, dense, wide-angle molecular Hydrogen ouflow. Observations suggest HH30 is a binary system system, surrounded by a circumbinary accretion disc. We investigated the propagation and interaction of dual atomic and molecular outflows from HH30, using a series of numerical simulations with parameters informed by observational campaigns. These 3-dimensional models were computed using the established Eulerian astrophysics code ZEUS-MP, with in-house modifications and an enhanced chemistry and cooling module. These simulations assumed off-domain launch and tracked the evolution of the jets over spatial scale of ~ 100 AU, and with a timescale ~ 100 - 200 years. The propagation in this region is of special interest, as this is where the greatest difference between the two scenarios is likely to emerge. Our work here differs from "classical" simulations of jet propagation by virtue of one or both outflow sources moving in an orbit. Two competing scenarios were investigated, in which the morphology of the light-year scale outflow from HH30 is explained by different kinds of motion of the atomic outflow source, and in which the launch site of the molecular outflow differs. In both cases a velocity-pulsed atomic jet emerges from the more massive binary object. In the Orbital scenario, the orbital motion of the primary explains the morphology seen at large scale, while the molecular flow is launched from the secondary partner; in the Precessional scenario, precession of the primary dominates the morphology, while launch of the molecular flow is from the inner edge of the circumbinary disc. The binary orbit and inner depletion zone of the circumbinary disc differs between the scenarios, with the Precessional scenario having a much smaller orbit and correspondingly reduced inner depletion zone. Clearly identifiable structural differences emerge between the simulated models. We compared the effects of the two different kinds of perturbing molecular outflow on the faster atomic jet; position, velocity, line mass per unit length, temperature and other variables, as a function of distance x (AU) from the binary source. Linear and quadratic fit functions were determined to facilitate comparison with observation. These quantify the expected behaviours of the atomic jet in the presence of the two different kinds of molecular flow. Where the fit function domains overlap direct comparisons may be drawn; where 26 < x < 42 AU, the average velocity as a function of distance is Vx(x) = (1.39×10^?1 ±2.15×10^?3)x + (246.82±1.29) km s^?1 in the Precessional model, while in the Orbital model we find Vx(x) = (?3.26 ± 0.26)x + (269.57 ± 6.75) km s^?1. In the region 10 < x < 60 AU, the Precessional model has temperature dependence T(x) = (64.53 ± 12.54)x + (3535 ± 330) K. Whilst in the same region of the Orbital model, T(x) = (401.99 ± 333.19)x + (4258.4 ± 1340.3) K. Synthetic Mass-Velocity Spectra have been generated for our models, to investigate distinguishing features of these spectra in the presence of the two different types of molecular outflow. The shallow-angle spectra matching the aspect angle of HH30 itself are examined and the link between outflow scenario and time variability discussed. Spectra from the same dual outflow systems observed at different aspect angles to the sky plane are given, to provide a means to confirm these senarios in other HH30-like T-Tauri stars. Using code written in-house to calculate emission using rate coefficients for photon production, we generated synthetic observations; spatially resolved images, velocity channel maps and position-velocity diagrams. The morphology of the synthetic images from the two scenarios when compared to HST R-band imaging of HH30 suggests that the Orbital case is unlikely, whilst the Precessional case is supported

Binary outflows from young stars: interaction of co-orbital jet and wind

Jets from young stellar objects provide insight into the workings of the beating heart at the centre of star-forming cores. In some cases, multiple pulsed outflows are detected such as the atomic and molecular jets from a proposed binary system in the T Tauri star HH 30. We investigate here the development and propagation of duelling atomic and molecular outflows stemming from the two stars in co-orbit. We perform a series of numerical experiments with the ZEUS-MP code with enhanced cooling and chemistry modules. The aim of this work is to identify signatures on scales of the order of 100 au. The jet sources are off the grid domain and so it is the propagation and interaction from ∼20 au out to 100 au simulated here. We find that the molecular flow from the orbiting source significantly disturbs the atomic jet, deflecting and twisting the jet and disrupting the jet knots. Regions of high ionization are generated as the atomic jet rams through the dense molecular outflow. Synthetic images in atomic and molecular lines are presented, which demonstrate identifying signatures. In particular, the structure within the atomic jet is lost and H α may trace the walls of the present CO cavity or where the walls have been recently. These results provide a framework for the interpretation of upcoming high-resolution observations

Results of 1/4-Scale Experiments. Vapor Simulant And Liquid Jet A Tests

A quarter-scale engineering model of the center wing tank (CWT) of a 747-100 was constructed. This engineering model replicated the compartmentalization, passageways, and venting to the atmosphere. The model was designed to scale the fluid dynamical and combustion aspects of the explosion, not the structural failure of the beams or spars. The effect of structural failure on combustion was examined by using model beams and spars with deliberately engineered weak connections to the main tank structure. The model was filled with a simulant fuel (a mixture of propane and hydrogen) and ignited with a hot wire. The simulant fuel was chosen on the basis of laboratory testing to model the combustion characteristics (pressure rise and flame speed) of Jet A vapor created by a Jet A liquid layer at 50C at an altitude of 13.8 kft. A series of experiments was carried out in this model in order to: (a) investigate combustion in a CWT geometry; and (b) provide guidance to the TWA 800 crash investigation. The results of the experiments were observed with high-speed film, video, and still cameras, fast and slow pressure sensors, thermocouples, photodetectors, and motion sensors. A special pseudo-schlieren system was used to visualize flame propagation within the tank. This report describes the test program, facility, instrumentation, the first 30 experiments, comparisons between experiments, and performance of the instrumentation; then examines the significance of these results to the TWA 800 crash investigation. The key results of this study are: Flame Motion: The motion of flame was dominated by the effects of turbulence created by jetting through the passageways and vent stringers. A very rapid combustion event (lasting 10 to 20 ms) occurred once the flame traveled outside of the ignition bay and interacted with the turbulent flow. Most of the gas within the tank was burned during this rapid event. Compartments: The combustion time decreased with an increasing number of compartments (bays) within the tank. With six bays, combustion took only 100 to 150 ms to be completed from the time of ignition until the end of the rapid combustion phase. The total combustion event was three to four times shorter with compartments than without. Venting: Venting to the outside of the tank through the model vent stringers had a negligible effect on the combustion progress or on the peak pressure reached at the end of the burn. Ignition Location: Variation of the ignition location produced distinctive pressure loads on the structural components. Liquid Fuel: Lofting of a cold liquid fuel layer was produced by the combustion-induced gas motion. Although this spray of liquid eventually ignited and burned, it did not contribute to the pressure loading. Structural Failure: Structural failure resulted in flame acceleration, decreasing the overall combustion time. TWA 800 Investigation: The pressure loads were sufficiently high, up to 4 bar, and the combustion events were sufficiently short, that the forward portion (spanwise beam 3, front spar) of the CWT structure would fail as a direct consequence of the explosion. A combination of pressure loads was produced in some tests consistent with the TWA 800 wreckage. Replica tests, structural modeling, and sensitivity studies on fuel concentration are needed before any conclusions can be drawn about probable ignition locations. Cargo Bay: Tests with a simplified model of a half-full cargo bay indicated that repeated pressure waves with an amplitude of 1 bar or less are produced when an explosion scenario similar to TWA 800 is tested. Future Testing: Future studies should include replica tests, tests with Jet A vapor and warm liquid Jet A layers, and sensitivity tests to examine ignition location, fuel concentration, and vent area perturbations. Summary: Explosion tests in a 747-100 CWT model reveal that a very complex pattern of combustion occurs due the interaction of the flame and the flow-generated turbulence. A wide range of structural load patterns occur, depending on the location of the ignition source. Some of these load patterns are consistent with damage believed to be associated with the initial explosion event in TWA 800. Sensitivity of the loading to the ignition location indicates that narrowing down the ignition location in TWA 800 may be possible. However, the complexity of the combustion and structural failure processes in the actual center wing tank mandates extremely careful consideration of the uncertainties that enter into this process

The Kinematic Evolution of Strong MgII Absorbers

We consider the evolution of strong (W_r(2796) > 0.3A) MgII absorbers, most of which are closely related to luminous galaxies. Using 20 high resolution quasar spectra from the VLT/UVES public archive, we examine 33 strong MgII absorbers in the redshift range 0.3 < z < 2.5. We compare and supplement this sample with 23 strong MgII absorbers at 0.4 < z < 1.4 observed previously with HIRES/Keck. We find that neither equivalent width nor kinematic spread (the optical depth weighted second moment of velocity) of MgII2796 evolve. However, the kinematic spread is sensitive to the highest velocity component, and therefore not as sensitive to additional weak components at intermediate velocities relative to the profile center. The fraction of absorbing pixels within the full velocity range of the system does show a trend of decreasing with decreasing redshift. Most high redshift systems (14/20) exhibit absorption over the entire system velocity range, which differs from the result for low redshift systems (18/36) at the 95% level. This leads to a smaller number of separate subsystems for high redshift systems because weak absorping components tend to connect the stronger regions of absorption. We hypothesize that low redshift MgII profiles are more likely to represent well formed galaxies, many of which have kinematics consistent with a disk/halo structure. High redshift MgII profiles are more likely to show evidence of complex protogalactic structures, with multiple accretion or outflow events. Although these results are derived from measurements of gas kinematics, they are consistent with hierarchical galaxy formation evidenced by deep galaxy surveys.Comment: Accepted to the Astrophysical Journa