609 research outputs found

    Clustering, Chaos and Crisis in a Bailout Embedding Map

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    We study the dynamics of inertial particles in two dimensional incompressible flows. The particle dynamics is modelled by four dimensional dissipative bailout embedding maps of the base flow which is represented by 2-d area preserving maps. The phase diagram of the embedded map is rich and interesting both in the aerosol regime, where the density of the particle is larger than that of the base flow, as well as the bubble regime, where the particle density is less than that of the base flow. The embedding map shows three types of dynamic behaviour, periodic orbits, chaotic structures and mixed regions. Thus, the embedding map can target periodic orbits as well as chaotic structures in both the aerosol and bubble regimes at certain values of the dissipation parameter. The bifurcation diagram of the 4-d map is useful for the identification of regimes where such structures can be found. An attractor merging and widening crisis is seen for a special region for the aerosols. At the crisis, two period-10 attractors merge and widen simultaneously into a single chaotic attractor. Crisis induced intermittency is seen at some points in the phase diagram. The characteristic times before bursts at the crisis show power law behaviour as functions of the dissipation parameter. Although the bifurcation diagram for the bubbles looks similar to that of aerosols, no such crisis regime is seen for the bubbles. Our results can have implications for the dynamics of impurities in diverse application contexts.Comment: 16 pages, 9 figures, submitted for publicatio

    Transport and diffusion in the embedding map

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    We study the transport properties of passive inertial particles in a 2−d2-d incompressible flows. Here the particle dynamics is represented by the 4−d4-d dissipative embedding map of 2−d2-d area-preserving standard map which models the incompressible flow. The system is a model for impurity dynamics in a fluid and is characterized by two parameters, the inertia parameter α\alpha, and the dissipation parameter γ\gamma. We obtain the statistical characterisers of transport for this system in these dynamical regimes. These are, the recurrence time statistics, the diffusion constant, and the distribution of jump lengths. The recurrence time distribution shows a power law tail in the dynamical regimes where there is preferential concentration of particles in sticky regions of the phase space, and an exponential decay in mixing regimes. The diffusion constant shows behaviour of three types - normal, subdiffusive and superdiffusive, depending on the parameter regimes. Phase diagrams of the system are constructed to differentiate different types of diffusion behaviour, as well as the behaviour of the absolute drift. We correlate the dynamical regimes seen for the system at different parameter values with the transport properties observed at these regimes, and in the behaviour of the transients. This system also shows the existence of a crisis and unstable dimension variability at certain parameter values. The signature of the unstable dimension variability is seen in the statistical characterisers of transport. We discuss the implications of our results for realistic systems.Comment: 28 pages, 14 figures, To Appear in Phys. Rev. E; Vol. 79 (2009

    The Effect of Misch Metal Additions on the Structure and Workability of Al-Mg (7-100/.) Alloys

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    ON the alloying elements used in aluminium alloys, copper was one of' the earliest employed commercially and for many years it has been the principal one. Aluminium-copper alloys to which manganese, magnesium or silicon has been added, belong to the important group generally known as "Duralumin". The binary alloys of aluminium with magnesium attra- cted the interest of investigators as early as 1900. There have been numerous attempts to utilise for general purposes alloys containing as Much as 10% magnesium ; alloys containing up to 30% magnesium have been used for special purposes

    Hot Dip Aluminising of Steel Wire- Laboratory Scale Investigations and Pilot Plant Studies

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    Protective quality of aluminium due to its adherent surface oxide film is well known. In hot-dip aluminising the use is made of this protective nature of aluminium by coating the steel base by dipping it in molten aluminium bath there-by getting an outer aluminium layer & an iron-aluminium layer at the interface. The interfacial alloy layer though possessing good atmospheric corrosion and resistance to oxidation at high temperature is brittle in nature and such must be kept to a minimum of thickness where the end use of aluminised product is for deep drawing, forming etc. Hot-dip aluminium coating on steel base comprising the outer aluminium layer and an alloy layer in the interface should possess both atmospheric & high temperature corrosion resistance

    Substitution of galvanising by aluminising of steels

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    ALUMINISING has been accepted by the Government of India as it substitute for galvanising because of the existing scarcity of zinc. Zinc resources of our country are limited whereas minerals for extraction of aluminium are available in plenty. The Hindustan Steel (P ) Ltd., has decided to have provision for strip aluminising plant at Rourkela and Tata Iron and Steel Co. Ltd., may also be going for strip alum-inising adopting the Sendzimir Process . Bokaro Steel Plant has also made provision for aluminising of steel strip

    COVID-19 as a global challenge: towards an inclusive and sustainable future

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    COVID-19 is a global challenge that demands researchers, policy makers, and governments address multiple dimensions which go far beyond the implications of this pandemic for health and wellbeing. Just as the UN Sustainable Development Goals call for focus on the connections between development policy sectors, the pandemic has exposed the complex global interdependencies that underpin economies and highlighted fault lines in societal structures that perpetuate ethnic, economic, social, and gender inequalities. Here, we highlight the pandemic's emerging potential consequences for achieving sustainable development with respect to the six global challenge areas we collectively address at the UK Research and Innovation's Global Challenges Research Fund:1 food systems; education; cities and sustainable infrastructure; security, protracted conflict, refugee crises, and forced displacement; environmental resilience; and global health. As the immediate health consequences of the pandemic unfold and begin to be superseded by the impact of public health containment measures, we call for a refocusing of research and action not only to mitigate these impacts but to build sustainability and strengthened resilience into future recovery

    Development of substitute high temperature creep resistant alloys

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    HIGH temperature creep resistant super strength alloys invariably contain considerable amounts of Ni,Co,W, etc. as alloying additions, in respect of which India lacks in raw material resources. Extensive work has been carried out on development of Cr-Mn-N type austenitic steels as substitute for 18 Cr 8 Ni austenitic stainless steel and their aging behaviour have been extensively studied at the National Metallurgical Laboratory in the last decade. The present work has been initiated to further study the high temperature creep behaviour of Cr-Mn-N type austenitic steels with a view to evolving suitable compositions and heat-treatment to obtain opti-mum high temperature creep strength and rupture ducti- lity in these alloys. In this group of steel Mn and N are used as the chief austenitic stabilizers besides C
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