Transport and diffusion in the embedding map

We study the transport properties of passive inertial particles in a $2-d$ incompressible flows. Here the particle dynamics is represented by the $4-d$ dissipative embedding map of $2-d$ 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 $\alpha$, and the dissipation parameter $\gamma$. 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

An Investigation into the Development of Prospective Indian Austenitic Stainless Steels

The development of substitute stainless steels in which all or the bulk of nickel in the standard austenitic stainless grades is replaced by manganese became it live issue in many steel -producing countries during world War 11 due to restricted or nonavailability of nickel . The research and development work carried out during the war period yielded a series of commercially useful alloy steels, which are enumerated. The paper goes on to refer to an investigation in progress in the National Metallurgical Laboratory into the development of substitute austenitic stainless steels based on the use of manganese, nitrogen , copper, chromium and rare earth additions.The results of experi-mental heats made are presented in terms of working prop-erties , metallographic studies, corrosion resistance under different media, interoranular brittleness and physical tests, etc. Tentative views are expressed on the merits of these austenitic stainless compositions under Indian conditions , which will be reviewed after further work which is being pursued in the National 'Metall-urgical Laboratory along lines stated

Manufacture in India of Ferro Alloys used in Alloy Steel Industry

The paper starts with an outline of established methods of manufacture of different ferro-alloys required for making alloy steels with a comparison of their merits as judged by the products made. The ferro-alloys discussed include those based on manganese, chromium, silicon, tungsten, vanadium and phosphorus and of different qual-ities and grades. The position of the production of the individual ferro-alloys in India is discussed and the great importance emphasized of expanding production of those required in relation to the expansion of the Indian iron and steel industry. A programme of ferro- alloy production is outlined, with discussion of availability of raw materials, manufacturing capacity and economic factors

Tempering of Die-steels based on indigenous materials

This paper present studies on the effects of quenching temperature, tempering temperature and time on the hardness of three die steels of similar carbon contents but having increasing chromium percentages. While tempering in the range of 150°C to 400°C it was observed that hardness decreased as quenching temperature was raised. All the steels showed secondary hardening phenomenon in relation to the variables mentioned above. It was also observed that on tempering the steels above 450°C, after prior quenching from increasing temperatures, hardness gradually increased upto the quenching temperature of 1100°C, beyond which followed a decrease in hardness. This phenomenon was the decrease in hardness. This phenomenon was the same at all tempering temperatures upto 601°C, but the increase in hardness from low quenching temperatures to the maximum quenching temperature was less at 450°C than at the higher temperatures and attained a maximum at 600°C secondary hardening decreased with the increase of quenching temperatur

Queue-length synchronization in a communication networks

We study synchronization in the context of network traffic on a $2-d$ communication network with local clustering and geographic separations. The network consists of nodes and randomly distributed hubs where the top five hubs ranked according to their coefficient of betweenness centrality (CBC) are connected by random assortative and gradient mechanisms. For multiple message traffic, messages can trap at the high CBC hubs, and congestion can build up on the network with long queues at the congested hubs. The queue lengths are seen to synchronize in the congested phase. Both complete and phase synchronization is seen, between pairs of hubs. In the decongested phase, the pairs start clearing, and synchronization is lost. A cascading master-slave relation is seen between the hubs, with the slower hubs (which are slow to decongest) driving the faster ones. These are usually the hubs of high CBC. Similar results are seen for traffic of constant density. Total synchronization between the hubs of high CBC is also seen in the congested regime. Similar behavior is seen for traffic on a network constructed using the Waxman random topology generator. We also demonstrate the existence of phase synchronization in real Internet traffic data.Comment: 13 Pages, 15 figure

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

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

Carbamate synthesis by solid-base catalyzed reaction of disubstituted ureas and carbonates

This is the published version. Copyright © The Royal Society of Chemistry 2001A simple and efficient methodology to prepare carbamates has been demonstrated for the first time from symmetrical ureas and organic carbonates in the presence of solid base catalysts

Study of Microstructure of Chill Cast Aluminium Bronzes (Cu-Al-Fe-Mn)

Substantial information is available on the microstr-uctures of high tensile aluminium bronzes but most of the literature is pertaining to the alloys containing nickel. In the present paper authors have studies and presented the microstructures of various nickel-free aluminium bronze alloys containing iron and manganese. As an exhau-stive amount of work had been done at National Metall-urgical Laboratory to study the mechanical properties of such aluminium bronze alloys in the chill cast condition, the present microstructure study is also limited to the as cast alloys

Study of microstructure of chill cast aluminium bronzes (Cu-AI-Fe-Mn)

SUBSTANTIAL information is available on the microstru-ctures of high tensile aluminium -bronzes but most of the literature is pertaining to the alloys containing nickel. Exhaustive amount of work was carried out by Gupta et al. at the National Metallurgical Laboratory to study the mechanical properties of aluminium-bronze alloys in the chill-cast condition without nickel addition, the results of which have already been reported in an earlier paper. The present paper relates to the study of microstructures of these chill-cast aluminium-bronze alloys. A few microstructures of Cu-Al-Fe system have been given by Copper Development Association in their recent publication on aluminium-bronzes.

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

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