On shock dynamics

This is in continuation of our paper On the propagation of a multi-dimensional shock of arbitrary strength’ published earlier in this journal (Srinivasan and Prasad [9]). We had shown in our paper that Whitham’s shock dynamics, based on intuitive arguments, cannot be relied on for flows other than those involving weak shocks and that too with uniform flow behind the shock. Whitham [12] refers to this as misinterpretation of his approximation and claims that his theory is not only correct but also provides a natural closure of the open system of the equations of Maslov [3]. The main aim of this note is to refute Whitham’s claim with the help of an example and a numerical integration of a problem in gasdynamics.     

A superspace formulation of BRS/anti-BRS symmetric Yang-Mills effective action

We give a superspace formulation that generates the BRS/anti BRS invariant Yang Mills effective action of Baulieu Thierry-Mieg. This work generalizes our earlier work on superspace formulation for Faddeev Popov effective action. Our work differs from earlier works by other workers in that our superfields are completely unconstrained and our superspace is not just a formal device but allows superrotations. We construct a generating functions W? that has (broken) invariance under two separate sets of superrotations that mix x^μ with grassmannian coordinates λ and θ.These allow the BRS and anti-BRS WT identities for W? formulated as two simple elegant equations involving (?W?/?θ) and (?W?/?λ). We also note that quadratic guages can be naturally included straightforwardly in this superspace formulation.     

Dynamical hysteresis and spatial synchronization in coupled non-identical chaotic oscillators

We identify a novel phenomenon in distinct (namely non-identical) coupled chaotic systems, which we term dynamical hysteresis. This behavior, which appears to be universal, is defined in terms of the system dynamics (quantified for example through the Lyapunov exponents), and arises from the presence of at least two coexisting stable attractors over a finite range of coupling, with a change of stability outside this range. Further characterization via mutual synchronization indices reveals that one attractor corresponds to spatially synchronized oscillators, while the other corresponds to desynchronized oscillators. Dynamical hysteresis may thus help to understand critical aspects of the dynamical behavior of complex biological systems, e.g. seizures in the epileptic brain can be viewed as transitions between different dynamical phases caused by time dependence in the brain’s internal coupling.     

New modifications in 15 UD pelletron at nuclear science centre

The 15 UD pelletron at NSC has been operational and performed well during the last 11 years. There have been major modifications performed for upgradation of pelletron system over this period. Major upgradations which have been implemented are new resistor network system for voltage gradient, doublet to singlet unit conversion for accelerator units, turbopump based gas stripper system etc. In addition accelerator mass spectroscopy program has also been started. A new multi-cathode source, Wien filter etc. have been procured and will be added soon in the system. An overview of the most significant upgradations undertaken and other activities for the system are being reported in the present paper.     

On quadratic fractional generalized solid bi-criterion transportation problem

In this paper bi-criterion quadratic fractional generalized solid transportation problem is studied. An algorithm is devoloped to obtain the time-cost trade-off pairs and hence identifies the optimum trade-off pairs giving the equal priority to both time and cost. A numerical example is illustrated to support the algorithm.     

Hyperfine fields at implanted119Sn in Fe

Metastable FeSn systems produced by high dose implantation of¹¹⁹Sn into Fe foils are studied by conversion electron Mössbauer spectroscopy. The hyperfine field experienced by Sn implanted in Fe depends on the implantation dose. Clustering and precipitation of Sn take place at doses of 5x10¹⁶/cm² and beyond. Isochronal annealing of the implanted sample at 500 C causes the Sn atoms to move towards the surface, probably due to vacancy assisted migration, resulting in the precipitation of almost the entire implanted Sn on the Fe surface. This precipitate acts as a source for the in-diffusion of Sn into Fe at 600 C.