Substitute magnetic materials

Magnetic materials are classified into two main groups : soft magnetic materials and permanent magnets. Soft magnetic materials are used on tonnage scale as cores of transformers and armatures of dynamos and motors and principally work in a.c. circuits. Permanent magnets can deliver a constant amount of energy in it given air gap with or without any external aid and are used in a wide variety of electrical and electronic instruments such as electricity meters, ammeters, voltmeters, loud speakers, telephones. teleprinters,motors, generators, televisions, lifting devices,etc. The manufacture of soft & permanent magnet materials presents a number of problems. They either contain metals like nickel and cobalt which do not occur in India or require high grade starting materials which are not manufactured at present or offer processing difficulties. To find suitable solutions of these problems and to develop suitable substitute materials a programme of research on the development of magnetic materials was initiated at the National Metall-urgical Laboratory sometime back and results are reported in this paper together with a review of the existing magnetic materials to bring out their technical and eco-nomic merits and demerits

Shape Approximation for Low-Thrust Constrained Space Trajectories Using Fourier Series with a Penalty on Transfer Cost

This report explores the concept of Shape- based approximation of Low-thrust Constrained Space Trajectories Using Fourier Series. In addition to the results obtained by the method developers Ehsan Taheri and Ossama Abdelkhalik on the aforementioned subject, a penalty was added to the transfer cost of the optimised trajectory. Its effects on the least squared error on the equations of motion were analysed. The two cases of orbit raising (moving from a Low-Earth Orbit to a Geo-Synchronous Orbit) and an orbit changing (from Earth to Mars) were analysed. The plots and tabulation compares the results of these two cases and its effects and future scope on space trajectory design and analysis

Physical Metallurgy of Aluminium Alloys

Aluminium is a soft and weak and is strengthened by alloying with suitable elements. The elements which are added to aluminium in appreciable quantities to increase its strength are limited to only four elements namely magnesium, silicon, copper and zinc. These may be, added singly or in combination. It will be Seen that the alloying elements magnesium and silicon belong to aluminium period itself while the copper and zinc metals belong to the copper period in the periodic table. Out of these foux elements magnesium has biggAr atomic diameter (3. 1906 A) than aluminium (d = 2.857 A), while silicon, gopper and zinc have smaller diameters, 2.345 A, 2.551 A and 2.659° respectively. These values are within 15% of the aluminium diameter values. Therefore these alloying elements are favourably placed fer- forming. Substitutional solid solutions with aluminium

Perturbations of planar algebras

We analyze the effect of pivotal structures (on a 2-category) on the planar algebra associated to a 1-cell as in \cite{Gho08} and come up with the notion of {\em perturbations of planar algebras by weights} (a concept that appeared earlier in Michael Burns' thesis \cite{Bur03}); we establish a one-to-one correspondence between weights and pivotal structures. Using the construction of \cite{Gho08}, to each bifinite bimodule over $II_1$-factors, we associate a {\em bimodule planar algebra} in such a way that extremality of the bimodule corresponds to sphericality of the planar algebra. As a consequence of this, we reproduce an extension of Jones' theorem (\cite{Jon}) (of associating `subfactor planar algebras' to extremal subfactors). Conversely, given a bimodule planar algebra, we construct a bifinite bimodule whose associated bimodule planar algebra is the one which we start with, using perturbations and Jones-Walker-Shlyakhtenko-Kodiyalam-Sunder method of reconstructing an extremal subfactor from a subfactor planar algebra. The perturbation technique helps us to construct an example of a family of non-spherical planar algebras starting from a particular spherical one; we also show that this family is associated to a known family of subfactors constructed by Jones.Comment: 28 page

Discription on a new species of Elasmus westwood (Hymenoptera:Chalcidoidea) with notes on host-parasitic relationship of some Indian species

A new Indian species of Elasmus in described in the sub family Elasminae Eulophidae from Bareilly district (U.P.), with a host parasite list of some species reared from plant hosts such as fig receptacles, fruits and galls. The parasites emerged from galls made by insects mostly belonged to family Encentidae, Aphelimidae, Eulopidae and Brachonidae. Host parasite list in compiled from the catalogue (Verma and Hayat, 1986)