5,532 research outputs found
Planning Instrumentation Monitoring in Dams
This paper outlines the seismic instrumentation being adopted for river valley projects in India, More than 60% of Indian sub-continent lies in an active seismic belt. Of this the middle and lower Himalayas constitute a major area wherein lies a huge untapped hydro-power potential, Being primarily constituted of younger rock formations, frequented by faults, thursts and shear zones and lying in a high seismic risk zone, observations through instruments play a significant role in perspective planning of projects in this area. Setting up of seismological observatories in advance of construction of dam projects, forms a part of investigative planning to assess the seismic status of the area. The observations are continued after construction to monitor any changes in seismicity due to reservoir impounding. Present approach is to also provide instrumentation and continued observation to a possible prediction of earthquake. A typical case of instrumentation for a dam on active fault is also cited
Effect of Strain Relaxation on Magnetotransport properties of epitaxial La_0.7Ca_0.3MnO_3 films
In this paper, we have studied the effect of strain relaxation on
magneto-transport properties of La_0.7Ca_0.3MnO_3 epitaxial films (200 nm
thick), which were deposited by pulsed laser deposition technique under
identical conditions. All the films are epitaxial and have cubic unit cell. The
amount of strain relaxation has been varied by taking three different single
crystal substrates of SrTiO_3, LaAlO_3 and MgO. It has been found that for
thicker films the strain gets relaxed and produces variable amount of disorder
depending on the strength of strain relaxation. The magnitude of lattice
relaxation has been found to be 0.384, 3.057 and 6.411 percent for film
deposited on SrTiO_3, LaAlO_3 and MgO respectively. The films on LaAlO_3 and
SrTiO_3 show higher T_{IM} of 243 K and 217 K respectively as compared to
T_{IM} of 191 K for the film on MgO. Similarly T_C of the films on SrTiO_3 and
LaAlO_3 is sharper and has value of 245 K and 220 K respectively whereas the TC
of the film on MgO is 175 K. Higher degree of relaxation creates more defects
and hence TIM (T_C) of the film on MgO is significantly lower than of SrTiO_3
and LaAlO_3. We have adopted a different approach to correlate the effect of
strain relaxation on magneto-transport properties of LCMO films by evaluating
the resistivity variation through Mott's VRH model. The variable presence of
disorder in these thick films due to lattice relaxation which have been
analyzed through Mott's VRH model provides a strong additional evidence that
the strength of lattice relaxation produces disorder dominantly by increase in
density of defects such as stacking faults, dislocations, etc. which affect the
magneto-transport properties of thick epitaxial La_0.7Ca_0.3MnO_3 films
Universality in heavy-fermion systems with general degeneracy
We discuss the relation between the T^{2}-coefficient of electrical
resistivity and the T-linear specific-heat coefficient for
heavy-fermion systems with general , where is the degeneracy of
quasi-particles. A set of experimental data reveals that the Kadowaki-Woods
relation; , collapses
remarkably for large-N systems, although this relation has been regarded to be
commonly applicable to the Fermi-liquids. Instead, based on the Fermi-liquid
theory we propose a new relation;
with and .
This new relation exhibits an excellent agreement with the data for whole the
range of degenerate heavy-fermions.Comment: 2 figures, to appear in Phys. Rev. Let
Korteweg - de Vries solitons with different co-ordinate stretchings
The differences between the soliton solutions of the K-dV equation for a homogeneous, collisionless plasma, consisting of cold ions and isothermal electrons arising due to the two different sets of stretched co-ordinates have been discussed. In particular, the differences between the amplitudes and the widths of the solitons and their variations with the soliton velocity have been indicated. Further, the experimental implications of these differences and also of the two sets of stretched co-ordinates have been discussed
Induced N=2 composite supersymmetry in 2+1 dimensions
Starting from N=1 scalar supermultiplets in 2+1 dimensions, we build
explicitly the composite superpartners which define a N=2 superalgebra induced
by the initial N=1 supersymmetry. The occurrence of this extension is linked to
the topologically conserved current out of which the composite superpartners
are constructed.Comment: 11 pages LATEX, no figure
Concurrent Development and Certification of SOFTCOMAG 49AA Alloy for Aeronautical Applications
Softcomag 49AA alloy consisting of 49 wt per cent Fe, 49 wt. per cent Co and 2 wt per cent V is a soft magnetic alloy with a combination of very high saturation magnetisation and high magnetostriction and used for several aeronautical applications such as generators (stators and rotors), fixed iron moving armature units etc. Though this alloy is brittle in nature, it can be formed into hot rolled bars and cold rolled sheets by adopting suitable thermo mechanical treatments. In order to indigenise and subsequent type certification for aeronautical applications, the alloy was produced using 100 per cent virgin raw materials in a vacuum induction melting (VIM) furnace which not only ensures substantial reduction of inclusions, but also the production of homogeneous alloy as a result of induction stirring. The chemical composition was examined and hot working parameters of the alloy were so optimised that they would result in the best combination of magnetic, physical and mechanical properties for the end use, which forms the central theme behind the developmental activity that was simultaneously covered by a comprehensive certification process. The material thus produced is subjected to stringent quality control checks in accordance with stipulated airworthiness norms. The paper discusses in detail the indigenisation efforts and airworthiness certification of the alloy Softcomag 49AA and its comparison with equivalent grades, namely PERMENDUR 49 and VACOFLUX 50.Defence Science Journal, 2012, 62(1), pp.67-72, DOI:http://dx.doi.org/10.14429/dsj.62.1093
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