7,561 research outputs found
Magnetocapacitance effect in perovskite-superlattice based multiferroics
We report the structural and magnetoelectrical properties of
LaCaMnO/BaTiO perovskite superlattices grown on
(001)-oriented SrTiO by the pulsed laser deposition technique. Magnetic
hysteresis loops together with temperature dependent magnetic properties
exhibit well-defined coercivity and magnetic transition temperature (T)
\symbol{126}140 K. electrical studies of films show that the
magnetoresistance (MR) is dependent on the BaTiO thickness and negative
as high as 30% at 100K are observed. The electrical studies reveal
that the impedance and capacitance in these films vary with the applied
magnetic field due to the magnetoelectrical coupling in these structures - a
key feature of multiferroics. A negative magnetocapacitance value in the film
as high as 3% per tesla at 1kHz and 100K is demonstrated, opening the route for
designing novel functional materials.Comment: To be published in Applied Physics Letter
A Ginzburg-Landau Analysis of the Colour Electric Flux Tube
In a simulation of SU(2) gauge theory we investigate, after maximal Abelian
projection, the dual Maxwell equations for colour field and monopole current
distributions around a static quark-antiquark pair Q_ Q in vacuo. Within the
dual superconductor picture we carry out a Ginzburg-Landau type analysis of the
flux tube profile. As a result we can determine the coherence length of the GL
wave function related to the monopole condensate, xi = .25(3) fm, to be
compared to the penetration length, lambda = >.15(2) fm (scaled with the string
tension).Comment: 3 pages, 5 figures, corrected typos, LATTICE98(confine
The role of ferroelectric-ferromagnetic layers on the properties of superlattice-based multiferroics
A series of superlattices and trilayers composed of ferromagnetic and
ferroelectric or paraelectric layers were grown on (100) SrTiO3 by the pulsed
laser deposition technique. Their structural and magneto-electric properties
were examined. The superlattices made of ferromagnetic Pr0.85Ca0.15MnO3 (PCMO)
and a ferroelectric, namely Ba0.6Sr0.4TiO3 (BST) or BaTiO3, showed enhanced
magnetoresistance (MR) at high applied magnetic field, whereas such enhancement
was absent in Pr0.85Ca0.15MnO3/SrTiO3 superlattices, which clearly demonstrates
the preponderant role of the ferroelectric layers in this enhanced MR.
Furthermore, the absence of enhanced MR in trilayers of PCMO/BST indicates that
the magneto-electric coupling which is responsible for MR in these systems is
stronger in multilayers than in their trilayer counterparts.Comment: to be published in J. Appl. Phy
Correlation between structure and properties in multiferroic LaCaMnO/BaTiO superlattices
Superlattices composed of ferromagnetics, namely LaCaMnO
(LCMO), and ferroelectrics, namely, BaTiO(BTO) were grown on SrTiO at
720C by pulsed laser deposition process. While the out-of-plane lattice
parameters of the superlattices, as extracted from the X-ray diffraction
studies, were found to be dependent on the BTO layer thickness, the in-plane
lattice parameter is almost constant. The evolution of the strains, their
nature, and their distribution in the samples, were examined by the
conventional sin method. The effects of structural variation on the
physical properties, as well as the possible role of the strain on inducing the
multiferroism in the superlattices, have also been discussed.Comment: To be published in Journal of Applied Physic
Prospects of Environmental Protection and Sustainability through Corporate Social Responsibility (CSR) in India
Healthy environmental is keys to economic development and growth. Thus, not paying attention to environmental problems sustainability can lead to degradation and depletion of natural resources which could prove detrimental to both the business and the society. The activities which are undertaken by the corporate and business houses for the welfare of people and society and also for ensuring healthy environment fall under the ambit of Corporate Social Responsibility (CSR). In past CSR activities were taken in philanthropic and charity mode. However, the recently enacted Companies Act, 2013 made the CSR obligatory with clear cut guidelines for its implementation. The Section 135 of Schedule VII of the Companies Act, 2013 as well as the provisions of the Companies (Corporate Social Responsibility Policy) Rules, 2014 became effective from April 1, 2014. Along with other provisions, the act has provided the list CSR activities to be undertaken by companies and guidelines for its implementation. One of the activities is about environmental protection and sustainability and includes elements like ‘ensuring environmental sustainability, ecological balance, protection of flora and fauna, animal welfare, agroforestry, conservation of natural resources and maintaining quality of soil, air and water’. Incorporation of environmental issues in CSR activities is positive step and if implemented properly it can be of great help for maintaining healthy environment. Different environmental elements of CSR activities are discussed with reference to environmental protection and sustainability. Key words: Corporate Social Responsibility (CSR): The Companies Act, 2013; Environmental protection and sustainability
Flow of an Elastico-viscous Fluid Past an Infinite Platewith Variable Suction
Unsteady state flow of an incompressible elastico-viscous fluid of second-order type pastan infinite vertical porous flat plate by considering uniform and variable suction normal to theplate has been studied and an exact solution is obtained for the velocity field. In the presentsituation, only two prescribed boundary conditions are available while the governing equationof motion is of third-order due to the presence of elastico-viscosity parameter. The conceptfollowing Walters has been used for a much more meaningful solution. The results for thevelocity distribution and skin friction have been analysed and discussed for different values ofthe parameters encountered in the governing equation of motion and skin friction on the plate.It is found that the effect of elastico-viscosity and suction has significant contribution on thebackflow at the wal
Exact Solutions of an Incompressible Fluid Flow of Second Order byForced Oscillations on the Porous Boundary
Exact solution of an incompressible fluid of second-order type by causing forced oscillationsin the liquid of finite depth bounded by a porous bottom has been obtained. The results presentedare in terms of nondimensional elastico-viscosity parameter () which depends on the non-Newtonian coefficient and the frequency of excitation () of the external disturbance whileconsidering the porosity (K) of the medium. The flow parameters are found to be identical withthat of Newtonian case as and K. It is seen that the effect of and the porosityof the bounding surface has significant effect on the velocity parameter. Further, the nature ofthe paths of the fluid particles have also been studied with reference to and the porosity ofthe bounding surface
Algorithms for Power Aware Testing of Nanometer Digital ICs
At-speed testing of deep-submicron digital very large scale integrated (VLSI) circuits
has become mandatory to catch small delay defects. Now, due to continuous shrinking
of complementary metal oxide semiconductor (CMOS) transistor feature size, power
density grows geometrically with technology scaling. Additionally, power dissipation
inside a digital circuit during the testing phase (for test vectors under all fault models
(Potluri, 2015)) is several times higher than its power dissipation during the normal
functional phase of operation. Due to this, the currents that flow in the power grid during
the testing phase, are much higher than what the power grid is designed for (the
functional phase of operation). As a result, during at-speed testing, the supply grid
experiences unacceptable supply IR-drop, ultimately leading to delay failures during
at-speed testing. Since these failures are specific to testing and do not occur during
functional phase of operation of the chip, these failures are usually referred to false
failures, and they reduce the yield of the chip, which is undesirable.
In nanometer regime, process parameter variations has become a major problem.
Due to the variation in signalling delays caused by these variations, it is important to
perform at-speed testing even for stuck faults, to reduce the test escapes (McCluskey
and Tseng, 2000; Vorisek et al., 2004). In this context, the problem of excessive peak
power dissipation causing false failures, that was addressed previously in the context of
at-speed transition fault testing (Saxena et al., 2003; Devanathan et al., 2007a,b,c), also
becomes prominent in the context of at-speed testing of stuck faults (Maxwell et al.,
1996; McCluskey and Tseng, 2000; Vorisek et al., 2004; Prabhu and Abraham, 2012;
Potluri, 2015; Potluri et al., 2015). It is well known that excessive supply IR-drop during
at-speed testing can be kept under control by minimizing switching activity during
testing (Saxena et al., 2003). There is a rich collection of techniques proposed in the past
for reduction of peak switching activity during at-speed testing of transition/delay faults
ii
in both combinational and sequential circuits. As far as at-speed testing of stuck faults
are concerned, while there were some techniques proposed in the past for combinational
circuits (Girard et al., 1998; Dabholkar et al., 1998), there are no techniques concerning
the same for sequential circuits. This thesis addresses this open problem. We
propose algorithms for minimization of peak switching activity during at-speed testing
of stuck faults in sequential digital circuits under the combinational state preservation
scan (CSP-scan) architecture (Potluri, 2015; Potluri et al., 2015). First, we show that,
under this CSP-scan architecture, when the test set is completely specified, the peak
switching activity during testing can be minimized by solving the Bottleneck Traveling
Salesman Problem (BTSP). This mapping of peak test switching activity minimization
problem to BTSP is novel, and proposed for the first time in the literature.
Usually, as circuit size increases, the percentage of don’t cares in the test set increases.
As a result, test vector ordering for any arbitrary filling of don’t care bits
is insufficient for producing effective reduction in switching activity during testing of
large circuits. Since don’t cares dominate the test sets for larger circuits, don’t care
filling plays a crucial role in reducing switching activity during testing. Taking this
into consideration, we propose an algorithm, XStat, which is capable of performing test
vector ordering while preserving don’t care bits in the test vectors, following which, the
don’t cares are filled in an intelligent fashion for minimizing input switching activity,
which effectively minimizes switching activity inside the circuit (Girard et al., 1998).
Through empirical validation on benchmark circuits, we show that XStat minimizes
peak switching activity significantly, during testing.
Although XStat is a very powerful heuristic for minimizing peak input-switchingactivity,
it will not guarantee optimality. To address this issue, we propose an algorithm
that uses Dynamic Programming to calculate the lower bound for a given sequence
of test vectors, and subsequently uses a greedy strategy for filling don’t cares in this
sequence to achieve this lower bound, thereby guaranteeing optimality. This algorithm,
which we refer to as DP-fill in this thesis, provides the globally optimal solution for
minimizing peak input-switching-activity and also is the best known in the literature
for minimizing peak input-switching-activity during testing. The proof of optimality of
DP-fill in minimizing peak input-switching-activity is also provided in this thesis
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