1,584 research outputs found
On Longitudinal Disturbances in a Semi-Infinite Piezoelectric Rod with a Body-Force in a Magnetic Field.
This article presents the solution of the problem of longitudinal disturbances in a semi-infinite piezoelectric rod being acted by & magnetic field in presence of a body-force
The Suppression and Recovery of the Ferroelectric Phase in Multiferroic
We report the discovery of a complete suppression of ferroelectricity in
by 10 % iron substitution and its restoration in external magnetic
fields. The spontaneous polarization in arises below 12
K in external fields above 4 T. The magnetic/ferroelectric phase diagram is
constructed from the anomalies of the dielectric constant, polarization,
magnetization, and heat capacity. The observations are qualitatively described
by a mean field model with competing interactions and strong anisotropy. We
propose that the magnetic field induces a non-collinear inversion symmetry
breaking magnetic structure in
Thermal expansion and pressure effect in MnWO4
MnWO4 has attracted attention because of its ferroelectric property induced
by frustrated helical spin order. Strong spin-lattice interaction is necessary
to explain ferroelectricity associated with this type of magnetic order.We have
conducted thermal expansion measurements along the a, b, c axes revealing the
existence of strong anisotropic lattice anomalies at T1=7.8 K, the temperature
of the magnetic lock-in transition into a commensurate low-temperature
(reentrant paraelectric) phase. The effect of hydrostatic pressure up to 1.8
GPa on the FE phase is investigated by measuring the dielectric constant and
the FE polarization. The low- temperature commensurate and paraelectric phase
is stabilized and the stability range of the ferroelectric phase is diminished
under pressure.Comment: 2 pages, 3 figures. SCES conference proceedings, houston, TX, 2007.
to be published in Physica
Polymetallic complexes: Part XXVI-Complexes of cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II) and mercury(II) with chelating bis-bidentate ON NO donor bases
533-535Schiffbases synthesized by the reaction of benzoinhydrazone with salicylaldehyde and o-hydroxyacetophenone form dimeric complexes with divalent metal ions. An octahedral geometry has been assigned to the complexes of Co(II), Ni(II), Cu(II) and Zn(II) whereas a tetrahedral
structure is suggested for the Cd(II) and Hg(II) complexes. The complexes are amorphous, have high melting points and are insoluble in common organic solvents. The complexes have been characterised on the basis of analytical, conductance, magnetic susceptibility, molecular weight, IR and electronic spectral data
Robust Ferroelectric State in Multiferroic MnZnWO
We report the remarkably robust ferroelectric state in the multiferroic
compound MnZnWO. The substitution of the magnetic Mn
with nonmagnetic Zn reduces the magnetic exchange and provides control
of the various magnetic and multiferroic states of MnWO. Only 5 % of Zn
substitution results in a complete suppression of the frustrated collinear
(paraelectric) low temperature phase. The helical magnetic and ferroelectric
phase develops as the ground state. The multiferroic state is stable up to a
high level of substitution of more than 50 %. The magnetic, thermodynamic, and
dielectric properties as well as the ferroelectric polarization of single
crystals of MnZnWO are studied for different substitutions up
to x=0.5. The magnetic phases have been identified in single crystal neutron
scattering experiments. The ferroelectric polarization scales with the neutron
intensity of the incommensurate peak of the helical phase.Comment: 6 pages, 8 figure
Fair and Efficient Allocations under Subadditive Valuations
We study the problem of allocating a set of indivisible goods among agents with subadditive valuations in a fair and efficient manner. Envy-Freeness up to any good (EFX) is the most compelling notion of fairness in the context of indivisible goods. Although the existence of EFX is not known beyond the simple case of two agents with subadditive valuations, some good approximations of EFX are known to exist, namely -EFX allocation and EFX allocations with bounded charity. Nash welfare (the geometric mean of agents' valuations) is one of the most commonly used measures of efficiency. In case of additive valuations, an allocation that maximizes Nash welfare also satisfies fairness properties like Envy-Free up to one good (EF1). Although there is substantial work on approximating Nash welfare when agents have additive valuations, very little is known when agents have subadditive valuations. In this paper, we design a polynomial-time algorithm that outputs an allocation that satisfies either of the two approximations of EFX as well as achieves an approximation to the Nash welfare. Our result also improves the current best-known approximation of and to Nash welfare when agents have submodular and subadditive valuations, respectively. Furthermore, our technique also gives an approximation to a family of welfare measures, -mean of valuations for , thereby also matching asymptotically the current best known approximation ratio for special cases like while also retaining the fairness properties
EFX exists for three agents
We study the problem of distributing a set of indivisible items among agents with additive valuations in a manner. The fairness notion under consideration is Envy-freeness up to any item (EFX). Despite significant efforts by many researchers for several years, the existence of EFX allocations has not been settled beyond the simple case of two agents. In this paper, we show constructively that an EFX allocation always exists for three agents. Furthermore, we falsify the conjecture by Caragiannis et al. by showing an instance with three agents for which there is a partial EFX allocation (some items are not allocated) with higher Nash welfare than that of any complete EFX allocation
Magnetoelectricity and Magnetostriction due to the Rare Earth Moment in TmAl(BO)
The magnetic properties, the magnetostriction, and the magnetoelectric effect
in the d-electron free rare-earth aluminum borate TmAl(BO) are
investigated between room temperature and 2 K. The magnetic susceptibility
reveals a strong anisotropy with the hexagonal c-axis as the hard magnetic
axis. Magnetostriction measurements show a large effect of an in-plane field
reducing both, the a- and c-axis lattice parameters. The magnetoelectric
polarization change in a- and c-directions reaches up to 300 C/m at 70
kOe with the field applied along the a-axis. The magnetoelectric polarization
is proportional to the lattice contraction in magnetic field. The results of
this investigation prove the existence of a significant coupling between the
rare earth magnetic moment and the lattice in Al(BO) compounds
( = rare earth). They further show that the rare earth moment itself will
generate a large magnetoelectric effect which makes it easier to study and to
understand the origin of the magnetoelectric interaction in this class of
materials.Comment: 4 pages, 5 figure
Using a gender lens to explore farmers’ adaptation options in the face of climate change: Results of a pilot study in Uganda
Uganda, and especially the Rakai district, is highly vulnerable to climate variability and likely to be amongst the worst hit under climate change. Any responses to climate change affected communities cannot be considered complete unless women-specific responses are interwoven in a variety of adaptation options considered in the target area. The overall objective of this short-term research was to test tools and methodologies developed by CCAFS, FAO on analysis of gender issues in climate change, agriculture and food security. The study took place from the 1–4 November 2011, in the village of Kyengeza village in Uganda
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