237 research outputs found
Ab initio study on the magneto-structural properties of MnAs
The magnetic and structural properties of MnAs are studied with ab initio
methods, and by mapping total energies onto a Heisenberg model. The stability
of the different phases is found to depend mainly on the volume and on the
amount of magnetic order, confirming previous experimental findings and
phenomenological models. It is generally found that for large lattice constants
the ferromagnetic state is favored, whereas for small lattice constants
different antiferromagnetic states can be stabilized. In the ferromagnetic
state the structure with minimal energy is always hexagonal, whereas it becomes
orthorhombically distorted if there is an antiferromagnetic component in the
hexagonal plane. For the paramagnetic state the stable cell is found to be
orthorhombic up to a critical lattice constant of about 3.7 Angstrom, above
which it remains hexagonal. This leads to the second order structural phase
transition between paramagnetic states at about 400 K, where the lattice
parameter increases above this critical value with rising temperature due to
the thermal expansion. For the paramagnetic state an analytic approximation for
the magnitude of the orthorhombic distortion as a function of the lattice
constant is given. Within the mean field approximation the dependence of the
Curie temperature on the volume and on the orthorhombic distortion is
calculated. For orthorhombically distorted cells the Curie temperature is much
smaller than for hexagonal cells. This is mainly due to the fact that some of
the exchange coupling constants in the hexagonal plane become negative for
distorted cells. With these results a description of the susceptibility as
function of temperature is given
Effectiveness of actions associated with the environmental protection and the sustainable development
The problem, which for many centuries measured globe is "coexistence" between man and
nature. The essential element of this process is the continuous satisfaction of human needs with the
use of what nature and the process of globalization have given of themselves. Therefore, the authors
of this article research has identified the following problems, namely. Do man can imagine himself
without essential environment? Is the action and the human conscience allows him to "surrender"
the gifts of fauna and flora? Is in the current progress in the development of society is the human
factor that causes people to become empathetic to the devastation of the environment? The present
article attempts to answer these questions, and the responses are the hypotheses
Code of ethics as a tool for resolving conflict in the organization
This article addresses the issues as selection tools to resolve conflicts in organizations
because of the importance and topicality of this issue. One such tool among these is the effective
functioning of the organization code of ethics. This document, the more detailed, the more effective.
Nowadays, more and more organizations have their own codes of ethics. Therefore, it would be
wrong underestimation of the code of ethics as a tool that could be used to resolve conflicts in
organizations
Cr cluster characterization in Cu-Cr-Zr alloy after ECAP processing and aging using SANS and HAADF-STEM
International audienceThe precipitation of nano-sized Cr clusters was investigated in a commercial Cu-1Cr-0.1Zr (wt.%) alloy processed by Equal-Channel Angular Pressing (ECAP) and subsequent aging at 550 °C for 4 hours using small angle neutron scattering (SANS) measurements and high-angle annular dark-field-scanning transmission electron microscopy (HAADF-STEM). The size and volume fraction of nano-sized Cr clusters were estimated using both techniques. These parameters assessed from SANS (d~3.2 nm, Fv~1.1 %) agreed reasonably with those from HAADF-STEM (d ~2.5 nm, Fv~2.3%). Besides nano-sized Cr clusters, HAADF-STEM technique evidenced the presence of rare cuboid and spheroid sub-micronic Cr particles about 380-620 nm mean size. Both techniques did not evidence the presence of intermetallic CuxZry phases within the aging conditions
Code of ethics as a tool for resolving conflict in the organization
This article addresses the issues as selection tools to resolve conflicts in organizations
because of the importance and topicality of this issue. One such tool among these is the effective
functioning of the organization code of ethics. This document, the more detailed, the more effective.
Nowadays, more and more organizations have their own codes of ethics. Therefore, it would be
wrong underestimation of the code of ethics as a tool that could be used to resolve conflicts in
organizations
Boundary critical behavior at m-axial Lifshitz points for a boundary plane parallel to the modulation axes
The critical behavior of semi-infinite -dimensional systems with
-component order parameter and short-range interactions is
investigated at an -axial bulk Lifshitz point whose wave-vector instability
is isotropic in an -dimensional subspace of . The associated
modulation axes are presumed to be parallel to the surface, where . An appropriate semi-infinite model representing the
corresponding universality classes of surface critical behavior is introduced.
It is shown that the usual O(n) symmetric boundary term
of the Hamiltonian must be supplemented by one of the form involving a
dimensionless (renormalized) coupling constant . The implied boundary
conditions are given, and the general form of the field-theoretic
renormalization of the model below the upper critical dimension
is clarified. Fixed points describing the ordinary, special,
and extraordinary transitions are identified and shown to be located at a
nontrivial value if . The surface
critical exponents of the ordinary transition are determined to second order in
. Extrapolations of these expansions yield values of these
exponents for in good agreement with recent Monte Carlo results for the
case of a uniaxial () Lifshitz point. The scaling dimension of the surface
energy density is shown to be given exactly by , where
is the anisotropy exponent.Comment: revtex4, 31 pages with eps-files for figures, uses texdraw to
generate some graphs; to appear in PRB; v2: some references and additional
remarks added, labeling in figure 1 and some typos correcte
On some Features of the Grain and Subgrain Size in a Cu-Cr-Zr Alloy After ECAP Processing and Aging
A Cu-1Cr-0.1Zr alloy has been subjected to ECAP processing via route Bc and aging at 250-800°C. Electron BackScatter diffraction (EBSD), Transmission Electron Microscopy (TEM) and X-Ray Diffraction Line Profile Analysis (XRDLPA) techniques have been used to unveil some peculiarities of the grain and subgrain structure with a special emphasis on the comparison of the grain size estimated by the three techniques. For the alloy ECAP processed and aged up to 16 passes, the grain size (from EBSD, 0.2 < d < 5 μm), subgrain size (from TEM, d ~ 0.75 μm) and “apparent” average crystallite size (from XRDLPA, d < 0.25 μm) are manifestly different. The results were compared to the published data and analyzed based on the fundamental aspects of these techniques
Can dissonance engineering improve risk analysis of human–machine systems?
The paper discusses dissonance engineering and its application to risk analysis of human–machine systems. Dissonance engineering relates to sciences and technologies relevant to dissonances, defined as conflicts between knowledge. The richness of the concept of dissonance is illustrated by a taxonomy that covers a variety of cognitive and organisational dissonances based on different conflict modes and baselines of their analysis. Knowledge control is discussed and related to strategies for accepting or rejecting dissonances. This acceptability process can be justified by a risk analysis of dissonances which takes into account their positive and negative impacts and several assessment criteria. A risk analysis method is presented and discussed along with practical examples of application. The paper then provides key points to motivate the development of risk analysis methods dedicated to dissonances in order to identify the balance between the positive and negative impacts and to improve the design and use of future human–machine system by reinforcing knowledge
Bulk and Boundary Critical Behavior at Lifshitz Points
Lifshitz points are multicritical points at which a disordered phase, a
homogeneous ordered phase, and a modulated ordered phase meet. Their bulk
universality classes are described by natural generalizations of the standard
model. Analyzing these models systematically via modern
field-theoretic renormalization group methods has been a long-standing
challenge ever since their introduction in the middle of the 1970s. We survey
the recent progress made in this direction, discussing results obtained via
dimensionality expansions, how they compare with Monte Carlo results, and open
problems. These advances opened the way towards systematic studies of boundary
critical behavior at -axial Lifshitz points. The possible boundary critical
behavior depends on whether the surface plane is perpendicular to one of the
modulation axes or parallel to all of them. We show that the semi-infinite
field theories representing the corresponding surface universality classes in
these two cases of perpendicular and parallel surface orientation differ
crucially in their Hamiltonian's boundary terms and the implied boundary
conditions, and explain recent results along with our current understanding of
this matter.Comment: Invited contribution to STATPHYS 22, to be published in the
Proceedings of the 22nd International Conference on Statistical Physics
(STATPHYS 22) of the International Union of Pure and Applied Physics (IUPAP),
4--9 July 2004, Bangalore, Indi
A transmission spectrum of the sub-Earth planet L98-59~b in 1.1-1.7 m
With the increasing number of planets discovered by TESS, the atmospheric
characterization of small exoplanets is accelerating. L98-59 is a M-dwarf
hosting a multi-planet system, and so far, four small planets have been
confirmed. The innermost planet b is smaller and lighter
than Earth, and should thus have a predominantly rocky composition. The Hubble
Space Telescope observed five primary transits of L98-59b in m,
and here we report the data analysis and the resulting transmission spectrum of
the planet. We measure the transit depths for each of the five transits and, by
combination, we obtain a transmission spectrum with an overall precision of
ppm in for each of the 18 spectrophotometric channels. With this level
of precision, the transmission spectrum does not show significant modulation,
and is thus consistent with a planet without any atmosphere or a planet having
an atmosphere and high-altitude clouds or haze. The scenarios involving an
aerosol-free, H-dominated atmosphere with HO or CH are inconsistent
with the data. The transmission spectrum also disfavors, but does not rules
out, an HO-dominated atmosphere without clouds. A spectral retrieval
process suggests that an H-dominated atmosphere with HCN and clouds or haze
may be the preferred solution, but this indication is non-conclusive. Future
James Webb Space Telescope observations may find out the nature of the planet
among the remaining viable scenarios.Comment: 17 pages, 5 figures, 7 tables, accepted for publication in A
- …