19,151 research outputs found
Orientational Melting in Carbon Nanotube Ropes
Using Monte Carlo simulations, we investigate the possibility of an
orientational melting transition within a "rope" of (10,10) carbon nanotubes.
When twisting nanotubes bundle up during the synthesis, orientational
dislocations or twistons arise from the competition between the anisotropic
inter-tube interactions, which tend to align neighboring tubes, and the torsion
rigidity that tends to keep individual tubes straight. We map the energetics of
a rope containing twistons onto a lattice gas model and find that the onset of
a free "diffusion" of twistons, corresponding to orientational melting, occurs
at T_OM > 160 K.Comment: 4 page LaTeX file with 3 figures (10 PostScript files
Charge and Orbital Ordering and Spin State Transition Driven by Structural Distortion in YBaCo_2O_5
We have investigated electronic structures of antiferromagnetic YBaCo_2O_5
using the local spin-density approximation (LSDA) + U method. The charge and
orbital ordered insulating ground state is correctly obtained with the strong
on-site Coulomb interaction. Co^{2+} and Co^{3+} ions are found to be in the
high spin (HS) and intermediate spin (IS) state, respectively. It is considered
that the tetragonal to orthorhombic structural transition is responsible for
the ordering phenomena and the spin states of Co ions. The large contribution
of the orbital moment to the total magnetic moment indicates that the
spin-orbit coupling is also important in YBaCo_2O_5.Comment: 4 pages including 4 figures, Submitted to Phys. Rev. Let
A Flattened Protostellar Envelope in Absorption around L1157
Deep Spitzer IRAC images of L1157 reveal many of the details of the outflow
and the circumstellar environment of this Class 0 protostar. In IRAC band 4, 8
microns, there is a flattened structure seen in absorption against the
background emission. The structure is perpendicular to the outflow and is
extended to a diameter of 2 arcminutes. This structure is the first clear
detection of a flattened circumstellar envelope or pseudo-disk around a Class 0
protostar. Such a flattened morphology is an expected outcome for many collapse
theories that include magnetic fields or rotation. We construct an extinction
model for a power-law density profile, but we do not constrain the density
power-law index.Comment: ApJL accepte
Event-triggered proportional-derivative control for nonlinear network systems with a novel event-triggering scheme: Differential of triggered state consideration
This article proposes event-triggered proportional-derivative control for a class of nonlinear network control systems. For derivative action of the proposed proportional-derivative control, a novel event-triggering scheme is devised together with the control that considers a differential of a triggered state. The class of the nonlinear network systems is represented as a Lur'e system to consider various nonlinear cases. Time varying transmission delay is considered which can be defined by lower and upper delay bounds. The proposed proportional-derivative control is designed by Lyapunov-Krasovskii stability analysis, and the design condition is presented by linear matrix inequalities. The proposed event-triggered proportional-derivative control and event-triggering condition are verified with numerical simulation. ? 2017 The Author(s).111Ysciescopu
Emergence of skew distributions in controlled growth processes
Starting from a master equation, we derive the evolution equation for the
size distribution of elements in an evolving system, where each element can
grow, divide into two, and produce new elements. We then probe general
solutions of the evolution quation, to obtain such skew distributions as
power-law, log-normal, and Weibull distributions, depending on the growth or
division and production. Specifically, repeated production of elements of
uniform size leads to power-law distributions, whereas production of elements
with the size distributed according to the current distribution as well as no
production of new elements results in log-normal distributions. Finally,
division into two, or binary fission, bears Weibull distributions. Numerical
simulations are also carried out, confirming the validity of the obtained
solutions.Comment: 9 pages, 3 figure
Back-Translation Practices in Organizational Research: Avoiding Loss in Translation
As organizational research continues to globalize, scholars increasingly must translate established scales into languages other than those in which the scales were originally developed. In organizational psychology research, back-translation is the dominant procedure for translating scales. Back-translation has notable strengths in maintaining the psychometric properties of an established scale in a translated version. However, cross-cultural methodologists have argued that in its most basic form, back-translation often does not result in translations with acceptable levels of equivalence between original and translated research materials. Fortunately, there are complementary procedures to back-translation that can evaluate and strengthen the extent to which scale translations have achieved equivalence between original and translated versions of scales. But how often organizational researchers use and report these procedures in tandem with back-translation is unclear. This article aims to address this lack of clarity by evaluating the state of the use of back-translation in organizational psychology research by reviewing every study in Journal of Applied Psychology that has employed translation over the past nearly 25 years (k = 333). Our findings suggest that the majority of the time that researchers engage in translation procedures, they report having done so. At the same time, the details of these procedures are commonly underreported, making it unclear whether additional techniques beyond back-translation have been used to examine and demonstrate equivalence between original and translated versions of scales. Based on the results of our review, we develop a set of recommendations for conducting and reporting scale translations in organizational research
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