6,488 research outputs found
Spinwave damping in the two-dimensional ferromagnetic XY model
The effect of damping of spinwaves in a two-dimensional classical
ferromagnetic XY model is considered. The damping rate is
calculated using the leading diagrams due to the quartic-order deviations from
the harmonic spin Hamiltonian. The resulting four-dimensional integrals are
evaluated by extending the techniques developed by Gilat and others for
spectral density types of integrals. is included into the memory
function formalism due to Reiter and Solander, and Menezes, to determine the
dynamic structure function . For the infinite sized system, the
memory function approach is found to give non-divergent spinwave peaks, and a
smooth nonzero background intensity (``plateau'' or distributed intensity) for
the whole range of frequencies below the spinwave peak. The background
amplitude relative to the spinwave peak rises with temperature, and eventually
becomes higher than the spinwave peak, where it appears as a central peak. For
finite-sized systems, there are multiple sequences of weak peaks on both sides
of the spinwave peaks whose number and positions depend on the system size and
wavevector in integer units of . These dynamical finite size effects
are explained in the memory function analysis as due to either spinwave
difference processes below the spinwave peak or sum processes above the
spinwave peak. These features are also found in classical Monte Carlo --
Spin-Dynamics simulations.Comment: 20 two-column page
NNLO predictions for Z-boson pair production at the LHC
We present a calculation of the NNLO QCD corrections to Z-boson pair
production at hadron colliders, based on the N-jettiness method for the real
radiation parts. We discuss the size and shape of the perturbative corrections
along with their associated scale uncertainties and compare our results to
recent LHC data at TeV.Comment: 19 pages, 2 Tables, 4 figures. Version to appear in JHE
HRM practices and organizations' internal context role in performance
Purpose - The main purpose of the present study is to test the association between Human Resource Management practices (HRMP) perceptions, internal context, and organizational performance. Design/methodology/approach - The data was collected based on a sample of 525 individuals from 22 stores, with performance indicators collected at the store level. Findings - The results showed (a) a positive relationship between perceived organizational integrity and organizational performance, as well as a negative relationship with staff turnover; (b) and a negative relationship between employment conditions and staff turnover. Research limitations/implications - The small sample size and the fact that the study was conducted in stores of the same organization doesn’t allow generalization of findings; results are based on data from cross-sectional design, longitudinal data would be needed to infer causal relationships. Practical implications - Managers should take in consideration that organizational integrity, as perceived by employees, can enhance organizational performance and reduce turnover, better employment conditions will also have this effect in turnover. Originality/value - These findings allow us to discuss the role of HRMP and of organizations internal context and characteristics on performance.info:eu-repo/semantics/publishedVersio
Diagnostics and control of wavenumber stability and purity of tunable diode lasers relevant to their use as local oscillators in heterodyne systems
Initial operation of the tunable diode lasers (TDL) showed that it was not possible to adjust the wavenumber to one selected a priori in the TDL tuning range. During operation, the operating point would change by 0.1/cm over the longer term with even larger changes occurring during some thermal cycles. Most changes during thermal cycling required using lower temperatures and higher currents to reach the former wavenumber (when it could be reached). In many cases, an operating point could be selected by changing TDL current and temperature to give both the desired wavenumber and most of the power in a single mode. The selection procedure had to be used after each thermal cycling. Wavenumber nonlinearities of about 10% over a 0.5 cm tuning range were observed. Diagnostics of the single mode selected by a grating monochromator showed wavenumber fine structure under certain operating conditions. The characteristics due to the TDL environment included short term wavenumber stability, the instrument lineshape function, and intermediate term wavenumber stability
Asymptotic behavior of mean fixation times in the Moran process with frequency-independent fitnesses
We derive asymptotic formulae in the limit when population size N tends to
infinity for mean fixation times (conditional and unconditional) in a
population with two types of individuals, A and B, governed by the Moran
process. We consider only the case in which the fitness of the two types do not
depend on the population frequencies. Our results start with the important
cases in which the initial condition is a single individual of any type, but we
also consider the initial condition of a fraction x, 0<x<1, of A individuals,
where x is kept fixed and the total population size tends to infinity. In the
cases covered by Antal and Scheuring (Bull Math Biol 68(8):1923-1944, 2006),
i.e. conditional fixation times for a single individual of any type, it will
turn out that our formulae are much more accurate than the ones they found. As
quoted, our results include other situations not treated by them.Comment: 29 pages, 6 figure
Image Processing based Classifier for Detection and Diagnosis of Induction Motor Stator Fault
Organic acids and biosolid trace elements phytoavailability.
Trace metals phytoavailability is a major concern related to land application of biosolids. Formation of soluble complexes between metals and organic acids exudates in the rhizosphere b plants or produced by microbial activity seems to play an important role on trace metals phytoavailability (Mench & Martin, 1991; Marschner, 1995). The present study was carried out; i)to determine organic acids present at the rhizosphere of different plant species cultivated in the presence or absence of biosolids; and ii) to assess the correlation between production of organic acids and the shoot content of trace elements
On the benefits of speech and touch interaction with communication services for mobility impaired users
Although technology for communication has evolved tremendously over the past decades, mobility impaired individuals still face many difficulties interacting with communication services, either due to HCI issues or intrinsic design problems with the services. In this paper we present the results of a usability study, conducted with a group of five mobility impaired users, comprising paraplegic and quadriplegic individuals. The study participants carried out a set of tasks with a multimodal (speech, touch, gesture, keyboard and mouse) and multiplatform (mobile, desktop) prototype, offering an integrated access to communication and entertainment services, such as email, agenda, conferencing and social media. The prototype was designed to take into account the requirements captured from these users, with the objective of evaluating if the use of multimodal interfaces for communication and social media services, could improve the interaction with such services. Our study revealed that a multimodal prototype system, offering natural interaction modalities, especially supporting speech and touch, can in fact improve access to the presented services, contributing to a better social inclusion of mobility impaired individuals.info:eu-repo/semantics/acceptedVersio
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