3,338 research outputs found
Optimal sampling strategies for multiscale stochastic processes
In this paper, we determine which non-random sampling of fixed size gives the
best linear predictor of the sum of a finite spatial population. We employ
different multiscale superpopulation models and use the minimum mean-squared
error as our optimality criterion. In multiscale superpopulation tree models,
the leaves represent the units of the population, interior nodes represent
partial sums of the population, and the root node represents the total sum of
the population. We prove that the optimal sampling pattern varies dramatically
with the correlation structure of the tree nodes. While uniform sampling is
optimal for trees with ``positive correlation progression'', it provides the
worst possible sampling with ``negative correlation progression.'' As an
analysis tool, we introduce and study a class of independent innovations trees
that are of interest in their own right. We derive a fast water-filling
algorithm to determine the optimal sampling of the leaves to estimate the root
of an independent innovations tree.Comment: Published at http://dx.doi.org/10.1214/074921706000000509 in the IMS
Lecture Notes--Monograph Series
(http://www.imstat.org/publications/lecnotes.htm) by the Institute of
Mathematical Statistics (http://www.imstat.org
The Relative Power of Employment-to-Employment Reallocation and Unemployment Exits in Predicting Wage Growth
We study the cyclical comovement nominal wage growth (either monthly earnings or hourly wage rate) and labor market flows. We use microdata from the Survey of Income and Program Participation over 1996-2013 to purge composition effects in worker and job characteristics and to isolate the reallocative effect of Employer-to-Employer (EE) transitions. We find an "EE wage Phillips curve": wage inflation comoves positively with EE as strongly as with the employment rate. This correlation holds for job stayers; we interpret the EE rate as a measure of labor demand. We find no analogous evidence for the job-finding rate from unemployment
Wage Posting and Business Cycles
The canonical framework of Burdett and Mortensen (1998) derives wage dispersion as the unique equilibrium outcome in a stationary environment with meeting frictions and random search. Firms derive monopsony power from search frictions and commit to wage offers. Workers earn rents: wages are not compressed to the opportunity cost of work, owing to the ability of employed workers to receive additional offers and quit directly from one job into another, without experiencing unemployment. In previous work (Moscarini and Postel-Vinay 2016), we explored the implications of this job ladder for the aggregate dynamics of unemployment, wages, and the firm size distribution at business cycle frequencies. The model establishes a natural connection between the average wage growth in the economy and the pace of
Employer-to-Employer (EE) transitions, through
two channels. First, a composition effect: workers
typically quit a job when they receive a better
offer, hence the faster these transitions the higher
the pace of reallocation toward high wages, and the higher average wage growth. Second, a strategic effect: the more opportunities workers have to quit, the more aggressive are their employers with their wage responses, to try and retain them. The first effect benefits only job movers, the second both movers and stayers. Therefore, we expect wage growth to be positively related
to the pace of EE reallocation for all workers, but especially for movers. We verify this empirically with longitudinal micro data from the Survey of Income and Program Participation (SIPP)
Decoherence without dissipation?
In a recent article, Ford, Lewis and O'Connell (PRA 64, 032101 (2001))
discuss a thought experiment in which a Brownian particle is subjected to a
double-slit measurement. Analyzing the decay of the emerging interference
pattern, they derive a decoherence rate that is much faster than previous
results and even persists in the limit of vanishing dissipation. This result is
based on the definition of a certain attenuation factor, which they analyze for
short times. In this note, we point out that this attenuation factor captures
the physics of decoherence only for times larger than a certain time t_mix,
which is the time it takes until the two emerging wave packets begin to
overlap. Therefore, the strategy of Ford et al of extracting the decoherence
time from the regime t < t_mix is in our opinion not meaningful. If one
analyzes the attenuation factor for t > t_mix, one recovers familiar behaviour
for the decoherence time; in particular, no decoherence is seen in the absence
of dissipation. The latter conclusion is confirmed with a simple calculation of
the off-diagonal elements of the reduced density matrix.Comment: 8 pages, 4 figure
Induction of Off-Season Flowering in Custard Apple (Annona squamosa L.) Cv. Balanagar
Pruning and defoliation are essential operations for inducing off-season flowering and fruiting to yield better quality and quantity of fruits in custard apple. Trees were subjected to two levels of pruning (25% and 50%) combined with use of chemical defoliants (urea 5%, Ethrel 2000ppm, potassium iodide 1%, or ortho-phosphoric acid 1%) besides the Control, with each treatment replicated thrice. Early initiation of flowering and better vegetative growth was seen in pruned (25%) and defoliated trees than in the Control or other treatments. Maximum off-season yield (10.33kg/ plant) was obtained in T4 (25% pruning, combined with 5% urea spray as defoliant) and T6 (25% pruning, combined with 1% potassium iodide-spray as defoliant). Findings of this investigation helped standardize pruning and defoliation practices on a scientific basis for off-season production of custard apple fruits
Viscoelastic Properties of Dynamically Asymmetric Binary Fluids Under Shear Flow
We study theoretically the viscoelastic properties of sheared binary fluids
that have strong dynamical asymmetry between the two components. The dynamical
asymmetry arises due to asymmetry between the viscoelastic stresses,
particularly the bulk stress. Our calculations are based on the two-fluid model
that incorporates the asymmetric stress distribution. We simulate the phase
separation process under an externally imposed shear and compare the asymmetric
case with the usual phase separation under a shear flow without viscoelastic
effects. We also simulate the behavior of phase separated stable morphologies
under applied shear and compute the stress relaxation.Comment: 10 pages text, 9 figure
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