Search results for "MOMENTS"
showing 10 items of 151 documents
GW170817: Measurements of Neutron Star Radii and Equation of State
2018
On 17 August 2017, the LIGO and Virgo observatories made the first direct detection of gravitational waves from the coalescence of a neutron star binary system. The detection of this gravitational-wave signal, GW170817, offers a novel opportunity to directly probe the properties of matter at the extreme conditions found in the interior of these stars. The initial, minimal-assumption analysis of the LIGO and Virgo data placed constraints on the tidal effects of the coalescing bodies, which were then translated to constraints on neutron star radii. Here, we expand upon previous analyses by working under the hypothesis that both bodies were neutron stars that are described by the same equation…
Sparse Image Representation by Directionlets
2010
Despite the success of the standard wavelet transform (WT) in image processing in recent years, the efficiency and sparsity of its representation are limited by the spatial symmetry and separability of its basis functions built in the horizontal and vertical directions. One-dimensional discontinuities in images (edges or contours), which are important elements in visual perception, intersect too many wavelet basis functions and lead to a non-sparse representation. To capture efficiently these elongated structures characterized by geometrical regularity along different directions (not only the horizontal and vertical), a more complex multidirectional (M-DIR) and asymmetric transform is requi…
Laser-assisted nuclear decay spectroscopy of Au-176,Au-177,Au-179
2021
ispartof: PHYSICAL REVIEW C vol:104 issue:2 status: published
Complementarities in innovation strategy: do intangibles play a role in enhancing firm performance?
2017
This article assesses the role of investments in intangible capital and their potential complementarities as a way to improve firm productivity. We focus on the three intangible resources that, according to the literature, have the greatest strategic importance: research and development (R & D), advertising, and human capital. To test our hypotheses, we use a large sample of Spanish manufacturing firms and consider estimates of total factor productivity through a generalized method of moments approach. Our results show evidence of complementarities between R & D and advertising investments and between advertising and human capital. However, they are not conclusive in the case of R & D and h…
Sampling properties of the Bayesian posterior mean with an application to WALS estimation
2022
Many statistical and econometric learning methods rely on Bayesian ideas, often applied or reinterpreted in a frequentist setting. Two leading examples are shrinkage estimators and model averaging estimators, such as weighted-average least squares (WALS). In many instances, the accuracy of these learning methods in repeated samples is assessed using the variance of the posterior distribution of the parameters of interest given the data. This may be permissible when the sample size is large because, under the conditions of the Bernstein--von Mises theorem, the posterior variance agrees asymptotically with the frequentist variance. In finite samples, however, things are less clear. In this pa…
Automatic optimization of multichip RFID tags
2012
The automatic optimization is proposed of the passive RF part of RFID, with special attention to multi-chip tags, and to the novel concept of RFID grids. Performance metrics follows a recent all-comprehensive approach. The proposed approach employs a Genetic Algorithm-based optimization, and an efficient electromagnetic problem parameterization and solution strategy. Resulting structures, while non-intuitive in shape, exhibit enhanced performance.
Testing the Role of Comparative Advantage and Learning in Wage and Promotion Dynamics
2012
PurposeThe purpose of this paper is to investigate empirically whether job assignment, based on comparative advantage and learning about workers’ abilities, can explain wage and promotion dynamics within firms.Design/methodology/approachThe Gibbons and Waldman model is estimated in a generalized method of moments (GMM) framework using a unique data set on white‐collar workers in Norway, for the years 1987‐1997. The estimation is carried out on two occupational groups: technical and administrative white‐collar workers.FindingsThe placing of workers in a given position within a firm's hierarchy is based on comparative advantage. Both measurable and unmeasurable skills are important. This hold…
Production Function Estimation in Stata Using the Ackerberg–Caves–Frazer Method
2016
We present a new e-class command, acfest, that implements the method of Ackerberg, Caves, and Frazer (2015, Econometrica 83: 2411–2451) to estimate production functions. This method deals with the functional dependence problems that may arise in the methods proposed by Olley and Pakes (1996, Econometrica 64: 1263–1297) and, particularly, Levinsohn and Petrin (2003, Review of Economic Studies 70: 317–341) (implemented in Stata by Yasar, Raciborski, and Poi [2008, Stata Journal 8: 221–231] and Petrin, Poi, and Levinsohn [2004, Stata Journal 4: 113–123], respectively). In particular, the acfest command yields (nonlinear, robust) generalized method of moments estimates using a Mata function an…
A novel exact representation of stationary colored Gaussian processes (fractional differential approach)
2010
A novel representation of functions, called generalized Taylor form, is applied to the filtering of white noise processes. It is shown that every Gaussian colored noise can be expressed as the output of a set of linear fractional stochastic differential equations whose solution is a weighted sum of fractional Brownian motions. The exact form of the weighting coefficients is given and it is shown that it is related to the fractional moments of the target spectral density of the colored noise.