6,210 research outputs found
How to avoid potential pitfalls in recurrence plot based data analysis
Recurrence plots and recurrence quantification analysis have become popular
in the last two decades. Recurrence based methods have on the one hand a deep
foundation in the theory of dynamical systems and are on the other hand
powerful tools for the investigation of a variety of problems. The increasing
interest encompasses the growing risk of misuse and uncritical application of
these methods. Therefore, we point out potential problems and pitfalls related
to different aspects of the application of recurrence plots and recurrence
quantification analysis
Chiral projected entangled-pair state with topological order
We show that projected entangled-pair states (PEPS) can describe chiral
topologically ordered phases. For that, we construct a simple PEPS for spin-1/2
particles in a two-dimensional lattice. We reveal a symmetry in the local
projector of the PEPS that gives rise to the global topological character. We
also extract characteristic quantities of the edge conformal field theory using
the bulk-boundary correspondence.Comment: 11 pages, 7 figure
Constructing Improved Overlap Fermions in QCD
We describe an explicit construction of approximate Ginsparg-Wilson fermions
for QCD. We use ingredients of perfect action origin, and further elements. The
spectrum of the lattice Dirac operator reveals the quality of the
approximation. We focus on beta =6 for optimisation. Such fermions are intended
to be inserted into the overlap formula. Hence we also test the speed of
convergence under polynomial evaluation of the overlap formula.Comment: 5 pages, poster presented at Lattice 2000 (Improvement and
Renormalisation
Analysis of Sting Balance Calibration Data Using Optimized Regression Models
Calibration data of a wind tunnel sting balance was processed using a search algorithm that identifies an optimized regression model for the data analysis. The selected sting balance had two moment gages that were mounted forward and aft of the balance moment center. The difference and the sum of the two gage outputs were fitted in the least squares sense using the normal force and the pitching moment at the balance moment center as independent variables. The regression model search algorithm predicted that the difference of the gage outputs should be modeled using the intercept and the normal force. The sum of the two gage outputs, on the other hand, should be modeled using the intercept, the pitching moment, and the square of the pitching moment. Equations of the deflection of a cantilever beam are used to show that the search algorithm s two recommended math models can also be obtained after performing a rigorous theoretical analysis of the deflection of the sting balance under load. The analysis of the sting balance calibration data set is a rare example of a situation when regression models of balance calibration data can directly be derived from first principles of physics and engineering. In addition, it is interesting to see that the search algorithm recommended the same regression models for the data analysis using only a set of statistical quality metrics
National Time Accounting: The Currency of Life
This monograph proposes a new approach for measuring features of societyâs subjective well-being, based on time allocation and affective experience. We call this approach National Time Accounting (NTA). National Time Accounting is a set of methods for measuring, comparing and analyzing how people spend and experience their time -- across countries, over historical time, or between groups of people within a country at a given time. The approach is based on evaluated time use, or the flow of emotional experience during daily activities. After reviewing evidence on the validity of subjective well-being measures, we present and evaluate diary-based survey techniques designed to measure individualsâ emotional experiences and time use. We illustrate NTA with: (1) a new cross-sectional survey on time use and emotional experience for a representative sample of 4,000 Americans; (2) historical data on the amount of time devoted to various activities in the United States since 1965; and (3) a comparison of time use and wellbeing in the United States and France. In our applications, we focus mainly on the Uindex, a measure of the percentage of time that people spend in an unpleasant state, defined as an instance in which the most intense emotion is a negative one. The U-index helps to overcome some of the limitations of interpersonal comparisons of subjective well-being. National Time Accounting strikes us as a fertile area for future research because of advances in subjective measurement and because time use data are now regularly collected in many countries.
Water vapor diffusion in Mars subsurface environments
The diffusion coefficient of water vapor in unconsolidated porous media is measured
for various soil simulants at Mars-like pressures and subzero temperatures.
An experimental chamber which simultaneously reproduces a low-pressure,
low-temperature, and low-humidity environment is used to monitor water flux from an ice
source through a porous diffusion barrier. Experiments are performed on four types of
simulants: 40â70 ”m glass beads, sintered glass filter disks, 1â3 ”m dust (both loose and
packed), and JSC Marsâ1. A theoretical framework is presented that applies to
environments that are not necessarily isothermal or isobaric. For most of our samples, we
find diffusion coefficients in the range of 2.8 to 5.4 cm^2 s^-1 at 600 Pascal and 260 K. This
range becomes 1.9â4.7 cm^2 s^-1 when extrapolated to a Mars-like temperature of 200 K.
Our preferred value for JSC Marsâ1 at 600 Pa and 200 K is 3.7 ± 0.5 cm^2 s^-1. The
tortuosities of the glass beads is about 1.8. Packed dust displays a lower mean diffusion
coefficient of 0.38 ± 0.26 cm^2 s^-1, which can be attributed to transition to the Knudsen
regime where molecular collisions with the pore walls dominate. Values for the diffusion
coefficient and the variation of the diffusion coefficient with pressure are well matched by
existing models. The survival of shallow subsurface ice on Mars and the providence of
diffusion barriers are considered in light of these measurements
The Metallicity of the Intracluster Medium Over Cosmic Time: Further Evidence for Early Enrichment
We use Chandra X-ray data to measure the metallicity of the intracluster
medium (ICM) in 245 massive galaxy clusters selected from X-ray and
Sunyaev-Zel'dovich (SZ) effect surveys, spanning redshifts .
Metallicities were measured in three different radial ranges, spanning cluster
cores through their outskirts. We explore trends in these measurements as a
function of cluster redshift, temperature, and surface brightness "peakiness"
(a proxy for gas cooling efficiency in cluster centers). The data at large
radii (0.5--1 ) are consistent with a constant metallicity, while at
intermediate radii (0.1-0.5 ) we see a late-time increase in
enrichment, consistent with the expected production and mixing of metals in
cluster cores. In cluster centers, there are strong trends of metallicity with
temperature and peakiness, reflecting enhanced metal production in the
lowest-entropy gas. Within the cool-core/sharply peaked cluster population,
there is a large intrinsic scatter in central metallicity and no overall
evolution, indicating significant astrophysical variations in the efficiency of
enrichment. The central metallicity in clusters with flat surface brightness
profiles is lower, with a smaller intrinsic scatter, but increases towards
lower redshifts. Our results are consistent with other recent measurements of
ICM metallicity as a function of redshift. They reinforce the picture implied
by observations of uniform metal distributions in the outskirts of nearby
clusters, in which most of the enrichment of the ICM takes place before cluster
formation, with significant later enrichment taking place only in cluster
centers, as the stellar populations of the central galaxies evolve.Comment: 13 pages. Accepted version, to appear in MNRA
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