1,318 research outputs found
RF and IF mixer optimum matching impedances extracted by large-signal vectorial measurements
This paper introduces a new technique that allows us to measure the admittance conversion matrix of a two-port device,using a Nonlinear Vector Network Analyzer.This method is applied to extract the conversion matrix of a 0.2 µµµµm pHEMT,driven by a 4.8 GHz pump signal,at different power levels,using an intermediate frequency of 600 MHz.The issue on data inconsistency due to phase randomization among different measurements is discussed and a proper pre- processing algorithm is proposed to fix the problem. The output of this work consists of a comprehensive experimental evaluation of up-and down-conversion maximum gain,stability,and optimal RF and IF impedances
CUBIC SPLINES FOR ESTIMATING LACTATION CURVES AND GENETIC PARAMETERS OF FIRST LACTATION HOLSTEIN COWS TREATED WITH BOVINE SOMATOTROPIN
The objective was to estimate genetic parameters and fit lactation curves for cows treated or not treated with bovine somatotropin (bST) and fit specific lactation curves for each animal for both random genetic and permanent environmental components from individual test-day milk, fat, and protein yields with a cubic spline model. A total of 70,752 test-day observations for first lactation Holstein cows recorded as treated bST and 73,387 test-day observations for untreated cows that calved between 1994 and early 1999 were obtained from Dairy Records Management Systems in Raleigh, North Carolina. The model included herd test-day, age at first calving, bST treatment, and days in lactation when test-day yield was recorded as fixed effects. Cubic splines were fitted for the overall lactation curve, additive genetic effects, and permanent environmental effects. The cubic splines used five predetermined intervals between days 0, 50, 135,220, and 305. Estimates of the (co)variances for the random components of cubic spline model with five knots were obtained with REML. Estimates of genetic parameters were calculated for the average test day model within each of the ten 30-d test day intervals. The estimates of heritability for milk, fat, and protein yields ranged from 0.09 to 0.15, 0.06 to 0.10, and 0.08 to 0.15 for test-day one to test-day ten. Estimates of genetic correlations between testdays ranged from 0.99 to 0.34 for milk yield, 0.99 to 0.49 for fat yield, and 0.99 to 0.36 for protein yield. Estimates of phenotypic correlations between test-days ranged from 0.67 to 0.27 for milk yield, 0.52 to 0.16 for fat yield, and 0.60 to 0.19 for protein yield. Differences between bST treated and untreated cows of 2 to 4 kg and 0.10 to 0.16 kg for milk and fat yields (smaller for protein yield) at day 90 were maintained until about day 305 of lactation
Kepler Presearch Data Conditioning I - Architecture and Algorithms for Error Correction in Kepler Light Curves
Kepler provides light curves of 156,000 stars with unprecedented precision.
However, the raw data as they come from the spacecraft contain significant
systematic and stochastic errors. These errors, which include discontinuities,
systematic trends, and outliers, obscure the astrophysical signals in the light
curves. To correct these errors is the task of the Presearch Data Conditioning
(PDC) module of the Kepler data analysis pipeline. The original version of PDC
in Kepler did not meet the extremely high performance requirements for the
detection of miniscule planet transits or highly accurate analysis of stellar
activity and rotation. One particular deficiency was that astrophysical
features were often removed as a side-effect to removal of errors. In this
paper we introduce the completely new and significantly improved version of PDC
which was implemented in Kepler SOC 8.0. This new PDC version, which utilizes a
Bayesian approach for removal of systematics, reliably corrects errors in the
light curves while at the same time preserving planet transits and other
astrophysically interesting signals. We describe the architecture and the
algorithms of this new PDC module, show typical errors encountered in Kepler
data, and illustrate the corrections using real light curve examples.Comment: Submitted to PASP. Also see companion paper "Kepler Presearch Data
Conditioning II - A Bayesian Approach to Systematic Error Correction" by Jeff
C. Smith et a
Minimum Decision Cost for Quantum Ensembles
For a given ensemble of independent and identically prepared particles,
we calculate the binary decision costs of different strategies for measurement
of polarised spin 1/2 particles. The result proves that, for any given values
of the prior probabilities and any number of constituent particles, the cost
for a combined measurement is always less than or equal to that for any
combination of separate measurements upon sub-ensembles. The Bayes cost, which
is that associated with the optimal strategy (i.e., a combined measurement) is
obtained in a simple closed form.Comment: 11 pages, uses RevTe
Drag in paired electron-hole layers
We investigate transresistance effects in electron-hole double layer systems
with an excitonic condensate. Our theory is based on the use of a minimum
dissipation premise to fix the current carried by the condensate. We find that
the drag resistance jumps discontinuously at the condensation temperature and
diverges as the temperature approaches zero.Comment: 12 pages, 1 Figure, .eps file attache
The cytoplasm of living cells: A functional mixture of thousands of components
Inside every living cell is the cytoplasm: a fluid mixture of thousands of
different macromolecules, predominantly proteins. This mixture is where most of
the biochemistry occurs that enables living cells to function, and it is
perhaps the most complex liquid on earth. Here we take an inventory of what is
actually in this mixture. Recent genome-sequencing work has given us for the
first time at least some information on all of these thousands of components.
Having done so we consider two physical phenomena in the cytoplasm: diffusion
and possible phase separation. Diffusion is slower in the highly crowded
cytoplasm than in dilute solution. Reasonable estimates of this slowdown can be
obtained and their consequences explored, for example, monomer-dimer equilibria
are established approximately twenty times slower than in a dilute solution.
Phase separation in all except exceptional cells appears not to be a problem,
despite the high density and so strong protein-protein interactions present. We
suggest that this may be partially a byproduct of the evolution of other
properties, and partially a result of the huge number of components present.Comment: 11 pages, 1 figure, 1 tabl
Independence in CLP Languages
Studying independence of goals has proven very useful in the context of logic programming. In particular, it has provided a formal basis for powerful automatic parallelization tools, since independence ensures that two goals may be evaluated in parallel while preserving correctness and eciency. We extend the concept of independence to constraint logic programs (CLP) and
prove that it also ensures the correctness and eciency of the parallel evaluation of independent goals. Independence for CLP languages is more complex than for logic programming as search space preservation is necessary but no longer sucient for ensuring correctness and eciency. Two
additional issues arise. The rst is that the cost of constraint solving may depend upon the order constraints are encountered. The second is the need to handle dynamic scheduling. We clarify these issues by proposing various types of search independence and constraint solver independence, and show how they can be combined to allow dierent optimizations, from parallelism to intelligent
backtracking. Sucient conditions for independence which can be evaluated \a priori" at run-time are also proposed. Our study also yields new insights into independence in logic programming languages. In particular, we show that search space preservation is not only a sucient but also a necessary condition for ensuring correctness and eciency of parallel execution
Bose-Einstein Condensation in a Harmonic Potential
We examine several features of Bose-Einstein condensation (BEC) in an
external harmonic potential well. In the thermodynamic limit, there is a phase
transition to a spatial Bose-Einstein condensed state for dimension D greater
than or equal to 2. The thermodynamic limit requires maintaining constant
average density by weakening the potential while increasing the particle number
N to infinity, while of course in real experiments the potential is fixed and N
stays finite. For such finite ideal harmonic systems we show that a BEC still
occurs, although without a true phase transition, below a certain
``pseudo-critical'' temperature, even for D=1. We study the momentum-space
condensate fraction and find that it vanishes as 1/N^(1/2) in any number of
dimensions in the thermodynamic limit. In D less than or equal to 2 the lack of
a momentum condensation is in accord with the Hohenberg theorem, but must be
reconciled with the existence of a spatial BEC in D=2. For finite systems we
derive the N-dependence of the spatial and momentum condensate fractions and
the transition temperatures, features that may be experimentally testable. We
show that the N-dependence of the 2D ideal-gas transition temperature for a
finite system cannot persist in the interacting case because it violates a
theorem due to Chester, Penrose, and Onsager.Comment: 34 pages, LaTeX, 6 Postscript figures, Submitted to Jour. Low Temp.
Phy
Saturation front evolution for liquid infiltration into a gas filled porous medium with counter-current flow
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