269,738 research outputs found
Universality of Long-Range Correlations in Expansion-Randomization Systems
We study the stochastic dynamics of sequences evolving by single site
mutations, segmental duplications, deletions, and random insertions. These
processes are relevant for the evolution of genomic DNA. They define a
universality class of non-equilibrium 1D expansion-randomization systems with
generic stationary long-range correlations in a regime of growing sequence
length. We obtain explicitly the two-point correlation function of the sequence
composition and the distribution function of the composition bias in sequences
of finite length. The characteristic exponent of these quantities is
determined by the ratio of two effective rates, which are explicitly calculated
for several specific sequence evolution dynamics of the universality class.
Depending on the value of , we find two different scaling regimes, which
are distinguished by the detectability of the initial composition bias. All
analytic results are accurately verified by numerical simulations. We also
discuss the non-stationary build-up and decay of correlations, as well as more
complex evolutionary scenarios, where the rates of the processes vary in time.
Our findings provide a possible example for the emergence of universality in
molecular biology.Comment: 23 pages, 15 figure
An Improved Differential Evolution Algorithm for Maritime Collision Avoidance Route Planning
High accuracy navigation and surveillance systems are pivotal to ensure efficient ship route planning and marine safety. Based on existing ship navigation and maritime collision prevention rules, an improved approach for collision avoidance route planning using a differential evolution algorithm was developed. Simulation results show that the algorithm is capable of significantly enhancing the optimized route over current methods. It has the potential to be used as a tool to generate optimal vessel routing in the presence of conflicts
Grown-in defects and defects produced by 1-Me electron irradiated in Al0.3Ga0.7As P-N junction solar cells
Studies of grown-in defects and defects produced by the one-MeV electron irradiation in Al sub 0.3 Ga sub 0.7As p-n junction solar cells fabricated by liquid phase epitaxial (LPE) technique were made for the unirradiated and one-MeV electron irradiated samples, using DLTS and C-V methods. Defect and recombination parameters such as energy level, defect density, carrier capture cross sections and lifetimes were determined for various growth, annealing, and irradiation conditions
Simplifying the mosaic description of DNA sequences
By using the Jensen-Shannon divergence, genomic DNA can be divided into
compositionally distinct domains through a standard recursive segmentation
procedure. Each domain, while significantly different from its neighbours, may
however share compositional similarity with one or more distant
(non--neighbouring) domains. We thus obtain a coarse--grained description of
the given DNA string in terms of a smaller set of distinct domain labels. This
yields a minimal domain description of a given DNA sequence, significantly
reducing its organizational complexity. This procedure gives a new means of
evaluating genomic complexity as one examines organisms ranging from bacteria
to human. The mosaic organization of DNA sequences could have originated from
the insertion of fragments of one genome (the parasite) inside another (the
host), and we present numerical experiments that are suggestive of this
scenario.Comment: 16 pages, 1 figure, Accepted for publication in Phys. Rev.
Amplifying single impurities immersed in a gas of ultra cold atoms
We present a method for amplifying a single or scattered impurities immersed
in a background gas of ultra cold atoms so that they can be optically imaged
and spatially resolved. Our approach relies on a Raman transfer between two
stable atomic hyperfine states that is conditioned on the presence of an
impurity atom. The amplification is based on the strong interaction among atoms
excited to Rydberg states. We perform a detailed analytical study of the
performance of the proposed scheme with particular emphasis on the influence of
many-body effects.Comment: 5 pages, 4 figure
Characterizing Ranked Chinese Syllable-to-Character Mapping Spectrum: A Bridge Between the Spoken and Written Chinese Language
One important aspect of the relationship between spoken and written Chinese
is the ranked syllable-to-character mapping spectrum, which is the ranked list
of syllables by the number of characters that map to the syllable. Previously,
this spectrum is analyzed for more than 400 syllables without distinguishing
the four intonations. In the current study, the spectrum with 1280 toned
syllables is analyzed by logarithmic function, Beta rank function, and
piecewise logarithmic function. Out of the three fitting functions, the
two-piece logarithmic function fits the data the best, both by the smallest sum
of squared errors (SSE) and by the lowest Akaike information criterion (AIC)
value. The Beta rank function is the close second. By sampling from a Poisson
distribution whose parameter value is chosen from the observed data, we
empirically estimate the -value for testing the
two-piece-logarithmic-function being better than the Beta rank function
hypothesis, to be 0.16. For practical purposes, the piecewise logarithmic
function and the Beta rank function can be considered a tie.Comment: 15 pages, 4 figure
Integration of an Active Filter and a Single-Phase AC/DC Converter with Reduced Capacitance Requirement and Component Count
Existing methods of incorporating an active filter into an AC/DC converter for eliminating electrolytic capacitors usually require extra power switches. This inevitably leads to an increased system cost and degraded energy efficiency. In this paper, a concept of active-filter integration for single-phase AC/DC converters is reported. The resultant converters can provide simultaneous functions of power factor correction, DC voltage regulation, and active power decoupling for mitigating the low-frequency DC voltage ripple, without an electrolytic capacitor and extra power switch. To complement the operation, two closed-loop voltage-ripple-based reference generation methods are developed for controlling the energy storage components to achieve active power decoupling. Both simulation and experiment have confirmed the eligibility of the proposed concept and control methods in a 210-W rectification system comprising an H-bridge converter with a half-bridge active filter. Interestingly, the end converters (Type I and Type II) can be readily available using a conventional H-bridge converter with minor hardware modification. A stable DC output with merely 1.1% ripple is realized with two 50-ÎĽF film capacitors. For the same ripple performance, a 900-ÎĽF capacitor is required in conventional converters without an active filter. Moreover, it is found out that the active-filter integration concept might even improve the efficiency performance of the end converters as compared with the original AC/DC converter without integration
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