34 research outputs found
Origin of Excitation Energy Dependence on Valence Nucleon Numbers
It has been shown recently that a simple formula in terms of the valence
nucleon numbers and the mass number can describe the essential trends of
excitation energies of the first states in even-even nuclei. By
evaluating the first order energy shift due to the zero-range residual
interaction, we find that the factor which reflects the effective particle
number participating in the interaction from the Fermi orbit governs the main
dependence of the first excitation energy on the valence nucleon numbers.Comment: 9 pages, 5 figure
Universal Expression for the Lowest Excitation Energy of Natural Parity Even Multipole States
We present a new expression for the energy of the lowest collective states in
even-even nuclei throughout the entire periodic table. Our empirical formula is
extremely valid and holds universally for all of the natural parity even
multipole states. This formula depends only on the mass number and the valence
nucleon numbers with six parameters. These parameters are determined easily and
unambiguously from the data for each multipole state. We discuss the validity
of our empirical formula by comparing our results with those of other studies
and also by estimating the average and the dispersion of the logarithmic errors
of the calculated excitation energies with respect to the measured ones.Comment: 10 pages, 5 figure
N_pN_n dependence of empirical formula for the lowest excitation energy of the 2^+ states in even-even nuclei
We examine the effects of the additional term of the type on the recently proposed empirical formula for the lowest excitation
energy of the states in even-even nuclei. This study is motivated by the
fact that this term carries the favorable dependence of the valence nucleon
numbers dictated by the scheme. We show explicitly that there is not
any improvement in reproducing by including the extra
term. However, our study also reveals that the excitation energies
, when calculated by the term alone (with the mass number
dependent term), are quite comparable to those calculated by the original
empirical formula.Comment: 14 pages, 5 figure
Empirical formula applied to the lowest excitation energies of the natural parity odd multipole states in even-even nuclei
We applied our recently proposed empirical formula, a formula quite
successful in describing essential trends of the lowest excitation energies of
the natural parity even multipole states, to the lowest excitation energies of
the natural parity odd multipole states in even-even nuclei throughout the
entire periodic table. Even though the systematic behavior of the lowest
excitation energies of odd multipole states is quite different from those of
even multipole states, we have shown that the same empirical formula also holds
reasonably well for the odd multipole states with the exception of a few
certain instances.Comment: 23 pages, 11 figure
Traveltime and amplitude calculation using a perturbation approach
Accurate amplitudes and correct traveltimes are critical
factors that govern the quality of prestack migration
images. Because we never know the correct velocity
initially, recomputing traveltimes and amplitudes
of updated velocity models can dominate the iterative
prestack migration procedure. Most tomographic velocity
updating techniques require the calculation of the
change of traveltime due to local changes in velocity.
For such locally updated velocity models, perturbation
techniques can be a significantly more economic way of
calculating traveltimes and amplitudes than recalculating
the entire solutions from scratch.
In this paper, we implement an iterative Born perturbation
theory applied to the damped wave equation
algorithm. Our iterative Born perturbation algorithm
yields stable solutions for models having velocity contrasts
of 30% about the initial velocity estimate, which is
significantly more economic than recalculating the entire
solution.This work was financially supported by National Research
Laboratory Project of the Korea Ministry of Science and Technology,
Brain Korea 21 project of the Korea Ministry of Education,
grant No. R05-2000-00003 from the Basic Research
Program of the Korea Science&Engineering Foundation, and
grant No. PM10300 from Korea Ocean Research & Development
Institute
Traveltime and amplitude calculations using the damped wave solution
Because of its computational efficiency, prestack
Kirchhoff depth migration remains the method of choice
for all but the most complicated geological depth structures.
Further improvement in computational speed and
amplitude estimation will allow us to use such technology
more routinely and generate better images. To this end,
we developed a new, accurate, and economical algorithm
to calculate first-arrival traveltimes and amplitudes for
an arbitrarily complex earth model. Our method is based
on numerical solutions of the wave equation obtained by
using well-established finite-difference or finite-element
modeling algorithms in the Laplace domain, where a
damping term is naturally incorporated in the wave
equation. We show that solving the strongly damped
wave equation is equivalent to solving the eikonal and
transport equations simultaneously at a fixed reference
frequency, which properly accounts for caustics and
other problems encountered in ray theory. Using our algorithm,
we can easily calculate first-arrival traveltimes
for given models. We present numerical examples for
2-D acoustic models having irregular topography and
complex geological structure using a finite-element modeling
code.This work was financially supported by National Research
Laboratory Project of the Korea Ministry of Science and
Technology, Brain Korea 21 project of the Korea Ministry of Education, grant No. R05-2000-00003 from the Basic Research
Program of the Korea Science&Engineering Foundation, and
grant No. PM10300 from Korea Ocean Research & Development
Institute
Variation block-based genomics method for crop plants
BACKGROUND: In contrast with wild species, cultivated crop genomes consist of reshuffled recombination blocks, which occurred by crossing and selection processes. Accordingly, recombination block-based genomics analysis can be an effective approach for the screening of target loci for agricultural traits. RESULTS: We propose the variation block method, which is a three-step process for recombination block detection and comparison. The first step is to detect variations by comparing the short-read DNA sequences of the cultivar to the reference genome of the target crop. Next, sequence blocks with variation patterns are examined and defined. The boundaries between the variation-containing sequence blocks are regarded as recombination sites. All the assumed recombination sites in the cultivar set are used to split the genomes, and the resulting sequence regions are termed variation blocks. Finally, the genomes are compared using the variation blocks. The variation block method identified recurring recombination blocks accurately and successfully represented block-level diversities in the publicly available genomes of 31 soybean and 23 rice accessions. The practicality of this approach was demonstrated by the identification of a putative locus determining soybean hilum color. CONCLUSIONS: We suggest that the variation block method is an efficient genomics method for the recombination block-level comparison of crop genomes. We expect that this method will facilitate the development of crop genomics by bringing genomics technologies to the field of crop breeding
Variation block-based genomics method for crop plants
This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.Abstract
Background
In contrast with wild species, cultivated crop genomes consist of reshuffled recombination blocks, which occurred by crossing and selection processes. Accordingly, recombination block-based genomics analysis can be an effective approach for the screening of target loci for agricultural traits.
Results
We propose the variation block method, which is a three-step process for recombination block detection and comparison. The first step is to detect variations by comparing the short-read DNA sequences of the cultivar to the reference genome of the target crop. Next, sequence blocks with variation patterns are examined and defined. The boundaries between the variation-containing sequence blocks are regarded as recombination sites. All the assumed recombination sites in the cultivar set are used to split the genomes, and the resulting sequence regions are termed variation blocks. Finally, the genomes are compared using the variation blocks. The variation block method identified recurring recombination blocks accurately and successfully represented block-level diversities in the publicly available genomes of 31 soybean and 23 rice accessions. The practicality of this approach was demonstrated by the identification of a putative locus determining soybean hilum color.
Conclusions
We suggest that the variation block method is an efficient genomics method for the recombination block-level comparison of crop genomes. We expect that this method will facilitate the development of crop genomics by bringing genomics technologies to the field of crop breeding