1,294 research outputs found
Evaluación de diferentes métodos de modelización para la estimación de la altura total del árbol de la Región Mediterránea de Turquía
Efficient management of timber resources and wood utilization practices require accurate and versatile information about important characteristics of forest resources for evaluating the numerous management and utilization alternatives for timber resources. Tree height is considered one of the most useful variables along with stocking and diameter at breast height, in estimating forest stand wood volumes and productivity. Six nonlinear growth functions were fitted to tree height-diameter data of three major tree species in Western Mediterranean Region’s forests of Turkey. The generalized regression neural network (GRNN) technique has been applied for tree height prediction, as well, due to its ability to fit complex nonlinear models. The performance of the models was compared and evaluated. Further, equivalence tests of the selected models were conducted. Validation showed the appropriatness of all models to predict tree height. According to the model performance criteria, the six nonlinear growth functions were able to capture the height-diameter relationships and fitted the data almost equally well, while the constructed generalized regression neural network (GRNN) models were found to be superior to all nonlinear regression models, in terms of their predictive ability. La gestión eficiente de los recursos forestales y la de utilización de la madera requieren de información precisa y versátil acerca de las características importantes de los recursos forestales para la evaluación de la gestión y de las alternativas de utilización de los recursos forestales. La altura del árbol es considerada como una de las variables más útiles, junto con la densidad, y el diámetro a la altura del pecho, en la estimación de volúmenes de madera y la productividad de masas forestales. Se ajustaron seis modelos de altura total-diámetro y se compararon con el fin de estimar con precisión la altura total del árbol de las tres principales especies de árboles en los bosques de la Región Occidental Mediterráneo de Turquía. La regresión generalizada de redes neuronales (GRNN) se presenta como una técnica alternativa de red neuronal a la técnica de regresión no lineal para estimar la altura total de los árboles debido a su capacidad para adaptarse a modelos complejos no lineales. Se compararon y evaluaron los modelos. Se llevaron a cabo otras pruebas, como la equivalencia de los modelos seleccionados. De acuerdo con los criterios del rendimiento de los modelos, las seis funciones no lineales de crecimiento fueron capaces de capturar las relaciones altura-diámetro y ajustaron los datos casi igual de bien, mientras que las construidas mediante modelos de regresión generalizados de redes neuronales (GRNN) resultaron ser superiores a todos los modelos de regresión no lineal, en términos de su capacidad predictiva
An algorithm to obtain global solutions of the double confluent Heun equation
A procedure is proposed to construct solutions of the double confluent Heun
equation with a determinate behaviour at the singular points. The connection
factors are expressed as quotients of Wronskians of the involved solutions.
Asymptotic expansions are used in the computation of those Wronskians. The
feasibility of the method is shown in an example, namely, the Schroedinger
equation with a quasi-exactly-solvable potential
Femtosecond response of J aggregates adsorbed onto silver colloid surfaces
The observation of stimulated emission from J aggregates adsorbed onto silver colloid surfaces using femtosecond excitation was reported. The stimulated emission was inferred from the excitation intensity and wavelength dependence of the emission band. The stimulated emission originated from the amplification of the one-exciton state emission by an induced transition from the two-exciton state to the one-exciton state
Supersymmetry and the relationship between a class of singular potentials in arbitrary dimensions
The eigenvalues of the potentials
and
, and of the special cases of these potentials such as the Kratzer and
Goldman-Krivchenkov potentials, are obtained in N-dimensional space. The
explicit dependence of these potentials in higher-dimensional space is
discussed, which have not been previously covered.Comment: 13 pages article in LaTEX (uses standard article.sty). Please check
"http://www1.gantep.edu.tr/~ozer" for other studies of Nuclear Physics Group
at University of Gaziante
Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV
The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8 TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum
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