20,027 research outputs found

### On the momentum-dependence of $K^{-}$-nuclear potentials

The momentum dependent $K^{-}$-nucleus optical potentials are obtained based
on the relativistic mean-field theory. By considering the quarks coordinates of
$K^-$ meson, we introduced a momentum-dependent "form factor" to modify the
coupling vertexes. The parameters in the form factors are determined by fitting
the experimental $K^{-}$-nucleus scattering data. It is found that the real
part of the optical potentials decrease with increasing $K^-$ momenta, however
the imaginary potentials increase at first with increasing momenta up to
$P_k=450\sim 550$ MeV and then decrease. By comparing the calculated $K^-$ mean
free paths with those from $K^-n$/$K^-p$ scattering data, we suggested that the
real potential depth is $V_0\sim 80$ MeV, and the imaginary potential parameter
is $W_0\sim 65$ MeV.Comment: 9 pages, 4 figure

### The properties of kaonic nuclei in relativistic mean-field theory

The static properties of some possible light and moderate kaonic nuclei, from
C to Ti, are studied in the relativistic mean-field theory. The 1s and 1p state
binding energies of $K^-$ are in the range of $73\sim 96$ MeV and $22\sim 63$
MeV, respectively. The binding energies of 1p states increase monotonically
with the nucleon number A. The upper limit of the widths are about $42\pm 14$
MeV for the 1s states, and about $71\pm 10$ MeV for the 1p states. The lower
limit of the widths are about $12\pm 4$ MeV for the 1s states, and $21\pm 3$
MeV for the 1p states. If $V_{0}\leq 30$ MeV, the discrete $K^-$ bound states
should be identified in experiment. The shrinkage effect is found in the
possible kaonic nuclei. The interior nuclear density increases obviously, the
densest center density is about $2.1\rho_{0}$.Comment: 9 pages, 2 tables and 1 figure, widths are considered, changes a lo

### Preparation of MAl2O4: Eu2+, Sm3+ (M = Ca, Sr, Ba) Phosphors by the Combustion Method and their Luminescent Properties

A series of MAl2O4: Eu2+, Sm3+ (M = Ca, Sr, Ba) phosphors was prepared by the combustion method, and the influence of these alkaline earth metals on the structure and luminescent performances for these phosphors was investigated. A relationship was established between their composition, crystallization capacity and luminescent properties. The results show that the CaAl2O4: Eu2+, Sm3+ and SrAl2O4: Eu2+, Sm3+ phosphors exhibit monoclinic crystal systems and that the BaAl2O4: Eu2+, Sm3+ phosphor exhibits a hexagonal structure. The alkaline earth metal has a positive effect on the crystallization process, the heat treatment procedure and the luminescent properties of the corresponding phosphors. According to the order Ca > Sr > Ba, the maximum emission wavelengths of the corresponding phosphors are found at 505 nm, 490 nm and 478 nm, and the relevant colours of emitted light are between blue and green, which indicates that there is a clear blue shift in the emission spectra, but their excitation spectra show almost no difference. The decay curve shows that the afterglow intensity and time are not only related to the activating processes and the hole transport, but also to the phase structure and the grain size,which is in the order Sr>Ca>Ba.Keywords: Long afterglow, alkaline earth aluminates, spectra, combustion metho

### A hybrid algorithm for predicting median-plane head-related transfer functions from anthropometric measurements

Since head-related transfer functions (HRTFs) represent the interactions between sounds and physiological structures of listeners, anthropometric parameters represent a straightforward way to customize (or predict) individualized HRTFs. This paper proposes a hybrid algorithm for predicting median-plane individualized HRTFs using anthropometric parameters. The proposed hybrid algorithm consists of three parts: decomposition of HRTFs; selection of key anthropometric parameters; and establishing a prediction formula. Firstly, an independent component analysis (ICA) is applied to median-plane HRTFs from multiple subjects to obtain independent components and subject-dependent weight coefficients. Then, a factor analysis is used to select key anthropometric parameters relevant to HRTFs. Finally, a regression formula that connects ICA weight coefficients to key anthropometric parameters is established by a multiple linear regression. Further, the effectiveness of the proposed hybrid algorithm is verified by an objective evaluation via spectral distortion and a subjective localization experiment. The results show that, when compared with generic Knowles Electronics Manikin for Acoustic Research (KEMAR) HRTFs, the spectral characteristics of the predicted HRTFs are closer to those of the individualized HRTFs. Moreover, the predicted HRTFs can alleviate front-back and up-down confusion and improve the accuracy of localization for most subjects

### In-medium Properties of $\Theta^{+}$ as a K$\pi$N structure in Relativistic Mean Field Theory

The properties of nuclear matter are discussed with the relativistic
mean-field theory (RMF).Then, we use two models in studying the in-medium
properties of $\Theta^+$: one is the point-like $\Theta^*$ in the usual RMF and
the other is a K$\pi$N structure for the pentaquark. It is found that the
in-medium properties of $\Theta^+$ are dramatically modified by its internal
structure. The effective mass of $\Theta^+$ in medium is, at normal nuclear
density, about 1030 MeV in the point-like model, while it is about 1120 MeV in
the model of K$\pi$N pentaquark. The nuclear potential depth of $\Theta^+$ in
the K$\pi$N model is approximately -37.5 MeV, much shallower than -90 MeV in
the usual point-like RMF model.Comment: 8 pages, 5 figure

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