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Register a new userA systematic study of the factors affecting central depletion in nuclei
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A systematic study of the central depletion of proton density has been performed in the isotonic chains of nuclei with neutron numbers $N = 20$ and $28$ using different variants of the relativistic mean-field (RMF) models. These models include either the non-linear contributions from the mesons with the coupling constants being density independent or the non-linearity of the mesonic fields realized through the density dependent coupling strengths. The central depletion in deformed nuclei tends to disappear irrespective of the occupancy of $2s_{1/2}$ state in contrast to the spherical nuclei in which the unoccupancy of $2s_{1/2}$ state leads to the central depletion. Due to the differences in the strength of spin-orbit potentials in these models, the central depletions are found to be model dependent. The influence of the central depletion on the neutron-skin thickness is also investigated. It appears that the effects of the central depletion do not percolate far enough to display its finger prints on the trends of the neutron-skin thickness.
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$alpha$ decay is usually associated with both ground and low-lying isomeric states of heavy and superheavy nuclei, and the unpaired nucleon plays a key role on $alpha$ decay. In this work, we systematically studied the $alpha$ decay half-lives of odd-$A$ nuclei, including both favored and unfavored $alpha$ decay within the two-potential approach based on the isospin dependent nuclear potential. The $alpha$ preformation probabilities are estimated by using an analytic formula taking into account the shell structure and proton-neutron correlation, and the parameters are obtained through the $alpha$ decay half-lives data. The results indicate that in general the $alpha$ preformation probabilities of even-$Z$, odd-$N$ nuclei are slightly smaller than the odd-$Z$, even-$N$ ones. We found that the odd-even staggering effect may play a more important role on spontaneous fission than $alpha$ decay. The calculated half-lives can well reproduce the experimental data.
Scaling existing applications and solutions to multiple human languages has traditionally proven to be difficult, mainly due to the language-dependent nature of preprocessing and feature engineering techniques employed in traditional approaches. In this work, we empirically investigate the factors affecting language-independent models built with multilingual representations, including task type, language set and data resource. On two most representative NLP tasks -- sentence classification and sequence labeling, we show that language-independent models can be comparable to or even outperforms the models trained using monolingual data, and they are generally more effective on sentence classification. We experiment language-independent models with many different languages and show that they are more suitable for typologically similar languages. We also explore the effects of different data sizes when training and testing language-independent models, and demonstrate that they are not only suitable for high-resource languages, but also very effective in low-resource languages.
Complete fusion excitation functions of reactions involving breakup are studied by using the empirical coupled-channel (ECC) model with breakup effects considered. An exponential function with two parameters is adopted to describe the prompt-breakup probability in the ECC model. These two parameters are fixed by fitting the measured prompt-breakup probability or the complete fusion cross sections. The suppression of complete fusion at energies above the Coulomb barrier is studied by comparing the data with the predictions from the ECC model without the breakup channel considered. The results show that the suppression of complete fusion are roughly independent of the target for the reactions involving the same projectile.
Temperature dependent relativistic mean-field (RMF) plus BCS approach has been used for the first time to investigate the anti-bubble effect of the temperature and deformation in the light, medium-heavy and superheavy nuclei. Influence of temperature is studied on density distribution, charge form-factor, single particle (s.p.) energies, occupancy, deformation and the depletion fraction (DF). At T $=$ 0, the quenching effect of deformation is predominant. DF is found usually less in oblate deformation than in prolate. DF decreases with increasing prolate deformation even though the 2s-orbit is empty which shows the role of deformation in central depletion apart from the unoccupancy in s-orbit as is usually believed. As T increases, the occupancy of s-orbit increases, shell structure melts, the deformation vanishes and the weakening of central depletion is solely due to the temperature. The bubble effect is eliminated at T $approx$ 3$-$5 MeV as indicated by DF and the charge form factor. The temperature effect is found less prominent in superheavy bubble nuclei where the role of shell effects is indicated.
We performed a systematic study of the formation of fragments with different mass ranges in 197Au+197Au collisions at incident energies between 20 - 1000 MeV/nucleon and at impact para- meter between ^b = 0-0.98. The aim of present study is to understand the complex dependence of fragment production on incident energy and impact parameter. Our results clearly indicate that the QMD simulations of 197Au+197Au predict different behavior for different mass ranges than for IMFs with a change in incident energy and impact parameter. All charge yields can be parameterized by a power law and no signal of liquid-gas phase transition is seen as no unique dependence of tau on impact parameter is seen.
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