Role of non-collective excitations in low-energy heavy-ion reactions

We investigate the effect of single-particle excitations on heavy-ion reactions at energies near the Coulomb barrier. To this end, we describe single-particle degrees of freedom with the random matrix theory and solve the coupled-channels equations for one-dimensional systems. We find that the single-particle excitations hinder the penetrability at energies above the barrier, leading to a smeared barrier distribution. This indicates that the single-particle excitations provide a promising way to explain the difference in a quasi-elastic barrier distribution recently observed in $^{20}$Ne + $^{90,92}$Zr systems.Comment: 8 pages, 7 figure

Non-collective excitations in low-energy heavy-ion reactions: applicability of the random-matrix model

We investigate the applicability of a random-matrix model to the description of non-collective excitations in heavy-ion reactions around the Coulomb barrier. To this end, we study fusion in the reaction $^{16}$O + $^{208}$Pb, taking account of the known non-collective excitations in the $^{208}$Pb nucleus. We show that the random-matrix model for the corresponding couplings reproduces reasonably well the exact calculations, obtained using empirical deformation parameters. This implies that the model may provide a powerful method for systems in which the non-collective couplings are not so well known.Comment: 6 pages, 4 figure

Subbarrier fusion reactions with dissipative couplings

Using the random matrix model, we discuss the effect of couplings to non-collective states on the penetrability of a one dimensional potential barrier. We show that these non-collective excitations hinder the penetrability and thus smear the barrier distribution at energies above the barrier, while they do not affect significantly the penetrability at deep subbarrier energies. The energy dependence of the Q-value distribution obtained with this model is also discussed.Comment: 4 pages, 2 figures. A talk given at the 10th international conference on nucleus-nucleus collisions (NN2009), Aug. 16-21, 2009, Beijing, Chin

Cooling of radiative quantum-dot excitons by terahertz radiation: A spin-resolved Monte Carlo carrier dynamics model

We have developed a theoretical model to analyze the anomalous cooling of radiative quantum dot (QD) excitons by THz radiation reported by Yusa et al [Proc. 24th ICPS, 1083 (1998)]. We have made three-dimensional (3D) modeling of the strain and the piezoelectric field and calculated the 3D density of states of strain induced quantum dots. On the basis of this analysis we have developed a spin dependent Monte Carlo model, which describes the carrier dynamics in QD's when the intraband relaxation is modulated by THz radiation. We show that THz radiation causes resonance transfer of holes from dark to radiative states in strain-induced QD's. The transition includes a spatial transfer of holes from the piezoelectric potential mimima to the deformation potential minimum. This phenomenon strongly enhances the QD ground state luminescence at the expense of the luminescence from higher states. Our model also reproduces the delayed flash of QD ground state luminescence, activated by THz radiation even $\sim1$ s after the carrier generation. Our simulations suggest a more general possibility to cool the radiative exciton subsystem in optoelectronic devices.Comment: 18 pages, 1 table, 8 figures, submitted to Physical Review B v2: major conceptual changes. The article was extended considerably to suit Physical Review B (instead of Physical Review Letters

Role of non-collective excitations in heavy-ion fusion reactions and quasi-elastic scattering around the Coulomb barrier

Despite the supposed simplicity of double-closed shell nuclei, conventional coupled-channels calculations, that include all of the known collective states of the target and projectile, give a poor fit to the fusion cross section for the $^{16}$O + $^{208}$Pb system. The discrepancies are highlighted through the experimental barrier distribution and logarithmic derivative, that are both well defined by the precise experimental fusion data available. In order to broaden our search for possible causes for this anomaly, we revisit this system and include in our calculations a large number of non-collective states of the target, whose spin, parity, excitation energy and deformation paramter are known from high-precision proton inelastic-scattering measurements. Although the new coupled-channels calculations modify the barrier distribution, the disagreemnt with experiment remains both for fusion and for quasi-elastic (QE) scattering. We find that the Q-value distributions for large-angle QE scattering become rapidly more important as the incident energy increases, reflecting the trend of the experimental data. The mass-number dependence of the non-collective excitations is discussed.Comment: 8 pages, 7 figure

Korelasi Pengujian Kepadatan Lapangan Dan Static Hand Penetrometer Terhadap Hasil Cbr Laboratorium Pada Beberapa Jenis Tanah

In highway design, it is necessary to check the subgrade bearing capacity since it influences the pavement thickness. There are several methods used to determine the subgrade bearing capacity such as DCP (Dynamic Cone Penetrometer) and HCP (Hand Cone Penetrometer). This research aims to compare between CBR and soil density combined with HCP; to find the initial correlation between HCP and CBR; and to find the correlation between HCP and soil density (yt). The correlation between HCP to soil density on peat is CBR = -2,1232 + (3,1162 x HCP) + (1,8329 x yt), and CBR = -13,4404 + (23,3252 x HCP) + (7,1014 x yt) in sand and clay composite

Korelasi Penentuan Daya Dukung Tiang Cara Empirik (Cpt) Dengan Pile Driven Analysis (Pda) Di Kota Pekanbaru

Axial bearing capacity of pile foundation can be estimated empirically from cone penetration test (CPT). Actual capacity of foundation can be obtained from static load test or pile driving analyzer (PDA). This research evaluated pile bearing capacity calculated by method of Schmertman (1978), de Reuter & Beringen (1979) and Bustamente & Gianeselli (1982) with PDA results at several location in Pekanbaru, that have been analyzed by Case Pile Wave Analysis Program (CAPWAP). Determination of coefficient correlation was carried statistically using Pearson Product Moment. Result showed that Schmertman method is best to estimate skin friction capacity with coefficient of correlation is 0.968. Those three methods gave good estimation of ultimate bearing capacity with coefficient of correlation between 0.957-0.974

Dwarf males in the barnacle Alepas pacifica Pilsbry, 1907 (Thoracica, Lepadidae), a symbiont of jellyfish

In the pedunculate barnacle Alepas pacifica Pilsbry, 1907, a symbiont of jellyfish, several small individuals were found attached to conspecifics rather than directly to the host. We investigated whether these individuals act as dwarf males, as is known in some other species of barnacles. The conspecific-attached individuals had longer penes than juvenile hermaphrodites of similar sizes attached directly to the jellyfish, although there was no other morphological difference between these two types of individuals. Only the largest conspecific-attached individual was ovigerous. We conclude that the conspecific-attached individuals are dwarf males, which develop the male function at a smaller size than hermaphrodites do, with a small possibility of becoming hermaphroditic. This is the first report of dwarf males, and hence of the coexistence of males and hermaphrodites (androdioecy), in the family Lepadidae. In addition, the record of A. pacifica attached to Nemopilema nomurai Kishinouye, 1922, is reported herein as new to science