Breakup Effects Research Articles

Fusion of light weakly bound nuclei

The effect of breakup in the fusion cross section in terms of suppression versus enhancement, discussed in a conflicting way in the literature is addressed. Data and theoretical predictions available in the literature are compared. Excitation functions of the sub- and near-barrier fusion cross-sections for a wide variety of light and heavy systems are presented and interpreted. We have measured fusion excitation functions and breakup correlation functions for the medium weight systems 6Li + 59Co and 7Li + 59Co. These measurements help to establish the influence of the projectile breakup on the fusion process at near-barrier energies and contribute to the determination of how the mass of the target affects the breakup role. The results indicate a light fusion enhancement at sub-barrier energies and a geometry dominated cross section at barrier energies.

Is the inhibition/enhancement of fusion due to breakup still a puzzle?

The effect of breakup in the fusion cross section in terms of suppression versus enhancement, discussed in a conflicting way in the literature, is addressed. Data and theoretical predictions available in the literature are compared. Excitation functions of the sub- and near-barrier fusion cross-sections for a wide variety of light and heavy systems are presented and interpreted. We have measured fusion excitation functions and breakup correlation functions for the medium weight systems 6Li + 59Co and 7Li + 59Co. These measurements help to establish the influence of the projectile breakup on the fusion process at near-barrier energies and contribute to the determination of how the mass of the target affects the breakup role. The results indicate a light fusion enhancement at sub-barrier energies and a geometry dominated cross section at barrier energies.

A new field‐sequential‐color LCD without moving‐object color break‐up

Abstract— A new display method for field‐sequential‐color liquid‐crystal displays (FS‐LCDs) that reduces the negative effects of color break‐up associated with moving objects has been developed. The method is called Adjustment of Color Element on the Eyes (ACE), and it relies on the position on the eyes of RGB color sub‐images. It was confirmed that color break‐up also does not occur for peripheral objects when using ACE.

Gravitational Radiation from Gamma‐Ray Burst Progenitors

We study gravitational radiation from various proposed gamma-ray burst (GRB) progenitor models, in particular compact mergers and massive stellar collapses. These models have in common a high angular rotation rate, and the final stage involves a rotating black hole and accretion disk system. We consider the in-spiral, merger and ringing phases, and for massive collapses we consider the possible effects of asymmetric collapse and break-up, as well bar-mode instabilities in the disks. We calculate the strain and frequency of the gravitational waves expected from various progenitors, at distances based on occurrence rate estimates. Based on simplifying assumptions, we give estimates of the probability of detection of gravitational waves by the advanced LIGO system from the different GRB scenarios.

Continuum-discretized coupled-channels study of the11Be→10Be+nbreakup effect on11Beelastic scattering

The ${}^{11}{\stackrel{\ensuremath{\rightarrow}}{\mathrm{Be}}}^{10}\mathrm{Be}+n$ breakup effect on the elastic scattering of ${}^{11}\mathrm{Be}$ by ${}^{12}\mathrm{C}$ at $E/A=49.3$ MeV is investigated by the method of continuum-discretized coupled-channels (CDCC) based on the ${}^{10}\mathrm{B}\mathrm{e}+n+\mathrm{t}\mathrm{a}\mathrm{r}\mathrm{g}\mathrm{e}\mathrm{t}$ three-body model. The CDCC calculation well reproduces the experimental data of the elastic scattering, which is consistent with the result of recent studies based on the adiabatic three-body models. The breakup effect is significant and the coupling to the p-wave continuum states and the d-wave resonance state have a dominant contribution to the breakup effect. Dynamical polarization potential which simulates the breakup effect is evaluated and found to have a weakly repulsive real part and a long-range imaginary part of absorptive nature, characteristic of the weakly bound projectile with neutron halo.

The initial stage of fuel spray penetration ☆

Effects of droplet evaporation, break-up and air entrainment on diesel fuel spray penetration have been studied theoretically at the initial stage of spray penetration when the influence of air entrainment is small (up to 0.1–0.2 ms after the start of injection). Theoretical plots of spray penetration versus time are compared with experimental results obtained using an optical single cylinder rapid compression test rig based on a Ricardo Proteus engine. Three models of spray penetration have been compared. In the first, neither break-up nor air entrainment are taken into account. The break-up processes (bag and stripping) are taken into account in the second model, while in the third model both bag break-up and air entrainment processes are considered. It has been found that the agreement between the predictions of the third model with experimental measurements is better than that for the first two models.

Effect of composition on phase morphology and mechanical properties of PP/PA66 in situ composites via extrusion-drawing-injection method

The reinforced and toughened PP/PA66 in situ composites were prepared via extrusion-drawing-injection method. The relationship among composition, phase morphology and mechanical properties, together with their functional mechanism, was investigated. The results show that in the range of PA66 weight fraction (fw) from 0 to 20% and under the experimental processing conditions, the main changes in phase morphology of the composites with fw are that the number of in situ formed PA66 microfibers and remained PA66 particles increases with fw whereas the fiber transverse size and its dispersity decrease till fw = 15% and then increase. This can be attributed to the combined effect of break-up, coalescence and deformation of the PA66 phase in the PP phase in the course of extrusion and drawing. The tensile strength of composites has a maximum value at fw of 15% and Young's modulus increases with fw up to a plateau level, while impact strength continuously rises with fw, an effect which can be ascribed to the distinct dependence of these properties on the phase-morphological factors mentioned above.

Relativistic effects in proton-induced deuteron break-up at intermediate energies with forward emission of a fast proton pair

Recent data of the reaction $pd \to (pp) n$ with a fast forward pp pair with small excitation energy is analyzed within a covariant approach based on the Bethe-Salpeter formalism. Relativistic effects in cross-section are extracted and found to be large. It is demonstrated that the node of the non-relativistic amplitude is shifted and masked by relativistic effects from Lorentz boost and the negative-energy P components in the 1 S 0 Bethe-Salpeter amplitude of the pp pair.

On the Development of Spray Submodels Based on Droplet Size Moments

Hitherto, all polydisperse spray models have been based on discretising the liquid flow field into groups of equally sized droplets. The authors have recently developed a spray model that captures the full polydisperse nature of the spray flow without using droplet size classes (Beck, 2000, Ph.D thesis, UMIST; Beck and Watkins, 2001, Proc. R. Soc. London A). The parameters used to describe the distribution of droplet sizes are the moments of the droplet size distribution function. Transport equations are written for the two moments which represent the liquid mass and surface area, and two more moments representing the sum of drop radii and droplet number are approximated via use of a presumed distribution function, which is allowed to vary in space and time. The velocities to be used in the two transport equations are obtained by defining moment-average quantities and constructing further transport equations for the relevant moment-average velocities. An equation for the energy of the liquid phase and standard gas phase equations, including a k–ε turbulence model, are also solved. All the equations are solved in an Eulerian framework using the finite-volume approach, and the phases are coupled through source terms. Effects such as interphase drag, droplet breakup, and droplet–droplet collisions are also captured through the use of source terms. The development of the submodels to describe these effects is the subject of this paper. All the source terms for the hydrodynamics of the spray are derived in this paper in terms of the four moments of the droplet size distribution in order to find the net effect on the whole spray flow field. The development of similar submodels to describe heat and mass transfer effects between the phases is the subject of a further paper (Beck and Watkins, 2001, J. Heat Fluid Flow). The model has been applied to a wide variety of different sprays, including high-pressure diesel sprays, wide-angle solid-cone water sprays, hollow-cone spray s, and evaporating sprays. The comparisons of the results with experimental data show that the model performs well. The interphase drag model, along with the model for the turbulent dispersion of the liquid, produces excellent agreement in the spray penetration results, and the moment-average velocity approach gives good radial distributions of droplet size, showing the capability of the model to predict polydisperse behaviour. Good submodel performance results in droplet breakup, collisions, and evaporation effects (see (Beck and Watkins, 2001, J. Heat Fluid Flow)) also being captured successfully.

Coupling effects in the elastic scattering of6Heon12C

To study the effect of the weak binding energy on the interaction potential between a light exotic nucleus and a target, elastic scattering of ${}^{6}\mathrm{He}$ at 38.3 MeV/nucleon on a ${}^{12}\mathrm{C}$ target was measured at Grand Acc\'el\'erateur National d'Ions Lourds (GANIL). The ${}^{6}\mathrm{He}$ beam was produced by fragmentation. The detection of the scattered particles was performed by the GANIL spectrometer. The energy resolution was good enough to separate elastic from inelastic scattering contributions. The measured elastic data have been analyzed within the optical model, with the real part of the optical potential calculated in the double-folding model using a realistic density-dependent nucleon-nucleon interaction and the imaginary part taken in the conventional Woods-Saxon (WS) form. A failure of the ``bare'' real folded potential to reproduce the measured angular distribution over the whole angular range suggests quite a strong coupling of the higher-order breakup channels to the elastic channel. To estimate the strength of the breakup effects, a complex surface potential with a repulsive real part (designed to simulate the polarization effects caused by the projectile breakup) was added to the real folded and imaginary WS potentials. A realistic estimate of the polarization potential caused by the breakup of the weakly bound ${}^{6}\mathrm{He}$ was made based on a parallel study of ${}^{6}\mathrm{He}{+}^{12}\mathrm{C}$ and ${}^{6}\mathrm{Li}{+}^{12}\mathrm{C}$ optical potentials at about the same energies.

Effect of tear film break-up on higher-order aberrations measured with wavefront sensor

PURPOSE: To investigate whether optical wavefront aberrations vary with tear film break-up.DESIGN: Observational case series.METHODS: Higher-order aberrations were examined for 20 eyes of 20 normal subjects with a Hartmann-Shack wavefront sensor before and after tear film break-up.RESULTS: Higher-order aberrations for photopic vision (central 4 mm diameter) after tear film break-up increased 1.44 fold compared to higher-order aberrations before tear film break-up (P = .001, paired t-test). Higher-order aberrations after tear film break-up for scotopic vision (central 6 mm diameter) were also 1.23 times higher than those before break-up (P = .005, paired t-test).CONCLUSION: Wavefront sensing enabled us to evaluate the induced irregular astigmatism caused by tear film break-up quantitatively. Wavefront aberrations should be measured carefully to avoid the effects of tear film break-up, especially in wavefront-guided refractive surgery.

Contact lens drying and visual performance: the vision cycle with contact lenses.

The purpose of this study was to measure the effect of precontact lens tear film break-up on visual performance. Four asymptomatic soft contact lens wearers had contrast sensitivity measured by a temporal, two-alternative, force choice paradigm combined with a self-paced methods of limits. Stimuli were vertically orientated sine wave gratings (0.5 to 14 cycles per degree [cpd] presented for 16.67 ms. Contrast sensitivity was measured before precontact lens tear break-up by a stimuli presented 2 s after the blink. A post-tear layer break-up measurement taken with the stimuli presented after break-up had been observed by the use of a video camera attached to a Tearscope. Contrast sensitivity was found to be reduced following precontact lens tear film break-up for stimuli of 4, 6, and 10 cpd; the data approached significance at 14 cpd. Further reductions in contrast sensitivity were observed for one subject when measurements were continued for 4 s following break-up. Contrast sensitivity is significantly reduced for middle to high spatial frequencies when the precontact lens tear film dries and breaks up. The combination of observations of visual performance immediately following the blink (from earlier experiments) and measurements following tear film break-up in this experiment allows description of a "vision cycle" for contact lens wearers in the interval between blinks. It is suggested that break-up of the precontact lens tear film could account for the complaints of intermittent blurred vision in some contact lens wearers and may provide a stimulus to blinking in these individuals.

Higher-order effects in the two-body breakup of 17F

The two-body breakup 17 F→ 16 O+ p on Ni and Pb targets at 10–40 MeV/u is calculated by solving the time-dependent Schrödinger equation numerically. Both Coulomb and the nuclear potentials are important in these reactions, but the Coulomb contribution cannot be calculated reliably in first-order perturbation theory. The most dramatic feature is a dynamic polarization effect, which reduces the Coulomb dissociation probability compared to first-order perturbation theory. Over most of the energy range, the correction is proportional to Z 3, the cube of the target charge, and the relative importance is nearly inversely proportional to the beam energy. At the lowest energies in the range considered, higher-order effects (⩾ Z 3) become significant as well. At the impact parameters where nuclear induced breakup is dominant, the diffraction dissociation is reduced whereas stripping is enhanced compared to the eikonal approximation. Here too the deviations decrease inversely with beam energy over most of the range considered.

Sub-barrier and near-barrier fusion study of halo nuclei

The near-barrier and sub-barrier fusion of light unstable nuclei and their respective stable isotopes with heavy targets ${(}^{4,6}\mathrm{He}{+}^{209}\mathrm{Bi},$ ${}^{4,6}\mathrm{He}{+}^{238}\mathrm{U},$ ${}^{9,11}\mathrm{Be}{+}^{209}\mathrm{Bi},$ and ${}^{9}\mathrm{Be}{+}^{208}\mathrm{Pb})$ is investigated via coupled channel calculations. The entrance channel optical potential is generated via a microscopic BDM3Y1 interaction. A rather satisfactory description of the experimental data is obtained under the condition that the real part of the optical potential has to be reduced for the weakly bound and halo systems. This reduction proves to be the fundamental difference in treating stable and weakly bound nuclei, and can be attributed to the loss of a flux due to breakup effects.

Angular momentum and cross sections for fusion with weakly bound nuclei: breakup, a coherent effect.

Results for the cross section and average angular momentum for complete fusion at energies around the Coulomb barrier are presented for 7Li with 165Ho. Comparison of the cross sections with a one-dimensional barrier penetration model, using a potential consistent with the measured elastic scattering, showed a reduction above the barrier and an enhancement below it. An increase in the measured average angular momentum, <l>, above the barrier and its consistency with that obtained from the fusion excitation function for weakly bound nuclei, is reported. These results together with a reanalysis of existing data conclusively demonstrate that the effect of breakup on fusion is coherent, like coupling to any nonelastic channel.

No evidence of break-up effects on the fusion of 9Be with medium-light nuclei

Fusion cross sections were measured for the 9Be+27Al and 19F+9Be, 12C systems, at energies above the Coulomb barrier, in order to investigate the possible effect of fusion hindrance due to the break-up of the weakly bound nuclei. Comparisons with one-dimensional barrier penetration models and with other similar systems, where no break-up is expected to occur, show no evidence of fusion hindrance.

A CDCC Study of11Be →10Be +nBreakup Effect on the11Be Elastic Scattering

The 1 1 Be→ 1 0 Be+n breakup effect on 1 1 Be+ 1 2 C elastic scattering at E/A=49.3 MeV is studied by continuum-discretized coupled-channels (CDCC) method based on the 1 0 Be+n+ 1 2 C three-body model. The CDCC calculation well reproduces the experimental data of the elastic scattering, and the breakup effect of the 1 1 Be nucleus is found to be significant. A dynamical polarization potential (DPP) evaluated shows a characteristic of the halo nucleus.

Custody and access issues with children whose parents are separated or divorced.

This article discusses the effects of family breakdown--and the resulting issues of custody and access--on children. It explores trends in child custody and access and issues surrounding those trends, particularly in terms of the benefits and limitations of joint custody. It then identifies the contextual problems of family breakups (including the relative poverty experienced by mother-led families, the unreliability of financial support from fathers, the complications for children which result from step-parent figures, including serial partners of their parents, the implications of interparental conflict, the need to fully address suspicions and/or allegations of abuse by one parent against another, and the problem of Parental Alienation Syndrome). Typical responses of children to family breakup are then considered, including feelings of loss, guilt, and responsibility, and a sense of divided loyalties--particularly in light of intense or violent parental conflict. And finally, recommendations are made to minimize the detrimental effects of family breakup on children: (a) allowing children choice and flexibility, (b) exploring the benefits of mediation for families, (c) promoting parental co-operation, and (d) encouraging an ongoing relationship with the nonresidential parent.

Eulerian simulations of bubble behaviour in a two-dimensional gas-solid bubbling fluidized bed

In the present study, the CFD model is based on a two-fluid model extended with the kinetic theory of granular flow. The simulation results of bubble diameter and bubble rise velocity are compared to the Darton equation and the Davidson model in a free bubbling fluidized bed. The predicted values are in reasonable agreement with the values from the Darton bubble size equation and the Davidson model for isolated bubbles. It is shown that the break-up and direct wall interaction effects influence the dynamic bubble behavior in the free bubbling fluidized beds. Copyright © 2002 John Wiley & Sons, Ltd.

The Effect of Device Parameters on the Emitter Transit Time of a PET

Polysilicon Emitter Transistors (PETs) which are now being widely used in high speed bipolar circuits because of their extremely low emitter transit time τE, have broken-up interfacial oxide layer due to annealing process which they undergo. The effect of oxide layer break-up at the mono-poly interface of the emitter region of a PET on τE is studied here. The effect of doping profile, peak doping concentration, thickness of interfacial oxide layer on τE is studied also. Exponential doping distribution alongwith concentration dependent bandgap narrowing effect and concentration dependent diffusion constant in the monosilicon emitter region are considered.