On single and bimodal optimum buckling loads of clamped columns

We study the problem of determining the optimum shape of a thin, elastic, clamped column of given length and volume, such that the fundamental buckling load is a maximum. The column cross-sections are assumed to be geometrically similar, and a minimum allowable value is specified for the cross-sectional area.Investigating the optimization problem parametrically in terms of this minimum constraint, we reveal a significant feature. There exists a threshold value for the constraint, beyond which the optimum columns are all associated with single mode optimum buckling loads, whereas, for any value of the constraint less than the threshold value, the optimum columns are associated with bimodal fundamental buckling loads.This bimodal behaviour necessitates an extension and a mathematical reformulation of the current optimization problem, which is outlined and solved in the paper. In particular, we revise the result hitherto considered to be the optimum solution for an unconstrained column with clamped ends.     

On the influence of shell structure and matrix element fluctuations on the pairing correlation in nuclei

The uniform model for the nuclear pairing-force problem is extended to take into account the effect of fluctuations in nucleon orbital level densityρ and in pairing matrix elementsG _vv′. Simple formulas for the average dependence of level density on energy are presented, and alternative ways of estimating effects of shell bunching on the pairing correlation are derived. It is argued also that the pairing constantG might be systematically overestimated in the usual BCS numerical calculations; a semiconstant pairing force with diagonal elements larger than off-diagonal is thus suggested.     

On the current-driven electrostatic ion-cyclotron instability: areview

Theoretical, numerical, and experimental investigations of the electrostatic ion-cyclotron instability (EICI) are critically reviewed. The discussion of theory focuses mainly on the linear theories, with particular attention to those that have been used in explaining experimental observations, but a short account of various nonlinear theories is also given. Numerical simulation results are surveyed. Experimental investigations in Q-machine plasmas and their interpretation in terms of various theories are then examined     

Performance improvement of direct detection systems using local and/or long-distance pumped fiber amplifiers

Erbium-doped fiber amplifiers (EDFAs) in eight different system configurations are investigated, using a full-scale model, and the midline placement of the amplifier is shown to be optimal. A distributed amplifier compared to the remote pumping scheme shows no system improvement. Use of a booster (next to the transmitter), a midline remote-pumped amplifier, and a preamplifier (next to the receiver) allows up to 180 km of extra transmission fiber to be added.     

Two-nucleon transfer reactions in deformed nuclei using very heavy ions

Semiclassical methods found to be highly accurate for inelastic scattering are applied to the calculation of rotational population signatures in heavy-ion two-neutron transfer reactions involving highly deformed targets. Basic features to be expected for such reactions are predicted, and are shown to have straightforward semiclassical interpretations. The rotational population signatures for 2-neutron transfer are shown to be quite different from those expected for the analogous inelastic scattering case. Several calculations are shown for Xe projectiles on rare-earth targets, and it is demonstrated that such reactions can provide a unique probe of nuclear structure in high angular momentum states. The extension of the general ideas employed here to 1-nucleon transfer in deformed nuclei and to several other examples of transfer to highly collective states in deformed and vibrational nuclei using very heavy ions is briefly considered. Experimental possibilities are discussed, and it is concluded that relevant experiments in this virtually unexplored area are possible using sophisticated particle-γ spectroscopic techniques.     

Application of a Bäcklund transformation in gravity driven two phase filtration

A nonlinear boundary value/initial value problem in two-phase filtration under gravity is solved analytically via the application of two successive Bäcklund transformations.     

Observation of pure quadrupole resonance in zinc metal

We report the first observation of nuclear quadrupole resonance (NQR) in Zn metal. A resonance line, which under the assumption of axial symmetry (η=0) corresponds to the $\text{|M| =}\text{3}\text{2}\text{?}\text{5}\text{2}$ transition in the $\text{I =}\text{5}\text{2}$ ground state of ⁶⁷Zn, has been found at v = 4.086(2) MHz at 4.2K. This yields (for η=0) a quadrupole coupling constant of $\text{e}{}^2\text{qQ}\text{h}\text{= 13.620(8)}$MHz, which is the most accurate value currently available.