In memory of Professor Ali H. Nayfeh

Nonlinear Dynamics - In this paper, we propose and numerically study a nonlinear, asymmetric, passive metamaterial that achieves giant non-reciprocity with (i) broadband frequency operation and...     

Geometric optimization andD P -completeness

In this paper we show a number of natural geometric optimization problems in the plane to becomplete for a classD ^P . The classD ^p contains both NP and Co-NP and is contained in ₂ ^P =P ^NP. Completeness inD ^p is exhibited under many-one and positive reductions. Further anOptP(O(logn)) result is also obtained for some of these optimization problems.Work on this paper by the first author was supported in part by NSF Grant No. MIP 85-21356 and ARO Contract No. DAAG29-85-C-0018 under Cornell/MSI. Work by the second author was supported in part by NSF Grant No. DCR 86-06366 at Ohio State and ONR Grant No. N00014-k-0045 at Harvard.On leave from Ohio State University.     

Effect of free carrier screening on the binding energy of D− centers in polar semiconductors

A calculation of the binding energy of a D^? center, defined as the energy required to remove one of the two electrons from the D^? center to infinity, in the presence of other free carriers is reported in polar crystals. It is assumed that the effective interaction between each of the two electrons and the positive ion is described by Thomas-Fermi potential. The effective interaction between the two electrons in polar crystals is, however, described by two recently proposed potentials. The binding energy of a D^? ion is calculated variationally in several polar crystals as a function of the screening parameter δ and the value of δ at which the binding energy goes to zero (D^? Mott transition) is determined. A possible experimental situations where this system may be studied is discussed.     

Decays of the mesons and the singlet photon

In an attempt to explain the recent measurements on the radiative decays of the vector-mesons (V→Pγ), we study the consequences of introducing a small admixture of SU (3) singlet piece in the electromagnetic current. We find that this leads to an excellent fit of the theory with the new measurements on theV→Pγ decays. However, this addition adversely affects the fit of the leptonic decays of the vector mesons (V→e ⁺ e ⁻) and of the radiative decay of the pion (π→2γ). We conclude that the overall fit to the available data does not favour a large (>10%) admixture of the SU(3) singlet. The decay rates have been calculated in the vectormeson dominance model. At the hadronic vertex (VVP), we assume asymptotic nonet symmetry. The electromagnetic couplings (V−γ) are the ones appropriate to vector-mixing.     

On experiments in harmonically excited cantilever plates with 1:2 internal resonance

Nonlinear Dynamics - This work presents some experimental results for resonant nonlinear response of hyperelastic plates for 1:2 internal resonance. Previously developed topology optimization...     

Nanocomposite ZnO/Au formation by pulsed laser irradiation

The ZnO/Au nanocomposite formation involves synthesis of Au and ZnO colloidal solutions by 532 nm pulse laser ablation of metal targets in deionized water followed by laser irradiation of the mixed colloidal solution. The transmission electron microscope (TEM) and high-resolution transmission electron microscope (HRTEM) images show evolution of spherical particles into ZnO/Au nanonetworks with irradiation time. The formation mechanism of the nanonetwork can be explained on the basis of near resonance absorption of 532 nm irradiation by gold nanoparticles which can cause selective melting and fusion of gold nanoparticles to form network. The ZnO/Au nanocomposites show blue shift in the ZnO exciton absorption and red shift in the Au plasmon resonance absorption due to interfacial charge transfer.     

Dye-sensitized solar cells concocted with dyes extracted from fresh and dried leaves of Henna using different solvents

Optical and Quantum Electronics - Nowadays, world is moving from conventional energy sources to non-conventional energy sources like solar energy, wind power, hydropower and those energy sources...