Long-Lived Non-Equilibrium Interstitial-Solid-Solutions in Binary Mixtures

We perform particle resolved experimental studies on the heterogeneous crystallisation process of two compo- nent mixtures of hard spheres. The components have a size ratio of 0.39. We compared these with molecular dynamics simulations of homogenous nucleation. We find for both experiments and simulations that the final assemblies are interstitial solid solutions, where the large particles form crystalline close-packed lattices, whereas the small particles occupy random interstitial sites. This interstitial solution resembles that found at equilibrium when the size ratios are 0.3 [Filion et al., Phys. Rev. Lett. 107, 168302 (2011)] and 0.4 [Filion, PhD Thesis, Utrecht University (2011)]. However, unlike these previous studies, for our system sim- ulations showed that the small particles are trapped in the octahedral holes of the ordered structure formed by the large particles, leading to long-lived non-equilibrium structures in the time scales studied and not the equilibrium interstitial solutions found earlier. Interestingly, the percentage of small particles in the crystal formed by the large ones rapidly reaches a maximum of around 14% for most of the packing fractions tested, unlike previous predictions where the occupancy of the interstitial sites increases with the system concentration. Finally, no further hopping of the small particles was observed

Inelastic Quantum Transport and Peierls-like Mechanism in Carbon Nanotubes

We report on a theoretical study of inelastic quantum transport in $(3m,0)$ carbon nanotubes. By using a many-body description of the electron-phonon interaction in Fock space, a novel mechanism involving optical phonon emission (absorption) is shown to induce an unprecedented energy gap opening at half the phonon energy, $\hbar\omega_{0}/2$, above (below) the charge neutrality point. This mechanism, which is prevented by Pauli blocking at low bias voltages, is activated at bias voltages in the order of $\hbar\omega_{0}$.Comment: 4 pages, 4 figure

Anderson Localization Phenomenon in One-dimensional Elastic Systems

The phenomenon of Anderson localization of waves in elastic systems is studied. We analyze this phenomenon in two different set of systems: disordered linear chains of harmonic oscillators and disordered rods which oscillate with torsional waves. The first set is analyzed numerically whereas the second one is studied both experimentally and theoretically. In particular, we discuss the localization properties of the waves as a function of the frequency. In doing that we have used the inverse participation ratio, which is related to the localization length. We find that the normal modes localize exponentially according to Anderson theory. In the elastic systems, the localization length decreases with frequency. This behavior is in contrast with what happens in analogous quantum mechanical systems, for which the localization length grows with energy. This difference is explained by means of the properties of the re ection coefficient of a single scatterer in each case.Comment: 15 pages, 10 figure

Correlation Effects in Side-Coupled Quantum Dots

Using Wilson's numerical renormalization group (NRG) technique we compute zero-bias conductance and various correlation functions of a double quantum dot (DQD) system. We present different regimes within a phase diagram of the DQD system. By introducing a negative Hubbard U on one of the quantum dots, we simulate the effect of electron-phonon coupling and explore the properties of the coexisting spin and charge Kondo state. In a triple quantum dot (TQD) system a multi-stage Kondo effect appears where localized moments on quantum dots are screened successively at exponentially distinct Kondo temperatures.Comment: 13 pages, 10 figure

Effectiveness of wetting agents for irrigating sandy soils

Soil hydrophobia, or water repellency, in the coarse sand typical of the Swan Coastal Plain in Perth in Western Australia is common, leading to reduced ater infiltration. The main practice recommended to alleviate water repellency is the use of wetting agents, most of which are surfactantbased. Five commercial wetting agents were evaluated for their effects on water infiltration into samples of native sandy soils. Capillary rise and double-ring infiltrometer methods were used for this purpose. The infiltration of water was somewhat improved with the application of wetting agents, but this was short-lived and, when measured a few days later, was similar to or lower than the infiltration in the untreated sand. These findings raise questions on the efficiency of surfactantbased wetting agents to treat waterrepellent soils. Further investigation into the interaction and adsorption between surfactants and soil particles is needed. Keywords: Wetting agents, water repellent soils, infiltration, capillary rise

Optimasi Parameter Mesin Laser Cutting Terhadap Kekasaran Dan Laju Pemotongan Pada Sus 316l Menggunakan Taguchi Grey Relational Analysis Method

Parameter optimization is used in manufacturing as an indicator to produce the best manufacturing product. This paper studies an optimization parameters of CNC laser cutting such as focus of laser beam, pressure cutting gases and cutting speed for reducing variation of surface roughness and cutting rate on material SUS 316L. Based on L9(34) orthogonal array parameters, it is analized using ANOVA based on Taguchi method. In order to optimaze the minimum surface roughness and maximum cutting rate in laser cutting process, it is used Grey relational analysis. The confirmation experiments used to validate the optimal results that has done by Taguchi method. The results show that the Taguchi Grey relational analysis is being effective to optimize the machining parameters for laser cutting process with two responses

Polaron effect on Raman scattering in semiconductor quantum dots

Strong coupling of a confined exciton to optical phonons in semiconductor quantum dots (QDs) leading to the formation of a polaron is considered for a model system including two lowest exciton states and several optical phonon modes. Both intra- and inter-level terms are taken into account. The Hamiltonian has been exactly diagonalized including a finite number of phonons allowed for each mode, large enough to guarantee that the result can be considered exact in the physically important region of energies. Based on this polaron spectrum, the Raman scattering probability is obtained, which is compared with the one calculated using the standard perturbation theory approach. It is shown that, when either diagonal or non-diagonal coupling is sufficiently strong, the Raman spectrum line shape and especially its resonant behaviour differ considerably from the perturbation theory predictions. The dependence of the scattering intensity on the excitation wavelength contains features similar to those expected in the optical absorption spectra of QDs