Study of theoretical models for the liquid-vapor and metal-nonmetal transitions of alkali fluids

Theoretical models for the liquid-vapor and metal-nonmetal transitions of alkali fluids are investigated. Mean-field models are considered first but shown to be inadequate. An alternate approach is then studied in which each statistical configuration of the material is treated as inhomogeneous, with the energy of each ion being determined by its local environment. Nonadditive interactions, due to valence electron delocalization, are a crucial feature of the model. This alternate approach is implemented within a lattice-gas approximation which takes into account the observed mode of expansion in the materials of interest and which is able to treat the equilibrium density fluctuations. We have carried out grand canonical Monte Carlo simulations, for this model, which allow a unified, self-consistent, study of the structural, thermodynamic, and electronic properties of alkali fluids. Applications to Cs, Rb, K, and Na yield results in good agreement with observations.Comment: 13 pages, REVTEX, 10 ps figures available by e-mail

Adaptive Signal Processing Strategy for a Wind Farm System Fault Accommodation

In order to improve the availability of offshore wind farms, thus avoiding unplanned operation and maintenance costs, which can be high for offshore installations, the accommodation of faults in their earlier occurrence is fundamental. This paper addresses the design of an active fault tolerant control scheme that is applied to a wind park benchmark of nine wind turbines, based on their nonlinear models, as well as the wind and interactions between the wind turbines in the wind farm. Note that, due to the structure of the system and its control strategy, it can be considered as a fault tolerant cooperative control problem of an autonomous plant. The controller accommodation scheme provides the on-line estimate of the fault signals generated by nonlinear filters exploiting the nonlinear geometric approach to obtain estimates decoupled from both model uncertainty and the interactions among the turbines. This paper proposes also a data-driven approach to provide these disturbance terms in analytical forms, which are subsequently used for designing the nonlinear filters for fault estimation. This feature of the work, followed by the simpler solution relying on a data-driven approach, can represent the key point when on-line implementations are considered for a viable application of the proposed scheme

The internet, E-commerce and older people: an actor-network approach to researching reasons for adoption and use

Many older people are discovering the Internet, and some are also making good use of electronic commerce and all that goes with it. Others, however, are not adopting these technologies. This paper questions why some older people adopt Internet technologies while others do not, and offers a research framework, based on actor-network theory, for investigating adoption of Internet technologies by older people. In this paper, innovation translation is used to illustrate how specific cases of adoption have occurred. Innovation translation presents a different view of innovation than the better known theory of innovation diffusion, but one that the authors argue is better suited for research in socio-technical situations like this

The Scaled-Charge Additive Force Field for Amino Acid Based Ionic Liquids

Abstract. Ionic liquids (ILs) constitute an emerging field of research. New ILs are continuously introduced involving more and more organic and inorganic ions. Amino acid based ILs (AAILs) represent a specific interest due to their evolutional connection to proteins. We report a new non- polarizable force field (FF) for the eight AAILs comprising 1-ethyl-3-methylimidazolium cation and amino acid anions. The anions were obtained via deprotonation of carboxyl group. Specific cation-anion non-covalent interactions have been taken into account by computing electrostatic potential for ion pairs, in contrast to isolated ions. The van der Waals interactions have been transferred from the CHARMM36 FF with minor modifications. Therefore, compatibility between our parameters and CHARMM36 parameters is preserved. Our FF can be easily implemented using a variety of popular molecular dynamics programs. It will find broad applications in computational investigation of ILs

Gradual Disappearance of the Fermi Surface near the Metal-Insulator Transition in La1−x_{1-x}Srx_{x}MnO3_{3}

We report the first observation of changes in the electronic structure of La$_{1-x}$Sr$_{x}$MnO$_{3}$ (LSMO) across the filling-control metal-insulator (MI) transition by means of in situ angle-resolved photoemission spectroscopy (ARPES) of epitaxial thin films. The Fermi surface gradually disappears near the MI transition by transferring the spectral weight from the coherent band near the Fermi level ($E_{F}$) to the lower Hubbard band, whereas a pseudogap behavior also exists in the ARPES spectra in the close vicinity of $E_{F}$ for the metallic LSMO. These results indicate that the spectral weight transfer derived from strong electron-electron interaction dominates the gap formation in LSMO associated with the filling-control MI transition.Comment: 11 pages, 4 figure

Manifestation of lattice distortions in the O 1s spectra in Ca1-xSrxRuO3

We investigate the effect of temperature on the electronic and crystal structures of Ca1-xSrxRuO3 via the evolution of O 1s core level spectra as a function of temperature and composition, x. O 1s spectra in SrRuO3 exhibit a dominant sharp feature at all the temperatures with a small trace of impurity feature at higher binding energies. The spectra in Ca doped samples, however, exhibit two distinct features. Analysis of the experimental spectral functions and the band structure results suggest that different Madelung potential at the two types of oxygen sites in the orthorhombically distorted structure leads to such splitting in the O 1s spectra. Interestingly, the energy separation of these two features becomes smaller at low temperatures in the Ca dominated samples concomitant to the observation of non-Fermi liquid behavior in their bulk properties. Such temperature evolution, thus, indicates a direct connection of the lattice degrees of freedom with the electronic properties of these compounds.Comment: four figure

2-Nitrophenyl 4-nitrophenyl disulfide

Peer reviewedPublisher PD