Investigation of a ship's propeller jet using momentum decay and energy decay

Previous researchers use the velocity decay as an input to investigate the ship’s propeller jet induced scour. A researcher indicated that most of the equations used to predict the stability of various protection systems are often missing a physical background. The momentum decay and energy decay are currently proposed as an initial input for seabed scouring investigation, which are more sensible in physics. Computational fluid dynamics (CFD) and laser Doppler anemometry (LDA) experiments are used to obtain the velocity data and then transforming into momentum and energy decays. The findings proposed several exponential equations of velocity, momentum and energy decays to estimate the region exposed to the seabed scouring.

Local Storage Meets Local Demand: A Technical Solution to Future Power Distribution System

Future power systems are expected to integrate large-scale stochastic and intermittent generation and load due to reduced use of fossil fuel resources, including renewable energy sources (RES) and electric vehicles (EV). Inclusion of such resources poses challenges for the dynamic stability of synchronous transmission and distribution networks, not least in terms of generation where system inertia may not be wholly governed by large-scale generation but displaced by small-scale and localised generation. Energy storage systems (ESS) can limit the impact of dispersed and distributed generation by offering supporting reserve while accommodating large-scale EV connection; the latter (load) also participating in storage provision. In this paper, a local energy storage system (LESS) is proposed. The structure, requirement and optimal sizing of the LESS are discussed. Three operating modes are detailed, including: 1) storage pack management; 2) normal operation; and 3) contingency operation. The proposed LESS scheme is evaluated using simulation studies based on data obtained from the Northern Ireland regional and residential network.

Density functional and Monte Carlo studies of sulfur. I. Structure and bonding in S-n rings and chains (n=2-18) (vol 118, pg 9257, 2003)

Density functional calculations have been performed for ring isomers of sulfur with up to 18 atoms, and for chains with up to ten atoms. There are many isomers of both types, and the calculations predict the existence of new forms. Larger rings and chains are very flexible, with numerous local energy minima. Apart from a small, but consistent overestimate in the bond lengths, the results reproduce experimental structures where known. Calculations are also performed on the energy surfaces of S8 rings, on the interaction between a pair of such rings, and the reaction between one S8 ring and the triplet diradical S8 chain. The results for potential energies, vibrational frequencies, and reaction mechanisms in sulfur rings and chains provide essential ingredients for Monte Carlo simulations of the liquid–liquid phase transition. The results of these simulations will be presented in Part II.

Population-based local search for protein folding simulation in the MJ energy model and cubic lattices

We present experimental results on benchmark problems in 3D cubic lattice structures with the Miyazawa-Jernigan energy function for two local search procedures that utilise the pull-move set: (i) population-based local search (PLS) that traverses the energy landscape with greedy steps towards (potential) local minima followed by upward steps up to a certain level of the objective function; (ii) simulated annealing with a logarithmic cooling schedule (LSA). The parameter settings for PLS are derived from short LSA-runs executed in pre-processing and the procedure utilises tabu lists generated for each member of the population. In terms of the total number of energy function evaluations both methods perform equally well, however. PLS has the potential of being parallelised with an expected speed-up in the region of the population size. Furthermore, both methods require a significant smaller number of function evaluations when compared to Monte Carlo simulations with kink-jump moves. (C) 2009 Elsevier Ltd. All rights reserved.

Shell Model Study of Local and Global Energy Barriers in KDP

We perform a study of the energetics of KH2PO4 (KDP) by using a shell model (SM) which was constructed by adjusting the interaction parameters to ab initio calculations, and was fitted to reproduce phonons, polarization-inversion energies and structural properties. We calculate the energy profiles by performing global displacements and local distortions following the ferroelectric (FE) mode pattern in clusters of different sizes embedded in a paraelectric (PE) phase matrix. These properties are expected to be relevant to the PE-FE phase transition. The obtained SM results are compared to corresponding ab initio (AI) data. The global instabilities are found in good agreement for both KDP and DKDP. We also find qualitative good agreement in the KDP structure and even quantitative agreement in the expanded DKDP structure for the local distortions. The SM results reproduce well different trends like increasing instabilities as the cluster sizes grows, as the heavier atoms are included, and as the volume is increased, in accordance with the corresponding data from AI calculations.

Theory of the near K-edge structure in electron energy loss spectroscopy

Arguments are given that lead to a formalism for calculating near K-edge structure in electron energy loss spectroscopy (EELS). This is essentially a one electron picture, while many body effects may be introduced at different levels, such as the local density approximation to density functional theory or the GW approximation to the electron self-energy. Calculations are made within the all electron LMTO scheme in crystals with complex atomic and electronic structures, and these are compared with experiment. (c) 2004 Elsevier B.V. All rights reserved.

Electron energy-loss near-edge shape as a probe to investigate the stabilization of yttria-stabilized zirconia

The electron energy-loss near-edge structure (ELNES) at the O K edge has been studied in yttria-stabilized zirconia (YSZ). The electronic structure of YSZ for compositions between 3 and 15 mol % Y2O3 has been computed using a pseudopotential-based technique to calculate the local relaxations near the O vacancies. The results showed phase transition from the tetragonal to cubic YSZ at 10 mol % of Y2O3, reproducing experimental observations. Using the relaxed defect geometry, calculation of the ELNES was carried out using the full-potential linear muffin-tin orbital method. The results show very good agreement with the experimental O K-edge signal, demonstrating the power of using ELNES to probe the stabilization mechanism in doped metal oxides.

The near-edge structure in energy-loss spectroscopy: many-electron and magnetic effects in transition metal nitrides and carbides

We investigate the ability of the local density approximation (LDA) in density functional theory to predict the near-edge structure in electron energy-loss spectroscopy in the dipole approximation. We include screening of the core hole within the LDA using Slater's transition state theory. We find that anion K-edge threshold energies are systematically overestimated by 4.22 +/- 0.44 eV in twelve transition metal carbides and nitrides in the rock-salt (B1) structure. When we apply this 'universal' many-electron correction to energy-loss spectra calculated within the transition state approximation to LDA, we find quantitative agreement with experiment to within one or two eV for TiC, TiN and VN. We compare our calculations to a simpler approach using a projected Mulliken density which honours the dipole selection rule, in place of the dipole matrix element itself. We find remarkably close agreement between these two approaches. Finally, we show an anomaly in the near-edge structure in CrN to be due to magnetic structure. In particular, we find that the N K edge in fact probes the magnetic moments and alignments of ther sublattice.

Light emission from scanning tunnelling microscope on polycrystalline Au films - what is happening at the single-grain level?

When operated with a metallic tip and sample the scanning tunnelling microscope constitutes a nanoscale, plasmonic light source yielding broadband emission up to a photon energy determined by the applied bias. The emission is due to tunnelling electron excitation and subsequent radiative decay of localized plasmon modes, which can be on the lateral scale of a single metal grain (similar to 25 nm) or less. For a Au-tip/Au-polycrystalline sample under ambient conditions it is found that the intensity and spectral content of the emitted light are not dependent on the lateral grain dimension, but are predominantly determined by the tip geometry. However, the intensity increases strongly with increasing film thickness (grain depth) up to 20-25 nm or approximately the skin depth of the Au film. Photon maps can show less emissive grains and two classes of this occurrence are distinguished. The first is geometrical in origin - a double-tip structure in this case - while the second is due to a contamination-induced lowering of the local work function that causes the tunnel gap to increase. It is suggested that differences in work-function lowering between grains presenting different crystalline facets, combined with an exponential decay in emitted light intensity with tip - sample distance, leads to grain contrast. These results are relevant to tip-enhanced Raman scattering and the fabrication of micro/nano-scale planar, light-emitting tunnel devices.

Post-depositional modification of atmospheric dust on a granite building in central Rio de Janeiro: implications for surface induration and subsequent stone decay

Extensive contour scaling of a 200 year old granite church is associated with the breaching of an apparently iron-rich crust and the widespread deposition of atmospheric dust within the canyon-like streetscape of Rio de Janeiro. Contemporary dust, accumulated dust from within the a depression on the building surface, the surface crust and the underlying granite are examined by a combination of total element analysis and sequential extraction, X-ray diffraction and energy dispersive X-ray fluorescence. Results indicate an increase in total organic carbon and a marked decrease in pH within the accumulated dust, and a rapid mobilization of anions and cations from the water-soluble and carbonate phases. It is considered that the latter is linked to salt accumulation within and eventual salt weathering of the granite. Post-depositional alteration of the dust is also linked with the de-silicification of clay minerals (Illite to kaolinite) and the loss of silica from the amorphous Fe/Mn phase of the accumulated dust under the initially saline and progressively more acidic conditions experienced at the stone - atmosphere interface. This mobilization of silica is associated with the formation of what is, in effect, a thin silica-rich surface crust or glaze. Within the glaze, assessory amounts of extractable iron are concentrated within the amorphous and crystalline Fe/Mn phases at levels that are significantly elevated with respect to the underlying granite, but much lower than the equivalent phases of the accumulated dust from which it is principally assumed to derive. The protection afforded to the stone work by the crust is not, however, permanent and within the last 15 years it has been possible to observe a rapid increase in the surface delamination of the church close to street level.

Cool Rationalities and Hot Air: A Rhetorical Approach to Understanding Debates on Renewable Energy.

A key obstacle to the wide-scale development of renewable energy is that public acceptability of wind energy cannot be taken for granted when wind energy moves from abstract support to local implementation. Drawing on a case study of opposition to the siting of a proposed off-shore wind farm in Northern Ireland, we offer a rhetorical analysis of a series of representative documents drawn from government, media, pro- and anti-wind energy sources, which identifies and interprets a number of discourses of objection and support. The analysis indicates that the key issue in terms of the transition to a renewable energy economy has little to do with the technology itself. Understanding the different nuances of pro- and anti-wind energy discourses highlights the importance of thinking about new ways of looking at these conflicts. These include adopting a “conflict resolution” approach and “upstreaming” public involvement in the decision-making process and also the counter-productive strategy of assuming that objection is based on ignorance (which can be solved by information) or NIMBY thinking (which can be solved by moral arguments about overcoming “free riders”).

Comparative seasonal acclimatization of food and energy consumption in adjacent populations of common spiny mice (Acomys cahirinus)

Animals inhabiting environments with low productivity and food availability commonly have reduced energy demands and increased digestive efficiencies. The dry matter intake (DMI), apparent digestible dry matter (ADDM), digestible efficiency (DE) and digestible energy intake (DEI) of two populations of common spiny mouse Acomys cahirinus were compared during both winter and summer under conditions of simulated water stress. Mice were captured from the north- and south-facing slopes (NFS and SFS) of the same canyon that represent mesic and xeric habitats, respectively. Measured variables were also compared between F-1 mice that had been born to either NFS or SFS mice, and raised in the laboratory. SFS mice were able to assimilate energy more efficiently than NFS mice during the summer. By comparison, NFS mice were able to assimilate more energy during the winter. During winter, NFS mice assimilated more energy at low levels of water stress, whereas SFS mice assimilated more energy at higher levels. Differences were also apparent in F-1 mice. It is therefore suggested that local climatic conditions can impose physiological adaptations that are retained in succeeding generations, creating unique meta-populations.

General local and rectilinear vibrational coordinates consistent with Eckart's conditions

We present a general method to construct a set of local rectilinear vibrational coordinates for a nonlinear molecule whose reference structure does not necessarily correspond to a stationary point of the potential-energy surface. We show both analytically and with a numerical example that the vibrational coordinates satisfy Eckart's conditions. In addition, we find that the Watson Hamiltonian provides a fairly robust description even of highly excited vibrational states of triatomic molecules, except for a few states of large amplitude motion sampling the singular region of the Hamiltonian. These states can be identified through slow convergence.

Local Conentration of Waves due to Abrupt Alongshore Variation of Nearshore Bathymetry

Small-scale physical and numerical experiments were conducted to investigate the local concentration of waves (monochromatic and group) due to abrupt change of nearshore bathymetry in alongshore direction. Wave run-up motions along the shoreline were measured using an image analysis technique to compare localized concentration of wave energy, when waves propagate a over bathymetry composing rhythmic patterns of mild/steep slope bottom configurations. Measured alongshore variation of maximum wave run-up heights showed significant peak near the boundary, which has sudden alongshore change of depth, both under monochromatic and group wave trains. This phenomenon is found to be due to interaction of waves with neashore currents, which is further enhanced by excitation of long wave components by breaking of group waves. Furthermore, this paper discusses results of preliminary experiments carried out to test the effectiveness of several shore protection structure layouts in mitigating such wave concentrations. Numerical simulations were performed by using a model developed based on Nwogu (1993) Boussinesq-type equations; coupled with a transport equation to model energy dissipation due to wave breaking.