6,498 research outputs found

    The Spectroscopy and Molecular Dynamics of the High Frequency ν1 6 Intermolecular Vibrations in HCN‐‐‐HF and DCN‐‐‐DF

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    Gas phase rovibrational analysis of the high frequency intermolecular hydrogen bonded bending overtone 2ν0 6 [ν0=1132.4783(2) cm− 1] in HCN‐‐‐HF and its corresponding perdeuterated fundamental ν1 6 [ν0=409.1660(2) cm− 1] are reported. Evaluated rovibrational parameters provide the basis for quantitative modeling of the molecular dynamics associated with this vibration. A quantum mechanical calculation permits determination of the quadratic and quartic force constants K 6 6=537(17) and K 6 6 6 6=4.98(12) cm− 1 which in turn are used to estimate the pertinent cubic band stretching interaction constants K 4 6 6=−149.3(50) cm− 1 and account for the unexpected behavior in the rotational constantB 1 6. Second order expansion of the vibrational term energies, give X 4 6=−21.61(2), X 6 7=−7.694(1), X 6 6=−14.84(90), g 6 6=−31.04(90) cm− 1, neglecting corrections for Fermi resonance. The common isotopic species equilibrium rotational constantB e is evaluated to be 3681.1(11) MHz

    Incoherent Transport through Molecules on Silicon in the vicinity of a Dangling Bond

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    We theoretically study the effect of a localized unpaired dangling bond (DB) on occupied molecular orbital conduction through a styrene molecule bonded to a n++ H:Si(001)-(2x1) surface. For molecules relatively far from the DB, we find good agreement with the reported experiment using a model that accounts for the electrostatic contribution of the DB, provided we include some dephasing due to low lying phonon modes. However, for molecules within 10 angstrom to the DB, we have to include electronic contribution as well along with higher dephasing to explain the transport features.Comment: 9 pages, 5 figure

    Extended Huckel theory for bandstructure, chemistry, and transport. II. Silicon

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    In this second paper, we develop transferable semi-empirical parameters for the technologically important material, silicon, using Extended Huckel Theory (EHT) to calculate its electronic structure. The EHT-parameters areoptimized to experimental target values of the band dispersion of bulk-silicon. We obtain a very good quantitative match to the bandstructure characteristics such as bandedges and effective masses, which are competitive with the values obtained within an sp3d5s∗sp^3 d^5 s^* orthogonal-tight binding model for silicon. The transferability of the parameters is investigated applying them to different physical and chemical environments by calculating the bandstructure of two reconstructed surfaces with different orientations: Si(100) (2x1) and Si(111) (2x1). The reproduced π\pi- and π∗\pi^*-surface bands agree in part quantitatively with DFT-GW calculations and PES/IPES experiments demonstrating their robustness to environmental changes. We further apply the silicon parameters to describe the 1D band dispersion of a unrelaxed rectangular silicon nanowire (SiNW) and demonstrate the EHT-approach of surface passivation using hydrogen. Our EHT-parameters thus provide a quantitative model of bulk-silicon and silicon-based materials such as contacts and surfaces, which are essential ingredients towards a quantitative quantum transport simulation through silicon-based heterostructures.Comment: 9 pages, 9 figure

    Determination of Dissociation Energies and Thermal Functions of Hydrogen‐bond Formation using High Resolution FTIR Spectroscopy

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    A technique which employs high resolution Fourier transform infrared spectroscopy is demonstrated for evaluation of hydrogen bonddissociation energiesD 0 and D e . Results for HCN‐‐HF give a D 0=20.77(22) and D e =28.77(45) kJ/mol which are compared with previously determined values obtained from microwave absolute intensity measurements and a b i n i t i o molecular orbital calculations. Rovibrational band information available for HCN‐‐HF also permits evaluation of thermal functions of dimer formation in kJ/mol: ΔU ○ 298.2 =20.1(2), ΔH ○ 298.2 =22.6(2), ΔG ○ 298.2 =59.4(2), ΔS ○ 298.2 =−0.1235

    Comparison of Kansei Engineering and AttrakDiff to Evaluate Kitchen Products

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    Kansei Engineering can be used to create scales to measure perceptions and evaluations of products in a particular context. To what extent do specifically constructed Kansei scales reveal more information about a product than a more generic, prestructured instrument, such as AttrakDiff? This case study identified relevant affective and pragmatic Kansei attributes that influence the purchase of a range hood (cooker hood). 102 customers rated the extent to which each of 10 range hoods possessed these attributes. In addition, AttrakDiff was used to measure hedonic and pragmatic quality perceptions. There was a general high correspondence between AttrakDiff and Kansei. While Kansei provided richer and more specific feedback, it was more resource intensive to carry out

    Milk lipid globules: control of their size distribution.

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    UK Large-scale Wind Power Programme from 1970 to 1990: the Carmarthen Bay experiments and the Musgrove Vertical-Axis Turbines

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    This article describes the development of the Musgrove Vertical Axis Wind Turbine (VAWT) concept, the UK ‘Carmarthen Bay’ wind turbine test programme, and UK government’s wind power programme to 1990. One of the most significant developments in the story of British wind power occurred during the 1970s, 1980s, and 1990s, with the development of the Musgrove vertical axis wind turbine and its inclusion within the UK Government’s wind turbine test programme. Evolving from a supervisor’s idea for an undergraduate project at Reading University, the Musgrove VAWT was once seen as an able competitor to the horizontal axis wind systems that were also being encouraged at the time by both the UK government and the Central Electricity Generating Board, the then nationalised electricity utility for England and Wales. During the 1980s and 1990s the most developed Musgrove VAWT system, along with three other commercial turbine designs was tested at Carmarthen Bay, South Wales as part of a national wind power test programme. From these developmental tests, operational data was collected and lessons learnt, which were incorporated into subsequent wind power operations.http://dx.doi.org/10.1260/03095240677860621
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