Vibrational dynamics of solid poly(ethylene oxide)

Molecular dynamics (MD) simulations of crystalline poly(ethylene oxide) (PEO) have been carried out in order to study its vibrational properties. The vibrational density of states has been calculated using a normal mode analysis (NMA) and also through the velocity autocorrelation function of the atoms. Results agree well with experimental spectroscopic data. System size effects in the crystalline state, studied through a comparison between results for 16 unit cells and that for one unit cell has shown important differences in the features below 100 cm^-1. Effects of interchain interactions are examined by a comparison of the spectra in the condensed state to that obtained for an isolated oligomer of ethylene oxide. Calculations of the local character of the modes indicate the presence of collective excitations for frequencies lower than 100 cm^-1, in which around 8 to 12 successive atoms of the polymer backbone participate. The backbone twisting of helical chains about their long axes is dominant in these low frequency modes.Comment: 19 pages, 7 figures (Phys.Rev.B submitted on 28.11.2002) Revised versio

Response of tall steel buildings in southern California to the magnitude 7.8 shakeout scenario earthquake

Currently, there is a significant campaign being undertaken in southern California to increase public awareness and readiness for the next large earthquake along the San Andreas Fault, culminating in a large-scale earthquake response exercise. The USGS ShakeOut scenario is a key element to understanding the likely effects of such an event. A source model for a M7.8 scenario earthquake has been created (Hudnet et al. 2007), and used in conjunction with a velocity model for southern California to generate simulated ground motions for the event throughout the region (Graves et al. 2008). We were charged by the USGS to provide one plausible realization of the effects of the scenario event on tall steel moment-frame buildings. We have used the simulated ground motions with three-dimensional non-linear finite element models of three buildings (in two orthogonal orientations and two different connection fragility conditions, for a total of twelve cases) in the 20-story class to simulate structural responses at 784 analysis sites spaced at approximately 4 km throughout the San Fernando Valley, the San Gabriel Valley and the Los Angeles Basin. Based on the simulation results and available information on the number and distribution of steel buildings, we have recommended that the ShakeOut drill be planned with a damage scenario comprising of 5% of the estimated 150 steel moment frame structures in the 10-30 story range collapsing (8 collapses), 10% of the structures red-tagged (16 red-tagged buildings), 15% of the structures with damage serious enough to cause loss of life (24 buildings with fatalities), and 20% of the structures with visible damage requiring building closure (32 buildings with visible damage and possible injuries). This paper details the analytical study underlying these recommendations

Structure of solid monolayers and multilayers of n-hexane on graphite

We present all-atom molecular dynamics simulations of n-hexane on the basal plane of graphite at monolayer and multilayer coverages. In keeping with experimental data, we find the presence of ordered adsorbed layers both at single monolayer coverage and when the adsorbed layer coexists with excess liquid adsorbate. Using a simulation method that does not impose any particular periodicity on the adsorbed layer, we quantitatively compare our results to the results of neutron diffraction experiments and find a structural transition from a uniaxially incommensurate lattice to a fully commensurate structure on increasing the coverage from a monolayer to a multilayer. The zig-zag backbone planes of all the alkane molecules lie parallel to the graphite surface at the multilayer coverage, while a few molecules are observed to attain the perpendicular orientation at monolayer coverage

An Experimental Investigation of Performance and Emission in Ethanol Fuelled Direct Injection Internal Combustion Engines with Zirconia Coating

This article presents the experimental investigation of use of neat ethanol (95% Ethanol +5% water) as a fuel in a four stroke single cylinder engine as regards to performance and emission characteristics. Two different ignition modes viz. (i) High Compression (16.5:1) Spark Ignition with high-pressure manifold injection of ethanol and (ii) Ultra High Compression (44.4:1) Compress Ignition with Direct Injection of ethanol have been experimentally analyzed with and without zirconia surface coating. As a benchmark, the results have been compared with data from the same engine run with diesel as fuel. In the first mode, the brake thermal efficiency with ethanol as fuel was found almost equal to that of diesel. However, the emissions were found to be significantly lower. In the second mode, the brake thermal efficiency was found to fall in between the diesel and ethanol manifold injection modes of operation. More significantly, the cost of running the engine was found to be lower than the operating cost incurred by using diesel. This assumes importance in the wake that ethanol can be obtained from non-fossil resources

Leveraging Global Resources: A Process Maturity Framework for Managing Distributed Software Product Development

Distributed software development is pervasive in the software industry as companies vie to leverage global resources. However popular quality and process frameworks do not specifically address the key processes needed for managing distributed software development. We develop an evolutionary process maturity framework for globally distributed software development that incorporates 24 new key process areas essential for managing distributed software product development We test the validity of our process framework using data collected from more than sixty large, distributed enterprise product development projects. We believe we have laid new ground for software process research by extending generic quality process frameworks to address the distributed development scenario

Synthesis of polythiophene n-type and p-type doping and compensation

The synthesis of pdythiophene leading to the formation of n-type potythiophene, p-type polythiophene and neutral polythiophene has been investigated through electropolymerization with different dopant ions. The influence of doping level over conductivity of the polymer matrix has also been studied which reveals that a preselected room temperature conductivity can easily be imparted to the parent polymer chain. It has also been found that the compensation of one type of conductivity over other occurs during the process of dedoping and redopin

Magnetic and FMR study on CoFe₂O₄/ZnFe₂O₄ bilayers

CoFe<sub>2</sub>O<sub>4</sub>/ZnFe<sub>2</sub>O<sub>4</sub> bilayers were deposited by the pulsed laser deposition on amorphous fused quartz substrate at substrate temperature of 350°C and in oxygen pressure of 0.16 mbar. The films were studied after ex-situ annealing for 2 h in air at various temperatures up to 650°C. The magnetic properties of the bilayers were studied at 300 K and at 10 K. Ferromagnetic resonance was carried out at x-band frequencies at room temperature. It was found that as a result of annealing, the diffusion between Co ferrite and Zn ferrite starts around 350°C and leads to a large line width system having magnetization, which remains undetected by Ferromagnetic resonance