Research in nonlinear structural and solid mechanics

Recent and projected advances in applied mechanics, numerical analysis, computer hardware and engineering software, and their impact on modeling and solution techniques in nonlinear structural and solid mechanics are discussed. The fields covered are rapidly changing and are strongly impacted by current and projected advances in computer hardware. To foster effective development of the technology perceptions on computing systems and nonlinear analysis software systems are presented

What blows in with the wind?

The shift toward renewable forms of energy for electricity generation in the electricity generation industry has clear implications for the spatial distribution of generating plant. Traditional forms of generation are typically located close to the load or population centers, while wind and solar-powered generation must be located where the energy source is found. In the case of wind, this has meant significant new investment in wind plant in primarily rural areas that have been in secular economic decline. This paper investigates the localized economic impacts of the rapid increase in wind power capacity at the county level in Texas. Unlike Input-Output impact analysis that relies primarily on levels of inputs to estimate gross impacts, we use traditional econometric methods to estimate net localized impacts in terms of employment, personal income, and property tax base. While we find evidence that both direct and indirect employment impacts are modest, significant increases in per capita income accompany wind power development. County and school property tax rolls also realize important benefits from the local siting of utility scale wind power

Structures and materials technology for hypersonic aerospacecraft

Major considerations in structural design of a transatmospheric aerospacecraft are discussed. The general direction of progress in structures and materials technology is indicated, and technical areas in structures and materials where further research and development is necessary are indicated. Various structural concepts under study and materials which appear to be most applicable are discussed. Structural design criteria are discussed with particular attention to the factor-of-safety approach and the probabilistic approach. Structural certification requirements for the aerospacecraft are discussed. The kinds of analyses and tests which would be required to certify the structural integrity, safety, and durability of the aerospacecraft are discussed, and the type of test facility needed to perform structural certification tests is identified

Geographic concentration and firm survival

If localization economies are present, firms within denser industry concentrations should exhibit higher levels of performance than more isolated firms. Nevertheless, research in industrial organization that has focused on the influences on firm survival has largely ignored the potential effects from agglomeration. Recent studies in urban and regional economics suggests that agglomeration effects may be very localized. Analyses of industry concentration at the MSA or county-level may fail to detect important elements of intra-industry firm interaction that occur at the sub-MSA level. Using a highly detailed dataset on firm locations and characteristics for Texas, this paper analyses agglomeration effects on firm survival over geographic areas as small as a single mile radius. We find that greater firm density within very close proximity (within 1 mile) of firms in the same industry increases mortality rates while greater concentration over larger distances reduces mortality rates.Firm Survival, Agglomeration, Localization, and Knowledge Externalities

Research universities and regional high-tech firm start-ups and exit

If localized knowledge spillovers are present in the university setting, higher rates of both start-ups and/or survival than in the broader economy would be observed in areas that are geographically proximate to the university. Using a fully-disclosed Quarterly Census of Employment and Wages for Texas for the years 1999:3-2006:2, this paper analyzes start-ups and exit rates for high-tech firms in Texas. We find that there is evidence that the presence of a research institution will affect the likelihood of technology start-ups. However, results suggest that geographic proximity to knowledge centers does not reduce hazard rates.Entry and Survival, R & D, Regional, Urban, and Rural Analyses

A comparison of the in vitro and in planta responses of Phytophthora cinnamomi isolates to phosphite

Research in plant pathology often relies on testing interactions between a fungicide and a pathogen in vitro and extrapolating from these results what may happen in planta. Likewise, results from glasshouse experiments are used to estimate what will happen if the fungicide is applied in the field. However, it is difficult to obtain conditions in vitro and in the glasshouse which reflect the conditions where the fungicide may eventually be used, in the field. The aim of this paper is to compare results of the effect of phosphite on P. cinnamomi isolates in vitro and in planta

Classical and quantum regimes of the superfluid turbulence

We argue that turbulence in superfluids is governed by two dimensionless parameters. One of them is the intrinsic parameter q which characterizes the friction forces acting on a vortex moving with respect to the heat bath, with 1/q playing the same role as the Reynolds number Re=UR/\nu in classical hydrodynamics. It marks the transition between the "laminar" and turbulent regimes of vortex dynamics. The developed turbulence described by Kolmogorov cascade occurs when Re >> 1 in classical hydrodynamics, and q << 1 in the superfluid hydrodynamics. Another parameter of the superfluid turbulence is the superfluid Reynolds number Re_s=UR/\kappa, which contains the circulation quantum \kappa characterizing quantized vorticity in superfluids. This parameter may regulate the crossover or transition between two classes of superfluid turbulence: (i) the classical regime of Kolmogorov cascade where vortices are locally polarized and the quantization of vorticity is not important; and (ii) the quantum Vinen turbulence whose properties are determined by the quantization of vorticity. The phase diagram of the dynamical vortex states is suggested.Comment: 12 pages, 1 figure, version accepted in JETP Letter

Trajectory structures and transport

The special problem of transport in 2-dimensional divergence-free stochastic velocity fields is studied by developing a statistical approach, the nested subensemble method. The nonlinear process of trapping determined by such fields generates trajectory structures whose statistical characteristics are determined. These structures strongly influence the transport.Comment: Latex file 19 pages, includes 12 EPS figures. Extended version of the invited talk at the ITCPP, Santorini, 200