Detailed analysis and test correlation of a stiffened composite wing panel

Nonlinear finite element analysis techniques are evaluated by applying them to a realistic aircraft structural component. A wing panel from the V-22 tiltrotor aircraft is chosen because it is a typical modern aircraft structural component for which there is experimental data for comparison of results. From blueprints and drawings supplied by the Bell Helicopter Textron Corporation, a very detailed finite element model containing 2284 9-node Assumed Natural-Coordinate Strain (ANS) elements was generated. A novel solution strategy which accounts for geometric nonlinearity through the use of corotating element reference frames and nonlinear strain displacements relations is used to analyze this detailed model. Results from linear analyses using the same finite element model are presented in order to illustrate the advantages and costs of the nonlinear analysis as compared with the more traditional linear analysis. Strain predictions from both the linear and nonlinear stress analyses are shown to compare well with experimental data up through the Design Ultimate Load (DUL) of the panel. However, due to the extreme nonlinear response of the panel, the linear analysis was not accurate at loads above the DUL. The nonlinear analysis more accurately predicted the strain at high values of applied load, and even predicted complicated nonlinear response characteristics, such as load reversals, at the observed failure load of the test panel. In order to understand the failure mechanism of the panel, buckling and first ply failure analyses were performed. The buckling load was 17 percent above the observed failure load while first ply failure analyses indicated significant material damage at and below the observed failure load

Apparatus and method of capturing an orbiting spacecraft

Apparatus and a method of capturing an orbiting spacecraft by attaching a grapple fixture are discussed. A probe is inserted into an opening, such as a rocket nozzle, in the spacecraft until a stop on the prove mechanism contacts the spacecraft. A lever is actuated releasing a spring loaded rod which moves axially along the probe removing a covering sleeve to expose spring loaded toffle fingers which pivot open engaging the side of the opening. The probe is shortened and tensioned by turning a screw thread, pressing the fingers inside of the opening to compress the spacecraft between the toggle fingers and the stop. A grapple fixture attached to the probe, which is thus secured to the spacecraft, is engaged by appropriate retrieval means such as a remote manipulator arm

Do We Expect Most AGN to Live in Disks?

Recent observations have indicated that a large fraction of the low to intermediate luminosity AGN population lives in disk-dominated hosts, while the more luminous quasars live in bulge-dominated hosts, in conflict with some previous model predictions. We therefore build and compare a semi-empirical model for AGN fueling which accounts for both merger and non-merger 'triggering.' In particular, we show that the 'stochastic accretion' model - in which fueling in disk galaxies is essentially a random process arising whenever dense gas clouds reach the nucleus - provides a good match to the present observations at low/intermediate luminosities. However it falls short of the high-luminosity population. We combine this with models for major merger-induced AGN fueling, which lead to rarer but more luminous events, and predict the resulting abundance of disk-dominated and bulge-dominated AGN host galaxies as a function of luminosity and redshift. We compile and compare observational constraints from z~0-2. The models and observations generically show a transition from disk to bulge dominance in hosts near the Seyfert-quasar transition, at all redshifts. 'Stochastic' fueling dominates AGN by number (dominant at low luminosity), and dominates BH growth below the knee in the present-day BH mass function (<10^7 M_sun). However it accounts for just ~10% of BH mass growth at masses >10^8 M_sun. In total, fueling in disky hosts accounts for ~30% of the total AGN luminosity density/BH mass density. The combined model also accurately predicts the AGN luminosity function and clustering/bias as a function of luminosity and redshift; however, we argue that these are not sensitive probes of BH fueling mechanisms.Comment: 13 pages, 5 figures, PDF updated to match published versio

MANURE HANDLING COSTS AND THE COMPETITIVENESS OF PORK PRODUCTION

Simulations of possible regulation-related manure handling costs are compared to base scenario costs for the three main regions and phases of modern hog production over widely varying scale levels. The base scenario confirms previous research suggesting that in Iowa net benefits occur at small scale levels from injecting slurry stored in an outside earthern basin for corn production using a phosphorus standard. Increased transportation costs result in Iowa costs surpassing costs in Utah at higher scale levels, while costs in North Carolina are highest at all scale levels. Requiring systems to be lined and covered in Iowa and North Carolina results in proportionately greater increased costs per head in North Carolina. Adding the requirement that manure be applied according to a phosphorus standard increases costs proportionately more in Iowa at larger scale levels, but not at all at the smallest scale, and costs in Iowa surpass those in North Carolina at the largest scale. The results of all scenarios underscore the advantages enjoyed by Utah in manure handling because scales of operation there are among the largest.Livestock Production/Industries,

WELFARE IMPLICATIONS OF THE WOOL ACT

A model of the U.S. sheep industry is estimated and simulated to determine the impact of the wool incentive program on actors in U.S. sheep product markets. The simulation analysis indicates that U.S. sheep producers and lamb and wool consumers are the programÂ’s gainers while lamb and wool exporters and taxpayers are its losers. Net societal losses averaged $26.4 million per year during the 1980-85 period, considering U.S. as well as exporter interests. This loss is about 2.5% of average U.S. consumer expenditures on lamb and wool over the period.Agricultural and Food Policy, Livestock Production/Industries,

The Evolution of Reaction-diffusion Controllers for Minimally Cognitive Agents

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Large and realistic models of Amorphous Silicon

Amorphous silicon (a-Si) models are analyzed for structural, electronic and vibrational characteristics. Several models of various sizes have been computationally fabricated for this analysis. It is shown that a recently developed structural modeling algorithm known as force-enhanced atomic refinement (FEAR) provides results in agreement with experimental neutron and x-ray diffraction data while producing a total energy below conventional schemes. We also show that a large model (500 atoms) and a complete basis is necessary to properly describe vibrational and thermal properties. We compute the density for a-Si, and compare with experimental results