Geometrically nonlinear analysis of adhesively bonded joints

A geometrically nonlinear finite element analysis of cohesive failure in typical joints is presented. Cracked-lap-shear joints were chosen for analysis. Results obtained from linear and nonlinear analysis show that nonlinear effects, due to large rotations, significantly affect the calculated mode 1, crack opening, and mode 2, inplane shear, strain-energy-release rates. The ratio of the mode 1 to mode 2 strain-energy-relase rates (G1/G2) was found to be strongly affected by he adhesive modulus and the adherend thickness. The ratios between 0.2 and 0.8 can be obtained by varying adherend thickness and using either a single or double cracked-lap-shear specimen configuration. Debond growth rate data, together with the analysis, indicate that mode 1 strain-energy-release rate governs debond growth. Results from the present analysis agree well with experimentally measured joint opening displacements

Incorporating Flexible Demand Systems in Empirical Models of Market Power

Measuring the degree of price coordination between firms in a differentiated products industry is particularly challenging because it is necessary to utilize a demand system that is sufficiently flexible, allows the imposition of theoretical restrictions, and allow for the derivation of the functional form of the corresponding price reaction functions. Previous research has relied on restrictive demand systems in order to maintain the tractability of the price reaction functions. The purpose of this paper is determine whether using more flexible demand systems can yield a set of first-order profit maximization conditions that are mathematically tractable and amendable to estimation. The demand systems considered are the Almost Ideal Demand System (AIDS), the Linear Approximate Almost Ideal Demand System (LAIDS), and the Rotterdam demand system. This paper also expands prior work on estimating brand level demand elasticities by endogenizing category level expenditures in the context of a weakly separable demand system. This yields some new and interesting insights for the measurement of market power in differentiated product industries. We show that while it is not possible to derive explicit price reaction functions for any of these demand systems, given certain assumptions, the Rotterdam demand system does yield an explicit set of profit maximization first-order conditions that can be estimated.Demand and Price Analysis,

Hyperfast Interstellar Travel in General Relativity

The problem is discussed of whether a traveller can reach a remote object and return back sooner than a photon would when taken into account that the traveller can partly control the geometry of his world. It is argued that under some reasonable assumptions in globally hyperbolic spacetimes the traveller cannot hasten reaching the destination. Nevertheless, it is perhaps possible for him to make an arbitrarily long round-trip within an arbitrarily short (from the point of view of a terrestrial observer) time.Comment: The final version, close to (but better than) what will be published in Phys. Rev. D. The explanatory part is made more detaile

Assessing the Effect of Stellar Companions from High-Resolution Imaging of Kepler Objects of Interest

We report on 176 close (<2") stellar companions detected with high-resolution imaging near 170 hosts of Kepler Objects of Interest. These Kepler targets were prioritized for imaging follow-up based on the presence of small planets, so most of the KOIs in these systems (176 out of 204) have nominal radii <6 R_E . Each KOI in our sample was observed in at least 2 filters with adaptive optics, speckle imaging, lucky imaging, or HST. Multi-filter photometry provides color information on the companions, allowing us to constrain their stellar properties and assess the probability that the companions are physically bound. We find that 60 -- 80% of companions within 1" are bound, and the bound fraction is >90% for companions within 0.5"; the bound fraction decreases with increasing angular separation. This picture is consistent with simulations of the binary and background stellar populations in the Kepler field. We also reassess the planet radii in these systems, converting the observed differential magnitudes to a contamination in the Kepler bandpass and calculating the planet radius correction factor, $X_R = R_p (true) / R_p (single)$. Under the assumption that planets in bound binaries are equally likely to orbit the primary or secondary, we find a mean radius correction factor for planets in stellar multiples of $X_R = 1.65$. If stellar multiplicity in the Kepler field is similar to the solar neighborhood, then nearly half of all Kepler planets may have radii underestimated by an average of 65%, unless vetted using high resolution imaging or spectroscopy.Comment: 23 pages, 12 figures. Accepted for publication in The Astronomical Journa

Some properties of water clay dispersions and their effect on flow

CER61WLH62.Includes bibliographical references.Fine sediments dispersed in water affect the apparent viscosity and specific weight of the resulting dispersion. Tests at 24 degrees centigrade with a Stormer viscosimeter showed that the apparent kinematic viscosity for a 10 percent by weight water-clay dispersion of an impure bentonite was 8.75 times greater than that of distilled water. A 10 percent water-kaolin dispersion was 1.40 times more viscous than distilled water. The change in viscosity and density of the water-fine sediment dispersion changes the fall velocity of the bed material. The fall velocity distribution of the bed material can be determined, as a first approximation, with the visual accumulation tube apparatus when water-clay dispersions are the sedimentation media. The results are comparable to the fall velocities computed by using the Reynolds number-drag relation, the measured viscosity of the water-clay dispersion and the density of the dispersion. Experiments conducted in water- sand flows with and without bentonite in the flumes at Colorado State University demonstrated that with bentonite in the flow the changes in fall velocity of the bed material particles, resulting from the changes in fluid properties, altered the bed configuration. Because the resistance to flow and bed-material transport are dependent on the form of the bed, they were appreciably affected. Generally, as concentration of fine sediment increases with a constant rate of stream flow, flow resistance and transport of bed material always increase in the upper flow regime and sometimes decrease in the lower flow regime

Study of flow in alluvial channels: the effect of large concentrations of fine sediment on the mechanics of flow in a small flume, A

CER60DBS44.Includes bibliographical references.A small flume study of the variance in resistance to flow, form of bed roughness, and total bed material transport caused by introducing large fine sediment concentrations into the flow over a sand bed.A flume study was made using a natural river sand as the bed material, median diameter = 0.54 millimeters. Clear-water flow was compared with flow containing from 6,000 to 65,000 parts per million of fine sediment (bentonite). The study shows that the form of bed roughness could be changed by adding sufficient fine sediment (bentonite) to the clear-water flow. The total bed material transport was decreased by 50 percent with increasing fine sediment concentration with the dune bed form and was increased by as much as 550 percent for the transition, standing wave, and anti-tune forms of bed roughness. Resistance to flow was less (C/√g increased by 45 percent) with fine sediment-laden flow than with clear-water flow for the dune, and transition bed forms; and was greater (C/√g reduced by 25 percent) for the standing waves and the anti-dunes. A narrow range of bentonite concentration for each form of bed roughness was established as a limit below which only minor changes in bed form, bed material transport, and resistance to flow occurred. The variation of the liquid proper ties, specific weight and viscosity, for water-bentonite dispersions were studied and their effect on the properties of the bed material particles measured. The fall velocity of the particles in a dispersion of 100,000 parts per million fine sediment in water was reduced to about one-half their fall velocity in clear water

FOREIGN AGRICULTURAL POLICY AND FAR EAST FARM MARKETS

Agricultural and Food Policy,

Limits on Stellar Companions to Exoplanet Host Stars With Eccentric Planets

Though there are now many hundreds of confirmed exoplanets known, the binarity of exoplanet host stars is not well understood. This is particularly true of host stars which harbor a giant planet in a highly eccentric orbit since these are more likely to have had a dramatic dynamical history which transferred angular momentum to the planet. Here we present observations of four exoplanet host stars which utilize the excellent resolving power of the Differential Speckle Survey Instrument (DSSI) on the Gemini North telescope. Two of the stars are giants and two are dwarfs. Each star is host to a giant planet with an orbital eccentricity > 0.5 and whose radial velocity data contain a trend in the residuals to the Keplerian orbit fit. These observations rule out stellar companions 4-8 magnitudes fainter than the host star at passbands of 692nm and 880nm. The resolution and field-of-view of the instrument result in exclusion radii of 0.05-1.4 arcsecs which excludes stellar companions within several AU of the host star in most cases. We further provide new radial velocities for the HD 4203 system which confirm that the linear trend previously observed in the residuals is due to an additional planet. These results place dynamical constraints on the source of the planet's eccentricities, constraints on additional planetary companions, and informs the known distribution of multiplicity amongst exoplanet host stars.Comment: 10 pages, 7 figures, 2 tables, accepted to Ap