Theory Andexperiment Research Articles

Breit-Pauli energy levels, lifetimes and transition data: boron-likespectra

Breit-Pauli results for energy levels, lifetimes and sometransition data are reported for all levels up to 2s2p(3P)3s2PJo of the B-like spectrum for5⩽Z⩽14. For all but the lowest members of the sequence, theseinclude the 2s22p, 2s2p2, 2p3, 2s23s, 2s23p, and 2s23d and 2s2p3s configurations, though only the2s2p(3P)3s terms of the latter.A simultaneous optimization scheme was applied so that a radial basiscould be determined for a set of terms that mix in the Breit-Pauliapproximation. Convergence of the LS line strength is used as a factorin estimating accuracy as well as the agreement of energy levels andtheir splitting between theory andexperiment. The results are evaluated by comparisonwith other theoretical results and experiment for transition rates.

Compression testing of pultruded carbon fibre-epoxy cylindrical rods

The fibre waviness inherent in conventional prepreg laminatessignificantly reduces their compressive strength. This waviness canbe reduced through the use of unidirectional fibre rods. In thiswork, the development of a new test procedure and specimen design isreported that was used to determine the compressive properties ofpultruted T300/828 and IM7/828 carbon fibre-epoxy unidirectionalrods at room temperature. The IM7/828 system demonstrates a highercompressive strength than the T300/828 composite due to strongerfibres used and fewer manufacturing defects. Since the fibres as intension primarily carry the compressive load, the final fracture ofthe rods occurs when the fibres fail. Post-failure examinationreveals that failure of the fibres is microbuckling-induced. This isa bending failure as a consequence of buckling. Other events such asfibre-matrix debonding (splitting) and matrix yielding do not bythemselves cause the final failure, but they facilitate fibrebuckling by reducing the lateral support for the fibres.Microbuckling failure models are used to predict the compressivestrength of the carbon fibre rods; agreement between theory andexperiment is acceptable.

Dynamics of the Cl+H2/D2 reaction: a comparison of crossed molecular beam experiments with quasiclassical trajectory and quantum mechanical calculations

In this paper we report angular distributions and time-of-flight spectra for the Cl+H2→HCl+H and Cl +D2→DCl+D reactions at 5.85 kcal mol−1 and 6.3 and 6.4 kcal mol−1 collision energies, respectively, obtained from high-resolution crossed molecular beam experiments. In addition, quasiclassical trajectory (QCT) and quantum mechanical (QM) dynamical calculations have been carried out for these reactions on the G3 potential energy surface (T. C. Allison et al., J. Phys. Chem., 1996, 100, 13575). Reaction probabilities, integral and differential cross sections have been calculated using the QCT and QM methodologies, and a comparison of these results is presented. The molecular beam results have been simulated using the theoretical calculations, and theory and experiment are in reasonably good agreement.

Application of the 1998 Version of the Aeroprediction Code

The U.S. Naval SurfaceWarfare Center aeroprediction code has been extended to the roll position of 45 deg (Ž ns in “ £ ” or cross-roll orientation) in addition to the roll position of 0 deg (Ž ns in “ ” or plus-roll orientation). It has also been extended to compute aerodynamics of nonaxisymmetricbodies based on an equivalent axisymmetric body. In addition, the nonlinear aerodynamic loads have been distributed over the body and lifting surfaces to provideamoreuseful tool forpreliminary structural analysis.Finally,new technologywas developed to improvethe predictionof axialforceat angleof attack.These new technologieshavebeen integrated into the1995Aeroprediction Code (AP95) and will be transitioned to legitimate users as the 1998 Aeroprediction Code (AP98). To make the AP98 more user friendly, an upgraded preand postprocessing, personal-computer interface was also developed. The theoretical methods of the AP98 are summarized, and a sample is shown of the comparisons of the AP98 predictions of static aerodynamics for several missile conŽ gurations to experimental data. Comparisons of theory andexperiment show that theAP98,on average, is at least as goodas theAP95and, in general,maybe slightlybetter.

Investigation of the force–distance relationship for a small liquid drop approaching an adhesive liquid/liquid interface

We have used a novel apparatus to investigate the forces between two liquid surfaces which are mutually attractive. An oil drop is formed at the tip of a thin flexible micropipette and the force exerted on the oil drop as it is pressed up to an oil/water interface is determined from the vertical deflection of the pipette shaft. The disjoining pressure in the thin, oil–water–oil emulsion film, formed by contact of the drop with the oil/water interface, is determined by the hydrostatic pressure applied to the oil contained in the micropipette. The radius and the thickness of the film are derived from the optical interference pattern observed using a microscope. A theory is presented for the variation in force and film radius as the drop is moved up to and down from the interface. Experimental results are given for dodecane–water–dodecane emulsion films stabilised by the anionic surfactant sodium decyl sulfate (SDS) in the presence of different aqueous phase concentrations of NaCl, which modifies the attractive force between the monolayers. Data for the force and film radius as a function of the pipette position relative to the oil–water monolayer show qualitative agreement with theoretical predictions. It is shown that differences between theory and experiment are not due to the existence of a line tension at the perimeter of the thin emulsion film formed as the oil drop is pressed up to the oil/water interface. Discrepancies between theory and experiment may be due to imperfect ‘pinning’ of the three-phase contact line at the inner diameter of the micropipette.

Fluid-Free-Surface Proximity Effect on a Sphere Vertically Accelerated from Rest

Theory is developed to estimate the effect of free surface proximity on the initial added mass of a sphere accelerated vertically upward from rest in an ideal fluid. It is assumed that the acceleration regime is sufficiently brief that inertial forces predominate and gravitational effects may be neglected. Results of tests in water indicate that while there are slight viscous and gravitational effects over the acceleration regime, the agreement between theory and experiment is good. It is concluded that over briefer acceleration regimes these effects would decrease and the agreement would improve.