Band 2, Heft 3-4

This paper describes an underwater glider motion control system intended to enhance locomotive efficiency by reducing the energy expended by vehicle guidance and control. In previous work, the authors obtained an approximate analytical expression for steady turning motion as a regular perturbation from wings level flight. Using this steady turn solution, one may easily construct feasible, energy-efficient paths for a glider to follow. Because the turning motion results are only approximate, however, and to compensate for model and environmental uncertainty, one must incorporate feedback to ensure precise path following. This paper describes the development and numerical implementation of a feedforward/feedback motion control system for a multi-body underwater glider model. The feedforward component issues actuator commands based on the analytical solution for a desired steady flight condition while the feedback component compensates for uncertainty and disturbances.

Considering geometry nonlinear of the bridge, the differential equations of vehicle-bridge coupled interaction system are established. Using numerical method, the numerical solution of the coupling nonlinear differential equation are obtained. As an example, single vehicle pass through the bridge is studied. The result shows nonlinear items has little effects to the response in this case. In the other example, the train is modeled as serious spring-mass system pass through bridge. In this case, the subharmonic resonance are studied. The result shows when the bridge is excited period force, nonlinear affect can not be ignored.

Imperfection sensitivity of cylindrical shells subjected to axial compressive load is investigated by means of non-linear buckling analysis and post-buckling analysis. Non-linear buckling analysis involves the determination of the equilibrium path (or load-deflection curve) upto the limit point load by using the Newton-Raphson approach, whereas post-buckling analysis involves the determination of the equilibrium path beyond the limit point load and up to the collapse load by using the arc-length approach. Limit point loads evaluated from these two approaches for various imperfection magnitudes show an excellent agreement which clearly confirms the numerical results obtained.

The double reduction when having been applied to the fourth-order spectral operator on a discrete spatial support is shown to inspire early unknown multicomponent semidiscrete integrable nonlinear systems associated with the nonsinglular spectral operator of third order and characterized by an additional coupling parameter. Two forms of zero-curvature representation yielding the proposed integrable systems are given. Relying upon the lowest local conservation laws the selfconsistent system with the symmetric parametrization of field amplitudes is selected. The variativity of its coupling parameters is expected to ensure a number of qualitatively distinct regimes of system nonlinear dynamics.

Cold spray is a material deposition process used to deposit metallic features for use in applications such as corrosion prevention, dimensional correction and repair, and wear resistant coatings. Micro Cold Spray Direct Write (MCS-DW) is a variant of the cold spray process in which metal particles are accelerated and focused to print fine features on flexible and rigid substrates with no postprocessing required. This paper presents results of numerical studies on the flow of 2 µm and 6 µm diameter silver particles through a converging-diverging micro nozzle with helium gas. The flow of helium was simulated by solving Navier Stokes equation using commercial software. The trajectory and velocity of the aerosol particles were determined using a Lagrangian particle tracking algorithm with a combination of Stokes drag force and Saffman lift force acting on the particles. A comparison of the effect of different corrections applied to Stokes and Saffman forces as well as the effect of Magnus force on the trajectory and velocity of aerosol particles is studied. The effect of particle rotation creating Magnus force is found negligibly small compared to Saffman force for particles of 2 µm diameter, however, the effect is found to be significant for particles of 6 µm diameter. A proposed converging-diverging nozzle is shown capable of accelerating silver particles to velocities as high as 600 m/s and enables aerosol beam widths as thin as 50 µm.

In the present work, we present a systematic study of the MHD heat transfer of a second grade fluid over a shrinking sheet. We are able to obtain an exact solution for the heat transfer problem in closed form, even for various values of the viscoelastic parameter. Such exact solutions are a rarity, and are useful for comparison with numerical solutions. The exact solutions strongly depend on the exact solutions for the flow field which were studied. Indeed, we obtain dual solutions for some parameter regimes, and no solutions for others. The exact solution method allows us to give the Nusselt number in terms of the model parameters, in closed analytic form. For parameter regimes where the exact solution may not be well-behaved (such as when two solutions branch apart), we also give a numerical method for comparison. This allows for the study of dual solutions, which are shown to exist in some parameter regimes. Results for the dimensionless velocity and temperature profiles, as well as for the Nusselt number, are obtained and displayed through tables and graphs. It is observed that an increase in the magnitude of the viscoelastic parameter increases the thermal boundary layer thickness for both upper and lower branch solutions.

An investigation has presented to analyze the heat transfer in a boundary layer flow of an incompressible couple stress fluid over a nonlinear stretching sheet. The heat transfer problem have been analyzed for the two heating processes, 1) PST (prescribed surface temperature case) and 2) PHF (prescribed heat flux case). The governing partial differential equations for flow and heat transfer are transformed to ordinary differential equations. The numerical solutions have been obtained by using fourth order Runge-Kutta method coupled with shooting method. The effects of dimensionless surface temperature, couple stress parameter beta, Prandtl number Pr, Eckert number Ec, nonlinear stretching sheet parameter n and lambda1; lambda2 have been observed by graphical illsurations.

Over the period January 2004 to present, the seas have experienced the lack of any warming, as finally properly measured in the ARGO project where a global array of more than 3,600 free-drifting profiling floats has measured the temperature of the upper 2000 m of the sea as it was not possible before. The warming of the seas has been a negligible 1.1*10 -3 °C/year on average over the layer 0 – 2000 dbar below the accuracy of the measure. Over the period January 2000 to present, the measured land and sea temperatures of the less reliable GISS, NCDC and HADCRUT4 data sets have shown a small warming of 4.2*10 -3 °C/year on average. Same period, the climate models propose for the land and sea temperatures an unrealistic warming of 20.5*10 -3 °C/year (average of CMIP3) and 18.2*10 -3 °C/year (average of the CMIP5). The “inconvenient truth” is that climate models are predicting a warming when there is no warming rather than simply overestimating the warming as discussed so far. The paper presents the failed validation of the climate models since their introduction and suggests the reasons of their failure in the overrated effect of the changed composition of the atmosphere and the neglected natural oscillations.