We evaluate the virial coefficients Bk for k ≤ 10 for hard spheres in dimensions D = 2, · · · , 8. Virial coefficients with k even are found to be negative when D ≥ 5. This provides strong evidence that the leading singularity for the virial series lies away from the positive real axis when D ≥ 5. Further analysis provides evidence that negative virial coefficients will be seen for some k > 10 ...

This paper gives a qualitative description how Young tableaux can be used to perform a Clebsch-Gordan decomposition of tensor products in SU(3) and how this can be generalized to SU(N).

This essay describes the development of groups used for the specification of symmetries from ordinary and magnetic point groups to Fedorov and magnetic space groups, as well as other varieties of groups useful in the study of symmetric objects. In particular, we consider the problem of some incorrectness in Vol. A of the International Tables for Crystallography. Some results of tensor calculus ...

The solution of a multiobjective multidisciplinary design optimization (MDO) using a genetic algorithm (GA) is considered. The objective functions in the optimization problem measure the aerodynamic feasibility based on the drag and lift coefficients and the electromagnetic feasibility based on the backscatter of the two-dimensional airfoil designs. The flow and backscatter are modeled by the t...

We will isolate a number of influences on air-sea transfer of momentum, heat, and moisture for weak wind conditions. We will focus on the important impact of swell amplitude and propagation direction and the explicit influence of large atmospheric eddies on the stability functions for the transfer coefficients for surface fluxes. Improved understanding of the various influences on sea surface f...

The unsteady compressible flow around a body tail projectile is numerically solved with a Large Eddy Simulation (LES) method, Smagorinsky-Lilly model was used as the Sub-Grid Scale (SGS). The computed results are obtained in supersonic flow regime for a viscous fluid in order to determine the aerodynamic coefficients with different angles of attack. The flow around a body tail projectile was so...

The six-degree equations of flight in their classic form do not provide a proper physical perception due to a number of interferences. Nor do they render visible the important role of attack angles. In this study, attempts have been made to develop a complete set of 3D acceleration equations from the equations of normal and tangential acceleration αN=vωv, αt=v ̇. For this purpose, a coordinate s...

System identification is evaluated as an efficient and accurate technique for modeling unsteady aerodynamic forces for use in time-domain aeroelastic analysis. In the system identification methodology, the constant coefficients of a linear system model are fit to the computed response time histories from a 3-D, unsteady CFD solver. The resulting model of the unsteady CFD solution is independent...

This paper presents an algorithm to estimate unknown parameters of parachute models from flight-test data. The algorithm is based on the simultaneous-perturbation-stochastic-approximation method to minimize the prediction error (difference between model output and test data). The algorithm is simple to code and requires only the model output. Analytical gradients are not necessary. The algorith...

n this paper, to overcome the problem of hovering a quadrotor system, under aerodynamic effects, an optimal recursive backstepping controller is designed. One of the main achievements of this study is to propose a nonlinear efficient observer based on extended kalman bucy filter (EKBF) to estimate the unmeasured states of the system. Our control method is robust against perturbations and ensure...