Abstract: Methods for computing the inverse dynamics of multibody systems with contacts are disclosed. Inverse dynamics means computing external forces that cause a system to move along a given trajectory. Such computations have been used routinely for data analysis and control synthesis in the absence of contacts between rigid bodies. The disclosed inverse dynamics methods include the ability to handle contacts. The disclosed methods include the following steps: projecting the discrete-time equations of motion from joint space to contact space; defining the forward dynamics in contact space as the solution to an optimization problem; using the features of this optimization problem to obtain a unique inverse—which turns out to correspond to the solution to a dual optimization problem; solving the latter using standard methods for numerical optimization; projecting the solution from contact space back to joint space and finding the external forces.

Abstract: An apparatus and method for performing periodic noise (Pnoise) simulation with full spectrum accuracy is disclosed herein. Noise contributions of a circuit under consideration are identified and separated for different computation treatment. The different computation treatment results in computational efficiency without sacrificing accuracy of simulation results.

Abstract: A method and apparatus for simulating effects of threats to aircraft communications. A simulation of an aircraft environment is run with the aircraft communications in an aircraft communications network in the aircraft environment. A number of conditions is introduced. The number of conditions comprises a threat configured to affect the aircraft communications in the aircraft communications network in an undesired manner. A change in traffic flow of aircraft in an airspace in the aircraft environment is identified in response to the number of conditions.

Abstract: A method, apparatus, and article of manufacture provide the ability to create a flow-grade solution. In a computer application, a curve from which a slope is to be projected and an elevation field depth buffer, that provides a 2D array with one element for each coordinate, are defined. A slope angle for the slope is specified. As grading shapes are rendered, by sweeping a cone with the slope angle along the curve, a grid is used to capture, into the buffer, an elevation for each vertex of the grid. A flow grade solution represented by the field depth buffer is thus obtained. The flow grade solution includes a path of steepest slope (determined from the elevations stored in the buffer) from any given location in the grid.

Abstract: A method of estimating lithologic properties of a geological zone represented by a grid, in which method facies are allocated to the nodes of the grid by sequential stochastic simulation. For a target node (x0) from a set of target nodes for scanning iteratively, and for each possible facies (ck0), a conditional probability (pk0/k1, . . . , kn) of observing said facies is estimated knowing that respective facies have already been allocated to other nodes in the neighborhood. A random draw weighted by these conditional probabilities is then performed. The estimation of the conditional probabilities makes use of univariate probabilities (pk0) and of bivariate probabilities (pk0,ki) of observing two facies at two respective nodes of the grid. Each bivariate probability used in estimating the conditional probability relates to the target node (x0) and to a node (xi) neighboring the target node.

Abstract: A system and method for determining a cross flow angle for a feature on a structure. A processor unit receives location information identifying a location of the feature on the structure, determines an angle of the feature, identifies flow information for the location, determines a flow angle using the flow information, and determines the cross flow angle for the feature using the flow angle and the angle of the feature. The flow information describes a flow of fluid across the structure. The flow angle comprises an angle of the flow of fluid across the structure for the location of the feature.

Abstract: A nuclear-characteristic calculating program for calculating a nuclear characteristic of a fuel rod that contains nuclear fuel and burnable poison includes a first scattering model that can represent a simple scattering of the neutron and a second scattering model that can represent a complicated scattering of the neutron. The nuclear-characteristic calculating program includes step of calculating, when a burnup of the fuel rod is before a set burnup at which the burnable poison is considered to lose neutron absorption capability, the nuclear characteristic of the fuel rod by using the second scattering model, step of switching, when the burnup of the fuel rod is the set burnup, the scattering model from the second scattering model to the first scattering model, and step of calculating, after performing step of switching, the nuclear characteristic of the fuel rod by using the first scattering model.