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Glossary

 Space Filling Experimental Design
A class of experimental designs that employ an algorithm to maximize the minimum distance between any two points.
 Space Mapping
A technique which uses a fine design model to improve a coarse surrogate model. The hope is, that if the misalignment between the coarse and fine models is not too large, only a few fine model simulations will be required to significantly improve the coarse model. The coarse model can be a response surface.
 Stage
A distinct step or operation in a process which typically reads input, processes the input and produces a result. Example: run a solver.
Different stages can be dependent on one another.
 Stage directory
A subdirectory of the work directory that bears the name of a solver and where database files resulting from extraction and the optimization process are stored.
 Stochastic
Involving or containing random variables. Involving probability or chance.
 Stopping Criterion
A mathematical criterion for terminating an iterative procedure.
 Strictness
A number between 0 and 1 which signifies the strictness with which a design constraint must be treated. A zero value implies that the constraint may be violated. If a feasible design is possible all constraints will be satisfied. Used in the design formulation to minimize constraint violations. See Slack variable.
 Subproblem
The approximate design subproblem constructed using response surfaces. It is solved to find an approximate optimum.
 Subregion
See region of interest.
 Successive (or Sequential) Approximation Method
An iterative method using the successive solution of approximate subproblems.
 System identification
A procedure in which a numerical model is calibrated by optimizing selected parameters in order to minimize the residual error with respect to certain targeted responses. The targeted responses are usually derived from experimental results.
 Target
A desired value for a response. The optimizer will not use this value as a rigid constraint. Instead, it will try to get as close as possible to the specified value.
 Template
An input file in which some of the data has been replaced by variable names, e.g. <>. A template may also contain the LS-DYNA *PARAMETER keyword with corresponding @-parameters. LS-OPT will recognize the parameters defined in the template and display them in the GUI.
 Trade-off curve
A curve constructed using Pareto optimal designs.
 Transformed variables
Variables which are transformed (mapped) to a different n-space using a functional relationship. The experimental design and optimization are performed in this space.
 Variable screening
Method to remove insignificant variables from the design optimization process based on a ranking of regression coefficients using analysis of variance (ANOVA). (See also ANOVA).
 Weight
A measure of importance of a response function or objective. Typically varies between 0 and 1.
 Work directory
The directory is which the input files reside and where output is produced. See also Run directory.