# 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- An input file in which some of the data has been replaced by variable names, e.g. 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.