Optimal Sampling Locations Research Articles

LOCATION OF THE OPTIMAL SAMPLING POINT FOR THE QUALITY ASSESSMENT OF CONTINUOUS STREAMS

SummaryThe paper makes an appraisal of the most appropriate sampling point for situations where a single sample must be used to estimate the mean flow of a continuous stream during a set time interval. Taking ‘optimal’ to mean the point at which the estimation error variance is minimised, optimal sampling locations are obtained for constant, linear and exponential flow rates when the process variogram is assumed linear or exponential. Numerical results illustrate the significance of failing to sample at the optimal point.

Selecting Nearly Optimal Sampling Locations Throughout an Area: Application to Cleanrooms and Federal Standard 209

Various types of environmental assessment are done by taking an array of samples throughout an area. In sampling an area by taking point samples, the choice of sampling locations becomes important. It is assumed here that the task is to take no less than N* samples in a fairly uniform array throughout an area that is a fairly simple shape, such as a rectangle or a combination of a small number of rectangles. Different formulations of the problem are explored. Except in rare instances, a strictly optimum solution would be difficult to compute. "Nearly optimal" solutions to the problem have the minimum or nearly the minimum number of samples required and produce square or nearly square subregions associated with the samples. Approaches for obtaining sampling grids that are nearly optimal are discussed, and one example is presented in detail.

The Design of Multivariate Field Programs

Abstract Development of a methodology for the optimal placement of multivariate sensors as an aid in the design of geophysical field experiments is shown. The optimal placement methodology relies on spatial correlation estimates, interpolation error estimates as provided by a multivariate optimal interpolation scheme, and optimization techniques using nonlinear programming. Atmospheric fields and their associated statistics are simulated by analytic functions to demonstrate the capabilities of the methodology. These include the ability to design new networks, to add sensors optimally to existing networks, and to place restrictions on the region in which sensors can be located by introducing physical and economical constraints on the nonlinear programming problem. It is demonstrated that the mean and variance of the interpolation error for all fields is generally smaller for analyses whose input is derived from optimal sampling locations rather than from subjectively chosen locations.

Invariant 8‐node hybrid‐stress elements for thin and moderately thick plates

AbstractEight‐node hybrid‐stress elements are developed for the analysis of plates ranging from arbitrarily thin to moderately thick. The displacement behaviour is characterized by a transverse displacement and independent cross‐section rotations, which are interpolated using the 8‐node Serendipity shape functions. All components of stress are included; alternative elements are developed which differe in the form of the inplane distribution of the stresses. Elements are sought for whic the stiffiness is invariant and of correct rank, and whic show on signs of deterioration in the thin‐plate limit. A discussion of the prospects for developing a 4‐node element with these characteristics is also presented. Example problems are used to compare the performance of the 8‐node elements including convergence behaviour, intraelement stress distributions and optimal sampling locations, and range of applicability in terms of plate thickness ratio.