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We have investigated the application of near-IR reflectance spectroscopy to the determination of motor oil contamination in sandy loam. Although the present work is concerned with a specific case of contamination, we discuss the possibility of applying the method to other organic contaminants and other types of soil. The spectral region considered was 1600–1900 nm, which contains the first overtone of the CH stretch. Using a commercial Fourier transform spectrometer together with cross-validated partial least-squares data analysis, the one-sigma precision for the determination of motor oil in sandy loam was 0.17 wt % (0.13 to 0.26 wt % at the 95% confidence level). The largest contribution to the precision of the determination was sampling error, or inhomogeneity in each sample. Given the precision limit imposed by the sampling error, we found that the performance of the spectrometer could be lowered without affecting the overall precision. In a modeling exercise, adequate performance was obtained with a spectrometer having only seven spectral channels with a spectral resolution of 10 nm and a spectral noise level of 10−3 absorbance units. A design for an inexpensive miniature instrument is presented.

Evolution strategies (ES) are very robust and general techniques for finding global optima in optimisation problems. As with all evolutionary algorithms, ES apply evolutionary operators and select the most fit from a set of possible solutions. Unlike genetic algorithms, ES do not use binary coding of individuals, working instead with real variables.Many recent studies have applied evolutionary algorithms to structural problems, particularly the optimisation of trusses. This paper focuses on shape optimisation of continuum structures via ES. Stress analysis is accomplished by using the fixed grid finite element method, which reduces the computing time while keeping track of the boundary representation of the structure. This boundary is represented by b-spline functions, circles, and polylines, whose control points constitute the parameters that govern the shape of the structure. Evolutionary operations are applied to each set of variables until a global optimum is reached. Several numerical examples are presented to illustrate the performance of the method. Finally, structures with multiple load cases are considered along with examples illustrating the results obtained.

Fixed Grid (FG) methodology was first introduced by García and Steven as an engine for numerical estimation of two-dimensional elasticity problems. The advantages of using FG are simplicity and speed at a permissible level of accuracy. Two dimensional FG has been proved effective in approximating the strain and stress field with low requirements of time and computational resources. Moreover, FG has been used as the analytical kernel for different structural optimisation methods as Evolutionary Structural Optimisation , Genetic Algorithms (GA), and Evolutionary Strategies . FG consists of dividing the bounding box of the topology of an object into a set of equally sized cubic elements. Elements are assessed to be inside (I), outside (O) or neither inside nor outside (N IO) of the object. Different material properties assigned to the inside and outside medium transform the problem into a multi-material elasticity problem. As a result of the subdivision N IO elements have non-continuous properties. They can be approximated in different ways which range from simple setting of N IO elements as O to complex noncontinuous domain integration. If homogeneously averaged material properties are used to approximate the N IO element, the element stiffness matrix can be computed as a factor of a standard stiffness matrix thus reducing the computational cost of creating the global stiffness matrix. An additional advantage of FG is found when accomplishing re-analysis, since there is no need to recompute the whole stiffness matrix when the geometry changes.This article presents CAD to FG conversion and the stiffness matrix computation based on non-continuous elements. In addition inclusion/exclusion of O elements in the global stiffness matrix is studied. Preliminary results shown that non-continuous N IO elements improve the accuracy of the results with considerable savings in time. Numerical examples are presented to illustrate the possibilities of the method.