a b s t r a c tRiver contaminant source identification problems can be formulated as an inverse model to estimate the missing source release history from the observed contaminant plume. In this study, the identification of pollution sources in rivers, where strong advection is dominant, is solved by the global space-time radial basis collocation method (RBCM). To search for the optimal shape parameter and scaling factor which strongly determine the accuracy of the RBCM method, a new cost function based on the residual errors of not only the observed data but also the specified governing equation, the initial and boundary conditions, was constructed for the k-fold cross-validation technique. The performance of three global radial basis functions, Hardy's multiquadric, inverse multiquadric and Gaussian, were also compared in the test cases. The numerical results illustrate that the new cost function is a good indicator to search for near-optimal solutions. Application to a real polluted river shows that the source release history is reasonably recovered, demonstrating that the RBCM with the k-fold cross-validation is a powerful tool for source identification problems in advectiondominated rivers.

An internally-illuminated photobioreactor was designed to maximize the astaxanthin production by Haematococcus pluvialis. Four optimization steps were conducted: 1. light wavelength 2. light intensity 3. astaxanthin formation and 4. astaxanthin extraction methods. Efficient biomass production of H. pluvialis of 4.58 ± 0.15 × 10 5 cells/ml and dry biomass of 520 ± 12.5 mg/L was accomplished under red LED light (660 nm) with 70 µmol m-2 s-1. Besides, the biomass production can be optimized to 5.31 ± 0.15 × 10 5 cells/ml and dry biomass of 680 ± 10.5 mg/L under 140 µmol m-2 s-1 in the light intensity of 70-210 µmol m-2 s-1. Furthermore, the astaxanthin accumulation was significant with 7 days encystment under 140 µmol m-2 s-1 blue LED lights. For extraction method, using hydrochloric acid could obtain the highest astaxanthin yield of 3.85 ± 0.05% (% to dry weight). Further studies were proposed whatever such photobioreactor can be applied to different microalgal strains.

Several templates for 2D and 3D structured mesh refinement are presented. The templates have the property that the minimum number of irregular points or edges (mesh singularities) are added. For a given set of external division numbers a variety of interior meshes can be generated. The positions of the internal vertices in the template are calculated explicitly using an extended transfinite mapping scheme, which has previously been shown to be equivalent to iterative iso-parametric smoothing. Since calculating the block vertex positions requires the solution of a small number of linear equations, the optimum mesh in the interior of the template can be evaluated very cheaply before the block structured mesh is generated.