Covariance Matrix Adaptation Evolutionary Strategy with Worst-Case Ranking Approximation for Min--Max Optimization and its Application to Berthing Control Tasks

In this study, we consider a continuous min--max optimization problem $\min_{x \in \mathbb{X} \max_{y \in \mathbb{Y}}}f(x,y)$ whose objective function is a black-box. We propose a novel approach to minimize the worst-case objective function $F(x) = \max_{y} f(x,y)$ directly using a covariance matrix adaptation evolution strategy (CMA-ES) in which the rankings of solution candidates are approximated by our proposed worst-case ranking approximation (WRA) mechanism. We develop two variants of WRA combined with CMA-ES and approximate gradient ascent as numerical solvers for the inner maximization problem. Numerical experiments show that our proposed approach outperforms several existing approaches when the objective function is a smooth strongly convex--concave function and the interaction between $x$ and $y$ is strong. We investigate the advantages of the proposed approach for problems where the objective function is not limited to smooth strongly convex--concave functions. The effectiveness of the proposed approach is demonstrated in the robust berthing control problem with uncertainty.ngly convex--concave functions. The effectiveness of the proposed approach is demonstrated in the robust berthing control problem with uncertainty

Strategy towards tailored donor tissue-specific pancreatic islet isolation.

BackgroundOptimizing the collagenase G (ColG):collagenase H (ColH) ratio is a key strategy for achieving tailored donor-tissue specific islet isolation. Collagen V (Col V) and collagen III (Col III) are crucial target matrices of ColG and ColH, respectively. We herein investigated the relevance between the expression of target matrices in pancreatic tissues and influence of ColG:ColH ratio on islet isolation outcome.MethodsIslet isolation was performed in Lewis and SD rats using different ColG:ColH ratios (5:1, 1:1 and 1:5; n = 7/group). The composition of Col III and Col V was examined using immunohistochemical staining, real-time polymerase chain reaction (PCR), Western blotting and mass spectrometry. Chain types in collagen I (Col I) were also assessed using mass spectrometry.ResultsNo beneficial effects were observed by increasing the ColG amount, irrespective of the rat strain. In contrast, the islet yield in Lewis rats was considerably increased by high amounts of ColH but decreased in SD rats, suggesting that Lewis pancreas contains more Col III than SD pancreas. Neither immunohistochemical nor real-time PCR showed correlation with isolation outcome. However, Western blotting revealed that Lewis contained considerably higher amount of Col III than SD (p = 0.10). Likewise, Col-I(α1)/Col-III(α1) and Col-I(α2)/Col-III(α1) were significantly lower in Lewis than in SD rats (p = 0.007, respectively). Furthermore, the isolation outcome was considerably correlated with the composition of homotrimeric Col I.ConclusionsThe Col III expression and the composition of homotrimeric Col I in pancreatic tissues determined using mass analyses appeared useful for optimizing the ColG:ColH ratio in islet isolation