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Your search keyword '"Vassiliadis, V. S."' showing total 9 results
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9 results on '"Vassiliadis, V. S."'

2. A threshold accepting metaheuristic for the heterogeneous fixed fleet vehicle routing problem

Author

Tarantilis, C. D., Kiranoudis, C. T., and Vassiliadis, V. S.

Subjects
Algorithms -- Usage, Combinatorial optimization -- Analysis, Logistics -- Analysis, Algorithm, Business, Business, general, Business, international
Abstract

A new metaheuristic, termed the backtracking adaptive threshold accepting algorithm, for solving the heterogeneous fixed fleet vehicle routing problem (HFFVRP) is presented. The numerical results show that the proposed algorithm is robust and efficient.

Published
2004

3. Dynamic Optimization for Controller Tuning with Embedded Safety and Response Quality Measures.

Author

Ahamad, I. S., Choong, T. S. Y., Yunus, R., Chuah, T. G., and Vassiliadis, V. S.

Subjects
PID controllers, QUALITY, NONLINEAR programming, DUALITY theory (Mathematics), AUTOMATIC control systems, MATHEMATICAL models, CONSTRAINED optimization, COMPUTER software, INTERPOLATION
Abstract

Controller tuning is needed to select the optimum response for the controlled process. This work presents a new tuning procedure of PID controllers with safety and response quality measures on a non-linear process model by optimization procedure, with a demonstration of two tanks in series. The model was developed to include safety constraints in the form of path constraints. The model was then solved with a new optimization solver, NLPOPTI, which uses a prima!-dual interior point method with a novel non-monotone line search procedure with discretized penalty parameters. This procedure generated a grid of optimal PID tuning parameters for various switching of steady-states to be used as a predictor of PID tunings for arbitrary transitions. The interpolation of tuning parameters between the available parameters was found to be capable to produce state profiles with no violation on the safety measures, while maintaining the quality of the solution with the final set points targeted achievable. [ABSTRACT FROM AUTHOR]

Published
2011

9. A new formulation for symbolic regression to identify physico-chemical laws from experimental data

Author

Pascal Neumann, Vassilios S. Vassiliadis, Liwei Cao, Danilo Russo, Alexei A. Lapkin, Russo, Danilo [0000-0003-1809-7309], Vassiliadis, Vassili [0000-0002-5415-7551], Lapkin, Alexei [0000-0001-7621-0889], Apollo - University of Cambridge Repository, Neumann, P., Cao, L., Russo, D., Vassiliadis, V. S., and Lapkin, A. A.

Subjects
Computer science, General Chemical Engineering, Symbolic regression, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Industrial and Manufacturing Engineering, Nonlinear programming, Redundancy (engineering), Environmental Chemistry, Applied mathematics, Binary tree, Physical model, General Chemistry, Chemical process development, Solver, 021001 nanoscience & nanotechnology, Automated model construction, 0104 chemical sciences, Model identification, Tree (data structure), Global optimization, 0210 nano-technology, Reduction (mathematics), Mixed-integer nonlinear programming (MINLP)
Abstract

A modification to the mixed-integer nonlinear programming (MINLP) formulation for symbolic regression was proposed with the aim of identification of physical models from noisy experimental data. In the proposed formulation, a binary tree in which equations are represented as directed, acyclic graphs, is fully constructed for a pre-defined number of layers. The introduced modification results in the reduction in the number of required binary variables and removal of redundancy due to possible symmetry of the tree formulation. The formulation was tested using numerical models and was found to be more efficient than the previous literature example with respect to the numbers of predictor variables and training data points. The globally optimal search was extended to identify physical models and to cope with noise in the experimental data predictor variable. The methodology was proven to be successful in identifying the correct physical models describing the relationship between shear stress and shear rate for both Newtonian and non-Newtonian fluids, and simple kinetic laws of chemical reactions. Future work will focus on addressing the limitations of the present formulation and solver to enable extension of target problems to larger, more complex physical models.

Published
2020

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