Engineering Optimization: Methods/Applications - Colorado State University

This course provides a comprehensive treatment of methods of optimization with focus on linear programming and its extensions, network flow optimization, integer programming, quadratic programming, and an introduction to nonlinear programming. The goal is to maintain a balance between theory, numerical computation, problem setup for solution by computer algorithms, and engineering applications. Course taught at Colorado State University

Commercial Regional Space/Airborne Imaging

In this work goal programming is used to solve a minimum cost multicommodity network flow problem with multiple goals. A single telecommunication network with multiple commodities (e.g., voice, video, data, etc.) flowing over it is analyzed. This network consists of: linear objective function, linear cost arcs, fixed capacities, specific origin-destination pairs for each commodity. A multicommodity network flow problem with goals can be successfully modeled using linear goal programming techniques. When properly modeled, network flow techniques may be employed to exploit the pure network structure of a multicommodity network flow problem with goals. Lagrangian relaxation captures the essence of the pure network flow problem as a master problem and sub-problems (McGinnis and Rao, 1977). A subgradient algorithm may optimize the Lagrangian function, or the Lagrangian relaxation could be decomposed into subproblems per commodity; each subproblem being a single commodity network flow problem. Parallel to the decomposition of the Lagrangian relaxation, Dantzig-Wolfe decomposition may be implemented to the linear program. Post-optimality analyses provide a variety of options to analyze the robustness of the optimal solution. The options of post-optimality analysis consist of sensitivity analysis and parametric analysis. This mix of modeling options and analyses provide a powerful method to produce insight into the modeling of a multicommodity network flow problem with multiple objectives

Neural network guided adjoint computations in dual weighted residual error estimation

In this work, we are concerned with neural network guided goal-oriented a posteriori error estimation and adaptivity using the dual weighted residual method. The primal problem is solved using classical Galerkin finite elements. The adjoint problem is solved in strong form with a feedforward neural network using two or three hidden layers. The main objective of our approach is to explore alternatives for solving the adjoint problem with greater potential of a numerical cost reduction. The proposed algorithm is based on the general goal-oriented error estimation theorem including both linear and nonlinear stationary partial differential equations and goal functionals. Our developments are substantiated with some numerical experiments that include comparisons of neural network computed adjoints and classical finite element solutions of the adjoints. In the programming software, the open-source library deal.II is successfully coupled with LibTorch, the PyTorch C++ application programming interface

Economic health-aware LPV-MPC based on system reliability assessment for water transport network

This paper proposes a health-aware control approach for drinking water transport networks. This approach is based on an economic model predictive control (MPC) that considers an additional goal with the aim of extending the components and system reliability. The components and system reliability are incorporated into the MPC model using a Linear Parameter Varying (LPV) modeling approach. The MPC controller uses additionally an economic objective function that determines the optimal filling/emptying sequence of the tanks considering that electricity price varies between day and night and that the demand also follows a 24-h repetitive pattern. The proposed LPV-MPC control approach allows considering the model nonlinearities by embedding them in the parameters. The values of these varying parameters are updated at each iteration taking into account the new values of the scheduling variables. In this way, the optimization problem associated with the MPC problem is solved by means of Quadratic Programming (QP) to avoid the use of nonlinear programming. This iterative approach reduces the computational load compared to the solution of a nonlinear optimization problem. A case study based on the Barcelona water transport network is used for assessing the proposed approach performance.Peer ReviewedPostprint (published version

Lifetime Maximization of Wireless Sensor Networks with a Mobile Source Node

We study the problem of routing in sensor networks where the goal is to maximize the network's lifetime. Previous work has considered this problem for fixed-topology networks. Here, we add mobility to the source node, which requires a new definition of the network lifetime. In particular, we redefine lifetime to be the time until the source node depletes its energy. When the mobile node's trajectory is unknown in advance, we formulate three versions of an optimal control problem aiming at this lifetime maximization. We show that in all cases, the solution can be reduced to a sequence of Non- Linear Programming (NLP) problems solved on line as the source node trajectory evolves.Comment: A shorter version of this work will be published in Proceedings of 2016 IEEE Conference on Decision and Contro

Flexible and intelligent network programming for cloud networks

As modern online services are evolving promptly and involving larger amount of data and computation than ever, the demand for cloud networks keeps growing rapidly, which also brings new challenges to network programming. Network programming is a complicated and crucial task for building high-performance cloud networks. Current network programming mainly presents two shortcomings: (1) it is inflexible as adding new data-plane features usually takes several years; (2) it is unintelligent as it heavily depends on human-designed heuristic algorithms to solve production-scale problems. To overcome these shortcomings, this dissertation realizes flexible and intelligent network programming by leveraging the recent development of new technologies both in hardware and software. Specifically, it presents four systems with new performance features that cannot be achieved by conventional network programming: (i) Harmonia: A new replicated storage architecture that provides near-linear scalability without sacrificing consistency. By exploiting the programming flexibility of new-generation programmable switches, Harmonia checks read-write conflicts in network for guaranteeing consistency, and enables any replica to serve reads for objects with no pending writes for near-linear scalability. (ii) RackSched: A microsecond-scale scheduler for rack-scale computers. It proposes a two-layer scheduling framework that integrates the inter-server scheduler in the top-of-rack (ToR) switch with intra-server schedulers on each server. The in-network inter-server scheduler is programmed to realize power-of-k-choices, ensure request affinity, and track server loads accurately and efficiently. (iii) NetVRM: A network management system that supports dynamic register memory sharing in the network. It orchestrates the register memory allocation between multiple concurrent network applications to optimize the multiplexing benefits. This goal is achieved with three major features: a virtual register memory abstraction, a dynamic memory allocation algorithm, and a domain-specific programming language extension. (iv) NeuroPlan: Automated and efficient network planning with deep reinforcement learning (RL). It leverages a two-stage hybrid approach that first uses deep RL to prune a large and complex search space and then uses an Integer Linear Programming (ILP) solver to find the final solution. Such an automated approach avoids human efforts to design heuristic algorithms manually and reduces network plan cost efficiently. We have done theoretical analysis, built testbeds, and evaluated these systems with prototype experiments and simulations under realistic setups from production networks

Suppliers Selection In Manufacturing Industries And Associated Multi-Objective Desicion Making Methods: Past, Present And The Future

Nowadays, many manufacturing companies have decided to use other companies’ competencies and outsource part of their manufacturing processes and business to suppliers globally in order to reduce costs, improve quality of products, explore or expand new markets, and offer better services to customers, etc. The decisions have rendered manufacturing organizations with new challenges. Organizations need to evaluate their suppliers' performance, and take account of their weakness and strength in order to win and survive in highly competitive global marketplaces. Hence, suppliers evaluation and selection are taken as an important strategy for manufactring enterprises. This paper aims to provide a comprehensive and critical review on suppliers selection and the formulation of different criteria for suppliers selection, the associated multi-objctive decision makings, selecion algorithms, and their implementation and application perspectives. Furthermore, individual and integrated suppliers selection approaches are presented, including Analytic hierarchy process (AHP), Analytic network process (ANP), and Mathematical programming (MP). Linear programming (LP), Integer programming (IP), Data envelopment analysis (DEA) and Goal programming (GP) are discussed with in-depth. The paper concludes with further discussion on the potential and application of suppliers selection approach for the broad manufacturing industry

A goal programming approach for the retrofit of supply chain networks

In order to achieve sustainability, the design and planning of a supply chain has to fulfil economic, social and environmental objectives. Traditionally the design of supply chains has been based on economic objectives. As societal environment concerns grow, environmental aspects are also emerging, not only at the industry level, but also within the context of supply chain management. The investment towards logistics structures that consider both economic and environmental performance is nowadays an important research topic. However, much is still to be done. This paper, addresses the retrofit of supply chain networks where planning aspects are also considered. The supply chain network design and planning is modeled through a Resource-Task-Network (RTN) methodology. A mixed integer linear programming (MILP) multi-objective approach is developed, which attempts to simultaneously maximize the annual profit of the supply chain, taking into account the network retrofit, while environmental impacts are minimized. The environmental impacts are accounted for through the Eco-indicator 99 methodology. Profit and environmental impacts are balanced through the use of goal programming. The model applicability is illustrated through the solution of an example