This paper addresses a critical question pertaining to manufacturing sustainability: is it economically viable to implement an island microgrid to power a flow shop system under power demand and supply uncertainty? Th...
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This paper addresses a critical question pertaining to manufacturing sustainability: is it economically viable to implement an island microgrid to power a flow shop system under power demand and supply uncertainty? Though many studies on microgrid sizing are available, the majority assume the microgrid is interconnected with main grid. This paper aims to size wind turbine, photovoltaic and battery storage to energize a multi-stage flow shop system in island mode. A mixed-integer, non-linear programming model is formulated to optimize the renewable portfolio and capacity with the goal of minimizing the levelized cost of energy. The island microgrid is tested in three locations with diverse climate profiles. The results show that net zero energy flow shop production is economically feasible in the areas where the average wind speed exceed 8 m/s at 80-meter tower height, or the battery cost drops below $100,000/MWh. Sensitivity analyses are further carried out with respect to installation cost, demand response program, production scalability, and weather seasonality.
The improvement in the efficiency of an energy plant depends on a rational development of its flowchart and choice of parameters along with the load schedule, equipment reliability, operating mode, etc. It is advisabl...
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The improvement in the efficiency of an energy plant depends on a rational development of its flowchart and choice of parameters along with the load schedule, equipment reliability, operating mode, etc. It is advisable to study such complex technical systems with the methods of mathematical modeling and optimization. The paper presents an approach to the development of optimal flowcharts and selection of parameters of energy plants. The approach is based on the combination of a method for optimization of the most complex flowchart and a method for solving discrete-continuous problems of nonlinear mathematical programming. A case study of the co-optimization of design parameters, operating parameters and equipment mix for the integrated gasification combined-cycle plant is demonstrated. The optimization calculations were carried out by the criterion of the minimum price of electricity for a given internal rate of return on investment and the maximum energy efficiency of the plant. Several optimal solutions meeting the different criteria are obtained. The proposed approach can be used for optimization of flowcharts and parameters of other complicated energy plants (high-efficiency combined-cycle plants, ultra-supercritical steam cycles, integrated power plants for electricity and synthetic liquid fuel co-production from coal, etc.). (C) 2019 Elsevier Ltd. All rights reserved.
The State of Colorado's Stream Simulation Model (StateMod) provides comparative analysis for historical and future water resource decisions and policies along the Lower South Platte River. In order to identify loc...
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The State of Colorado's Stream Simulation Model (StateMod) provides comparative analysis for historical and future water resource decisions and policies along the Lower South Platte River. In order to identify locations for increased water storage, our research uses simulated data produced by StateMod as input to a mixedinteger-linear optimization model. This model minimizes the cost of meeting unmet demands by assigning network flow of, and designing additional storage for, excess water while adhering to constraints that force the physical and topographical structures of the river. Using historical, measured flow data from 1962 through 2012, we extend the capability of StateMod by considering solutions with the following characteristics: (1) a single-reservoir solution, (2) a solution in which we only expand existing reservoirs, and (3) a solution without the constraints in (1) or (2). We conclude that, for the time horizon considered, the optimal method to mitigate shortages is with the construction of a combination of smaller surface and sub-surface reservoirs, and a corresponding prescribed flow. The total increased storage volume is 25,378 acre-feet (AF). Our work can be used as a strategic analysis tool by planners and engineers to quickly identify the most effective reservoir locations and the order in which to build them, rather than examining every potential storage site and the time at which it should be built, if at all. (C) 2019 Elsevier Ltd. All rights reserved.
Frame structures are extensively used in mechanical, civil, and aerospace engineering. Besides generating reasonable designs of frame structures themselves, frame topology optimization may serve as a tool providing us...
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Frame structures are extensively used in mechanical, civil, and aerospace engineering. Besides generating reasonable designs of frame structures themselves, frame topology optimization may serve as a tool providing us with conceptual designs of diverse engineering structures. Due to its nonconvexity, however, most of existing approaches to frame topology optimization are local optimization methods based on nonlinear programming with continuous design variables or (meta)heuristics allowing some discrete design variables. Presented in this paper is a new global optimization approach to the frame topology optimization with discrete design variables. It is shown that the compliance minimization problem with predetermined candidate cross-sections can be formulated as a mixed-integer second-order cone programming problem. The global optimal solution is then computed with an existing solver based on a branch-and-cut algorithm. Numerical experiments are performed to examine computational efficiency of the proposed approach.
Medium-term development planning of underground mines requires scheduling multiple activities to comply with long-term milestones, and to obtain a time span as short as possible. However, the planning must also respec...
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Medium-term development planning of underground mines requires scheduling multiple activities to comply with long-term milestones, and to obtain a time span as short as possible. However, the planning must also respect the availability of construction resources and precedence constraints, which in our case can be disjunctive, that is with more than one alternative predecessor. In this paper, we present an optimisation model to find the schedule of minimum length, satisfying all the constraints mentioned. We develop a heuristic approach to solve it and show that it can be used to produce feasible development plans in a real mine.
The definition of caving economic limits is one of the initial steps in the planning and design of caving projects. This paper proposes a binary optimization framework to integrate the caving envelope and production s...
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The definition of caving economic limits is one of the initial steps in the planning and design of caving projects. This paper proposes a binary optimization framework to integrate the caving envelope and production schedule that maximizes the net present value of the project under technical constraints that model the caving operation mechanics. The constraints considered in the framework are mining capacities, draw rates, maximum and minimum column heights, horizontal and vertical precedences, undercut development rates and the maximum relative adjacent height of draw between columns. An early-start algorithm is used to reduce the number of decision variables and a sliding-time heuristic is applied to significantly reduce the computing time. The framework is implemented in a MATLAB environment with CPLEX as the optimization engine. A case study is presented for the section of a copper deposit, where different horizons were evaluated to select the optimal undercut level and define the caving envelope and initial production schedule. Results were obtained in under 20 min, which allows the method to be efficiently used to evaluate multiple scenarios.
We consider a flexible job shop scheduling problem that incorporates machine operators and aims at makespan minimization. In a detailed overview of the related literature, we reveal the fact that the research in this ...
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We consider a flexible job shop scheduling problem that incorporates machine operators and aims at makespan minimization. In a detailed overview of the related literature, we reveal the fact that the research in this field is mainly concerned with (meta-)heuristic approaches. Only few papers consider exact approaches. In order to promote the use of exact approaches and in order to facilitate the evaluation of the performance of heuristic approaches, we present two mathematical models, a mixed-integer programming model and a constraint programming model, that are analyzed and compared with a state-of-the-art heuristic in computational tests with a standard solver. (C) 2019, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.
Boolean quadratic optimization problems occur in a number of applications. Their mixedinteger-continuous nature is challenging, since it is inherently NP-hard. For this motivation, semidefinite programming relaxation...
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Boolean quadratic optimization problems occur in a number of applications. Their mixedinteger-continuous nature is challenging, since it is inherently NP-hard. For this motivation, semidefinite programming relaxations (SDR’s) are proposed in the literature to approximate the solution, which recasts the problem into convex optimization. Nevertheless, SDR’s do not guarantee the extraction of the correct binary minimizer. In this paper, we present a novel approach to enhance the binary solution recovery. The key of the proposed method is the exploitation of known information on the eigenvalues of the desired solution. As the proposed approach yields a non-convex program, we develop and analyze an iterative descent strategy, whose practical effectiveness is shown via numerical results.
Citizen science programs have been instrumental in boosting sustainability projects, large-scale scientific discovery, and crowd-sourced experimentation. Nevertheless, these programs witness challenges in submissions&...
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ISBN:
(纸本)9781450367141
Citizen science programs have been instrumental in boosting sustainability projects, large-scale scientific discovery, and crowd-sourced experimentation. Nevertheless, these programs witness challenges in submissions' quality, such as sampling bias resulting from citizens' preferences to complete some tasks over others. The sampling bias frequently manifests itself in the program's dataset as spatially clustered submissions, which reduce the efficacy of the dataset for subsequent scientific studies. To address the spatial clustering problem, programs use reward schemes obtained from game-theoretical models to incentivize citizens to perform tasks that are more meaningful from a scientific point of view. Herein we propose a GPU-accelerated approach for the Avicaching game, which was recently introduced by the eBird citizen science program to incentivize birdwatchers to collect bird data from under-sampled locations. Avicaching is a Principal-Agent game, in which the principal corresponds to the citizen science program (eBird) and the agents to the birdwatchers or citizen scientists. Previous approaches for solving the Avicaching game used approximations based on mixed-integer programming and knapsack algorithms combined with learning algorithms, using standard CPU hardware. Following the recent advances in scalable deep learning and parallel computation on Graphical Processing Units (GPUs), we propose a novel approach to solve the Avicaching game, which takes advantage of neural networks and parallelism for large-scale games. We demonstrate that our approach better captures agents' behavior, which allows better learning and more effective incentive distribution in a real-world bird observation dataset. Our approach also allows for massive speedups using GPUs. As Avicaching is representative of games that are aimed at reducing spatial clustering in citizen science programs, our scalable reformulation for Avicaching enables citizen science programs to tackle sampling b
When using the mixed-integer programming to model situations where the limit of the variables follows a box constraint, we find nonlinear problems. To solve this, linearization techniques of these disjunctive inequali...
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ISBN:
(纸本)9783030337490;9783030337483
When using the mixed-integer programming to model situations where the limit of the variables follows a box constraint, we find nonlinear problems. To solve this, linearization techniques of these disjunctive inequality constraints are typically used, including constants associated to the variable bounds called M-constants or big-M. Calculation of these constants is an open problem since their values affect the reliability of the optimal solution and convergence of the optimization algorithm. To solve this problem, this work proposes a new population-based metaheuristic optimization method, namely wound treatment optimization (WTO) for calculating the M-constant in a typical domain known as the fixed-charge transportation problem. WTO is inspired on the social wound treatment present in ants after raids. This method allows population diversity that allows to find near-optimal solutions. Experiments of the WTO method on the fixed-charge transportation problem validated its performance and efficiency to find tighten solutions of the M-constant that minimizes the objective function of the problem.
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