Continuous process industries engaged in large scale manufacturing of chemicals and fertilizers are highly energy intensive and contribute significantly to system peak demand. Consequent to the introduction of TOU tar...
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Continuous process industries engaged in large scale manufacturing of chemicals and fertilizers are highly energy intensive and contribute significantly to system peak demand. Consequent to the introduction of TOU tariff rates by the utilities, industrial load management programs aimed at economic reduction of electric energy demand of the industries during utility's peak generation period, gained importance. This paper presents an optimization model and formulation for peak demand and electricity cost reduction in continuous process industries. The formulation utilizes non - linearprogramming technique for minimizing the electricity cost by rescheduling the loads satisfying the process, production, and maximum demand constraints. The proposed optimal schedules when applied to a typical chemical plant resulted in significant reduction in peak demand (about 16.8%) and electricity cost (about 4.6%) under the TOU tariff.
In this paper we consider the practical implementation of the disaggregated simplicial decomposition (DSD) algorithm for the traffic assignment problem. It is a column generation method that at each step has to solve ...
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In this paper we consider the practical implementation of the disaggregated simplicial decomposition (DSD) algorithm for the traffic assignment problem. It is a column generation method that at each step has to solve a huge number of quadratic knapsack problems (QKP). We propose a Newton-like method to solve the QKP when the quadratic functional is convex but not necessarily strictly. Our O(n) algorithm does not improve the complexity of the current methods but extends them to a more general case and is better suited for reoptimization and so a good option for the DSD algorithm. It also allows the solution of many QKP's simultaneously in a vectorial or parallel way. (c) 2005 Elsevier B.V. All rights reserved.
Since Pigou proposed that the internalization of the negative externalities could be done calculating a tax in order to correct the difference between private costs and social costs;this will recover the conditions of...
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Since Pigou proposed that the internalization of the negative externalities could be done calculating a tax in order to correct the difference between private costs and social costs;this will recover the conditions of economic efficiency in all the hydraulic legislations of the world, however this advice has been applied in conditions of great shortage;it could be thought that to burden the consumptive use could be more suitable than to burden the production of residual water reaching this way not only the recovering of social efficiency but also a double dividend. to stimulate the water recycling. This work evaluates the effect of the tax charging to the consumptive use will have over a fake economy The achieved results of a residual water production tax. The contrast is done using a model of computable general equilibrium with the Arrow-Debreu assumptions relaxed with the introduction of a government that collect the proposed taxes in a previously distorted economy. The collection distributes through a direct transference to the revenue of the consumers, the model calibrates and resolves following the methodology proposed by Shoven & Whalley (1984).
In this paper, we present a new technique for modeling and characterization of Power Amplifier (PA) by parameter estimation using continuous-time representation. Firstly, we study a continuous model which takes into a...
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In this paper, we present a new technique for modeling and characterization of Power Amplifier (PA) by parameter estimation using continuous-time representation. Firstly, we study a continuous model which takes into account nonlinearities and PA filtering. The filter structure includes a nonlinear polynomial representing amplitude and phase conversion in addition to a MIMO Laplace plant. Then, we propose a new approach for PA model characterization based on parameter estimation with several excitations. Using time-domain measurements, this method deduces recursively an optimal estimation with non linear programming technique. The experimental results show good agreement and demonstrate the possibility of this technique to explain power amplifier dynamics.
This paper deals with the control of processes that present different dynamic responses for equal increments and decrements of its manipulate variable, showing a non symmetric response. Being non-linear systems, inste...
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This paper deals with the control of processes that present different dynamic responses for equal increments and decrements of its manipulate variable, showing a non symmetric response. Being non-linear systems, instead of using nonlinear general methods directly, the paper explores two alternative formulations based on an MPC approach that take advantage of its structure. An application example is provided showing the behaviour of the proposed methods.
This paper presents a method for improving model-updating methods used for the real-time optimization (RTO) of plant operations. Previous work on updating and results analysis and diagnosis is extended to the use of m...
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This paper presents a method for improving model-updating methods used for the real-time optimization (RTO) of plant operations. Previous work on updating and results analysis and diagnosis is extended to the use of multiple data sets for updating the steady-state plant model and to use prior knowledge to categorize the parameters as fast or slow changing. A key challenge in real-time estimation is identifying the maximum number of parameters that can be estimated reliably using the current data;this number changes due to differences in variability in operating condition and sensor availability. Since reliable parameter estimation yields a parameter covariance matrix with a small condition number and determinant, the number is based on a real-time diagnostic that is based on the covariance matrix. Case studies demonstrate the importance of a real-time updating diagnostic and indicate that when plant variation exists in multiple data sets, increased profit can be obtained by updating the additional parameters to reduce the plant/model mismatch. (C) 2002 Elsevier Science Ltd. All rights reserved.
We describe an enhanced version of the primal-dual interior point algorithm in Lasdon, Plummer, and Yu (ORSA Journal on Computing, vol. 7, no. 3, pp. 321-332, 1995), designed to improve convergence with minimal loss o...
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We describe an enhanced version of the primal-dual interior point algorithm in Lasdon, Plummer, and Yu (ORSA Journal on Computing, vol. 7, no. 3, pp. 321-332, 1995), designed to improve convergence with minimal loss of efficiency, and designed to solve large sparse nonlinear problems which may not be convex. New features include (a) a backtracking linesearch using an L1 exact penalty function, (b) ensuring that search directions are downhill for this function by increasing Lagrangian Hessian diagonal elements when necessary, (c) a quasi-Newton option, where the Lagrangian Hessian is replaced by a positive definite approximation (d) inexact solution of each barrier subproblem, in order to approach the central trajectory as the barrier parameter approaches zero, and (e) solution of the symmetric indefinite linear Newton equations using a multifrontal sparse Gaussian elimination procedure, as implemented in the MA47 subroutine from the Harwell Library (Rutherford Appleton Laboratory Report RAL-95-001, Oxfordshire, UK, Jan. 1995). Second derivatives of all problem functions are required when the true Hessian option is used. A Fortran implementation is briefly described. Computational results are presented for 34 smaller models coded in Fortran, where first and second derivatives are approximated by differencing, and for 89 larger GAMS models, where analytic first derivatives are available and finite differencing is used for second partials. The GAMS results are, to our knowledge, the first to show the performance of this promising class of algorithms on large sparse NLP's. For both small and large problems, both true Hessian and quasi- Newton options are quite reliable and converge rapidly. Using the true Hessian, INTOPT is as reliable as MINOS on the GAMS models, although not as reliable as CONOPT. Computation times are considerably longer than for the other 2 solvers. However, interior point methods should be considerably faster than they are here when analytic second
Process flexibility and design under uncertainty have been researched extensively in the literature. Problem formulations for flexibility include nested optimization problems and these can often be refined by substitu...
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Process flexibility and design under uncertainty have been researched extensively in the literature. Problem formulations for flexibility include nested optimization problems and these can often be refined by substituting the optimality conditions for these nested problems. However, these reformulations are highly constrained and can be expensive to solve. In this paper we extend algorithms to solve these reformulated NLP problem under uncertainty by introducing two contributions to this approach. These are the use of a Constraint Aggregation function (KS function) and Smoothing Functions. We begin with basic properties of KS function. Next, we review a class of parametric smooth functions, used to replace the complementarity conditions of the KKT conditions with a well-behaved, smoothed nonlinear equality constraint. In this paper we apply the previous strategies to two specific problems: i) the 'worst case algorithm', that assesses design under uncertainty and, ii) the flexibility index and feasibility test formulations. In the first case, two new algorithms are derived, one of them being single level optimization problem. Next using similar ideas, both flexibility index and feasibility test are reformulated leading to a single non linear programming problem instead of a mixed integer non linear programming one. The new formulations are demonstrated on five different example problems where a CPU time reduction of more than 70 and 80% is demonstrated. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.
An industrial application of mathematical programming is presented. The objective is to propose a tool for computer aided design of compact plate fin heat exchangers. A proprietary sizing procedure, COLETH, is used to...
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An industrial application of mathematical programming is presented. The objective is to propose a tool for computer aided design of compact plate fin heat exchangers. A proprietary sizing procedure, COLETH, is used to initialize the optimization problem and to evaluate the objective function and the constraints during the optimization problem resolution. The main features of COLETH are presented. The partial infeasible path strategy is discussed: at each optimization step, duty requirements are satisfied, but pressure drop constraints are not. Intermediate information can be used and the cpu time is quite low. A non linear programming optimization problem is formulated. Then the problem is solved using a reduced Hessien Successive Quadratic programming algorithm, which can take advantage of the system sparcity. Other features of this algorithm are discussed. Three test problems are presented and the program abilities are illustrated.
Minimizing the Lennard-Jones potential, the most-studied model problem for molecular conformation, is an unconstrained global optimization problem with a large number of local minima. In this paper, the problem is ref...
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Minimizing the Lennard-Jones potential, the most-studied model problem for molecular conformation, is an unconstrained global optimization problem with a large number of local minima. In this paper, the problem is reformulated as an equality constrained nonlinearprogramming problem with only linear constraints. This formulation allows the solution to approached through infeasible configurations, increasing the basin of attraction of the global solution. In this way the likelihood of finding a global minimizer is increased. An algorithm for solving this nonlinear program is discussed, and results of numerical tests are presented.
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