In recent years, research has identified the spatial spreading of freight distribution patterns as one of the largest drivers of the rapid growth in freight transport ton-miles, and of related growth in overall energy...
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In recent years, research has identified the spatial spreading of freight distribution patterns as one of the largest drivers of the rapid growth in freight transport ton-miles, and of related growth in overall energy use and other forms of environmental impact. In this paper, prospects for long-term redistribution of freight flows are explored using origin-destination (OD) flow data from the 1993 US Commodity Flow Survey and a minimum-error technique for estimating disaggregate commodity flows. A prototype analysis of the pulp and paper sector was carried out. The analysis found that matching demand for paper products with geographically optimal production centers and producing an optimal mix of outputs in each center could lead to substantial reductions in total ton-miles (on the order of 17-38%) compared to the 1993 base case. A conceptual example of the implementation of the methodology and an analysis of potential energy savings from spatial redistribution are also presented. (C) 2001 Elsevier Science B.V. All rights reserved.
In this paper, a mathematical programming based discontinuum approach is developed for modelling jointed rock slopes. The formulation naturally leads to a standard second-order cone program, which can be solved using ...
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In this paper, a mathematical programming based discontinuum approach is developed for modelling jointed rock slopes. The formulation naturally leads to a standard second-order cone program, which can be solved using efficient optimisation solvers, and a purely static method is derived that does not require artificial damping parameters. Notably, the approach provides somewhat of a unification of two distinct discontinuum approaches: the soft-particle model and the hard-particle model. A series of numerical examples are conducted to validate the proposed approach. The soft-particle model is more versatile than the hard-particle model while the hard-particle model is more efficient.
The problem of tuning stabilizers in multimachine power systems has been formulated here as a sequence of optimization problems. Both quadratic and linear programming problems have been considered. In the former case,...
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The problem of tuning stabilizers in multimachine power systems has been formulated here as a sequence of optimization problems. Both quadratic and linear programming problems have been considered. In the former case, stabilizers with complex zeros have been included in the compensator model. In each case a particular measure of the stabilizers' gain has been defined. The constraints have been written to represent the region allowed for eigenvalue shifting together with specific constraints. The objective has been to shift the lightly damped eigenvalues associated to the system electromechanical modes. The results have shown that the quadratic programming formulation may be an important auxiliary tool for stabilizers tuning.
We propose a structural optimisation method, based on the level set method and using mathematical programming such as the method of moving asymptotes (MMA), which we apply to the design of compliant mechanisms. A comp...
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We propose a structural optimisation method, based on the level set method and using mathematical programming such as the method of moving asymptotes (MMA), which we apply to the design of compliant mechanisms. A compliant mechanism is a monolithic joint-free mechanism designed to be flexible to obtain a specified motion. In the design of compliant mechanisms, several requirements such as the direction of the deformation and stress concentrations must be considered to obtain the specified mechanical function. Topology optimisation, the most flexible type of structural optimisation, has been successfully used as a design optimisation method for compliant mechanisms, but the utility of topology optimisation results is often spoiled by a plethora of impractical designs such as structures containing grayscale areas. Level set-based topology optimisation methods are immune to the problem of grayscales since the boundaries of the optimal configuration are implicitly represented using the level set function. The proposed method updates the level set function using mathematical programming to facilitate the treatment of constraint functionals. To verify its capability, we apply our method to compliant mechanism design problems that include displacement constraints and stress constraints.
This paper exploits the potential of siphons for the analysis of Petri nets, It generalizes the well-known Commoner condition and is based on the notion of potential deadlocks which are siphons that eventually become ...
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This paper exploits the potential of siphons for the analysis of Petri nets, It generalizes the well-known Commoner condition and is based on the notion of potential deadlocks which are siphons that eventually become empty, A linear programming based sufficient condition under which a siphon is not a potential deadlock is obtained. Based on the new sufficient condition, a mathematical programming approach and a mixed-integer programming approach are proposed for checking general Petri nets and structurally bounded Petri nets respectively without explicitly generating siphons, Stronger results are obtained for asymmetric choice nets and augmented marked graphs. In particular, we show that an asymmetric choice net is live iff it is potential-deadlock-free and an augmented marked graph is live and reversible hi it is potential-deadlock-free.
Starting from rigid-plasticity, we develop variational formulations of first incremental elastoplasticity and then elastoplastodynamics. These formulations are discretized using standard finite element techniques whic...
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ISBN:
(纸本)9789609875011
Starting from rigid-plasticity, we develop variational formulations of first incremental elastoplasticity and then elastoplastodynamics. These formulations are discretized using standard finite element techniques which results in discrete optimization problems that can be solved efficiently by modern mathematical programming methods. Finally, the extension from associated perfect plasticity to general nonassociated and hardening plasticity is detailed.
Hesitant fuzzy linguistic information can be a useful decision-making tool in uncertain and complex environments. In this paper, we establish a new group decision making (GDM) model based on mathematical programming w...
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Hesitant fuzzy linguistic information can be a useful decision-making tool in uncertain and complex environments. In this paper, we establish a new group decision making (GDM) model based on mathematical programming with incomplete hesitant fuzzy linguistic preference relations (HFLPRs). After developing a definition of incomplete HFLPR and its multiplicative consistency, we propose an equivalence theorem of multiplicative consistency between linguistic preference relation (LPR) and corresponding fuzzy preference relation (FPR). Based on this framework, a mathematical programming to address incomplete HFLPR is established. The proposed mathematical programming method has the dual functionality of finding the incomplete LPR with the highest consistency and increasing inconsistent LPR to complete consistent LPR using multiplicative consistency based on given incomplete HFLPR. In this manner, we construct a novel GDM model based on obtained multiplicative consistency LPRs in consideration of the group consensus reaching process. Finally, a real-world emergency management problem is solved to demonstrate the effectiveness of the proposed GDM model.
Although the weighted least of squares technique is an efficient and well-established power system state-estimation procedure, a number of alternative estimation approaches have been proposed in the technical literatu...
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Although the weighted least of squares technique is an efficient and well-established power system state-estimation procedure, a number of alternative estimation approaches have been proposed in the technical literature. This study presents and compares the most-common estimators formulating them as mathematical programming problems. The numerical accuracy and computational efficiency of the different estimators are analysed using an illustrative case study.
This paper presents a hybrid genetic algorithm/mathematical programming heuristic for the n-job, m-machine flowshop problems with lot streaming. The number of sublots for each job and the size of sublots are directly ...
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This paper presents a hybrid genetic algorithm/mathematical programming heuristic for the n-job, m-machine flowshop problems with lot streaming. The number of sublots for each job and the size of sublots are directly addressed by the heuristic and setups may be sequence-dependent. A new aspect of the problem, the interleaving of sublots from different jobs in the processing sequence, is developed and addressed. Computational results from 12 randomly generated test sets of 24 problems each are presented. (C) 2006 Elsevier Ltd. All rights reserved.
Solution of steady-state scalar conservation laws [f(u)]x + pi[f(u)]y = 0 (tau-constant) on the unit square is considered for the two cases f(u) = u and u2. Piecewise constant Dirichlet conditions producing shocked so...
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Solution of steady-state scalar conservation laws [f(u)]x + pi[f(u)]y = 0 (tau-constant) on the unit square is considered for the two cases f(u) = u and u2. Piecewise constant Dirichlet conditions producing shocked solutions are given on the boundary of the unit square. A nonsingular perturbation 2-epsilon-u (epsilon a sufficiently small positive number), rather than a singular perturbation such as -epsilon(u(xx) + u(yy)), is added to the conservation law. The perturbed equation is discretized in a finite-volume sense on each of the cells of a grid of mm equal rectangular cells (m in the x-direction and n in the y-direction). Numerical values of u are located at the cell vertices. The arclength and area integrals of the finite-volume formulas are discretized by the trapezoidal rule. A system of mn equations results for the (m - 1)(n - 1) unknown values of u in the interior of the domain. This system is solved in the l1 sense;that is, the sum of the absolute values of the residuals of the equations is minimized. An algorithm requiring only O(mn) operations is introduced to solve this mathematical programming problem. The numerical solutions have discontinuities in or near the cells containing the shocks of the physically relevant solutions of the original conservation laws and are O(epsilon) approximations of these solutions. A complete theory for the linear case f(u) = u and computational results for the nonlinear case f(u) = u2 are presented. The l1 procedure captures boundary shocks as well as oblique and even zigzag interior shocks in one cell. The results presented here demonstrate that the l1 procedure is a robust, efficient, and highly accurate numerical procedure for solving certain two-dimensional scalar conservation laws.
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