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1.
We consider the problem of optimal control of one-dimensional nonstationary temperature regimes of inhomogeneous bodies with respect to speed of action with restrictions on the control and normal thermoelastic stresses 22 of maximum absolute value (in cylindrical and spherical coordinates the circumferential stresses .Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 34, 1991, pp. 61–65.  相似文献   

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In this note, a simple and quick method is shown for reducing some trigonometric expressions by using a diagram called a ‘carousel’. These expressions can be reduced using other methods, such as: (i) reduction formulae for sum/difference of angles; and (ii) graph shifting techniques.  相似文献   

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For a given set of data points in the plane, a new method is presented for computing a parameter value (knot) for each data point. Associated with each data point, a quadratic polynomial curve passing through three adjacent consecutive data points is constructed. The curve has one degree of freedom which can be used to optimize the shape of the curve. To obtain a better shape of the curve, the degree of freedom is determined by optimizing the bending and stretching energies of the curve so that variation of the curve is as small as possible. Between each pair of adjacent data points, two local knot intervals are constructed, and the final knot interval corresponding to these two points is determined by a combination of the two local knot intervals. Experiments show that the curves constructed using the knots by the new method generally have better interpolation precision than the ones constructed using the knots by the existing local methods.  相似文献   

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We consider a single retailer with a given potential revenue, who sells a product that is subject to shoplifting. In order to decrease losses due to shoplifting and to maximize his profit, the retailer can invest in security measures. In particular, we assume that the retailer purchases security services from a single security supplier. The security supplier decides which price to charge the retailer for these services, with the purpose of maximizing his own profit, and the retailer decides on the quantity of security services to purchase. We address this problem using a game theoretic approach, where the retailer competes with the supplier—the leader—who specifies first the service price. The retailer responds by deciding how much to invest in security. We study the conditions under which both players are profitable and the extent to which double marginalization affects the supply chain performance.  相似文献   

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A set of phylogenetic trees with overlapping leaf sets is consistent if it can be merged without conflicts into a supertree. In this paper, we study the polynomial-time approximability of two related optimization problems called the maximum rooted triplets consistency problem (MaxRTC) and the minimum rooted triplets inconsistency problem (MinRTI) in which the input is a set R of rooted triplets, and where the objectives are to find a largest cardinality subset of R which is consistent and a smallest cardinality subset of R whose removal from R results in a consistent set, respectively. We first show that a simple modification to Wu’s Best-Pair-Merge-First heuristic Wu (2004) [38] results in a bottom-up-based 3-approximation algorithm for MaxRTC. We then demonstrate how any approximation algorithm for MinRTI could be used to approximate MaxRTC, and thus obtain the first polynomial-time approximation algorithm for MaxRTC with approximation ratio less than 3. Next, we prove that for a set of rooted triplets generated under a uniform random model, the maximum fraction of triplets which can be consistent with any phylogenetic tree is approximately one third. We then provide a deterministic construction of a triplet set having a similar property which is subsequently used to prove that both MaxRTC and MinRTI are -hard even if restricted to minimally dense instances. Finally, we prove that unless , MinRTI cannot be approximated within a ratio of c⋅lnn for some constant c>0 in polynomial time, where n denotes the cardinality of the leaf label set of R.  相似文献   

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We study flow-induced enhancement of the speed of pulsating traveling fronts for reaction-diffusion equations, and quenching of reaction by fluid flows. We prove, for periodic flows in two dimensions and any combustion-type reaction, that the front speed is proportional to the square root of the (homogenized) effective diffusivity of the flow. We show that this result does not hold in three and more dimensions. We also prove conjectures from Audoly, Berestycki and Pomeau (2000) [1], Berestycki (2003) [3], Fannjiang, Kiselev and Ryzhik (2006) [11] for cellular flows, concerning the rate of speed-up of fronts and the minimal flow amplitude necessary to quench solutions with initial data of a fixed (large) size.  相似文献   

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We study reducing subspaces for an analytic multiplication operator Mzn{M_{z^{n}}} on the Bergman space La2(Ar){L_{a}^{2}(A_{r})} of the annulus A r , and we prove that Mzn{M_{z^{n}}} has exactly 2 n reducing subspaces. Furthermore, in contrast to what happens for the disk, the same is true for the Hardy space on the annulus. Finally, we extend the results to certain bilateral weighted shifts, and interpret the results in the context of complex geometry.  相似文献   

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This paper studies an optimization problem in which the objective function can not be completely given in closed form. In particular, we assume that some part of the objective function must be computed by an approximation process. This paper develops a technique for solving a class of such problems. Examples demonstrating the technique and problem areas in which it has been successfully applied are also given.  相似文献   

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This note is focused on computational efficiency of the portfolio selection models based on the Conditional Value at Risk (CVaR) risk measure. The CVaR measure represents the mean shortfall at a specified confidence level and its optimization may be expressed with a Linear Programming (LP) model. The corresponding portfolio selection models can be solved with general purpose LP solvers. However, in the case of more advanced simulation models employed for scenario generation one may get several thousands of scenarios. This may lead to the LP model with huge number of variables and constraints thus decreasing the computational efficiency of the model. To overcome this difficulty some alternative solution approaches are explored employing cutting planes or nondifferential optimization techniques among others. Without questioning importance and quality of the introduced methods we demonstrate much better performances of the simplex method when applied to appropriately rebuilt CVaR models taking advantages of the LP duality.  相似文献   

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Maritime cabotage is a legislation published by a particular coastal country, which is used to conduct the cargo transportation between its two domestic ports. This paper proposes a two-phase mathematical programming model to formulate the liner hub-and-spoke shipping network design problem subject to the maritime cabotage legislations, i.e., the hub location and feeder allocation problem for phase I and the ship route design with ship fleet deployment problem for phase II. The problem in phase I is formulated as a mixed-integer linear programming model. By developing a hub port expanding technique, the problem in phase II is formulated as a vehicle routing problem with pickup and delivery. A Lagrangian relaxation based solution method is proposed to solve it. Numerical implementations based on the Asia–Europe–Oceania shipping services are carried out to account for the impact analysis of the maritime cabotage legislations on liner hub-and-spoke shipping network design problem.  相似文献   

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We show that any n × n conjugate-normal matrix can be brought by a unitary congruence transformation to block-tridiagonal form with the orders of the consecutive diagonal blocks not exceeding 1, 2, 3, ..., respectively. The proof is constructive; namely, a finite process is described that implements the reduction to the desired form. Sufficient conditions are indicated for the orders of the diagonal blocks to stabilize. In this case, the condensed form is a band matrix.  相似文献   

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Lagrangian bounds, i.e. bounds computed by Lagrangian relaxation, have been used successfully in branch and bound bound methods for solving certain classes of nonconvex optimization problems by reducing the duality gap. We discuss this method for the class of partly linear and partly convex optimization problems and, incidentally, point out incorrect results in the recent literature on this subject.  相似文献   

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This paper considers the problem of optimizing a nonlinear convex function which is, in part, defined by a simulation process. An iterative technique, based on contractive mapping properties, is given by which a selected class of such functions can be optimized.  相似文献   

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This survey presents the brief history and recent development on commutants and reducing subspaces of multiplication operators on both the Hardy space and the Bergman space, and von Neumann algebras generated by multiplication operators on the Bergman space.  相似文献   

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Execution time optimization is one of the most important objectives to accomplish for experiments launched on grid environments. However, the computing community is becoming more conscious about energy savings, seeking their optimization. In this work, both execution time and energy consumption are optimized through two swarm and multi-objective algorithms based on both physics and biology fields. On the one hand, multi-objective gravitational search algorithm (MOGSA) is inspired by the gravity forces between the planet masses. On the other hand, Multi-Objective Firefly Algorithm is based on the light attraction between the fireflies. These swarm algorithms are compared with the standard multi-objective algorithm non-dominated sorting genetic algorithm II to study their efficiency as multi-objective algorithms. Moreover, the best algorithm proposed, MOGSA, is compared with MOHEFT (a multi-objective version of one of the most-used algorithms in workflow scheduling, HEFT), and also with two real grid schedulers: Workload Management System and deadline budget constraint. Results show the superior performance of MOGSA regarding the others.  相似文献   

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In this paper, we examine the possibility of the arrangement for multiple deliveries in each order cycle for the continuous review inventory system. The problem is mainly found in the retail sector where inventory often makes up the majority of a company's assets. Most works recently have focused on the reduction of safety stock in the multiple sourcing setting. This research, instead, considers the reduction of cycle stock in the sole sourcing environment. The formulation where a predetermined service level serves as a constraint for the objective function is employed throughout this research. We show that splitting the order into multiple deliveries can significantly reduce the inventory carrying cost especially when the interarrival times between deliveries are determined optimally.  相似文献   

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In this paper, we first analyze the relationship between curricula, teachers, classes, time slices and classrooms in a graph. Then on the basis of constraint conditions in curriculum schedule practically in universities, we presents its optimization model, in which the fuzzy synthetic decision-making (FSDM) is used to optimize genetic algorithm (GA), and a new GA encoding scheme is employed to design fitness and punishment functions for the curriculum schedule problem. This model effectively improved a running performance, which provides a better implementation approach to improvements of the existing curriculum schedule systems. The experimental results show that fitness values of the FSDM-based GA are of obvious evolutional tendency, the chromosome encoding scheme and the fitness function can meet its requirements preferably, and the more adequate computation resources, the greater possibilities of no restoration for the obtained optimal individual.  相似文献   

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