Per partum fetal asphyxia is a major cause of neonatal morbidity and mortality. Fetal heart rate monitoring plays an important role in early detection of acidosis, an indicator for asphyxia. This problem is addressed ...
详细信息
Per partum fetal asphyxia is a major cause of neonatal morbidity and mortality. Fetal heart rate monitoring plays an important role in early detection of acidosis, an indicator for asphyxia. This problem is addressed in this paper by introducing a novel complexity analysis of fetal heart rate data, based on producing a collection of piecewise linear approximations of varying dimensions from which a measure of complexity is extracted. This procedure specifically accounts for the highly nonstationary context of labor by being adaptive and multiscale. Using a reference dataset, made of real per partum fetal heart rate data, collected in situ and carefully constituted by obstetricians, the behavior of the proposed approach is analyzed and illustrated. Its performance is evaluated in terms of the rate of correct acidosis detection versus the rate of false detection, as well as how early the detection is made. Computational cost is also discussed. The results are shown to be extremely promising and further potential uses of the tool are discussed. MATLAB routines implementing the procedure will be made available at the time of publication.
The problem we treat is defined on a graph where each node is associated with a variable and there are loss functions defined on the arcs, depending on the difference between the corresponding node variables. The obje...
详细信息
The problem we treat is defined on a graph where each node is associated with a variable and there are loss functions defined on the arcs, depending on the difference between the corresponding node variables. The objective is to compute values for the node variables so as to minimize the sum of losses. We exploit the relation between this problem and networkflows optimization and use it in developing an approximation algorithm for the problem A main application of the problem is the synchronization of fixed cycle traffic signals.
This scheduling model is derived from the real problem of scheduling looms in a textile industry. Jobs may be independently split. over several specified machines, and preemption is allowed. Deadlines are specified fo...
详细信息
This scheduling model is derived from the real problem of scheduling looms in a textile industry. Jobs may be independently split. over several specified machines, and preemption is allowed. Deadlines are specified for each job, and jobs are assumed to be available. It is shown that minimizing maximum weighted tardiness can be done in polynomial time. The case of uniform machines (as in the considered application) can be modeled as a networkflow, and minimization of maximum tardiness can be done in strongly polynomial time. The case of unrelated machines can be solved either by generalized flow techniques or by Linear Programming. Attention is also focused on the problem of finding so-called Unordered Lexico Optima, in order to schedule nonbinding jobs as early as possible.
In this paper we show that by using path following interior point methods with nonlogarithmic potential functions that vary inversely with the beta th power of the distances from the hyperplane (with beta = O(log v), ...
详细信息
In this paper we show that by using path following interior point methods with nonlogarithmic potential functions that vary inversely with the beta th power of the distances from the hyperplane (with beta = O(log v), it is possible to obtain an approximate bipartite matching with the number of edges within a factor of (1 - 1/p) of that in the optimal matching for arbitrarily specified p in O*(p) matrix inversions (O*(X) = O(X log(k) n), i.e., we ignore logarithmic factors of n in stating most bounds in this paper). At present the best-known logarithmic time parallel algorithm for finding an approximate matching is that for finding a maximal matching that contains at least half of the edges in the optimal matching by Karp and Wigderson [J. ACM, 32 (1985), pp, 762-773]. By combining the approximate matching algorithm discussed in this paper with an augmenting path algorithm it is possible to derive the optimal matching in O*(v(1/2)) time. The previous fastest parallel algorithms for general bipartite graphs are those by Vaidya [Proc. 22nd Ann. ACM Symp, Theory Computing, 1990, pp. 583-589], which runs in O*(ve)(1/4)) time and that by Goldberg, Plotkin, and Vaidya [Proc 29th IEEE Symp. Foundations of Computer Science, 1990, pp. 175-185], which obtains solutions in O*(v(2/3)) time.
This paper is concerned with the Short-Term Hydrothermal Scheduling (STHS) of hydro-dominated power systems. The problem's formulation includes the representation of operational constraints such as the hydraulic c...
详细信息
This paper is concerned with the Short-Term Hydrothermal Scheduling (STHS) of hydro-dominated power systems. The problem's formulation includes the representation of operational constraints such as the hydraulic coupling between hydro plants in cascade and the transmission limits in the electric network. In order to allow the problem's decomposition into hydraulic and electric subproblems, a linear-quadratic penalty approach is applied to enforce the coupling between hydro and electric variables. As a result, the problem's natural networkflow structure is fully exploited through special-purposed network flow algorithms. The technique has been implemented in FORTRAN in a SUN SPARCstation IPX and tested in a 440 KV subsystem of the main interconnected Brazilian power system.
This paper presents a short term hydrothermal scheduling approach for dominantly hydro systems. The problem modelling takes into account both the hydroelectric system operating and the electric transmission network co...
详细信息
This paper presents a short term hydrothermal scheduling approach for dominantly hydro systems. The problem modelling takes into account both the hydroelectric system operating and the electric transmission network constraints in detail. It basically consists of a simulation of the hydraulic system with the discharge decisions given by an optimal DC power flow algorithm. The release targets of the reservoirs, established by the long term operational planning, are enforced by a dual Lagrangean approach that fixes a penalty for the use of water in the reservoirs. Two illustrative examples have been solved in order to evaluate the efficiency of the approach.
It is computationally very convenient to view the problem of reconstructing a homogeneous 3-D object from two orthogonal projections as a flow problem in a capacitated network. This networkflow approach is extended h...
详细信息
It is computationally very convenient to view the problem of reconstructing a homogeneous 3-D object from two orthogonal projections as a flow problem in a capacitated network. This networkflow approach is extended here to incorporate the Poisson nature of the projection data, as is the case in X-ray imaging.
Labeling procedures for the basis graph of a generalized network are introduced which build on procedures designed for pure networks. Computational results are presented which show that a primal simplex code which use...
详细信息
Labeling procedures for the basis graph of a generalized network are introduced which build on procedures designed for pure networks. Computational results are presented which show that a primal simplex code which uses these procedures is about 60 times faster than a general purpose linear programming code.
This paper presents and solves the maximum throughput dynamic networkflow problem, an infinite horizon integer programming problem which involves networkflows evolving over time. The model is a finite network in whi...
详细信息
This paper presents and solves the maximum throughput dynamic networkflow problem, an infinite horizon integer programming problem which involves networkflows evolving over time. The model is a finite network in which the flow on each arc not only has an associated upper and lower bound but also an associated transit time. flow is to be sent through the network in each period so as to satisfy the upper and lower bounds and conservation of flow at each node from some fixed period on. The objective is to maximize the throughput, the net flow circulating in the network in a given period, and this throughput is shown to be the same in each period. We demonstrate that among those flows with maximum throughput there is a flow which repeats every period. Moreover, a duality result shows the maximum throughput equals the minimum capacity of an appropriately defined cut.A special case of the maximum dynamic networkflow problem is the problem of minimizing the number of vehicles to meet a fixed periodic schedule. Moreover, the elegantsolution derived by Ford and Fulkerson for the finite horizon maximum dynamic flow problem may be viewed as a special case of the infinite horizon maximum dynamic flow problem and the optimality of solutions which repeat every period.
Applying standard transformations of generalized upper bounding (GUB) theory to a pure or generalized network basis is shown to yield a reduced working basis that is itself a basis for a reduced network. As a result, ...
详细信息
Applying standard transformations of generalized upper bounding (GUB) theory to a pure or generalized network basis is shown to yield a reduced working basis that is itself a basis for a reduced network. As a result, the working basis can be represented via specialized data structures for networks. The resultant GUB based specializations to the network simplex algorithm are described.
暂无评论