Most of integer, convex, and large-scale linear problems are solved using cutting plane and column generation algorithms. Therefore, to handle large-size problems and to reduce the computing times, it may be very useful to accelerate cutting plane algorithms. We show in this article that we can achieve this goal by choosing good separation points. Focus is given on problems for which we have an exact separation oracle. An in-out algorithm is proposed, and the convergence is proved under some general assumptions. Computational experiments related to three classes of problems, survivable network design, multicommodity flow problems, and random linear programs, clearly point out the savings of time allowed by the simple in-out approach proposed in this article.

No abstract

No abstract

The maximum cut problem is a classical combinatorial optimization problem that is known to be NP-hard in general. In the present article, we provide some new lower and upper bounds that are based on the eigenvalues of the weight matrix with modified diagonal entries. Namely, we show that some upper bounds presented here are generally better than the SDP bound introduced by Goemans and Williamson, JACM 42 (1995), 1115-1145. We also discuss the complexity of computing these bounds and provide some preliminary computational results.

Abstract.A location estimation system for online Partial Discharge (PD) detection is proposed as a low-cost approach to real-time condition monitoring, asset management and operation optimization in future smart grid. Some early progress in the development of subsystems (specifically the antenna, radiometer device, PD emulator and PD generator) for a proof-of-principle prototype system is described. The proposed PD Wireless Sensor Network (WSN) uses a novel approach to PD location which obviates the need for synchronization between sensors thereby improving scalability.

No abstract

Progress on the development of an insulation defect detection and location system using a partial discharge (PD) wireless sensor network (WSN) will be presented. Such a PD WSN based on intensityonly measurements has cost and scalability advantages over existing detection and location technologies based on timedifference-of-arrival measurements such as described in (I. E. Portugues, P. J. Moore, I. A. Glover, IEEE Trans. on Power Delivery, 1, 2009, pp. 20-29). Figure 1 shows a hypothetical deployment of the PD WSN in an electricity substation. The (red) pentagram denotes a PD source, yellow circles and triangles denote sensor nodes, and the yellow St George's cross denotes the data collection/processing node. Each node of the WSN is a broadband radiometer with a measurement band of 50-800 MHz, Figure 2. Three measurement sub-bands allow the radiometer to distinguish different forms of PD; in particular internal PD and corona discharge. WirelessHart has been selected as the network communications technology since this offers improved reliability over other standards (e.g. Zigbee) in harsh industrial environments.

Abstract-The work reported here is part of a PhD research relates to the development of a new type of radiometric system applied to detection of partial discharges signals. A simulation model for the radiometric transmission of a partial discharge pulse is presented. The model is based on a replay model, which acts as a source, which is based on real data to simulate the pulses. The structure considers losses due to the free space transmission path and interferences caused by carriers from broadcast transmissions. A receiver, focus of this research, is based on a radiometer structure, which includes an amplifier, a filter and an envelope detector to minimize the necessity of a high sample rate ADC.