State Estimation for the Localization of Harmonic Sources in Electric Distribution Systems

Throughout the last years, with the liberalization of the energy market, the localization of the sources of power quality disturbances has become a nodal point for operators and customers. In the liberalized market, knowledge of the system status, along with the uncertainty affecting the estimated data, is required to operate management and control issues such as energy dispatching and protection coordination. In distribution systems, too many measurement instruments would be needed to obtain a complete observation of the electric quantities. Thus, model-based state-estimation techniques can be implemented to exploit the few real-time measurements from the field and all the other available information to estimate the desired quantities. In this paper, a novel approach to the estimation of the harmonic sources by means of a Bayesian approach is proposed. The procedure also allows the ldquoqualityrdquo of the obtained estimates to be assessed. The theoretical fundamentals of the method are discussed, and results relevant to a simple distribution network are presented.     

Artificial intelligence in science of measurements: from measurement instruments to perceptive agencies

This paper motivates, from historical, philosophical, and industrial points of view, the adoption of a novel scheme for developing complex measuring systems as perceptive agencies. The general concept of agency, a cooperative multiagent system defined within distributed artificial intelligence and robotics, is discussed together with its particular application to the field of intelligent instruments. An embryonic example of perceptive agency applied to the field of environmental monitoring is reported.     

On the equivalence and range of applicability of graph-based representations of logic programs

Logic programs under Answer Sets semantics can be studied, and actual computation can be carried out, by means of representing them by directed graphs. Several reductions of logic programs to directed graphs are now available. We compare our proposed representation, called Extended Dependency Graph, to the Block Graph representation recently defined by Linke [Proc. IJCAI-2001, 2001, pp. 641-648]. On the relevant fragment of well-founded irreducible programs, extended dependency and block graph turns out to be isomorphic. So, we argue that graph representation of general logic programs should be abandoned in favor of graph representation of well-founded irreducible programs, which are more concise, more uniform in structure while being equally expressive.     

The role of echography in the evaluation of gynecological neoplasia

Physiological and pathological echograms of the female genital tract are examined. Following a rapid review of the literature, the role of echography in gynecology is evaluated on their decennial experience.     

A Decentralized Observer for Ship Power System Applications: Implementation and Experimental Validation

In the last few years, the growing complexity of the electrical power networks, mainly due to the increased use of electronic converters together with the requirements of a higher level of reliability and security, pushed the development of new techniques for the state estimation of the power systems. In this paper, the authors focus their attention on the implementation and experimental validation of a decentralized observer for the state estimation in an electric ship, whose power network is characterized by fast dynamics and by the presence of many electronic devices. The proposed solution implements a decentralized information filter (DIF).      

A real-time instantaneous frequency estimator for rotating magneticislands in a tokamak thermonuclear plasma

The evolution of rotating magnetic islands is a limit for the regime of stable operation in tokamak plasma confinement systems for nuclear fusion research, working close to operating conditions required in a future reactor. It is possible to counteract the growth of the magnetic islands by applying an external magnetic field, provided that the rotating speed of the magnetic islands is measured. The rotating speed can be determined from the measurement of the frequency of the electromotive force induced on a set of magnetic detectors. This paper proposes a digital method for the estimation of this frequency. The results of some laboratory tests performed on a prototype device of the estimator are reported     

Maximum Entropy Multivariate Analysis of Uncertain Dynamical Systems Based on the Wiener–Askey Polynomial Chaos

Many measurement models are formalized in terms of a stochastic ordinary differential equation that relates its solution to some given observables. The expression of the measurement uncertainty for the solution that is evaluated at some time instants requires the determination of its (joint) probability density function. Recently, the polynomial chaos theory (PCT) has been widely recognized as a promising technique in order to address the problem. The uncertainty estimation via PCT requires the use of a Monte Carlo integration sampling strategy. In this paper, a novel approach will be presented in order to achieve PCT uncertainty estimation on the basis of an analytical methodology, requiring only optimization calculus     

Evaluation of serum inhibin A as a surveillance marker after conservative management of tubal pregnancy

Tubal pregnancy is now commonly managed by laparoscopic salpingostomy or systemic methotrexate. A disadvantage of such conservative management is the need for appropriate follow-up, with serial measurement of serum concentrations of human chorionic gonadotrophin (HCG), to exclude persistent ectopic pregnancy (PEP). Concentrations of inhibin A, also a placental product, are significantly increased during pregnancy and the half-life of inhibin A is significantly shorter than that of HCG. To assess the suitability of inhibin A as a marker of PEP, we studied 16 women who had undergone surgery for a tubal pregnancy, measuring HCG and inhibin during follow-up. The mean +/- SEM time taken to achieve non-pregnant concentrations of inhibin A was significantly shorter than for HCG (4.2 +/- 0.8 days versus 21.6 +/- 4.4 days respectively; P < 0.001 Wilcoxon signed rank test). However, in all women the inhibin A concentration increased rapidly after reaching a nadir, reflecting the return of ovarian function, complicating the interpretation of results. In four women inhibin A was almost undetectable preoperatively, while the corresponding HCG concentration was high. These data suggest that inhibin A will not be a useful marker for PEP but that it may provide a more accurate preoperative assessment of trophoblast viability than HCG, thereby improving management.