A didactic procedure for designing power oscillation dampers of FACTS devices

An important issue related to power system stability is to properly damp low frequency oscillations. Traditionally, these oscillations have been damped by means of power system stabilizers. In recent years, FACTS devices equipped with a power oscillation damper have been also efficiently used for damping oscillations. This paper is a tutorial for designing such power oscillation damper. The paper presents design projects suitable for students in the power system control area at the M.Sc. and Ph.D. levels. For educational purposes, the procedure is based on Matlab and on two specific toolboxes, namely the Power System Analysis Toolbox and the Control System Toolbox. A single-machine infinite bus and a two-area test systems, with a thyristor controlled series compensator and an unified power flow controller, respectively, are used as examples for the POD design. Classroom experience has shown that the procedure helps in consolidating a better understanding of power system stability and control.     

The effect of packing and conformation on free radical yields in films of variably hydrated DNA

Cellular proteins (biomarkers) specific to any individual microorganism, determined by the direct mass spectral analysis of the corresponding intact cellular suspension, can be applied for the rapid and specific identification of the organisms present in unknown samples. The components of the bacterial suspensions, after a rapid separation over a C18 reversed-phase microcapillary column, were directly subjected to on-line electrospray ionization followed by analysis using an ion trap tandem mass spectrometer. This approach is equally effective for gram-positive as well as gram-negative bacteria but has a distinct advantage over our earlier reported method involving matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). During electrospray ionitation mass spectrometry (ESI-MS), liquid samples can be directly analyzed and there is the potential for developing tandem mass spectral methods for more specific identification of the individual organisms present in crude bacterial mixtures. The total analysis time leading to unambiguous bacterial identification in samples was less than 10 minutes and the results were quite reproducible. Miniaturization of the instrumentation along with total automation of this simple process could have immense impact on field operations. Routine, rapid, cost-effective field monitoring of environmental samples, agricultural products, samples from food processing, industrial sites and health institutions for suspected bacterial contamination could be a reality in the near future. Potential utility in biological, medical, bioprocessing, pharmaceutical, and other industrial research is also enormous.     

Linear quadratic state feedback and robust neural network estimatorfor field-oriented-controlled induction motors

A field-oriented control scheme for an induction motor with a linear quadratic optimal regulator and a robust neural network estimator is proposed. The state feedback is designed by using the synchronous frame motor model. The number of the states is increased in order to take into account the presence of two integrators on the flux and torque errors. The resulting model is suitably simplified and the corresponding approximations are discussed. The procedure proposed is shown to be suitable also for the design of the state feedback via the pole placement technique. A comparison with standard proportional integral regulators is provided. The rotor flux is estimated by using a robust neural network observer. The network training set is suitably designed in order to preserve the drive effectiveness also in the presence of large parameter uncertainties. The robust neural observer is compared with an extended Kalman filter and a standard neural network observer. Using a 250 kW induction motor as a case study, the simulation results show the effectiveness of the proposed solution, both during transient and steady-state operating conditions     

Enhancing CLP branch and bound techniques for scheduling problems

In this paper, we propose a constraint logic programming (CLP) approach to the solution of a job shop scheduling problem in the field of production planning in orthopaedic hospital departments. A pure CLP on finite domain (CLP(FD)) approach to the problem has been developed, leading to disappointing results. In fact, although CLP(FD) has been recognized as a suitable tool for solving combinatorial problems, it presents some drawbacks for optimization problems. The main reason concerns the fact that CLP(FD) solvers do not effectively handle the objective function and cost‐based reasoning through the simple branch and bound scheme they embed. Therefore, we have proposed an improvement of the standard CLP branch and bound algorithm by exploiting some well‐known operations research results. The branch and bound we integrate in a CLP environment is based on the optimal solution of a relaxation of the original problem. In particular, the relaxation used for the job shop scheduling problem considered is the well‐known shifted bottleneck procedure considering single machine problems. The idea is to decompose the original problem into subproblems and solve each of them independently. Clearly, the solutions of each subproblem may violate constraints among different subproblems which are not taken into account. However, these solutions can be exploited in order to improve the pruning of the search space and to guide the search by defining cost‐based heuristics. The resulting algorithm achieves a significant improvement with respect to the pure CLP(FD) approach that enables the solution of problems which are one order of magnitude greater than those solved by a pure CLP(FD) algorithm. In addition, the resulting code is less dependent on the input data configuration. Copyright © 2001 John Wiley & Sons, Ltd.     

Evolution non biologique dans l'eau de composes organohalogenes a trois et quatre atomes de carbone: Hydrolyse et photolyseNon biological evolution, in water, of some three- and four-carbon atoms organohalogenated compounds: Hydrolysis and photolysis

The purpose of this paper is to make a contribution to the study of chemical decomposition, in situ and during water treatment, of some average weight molecular aliphatic compounds. Effectively, few studies concern these three- or four-carbon atom compounds, most publications of recent years are relative to very volatile halogenated hydrocarbons with one or two carbon atoms: halomethanes, haloethanes and halogenoethylenes. However these average weight molecular compounds are widely used as reactives or solvents in industrial chemistry, or as pesticides. Many of these products are able to take form during the water treatment by chlorine or its by-products. Effectively most compounds, widely estimated as toxic, have been found in waters, and especially drinking water. They are very resistant to biological degradation. Therefore we have studied their evolution in waters, considering the two principal processes of chemical degradation in the environment: hydrolysis and photolysis. We have determined, for each of the seventeen products studied, their degradation velocity by hydrolysis (Tables 1, 2 and 3), and the nature of the compounds formed. The degradation products are halogenated alcohols. The formation of compounds derivated from elimination reactions is never observed. The photochemical degradations are realized with a medium pressure mercury vapour u.v. lamp in quartz and pyrex tubes. We have specified, each time, the degradation velocity (Table 4) and the structure of the photoproducts. Moreover, the influence on the photochemical degradation of acetone (Tables 6 and 7) hydrogen peroxide (Tables 4 and 5), compounds often present in the natural waters, is studied. Hydrogen peroxide, as traces in water, considerably increases the photodegradation velocities. Reactional mechanism hypotheses are proposed in pure demineralized water and in the presence of hydrogen peroxide and acetone. The degradation begins by a homolytic rupture of the most labile bond halogen carbon to yield the most stable halogenated hydrocarbon radical, by reaction with molecular oxygen present in the medium and by reaction with water. These mechanisms explain the formation, during the reaction, of halogenated alcohols, cetones, alcenes and epoxides, and also of allylic alcohol, acetone and methanol.     

Dynamic REI equivalents for short circuit and transient stability analyses

This paper proposes a systematic approach for dynamic power system equivalents based on power transfer distribution factors. The proposed method divides the original network into an internal interconnected system and an external one. Static equivalents are computed at frontier buses that separate the retained internal system from the external one. The equivalents are formed using REI (Radial, Equivalent and Independent) networks and generator model aggregation. Generator parameters are computed based on power transfer distribution factors of the generated active power. The equivalent models are able to accurately approximate the behavior of the original system for short circuit and transient stability analyses. Two test systems, namely the Kundur’s 2-area test system and a 1213-bus network that model a real transmission system are used to illustrate and test the proposed technique.     

A Wideband InP DHBT True Logarithmic Amplifier

A wideband logarithmic amplifier is demonstrated in this paper using InP-InGaAs double heterojunction bipolar transistor technology. The amplifier uses cascaded gain stages including the limiting and unity amplifiers to achieve a piecewise approximation to the ideal logarithmic response. The performance of 43-dB dynamic range, 22-GHz bandwidth, and 2     

Optimal methods for resource allocation and scheduling: a cross-disciplinary survey

Classical scheduling formulations typically assume static resource requirements and focus on deciding when to start the problem activities, so as to optimize some performance metric. In many practical cases, however, the decision maker has the ability to choose the resource assignment as well as the starting times: this is a far-from-trivial task, with deep implications on the quality of the final schedule. Joint resource assignment and scheduling problems are incredibly challenging from a computational perspective. They have been subject of active research in Constraint Programming (CP) and in Operations Research (OR) for a few decades, with quite difference techniques. Both the approaches report individual successes, but they overall perform equally well or (from a different perspective) equally poorly. In particular, despite the well known effectiveness of global constraints for scheduling, comparable results for joint filtering of assignment and scheduling variables have not yet been achieved. Recently, hybrid approaches have been applied to this class of problems: most of them work by splitting the overall problem into an assignment and a scheduling subparts; those are solved in an iterative and interactive fashion with a mix of CP and OR techniques, often reporting impressive speed-ups compared to pure CP and OR methods. Motivated by the success of hybrid algorithms on resource assignment and scheduling, we provide a cross-disciplinary survey on such problems, including CP, OR and hybrid approaches. The main effort is to identify key modeling and solution techniques: they may then be applied in the construction of new hybrid algorithms, or they may provide ideas for novel filtering methods (possibly based on decomposition, or on alternative representations of the domain store). In detail, we take a constraint-based perspective and, according to the equation CP = model + propagation + search, we give an overview of state-of-art models, propagation/bounding techniques and search strategies.     

Myocardial beta-adrenergic receptor signaling in vivo: insights from transgenic mice

Heart failure is a problem of increasing importance in cardiovascular medicine. An important characteristic of heart failure is reduced agonist-stimulated adenylyl cyclase activity (receptor desensitization) due to both diminished receptor number (receptor downregulation) and impaired receptor function (receptor uncoupling). These changes in the section-adrenergic receptor (section-AR) system may in part account for some of the abnormalities of contractile function in this disease. Myocardial contraction is closely regulated by G protein coupled beta-adrenergic receptors through the action of the second messenger cAMP. The beta-adrenergic receptors themselves are regulated by a set of specific kinases, termed the G-protein-coupled receptor kinases. The study of this complex system in vivo has recently been advanced by the development of transgenic and gene targeted ("knockout") mouse models. Combining transgenic technology with sophisticated physiological measurements of cardiac hemodynamics is an extremely powerful strategy to study the regulation of myocardial contractility in the normal and failing heart.     

A computational intelligence-based suite for vulnerability assessment of electrical power systems

This paper discusses the feasibility of implementing computational intelligence algorithms for power system analysis in an open source environment. The scope is specially oriented to education, training and research. In particular, the paper describes a software package, namely Computational Intelligence Applications to Power System (CIAPS), that implements a variety of heuristic techniques for vulnerability assessment of electrical power systems. CIAPS is based on Matlab and suited for analysis and simulation of small to large size electric power systems. CIAPS is used for solving power flow, optimal power flow, contingency analysis based on artificial neural networks and fuzzy logic techniques. A variety of illustrative examples are given to show the features of the developed software tool.