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Relationships between the Ricci curvature and the squared mean curvature and between the shape operator associated with the mean curvature vector and the sectional curvature function for slant submanifolds of an S-space-form are proved, particularizing them to invariant and anti-invariant submanifolds tangent to the structure vector fields.

Using the notion of discrete Morse function introduced by R. Forman for finite cw-complexes, we generalize it to the infinite 2-dimensional case in order to get the corresponding version of the well-known discrete Morse inequalities on a non-compact triangulated 2-manifold without boundary and with finite homology. We also extend them for the more general case of a non-compact triangulated 2-pseudo-manifold with a finite number of critical simplices and finite homology.

This paper is about Astrodata, a Supervisory, Control and Data Adquisition system (SCADA). It was designed and implemented employing two important concepts: the effective cost and the sustainable automation. The SCADA is working at the Radio Astronomical Station of Havana. This solution has demonstrated to be more economical than the former solution implemented.

The increasing wind power penetration on power systems requires the development of adequate wind farms models for representing the dynamic behaviour of wind farms on power systems. The behaviour of a wind farm can be represented by a detailed model including the modelling of all wind turbines and the wind farm electrical network. But this detailed model presents a high order model if a wind farm with high number of wind turbines is modelled and therefore the simulation time is long. The development of equivalent wind farm models enables the model order and the computation time to be reduced when the impact of wind farms on power systems is studied. In this paper, equivalent models of wind farms with fixed speed wind turbines are proposed by aggregating wind turbines into an equivalent wind turbine that operates on an equivalent wind farm electrical network. Two equivalent wind turbines have been developed: one for aggregated wind turbines with similar winds, and another for aggregated wind turbines under any incoming wind, even with different incoming winds. The proposed equivalent models provide high accuracy for representing the dynamic response of wind farm on power system simulations with an important reduction of model order and simulation time compare to that of the complete wind farm modelled by the detailed model.

A new class of Lie algebras of finite dimension, those which are associated with a certain combinatorial configuration made up by triangles of weighted and non-directed edges, is introduced and a characterization theorem for them is proved. Moreover, some subclasses of such Lie algebras are classified.

We study some special types of slant submanifolds of S-manifolds related to the second fundamental form of the immersion: totally f-geodesic and f-umbilical, pseudo-umbilical and austere submanifolds. We also give several ex- amples of such submanifolds.

ON PSEUDO-EINSTEIN HYPERSURFACES OF H 2n + s

ON ξ-CONFORMALLY FLAT CONTACT METRIC MANIFOLDS

This paper is about Low Cost Automation. In it, a basic background about Havana Radioastronomical Station is described. It is showed a Real Time Supervisory and Control System named Astrodata. The System employs Virtual Instruments and Distributed I/O. Transfer information from sensors to computer it is made by communication network. Astrodata creates a database for off-line data processing. Data's primary processing is made by system on-line.

In this paper we study a class of K-contact manifolds, namely φ-conformally flat K-contact manifolds and we show that a compact φ-conformally flat K-contact manifold with regular contact vector field is a principal S1-bundle over an almost Kaehler space of constant holomorphic sectional curvature.

We define and study both bi-slant and semi-slant submanifolds of an almost contact metric manifold and, in particular, of a Sasakian manifold. We prove a characterization theorem for semi-slant submanifolds and we obtain integrability conditions for the distributions which are involved in the definition of such submanifolds. We also study an interesting particular class of semi-slant submanifolds.

This chapter provides a basic understanding of modelling of wind turbines, including both the mechanical and electrical systems, and control schemes that enable a suitable operation of the wind turbines. An overview of the most widely used wind turbine concepts is performed and their models for integration in large power system dynamic simulations are described. The wind turbine concepts studied are: fixed-speed squirrel cage induction generator (FS-SCIG), wound rotor induction generator (WRIG) with variable rotor resistance (VRR), doubly fed induction generator (DFIG), and direct drive synchronous generator (DDSG).

We introduce and study generalized S-space-forms. Moreover, we investigate generalized S-space-forms endowed with an additional structure and we obtain some obstructions for them to be S-manifolds.

Wind parks have experienced a great increase over the last years, from small wind parks with a few wind turbines connected to utility distribution systems, to large wind parks connected to transmission networks that may be considered, from the network system operators point of view, as a single wind power plant with operational capabilities similar to a conventional power plant. In this chapter, three main aspects concern to wind park grid integration are considered: the necessity of suitable wind park models for transient stability studies; the wind park control to fulfill system requirements and the application of special devices to enhance grid integration capabilities.

In this study, S-manifolds endowed with a semi-symmetric metric connection naturally related with the S-structure are considered and some curvature properties of such a connection are given. In particular, the conditions of semi-symmetry, Ricci semi-symmetry and Ricci-projective semi-symmetry of this semi-symmetric metric connection are investigated.

This paper presents a comparative study of two new methods for voltage harmonic compensation of a stand-alone single phase inverter-based FC. The system under study is composed of: 1) Proton-Exchange-Membrane (PEM) FC including a unidirectional DC/DC converter, which converts the DC voltage delivered by the FC to the DC bus voltage; 2) single-phase pulse width modulated (PWM) inverter; 3) transformer; 4) L passive filter; and 5) linear and non-linear loads. The dynamic model of this system and the controls applied to the PWM inverter for voltage regulation and harmonic compensation are detailed in this paper. Simulation results show the effectiveness of the two purposed methods for voltage harmonic compensation to acceptable levels defined in grid codes.

Objective: This evidence-based clinical practice guideline (CPG) aims to improve clinical decision making of general practitioners and specialists in the treatment of acute tonsillitis and adenoid ...

This paper presents a sizing method and supervisory control for the suitable energy management of a stand-alone hybrid system with photovoltaic (PV) solar panels, hydrogen subsystem and battery. The battery and hydrogen subsystem, composed of fuel cell (FC), electrolyzer and hydrogen storage tank, act as energy storage and support system. A sizing method based on Simulink Design Optimization (SDO) of MATLAB is used to perform a technical optimization of the components of the hybrid system. The dynamic model of the designed hybrid system is detailed in this paper. The models, implemented in MATLAB-Simulink environment, are designed from commercially available components. It is designed, primarily, to satisfy the load power demand and, secondly, to maintain certain level at the hydrogen tank (hydrogen energy reserve), and at the state of charge (SOC) of the battery bank to extend its life.

In recent years, Fuel Cells (FC) have gained interest as energy source for stand-alone and grid connected applications, because they are very high-efficiency and multi-fuel power generators that require neither the burning of conventional fuels nor the mechanical equipment of conventional power generators. When FC are used with inverters for supplying AC loads, harmonic distortion in the supply voltage results in increased heating losses in loads, excite resonances and overload customer power factor correction equipment. Sensitivity of customer equipment to voltage distortion may be dependent on both the magnitude of the distortion levels and the specific harmonic components. For these reasons, it is important to keep the voltage harmonics within recommended levels. This paper presents a new method for voltage harmonic compensation of a stand-alone single phase inverter-based FC. The system under study is composed of: 1) Proton- Exchange-Membrane (PEM) FC including a unidirectional DC/DC converter, which converts the DC voltage delivered by the FC to the DC bus voltage; 2) single-phase pulse width modulated (PWM) inverter; 3) transformer; 4) L passive filter; and 5) linear and non-linear loads. The dynamic model of this system and the control applied to the PWM inverter for voltage regulation and harmonic compensation are detailed in this paper. Simulation results show the effectiveness of the purposed method for voltage harmonic compensation to acceptable levels defined in grid codes.

This paper presents a comparative study of four sizing methods for a stand-alone hybrid generation system integrating renewable energies (photovoltaic panels and wind turbine) and backup and storage system based on battery and hydrogen (fuel cell, electrolyzer and hydrogen storage tank). Two of them perform a technical sizing. In one case, the sizing is based on basic equations, and in the other case, an optimal technical sizing is achieved by using Simulink Design Optimization. The other two methods perform an optimal techno-economical sizing by using the hybrid system optimization software HOMER and HOGA, respectively.

Energy storage is key to expanding the use of wind power, since it allows the wind turbines to smooth the power fluctuations caused by the intermittent and largely unpredictable nature of wind power. This paper presents the modeling and control of a doubly fed induction generator (DFIG) wind turbine with a lead-acid battery as energy storage system. A supervisory control system is developed for a suitable energy management of the energy sources. The modeling and control of this hybrid generation system is evaluated by simulation under different operating conditions.

Many authors have studied the geometry of submanifolds of Kaehlerian and Sasakian manifolds. On the other hand, David E. Blair has initiated the study of S-manifolds, which reduce, in particular cases, to Sasakian manifolds [1]. I. Mihai [7] and Ornea [8] have studied CR-submanifolds of S-manifolds. The purpose of the present paper is to investigate some properties ofinvariant and anti-invariant submanifolds of an S-manifold whose invariant f-sectional curvature is constant, that is, of an S-space form. Specifically, those ones related with the curvature tensor fields and with the scalar curvature on the submanifold. In Section 1 we review basic formulas for submanifolds in Riemannian manifolds and, in Section 2, for S-manifolds. In Sections 3 and 4 we study anti-invariant and invariant submanifolds, respectively, of an S-space form. Finally, in the last section we give some examples.

0. Introduction. Many authors have studied the geometry of sub-manifolds of Kaehlerian and Sasakian manifolds. On the other hand, DavidE. Blair has initiated the study of S-manifolds, which reduce, in particularcases, to Sasakian manifolds ([1, 2]).I. Mihai ([8]) and L. Ornea ([9]) have investigated CR-submanifolds ofS-manifolds. The purpose of the present paper is to study a special kind ofsuch submanifolds, namely the normal CR-submanifolds.In Sections 1 and 2, we review basic formulas and definitions for sub-manifolds in Riemannian manifolds and in S-manifolds, respectively, whichwe shall use later. In Section 3, we introduce normal CR-submanifolds ofS-manifolds and we study some properties of their geometry. Finally, in Sec-tion 4, we consider those submanifolds in the case of the ambient S-manifoldbeing an S-space form.1. Preliminaries. Let N be a Riemannian manifold of dimension nand M an m-dimensional submanifold of N. Let g be the metric tensor fieldon N as well as the induced metric on M. We denote by ∇ the covariantdifferentiation in N and by ∇ the covariant differentiation in M determinedby the induced metric. Let T(N) (resp. T(M)) be the Lie algebra of vectorfields in N (resp. in M) and T(M)

This paper compares two control strategies of a fuel cell (FC)-battery powered hybrid system integrating two dc/dc converters for the Metro-Centro tramway (400 kW) from Seville, Spain. Besides, modeling of each component is briefly presented. These models have been implemented in MATLAB/SIMULINK environment. A Polymer Electrolyte Membrane (PEM) FC is used in this work. The FC model characteristics are selected from a Nuvera 127 kW PEM FC. Two PEM FCs connected in parallel operate as primary energy source and a group of Ni-MH battery supplements the output of the FC during tramway acceleration or whenever else needed and provides regenerative braking energy recapture capability. Finally, the simulation results of both control configurations (Cascade and States Control Strategies) are presented for the real driving cycle of the tramway. The results demonstrate the hybrid system capability to meet appropriate driving cycle in both cases.

This paper compares two control configurations for a fuel cell (FC)-battery powered hybrid system for the Metro-Centro tramway (800 kW) from Seville, Spain. Besides, modeling of each components is briefly presented. These models have been implemented in MATLAB/SIMULINK environment. Polymer Electrolyte Membrane (PEM) FC model used in the simulations realized is a simplification of Jay T. Pukrushpan et al. model. The model characteristics are selected from a Nuvera 127 kW PEM FC. Four of this PEM FC´s are the primary energy source and a group of Ni-MH battery supplements the output of the FC during tramway acceleration or whenever else needed and provides regenerative braking energy recapture capability. Finally, the simulation results for both control configurations (States and Cascade Control Strategies) are presented for the real driving cycle of the tramway. The results demonstrate the hybrid system capability to meet appropriate driving cycle in both caseshese instructions give you basic guidelines for preparing camera-ready papers for conference proceedings.

This paper presents the arrangement, modeling and control of a hybrid system for a tramway. In order to supply the power consumption of the tramway (due to the auxiliary services and four traction induction motor drives), the hybrid system presents two power sources: 1) a Polymer Electrolyte Membrane (PEM) Fuel Cell (FC) as primary energy source; and 2) a Ni-MH battery as secondary energy source, which serves as a supplement to the FC for tramway acceleration or for energy recovery during braking. In addition, a braking chopper is required to absorb the regenerative energy produced by motors deceleration when it cannot be absorbed by the battery due to its limitations. Both FC and battery are coupled to a dc/dc power converter, which enables an active control of the two power sources. An energy management system (EMS) is responsible for: 1) the appropriate distribution of the power demanded by the tramway between the power sources; and 2) the braking chopper operation when required during regenerative braking. The simulation results show the hybrid system capability to allow the tramway to properly follow the driving cycle.

This paper presents a fuel cell-battery powered hybrid system for transport applications, more specifically for a tramway. It uses a Polymer Electrolyte Membrane (PEM) fuel cell (FC) as primary energy source and a Ni-MH battery as secondary energy source, which serves as a supplement to the FC during the driving cycle. The hybrid system supplies the power consumption of the auxiliary services and the traction system, which is composed of four traction induction motor drives. The energy management system (EMS) of the hybrid tramway fixes the reference signals for: 1) the FC dc/dc boost converter in order to accurately distribute power between two electrical sources; 2) the electric motor drives; 3) energy dissipation in the braking chopper when required during regenerative braking. The proposed hybrid system is assessed for a real driving cycle. The results show the hybrid system capability to allow the tramway to properly follow the driving cycle.

We study the conformal curvature tensor and the contact con- formal curvature tensor in Sasakian and/or K-contact manifolds. We flnd a necessary and su-cient condition for a Sasakian manifold to be '-conformally ∞at. We also flnd some necessary conditions for a K-contact manifold to be '-contact conformally ∞at. Then we give a structure theorem for '-contact conformally ∞at Sasakian manifolds. It is also proved that a Sasakian mani- fold cannot be »-contact conformally ∞at.

Background: Adverse drug reaction (ADR) spontaneous reporting is the primary method of postmarketing drug surveillance: although it is an important part of postmarketing drug surveillance, it is underused. Before 2004, almost no ADRs were reported in our 400-bed hospital. As an electronic hospital information system was available in our hospital, we developed a tool (ADR-RS-IHIS) for ADR reporting integrated into the hospital information system to facilitate reporting through easy use, automatic input of certain information, increased accessibility, real-time review, and intervention. Objective: To analyze the efficacy of the ADR-RS-IHIS in increasing ADR reporting to the national drug surveillance system, propose and implement improvements to increase ADR reporting, and evaluate the impact of these improvements, Methods: Every ADR reported through the ADR-RS-IHIS was evaluated retrospectively. Two study phases for evaluating ADR-RS-IHIS efficacy were identified. Phase I took place April 2004-August 2006; in April 2006, an interim analysis was performed to propose improvements. Phase II took place September 2006-April 2007 for evaluation of the impact made by the proposed improvements. Efficacy in the phase I and improvement impact on phase II were measured as the number of ADRs reported to the national drug surveillance system Results: The rate of ADRs reported per month to the national system increased from 0 before 2004 to 0.91 in phase I and 1.62 in phase II (2.25 if delayed reporting was considered). Improvement measures included: allowing nurses to report ADRs in the same way as physicians and pharmacists, automatic form filling of certain information from the electronic hospital information system, easier ADR report analysis, and automatic notification to the allergy department regarding suspected allergies. Conclusions: An ADR reporting system integrated into the electronic hospital information system is effective for increasing the number of ADRs reported to the national drug surveillance system. Allowing nurses to report ADRs in a manner similar to that of physicians and pharmacists, as well as automatic entry of certain data into the form, contributes to the improvement of the system.

The increasing wind power penetration in power systems requires the development of adequate wind farms models to be included in power system simulation software in order to represent the behavior of wind farms in power systems. The modeling of wind farms with high number of wind turbines requires the development of a high order model if all the wind turbines are modeled and therefore it is necessary a long simulation time. This paper presents a new way of aggregation of doubly fed induction generators wind turbines under different incoming winds by an equivalent wind turbine to approximate the active and reactive powers of aggregated wind turbines. The proposed aggregation method allows the wind farm to be represented by one single equivalent wind turbine with an important reduction of both model order and simulation time.

We study slant submanifolds of S-manifolds with the smallest dimension, specially minimal submanifolds and establish some relations between them and anti-invariant submanifolds in S-manifolds, similar to those ones proved by B.-Y. Chen for slant surfaces and totally real surfaces in Kaehler manifolds. Plan Andaluz de Investigación (Junta de Andalucía)

The present document explores how air pollution can be assessed from a multiagent point of view. In order to do so, a traffic system was simulated using agents as a way to measure if air pollution levels go down when the traffic lights employ a multigent cooperative system that negotiates the green light duration of each traffic light, in order to minimize the time a car has to wait to be served in an intersection. The findings after running some experiments where lanes of each direction are congested incrementally showed, that using this technique, there is a significant decrease in air pollution over the simulated area which means that traffic lights controlled by the multiagent system do improve the levels of air pollution.

Doubly fed induction generators based wind turbines are today one of the most widely used generation systems in wind farms due to the ability of variable speed operation and with decoupled control of active and reactive power. Nowadays these wind turbines are operating without generation limits, but the increasing wind power penetration in power systems must lead to that the wind farms have to operate with production limits imposed by the electrical system operators to maintain the stability of the electrical network. In this paper, a new control system of doubly fed induction generators based wind turbines is proposed for the control of active and reactive powers according to the imposed power limitations. This control system presents an active power controller, reactive power controller and pitch angle controller, in order to operate the wind turbine with optimum power efficiency or with limited active power and the demanded reactive power. This generation control provides a better grid integration of doubly fed induction generators

This paper describes the application of a solid-oxide fuel cell for compensation of distribution system voltage. A grid-connected fuel-cell plant consists of the fuel cell and the voltage-source inverter. The flux-vector control is used very effectively for the control of this inverter, where artificial neural networks implement the space-vector pulse width modulation. Comprehensive results are presented to assess the performance of this device to alleviate power quality problems present on the ac grid.

Se describe un sistema telemétrico de micro-ondas, para una red cuadripartita para una red sismológica. Se detallan los instrumentos, circuitos y métodos de análisis empleados para los datos a obtener. Su principal uso es la determinación, con suficiente rapidez y exactitud, de los epicentros, con fines de información para medidas de emergencia y prevención de maremotos.

We characterize the topology of a graph in terms of the critical elements of a discrete Morse function defined on it. Besides, we study the structure and some properties of the gradient vector field induced by a discrete Morse function defined on a graph. Finally, we get results on the number of non-homologically equivalent excellent discrete Morse functions defined on some kind of graphs.

Given a Lie algebra of finite dimension, with a selected basis of it, we show in this paper that it is possible to associate it with a combinatorial structure, of dimension 2, in general. In some particular cases, this structure is reduced to a weighted graph. We characterize such graphs, according to they have 3-cycles or not.

The goal of this work is to study the structure of the pure Morse complex of a graph, that is, the simplicial complex given by the set of all possible classes of discrete Morse functions (in Forman's sense) defined on it. First, we characterize the pure Morse complex of a tree and prove that it is collapsible. In order to study the general case, we consider all the spanning trees included in a given graph G and we express the pure Morse complex of G as the union of all pure Morse complexes corresponding to such trees.

This paper is focused on looking for links between the topology of a connected and non-compact surface with finitely many ends and any proper discrete Morse function which can be defined on it. More precisely, we study the non-compact surfaces which admit a proper discrete Morse function with a given number of critical elements. In particular, given any of these surfaces, we obtain an optimal discrete Morse function on it, that is, with the minimum possible number of critical elements.

To determine the potential impacts of fuel cells on future distribution system, dynamic models of fuel cells should be created, reduced in order, and scattered throughout test feeders. This paper presents the implementation of an efficient method for computing low order linear system models of solid oxide fuel cells (SOFCs) from time domain simulations. The method is the Box-Jenkins algorithm for calculating the transfer function of a linear system from samples of its input and output.

In this paper, we show new results on slant submanifolds of analmost contact metric manifold. We study and characterize slant submanifolds of K-contact and Sasakian manifolds. We also study the special class of three-dimen-sional slant submanifolds. We give several examples of slant submanifolds.1991 Mathematics Subject Classification. 53C15, 53C40.0. Introduction. Slant immersions in complex geometry were defined by B.-Y.Chen as a natural generalization of both holomorphic immersions and totally realimmersions [2]. Examples of slant immersions into complex Euclidean spaces C 2 andC 4 were given by Chen and Tazawa [2, 4, 5], while slant immersions of Ka¨hler C-spaces into complex projective spaces were given by Maeda, Ohnita and Udagawa[9].In a recent paper [7], A. Lotta has introduced the notion of slant immersion of aRiemannian manifold into an almost contact metric manifold and he has provedsome properties of such immersions. A. Lotta and A. M. Pastore have obtainedexamples of slant submanifolds in the Sasakian-space-form R

In this paper, a new reduced model of wind farms with doubly-fed induction generators wind turbines is proposed for representing all the wind turbines of a wind farm by one single equivalent wind turbine. The simulation results demonstrate the effectiveness of the proposed reduced model to represent the collective response of a wind farm in the point of common coupling to grid during power system dynamic simulations. This model can be used for voltage and angle stability investigations of large power system with an important reduction of the model order and computation time.

The goal of this paper is to extend to infinite graphs the known Morse inequalities for discrete Morse functions proved by R. Forman in the finite case. In order to get this result we shall use a special kind of infinite subgraphs on which a discrete Morse function is monotonous, namely, decreasing rays. In addition, we shall use this result to characterize infinite graphs by the number of critical elements of discrete Morse functions defined on them.