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This article presents a method for selecting the best battery sizing based on an optimal market participation strategy in a hybrid renewable power plant. The proposed formulation considers different scenarios to ensure the reserve provision compliance and includes two terms. The first one maximizes the day-ahead and automatic frequency restoration reserve (aFRR) market revenues. The second minimizes the battery degradation, accounting for both cycling and calendar ageing effects. The Iberian Electricity Market is selected as the study case, and two different market scenarios are compared: the current market scenario and the upcoming one, in which the upward and downward aFRR band offers are independent. The operation of a set of batteries is simulated until their end of life, and results reveal that energy/power ratios higher than 3 h for the current market scenario, and than 4 h for the upcoming one, are less cost effective. Regarding the best battery energy storage systems sizing, the selection varies considering incomes or profitability criteria. Moreover, keeping the current prices, in the upcoming market scenario hybrid renewable power plants are encouraged to participate more in the downward than in the upward aFRR market. [ABSTRACT FROM AUTHOR]

This paper provides a summary of media distribution in the 3GPP 5G System. We provide a status overview on the basics of 5G and in particular the Release 16 technologies on 5G Media Streaming and 5G Broadcast. Particular focus in this document are the recent Release-17 activities including extensions to 5G Media Streaming and 5G Broadcast. On the former, for example the integration of edge computing into media streaming is a major focus. On the latter, 5G Broadcast is extended to support co-existence of the technology with other broadcast technologies in the UHF band. A new set of functionalities is developed under the 5G Multicast–Broadcast Services (5MBS) umbrella work item. This includes new user service and system architecture functions to support broadcast and multicast throughout the 5G system. Particular focus in this paper are the radio layer and physical layer extensions to support point-to-multipoint delivery on top of New Radio (NR). We also touch briefly on the relevance of the 5G media distribution for third party ecosystems and industry with special focus on collaboration of media verticals and the 5G ecosystem. [ABSTRACT FROM AUTHOR]

Power quality in electrical systems is a basic requirement that should be guaranteed. Nonetheless, the increase of power-electronics-based applications and other nonlinear loads have induced harmonic distortion degrading the power quality; therefore, effective methods to measure and suppress such distortion need to be developed. The main contributions of this article are the following: the development of a novel fast-converging optimal estimator to determine online the harmonic components of a time-varying signal, which can be used for analysis and control purposes; the usage of the estimator to generate reference signals for an optimal control system in order to suppress the harmonics components; and the experimental validation of the proposed methodology as a feasible solution for industrial applications. The proposal considers practical assumptions such as the signal to be analyzed is corrupted with noise and contains time-varying harmonics (i.e., no steady-state condition is assumed). As an application of the harmonic estimator, the following two experimental tests are carried out: first, the optimal determination of the harmonic components of the current waveform in a nonlinear load, and second, the usage of harmonics information to mitigate them through of an active power filter, which is controlled by using an optimal trajectory tracking control scheme. [ABSTRACT FROM AUTHOR]

We present the latest developments in the physical layer evolution for the transmission of Multimedia Broadcast Multicast Service (MBMS) over fifth generation (5G) cellular networks. We first provide an overview of how the MBMS physical layer has evolved during the initial releases of the Third Generation Partnership Project (3GPP) specifications and provide motivations and insights for key developments that have helped mature MBMS into a competitive broadcasting solution. We provide an overview of dedicated MBMS carriers for Multimedia Broadcast multicast service Single Frequency Network (MBSFN) transmission as well as Orthogonal Frequency Division Multiplexing (OFDM) numerologies with longer cyclic prefixes to support MBSFN transmission over large geographical areas with large distances between cooperating cell sites. Next, we describe the most recent enhancements to the MBMS physical layer, addressing advanced use cases in the recently completed release of the 3GPP specifications (Release 16). First, we describe the physical layer design for enabling MBSFN-based MBMS services for rooftop receivers with inter-site distances between cooperating cell sites as large as 125 km. In this realm, we demonstrate the need for an OFDM numerology with a 300-microsecond cyclic prefix to communicate effectively over channels with very large delay spreads. Next, we explain how support for high mobility up to 250 kmph was added to the standards by using an OFDM numerology that gracefully trades off inter-symbol interference due to large delay spreads and inter-carrier interference due to large doppler spreads to achieve better performance than existing numerologies at high speeds. Finally, we describe the enhancements that were made to the Cell Acquisition Subframe (CAS)—specifically, the introduction of larger aggregation levels for the Physical Downlink Control Channel (PDCCH) and the support of Physical Broadcast Channel (PBCH) repetitions—that significantly increase the coverage for the control and system information associated with MBMS that are carried by these subframes. [ABSTRACT FROM AUTHOR]

Heterogeneous systems composed of CPUs and accelerators sharing communication channels of different performance are getting mainstream in HPC but, at the same time, they show a complexity that makes it difficult to optimize the deployment of a data parallel application. Recent analytical tools such as Functional Performance Models, combined with advanced partitioning algorithms, manage to achieve a balanced configuration by distributing the workload unevenly, according to the performance of the different processing units. Unfortunately, such uneven distribution of the computation load leads to communication unbalances that, very often, render worthless the previous workload balancing efforts. Finding the optimal communication scheme without expensive testing on the executing platform requires an analytical approach to the estimation of the communication cost of different configurations of the application. With this goal in mind, we propose and discuss an extension of the $\tau$ -Lop communication performance model to cover heterogeneous architectures. In order to provide a quantitative assessment of this extended model, we conduct experiments with two representative computational kernels, the SUMMA algorithm and the 2D wave equation solver. The $\tau$ -Lop predictions are compared against the HLogGP model and the observed costs for a variety of configurations, hardware resources and problem sizes. [ABSTRACT FROM PUBLISHER]

As performance and energy efficiency have become the main challenges for next-generation high-performance computing, asymmetric multi-core architectures can provide solutions to tackle these issues. Parallel programming models need to be able to suit the needs of such systems and keep on increasing the application’s portability and efficiency. This paper proposes two task scheduling approaches that target asymmetric systems. These dynamic scheduling policies reduce total execution time either by detecting the longest or the critical path of the dynamic task dependency graph of the application, or by finding the earliest executor of a task. They use dynamic scheduling and information discoverable during execution, fact that makes them implementable and functional without the need of off-line profiling. In our evaluation we compare these scheduling approaches with two existing state-of the art heterogeneous schedulers and we track their improvement over a FIFO baseline scheduler. We show that the heterogeneous schedulers improve the baseline by up to 1.45$\times$ in a real 8-core asymmetric system and up to 2.1$\times$ in a simulated 32-core asymmetric chip. [ABSTRACT FROM AUTHOR]

This paper presents a practical approach to obtain reduced-order models for electric networks expressed in the dynamic harmonic domain (DHD). The proposed method reduces the DHD system of ordinary differential equations first in the harmonic sense via a voltage-based frequency-scan procedure and subsequently in the state sense via truncated balanced realizations. The harmonic-selection and truncation stage substantially reduces the original full-size system. The state-reduction process is applied to the already harmonic-reduced system, achieving further reduction. Two networks are used as case studies to demonstrate the reduction properties of the proposed model-order reduction methodology. [ABSTRACT FROM AUTHOR]

The broad connection of devices to the Internet, known as the IoT or M2M, requires lowcost power-efficient global connectivity services. New physical layer solutions, MAC procedures, and network architectures are needed to evolve the current LTE cellular systems to meet the demands of IoT services. Several steps have been taken under the 3GPP to accomplish these objectives and are included in the upcoming 3GPP LTE standards release (3GPP Release 13). In this tutorial article, we present an overview of several features included in 3GPP to accommodate the needs of M2M communications, including changes in the physical layer such as enhanced machine type communications, and new MAC and higher-layer procedures provided by extended discontinuous reception. We also briefly discuss the narrowband IoT, which is in the development stage with a target completion date of June 2016. [ABSTRACT FROM PUBLISHER]

Metrology at W7-X is an integral part of device assembly. Lots of assembly steps are guided by metrology. In addition to that, metrology performs final geometry checks at the end of most of assembly steps. This paper presents some general assembly tolerances and the metrology equipment that found the accuracy basement to gain these tolerances. Exemplified by magnet system assembly, metrology methods used and the alignment as well as the measurement accuracies achieved are presented. It is shown that the final geometric position accuracy of the main field coils meets the requirements at a high quality of the magnet field. A procedure to transfer coordinates from the main coordinate system, fixed on the torus hall building, into the vacuum vessel is given in detail. The accuracy obtained for the coordinate transfer is presented. The first results of in-vessel component assembly are shown with special focus on incoming inspection and the experience gained during installation of fixation elements and wall protection components. [ABSTRACT FROM PUBLISHER]

This paper presents the results of a study designed to evaluate the performance of attenuation correction algorithms due to heavy precipitation at operational C-band weather radar frequencies and using differential phase measurements. This paper proposes the extension of two attenuation correction algorithms and shows a methodology to validate attenuation-corrected reflectivity measurements by using a nearby radar as opposed to the traditional use of rain gauge or disdrometer measurements. The results showed that the the adaptive attenuation correction techniques have a higher performance than the nonadaptive ones when comparing the measured and computed ΦDP profiles and also when comparing with reflectivity measurements from a nearby radar. The results also showed that the difference in the performance of the adaptive attenuation correction algorithms is minimal and optimizing a single parameter (e.g., α in the BRI algorithm) rather than three unknown parameters (e.g., a, b, and α in the AHB or AFV algorithms) is a more robust procedure. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study designed to classify weather radar clutter echoes obtained from ground-based dual-polarization weather radar systems. The clutter signals are due to ground clutter, sea clutter, and anomalous propagation echoes, which represent sources of error in quantitative radar rainfall estimation. Fuzzy and Bayes classifiers are evaluated as an alternative approach to traditional polarimetric-based methods. Both systems were trained and validated by using C-band dual-polarization radar measurements, and a novel technique is proposed to calculate the texture function to mitigate against the edge effects at the boundaries of precipitation regions. A methodology is presented to extract the membership functions and conditional probability density functions to train the classifiers. The critical success index indicates that the Bayes classifier has, on average, a slightly better performance than the fuzzy classifiers. However, when optimal weighting was applied, the fuzzy classifier gave one of the best performances. The classifiers are sufficiently robust to be used when only single-polarization radar measurements are available. [ABSTRACT FROM AUTHOR]

A non-resonant electronic ballast based on one power switch and on one reactive element-one inductance-is described in this paper. The special current mode control implementation provides an intrinsic short-circuit protection and a very simple control circuitry. Filament heating time, current during the heating period, and protection against broken tube can be easily implemented with the proposed circuitry. A greenhouse application with a 120-V dc bus power distribution is presented in this paper. The dc bus voltage is easily obtained (in this particular application) from a classical series-connected 12-pulse rectifier in combination with a transformer with two secondary windings (one in Wye connection and other one in Delta connection). An additional advantage of this configuration is the high power factor obtained at the input stage. [ABSTRACT FROM AUTHOR]

Nowadays, Permanent Emergency Lighting Systems (PELSs) are widely used in many applications, including emergency exit indication and lighting in critical or strategic points. Limitation in operation hours in classical lamps (10 000-20 000 h for fluorescent lamps) implies short lamp replacement times and, therefore, high maintenance costs. This paper shows an alternative solution based on high-efficiency LEDs. The long operation life (above 100 000 h) of high-efficiency LEDs with a very simple electronics circuitry implies an interesting solution for these types of applications. A 30-lm and 1-h PELS has been built and tested. A low-cost power supply has been built and used as a battery charger and LED driver. [ABSTRACT FROM AUTHOR]

Finite-difference time-domain (FDTD) algorithms are affected by numerical artifacts and noise. In order to obtain better results we propose the use of the principal component analysis based on multivariate statistical techniques. It allows a straightforward discrimination between the numerical noise and the actual electromagnetic field distributions, and the quantitative estimation of their respective contributions. Besides, the FDTD results can be filtered to clean the effect of the noise. The method has been applied successfully to two dimensional simulations: propagation of a pulse in vacuum using total field—scattered field techniques, and mode computation in a two-dimensional photonic crystal. In this last case, PCA has revealed hidden electromagnetic structures related to actual modes of the photonic crystal. [ABSTRACT FROM AUTHOR]

In this paper, a low-cost electronic ballast for high-pressure sodium vapor lamps is presented. The proposed ballast is a two-stage circuit that requires only one switch and one inductor for each stage. The power-factor-correction stage is a buck dc-to-dc converter operating in discontinuous conduction mode to meet the IEC-61000-3-2 Class C requirements. The inverter stage is a low-cost nonresonant topology, based on a buck-boost inverter controlled by means of a specific current-mode control implementation. In addition, a novel and simple circuit, compatible with the presented inverter, is proposed to ignite the lamp. Furthermore, this circuit implementation provides protection against broken lamps. [ABSTRACT FROM AUTHOR]

A novel methodology is presented in this paper for conducting transient and steady-state analysis of electric networks containing nonlinearities and switching plants components. The method is termed the extended harmonic domain (EHD) method as may be seen as an extension of the harmonic domain (HD) method used in steady-state analysis. It is shown in the paper that EHD is a natural approach for conducting dynamic and steady-state studies of the evolution of harmonics in power circuits containing nonlinear components and flexible ac transmission systems (FACTS) devices. It is also shown in the paper that EHD provides a suitable basis for extending the well-known steady-state power quality indices to the transient range. To illustrate the use of the theory, a three-phase linear circuit and a three-phase PWM-STATCOM are modeled using EHD. The results are compared against those provided by industry standard tools as PSCAD/EMTDC and Matlab. [ABSTRACT FROM AUTHOR]

Presents a methodology for calculating magnetizing inrush currents. Operational matrices; Inrush current calculation; Long-term over-voltages.

Presents an algebraic approach for identifying operating point dependent parameters of synchronous machines. Use of operational properties of orthogonal series expansions; Implication of algebraic formulation and operational calculus in reducing identifying parameters problem; Variation of the parameters with operating point.

Proposes a novel model which is based on Walsh series which can be used to assess the steady state operation of three phase Thyristor Controlled Reactors (TCR). Background information on high voltage direct current; Advantages of using TCR; Comparison between the Walsh series and the Fourier series.

Gives details on a frame-of-reference based on the use of Hartley's transform while focusing on a three phase Thyristor Controlled Reactor (TCR) harmonic model which uses Hartley's domain. Comparison in solutions using the frame-to-reference and solutions using an established frame-of-reference based on Fourier's transform; Details on the TRC model; Tests conducted to validate the results given by the Harley's harmonic Norton equivalent.

Reports on a developed three phase thyristor controlled reactor (TCR) model based on the use of harmonic switching vectors and discrete convolutions. Direct frequency domain operations; TCR plant performance assessment; Use of alternate time domain representations; Quadratic convergence exhibited in the study.

This letter presents a methodology for the study of periodical dynamic systems. The method is based on the use of orthogonal series expansions and their operational properties. As opposed to the conventional use of the series expansions, in this work it is considered that the expansion coefficients may slowly vary with time. This salient feature allows for traditional steady-state methods such the harmonic domain to be used in dynamical systems. An important use of the method is the analysis of switched networks. The use of the method is illustrated with simple but of practical value systems. [ABSTRACT FROM AUTHOR]

Sampled simulation is a mature technique for reducing simulation time of single-threaded programs. Nevertheless, current sampling techniques do not take advantage of other execution models, like task-based execution, to provide both more accurate and faster simulation. Recent multi-threaded sampling techniques assume that the workload assigned to each thread does not change across multiple executions of a program. This assumption does not hold for dynamically scheduled task-based programming models. Task-based programming models allow the programmer to specify program segments as tasks which are instantiated many times and scheduled dynamically to available threads. Due to variation in scheduling decisions, two consecutive executions on the same machine typically result in different instruction streams processed by each thread. In this paper, we propose TaskPoint, a sampled simulation technique for dynamically scheduled task-based programs. We leverage task instances as sampling units and simulate only a fraction of all task instances in detail. Between detailed simulation intervals, we employ a novel fast-forwarding mechanism for dynamically scheduled programs. We evaluate different automatic techniques for clustering task instances and show that DBSCAN clustering combined with analytical performance modeling provides the best trade-off of simulation speed and accuracy. TaskPoint is the first technique combining sampled simulation and analytical modeling and provides a new way to trade off simulation speed and accuracy. Compared to detailed simulation, TaskPoint accelerates architectural simulation with 8 simulated threads by an average factor of 220x at an average error of 0.5 percent and a maximum error of 7.9 percent. [ABSTRACT FROM AUTHOR]

The control of multi-input and multioutput (MIMO) systems with multiple time delays is difficult to be done using classical control techniques, especially if the process is not open-loop stable. Model predictive control (MPC) is the natural choice in industry for this case, but its tuning and implementation are not trivial and, in general, cannot be done in the low level of the process control system. This paper aims to show a method to design MIMO filtered Smith predictors for $n \times n$ processes with multiple time delays based on the decentralized direct decoupling structure. This method allows an easy tuning of the primary controller by simplifying the problem to multiple single loops if the realizability conditions presented in the paper are met. The proposed method can also be used in MPC to remove the interactions between process variables. The effectiveness of the method is illustrated through two case studies. [ABSTRACT FROM AUTHOR]

In this paper, a new control method for electronic ballasts based on the use of a variable inductor is presented. The main goal is to perform the complete control of the electronic ballast by maintaining the switching frequency constant and without using other parameters of the power converter, such as input voltage or duty cycle. The magnetic regulator is controlled by means of a dc current, which allows performing both lamp soft starting and lamp dimming. Apart from the important advantage of keeping a constant frequency during full electronic ballast operation, the proposed method presents additional advantages when compared to other control methods, such as inherent isolated control, more linear control characteristics, constant electrode power, and higher efficiency. Experimental results from a 36-W linear fluorescent lamp prototype are presented. [ABSTRACT FROM AUTHOR]

In this paper, a novel topology to supply metal halide (MH) lamps using sinusoidal waveform with superposed third harmonic is proposed. By employing this technique, the lamp is supplied with an approximated square waveform, but it reduces the harmonic content and, therefore, electromagnetic interference and radio-frequency interference. The proposed topology is analyzed and designed for a 35-W MH lamp with ceramic discharge tube. Experimental results prove that lamp operation is stable at operating frequencies where acoustic resonances were previously observed when supplied with purely sinusoidal waveforms. In conclusion, the proposed technique could be a feasible solution for stable operation of MH lamps. [ABSTRACT FROM AUTHOR]

The article discusses the expansion of the mobile Internet via services that employ user-generated content, geospatial functionality, and social networking capability. A team of researchers at the Center for Data-Intensive Systems at Aalborg University have developed a prototype called Streamspin that helps users build websites and supports user-generated mobile services. Topics include: the challenges in creating a mobile service deployment system; the structure of a piece of content; the photo- and video-sharing websites Facebook and YouTube; and subscription platforms and content delivery.

In this article we present options for the evolution from G.fast-based access networks to multi-gigabit access networks with a focus on solutions based on G.mgfast. The corresponding evolutions of the network architecture as well as a framework for the cost modeling are shown. The starting point for future architecture evolutions is the ongoing wireline access rollout in Switzerland. Based on this, different evolution steps are possible. These architectures are described and compared to each other based on the cost modeling framework, which shows that for certain building sizes different options are cost optimal. [ABSTRACT FROM AUTHOR]

This article describes the ARM Scalable Vector Extension (SVE). Several goals guided the design of the architecture. First was the need to extend the vector processing capability associated with the ARM AArch64 execution state to better address the computational requirements in domains such as high-performance computing, data analytics, computer vision, and machine learning. Second was the desire to introduce an extension that can scale across multiple implementations, both now and into the future, allowing CPU designers to choose the vector length most suitable for their power, performance, and area targets. Finally, the architecture should avoid imposing a software development cost as the vector length changes and where possible reduce it by improving the reach of compiler auto-vectorization technologies. SVE achieves these goals. It allows implementations to choose a vector register length between 128 and 2,048 bits. It supports a vector-length agnostic programming model that lets code run and scale automatically across all vector lengths without recompilation. Finally, it introduces several innovative features that begin to overcome some of the traditional barriers to autovectorization. [ABSTRACT FROM PUBLISHER]

Cognitive radio technology is a key enabler to reuse a finite, scarce, and expensive resource: the radio spectrum. Guaranteeing required levels of QoS to cognitive users and ensuring necessary protection to incumbent users are the two main challenges in opportunistic spectrum access. This article identifies the main requirements and challenges for QoS support in cognitive radio networks. A framework for a twofold cognitive manager is presented; one part managing spectrum availability on longer timescales and the other handling resource management on shorter timescales. This article gives particular focus to the functionalities of the latter cognitive manager related to resource management. Finally, we present a few key scenarios and describe how QoS can be managed with the proposed approach without disturbing the communications of incumbent users. [ABSTRACT FROM PUBLISHER]

This paper deals with the development of a magnetic lead screw (MLS) for wave energy conversion. Initially, a brief state of the art regarding linear permanent-magnet generators and MLSs is given, leading to an introduction of the MLS and a presentation of the results from a finite-element analysis used to find the magnetic forces. Furthermore, the force per magnet surface area measure is presented as a better alternative to the force density measure, which is often used for linear magnetic devices. Based on this, the overall design of a 500-kN MLS is presented focusing on the bearing supports used to compensate for the magnetic attraction forces and the resulting deflection of the rotor. In addition, in order to avoid some of the assembling-related disadvantages of using surface-mounted magnets, an embeddedmagnet topology is proposed. To demonstrate the technology, a scaled 17-kN MLS is presented together with experimental results. [ABSTRACT FROM PUBLISHER]

In the prior literature, the small-signal incremental impedance of fluorescent lamps has been characterized using a single-pole single-zero transfer function. This transfer function provides a good estimation of the lamp dynamics at rated power. However, when this model is used at low power levels, the accuracy is severely reduced, particularly at high perturbation frequencies (5–20 kHz). In this paper, a new double-zero double-pole transfer function is used to model the lamp dynamics with great accuracy even at low power levels. The best results have been obtained using a transfer function with two real zeros and a double complex pole. Using a new characterization procedure, the small-signal model of a 26-W compact fluorescent lamp has been obtained. All the terms of the transfer function (static gain, poles, and zeros) have been calculated at different power levels. Different polynomial expressions have been used to approximate these terms as power-dependent functions. The proposed characterization procedure also allows obtaining the equivalent resistance of the electrodes. This feature has been used to measure the effect of the extra heating imposed by IEC 60901 during dimmed operation. [ABSTRACT FROM AUTHOR]

This paper deals with the capability of pulse width modulation (PWM) dimming operation added to the high-power factor-integrated buck-flyback converter (IBFC), which was developed in previous works for LED lighting applications. First, the two main dimming techniques will be introduced, namely, analog dimming and PWM dimming. Then, the three main PWM dimming schemes found in the literature, that is, enable dimming, series dimming, and parallel dimming, will be briefly discussed. Afterwards, the IBFC topology will be tested performing both analog and enable dimming. In addition, a new proposal is introduced: the high-frequency series PWM dimming technique, which overcomes all the challenges faced when developing PWM dimming capabilities in low slew-rate constant-current fixed-frequency-controlled converters and offers all the advantages of PWM dimming over analog dimming while maintaining good efficiency. The proposed dimming-technique control loop, as well as the laboratory tests, will be presented, discussed, and compared to analog dimming and PWM dimming, showing satisfactory results in terms of dimming ratio, input current total harmonic distortion (\THDI), and power factor. [ABSTRACT FROM AUTHOR]

Due to the high rise in luminous efficiency that high-brightness light-emitting diodes (HB-LEDs) have experienced in recent years, many new applications have been researched. This paper covers a streetlight LED application using the offline integrated buck–flyback converter (IBFC) developed in previous works. In this application, the converter is used to provide power-factor correction from a universal ac source. A control loop using the LM3524 IC has been implemented for testing the feasibility of Enabling pulsewidth modulation dimming mode. First, the LED load has been linearized and modeled in order to calculate the IBFC topology properly. Second, the converter has been designed and tested at the laboratory. The converter has also been modeled in order to design a fixed-frequency constant-current control. The dynamics of all the stages involved in the closed loop have been taken into account in order to develop an adequate controller. Finally, the experimental results obtained from the laboratory tests are discussed. [ABSTRACT FROM AUTHOR]

Pervasive computing services exploit information about the physical world both to adapt their own behavior in a context-aware way and to deliver to users enhanced means of interaction with their surrounding environment. The technology to acquire digital information about the physical world is becoming more available, making services at risk of being overwhelmed by such growing amounts of data. This calls for novel approaches to represent and automatically organize, aggregate, and prune such data before delivering them to services. In particular, individual data items should form a sort of self-organized ecology in which, by linking and combining with each other into sorts of "knowledge networks" (KNs), they are able to provide compact and easy-to-be-managed higher level knowledge about situations occurring in the environment. In this context, the contribution of this paper is twofold. First, with the help of a simple case study, we motivate the need to evolve from models of "context awareness" toward models of "situation awareness" via proper self-organized "KN" tools, and we introduce a general reference architecture for KNs. Second, we describe the design and implementation of a KN toolkit that we have developed, and we exemplify and evaluate algorithms for knowledge self-organization integrated within it. Open issues and future research directions are also discussed. [ABSTRACT FROM AUTHOR]

Abstract-The use of high-efficiency LEDs in low-power lighting applications is growing continuously due to new advances in LED features. The lifetime of a low-power fluorescent lamp is around 5000 h. This implies short lamp-replacement times and high maintenance costs. The use of high-efficiency LEDs reduces drastically the maintenance costs due to the long lifetime (>50000 h). One of the applications where using LED is very interesting is permanent emergency light systems. Generally, these circuits are based on a two-stage design, using two magnetic cores. This paper presents offline power LED driver and battery charger integrated in one magnetic core topology. Besides, the converter allows driving the LEDs in case of a line failure and it complies with the IEC 61000-3-2 Class C Standard. [ABSTRACT FROM AUTHOR]

Usually, pulsewidth modulation (PWM) operation is selected as the best dimming strategy to drive high-brightness LEDs. Nevertheless, to obtain an enhanced full linear dimming control of the device, the luminous flux should be measured. This paper proposes a control method based on an estimator of the luminous flux emitted by the LED. Based on the characterization of the LEDs, this estimator is defined. The estimator provides the flux value from Only two temperature values (the case temperature and the ambient temperature). Once the estimator is validated, the electronic driver to supply the LEDs, as well as the digital control scheme, are presented. Such a control scheme is suitable for both AM and PWM dimming strategies. A prototype of the electronic driver has been built and tested, and experimental measurements of AM and PWM dimming are presented. It can be concluded that with the proposed estimator, the flux emitted by the LEDs can be accurately estimated. Thus, the output light control of the LEDs can be accomplished by sensing temperature rather than luminous flux. The final output characteristic of the system shows linearity between the output flux and the reference value, with AM as well as with PWM dimming of the LEDs. [ABSTRACT FROM AUTHOR]

This paper presents the application of predictive control to drug dosing during anesthesia in patients undergoing surgery. The performance of a generic predictive control strategy in drug dosing control, with a previously reported anesthesia-specific control algorithm, has been evaluated. The robustness properties of the predictive controller are evaluated with respect to inter- and intrapatient variability. A single-input (propofol) single-output (bispectral index, BIS) model of the patient has been assumed for prediction as well as for simulation. A set of 12 patient models were studied and interpatient variability and disturbances are used to assess robustness of the controller. Furthermore, the controller guarantees the stability in a desired range. The applicability of the predictive controller in a real-life environment via simulation studies has been assessed. [ABSTRACT FROM AUTHOR]

Focuses on the preservation of the monopolistic model by the telecommunication industry in Canada. Offer of the long-distance market to competition; Formation of an alliance by oligopolies.

The transmit capacity of the access link that connects homes to the Internet is often not fully used, either because of a selected light subscription or because the user is not constantly online, leaving a surplus capacity. Many home networks are equipped with WLAN that can be received outside the walls of the home. This signal can be used to offer access to passing WLAN users who are sufficiently near the homes, potentially realizing a contiguous public radio coverage land- scape of WLAN access points in urban areas. This article describes the challenges and solutions when using the surplus capacity available in broadband residential access for offering WLAN access to public subscribers, and how to integrate this solution with access and services offered by 3G and WiMAX. [ABSTRACT FROM AUTHOR]

Discharge lamps present a negative dynamic characteristic that makes necessary to use a current limiting element. In high-frequency resonant ballasts, current limitation is performed by the output resonant tank; but in low-frequency square-wave electronic ballasts, arc stabilization is accomplished by the stage feeding the square wave inverter. Therefore, the design of the input converter must be made taking into account the lamp dynamic characteristic. In the present paper, a new procedure to obtain the small-signal dynamic characteristic of metal halide lamps is proposed. Using the proposed methodology, the small-signal characteristic of a 70-W lamp is obtained. This characteristic is then used for the design of an electronic ballast based on a buck-boost converter followed by a full bridge inverter. The limits for stable operation obtained are verified using a laboratory prototype. [ABSTRACT FROM AUTHOR]

In this paper, a study about acoustic resonance (AR) in low-wattage metal halide lamps is presented. The lamps are supplied with a typical low frequency square waveform on which a high frequency sinusoidal ripple is superposed. The goal is to emulate the same waveforms generated by a low frequency electronic ballast. In this way, the ARs that appear in the lamp can be characterized against ripple amplitude and frequency. Different lamp's manufacturers and burning hours are used. The obtained results are intended to be employed in further reliable designs of low-frequency square-waveform electronic ballasts. An example of application of the accumulated AR signatures in this type of electronic ballasts is carried out, and a standard proposal is presented. [ABSTRACT FROM AUTHOR]

The continuous-wave laser operation of Nd-doped tetragonal NaLa(WO4)2 crystal is studied at room temperature by optical pumping in the spectral region overlapping AIGaAs diode laser emission. This crystal has inhomogenously broadened optical bands. From the room-temperature spectroscopic parameters determined it is found that the optimum Nd concentration for the 4F3/2 → 4Ij laser channels must be in the 3-5 at. % range. For J = 11/2 and 13/2 channels (ƛ ≈ 1.06 and 1.3 μm) the most favourable polarization configuration is parallel to the crystallographic c axis, while for J = 9/2 little polarization dependence of the laser efficiency is predicted. Laser operation was achieved with a 3.35 at.% Nd-doped sample grown by the Czochralski method. The laser operation was tested in an hemispherical optical cavity pumped by a Ti:sapphire laser. Stimulated emission at ƛ = 1056 nm was achieved for a wide spectral pumping range, ƛ = 790-820 nm. Stimulated Raman scattering was achieved in the picosecond regime with an efficiency similar to that of monoclinic KY(WO4)2 reference compound. [ABSTRACT FROM AUTHOR]

High intensity discharge (HID) lamps are the most suitable when both high light power levels and good color rendering are researched. Some remarkable theoretical advantages would be obtained if these kinds of lamps were driven with high frequency (HF) electronic ballasts. Nevertheless, at these frequencies, acoustic resonances (AR) phenomenon appears. Low wattage metal halide (MH) lamps are, among all HID lamps, the most affected by this phenomenon. To obtain lack of AR in HID lamps, lamp power frequency harmonics must have a lower amplitude than a certain threshold value, related to activation energy. An electronic ballast may be designed to guarantee power harmonics levels lower than this threshold level at nominal operation. Nevertheless, the equivalent resistance of HID lamps varies highly in starting and warm-up stages, as well as in the aging process. Therefore, the system must be designed to be adequate for the necessary "supplying conditions" for these load variations. In this paper, a new control strategy for a HF square-wave inverter is presented. This ballast keeps lamp power harmonics at low levels, regardless of the lamp equivalent load. The proposed ballast, along with the control strategy, is presented, as well as the built prototypes and experimental results carried out. From these experiments, it can be concluded that the proposed method supplies low wattage MH lamps with lack of acoustic resonances. [ABSTRACT FROM AUTHOR]

Currently, the main drawback in high-intensity discharge lamps supplied by means of high-frequency (HF) electronic ballasts are the so-called acoustic resonances. In this paper, two HF nonresonant inverters for low wattage metal halide (MH) lamps are analyzed, from the point of view of its behavior regarding the acoustic resonances' phenomenon. Thus, a HF electronic ballast, operating with a lack of acoustic resonances, is proposed. From a dc voltage bus, the inverters provide an ac waveform to the lamp. The power stage operation of the inverters is first analyzed. Then, the characteristics of these waveforms are analyzed, from the point of view of minimizing the acoustic resonances' appearance. Then, upon these theoretical results, a comparison between inverters is done, selecting the most appropriate for lighting purposes. After that, a built prototype of the chosen inverter topology is presented, and the experimental results are shown. These experiments were carried out on several 70-W MH lamps. Finally, some conclusions are presented. [ABSTRACT FROM AUTHOR]

This paper deals with the use of microprocessor-based control circuits in automotive and railway lighting applications. Thus, the design and implementation of an electronic ballast for fluorescent lamps using a low-cost microcontroller (μC) is presented. The ballast has been especially developed for lighting applications in railways, where the International Union of Railways (UIC) 555 Code must be fulfilled. The μC is used to optimize the lamp ignition and supply, and to regulate lamp power against line voltage, thus fulfilling UIC 555 requirements. Also, protection features such as lamp soft reignition, overcurrent, and undervoltage are included using the μC. [ABSTRACT FROM AUTHOR]

In this paper, a low-cost power control for LCC series-parallel inverters with resonant current mode control for high intensity discharge (HID) lamps is presented. These resonant inverters require controlling the power supplied to the lamp in order to avoid exceeding the maximum lamp power recommended by the lamp manufacturer. The classical control method measures the lamp voltage and current and they are multiplied analogically, obtaining the lamp power consumption measure. This control circuitry results very complex due to the lamp voltage and current wide variations range during ignition and discharge processes. Assuming a regulated input dc voltage (bus voltage) provided by the power factor correction (PFC) pre-regulator and an inverter constant efficiency along the lamp aging, the lamp power consumption may be estimated and regulated properly measuring the inverter average input current. Also, the small-signal analysis performed allows obtaining the small-signal resonant inverter input impedance and studying the connection stability between PFC pre-regulator and inverter. The inverter small-signal analysis has been performed and an electronic ballast prototype for 250-W HPS lamps has been implemented and tested verifying the low-cost lamp power control method proposed. [ABSTRACT FROM AUTHOR]