There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

This International Myeloma Working Group consensus updates the disease defi nition of multiple myeloma to include validated biomarkers in addition to existing requirements of attributable CRAB features (hypercalcaemia, renal failure, anaemia, and bone lesions). These changes are based on the identifi cation of biomarkers associated with near inevitable development of CRAB features in patients who would otherwise be regarded as having smouldering multiple myeloma. A delay in application of the label of multiple myeloma and postponement of therapy could be detrimental to these patients. In addition to this change, we clarify and update the underlying laboratory and radiographic variables that fulfi l the criteria for the presence of myeloma-defi ning CRAB features, and the histological and monoclonal protein requirements for the disease diagnosis. Finally, we provide specifi c metrics that new biomarkers should meet for inclusion in the disease defi nition. The International Myeloma Working Group recommends the implementation of these criteria in routine practice and in future clinical trials, and recommends that future studies analyse any diff erences in outcome that might occur as a result of the new disease defi nition.

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International Myeloma Working Group updated criteria for the diagnosis of multiple myeloma.

Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

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A review of single-phase improved power quality AC-DC converters

Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

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Light-emitting diodes

Solid-state switch mode AC-DC converters having high-frequency transformer isolation are developed in buck, boost, and buck-boost configurations with improved power quality in terms of reduced total harmonic distortion (THD) of input current, power-factor correction (PFC) at AC mains and precisely regulated and isolated DC output voltage feeding to loads from few Watts to several kW. This paper presents a comprehensive study on state of art of power factor corrected single-phase AC-DC converters configurations, control strategies, selection of components and design considerations, performance evaluation, power quality considerations, selection criteria and potential applications, latest trends, and future developments. Simulation results as well as comparative performance are presented and discussed for most of the proposed topologies.

Comprehensive Study of Single-Phase AC-DC Power Factor Corrected Converters With High-Frequency Isolation

In recent literature, several small-signal dynamic models for fluorescent lamps have been presented. These models have been used to analyze the lamp-ballast interaction for linear high frequency electronic ballasts. In the present paper, a new analysis method based on the generalized multi-frequency averaging technique is proposed. This method allows obtaining the small-signal dynamic model of an inverter in a straightforward way, even when the inverter behavior is not fully linear. The proposed analysis procedure is illustrated using an example. The frequency response of the small-signal transfer functions obtained with this method are compared with those experimentally measured using a laboratory prototype.

Analysis of lamp-ballast interaction using the multi-frequency-averaging technique

This paper presents comparison of single-stage Single Ended Primary Inductance Converter (SEPIC) and integrated SEPIC-Buck converter to drive Light Emitting Diodes (LED) in general lighting from a storage capacitance reduction point of view. Considering the low lifetime of electrolytic capacitors compared to that of LEDs, this study aims to compare which topology allows for using the smaller bus capacitance replacing it by a longer lifetime capacitor technology, increasing the overall system reliability. The analysis considers the same input/output parameters for both converters. The single-stage topology is a SEPIC operating in discontinuous conduction mode (DCM), which performs both power factor correction (PFC) and power control (PC) functions. In the integrated topology the PC stage is implemented by a Buck converter taking advantage of its output current source behavior, suitable for LED application. The design and implementation allows for a quantitative analysis between both topologies. The single-stage topology requires a 2.119 mF storage capacitance and achieves 85.12% efficiency, while the integrated topology requires a 187.5 μF storage capacitance and attains 83% efficiency for the same input/output parameters.

Comparison of single stage SEPIC and integrated SEPIC-Buck converter as off-line LED drivers

A simple method to obtain the dynamic behaviour of discharge lamps is proposed. A DC voltage source with a series resistor is used to supply the lamp at the required power level. The lamp response against an input voltage step transient is then analysed. From this analysis, the parameters of the equivalent lamp model can easily be obtained. The proposed method allows the lamp model to be obtained in a rapid manner from a single test, avoiding other time-consuming methods, e.g. lamp characterisation in the frequency domain. Experimental results for a 35 W metal halide lamp are presented.

Dynamic modelling of discharge lamps through step response

Halogen cycle lamps are being used for outdoor and indoor lighting. For indoor lighting, low power halogen cycle lamps are used. When lamp power is below 50 W, it is not possible to connect these lamps directly to power lines because they need a low input voltage, between 6 V and 24 V. Traditional supply equipment for low power halogen lamps are 50/60 Hz transformers, but they have large size and weight. A low cost and reliable high frequency supply system, an electronic power transformer, for low power halogen cycle lamps based on a self-oscillating half bridge inverter is described in this paper. Compared with a 50 Hz transformer, weight and size have been minimized. Moreover a high power factor, more than 0.9, has been achieved, and the circuit is both reliable and flexible. >

An improved electronic transformer for low power halogen cycle lamps

In this paper a detailed study about acoustic resonance in low-wattage metal halide lamps is presented. In order to analyze the acoustic resonance behavior, the lamps are supplied by DC current and a controlled variable-frequency small-signal is superposed. By using this method, theoretical and experimental resonances can be compared, verifying their amplitudes, and the threshold power value for their excitation. Besides, this analysis is done for same lamps with different operation hours, in order to verify its influence in the resonance behavior

J.M. Alonso

Papers

Analysis of lamp-ballast interaction using the multi-frequency-averaging technique

Comparison of single stage SEPIC and integrated SEPIC-Buck converter as off-line LED drivers

Dynamic modelling of discharge lamps through step response

An improved electronic transformer for low power halogen cycle lamps

Small-Signal Characterization of Acoustic Resonances in Low-Wattage Metal Halide Lamps