Linearized large signal modeling, analysis, and control design of phase-controlled series-parallel resonant converters using state feedback

This paper proposes a linearized large signal state-space model for the fixed-frequency phase-controlled series-parallel resonant converter. The proposed model utilizes state feedback of the output filter inductor current to perform linearization. The model combines multiple-frequency and average state-space modeling techniques to generate an aggregate model with dc state variables that are relatively easier to control and slower than the fast resonant tank dynamics. The main objective of the linearized model is to provide a linear representation of the converter behavior under large signal variation which is suitable for faster simulation and large signal estimation/calculation of the converter state variables. The model also provides insight into converter dynamics as well as a simplified reduced order transfer function for PI closed-loop design. Experimental and simulation results from a detailed switched converter model are compared with the proposed state-space model output to verify its accuracy and robustness

Acute lung injury outside the ICU: a significant problem

The incidence of acute lung injury (ALI) is influenced by nature of the underlying clinical condition. The frequency with which ALI is likely to be encountered by those practicing outside the intensive care unit (ICU) setting is largely unknown. Data from the paper under discussion [1] indicates that ALI is seen relatively frequently in general wards and can be managed there until death or recovery. In patients with predisposing illnesses directly involving the lung, progression to ALI can be rapid

Evidence for prelocalization of cytoplasmic factors affecting gene activation in early embryogenesis

Differentiation begins early in embryogenesis as different genes become active in different cells. Within the closed system of the early embryo, equal genomes thus direct the creation of diverse cell types. Though the nuclei of these cells contain complete copies of the same genome,(1,2) the nucleoplasmic and cytoplasmic environments of these genomes are not the same, as a result of the distribution of cleavage nuclei into diverse areas of egg cytoplasm early in the cleavage process. In some cases the fate of these nuclei, i.e., the type of differentiated cell to which they or their descendants give rise, has been seen to depend on the area of cytoplasm in which they come to lie

Bench-to-bedside review: Sepsis, severe sepsis and septic shock – does the nature of the infecting organism matter?

International guidelines concerning the management of patients with sepsis, septic shock and multiple organ failure make no reference to the nature of the infecting organism. Indeed, most clinical signs of sepsis are nonspecific. In contrast, in vitro data suggest that there are mechanistic differences between bacterial, viral and fungal sepsis, and imply that pathogenetic differences may exist between subclasses such as Gram-negative and Gram-positive bacteria. These differences are reflected in different cytokine profiles and mortality rates associated with Gram-positive and Gram-negative sepsis in humans. They also suggest that putative anti-mediator therapies may act differently according to the nature of an infecting organism. Data from some clinical trials conducted in severe sepsis support this hypothesis. It is likely that potential new therapies targeting, for example, Toll-like receptor pathways will require knowledge of the infecting organism. The advent of new technologies that accelerate the identification of infectious agents and their antimicrobial sensitivities may allow better tailored anti-mediator therapies and administration of antibiotics with narrow spectra and known efficacy

Enhanced control strategy of full-bridge modular multilevel converter

This paper describes a control approach that allows the cell capacitor voltages of the full-bridge modular multilevel converter (FB-MMC) to be controlled independent of the input dc link voltage. Moreover, this control approach offers the possibility of operating FB-MMC from bi-polar dc link voltages; thus, creating new possibilities for building generic hybrid dc grids with reversible dc link voltage, where the conventional line commutated current source converters can operate alongside voltage source converters. Furthermore, the presented control approach improves the dc fault ride-through of the FB-MMC compared to existing approaches. This could be achieved by an active control of the arm currents and cell capacitor voltages, and full exploitation of the FB-MMC redundant switch states. Operation of the FB-MMC with reversible DC link voltage and decoupled control of the cell capacitor voltages from the dc link voltage are demonstrated using simulations. The major findings and implications of this work are highlighted

A comparative study of the physiological effects of immersion and bed rest

Human physiological response during periods of silicone immersion and bed res

Successful fault current interruption on DC circuit breaker

This study focus on the interruption capability of the DC circuit breaker employing a current commutation approach and evaluates the two main factors that determine the success rate for breaker current interruption, namely the current slope di/dt before current zero and the rate of rise of the transient recovery voltage dv/dt across the mechanical breaker contacts after current zero. A vacuum circuit breaker is used to evaluate DC breaker characteristics. Detailed mathematical and graphical analysis are presented for the proposed circuit operation used in analysing the circuit breaker properties, with simulation and experimental results at fault current levels up to 330 A