Trapezoidal cross-sectional influence on FinFET threshold voltage and corner effects

Fin field effect transistors (FinFETS) are silicon-on-insulator (SOI) transistors with three-dimensional structures. As a result of some fabrication-process limitations (as nonideal anisotropic overetch) some FinFETs have inclined surfaces, which results in trapezoidal cross sections instead of rectangular sections, as expected. This geometric alteration results in some device issues, like carrier profile, threshold voltage, and corner effects. This work analyzes these consequences based on three-dimensional numeric simulation of several dual-gate and triple-gate FinFETs. The simulation results show that the threshold voltage depends on the sidewall inclination angle and that this dependence varies according to the body doping level. The corner effects also depend on the inclination angle and doping level. (C) 2008 The Electrochemical Society.

The influence of different voltage waveforms and grain sizes in electrical steels losses

Square and two-level pulse width modulation (PWM) magnetic induction waveforms are investigated and their effect on electrical steels losses as a function of the grain size is determined. The increase of hysteresis losses-as compared to that resulting from sinusoidal voltages-occurs only for two-level PWM waveforms. Total losses are lower for square waveform, and the difference between losses under square and sinusoidal waveform increase with increasing grain size, result explained with the loss separation model. (C) 2008 Elsevier B.V. All rights reserved.

Detrusor overactivity is associated with downregulation of large-conductance calcium- and voltage-activated potassium channel protein

Chang S, Gomes CM, Hypolite JA, Marx J, Alanzi J, Zderic SA, Malkowicz B, Wein AJ, Chacko S. Detrusor overactivity is associated with downregulation of large-conductance calcium-and voltage-activated potassium channel protein. Am J Physiol Renal Physiol 298: F1416-F1423, 2010. First published April 14, 2010; doi: 10.1152/ajprenal.00595.2009.-Large-conductance voltage-and calcium-activated potassium (BK) channels have been shown to play a role in detrusor overactivity (DO). The goal of this study was to determine whether bladder outlet obstructioninduced DO is associated with downregulation of BK channels and whether BK channels affect myosin light chain 20 (MLC(20)) phosphorylation in detrusor smooth muscle (DSM). Partial bladder outlet obstruction (PBOO) was surgically induced in male New Zealand White rabbits. The rabbit PBOO model shows decreased voided volumes and increased voiding frequency. DSM from PBOO rabbits also show enhanced spontaneous contractions compared with control. Both BK channel alpha- and beta-subunits were significantly decreased in DSM from PBOO rabbits. Immunostaining shows BK beta mainly expressed in DSM, and its expression is much less in PBOO DSM compared with control DSM. Furthermore, a translational study was performed to see whether the finding discovered in the animal model can be translated to human patients. The urodynamic study demonstrates several overactive DSM contractions during the urine-filling stage in benign prostatic hyperplasia (BPH) patients with DO, while DSM is very quiet in BPH patients without DO. DSM biopsies revealed significantly less BK channel expression at both mRNA and protein levels. The degree of downregulation of the BK beta-subunit was greater than that of the BK alpha-subunit, and the downregulation of BK was only associated with DO, not BPH. Finally, the small interference (si) RNA-mediated downregulation of the BK beta-subunit was employed to study the effect of BK depletion on MLC(20) phosphorylation. siRNA-mediated BK channel reduction was associated with an increased MLC(20) phosphorylation level in cultured DSM cells. In summary, PBOO-induced DO is associated with downregulation of BK channel expression in the rabbit model, and this finding can be translated to human BPH patients with DO. Furthermore, downregulation of the BK channel may contribute to DO by increasing the basal level of MLC(20) phosphorylation.

A low-temperature insulating phase at v=1.5 for 2D holes in high-mobility SiSi1-xGex heterostructures with Landau level degeneracy

Magneto-transport measurements of the 2D hole system (2DHS) in p-type Si-Si1-xGex heterostructures identify the integer quantum Hall effect (IQHE) at dominantly odd-integer filling factors v and two low-temperature insulating phases (IPs) at v = 1.5 and v less than or similar to 0.5, with re-entrance to the quantum Hall effect at v = 1. The temperature dependence, current-voltage characteristics, and tilted field and illumination responses of the IP at v = 1.5 indicate that the important physics is associated with an energy degeneracy of adjacent Landau levels of opposite spin, which provides a basis for consideration of an intrinsic, many-body origin.

On the Problem of Balancing the DC Capacitor Voltage Divider in Back-to-Back Multilevel Converters

This paper presents a new generalized solution for DC bus capacitors voltage balancing in back-to-back m level diode-clamped multilevel converters connecting AC networks. The solution is based on the DC bus average power flow and exploits the switching configuration redundancies. The proposed balancing solution is particularized for the back-to-back multilevel structure with m=5 levels. This back-to-back converter is studied working with bidirectional power flow, connecting an induction machine to the power grid.

Fast optimum-predictive control and capacitor voltage balancing strategy for bipolar back-to-back NPC converters in high-voltage direct current transmission systems

Multilevel power converters have been introduced as the solution for high-power high-voltage switching applications where they have well-known advantages. Recently, full back-to-back connected multilevel neutral point diode clamped converters (NPC converter) have been used inhigh-voltage direct current (HVDC) transmission systems. Bipolar-connected back-to-back NPC converters have advantages in long-distance HVDCtransmission systems over the full back-to-back connection, but greater difficulty to balance the dc capacitor voltage divider on both sending and receiving end NPC converters. This study shows that power flow control and dc capacitor voltage balancing are feasible using fast optimum-predictive-based controllers in HVDC systems using bipolar back-to-back-connected five-level NPC multilevel converters. For both converter sides, the control strategytakes in account active and reactive power, which establishes ac grid currents in both ends, and guarantees the balancing of dc bus capacitor voltages inboth NPC converters. Additionally, the semiconductor switching frequency is minimised to reduce switching losses. The performance and robustness of the new fast predictive control strategy, and its capability to solve the DC capacitor voltage balancing problem of bipolar-connected back-to-back NPCconverters are evaluated.

Simulation of offshore wind system with two-level converters: HVDC power transmission

A new integrated mathematical model for the simulation of offshore wind energy conversion system performance is presented in this paper. The mathematical model considers an offshore variable-speed turbine in deep water equipped with a permanent magnet synchronous generator using full-power two-level converter, converting the energy of a variable frequency source in injected energy into the electric network with constant frequency, through a high voltage DC transmission submarine cable. The mathematical model for the drive train is a concentrate two mass model which incorporates the dynamic for the structure and tower due to the need to emulate the effects of the moving surface. Controller strategy considered is a proportional integral one. Also, pulse width modulation using space vector modulation supplemented with sliding mode is used for trigger the transistor of the converter. Finally, a case study is presented to access the system performance. © 2014 IEEE.

PV inverters for module level applications

Dissertação para obtenção do Grau de Mestre em Energias Renováveis – Conversão Eléctrica e Utilização Sustentáveis

A multi-objective optimization of the active and reactive resource scheduling at a distribution level in a smart grid context

In the traditional paradigm, the large power plants supply the reactive power required at a transmission level and the capacitors and transformer tap changer were also used at a distribution level. However, in a near future will be necessary to schedule both active and reactive power at a distribution level, due to the high number of resources connected in distribution levels. This paper proposes a new multi-objective methodology to deal with the optimal resource scheduling considering the distributed generation, electric vehicles and capacitor banks for the joint active and reactive power scheduling. The proposed methodology considers the minimization of the cost (economic perspective) of all distributed resources, and the minimization of the voltage magnitude difference (technical perspective) in all buses. The Pareto front is determined and a fuzzy-based mechanism is applied to present the best compromise solution. The proposed methodology has been tested in the 33-bus distribution network. The case study shows the results of three different scenarios for the economic, technical, and multi-objective perspectives, and the results demonstrated the importance of incorporating the reactive scheduling in the distribution network using the multi-objective perspective to obtain the best compromise solution for the economic and technical perspectives.

Three-phase three-level current-source converter for EVs fast battery charging systems

This paper presents a three-phase three-level fast battery charger for electric vehicles (EVs) based in a current-source converter (CSC). Compared with the traditional voltage-source converters used for fast battery chargers, the CSC can be seen as a natural buck-type converter, i.e., the output voltage can assume a wide range of values, which varies between zero and the maximum instantaneous value of the power grid phase-to-phase voltage. Moreover, using the CSC it is not necessary to use a dc-dc back-end converter in the battery side, and it is also possible to control the grid current in order to obtain a sinusoidal waveform, and in phase with the power grid voltage (unitary power factor). Along the paper is described in detail the proposed CSC for EVs fast battery charging systems: the circuit topology, the power control theory, the current control strategy and the grid synchronization algorithm. Several simulation results of the EV fast battery charger operating with a maximum power of 50 kW are presented.

Simulation of OWES with five-Level converter linked to the grid: Harmonic assessment

This paper deals with a computing simulation for an offshore wind energy system taking into account the influence of the marine waves action throughout the floating platform. The wind energy system has a variable-speed turbine equipped with a permanent magnet synchronous generator and a full-power five level converter, injecting energy into the electric grid through a high voltage alternate current link. A reduction on the unbalance of the voltage in the DC-link capacitors of the five-level converter is proposed by a strategic selection of the output voltage vectors. The model for the drive train of the wind energy system is a two mass model, including the dynamics of the floating platform. A case study is presented and the assessment of the quality of the energy injected into the electric grid is discussed.

Experimental validation of a proposed single-phase five-level active rectifier operating with model predictive current control

This paper presents a model predictive current control applied to a proposed single-phase five-level active rectifier (FLAR). This current control strategy uses the discrete-time nature of the active rectifier to define its state in each sampling interval. Although the switching frequency is not constant, this current control strategy allows to follow the reference with low total harmonic distortion (THDF). The implementation of the active rectifier that was used to obtain the experimental results is described in detail along the paper, presenting the circuit topology, the principle of operation, the power theory, and the current control strategy. The experimental results confirm the robustness and good performance (with low current THDF and controlled output voltage) of the proposed single-phase FLAR operating with model predictive current control.

Effect of rufinamide on gating properties of voltage-gated sodium channel Na(v)1.7

Background: Voltage-gated sodium channels (Nav1.x) are important players in chronic pain. A particular interest has grown in Nav1.7, expressed in nociceptors, since mutations in its gene are associated to two inherited pain syndromes or insensitivity to pain. Rufinamide, a drug used to treat refractory epilepsy such as the Lennox-Gastaut syndrome, has been shown to reduce the number of action potentials in cortical neurons without completely blocking Na channels. Aim: The goal of this study was to investigate the effect of rufinamide on Nav1.7 current. Methods and results: Whole-cell patch clamp experiments were performed using HEK293 cells stably expressing Nav1.7. Rufinamide significantly decreased peak sodium current by 28.3, 21.2 and 12.5% at concentrations of 500, 100 and 50μM respectively (precise EC50 could not be calculated since higher rufinamide concentrations could not be achieved in physiological buffer solution). No significant difference on the V1/2 of voltage-dependence of activation was seen; however a shift in the steady-state inactivation curve was observed (-82.6 mV to -88.8 mV and -81.8 to -87.6 mV for 50 and 100 μM rufinamide respectively, p <0.005). Frequency-dependent inhibition of Nav1.7 was also influenced by the drug. One hundred μM rufinamide reduced the peak sodium current (in % of the peak current taken at the first sweep of a train of 50) from 90.8 to 80.8% (5Hz), 88.7 to 71.8% (10 Hz), 69.1 to 49.2% (25 Hz) and 22.3 to 9.8% (50 Hz) (all p <0.05). Onset of fast inactivation was not influenced by the drug since no difference in the time constant of current decay was observed. Conclusion: In the concentration range of plasma level in human treated for epilepsy, 15 μM, rufinamide only minimally blocks Nav1.7. However, it stabilizes the inactivated state and exerts frequencydependent inhibition of Nav1.7. These pharmacological properties may be of use in reducing ectopic discharges as a causal and symptom related contributor of neuropathic pain syndrome.

Decoding stimulus-related information from single-trial EEG responses based on voltage topographies

Neuroimaging studies typically compare experimental conditions using average brain responses, thereby overlooking the stimulus-related information conveyed by distributed spatio-temporal patterns of single-trial responses. Here, we take advantage of this rich information at a single-trial level to decode stimulus-related signals in two event-related potential (ERP) studies. Our method models the statistical distribution of the voltage topographies with a Gaussian Mixture Model (GMM), which reduces the dataset to a number of representative voltage topographies. The degree of presence of these topographies across trials at specific latencies is then used to classify experimental conditions. We tested the algorithm using a cross-validation procedure in two independent EEG datasets. In the first ERP study, we classified left- versus right-hemifield checkerboard stimuli for upper and lower visual hemifields. In a second ERP study, when functional differences cannot be assumed, we classified initial versus repeated presentations of visual objects. With minimal a priori information, the GMM model provides neurophysiologically interpretable features - vis à vis voltage topographies - as well as dynamic information about brain function. This method can in principle be applied to any ERP dataset testing the functional relevance of specific time periods for stimulus processing, the predictability of subject's behavior and cognitive states, and the discrimination between healthy and clinical populations.

Regulation of the expression of Nav1.5, the cardiac voltage-gated sodium channel

Abstract The cardiac sodium channel Nav1.5 plays a key role in cardiac excitability and conduction. Its importance for normal cardiac function has been highlighted by descriptions of numerous mutations of SCN5A (the gene encoding Nav1.5), causing cardiac arrhythmias which can lead to sudden cardiac death. The general aim of my PhD research project has been to investigate the regulation of Nav1.5 along two main axes: (1) We obtained experimental evidence revealing an interaction between Nav1.5 and a multiprotein complex comprising dystrophin. The first part of this study reports the characterization of this interaction. (2) The second part of the study is dedicated to the regulation of the cardiac sodium channel by the mineralocorticoid hormone named aldosterone. (1) Early in this study, we showed that Nav1.5 C-terminus was associated with dystrophin and that this interaction was mediated by syntrophin proteins. We used dystrophin-deficient mdx5cv mice to study the role of this interaction. We reported that dystrophin deficiency led to a reduction of both Nav1.5 protein level and the sodium current (INa). We also found that mdx5cv mice displayed atrial and ventricular conduction defects. Our results also indicated that proteasome inhibitor MG132 treatment of mdx5cv mice rescued Nav1.5 protein level and INa in cardiac tissue. (2) We showed that aldosterone treatment of mice cardiomyocytes led to an increase of the sodium current with no modification of Nav1.5 transcript and protein level. Altogether, these results suggest that the sodium current can be increased by distribution of intracellular pools of protein to the plasma membrane (e.g. upon aldosterone stimulation) and that interaction with dystrophin multiprotein complex is required for the stabilization of the channel at the plasma membrane. Finally, we obtained preliminary results suggesting that the proteasome could regulate Nav1.5 in mdx5cv mice. This study defines regulatory mechanisms of Nav1.5 which could play an important role in cardiac arrhythmia and bring new insight in cardiac conduction alterations observed in patients with dystrophinopathies. Moreover, this work suggests that Brugada syndrome, and some of the cardiac alterations seen in Duchenne patients may be caused by overlapping molecular mechanisms leading to a reduction of the cardiac sodium current.