Search results for "ripple"
showing 10 items of 38 documents
Structure of lateral heterogeneities in a coarse-grained model for multicomponent membranes
2019
We study the lateral domain structure in a coarse-grained molecular model for multicomponent lipid bilayers by semi-grandcanonical Monte Carlo simulations. The membranes are filled with liquid ordered (lo) domains surrounded by a liquid disordered (ld) matrix. Depending on the membrane composition and temperature, we identify different morphological regimes: one regime (I) where the lo domains are small and relatively compact, and two regimes (II, II') where they are larger and often interconnected. In the latter two regimes, the ld matrix forms a network of disordered trenches separating the lo domains, with a relatively high content of interdigitated line defects. Since such defects are a…
On the design of a high current power supply for superconducting magnet
2002
The purpose of the article is the description, considerations of design and presentation of experimental results of a high current (1000 A) and low voltage (up to 15 V) converter for the excitement of superconducting corrector magnets in particle accelerators. The power source, which is based on a ZVT converter, presents high efficiency, small output ripple, excellent regulation of line, and fulfilment of the EMC normative (VDE 0871 A).
A study on the influence of permanent magnet dimensions and stator core structures on the torque of the disc-type brushless DC motor
2000
This paper presents a three-dimensional analysis of the magnetic field distribution for a disc-type, double-sided, permanent magnet, brushless dc motor with a toroidal stator core. Calculations are carried out using the OPERA (3D) package with the TOSCA module. The electromagnetic torque is determined from the Maxwell stress tensor. For comparison, various permanent magnet dimensions and slotless vs. quasi-slotted stator cores are analysed, with an iron powder-resin composite effectively used to imitate the slotted core. The torque ripple is shown to be effectively reduced by appropriate permanent magnet dimensions. The simulation results are in good agreement with experimental data obtaine…
Enhanced Modelling for Extended Performance Analysis of Interior Permanent Magnet Synchronous Machine Drive fed with Cascaded H-Bridges Multilevel In…
2021
This paper presents a comparative simulation analysis of an Interior Permanent Magnet Synchronous Machine (IPMSM) performance once fed by a traditional three-phase two-level inverter and then using a three-phase five-level Cascaded H-Bridges Multilevel Inverter (CHBMI). For this purpose, an enhanced mathematical model of the IPMSM, that take into account simultaneously saturation, cross-coupling, spatial harmonics and iron loss effects, has been employed. Furthermore, two different PWM modulation strategies have been considered. The study was conducted for several working conditions, evaluating the impact of CHBMI adoption on the IPMSM performance in terms of improved efficiency and torque …
Design of a LLC Resonant Converter for Powering a PEM Electrolyzer
2021
International audience; This paper proposes the design of a LLC resonant converter to supply a proton exchange membrane (PEM) electrolyzer. The PEM requires a low voltage with high current, a reduced output voltage ripple, and an overdamped dynamic behavior of the converter to avoid voltage overshoots. The designed converter allows satisfying the design constraints, minimizing switching and reverse recovery losses; the efficiency is influenced mainly by the output rectifier's conduction losses.
Optogenetically blocking sharp wave ripple events in sleep does not interfere with the formation of stable spatial representation in the CA1 area of …
2016
During hippocampal sharp wave/ripple (SWR) events, previously occurring, sensory inputdriven neuronal firing patterns are replayed. Such replay is thought to be important for plasticity-related processes and consolidation of memory traces. It has previously been shown that the electrical stimulation-induced disruption of SWR events interferes with learning in rodents in different experimental paradigms. On the other hand, the cognitive map theory posits that the plastic changes of the firing of hippocampal place cells constitute the electrophysiological counterpart of the spatial learning, observable at the behavioral level. Therefore, we tested whether intact SWR events occurring during th…
Phase diagram of a mixed polymer brush
2001
We investigate the structure and phase behavior of a two-component (binary) polymer brush in a solvent within self-consistent field theory as a function of the chains' stretching, the composition, and the incompatibility. Grafting the chains irreversibly prevents macrophase separation and the chains assemble into three-dimensional structures with lateral periodicity. At small incompatibilities a "ripple" phase is formed where different species aggregate into an array of parallel cylinders. At larger incompatibilities or asymmetric composition two "dimple" phases become stable, where different species form clusters which arrange on a quadratic (checkerboard structure) or hexagonal lattice.
Disrupting neural activity related to awake-state sharp wave-ripple complexes prevents hippocampal learning
2012
Oscillations in hippocampal local-field potentials (LFPs) reflect the crucial involvement of the hippocampus in memory trace formation: theta (4–8 Hz) oscillations and ripples (~200 Hz) occurring during sharp waves are thought to mediate encoding and consolidation, respectively. During sharp wave-ripple complexes (SPW-Rs), hippocampal cell firing closely follows the pattern that took place during the initial experience, most likely reflecting replay of that event. Disrupting hippocampal ripples using electrical stimulation either during training in awake animals or during sleep after training retards spatial learning. Here, adult rabbits were trained in trace eyeblink conditioning, a hippoc…
A device for PV modules I-V characteristic detection
2013
In this paper an electronic load suitable for the PV module I-V characteristic curve fast detection is presented. This device is designed in agreement with the IEC 82 Techinical Committee Standard since it allows the detection of the characteristic starting from voltage values even lower than 3% of the PV module open circuit voltage. The device main features are short time characteristc detection (2 s), limited ripple of the detected characteristic and low cost. Its validation is carried out by comparing measured data with data from simulations. Simulations are carried out considering two different commercial PV modules and by implementing in Matlab-Simulink environment the four lumped para…
The Effect of the Harmonic Content Generated by AC/DC Modular Multilevel Converters on HVDC Cable Systems
2019
With the increasing penetration of renewable and decentralized energy sources into the power grid, an extended use of DC voltages is expected on both distribution and transmission levels. Generation of DC voltages by means of voltage source converters is associated with a wide spectrum of harmonic distortions at converter terminals, both on the ac and on the dc sides. This can lead to partial discharges in power cables, which deteriorate insulation material thus weakening its performance and reducing cable life-time. In the previously published paper, the effect of harmonic distortion on appearance of partial discharges in cable insulation was evaluated. Here, the study related to the PD be…