Search results for "current"

1/f noise in streaming electrification

2005

The paper presents the measurement results of the noise generated by static electricity. The tests were performed in the spinning-disk system. Insulation liquid (transformer oil) was used for electrostatic charge generation. The element measured was the current flowing to the disk surface. A stochastic term is present in the current. Existance of this term is due to the complex chemical constitution of the oil. A relaxation of the polar molecules has inertial character. The spreading of a large amount of the relaxation phenomena can lead to forming a compounded spectrum close in shape to 1/f noise. Power spectral density of the polarization was defined for periodic step function. The calcul…

Local Metamaterial-Based Waveguides in Gaps Between Parallel Metal Plates

2009

This letter presents a new metamaterial-based waveguide technology referred to as ridge gap waveguides. The main advantages of the ridge gap waveguides compared to hollow waveguides are that they are planar and much cheaper to manufacture, in particular at high frequencies such as for millimeter and sub- millimeter waves. The latter is due to the fact that there are no mechanical joints across which electric currents must float. The gap waveguides have lower losses than microstrip lines, and they are completely shielded by metal so no additional packaging is needed, in contrast to the severe packaging problems associated with microstrip circuits. The gap waveguides are realized in a narrow …

Spark Plasma Sintering tool design for preparing alumina-based Functionally Graded Materials

2016

Abstract A way to produce Functionally Graded Materials (FGM) is by means of Spark Plasma Sintering (SPS) and specifically designated tools. These new tools permit a current density modulation and therefore a temperature variation along the z-axis. The key feature relies on a varying die section. FEM modelling has given the suitable range of die dimensions between the top and the bottom to obtain a given temperature gradient (around 300 °C) out of roughly a 15 mm height. Experiments conducted in different configurations (with or without samples) and the measurement of the associated thermal gradient led to improvements of the mould (in particular the introduction of a counter-piston). By th…

Investigation of recovery mechanisms in dye sensitized solar cells

2016

Abstract We study the spontaneous recovery phenomenon displayed by solar cells sensitized with a ruthenium complex-based dye N719, which manifests with the increase over the time (from several minutes up to some days) of the short circuit current density J sc and the open circuit voltage V oc , during cell illumination. Under dark conditions the current decreases over time after the application of forward bias voltages. We investigate the effects of temperature and electrolyte composition by means of current–voltage measurements and electrochemical impedance spectroscopy, both under dark and illumination conditions. The main result is that the recovery of the performances depends on the cha…

Electrical and emission properties of current-carrying silver nanocluster films investigated by emission electron microscopy

2003

Effects of Frequency Dependence of the External Quantum Efficiency of Perovskite Solar Cells

2018

Perovskite solar cells are known to show very long response time scales, on the order of milliseconds to seconds. This generates considerable doubt over the validity of the measured external quantum efficiency (EQE) and consequently the estimation of the short-circuit current density. We observe a variation as high as 10% in the values of the EQE of perovskite solar cells for different optical chopper frequencies between 10 and 500 Hz, indicating a need to establish well-defined protocols of EQE measurement. We also corroborate these values and obtain new insights regarding the working mechanisms of perovskite solar cells from intensity-modulated photocurrent spectroscopy measurements, iden…

Microwave photoassisted dissipation and supercurrent of a phase-biased graphene-superconductor ring

2021

Irradiating normal-superconducting junctions with microwave photons produce spectacular effects, such as Shapiro steps and photoinduced modifications of the dc supercurrent. Moreover, microwave irradiation can also have other, hitherto unexplored consequences, such as a photoassisted dissipation which is phase dependent. Here we present a finite-frequency measurement of both the dissipation and the supercurrent of a phase-biased graphene-superconductor junction in response to microwave photons. We find that, while the supercurrent response is well described by existing theory, the dissipation exhibits unexpected effects which need new theoretical elucidation. Especially with high frequency …

Integrated Modeling of the Beam Formation and Extraction in the Linac4 Hydrogen Negative Ion Source

2018

In order to make the predictive simulation tools for the extracted beam current and emittance in the Linac4 H− ion source, we have launched the development of the integrated model for the H− ion beam formation and extraction process. More specifically, our 3D KEIO-Beam Formation and eXtraction (3D KEIO-BFX) is coupled with the NINJA, IBSIMU and TRAVEL. The extracted H− ion beam current and co-extracted electron current obtained by the integrated model have shown reasonable agreement with the experiments. peerReviewed

Stabilizing organic photocathodes by low-temperature atomic layer deposition of TiO2

2017

Organic semiconductor light absorbers are receiving attention for their potential application in photoelectrochemical (PEC) cells for renewable fuels generation. Key to their advancement is precise control of the interfaces between charge-selective contacts, absorber layers, and electrocatalysts, while maintaining compatibility with an aqueous electrolyte environment. Here we demonstrate a new process for low-temperature atomic layer deposition (ALD) of TiO2 onto a P3HT:PCBM polymer blend surface for stable high-performance organic PEC photocathodes. This ALD TiO2 layer provides three key functions: (1) formation of an electron-selective contact to the polymer to enable photovoltage and pho…

A Simple Model for Ac Impedance Spectra in Bipolar Membranes

1996

A new model accounting for the ac impedance spectra of synthetic ion-exchange bipolar membranes is presented. The theoretical approach is based on the Nernst−Planck and Poisson equations and applies some of the concepts used in the semiconductor pn junctions to the case of a bipolar membrane. The results presented are the current−voltage curves and the impedance spectra at electric currents above the limiting current. It is shown that the model is able to identify the main contributions to the bipolar membrane impedance and gives valuable information about the bipolar junction structure and its influence on the characteristic parameters involved in the field-enhanced water dissociation phen…