Maxwell Technologies (Switzerland)

Nowadays, more and more studies present the results obtained while testing the lightning impulse breakdown behavior of newly developed, innovative dielectric oils. As showed for industrial frequencies, clear standardized test conditions are mandatory to allow the interpretation of test results without uncertainties. This paper addresses the characteristics of the measuring cell suggested by ASTM and IEC standards and their influence on performing impulse breakdown measurements. As an addition to the results recently published by other research teams, this work intends to discuss several aspects that could be further investigated in a working group. The joint research could provide the ASTM and the IEC standards organizations with a broader view of lightning impulse breakdown (LI) and withstand data that can benefit and improve their regulation.

Microelectrode arrays (MEAs) enable fast and high-throughput readout of cell's electrical signals. MEAs are currently used for phenotype characterization and drug toxicity/efficacy testing with iPSC-derived neurons and cardiomyocytes. A key advantage of MEAs is the capability to record and stimulate individual neurons at multiple sites simultaneously. We will present ongoing advancements of MEA technology, with a focus on achieving higher quality recordings by means of monolithic co-integration of circuitry on chip by using CMOS technology [1]. Such high-density MEAs with more than 3000 electrodes per mm2 are a suitable tool for capturing neuronal activity across various scales, including axons, somas, dendrites, entire neurons, and networks.

A new thermal model which allows the temperature distribution determination inside the supercapacitor cell is developed. The model is tested for supercapacitor based on the activated carbon and organic electrolyte technology. In hybrid vehicle applications, supercapacitors are used as energy storage devices offering the possibility to provide peak power requirement. They are charged and discharged at a high current rate. The problematic of this operating mode is the big amount of heat produced in the device which can lead to its destruction. An accurate thermal modelling of the internal temperature is required to design a cooling system for supercapacitors module meeting safety and reliability of the power systems. The purpose of this paper is to study the supercapacitor temperature distribution in steady and transient states. A thermal model is developed; it is based on the finite-differential method which allows the supercapacitor thermal resistance determination. A test bench is realized. The cases of supercapacitor thermal distribution using natural and forced convection are studied. Simulations and experimental results are reported to validate the proposed model. The results obtained with this model may be used to determine the cooling system required for actual supercapacitor applications. The originality of this study is in the fact that a thermocouple is placed inside the supercapacitor.

We have measured double-layer capacitance and electronic conductance of an activated carbon electrode in an aprotic electrolyte solution, 1 mol/L in acetonitrile. Both quantities show a similar dependence on the electrode potential with distinct minima near the potential of zero charge. This correlation suggests that the capacitance like the conductance is governed substantially by the electronic properties of the solid, rather than by the properties of the solution side of the double layer. These findings can be explained by treating activated carbon as a metal with a finite density of electronic states at the Fermi level, and with hopping conduction between these states. © 2003The Electrochemical Society. All rights reserved.