Impedance spectroscopy for piezoceramics under high-power application was investigated. Impedance spectra under bipolar high electric field were completely different below and above TC. Below TC, high-power impedance spectra could be successfully fitted to a three resistance-constant phase element (3 R-CPE) equivalent circuit. Above TC, however, a 2 R-CPE equivalent circuit was sufficient to fit with high-power impedance spectra. For this reason, there was another relaxation factor caused by high-power application in the ferroelectric phase. From the high-power impedance spectra below TC, the nonlinear response of capacitance under a high electric field was calculated. Hence, domain wall motion would appear as a relaxation factor. Subsequently, high-power impedance spectra before and after cyclic unipolar fatigue treatment were compared. Considering the assumption that domain wall motion appeared as a relaxation factor, the capacitance caused by domain wall motion was decreased after cyclic fatigue. In conclusion, we believe that domain wall pinning could be evaluated by separating other electrical properties. In this work, the measurement possibility by impedance spectroscopy for high-power application for piezoceramics was investigated.
One of the methods to improve the lifetime of a multilayer ceramic capacitor with Ni electrode (Ni-MLCC) is vanadium addition. With the addition of vanadium, insulation resistance deteriorates and reliability improves. The resistance elements of the three resistor-capacitor electrical equivalent circuit: dielectric-electrode interface, grain boundary, and grain, all deteriorated. In particular, the interface resistance significantly deteriorated with the increase in vanadium. The experimental results suggest that the high interface resistance is not always necessary to improve reliability of Ni-MLCCs. It is deduced that oxygen vacancy formation is suppressed with vanadium addition from the first principles calculation and the thermally stimulated depolarization current analysis. Therefore, the decrease in oxygen concentration is the main factor for improving reliability with vanadium addition.
Accurate lifetime prediction for multilayer ceramic capacitors (MLCCs) is essential to ensure the reliability of electronic systems. A prediction formula based on a physical model has been recently proposed as an alternative to the widely used empirical formula. In this study, we used thermally stimulated depolarization current measurements to demonstrate that the physical model should be modified for low electric fields (<10 V/µm). We propose a new formula for the conditions as well as a modified model that involves an overpotential factor. The new formula suggests that if the applied dc field is less than the threshold value, the breakdown of MLCCs will not occur.
This paper proposes a clustering-based judgment method for false positive alerts generated by security devices. In the proposed method, firstly, alerts with the same attack source IP address over a certain period of time in the past are extracted. After the extraction, using the accumulated signature amount from extracted alerts, the alerts with si milar patterns are classified into several clusters using a method combining DBSCAN and K-means++. Then, the judgment of false positive alerts is done based on the number of alerts in each cluster. From a trial usage of the proposed method on two 7-day alert sets from two different networks, it was found that the recall rate was 100%, the precision rate was 34%, and the F-measure was 50%. The precision rate was improved by more than ten times compared to K-means++ alone, and about 2.4 times compared to DBSCAN alone.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.