Improved micro-contact resistance model that considers material deformation, electron transport and thin film characteristics

This paper reports on an improved analytic model forpredicting micro-contact resistance needed for designing microelectro-mechanical systems (MEMS) switches. The originalmodel had two primary considerations: 1) contact materialdeformation (i.e. elastic, plastic, or elastic-plastic) and 2) effectivecontact area radius. The model also assumed that individual aspotswere close together and that their interactions weredependent on each other which led to using the single effective aspotcontact area model. This single effective area model wasused to determine specific electron transport regions (i.e. ballistic,quasi-ballistic, or diffusive) by comparing the effective radius andthe mean free path of an electron. Using this model required thatmicro-switch contact materials be deposited, during devicefabrication, with processes ensuring low surface roughness values(i.e. sputtered films). Sputtered thin film electric contacts,however, do not behave like bulk materials and the effects of thinfilm contacts and spreading resistance must be considered. Theimproved micro-contact resistance model accounts for the twoprimary considerations above, as well as, using thin film,sputtered, electric contact

Applications of plasma-liquid systems : a review

Plasma-liquid systems have attracted increasing attention in recent years, owing to their high potential in material processing and nanoscience, environmental remediation, sterilization, biomedicine, and food applications. Due to the multidisciplinary character of this scientific field and due to its broad range of established and promising applications, an updated overview is required, addressing the various applications of plasma-liquid systems till now. In the present review, after a brief historical introduction on this important research field, the authors aimed to bring together a wide range of applications of plasma-liquid systems, including nanomaterial processing, water analytical chemistry, water purification, plasma sterilization, plasma medicine, food preservation and agricultural processing, power transformers for high voltage switching, and polymer solution treatment. Although the general understanding of plasma-liquid interactions and their applications has grown significantly in recent decades, it is aimed here to give an updated overview on the possible applications of plasma-liquid systems. This review can be used as a guide for researchers from different fields to gain insight in the history and state-of-the-art of plasma-liquid interactions and to obtain an overview on the acquired knowledge in this field up to now

The Recognition of Fires Originating from Photovoltaic (PV) Solar Systems

There has been an observable increase in the fitting of photovoltaic (PV) solar panels on the roofs of buildings in the UK over the last decade. The origin of some fires in domestic and commercial properties has been attributed to PV systems. This thesis examines the ability of fire examiners to recognise and record details of fires believed to have originated from PV systems, as well as investigating the effect of internal heating in direct current (DC) isolators to the point at which they fail. National fire data was examined along with the methods for collecting and collating these data. This clarified that national fire data cannot identify the specifics of electrical fires. Validity of these data was then tested by identifying the confidence and competence in the recognition of the origin of fire, (especially when associated with PV systems), of some fire staff responsible for collecting fire data. This suggests that some fire scenes examiners are not confident in their own ability to recognise fires originating from PV systems. Evidence for fires occurring in PV systems in Kent between 2009 and 2014 was then examined, including a cold case forensic review of the evidence. This provided an indication that a potential common point of failure, which may lead to fire originating from a PV system, was to be found within the DC section of the PV circuits and probably within the DC isolator switch itself. Experimentation revealed that internal heating of a terminal connection can lead to changes of the phase of the insulating material, causing failure of structural integrity and therefore allowing an arc to be established. Observable post fire indicators associated with this mechanism of failure have been identified as well as hydrocarbons evolved from pyrolysis of isolator insulating material. Finally, areas for further experimental research and training of fire staff are suggested as well as the modification of recording mechanisms and building regulations

Arcing High Impedance Fault Detection Using Real Coded Genetic Algorithm

Safety and reliability are two of the most important aspects of electric power supply systems. Sensitivity and robustness to detect and isolate faults can influence the safety and reliability of such systems. Overcurrent relays are generally used to protect the high voltage feeders in distribution systems. Downed conductors, tree branches touching conductors, and failing insulators often cause high-impedance faults in overhead distribution systems. The levels of currents of these faults are often much smaller than detection thresholds of traditional ground fault detection devices, thus reliable detection of these high impedance faults is a real challenge. With modern signal processing techniques, special hardware and software can be used to significantly improve the reliability of detection of certain types of faults. This paper presents a new method for detecting High Impedance Faults (HIF) in distribution systems using real coded genetic algorithm (RCGA) to analyse the harmonics and phase angles of the fault current signals. The method is used to discriminate HIFs by identifying specific events that happen when a HIF occurs

Index to 1981 NASA Tech Briefs, volume 6, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1981 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

On the long-term correlations and multifractal properties of electric arc furnace time series

In this paper, we study long-term correlations and multifractal properties elaborated from time series of three-phase current signals coming from an industrial electric arc furnace plant. Implicit sinusoidal trends are suitably detected by considering the scaling of the fluctuation functions. Time series are then filtered via a Fourier-based analysis, removing hence such strong periodicities. In the filtered time series we detected long-term, positive correlations. The presence of positive correlations is in agreement with the typical V--I characteristic (hysteresis) of the electric arc furnace, providing thus a sound physical justification for the memory effects found in the current time series. The multifractal signature is strong enough in the filtered time series to be effectively classified as multifractal

The Novel ''Controlled Intermediate Nuclear Fusion'' and its Possible Industrial Realization as Predicted by Hadronic Mechanics and Chemistry

In this note, we propose, apparently for the first time, a new type of controlled nuclear fusion called "intermediate" because occurring at energies intermediate between those of the ''cold'' and ''hot'' fusions, and propose a specific industrial realization. For this purpose: 1) We show that known limitations of quantum mechanics, quantum chemistry and special relativity cause excessive departures from the conditions occurring for all controlled fusions; 2) We outline the covering hadronic mechanics, hadronic chemistry and isorelativity specifically conceived, constructed and verified during the past two decades for new cleans energies and fuels; 3) We identify seven physical laws predicted by the latter disciplines that have to be verified by all controlled nuclear fusions to occur; 4) We review the industrial research conducted to date in the selection of the most promising engineering realization as well as optimization of said seven laws; and 5) We propose with construction details a specific {\it hadronic reactor} (patented and international patents pending), consisting of actual equipment specifically intended for the possible industrial production of the clean energy released by representative cases of controlled intermediate fusions for independent scrutiny by interested colleagues.Comment: 32 pages, 5 figures. Journal of Applied Sciences, in pres

Index to NASA Tech Briefs, 1975

This index contains abstracts and four indexes--subject, personal author, originating Center, and Tech Brief number--for 1975 Tech Briefs

A Review of Micro-Contact Physics for Microelectromechanical Systems (MEMS) Metal Contact Switches

Innovations in relevant micro-contact areas are highlighted, these include, design, contact resistance modeling, contact materials, performance and reliability. For each area the basic theory and relevant innovations are explored. A brief comparison of actuation methods is provided to show why electrostatic actuation is most commonly used by radio frequency microelectromechanical systems designers. An examination of the important characteristics of the contact interface such as modeling and material choice is discussed. Micro-contact resistance models based on plastic, elastic-plastic and elastic deformations are reviewed. Much of the modeling for metal contact micro-switches centers around contact area and surface roughness. Surface roughness and its effect on contact area is stressed when considering micro-contact resistance modeling. Finite element models and various approaches for describing surface roughness are compared. Different contact materials to include gold, gold alloys, carbon nanotubes, composite gold-carbon nanotubes, ruthenium, ruthenium oxide, as well as tungsten have been shown to enhance contact performance and reliability with distinct trade offs for each. Finally, a review of physical and electrical failure modes witnessed by researchers are detailed and examined