Enhancement and tunability of near-field radiative heat transfer mediated by surface plasmon polaritons in thin plasmonic films

The properties of thermal radiation exchange between hot and cold objects can be strongly modified if they interact in the near field where electromagnetic coupling occurs across gaps narrower than the dominant wavelength of thermal radiation. Using a rigorous fluctuational electrodynamics approach, we predict that ultra-thin films of plasmonic materials can be used to dramatically enhance near-field heat transfer. The total spectrally integrated film-to-film heat transfer is over an order of magnitude larger than between the same materials in bulk form and also exceeds the levels achievable with polar dielectrics such as SiC. We attribute this enhancement to the significant spectral broadening of radiative heat transfer due to coupling between surface plasmon polaritons (SPPs) on both sides of each thin film. We show that the radiative heat flux spectrum can be further shaped by the choice of the substrate onto which the thin film is deposited. In particular, substrates supporting surface phonon polaritons (SPhP) strongly modify the heat flux spectrum owing to the interactions between SPPs on thin films and SPhPs of the substrate. The use of thin film phase change materials on polar dielectric substrates allows for dynamic switching of the heat flux spectrum between SPP-mediated and SPhP-mediated peaks.Comment: 25 pages, 11 figure

Special Libraries, December 1954

Volume 45, Issue 10https://scholarworks.sjsu.edu/sla_sl_1954/1009/thumbnail.jp

Modal pattern stability factor as a figure of merit for characteristic modes

This paper is a postprint of a paper submitted to and accepted for publication in Electronics Letters and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at the IET Digital Library.This Letter proposes the use of a modal pattern stability factor (MPSF) parameter to quantify the pattern stability associated to characteristic modes (CM). The proposed parameter can be used as a figure of merit for CM associated to arbitrary-shaped structures, aiding the antenna design process. This parameter can be used (together with other modal parameters) to optimise the geometry of a radiating element in order to improve the radiation pattern stability in a desired range of frequencies. Two examples are presented for analysis. First, MPSF for the CM of three ring antennas with different width are analysed, showing how pattern stability of CM depend on this geometrical parameter. Secondly, three metallic plates with different shapes are analysed in terms of MPSF, in order to assess the stability of the CM for each geometry.This work was supported by the Spanish Ministry of Economics and Competitiveness under project TEC2013-47360-C3-3-P, and by Generalitat Valenciana under project GV/2015/065.Antonino Daviu, E.; Mohamed Mohamed-Hicho, N.; Cabedo Fabrés, M.; Ferrando Bataller, M. (2016). Modal pattern stability factor as a figure of merit for characteristic modes. Electronics Letters. 52(20):1658-1659. https://doi.org/10.1049/el.2016.1926S16581659522

Inactivation of bacteria under visible light and in the dark by Cu films. Advantages of Cu-HIPIMS-sputtered films

Introduction: The Cu polyester thin-sputtered layers on textile fabrics show an acceptable bacterial inactivation kinetics using sputtering methods. Materials and methods: Direct current magnetron sputtering (DCMS) for 40s of Cu on cotton inactivated Escherichia coli within 30min under visible light and within 120min in the dark. For a longer DCMS time of 180s, the Cu content was 0.294% w/w, but the bacterial inactivation kinetics under light was observed within 30min, as was the case for the 40-s sputtered sample. Results and discussion: This observation suggests that Cu ionic species play a key role in the E. coli inactivation and these species were further identified by X-ray photoelectron spectroscopy (XPS). The 40-s sputtered samples present the highest amount of Cu sites held in exposed positions interacting on the cotton with E. coli. Cu DC magnetron sputtering leads to thin metallic semi-transparent gray-brown Cu coating composed by Cu nanoparticulate in the nanometer range as found by electron microscopy (EM). Cu cotton fabrics were also functionalized by bipolar asymmetric DCMSP. Conclusion: Sputtering by DCMS and DCMSP for longer times lead to darker and more compact Cu films as detected by diffuse reflectance spectroscopy and EM. Cu is deposited on the polyester in the form of Cu2O and CuO as quantified by XPS. The redox interfacial reactions during bacterial inactivation involve changes in the Cu oxidation states and in the oxidation intermediates and were followed by XPS. High-power impulse magnetron sputtering (HIPIMS)-sputtered films show a low rugosity indicating that the texture of the Cu nanoparticulate films were smooth. The values of R q and R a were similar before and after the E. coli inactivation providing evidence for the stability of the HIPIMS-deposited Cu films. The Cu loading percentage required in the Cu films sputtered by HIPIMS to inactivate E. coli was about three times lower compared to DCMS films. This indicates a substantial Cu metal savings within the preparation of antibacterial film

An Overview of Orthodontic Bonding

Bonding brackets with composite resin is considered the gold standard in orthodontics. However, this can be challenging, especially where there is a requirement to bond to surfaces other than enamel, or where the enamel is defective. A choice of bonding modalities exists for these situations, and it is important that clinicians keep up-to-date with current techniques and practice. An overview of the evidence and techniques available for bonding to enamel and other surfaces (composite, porcelain, gold, amalgam and acrylic) is presented. Furthermore, a summary table providing a step-by-step guide for bonding techniques to various surfaces is provided

A Fiber Bragg Grating—Bimetal Temperature Sensor for Solar Panel Inverters

This paper reports the design, characterization and implementation of a Fiber Bragg Grating (FBG)-based temperature sensor for an Insulted-Gate Bipolar Transistor (IGBT) in a solar panel inverter. The FBG is bonded to the higher Coefficient of Thermal Expansion (CTE) side of a bimetallic strip to increase its sensitivity. Characterization results show a linear relationship between increasing temperature and the wavelength shift. It is found that the sensitivity of the sensor can be categorized into three characterization temperature regions between 26 °C and 90 °C. The region from 41 °C to 90 °C shows the highest sensitivity, with a value of 14 pm/°C. A new empirical model that considers both temperature and strain effects has been developed for the sensor. Finally, the FBG-bimetal temperature sensor is placed in a solar panel inverter and results confirm that it can be used for real-time monitoring of the IGBT temperature

Design, Simulation of Low Actuation RF MEMS Shunt Switches With Electromagnetic Characterization

Micro Electro Mechanical Systems (MEMS) is an integration of sensors, actuators, microstructures and microelectronics. Components of MEMS that comprises of moving sub milli-meter sized parts, capable of providing Radio Frequency (RF) functionality are collectively referred as RF MEMS. In this work, low actuation RF MEMS switches have been designed and simulated and they have also been analysed for electromagnetic characterization. The switches so analyzed show an actuation voltage of as low as 2V. The electromagnetic analysis gives an isolation of as high as 55-65dB and a very low insertion loss of 0.01dB. DOI: 10.17762/ijritcc2321-8169.15068

Catching the rebound : economy-wide implications of an efficiency shock in the provision of transport services by households

We investigate the rebound effect of a 10% energy efficiency improvement in the provision of private transport services by German households. In the process, we take into account that household behaviour may be in uenced by habits, build on a detailed representation of the provision of private transport services, and disentangle the direct and indirect rebound effect. Our analysis shows that rebound has the potential to significantly reduce the expected energy savings of an energy efficiency improvement at households. In particular if households have a exible demand structure, rebound can erode large parts of efficiency increases. Household habits have an initial detrimental effect on rebound. They limit the ability of households to adapt to changes in the prevailing price and income system and therewith temporally block parts of the channels that lead to rebound. In the long run, however, if habits are formed on the basis of historic consumption, habits do not affect rebound. In isolation, the direct and indirect rebound effect of the efficiency shock are positive, but direct rebound is much stronger