Comparison of integral equations for the Maxwell transmission problem with general permittivities

Two recently derived integral equations for the Maxwell transmission problem are compared through numerical tests on simply connected axially symmetric domains for non-magnetic materials. The winning integral equation turns out to be entirely free from false eigenwavenumbers for any passive materials, also for purely negative permittivity ratios and in the static limit, as well as free from false essential spectrum on non-smooth surfaces. It also appears to be numerically competitive to all other available integral equation reformulations of the Maxwell transmission problem, despite using eight scalar surface densities.

4D smart porous scaffolds based on polyHIPE architecture and electroactive PEDOT

3D porous polymeric materials have a wide range of applications and can be obtained from different approaches as passive materials, permanently set after fabrication. Stimuli-responsive materials gives the opportunity to...

Sensors Made of Natural Renewable Materials: Efficiency, Recyclability or Biodegradability—The Green Electronics

Nowadays, sensor devices are developing fast. It is therefore critical, at a time when the availability and recyclability of materials are, along with acceptability from the consumers, among the most important criteria used by industrials before pushing a device to market, to review the most recent advances related to functional electronic materials, substrates or packaging materials with natural origins and/or presenting good recyclability. This review proposes, in the first section, passive materials used as substrates, supporting matrixes or packaging, whether organic or inorganic, then active materials such as conductors or semiconductors. The last section is dedicated to the review of pertinent sensors and devices integrated in sensors, along with their fabrication methods.

Cross-wavelength invisibility integrated with various invisibility tactics

As a superior self-protection strategy, invisibility has been a topic of long-standing interest in both academia and industry, because of its potential for intriguing applications that have only appeared thus far in science fiction. However, due to the strong dispersion of passive materials, achieving cross-wavelength invisibility remains an open challenge. Inspired by the natural ecological relationship between transparent midwater oceanic animals and the cross-wavelength detection strategy of their predators, we propose a cross-wavelength invisibility concept that integrates various invisibility tactics, where a Boolean metamaterial design procedure is presented to balance divergent material requirements over cross-scale wavelengths. As proof of concept, we experimentally demonstrate longwave cloaking and shortwave transparency simultaneously through a nanoimprinting technique. Our work extends the concept of stealth techniques from individual invisibility tactics targeting a single-wavelength spectrum to an integrated invisibility tactic targeting a cross-wavelength applications and may pave the way for development of cross-wavelength integrated metadevices.

A Review of Acoustic Impedance Matching Techniques for Piezoelectric Sensors and Transducers

The coupling of waves between the piezoelectric generators, detectors, and propagating media is challenging due to mismatch in the acoustic properties. The mismatch leads to the reverberation of waves within the transducer, heating, low signal-to-noise ratio, and signal distortion. Acoustic impedance matching increases the coupling largely. This article presents standard methods to match the acoustic impedance of the piezoelectric sensors, actuators, and transducers with the surrounding wave propagation media. Acoustic matching methods utilizing active and passive materials have been discussed. Special materials such as nanocomposites, metamaterials, and metasurfaces as emerging materials have been presented. Emphasis is placed throughout the article to differentiate the difference between electric and acoustic impedance matching and the relation between the two. Comparison of various techniques is made with the discussion on capabilities, advantages, and disadvantages. Acoustic impedance matching for specific and uncommon applications has also been covered.

Cathodic Activity on Passive Materials in Deep Seawater

In this study, the cathodic activity of biofilmed stainless steel surfaces was investigated at two exposure depths at the same location at 1,020 m and 2,020 m depth. For this purpose, a set of passive materials and sensors were exposed for 11 months in Azores, in the Atlantic Ocean. Characteristic cathodic depolarizations due to biological activity were observed in intermediary and deep water. However, a strong cathodic activity was only measured in deep water. Potential ennoblement appeared between 80 d and 200 d, depending on the exposure depth and the experimental setup used. In a given environment, the biological cathodic activity appears to be strongly related to the limiting parameter of the reaction, which can be anodic or cathodic. The biofilm sensors exposed for the first time in open, deep water appear relevant to discriminate cathodically “strongly-active” and “weakly-active” biological activity. Under cathodic control, a high current density was measured on stainless steel in deep seawater. The experimental setup used is particularly relevant as it allows determination in situ of the maximal cathodic current density.

Post-Mortem Analysis of Inhomogeneous Induced Pressure on Commercial Lithium-Ion Pouch Cells and Their Effects

This work conducts a post-mortem analysis of a cycled commercial lithium-ion pouch cell under an induced inhomogeneous pressure by using a stainless-steel sphere as a force transmitter to induce an inhomogeneous pressure distribution on a cycled lithium-ion battery. After the cycling, a macroscopic and microscopic optical analysis of the active and passive materials was executed. Also, scanning electron microscopy was used to analyze active material particles. The sphere shape results in a heterogenic pressure distribution on the lithium-ion battery and induces a ring of locally high electrochemical activity, which leads to lithium plating. Furthermore, a surface layer found on the anode, which is a possible cause of electrolyte degradation at the particle–electrolyte interface. Significant deformation and destruction of particles by the local pressure was observed on the cathode. The analysis results validate previous simulations and theories regarding lithium plating on edge effects. These results show that pressure has a strong influence on electrolyte-soaked active materials.

Research on the Comprehensive Performance of Hygroscopic Materials in an Office Building Based on EnergyPlus

This paper presents the research status of hygroscopic materials, points out the weak links as targets for major breakthroughs, and introduces humidifying mechanisms and their categories. In this paper, we simulated a single-monomer Shenyang office building with different envelopes of inner-surface hygroscopic materials for indoor humidity conditions, energy consumption, and economy, which are three aspects of energy consumption analysis in EnergyPlus software. To obtain the best moisture buffering performance from hygroscopic materials, we also simulated different cases including the laying area, ventilation strategy, thickness, and initial moisture content of different hygroscopic materials. The humidity fluctuation, with changes in the style of hygroscopic materials and usage conditions, of a room in a building can be analyzed by numerical simulation. This allows the determination of the best moisture buffering performance of the building structure. The results show that hygroscopic materials have great advantages in three energy saving aspects of building assessment. Hygroscopic materials can regulate indoor air humidity and reduce energy consumption. In addition, the entire life-cycle cost can be minimized. Lower rates of air exchange and larger usable areas can help enhance the level of performance of hygroscopic materials. The thickness and initial moisture content of hygroscopic materials have little impact on the moisture buffering value. This study strived to provide a theoretical basis and technical guidance for the production and installation of hygroscopic materials. It also promoted the passive materials market and the building’s energy savings. The best moisture buffering performance, evaluated at room level in this paper, can be obtained through real-world environmental simulation.

(ECS 234th) Fluid Flow and Current Distribution during Pulse-Reverse Electropolishing of Niobium Superconducting RF Cavities

The International Linear Collider (ILC) is a 200–500 GeV center-of-mass linear electron-positron collider, based on 1.3 GHz superconducting radio-frequency accelerating technology. This installation will require ~16,000 RF superconducting cavities operating within two linear accelerators at near absolute zero [[1]]. These SRF cavities are fabricated from pure Nb; to take full advantage of the Nb superconducting properties, the inner surface must be polished to a microscale roughness, and cleaned to be free of impurities that could degrade performance. Current methods use high viscosity electrolytes containing hydrofluoric acid, which is not conducive to low-cost, high volume manufacturing and is potentially harmful to workers. Faraday is developing an electropolishing process for niobium SRF cavities, based on a new and evolving paradigm of non-viscous dilute acid processing, enabled by a pulse-reverse electric field. Based on our understanding to date [[2]], we have speculated that the process works via oxide film formation controlled during a designed anodic pulse, followed by an off-time to remove heat and waste byproducts, followed by a cathodic pulse that removes the oxide film from the surface. This cycle is repeated many times per second, effectively removing niobium. The waveform design is such that the niobium is preferentially removed from the peaks on the surface, thus smoothing the surface.This talk will describe two recent efforts undertaken to improve understanding of various factors influencing the uniformity and speed of pulse-reverse electropolishing of niobium SRF cavities. The first is a flow study performed in a transparent plastic model of a single-cell (single-bell) cavity, to examine the flow dynamics in the absence and presence of an axisymmetric baffle fixed to the rod counter-electrode within the cavity bell. High-speed photography clearly shows the presence of a slow-moving eddy in the equatorial region of the bell, which is appreciably reduced in size when the baffle is present. Furthermore, rapid clearance of electrolysis gases and niobium oxide precipitates from the bell is expected to be strongly dependent on a proper configuration of flow throughout the bell.The second effort to be discussed comprises multiphysics modeling of the actual distribution of material removal in the EP process, as a function of position within the cavity. Modeling of EP of passive materials is complex, as numerous coupled phenomena must be accounted for, including: primary, secondary and tertiary current distributions; multi-phase effects, including fluid flow; and oxide formation/removal at the working surface. The strongest effects appear to be the primary and secondary current distributions, along with the surface oxide dynamics, inclusion of these physics (or semi-empirical approximations thereof) provides a significantly improved match between the model to the experimentally observed distribution of material removal, as compared to simulations incorporating only the primary current distribution.[1] http://www.linearcollider.org/ILC/What-is-the-ILC/The-project[2] M. Inman et al “Electropolishing of Passive Materials in HF-Free Low Viscosity Aqueous Electrolytes, J. Electrochem. Soc., 160 (9) E94-E98 (2013).