There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Many-particle charged-particle plasma simulations using spatial meshes for the electromagnetic field solutions, particle-in-cell (PIC) merged with Monte Carlo collision (MCC) calculations, are coming into wide use for application to partially ionized gases. The author emphasizes the development of PIC computer experiments since the 1950s starting with one-dimensional (1-D) charged-sheet models, the addition of the mesh, and fast direct Poisson equation solvers for 2-D and 3-D. Details are provided for adding the collisions between the charged particles and neutral atoms. The result is many-particle simulations with many of the features met in low-temperature collision plasmas; for example, with applications to plasma-assisted materials processing, but also related to warmer plasmas at the edges of magnetized fusion plasmas. >

Particle-in-Cell Charged Particle Simulations, plus Monte Carlo Collisions with Neutral Atoms, PIC-MCC

Electromagnetic Metamaterials: Transmission Line Theory and Microwave Applications. By Christophe Caloz and Tatsuo Itoh.

Resonance conditions for a substrate-superstrate printed antenna geometry which allow for large antenna gain are presented. Asymptotic formulas for gain, beamwidth, and bandwidth are given, and the bandwidth limitation of the method is discussed. The method is extended to produce narrow patterns about the horizon, and directive patterns at two different angles.

Gain enhancement methods for printed circuit antennas

As the demand for wind energy continues to grow at exponential rates, reducing operation and maintenance (OM) costs and improving reliability have become top priorities in wind turbine (WT) maintenance strategies. In addition to the development of more highly evolved WT designs intended to improve availability, the application of reliable and cost-effective condition-monitoring (CM) techniques offers an efficient approach to achieve this goal. This paper provides a general review and classification of wind turbine condition monitoring (WTCM) methods and techniques with a focus on trends and future challenges. After highlighting the relevant CM, diagnosis, and maintenance analysis, this work outlines the relationship between these concepts and related theories, and examines new trends and future challenges in the WTCM industry. Interesting insights from this research are used to point out strengths and weaknesses in today’s WTCM industry and define research priorities needed for the industry to meet the challenges in wind industry technological evolution and market growth.

/pdf/wind-turbine-condition-monitoring-state-of-the-art-review-29t23u97yb.pdf

Wind Turbine Condition Monitoring: State-of-the-Art Review, New Trends, and Future Challenges

Reconfigurable and tunable frequency selective surfaces (FSSs) are of significant interest in applications such as tunable radomes and adaptive screening of unwanted wireless transmissions Conventional FSSs require additional bias circuitry to tune the operating frequency or to change its characteristics In this letter, a new tuning technique using a spring resonator element is proposed This technique can be applied to FSS design to make it reconfigurable and/or to fine-tune the response The FSS frequency response can be adjusted by changing the spring height $h$ with applied pressure The functional characteristic of the FSS can also be altered between a bandstop and bandpass filter response A parametric analysis of the novel spring FSS is undertaken in CST software, and the results are validated with experimental measurement 

A Reconfigurable FSS Using a Spring Resonator Element

Increasing the thermal conductivity of PDMS (polydimethylsiloxane) based microfluidics is an important issue for the thermal management of hot spots produced by embedding electronic circuits in such systems. This paper presents a solution for enhancing the thermal conductivity of such PDMS based microfluidics by introducing thermally conductive alumina (Al2O3) nanoparticles, forming PDMS/Al2O3 nanocomposites. The materials are fully characterized for different concentrations of Al2O3 in PDMS for experiments which are conducted at different flow rates. Our results suggest that incorporation of Al2O3 nanoparticles at 10% w/w in the PDMS based nanocomposite significantly enhances the heat conduction from hot spots by enhancing the thermal conductivity, while maintaining the flexibility and decreasing the specific heat capacity of the developed materials. This proof-of-concept study offers potential for a practical solution for the cooling of future embedded electronic systems.

PDMS nanocomposites for heat transfer enhancement in microfluidic platforms

Wireless interrogation of circular microstrip patch antennas (CMPAs) for strain sensing is investigated by experimental measurements and computational simulations. The effect of the conductivity of the host structure on the wireless monitoring efficiency is also considered. It is shown that strain can be measured wirelessly in any desired direction using a linearly polarised horn antenna, up to a distance of 5 cm. Beyond this distance, the signal-to-noise ratio diminishes for the CMPAs employed in this study. This new contactless strain sensing technique offers significant potential for wireless structural health monitoring of civil and aerospace structures.

Wireless strain measurement using circular microstrip patch antennas

In this work, we characterize the electromagnetic properties of polydimethylsiloxane(PDMS) and use this as a free-standing substrate for the realization of flexible fishnet metamaterials at terahertz frequencies. Across the 0.2–2.5 THz band, the refractive index and absorption coefficient of PDMS are estimated as 1.55 and 0–22 cm−1, respectively. Electromagnetic modeling, multi-layer flexible electronics microfabrication, and terahertz time-domain spectroscopy are used in the design, fabrication, and characterization of the metamaterials, respectively. The properties of PDMS add a degree of freedom to terahertz metamaterials, with the potential for tuning by elastic deformation or integrated microfluidics.

Elastomeric silicone substrates for terahertz fishnet metamaterials

A new type of Frequency Selective Surface (FSS) with miniaturized resonator element is proposed. The FSS structure is shown to have a FSS unit cell dimension that is miniaturized to 0.067 $\lambda_{{{0}}}$ . Miniaturization of the FSS unit cell is achieved by coupling two meandered wire resonators separated by single thin substrate layer. The capacitance due to the small separation between the meandered wire elements results in a lowering of the resonant frequency. To demonstrate the validity of the design, the meandered wire resonator FSS was fabricated and tested using a free space measurement facility. The FSS produces a stable angular response up to 80 degrees for TE and TM incident angles.

Wayne S. T. Rowe

Papers

A Reconfigurable FSS Using a Spring Resonator Element

PDMS nanocomposites for heat transfer enhancement in microfluidic platforms

Wireless strain measurement using circular microstrip patch antennas

Elastomeric silicone substrates for terahertz fishnet metamaterials

Angularly Stable Frequency Selective Surface With Miniaturized Unit Cell