Mimicking natural superhydrophobic surfaces and grasping the wetting process: A review on recent progress in preparing superhydrophobic surfaces

https://ecor.mgh.harvard.edu/content/files/SAC/TalkowskiMartin2013.pdf

Sequencing Chromosomal Abnormalities Reveals Neurodevelopmental Loci that Confer Risk across Diagnostic Boundaries

This chapter contains sections titled: Introduction Overview of Multicarrier CDMA Systems Channel Model Performance of MC-CDMA System Performance of Overlapping Multicarrier DS-CDMA Systems Performance of Multicarrier DS-CDMA-I Systems Performance of AMC DS-CDMA Systems Performance of SFH/MC DS-CDMA Systems Chapter Summary and Conclusion 
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Overview of Multicarrier CDMA

During the past few years, metasurfaces have been used to demonstrate optical elements and systems with capabilities that surpass those of conventional diffractive optics. Here, we review some of these recent developments, with a focus on dielectric structures for shaping optical wavefronts. We discuss the mechanisms for achieving steep phase gradients with high efficiency, simultaneous polarization and phase control, controlling the chromatic dispersion, and controlling the angular response. Then, we review applications in imaging, conformal optics, tunable devices, and optical systems. We conclude with an outlook on future potentials and challenges that need to be overcome.

https://www.degruyter.com/document/doi/10.1515/nanoph-2017-0129/pdf

A review of dielectric optical metasurfaces for wavefront control

This review gives an overview of techniques used for high-resolution jet printing that rely on electrohydrodynamically induced flows. Such methods enable the direct, additive patterning of materials with a resolution that can extend below 100 nm to provide unique opportunities not only in scientific studies but also in a range of applications that includes printed electronics, tissue engineering, and photonic and plasmonic devices. Following a brief historical perspective, this review presents descriptions of the underlying processes involved in the formation of liquid cones and jets to establish critical factors in the printing process. Different printing systems that share similar principles are then described, along with key advances that have been made in the last decade. Capabilities in terms of printable materials and levels of resolution are reviewed, with a strong emphasis on areas of potential application.

Mechanisms, Capabilities, and Applications of High-Resolution Electrohydrodynamic Jet Printing.

The theoretical limit for small antenna performance that was derived decades ago by Wheeler and Chu governs design tradeoffs for size, bandwidth, and efficiency. Theoretical guidelines have also been derived for other details of small antenna design such as permittivity, aspect ratio, and even the nature of the internal structure of the antenna. In this paper, we extract and analyze experimental performance data from a large body of published designs to establish several facts that have not previously been demonstrated: (1) The theoretical performance limit for size, bandwidth, and efficiency are validated by all available experimental evidence. (2) Although derived for electrically small antennas, the same theoretical limit is also generally a good design rule for antennas that are not electrically small. (3) The theoretical predictions for the performance due to design factors such as permittivity, aspect ratio, and the internal structure of the antenna are also supported by the experimental evidence. The designs that have the highest performance are those that involve the lowest permittivity, have an aspect ratio close to unity, and for which the fields fill the minimum size enclosing sphere with the greatest uniformity. This work thus validates the established theoretical design guidelines.

Experimental Validation of Performance Limits and Design Guidelines for Small Antennas

We present the first use of a waveform-dependent absorbing metasurface for high-power pulsed surface currents. The new type of nonlinear metasurface, composed of circuit elements including diodes, is capable of storing high-power pulse energy to dissipate it between pulses, while allowing propagation of small signals. Interestingly, the absorbing performance varies for high-power pulses but not for high-power continuous waves (CW's), since the capacitors used are fully charged up. Thus, the waveform dependence enables us to distinguish various signal types (i.e., CW or pulse) even at the same frequency, which potentially creates new kinds of microwave technologies and applications.

/pdf/waveform-dependent-absorbing-metasurfaces-38lvkij6h8.pdf

Waveform-dependent absorbing metasurfaces.

High-power signals traveling along the surface of the shielding of transmitter systems may leak into the system through openings between connecting parts and cause damage to vulnerable electronic devices. This problem could be alleviated by implementing lossy coatings or recently developed passive power-dependent nonlinear surfaces. However, these solutions will either suppress the performance of the electromagnetic devices being shielded or be highly power-dependent. Applying transistors creates an active nonlinear metasurface that can allow the absorption of the surface to be directly controlled by the system, or tuned in response to the local power level using feedback control. This can provide a sharp absorption response with a wide range of controllable power threshold. Different absorption rates at the same power level can also be achieved by applying different biasing to the transistors. In this paper, the first transistor-based, thin, switchable, and tunable high-power surface wave absorber is proposed with full wave and circuit cosimulation analysis as well as waveguide and anechoic chamber measurement.

/pdf/high-power-transistor-based-tunable-and-switchable-3ltrkm7sz5.pdf

High-Power Transistor-Based Tunable and Switchable Metasurface Absorber

We present the first use of a waveform-dependent absorbing metasurface for high-power pulsed surface currents. The new type of nonlinear metasurface, composed of circuit elements including diodes, is capable of storing high power pulse energy to dissipate it between pulses, while allowing propagation of small signals. Interestingly, the absorbing performance varies for high power pulses but not for high power continuous waves (CWs), since the capacitors used are fully charged up. Thus, the waveform dependence enables us to distinguish various signal types (i.e. CW or pulse) even at the same frequency, which potentially creates new kinds of microwave technologies and applications.

Waveform-dependent absorbing metasurfaces

We demonstrate a concept of circuit-based nonlinear metasurface absorbers that absorb high power surface currents but not small signals. The nonlinear absorbing behavior is achieved through the use of diodes integrated into the metasurface. The diodes rectify high power signals to produce a static field, whose energy is stored in capacitors and then dissipated with resistors. We present electromagnetic simulations of these structures and validate the results with the first measurements of nonlinear metasurface absorbers. The metasurfaces can potentially contribute to solving a wide range of microwave interference issues due to their power dependent electromagnetic response.

Sanghoon Kim

Papers

Experimental Validation of Performance Limits and Design Guidelines for Small Antennas

Waveform-dependent absorbing metasurfaces.

High-Power Transistor-Based Tunable and Switchable Metasurface Absorber

Waveform-dependent absorbing metasurfaces

Circuit-based nonlinear metasurface absorbers for high power surface currents