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

Additive manufacturing of metallic components – Process, structure and properties

Freedom of design, mass customisation, waste minimisation and the ability to manufacture complex structures, as well as fast prototyping, are the main benefits of additive manufacturing (AM) or 3D printing. A comprehensive review of the main 3D printing methods, materials and their development in trending applications was carried out. In particular, the revolutionary applications of AM in biomedical, aerospace, buildings and protective structures were discussed. The current state of materials development, including metal alloys, polymer composites, ceramics and concrete, was presented. In addition, this paper discussed the main processing challenges with void formation, anisotropic behaviour, the limitation of computer design and layer-by-layer appearance. Overall, this paper gives an overview of 3D printing, including a survey on its benefits and drawbacks as a benchmark for future research and development.

Additive manufacturing (3D printing): A review of materials, methods, applications and challenges

This paper reviews the state-of-the-art of an important, rapidly emerging, manufacturing technology that is alternatively called additive manufacturing (AM), direct digital manufacturing, free form fabrication, or 3D printing, etc. A broad contextual overview of metallic AM is provided. AM has the potential to revolutionize the global parts manufacturing and logistics landscape. It enables distributed manufacturing and the productions of parts-on-demand while offering the potential to reduce cost, energy consumption, and carbon footprint. This paper explores the material science, processes, and business consideration associated with achieving these performance gains. It is concluded that a paradigm shift is required in order to fully exploit AM potential.

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Metal Additive Manufacturing: A Review

Natural structural materials are built at ambient temperature from a fairly limited selection of components. They usually comprise hard and soft phases arranged in complex hierarchical architectures, with characteristic dimensions spanning from the nanoscale to the macroscale. The resulting materials are lightweight and often display unique combinations of strength and toughness, but have proven difficult to mimic synthetically. Here, we review the common design motifs of a range of natural structural materials, and discuss the difficulties associated with the design and fabrication of synthetic structures that mimic the structural and mechanical characteristics of their natural counterparts.

Bioinspired structural materials

The aim of this paper is to propose a new simple design of a ultra-wide bandpass filter (3.1 to 10.6 GHz) based on the cascading of a low pass and a high pass section. They are separately designed using convenient structures leading to compactness and easy fabrication. A stepped impedance structure providing elliptic response has been used for the low pass filter. The high pass section is implemented using a quasi-lumped LC network consisting of three capacitors and an inductor. Planar circuit implementation is feasible thanks to the simultaneous use of microstrip and coplanar waveguide technologies. The high pass section has been optimized for size reduction and additional transmission zero. Good rejection at low and high frequencies and good band pass impedance matching is achieved. The filter is a useful alternative to other recently proposed structures. Experimental validation is provided.

http://ieeexplore.ieee.org/iel5/5286913/5295900/05296276.pdf

Design of ultra-wide bandpass filter using hybrid microstrip/CPW structure

Summary form only given, as follows. This paper presents an equivalent transmission-line circuit that accounts for the scattering of a TE polarized plane wave that impinges obliquely on a periodic array of metallic patches sandwiched in a dielectric slab. The proposed approach gives a very efficient reduced-order model of the electromagnetic phenomenon and able to reproduce all the fine quantitative details of the reflection/transmission spectrum. Also, our model provides a simple theoretical framework to predict and/or understand all the qualitative behavior of the scattering when both oblique incidence and dielectric slabs are considered.

Equivalent circuits for conventional and extraordinary reflection in dipole arrays

The myelinated axon can be modeled by means of a distributed RGC circuit. The Green function of this model allows for a generic formulation of the internodal segment response to any kind of stimulus, and accounts for the delay of the action potential associated with this segment. The RGC model accuracy is comparable to that of a more complex electromagnetic model, and predicted delay agrees with experimental measurements.

Internodal myelinated segments: delay and RGC time-domain Green function model

In this paper, we present a method for calculating the propagation parameters of shielded broadside- end broadside edge-coupled microstrip transmission lines. Conductor strips are assumed to be embedded in a multilayered isotropic and/or anisotropic medium. This method provides accurate expressions for computing upper and lower bounds for the true values of mode capacitances, The effects of side wall-shielding and anisotropy of the material are investigated. Some particular multilayered structures are analyzed, which could be applied to the design of directional couplers and filters.

Accurate Approach for Computing Quasi-Static Parameters Off Symmetrical Broadside-Coupled Mlcrostrips in Multilayered Anisotropic Dielectrics

The phenomenon of extraordinary optical trans- mission (EOT) through electrically small holes perforated on opaque metal screens has been a hot topic in the optics com- munity for more than one decade. This experimentally ob- served frequency-selective enhanced transmission of electro- magnetic power through holes, for which classical Bethe's theory predicts very poor transmission, later attracted the attention of engineers working on microwave engineering or applied electromagnetics. Extraordinary transmission was first linked to the plasma-like behavior of metals at opti- cal frequencies. However, the primary role played by the periodicity of the distribution of holes was soon made ev- ident, in such a way that extraordinary transmission was disconnected from the particular behavior of metals at op- tical frequencies. Indeed, the same phenomenon has been observed in the microwave and millimeter wave regime, for instance. Nowadays, the most commonly accepted theory explains EOT in terms of the interaction of the impinging plane wave with the surface plasmon-polariton-Bloch waves (SPP-Bloch) supported by the periodically perforated plate. The authors of this paper have recently proposed an alter- native model whose details will be briefly summarized here. A parametric study of the predictions of the model and some new potential extensions will be reported to provide addi- tional insight.

Francisco Medina

Papers

Design of ultra-wide bandpass filter using hybrid microstrip/CPW structure

Equivalent circuits for conventional and extraordinary reflection in dipole arrays

Internodal myelinated segments: delay and RGC time-domain Green function model

Accurate Approach for Computing Quasi-Static Parameters Off Symmetrical Broadside-Coupled Mlcrostrips in Multilayered Anisotropic Dielectrics

Some Advances in the Circuit Modeling of Extraordinary Optical Transmission