BROADBAND POLARIZATION CONVERSION BASED ON SMALL-SIZE METAMATERIAL IN THE GHz BAND

We proposed a small GHz metamaterial perfect absorber, which can operate in two different functional modes depending on the orientation of unit-cell structure. Firstly, when the unit-cell structure is oriented symmetrically to the external electric-field direction, an absorption mode is achieved with a near perfect absorption peak. Secondly, by rotating the resonator structure on top layer, metamaterial is asymmetric to the external field, leading to the excitation of cross-coupling effect.

Tunable frequency bandgaps in elastic metamaterials with internal contacts

We design an elastic metamaterial with internal contacts and study the tunable frequency band structure of the metamaterial. It is well-known that the frequency band of granule structures consisting of particles changes depending on the system's compression because of the nonlinearity of the contact between particles. We adopt this efficient tunning mechanism, i.e., contact, in the design of continuum type elastic metamaterials. We first design a unit cell structure showing internal contacts under compression and fabricate it using a 3D printer. We numerically and experimentally identify that the unit cell's stiffness suddenly increases when the internal contact happens. This sudden change of the stiffness induces a change of frequency characteristics of the structure. Here, we demonstrate that internal contacts are useful for designing various frequency bandgaps and tuning them efficiently.

Kittel’s Brief Comments Endorsing an Alternative View on Barium Titanate

Charles Kittel has written a masterpiece book, “Introduction to Solid State Physics” (ISSP). He mentions in the chapter on ferroelectrics in detail that barium titanate is the typical displacive-type ferroelectric compound where the Ti4+ displacement develops a dipole moment, which has made a deep impression in our mind. The author’s group, however, has arrived at an alternative viewpoint on the unit cell structure of barium titanate based on their exhaustive experimental studies. Accordingly, the author sent his relevant papers in 2006 and 2007 to Kittel. He endorsed the results frankly with reminiscence. He mentioned revising the ferroelectric chapter of ISSP according the author’s suggestions. It appears to be admissible to publish details now after Kittel has passed away. A long time misunderstanding of the phase transition in barium titanate is due to the text book knowledge of ISSP.

Development of Interdigitated-Type Planar Capacitive Flex-Sensor Array for the Detection of Damages in Civil Engineering Structures

A modified Interdigitated Planar Electrode (IDE) design is presented and used in the development of flex-sensor for Structural Health Monitoring (SHM). The design of IDE consists of a U-shaped electrode with integrated interdigitated electrodes. The overall size of the unit-cell structure is 25 × 25 mm2. Different civil engineering blocks were tested using the proposed sensor and a comprehensive crack analysis is presented based on the crack parameters. The sensor offers a lowest average sensitivity of 0.863157 pF/mm. The proposed flex-sensor can also be potentially used for the detection and monitoring of other structural parameters like corrosion, moisture content etc.

Single layer miniaturized ultra-thin FSS with five closely spaced bands

This Paper reveals a novel single layer five band frequency selective surface (FSS). Novelties of the proposed FSS lie in its five closely spaced stop bands at 2.4, 3.38, 4.82, 6.32, and 7.75 GHz as well as the reduced single layer structural thickness (0.0016 λ0) and the miniaturized unit cell size (0.0656 λ0) at lower resonant frequency as compared to the existing multiband FSS. The unit cell structure consists of six octagonal concentric interconnected loops. Adjacent loop interconnection technique reduces the cell size by more than 44%. Furthermore, arrow-shaped rings are also introduced on each corner of the outermost octagonal loop, and using this technique approximate 23% cell miniaturization can be achieved. In addition, the proposed FSS exhibits excellent angular stability.

Orthorhombic SnO2 phase observed composite (Sn1−xCex)O2 synthesized by sol–gel route

Schematic representation of unit cell structure of the phases: (a) tetragonal SnO2; (b) orthorhombic SnO2. Tin atoms (Sn) are represented in gray and oxygen atoms (O) in red. K. Momma and F. Izumi, J. Appl. Crystallogr., 2011, 44, 1272–1276.