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

A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Singular Integral Equations. By N.I. Muskhelishvili. Translated fromthe 2nd Russian edition by J.R.M. Radok. Pp. 447. F1. 28.50. 1953. (Noordhoff, Groningen)

Energy harvesting generators are attractive as inexhaustible replacements for batteries in low-power wireless electronic devices and have received increasing research interest in recent years. Ambient motion is one of the main sources of energy for harvesting, and a wide range of motion-powered energy harvesters have been proposed or demonstrated, particularly at the microscale. This paper reviews the principles and state-of-art in motion-driven miniature energy harvesters and discusses trends, suitable applications, and possible future developments.

/pdf/energy-harvesting-from-human-and-machine-motion-for-wireless-3lsf4oudvo.pdf

Energy Harvesting From Human and Machine Motion for Wireless Electronic Devices

Guided Lamb waves for identification of damage in composite structures: A review

A new class of vibration energy harvester based on magnetostrictive material (MsM), Metglas 2605SC, is designed, developed and tested. It contains two submodules: an MsM harvesting device and an energy harvesting circuit. Compared to piezoelectric materials, the Metglas 2605SC offers advantages including higher energy conversion efficiency, longer life cycles, lack of depolarization and higher flexibility to survive in strong ambient vibrations. To enhance the energy conversion efficiency and alleviate the need of a bias magnetic field, Metglas ribbons are transversely annealed by a strong magnetic field along their width direction. To analyze the MsM harvesting device a generalized electromechanical circuit model is derived from Hamilton’s principle in conjunction with the normal mode superposition method based on Euler‐Bernoulli beam theory. The MsM harvesting device is equivalent to an electromechanical gyrator in series with an inductor. In addition, the proposed model can be readily extended to a more practical case of a cantilever beam element with a tip mass. The energy harvesting circuit, which interfaces with a wireless sensor and accumulates the harvested energy into an ultracapacitor, is designed on a printed circuit board (PCB) with plane dimension 25 mm × 35 mm. It mainly consists of a voltage quadrupler, a 3 F ultracapacitor and a smart regulator. The output DC voltage from the PCB can be adjusted within 2.0‐5.5 V. In experiments, the maximum output power and power density on the resistor can reach 200 μW and 900 μ Wc m −3 , respectively, at a low frequency of 58 Hz. For a working prototype under a vibration with resonance frequency of 1.1 kHz and peak acceleration of 8.06 m s −2 (0.82 g), the average power and power density during charging the ultracapacitor can achieve 576 μ Wa nd 606 μ Wc m −3 , respectively, which compete favorably with piezoelectric vibration energy harvesters. (Some figures in this article are in colour only in the electronic version)

https://iopscience.iop.org/article/10.1088/0964-1726/17/4/045009/pdf

Vibration energy harvesting by magnetostrictive material

Group velocity and characteristic wave curves of Lamb waves in composites: Modeling and experiments

Simulation of elastic properties of single-walled carbon nanotubes

Carbon nanotube (CNT) based sensors are often fabricated by dispersing CNTs into different types of polymer. In this paper, a prototype carbon nanotube (CNT) yarn strain sensor with excellent repeatability and stability for in situ structural health monitoring was developed. The CNT yarn was spun directly from CNT arrays, and its electrical resistance increased linearly with tensile strain, making it an ideal strain sensor. It showed consistent piezoresistive behavior under repetitive straining and unloading, and good resistance stability at temperatures ranging from 77 to 373 K. The sensors can be easily embedded into composite structures with minimal invasiveness and weight penalty. We have also demonstrated their ability to monitor crack initiation and propagation.

https://iopscience.iop.org/article/10.1088/0957-4484/21/30/305502/pdf

Carbon nanotube yarn strain sensors

In this letter, a class of honeycomb acoustic metamaterial possessing lightweight and yet sound-proof properties is designed, theoretically proven, and then experimentally verified. It is here reported that the proposed metamaterial having a remarkably small mass per unit area at 1.3 kg/m2 can achieve low frequency (<500 Hz) sound transmission loss (STL) consistently greater than 45 dB. Furthermore, the sandwich panel which incorporates the honeycomb metamaterial as the core material yields a STL that is consistently greater than 50 dB at low frequencies. The proposed metamaterial is promising for constructing structures that are simultaneously strong, lightweight, and sound-proof.

Fuh-Gwo Yuan

Papers

Vibration energy harvesting by magnetostrictive material

Group velocity and characteristic wave curves of Lamb waves in composites: Modeling and experiments

Simulation of elastic properties of single-walled carbon nanotubes

Carbon nanotube yarn strain sensors

A lightweight yet sound-proof honeycomb acoustic metamaterial