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Recent progress in engineering approaches for stretchable electronics and electronic components, including strategies focused on materials science or structural engineering, offer high signal-to-noise detection of vital signs via systems that provide conformal, noninvasive contact to curvilinear skin and are unobtrusive during human activity, such as general motion, exercise, and respiration. Structural engineering strategies with flexible thin films, whose deformation can be categorized as two-dimensional (2D) in-plane or three-dimensional (3D) out-of-plane, provide a release of stress created by stretching, bending, or twisting. Beyond 2D in-plane structural engineering techniques, 3D out-of-plane structural engineering techniques effectively distribute nonlinear and multidirectional 3D strain. Here, we review recent advances in 3D out-of-plane engineering techniques, including wavy and wrinkled structures, pop-up structures, kirigami and origami structures, and nature-inspired structures, and describe the strain distribution mechanisms, fabrication processes, applications, and characteristics of these approaches. We conclude with perspectives on applications of stretchable electronic devices with multidirectional stretchability and the existing challenges for future research.

The thermal stability and quench propagations are one of the most fundamental issues for the High Temperature Superconducting (HTS) coil. Superconductivity is confined within the phase surface bounded by magnetic field, temperature, and current. Of these three parameters, the temperature is neither completely controllable, nor predictable, because the energy stored in the magnet, can easily be converted into heat up setting the thermal equilibrium within the winding. Therefore, in HTS coil operation, the temperature stability or more generally the thermal behavior of the conductor is the most important. In this paper, a HTS double racetrack pancake coil was prepared to examine the thermal stability, quench propagation and minimum quench energy (MQE). HTS coil was wound using the AMSC Bi-2223. The experimental results are discussed in this paper.

A 1 MW class superconducting synchronous rotating machine has been designed as a draft based on 2-dimensional (2D) magnetic field distribution considering several conditions such as superconducting wire length, machine efficiency, size and so on. By the way from 2D design it is not possible to consider the effect of end coils and end portions of stator iron yoke especially in superconducting machine with air-cored structure which increases magnetic field difference between 2D and 3D analysis. In this paper electrical design based on the 3D magnetic field distribution is conducted to get more proper design result and reduce design errors from 2D design approach. As the machine has larger capacity, the superconducting machine will show the advantages more and more over the conventional machine. Although the advantages at 1MW rating are not so great, the 3D design approach to get more optimized result would be very helpful for larger superconducting synchronous machine design. Through 3D analysis such as EMCN (equivalent magnetic circuit network) method and Flux-3D FEM (finite element method), we could get smaller machine size, higher efficiency, and smaller Bi-2223 HTS (high temperature superconducting) wire length than the 2D design result. Moreover influence of an important parameter, synchronous reactance, has been analysed on the machine performances such as voltage variation and output power.

In large scale applications, such as SMES, motors and generators, High Temperature Superconducting (HTS) magnets are constructed with many stacks of the double-pancake coils connected in series. In spite of its higher thermal stability, HTS magnet can experience a severe quench, which can resulted from a very small portion. From HTS magnet design point of view, it is very important to predict the possibility of occurrence quench in the designed magnet to provide a suitable quench protection device. In this paper a highly instrumented HTS race track double-pancake coil was prepared to examine the quench development characteristics. It is wound using the Bi-2223 tape. Many voltage taps, cryogenic thermocouples and heater were installed in the winding. Conduction cooling method is adapted for the convenience of temperature. Quench development in the coil was measured under different operating current. The experimental details and results are presented in this paper.

The electroplating of the gate electrode on a flexible polyimide (PI) substrate was successfully applied to the fabrication of inverted-staggered poly(3-hexylthiophene) (P3HT) organic thin film transistors (OTFTs). The Ni gate electrode was electroplated through patterned negative photo-resist (KMPR) masks onto Cu (seed)/Cr (adhesion) layers that had been sputter-deposited on O 2 -plasma-treated PI substrates. The electrical measurements of the fabricated OTFTs with the SiO 2 gate insulator indicated non-ideal output characteristics, which are similar to the model of electrical transport by a space-charge limited current (SCLC). The use of a poly(4-vinyl phenol) (PVP) and SiO 2 /PVP bilayer gate dielectric produced output characteristics that were closer to the ideal TFT behavior but led to a lower effective mobility and on / off current ( I on / I off ).

The electroplating of source–drain (S/D) electrodes on a flexible polyimide (PI) substrate was applied to the fabrication of staggered poly(3-hexylthiophene) (P3HT) organic thin film transistors (OTFTs). Au or Au/Ni bilayer S/D electrodes were additively electroplated into patterned SU-8 photoresist masks on Cu(seed)/Cr(adhesion) layers sputter-deposited on O 2 -plasma-treated PI substrates. The electrical measurements of the fabricated OTFTs showed that their non-ideal output characteristics were similar to those predicted by the model of electrical transport by the space-charge limited current (SCLC), regardless of the surface preparations used for the Au S/D electrodes.

This paper deals with the fuzzy modeling for the complex and uncertain nonlinear systems, in which conventional and mathematical models may fail to give satisfactory results. Finally, we provide numerical examples to evaluate the feasibility and generality of the proposed method in this paper. The expert system which introduces fuzzy logic in order to process uncertainties is called fuzzy expert system. The fuzzy expert system, however, has a potential problem which may lead to inappropriate results due to the ignorance of some information by applying fuzzy logic in reasoning process in addition to the knowledge acquisition problem. In order to overcome these problems, We construct fuzzy inference network by extending the concept of reasoning network in this paper. In the fuzzy inference network, the propositions which form fuzzy rules are represented by nodes. And these nodes have the truth values representing the belief values of each proposition. The logical operators between propositions of rules are represented by links. And the traditional propagation rule is modified.

An effective modeling and simulation schemes of a resistive type Superconducting Fault Current Limiter (SFCL) and DC reactor type SFCL using PSCADIEMTDC are proposed in this paper. In case of resistive type SFCL, current limiting is implemented by the ultra-fast transition characteristics from the superconducting (non-resistive) state to the normal (resistive) state by overstepping the critical current density. The states can generally be divided into three sub-states: the superconducting state, the quench state and the recovery state, respectively. In case of DC reactor type SFCL, it is composed of a superconducting coil and a diode bridge through which AC line current is rectified, and the increase in fault current is limited by the inductance of a superconducting coil. An actual experiment based component model of the real resistive type SFCL is developed and applied for the simulation. The proposed modeling and simulation schemes can be implemented to the grid system readily under various system conditions including sort of faults and the system capacity as well. The simulation results demonstrate the effectiveness of the proposed model and simulation schemes.

Using a general-purpose multivariate optimization program that we have developed for the design of the fiber-index profile for a given set of several fiber optimization parameters, we have designed and fabricated nonzero-dispersion fibers with a maximally flat chromatic dispersion spectrum, which have shown improved dispersion-spectrum curves compared to those of commercially available fibers developed for the same purpose.

In multi-agent systems, the common goals of each agent are established and the problems are solved through cooperation and control among agents. Because each agent performs parallel processes in a multi-agent system, this approach can be easily applied to problems requiring parallel processing. The parallel processing prevents system performance degradation due to local error operation in the system. It also can reduce the solution time when the problem is divided into several sub-problems. In this case, each agent is designed independently providing a relatively simple programming model for solution of the problem. Further, the system can be easily expanded by adding new function agents. In the study of multi-agent systems, the main research topic is the coordination and cooperation among agents.

The feedback control method proposed in this paper predicts the queue length in the switch using the slope of queue length prediction function and queue length changes in time-series. The predicted congestion information is backward to the node. NLMS and neural network are used as the predictive control functions, and they are compared from performance on the queue length prediction. Simulation results show the efficiency of the proposed method compared to the feedback control method without the prediction. Therefore, we conclude that the efficient congestion and stability of the queue length controls are possible using the prediction scheme that can resolve the problems caused from the longer delays of the feedback information.

Novel concept of a photovoltaics (PV) power generation system adding the function of active filter (AF) is proposed in this paper. So far, because the PV power generation system can be treated to a harmonics source for the power distribution systems, the PV system combined the function of AF systems as well as the AF systems using the PV module as the power source have never been reported. Here, the control strategy of PV-AF system is for the first time introduced. Also, in order to stabilize the output current of VSI, the reference voltage MPPT control is applied. Using simulation analysis, it is confirmed that it is possible to combine AF theory to the three phase PV system connected up to utility, and results gave us that it was theoretically positive to actualize the PV-AF system.

All-optical harmonic frequency upconversion into the microwave frequency band for a WDM-based radio over fibre application is experimentally demonstrated by using a cross-phase modulation effect in a semiconductor optical amplifier. Maximum frequency conversion efficiencies from 2.5 GHz (f IF ) to 12.5 GHz (f LO ± f IF ) and 22.5 GHz (2f LO ± f IF ) are 13.2 dB and 3.1 dB, respectively. The conversion efficiency to 2f LO ± f IF is larger than unity for the IF signal wavelength range between 1547.22 and 1556 nm. The phase noise of the upconverted signal at 22.5 GHz is -80.0 dBc/Hz with 1 kHz offset frequency, which is limited by that of the LO source.

A new design and fabrication method is proposed for a dispersion-managed fibre from a preform prepared by a single session of the modified-chemical-vapour-deposition (MCVD) process. Periodic etching during the MCVD process is used to change the index structure of the preform periodically alone the axial direction. The dispersion measurement of the fabricated prototype fibre shows that desired dispersion management characteristics can be achieved.

Coaxial-core erbium-doped fibre amplifiers (EDFAs) with self-regulating gain spectrum are presented. A cascade experiment demonstrates the effect of coaxial-core EDFAs on channel-power equalisation in fibre links with a small number of WDM channels.