The novel optical path routing architecture named flexible waveband routing networks is reviewed in this paper. The nodes adopt a two-stage path routing scheme where wavelength selective switches (WSSs) bundle optical paths and form a small number of path groups and then optical switches without wavelength selectivity route these groups to desired outputs. Substantial hardware scale reduction can be achieved as the scheme enables us to use small scale WSSs, and even more, share a WSS by multiple input cores/fibers through the use of spatially-joint-switching. Furthermore, path groups distributed over multiple bands can be switched by these optical switches and thus the adaptation to multi-band transmission is straightforward. Network-wide numerical simulations and transmission experiments that assume multi-band transmission demonstrate the validity of flexible waveband routing.

To facilitate the reuse of environmental waste heat in our society, we have developed high-efficiency flexible thermoelectric power generators (TEPGs). In this study, we investigated the thermoelectromotive force (TEMF) and output power of a prototype device with 50 pairs of Π-type structures using a homemade measurement system for flexible TEPGs in order to evaluate their characteristics along the thickness direction. The prototype device consisted of C fabrics (CAFs) used as p-type materials, NiCu fabrics (NCFs) used as n-type materials, and Ag fabrics (AGFs) used as metal electrodes. Applying a temperature difference of 5K, we obtained a TEMF of 150μV and maximum output power of 6.4pW. The obtained TEMF was smaller than that expected from the Seebeck coefficients of each fabric, which is considered to be mainly because of the influence of contact thermal resistance at the semiconductor-fabric/AGF interfaces.

In this paper, an experimental method is proposed for extracting the primary and secondary parameters of transmission lines with frequency dispersion. So far, there is no report of these methods being applied to transmission lines with frequency dispersion. This paper provides an experimental evaluation means of transmission lines with frequency dispersion and clarifies the issues when applying the proposed method. In the proposed experimental method, unnecessary components such as connectors are removed by using a simple de-embedding method. The frequency response of the primary and secondary parameters extracted by using the method reproduced all dispersion characteristics of a transmission line with frequency dispersion successfully. It is demonstrated that an accurate RLGC equivalent-circuit model is obtained experimentally, which can be used to quantitatively evaluate the frequency/time responses of shielded-FPC with frequency dispersion and to validate RLGC equivalent-circuit models extracted by using electromagnetic field analysis.

In 2017, Tang et al. provided a complete characterization of generalized bent functions from ℤ2n to ℤq(q = 2m) in terms of their component functions (IEEE Trans. Inf. Theory. vol.63, no.7, pp.4668-4674). In this letter, for a general even q, we aim to provide some characterizations and more constructions of generalized bent functions with flexible coefficients. Firstly, we present some sufficient conditions for a generalized Boolean function with at most three terms to be gbent. Based on these results, we give a positive answer to a remaining question proposed by Hodžić in 2015. We also prove that the sufficient conditions are also necessary in some special cases. However, these sufficient conditions whether they are also necessary, in general, is left as an open problem. Secondly, from a uniform point of view, we provide a secondary construction of gbent function, which includes several known constructions as special cases.

We propose an efficient network upgrade and expansion method that can make the most of the next generation channel resources to accommodate further increases in traffic. Semi-flexible grid configuration and two cost metrics are introduced to establish a regularity in frequency assignment and minimize disturbance in the upgrade process; both reduce the fragmentation in frequency assignment and the number of fibers necessary. Various investigations of different configurations elucidate that the number of fibers necessary is reduced about 10-15% for any combination of upgrade scenario, channel frequency bandwidth, and topology adopted.

The application of network function virtualization (NFV) and software-defined networking (SDN) to passive optical networks (PONs) is attracting attention for the deployment of cost-effective access network systems. This paper presents a novel architecture of a programmable finite state machine (P-FSM) as a hardware accelerator for protocol processing in an optical line terminal (OLT). The P-FSM is programmable hardware that manages various types of FSMs to enhance flexibility in OLTs and achieve wired-rate performance with a negligible increase in total chip area. The P-FSM is implemented using three key technologies: a specific architecture for state management of communications protocols to minimize the logic area, a memory distributed implementation to minimize the program memory, and a new branch operation to minimize the memory area and reduce processing time. Evaluation results show that the P-FSM can handle 10G-EPON/NG-PON2 communications protocols in the same architecture while achieving wired-rate performance. The increase in the total designed area is only 1.5% to 4.9% depending on the number of protocols supported compared to the area of a conventional communications SoC without flexibility. We also clarify that our architecture has the scalability needed to modify the number of FSMs and the maximum number of ONU connections according to the system scale.

In recent years, flexible liquid crystal displays (LCDs) have attracted much attention due to their thin and lightweight designs, as well as their ease of installation compared with conventional flat-panel LCDs. Most LCDs require backlight units (BLUs) to yield high-quality images. However, the luminance uniformity of flexible BLUs is drastically reduced in the curved state, as the light emitted from a typical BLU is mainly directed in the normal direction. Conventional BLUs do not provide the image quality of flexible BLUs due to uneven luminance distribution from the perspective of the observer. To overcome these issues, here we introduce a novel oblique-angled notched film for improved light distribution of a conventional BLU. The notched structure of the proposed film exhibits V-shaped split behavior during curvature. This elastic deformation is expected to compensate for the spatial luminance of the light emitted from the BLU. We investigated the design requirements for the proposed film based on geometrical calculations. The luminance distribution of a flexible BLU was then simulated using the proposed film, based on geometrical optics theory. The simulation results confirmed that the direction of travel of the light is controllable according to the total internal reflection of the proposed film, thus improving the luminance uniformity of the BLU in a convex-curved state. Based on these results, the proposed approach is expected to improve the luminance uniformity of convex-curved flexible LCDs.

Real-time monitoring of heart rate (HR) and body temperature (BT) is crucial for the prognosis and the diagnosis of cardiovascular disease and healthcare. Since current monitoring systems are too rigid and bulky, it is not easy to attach them to the human body. Also, their large current consumption limits the working time. In this paper, we develop a wireless sensor patch for HR and BT by integrating sensor chip, wireless communication chip, and electrodes on the flexible boards that is covered with non-toxic, but skin-friendly adhesive patch. Our experimental results reveal that the flexible wireless sensor patch can efficiently detect early diseases by monitoring the HR and BT in real time.

We have developed the flexible dual-gate OFET based pressure sensor using a thin polyethylene naphthalate (PEN, 25 µm) film as a substrate. The performance was equivalent to that fabricated on the glass substrate, and it could also be used on the curved surface. Drain current in the flexible pressure sensor was increased according to the pressure load without application of gate voltage. The magnitude of the change in drain current with respect to pressure application was about 2.5 times larger than that for the device on the glass substrate.

In this paper, dependency of transmission loss of shielded-flexible printed circuits (FPC) for differential-signaling on thickness of conductive shield is studied by numerical modeling based on an equivalent circuit model compared with the experimental results. Especially, the transmission loss due to the thin conductive shield is focused. The insufficient shielding performance for near magnetic field decreases the resistance due to the thin conductive shield. It is shown that the resistance due to the thin conductive shield at lower frequencies is smaller than that in the “thick conductive shield” case.

We have measured the Seebeck coefficient of a carbon fabric (CAF) using a homemade measurement system for flexible thermoelectric materials to evaluate Seebeck coefficient along the thickness direction. Our equipment consists of a thermocouple (TC) electrode contacted with a resistive heater and another TC electrode attached to a heat sink. A flexible sample is sandwiched with these TC electrodes and pressed by weights. The equipment is set on a weighing machine in order to confirm and hold the pressing force at the contact between the electrodes and the soft sample. Cu and Pb plates were measured as a reference material to calibrate and clarify the accuracy of our measurement system, and its validity was confirmed. The Seebeck coefficient of a single CAF layer ranged 4.3-5.1 µV/K, independent of extra weight. This fact indicates that the weight of heat sink is enough for stable contact at the TC-electrode/CAF interface. It was found that the Seebeck coefficient of layered CAF increases with an increase in the number of layers, which suggests the influence of the air between the CAF layers even though the heavy weight is used.

We developed flexible liquid crystal devices using ultra-thin polyimide substrates and bonding polymer spacers, and discussed the effects of polymer spacer structure on the cell thickness uniformity of flexible LCDs. We clarified that the lattice-shaped polymer spacer is effective to stabilize the cell thickness by suppressing the flow of the liquid crystal during bending process.

Novel roll-to-roll (R2R) deposition and patterning of ITO on ultra-thin glass were developed with no photolithography and applied to flexible organic light emitting diodes (OLEDs). The developed deposition consists of low temperature sputtering and annealing. The developed patterning utilizes an etching paste printed by novel R2R screen printing.

We investigated the effects of a bending stress on the change in phase retardation of curved polycarbonate substrates and optical characteristics of flexible liquid crystal displays (LCDs). We clarified that the change in phase retardation was extremely small even for the substrates with a small radius of curvature, because bending stresses occurred in the inner and upper surfaces are canceled each other out. We compensated for the phase retardation of polycarbonate substrates by a positive C-plate and successfully suppressed light leakage in both non-curved and curved states. These results indicate the feasibility of high-quality flexible LCDs using polycarbonate substrates even in curved states.

We numerically investigate a PDM-QPSK multi-rate coherent burst-mode optical receiver capable of receiving 3 different line-rates, suitable for next generation optical networks such as hybrid optical circuit switching (OCS)/optical packet switching (OPS) networks, access networks and datacenter networks. The line-rate detection algorithm relies on a simple-to-generate optical header, it is based on the fast Fourier transform (FFT) which can be efficiently implemented with the Goertzel algorithm, and it is insensitive to polarization rotations and frequency offset. Numerically, we demonstrate that performance in terms of packet detection rate (PER) can be tailored by controlling the sizes of the packet header and the line-rate estimator.

In order to tackle rapidly increasing traffic, dramatic performance enhancements in radio access technologies (RATs) are required for fifth-generation (5G) mobile communication system. In 5G, small/semi-macro cells using Massive MIMO (M-MIMO) with much wider bandwidth in higher frequency bands are overlaid on macro cell with existing frequency band. Moreover, high density deployment of small/semi-macro cell is expected to improve areal capacity. However, in low SHF band (below 6GHz), antenna array size of M-MIMO is large so that it cannot be installed on some environments. Therefore, to improve system throughput on various use cases in 5G, we have proposed distributed Massive MIMO (DM-MIMO). DM-MIMO coordinates lots of distributed transmission points (TPs) that are located in ultra-high density (UHD). Furthermore, DM-MIMO uses various numbers of antenna elements for each TP. In addition, DM-MIMO with UHD-TPs can create user-centric virtual cells corresponding to user mobility, and design of flexible antenna deployment for DM-MIMO is applicable to various use cases. Then, some key parameters such as the number of the distributed TPs, the number of antenna elements for each TP, and proper distance between TPs, should be determined. This paper presents such parameters for 5G DM-MIMO with flexible antenna deployment under fixed total transmission power and constant total number of antenna elements. Computer simulations show that DM-MIMO can achieve more than 1.9 times higher system throughput than an M-MIMO system using 128 antenna elements.

A Uniform Lying Helix (ULH) liquid crystal device (LCD) fabricated by utilizing the characteristics of shear flow alignment as well as dielectric anisotropy was demonstrated. Cholesteric liquid crystals with a short helical pitch can exhibit an electric field-induced tilt. These experimental results indicate that it is possible to realize a high-speed response flexible LCD using plastic substrates.

We developed flexible LC devices using coat-debond polyimide substrates with a low birefringence and etched post spacers, and clarified that flexible LCDs using post spacers with small spacer distance have a high flexibility without degradation of the image quality. This result ensured the feasibility of flexible LCDs using coat-debond method.

This paper presents a non-crossover and multi-mutation based genetic algorithm (NMGA) for the Flexible Job-shop Scheduling problem (FJSP) with the criterion to minimize the maximum completion time (makespan). Aiming at the characteristics of FJSP, three mutation operators based on operation sequence coding and machine assignment coding are proposed: flip, slide, and swap. Meanwhile, the NMGA framework, coding scheme, as well as the decoding algorithm are also specially designed for the FJSP. In the framework, recombination operator crossover is not included and a special selection strategy is employed. Computational results based on a set of representative benchmark problems were provided. The evidence indicates that the proposed algorithm is superior to several recently published genetic algorithms in terms of solution quality and convergence ability.

An encountered-type haptic interface generates touch sensation only when a user's hand “encounters” virtual objects. This paper presents an effective encountered-type haptic interface that enables rendering of surfaces with variable curvature. The key idea is to systematically bend a thin elastic plate so as to create a curved surface with desired curvature, which becomes a contacting end effector that follows the user's finger and becomes an interface a user can touch when needed. The pose of the curvature is controlled in a way that it corresponds to the curved surfaces of virtual objects and user's finger position. The idea is realized by attaching two commercial haptic interfaces to both edges of a thin acryl plate and squeezing the plate. This setup allows us to generate a cylindrical object with curvature up to 0.035 mm-1 and gives 3DOF position control and 1DOF rotational control of the curved surface. Achievable workspace and curvature range are analyzed, and the feasibility and physical performance are demonstrated through a visuo-haptic grabbing scenario. In addition, a psychophysical experiment shows perceptual competence of the proposed system.