Electronics and Communications in Japan最新文献

This paper proposes a three-phase wireless power transfer (WPT) system with a three-phase-to-three-phase matrix converter. The proposed system directly converts power from an AC grid to high-frequency AC for WPT. The three-phase WPT system with the matrix converter is effectively expands the lifetime of the WPT system. A novel hybrid commutation method, which is suitable for the WPT system with a resonant characteristic, is proposed to avoid the commutation failure of the matrix converter. The strategy of the proposed hybrid commutation is based on an estimation of the current direction considering the resonant characteristics and elimination of commutation in the critical area. The proposed commutation method achieves an AC input-current total harmonic distortion (THD) of 4.7% with the resonant three-phase load without a current sensor on the high-frequency side. Furthermore, the proposed WPT system achieves a system efficiency of 88.2% at a load of 4 kW.

Epitaxial thin films of a ferroelectric perovskite-type oxide grown on single-crystalline SrTiO₃ (100) were transferred onto a flexible printed circuit (FPC). In the case that the thin films were directly adhered onto FPC using a copper foil double-coated conductive adhesive tape (Cu double-sided tape), serious cracking and exfoliation occurred during the transfer process. To avoid these damages, we have tried to insert a metal buffer layer with excellent ductility between the ferroelectric oxide thin film and the Cu double-sided tape. The platinum buffer layer was found to be appropriate to establish a crack- and exfoliation-free transfer process.

Information on fabric material is necessary in washing and ironing clothing. However, indication on a care tag may peel off or the tag may come off due to deterioration over time. Discrimination of the material from the fabric itself is not easy for a general person. Estimating the material of an object is one of the challenging tasks in computer vision. This paper deals with the identification of cloth materials using computer vision. We studied a method to discriminate the fabric material from the image of clothing taken by a smartphone camera. First, we investigated the relationship between image resolution and discrimination accuracy using a convolutional neural network (CNN). As a result, we observed that the accuracy changes with resolution and that the resolution at which the accuracy is highest differs depending on the material. Based on these results, we proposed a fabric material discrimination method using multi-resolution images by combining two CNNs. As a result of the evaluation experiment, the proposed method discriminated six kinds of fabric materials with 87.1% accuracy, and the accuracy was significantly higher than that of the comparison method without using multi-resolution images.

This paper reports a microfluidic device that allows us to measure the effect of local differentiation stimulation on embryoid bodies for the purpose of elucidating the role of the cell-cell interaction of iPS cells in differentiation induction. We developed the local stimulation device having two chambers separated by thin polydimethyl siloxane (PDMS) membrane with through-holes of the diameter smaller than single cell. Embryoid bodies of iPS cells are formed on the membrane and seal the holes, separating the aqueous environments of two chambers without leakage. This configuration brings localized exposure to chemicals for differentiation induction at the area defined by the holes. In this paper, we demonstrated the function of local stimulation using fluorescent solution.

In this paper, we have analyzed quantum confinement effects in nanosheet MOSFETs by using a quantum drift-diffusion (QDD) model. The QDD model is a device simulator which allows to simulate quantum confinement effects in the inversion layer for advanced MOSFETs. The quantum confinement effects in nanosheets have been analyzed by comparing the simulation results by QDD and drift-diffusion (DD) model. The drain current ratio of DD to QDD is 250.1% at VG = 0.5 V and 180.1% at VG = 0 V. While the maximum electron density of DD exists at the interface between the insulator and the silicon sheet, that of QDD goes to near the center of the silicon sheet. The electron areal density ratio of DD to QDD is 118.3% in the direction of the 10 nm width of the silicon sheet and 176.9% in the direction of the 4 nm width.

The interaction between diamond surfaces and alkali metals was studied experimentally and computationally. Li reacted with diamond above 600°C and significant etching of (100) surface was observed. An attempt was made to apply this etching reaction for electrical discharge machining of diamond tools.

In industries, it is difficult to measure physical quantities such as product quality. In order to estimate it, soft sensors have been proposed. In recent years, the Just-In-Time (JIT) method has attracted attention. According to this method, the output is estimated by extracting data from the database similar to the current situation. On the other hand, a database-driven control system has been proposed in which the JIT is equipped with a learning algorithm. This method calculates the control parameters using a database and has the scheme to learn the control parameters to minimize the control error. This paper proposes a new design method for soft sensors which uses a database-driven approach. Specifically, this paper proposes a method to improve the estimation accuracy without modifying the stored past data by introducing a new modifier c into the learning algorithm. Furthermore, a control system is designed in which the estimated value using the soft sensor is fed back.

In this paper, we propose an efficient method for human dense avoidance based on a coverage control. Our motivation is to avoid crowding in public facilities such as stations and government offices, and human dense in the current situation of COVID-19 from system and control theory. In this paper, humans and robots are modeled as heterogeneous and homogeneous agents, respectively, which make decisions based on their local information. We suppose a dense situation caused by the rendezvous among humans due to their own inherent dynamics. As a main result, we propose a coverage control for a distributed movement of multiple humans. We also characterize the stationary point analytically in terms of the gains that describe a strength of the interconnection of the agents, and the centers of the Voronoi regions related to the agents. Moreover, we verify the meaning of the characterization from an engineering viewpoint of the dense avoidance. Finally, we show the efficiency of the method based on a numerical simulation.

Wireless communication devices such as wireless LANs and RFIDs are essential for smart home appliances and IoT (Internet of Things) devices in Smart Cities. When measuring the high-frequency noise generated by devices, wireless signals of wireless communication devices and high-frequency noise are measured at the same time. As a result, spectrum analyzers have insufficient dynamic range, or the excess signal from wireless communication devices causes harmonic distortion of the mixer inside the receiver, resulting in inaccurate measurements. Accordingly, a band rejection filter (BRF) is required to attenuate the radio signal. CISPR 16-2-3:2016+A1: 2019 assumes that impedances are matched for measurement, so if the impedance mismatch is large, the expanded uncertainty specified in CISPR 16-4-2:2011+A1:2014+A2:2018 increases. In this study, we propose a new BRF with impedance matching in the attenuation range and show its principle. As a result, the extended uncertainty could be reduced to 3.96 dB for the BRF of this study compared to 10.63 dB for the conventional BRF. In addition, the method comparison of CISPR 16-2-3:2016+A1: 2019 and vector network analyzer shows that the difference in attenuation of the conventional BRF was about −0.8 to 3.3 dB, whereas the BRF in this study were about −0.2 to 0.3 dB. The reduction of the expanded uncertainty and the good measurement results confirm the high usefulness of the CISPR 16-2-3 measurement system for the measurement of weak electromagnetic noise.