Electronics and Communications in Japan最新文献

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.

Residential appliances remotely controlled by IoT for demand response has attracted much attention for effective peak demand reduction of the uncertainty of consumers’ behaviors. To promote the technology development of such appliances, estimation of the potential for peak demand reduction according to the type of appliances is strongly needed. With this background, the authors conducted a data analysis of demand curves of not only the entire household but also the branches acquired at 496 dwellings in Osaka. Based on this analysis, the potential of peak reduction of aggregated demand of various groups with different dwelling size were quantified for major five appliances, namely air conditioners, microwave ovens, refrigerators, washing machines, and dish washers.

In this paper, we investigate an assist control for a system in which a human and a robot cooperate to transport an object toward a designated position and angle. We consider a situation where the force due to the human to the object cannot be measured directly. In order to tackle this situation, an assist control with a nonlinear disturbance observer is proposed. By using the observer, we estimate the control input due to the human from position and angle of the object. Moreover, we design the control input by the robot to assist the human input based on the estimates by the disturbance observer. The effectiveness of the proposed method is discussed by numerical simulations for the minimum jerk model.

In this work, oxidative decomposition reaction of organic reactant on TiO₂ surface was investigated under soaking conditions by combination of applying voltages and light illumination. Since carriers of TiO₂ thin films originate from point defects such as oxygen vacancies, reactive carriers possibly exist on TiO₂ thin films even under room light illuminating condition and dark condition. Thus, enhancement degrees of photooxidation by applying bias voltages onto TiO₂ thin films were compared under dark, visible light illumination and UV illumination conditions. Bias voltages were applied to localize the photogenerated carriers at the vicinity of TiO₂ surface for enhancing photooxidation. Sol-gel derived TiO₂ thin films with porous nano structure exhibited a stronger oxidative decomposition reaction than sputter-deposited TiO₂ thin films.

Several studies for partial discharge (PD) pattern recognition using artificial neural network (ANN) were reported in the early 1990s. Usually, in an actual field such as a substation, data on partial discharge is scarcely available, or even rare. In many cases, the power supply phase required for the PRPD pattern cannot be easily obtained. We propose an ANN method that shifts the phase in which the maximum signal intensity detected with PD sensors is generated and used it as training and input data, even for the few phases resolved PD data available in the field. This ANN method was applied to the PRPD pattern obtained in a practical field. As a result, it was shown that the discrimination rate between PD and noise was improved, and therefore the proposed ANN method was found to be effective.

The effect of sheet- and film-type electromagnetic noise suppressors on differential mode (DM) and common mode (CM) transmission characteristics in two parallel lines was investigated. Simple two parallel microstrip lines with a Co-Zr-Nb film were used as a test bench. The transmission characteristics of DM and CM were measured by four-port network analyzer. The ferromagnetic resonance (FMR) and eddy current losses generated in the Co-Zr-Nb film were calculated by 3D full wave simulator, and the effects of these losses on the transmission characteristics were estimated. The results show that the transmission characteristics are different in DM and CM because the frequency characteristics of the losses are different according to the different FMR frequency in each mode. Furthermore, the feasibility of the application of the magnetic film as a frequency-selective CM filter is demonstrated by using the difference in frequency characteristics of loss of DM and CM.

This paper presents a formulation of an optimization of uncertain systems and the solution technique. The optimization under uncertainties is formulated as an optimization problem which includes unknown variables in equality constraints called system equations as well as in an objective function and inequality constraints. As countermeasures against the uncertainties, a min-max criterion is applied to the objective function and robustness criteria are introduced to the inequality constraints. By differentiating state variables satisfying the equality constraints from the decision variables, we reformulate the optimization problem based on the worst-case scenario of the state variables corresponding to the uncertain variables and we propose a “constraints-relaxation procedure” based method considering the equality constraints to solve the reformulated problem. In this method, a constraints-relaxed problem is solved corresponding to a finite number of samples of uncertain variables. Furthermore, a new sample of uncertain variables is sequentially generated corresponding to the inequality constraint which the solution violates most, together with state variables satisfying the system equations at the new worst-case scenario. Finally, the effectiveness of the proposed method is illustrated by numerical examples including robust AC optimal power flow considering distributed energy resources.

We have developed a tactile stimulation system that can apply air puffs locally to any two points on a skin's surface. This system consists of an air output device and a reaction recording device, both controlled by dedicated software. The air output device is equipped with a microcontroller ESP32, which can produce an airflow from two ports by controlling the intensity of the compressed air, the duration of its output, and the inter-trial time interval between applications. The reaction recording device is equipped with a push-button to record the subject's response when the air is applied to the skin. We verified the applicability of this system by a two-point discrimination test. In 14 healthy human subjects, the shortest distance at which they correctly answered that the given air was at two points was 35 mm. When we applied the air at 30 mm, the majority of the human subjects answered incorrectly that the air was only at one point when in fact it was at two points. This result was in close agreement with previously reported results obtained by direct skin stimulation methods.

Electrets were prepared by spin-coating the dispersion of fine silica powders, and their charge retention characteristics were investigated. Finer silica aggregates were formed on the PTFE surface layer by spin-coating the dispersed solution of fine silica powder than those formed by spray-coating colloidal silica. Electrets using fine silica powder also showed better charge retention characteristics than those using colloidal silica. Such an improvement in the charge retention might be due to the suppression of discharge in the excessive gap caused by coarse silica aggregates. Then, ECSs were fabricated using the prepared electrets, and their transmitting and receiving characteristics of airborne ultrasound were also investigated. The peak sensitivity of the ECS using a spin coating of fine powdered silica dispersion was slightly improved from those using spray coating of colloidal silica. On the other hand, the peak frequency and frequency band were greatly improved using spin coating of fine powdered silica dispersion. Therefore, ECS using fine silica powder is expected to be applied as a broadband airborne ultrasonic sensor.

Due to the optical fiber have a small diameter and it can propagate light efficiently, it is possible to realize ultra-compact remote sensors. We have invented to the fiber-optic pressure sensor utilizes magneto-optical effect with polarized light, ring-type interferometer and a magnetic material, in order to propose the pressure measurement system which can measure in vivo or in harsh environments. We have confirmed that the prototype sensor based on magneto-optical effect was possible to detect pressures in range of −4 to +40 kPa.