Electronics and Communications in Japan最新文献

High-reliability assembly techniques for miniaturized in-line pressure sensor with diaphragm using a thin strain sensor have been developed to monitor the hydraulic pressure in the pipetting such as dispensing devices. The pressure sensor with a thin strain sensor as a diaphragm has two problems, (i) water leakage and (ii) sensitivity reduction by adding hydraulic pressure. These problems were clarified to generate tensile stress in the adhesive (Ag paste) by adding hydraulic pressure and peeling a strain sensor from SUS housing. To overcome these problems, the stress in Ag paste was needed to keep compressive stress even when adding pressure. In this paper, a pressing mechanism is newly proposed to make compressive stress in Ag paste and assemble on the pressure sensor. First, to press the strain sensor to the SUS housing, a lid was bonded on the strain sensor with wafer-level-packaging (WLP) technique. Next, a pressing mechanism was designed to assemble the miniaturized pressure sensor. The pressing mechanism was composed of a cover, two coil springs, and a spring base with a pressing point. The pressing mechanism generates compressive stress to Ag paste even under high hydraulic pressure. The pressure sensor which implements the pressing mechanism has high-pressure resistance and high reliability under the repetitive hydraulic pressure of 10 million times, without water leakage and sensitivity decrease.

This paper presents a new method for fast simultaneous monitoring of individual gas concentrations in a gas mixture by using small micromachined sensors. The developed method uses output data from multiple micromachined thermal conductivity detectors of different sensitivities. We confirmed that the fabricated sensors can accurately determine the concentrations of each of three gases in a mixture. The prototype sensor module was miniaturized to less than 1/72th the size of conventional gas chromatography (GC) equipment. Demonstration tests were conducted in a CO₂ electrolysis cell for CO₂ capture and utilization technologies, and each gas concentration was successfully monitored 176 times faster than conventional GC could for a mixture of H₂, CO₂, and CO gases.

A method of student experiment for high-frequency circuits is developed. This training method is based on a quasi-experiment system and movies for educational materials. The quasi-experiment system provides electromagnetic simulation with three-dimensional models of chip inductors and capacitors. It reduces the time for making prototypes and measuring them. Visualized electromagnetic fields can be used to design the high-frequency circuits using chip components in the system. A part of the circuits is easily evaluated by the system. The student experiment includes fundamental circuits and an applied circuit for a design contest. The method is suitable for obtaining knowledge on practical high-frequency circuit design within a limited amount of time.

In recent years, more and more server administration exercises have been conducted at universities. Some students get stuck on the answer to a task. In this case, the student requests a hint for the task. The teacher hears the student, assesses the progress, and offers a hint. Also, teachers want students to conduct trial and error on a task before asking for hints. Many students ask for hints during exercises, which is a burden for teachers. We develop a system that presents hints based on the student's learning status. The teacher registers the learning status and corresponding hints in the system in advance. The student's command input/output and edited files are monitored by the system to check the student's progress. The system can suggest many hints based on learning status. As a result of the evaluation experiment, unnecessary hints were not presented to the students. Also, the system can guide students to conduct trial and error in the learning situation the teacher expects. In this paper, we describe the developed system and the results of evaluation experiments using the system.

In this paper, we have analyzed sheet thickness and gate voltage dependence of electrical characteristics for nanosheet MOSFETs using a device simulation that takes quantum confinement effects into account. Since the sheet thickness of nanosheet MOSFETs decreases to several nanometers, the simulated on-current shows significant reduction compared to the on-current required in the device design due to the quantum confinement effect. We analyze the relative difference between the on-current required in the device design and the simulated on-current and propose a design guideline using the relative difference. In order to suppress the relative difference of the on-currents within 3%, the minimum sizes of the sheet thickness are 3.4, 4.5, and 5.5 nm at supply voltages of 0.70, 0.60, and 0.50 V, respectively.

We propose a system targeting visually impaired individuals that provides a couple of functions that help when they claim they are always in trouble when going out using public transportation. One of the functions alerts users when the bus that they are planning to ride gets closer to the bus stop where they are waiting for the bus. It runs as a multi-thread system. One of the threads periodically obtains the location of the bus driver utilizing a GPS receiver and uploads it to a specific shared location on the web. The other thread fetches the stored shared location from the web and calculates the distance to the location of the bus stop where the user is waiting for the bus. The latter thread alerts the user when the distance gets lower than a threshold. The other function we propose alerts users when their intended bus stop is approaching within a certain distance during bus rides. The system utilizes the GPS functionality embedded in smartphones to acquire the user's latitude and longitude. By comparing this information with the coordinates preregistered in the system for each bus stop, it detects when the user reaches within a certain distance of the destination bus stop. The implementation of the proposed system demonstrated the intended functionality in an experiment.

Citrus greening disease (CG) is the most destructive disease of citrus, leading to branch dieback and plant death. Currently, there is no cure for CG, the early detection and removal of infected trees is important to prevent the spread of the disease. In recent years, there have been growing expectations for CG detection with digital images, especially deep learning techniques applied to digitized herbarium specimen image data. However, this approach faces challenges in practical applicability and detection efficiency. In this paper, we proposed a simple diagnostic method for CG using transfer learning with the Faster RCNN architecture. We collected in-field images from a citrus orchard in Thailand where CG has caused significant damage. We compared the performance of two annotation methods with the in-field leaf dataset and discussed their effects on pre-trained VGG and Resnet models. Five-fold cross-validation was utilized for model training and evaluation, with average precision (AP) used as the performance metric. The results showed that the Resnet models performed better than the VGG models, with the Resnet152 model scoring the highest in this task. The annotation method which included annotations of healthy and other disease leaves achieved an AP of 84.13% lower than another one but indicated better performance in practical applications with more robustness. Additionally, we developed a web application that performs real-time diagnosis using our trained models and verified the effectiveness of our system.

Collision ESD between charged metallic objects below 1000 V causes electromagnetic interference in electronic equipment and devices. This interference is being observed to intensify at lower charging voltages. The phenomenon was first identified by Masmitsu Honda, but its underlying mechanism remains unclear even today. Originally, the charging voltage and spark length of collision ESD are unknown due to measurement difficulties, making it extremely challenging to establish the relationship between the radiated electric field strength and the spark property in such cases. In this study, to clarify the above mentioned electromagnetic phenomenon in collision ESD, a method of calculating the radiated electric field along with a spark length estimated from the measurement strength of radiated field peak is presented using the spark resistance law developed by Rompe and Weizel. The validity is confirmed by our previous measurement data on radiated electric field due to the collision ESD between charged spherical electrodes with a diameter of 30 mm at charging voltages from 300 to 600 V, employing an optical field probe with a wideband up to 10 GHz. The estimated spark length is verified by comparing it with the spark lengths based on an empirical Paschen's formula between fixed electrodes and the discharge data from past literature on metal electrodes, revealing the peculiarity effect of the radiated electric field strength caused by “constant breakdown potential gradient” that occurs at charging voltages below 1000 V.

Recently, optically pumped magnetometers (OPMs), which use the spin polarization of alkali metal atoms to measure magnetic fields, have attracted much attention. However, in order to realize high-sensitivity biomagnetic field measurements using OPMs, it is necessary to reduce environmental magnetic noise and system noise. In this study, we investigate the effectiveness of the noise reduction of OPM signals when principal component analysis, independent component analysis, and empirical mode decomposition are used for signal processing.

This paper analyzes the stability of a grid-following inverter by the complex vector control in αβ domain and by the PLL synchronization control in dq domain. It is known that the frequency transfer function of the PLL may affect mutual interactions between grid and line impedances. This paper analyzes the frequency characteristics of the inverter based on the mixed-domain control for stability by the impedance method. Considering frequency coupling effects by the PLL control, it is found that the passivity of the inverter is violated and it may become unstable for a weak grid. This result is validated by analytical derivation, simulation, and experiment.