IEEJ Transactions on Electrical and Electronic Engineering最新文献

In this study, we present an on-chip analytical method using a microfluidic device to characterize the mechanical properties in growing roots. Roots are essential organs for plants and grow under heterogeneous conditions in soil. Especially, the mechanical impedance in soil significantly affects root growth. Understanding the mechanical properties of roots and the physical interactions between roots and soil is important in plant science and agriculture. However, an effective method for directly evaluating the mechanical properties of growing roots has not been established. To overcome this technical issue, we developed a polydimethylsiloxane (PDMS) microfluidic device integrated with a cantilevered sensing pillar for measuring the protrusive force generated by the growing roots. Using the developed device, we analyzed the mechanical properties of the roots in a model plant, Arabidopsis thaliana. The root growth behavior and the mechanical interaction with the sensing pillar were recorded using a time-lapse microscopy system. We successfully quantified the mechanical properties of growing roots including the protrusive force and apparent Young's modulus based on a simple physical model considering the root morphology. © 2025 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

DC power systems require reliable and cost-effective DC circuit breakers (DCCBs). In a previous study, we introduced a hybrid DCCB featuring a current-limiting fuse, insulated gate bipolar transistor (IGBT), and a varistor connected in parallel. However, this DCCB could not seamlessly mitigate IGBT voltage stress caused by factors such as the arc voltage induced by the fuse during current limitation, the transient recovery voltage during current interruption, and the source voltage. Traditionally, multiple IGBT connections in series have been utilized to address the risk of IGBT breakdown caused by overvoltage. However, this method may lead to voltage imbalances among the serially connected IGBTs, causing them to break. In this study, we present a novel commutation-path design for DCCBs that incorporates a vacuum contactor (VC) connected in series with the IGBT, alongside a capacitor connected in parallel with the IGBT path. The inclusion of the VC reduces the voltage across the IGBT; the inclusion of the parallel capacitor also reduces it at the moment of current interruption. This new commutation path design enables the voltage across the IGBT to be suppressed below original design requirements throughout the entire interruption process. © 2025 The Author(s). IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

In various forms of pyrotechnic devices for aerospace and defense systems, the safety and reliability of device functioning heavily relies on the electrical explosion of a thin metallic bridgewire in an exploding bridgewire (EBW) detonator unit for the ignition of primary explosive charges. This study presents the modeling and simulation of pulsed power deposition in a gold bridgewire of micron-sized diameter which undergoes intense joule heating followed by vaporization and bridgewire burst. The present modeling approach is based on the bulk approximation of bridgewire resistance, and it includes the circuit model of a high-voltage charging capacitor discharge unit (CDU) and the energy conservation principle with the consideration of phase changes in the bridgewire. The prediction results are well validated against the EBW firing test measurements in terms of electrical current traces and burst current for a wide range of CDU charging voltages. Threshold charging voltages for bridgewire burst and explosive ignition are investigated for the cases of varying bridgewire diameter and length, which results are found to be consistent with the EBW firing test analysis. © 2025 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Focusing on containerized environments like Docker, we examine performance degradation in these environments using extended Berkeley Packet Filter (eBPF) technology. We develop a monitoring application with eBPF to analyze the relationship between system resources (CPU, memory, and disk I/O) and system calls. Using random forest regression to analyze a Web 3-tier application, we found that the system calls writev, epoll_wait, and sched_yield significantly impact Web application performance, particularly in terms of CPU, memory, and disk I/O. © 2025 The Author(s). IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

In order to design an optimal off-grid microgrid, understanding the factors influencing demand growth over time is essential to ensure the reliability and sustainability of an off-grid microgrid, particularly in rural areas. This study aims to identify these influencing factors through surveys and interviews to assess future demand growth following the implementation of an off-grid microgrid system in Lao PDR. The study highlights two primary factors, age and income level, that directly affect the number of desired electrical appliances, increasing future energy consumption. To ensure optimal sizing of off-grid components, a scenario analysis was conducted based on projected trends in energy consumption growth. The study proposes three scenarios, including restrictive (low), business-as-usual (medium), and optimistic (high) trends, along with the optimal combinations of off-grid microgrid components. The low energy consumption growth in 5th year is deemed appropriate for rural electrification in Laos and serves as a baseline model intended to guide policymakers and stakeholders in preventing system failure shortly after implementation. © 2025 The Author(s). IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

The increasing integration of renewable energy into power grids highlights the importance of voltage stability and the control stability of inverters at connection points. This study proposes a method for estimating the short-circuit capacity at the point of common coupling (PCC) using fluctuation data from the inverter's active power output and frequency under normal operating conditions. © 2025 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

This study presents an enhanced nonnegative matrix factorization (NMF) algorithm designed for speech signal modeling. NMF has demonstrated efficacy across various applications to musical instrument signals, including audio source separation and music transcription. Nevertheless, its application to speech signals often results in diminished performance due to inadequate modeling arising from the spectral continuity of the speech signal. Hence, we introduced a pioneering approach termed cepstral-basis-decomposed NMF (CBD-NMF), which incorporates cepstrum analysis to enhance the modeling of speech signals. In the practical experiment, CBD-NMF is not necessarily convergence-guaranteed due to the flooring process; however, the experiment has revealed parameters that allow for stable optimization, ensuring that the cost function does not increase. By experimentally modeling Japanese vowel speech signals, we demonstrate that CBD-NMF induces better representation, in which one basis arises for one mora in Japanese. Additionally, when modeling a word in Japanese speech signals, CBD-NMF tends to induce a sparse representation equivalent to a sparse NMF with an extremely large weight coefficient. Our proposed framework can be applied to practical applications such as audio source separation and is expected to contribute to performance improvements when targeting speech signals. © 2025 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

One major challenge of QRS wave detection is the deleterious impact of inevitable noise in electrocardiogram (ECG) signals, which can deteriorate the detection performance of algorithms. Previous research has shown a nonlinear monostable potential-based algorithm for enhancing the QRS complex in a noisy environment. Its main mechanism is the stochastic resonance effect, which transfers noise energy to information-carrying ECG signals in the nonlinear potential. However, the QRS detection algorithm based on monostable stochastic resonance (MSR) exhibits a limited noise margin to maintain extremely good performance. To further improve noise robustness, we propose a multi-parameter constrained bistable SR (MCBSR) module for the QRS detection algorithm without requiring a large amount of training data. The MCBSR module can maximize the ECG signal while suppressing noise when there is a QRS complex and minimizes the ECG signal otherwise. Using four publicly available databases for testing, the MCBSR-based QRS detection algorithm has been proven to achieve superior performance among state-of-the-art algorithms. Compared to the conventional nonlinear method, the MCBSR enables the QRS detection algorithm to have significantly stronger noise robustness under various noise types. Therefore, this study successfully provides a more excellent nonlinear potential and greatly enhances the noise robustness of the QRS detection algorithm in large noise environments. © 2025 The Author(s). IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

To improve the speed tracking precision and overall steady-state performance of the permanent magnet synchronous motor (PMSM) drives, a sliding-mode predictive speed control method is proposed. Firstly, an ultra-local model (ULM) is built to ensure the anti-disturbance ability. Then, a novel discrete sliding-mode surface (SMS) is designed to achieve finite-time convergence of the motor speed. Simultaneously, a quadratic cost function is developed based on the predicted values of SMS. And then, the implemented model predictive control (MPC) algorithm not only efficiently generates the optimal q-axis reference current by the ULM, but also autonomously optimizes the motion trajectory of the motor speed. Specifically, the overall motor performance ultimately depends on the designed SMS, which also emphasizes the crucial role of MPC. Additionally, by evaluating the key controller gain that affects the balance between speed dynamics and system steady-state performance using mathematical and transfer function methods, an adaptive gain based on the Gaussian function is designed to effectively address this issue. Finally, the experiments are performed, and the results validate the superior performance of the proposed method. © 2025 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

High-spatial-resolution Brillouin optical correlation-domain reflectometry (BOCDR) in perfluorinated graded-index polymer optical fibers (PFGI-POFs) is gaining attention for structural health monitoring. A major challenge has been accurately predicting Rayleigh noise behavior, which constrains the modulation amplitude and spatial resolution. However, prior models did not consider differences in optical path lengths caused by the refractive indices of silica fibers (used in circulators) and PFGI-POFs. We refine the noise model to incorporate these differences. Experiments with varying fiber lengths show that the revised model more accurately predicts Rayleigh noise bandwidth, especially with longer circulator fibers. Errors of up to 120 MHz in the conventional model are reduced to within 25 MHz, showing the importance of proper optical path modeling in BOCDR. © 2025 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.