Search Results (83)

Memory performance is regulated by circadian rhythms, and electroencephalograms (EEG) measure biological signals related to memory mechanisms and circadian rhythms. Therefore, EEG could be used to detect changes in diurnal memory. In this study, we measured the EEG signals of participants conducting a memory-related task and tested the effectiveness of a convolutional neural network (CNN) in predicting memory task performance at different times. EEG signals from participants performing N-back tasks at 8–9 a.m. and 3–4 p.m. were recorded. While performance showed no significant differences between times, differences were observed in EEG relative power. A CNN was trained using the relative power and raw waveform data of the EEG signals recorded during the tasks. When predicting the time at which the working memory (WM) was enhanced, the relative power CNN exhibited a significantly higher accuracy than the raw waveform CNN. However, the performance dropped in the test where the training data did not include the EEG data of the same participant. Overall, these results suggest that while EEG signals using a relative power CNN have high predictive potential, developing a personalized classification system that reflects individual chronotypes is effective for practical applications. Full article

This study aimed to experimentally investigate the differences in metallic structures owing to the gas nitriding and quenching process (GNQP) temperature of the Ti-15mass%Nb alloy and differences in the tribological properties of the surface layer. The GNQP heating temperature was 1023 K or 1223 K, and the holding time was set to 1 h. In the X-ray diffraction profiles, the diffraction peak of the (10$\overline{1}$1) plane of the hexagonal close-packed phase exhibited a shift toward lower angles, following the sequence AN:α, AQ:α′, and GNQP:α-TiN_0.3. In both the 1023 K and 1223 K GNQP specimens, the α″ phase exhibited lower values than the α′ phase; nonetheless, it still exhibited larger values than the annealed α phase. Based on transmission electron microscopy observations, the high core hardness of the 1223 K GNQP specimen was attributed to solid-solution strengthening caused by nitrogen diffusion or to strain hardening associated with the diffusion and was not attributed to the influence of precipitation phases, such as the ω phase. In the friction and wear tests, both the 1023 K and 1223 K GNQP specimens exhibited narrower wear track widths, clearly demonstrating that the GNQP enhanced the wear resistance. Moreover, the TiO₂ layer was effective in maintaining a low coefficient of friction. Full article

To determine the optimal arrangement of vertical-axis wind turbines (VAWTs) within wind farms, we previously developed a technique (method-1) that constructs a flow field based on two-dimensional (2D) velocity data derived from computational fluid dynamics (CFD) simulations. In this study, we introduce an improved approach (method-2), which follows the same fundamental concept as method-1 but incorporates a more efficient algorithm for generating the flow field. Comparative analyses confirmed that method-2 produces results equivalent to those of method-1 while significantly reducing computational time and cost. Method-2 reduces the computation time of method-1 by approximately 50% for parallel layouts (θ = 0°) and up to 60% for slanted layouts (θ = ±45°). Using method-2, we further investigated the performance of a wind farm composed of eight VAWT rotors arranged in a linear configuration under the assumption of a 2D flow. The results highlighted two important aspects. First, the predicted power output is unaffected by the order in which the flow fields are superimposed during calculation; second, the method exhibits high sensitivity to even small variations in rotor placement within the layout when the spacings between rotors are short. Additionally, we examined how rotor spacing affects the distribution of power generation across the rotor array. These findings of this study validate the efficiency of method-2 and offer practical insights for designing optimized VAWT layouts. Full article

The functional integration of chiral liquid crystals and π-conjugated compounds has great potential for creating novel exotic materials. A series of chiral donor–acceptor (D–A)-type fluorenone derivatives was synthesized to investigate the influence of molecular structure upon their liquid-crystalline phase-transition behavior, ferroelectricity, photophysical properties, and photoconductive properties. Polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) analyses revealed that several D–A-type fluorenone derivatives exhibited liquid crystal (LC) phases. These chiral LC fluorenone derivatives exhibited polarization hysteresis in the chiral smectic C (SmC*) phase. Among the four fluorenone-based ferroelectric liquid crystals (FLCs), (R,R)-2a exhibited the largest spontaneous polarization (over 3.0 × 10² nC cm⁻²). The formation of intramolecular charge-transfer (ICT) states in each compound was evidenced by the UV–vis absorption spectroscopy. Ambipolar carrier transport in the SmC* phases of the fluorenone-based FLCs was elucidated by the time-of-flight (TOF) method. The mobilities of holes and electrons in the SmC* phases were on the order of 10⁻⁵ cm² V⁻¹ s⁻¹, which is on par with the carrier mobilities of low-ordered smectic phases in conventional LC semiconductors. Full article

IRS 16CC and IRS 33N are among more than 100 young, massive stars identified within 0.5 pc from the Galactic central supermassive black hole Sgr A*, where conventional star formation processes are expected to be strongly suppressed. A subset of these stars, including IRS 16CC, has been confirmed to reside in a clockwise rotating stellar disk, and is thought to have formed in a massive, gaseous disk around Sgr A*. In contrast, other young massive stars, such as IRS 33N, exhibit dynamical behaviors that deviate significantly from those of the disk population, and their formation mechanism is still uncertain. To investigate their formation mechanism, we carried out near-infrared, high-resolution spectroscopic observations of IRS 16CC and IRS 33N using the Infrared Camera and Spectrograph on the Subaru telescope, equipped with an adaptive optics system. We compared the profiles of He I absorption lines with synthetic spectra generated from model atmospheres, and then compared derived stellar parameters with stellar evolutionary tracks to estimate their ages and initial masses. Our analysis yields their effective temperatures of ∼23,000 K, surface gravities of ∼2.8, and initial masses of $37\pm 6M_{\odot }$ and ${27}_{-3}^{+4}{M}_{\odot }$, consistent with spectral types of B0.5–1.5 supergiants. The ages of IRS 16CC and IRS 33N are estimated to be $4.4\pm 0.7$ Myr and $5.3_{-0.7}^{+1.1}$ Myr, respectively. These results suggest that, despite their different dynamical properties, the two stars are likely to share a common origin. Full article

Biofilms cause a variety of problems, such as food spoilage, food poisoning, infection, tooth decay, periodontal disease, and metal corrosion, so knowledge on biofilm prevention and removal is important. A detailed observation of the three-dimensional structure of biofilms on the nanoscale is expected to provide insight into this. In this study, we report on the successful in situ nanoscale observations of a marine bacterial biofilm on glass in phosphate buffer solution (PBS) using both scanning ion conductance microscopy (SICM) and confocal laser scanning microscopy (CLSM) over the same area. By observing the same area by SICM and CLSM, we were able to clarify the three-dimensional morphology of the biofilm, the arrangement of bacteria within the biofilm, and the difference in local ion conductivity within the biofilm simultaneously, which could not be achieved by observation using a microscope alone. Full article

Gait evaluation approaches using small, lightweight inertial sensors have recently been developed, offering improvements in terms of both portability and usability. However, accelerometer outputs include both the acceleration that is generated by human motion and gravitational acceleration, which changes along with the posture of the body part to which the sensor is attached. This study presents a gait analysis method that uses the gravitational, centrifugal, tangential, and translational accelerations obtained from sensors attached to the lower legs. In this method, each sensor pose is sequentially estimated using sensor fusion to combine data obtained from a three-axis gyroscope, a three-axis accelerometer, and a three-axis magnetometer. The estimated sensor pose is then used to calculate the gravitational acceleration that is included in each axis of the sensor coordinate system. The centrifugal and tangential accelerations are determined from the gyroscope output. The translational acceleration is then obtained by subtracting the centrifugal, tangential, and gravitational accelerations from the accelerometer output. As a result, the acceleration components contained in the outputs of the accelerometers attached to the lower legs are provided. As only the acceleration components caused by walking motion are captured, thus reflecting their characteristics, it is expected that the developed method can be used for gait evaluation. Full article

Inverter-equipped heat pumps allow for increased energy efficiency. However, air conditioning (AC) systems often operate at low load ratios below where inverter control is effective, which reduces their energy efficiency. We developed an AC system that increases the apparent load ratio of the heat pump by using a phase-change material (PCM). Cooling and heating experiments were conducted with a PCM heat exchanger, which comprised aluminum plates and fins filled with paraffinic PCM. The result indicated a high heat transfer coefficient of >70 W/(m²·K). A simplified numerical model of the PCM heat exchanger as a lumped constant system was created based on the experiment. The calculations generally reproduced the experimental results, with root mean squared errors of 0.39 K for cooling and 0.84 K for heating, confirming their accuracy. Simulations were then conducted to evaluate the energy performance of the proposed system for the cooling season. While low load operation accounted for 39% of the total AC time for a non-PCM system, it was reduced to 2.7% for the proposed system. The proposed system demonstrated load ratios of 50–60% for most of the season, achieving an energy reduction of 11.4% owing to the improved efficiency at partial load ratios. Full article

This study presents a case of community-integrated project-based learning (PBL) at a Japanese National Institute of Technology (KOSEN). Three students collaborated to design and build a rideable 5-inch gauge railway system, integrating mechanical design, brushless motor control, and computer vision. The project was showcased at public events and a partner high school, providing authentic feedback and enhancing learning relevance. Over 15 weeks, students engaged in hands-on prototyping, interdisciplinary teamwork, and real-world problem-solving. The course design was grounded in four educational frameworks: experiential learning, situated learning, constructive alignment, and self-regulated learning (SRL). SRL refers to students’ ability to plan, monitor, and reflect on their learning—a key skill for managing complex engineering tasks. A mixed-methods evaluation—including surveys, reflections, classroom observations, and communication logs—revealed significant gains in technical competence, engagement, and learner autonomy. Although limited by a small sample size, the study offers detailed insights into how small-scale, resource-conscious PBL can support meaningful interdisciplinary learning and community involvement. This case illustrates how the KOSEN approach, combining technical education with real-world application, can foster both domain-specific and transferable skills, and provides a model for broader implementation of authentic, student-driven engineering education. Full article

Microbially induced calcite precipitation (MICP) has attracted attention as an environmentally friendly soil stabilization method, with Sporosarcina pasteurii being a key ureolytic bacterium in this process. However, its behavior in oxygen-limited environments remains poorly understood, limiting the predictability of MICP outcomes in natural soils. This study investigated the population dynamics of Sporosarcina in compacted soil reactors operated under aerobic and anaerobic conditions, including saturated environments. Quantitative PCR and 16S rRNA gene sequencing revealed that Sporosarcina thrived and became dominant under aerobic, unsaturated conditions, but failed to maintain a high abundance under anaerobic or saturated conditions. These findings indicate that gas-phase oxygen—not merely its presence in the overlying atmosphere—is essential for effective Sporosarcina-driven MICP. The results highlight a critical environmental constraint that limits the application of biostimulation strategies relying on indigenous Sporosarcina in oxygen-poor soils. This study provides the first in situ evidence linking oxygen availability and microbial dominance in MICP systems, with implications for optimizing microbial soil stabilization in real-world conditions. Full article

In the V-bending of sheet metals using a pair of plastic punch and die manufactured by a 3D printer, the effects of two different dimensions designed with the same tool geometry on the deformation behaviors of the punch, die, and sheet were evaluated. The deformation behavior and strain distribution of the punch, die, and sheet were analyzed using a digital image correlation method. Sheets from pure aluminum to ultra-high-strength steel were bent using the two tools with different spans; one was designed on the assumption of tool steel material, and the other was designed on the assumption of plastic material. In both tools, the large compressive strain appeared around the center of the punch tip and on the corners of the die. The tools with a long span for the plastic material gave a lower bending force and small deformation of the plastic tools. The angle difference between a bent sheet at the bottom dead center and a tool was smaller for the tools with the long span, although the springback in the bent sheet appeared. It was found that the design method on the assumption of the plastic material is effective for the V-bending plastic tools. Full article

The effects of an increase in output power owing to the close arrangement of vertical-axis wind turbines (VAWTs) are well known. With the ultimate goal of determining the optimal layout of a wind farm (WF) for VAWTs, this study proposes a new method for quickly calculating the flow field and power output of a virtual WF consisting of two-dimensional (2-D) miniature VAWT rotors. This new method constructs a flow field in a WF by superposing 2-D velocity numerical data around an isolated single VAWT obtained through a computational fluid dynamics (CFD) analysis. In the calculation process, the VAWTs were gradually increased one by one from the upstream side, and a calculation subroutine, in which the virtual upstream wind speed at each VAWT position was recalculated with the effects of other VAWTs, was repeated three times for each arrangement with a temporal number of VAWTs. This method includes the effects of the velocity gradient, secondary flow, and wake shift as models of turbine-to-turbine interaction. To verify the accuracy of the method, the VAWT rotor power outputs predicted by the proposed method for several types of rotor pairs, four-rotor tandem, and parallel arrangements were compared with the results of previous CFD analyses. This method was applied to four virtual WFs consisting of 16 miniature VAWTs. It was found that a layout consisting of two linear arrays of eight closely spaced VAWTs with wide spacing between the arrays yielded a significantly higher output than the other three layouts. The high-performance layout had fewer rotors in the wakes of the other rotors, and the induced flow speeds generated by the closely spaced VAWTs probably mutually enhanced their output power. Full article

A fundamental study has been conducted on the effective utilization of rice husk ash (RHA) in concrete. RHA is an agricultural byproduct characterized by silicon dioxide as its main component, with a content of 90% or more and a porous structure that absorbs water during mixing, thereby reducing fluidity. The quality of RHA varies depending on the calcination environment; however, the effect is not consistent. In this study, the pore structure was modified, and fluidity was improved by adjusting the particle size of the RHA. From a quality control perspective, this study aims to classify grades using Luxan values. While the characterization of RHA is based on Luxan values, the methodology for measuring its hydration response has not been reviewed. The test methods used in this study are as follows. To test the raw materials, density, specific surface area, XRF, SEM, and isothermal adsorption–desorption curves were measured, and fluidity was measured in fresh mortar. In a hardened mortar, compressive strength and drying shrinkage length change rate were measured. In addition, XRD and TG were measured for specimens after the compressive strength test. The selective dissolution method was used to measure the hydration rate. By adjusting the particle size of RHA to 45 µm, fluidity was enhanced. The relationship between the Luxan value and the basic properties of the mortar indicates that higher Luxan values correspond to greater compressive strength and drying shrinkage. We believe that the method used in this experiment can be used to quantify RHA. Full article

Variable refrigerant flow (VRF) systems are common air-conditioning systems used in regions with moderate climates that have cooling and heating demands. Unlike typical air-source VRF systems, ground-source VRF systems require heat-source water circulation, and reducing the pumping power remains a significant problem. Herein, the intermittent pump control for circulating heat source water was achieved by installing a buffer water tank between the ground heat exchangers and VRF units. An intermittent control methodology was developed based on the indices of water transport efficiency and incorporated into a system simulation model with 72 boreholes, a cooling capacity of 252 kW, and a buffer water tank of 30 m³. Results indicated that intermittent control was achieved at heat load ratios lower than 40% as expected. This intermittent control allowed more efficient water transport with 38% lower pumping power than conventional inverter controls. Although the proposed system equipped more pumps and heat exchangers than conventional systems, it exhibited higher energy efficiencies for most measurement days than the conventional air-conditioning systems. The annual energy consumption was thus reduced by 34% and 8% compared to air-source VRF systems and conventional ground-source VRF systems, respectively. Full article

Many countries are adopting renewable energy (RE) and electric vehicles (EVs) to achieve net-zero emissions by 2050. The indicators of RE and EV potentials are different. Decision-makers want to introduce RE and EVs; however, they need a method to find suitable areas. In addition, this is required in the time-series analysis to provide a detailed resolution. In this study, we conducted a time-series analysis in Japan to evaluate suitable areas for the combined use of RE and EVs. The results showed the surplus RE areas and shortage RE urban areas. The time-series analysis has quantitatively shown that it is not enough to charge EV batteries using surplus RE. Moreover, a ranking methodology was developed for the evaluation based on electric demand and vehicle numbers. This enables the government’s prioritization of prefectures and the prefectures’ prioritization of municipalities according to their policies. Full article