Electronics and Communications in Japan最新文献

Muscle condition is evaluated primarily based on physical therapy; however, evaluation has not been quantitative. To quantify muscle fatigue, the authors previously derived and defined “muscle fatigue time,” which quantifies muscle fatigue using frequency analysis based on the surface-ElectroMyoGram of the biceps brachii. The authors also constructed a muscle fatigue time estimation model based on the relationship between muscle fatigue time and muscle load for each participant. However, since the values of the model parameters differ from subject to subject, generalization of the model requires deriving the relationship between subject characteristics and the parameters. In this study, we attempted to select physical features that influence method parameters and estimate those parameters from selected physical features using multiple regression analysis. Percent body fat and biceps skinfold thickness were selected as physical features, and parameters were determined that yielded data with an error rate of approximately 13%. These results suggest that the variation in model accuracy between individuals can be eliminated using physical features.

The organic flexible electronics is an attractive research due to which the wearable human sensing devices are on human fingernails distortion using functional organic materials. Generally, the strain gauge for human sensing is formed on plastic films. Therefore, while fixing the film sensor on a curved surface, such as human nails, it is difficult to make good contact. In this study, we proposed a process, which forms a patterned film of PEDOT:PSS (Poly(3,4-ethylenedioxythiophene):Poly(4-styrenesulfonate)) on a 3D-curved plastic substrate by the micro contact printing method. Moreover, we fabricated a strain gauge on a flexible polyimide substrate and measured static electrical characteristics. It enables to form a patterned film on surfaces, such as human nails, and fabricates a strain gauge directly. The results show that directly printed PEDOT:PSS films on curved surfaces can be used to strain sensor, which leads to monitoring the human body by sensing of human nail anytime.

W-type ferrites are easily decomposed into M-type ferrite and spinel ferrite during the sintering process, so it is difficult to obtain W-type single-phase sintered bodies. Therefore, carbon as a reducing agent is added and heat treatment before sintering is performed. However, the effect of these treatments on the change in the crystal phase during sintering has not been clarified in detail. In this study, the effect of carbon addition and heat treatment before sintering on the change in the crystal phase during sintering was investigated in detail by removing the samples from the electrical furnace during sintering. Furthermore, similar experiments were carried out with the addition of CaCO₃ and SiO₂ as sintering aids.

In this research, we developed a complex capacitance sensor with a crystal oscillator circuit for measuring the water retention and permeability of concrete. Differences in watertightness due to aggregate size, curing method, and admixture were successfully measured. This technology is expected to be applied to on-site watertightness evaluation of concrete, contributing to the diagnosis of durability and deterioration of concrete, and extending its service life through appropriately timed maintenance.

In recent years, stiffness measurements of micro-order objects are required. For example, analysis of the mechanical properties of a new material, such as a soft crystal, has been attracting attention. In the conventional methods to measure the stiffness, the grasping object is held without force feedback. Therefore, there is a possibility of damaging the objects. To solve this problem, this paper proposes a stiffness measurement method based on micro-macro bilateral control for micro-order objects. The micro-macro bilateral system consists of the leader system that is easy for the operator to manipulate, and the follower system that is sized to operate in a small environment. For the precise measurement, grasping the object is achieved by the micro-macro bilateral control. In this grasping, the total stiffness, including the object and the follower system, is measured in real-time. The stiffness of the follower system is identified by the preliminary experiment. As a result, the stiffness of the object is estimated by subtracting the total stiffness from the identified stiffness of the follower system. The validity of the proposed method was confirmed by the experimental results.

Previous studies have aimed to elucidate the principles of whistling by constructing vocal tract models using computed tomography data of the vocal tract during whistling. In addition, studies have been conducted on whistling pitch change models, in which the plates of the vocal tract model are adjusted to simulate changes in the vocal tract shape due to pitch changes. However, these studies often required manual operation of measuring devices and the interpretation of gauges. In this study, we developed a device that automates the measurement of sounds emitted by a vocal tract model during whistling. Using this device, we estimated the duration during which a stable whistling sound was generated and examined a method to measure the fundamental frequency and flow rate when the sound quality was optimal. Consequently, the device can automatically adjust, measure the flow rate, and analyze the generated sound. Furthermore, by using the distortion rate, we could estimate the period during which a whistling sound was generated and determine the fundamental frequency at which the sound quality was optimal.

Core body temperature, which is the temperature inside the body, is a useful biological indicator for understanding changes in various physical activities due to its characteristics of being insensitive to external disturbances. However, the gold standard measurement methods require inserting probes in the body, which is highly invasive and unsuitable during activity. Conversely, a patch-type sensor that estimates core body temperature from heat flow changes near the skin surface has been attracting attention as a suitable method during activity. However, its practical challenge has been to improve robustness to environmental changes. Recently, we have solved this problem by improving the conventional measurement probe. Nevertheless, the weight reduction of the measurement probe has been an additional challenge. Here, we focused on the probe cover, which had previously been identified as a significant obstacle to weight reduction. We investigated the potential of applying a typical lightweight structure, such as a hollow or stepped structure, to the probe cover in order to achieve both weight reduction and high accuracy of the measurement probe.

This paper proposes a novel control strategy for wireless power transfer (WPT) circuits that achieves both load voltage regulation and maximum efficiency control for varied resistive loads. The proposed method is based on the characteristic that the input impedance of a switching voltage regulator depends on its input voltage. The switching regulator is utilized not only for load voltage regulation but also for impedance conversion to maximize the transfer efficiency. External communication circuits for feedback control from the secondary side to the primary side are unnecessary as the controllers on both sides operate independently. Experimental results approximately match the derived theoretical values and validate the proposed method.

This paper describes a new ultra-low-power and ultra-low-frequency oscillator using the GIDL current used in edge AI devices for long-term and intermittent monitoring applications. Various characteristics of the GIDL current were measured and compared with the subthreshold current. An ultra-low frequency GIDL ring oscillator was designed and evaluated with the measurement results. As a result, ultra-low frequency oscillation from 0.94 to 5.1 Hz was successfully achieved. An extremely small circuit area was achieved because integrated resistors and capacitors were not used. From the power consumption analysis, a new low-power design was conducted from the viewpoints of “shortening the signal transition time of the buffer circuit” and “reducing the short-circuit current of the buffer circuit,” and ultra-low power operation of 71.6 pW was successfully achieved in circuit simulation. GIDL ring oscillator is a promising candidate for an ultra-low-power and ultra-low-frequency oscillator with high environmental stability.

Assessment of impaired insulin secretion and insulin resistance is critical to determining the type of diabetes and planning optimal management and preventive strategies in clinical practice. To measure insulin resistance, a minimally invasive needle with measurement and administration flow channels for local glucose tolerance tests was fabricated. The administration flow channel has a hole on the tip end of the flow channel. The microperfusion flow channel starts from the root side of the needle, turns around at the needle-tip end, and returns back to the root side of the needle. It has a perforated membrane on the surface of the area placed in the skin when inserted. Glucose is administrated through the flow channel, and glucose concentration of the skin is measured by microperfusion before and after administration. When the perfusate is perfused into the microperfusion flow channel, since the glucose concentration of the skin is higher than the perfusate, glucose contained in the skin's interstitial fluid moves into the flow channel through the perforated membrane by concentration diffusion, and the glucose can be collected. The needle's administration and glucose-collecting functions were evaluated in the skin of mice.