Electronics and Communications in Japan最新文献

The isolation characteristics between the antennas of transmission and reception are important for signal quality. In this paper, we propose a small dual-polarized antenna with dual vertical split-ring resonators and differential feeding. This novel antenna is based on artificial magnetic conductors (AMCs) modified to radiate directly. A high isolation characteristic between two ports of over 70 dB was achieved.

Skeletal muscle is a collection of motor units (MUs) composed of motoneurons and muscle fibers; muscle contraction is regulated by the number and type of MUs. Since sarcopenia and disuse atrophy are caused by atrophy of specific muscle fiber types, it is important to observe mobilized MUs for skeletal muscle diagnosis. In a previous study, we proposed a method to measure multi-channel surface electromyography (EMG) and quantitatively acquire conducting waves, which are potential waveforms propagating on the muscle surface. The mode of MU mobilization by prolonged muscle contraction is not well known. It is necessary to be able to estimate the mobilized MU over time to diagnose slow muscle fibers and to realize the evaluation of muscle activity during training. This study analyzed the conducting waves of multi-channel surface EMG during prolonged muscle contraction in 20 adult male subjects. The results of the changes in the conducting wave during long-duration muscle contractions at high and low loads showed different characteristics, suggesting the possibility of using the propagating wave to elucidate skeletal muscle.

The citrus aroma, which affects the consumer's preference, is an important parameter for breeding. However, the quantitative evaluation of citrus aroma was difficult because the aroma accumulates in the oil glands of the peel. In this study, we improved the aroma evaluation method using a portable electronic nose and the odor-emitting device (OED) that we had invented previously. By standing after shaking the sample and OED, repeatability was improved, and it enabled the quantitative evaluation and comparison of aromas emitted from different citrus cultivars peel. Furthermore, nine parameters calculated from four sequential data were used for PCA and k-means clustering, and they show the classification of citrus aromas. As a result, Lisbon Lemon and Rinoka were clustered in Cluster 1; Encore, Yoshida Ponkan, and Sweet Orange were clustered in Cluster 2; and Ueno Wase and Miyagawa Wase were clustered in Cluster 3. Based on the result of clustering, decision tree analysis was conducted, and the factors contributing to the clustering of the aromas were shown. In this study, we have developed aroma evaluation methods consisting of e-nose, OED, and an algorithm optimized for aroma classification of citrus peels, and this result would contribute to accelerating breeding of valuable citrus cultivars.

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.