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Background: Natural sounds are reportedly restorative, but most research has used one-off experiments conducted in artificial conditions. Research based on field experiments is still in its infancy. This study aimed to generate hypotheses on the restorative effects of listening to natural sounds on surgeons, representing professionals working in stressful conditions. Methods: Each of four surgeons (two experts and two residents) participated six times in an experiment where they took a 10-min break listening to natural sounds (four times) or without natural sounds (twice) after a surgical operation. We measured their skin conductance level, an indicator of sympathetic arousal, continuously during the break (measurement occasions N = 2520) and assessed their mood using two questionnaires before and after the break (N = 69 and N = 42). We also interviewed them after the break. Results: Based on statistical Linear Mixed-Effects modeling, we developed two hypotheses for further, more detailed studies: (H1) Listening to natural sounds after an operation improves surgeons’ mood. (H2) Inexperienced surgeons’ tension persists so long that the effect of natural sounds on their sympathetic arousal is negligible. Conclusions: This risk-free, easy-to-use means of stress alleviation through natural sounds could benefit highly-stressed people working indoors.

Many studies have reported that natural sounds (e.g., birdsong) are more restorative than urban noise. These studies have used physiological and psychological indicators, such as the skin conductance level (SCL) and the Perceived Restorativeness Scale (PRS), to evaluate the restorative effect of natural sounds. However, the effect of faint background noise mixed with birdsong on the restorativeness of birdsong has not been described yet. In the current experiment, we examined whether traffic noise affects the perceived restorativeness and the physiological restorativeness of birdsong in a low-stress condition using the SCL and the PRS. The scores of the PRS showed that birdsong significantly increased the perceived restorativeness of the place regardless of the car noise, but no significant difference was found between these two birdsongs. In contrast, physiologically, the birdsong without car noise decreased the participants’ SCL significantly more than the birdsong with car noise did. These results indicate that the SCL would be useful to detect the effect of background noise on natural sound when the noise is too low to affect the perceived restorativeness. This study highlights the importance of measuring the SCL besides assessing perceived restorativeness to describe the characteristics of restorative natural sound in future research.

Improvements in lighting and other indoor environmental conditions have gained considerable attention in different areas, including health and economics. Controlling the lighting environment is essential because, among the indoor factors, visual stimulation affects numerous human characteristics. Further, visual stimulation, including peripheral vision, affects people differently. Therefore, to improve the indoor environment with multiple occupants, each occupant must have an independent lighting environment. However, this cannot be achieved through conventional approaches. In this study, we propose a multiplexed lighting environment that can simultaneously realize multiple mutually independent lighting environments within a single space. We developed the proposed system using time-division multiplexing and conducted an experiment to clarify the influence of light multiplexing on human behavior and impression of the indoor environment. The experimental results showed that the proposed method changed the lighting operations of the users and improved their impression of the lighting environment. Furthermore, the proposed method provides a desirable lighting environment for all people within a single space, even when people in the same space desire different lighting environments.

Car-sharing services have recently attracted considerable attention. We proposed a platooning system to reduce the number of vehicle distributors. The platooning system uses a measurement device embedded with low-cost infrared distance sensors to measure the relative position and orientation of vehicles. The relative positions and orientations are obtained from the training data. However, preparing training data is time consuming. In this study, a sensor clustering method that selects sensors with similar output characteristics is proposed. Consequently, a set of training data are used repetitively for all relative positions and orientation measurement devices embedded with sensors with similar output characteristics. The verification experiment of the sensor clustering revealed that the calculation range restriction is the key technique. Platooning has been successful in various courses by using sensors with similar output characteristics. Based on the results, the proposed clustering method can effectively collect sensors with similar output characteristics and it realizes the training data transfer to the newly manufactured devices. In addition, it has the potential to improve production efficiency for the mass production of relative position and orientation measurement devices.

At urban production sites, laser cutting is an essential technology for high-speed flexible sheet-metal processing. This study aims to detect defective cuts by sensing laser-cutting-induced light emission and elucidate meaningful features for processing-based detection. The proposed method comprises three steps. In the first step, the sensors installed in the laser head acquire the spectra of light generated during processing, and data analysis software converts the spectral data into spectrograms and stacked-graph images. In the second step, image processing software extracts the edges of both images and emphasizes the periodic features in normal laser cutting. In the final step, a one-class support vector machine recognizes defective cuts from the extracted features. Verification tests using multiple normal and abnormal cut data confirmed that the proposed method accurately detected defective cuts.

Recently, the promotion of the utilization of data mining in Japanese agriculture has become noteworthy. The purpose of such data mining is to transform the knowledge and know-how of experienced farmers into an explicit form. In particular, it is required for creating a tomato cultivation database to acquire the growth data of not only red mature tomatoes, but also green immature tomatoes. We are developing a robot to estimate the volume of a tomato that actively searches an appropriate measurement position. While patrolling a tomato bed, the robot first detects a tomato by using saliency-based image processing technology. When a tomato has been detected, a motion stereo camera installed on the robot generates a point cloud and a clustering process extracts the fruit region. A three-point-algorithm-based ellipse detector then estimates the width of the extracted fruit region. Finally, the estimation result is immediately evaluated using multiple indicators. This immediate evaluation process rejects unreliable data and suggests the correct position for re-measurement.

For decommissioning of the Fukushima Daiichi Nuclear Power Station, we are developing an “automated construction system for a modularized rail structure.” The intersection module developed in this study produces structure branches and changes robot attitudes. To maintain module functions, assuming the anticipated malfunctions caused by high-radiation environments, remotely controlled robots are used to replace malfunctioning parts of the module. To facilitate maintenance tasks, small positioning errors must be accommodated. This compliant function can be realized by the maintenance robot or the module. To elucidate effective combinations of the compliant mechanisms, experiments are conducted using prototypes. Experimental results confirm that the compliant mechanism of the robot contributes more efficiently than that of the module. This study is expected to be applied to practical distributed robotic systems because it is necessary to replace malfunction parts as simply as possible if they are replaced by remotely controlled robots.

The ceiling serves as an ideal location for robots to handle transportation tasks, as it ensures minimal interference between automated guided vehicles (AGV) and human activities. A previous study developed a ceiling mobile robot called HanGrawler 2. It can travel at a high speed of 1.0 m/s to compete with ground vehicles. However, it occasionally fails during high-speed travel. This study aims to improve the reliability of starting, accelerating, and traveling at high speed. Optical motion capture is used to observe the crawler behavior of HanGrawler 2. The observation of the crawler behavior revealed that the crawler moves on an inflated trajectory during the high-speed movement. In addition, the experimental results show that the collision is not caused by the inflation, but by the push-in timing. The reliability of high-speed travel was improved by installing an encoder and optimizing the push-in timing in accordance with speed fluctuations.

The Young’s modulus of abrasive and the material to be cut will have different influences on the cutting performance of the abrasive suspension jet (ASJ). It is found that the relative ratio of their Young’s modulus seems to show a better law on cutting performance of ASJ. In this paper, the concept of relative Young’s modulus was proposed, the influence of relative Young’s modulus on cutting performance of ASJ was explored, and the experiment of the influence of relative Young’s modulus on the kerf depth and surface roughness of ASJ was carried out. The results showed that the kerf depth increases with the increase of relative Young’s modulus. When the value is larger than 1, the density of the abrasive is the main factor affecting the kerf depth. When the value is smaller than 1, the Young’s modulus of the abrasive is the main factor affecting the kerf depth. The surface quality is divided into three degrees according to roughness. When the relative Young’s modulus is smaller than 1.5, it is a poor erosion degree. When the relative Young’s modulus is between 1.5 and 4, it is the best quality degree. When the relative Young’s modulus is larger than 4, it is an over erosion degree.