Osaka Sangyo University

This study aimed to measure tritium (3H) concentrations in Thailand. Nationwide tap water samples were collected in July 2021. Rainwater samples were collected monthly during May–October 2020, April–October 2021, and February–March 2022 in Chonburi province and in Chiang Mai province during July–November 2021, January 2022, and March–June 2022. The measurements of 3H activity concentrations were conducted by Osaka Sangyo University (OSU) and were compared with measurements by the Thailand Institute of Nuclear Technology (TINT). The results from OSU and TINT showed that 3H concentrations in tap water were matched in the ranged from 0.08 ± 0.03 to 0.28 ± 0.04 Bq L−1, while those in rainwater samples collected from Chonburi province and Chiang Mai province are also matched in the ranged from 0.11 ± 0.02 to 0.21 ± 0.03 Bq L−1 and 0.19 ± 0.02 to 0.57 ± 0.04 Bq L−1, respectively. Our measured result suggests that 3H concentration in tap water and rainwater shows a similar relation depending on latitude.

Highly realistic sound-field reproduction systems have been attracting attention owing to their ability to reproduce a sound field. These systems commonly use electrodynamic loudspeakers (EDLs) to construct sound images. The directivity of EDLs is broad, so the constructed sound images become diffused owing to the reverberation characteristics of the room. Therefore, sharp sound-image construction requires a large, complex system. As a more feasible approach, we focus on parametric array loudspeakers (PALs). The directivity of PALs is narrow, so the constructed sound image is sharp. Therefore, we propose a sound-field reproduction system that involves using a PAL to construct a sharp sound image and EDLs to reproduce the sensation of reverberation. To reproduce the sensation of reverberation, the early reflections of the target sound field are calculated using the mirror-image method, and virtual early reflections are produced. Thus, the sharpness of the sound image and the sensation of reverberation can be easily controlled to reproduce a highly realistic sound field. We conducted objective evaluation experiments to verify the effectiveness of the proposed system.

Given the connection between the feet and the brain via sensory receptors, it is believed that improving the sensitivity of the toes and the soles of the feet could help prevent injuries and improve performance in athletes and prevent falls and improve cognitive function in the elderly. Associate Professor Ryota Tsuyuguchi was a coach of the Osaka Sangyo University Athletic Association Men’s Basketball Team, which enabled him to observe, first-hand, the importance of feet to performance. This prompted him to consider the wider implications of improving sensation in toes and feet. At the Faculty of Sports and Health Sciences at Osaka Sangyo University in Japan, Tsuyuguchi and the team are conducting research to expand on the belief that training related to toe grip could enhance the benefits of exercise. Indeed, training interventions related to conscious toe grip might affect brain metabolism and brain nerve activity, helping to improve cognitive function. The researchers have studied most age sectors of society and found that the output of the motor association cortex in the frontal lobe was strengthened and the function of the A10 nerve nucleus was improved, which suggests that the prefrontal cortex was also affected. The researchers believe that the activation of mechanoreceptors on the soles of the feet will improve toe grip function to ensure support and safety. They also believe that moving the centre of gravity forward through training of toe grip will encourage autonomic posture adjustment through the spinal reflexes, which may also be an effective approach in the prevention of falls.

This study examines asymmetric supply chain competition between integrated and non-integrated supply chains under emission taxes when firms choose competition mode in the final goods market endogenously. We find that higher emission taxes may lead the non-integrated downstream firm to adopt aggressive pricing to induce its upstream firm to lower prices, leveling competition with an integrated one. When the non-integrated chain integrates, however, quantity contracts become dominant strategies, which might distort welfare under lower emission taxes if both environmental damage and product substitutability are sufficiently high. Our finding indicates the welfare-reducing effects of government interventions post-integration when emission tax policy and endogenous competition mode are relevant.

Glass cullet (GC) generated from the disposal of photovoltaic (PV) panels are typically landfilled, and effective GC utilization methods must be established for PV generation. In this study, alkali-activated material (AAM) mortars were prepared from the paste of fine blast-furnace slag powder, fly ash, and sodium orthosilicate (SO) and mixed with crushed sand and GC to investigate the potential use of GC as a fine aggregate in AAM. The replacement of crushed sand with GC did not considerably affect the flowability of the mortar, whereas the compressive strength decreased with the increasing GC replacement rates. Although expansion due to the alkali–silica reaction (ASR) was observed in mortars wherein GC replaced crushed sand, the expansion can be controlled by reducing the amount of mixed SO, autoclaving the GC, performing preleaching to remove the Si that causes the ASR, and replacing the blast-furnace slag with fly ash. By enforcing measures against the expansion, the possibility of using GC as fine aggregate is enhanced considerably, thus increasing the feasibility of continuous PV production.

In this paper, we propose a method for visualizing the influence of wind on sound propagating in a room where wind is blowing, and rating the degree of influence. Since non-uniform airflow affects sound propagation and gives time-variant characteristics to the transfer function, a method is needed to understand the influence of wind. Therefore we propose a method that measures impulse responses multiple times indoors, determines a similarity matrix between impulse responses, and visualizes it as a heatmap. We evaluate the proposed method in four types of average wind velocity (0.0 m/s, 2.7 m/s, 3.3 m/s, 3.9 m/s). The result of the evaluation showed that the greater the influence of the wind, the higher the value of diagonal elements of the similarity matrix than off-diagonal elements, and the tendency for diagonal elements to be emphasized. We also confirm that the rating based on the Frobenius norm of the similarity matrix takes a lower value as the influence of the wind is greater.

Unpleasant noise is a crucial problem, that we often face in daily life. One of such a problem is in the case of dental treatment. A dental instrumental noise that includes peaky components in the high-frequency band makes doctors and patients discomfort. To reduce discomfort, we proposed a method to mask unpleasant noise with a comfortable sound. The proposed method was automatically generating a comfortable cord progression. In previous subjective test results, it shows that degree of discomfort reduces. The remaining problem is that degree of comfort improves. This is due to the fact that the previous method utilizes the musical element of chord, but does not introduce the musical elements of melody and rhythm. Therefore, in this paper, we propose a new method to introduce the melody generation with automatic composition (AI composition) into the previous method based on the automatic generation of the chord progression. The proposed method automatically generates a chord progression to follow the peak frequency of dental treatment sounds and to add a melody following the chord progression with AI composition assistance tool to improve comfort and to design comfortable sound.

Among the various high-presence sound field reproduction technologies, we focus on wave field synthesis (WFS) using a loudspeaker array, as it can construct a virtual sound source (VSS) with few restrictions. A VSS using parametric array loudspeakers (PALs) can provide more accurate direction perception than VSS using electro-dynamic loudspeakers (EDLs) because PALs hold sharp directivity by utilizing ultrasounds. However, the distance perception tends to be degraded. We previously proposed a VSS construction based on WFS with hybrid control of an EDL and a PAL arrays. This method enhances distance perception by exploiting the difference in radiation characteristics between PALs and EDLs. However, the difference in frequency responses between PAL and EDL is noticeable to the listener when switching between them. In this paper, to enable more smooth transition of the EDL and PAL arrays, we propose a VSS construction method based on adaptive crossfade processing with EDL and PAL arrays. For an arbitrary VSS construction position, the coefficients of crossfade for each frequency are determined by an adaptive filter based on measured impulse responses of VSSs with EDL and PAL arrays. We demonstrated the effectiveness of the proposed method through evaluation experiments.

Shot peening (SP) and fine particle peening (FPP) were performed as post‐treatments on induction‐hardened and tempered AISI 4140 steels. Furthermore, the combined effects of surface characteristics including changes in surface morphology, compressive residual stress, and hardness on the fatigue limit were quantitatively examined. The surface characteristics of the prepared specimens were investigated using a laser and stereomicroscope, a micro‐Vickers hardness tester, and an X‐ray device for residual stress measurements. The rotating bending fatigue properties were also examined. FPP increased the fatigue limit of induction‐hardened and tempered steel samples by introducing compressive residual stress and increasing their surface hardness. Conversely, the fatigue limit of the steel treated with SP was lower than that of the electrochemically polished sample owing to the formation of large dents. The fatigue limits of post‐peened induction‐hardened and tempered steels can be estimated using a modified Goodman diagram considering changes in surface properties.

In this review, three technical processes were proposed for constructing a next-generation textile laundry system. The detergency experiments using artificially soiled fabrics and mechanical action test pieces were performed using a beaker-level equipment and a horizontal drum-type washer. The soiled fabrics were prepared using mainly three polyester fabrics with different structure as substrates, and carbon black, red clay, oleic acid, or stearic acid as a model contaminant. The detergency was evaluated from the change in the Kubelka–Munk function value of artificially soiled fabrics and the original fabric due to washing. The effects of artificially soiled fabrics by atmospheric pressure plasma jet treatment before washing, application of ultrasound as a mechanical action during washing, and rinsing by the fine bubble water after washing on detergency were discussed. Conclusively, combination of three techniques enabled particulate and oily soil to remove from polyester fabric at a level comparable to a drum-type washer with little fabric damage.

We consider a vertically related market, in which each downstream firm produces a differentiated product by assembling a key input produced by a common supplier and another input produced by a dedicated upstream firm. On the one hand, vertical integration has the advantage of inducing the common supplier to set a lower input price, but the disadvantage of reducing downstream firms' competitiveness in the downstream market. On the other hand, vertical separation has the advantage of increasing downstream firms' competitiveness in the downstream market but the disadvantage of inducing the common supplier to set a higher input price. Contrary to results of previous studies, we find that the existence of a common supplier can lead to vertical integration under Cournot competition, which emerges as a unique equilibrium when a common supplier adopts input discrimination. Although vertical integration is better for the individual firms, it reduces the total welfare. Even when the common supplier uses uniform input pricing, vertical integration also emerges in equilibrium.

The Mini 4WD AI competition executive committee of Japan Society for Fuzzy Theory and Intelligent Informatics has been organizing competitions for Mini 4WD AI vehicles equipped with microcomputers, sensors, motor drivers, etc., since around 2014. Maintaining a high average speed is crucial for cars, including Mini 4WD, to run fast on the course. Additionally, to further advance Mini 4WD AI research, it is important to present the design principles for vehicles that can achieve the fastest speed using engineering theory, calculation formulas, and numerical values. The purpose of this research is to clarify the theory of the driving performance of Mini 4WD based on automotive engineering theory and to design an AI system using the Profit Sharing method, a sequential experience reinforcement learning algorithm, and study the learning results. The results showed that changing the vehicle speed in stages can produce a learning effect that maintains a high speed. Furthermore, from the perspective of maneuverability, it was shown that improving the ability to re-accelerate after decelerating on a slope is necessary to enhance the average speed.

The objectives to extend the available range of pipe supports up to plastic region are below; one is to enlarge the loading capacity, and the other is to add damping to piping systems using the absorption effect of seismic energy due to the elastic-plastic hysteresis property. However, the pipe support design that balances these two functions is difficult. In this study, a design concept to achieve both of these functions is proposed and its feasibility is shown. First, the effectiveness of the elastic-plastic design with the allowable load for the existing elastic-plastic pipe supports was compared. The results showed that although an increase in loading capacity can be expected due to elastic-plastic pipe supports, the damping effect depends on the shape of the supports, so that damping due to plasticity cannot be expected much. To obtain sufficient damping effect, an additional design process is required to adjust the yield load for each support. Next, to overcome this drawback, an elastic-plastic pipe support with a hybrid structure of frame type structure and cantilever structure was proposed. The frame-type structure ensures pipe support and prevents excessive deformation of the piping, and the cantilever structure increases the damping effect. This proposed design makes it easy to optimize both functions.

In order to reduce the environmental impact, it will be important to make effective use of low-quality coarse aggregate to the extent that it satisfies the performance requirements of concrete. However, there are physical properties such as drying shrinkage and thermal expansion that cannot be captured by routine quality tests of coarse aggregate. In order to determine the drying shrinkage and thermal expansion coefficient of coarse aggregate, the authors have previously proposed a method to determine the length variation characteristics by directly attaching strain gauges to the coarse aggregate particles. In this study, we measured the temperature strain of low-quality coarse aggregate particles using strain gauges, which has not been clarified so far, and also investigated the method for calculating the coefficient of linear thermal expansion. As a result, it was clarified that even low-quality coarse aggregate particles can be measured by strain gauges to determine the temperature strain. It was also revealed that the coefficient of thermal expansion of low-quality coarse aggregate particles is not much different from that of normal-quality coarse aggregate particles, with no significant difference. Furthermore, it was found that the coefficient of linear thermal expansion of coarse aggregate particles can be roughly determined by using the test report attached to a commercially available strain gage. The calculated coefficient of thermal expansion of coarse aggregate particles by this method differs by a maximum of ±1 μ/°C from the exact coefficient of linear thermal expansion referring to quartz glass.

A railway wheel flat occurs when the wheel locks and slides along the rail, forming a white etching layer (WEL) just under the flat surface where rolling contact fatigue cracks often form that can propagate into the wheel and spall during service. This study comprehensively investigated the influencing factors on wheel crack propagation that lead to spalling. Experiments were conducted to test wheel specimens with WELs of various dimensions, and simulations were performed to evaluate the stresses near the WELs as well as the rate and direction of crack propagation.

Employing an overlapping generations model with endogenous education choice and corruption, we investigate how child labor and corruption influence human capital accumulation and development. We show that multiple steady states exist in the economy. One steady state has a high level of human capital, while the other has a low level of human capital. In the steady state with a low level of human capital, child labor and corruption exist, fertility and child mortality rates are high, and the welfare level is low. Conversely, in the steady state with a high level of human capital, child labor and corruption are diminished, fertility and child mortality rates are low, and welfare is high. In addition, we show that it is difficult to steer an economy away from a poverty trap with child labor and corruption because bureaucrats of the current generation are opposed to policy changes, such as the reinforcement of monitoring and penal regulations. However, we highlight the possibility for the government to develop the economy in the poverty trap by implementing an education policy, which is Pareto improving.

The surface morphology of silicon solar cells irradiated with KrF excimer laser pulses (λ = 248 nm, τ = 20 ns) was investigated below the experimentally observed melting threshold fluence (F th) of 0.47 J cm⁻² (±20%). At laser fluences of 0.23–0.48 J cm⁻² (equivalent to 0.49F th to 1.0F th), nanodot structures with a height and width of approximately 60–120 nm were periodically formed with an interdot spacing similar to the laser wavelength. The observed nanodot density (29 dots μm²) was higher than that previously obtained at longer wavelengths. Furthermore, crystallinity analysis by micro-Raman spectroscopy revealed a Raman shift of 519.56 cm⁻¹ after irradiation (N= 1500 pulses), compared with 518.27 cm⁻¹ prior to irradiation. A laser fluence of 0.41 J cm⁻² ( = 0.87F th) was found to induce compressive stress on the silicon solar cell surface.