Fatigue cracks have been observed in the boiler water wall tubes of pulverized coal-fired power plants in high-temperature sulfide corrosive environments, and there is concern that thermal fatigue cracks will increase and propagate as the power output of pulverized coal-fired power plants increases to support the massive introduction of variable renewable energy. Therefore, we confirmed the corrosion fatigue characteristics of water wall tube material by fatigue tests in a high-temperature sulfide corrosive environments simulating the inside of the boiler. The corrosion environments were gas condition A, in which iron sulfides mainly occur, gas condition B, in which iron sulfides and oxides mainly occur, and gas condition C, in which iron oxides mainly occur. Note that water vapor was not added due to equipment restrictions. A best-fit curve (regression line) from the corrosion fatigue test results showed that the number of failure cycles (the number of cycles in which the stress range during the test decreased by 25% from the maximum value) was smaller for gas conditions A and B (sulfide corrosion atmosphere) compared to gas condition C (oxide corrosion atmosphere) for the same strain amplitude (calculated from the stroke of the fatigue equipment). We believe that the decrease in the number of failure cycles under gas conditions A and B (sulfidic corrosive environment) is due to the corrosion pits on the specimen surface, which are the starting point of fatigue cracks.

As concerns over climate change grow and large-scale introduction of variable renewable energy is expected in many countries, the importance of energy storage systems is more strongly recognized than ever before. While batteries have been one of the most widely preferred storage methods, the use of thermal storage technology is also beginning to attract attention. Thermal storage has a lower installation cost than electricity storage, but its cycle efficiency is poor, so it is expected that the two options will be used complementarily in energy systems. In this study, we used a technology selection model based on linear programming to quantitatively evaluate the economic value of thermal storage in a situation in which Japan aims to achieve zero energy-related CO₂ emissions by 2050. As a result, it was shown that if the cost of thermal storage exceeds 10,000 yen/kWh in 2050, compared to the assumed cost of lithium-ion batteries of 15,000 yen/kWh, its feasibility is lost, but if the cost falls below 5,000 yen/kWh, a large amount of thermal storage systems will be introduced in the optimal solution. It was also shown that cycle efficiency largely influences the value of thermal storage systems. These results suggest that with continued technological development to improve costs and cycle efficiency, thermal storage technology can make a significant contribution to stable supply in future power systems.

This paper describes a waste-heat recovery and power-generation system based on a thermo-electric module (TEM) for a water-cooled diesel engine using a carbon-neutral fuel such as biodiesel. The system integrates a heat exchanger for the engine exhaust gas, a TEM and a power-conversion circuit using maximum power point tracking control and a DC-DC converter. The power generated by the system was used to charge a 12 V lead-acid battery. The results indicated that during continuous engine operation, the TEM voltage decreased almost linearly with increasing output current. Simultaneously, as the current increased, the temperature difference between opposing surfaces of the TEM decreased due to the Peltier effect. Consequently, the maximum electric power output from the TEM during power generation was about 60 to 70% of that calculated based on the measured open-circuit voltage. Regardless of the engine operating conditions, the battery was steadily charged because the TEM output power was maintained at a maximum by the control circuit. An evaluation of the circuit performance during power generation showed that the power utilization efficiency, i.e., the ratio of the circuit input power to the maximum output power of the TEM, was around 88 %. In addition, the power conversion efficiency, i.e., the ratio of the circuit output power to the input power, was about 91%. When considering the internal resistance of the conductor wire in P_uti, these values are similar to those previously determined using a DC power supply to simulate the TEM output power.

Japan Atomic Energy Agency is developing an integrated evaluation tool as a design system named ARKADIA to achieve the innovative design of an advanced nuclear reactor with safety and economy for a sustainable carbon-free energy source. ARKADIA consists of three sub-systems: the Enhanced and AI-aided optimization System (EAS), the Virtual plant Life System (VLS), and the Knowledge Management System (KMS). In the first phase of development by 2023, ARKADIA-Design for design study, ARKADIA-Safety for safety assessment, and ARKADIA-KMS for knowledge-base are being developed individually. From 2024, they have been integrated into one system of ARKADIA within five years. This paper focuses on the ARKADIA-Design and the development status of the optimized design evaluation procedure, which is specified by the module combination, in the fields of the core and design and the plant structure design, as well as the maintenance schedule planning process are described as achievements in the first phase. In the evaluation procedures, the design optimization process using the Bayesian optimization algorithm to deliver the candidate of the optimized design specifications of the core or plant structure is implemented first and the performance evaluation process is done consecutively to confirm the performances of the core and the plant structure with the candidate specifications using numerical analysis methods with the coupling technology of the modules (numerical analysis codes) in VLS.

The objective of this study is to evaluate a shear modulus of cylindrical honeycomb core structures with various core sizes and curvatures. Honeycomb core structures exhibit high rigidity only in the out-of-plane direction and cannot effectively support multidirectional loads. Especially for rotating machinery including vehicle tires, the structures are required to support radial loads and also shear loads generated by torque under acceleration and deceleration. The cylindrical honeycomb core structures are a potential solution for applications to rotating machinery, as they feature hexagonal cells arranged radially to support radial loads during rotation. Given the necessity to elucidate the mechanical properties for practical applications, this study quantitatively evaluates the relationship between the geometry and shear modulus of the cylindrical honeycomb core structures by using finite element analysis and experiment. In the experiment, paper-made specimens of the cylindrical honeycomb core structures were mounted and tested on the experimental devices converting translational displacement to rotational displacement via a slider-crank mechanism. As for the structural analysis, the experimental conditions were reproduced by applying rotational displacements to the cylindrical honeycomb core structures and measuring the corresponding reaction forces. The material properties used in the analysis were derived from compression tests of the paper used in the experiments. The experimental and numerical results indicated that as the core size increased, the shear modulus decreased, similar to the conventional flat honeycomb core structures, and the shear modulus on the outer periphery while inner periphery was fixed was smaller than that on the inner periphery while outer periphery was fixed. Additionally, as the inner diameter increased and approached the outer diameter, the shear modulus at the outer and inner peripheries ultimately converged to that of a flat honeycomb core structure with a geometry equivalent to the outer periphery of the cylindrical core structures.

Effects of lift-off were investigated in thickness measurement of steel plates using electromagnetic acoustic transducers (EMATs) for shear wave. In power plants, steel mills and chemical plants, inner surfaces of tanks and pipes are exposed to severe environments, such as corrosive fluids, elevated temperature and high pressure, which may cause internal corrosion and thinning of tank and pipe walls, potentially leading to leaks, reduced efficiency, environmental pollution and serious accidents. Nondestructive thickness measurement is then necessary, and ultrasonic method is promising. However, deposits on outer surfaces create lift-off, hindering the use of piezoelectric transducers. EMATs are suitable for this situation, which can generate and detect ultrasonic waves through electromagnetic interaction without direct contact. In this study, we suggest EMATs with E-shaped cores and butterfly coils, instead of conventional one which consists of magnets and racetrack coil. Assuming application to heat exchanger tubes, the height of EMAT was limited to 20mm, and the effective area to 10mm square. Using numerical analysis, we refined the EMATs by enhancing the magnetic flux density in the thickness direction and the eddy current density. Thickness measurement of steel plate was executed to explore allowable lift-off of each EMAT. Since the analytical results showed that placing steel core on the effective area of the coil reduces eddy current density, we replaced the bottom part of steel core for tapered magnet. The allowable lift-off could be improved up to 6mm. Finally, we calculated the errors in thickness measurements due to lift-off, showing that the errors were generally less than approximately 1%.

High-temperature heat pumps represent a pivotal technology in the pursuit of decarbonizing industrial process heating with the utmost efficiency. Steam serves as the energy carrier for many industrial systems, making steam supply heat pumps as a promising approach for efficient decarbonization. An existing heat pump-based steam supply system with a supply steam temperature of 135°C or higher consists of the following 3 units; a heat pump unit with the mixture of R245fa and R134a, a flash tank unit, and a steam compressor unit. However, recent developments in refrigerants for higher applications have increased the technology options for the system configuration of steam supply heat pump. Specifically, it will be possible to supply steam at a level of 150°C, which could not be achieved with conventional refrigerants such as R245fa and R134a due to the critical temperature constraints. In this paper, a thermal and economic model for a steam supply heat pump system is developed based on the test results with the existing system. The model is applied to analyze the change in COP (coefficient of performance) and LCOH (levelized cost of heat) when changing to new refrigerants under the condition of 150°C steam supply. As a result, we clarify the couple of changing the refrigerant form the conventional R245fa to R1336mzz(Z) or R601 and removing the steam compressor can improve the COP and also reduce the LCOH.

This paper proposes a power assist control system for an inverted pendulum-type luggage transport support vehicle for stair climbing. Due to the rapid growth of the e-commerce industry, the volume of parcel deliveries has increased significantly. Fully automated parcel delivery is still challenging because it must deal with uneven terrain, stairs, and numerous moving obstacles. Therefore, the development of delivery support technology that supports human labor in staircases is desired. Two-wheeled inverted pendulum vehicles are small and highly maneuverable, can turn in narrow spaces, and can operate at the same speed as humans. Some works have proposed the use of two-wheeled vehicles that can be operated in environments with steps and stairs for supporting luggage transport. In the conventional method, fixed admittance control is used to assist human tasks with stair environments. However, the fixed controller makes it difficult to realize appropriate assistance in uneven environments including stairs that have strong nonlinearity. Therefore, this study proposes a control system using variable admittance control based on the estimation of human motion intentions for the two-wheeled vehicle. In addition, the proposed method includes a method to realize power assist that takes the variation of load mass into account, which has been overlooked in previous studies. The effectiveness of the proposed method has been demonstrated with an actual vehicle on a staircase.

In this study, we propose a multi-finger robotic hand with an iris mechanism that positions the blades of the hand, with fingers extending perpendicular to the blades attached to the blade tips, using a swing mechanism external to the iris mechanism. A single actuator drives the hand, which can concentrically grasp objects at multiple points while maintaining a regular polygonal shape around the entire circumference. The proposed structure can use the same mechanism to realize a hand with an arbitrary number of blades. Furthermore, the gears can be arranged in a planar configuration within the iris mechanism, thereby enabling adjustments to the grasping torque and speed by changing the gear ratio. This study examines the appropriate number of fingers for this iris multi-finger robotic hand, along with the cross-sectional shape of those fingers, according to the object to be grasped. We perform a geometric analysis of the relation between the rotational angle of the blades and the sizes of graspable objects, considering both the circumferential multi-point grasping of cylindrical objects and the multi-point pinching of rectangular objects. By comparing the analysis results of these different grasping methods, we consider how differences in the number of fingers and their cross-sectional shapes affect the size of graspable objects. The findings provide specific guidelines on the selection of an appropriate iris multi-finger robotic hand configuration for specific target objects.

Industrial vehicles such as construction machineries are exposed to severe vibration during use, which can cause structural damage. Currently, vibration endurance testing for non-strengthen members such as doors and covers, requires the assembly of the vehicle to accurately reproduce vibration, which involves significant labor and cost. On the other hand, real time hybrid testing (RTHT), which combines real time numerical simulation and vibration testing, are expected to reduce the cost of endurance testing. In some past studies, RTHT has been used for vibration tests of large structures, such as factory piping systems and bridge piers. These studies have indicated that the application of RTHT is limited to large structures because it could be difficult to apply it to lighter structures whose natural frequencies are higher. Therefore, a trial to develop vibration reproduction system for light structure have been investigated by simulation, based on some previous studies. RTHT has been applied experimentally to a structural sample composed of frame and door, and shows fairly good performance to reproduce vibration of door using a voice coil motor (VCM), which is compact and capable. This paper describes the results of RTHT to reproduce the vibration of non-strengthen members. In this study, RTHT is applied to a structural sample consisting of a frame and a door using some VCMs to successfully reproduce door vibration.

To achieve high-efficiency production, it is essential to develop accurate production plans and engage in continuous on-site improvements. In recent years, with the diversification of customer preferences, there has been an increasing demand for customized products. In the case of customized products, the working time can vary significantly depending on the model and specifications, even for the same process. Therefore, to improve the accuracy of the production plan, it is necessary to identify the attributes that cause variation and set standard working times. Furthermore, to extract improvement points in an environment with few expert workers, it is necessary to quantify the experience and know-how of exerting workers. In this paper, we propose an approach to integrate and analyze 4M information (huMan, Machine, Material, Method) from MES (Manufacturing Execution System), cameras, and sensors. We develop technology to accurately estimate standard working time for each process and a technology to automatically extract improvement points. The experimental results for the manual assembly process of customized products show that the accuracy of standard working time can be improved by 34%. Additionally, we confirmed that this technology can extract 85% of the work improvement points extracted by expert workers.

Designers aim to create designs that resonate with users, the consumers. However, there is often a gap between the sensory and emotional “words” expressed by users and the “words” understood by designers. To address this issue, we propose a method called “Language-based engineering” to reflect the meanings users seek in designs accurately. Using the packaging design of golf gloves as an example, we conducted a survey on six sensory words (I want to pick up, novel, visible, cool, cute, luxurious) to gather user feedback. We analyzed the relationship between user ratings and design elements using Quantification Theory Type I and created a database of these relationships. Furthermore, we converted the sensory word ratings into aspiration levels using the satisficing trade-off method and proposed a method to determine the combination of design elements that satisfy these desired levels as a multi-objective optimization problem. We conducted trade-off analyses on all 30 patterns of the six sensory words to identify the trade-off relationships based on users’ impressions of the packaging design. Additionally, we presented design examples and guidelines that align with users’ sensibilities by combining design elements that meet the aspiration levels.

Human affects and emotions are reflected in own eyes and metaphorized as impressions of the eyes such as “Eyes are smiling/not smiling.” Especially, when human has strongly interest or highly motivation, the metaphor is “The eyes are twinkling,” and others are fascinated and attracted to such twinkling eyes. Therefore, it is expected that it will lead to the investigation of factors that fascinate humans or the development of social robots and interfaces that attract humans by reproducing the twinkling eyes using an engineering approach. In this study, we proposed a twinkling eyes expression method that focuses on the reflection on the eyeball surface. This method simulates the specular reflection by superimposing a self-shadow on the pupil as a pseudo self-image. Furthermore, we developed a twinkling eyes interface by applying the proposed method to the pupil response system that has been developed. This interface can express the pupil response and the shade of self-shadow depending on the distance between the interface and the talker. The communication experiments were conducted under conditions with or without a self-shadow and with or without pupil dilation. The results demonstrated that the developed interface was effective, especially for male.

To enhance the water quality in stratified reservoirs in summer, a novel air-lifting tower for destratifying water has been deployed since the 2010s in Japan. Compared to conventional water mixing systems that intermittently diffuse air into water bodies to induce water circulation, this air-lifting tower is equipped with nozzles that diffuse air continuously. Simulations using the newly developed system have shown that it is more efficient than conventional systems for increasing the flow rate of water. However, despite the potential benefits of the new system, empirical evaluations are scarce because of limited implementation in reservoirs. Here we present the results of field experiments designed to evaluate the performance of new air-lifting towers that were installed in 2012 as upgrades to conventional air-lifting systems in Yamaguchi Regulating Reservoir in Fukuoka Prefecture. The experiment utilized four air-lifting towers with different diameters (0.5 m, 1.0 m) and lengths (4.0 m, 8.0 m), and water flow velocity was measured at their bottom intakes and near the water surface where the emitted bubble plumes ascend. The data facilitated an estimation of the volume of water flowing into the bottom intakes and rising up to the reservoir surface. Finally, the data were compared with predictions of a previous study, and it was found that they generally corroborated each other.

In this study, as part of the development of a generic track structure design method, a method for verifying the fatigue life of rails on curves was investigated. To determine the design force for verifying the fatigue life of rails on curves, the lateral force during a vehicle run was estimated by the wheel / lateral force estimation formula by varying various parameters such as the curve radius. Taking a curve segment 800 m > R ≥ 600 m as an example, it was assumed that curves of the same extension existed for each curve radius and superelevation, and the probability frequency distribution of the variable lateral force coefficient was determined. Then, all curves on all lines laid by a certain operator were classified into three curve categories, (i) R ≥ 800 m, (ii) 800 m > R ≥ 600 m and (iii) 600 m > R. The total curve length was classified into each category, and the probability of occurrence of the lateral force was determined. When the mean and standard deviation coefficient of variation of the lateral force coefficient was calculated for the results, it was 0.25 for (i) R ≥ 800 m, 0.30 for (ii) 800 m > R ≥ 600 m and 0.35 for (iii) 600 m > R. Then, methods for estimating the bending stress at the bottom of the rail under lateral force, which is the response value, were investigated. A FEM model of both rail tracks was constructed considering vertical and horizontal bending and torsional bending, nonlinearity of the fastening systems, and lateral force on the high and low rails. The results of the analysis using this model confirmed that the bending stresses at the bottom of the rails can be estimated to be within 10 % accuracy at the bottom of the rails during vehicle passage on the service line.

This paper proposes frictional dampers as new absorbers for landing legs of reusable launch vehicle. At first benefits of frictional dampers compared with other mechanism is discussed. Next characteristics of a certain frictional damper are investigated by drop-weight tests. Landing legs of certain reusable vehicle using the frictional dampers are designed based on the drop-weight test results. At last the design of the legs and frictional dampers are verified by drop tests of the whole vehicle. The test results of damper stroke are different from estimation based on rigid body, and modification considering elasticity of the vehicle improves the estimation.