Search

Origami is a traditional Japanese craft that is based on the folding of the designed structure and can be widely used by industry. Origami folding is not a difficult task for human hands; however, folding by robot hands is such a challenge. In this paper, we suggest a novel approach for designing the origami-performing robotic systems. The main idea of the proposed method is to simulate the forming crease lines in origami models and folding behavior of a sheet of paper by robot end-effectors. The simulation approach becomes the main option in the real-world related with a robotic activity. Our investigation results show that many design parameters of a robot such as geometrical and topological, shape and configuration of the robotic arms, type of forces and their distributions, and others can be defined by the simulation of the folding origami structures. It means that the results of the simulation can be used as a basis of the final robot design without a series of experimental tests. Problems of the numerical simulation, including paper material structure, simulation origami model, the distribution and values of the applying forces, and others are considered carefully. The results of the design process of the robotic system based on the simulation of origami crease forming confirm our idea to use simulation approach with LS-DYNA solver to build the origami-performing robot for complex origami structures. The origami model “Star” was taken as an example to demonstrate the method for the different types of the creases in origami.

Periodic structures are known to have specific frequency ranges called band gaps, where the transmission of elastic waves is suppressed. Research on band gap formation in mechanical structures has recently gained considerable attention, and there is a need for analytically versatile and cost-effective methods to address the band gap effect in various structural elements. In this paper, we investigate band gap characteristics and frequency response analysis of periodic beams using an energy method that allows for easy extension to plates and shells. In using the energy method for vibration problems with non-uniform systems like periodic structures, the selection of admissible functions becomes crucial, and the treatment of boundary and connecting conditions is also essential. This study focuses on those subjects by employing elastic beams with a periodic structure of unit cells; a unit cell consists of two parts with different structural characteristics. Since band gaps can be determined by dispersion curves, the analytical process for obtaining dispersion curves by the energy method is described in detail in this paper. Three treatments to express a unit cell and three admissible functions are tested. Calculated dispersion curves are compared with those obtained by the differential quadrature method (DQM), which is widely used in band gap research. The frequency response analysis is also carried out using the energy method and compared with the results by finite element analysis using ANSYS and experimental results, and good agreement has been demonstrated among them. No resonant peaks exist in the frequency range corresponding to the band gap in the dispersion curves for both experimental and numerical results, and this shows that the formation of the band gap in the actual periodic beam and the validity of the numerical approach using the energy method for dispersion analysis and FRF calculation of periodic beams.

This paper examines the applicability of the hot spot method using a small wireless system and the effect of data loss during data communication on fatigue evaluation. Fatigue failure is a phenomenon that progresses due to repeated loading. Since it is not practical to monitor all structural members, it is important to monitor the structural integrity of damage-prone areas. In addition, due to cost and installation space constraints, the use of inexpensive, compact IoT devices is effective. Compact wireless fatigue monitoring methods using strain gauges have been proposed, and systems based on the nominal stress method have been considered. However, there are cases where the nominal stress cannot be defined due to the complex structure of the weldment, making fatigue evaluation difficult. In such cases, the hot spot method, which measures the structural stress concentration, is effective. However, the application of the hot spot method to a small wireless monitoring system has not been sufficiently studied. In this paper, a small wireless monitoring system was fabricated and its applicability to fatigue evaluation of welded joints was confirmed. From the test results, it was confirmed that the data loss was caused by the data communication condition of the small wireless system and the accumulated fatigue damage degree was underestimated. It is necessary to select an appropriate small wireless monitoring system considering the information on fatigue and stress state required for the target structure. This selection should consider the trade-off between transmitting raw data and performing edge processing before transmission. The former provides richer information but can cause data loss and high-power consumption due to the large volume of transmission. On the other hand, the latter reduces data loss and saves power, but can provide less information.

As an aftermath of the Fukushima nuclear accident and its implications for public acceptance of nuclear energy, the nuclear industry has begun to seriously rethink and improve the safety strategies of nuclear power plants. The beyond-design-basis external events, such as the earthquake and tsunami in Fukushima nuclear accident, may lead to an extreme accident which may lead to the failure of the traditional strategies. In the recent decade, the concept of FLEX strategies has been accepted in the nuclear engineering community and attracted a large number of researchers to investigate it for nuclear accident mitigation. The development of FLEX strategies is divided into two steps. One is an uncertainty study of system response, especially the safety injection system. The other is training and testing of machine learning (ML)-based FLEX strategies and to verify the effectiveness of ML algorithms in the development of FLEX strategies for nuclear power plants. This paper focuses on first step uncertainty study of the nuclear accidents by using statistical algorithm to generate a database of incidents and system responses. The conclusion of this paper is useful for analyzing the characteristic of typical nuclear accidents and benefits to the FLEX strategy development, which will be focused on in the near future.

This paper proposed a novel cooling system that combines a phase change material (PCM) with an indirect dry cooling system to enhance exhaust steam condensation of the Rankine cycle for a coal-fired power plant (CFPP), especially in high ambient temperature conditions. A PCM heat storage tank (PCMHST) is embedded in series between the natural draft dry cooling tower (NDDCT) and condenser to realize peak and valley shifting of cooling capacity, and RT35HC is selected as the PCM. During discharging process of the PCMHST, RT35HC is chilled by low-temperature circulating water; during charging process of the PCMHST, the circulating water is cooled in the PCMHST and NDDCT. This paper first reveals the effects of cooling load distribution in the novel cooling system on the CFPP operating economy during charging and discharging process. In addition, the PCMHST in series before the tower can reduce the circulating water temperature more efficiently than that in series behind the tower. Results show that integrating a PCMHST can reduce the coal consumption of the CFPP by 5325 kg within a complete back pressure regulation process.

In excavation by hydraulic excavators, automation of excavation is effective in reducing the burden on operators and improving work efficiency. This paper focuses on automatic control of the weight of excavated soil. To control the weight of excavated soil, a soil dynamic model is required. However, the interaction between soil and bucket is complex and computationally expensive, making it unsuitable for real-time control. In this paper, we propose a dynamic model of excavation based on the experimental data of the weight of excavated soil and the workload done by the bucket. In addition, a differential equation that expresses the relationship between the data is derived. Based on the proposed model, a control method is also proposed to achieve the reference weight of excavated soil by changing the dragging length, assuming that the power done by the bucket during excavation is equivalent to the swept volume. Furthermore, we evaluate the effectiveness of the proposed method by excavating under several soil conditions using the proposed method.

In a previous paper, a closed-loop mechanism represented by successive excitation processes was introduced to explain the reason for the nonlinearity-induced transition from unstable response to stable vibration. In one of the processes, the dynamic pressure is excited by the centrifugal force. Based on this, this paper investigates a vibration reduction method that introduces a circumferential flow whose velocity relative to the rotor is negative. This flow is predicted to weaken the excitation effect of the centrifugal force on the dynamic pressure. An improved semi-analytical model is developed for conservative estimate of the vibration reduction effect by considering the boundary condition that the relative flow velocity vanishes at the cylindrical wall. Because there arise circumferential flow velocity terms in various governing equations, the influences of the terms on the response are examined, thereby identifying important mechanism that contributes to the vibration reduction. The present semi-analytical method is helpful for this identification as well as computationally efficient analysis.

When railway vehicles run on sharp curves, the coefficient of friction (COF) between the outer rail and the leading-outside wheel flange of a bogie is an important value related to problems such as wheel/rail severe wear, squeak noise arising from wheel/rail contact, and running safety against flange-climb derailment. In general, it is difficult to grasp the actual state of COF, which changes from moment to moment during commercial operations. From the viewpoint of running safety and maintenance, it is desirable to detect curved tracks with relatively high COF from the entire service line. The monitoring bogie, which can measure wheel/rail contact forces during commercial operations, has realized a long-term observation of wheel/rail contact forces. For further applications of the monitoring bogie, the simulation-based estimation method of COF at the wheel flange have been proposed in the author’s previous paper. Furthermore, an investigation based on roller-rig tests have been conducted. However, the probability of the flange wear progress cannot be determined only by COF at the wheel flange, and other factors should be involved. The wear number is used to assess rolling contact fatigue and wheel/rail wear progress. In the present paper, on the basis of a multi-body dynamics simulation model of the roller-rig equipment, the difference of the wear number among four lubrication conditions on the bogie is clarified. The estimation method of COF is extended to estimate the wear number simultaneously. The extended method is applied to the roller-rig test and the wear number is estimated. The estimated wear number shows qualitative agreement with the amount of wear debris, which is observed in the roller-rig test conducted in previous research.

Spacecraft are exposed to acoustic loads during flights to space by launch vehicles. The endurance of spacecraft structure is verified by a ground acoustic test specified in test standard documents of the aerospace community. These standard documents require the execution of ground acoustic tests in a reverberant chamber on the assumption that it can generate a diffuse sound field which is normally defined as “completely isotropic and equal probability of energy flow in all directions”. However, in the space development industry and related studies, the directions of incident sounds which cause non-diffuseness has not been identified by the experimental comparison with the theoretical values of an ideal diffuse sound field (e.g. reverberation times, homogeneity of sound pressures and spatial correlation functions). Therefore, the conventional standard documents do not clearly specify the quantitative requirements regarding the directional properties of sound fields inside reverberant chambers. To specify the quantitative requirement on the directional properties of sounds, this paper focused on calculating the degree of isotropy of a sound field by the direct measurement of directional properties of sound waves as angular spectra. In this paper, the method to obtain the angular spectrum based on the theory of the expansion of the plane wave into spherical harmonics by using a spherical microphone array was firstly combined with the existing formula of the isotropy indicator, which allowed us to determine the frequency range when we apply the combined method to sound fields. The method to determine the applicable frequency range was demonstrated and the process of obtaining the angular spectrum and isotropy indicator was verified by numerical simulation. Finally, the combined method was applied to the sound field in the reverberant chamber of JAXA 1600m3 acoustic test facility.

This paper discusses a new identification method for a linear single-degree-of-freedom system that uses a Gaussian random response and is based on the maximum likelihood estimation (MLE) method. The likelihood function of the proposed method consists of the analytical solution of the Fokker–Planck equation. We have already published a paper on theoretical and numerical considerations. However, in that study, the experimental verification of the proposed identification method was not performed. Therefore, in this study, we conduct an experimental verification of the proposed identification method. First, the identification algorithm is formulated in a spring-mass-damper system subjected to white noise excitation by a moving foundation to correspond to the actual experimental setup. A preliminary experiment in terms of the excitation source is conducted using a vibration speaker. In addition, the experimental modal analysis is performed to confirm the validity of the vibratory system. The fundamental operation test of the identification method is performed using the actual experimental random response data, and a dependency survey of the number of samples is conducted. From the results, the convergence behaviors of the estimation value are observed with an increasing number of samples in the spring constant and the ratio between the diffusion coefficient and the damping constant. In addition, benchmark tests are conducted using the half–power method (HPM) based on spectral analysis and the auto-regressive method (ARM) based on time–series analysis. In the case of spring constant estimation, the behaviors of the estimation value that converge to the true value are observed in all identification methods. In the ratio between the diffusion coefficient and damping constant, the behavior of the estimation value that converges to the true value is observed only in the proposed identification method.

A class of optimization problems which are formulated using solutions to boundary value problems of partial differential equations (PDEs) as equality constraints is called PDE-constrained optimization problems. Specifically, when the variable in the optimization problem is given by a function defined in the PDE, the problems are classified as PDE-constrained non-parametric optimization problems. The topology and shape optimization problems of density and domain variation type, respectively, are included in this category. This paper is written to convey the idea of the author who worked on this topic for over 30 year, unlike the usual review papers. After showing real images of the problems, the author’s theoretical image is introduced. Based on the theoretical image, basic questions about the structure of the problems when viewed as a function optimization problem are proposed. The author’s answers to these basic questions are presented in the next section. Based on the understanding, some numerical results in which anxious phenomena are observed are presented and their causes are discussed. The expectation of applying the basic theory to real-world problems is presented using examples. Applying the theory of shape optimization problem of domain variation type, a problem finding the optimum shape of a sole in sports shoes that maximizes the stability under keeping the ideal cushioning is introduced. Applying the theory of topology optimization problem of density variation type, a problem identifying the muscle activity in a tongue during swallowing is explained. From these examples, it is concluded that PDE-constrained non-parametric optimization problems can be effectively applied to real-world.

Establishing sustainable and economical pathways for the deployment of variable renewable energy (VRE) is essential for reducing greenhouse gas emissions and increasing energy security. However, due to VRE power output fluctuations, high shares of VRE are associated with increases in surplus power generation, which increases the cost of power supply. This paper examines the effects of power fluctuation mitigation measures on the integration of high shares of VRE in power supply systems. The paper takes a systematic approach to evaluate the effects of the geographical distribution of VRE locations, the increase in transmission capacity, and the introduction of large-scale battery storage while increasing the VRE share. The methodology used in this analysis is a linear programming-based power supply mix model which was developed to optimize installed capacities and operation patterns of a power supply system with geographically distributed VRE locations by minimizing the total cost of power supply. The developed methodology is applied to the power supply system of Hokkaido, Japan, as a case study. The results demonstrate that VRE shares of up to 40 % can be achieved by geographically distributing the VRE locations with no increase in the total cost of the power supply. This is because the geographical distribution of VRE locations suppresses the increase in surplus power generation. Further, achieving 40 % to 60 % VRE shares only requires an increase in the power transmission capacity. However, for higher VRE shares from 60 % to 80 %, a combination of the geographical distribution of VRE locations, transmission capacity increase, and the introduction of power storage are required to effectively minimize the amount of surplus power generated.

In the present investigation, a method of overlaying models of isogeometric analysis (IGA) is proposed. We call this technique s-version IGA (S-IGA). In S-IGA, a local IGA model representing the localized features of structures such as holes, cracks, notches, etc. is superimposed on a global IGA model that represents the structure as a whole. Although IGA is known as a highly accurate analysis methodology which has a potential to replace the finite element method, building analysis models for IGA is a quite troublesome task. That is because IGA is based on B-Spline or NURBS volume represented by the multiplication of B-Spline or NURBS basis functions in three-natural coordinates for three-dimensional space. In this paper, S-IGA is proposed for the purpose of reducing analysis model generation task in IGA and is critically examined for its accuracy. Discussions are extended to a modeling of mixed mode crack problem.

Non-contact detection methods based on computer vision are widely used in industrial production. When collecting images, different light source schemes are often used to meet the detection requirements of different objects. The image styles collected under different lighting scenes are diverse, and the image semantic segmentation model trained with a specific dataset has unsatisfactory performance when processing images in different domain. This paper designs a mechanical part image semantic segmentation model based on domain adaptation and GAN. In order to verify the effectiveness of the proposed method, this paper collects and labels some gear images and constructs a dataset. The first step is to train encode-decoder structure with an enhanced memory module with source dataset to achieve semantic segmentation, then the dataset is transformed into a target domain by GAN, and finally the image semantic segmentation model is fine-tuned with the target dataset. The advantage is that since the cycle-consistency loss is used to constrain the spatial structure of the reconstructed image, the two datasets can share a semantic segmentation label. Experiments show that the image semantic segmentation method based on domain adaptation has achieved good results on different styles of gear parts image datasets, and achieved a pixel accuracy of 94.1%.

This paper presents a method for reducing the computational time required to solve the shape optimization problem of a hyperelastic body. In a previous report, the authors presented a method for applying a model order reduction technique based on the Karhunen-Loève expansion (KLE) in a shape optimization problem of a linear elastic body. In the investigated case, we applied this method solely to solve a linear state determination problem. In this paper, we show that this idea is applicable not only to the adjoint problem and to the problems seeking domain variations through the H1 gradient method, but also to a nonlinear state determination problem. From a theoretical perspective, we assume that the solutions to these three problems for the domain obtained using a conventional shape optimization method at a prescribed number of iterations are random variables, and we apply the idea of KLE to such variables using the solutions obtained in the steps prior to the prescribed number of iterations through a conventional method as a sampling dataset. The orthonormal bases of KLE are defined as the eigenfunctions of the eigenvalue problems obtained as the optimality conditions of the variance maximization problems for the random variables. In the case of a nonlinear state determination problem, we use the incremental solutions instead of the solutions themselves. When using the finite element method to solve the three problems, these eigenfunctions become eigenvectors. Using the eigenvectors as the orthonormal bases in KLE, we define transformations from the coordinates of KLE to the physical coordinates and construct small problems for the variables of KLE. Our proposal is to solve the small problems instead of the original ones. The feasibility of the proposed method is illustrated by testing the numerical schemes using an end mean compliance minimization problem of a three-dimensional hyper elastic body.

This paper describes the vibration damping characteristics of elevator ropes acted on by air. High-rise buildings sometimes resonate during earthquakes, and the elevator ropes in the building may swing significantly as a result. The vibration analysis of the elevator ropes is required because the swing of the ropes may interfere with the subsequent operation. However, there is no sufficient study on the damping force of air acting on the elevator rope, which is necessary for vibration analysis. We established a damping theory to estimate the damping force and loss factor of air acting on a vibrating rope, and conducted principle experiments using silicon rope and piano wire. Theoretically, the vibrating rope was considered as a cylindrical object placed in a flow field, and the drag force derived in the field of fluid mechanics was considered as the damping force exerted by the air on the rope. In particular, the vibration damping of ropes by air can be classified into two major types: viscous damping—proportional to the 1.5th-power of the vibration velocity—and vortex damping—proportional to the square of the velocity. Additionally, the loss factor of the vibrating rope was evaluated from the displacement transfer function of the excitation amplitude and the rope vibration amplitude. As the loss factor exhibited large values for large-amplitude vibrations of the rope, the loss factor was influenced by the vibration velocity of the rope. Moreover, the damping theory presented in this paper can be applied to nonlinear rope vibrations as well.

This paper describes the optimum tuning of damped Helmholtz silencers. In this study, Helmholtz resonators are used as silencers that suppress acoustic resonance in host acoustic fields. Side branch silencers and Helmholtz silencers are commonly known as a type of vibration absorber; however, damped silencers have not been thoroughly studied thus far. Therefore, prior to this paper, we reported the optimum tuning of damped side branch silencers using modal analysis and two fixed point method. In this paper, we additionally describe the optimum tuning of damped Helmholtz silencers in a similar fashion as in our previous paper. The resonance mechanism of Helmholtz silencers is different from that of side branch silencers. The coupled vibration between the host acoustic field and Helmholtz silencer was theoretically analyzed using modal analysis in this study. An equivalent discrete model was obtained using the equations of motion using modal coordinate systems. Using the equivalent discrete model, the open-end correction of the neck of the Helmholtz silencer was considered, and the number of degrees of freedom of the equivalent discrete model was reduced to two to derive optimum tuning conditions using the two fixed point method. The optimum natural frequency ratio and loss factor of the Helmholtz silencer were derived using the vibration model with two degrees of freedom. The theoretical analysis was validated through simulations and experiments.

This paper proposes a novel DVA (Dynamic Vibration Absorber) consisting of a ball-like mass embedded in a spherical viscoelastic material to meet practical demands for the multi-modal and multi-axis vibration reduction against elastic vibrations of structures. This DVA is called eMDVA (embedded Mass DVA) here, and the embedded mass can vibrate every direction in the viscoelastic medium. The unique concept of the eMDVA is inspired by the damping effect caused by passengers on railway vehicles. This paper describes a basic configuration of the eMDVA and some numerical studies using finite element (FE) vibration analysis to design the eMDVA. From the numerical investigation, it has been found that the natural frequency of a single-mass eMDVA can be controlled by changing the combination of the sizes of the viscoelastic sphere and the embedded mass. The frequency response function (FRF) of the acceleration of the embedded mass versus excitation force has a dominant single peak corresponding to one of the natural frequencies. These results indicate that the proposed eMDVA is suitable as a DVA, and it can be designed to tune the target vibration frequencies of host structures. As a more realistic analysis, numerical investigation for the thin and long plate-like host structure (a 1:10 scale model of the floor structure of a railway vehicle) was conducted, and multi-modal vibration reduction has been observed by applying the eMDVA consisting of two sets of viscoelastic spheres and embedded masses with different sizes. From these numerical investigations, it has been shown that the proposed eMDVA has promising potential as a multi-modal damper for elastic vibrations.

This paper presents a new structural design framework that incorporates the concept of topology optimization and genetic algorithms to improve the manufacturability and structural robustness of the optimal structure. The level set function is employed as a topological design variable to obtain clear structural boundaries, and the manufacturability of the structure is mathematically defined based on the manufacturing directions and the fictitious heat fluxes. To gain the manufacturable structure design, the optimization problem is formulated to find both the optimal shape of the structure and the optimal directions of the adjustable manufacturing tools. A level set-based optimization regarding manufacturability has been studied in previous papers, however, due to the influence of the manufacturing directions, the objective value tends to be captured in local optima as the structure becomes more complex. To cope with this issue, we decided to adapt a heuristic based approach, genetic algorithm, to the optimization method. Simultaneously, to reduce the computation time, we applied Design of Experiments for the initial population of the genetic algorithm. The initial population of the manufacturing directions is installed using Latin Hypercube sampling for both a good representation and computational efficiency. To demonstrate the effectiveness of the proposed method, several design examples are provided, and the differences from the optimal solution, derived by a previous gradient-based optimization scheme, are mentioned.

In most dynamic vibration absorbers (DVAs) used in practical applications, polymeric materials that have both restoring capabilities and damping effects are used instead of coil springs as spring elements. It is known that the damping force for such polymeric materials has hysteretic characteristics and varies in proportion to the relative displacement rather than the relative velocity between objects. This paper proposes an optimal design formula for a double-mass hysteretically damped DVA with two masses connected in series. For the design of the DVA in this study, the stability maximization criterion, which attenuates the free-vibration response of the primary system in the shortest time, was adopted. It was found that the optimal design expression for installing the series-type double-mass DVA on an undamped primary system can be expressed by a very simple formula. The maximized stability, which determines the speed of vibration convergence, of the double-mass DVA was 1.7 times that of the corresponding single-mass DVA. When there is damping in the primary system, the optimal design condition for the DVA cannot be expressed with such a simple formula, but an equation to calculate it is presented in this paper. The equation can be easily solved numerically, and the results show that the stability of the system is further increased compared to the undamped primary system.

Annular Blowout Preventer (BOP) is the core device for snubbing service in gas wells. The wellhead can be sealed by operating the BOP. Rubber core of annular BOP is the main part of the sealing process, and its failure will cause blowout accidents and endanger the operators. Rubber core failure is mainly caused by the serious wear and fracturing damage, compared with oil well, during the snubbing service of the gas well, there is dry friction between rubber core and tubing, which is more prone to rubber core wear. Based on the Yeoh constitutive model, this paper fits the material parameters through the data measured by the rubber tensile experiment, and establishes the sealing performance evaluation model of the annular BOP based on the theory of rubber hyperelastic, large deformation theory and dynamic sealing theory. Meanwhile, compare it with the rubber core failure cases which used in field to verify the accuracy of the model. Based on these, this paper studies the influence of piston stroke, tubing size, friction coefficient between rubber core and tubing, rubber core attrition rate on sealing performance, and fitting the relationship between tubing size and piston stroke. The results show that: properly increasing the piston stroke by 2 to 3 mm will help to improve the sealing performance; when the tubing size is smaller, the rubber core is deformed too much while the seal process completed, which is easy to cause the rubber core to fracturing; friction coefficient between rubber core and tubing has no significant effect on static sealing performance; the friction coefficient less than 0.2 has little effect on the dynamic sealing performance; when the friction coefficient exceeds 0.4, the dynamic sealing performance is reduced significantly; when the wear of rubber core is within 10 mm, the sealing performance gradually decreases, but the sealing requirements can still be met. When it is more than 10 mm, it cannot meet the sealing requirements of 35 MPa. The research work in this paper has certain guiding significance for the design, selection and use of the rubber core of annular BOP.

A model-based controller is effective for highly accurate and fast control of a robot. The dynamics model is derived from its equations of motion, and the minimum set of the dynamics parameters are experimentally identified. However, the experimental data includes the influence of both noise and un-modeled dynamics, the obtained model will be one of approximated solutions. From these considerations, the approximated model has to well represent the robot dynamics around the reference motion, and for high accuracy, new data needs to be added every time an experiment is conducted, which causes a lot of computation. The authors have proposed stochastic identification method to obtain suitable parameters for control system design. However, in this method, because of computational complexity of weighted least square mean, it is difficult to add new motion data. In this paper, we propose a sequentially updating parameter identification method based on statistical properties of the conventional method. By synthesizing the covariance of the parameter error, the nominal parameters are updated. The proposed method is performed to experiments using a planar 3-link manipulator, and its effectiveness is evaluated.

The reliability of turbine blades and vanes of modern high temperature gas turbines is assured by turbine blade cooling technologies. Among the various cooling methods, film cooling has been a key technology to ensure the long-term operation of turbine blades and vanes that are exposed to hot gas-path flows. Therefore, many papers have been published aiming at the improvement of film cooling effectiveness by optimization of film cooling hole geometries. Although the turbulence intensity of the mainstream generated in the gas turbine combustor is very high and may reduce the film cooling effect on the turbine vane and blade, there are few papers investigating quantitatively the effect of the mainstream turbulence on the film cooling. For this reason, the influence of mainstream turbulence intensity on film cooling effectiveness was investigated with an active turbulence generator equipped with electric-motor driven propellers for circular and fan-shaped film cooling holes. Spatial distributions of the turbulent mixing field between turbulent mainstream and film coolant jet were measured with quantitative measurement methods, such as PIV and LIF. As a result, it was revealed that when the mainstream turbulence is high the counter-rotating vortex pair is weakened, the film cooling air spreads in the span-wise direction and the lateral-averaged film cooling effectiveness decreases about 10%.

This paper addresses the compensation of the vibration caused by flow disturbance, which is the pressure fluctuation of compressed air supplied to a pneumatic anti-vibration apparatus (AVA). The pressure of the compressed air changes periodically during compression process. For this reason, proportional-integral-sinusoidal (PIS) control is utilized so that the flow disturbance can be attenuated. In this control method, a Sinusoidal compensator (S compensator) provides a periodic control input signal whose frequency is the same as the frequency of the disturbance. However, when the PIS control is applied to the vibration attenuation for the pneumatic AVA, there arise two practical problems that have to be solved. First, the vibration of an isolated table occurs in transient state at the start-up/shut-down of the S compensator. This is due to the switching of the S compensator. To deal with the first practical problem, soft switching approach is presented. Second, high-frequency vibration is observed in steady state after the S compensator is started up. Since the source of the high-frequency vibration is the phase-lag of the S compensator, a phase-lead type PIS compensator is employed. By using this compensator, the phase margin of a control system can be increased and the high-frequency vibration can be attenuated. Moreover, in this paper, vibration transmissibility is analyzed so as to investigate effects of the PIS control on the isolation from floor vibration. It is shown that 1) when the PIS control is used, anti-resonance and resonance are excited and 2) there is a trade-off between flow disturbance attenuation and vibration transmissibility reduction.

This paper describes a novel method for blind source separation using multilayer neural networks when an audio signal has been recorded in a room with reverberation or with moving signal sources. In conventional applications, speech-recognition specialists can identify the signal from a specific speaker in a recording of many speakers by analyzing a spectrogram of the recording. The spectrogram is a visual representation of the time series of frequency spectra of a target signal. To use multilayer neural networks for a similar classification task, the proposed method begins by preparing a spectrogram of a mixed signal using the short-time Fourier transform, which is then regarded as a visual object. The spectrogram is then divided into small time-frequency segments and each segment is classified into a class of the corresponding signal source by the multilayer neural networks. After that, an inverse short-time Fourier transform is employed to extract the separated signals. The paper also evaluates the separation performance of this classification algorithm. With the transformation of the blind source separation problem into a classification problem, multilayer neural network classifiers can be used, and they do not require information about the mixing environment, or statistical characteristics of the target signals, or multiple microphones. Simulated tests indicate that the proposed method achieves good separation performance under conditions with reverberation or moving signal sources. The proposed method may be adapted for separating signals from unknown convolutive mixtures and time-varying systems.

The moon images have been in recent years employed as a referential light source for in-orbit radiometric characterization of on-board radiometer in spacecraft. The irradiance obtained by the integration of the radiance of moon pixels is compared to the referential irradiance that derives from the astrophysical model, and the comparison result includes the gain characteristics of radiometer. In addition to this radiometric purpose, the limb between moon disk and deep space is also an ideal edge in optical aspect. The edge response of radiometer obtained in the limb includes the characteristics of MTF (modulation transfer function) and straylight. In this paper, in-orbit straylight characterization and correction of SGLI (Second Generation Global Imager) radiometer that is flying on JAXA's remote sensing satellite "SHIKISAI" is reported. It is shown that LSF (line spread function) measured in the moon limb is effective trend monitor of radiometer's geometric property in orbit and is also a key to verify the validity of straylight correction model implemented in the ground data processing system. This paper proposes the methodology that constructs PSF (point spread function) by LSFs in two orthogonal direction and corrects straylight of not only the Moon but the earth image by using the constructed PSF.

In the present paper, the multiple applications of high-density pulsed electric current (HDPEC) with current densities between 100 and 200 A/mm2 made fatigue crack growth (FCG) slow, in which a current density of more than 150 A/mm2 provided high efficiency to refrain from FCG. The application of multiple HDPECs under the current density of 200 A/mm2 showed a significantly reduced fatigue crack growth rate (FCGR). The fracture surfaces without the HDPEC effect showed signs of FCG along the crystal structure elongated in the rolling direction, on the other hand, a series of welded joints were formed at the crack tips due to the effect of applying multiple HDPECs, which provided different patterns of FCG leading to crack arrest. When initial HDPEC is applied in a short crack under the same HDPEC condition, it shows partial welding at the crack tip, while more concentrated welding at the crack tip by moderate Joule-heating is shown as fatigue progresses and the fatigue crack length increases. Elemental analysis by energy-dispersive X-ray spectroscopy and crystallographic analysis by electron backscatter diffraction also provided the microstructure features at the crack tip subjected to the application of multiple HDPECs. It is most efficient to perform in a short crack with multiple applications, and applying multiple manners as the crack progresses contributes to the accumulated improvement of fatigue properties by slowing the FCGR based on each application.

In this paper, a series of molecular dynamics (MD) simulations was performed to identify the high-temperature tensile properties of nanostructured polycrystalline CoCrCuFeNi high entropy alloy (HEA). The mechanism of strength reduction at elevated temperatures was understood through nanostructure observation such as phase transformation and dislocation evolution in MD simulation. The applicability of this material from room temperature to 1200 ℃ as a high-temperature use of structural material was identified. The stress-strain curve was found to gradually decrease ultimate tensile strength and yield stress as the temperature applied to the material increases. The elastic modulus decreases rapidly at slightly high temperatures but decreases gradually as it goes to the extremely high temperatures. Face-centered cubic (FCC)→hexagonal close-packed (HCP) phase transformation, which is energetic process between atoms due to tensile loading, was revealed. From the vicinity of the yield stress to the quasi-plastic regime, it competitively contributes to tensile properties between FCC→HCP phase transformation and growth of voids. In dislocation analysis, the typical partial dislocations such as perfect, Shockley, stair-rod and others were measured, in which Shockley and stair-rod partial dislocations show its characteristics that contribute to tensile properties. The results in this study contribute to understanding the high-temperature applicability of nanostructured polycrystalline CoCrCuFeNi HEA.

Progressive damage behavior of woven composite structure is simulated, based on decoupled multi-scale damage analysis to consider microscopic woven structure. Since woven composites have complex microstructure, it is difficult to predict their damage behavior by only experimental approaches. Evaluating damage process is important for the assessment of safety, and numerical method of simulating damage behavior is demanded. In this paper, decoupled multi-scale analysis method was adopted. The constitutive law used in analysis of structural member scale (macroscopic scale) was identified by analysis of weave-structure scale (microscopic scale) and two-scale simultaneous analyses are no longer necessary. In microscopic scale, representative unit cell (RUC) of woven structure was considered, and in-plane periodicity was assumed to reflect inhomogeneity caused by woven structure. Microscopic analysis was carried out to identify the constitutive law which is used in the macroscopic analysis. Transverse crack of fiber bundle was modeled using enhanced continuum damage mechanics (ECDM) model. Fiber/matrix interface debonding was also modeled by cohesive zone model (CZM). In the macroscopic scale, structural member was modeled. Macroscopic analysis was carried out to investigate initial damage occurrence location and damage process. Damage progress was modeled by stiffness degradation, using CDM model and microscopic analysis results were reflected to determination of macroscopic damage variables. Four-point bending test of macroscopic specimen was carried out for validation of the analysis. Damage observation showed the macroscopic analysis effectively simulated damage occurrence and propagation. Localization analysis was then carried out to investigate damage behavior of woven structure, reflecting deformation history of macroscopic initial damage occurrence location to microscopic analysis. By comparing the analysis to cross-section observation, initial damage simulation showed good agreements with experiment.

Skilled technicians primarily use manual tools to maintain the geometry and surface conditions of railcar wheels. To ensure efficient wheel maintenance, the development of an automated inspection system is required. Herein, an inspection method for railcar wheels is proposed based on the assessment of wheel tread dimensions and surface conditions and investigation results of the method are presented. The parameters of wheel tread dimensions and surface conditions are considered because they are crucial for railway operation safety and manually inspecting them requires a large workforce. To improve the efficiency of the system, a combined inspection method through laser measurement and machine vision is used, both the techniques compensate for each other’s shortcomings. The experiments are conducted using laser sensors and machine vision techniques, including defect detection using AI model based on YOLOv5, as well as image data captured via a digital video camera to obtain high-accuracy automatic measurements and determine the feasibility of such measurements. Additionally, the measurement accuracy of the proposed method is verified based on experiments on sample wheel having wheel tread surface defects. In this paper, sample wheel including various wheel tread surface defects is used.

This study modeled the behavior of pedestrians who avoids moving obstacles, especially other pedestrians or bicycles are approaching, which are common in daily life. In our previous research, we modeled the behavior of a pedestrian when they avoided a static obstacle, such as a parked car, parked bicycle, or poles on a roadside. However, pedestrian motion might be affected by movement of an obstacle or its size. Accurate behavior modeling of pedestrians should include these factors. Typically, previous studies have treated pedestrian motion as a deterministic model. However, human behavior should be considered as stochastic motion even though deviations, such as walking speed, are not very large when considering local motion. When pedestrians avoid an obstacle, their motion or behavior is determined by their own individual factors, such as age, gender, etc. In this paper, we focus on the effect of obstacle speed and relative distance. To model pedestrian behavior during avoidance of a moving obstacle, walking loci were measured at first. Then, we derived and evaluated differences in avoidance behavior with respect to the obstacle speed. One result showed that the speed of a moving obstacle is one of the most important factors as the pedestrian begins avoidance, that is, the time factor that is determined by the relative speed and the relative distance affects the timing of avoidance behavior of a pedestrian.

Different from a gas expander, there is a phase change from liquid to vapor called the flash inside the two-phase expander. But, same with the gas expander, only the vapor phase expands and pushes the rotation of the expander to output power in the two-phase expander. It means that the amount of the vapor is increased during the expansion by the flash. Obviously, the flash rate of the working fluid from liquid to vapor is critical to the expansion power recovery. In this paper, an experiment system with water as the working fluid was established to study the heat transfer characteristics of flash evaporation during the two-phase expansion process. The flash was controlled inside a flash chamber, under the initial temperature from 100 ℃ to 130 ℃, and the initial liquid level height from 110 mm to 175 mm. The pressure evolution of the flash evaporation was limited by the pressure regulating valve. The obtained results showed that the level of the instant liquid superheat was positively associated with the flash rate of evaporation. The temperature drop rate behaved negatively correlated with the instant superheat, while higher the instant superheat resulted in faster liquid temperature reduction. Both the liquid-vapor heat transfer coefficient and the instant flash rate were increased with the increase of instant superheat. Generally, the peak of instant superheats occurred earlier than that of instant flash rate and instant heat transfer coefficient. The instant superheat level was increased and affected by the initial temperature and initial liquid level height.

This paper presents a case study of the design, fabrication, and evaluation of an automotive rear-frame model made of variable axial composites (VAC), using a tailored fiber placement (TFP) technique. Conventionally, the design of a three-dimensional complex VAC structure places significant demands on mechanical engineering expertise (for anisotropic structural design) and on man-hours (for fiber-path CAD). The proposed methods facilitate the design of complex VAC structures with significantly reduced manpower requirements. A computational design method, anisotropic topology optimization, was used to create the base design. The fiber paths on the preform surfaces were generated using a Turing pattern algorithm (based on optimized fiber orientation distributions) subsequent to designing developable three-dimensional surfaces to fill the interior of the target structure. The preforms were fabricated using a computer numerical control (CNC) embroidery machine by stitching the raw fiber tow onto the base fabric in accordance with the generated fiber path data. After stacking the preforms in the mold, they were formed using vacuum-assisted resin-transfer molding (VaRTM). The static stiffness of the prototype was evaluated experimentally, and the results were compared with numerical simulations. This study demonstrates the potential for achieving further weight reduction in large-scale 3D structures by combining innovative computational design techniques with advanced fabrication methods.

After the Great East Japan earthquake, measures for beyond design basis events have become more important. For a component, mitigation of an influence of a failure on its safety performance is required in addition to prevention of the failure. These kinds of measures are reduced the risk of safety performance defined as multiplication of failure frequency and failure consequence regarding impact on safety performance. One of safety analyses regarding such measures is fragility analysis. However, the existing fragility is represented using failure probability, and does not take into account the failure consequence. In this paper, for the purpose of more rational fragility analysis, we propose a new concept of performance-based fragility incorporating failure consequence, which represents the risk of safety performance degradation. In addition, to present the effectiveness, the proposed fragility is quantified by applying to a piping system subjected to excessive earthquakes which is a key issue of beyond design basis event. A piping system subjected to excessive earthquake can fail by ratchet, fatigue, collapse, and break. These failure modes have different occurrence conditions and lead to different consequences about core cooling performance. After the analyses on occurrence probability and failure consequence on each failure modes, the proposed fragility is calculated as the multiplication of them.

This paper presents a vibration analysis using the substructure elimination and binding method for vibration systems governed by a one-dimensional wave equation. Coupled vibration analysis has been developed, and the component mode synthesis method is commonly used for dynamic analysis. In the component mode synthesis method, each substructure is formulated, and then coupling between substructures is considered. The component mode synthesis method is a type of modal analysis, and the coupled vibration between vibration systems with different governing equations can be easily formulated. The component mode synthesis method has the problem of increasing the degrees of freedom when the entire structure is complicated and needs to be divided into many substructures. Therefore, the first author proposed methods to analyze the entire vibration system without dividing it into substructures, for example, when a structure is installed inside an acoustic field or when acoustic fields with different media are in contact. These methods have the advantage that only the eigenmodes of the entire acoustic field are used. However, the calculation accuracy has been found to deteriorate because of the discontinuities or non-smooth points in sound pressure and particle displacement at the interface between air and a structure or between two acoustic fields. This study proposed a method to set a virtual elimination region at the interface and then bind the two ends of the virtual elimination region to solve this problem. The analytical model for this method was presented, and a wave equation was derived in this study. Modal analysis was applied to the wave equation. The simulations revealed that the density and bulk modulus of the virtual elimination region should be zero and that its length should be set at 2.5–3.5 times the wavelength of the highest eigenmode of the entire vibration system. To investigate the advantage of low DOFs, the simulation results obtained using the proposed method were compared with those obtained using the component mode synthesis method based on the exact solutions.

Japan Atomic Energy Agency is developing extraction chromatography technology to recover MA(III) from spent nuclear fuel. Developments in the extraction chromatography system especially focusing on safety and stable operation are required for practical application of the technology. This paper discusses the main tasks that have to be challenged preferentially based on achievements obtained by previous studies and potential MA(III) recovery process flow. For the safety assessment, removal of fine particles, optimization in adsorbent for a reduction in pressure drop of the column, degradation behavior of the adsorbents, and recycling of the adsorbents are topics for development. Enhancement in resistance against radiation and acid of material in pump and development of automated operation system is required to maintain product quality during long time operation. Those studies are carried out simultaneously in a research project of 2019-2024, and new technologies such as a filter with porous media, porous adsorbents for low-pressure drop column, used adsorbent recycling, radiation resistant pump, and automated valve switching system using online analysis are developed in this project. A demonstration of the total system with a large-scale apparatus will be carried out at the end of the project.

A sodium-cooled fast reactor (SFR) considers adopting 3-dimensional seismic isolation devices for withstanding seismic loads not only horizontal but also vertical direction. A seismic isolation device consists of a laminated rubber bearing and horizontal oil dampers for horizontal direction, coned disc springs and vertical oil dampers for vertical direction, respectively. And also, in order to make horizontal and vertical motion independent, sliding elements are adopted. In order to investigate the performance of each component and the feasibility of integrated system for SFR, the experiments such as load-displacement tests, vibrating tests, etc., to each component of seismic isolation devices and seismic response analysis are carried out. As those experimental results, the mechanical characteristics of each component and the devices are grasped, then it is demonstrated that components and devices have expected performances to reduce the seismic loading within the design range. As the analytical results of seismic response, it is indicated that this 3-dimesional seismic isolation device and system can reduce the seismic response on horizontal and vertical simultaneously. Based on the analytical studies and experimental results, the feasibility of newly developed 3-dimensional seismic isolation system is obtained and the prospect of practical application of 3D seismic isolation system for fast reactor is implied in this paper.

An importance for risk management has come to be re-recognized in Japan after the accident of the Fukushima Daiichi nuclear power plants. A Probabilistic Risk Assessment (PRA) fulfills a significantly important role in the framework of the risk management. Technical adequacy of PRA model and high quality of data are required in order to utilize PRA for such risk-informed activities. Therefore, Japanese utilities launched the project for enhancing the quality of PRA models and are upgrading PRA models to comply with international standards. Chugoku Electric Power Company (Chugoku) is also upgrading the internal events at power PRA model including both the level 1 and level 2 (except the source term analysis) and enhancing PRA quality in order to utilize risk insight for improving nuclear safety. The aim of the PRA upgrade is to reflect international state-of-the-practice approaches and to meet ASME/ANS PRA standard (ASME/ANS 2013) requirements (Capability Category II). Our PRA upgrading process is divided into 3 phases: “Phase I”, “Phase II” and “As-is”. This paper reports the detail of PRA upgrade implemented in Phase I and Phase II such as initiating event refinement, accident sequence re-evaluation, detailed fault tree (FT) analyses, modeling severe accident measures and updating human reliability analysis (HRA).

Aircraft impact analysis is needed for safety assessment of nuclear power plants. One of the items which should be analyzed for aircraft impact is physical damage to a reinforced concrete (RC) building and this can be estimated by numerical simulation. In the simulation, a simulation model which has been validated by some experimental data needs to be established. In 1988, an aircraft impact test using an F4 Phantom fighter was conducted at the Sandia National Laboratories in the US and a lot of important experimental data were measured. The numerical simulation results for this aircraft impact test are also introduced in this paper. The relationship between the thickness and the deceleration of the aircraft model is studied and then the differences in the deceleration between the simulation and test results are discussed. The relationship between the failure strain and the destruction modes of the aircraft and the target in the simulation are also studied, and then the differences between the simulation and test results are discussed as well. Through these parametric simulations, the validations of the aircraft and the target model are demonstrated. In evaluating the physical damage area inside the buildings, or discussing the necessary numbers of RC walls until the impacting aircraft stops, it is important to estimate whether the RC walls are perforated by an impacting aircraft. Besides numerical simulations, some empirical equations to estimate them are reported. One of them is the UKAEA equation. This equation estimates a dynamic punching strength of a RC wall. It is determined whether an impacting aircraft perforates a RC wall by comparing the dynamic punching strength with the dynamic impact load of the aircraft. In this paper, several aircraft impact simulations using the established aircraft model with different RC wall thicknesses are conducted. Dynamic punching strength of these RC walls are measured in each simulation. The obtained values in the simulations are compared with the estimated values by the UKAEA equation. The differences between them are investigated and the reasons of these differences are discussed.

Six-pole active magnetic bearings (AMBs) have fewer poles than the more common eight-pole AMBs making it possible for them to be miniaturized and used in the development of small motors. In this paper, we propose a novel control method for the six-pole AMB, which switches between three-coil and five-coil modes. The three-coil mode excites three coils to generate a suspension force and reduce power consumption. In contrast, the five-coil mode excites five coils and can generate a larger maximum force than the three-coil mode. By switching between the two modes, it is possible to realize both an increase in the maximum suspension force and a reduction in power consumption. This paper derives the coil currents in the three- and five-coil modes, and introduces a switching method between them. The proposed method is verified with a test rig, and results show that the proposed method enables stable levitation with a lower current limit compared with the method that uses the three-coil mode alone. Moreover, a start-up procedure with a low current limit is proposed and experimentally verified.

The derailment coefficient, which is calculated based on the wheel-rail contact forces, indicates the running safety of a railway vehicle with respect to flange climb derailment. The value of the derailment coefficient changes constantly due to numerous factors associated with the vehicle and track conditions while the vehicle runs on a service line. Therefore, it is desirable to monitor the state of the wheel/rail contact in order to ensure the running safety. Recently, a new monitoring bogie, which can measure the derailment coefficient during commercial operations, has been developed and introduced into some service lines. Large-scale data have been collected by this monitoring bogie. In this paper, the temporal subtraction analysis is carried out for preparing appropriate plan for reducing the derailment coefficient based on these data. In the analysis, the vehicle running position is important for accurate calculation of the difference between two waveforms. However, the vehicle running position contains errors because of the accumulated error of integral calculation of the vehicle velocity. The present paper proposes a method which modifies the running position along track so that the two waveforms are well matched. The proposed method is based on DP matching, and the waveforms of the track irregularity of twist estimated by the monitoring bogie are used in the method. After DP matching, an example of temporal subtraction analysis of the derailment coefficient between two periods is performed. Finally, by using the long-term measurements acquired by the monitoring bogie, the monthly variation of the derailment coefficient for a certain spot on the track is shown as a practical example.

This paper describes the fabrication of a metal matrix piezoelectric composite using surface-oxidized nickel fiber as the internal electrode. Piezoelectric ceramics, which have excellent piezoelectric properties, are widely used as energy conversion materials. However, their application is limited by their brittleness. To solve this problem, a metal-core piezoelectric ceramic fiber/aluminum composite has been developed by using the interphase forming/bonding method. Here, a piezoelectric ceramic is reinforced by embedding it in an aluminum matrix, and this process causes the piezoelectric ceramic to have better mechanical properties than a bulk ceramic. However, this composite has some serious disadvantages considering that it cannot be designed to possess arbitrary piezoelectric properties because the metal-core piezoelectric fiber is formed by the extrusion method, so that the sectional shape cannot be arbitrarily changed. In this paper, a metal matrix piezoelectric composite using a surface-oxidized nickel fiber as the internal electrode is proposed. This composite provides design flexibility in that its piezoelectric property can be changed by varying the size and materials of the composite. The fabrication procedure of this composite consists of three steps: oxidation of the internal electrode, molding and sintering of the piezoelectric ceramic, and embedding of the piezoelectric ceramic into the metal matrix. The proposed composite is fabricated under optimized oxidizing and molding conditions. An impact test is performed on the fabricated composite, and the output voltage is measured. The test results indicate that the composite is capable of generating piezoelectricity. Overall, the study results substantiate the validity of the concept and fabricating method of the proposed composite.

Fires in nuclear fuel fabrication and reprocessing plants can cause the rupture of the glove box (GB) containment with a risk of dispersion of plutonium dioxide (PuO2) within the facility. Fire safety analyses need to assess the resulting radiological consequences to strengthen the appropriate prevention and protection measures in these plants. To this end, the French Institute for Radiation Protection and Nuclear Safety (IRSN), in partnership with the Japanese Nuclear Regulation Authority (NRA), has carried out since 2019 a research project that aims at assessing the airborne release fraction (ARF) of PuO2 involved in GB fires. This project, named FIGARO (Fires Involving Glove boxes with Aerosol Release Occurrences) follows a progressive approach, that has started with small and medium-scale analytical tests to study separately the various mechanisms involved in the GB fires and the PuO2 airborne release and will end with large-scale GB fire tests to transpose and validate the analytical works for realistic assessments of the ARF of PuO2 both in open and confined conditions. This project also includes the development of a GB fire model in the IRSN SYLVIA and CALIF3S-ISIS softwares and its validation. In addition to presenting the FIGARO program, this paper provides its first outcomes.

Tornadoes represent a substantial hazard to nuclear power plant infrastructures, particularly in terms of potential damage caused by wind-borne debris. A comprehensive understanding of the three-dimensional flow structure of tornadoes is essential to assess such hazards. Ward-type tornado-like vortex (TLV) generators have been used to provide experimental insight into the influence of wind loading on potential debris and infrastructures. However, these experiments address challenges arising from highly turbulent and three-dimensional flow structures. Recent advancements in the area of TLVs have seen a surge in numerical analyses. Three-dimensional simulations are capable of reproducing the flow field, although the computational requirements appear to be prohibitive for hazard assessment applications. A numerically proficient model that could reproduce the velocity profile from TLV generators is highly regarded. To achieve this, axisymmetric modeling of TLV in a Ward-type chamber is attempted. This paper uses the VorTECH facility at Texas Tech University, a large-scale Ward-type TLV generator, as a reference case. Through a series of simulations, the critical role of the mesh resolution in the development of the boundary layer is revealed. The axisymmetric model underestimated the experimentally observed pressure at the core center while showing good agreement for the core width and velocity distribution for both single-cell and two-cell TLV flow fields. Through alterations in the domain configuration, including the influence of the inflow, floor roughness, and the presence of a honeycomb rectifier, the effect of such factors on the velocity profiles near the touchdown region was identified. The boundary layer development by the inflow inside the confluence region, the floor roughness of the touchdown region, and flow resistance at the rectifier should be carefully discussed to develop a reproducible axisymmetric TLV model.

Japan Atomic Energy Agency (JAEA) is developing an artificial intelligence (AI) aided integrated digital system: “Advanced Reactor Knowledge- and AI-aided Design Integration Approach through the whole plant lifecycle (ARKADIA)”, to provide the best possible solutions for challenges arising during the design process, safety assessment, and operation of a nuclear plant over its life cycle. Until 2023, the platform for a common function and subsystems, namely ARKADIA-Design for design study, ARKADIA-Safety for safety assessment, and ARKADIA-knowledge management system (KMS) for the knowledge base, are separately being developed. This paper describes the development concepts of the platform, the progress of the application study of design optimization in ARKADIA-Design, the progress of optimization model development and optimization functionality based on AI technology in ARKADIA-Safety, and the structure of the knowledge base and application of AI technology to ARKADIA-KMS. In subsystems, necessary modules and process integration to obtain an optimal solution in a designated problem of plant design have been advanced. For further development, a strategy for unifying the subsystems with the AI-aided platform into one system, ARKADIA, and the extension of capabilities of the numerical analyses and evaluation technologies required for plant design until 2028 are presented.