In this study, the critical buckling temperature of a lattice sandwich panel was investigated by using FEM. In particular, the effects of geometric properties, for example a core height h, a core length L, and the number of cells N_c on the buckling temperature, were discussed. It is confirmed that the lattice sandwich panel also has the global and local buckling modes that are common in a latticed members, and a correction factor which includes the effect of the number of cells N_c is presented for estimating the global buckling temperature of the panel. Multiplying the analytical equation of the buckling temperature which was derived from the conventional homogenization method by the correction factor, the buckling temperature can be estimated with a good accuracy. On the other hand, the local buckling temperature can be estimated by considering the buckling behaviour of a small plate surrounded by the cells and supported by four corners.

This paper reports the deflection behavior of the sandwich panel with corrugated core of trapezoidal cross section. The size of the top and bottom plates were 200 mm square, and the height of the sandwich panel was fixed at 13.6 mm. The models for finite element method were created by taking into account the geometrical limitations of the corrugated core due to the space between both plates and the manufacturing condition. The four sides of the sandwich panel were rigidly fixed, and a uniformly distributed load was applied to the surface of the top plate. The deflection always became maximum at the center of the panel. The analysis was performed by changing the inclination angle of the trapezoidal patterns of the core. It was found that there is an inclination angle of the patterns at which the deflection of the sandwich panel becomes minimal. The deflection of the corrugated core itself increased with decrease in the inclination angle of the trapezoidal patterns. On the other hand, the shear stress developed in the plates and the core increased with decrease in the inclination angle, which had the effect of reducing the deflection of the sandwich panel. It was found that these synergistic effects cause the minimal inclination angle occur. Moreover, the anisotropy of deflection of the sandwich panel, which is the difference in the deflection depending on the selected two sides of the panel when the relative two sides are fixed and loaded, was investigated. It was found that the anisotropy of deflection also became smaller at the inclination angle of the trapezoidal patterns at which the deflection of the panel became minimal.

The purpose of this study is to clarify the effect of the tapered triangular tubes added to the four corners of a 2:1 rectangular nozzle on the flow characteristics and vortical structures of a rectangular jet. The angles of tapered triangular tubes were changed α = +6° and −6°. The mean bulk velocity U₀ from the nozzle exit was about 4.5 m/s. The Reynolds number Re (= U₀H/ν; ν, kinematic viscosity of air) of the jet was 9,000. In the case of the jet without tapered triangular tubes, the three–dimensional deformation of the vortex ring produces strong positive and negative vorticity around each axis and also increases the turbulent kinetic energy at the jet corners. The spread of the jet is larger than that of other jets. In the case of jet with divergent tapered triangular tubes with α = +6°, the local vorticity and turbulent kinetic energy increase at the corners of the jet were suppressed and the profile followed the jet shape. As a result, the jet becomes a circular jet shape until relatively downstream, and the jet spread was smaller than that of the other jets. On the other hand, in the case of the jet with convergent tapered triangular tubes with α = −6°, the jet maintains a relatively rectangular jet shape upstream due to the local increase in vorticity on the long side of the nozzle and the increase in turbulent kinetic energy along the nozzle shape. However, the overall spread of the jet is almost the same as that without the tapered triangle tubes due to the diffusion of the jet along the nozzle span length. Therefore, it is possible to change the flow characteristics and vortical structures of the rectangular jet by adding tapered triangular tubes with different angles.

In recent years, hydrogen has been attracting attention as a long-term energy storage that can absorb fluctuations of the output of variable renewable energy sources. While there are several hydrogen storage methods, hydrogen storage alloy is one of the most suitable methods for stationary hydrogen storage. Since hydrogen storage alloy’s characteristics of absorption and desorption heavily depends on operating temperature, temperature control is one of the critical issues in the design of the hydrogen storage alloy system. As a new method for controlling alloy’s temperature, the authors have developed the air heat exchanged hydrogen storage alloy system that is supplying an air temperature for hydrogen storage alloy. In this study, the year-round hydrogen balance and the heat input required for temperature control of this air heat exchanged hydrogen storage alloy system are simulated for an independent electric power utilization system using photovoltaic power generation with hydrogen energy storage system assuming arbitrary regions and electric power demand patterns in Japan. Based on the simulation results, the external heat input of the system was systematically evaluated, and the energy-saving performance of the alloy temperature control of the storage alloy system in each region and the feasibility of seasonal energy shift by the hydrogen storage system were evaluated. The results show that the air heat exchanged hydrogen storage alloy system is a highly energy-efficient system that can adjust the temperature using less energy than the heat of alloy chemical reaction heat regardless of the regional variation of temperature or type of electric demand pattern, although the amount of energy input varies depending on the region.

If pressurized water/water-vapor leaks from a heat transfer tube in a steam generator (SG) in a sodium-cooled fast reactor, the leakage forms high-velocity, high-temperature, and corrosive jet due to the pressure difference and sodium-water reaction. It would damage the other tubes and might propagate the tube failure in a SG. Thus, it is important to evaluate the effect of the tube failure propagation for safety assessment of a sodium-cooled fast reactor. The computational code LEAP-III can evaluate water leak rate during the tube failure propagation with short calculation time, since it consists of empirical formulae and one-dimensional equations of conservation. One of its models, the temperature distribution evaluation model, evaluates the temperature distribution in SG as circular arc isolines determined by experiments and preliminary analyses instead of complicated real distribution. Although this model has advantages of short calculation time and good agreement about maximum temperature, it provides broader high temperature region than the real one in some case. In order to improve this model to get more realistic temperature distribution, we have developed the Lagrangian particle method based on engineering approaches. In this study, we have focused on evaluating gas flow in a tube bundle system and constructed new models for the gas-particles behavior around a tube to evaluate void fraction distribution near the tube. Through the test analysis simulating vapor discharge in one target tube system and comparison with an existing computational fluid dynamics code, SERAPHIM, it was confirmed that basic behaviors of these models, which is the particles spread out around the target tube without significant inflow into the tube inside, and finally these went along the buoyancy force direction.

This paper presents the merging support system considering the constraint of the merging zone. Merging in a highway is one of the most difficult driving tasks. In lane changing and merging, drivers consider about safety and longitudinal ride comfort. In addition, drivers must finish merging in the merging zone. To achieve these objectives, we propose the merging support system. It consists of the merging decision maker, the merging planner, the longitudinal controller and the lateral controller. The merging decision maker compares the selectable merging positions and selects one with smallest acceleration. The merging planner generates the velocity plan and the lateral path plan to reach to the selected merging position. The longitudinal and lateral controllers follow these plans by the feedback controller and the feedforward controller. The performance of the proposed system is tested by simulations. In these simulations, the merging decision maker and the merging planner calculates the velocity plan and the lateral path plan to finish merging in the merging zone with the smallest acceleration, and the longitudinal and lateral controllers follows these plans accurately. These results show that the proposed merging support system contributes safe and comfortable merging. In addition, we demonstrate that the length of the merging zone affects the merging decision.

Recently, welfare vehicles are widely used among the aged. However, it is not easy for inexperienced beginners or the aged to control the welfare vehicle in the narrow place. For the problem, the driving assistance system was proposed in which a virtual vehicle is projected on head mounted display (HMD) and controlled by a third person viewpoint. However, as a user wears HMD to control the virtual vehicle, the driving situation of the virtual vehicle was not visible from outsiders and the appropriate guidance was not provided to beginners. In order to get the driving skill of the vehicle more quickly, it is important to utilized the mixed reality (MR) space using the virtual object and to provide timely guidance while checking the movements of the virtual vehicle. In this paper, we propose a drive assist system of welfare vehicle for beginners using Mixed Reality. A virtual course that automatically displays virtual objects using MR is constructed and the virtual space is shared with the instructor. To evaluate the practice of the driving skill for beginners, NASA task load index (NASA-TLX) is used for quantifying the mental work-load. As a result, proposed method suppresses the weighted workload (WWL) score, and it is clarified that the driving skill is improved in a smaller number of trials.

Bolt loosening may lead to severe accidents in machine and infrastructure facilities. Hence, it is pertinent to detect bolt loosening early. This study proposes a new non-destructive testing method for bolt loosening using ultrasonic pulses projected onto a screw thread of the bolt. This method focuses on the pulse transmitted through the bolt. The mode conversion of the ultrasonic pulse occurs when the pulse reflects and transmits on the flanks of the screw thread. The amplitude of the mode-converted pulse is affected by the contact condition on the screw thread. The transmitted pulse consists of several pulses with different transmission paths. The proposed method calculates an instantaneous frequency of the superimposed transmitted pulse and detects the bolt loosening as a change in the instantaneous frequency, which is caused by the amplitude change of the mode-converted pulses. A simple experiment using an aluminum block and a stainless steel bolt tightened with several kinds of torque is demonstrated in this study. Upon decreasing the tightening torque, the maximal instantaneous frequency of the transmitted pulse drops and appears earlier. To verify the mechanism of the proposed method, identification of the transmission paths and a numerical simulation were implemented. It is elucidated that the two mode-converted pulses that were transmitted through the pressure flanks and were reflected on the clearance flanks primarily affect the instantaneous frequency of the transmitted pulse. Additionally, their amplitude decreases with the decrease in the contact ratio of the pressure flanks. The contact ratio correlates with the tightening torque. This analytical study shows that the maximal instantaneous frequency and the time of the maximal value vary owing to the tightening torque. Therefore, the proposed method provides a reasonable index for non-destructive testing for bolt loosening.

We propose the mechanism and control method of the air jet based parallel link actuator with 6 degrees of freedom. The rotor of the actuator is called a platform which is constructed by connecting multiple spheres that are located in vertex of a regular polygon with high rigid wires. Each sphere is spatially levitated using coanda effect and its 3D position is feedback controlled by the dedicated air jet driven by a pan-tilt motor on the stator of the actuator. First, we discuss the platform structure in which n spheres are arranged at the vertices of a regular polygon, and the kinematics and control of the parallel link mechanism in which each sphere is operated by one of n air jet nozzles arranged in the same structure as the platform. Then we created an experimental system using the case of the minimum number n = 3, implemented a control system based on the inverse kinematics, and conducted operation experiments. The basic validity of the proposed method was confirmed by evaluating the experimental results obtained from an external measuring system which can accurately calculate the position and the orientation of the platform.

To improve robot manipulability, force sensing for scissors is expected to be significant. In general scissors, the moment and the crossing angle of the blade depends on the cutting position, resulting in the difference of the required input force for cutting. Though logarithmic spiral scissors enables to equalize crossing angle of scissors blade, the scissors also causes the moment difference. This paper proposes a mechanical motion conversion mechanism which equalizes the cutting input force of logarithmic spiral scissors. For the mechanical motion conversion mechanism, we suggest a curved slider mechanism which is combined with a linear slider. Because the curved shape can be calculated by analytic method, the linear slider stroke design procedure is simple compared with 4 linkage mechanism. Furthermore, the proposed mechanism enables to control the cutting speed easily compared with the former studies because the cutting speed is proportional to the linear slider speed. In the geometric and mechanical experiments using dummy scissors(40 mm in blade length), we confirmed that the cutting input force was independent of the cutting position if the constant load is applied. In the kent paper experiments using usual logarithmic spiral scissors (65 mm in blade length), the proposed mechanism could convert the constant load excepting friction effect.

McKibben type artificial rubber muscle has high affinity with human body due to mechanical flexibility and light-weight. It is widely used for personal care robots as the reason for above. Therefore, several models of artificial muscle based on energy conservation law to control the artificial muscle had been proposed in previous studies. However, parameters in the previous study are determined from trial-and-error to decrease the modeling error, but these determined parameters do not necessarily show the actual values of physical property of material. Purpose of this study is to construct a model from which the characteristic of McKibben type artificial muscle can be calculated based on only design parameters and actual rubber physical property. In this paper, first of all we propose expansion plane model to consider balance state of several forces. Subsequently, elastic force owing to rubber material is modeled based on Mooney-Rivlin model. And then the precision of proposed model is confirmed experimentally.

In order to deflect the radiated sound waves by an array of sound sources, temporal phase differences between the adjacent sound sources are necessary. Usually, the sound can be deflected by electronically providing the phase-shifted driving signal to sound sources comprising the array. In this study, we propose a new method for deflecting sound emitted from a linear array of sound sources whose driving frequency, amplitude, and phase characteristics are all consistent. Instead of directly changing the phase of the driving signal, the dynamic characteristics of the vibration systems installed in front of the emitter are adjusted to cause a physically phase-shifted response. Such an indirect phase difference caused by the vibrator array achieves the deflection of the interfered sound waves. Firstly, numerical calculations are performed by assuming different natural frequencies to the vibrators composing an array so that the radiated sound could be deflected at angles of θ = 20°, 30°, 40°, 50°, and 60°. It was found that the desired deflection angle could be obtained under all conditions. Secondly, experiments were conducted to verify the numerical predictions. Thin resin plates with different elastic moduli were manufactured that mimicked vibrators. We confirmed that the sound wave could be deflected for all deflection angles at the sound source frequency of 4 kHz.

We developed a technique which can increase the yield of one-to-one particle encapsulation by applying the dielectrophoretic particle alignment technique using boxcar-type electrodes. Dielectrophoretic force generated by the boxcar-type electrodes accelerate and decelerate the particles periodically as they flow in the electrode region. Further, the dielectrophoretic force is turned on and off at constant frequency. The force exerted on the particle periodically over space and time can align them in the streamwise direction with even interval. In this study, the boxcar-type electrodes were installed in the microchannel in the region upstream of the flow-focusing channel in which the water-in-oil droplets were generated. By adjusting the on-off period of the applied voltage generating the dielectrophoretic force to the period of the droplet generation, each particle could be separately encapsulated in the droplets. The principle of particle alignment using periodic force was first described based on a one-dimensional model. The flow structure and the characteristics of the droplet generation in the flow-focusing channel was then discussed in relation to the surface tension of the fluids and the wettability of the wall. We measured the velocity distribution of the particles flowing in the boxcar electrode region to evaluate the effects of the droplet generation on the motion of the particles and the alignment performance. The results showed that the particle could be aligned in the fluctuating flow caused by the droplet generation, and each particle can be encapsulated in different droplets. This was further demonstrated by measuring the probability function of the droplets containing specific number of particles, which showed that 100% yield of one-to-one particle encapsulation can be achieved under the investigated condition of particle number density of 0.4. Moreover, the throughput increased 46% compared to the case of having the particles supplied randomly.

Generating novel design concepts in the conceptual design phase is a cornerstone for producing innovative products. This paper proposes a method to support the generation of new design concepts from patent documents. The proposed method is based on the theory of novelty potential that the combination of abstract concepts leads to the generation of the novel design concept and that the distance between the combined abstract concepts correlates to the possibility of generating it. This research adopts the distributed word representation model of word2vec to extract abstract concepts from patent documents and to measure the concept distance. The two matrices are introduced to visualize the relationships of the extracted abstract concepts; the novelty potential matrix which shows the value of the novelty potential between the abstract concepts, and the void matrix which shows the numbers of existing patents of the abstract concepts. They help a designer to identify the combinations of abstract concepts that are high novelty potential and no existing patent. This paper demonstrates a case study of generating novel ideas of sports business with blockchain using the proposed method. The results show its uniqueness and effectiveness.

In order to prevent timing belt jumping, which often occurs under high loads, a practical jumping torque prediction formula was studied and the following results were obtained. (1) Jumping occurs when the amount of belt elongation on the tight side span due to the increase in load after the slack side tension becomes zero is equal to the amount of belt elongation due to the belt lifting on the pulley when the lifting reaches the belt tooth height in the whole wrapping area. A jumping torque prediction formula was derived based on this mechanism. The prediction formula includes parameters such as pulley diameter, span length, wrapping angle, belt tooth height, belt extensional rigidity, initial tension, and belt speed. (2) To compensate for the difference between the basic theory of frictional transmission applied in the prediction formula and the actual phenomenon, four correction factors were introduced for the amount of belt elongation caused by the belt lifting, etc., and physical properties of belt teeth. This makes it possible to predict the jumping torque of not only the driven pulley but also the driving pulley, and to expand the application range and improve the prediction accuracy. (3) The four correction factors were obtained by running tests using curvilinear profile S8M type belt, but it was shown that they are also applicable to a trapezoidal profile L type belt. (4) Jumping tests at rest with the driven pulley shaft fixed were conducted, and it was confirmed that the jumping torque of the driving pulley at running was about twice that of the driven pulley, and almost equal to that of the driving and driven pulleys at rest.

By using sparse modeling to formulate the relationship between the data of the design image of an automobile body frame and the amount of frame function, we developed a method to extract the features of the image that are important for improving the function. The important areas of the cross-sectional shape visualized by the method and the design guidelines for the cross-sectional shape derived from the visualization are consistent with the findings obtained in previous studies. In addition, we were able to obtain new findings that were not previously available. In other words, this method has the potential to elucidate unknown important factors that are not assumed by designers and to derive general purpose design guidelines by utilizing a large amount of design image data obtained in shape optimization.

Wheel slips in railway vehicles cause poor acceleration and damage to wheels and rails. Re-adhesion control is widely used to resolve wheel slips in electric motor cars. In re-adhesion control, it has been an important problem to consider appropriately the vehicle dynamic motion, which affects the control performance greatly. In this study, we investigate the mechanism and characteristics of slip misdetection phenomena which occur due to bogie vibration excited during re-adhesion control. We construct a three-dimensional vehicle model including roll motion with parallel Cardan drives. The tangential force coefficient model between wheels and rails includes the influence of translational velocity, slip velocity and wheel loads. The simulation model is validated by comparison with measurements in a test run of a real vehicle conducted in previous research. Simulation results illustrate the behavior of the bogie under traction such as the difference of wheel loads of four wheels and the attitude of the bogie frame. It is shown that continual slip misdetection can occur because of pitch and roll vibration of the bogie frame which is excited during re-adhesion control when the primary vertical damping coefficient is small. The misdetection is prevented by changing the amount of motor torque reduction in re-adhesion control. The appropriate range of the amount of reduction to avoid the misdetection gets narrower as the primary vertical damping coefficient decreases. The primary vertical suspension stiffness and characteristic of tangential force coefficient also affect the occurrence of the misdetection.