Various testing methods for adhesive strength are prescribed in JIS but no testing method is indicated under no singular stress field. Usually, strength of materials should be considered for plane specimens where uniform stress distributions can be expected. However, in the case of adhesive strength evaluation, all bonded specimens exhibit a singular stress field, the intensity of which (ISSF) varies depending on the adhesive layer geometry. This is the reason why the adhesive strength varies depending on the adhesive layer geometry. In this paper, therefore, a protruding butt joint is proposed to obtain a constant interface stress distribution. Then, the essential adhesive strength is clarified under uniform interface stress without localized stress concentrations. Unlike standard butt joints, where strength is significantly affected by adhesive layer thickness h, it was found that the adhesive strength in the proposed joint remains constant at critical stress σ_B = 47.7 MPa, regardless of h. It is also found that in JIS butt joints, the border at h=0.1 mm allows a distinction between fracture due to internal stress and fracture due to a singular stress field. In the case of failure due to a singular stress field, by calculating the region (process zone) where the average stress is the original strength of the butt joint, σ_B = 47.7 MPa, it is thought that failure will occur at a position r_B = 14.7 μm from the adhesive end. This is almost equal to the fracture origin of a rectangular column butt joint reported in a previous study, and can be said to be a reliable evaluation method.

A method for detecting misfires in internal combustion engines using information from the ignition coil's discharge has been developed. A dual discharge concept has been adopted, in which a sub-discharge for detecting misfires is carried out during the expansion stroke following the main-discharge for ignition. The peak value of the primary voltage of the ignition coil and the discharge duration have been selected as discharge feature values for determining misfires. Verification results using a single-cylinder engine confirmed that high misfire detection accuracy can be obtained by optimising the timing of the sub-discharge and the dwell period.

There are many requirements, issues and complexities that engineering design problems must take into account, and these engineering items are often treated as constraints in optimization problems. The constraint optimization problems (COPs) are the most popular type of problems, therefore, optimization algorithms for the COPs have been attracted more and more attention. Particle swarm optimization is one of the most popular algorithms for solving the COPs due to the simplicity and efficient convergence performance, and various types of PSO are actively developed in recent years. However, despite the popularity, they still have limitations in terms of search efficiency. Notably, it takes a lot of calculation costs to obtain the optimal solution on the boundary of constraints or the complicated feasible area. To overcome the difficulties, this paper presents a novel particle swarm optimization algorithm named independent 2-group particle swarm optimization (I2GPSO). I2GPSO is based on the following ideas - a constraint handling method, a novel structure of particles and a novel local search operator. The constraint handling method uses the existing penalty function method. The structure of particles defines two particle groups that have original roles, efficiently enabling PSO to search globally and locally. The local search operator is introduced into one group and enables particles to search near the boundary of constraints efficiently or candidates of the optimal solution. These novel approaches effectively reinforce the optimization efficiency of the PSO algorithm. The optimization capability and character of I2GPSO is illustrated in 11 benchmark problems. The results are compared with other state-of-the-art PSOs, and it is shown that the proposed algorithm possesses competitive search efficiency.

Helical springs are used for many mechanisms. Rectangular wire helical springs are used in machines that require large spring loads, such as press machines, die machines, injection molding machines, construction machines, and load testing machines. Design formulas for the rectangular wire helical springs were given by Liesecke. However, pitch angle of the helical spring is neglected in his formulas, and they are inconvenient because we have to read factors used in the formulas from graphs. And, Shimizu et al. derived a theoretical equation, but there are still differences between values calculated by the equations and the FEM analysis results although a trend is consistent. And, the practical design equations are desired to be simple. Therefore, in this paper, simple practical design equations of the spring constant and the maximum shear stress are derived by using a fractional expression to FEM results by focusing on that the displacement and the stress generated in the helical spring are mainly caused by a tortional moment to the spring wire. Errors of the spring constant equations to the FEM results are less than 3 percents and errors of the maximum shear stress equation to the FEM results are less than 3.5 percents. Therefore, these equations are very useful for the practical design of the rectangular wire helical springs.

Table tennis, a sport that is played widely around the world, and even at the Olympics, is also a recreational sport enjoyed in diverse facilities that can accommodate table tennis tables. Table tennis ball rotation during the game is not well understood because the ball rotation is nearly invisible to observers and players. This study was conducted to elucidate table tennis ball behavior, such as its rotation, that a table tennis player senses through the table tennis racket with eyes, ears, and tactile sense. The rotational and translational motions of balls of various rotations launched from a table tennis machine were assessed using a high-speed camera. After balls with various rotations were made to collide with a racket fixed at 90 degrees to the ground, the racket strain was examined at eight points. A ball with no rotation was free-fallen; it collided with a racket fixed horizontally. Fast Fourier transform analysis was applied to the strain values of the ball impacting the racket tip and the racket center. The kinetic energy values of the ball before and after impact were compared. Findings indicated that the number of rotations of the ball decreased after the struck the racket. When a ball with rotation is struck with the racket, the vibration caused by the grip strain persists for a long time (0.2 s). When the ball has free-fallen in the racket center, the vibration is less than when it has free-fallen at the racket edge area. Players are thought to sense the ball rotation not only with their eyes and ears, but also as tactile information related to the vibration strength of the grip section. The racket vibration shapes differ when a ball strikes the racket center and when it hits the racket edge area. Specifically, less vibration is felt when the ball hits the racket center, thereby enabling the player to return the ball skillfully with high speed, power, high ball rotation, etc.

We expect that gait will be useful information for detecting wandering and managing the health of elderly people utilizing a monitoring support robot. However, some kind of sensor is needed to extract pedestrian gait features. In this paper, we proposed a privacy-aware method of extracting gait features from pedestrians’ feet only. This paper describes methods for detecting frames in which heel-strike and toe-off events occurred in foot video, and for extracting the heel contact position in the image. Firstly, dynamic regions were extracted utilizing edge detection and optical flow, and then clustering was used to extract pedestrians’ feet regions. Subsequently, the acceleration field was estimated using optical flow, the acceleration was decomposed into tangential and radial components, and the radial component acceleration was used to detect heel-strike frame. Next, we extracted static regions in the pedestrians’ feet region by utilizing edge detection, optical flow, clustered foot regions, and motion characteristics during gait, and finally performed toe-off frame detection. The heel contact position in the image was extracted by using Otsu’s binarization and static region. We conducted gait experiments with several camera direction conditions and applied it to the system. The RMSE of the estimated and true values for heel-strike and toe-off frame detection were within about one frame in all conditions, and the F-measure was above 80 % in all conditions. The F-measure for heel contact position detection also exceeded 80 % in all conditions.

Approximately half of all traffic fatalities involve pedestrians and cyclists, and exceeding the speed limit is one of the most serious factors causing fatal accidents. The use of an Intelligent Speed Assistance system (ISA) is being considered to reduce the number of traffic accidents caused by exceeding the speed limit. ISAs indicate the speed limit information to drivers or perform a control intervention to avoid exceeding the speed limit. The purpose of this study was to investigate the effects of compliance with the speed limit on reducing the number of vehicle-cyclist collisions, by using a near-miss incident database. This study sought to estimate the effects of an ISA, which provides control interventions to ensure that travel speeds do not exceed the speed limit. In the database, we extracted near-miss incident data that cyclists initiated a road-crossing from blind intersections with speed limits of 30 km/h (i.e., 956 cases), and defined a safety margin as the axis of the effect of accident prevention. Subsequently, the effect of compliance with the speed limit by the ISA on ensuring the safety margin under hazardous events caused by exceeding the speed limit was analyzed. The limitations of the effect of compliance with the speed limit by the ISA were also assessed. The data analysis revealed the following. Of the 956 cases, 129 cases (13 %) showed insufficient safety margins due to exceeding the speed limit. The frequency with which the use of the ISA can be effective in ensuring safety was not high. However, of the 129 cases, 100 cases (78 %) showed that the use of the ISA led to an adequate safety margin; the use of the ISA increased the time available for accident prevention by an average of 0.74 s. The results of this data analysis can contribute to the discussion on the social implementation of ISAs.