A large quantity of engineering plastics are used in electric industrial products. It is necessary to estimate the life of the product made of engineering plastics because of its shorter life and lower strength than some of ceramics or metals. New test device was developed for accelerated stress test. It can make the unsaturated environment above 100 oC under atmospheric pressure using superheated water vapor. Then it becomes possible to set wide range condition of temperature and humidity. Polybutylene terephthalate (PBT) is one of the hydrolyzed engineering plastics. Test pieces of PBT were submitted to accelerated stress test under some conditions of elevated temperature and humidity. Then they were provided to three point bending test. The time required for strength degradation has a good relation with water vapor pressure at each temperature. Then it became clear that the time required for strength degradation on each water vapor pressure was accelerated with temperature using the Arrhenius type equation.
In our previous study, it was found that the wear life of the DLC/AlN multilayer hybrid coating could be improved by approximately 80 times of that of a DLC film deposited directly onto an aluminum (Al)-alloy. This was done by controlling the hardness gradient of the AlN intermediate layer film. In this study, the frictional wear characteristics of DLC/AlCrN/AlN multilayer hybrid coating, in which the intermediate layer film was further hardened using the hardness graded AlCrN film, were investigated. This was done to improve the wear life of Al-alloy further and to require for application to machine parts. The frictional wear characteristics of the aluminum alloy-coated DLC/AlCrN/AlN multilayer hybrid film showed a longer life and lower friction coefficient when compared to a DLC/AlN hybrid film. In addition, the DLC/AlCrN/AlN wear life increased when a thicker DLC film was applied. In the wear tracks after the wear test, no cracking or peeling was observed in the DLC/AlCrN/AlN multilayer hybrid film. This was due to the improvement of fracture toughness value of the multilayer hybrid film by increasing the hardness gradient of the intermediate layer. Finite element simulations demonstrated that the DLC/AlCrN/AlN multilayer hybrid coating reduced the stress and strain in the film. Differences in stress and strain at the interface of the DLC film and the intermediate layer film were small. This simulation also demonstrated that a thicker DLC film further reduced the stress and strain in it. As a result, DLC/AlCrN/AlN multilayer hybrid coating is considered to represent a simple and effective means of improving the wear resistance of Al-alloy components.
For the simple friction grip joint consists of two joined parts, one of which is tapped and bolted with the other with a bolt, the load capacity (Here, this is expressed by n described below) of the friction grip joint is analyzed using the strength of materials, and FEM analysis is carried out on 10 cases, which result in the following conclusions. [Here, F:Bolt axial tension, μCS : Friction coefficient on the contact surfaces between joined parts and also on the bolt bearing surface, WSCr : Critical applied shear force without any slip, n : Equivalent number of contact surface (=WSCr /FμCS).] (1) Introducing the shear spring constant of the bolt KBS and that of the joined part KCS, the theoretical equation to calculate the load capacity n, which contains only KBS and KCS, is derived. (2) The load capacity nth, calculated by the theoretical equation substituting KBS and KCS obtained through FEM analysis, coincides very well with nFEM obtained through FEM analysis. Therefore, it is concluded that the theoretical equation to calculate n using KBS and KCS is correct. (3)According to this theoretical equation, to increase the load capacity n, it is necessary to develop the joint structure which gives smaller KCS/KBS. (4) The maximum load capacity n=2 is obtained only under KCS=KBS in the case of the concentrated shear load applied on the upper corner of the joined part. (5) The problem left to predict n is to derive the equation that can accurately calculate KCS. (6) From the results of this analysis, the number “qF”, which is described in VDI 2230 Part 2 and corresponds to n, is judged to be too large from the viewpoint of slip.
In recent years, the use of renewable energy has been dramatically increased all over the world. Especially the photovoltaics power generation system is attracting wide attention, and the scale of market is expanding. In Japan, the introduction of photovoltaic system is beginning to advance, and the number of large-scale solar power plants has been rapidly increasing because the Feed-in Tariff Law (FIT) for renewable electric energy takes effect from July 1, 2012. However, accidents have frequently occurred under the rapid spread of photovoltaic power generation system. The support structures of the system were deformed or destroyed due to strong wind or heavy snow when the support structure was designed improperly. The main cause is considered to be a mistake in the structural calculation model, especially the model for joint parts. In this study, we conducted a full-scale experiment by simulating wind load and snow load on photovoltaic system. Furthermore, it was examined whether the joint parts model proposed by the Authors is valid for safety design of the support structure. In addition, we examined the stress condition and deformation of a member where buckling occurs, then, the buckling load was obtained by using the FEM model.
Carbon fiber reinforced plastics (CFRPs) are widely used as components of marine structures. Thus, it is important to understand the degradation of the mechanical properties and its mechanism under seawater immersion. The object of this study is the influence of seawater immersion on the mechanical properties of plain woven CFRP laminates. Static tensile test and tensile fatigue test were carried out on the CFRP immersed different time under seawater for 300, 2500 and 5400 hours. The mechanical properties immersed for 300 hours was almost the same value compared with those of no immersion. However, the tensile strength immersed for both 2500 and 5400 hours reduced by 22.5% compared with that of no immersion. Then, from the fatigue results, in the low-cycle fatigue region, the fatigue strengths decreased as immersion time was longer, on the other hand, in the high-cycle fatigue region, the fatigue strength did not change significantly regardless of immersion time. As a result, the inclination of S-N curves became gentle as immersion time was longer. From observation of fracture surfaces by scanning electron microscopy (SEM), it was shown that the fiber/matrix interface deteriorated remarkably after seawater immersion. Moreover, the difference of damage growth behaviors due to immersed in seawater under fatigue loading was investigated using soft X-ray photography. On specimen immersed in seawater, the accumulation of damage expanded more widely due to interface degradation compared with that of no immersion. Considering these results, it was suggested that the static tensile strength depended on load transmission efficiency between fiber and matrix, on the other hand, the fatigue strength in high cycle fatigue region depended on the strength of fiber along 0° that had small influences by seawater immersion.
In the present study, we have analyzed the flow field around a cube in a Stokes flow regime in order to estimate the diffusion coefficients of cube-like particles that are required for performing Brownian dynamics simulations of a cubic particle suspension. The main results obtained here are summarized as follows. In the situation of a uniform flow field with a Reynolds number sufficiently smaller than unity, the force acts on the cube only in the flow field direction, and the torque does not act on the cube. Therefore, the uniform flow does not induce the rotational motion of the cube. In the situation of a rotational flow field with a sufficiently low Reynolds number, the torque acts on the cube only in the direction of angular velocity of the rotational flow field, and the force does not act on the cube. This implies that the translational motion of the cube is not induced due to the rotational flow field. These characteristics are in good agreement with those for the case of spheres in a Stokes flow situation. From these results, we may conclude that the diffusion coefficients of the cube-like particles can be expressed by applying a correction factor to those of the spherical particles. Moreover, we understand that the translational and the rotational motion of a cube are not coupled in the condition of the flow filed with a low Reynolds number sufficiently smaller than unity. Furthermore, in Brownian dynamics simulations, the equations of translational and rotational motion of cube-like particles can be treated in the same way as the spherical particles by applying the correction factor.
Cycle-to-cycle variation (CCV) of in-cylinder flow occurs in internal combustion engines. It is necessary to analyze CCV of flow to separate averaged-flow (as low frequency / low wave number) from turbulence (as high frequency / high wave number), because an averaged flow varies from cycle to cycle. Two averaging methods are used for the extraction of mean component from instantaneous flow. One is temporal-averaging method, the other is spatial-averaging method. In the temporal -averaging method, a fluctuation of flow is captured at fixed point in Eulerian, turbulence is regarded as the high frequency component, and it is removed by a low pass filtering. In the spatial-averaging method, the turbulence in spatial arrangement of flow velocity is directly averaged by using vortex scale as a threshold (e.g. Moving-averaging filter and Gaussian-averaging filter). However, the temporal-averaging and the spatial-averaging have completely different characteristics. Therefore, it is necessary to clarify the difference of filtering characteristics in each averaging filter. In this study, comparisons of averaged flow patterns of temporal-average and spatial-average are carried out. Moreover, variable sized spatial filter which is based on Taylor's frozen-turbulence hypothesis is proposed. As a result, variable sized filtering is found close to the filter characteristic of the time average method.
The purpose of this study is to develop an analytical model of cross-flow heat exchangers with offset strip fins which are usually equipped in the aircraft air conditioning system (so called the environmental control system, ECS). The ECS mainly consists of four cross-flow heat exchanges, i.e., a primary heat exchanger, a secondary heat exchanger, a reheater and a condenser. Because of the special requirements of the design for the aircraft, the primary and secondary heat exchangers are set adjoiningly; the reheater and the condenser are also set adjoingly. Therefore, in both the pairs, the effect of the temperature profile of the upstream component (the secondary heat exchanger or the reheater) on those of the downstream component (the primary heat exchanger or the condenser) should be taken into account for precise prediction of the system. To this end, a core element model was newly proposed in this study. In addition to the effect of temperature profile, phase changes (condensation and evaporation) of water included in the humid air simultaneously occur except for the primary heat exchanger. Regarding these phenomena, the method of sensible heat fraction (SHF) to convert the latent heat into the equivalent sensible heat was introduced, and the global and local SHF models were examined by comparison with the experiments. The prediction by these models were found to agree well with the actual performance of the ECS operations.
The purpose of this paper is to develop an analytical model of frost/ice formation on the heat exchanger (condenser) of high-pressure water separation used in the air conditioning system of commercial jet aircraft. The high-pressure water separation is based on the heat exchange between the upstream and downstream sides of the same air flow with pressure difference. That is, relatively high-pressure and warmer air upstream of a condenser with high humidity is cooled by relatively low-pressure and cooler air discharged from a turbine downstream of the condenser; condensed water in the high-pressure side is removed by a water separator while in the low-pressure side the super-cooled water mist is produced by adiabatic expansion process in the turbine. In the both sides, when the heat-exchange fins are below the freezing temperature of the humid air, frost/ice formation occur, although their physical mechanism are utterly different. In this study, a phase-change model taking the features of a cross-flow heat exchanger into account is newly proposed. In particular, attention is focused on the increase of the pressure drop in the lower pressure side due to frost/ice formation. The validity of the analytical model is checked by the comparison with the experiment.
The initiation mechanism and its reduction method for combustion driven oscillation of industrial boilers with a center firing gas burner have been investigated experimentally and numerically. Eight fuel injection nozzles are arranged radially at the burner. The burner with two different diameter nozzles, main nozzle and sub nozzle, arranged alternately is proposed. When the burner proposed is set in the burner, the flame base becomes much stable compared with the standard burner in which the diameter of all fuel injection nozzles is the same because the small flame of sub nozzles is formed around the flame base of large flame of main nozzles. The ratio of diameters of main nozzle and sub nozzle and the angles of main nozzle and sub nozzle are important parameters on flame base structure. Numerical simulation confirms the stability mechanism experimentally observed.
Improvement of thermal efficiency is strongly required in internal combustion engine to promote environmental protections, it is important to clarify the mechanism and reduce cooling loss. Various methods have been proposed for measuring the cooling loss from the combustion gas to the combustion chamber wall, coaxial type thin-film temperature sensor is developed for wall temperature and heat flux measurement in this study. This sensor consists of thin-film and body and center wire, and there are three junction positions when the three materials are different. Therefore, it is necessary to use the same materials for thin-film and body or thin-film and center wire to make two junction points. In this study, as a method of forming thin-film on the sensor surface, not conventional metal plating method but sputtering method capable of forming various kinds of alloy materials and thickness of 0.1~1μm was chosen. It was evaluated the influence of differences in thin-film material on wall temperature and heat flux measurement by numerical analysis, as a result, the surface of sensor body (the same material as the combustion chamber) was hot junction by using the same material for the thin-film and center wire, it was suggested that high accuracy measurement is possible. And the sensor was attached to the cylinder head of gasoline engine and conducted experiments, and it was obtained the same result as the numerical analysis results. From these result, when high accuracy measuring wall temperature and heat flux with thin-film temperature sensor, it was found that it is important to use the senor body is the same material as combustion chamber wall and the thin-film is the same material as center wire.
In recent years, attention has been focused on woody biomass energy from the viewpoint of reducing environmental burden and effective use of local energy resources. However, the knowledge concerning the drying of the wood which becomes the fuel is poor, and it depends on the experience of the technician. Therefore, it is beneficial to develop a method that can obtain optimum drying and combustion conditions. However, in the drying process, complicated phenomena must be considered, and analysis of the drying process is difficult. In this study, we focused attention on the viewpoint of heat transfer considering evaporation. To establish a simple analysis method of the drying process, a heat transfer analysis program modeling the drying of wood balls containing moisture was created and analyzed. An experimental apparatus was also fabricated, and a dry experiment of filling wood ball group containing moisture was carried out. Numerical analysis of the temperature responses of spheres and air currents when hot air is flowed through a filled wooden group containing moisture and the drying process of the filled wood ball group was investigated. We compared the numerical analysis results obtained from the simulation with the temperature response characteristics by experiments on wood balls. In addition to investigating the validity of the simulation, the predictability of the dry completion time was evaluated.
Natural convective heat transfer from a horizontal row of heated vertical plates to air has been investigated experimentally. The average Nusselt numbers NuL of the plates were measured by varying the plate height L, the gap between plates G and the total number N of the plates contained in the row as, L=50 & 100mm, G=5.2-50.8mm and N=2-10, respectively. The result depicted that the Nusselt numbers for the fixed plate height and gap increase first with increasing the number of plates from N=2 to 7, while they show almost identical values with further increase in N. The latter Nusselt numbers were, then, rearranged with non-dimensional parameters to obtain heat transfer correlation for the rows having large numbers of plates. It was found that their Nusselt numbers NuG are well correlated with the parameter [RaG (G/L)], where NuG and RaG stand for the Nusselt and the Rayleigh numbers based on the gap G. Moreover, the optimum gaps (G/L) to make the Nusselt numbers maximum were discussed from the proposed heat transfer correlation.
Diagnosis of the bolt loosening is important in the industrial field and the medical field such as dental implants. This study proposes a new non-destructive testing method for the bolt loosening using ultrasonic pulse projected to the side of the bolt. This method focuses on the reflected pulse from the screw thread and its instantaneous frequency. A basic experiment with aluminum block and a stainless steel bolt shows that the tightening torque of the bolt can be evaluated via the instantaneous frequency of the reflected pulse from the screw thread. Decreasing the tightening torque, the instantaneous frequency reaches a maximal value earlier. We tried to verify the mechanism of the proposed method through an identification of the transmission paths and a numerical simulation. Real contact area on the load flank decreases, and the reflectance on the load flank changes when the tightening torque decreases. The analytical study shows that the change of the reflectance affects the received pulse. Especially, a peak time of the instantaneous frequency of the received pulse varies owing to the amplitude ratio of the reflected pulses from the load flank to the pulses reflected from the other contact surfaces. These analytical results follow the experimental results. Therefore, observing the peak time of the instantaneous frequency of the received ultrasonic pulse, we can obtain the reasonable index to diagnose the bolt loosening.
Technology development to improve road induced noise is necessary with the market expansion of the electric motor drive vehicles, because road induced noise is noticeable under no engine noise condition. One of the effective ways to achieve good performance is to avoid the natural frequencies of vehicle bodies from dominant frequencies of the transmitted forces between a suspension and a vehicle body, which vary as the characteristics of road surfaces. For this background, this paper proposes a new method for shifting the natural frequency of coupled two vibration systems which are connected at multi-points by coupling springs assuming semi-active control. Firstly, based on the sub-structuring method, the relation between column vectors in the compliance matrix at connection points of two systems is analyzed to make clear the condition of resonance occurrence. This condition is equivalent that all column vectors of the compliance matrix at connection points exist in a hyperplane. Secondly, utilizing the independence of each coupling spring’s degree of freedom, simple equation to calculate a coupling stiffness is derived to satisfy the condition of resonance occurrence. Finally, in a feasibility study, the method was applied to two beams connected with three translational springs. It is showed that the proposed method can shift an initial natural frequency to target frequency with a simple calculation.
A Perforated plate is used as an acoustic absorption material for compressors and acoustic barriers for roads and railways. There are many studies of the perforated plate from the aspect of the acoustic absorption. In this paper, the effect of set positions of the perforated plate on the acoustic natural frequency is considered with the TMM and the experiment. And the reason why the analytical result due to the TMM and the equation of Melling are in good agreement is clarified. From the analytical and experimental results, it is clarified that the smaller the aperture ratio becomes, the lower the acoustic natural frequency becomes with increasing of the hole length of the perforated plate. And the set position of the perforated plate can control the excitation of an acoustic specific mode. And the TMM is useful for obtaining the acoustic natural frequency, because the imaginary part of the acoustic impedance of an orifice obtained by Melling coincides with the analytical result by the TMM.
At present, there are many types of isolation system, and many of them are designed for the short-period ground motion. The long-period ground motion has recently attracted the attention, though the isolation system for the short-period ground motion does not have an ability to suppress the vibration due to the long-period ground motion because the frequency of the long-period ground motion is near the natural frequency of the isolation system. In this study, a new isolation system is proposed for not only the short-period ground motion but also the long-period one. The basic concept is that the dynamic property, which is the natural frequency, is changed by adding a spring when the amplitude of isolation table exceeds a threshold value. The validity of the method is checked by the numerical simulation using a single-degree-of-freedom system against the sine sweep ground motion and the actual earthquake ground motion. As a result, it is shown that the resonance can be suppressed by the proposed method. Then the applicability is checked by using the experimental setup. In the experiment, the additional spring is connected with the isolation table by using the clamping mechanism. The adequate clearance between the isolation table and the additional spring is determined in advance. As a result, the system can suppress the resonance phenomenon, so that it was concluded that the proposed system has a sufficient ability to suppress the resonance due to the long-period ground motion.
In this work, lattice structures appropriate for Additive Manufacturing (AM) are discussed and designed. By using AM, it becomes easy to realize original arbitral mechanical properties, in terms of anisotropy, vibration characteristic, light weight, and so on, by creating objects which have lattice structures inside their bodies. However, since the internal structures are very small, the influence of fabrication conditions such as deposition direction, nozzle diameter, and layer thickness is large. When the size of the cell strut diameter with respect to the nozzle diameter is relatively small, the shape of the struts becomes rough. In this study, the body-centered cubic (BCC) structure fabricated with ABS resign is chosen as a target lattice structure. BCC structure can reduce anisotropic properties due to the AM process. Specimens having different sizes of the same lattice cell structure are modeled by 3D-CAD. These specimens are fabricated by fused filament manufacturing (FFM) process, and tensile strength is examined. After the effect of the deposition direction and the nozzle path on mechanical strength of lattice cell structures was revealed, a design method for isotropic-tensile-strength structures was proposed. By scaling the size of BCC, isotropic-tensile-strength lattice structure was designed and specimens having the structure was fabricated by FFM process. Tensile strength test results showed the isotropy of tensile strength.
Much emphasis is now being given to research and development of plant factories which daily produce a large volume of high-quality vegetables under artificially controlled environments. One of the important issues to be considered for the management and the daily operations of the plant factories is to find a set of suitable customers and/or markets to which the daily produced vegetables are sold and delivered. The current wholesale markets of the vegetables are not suitable for trading the high-quality vegetables produced by the plant factories, therefore, a new market is required to sell and to buy the products made by the plant factories. A new trading market system is proposed, to sell and to buy the lettuces supplied by the plant factories, based on the stock exchange mechanisms, in this paper. An estimation method of yield rate is also proposed to generate a suitable volume of sales for the plant factories. Some case studies have been carried out to verify the effectiveness of the proposed trading market.
Our previous research (Naganuma, Hashimoto, 2018) demonstrates that the anomaly detection in the injection molding clamping unit will be made possible by evaluating the operating mode. Based on our previous research, this article suggests the sign of failure in the injection molding clamping unit can detected the anomaly detection through the unusual values of the production machine. A plastic injection molding manufacturing company built a data network system that collects a machine state log in the factory and saves data in the server. Over the past two years, two failures of clamping unit in the injection molding machine occurred under the production and the machine data of both cases are logged . We use a threshold method to detect the anomaly of the clamping unit. This thresholding is obtained by the maximum accuracy of the confusion matrix. It was tested against the two failure cases, which number of data is about 1.8 million cycle data. As a result, we discovered that this threshold method can detect the anomaly for both cases before the machine has to be shut down by the failure. Thus, it is expected to be useful for the preventive maintenance and the quality assurance of products due to its ability to detect the sign of failure in the injection molding machine.
The purpose of this study is to generate training data for failure detection by Neural Network, which estimates extent of damage from vibration data of meshing plastic gear pairs. Generally, measurement of meshing vibration with accelerometers installed on a gear system is not difficult. Therefore, one can automatically acquire vibration data under operation and obtain a large amount of vibration data. However, it is not easy to obtain a large amount of evaluation data of the damage extent. Evaluation of the damage extent is possible if the operation has stopped. It means that the procedure of this data acquisition requires additional work, and there is a need for acquiring data of the damage extent, automatically. This research addresses this need by developing an automatic data acquisition system of the meshing vibration and the extent of damage. In the developed system, an accelerometer installed on the housing of bearings is used for acquisition of vibration data, and a high-speed camera observes cracks occurring at the root of the target tooth. The measurement condition was discussed, and the effectiveness of the system was confirmed through experiments. Additionally, a damage index of the crack at the root was proposed, and the computed index was used as labels for training data. Finally, the measured meshing vibration data was visualized for generating training data of Convolutional Neural Network.
In this study, we intended to predict bearing temperature of oil bath tilting bearings with high degrees of accuracy, and developed a more detailed formula estimating mixing temperature at the inlet of the oil film on the pad. In order to consider the complicated flow in terms of the fluid and heat between pads, we precisely solved the conservation laws of the flow and energy at the control volume adding effects of rise of temperature due to agitation loss and leak between the shaft and the seal, and we got the accurate temperature of the mixing inlet oil. Moreover, we measured the bearing temperature distributions under various conditions with a test bearing bored 280mm in diameter to validate the analysis. Eventually, we got the following conclusions. (1) Compared with the analysis using the conventional model, the proposed model can reduce the errors of the oil film temperature distribution by one third. (2) In terms of prediction of the mixing inlet temperature that affects degrees of precision of the oil film distribution, the proposed model can improve 2 oC of variability and 10 oC of average errors, compared with He's model, and it found the fact that the method can improve the accuracy of the calcuration of bearing temperature. (3) The proposed model can predict temperature at the evaluation point within -8.6~+5.4 oC.
This research aims to develop a human-wearable type equipment that enables people to perform accurate motion without assistance of others. The equipment can be used for manually processing such as welding, rehabilitation, meal care for people with disabilities etc. The proposed equipment consists of a wire-driven mechanism with rotational degree of freedom. Thus, the equipment is expected to be lightweight and easy to wear. Although a wire-driven mechanism is generally required to adjust the wire tensions by actuators, the proposed mechanism can adjust the tensions by a constant-force spring device. As a result, the proposed wire-driven mechanism can move passively by external operation without complicated force control. Furthermore, the wire-driven mechanism can control its position correctly. Thus, while the proposed mechanism can be passively operated, it can assist the movement of people to draw accurate trajectories so as to follow target paths and motion. In this research, the proposed equipment was fabricated for assistance of positioning motion of forearm and experiments of drawing some trajectories were performed. The experiments were conducted with and without the motion assistance and were evaluated based on the error between the actual drawn and target trajectories. As a result, the average and maximum errors induced with the fabricated equipment was smaller than those without the motion assist. Therefore, the proposed equipment was available for human motion assistance.
Polydimethylsiloxane (PDMS) is used as a flexible cell culture substrate in medical and biological research fields. It has been demonstrated that surface modification by oxygen plasma irradiation was performed to improve cell adhesion, because PDMS has poor cell adhesiveness. However, the surface modification effect was not sufficient due to the flexibility of PDMS. In this study, active oxygen and UV lights were exposed to PDMS surface to improve the cell adhesion. The active oxygen was generated by a UV lamp emitting at wavelengths of 185 nm and 254 nm. The surface modification effect of PDMS before and after exposure of active oxygen and UV lights were evaluated. As a result, although the surface roughness did not change before and after exposure of active oxygen and UV lights, the wettability was improved. In addition, temporal change of PDMS surface after exposure of active oxygen and UV lights was smaller than that after plasma irradiation. Because the formation of silicon oxide layer on the surface was confirmed, it was considered that this layer prevented the penetration of polar groups getting into the PDMS substrate. Furthermore, osteoblast-like cells on the PDMS after exposure of active oxygen and UV lights were adhered and extend well. Therefore, it was demonstrated that a stable surface modification of PDMS surface was achieved by exposure of active oxygen and UV lights.
Human errors of train drivers may cause serious damage. Therefore, research on human error prevention has been conducted by many researchers. In this context, brain activity measurement of train drivers using Near-infrared Spectroscopy (NIRS) has been conducted to monitor the condition of train drivers. In this study, we developed a compact wireless wearable NIRS that can be used in natural environments. The wearable NIRS has been used to measure train drivers brain function using a train driving simulator. Experimental results showed that brain activity of DLPFC increased when the driver made braking operation. The experiment for train driving with an accidental event was carried out to evaluate the relation between driver's attention and the brain activity. As a result, there was a difference in brain activity between with and without prior notice. Results showed that the increased attention of the train driver can be appeared in NIRS signal from the outer part of prefrontal cortex.
In preparation for optimal routing of patients to a hospital, this paper presents a traveling model of the ambulance that moves from the scene of an emergency to a hospital. The model is given in the form of a speed diagram along the route and constructed based on some rules: The ambulance moves with either a constant speed, a constant acceleration speed or a constant deceleration speed. The maximum speed changes depending on the legal speed limit for private vehicles. The ambulance decreases its speed to a specified level when it passes through an intersection with traffic lights or turns left or right. The model has eight adjustable parameters. They were optimized in the framework of the multi-objective optimization problem involving three objective functions, which are defined as modeling errors relevant to the traveling time, the fluctuation of blood pressure and the pressing force acting on the back of a patient. The genetic algorithm was used to obtain Pareto solutions to the problem. An optimal set of parameters was selected from among them. The validity of the model was confirmed by checking the objective functions for the validation data set. However, there was a limitation: The model does not match to the actual speed of the ambulance in such a case that it moves on the road where many traffic lights are placed close to each other and controlled synchronously.
In the development of spacecraft and space hardware, qualification tests are conducted to demonstrate the validity of their design. In the qualification test, in order to confirm that the qualified hardware has a design margin, the qualification test condition is set with a margin against the flight environment. As the qualification margin greatly affects the hardware design of tolerance against the flight environment, it is important to optimize the qualification margin. However, the qualification margin has been determined empirically based on the development experience of the government procurement large satellite of each space agency, and there is very few discussion and assessment on proper and optimal qualification margins. Therefore, in this paper, we propose a method to optimize qualification margin from the viewpoint of minimizing the loss cost caused by miss-qualification due to inappropriate qualification margin. Based on the proposed model, it was found that the optimum qualification margin depends on the uncertainty of the test environment and the strength of the hardware, and the loss cost due to miss-qualification.