In recent years, wing characteristics in low Reynolds number regions such as planetary spacecraft and micro air vehicle (MAV) have begun to be discussed. It is known that birds in the nature obtain lift not only the flapping motion (plunging motion), but also the forward and backward movement. This combined motion can be modeled as an elliptical motion. In this study, two-dimensional unsteady incompressible calculation was done for the elliptical motion of NACA0012 at Reynolds number of 1,000. It was found that the large propulsion coefficient that at an ellipticity of 0.5 occurs when the dimensionless frequency is 0.65, 0.8 during the upstroke and back motion of the wing. This trend is different from the result shown at Reynolds number of 40,000.

For the application of energy deposition method to the actual supersonic aircraft, the vortex generation effect due to the interference between the modulated density field and the shock wave is important, and experiments using a DC discharge and a shock wave tube are expected to be useful for understanding such phenomena. In the experiment, it is expected to obtain further information from the visualized data by deducing the shock angle, turning angle and velocity component behind the shock wave. In this study, the feasibility of the method to deduce the flow property behind the shock wave interacted with the discharge field was investigated.

Based on the Near Space testing service and balloon capabilities developed with ESA, we are adapting our stratospheric balloon platforms to perform different HAPS missions, and already have signed 5 LoIs from customers. Example applications.

For the improvement of the aerodynamic characteristics of the future supersonic transportation, the shock wave modulation effect by utilizing baroclinic effect are expecting attention as new technology. The baroclinic effect is known as one of the vortex generation effects of compressible flow and are occurred by interacting between shock wave and modulation density field deposited energy into the flow field. In this phenomena, the three-dimensional effect has been pointed out. Therefore, we begin to address three-dimensional numerical analysis. In this study, as a first step, for the verification of the developed code, reproducibility of the two-dimensional model based on past research was examined by comparing the past two-dimensional numerical analysis results. As a result, we confirmed that the reproducibility analyzed by using the presently developed three-dimensional code. In the near future, we will create three-dimensional temperature modulation field model and examine three-dimensional phenomena by using the presently developed code.

For the comprehension of the flow filed behind the shock wave interacted with the discharge field, the deduction of the flow properties behind the shock wave based on the experimentally obtained visualized data is one of the promising methods. In this method, the shock angle can be estimated from the visualization data, and then the deflection angle and the velocity component can be deduce based on the oblique shock wave theory in the compressible fluid dynamics. For the development of this method, the assessment of the deduction accuracy is inevitable. In this study, by using the numerical simulation, we tried to assess the deduction method. As a result, it was suggested that some kind of the average operation should be imposed for the estimation of the shock angle from the shock wave configuration data.

HSU-SAT1 is a nanosatellite. The purpose of this paper is to implement the downlink function of SSTV earth image and GMSK data communication function. In addition, we developed software to improve line quality. The results of the line calculation show that the SSTV downlink service and the GMSK data downlink service are feasible.

One of the missions of HSU-SAT1 is the on-orbit demonstration of the self-made bus system. As elements of the self-made electric power supply system, it is required to have a power control circuit to prevent heat generation and save power, safety designs to prevent fatal failures caused by radiation damage to the microcontroller and other devices, and to enable autonomous recovery from transient failures. In this study, we have designed and tested a power control circuit with an overcurrent detection function, a periodic reset circuit using timer circuits, and a circuit to shutdown the transceiver. As a result, we confirmed the operation of the intended function.

We evaluated the internal resistance of a commercial cylindrical lithium-ion battery (LIB) for an electric power system of Cubesats by two kinds of measurements, electrochemical impedance spectroscopy (EIS) and current-rest-method (CRM), and compared the resistive behavior vs. state of charge (SOC) of the battery. The SOC dependence of the internal resistance of the LIB in various temperature environments indicated that the SOC dependences of internal resistance of the LIB evaluated by the EIS and CRM were significantly different, presumably due to the difference in the chemical state of the LIB, in the steady-state or the unsteady state. Furthermore, the feasibility of the in-orbit simulation of the LIB operation based on its obtained resistive behavior was discussed. The SOC behavior simulated with the internal resistance by the EIS method was different from the experimentally obtained SOC curve, while the simulation of the SOC based on the internal resistance by the CRM almost corresponded with the experimental value. Thus, the simulation of the LIB or power system operation based on the internal resistance by CRM method will be applicable to the operation management and the risk evaluation of a power system for Cubesats.

Antennas aboard satellites are used for data communication and radar observations, and by improving their gain, communication speed and distance can be increased. In order to improve the gain, it is necessary to construct an antenna with a larger aperture area in space. However, due to the volume limitation at launch, they are required to have high stowage efficiency. Conventional space antennas use rigid structures, thus their stowage efficiency has been limited. Therefore, antennas using space membrane structures with high storage efficiency are studied herein. For larger storage efficiency, a non-planar space membrane array-antenna that can be established under low tension was proposed. In order to achieve this concept, we need to make a stowable dielectric layer between the patch-element layer and the ground layer. In this paper, we propose a new support mechanism that can stabilize the dielectric layer under low tension by using a pop-up book mechanism. This study fabricates a prototype, and evaluates its storage efficiency and shape stability.

The authors are developing a safe, low-cost, compact, and lightweight reignition device to provide reignition capability to a hybrid kick motor as a propulsion system for small satellites. So far, only HDPE has been used as a solid fuel for the reignition device, with which the desired results have not been obtained. In this study, we measured the amount of gasification of fuel due to the radiant heat of glow plugs using multiple filaments for 3D printing, with the aim of identifying suitable replacement materials for HDPE. A total of more than 100 experiments, including preliminary experiments, revealed that HDPE was the least suitable fuel for the reignition system. On the other hand, it was found that Carbon Fibered PLA is the most effective as it has a large amount of fuel gasification and can maintain the fuel shape.

Hybrid rockets use different phases of oxidizer and fuel as the propellant to obtain thrust. Hybrid rockets have advantages such as higher safety, lower cost compared to conventional type rockets, and restart ability. However, they have a disadvantage of low thrust. In FY2019 research and development of our rated thrust 50kgf class engine, the target thrust was achieved and the engine development was successful. On the other hand, the launch of the rocket powered by the engine failed due to insufficient initial thrust in the launch experiment. In this study, authors aim’s is to develop a small hybrid rocket engine with a rated thrust of 70kgf class, using LOX as an oxidizer and PMMA as a fuel and to increase the thrust by improving the design of the internal parts of the engine without changing the size of engine casing. Static firing tests and performance evaluations of the engine were conducted. As a result, (1) a target thrust of 686N (70kgf) was achieved by increasing the fuel port inner diameter, nozzle throat diameter, and the oxidizer mass flow rate. (2) Compared to the 50kgf engine, there was a decrease in combustion pressure and thrust with time. The reason of the decrease in the combustion pressure and thrust with time is that the relatively fast decrease of He gas pressure for pressurization which was caused by the faster decrease LOX residual due to the increased LOX flow rate.

In this study, we perform basic investigations for the construction of a self-sensing control system using magnetostrictive elements, mainly for the purpose of controlling a three-dimensional tensegrity structure. In the past, systems using piezoelectric elements and linear actuators have been developed, but they have problems such as the installation cost of a controller and the need for a separate sensing system. In this study, we focus on the magnetostrictive element, which has both sensor and actuator functions in a single element, and develop a compact and cost-effective control system to precisely control the shape of the tensegrity structure. In this study, we evaluate the characteristics of magnetostrictive elements and design and develop a displacement control mechanism for the shape control system. The basic displacement measurement experiment of the magnetostrictive element using a laser displacement meter and magnetic flux density analysis using magnetic analysis software are conducted, and the effectiveness of the smart tensegrity structure is demonstrated through both numerical simulation and experiment by actually incorporating the displacement control mechanism into the tensegrity model.

The authors studied the method to attach a de-orbit system to the space debris with a metal harpoon. The shape of the metal harpoon tips is considered to have a significant influence on penetration behavior. Therefore, it is necessary to design the shape of the harpoon tip appropriately to penetrate the debris at any angle. In this study, we investigated the effects of the shapes of harpoon tips on the penetration behavior in the fixed target with oblique angles of 0, 30, and 45 degrees. For example, in the fixed target with the oblique angle of 30 degrees, the flat harpoon tip penetrated at a lower velocity than when the target was placed horizontally. The edge of the flat harpoon tip affected decreasing the penetration velocity. However, with the oblique angle of 45 degrees, penetration velocity was still higher than when the target was placed horizontally. Regarding penetration hole, the conical harpoon tip is most appropriate. However, it significantly influences penetration velocity because its side impacts the target at first with the oblique angle of 45 degrees.

In recent years, low-cost planetary landing explorations have been proposed from a viewpoint of downsizing and mass reduction of space probes. In those mission, porous materials are being considered for shock absorption at landing. Therefore, it is necessary to numerically simulate the phenomena caused by the impact of a porous material onto the planetary regolith, and to assess the performance of such shock absorber. In this study, a new simulation model was developed based on Distinct Element Method to express the macroscopic deformation of a porous material receiving the compressive force. An impact and penetration problem onto regolith was numerically analyzed assuming polyurethan foam as a shock absorber. In the numerical analysis, the rectangular shock absorber was set in front of a cylindrical 10kg weight, and was dropped from a height of 1 m onto a box of silica sand. From the time history of calculated acceleration, it was successfully demonstrated that the deceleration G was significantly relaxed by the presence of the polyurethan foam and that such porous materials are promising for a shock absorbing material at landing on the lunar and planetary surface covered with regolith layer.

It is difficult to determine experimentally the nanometer level structure of shockwave in solid materials. In present study, molecular dynamics (MD) simulation is performed to clarify quantitatively the structure of propagating shockwave in fcc crystalline Al in <100> direction. Simulated metal/metal collision system is similar to the equipment of the split Hopkinson pressure bar which is used for a high-speed deformation test. The non-closed pack (100) crystal plane of the fcc crystal is the collision plane. A new fitting function is suggested for the sturucture of the shock wave. The fitting function has many parameters. The time dependence of these parameters are analyzed.

Recently, components of automobiles and aircrafts have been required to be both lightweight and high strength in order to improve their dynamic performance and fuel efficiency. Therefore, in order to design lightweight and lean structures within the given design specifications, it is important to understand the characteristic in terms of structural property. By evaluating quantitatively the importance of load transfer in the structure, it is possible to use this information as a guideline evaluating the structure that satisfies the requirements of weight and strength simultaneously. In this study, we propose a new method to express the load transfer by defining the spring stiffness K and quantitatively calculating it. It represents the transition of stiffness in each part of the elastic structure. In this paper, the distribution of spring stiffness K is demonstrated by calculating for a flat plate and a perforated flat plate assuming mechanically equivalent simple tension, and is confirmed in the law of action-reaction as stress distribution.

In this work, a single phase of Ni-Al-Ti-based Heusler alloy was prepared by spark plasma sintering (SPS), and the thermoelectric property was measured. In addition, the electronic structure was analyzed by first principles calculation. The results show that the density of states of the as-prepared Ni-Al-Ti-based Heusler alloy in EF is very small, and there is a sharp change in the density of states near Fermi level.

In this research, we aimed to establish a new measurement method of internal stress using MEMS structures. The measurement sample was a thin film metallic glass, which has higher strength and lower Young's modulus compared to Poly-Si. The thin film metallic glass samples were formed by sputtering, and their shape was a fixed beam at both ends. In order to avoid the deterioration of the cross-sectional shape of the structure caused by the film thickening, we used a reverse lift-off method. It is the method that forms film on a desired pattern and remove the others to obtain the flat and uniform thickness structure. We devised a process to fabricate devices to measure the internal stress of a thin film metallic glass samples and confirmed the feasibility of fabricating the devices by carrying out the process. We also tried to measure the displacement of the devices that were successfully fabricated devices.

Recently, developments of micro- and nanofluidic devices have attracted much attention. Electrical sensing of single nanoparticles using micro- and nanofluidic channels is one of the most featured technologies. However, details in ionic current responses induced by nanoparticle transport phenomena have not yet been understood because there is not a useful method to measure local conditions in liquids. Especially, local electric fields and concentrations far from the electrode surfaces in liquids are required to be clarified. Herein, we have developed a glass microelectrode that has a small tip less than 1 μm in diameter and that enables us to measure electric potential distributions in electrolyte solutions. Sequencing the glass microelectrode along a fluidic channel that has an orifice of the sensing portion, electric potential differences is locally measured with a spatial resolution comparable with the glass tip size. It is also found that an electric field almost uniform is formed at the orifice, where concentrations are uniform and current-voltage characteristics obeys Ohm’s law.

The dewetting process of a liquid film is important for circuit fabrication using the surface-selective coating method, which is one of the methods to realize printed electronics. In this study, reflection interference contrast microscopy was employed to observe the three-dimensional shape of a liquid film during dewetting process. Pure water and silver nanoparticle ink were barcoated on substrates with different wettability patterns. We classified dewetting processes into two modes: successful patterning, in which a liquid film splits along the hydrophilic region, and unsuccessful patterning, in which adjacent hydrohilic regions were covered with a continuous liquid film, and sorted out which mode occurs depending on the width of the hydrophilic and hydrophobic regions.

Sharing the sam principle of tracking the bright spots in the time-series images, single particle/molecule tracking (SPT/SMT) and particle tracking velocimetry (PTV) makes contrast in the typical quantity of interest. Namely, characteristics of random motion is also of great importance in the SPT/SMT, whereas PTV solely focus on the velocity field. Brownian motion, the random motion basically caused by the thermal fluctuation in the system, is evaluated as some kinds of diffusion by sampling sufficient data in terms of amount as well as the resolution and precision. The diffusion coefficients are usually evaluated by the mean squared displacements (MSDs) as a function of time. On the other hand, it is often the case that the system of interest exhibits multiple modes of diffusion. While the time evolution of the whole MSD tells us the representative single value, it is often insufficient for the discussion to address the mechanism that results in the multimodal diffusion. Furthermore, it is often desired to detect the multimodality if it exists in the system of interest. Here I would like to introduce the simple method, “logarithmic measure” of diffusion, to enable such detection and evaluation without any prior knowledge of the system.

In this research, the convection dynamics of surrounding fluid in optical trapping of tiny particles is investigated both experimentally and numerically. In the experimental part, a tightly focused laser with the wavelength of 1064 nm is irradiated to polystyrene beads with the diameter of 500 nm or 1 um dispersed in water.. The laser plays two roles: (i) it optically traps the particle at the focal spot and (ii) drives the overall particle motion toward the focal spot. The latter effect occurs away from the region where the laser is irradiated, and reaches several tens of micrometers; thus, this long-range particle transport is not induced by the direct action of the laser, but rather by the surrounding fluid motion. In the numerical part, we try to explain this long-range transport by using the simulation of a simple fluid model that includes optical effects both on the particles and the fluid. The model is based on the Navier-Stokes equations with the Boussinesq approximation and additionally includes two optical effects. One is a force acting on the fluid generated by the optically induced motion of suspended particles and the another is a local heat generated in the fluid by the photothermal effect due to the absorption of the laser. By comparing the experimental and numerical results, it is shown that the buoyancy effect by photothermal heating, which has been considered as the cause of the long-range particle transport, is overwhelmed by the effect of the optically induced particle motion.

Local ion distributions in micro- and nanochannels are influenced by electrical charges and electric fields near wall surfaces, and the behavior of ions is different from that in bulk solutions. Using such unique characteristics, novel sensors and energy converters have been developed, such as pH sensors and electric double-layer capacitors. In the present study, we developed glass micro-electrodes, which has a double-barreled structure, for a small sensor of ionic current responses to liquid flows. A glass micro-electrode showed a diode characteristic due to its ion selectivity, and it was usually sensitive to cation transport. A sub micrometer-sized pore at the tip of electrodes was exposed to a liquid flow in a fluidic channel, and an electric potential was measured under a constant current condition maintained by a galvanostat. When a liquid flow was changed, the electric potential difference increased, responding to the flow rate. It was suggested that the resistivity between glass tips was modulated by a liquid flow, which was sensed by ionic current responses. The proposed glass micro-electrode will shed light on the development of measurement techniques for local flow fields.

A porous material contains many pores inside it. It is widely used as catalyst and adsorption filter because of the excellent properties such as adsorption and permeability, which are not found in ordinary materials. In order to utilize these properties more efficiently, it is necessary to clarify the characteristics of particle motion in porous materials at single particle level. In this study, we have investigated the mechanism of particle motion in porous media by using a single-particle measurement method directly observing the motion of individual particles in a porous material.

Elastomeric gels are soft--elastic materials consisting of a three-dimensional crosslinked polymer network and liquid filling the space among such network. To take advantage of the swelling-deformation behavior of elastomeric gel and explore its possibility for applications in engineering as a structural member, the construction of its mechanical model is indispensable. Therefore, in this study, we at first proposed a nonaffine model for the elastomeric gel to account for the change of the entangling structure of polymer chains during the swelling-deformation process, in which the change of the number of polymer chains per unit volume N is depending on the first invariant of right Cauchy-Green tensor I₁. And then, to investigate the effect of the nonaffine movement of the polymer chain on the mechanical behavior of the elastomeric gel, we performed a FEM simulation for a spherical gel under quasi-static compressive loading condition. The results show that the nonaffine movement of the polymer chain may leads to the decrease of the deformation resistance of the elastomeric gel, whereas it has no effect on its swelling ratio.

Thermoelectric power generation using nanogaps is attracting attention as a highly efficient direct power generation method from heat that can be operated at room temperature, but it is still a theoretical prediction and has hardly been experimentally verified. In this study, we created a nanogap by cleavage fracture of a single-crystal silicon beam fabricated on a micro electro mechanical system (MEMS) device in order to clarify the temperature characteristics of field electron tunneling between the nanogaps. This MEMS device can change the gap distance by electrostatic actuators after the fabrication of the gap, apply bias voltage between the gap, and Joule heating at one end of the gap. We measured the tunneling current across the gap as a function of bias voltage and temperature. As a result, the tunneling current increased proportionally to the temperature difference at the gap, which is consistent with the theoretical calculation of the field electron tunneling between the gaps considering the thermal excitation of electrons. This result strongly suggests that the measured current is due to the electron tunneling through the nanogap, indicating the effectiveness of the proposed method.

Tensile strength of a single-crystal silicon (SCS) microstructure with an alternating hydrogenated amorphous carbon (a-C:H) coating was investigated to explore the enhancement to the coating−substrate system. All sides of the SCS microstructure were coated uniformly with a 300-nm-thick a-C:H film deposited by plasma enhanced chemical vapor deposition (PECVD). Four different single layer thickness (λ) of 25, 37.5, 75, and 150 nm were deposited. The tensile strength of a-C:H coated microstructure was investigated by a quasi-static tensile test, which showed a significant increase for samples with a multilayer alternating coating and a maximum of ~37.8% (4.34 GPa) improvement was found for a λ of 75 nm as compared with the bare SCS sample (3.15 GPa).

A closed form expression of crack velocity of static fatigue of SiO₂ is derived taking into account the effects of material properties such as Young’s modulus, whose values are considerably different among SiO₂ materials made under different fabrication conditions. The calculated results of this expression show that the crack velocity is controlled by the transport process of atmospheric H₂O molecules to the crack tip and has high dependency of temperature in usual velocity range in the case of high Young’s modulus materials. On the other hand, in the case of low Young’s modulus materials, the crack velocity is controlled by the reaction process of crack tip atomic bond with H₂O molecules and has high dependency of humidity.

Carbon nanotube (CNT) is nanomaterial made of carbon, which theoretically have mechanical properties far superior to those of conventional metal and carbon fiber materials and are expected to be used as structural materials for space elevators. In order to utilize CNTs as an engineering material, it is necessary to increase the size of CNTs to a size that can be handled, i.e., several hundred nanometers in diameter. Bundles CNT is bonded by van der Waals forces at the interface of adjacent CNTs, but the strength of the bundle CNTs decreases as the diameter increases. However, the strength of bundle CNTs decreases as the diameter increases. In this study, we apply various chemical treatments to the bundle CNT and investigate the effect on the tensile strength. In order to improve the tensile strength of bundle CNTs, not only chemical treatment but also dispersion treatment is find to improve the tensile strength. Because the chemical treatment can sufficiently penetrate into the bundle CNTs. This indicate that dispersion treatment before chemical treatment is also important to improve the tensile strength of bundle CNTs.

In recent years, as power modules have become more powerful and smaller, mechanically joints are required to have high mechanical strength and low thermal resistance. Nano-Ag sintering and Ni/Sn liquid phase diffusion bonding are known as examples of high heat resistant bonding technologies, but problems remain such as voids. One possible solution is using Al/Ni, a self-propagating exothermic multilayer film, as a heat source and using Al film as an adhesive layer for bonding. In this study, we focus on mechanical reliability of Al/Ni reactive bonding element with Al adhesion layer by four point bending test. The specimens were cut to 0.5 x 0.5 x 3.1 mm using a dicing saw after bonding, and the bond strength of each interface were measured using a four-point bending tester which was designed ourselves in our laboratory. Result of testing with different thicknesses of Al as the adhesive layer that the smallest variation and the highest bending strength were obtained when the thickness of Al was 10 μm. The average bending strength was 1.2 times higher than that of the conventional Sn-3.5Ag instantaneous joint, although the dispersion was larger than solder bonding.

This paper reports on the strength of single crystal silicon beam in torsional resonators fabricated with two different processes to realize a cost-effective high-performance micromirror device using microelectromechanical system technology. One is made from a bulk silicon wafer and the torsional beam was fabricated using a combination of anisotropic and isotropic reactive ion etching (RIE) processes with inductively coupled plasma (ICP), called as Silicon mirror, the other is made from a silicon-on-insulator wafer and the beam was fabricated using anisotropic ICP-RIE and sacrificial etching of the buried oxide film, called as SOI mirror. The torsional strength was measured by a ramping vibration test at the resonant frequency actuated by a piezoelectric actuator. The strength of the silicon mirror and SOI mirror were 0.4 – 1.7 GPa and 2.0 – 3.5 GPa, respectively. The lower strength of silicon mirror is caused by the roughened bottom surface of the torsion beam formed by isotropic RIE.

In this paper, we report a kirigami metamaterial structure that can adjust the gradient of the deformation of the structure. Slits were formed on a polyimide substrate by a laser cutter to fabricate kirigami structures, and aluminum was deposited on the kirigami pattern with a stencil mask. As a structural characteristic, we fabricated several devices with different slit lengths at different locations in the same structure and measured the amount of deformation against external force. It was found that it was possible to adjust the gradient of the wall surface independently for each slit by arbitrarily varying the length of the slit. The transmittance of the proposed device was measured, and the transmittance of the component perpendicular to the direction of incidence increased. It was confirmed that the proposed device has circular dichroism due to deformation. This kirigami can adjust the shape of the 3D metamaterial to show strong circular dichroism and weak circular dichroism frequencies.

Selenium is one of the promising materials for optical absorbers of photovoltaic conversion under room lighting conditions. According to the bandgap energy of selenium (E_g = 1.91 eV), selenium thin film photodiode exhibits high sensitivity at visible wavelengths. We developed the patterning process of selenium photodiode. The adhesion strength of selenium is an important factor to fabricate micro photodiodes. While insertion of a very thin tellurium layer below the selenium layer increases adhesion strength between the selenium layer and the substrate, however the excessive addition of tellurium increases dark current by increasing carrier densities of selenium layer. This paper investigates the influences of insertion of a variety of tellurium underlying layer on material properties of selenium optical absorber layer, such as optical properties, crystallinity and mechanical characteristics. In conclusion, it is suggested that adding thicker tellurium increased adhesion strength between a selenium layer and a substrate. On the other hands, the excessive thickness of tellurium (> 0.9 nm) deteriorated crystallinity of selenium and increased both dark current and undesirable photogenerated current at infrared wavelengths.

Tactile perception is important for capturing and computerizing the grasping state of objects. Based on MEMS technology, our laboratory has developed a tactile sensor using microcantilevers embedded in the elastomer. How to improve the sensitivity of this sensor has always been a problem in the case of grasping lightweight or soft objects. In this work, we investigated the influence of the substrate temperature during sputtering the strain-gauge film on the sensitivity of the sensor. NiCr thin films as strain gauge sputtered at room temperature, 150°C, 175°C, and 200°C, and the tactile sensors using them were fabricated. It is found that the sensitivity of the tactile sensor is significantly improved by using NiCr deposited at higher substrate temperature because their crystalline structure is different from that deposited at room temperature.

A spot periodic heating method is a highly accurate, non-contact method for evaluation of anisotropy and relative thermophysical property distribution. However, accurately evaluating thermal diffusivity is difficult due to the influence of temperature wave reflection from the whole surface of the sample. In a previous paper, we proposed a method to derive thermal diffusivity using a parameter table based on heat transfer equations using the concept of optimum distance between of heating-point and measurement point considering the finite sample size, sensitivity distribution of infrared ray detector, intensity distribution of heating laser and sample thickness. In these results, the obtained thermal diffusivity of pure copper was in good agreement with some literature values. However, in the measurement of pure copper with different thicknesses, the temperature response was different from that obtained by the analytical solution. The effect of reflection of temperature waves is significant and needs to be verified by numerical analysis using the finite element method.

Recently, the Al/Ni multilayer material has been paid attention as a novel heat source for assembling electronic package to improve a solder joint “re-flow” process which could lead to the entire substrate being damaged by excessive heat, because the material has some outstanding characteristics such as ease to get high temperature and instantaneous reaction. In our laboratory, Al/Ni multilayer powder fabricated by cold-rolling has been developed and investigated about the relationships between exothermic characteristics and the number of rolling passes. In this study, commercially available general-purpose Aluminum alloy sheets were annealed and cold-rolled to be changed their crystallite sizes. After that, their thermal conductivities were calculated from thermal diffusivity measured by Thermowave-analyzer based on a spot periodic heating method, and their crystallite sizes were analyzed by X-ray diffraction method. From these measurement results, we evaluated the transition of thermal characteristics according to the crystallite sizes which change with the number of rolling passes.

We used the periodic heating thermoreflectance (TR) method with micro-scale spatial resolution to measure thin films of Al and Mo. The TR method evaluates the phase lag of the thermoreflectance signal (TR signal) from the sample of the detection laser to the periodically modulated heating laser. In this paper, the effects of different physical properties of the thin film are evaluated from simulations and measurements using 3D heat conduction analysis. In the simulations, the beam diameter was measured by image processing in order to approximate the actual measurement conditions. Comparing the simulation results with the measurement results, the frequency dependence of the thermal diffusion length was confirmed for Mo thin film samples, but for Al thin film samples, Si and Ge showed different frequency characteristics from the simulation results. In actual measurements, the YSZ and pyrex of Al thin film did not show any difference in phase delay between the samples compared to that of Mo thin film. Future work includes finding measurement conditions that are compatible with the reflection coefficient of Al thin film and evaluating the TR signal.

Sintered silver (s-Ag) material is expected as a next-generation die-attach material in wide-band gap device packaging owing to its high thermal conductivity. However, micro pore structure is inevitably included into the die layer even with pressure assist, which gives rise to complicated thermal reliability of the packaging. Toward reliable packaging design with s-Ag die-attach, this study focuses on micro pore structure dependence on pressured-type s-Ag tensile mechanical properties. Only nano-sized silver paste was sintered under 60MPa process pressure at 300℃ for 10min (Type A). To control micro pore structure, two types of annealing process was performed after sintering: 350℃ annealing for 30min (Type A’) and 120min (Type A’’). From cross sectional scanning electron microscopy (SEM), mean local porosity rate (p) was 2.4%, 3.2%, and 4.0% for Type A, A’, and A’’, respectively. Quasi-static tensile tests were performed at room temperature (RT), 100℃, and 150℃, where all types of s-Ag showed brittle to ductile transition around 100℃ and ductile behavior at each temperature depended on its initial micro pore structure.

Small and light-weight 9-axis sensor modules have been developed with the MEMS technology progresses. A sensor fusion that corrects drift errors in the gyro sensor output using the measurement information from the accelerometer and magnetometer has been proposed, and is used for posture estimation in daily activities such as walking and sports activities. However, during bicycle riding, the translational acceleration changes and impact from the road surface occurs. This paper presents an extended Kalman filter for pose estimation during bicycle riding using noise covariance matrices based on sensor output. Postural change appears in the gyroscope output because the rotational motion of the joints produces human movement. Therefore, the process noise covariance matrix was determined based on the gyroscope output. An observation noise covariance matrix was determined based on the accelerometer and magnetometer output because the acceleration and geomagnetic sensors’ outputs were used as observation values. The sensor fusion algorithm also uses information obtained from the nine-axis motion sensors to estimate the lower limb joint angles by correcting the centrifugal acceleration and tangential acceleration.

In recent years, various problems have occurred with the spread of automobiles. It’s the illegal entry for which a car was used as one of the problems. In this study, Authors devised the system to distinguish human being presence in a car. Piezoelectric ceramics were used to measure micro-vibrations generated by humans in the car. This sensor was placed under a tire. This sensor was used to measure the vibration of the vehicle body when a person was or was not in the car. By using the cross-correlation function for the measurement results, the presence or absence of people in the car was determined. The maximum of the cross-correlation coefficient and a total were acquired and that was classified using the distribution. As a result, between when human being was not in the inside of car and when it was in car, meaningful difference was seen in many cases and was able to distinguish it.

Using motion capture system and floor reaction force gauge, we studied whether trunk posture relates to shoulder condition during piano playing or not. Eleven music college school students having ill or well-conditioned shoulders (four and seven volunteers, respectively) played two kinds of piano etude (scales and arpeggio), and we audited possible influencing factors. As the results, two factors associated with trunk spin are found. One is steady spin of part of trunk and the other is reverse spin of trunk toward shoulder spin. We recognized that the ill-condition group has lower reverence spin force against degree of spin at lower part than the other group, although sample numbers is very small.

In this study, we focus on the phenomenon that the human body potential fluctuates with the walking motion in order to detect the walking motion under non-contact conditions without attaching the device to the human body. In order to simulate gait disturbance, five healthy male subjects were fitted with ankle weights on their feet to detect gait signals. The electrostatic induction current induced by this walking motion was measured wirelessly. The electrostatic induction current waveform induced by this walking motion shows characteristics according to the degree of inconvenience in walking. Therefore, we are trying to detect the degree of inconvenience in the walking movement of the subject by using deep learning. A recurrent neural network (RNN) using long short-term memory (LSTM) is used for deep learning. From the discrimination results using the obtained learning model, it is clarified that the degree of walking inconvenience can be discriminated to some extent.

The surface of a golf ball is provided with numerous dents called dimples to improve the flight distance. No studies have been conducted focusing on the dimple surface occupancy, which indicates the ratio of these dimples occupying the ball surface, and the dimple volume ratio at the same time. Therefore, we perform a lift and drag measurement experiment by wind tunnel experiment using a model ball when the occupancy rate is changed by changing the dimple diameter and the number of dimples, and the dimple depth is also changed. Then, a flight trajectory simulation was performed based on the obtained results, and it was clarified how the dimple surface occupancy and the dimple volume ratio affect the flight distance.

Dakekanba is the most popular broad leaf tree in Hokkaido. The amount of resource in Hokkaido may be enough for replacing a part of the mass production of bats with Sugar maple, White ash, and Aodamo, which have been used so far in the world. Yellow birch of North America is the same attribute with Dakekanba of Japan. Full baseball bats with the quality to be used in official games were prepared; those fulfilled the standard of the Baseball Federation of Japan. As the preliminary test at bat in baseball fields, present study conducted an experiment of impact with fast pitched ball up to 160 km/h by means of air gun. The apparatus of the Toyama Industrial research and development center of Nanto city was used. The result showed that the deflection, vibration, and damping properties of Dakekanba were close to those of Yellow birch, which were intermediate between those of Sugar maple and Aodamo.

The purpose of this study was to clarify the relationship between psychological skills and mindfulness, which indicates receptive awareness of present experience, in athletes engaged in various athletic activities. To elucidate these relationships, a questionnaire survey using the Diagnostic Inventory of Psychological Competence in Athletics (DIPCA.3) and the Six-Factor Mindfulness Scale (SFMS) was conducted on athletes belonging to the university baseball and rugby teams. Statistical analysis of the survey results showed the relationship between psychological athletic performance and mindfulness constructs, and the psychological characteristics of athletes that differed by sport.

This study conducted a questionnaire for Chinese collegiate athletes in order to clarify relationships between mental toughness and mindfulness as psychological characteristics related to sports performance. Based on answers to the questionnaire, the participants’ scores of mental toughness and mindfulness were calculated and a statistical analysis was performed for these scores. The results of the analysis were discussed based on psychological traits of the collegiate athletes and characteristics of their competitive environment.

This study focuses on meta-cognition, which recognizes one's own mental state, and procrastination consciousness that occurs before, during, and after procrastination, and these psychological characteristics affect procrastination behavior and procrastination tendency. The impact was investigated.

Data were collected from a web questionnaire for college students, and multiple regression analysis was performed with the scores for metacognition / procrastination as the independent variable and the scores for task procrastination behavior / procrastination as the dependent variable. The analysis suggests that metacognition and procrastination have different effects on procrastination behaviors such as procrastination and delays in appointments.

Japanese society is said to be the "stressed society" and physical and mental disorders caused by excessive stress have become a problem that interferes with daily life. Therefore, it is necessary to study more effective stress reduction methods. In this study, the Self-Affirmation Scale, the Interpersonal Stress Coping Scale, and the Self-Affirmation Scale were used. In this study, we examined the relationship between self-affirmation and stress coping using the SelfAffirmation Awareness Scale and the Interpersonal Stress Coping Scale. The results showed that positive relationship coping was associated with self-actualizing attitudes and interpersonal positivity, while negative relationship coping was associated with self-enclosedness and interpersonal aggressiveness. As a result, positive relationship coping was associated with self-fulfilling attitude and interpersonal positivity, while negative relationship coping was associated with self-closeness, distrust of people, victim consciousness, and interpersonal tension.

Wearing a mask is mandatory because it is believed to prevent the spread of COVID-19 infection. However, wearing a mask makes it difficult to read facial expressions, which may lead to miscommunication. The purpose of this study is to clarify whether facial expressions and emotions are correctly conveyed to the other person when masks are worn and when they are not. We used a morphing application to create 12 facial images with 100% of the six basic emotions (happiness, surprise, fear, anger, sadness, and disgust) and 50% of the emotions expressed in daily life. In addition, mask images were combined with the mug shots to create a total of 24 patterns of photo samples. A questionnaire survey was conducted on 172 respondents (26 males and 146 females) to evaluate their emotions. The questionnaire consisted of selecting one of the six basic emotions for each evaluation sample. In the "Happiness 100%" category, 100% of the respondents selected "Happiness" for both the masked and unmasked samples, and in the "Surprise 100%" category, 98% of the respondents selected "Surprise" for both the masked and unmasked samples. The increase in the percentage of correct responses without the mask was seen in "50% surprise" (+39%), "50% sadness" (+36%), and "50% happiness" (+30%), indicating that the facial expression intensity was affected by the mask.

This study conducted a survey for undergraduates in order to clarify psychological effects of appreciation of traditional Japanese, Chinese, and Korean dances. A web-based questionnaire was used for the survey, and the participants were asked to answer free-response questions after watching videos of Japanese, Chinese, and Korean dance works. As a result of the survey, we obtained free-description answers regarding the impressions received from the dances, the changes in psychological state through the appreciation, and the physical movements and expressions that attracted attention. The obtained answers were analyzed using text mining techniques, and the psychological effects of traditional dances of each country were discussed by comparing the results of the analysis among different dances.