In falling accidents in the elderly, there might be a delay in reaction time or movement time in lower extremity. The purpose of this study was to measurement of three axis acceleration during step descending. The subjects were 10 healthy young men. We measured three axis acceleration during step descending with the eyes open and closed. As a result of measurement, the acceleration during step descending greater than the acceleration during walking. There was no significant difference in during walking that the acceleration with eyes open and closed. However, during step descending that the acceleration with eyes closed greater than the acceleration with eyes closed. The results suggest the possibility that three axis acceleration reflects the balance.

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Phase reset of the walking rhythm in response to external perturbations is considered to be one of effective strategies for generating robust locomotion in animals. However, the mechanisms underlying the generation of robust human bipedal walking by appropriate modifications of the phase still remain unclear. In this study, we investigated perturbation response of human bipedal walking by experimentally obtaining phase response curve. Two participants were asked to walk on a split-belt treadmill at 4km/h and impulsive perturbations were applied by sudden decrease in the speed of one-side of the belt at various gait phases. Our results demonstrated that the walking rhythm was consistently delayed for this perturbation, and the amount of the phase reset depended on the phases of the applied perturbations. Phase-dependent modifications of the walking rhythm seem to play an important role for generation of robust human locomotion.

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We constructed a two-dimensional musculoskeletal model of the Japanese macaque for simulation of bipedal walking based on forward dynamic simulation. The musculoskeletal system was constructed as 9 rigid links with 10 principal muscles. To generate locomotion, phase oscillators were used as a model of the spinal central pattern generator and motor commands sent to each muscle was modeled as a combination of square waves. By determining the parameters defining the shape of motor commands using genetic algorithm such as to maximize walking distance and to minimize energy expenditure, bipedal locomotion was generated. Although the generated walking pattern did not coincide with that of actually measured, we found that incorporating restricted joint motions due to muscle's passive resistive property is important for simulating monkey-like bent-hip, bent-knee bipedal walking.

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For the research, we have developed a micro-lathe and a micro-cutting force measurement device. In this paper, we describe the cutting characteristics and empirical equation of cutting force in micro-turning processes using micro-lathe. The work piece materials used were copper alloy (C3604) and aluminum alloy (A5056). From these experimental results, we have obtained the cutting force characteristics by deriving the empirical equation of cutting force. It has been made clear that the cutting force depend on the area of chip section and the cutting speed, and also the specific cutting force in the micro-area of chip section is much bigger than the theoretical shear strength.

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Measurement of an inner wall of micro-hole is mainly target for a miniaturized 3D-CMM. In this paper, we describes about μEDM/μ3D-CMM complex apparatus, and μ3D-CMM with a rotatable probe. Therefore we eliminate the processes of de-installation and installation of the probe. And we can measure 3D coordinate without the installation error of the probe. The μEDM has 5-axis motion and a small tabular electrode. Two axes control linear motions of the electrode and the mandrel. And two axes control tilts of the electrode and the mandrel. This machine can form the rod (φ=300μm) into various shapes (L-, T- or needle-shape, etc). In the μ3D-CMM, it can measure an inner wall of micro-hole (50μm<D<800μm) by rotating the L-shape probe.

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We have been developing the measuring device for motion accuracy of NC machine tools using rotary encoders and link mechanisms (RELM). In previous report, we show analysis of forces acting on links, which is caused by a counter weight and adsorption force of a magnetic tool cup, and compared the path of a steel ball with the actual measurement path. In this report we show the effect of the error in RELM to the path of the steel ball. Also we developed a new magnetic tool cap which is made of polyacetal. This tool cap is low of friction and it can vary the magnetic force against the steel ball.

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This paper deals with a method to construct the mathematical model of the 3D form of a functional part with complex shape based on measurement data. The first process is to smooth measurement data based on a hypothesis that a small area of curved surfaces can be approximated to a part of an ellipsoid. The second process is to construct 3D lattice point data by interpolating and thinning of measurement points. The third process is to extract boundary lines of surfaces composing a physical model form according to changing rate of curvatures and normal vectors. The last process is to approximately define the NURBS surface for each segmented points by the minimum square method. In order to validate the effectiveness of the proposed method, it is described to construct the mathematical model of a crankshaft from measurement data.

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This paper describes a system to predict positions and dimensions of burrs formed in end-milling. Two kinds of burr models are applied for the prediction, that is, "Poisson burr model" estimates the burr formed by cutting edge entering to a workpiece and "Rollover burr model" estimates the burr formed by cutting edge leaving from a workpiece. In the prediction, geometric parameters of a cutting tool, physical properties of a workpiece, cutting conditions and cutting force are used. Some values of these are derived by NC simulator. Predictions and examinations were performed in some cutting conditions. The predictions of top burr agree with the results of examinations.

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An external sensor is generally mounted on a machine tool in case cutting force information is needed. Mounting the external sensor, however, requires mounting space and lowers the stiffness of the system. We have been developing the sensor-less cutting force monitoring method, which can estimate cutting force without an external sensor by using servo information. The estimation accuracy of this method is influenced by friction force arising on guides and the gravity force is needed to be compensated in z-axis. Therefore, high-accuracy z linear-motor-driven stage applying aerostatic guideways and an air balancer is developed to achieve high-accuracy cutting force monitoring. In this study, the sensor-less cutting force control system is developed applying the sensor-less cutting force monitoring. The cutting force controlled drilling of glass is carried out and its validity is evaluated.

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Glass micromachining process is effective to manufacture a wide variety of microfluidic chips in small quantity. This process has advantages, such as fabrication of 3D shaped channels, accurate and fast production in micro order and low environmental load compared with chemical one. However, it is technically difficult in cutting process to detect a contact position of micro tool edge on the glass workpiece. In this study, a novel technology applying the polarization of laser beam is proposed to detect the contact position. As the experimental result, the drastic change of polarized light intensity is observed just after the micro end mill comes in touch with glass plate.

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In welding of aluminum pipes without control, the heat flow causes too much heating and over penetration at the last quarter, and wide bead or melt down often occurs. In order to avoid these problems and to obtain a uniform weld bead over the entire circumference of the pipe, a new system was developed for automatic Tungsten Inert Gas (TIG) welding of horizontally fixed pipes. In the welding control system, a vision sensor for monitoring the molten pool, welding speed controller and neural networking were adopted. The vision sensor consists of a CCD camera and a specially designed mirror which is set in the pipe, and captures the inner image of the molten pool during welding process. Then, the optimum welding speed which depends on the width of molten pool was calculated by the neural network. Finally, the effectiveness of the welding control system is confirmed by welding control experiments.

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5052/6061 aluminum alloy were friction seam butt welding using a numerical controlled friction stir welding machine. The effect of welding conditions on mechanical properties of friction seam butt welded joint were investigated. The burr of weld zone was increased with increasing of welding speed. Weld defects were not observed in weld interface and weld zone showed tine structures than that of the base metal. Maximum temperature during seam welding of the retreating side was higher than the advancing side. Maximum tensile strength of joint showed 217MPa. The joints were fractured at heat attached zone near the advancing side of weld zone.

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AZ61 magnesium alloy plate with 0.6mm thickness was friction seam welding using a rotating disk. The rotating disk was made with SUS304 stainless steel to 100mm in diameter, 10mm in thickness. The microstructure of the weld interface showed finer than that of the base metal. The weld interface had an irregularity. The hardness of weld zone of the joint showed lower value than the base metal. The maximum tensile shear load of the joint was 2.4kN under conditions of down welding and welding speed 4mm/s.

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SPCC steel to 6061-T6 aluminum alloy were lap welded by friction stir welding using a numerical fiction stir welder. The rotational tool with a probe of 1.1mm in length was inserted to A6061 sheet such as upper sheet. A thin compound layer was formed at the weld interface between SPCC and A6061. And microstructure of stir zone showed fine grain structure than that of the base metal. The hardness of stir zone and heat affected zone of A6061 side were softened than the base metal. Maximum tensile shear load of joint showed 6.2kN.

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The automatic welding is widely used for the production of machine and assembly of constructions. It will increase the efficiency of a welding process, productivity and quality of welded joints, it the ability of welding robot,sensors which can monitor a welding process increases. However, there are two problems that the arc welding process is unstable welding and spatters occur in MAG welding and they disturb the vision sensing of welding process. A purpose of this research is construction of a system which is possible to maintain strength of joints in the automatic MAG welding. This system monitors the welding area by CCD camera and the images are processed. Then the system detects welding wire and welding line position, and controls the welding robot to realize the automatic seam-tracking. The new image processing algorithm was constructed to eliminate the bad influence of spatters on a welding image and increase the successful percentage of the welding line detection and the welding wire detection.

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TIG welding process is often used to join thin metal plates because of the stability of arc compared with the other arc welding processes. However, the temperature of the tungsten electrode of the TIG welding torch increases and oxidation occurs during welding process. Therefore, the electrode tip is consumed considerably, and the arc stability tends to decrease with welding time. Accordingly, it is important to administrate the electrode tip condition in order to keep the welding process stable. On the contrary, the laser beam has extraordinary stability and directivity because of the nature of the light beam. Therefore, stabilization and control of the unstable TIG arc by the laser beam has been tried. In this study, the control of the arc behavior in welding of thin metal plates using the hybrid welding process combining TIG arc and YAG laser with relatively low power.

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In general, the diffusion-bonded joint of hard and brittle materials has the low impact resistance. The grain-boundary arranged flatly near the former mating surface is considered to suppress the toughness of the diffusion-bonded joint. In order to improve its impact resistance, the phase-transformation was deliberately induced to encourage the displacement of the grain-boundary at the bonding interface. The tool steel (SKD61 in JIS) square bars were diffusion-bonded at higher temperature than the austenitizing temperature, followed by the various heat treatment to induce the martensitic, bainitic and pearlitic transformations. By the martensitic transformation after the diffusion bonding process, the joints had the comparable Charpy impact value with the bulk material which experienced the same heat treatment. The optical observation of the microstructure revealed that the flat grain-boundary was vanished due to the growth of the martensitic microstructure. The results showed the effectiveness of the successive phase transformation process just after the diffusion bonding process.

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The effect of friction process include of initial contact process on mechanical properties of friction welded S35C carbon steel joint using a brake type friction welder was investigated. The faying surface of works were machined to turning and sawing. The burr and the heat affected zone were increased with increasing of initial contact pressure and friction time. Microstructures of the weld interface showed fine structure than that of the base metal, but the effect of welding conditions were small. The hardness of weld interface showed higher value than the base metal. The tensile strength of joint with faying surface specimen showed as same as base metal.

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For the future construction of the large scale space platform on the earth orbit, the structural engineering materials with the high specific strength and modulus is required to braze in space. The combination of carbon/carbon composites and titanium is one of those candidates. In the brazing process of the combination, the infiltration of the brazing filler occurs and it is harmful to the joint's characteristics. In this research, a 2-D laminated C/C composites plates with cross-ply angle of [0°/90°]S, [+45°/-45°]S and [30°/-60°]S were prepared. They were brazed to pure titanium tablet in the vacuum using the active brazing filler of Ag-32.25Cu-1.75Ti at 830℃ for 300s. The shear strength of the brazed joint was measured by the tensile shear rupture test. All of the obtained joints were fractured at the bulk C/C composites. On the case of [0°/90°] cross-ply laminated C/C composites, the shear strength reached to the maximum value up to 24MPa. The cross sections of the brazed joints were observed by optically and through SEM. The brazing filler was infiltrated along the fiber. The infiltrated brazing filler was not acted as anchors but the crack initiation points.

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Microbubbles oscillating nonlinearly in the ultrasound field are used for contrast agents. In particular, microbubbles surrounded by a protein, lipid, or polymer shell show a mechanical property different from micobubbles without shell. This research, after deriving an analytical model and the governing equation including effects of the shell, investigated the dynamical behavior of insonified shell-coated microbubbles by numerical simulation. Our numerical results show that the oscillation center shifts to the side of bubble compression because the surface tension changes with the bubble radius if the bubble shell exists. These results are in qualitative agreement with experimental ones.

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Recently, microbubbles attract attention as ultrasound contrast agents in the medical field because of their excellent ultrasound scattering including superharmonic response. Such superharmonic signals obtained by detecting ultrasound waves can be used for distinguish responses of contrast agents from those of surrounding tissues. Therefore, nonlinear oscillation of insonified microbubbles has been studied actively. However, most of such studies focus on dynamics of single microbubble. This research investigates how interaction between a pair of microbubbles affects their oscillation. Our numerical simulation shows that I to 2 natural frequency ratio of the two microbubbles can result in their superharmonic resonance. Its mechanism was discussed on the basis of their equations of motion coupled through nonlinear terms.

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An experimental and theoretical investigation was conducted into the spatial motion of the self-excited oscillation of a pipe which is built-in at upper end and has an attached mass at the other. A certain characteristic mode of the pipe vibration is self-excited when the axial flow velocity in the pipe exceeds a certain value. For higher flow velocity,the two distinct eigen modes of the pipe can be simultaneously self-excited with two different natural frequencies,which called mixed-mode flutter. Equations governing amplitudes and the phases were derived and used to clarify nonlinear modal intereractions numerically. It is theoretically clarified that the planes,on which second modal oscillation and the third modal oscillation are produced,are perpendicular .Furthermore experiments were conducted with the silicon rubber pipe conveying fluid. As a result,typical features of the mixed-mode flutter were confirmed qualitatively by experiments.

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A new type of vibration-absorber is proposed using the characteristics of chaotic response generated by a bowed-type beam constrained with stretched strings. The bowed-typed beam is clamped at the center and deformed to a curved configuration by stretched strings which connect both ends of the beam. An elastic structure, which is the target of vibration-suppression, consists of moving block and spring plates. The bowed-type beam is mounted on the elastic structure to decrease the vibration-amplitude on the structure. In the experiment, the structure is excited by an electromagnetic shaker through a ring-spring. Non-periodic responses are generated on the vibration-absorber in a finite region of excitation frequency, then the vibration-amplitude of the structure is suppressed sufficiency. To confirm the mechanism of the vibration-absorber, Non-periodic responses are examined by the Fourier spectrum, the maximum Lyapunov exponent and the Principal Component Analysis. It is found that the vibration-amplitude on the structure with the vibration-absorber is decreased by chaotic response of the absorber.

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Rotary machine is a significant component of many mechanical systems. It is important to clarify the dynamic characteristics in several conditions. This study deals with nonlinear dynamics of a horizontally supported Jeffcott rotor. The equations of motion are derived by considering the effects of gravity and the cubic nonlinearity of restoring force by the support condition. These effects produce the difference between the linear natural frequencies in the vertical and horizontal directions and make the stiffness in the vertical direction unsymmetric. It is theoretically and experimentally shown that due to such effects, the 1/2-Order subharmonic resonances is produced, and the frequency response curve is hardning-type.

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This paper reports the multi-phase-field simulation of isothermal austenite to ferrite transformation in Fe-C-Mn alloy. In this study, in order to estimate nucleation site of ferrite phase in the deformed austenite phase, plastic forming simulation of the austenite phase is also performed with the crystal plasticity finite element method. Based on the simulation results, effects of plastic deformed microstructure in the austenite phase on the final morphology of ferrite phase are investigated.

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The mechanical behaviors of FCC polycrystal are numerically evaluated and the effect of crystal grain shape on macroscopic material property is investigated. The homogenization method, which combines the crystal and macroscopic scales, is introduced to include the effect of crystalline scale behaviors. In the homogenization method, a minimum periodic unit of microstructure to represent the macroscopic property has to be determined, and this unit called as unit cell. There is no unit cell in realistic metals because the actual metals have no periodicity; however, if we can find a representative volume element to reproduce macroscopic properties of a material, it can be employed as a unit cell. In this paper, the material behavior with irregular shaped grains is analyzed, and the effect of the grain shape is investigated.

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Crystal defects induced by irradiation obstruct dislocation movement. Hence, the critical resolved shear stress of irradiated material increases. While part of the radiation defects is swept by dislocations released from dislocation sources, therefore localization of plastic deformation are caused by decrease of radiation defects at the partial region. In this study, in order to predict increase of flow stress due to irradiation, information of densities of radiation defects is introduced into a hardening modulus of crystal. Moreover, decrease of work-hardening ratio is represented by considering disappearance of radiation defects originating in dislocation movement. Values of controlling parameters operating effect of radiation defects on flow stress are decided by a molecular dynamics simulation. We conduct crystal plasticity simulations for copper single crystal under simple tensile condition. The macroscopic stress-strain responses such as increase of yield stress and decrease of work-hardening ratio due to irradiation are numerically predicted.

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In this report, we conduct a multi-physics simulation coupling dislocation patterning with crystal deformation. We use reaction-diffusion equations for dislocation patterning of cell and subgrain. We derive interaction equations between dislocation field and internal stress field induced by long-range dislocation structure through the lattice misfit due to the existence of dislocations. At this time, a number fraction of immobile dislocations assume a role of an order parameter for dislocations. Moreover, we develop a multi-physics crystal plasticity model based on dislocation patterning. Then we carry out two-dimensional FE-FD simulation for a compression of FCC polycrystal plate using the present model.

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In the previous work, the authors developed a dynamic recrystallzation model by coupling the multi-phase-field and the dislocation-crystal plasticity models. Also, a calculation was performed using that model. However, since the free energy of bulk in conventional multi-phase-field model is adopted, the stored dislocation energy is not considered as a driving force of recrystallization. So as to work out this problem, a new double well potential is proposed in this study. This potential function represents the energy of dislocations stored locally in matrix that starts nuclei growing. In addition, the multi-phase-field model with the new double well potential is coupled with the dislocation-crystal plasticity model through the order parameter and the dislocation density. The developed model can be regarded as not only a multiphysics model but also a multiscale one. Furthermore, a simulation is carried out based on the present model to reproduce the nucleus growth and crystal deformation simultaneously.

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The ultrasonic propagation attenuation in a magnetorheological (MR) fluid subjected to a magnetic field is examined experimentally. The cluster formation appears when MR fluid is subjected to a magnetic field. Based on the experiment result, the clustering structures in MR fluid were analysed experimentally in terms of elapsed time dependence. The influence of the inner structure of the MR fluid to the ultrasonic propagation is studied.

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In the past study, seat swing function was optimized from dynamics aspect (hip-sliding force) in diverse conditions. And the influence of seat-swing function on physiological aspect (blood flow) was elucidated. But in the design of seat swing function, it is not had clarified considering both dynamics and physiology yet. In this study, design solution of seat-swing function was clarified considering dynamics aspect and physiological aspect (compressive force at head of the seat cushion that is substitute of blood flow). The design solution of seat swing function is the combination of B.A. and C.A. to decrease both hip-sliding force and compressive force. As a result, it was indicated that design solution was close to hip-sliding preventing curve, when decreasing hip-sliding force was taken precedence, compared decreasing compressive force. On the other hand, design solution was that C.A. close to 0 degree, when decreasing compressive force was taken precedence.

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In the present day, it is important for the artifact design to consider the condition surrounding the design object. it is called circumstance (it is called "Ba" in japanese) in design discipline. The concept of "Ba" has been introduced into various disciplines including natural science, social science and humanities. In the present study, the concepts of "Ba" in the various disciplines are overviewed focusing on the timing of the introduction of the concept of "Ba" and the relationship among various disciplines. Moreover, the previous concept of "Ba" in design discipline are overviewed.

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In innovation thinking, creation and idea generation capability attract attention in recent years. This research focuses on the idea generation method of designers who visualize abstract expression of the concept in a beautiful product. In it, we focus on the display technique which many designers utilize. The comparative analysis was made for the purpose of analysis of the relation between drawing skill and the design idea generation. Furthermore, based on the multi-space design model which is a framework of design theory, the role of the display technique in the design idea generation was analyzed. The result checked the conversion function to the attribute expression from abstract expression. And the tendency which develops and displays many appearance attributes from a structure attribute was shown.

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In the design of the 21st century, it is important to consider the diversity of circumstance and sense of values and those timeaxis changes. However, it is thought that correspondence becomes difficult in the method used to design an existing artifact to which value declines as time passes. To solve it, the timeaxis design is advocated as a paradigm of a new design corresponding to the diversity of circumstance and sense of values and those timeaxis changes. This text is to be shown the concept of the timeaxis design corresponding to the timeaxis change of the artifact and circumstance, and to make a proposal of the timeaxis design model based on multispace design model, in addition to its application.

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An application of emergence behavior for mechanical design calculation is discussed. Although prevailing simulation methods, such like FEM, suppose well-posed configuration for their problems and this nature limits application area of the methods in downstream design stages, importance of simulations in upstream design stages has been getting bigger year by year. The breakthrough can be possible by introducing emergence behavior in the simulations. Beginning with a brief introduction of emergence notion and preceding researches, our emergence based calculation scheme is proposed, followed by examinations of qualitative comparison with a iterative solution and observation of dynamical states of the proposed scheme.

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In the design of product texture, it is important for a designer to grasp the difference of user's affective characteristics between single-modal sensations and multi-modal one. Customers' emotional responses may differ depending on visual, touch and their combination. In this paper, we propose an evaluation framework to visualize the difference of kansei structure towards product texture between different modalities. In the method, we apply the simultaneous relationship analysis and ISM (Interpretive Structure Model) to structure words for evaluating texture's kansei. The framework considers actions for evaluating touch i.e. haptics and affordances towards texture. To demonstrate the effectiveness of the framework, we conducted a sensory evaluation experiment using plastic texture samples and cylindrical shapes having different textures as case studies.

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In the design of matured product, it is important to design a product sound as a kansei(affective) quality. Most of product sounds have ultiple tones e.g. harmonic overtones caused by frequency of fans. In the music theory, tones have chords. People often feel comfortable in chordal tones. The authors assume that chordal harmony in machine sound improves the product kansei quality. To verify the assumption, we synthesized product sound samples (vacuum cleaner) having different tone frequencies and powers. Using the synthesized samples, we conducted kansei evaluation experiments. The result shows that the chordal features of tones are effective to improve product kansei quality.

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The injection-molded-plastic-gears are used in such many fields as home electric appliances, information processing equipments, automobiles and so on. Many factors have an effect on load carrying characteristics of an injection-molded-plastic-gear pair. Among others, the materials and the temperature of plastics are the most important factors, because the plastic physical property is greatly different in each plastics type, and the high temperature causes the decrease in Young's modulus of plastic. Therefore, the plastic gears are mixed with the reinforcing materials, which are glass fibers, chemical fibers, and graphite for keeping strength even in high temperature. On the other hand, natural materials are used to focus on the ecological recycling. Based on the above background, the authors focused on using a rice-hull-silica-carbon (RHSC) with a reinforcing material in plastics. In this study, the strength of the plastic filled RHSC gears was compared with the polyacetal (POM) gears.

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The injection-molded-plastic-gears are used in such many fields as home electric appliances, information processing equipments, audio-visual equipments, automobiles and so on. In this study, the injection-molded-plastic spur gears were used. The test gears are made from two types of plastic. One of these plastics is polyacetal (POM), and the other one is the plastic filled with rice-hull-silica-carbon (RHSC) as reinforcing materials. The experimental results showed that the RHSC has a beneficial effect on the filler of plastic. Based on the experimental results, the effects of RHSC were discussed. From the discussions, it seems reasonable to conclude: (1) The RHSC decreases the friction of tooth surfaces. So, the high frequency noise is reduced. (2) The process of tooth wears differs in existence of RHSC. Therefore, the gear noise is affected by the wear of tooth surface. (3) The median diameter of RHSC has no effect on the sound-pressure level.

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The spur gears have teeth parallel to the axis. In contrast, helical gears have teeth leaned to the axis. A combination of helical gears is called the crossed helical gear. A lot of knowledge of crossed helical gear has been obtained. But the most knowledge is about the combination of the metal gear. In recent year, plastic gears are widely used in AV equipment, OA equipment and electronic equipment. But, research reports for plastic crossed helical gear is not enough. Then, in this paper, we conduct experiment in the life of the plastic crossed helical gear and the characteristic is clarified.

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Worm gears have several advantages. For example, the large reduction ratio is easily obtained, the noise is small and the power can be transmitted at right angles. But, there are also some disadvantages that the frictional heating is large. Therefore, when a plastic gear is used, it is necessary to be careful. Actually when a plastic is used, it is often used a helical gear instead of the worm wheel. And so the running tests for a plastic helical gear meshed with a steel worm were carried out in a state of unlubricated and grease lubricated conditions using a power-absorbing-type gear test machine. The tooth surface temperatures of a plastic helical gear were examined under various operating condition. On the basis of these results, operating condition and temperature rise from atmospheric temperature of meshing teeth has been confirmed that there is a relationship.

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The objective of this study is to understand aerodynamic characteristics of the three dimensional flow around square cylinder with grooves. Especially, we focus on dependency on the characteristics of three dimensional flows. We carried out wind tunnel tests for the measurements of drag forces, which act on a 2D and a 3D square cylinder. Experimental investigations on the flow around square cylinders were carried out in the range of 5.6×10^4≦Re≦1.69×10^6. As a result, drag coefficient reduction of a square cylinder with groove is lower in 3D flow compared to 2D flow.

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The influence of wall compliance on the turbulent boundary layer on a flat plate was investigated experimentally by measuring the frictional drag on the wall surface. Test compliant walls are made of silicon resin having Young's modulus of E=1.25〜1.47MPa, density of p_c=1.12×10^3〜1.22×10^3kg/m^3, and the thickness of t=7mm. The mean velocities over the flat plate are U_m=0.1〜0.7m/s (Re=3.6×10^4〜2.5×10^5). The experimental results of the drag measurement show that turbulent frictional drag is reduced by up to 7% for one of the compliant walls tested.

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In the present study, we investigated characteristics of a swirling flow in an air channel of a disk shape planar solid oxide fuel cell (SOFC) by using a particle image velocimetry (PIV). In the case of applying circle involute shape current collectors in a lower section of the air channel, the swirling flow maintained constant speed in the free stream region toward the channel exit. This is because a flow passage consisting of two adjacent involute curves functions as a constant-area channel. Furthermore, when involute shape current collectors were arranged in the reverse direction of involute support plates installed in the upper section of the air channel, a flow uniformity was achieved over the wide range of Reynolds numbers by optimizing flow directions.

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Drag reduction is a technical issue on the reduction of carbon dioxide gas emission. Particularly, DBD plasma actuator is a promising technology on active control of the flow separation. In the present work, efficiency of the plasma actuator is investigated experimentally for a variety of parameters including dielectric material, thickness of the dielectric plate, and gap between two electrodes. It is found that: (a) efficiency increases substantially with decreasing thickness of the dielectric plate, however maximum value exists for the applied voltage; (b) as for materials, efficiency of polytetrafluoroethylene (PTFE) is 〜400% larger compared to polyoxybenzylmethylenglycolanhydride (Bakelite).

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Characteristics of a plasma actuator driven by direct-current discharge were studied experimentally in a supersonic flow. The discharge is generated between two small pin electrodes mounted on a Laval nozzle wall with a circle constant cross-sectional area in a Mach 3 flow. In order to investigate the plasma phenomena, two types of electrode arrangements were examined. Current and voltage measurements indicated the generation of the discharge at low power consumption. It was confirmed that the wall static pressure increased beside each electrode and decreased just behind the anode for a 100mA discharge. Furthermore, the increase in stagnation pressure was observed close to the anode surface. It was suggested that enthalpy elevation due to the Joule heating of the flow led to the change in the stagnation pressure.

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Because the operation of a passive type polymer electrolyte fuel cell (passive type PEFC) is accompanied with complex phenomena such as an electrochemical reaction, heat and flow, it is hard to obtain an appropriate orientation for the improved design. Numerical analysis is conducted for the purpose of obtaining the parameters in the improved design, which leads to reduction of time and expense in a trial production and an experiment. In this paper, using the COMSOL Multiphysics, a general commercial software, was used to compute the multiphysics of the passive type PEFC. The model uses current balances, mass transport equations (Maxwell-Stefan diffusion for reactant, water and nitrogen gas), and momentum transport (gas flow) to simulate a passive type PEFC's behavior. The results showed that the computed diffusion velocity vectors of 02 and H2O, the mass fraction of H2O, and the current density on the MEA surface were qualitatively reasonable well.

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It was found in our previous study that the passive type polymer electrolyte fuel cell (PEFC) with the dead end system, suffused from power breakdown after in a short time the start of the experiment because anode of flooding. In order to overcome this short coming without relying on pumps, the hydrogen circulation system utilizing the pressure difference was developed. The influence of pressure and flow rate was also investigated. The tested PEFC module consisted of 20 cells laid out in plain and they were connected in series. The system was controlled so that the hydrogen pressure in the module was kept between 5kPa and 15kPa with a valve and two check valves. In this system, the valve repeated the ON-OFF operation and produced hydrogen circulating flow and removed the water. This system demonstrated a long time operation more than 6 hours.

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Only the water drop discharged on the channel surface has been observed at this laboratory. Therefore, it was difficult to observe the internal situation of the gas diffusion layer which diffuses reactive gas. It was found in the past research that generated water moved from a pore to a bigger pore in GDL their influence on. In this research, the porosity and thickness of GDL were varied in the in-situ experiments, and the discharge of water droplets and power generation performance were investigated. As a result, as the porosity varied in condensation conditions, because the stoma distribution inside GDL differed. The discharge behavior of water changed. Since water would be sucked up for the direction of a thick thing by the action of capillary-tube pressure if what has thin thickness is compared with a thick thing, it becomes difficult to produce flooding and the improvement in the engine performance was found.

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In order to realize of CO_2 ocean sequestration, it is important to reveal the knowledge of CO_2 hydrate film thickness which forms on the interface between liquid CO_2 and sea water. However, knowledge of CO_2 hydrate film thickness under various parameter conditions such as temperature, pressure, convective motion of surrounding fluid, and elapsed time from hydrate formation is little. The objective of the present study is to investigate the influence of the elapsed time from CO_2 hydrate formation on the CO_2 hydrate film thickness. In this study, CO_2 hydrate film thickness is measured with laser interference method in time series. As the result, CO_2 hydrate film thickness of about 21μm was kept at 7.0〜9.6℃ and 6MPa during 3 hours.

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