Dragonflies can perform both of gliding and flapping flight and have high maneuverability in spite of small-size. The aim of this study is to develop Micro Air Vehicle (MAV) based on the flight of dragonfly. The characteristics of wings are very important for development of MAV. Dragonfly wing is easy to be passively deformed in the tip side from the nodus in flapping flight, and thereby, aerodynamic force is generated effectively. In this study, the effect of passive deformation of wing on aerodynamic force was investigated using fluid-structure interaction analysis to develop the artificial wing suitable for dragonfly-like MAV. In this study, aerodynamic characteristics of wings in the gliding flight and aerodynamic force generated in flapping flight are numerically analyzed. In this analysis, nodus wing models, which can deform passively, and rigid wing model, which cannot deform, are used. Nodus wing model imitates the nodus structure; the tip side of this model is free to rotate around leading edge. As a result of gliding flight, the lift coefficient of the nodus wing was lower in low-angle of attack and was higher in high-angle of attack, compared to rigid wing. Moreover, the more flexible wings are, the more change. The gliding flight is low-angle of attack usually. Therefore, flexible wing is less suitable for the gliding flight than inflexible wing. As a result of flapping flight, the nodus wing made drag force generated during down stroke lower compared with the rigid wing. However, thrust forces generated during up stroke in both wings were the same. Therefore, flexible wing is more suitable for the flapping flight than inflexible wing. The wings of dragonfly-like MAV need to appropriate level of flexibility to upgrade the performance in both case of gliding and flapping flight.
The mosquito's wing is deforming during flapping stroke and the pitching angle is changed. The motion called “feathering motion” is considered that the wing is deformed passively by the aerodynamic force. But it is not established yet. In this paper, first, the bending stiffness of mosquito's wing for chord direction was measured with cantilever. Secondly, the flexible 10 times enlarged wing models which have same planar shape and wing area and different thickness were made with Polyphenylenesulfide resin films. Finally, the behavior of each enlarged wing models during flapping motion in the wind tunnel was measured and was compared with the motion of the real mosquito's wing. Then, both Reynold number and Strouhal number of model experiments were conformed to those of real mosquito. The results of measuring the bending stiffness of mosquito's wing for the chord direction showed the wide range values from 2 to 125 pNm2 and the averaged value of 53 pNm2. The results for the enlarged wing model showed that the amplitude of change of inclination angle during flapping motion decreased as the thickness of film increased. The enlarged wing model in which the bending stiffness was almost similar to that of real mosquito's wing showed the feathering motion like those of the real mosquito.
Many features of organisms have the possibility that can be applied to the infrastructure and network system for the communication. From the previous studies, the network system of the venation is known as the strong network on the damage. This relates the structure of leaf vein. In this study, we are focusing on the network of leaf vein to understand the strong network system. First, we study the network structure to know the relation between damage on leaf and the strong network. Then, the influence of damage on leaf vein for the water absorption on the leaf was studied with the dye flow visualization. The result shows that the network type of vein on real leaf is the mesh type network. The mesh type network has the benefit to make a bypath when the vein has the damage. The result of dye flow visualization shows that the real leaf requires the single vein to make a bypath for damage region. The increasing of area on water absorbed relates the distance of water absorption. This means that number of vein is not dominant for the speed of water absorption. Therefore, the network of leaf vein has a high robustness from the damage of vein by the mesh type network.
The typhoon often causes a serious damage of the apple before harvest. Many apples fall from trees by the strong wind. These apples are bagged to protect them from insects and control sun light for the apples coloring while they are ripening on the tree. We conceive that the wind-force acting on the bagging apple exceeds one without bag. Thus, we investigate the drag coefficient CD of the bagging apple by measuring drag force acting on an apple model experimentally. The shear stress on a stem under the typhoon is estimated for understanding one of mechanism for dropping apple due to the strong wind. The shear stress of a stem whose apple encounters the maximum velocity recorded at the past typhoon is estimated by the obtained CD. The drag force of the bagging apple becomes bigger than that of the apple without the bag. The bagging apple is not a rotational symmetry so that the CD is different with the different wind direction. The angle against the flow of model with the bag is changed from 0 deg. to 90 deg. to understand the influence of shape, since CD depends on the geometry. The shear force acting on the stem depends on the drag. Thus, the shear stress is larger if the drag is larger. The obtained shear stress is compared with allowable shear stress of a real tree. We suggest that there is possibility to decrease damage if we can decrease the drag of the bagging.
In order to investigate an effect of glycocalyx layer covering vascular endothelial cell surface on molecular transport, a super resolution LIF (Laser Induced Fluorescence) technique for concentration distributions measurement with high spatial resolution based on super resolution microscope, stimulated emission depletion (STED) microscope, was developed. Culturing of endothelial cells on side wall of a microchannel with the width of 500 μm and the depth of 88 μm made from PDMS (Polydimethylsiloxane) was achieved by optimizing surface modification. Time series of concentration distributions of dextran stained with Alexa Fluor 488, excited at 495 nm and emitted at 519 nm, near surface area of an endothelial cell including glycocalyx layer attached on side wall was obtained. The visualized images were 2048×2048 pixels, 16 bit grayscale and pixel size of 37.9 nm corresponded with 77.5×77.5 μm, and time interval of 165 seconds. Furthermore, a dimension of glycocalyx by stained with wheat germ agglutinin Alexa Fluor 488 conjugate was measured using super resolution microscopy. Although concentration of dextran within glycocalyx layer was constant as time proceeds, that around outside of the cell surface increased gradually. The measurement results suggested that glycocalyx layer with 0.43 μm thickness affected molecular transport out of the layer with a distance of around 10 μm from the layer.
Purpose of this study is to investigate the relation between the shape of a thin plate and thrust force. The thin plate is what imitates the fish’s caudal fin. We adopt an equilateral triangular, square, regular pentagon and hexagon as the shape of the plate. There are two ways of yielding thrust of fish; 1) drag-type as seen in flatfish and cod, and 2) lift-type as seen in tuna and shark. We focus on the drag-type fin, and consider reasons of different thrust with different shape of the fin. We simulate the reciprocal motion with some frequency of the plate as the fish tail at both situations in water being at rest and under a uniform flow. We measure the force acting on the plate directly, and consider the generating mechanism of the thrust due to the motion of the plate. To estimate force acting on the plate, we introduce the momentum consideration and the circulation of vortices due to the impulsive pressure of an edge of the plate starting suddenly. We discuss the relation between the shape of the plate and force due to the accelerating and decelerating motion of the plate in this paper. The most powerful shape of the fin is the triangular for an impulsive start. The spin parameter has to exceed 0.84 to produce the thrust force in the flow.
A number of studies on not only the mechanism of insect flight but also the flow field around insect wings have been performed. Especially, a number of recent studies have examined the flow field around insect wings using experimental and numerical approaches. The vortex structure and the dynamic behavior generated by the wings of insect are expected to be important for generating the aerodynamic forces required for flight. In the present study, we attempt to clarify three-dimensional vortex structure in the wake of a free-flight butterfly from the viewpoint of the velocity fields. We conducted two kinds of PIV measurements, such as a stereo PIV and a scanning PIV, in the wake of a free-flight butterfly (Idea leuconoe) and visualized a three-dimensional vortex structure in the wake. The three-component velocity vectors formed in the wake of a free-flight butterfly were obtained by stereo PIV measurements. Jets induced by the vortex rings in the wake were visualized clearly and a three-dimensional vortex structure in the wake was expected by the dynamic behaviors of jets. The formation of an L-shaped wake structure due to an interaction of the vortex rings produced during upward and downward flapping was obtained by scanning PIV measurement. On the basis of these results, the vortex rings produced during upward and downward flapping were formed continuously in the wake of the free-flight butterfly and they became the formation of an L-shaped wake structure.
Hydraulic excavators and cranes are major heavy equipment with numerous one-sided welded joints. Although fillet weld joints are easily implemented and economical, the unwelded portion frequently initiates crack propagation. Therefore, the welded portion is reduced by side welding and by adding a groove. However, attachments with box like structures are difficult to weld at both sides, and grooving cannot completely remove the welded portion because high-quality full penetration welds are difficult to achieve. Despite the need for an accurate evaluation method of crack propagation, the fatigue fracture mechanism and the fatigue damage in practical fillet joints with one-sided welding remains poorly understood. In this study, the fatigue properties and the fracture mechanism of the load carrying type fillet joints with one-sided welding were investigated experimentally to evaluate its fatigue damage with high accuracy based on the experimental results. As the results, fatigue cracks in the test piece initiated from the tip of the unwelded portion and propagated into the welding materials. The three-dimensional observations revealed that fatigue cracks initiate at an early stage of the fatigue development. So, we infer that the fatigue lifetime is chiefly governed by the crack propagation lifetime. Furthermore, from the three-dimensional observation results, cracks were initiated at multiple sites in the test piece. As the number of cycles increased, these cracks propagated and combined.
This paper describes the elucidation about the surface modification processing of permalloy 45 using Na2SO4-electrolyzed oxidizing water (It abbreviates as Na2SO4 EO water). Firstly, as for the influence of Na2SO4 EO water on the surface micro shape of permalloy 45 which was processed in the polish to the mirror surface, it was made clear using the results of FE-SEM observation and AFM measurement of the test pieces surface before and after immersion processing. The results is as follows. In the case of non-heating processing, if using Na2SO4 EO water compared with the H2SO4 solution and NaCl EO water, the test pieces surface is more uniformly done by the etching. In the case of heating processing, Na2SO4 EO water, H2SO4 solution and NaCl EO water are same and don't have big influence on the test pieces surface. Next, it reviewed about the removal of surface oxidation layer in the test pieces surface after heating processing. The results showed the surface oxidation layer can be more efficiently removed if using Na2SO4 EO water compared with H2SO4 solution; however, there is possibility that surface oxidation layer which is thicker than a natural-oxidation layer is formed. By this study, it got the possibility that Na2SO4 EO water can be applied to the surface modification processing of permalloy 45.
Singular stress occurs at the vertex of interface in three-dimensional joint structures under an external force and a temperature variation. It is very important to estimate the intensity of singularity for evaluating the strength of joints. Until now, the intensity of singularity in the three-dimensional joints is usually obtained by approximating the stress distribution using a power-law equation. In the present paper, a conservative integral proposed by the authors is applied to estimate the intensity of singularity. A suitable radius for integral domain is investigated by varying the size of minimum mesh and the ratio of the radius of integral domain to the width, L1, of model. It was found that the intensity of singularity was obtained within error of 3% even if the minimum radius of integral domain was equal to the minimum size of element in our conservative integral. The accuracy of calculation reduced with the decrease of the radius of integration domain. The intensity of singularity was obtained within the error of 3% for several values of width in the joint using data of displacements and stresses by the boundary element method. The intensity of singularity could be calculated within error of 3% using an arbitrary radius of integration domain under w/L1<a/L1<10-1 in the range where the radius, a, of integration domain is larger than the minimum size of element and in the singular stress fields.
Peel test is widely used to evaluate interfacial strength of adhesive tape. The interface strength is usually obtained by subtracting energy consumed for plastic deformation of substrate film from external work for peeling. Deformation of substrate results from interface strength generated in adhesive layer, whose mechanical property is regarded as elastic when substrate is thick enough. It is also convenient to calculate deformation of substrate with assuming elastic behavior of adhesive layer. However, substrates thinner than 100 μm may be affected by viscoelastic property of adhesive layer since thickness of adhesive layer is no longer negligible. It is indispensable to investigate the influence of viscoelastic behavior of adhesive layer on evaluating interface strength of particularly thin adhesive film. In this study, 90° peel test was conducted and the interface strength was evaluated by modifying conventional elastic model to consider viscoelastic behavior of adhesive layer. Stress in adhesive layer caused from displacement of substrate is a function of strain and strain rate, and the corresponding deformation of substrate was computed by finite element method. The shape of substrate deformation was compared with one obtained from conventional elastic model in terms of thickness of substrate and peel speed. The interface strength was also obtained from directly observing peel shape using high speed camera to validate the proposed model. As a result, it was found that the substrate shapes were similar regardless of models when substrate was thick, but proposed model more accurately reflected the influence of peel speed in the thin substrate.
One of the advantages of polymer quenching is that it has slower cooling characteristics than water quenching. On the other hand, in polymer quenching, unlike oil quenching and water quenching, cooling effect changes with an increase of the number of quenching times. When slow cooling performance in polymer quenching deteriorates, quenching cracks sometimes occur. One of the causes of quenching cracks is regarded as the stress that occurs due to quenching. Quenching stress is affected by a cooling rate. Therefore, in order to prevent the quenching crack in polymer quenching process, it is important to understand the relationship between the change of cooling performance with deterioration of polymer solution and the quenching stress. The change of slow cooling performance of polymer solution with the number of quenching times was investigated. The cooling performance was evaluated by heat transfer coefficient which was obtained from quenching experimentation. The slow cooling performance of deteriorated polymer solution decreases below the solution temperature of 350°C comparing to the fresh polymer solution at the same polymer concentration. As a result of quenching stress analysis, it was found that the largest quenching stress was obtained in deteriorated polymer quenching. In addition, in order to investigate the cause of the decrease of slow cooling performance, molecular weight of polymer solution was measured. The percentage of low molecular weight contents increased in deteriorated polymer solution. In order to confirm the effects of molecular weight, the cooling performance was investigated using deterioration-simulated polymer solution, which was prepared by mixing polymers having different average molecular weight. As a result, it was confirmed that the slow cooling performance of simulated polymer solution also decreased as well as actual deteriorated polymer solution.
In this paper, we study the optimization of the burst frequency applied to the plasma synthetic jet actuator (PSJA) using extremum-seeking method. Experiments were performed to detect the optimum frequency that maximizes the effect of reducing flow separation around an NACA0015 airfoil. The burst input is expected to improve the effect of flow control and to reduce the power consumption. The optimality is determined based on the correlation of the modulation frequency and the wake velocity. The optimum frequency was searched in the interval from 30Hz to 310Hz and was detected within few seconds. The main flow velocity was set from 5m/s to 10m/s and the angle of attack was fixed at 10deg and 15deg. For 15deg angle of attack, the multiple frequencies were detected as local maximums under each main flow velocity. We found that the flow velocity is maximized at around 50Hz burst frequency for 9m/s main velocity and 15deg angle of attack. At this frequency, the flow velocity is approximately 37% higher than the minimum velocity over the search region of the modulation frequency. The optimum non-dimensional frequencies are in the range from 0.3 to 2.5. For 10deg angle of attack, the flow velocity monotonically increases with respect to the modulation frequency at all main flow velocities.
A mutual compensator for a thermo-anemometer was investigated to realize a high precision simultaneous measurement of temperature and velocity fields in a temperature stratified flow. The frequency characteristic of the cold wire thermometer deteriorates in accordance with the first order delay due to the heat capacities of the fine wire sensor and its prongs. In this paper, the new compensation method was proposed to digitize the frequency compensator for the cold wire thermometer. The compensator with the first order progress characteristics was built by utilizing the bilinear transform, which is one of the mappings from an analog region to a digital one. The realization of the intended characteristics indicated the effectiveness of the present method for constructing the digital compensator. The digitized compensator was mounted on the FPGA device capable of fully parallel operation. The executing of the algorithm was limited a fixed-point arithmetic on the FPGA. Thus, the operational precision was assured by using bit shift processing for every calculation. As a result, the adequate first order progress characteristics were obtained in the frequency range to 5 kHz. The developed compensator was evaluated by directly applying the periodic temperature fluctuations to the sensor in the frequency range from 0.01 to 10 Hz. The results showed the gain error of this system against 0 dB was ±0.8% or less. It means that the digital frequency compensator with the enough accurate for the thermal fluid measurements is realized through the bilinear transform and the FPGA device.
A novel method of controlling gas flow rate using magnetic fluid is proposed. Magnetic fluids under non-uniform magnetic field have strong dynamic pressure distribution along the magnetic field gradient at the gas-liquid interface with bulk magnetic body force. The principle of proposed gas flow rate control technique is based on controlling the pressure distribution, which can be controlled by magnetic field. In this report, controlling technique is introduced and the accuracy of the flow rate control with resolution of the control technique is reported. From measured data (giving a reference for measuring the small gas flow rate), it was found that the flow rate decreases with increasing magnetic flux intensity, and is largely dependent on the magnetic pressure which acts on magnetic fluid, particularly to the interface of gas-liquid phase. The flow rate and the magnetic pressure have a definite relation with the flow coefficient, so that, the flow rate can be controlled only by the magnetic pressure. It was satisfactory verified from the proposed controlling technique that the proposed gas flow controlling method is useful to control the low gas flow rate as low as 0.3×10-5m3/s with the excellent resolution.
This paper deals with the influence of the number and combination of frequency components in an input signal on the spatial evolution of turbulence using a multi-fan type wind tunnel, where 99 fans were driven to generate turbulence. In order to understand the elementary process of the evolution, we compose the input signal of a small number of frequencies (i.e. one or two). The input frequencies are defined as integer multiples of f0, the reciprocal of a basic input data period. In the single-frequency case, the evolution of the spectrum of the streamwise velocity fluctuations shows that the peaks associated with the input frequency and its harmonics remain over the tunnel length. In the two-frequency case, f1 and f2 (f1 = n1f0 and f2 = n2f0;n1 < n2), where n1 and n2 are integers, the generated turbulence characteristics depend on the relation between n1 and n2. When n1 and n2 are not coprime, dominant spectral peaks associated with f1 and f2 remain over the tunnel length as in the single-frequency case. However, when n1 and n2 are coprime (i.e., the only common positive factor of the two number is one), the spectral shape becomes broader as the turbulence convects downstream, with the peaks gradually merging into the background turbulence and also identified is a scaling region, known as the inertial subrange. Thus, we select this way as a driving mode. The evolutions of the turbulence characteristics including turbulence Reynolds number, intensity, homogeneity, and isotropy are examined. In the downstream region for X/MD ≥ 46.5, the evolutions are in good agreement with those of the forty-frequency case obtained in a previous study, although the development of turbulence is much slower for the two frequency case than for the forty-frequency case.
In this paper, we deal with a design method for nonlinear systems, focusing on flat outputs of the dynamical systems. The reason why flat outputs are focused on is as follows. Once flat outputs are found for nonlinear systems, all we have to do is to apply a linear design method to such nonlinear systems. This paper proposes a new type of practical computation method for flat outputs, because the existing computation methods are complicated and not suitable to a control design from a practical point of view. Simulation is given for illustrating the usefulness of the proposed design method.
This paper describes new mechanisms, principle, control methods and experimental results of the jumping and rolling spherical robot which has not any projection. The robot consists of spherical mono wheel, internal drive unit and internal jumping mechanism using a compression coil spring. Straight running is performed by movement of the centroid when the drive unit moves along the inner surface of the spherical wheel, and turning is performed by rotating of the drive unit and friction torque of the spherical wheel with the ground. Theoretical result of straight running and turning movement coincide with experimental results of the robot. Jumping movement is caused by impact force between whole internal mechanisms and the inner surface of the spherical wheel by releasing stored energy in the spring. It was confirmed experimentally that the new robot has high jumping faculty in addition to the basic movement of spherical robot. Furthermore, jumping in any oblique direction is performed by control the posture of internal mechanism, and it becomes possible for the robot to go up the steps of stairs in this way. Therefore, we conclude that the all direction jumping and rolling spherical robot which has not any projection is achieved, and expect that the robot is useful as a rescue robot which can correspond to a variety of use environments.
In this paper, we consider controller synthesis problem of power assisting system for almost-periodic motions. The simplest assist method would be to apply assist force generated by actuators in proportion to the instantaneous value of the force generated by human. There seems to be no other choice when the motion is irregular and unpredictable. However, human persistent tasks are sometime periodic and it can be shown that such a strategy is not optimal in the sense of energy efficiency. In our previous works, an optimality condition for periodic motion is derived. This result implies that to flatten the force pattern by removing the input pulsation improve the efficiency. Thus, optimal power assisting control methods for periodic motions based on a frequency shaping were investigated. However, we observed that the pedaling frequency of human is not constant and fluctuates to some extent. In order to deal with such a situation, an adaptive compensation is introduced here. In particular, we propose a power assisting control with an adaptive notch filter to suppress the velocity pulsation. The effectiveness of the proposed assisting control method is verified through numerical simulations and experiments by using a commercial electric power assisted bicycle. Finally, the energy efficiency is evaluated by monitoring voltage drops of the battery during our experiments.
A significant fire and explosion accident on spherical tanks for Liquefied Petroleum Gas (LPG) storage at Chiba prefecture in Japan were induced by the strong ground motion of the 2011 Great East Japan Earthquake and its aftershock. The braces made by steel pipe, of which ends were connected to support legs of one spherical tank filled with water, were broken due to the strong seismic inertia force, and then buckling of support legs were caused. To clarify the failure mechanism of the pipe braced supporting frame of a spherical tank, we performed the elastic and elastic-plastic finite element analysis. From FEA results, it was concluded the fracture mechanism of the pipe braced supporting frame of a spherical tank as follows; (1) high stress was generated in the cross point of two braces due to the structural discontinuities, (2) the generated high stress triggered for the failure initiation of the supporting frame damage, (3) resulting the spherical tank overturn during the aftershock of predominant earthquake. In this paper, the fracture mechanism of the spherical storage tank was clarified for heading off the same type accident, and the effective reinforcement of spherical tanks were proposed for securing safety.
This paper proposes an integrated robot design method which designs a robot body and a robot motion simultaneously to maximize the robot motion performance. The integrated robot design method is available to design a multi degrees of freedom (DOFs) robot, and it is validated by experiments of a ball throwing robot which has 9 DOFs. The design parameters are the motion pattern and the robot body parameters, and these initial values are optimized by a gradient method to maximize (or minimize) evaluation functions which are given from throwing task conditions. The throwing task conditions contain (i) maximization of ball flyingdistance, (ii) collision avoidance between flying ball and robot hand, (iii)velocity evaluation of motion , (iv) self collision avoidance and (v) limitations of joint angle, angular velocity and torque, etc.. These conditions are utilized as the constraints to obtain the realizable robot motion. A ball throwing motion performed by a human is transformed to a motion pattern of the ball throwing robot, and the robot body parameters are designed simultaneously. Two cases, which contain the improved motion 1 (the robot motion pattern is only designed) and improved motion 2 (the robot motion pattern and the robot body parameters are designed simultaneously), are compared, and these average ball flying distances are 1.33 m and 1.87 m. As a result, the robot motion performance is improved, and effectiveness of the integrated robot design method is demonstrated.
In grasping of a robot hand, a contact timing of each finger has a influence on grasp success. In order to eliminate the gap and grasp an object quickly, proximity sensing from the robot surface is effective way. The sensor detects the object posture and distance in a several tens of millimeters from the robot surface. It enables that the robot adjusts postures and distance between the object and fingertips along the object surface. In this paper, we demonstrate a quick grasp with contacting each finger simultaneously by proximity sensors on fingertips. In order to realize the grasp by optical proximity sensors, we introduce our reflectance estimation of the object surface and calibration of the sensor output. This approach uses only the proximity sensor output and a relative moving distance of the fingertip. It is unnecessary to add extra equipment or sensor for estimation and calibration. It is possible to achieve the grasp regardless of the reflectance of the object surface. In the experiment, we confirmed that the approach can be applied to surface with different reflection characteristics (iron plate, aluminum plate, paper: cylinder and plane ), and the hand can grasp a object with various reflectance surfaces (31.9∼76.1%) quickly with contacting each fingertip within 0.056s.
At demolition or construction sites, workers have to handle heavy tools and materials over head. It is difficult to continue such works, and the work efficiency will be reduced. A wearable support system with enough range of motion (ROM) and power will be effective to continue these heavy works for a long time. The purpose of this study is to develop a wearable upper limb support system for the heavy work over head, and to confirm the effectiveness of the developed system through basic experiments conforming to the actual works. Link structure with redundant Degree Of Freedom (DOF) was designed to move joints of wearers smoothly, and a prototype was developed for evaluation. Basic experiments with and without the developed system were conducted to confirm the effectiveness of the system. In the experiment to assess the mobility, we measured ROMs of each joint of the subjects. In the experiment to assess the effect of the system, each subject held a heavy load and moved it vertically over head, and we measured the holding time and the number of times of vertical motion. As results, we confirmed that the system had enough ROM to move smoothly. Moreover, we confirmed that the average holding time with the system increased 3.5 times than without the system, and the average number of vertical motion with the system increased 3.1 times than without the system. In conclusion, we could develop the wearable upper limb support system for the heavy work over head that had enough ROM by the link structure with redundant DOF, and confirm that the developed system was effective in continuing the heavy work over head for a long time.
This paper describes an active noise control technique to suppress the transmitted sound from a movable louver that is attached to a ventilation aperture and machinery opening. In this experimental study, proposed ANC (Active Noise Control) system is independent parallel control system using two IMC (Internal Model Control) feedback ANC systems. Each system is controlled using filtered-X LMS algorithm to minimize sound pressure at error microphone. One of them, louver-ANC system which secondary noise source is set at each bottom side of the louver vane. An opening of each movable louver vane is one-dimensional space similarly a duct. Transmitted sound is attenuated in this area which error microphone was set on outside near louver opening. The other one is slit-ANC system that is installed on an opening of machinery wall. The slit-ANC system is combined a slit resonator with active noise control. The slit resonator with ventilation aperture composed of thin air layer expanded with very short wall width is useful to reduce leakage noise at machinery wall. The thin air layer acts an acoustic resistance, inertance and capacitance. The secondary noise source oscillates the air layer with appropriate amplitudes and phases. The error microphone is located same position in case of the louver-ANC system. The rectangular slit resonator is designed to reduce resonant frequencies of an enclosure box in this experiment. Noise reduction is visualized by sound intensity measurement system, and sound power is calculated by distribution of sound intensity. The experimental results show that noise reduction is obtained from 5 dB to 13 dB of sound power in sound field on this proposed ANC system. And it is expected that the transmission loss of movable louver will be able to improve by using independent parallel control system of louver-ANC and slit-ANC.
Many infrastructures such as bridges and tunnels had been constructed in various parts of Japan during the high economic growth period. They need periodic inspection because they are aging. Inspecting them by inspector is both costly and time-consuming. There is a strong demand for practical bridge inspection robots to reduce the costs and times. The inspection robot running autonomously on the bridge needs to determine moving route and to estimate self-position. The robot must have a three dimensional map of the bridge to take these actions. This paper proposes a method of making a three-dimensional occupancy grid map of the large scale infrastructure where the inspector cannot go easily such as an underside of the bridge. A bridge inspection robot equipped with magnets had been developed in present study. We attached a measuring device which consists of a small 2D laser range finder and a servo motor. Experiments were conducted to make the 3D map by using the robot. The robot climbed to target position on the wall without falling although it was equipped with the measuring device which is heavy. Moreover, the robot can make the 3D occupancy grid map and the map can be useful to inspect bridges.
Transmission demonstration experiment of 0.1-0.2THz beam was performed with transmission system consisted of polymer fibers of φ3mm×300mmL coated with gold metal. THz beam was generated by high power compact gyrotron designed output power of 0.25kW and measured output power at terminal of metallic cladding polymer fibers in the transmission system and the following results were derived; (1) It was demonstrated that maximum output power of the order of 0.84W through the polymer fibers was observed by SBD detector at input power of the order of 7.5W. (2) Loss factor α(dB/m) of PMMA and PEEK polymer fiber was obtained in the range of 150-850(dB/m) and exhibits frequency dependence in the range of 0.1-0.2THz. (3) Present transmission system with metallic tapered wave guide and φ2-3mm×60mm polymer fiber is applicable with 10% power transmittance for hyperthermia therapy.
Significant fire and explosion accident on spherical tanks for Liquefied Petroleum Gas (LPG) storage was induced by the strong ground motion of the 2011 Great East Japan Earthquake. Steel pipe braces were broken due to the strong seismic inertia force, and then buckling of support legs occurred. To prevent recurrence, reinforcing the intersection of braces was needed. Currently, in the Japanese seismic resistance design standard for high pressure equipment including spherical tanks for storage, when subjected to a large earthquake, it is allowed to occur a certain degree of plastic deformation, witch way not lead to release high pressure gases. When receiving a high-level seismic motion, seismic response of high pressure equipment could be non-linear due to plastic deformation and the mechanical damping could be increased as well. On the other hand, a vibration test for spherical tank has not conducted in the past. Deformation behavior of the spherical tank and pipe braces was not clear against real ground motion. In addition, there are not many precedent studies done on the effectiveness of the reinforcement of pipe braced supporting frame against high-level ground motion. In this study, we conducted vibration tests using small models of spherical tank and examined non-linear response characteristics and failure mode due to plastic deformation. From the test results, it was concluded the effectiveness of reinforcement and the response characteristic of the pipe braced supporting frame of a spherical tank as follows; (1) The natural frequency indicates substantially the same value with or without reinforcement, because a large difference in the response characteristics of the whole structure was not observed. (2) In a case of brace intersection was reinforced, the maximum response acceleration increased at collapse. (3) In a case of brace intersection was reinforced there is no reinforcement to brace intersection, structural strength indicated the lowest at the load direction acting tensile force on long brace, cross section of long brace were deformed largely.
This paper describes a 2D laser range sensor system for scanning a front side and lateral sides of an object. I developed the 2D laser range sensor system, in which a 2D laser range sensor and a mirror based ellipse. The 2D laser range sensor can scan the front side of the object. The sensor can scan densely the lateral sides of the object using the reflected laser by the mirror. The developed sensor system can scan the front side and the lateral sides of the object at the same time. I showed some design conditions of the mirror from relation between the sensor and the object in the sensor system. I designed and made the mirror by the design conditions. I made up a hardware of the sensor system using the sensor and the made mirror. I took actual reflecting points on the object experimentally by using the developed sensor system. I checked positions of scanned reflecting points to evaluate the performance of the developed sensor system. The results have shown the usefulness in the developed sensor system for scanning the front side and the lateral sides of the object.
The self-excited vibration, such as galloping, dry friction induced vibration and so on, often occurs in many mechanical systems and structures. For several years, the effectiveness of a dynamic absorber for self-excited vibration has been known. However, the operating mechanism of a dynamic absorber for self-excited vibration is still poorly understood and a rational optimization procedure based on the operating mechanism is not established. In this paper, a simple and fundamental model with two degrees of freedom (DOFs), that is, a single-DOF system with negative damping in which one dynamic absorber is attached, is considered and the operating mechanism is investigated from the viewpoint of the energy balance. In order to clarify the operating mechanism, we apply a new type of complex modal analysis proposed by the authors to the system with negative damping, and the modal equations with the diagonalized mass, stiffness and damping matrices in the form of real second-order differential equations can be obtained. Using approximate solutions obtained from the modal equation, the energy generated due to negative damping and that dissipated due to positive damping can be estimated accurately. The results show that the appropriate decentralization of the excitation energy to each mode and the increase of the dissipation energy, caused by the dynamic absorber, play dominant roles in the stabilization of the system. In addition, the optimization procedure is formulated. The validity of the analytical results is verified by comparing with the numerical solution.
We proposed gel-fibers reeling system (Gel-FRS) with embedding biological cells for small diameter cellular vessels. To realize artificial 3D tissue, capillary blood vessels are important to be built in it as one of the typical small diameter cellular vessels. As previous works, a method to fabricate patient-specific vascular scaffolds was proposed using a biodegradable polymer, PLCL (poly(L-lactide-co-ε-caprolactone)). In this paper, we demonstrated a way for seeding smooth muscle cells and fibroblast cells outside the PLCL scaffold using the gel-fibers reeling system. At first, the mechanical stiffness of gel fibers was determined to achieve fiber reeling. The tensile stress of gel fibers was also evaluated without breaking down. The reeling speed of gel fiber was determined for seeding cells uniformly on a scaffold. The multiple hydrogel fibers embedding biological cells were reeled onto tubular PLCL scaffold, and then the alginate gel were melted by an alginate lyase. A uniform cell seeding onto upper and under surfaces of PLCL scaffold was achieved by rotating scaffold at 180 degrees every one hour. As a result, we achieved seeding cells onto scaffold and the cells viability was more than 90%. The proposed gel-fibers reeling system is important to be applicable in wide areas such as tissue engineering and bio simulators.
Actual problems in science and industrial applications are modeled by multi-materials and large-scale unstructured mesh, and the finite element analysis has been widely used to solve such problems on the parallel computer. However, for large-scale problems, the iterative methods for linear finite element equations suffer from slow or no convergence. Therefore, numerical methods having both robust convergence and scalable parallel efficiency are in great demand. The domain decomposition method is well known as an iterative substructuring method, and is an efficient approach for parallel finite element methods. Moreover, the balancing preconditioner achieves robust convergence. However, in case of problems consisting of very different materials, the convergence becomes bad. There are some research to solve this issue, however not suitable for cases of complex shape and composite materials. In this study, to improve convergence of the balancing preconditioner for multi-materials, a balancing preconditioner combined with the diagonal scaling preconditioner, called Scaled-BDD method, is proposed. Some numerical results are included which indicate that the proposed method has robust convergence for the number of subdomains and shows high performances compared with the original balancing preconditioner.
We propose a Newton-gradient-hybrid optimization method for fluid topology optimization. The method accelerates convergence and reduces computation time. In addition, the fluid-solid boundaries are clearly distinguished. In the method, the optimization process and flow computation are executed concurrently. The flow computation utilizes the lattice Boltzmann method (LBM), and the optimization algorithm partly utilizes a Hessian matrix. Due to the formulation of LBM and the optimization algorithm, the Hessian matrix is a diagonal matrix. Since the optimization problem is nonconvex problem, the Hessian matrix is not generally positive semidefinite. Hence, we employ a gradient method for a component whose corresponding Hessian matrix elements are negative. We compare the optimization results with those of conventional gradient method and show that the convergence is accelerated and the fluid-solid boundaries are clearly distinguished.
Ultra Large Scale Integration (ULSI) are usually realized by a reduction of the size and high integration of semiconductor devices. In recent years, representative length scale of ULSI cells is going to be at a nanometre order. Several atomic level problems like a generation of lattice defects are taking place in the fabrication processes when the semiconductor device size becomes small. Dislocations often appear near hetero-interfaces and accumulate in the electron channel of semiconductor device is one of the most serious problems. Therefore, the evaluation and control of dislocation accumulation are crucially important for the design and development of semiconductor device structure. Generation and accumulation of dislocations are known to take place during the formation of thermal oxide film, and the cooling processes of semiconductor device fabrication. In this study, we simulate the dislocation accumulation during the formation of thermal oxide film of device fabrication process. Accumulation of dislocation is analysed by employing a technique of crystal plasticity analysis and evaluate the stress distribution, dislocation density distribution in the silicon substrate and structure of dislocation accumulation. Relations between the geometry of the shallow trench isolation type ULSI cells and dislocation accumulation are discussed.
This paper presents a numerical solution to shape identification of unsteady natural convection fields to control temperature to a prescribed distribution. The square error integral between the actual temperature distributions and the prescribed temperature distributions on the prescribed sub-boundaries during the specified period of time is used as the objective functional. Shape gradient of the shape identification problem is derived theoretically using the Lagrange multiplier method, adjoint variable method, and the formulae of the material derivative. Reshaping is carried out by the traction method proposed as an approach to solving shape optimization problems. Numerical analyses program for the shape identification is developed based on FreeFem++, and the validity of proposed method is confirmed by results of 2D numerical analyses.
For manufacturing industries to promote globalization, it is important to optimize the strategic design of supply networks. In early stages of strategic design of global supply networks, with regards to the market strategy (what sale volume of which product to which market) and the manufacturing strategy (production capacity and number of manufacturing facilities), we have to optimize the facility locations. At this point, instead of determining the details of product types and delivery routes, we should focus on minimizing the total cost of the supply networks. After performing a conceivable risk assessment, we determine the locations of manufacturing facilities. In this paper, based on the information that can be learned in early stages of strategy design, we build a model of one-echelon supply network for facility locations design problem with capacity constraints. Next, we perform numerical experiments of the optimization using mixed-integer programming. As a specific example, the manufacturing plant is assumed to supply products to the 43 global markets. Our experiments evaluated the effectiveness of the proposed method with respect to this facility locations design problem.
Near-dry cutting is a key technology to decrease in the usage of cutting fluid. A lot of research achievements revealed that near-dry cutting technology was available, and we hope this technology will contribute to the improvement of the working environment in the manufacturing industry. On the other hand, a large diameter deep hole drilling process still needs a large amount of cutting fluid. This paper describes the results of feasibility study on deep hole counter boring with a BTA(Boring and Trepanning Association) tool using near-dry technology. In the experiments, the work material was JIS A2017 aluminum alloy and JIS S35C carbon steel. Their workpiece has a prepared hole with various diameters. The workpiece temperature increase was recorded during drilling, and the maximum height roughness on inner wall of hole was measured with a surface roughness measuring instrument by stylus method. The cutting lubricant supply system affected the chip discharging efficiency and the temperature rise of workpiece. As a result, the difference of supply method affected the roughness on inner wall of hole. The results of this experiment revealed the following things. In the case of a deep hole machining of an aluminum alloy, the wet method is more excellent in surface roughness than the method using MQL. On the other hand, MQL is effective for drilling of a carbon steel. And furthermore, the fundamental guidelines of the diameter and position of oil hole was revealed with the object of putting near-dry deep hole drilling to practical use in the future.
An advantage of the indentation test is that it can be used to easily measure the elastic modulus of biological soft tissue in noninvasive. To measure Young's modulus, E*, of skin tissue by an indentation test, we expanded the Hertz contact theory to a contact problem of pressurizing an elastic plate of a finite thickness with an spherical indenter and devised a method to properly evaluate the modulus of skin tissue. To verify the validity of the indentation test method, we performed a tensile test and indentation test using artificial skin, and then, the optimum indent depth, δT0, was calculated at which the stiffness of both became equivalent. The modulus for the depth, δT0, was estimated for finite thickness plate from the modified Hertz contact equation, FTn = CδmT. Furthermore, we measured the strain distribution of subcutaneous tissue from ultrasonic echo tomography of human skin and found the effective depth, <z>, relating to stress transfer. Thus, we considered the practical applicability of a method for measuring the Young's modulus of skin tissue using an indentation tester.
As management resources of the company, generally people, goods, money (capital) has been called that three elements of the management. Appropriate investment and its efficient use to these resources have been sought to management. Further information as a fourth element has been added recently. In this paper, furthermore, for the medium-sized manufacturing company that manufactures and sells the product with long life as mechanical elements, “outward activities ” are proposed as the fifth element to add to the above four management elements. The importance of these five management elements, are different by market needs and corporate scale and strategy. So, the key method to evaluate importance of the technology management is discussed systematically for mid-sized manufacturing company's management on the basis of these management elements. In the technology management system are classified into three layers, and the evaluation factors based on the management elements in each layer are composed by a tree structure. The first layer is defined as the important key factor, the second layer is defined as the theme to raise the quality of the first layer and the third layer is defined as the theme judged on site objectively. Intended for mid-sized manufacturing company that manufactures and sells the Universal Joint, which is one of the mechanical elements product for the proposed technology management system was performed out as case study. As a result, the effectiveness of the proposed five elements and technology management were verified. Also, in this case study, it's also done clearly about how various innovation is classified by technological management, and how product innovation and process innovation also influence technological management.
At Japan Organization for Employment of the Elderly, Persons with Disabilities and Job Seekers, job trainings are provided for job seekers to attain basic skills for employment. This time, two more training courses have been added to instruct trainees in a hands-on training through industrial production process with course tasks assigned. One course is designed for firstly attaining basic skills, and then enhancing the skill level through the repetitive exercise on the tasks assigned. Another is also schemed primarily to attain the basic skill, and successively to enhance the ability to utilize the learned skills through the tasks assigned for developing new products. These vocational trainings were planned and piloted at nine Polytechnic Centers. Among them, the enhancing training of the ability to utilize the skills has resulted in an increase of more applicants. Moreover, the trainees for the training succeeded in obtaining the job offers more, so the rate of their employment increased. In addition, at Kanto Polytechnic Center, the trainees in the job hunting presented the products of their own creation with the course tasks toward the potential employers. As a result, those trainees succeeded considerably in their job search. In this study, the effectiveness of newly added two courses for job training is evaluated and the way of utilization is proposed in relation to the products of the assigned tasks within the course.