Carbon fiber reinforced plastic (CFRP) laminates are expected to be expanded as structural members due to their excellent mechanical properties. It is essential to evaluate theirfatigue propertiesto ensure long-term reliability and durability. The fatigue damage growth behavior of CFRP laminates differs greatly depending on the load condition, laminate configuration and dimensions. In particular, it is necessary to predict the initiation of transversal crack since they are become a starting point of fiber breakage and delamination. In this study, the fatigue tests were performed using quasi-isotropic CFRP laminates with stress ratios of R = 0.1 and -1. Then, the fatigue life to the transversal crack initiation was predicted using a modified Walker model. In addition, the results were compared with those of cross-ply CFRP laminates previously performed by the authors. As a result, it was found that if the stress applied to the 90° layers is a tension-tensile condition, the initiation of transverse cracks can be predicted regardless of the laminate configuration and the stress ratio.
It is known that the thermal residual stress generated in the process of molding carbon fiber reinforced plastic (CFRP) laminates affects their damage growth behavior, such as transverse crack and delamination growth. Furthermore, CFRP laminates with heat resistant resin as matrix have greater thermal residual stress due to their high molding temperature. Especially, since 90° layers of CFRP laminates generates tensile thermal residual stress, it greatly affects the transverse crack growth behavior. Thus, the influence of the thermal residual stress on the fatigue properties of modified CF/PEEK laminates with a modified coefficient of thermal expansion (CTE) of matrix resin was evaluated. The damage initiation and growth behavior were investigated, and their influences of those on the fatigue properties were evaluated. As a result, the fatigue damage initiation and growth of transverse crack and delamination of the modified CF/PEEK laminates were different compared with those of unmodified CF/PEEK laminates. Delamination initiated on the surface at the edges of the specimen before transverse crack initiation in modified CF/PEEK laminates and the initiated delamination hardly propagated until the specimen fractured. In addition, it was found that the edge delamination releases the stress singularity at the specimen edges and that suppresses transverse crack initiation and growth.
Carbon fiber reinforced plastics (CFRPs) are expected to be applied for rotating members such as fan blades of turbofan engines. They are subjected over 108 loading cycles during their operation time, since it is essential to investigate the very high cycle fatigue (VHCF) behavior of CFRPs. To accelerate the test time up to VHCF regime, ultrasonic fatigue testing machine which can apply the specimen ultrasonic load at a frequency of 20 kHz was used. Hydraulic fatigue test was also conducted to evaluate the transverse crack initiation in the high cycle fatigue (HCF) regime and to confirm the consistency of the ultrasonic fatigue test. The S-N diagram showed the linear decrease in HCF regime. On the other hand, the slope of the S-N curve became gentle in the VHCF regime. Furthermore, no cracks occurred in all specimens tested with the initial maximum strain less than εmax=0.193% up to 6.56×109 cycles in maximum.
Porous polymer membrane having numerous pores may exhibit large deformation and its anisotropy, which is dependent on inherent porous structure. For such anisotropic porous materials, it is important to investigate the deformation behavior under multiaxial and biaxial tensile loadings. However, such experiment may be difficult using conventional testing machines due to the future of the porous polymer membrane. This study developed a testing machine of the biaxial tension for porous polymer membrane, and the deformation characteristics under uniaxial and biaxial tensile loading was evaluated. First, uniaxial tensile tests were conducted in each direction, and changes in Young's modulus and yield stress were examined according to the tensile direction. Next, a new biaxial tensile testing machine for porous polymer membranes was developed. The results of the biaxial tensile test indicated anisotropy in elastoplastic deformation.
In this study, a self-contraction structure of porous rubber material specialized compression deformation was evaluated. The self-contraction structure called an auxetic structure is expected to be used for a cushioning material. In this paper, 2-dimensional finite elemental models which have many elliptical pores ware determined, and numerical simulations ware conducted to evaluate the effect of elliptical pore angle θ. Compress the finite element model by constrain the bottom side of models and displace the top side forcibly. The simulation carried out at multiple elliptical pore angle θ. The self-contraction was quantified from the ratio of longitudinal strain and transverse strain. From the results, effects of the angles of the micro-structure on the self-contraction characteristic of porous rubber was investigated. The micro-structure of base material rotates when it becomes asymmetrically. Rotate micro-structure alternately is requirement for self-contraction characteristic.
Creep damage preferentially extends at a stress concentration portion under multiaxial stress. Therefore, it is necessary to clarify the relationship between the creep damage extension process under the multiaxial stress states. In this study, creep tests using a plain specimen and three kinds of round bar notch specimens with different notch radius (notch tip radius 0.1mm (R0.1) and 0.5mm (R0.5) and 2.0mm (R2.0)) on a 2.25Cr-1Mo steel were carried out. Creep rupture times of the notch specimens were longer than those of plane specimens. Greater number of voids were observed at around 0.1 mm from notch root in R0.1, and around 0.5 mm from notch root in R0.5, and around center of the specimen in R2.0. The finite element creep analysis of the notch specimens showed that triaxial tensile stress yields at the notch root sections with different distribution of the triaxiality factor depending on the notch radius. Creep rupture times of three kinds of round bar notch specimens were accurately predicted by the area average creep damage evaluation method.
Ni based superalloy IN 738 LC is used for the first stage blades of power generation gas turbines and aircraft jet engines. Creep damage occurs preferentially in stress concentration portions. In this study, creep tests have been conducted by using smooth and round bar notch specimens on IN 738 LC to clarify relation between creep damage extension and stress conditions, and crystal orientation parameters. Creep rupture time of the notch specimen was longer than that of the plain specimens showing notch strengthen. Significant difference of void growth behavior between the plain and notch specimens was not observed. The maximum void length took the maximum value within 0.5mm from the notch root. This corresponds to higher axial tensile stress and axial creep strain yielding at around the notch root. The results of the crystal misorientation measurement for both specimens suggest that the change in GRODave may be caused not only by intragranular deformation but also by the formation and growth of voids, and that in KAMave seems to be related to the void initiation and growth.
Modified 9Cr-1Mo steel is used in the steam turbine rotors because of its superior high-temperature property. Creepfatigue damage progresses preferentially at stress concentration portions in the steam turbine rotors. In this study，creepfatigue tests using round bar notch specimens on a modified 9Cr-1Mo steel have been conducted to clarify effect of multiaxial stress conditions on failure life. The failure life of round bar notch specimen was much shorter than that of plain specimen under the same conditions. From observation of notch root of the creep-fatigue damage specimens，it suggested that most of the creep fatigue life was occupied by crack propagation up to 1mm from the notch root surface. A new creep-fatigue life evaluation method of round bar notch specimens，in which concept of a damage evaluation area was introduced，was applied. As a result，creep-fatigue lives of the round bar notch specimens were accurately predicted by coupling of the new procedure and the nonlinear damage accumulation rule.
The outer diameter of the drawn tubes of various materials was evaluated to clarify the effect of the plastic anisotropy on the outer diameter reduction in hollow sinking. Stainless steel, copper, and aluminum tubes were used as the starting materials. They were drawn for one pass by using a draw-bench machine without an inner tool. Tensile tests were conducted on the starting materials to obtain the Lankford value, which shows the plastic anisotropy. The outer diameter became smaller than the die diameter as the Lankford value increased for each drawing speed ratio. The outer diameter became smaller than the die diameter as the drawing speed ratio increased, although the Lankford value decreased. Therefore, the drawing speed ratio is more dominant for outer diameter reduction from the die than Lankford value.
Recently, many new technologies development relating to seismic design of bridge piers for the earthquakes have been produced. From this reason, the seismic performance has been improved. When an earthquake is generated for the Rahmen structure, bending failure occurs at the base and shear deformation occurs at the center of the beam. Normally, metal materials can absorb the energy by being plasticized from earthquakes. However, when shear buckling is happened, the hysteresis of the material can’t be maintained and the amount of absorbed energy decrease. In this research, we focus on the Rahmen structure, simulate nonlinear Finite Element Method (FEM) “Marc” and test that imitated the center of the beam. By carrying out a four-point shear experiment using this test piece, we aim to reproduce shear deformation. This experiment can confirm the decrease in absorbed energy. Furthermore, absorbed energy can be suppressed by applying appropriate reinforcement.
Rapid decrease of compressive stress in the plateau region is one of the issues in compressive behavior of porous metals. In this research, the compressive deformation behavior of porous metals with unidirectional pores was investigated experimentally and numerically. Cubic specimen with irregular pore geometry was used to avoid the effect of macroscopic shear bands which are commonly observed in porous metals with aligned pore geometry. Fractures of the cell walls were observed as well as a rapid decrease of compressive stress and thin ones preferentially fractured at the beginning. Equivalent strain localization at the vertical cell walls between pores was also confirmed by digital image correlation. Results of finite element analysis showed that von Mises stresses concentrate at the cell walls around fractured and locally deformed cell walls. This mechanism is considered to be the main cause of the fractures of the cell walls.
Mechanical coating technique (MCT) as a novel film formation process has been proposed and performed based on mechanical frictional wear and impacts among Al2O3 balls, columns, disks used as the substrates, and metal powder particles used as the coating metal in the bowl of planetary ball mill or pot mill. Also, MCT was developed to 2-step MCT, Bead mill mechanical coating technique (BMCT)，Wet mechanical coating technique (WMCT). In this work, BMCT and WMCT were performed to coat Ti films on Al2O3 balls as the substrates. The formation process of the Ti films was investigated and discussed. BMCT and WMCT are effective processes for coating metal films, and which are thinner than these by MCT. Mechanical frictional wear and impacts in BMCT and WMCT are different to these in MCT.
Magnetic pulse welding with an insert sheet of A1050-O is effective for lap-joining of aluminum alloy A5052 and magnesium alloy AZ31. In this study, we investigated the optimum thickness of the insert sheet. We experimented with insert sheets 0.01, 0.02, 0.05, 0.1, 0.2 and 0.3 mm thick, respectively. Also, the A5052 and AZ31 sheets are the same 0.4 mm thick. These were welded when using insert sheet 0.05 mm, 0.1 mm, 0.2 mm and 0.3 mm thick, however not welded when using insert sheet 0.01 mm and 0.02 mm thick. The joint properties were evaluated by joint width and joint efficiency of weld. Joint width was measured by microscopic observation of the cross-section. Also, joint efficiency was calculated by the ultimate tensile strength of the joint and A5052. The joint width and the joint efficiency was the maximum value when the thickness of the insert sheet was 0.1 mm. The present results suggested that the optimum thickness of the insert sheet is 0.1 mm in this case.
Free surface roughening is the phenomenon in which the surface roughness on the free surface of polycrystalline metals increases with plastic deformation. The free surface roughening adversely affects the forming limit, aesthetics, and surface characteristics. Thus, it is important to clarify its mechanism. The series of conventional studies on the free surface roughening show empirically that the surface roughness increases linearly with the equivalent strain. However, the influence of deformation mode on the rate of the surface roughening has not been clarified. The authors continuously observe the evolution of the surface roughening in C1220 under various deformation modes such as uniaxial tension, plane strain tension, and equal biaxial tension using a laser microscope. The deformation modes affect the surface roughening especially as the equivalent strain increases. It is thought that this result is caused by the change in the surface area with the plastic deformation. By removing the effect, new deformation mode independent material constant of free surface roughening can be determined successfully.
Currently, there are about 700,000 bridges in Japan. However, about 20[%] of these have been over 50 years old, and aging such as fatigue cracks and corrosion is considered serious. Therefore, it is important to grasp the deterioration situation on-site as soon as possible. One method is non-destructive inspection. But there are drawbacks such as high skill required for inspectors and inspection only within a narrow range. Accordingly, we focus on a material called ML and aim to develop a new non-destructive inspection technology that can be inspected for simpler and wider than the conventional method. ML has the property that the stress concentration part emits light when mechanical external force is applied in the phosphorescent state. The purpose of this study is to verify whether the luminance distribution and Finite Element Method (FEM) have a high correlation even when the stress distribution is complicated by multiple defects. Tensile test was performed by applying ML to a test pieces with three and five holes damaged. In comparison with the maximum principal stress, the distribution was similar. In comparison with the equivalent stress, the distribution was close to more than the maximum principal stress between the two test pieces. Therefore, it is considered that the equivalent stress is more appropriate than the maximum principal stress as a comparison object.
In recent years, a highly efficient cooling system is eagerly desired because of high heat flux associated with
miniaturization of electronic devices and large amount of heat with upsizing of space equipment. The heat removal performance of cooling system using flow boiling is much higher than that of single phase flow. There are several known parameters that affect boiling heat transfer. One of these is the concentration of dissolved air in coolant but its effect on the flow boiling is not still understood. Over the past long years, although there are some researches, there is less clarification on heat transfer and its mechanism. We focused on the bubble growth rate at heat transfer surface. The growth rate of both boiling steam and dissolved air generated in the test section is considered to affect the heat transfer.
Microbubbles have various properties and are expected to be used in a wide range of fields. Although there are various generation methods, the generation method using a Venturi tube is a simple system and has attracted attention. However, the flow in the Venturi tube is very complex and has not been elucidated. The purpose of this paper is to clarify the effect of the cavitation phenomenon on the generated bubbles. In the visualization experiment, the cavitation phenomenon in which bubbles are generated and disappeared in the throat in the liquid single-phase flow was confirmed. It was possible to evaluate the occurrence of cavitation in the bubble flow by using the pressure loss coefficient. Furthermore, it was confirmed that the bubbles were further refined under the cavitation generation conditions.
The effects of synthetic jet array on the aerodynamic drag of a simplified car model is experimentally investigated. Experimental model is an Ahmed body with a rear slant angle of 25° scaled at 0.2 of the original Ahmed model. Synthetic jets are produced by periodic ejection and suction of fluid from an orifice induced by movement of a diaphragm inside a cavity. Aerodynamic force measurements were performed by changing the jet-to-freestream velocity ratio, jet frequency and jet orifice locations. In this experiment, two jet positions are tested to investigate the effect of the jet location on drag reduction. The jet orifices had a diameter of 2 mm, and eight circular orifices were arranged at equal intervals in the spanwise direction. In the flow visualization with a smoke wire method, the suppression of flow separation was confirmed. Drag reductions up to 7% were attained when the jet orifice location was on the slanted surface and it was also confirmed that the drag reduction was affected by the jet orifice location.
Around a normal flat plate of finite width in a uniform flow, a vortex with a structure peculiar to three-dimensional object is generated. The flow field around the flat plate can be improved by establishing fluid control methods. A DBD plasma actuator (DBDPA), which controls a flow by using the induced jet generated by dielectric barrier discharge, has attracted attention as one of the fluid control devices that can meet the above-mentioned needs. In this study, a DBDPA was attached to the wall surface in front of the flat plate and the effect of the induced jet on the vortex generated in front of the flat plate at free stream velocity of 3 m/s was experimentally investigated. The experiment was carried out in a circuit-type wind tunnel having a working section of 2000 mm in length and 200 mm × 200 mm in cross-sectional area. DBD plasma was produced using a high voltage power supply with amplitude 5 kV and frequency 4 kHz. As a result of measuring the velocity field around the flat plate using PIV, the vortex in front of the flat plate was restrained by the induced jet of the DBDPA. Moreover it was found that the DBDPA also affected the flow behind the flat plate.
The study focuces on aerodynamic brakes that increase the range of safe and operable wind speeds when the rotational speed of the rotating shaft of a small vertical axis wind turbine increases,the horizontal axis extends and the rotational speed is limited by air resistance.In this study,we discuss the experimental results obtained by changing the brake plate of the aerrodynamic brake attched to the experimental wind turbine and the compression spring that presses the brake plate to the rotational shaft.As a result,it was confirmed that the rotational speed at which the brake plate was deloyed increased as the springs of a larger spring constant were used and as the radius of rotation of the brake plate was reduced.
Due to structural reasons, lattice tower mast can measure high attitude wind speed data compared with cylindrical observation tower mast. However, even in case of measuring wind data using lattice tower mast, there are some uncertainty of flow distortions by tower shadowing. This paper shows accuracy evaluation of wind speed correction method of lattice tower mast using CFD (Computational Fluid Dynamics) simulations. In addition, this paper shows comparison between one-year measurement LiDAR (Light Detection and Ranging) data that can be compared directly and corrected wind data of lattice tower mast by CFD calculation. As a result of performing the wind speed correction using the inflow wind speed ratio by CFD, the uncertainty of corrected wind speed fell by less than uncorrected data.
Flying badminton shuttlecocks automatically rotate counter-clockwise (forward rotation) about the major axis as viewed from downstream because of a skirt structure having a diverging array of stems with overlapping feathers. The badminton shuttlecock is known that it has high deceleration characteristics and a high aerodynamic stability. The effect of spin rate on aerodynamic drag of the shuttlecock has not been clarified yet. The aim of this study is to investigate the effect of spin on the aerodynamic characteristics of a shuttlecock. The wind tunnel experiments were performed using YONEX feather shuttlecock (NEW OFFICIAL, No.4, YONEX Co. Ltd.) in a low-turbulence wind tunnel. The fluid force measurements and smoke flow visualization were conducted by changing the rotational speed and the rotational direction of a shuttlecock using a DC motor. During revers rotation, the drag coefficient increases with increasing the spin speed. The drag for the shuttlecock with spin is affected by rotational direction.
Designing a control system and a reference trajectory for a small single-rotor helicopter for flight control of a hammer head turn with a load of 2G or more, a vertical attitude and a non-thrusting flight state from a high-speed straight flight, and verification by flight experiments went. In the control system design, a control law for velocity compensation near the reference trajectory in a flight with no thrust was implemented. The reference trajectory was designed as a periodic function of the nose vertical angle using the monotonicity of the attitude change in order to design an asymmetric thrust trajectory in ascent and descent.
This report describes the development of the ultrasonic three-dimensional low-airspeed sensor and the navigation system by using the neural network for small helicopters. Developed ultrasonic-anemometer-based three-dimensional airspeed sensor is light-weight and highly-rigid for the installation in small helicopter. With a structure devised to withstand downwash, it measures the airspeed from low speed including the main-rotor's downwash turbulence. Average measurement error of the horizontal speed is below 1 m/s. For the vertical airspeed measurement, the navigation filter based on the neural network is developed to eliminate the downwash airspeed that changes complexly depending on the condition of the aircraft from measured values with integration of multiple aircraft state variables. RMS error smaller than 1 m/s between the filter output and the reference airspeed is achieved.
Ultra-compact mobility has excellent environmental performance and are extremely convenience for short-distance travel. However, owing to cabin space limitations, it is difficult to massively change the amount of seat slide. Our research group constructed ultra-compact EVs equipped with the steer-by-wire system and investigated the reduction of muscle burden during the steering operation by change of reaction torque that the reduction of driver muscle burden was expected. And, it is necessary to examine the muscle burden on drivers with varying physiques for using of share the ultra-compact mobility. However it is impossible to know the operation burden by surface electromyography or subjective evaluation, when the driving position is different. In this study, we established a two-dimensional model of the arm and calculated the static moment generated at the arm joint when the driver holds the steering wheel, and conducted a basic study about moment of joint change due to steering wheel position.
In recent years, the number of switches installed in automobiles has increased, which has contributed to prolonging the design of the driving operation space. The purpose of this study is to evaluate the visibility of instrument panels of automobiles using an eye-body-coordination movement model that minimizes physical load and eye load and maximizes the visibility rate. The human body movement is calculated by a musculoskeletal model, and the visibility evaluation system is realized by a visual geometric model using 3-dimensional computer graphic software. In order to evaluate the validity of this system, a verification experiment compared with the simulation output. As a result, eye-body-coordination movement were confirmed under all conditions. The correlation between the visibility score of simulation and the sensory test was strong, and the validity of the evaluation index was confirmed. This system is assumed to be used in actual design, and the user can execute a simulation without knowing the details of the system.
Inconel 718, a kind of Ni-based superalloy, shows high mechanical properties even in high temperatures up to 700℃. However, Inconel 718 causes severe wear of machining tools because it is a difficult-to-cut material. Fabricating Inconel 718 by using selective laser melting, a kind of additive manufacturing, is therefore expected as the most promising way to deal with this problem. Fatigue properties of parts fabricated by selective laser melting are inferior to parts fabricated by conventional ways. Revealing the fatigue fracture is necessary to improve fatigue properties. In this study, fatigue test was conducted with Inconel 718 fabricated by selective laser melting and the fatigue fracture surface was observed. Fatigue fracture origins shifted from the surface of specimensto the internal part of specimens by hot isostatic pressing. In specimens with hot isostatic pressing, TiN inclusions were found in fatigue fracture origins. To raise fatigue properties of parts fabricated by selective laser melting needs to remove these TiN inclusions.
One body production of electrical and mechanical products by AM expand the application, most AM machines that can use metal are powder-bed type that cost much. FFF is a relatively inexpensive additive manufacturing method, but the materials are basically limited to thermoplastic resins, and other materials are used as composites. In this study, we focused on the conductivity of metal materials and took the method of giving conductivity to the printed object by metal wire composites. A prototype AM machine was realized. In order to confirm the conductivity, two solenoids with different diameters were fabricated. The measurement result showed that the diameter of the solenoid was smaller than expected, and the one with the larger diameter had the higher accuracy
Recently, Unmanned Aerial Vehicles (UAVs) have been developed which can fly by using remote control and automatic operation technology and can also take pictures. However, when these UAVs are flapped by the wind, they may lose stability and fall or become out of control. As a solution to this problem, the development of a dragonfly micro projectile that mimics the shape and flight method of dragonfly wings is underway. However, the dragonfly micro projectile is currently under development, as it cannot fly continuously because its posture becomes unstable after takeoff and it falls. For this reason, it is necessary to control the posture of the dragonfly micro projectile in order to maintain its posture during the flight. Therefore, in this study, a pressure sensor mounted on the wing surface is developed for the purpose of controlling the posture of a dragonfly micro projectile. P (VDF-TrFE) which shows especially strong piezoelectricity was used as a material of the pressure sensitive part of the sensor. The response of the sensor was confirmed by measuring the electromotive force of 2.5mV when pressure of 0.01kPa is applied to the fabricated 100nm nanosheet sensor using a bulge tester.
The purpose of this study is to examine the feasibility of 100 % renewable energy systems in the residential area. The boundary of the residential area was a set of “all-electric houses” that have electric vehicles, photovoltaic and heat pump water heaters. In each case, we derive the power self-sufficiency ratio and power self-consumption ratio by photovoltaic defined by the boundary. Comparing the presence or absence of power interchange, in the case of electricity interchange, the photovoltaic surplus in a home that does not stay the electric vehicle in the daytime can be charged to another home's electric vehicles and used for power supply at night. It was confirmed that the power interchange in residential areas has the effect of increasing the self-sufficiency ratio by up to 14.0 % and the self-consumption ratio of electricity by up to 15.7 % and reducing the annual CO2 emission by up to 18.3 %. In comparison with regional characteristics, in areas where there are many commuting electric vehicles such as the sub-urban area, the electric vehicle does not stay home in the daytime, and the photovoltaic power generation cannot be charged. Therefore, the effect of the photovoltaic - electric vehicles system on the realization of RE100 is small. When there are multiple electric vehicles in one household as in the rural area, it was confirmed that the photovoltaic - electric vehicles system was effective in realizing RE100 by introducing mega solar in the area.
In order to contribute to electricity supply and demand adjustment, consolidation of household responses is essential. A typical example of adjustment power is the preheating/precooling operation of air conditioners in houses. The operation model of an air conditioner requires an understanding of the insulation and heat storage characteristics of a housing. However, it is difficult to precisely model the detailed energy use of each household. In this study, we propose a framework to derive an optimal operation plan for residential air conditioner pre-heating and pre-cooling operation using a system identification method. The purpose of this study is to estimate the coordinating electricity for 500 households and to clarify the combination of the insulation and heat storage characteristics of the equipment and the housing, which contribute to the adjustment of power supply and demand, from the power saving plan selected by the aggregator. As a result, it was shown that the load estimation model of the residential air conditioner identified could derive a response to demand response while maintaining the comfort of level of residents. Also, the results of consolidation of 500 households showed that the pre-heating and pre-cooling of the air conditioner was selected secondarily after the heat pump water heater and that the higher the heat insulation performance, the lower the power saving and the lower the incentive price.
Demand Response (DR) that controls energy consumption based on a margin of power supply capability has been drawing increasing attention. In the residential sector, however, aggregators have to aggregate saving power because the capacity of saving power per customer is less than the industrial sector. Because of this, improving the calculation time that is spent on deriving an operation plan is necessary. Therefore, we derive operation plans using Convolutional Neural Network (CNN). And then, we analyze the classifier to clear up the efficient operational logic of residential energy equipment. We target a household that an air conditioner and polymer electrolyte fuel cell co-generation system (PEFC-CGS) are installed. To create CNN that reduces operational cost, we added a term for the operational cost to the loss function which is used during learning. After that, we analyze constructed CNN by LIME (Local Interpretable Model-agnostic Explanations). As a result, an average relative error rate from the optimal result is decreased to 5.67 %. We found that the hot water demand, the amount of remaining hot water and operation state have a big impact on the operation plan of PEFC while the electricity demand has no impact on it.
In recent years, “CO2 network system” has been proposed by researchers in EPFL, Switzerland. The system uses the latent heat of CO2 refrigerant to transport and exchange unused heat to specific areas by employing distributed heat pumps on demandside. The purpose of this study is to derivate of optimum equipment configuration of the decentralized heat pump and the CO2 temperature supplying to the network from the central plant for the cooling/heating ratio of demand. In this report, first, we analyzed the effect of the cooling/heating ratio of demand and the temperature of CO2 refrigerant on the performance of CO2 network system. As a result, we found that when the cooling/heating ratio of demand is 1.13 or more, the connection pattern in which CO2 supplied from the network and indoor air exchange heat directly was optimal for the air conditioner for cooling. In other cases, the connection pattern in which CO2 supplied from the network was directly used as the refrigerant for the decentralized heat pump was suitable. Second, we calculated the annual energy consumption using the derived optimal CO2 temperature supplying to the network from the central plant for typical energy demand in urban areas in Japan where a district heating and cooling system using steam and chilled water as a heat transport medium was introduced. It was clarified that when the CO2 temperature supplying to the network from the central plant was constant at 12 °C for a year, the electricity consumption was almost the same as that when the CO2 temperature was set optimally.
The SYNTHSEP methodology that presents a general procedure to derive a complex system configuration of thermodynamic systems operating with a pure working fluid has been proposed by A.Lazzaretto and A.Toffolo et., al. Designers focus on a set of fundamental thermodynamic processes (compression, heating, expansion, cooling) in the flowsheet which is called “basic configuration” in this methodology. The basic configuration is defined by aggregating certain elementary thermodynamic cycles. In previous studies, this technology was applied to absorption refrigeration cycle by K.Seki et., al, in case of waterlithium bromide system as working fluids pair. By aggregating certain elementary thermodynamic cycles, the cycle configuration and operating point equivalent to the absorption refrigerator which had been considered optimal were demonstrated by case study. Based on these works, this research aims to apply the SYNTHSEP methodology to generate basic configurations of an absorption power cycle. In a case study, elementary cycles are operated with an ammonia-water mixture. Demonstration of the proposed method for optimization is shown by performing a case study for an absorption power cycle in which thermal efficiency is regarded as a system product. Calculated solutions are evaluated by comparing with publicly available solutions of an existing design.
A real time parameter estimation method of cantilevered beam is presented. In this method, a point load acting on deforming cantilevered beam is estimated in real time by using the Kalman filter, which is one of the procedures of data assimilation. Data assimilation is widely known as the method which estimates uncertain parameters utilizing both numerical model and experimental data in sequential processing. And the parameters estimated by above-mentioned method can be strong likelihood for actual phenomenon included in analysis object. In this study, a simple experiment is conducted to verify the effectiveness of real time estimation of a model parameter in deforming cantilevered beam by using Kalman filter and strain measurement. Experimental results show that the estimation is operated satisfactorily with motion of cantilevered beam. From the point of view of high accuracy estimation, it is considered that nonlinear numerical model and working environment which is able to operate Kalman filter at high frequency can be necessary.
Kinematic coupling is attracting attention as one of the technologies to achieve development of a large highly precise space structured system in the space engineering field in recent years. The location difference between upper and lower parts of kinematic coupling can cause position error. So elucidation of a mechanical mechanism is required about the influence by which this difference gives it to the whole structure. In this research, we investigate vibration transfer characteristics of the kinematic coupling by using the finite element analysis. We construct a precise finite element analysis model which can consider the frictional contact effects at joints. The kinematic coupling constructed is the twodimensional model in which 1DOR and 2DOR are included. Vibration is given to the base plate when the coupling has been completed, and the transfer characteristics are evaluated at 3 points, the center of lower side, 1DOR contact point, and the center of upper side. In the analysis, we investigate the effects of the friction and the pressing load on the transfer characteristics.
In the development of large precise space structures, thermal deformation tests with high measurement accuracy are required. The conventional thermal deformation test conducted in atmospheric pressure is influenced by disturbances such as the change in room temperature and the thermal deformation of the jigs fixing the test article and measurement devices. The effect of room temperature can be eliminated through vacuum tests, but they require specialized measurement devices and the test results are influenced by the thermal deformation of the jigs. The authors proposed a thermal deformation test method using periodic heating. Sine-wave heating is applied to the test article and the test results are evaluated in the frequency domain. The effect of disturbance is eliminated if it occurs at a frequency with enough difference from the applied heating. This paper validates the elimination of the effect of the change in room temperature on the thermal deformation test using periodic heating. The validation was carried out through experiments using a truss structure and numerical analysis. The experimental and numerical results showed that effect of the change in room temperature was eliminated from the thermal deformation caused by the applied heating.
Shape stabilities of reflector surface consisting of cable-networks were studied. The effects of initial cable length errors on tension states in the cable-network structure were investigated. Surface accuracies and tension states were evaluated while changing the magnitude of the cable length errors. Their results indicate that the changes in the initial length of the cables affect the tension states in the cable-network and the surface cables connected to the catenary cables have an great impact on the slacks of the cables. In most cases, the cable-networks were stable even some cables were slack.
The beam configuration of the outer cylinder for twist-type morphing wing with the double cylinder structure was investigated to improve the bending rigidity and reduce the torsional rigidity. The theoretical formula of bending of multi-beam structure was derived, and its usefulness was evaluated through comparisons with numerical analysis results. In this study, it was assumed that the inner cylinder of the double cylinder structure consisted of four rectangular cross-section beams arranged on a circle with a radius of 4 mm, and the shapes of the four types of beams were changed to investigate effectiveness of the beam shapes. The length of the beam was changed to 20𝑚𝑚, 30𝑚𝑚, 40𝑚𝑚, 60𝑚𝑚, 80𝑚𝑚, and 100mm, and a total of 24 models were compared. It is clearly demonstrated that the derived theoretical formula is effective when the beam length is long. However, if the beam is short, a slight error occurs between the theoretical value and the analysis value due to the shear deformation.
Maker Faire is a meeting of makers which American O'Reilly Corporation hosts. The exhibitors display result of the making original products there. The visitors observe and share the result of the making and participate in a workshops. The author has exhibited Maker Faire Tokyo and Maker Faire Taipei and watched Taiwanese teachers work on STEM education and Maker education eagerly. Many students utilize 3D printers and laser cutters and work on making products such as robots and cars. Changes from DIY (Do It Yourself) to DIWO (Do It With Others) are also seen. The STEM education of Taiwan makes progress than Japan. This paper describes Taiwanese Make Faire compared with Japanese one from the viewpoint of STEM education.
The purpose of this study is development of the teaching material to promote understanding of train control system using a front imaging device. As a result of class practice at the university, it was confirmed that a certain effect was obtained as a teaching material for understanding the mechanism of measurement and control system. In addition, knowledge of control and interest in control is a statistically significant result, and interest in creating new things on their own is a marginally significant.
In recent years, autonomous driving technology has been developed due to factors such as aging, safety of traffic environment, and population decline. However, full automation takes time. Therefore, driver intervention is required. Here, vehicle control from outside is effective in avoiding danger or stopping safely when it becomes difficult to continue driving due to misunderstanding or loss of consciousness of the driver. Therefore, we developed an external vehicle control system (teleoperation) and aimed at controlling small vehicles.
While searching for lecture papers in the technical and social sectors, I found the lack of public information on the Japan Society of Mechanical Engineers department website. This is a matter that should be taken into consideration regarding the way the organization should be, and considering the impact of future departmental activities, we would like to make an immediate improvement proposal, and make a status report and an improvement proposal.
The oxidation processes of soot particles in the cylinder of direct-injection gasoline engine and at the oxidation-dominant periphery of diesel spray flame were investigated using newly developed nano-structure concentricity analysis on HRTEM images of the soot particles. The results for direct-injection gasoline in-cylinder soot at different fuel injection pressures showed that the soot for 15MPa injection pressure case exhibits more disordered outer-shell structure and more indistinguishable concentricity distributions between the outer-shell/inner-core structures compared to the 5MPa injection pressure case. These results support the conjecture of preceding study that higher injection pressure helps to form more oxidation-reactive soot particles. The results for diesel flame core/periphery soot demonstrated that the concentricity analysis can reveal the inner-core/outer-shell structural distribution changes of soot particles during rapid oxidation at the diesel flame periphery to which the conventional morphological analysis is not readily applicable due to indistinguishable primary particle boundaries. Compared to wider and more distinctive distribution of concentricity for flame core soot, flame periphery soot showed narrower concentricity distribution, significantly reduced areas of lower (<0.35) and higher (>0.55) concentricity, and more indistinguishable concentricity distributions between the outer-shell/inner-core structures, indicating rapid oxidation of soot by in-flame OH radicals.
This paper describes a small unmanned aerial vehicle (UAV) attitude estimation method using multiple global navigation satellite system (GNSS) doppler. In 3D measurement by a UAV with light detection and ranging (LiDAR), it is most important to estimate UAV attitude precisely. We have been developed a UAV with a LiDAR and six GNSS receivers to generate a 3D map. By using the developed method, we can estimate UAV attitude with 0.2 deg accuracy. And we also have been developed a UAV attitude estimation method with six GNSS receivers and inertial measurement unit (IMU). By using this method, we can estimate UAV attitude with 0.1 deg accuracy. However, in these previous researches, system configuration tends to be complicated by using IMU other than six GNSS receivers. Therefore, we now propose a UAV attitude estimation method with about same accuracy without using IMU by using only six GNSS receivers. In proposed method, we focus on GNSS doppler that we did not use in previous method. By calculating UAV angular velocity using multiple GNSS doppler and using it with Kalman Filter, we achieved 3D measurement in 55.4 mm horizontal Root Mean Square (RMS) error. In addition, by using six GNSS antenna positions that we did not use in the previous method with Extended Kalman Filter (EKF), we achieved 3D measurement in 54.3 mm horizontal RMS error.
The use of GNSS(Global Navigation Satellite System) has become common worldwide. However, in urban environment, the positioning accuracy of GNSS is lowered by the effect of multipath. There are two types of multipath, LOS multipath and NLOS multipath, and effective countermeasures are required for both. We propose a method using a rotating antenna or antenna switching. The arrival direction of the satellite signal is obtained from the doppler shift generated with the movement of the antenna. Then, the direction of arrival of the signal and the arrangement of the satellite are compared to judge the NLOS, and reject from the positioning calculation. The effect of LOS multipath is averaged by moving the antenna. As an experimental equipment, in the rotating antenna technique, GNSS antenna and receiver are mounted on the rotating arm. In the antenna switching technique, multiple GNSS antennas are switched by elements. By using this technique, the positioning rate of the rotating antenna increased from 0.23% to 100%. In another test, the positioning rate increased from 40.74% to 93.86% using the switching antenna.
Positioning accuracy of global navigation satellite system (GNSS) is deteriorates when non-line-of-sight (NLOS) multipath signals are received in urban environments. Therefore, it is important to determine satellite visibility and reject NLOS satellites from positioning calculation to improve positioning accuracy. In this paper, we focus on a correlation waveform which is affected by multipath signals. To detect NLOS multipath signals, we use convolutional neural networks (CNN) for machine learning to generate the NLOS discriminator. From the evaluations of proposed method, the global positioning system (GPS) accuracy of satellite visibility determination by using the CNN was 98.0 %. In addition, the GPS accuracy of NLOS satellites determination by using the CNN was 97.9 %. Similarly, GLONASS, Galileo and BeiDou accuracy of it were about 90 %. We confirmed the effectiveness of the proposed method with experiments in urban environments by comparing with conventional method.The positioning accuracy without NLOS signals is also improved compared with the conventional positioning method in urban environments.
The author proposed a new identification method of linear single-degree-of-freedom system using Gaussian random vibration based on asynchronous data in a previous paper. However, there is a problem that conventional study including the estimation accuracy. In this paper, accuracy update method focused on variance error of velocity distribution is proposed. First, previous identification method is considered to base on three type numerical differentiation. Moreover, the numerical verification is performed in order to represent the operation of the proposed method. Furthermore, the accuracy update algorithm is derived based on the likelihood function that including variance error of velocity distribution. In addition, numerical verification of accuracy update algorithm is performed.
In order to conduct the efficient replacement of water pipe, it is required the non-destructive pipe inspection technology. Furthermore, optimal planning of inspection pass and replacement pass using inspection result is more important. In this research, we consider the optimal method based on the annealing method for inspection pass planning. The planning problem is formulated by the traveling salesman problem. However, the problem has not established the determination method of Lagrange multiplier for constraint. In this paper, we proposed the determination method of Lagrange multiplier based on the Hamiltonian decomposition. First, the analysis of Lagrange multiplier dependency in terms of probability in two-level system is conducted. Furthermore, determination method of Lagrange multiplier is proposed. Moreover, the numerical verification of proposed algorithm is conducted using SDK (Software Development Kit) of D-Wave.
To reduce carbon dioxide emissions, ZEB (Net Zero Energy Building), which aims to promote energy saving in buildings, has attracted attention. Particularly, solar cooling systems that use solar radiation as renewable energy for ZEB are an effective heat source. However solar cooling systems have not become widespread. Therefore, it is necessary to clarify the methodology to design and operate equipments in ZEB with solar cooling systems. In this study, a two-step design process of equipments including solar cooling system was proposed. First, optimizations of configuration of the equipments including an adsorption chiller using solar heat as a heat source is performed using a mathematical model. Then, TRNSYS simulations are performed using the optimization results to derive the operation of the equipments against air conditioning load. Applying the proposed method to a hospital of 5,000 m2 , the optimal configuration of the equipments was obtained minimizing the annual cost. Then, the results of the equipment operation analysis showed that the primary energy consumption could reduce by 43% for the building with a solar cooling system than that without a solar cooling system.