日本機械学会論文集
Online ISSN : 2187-9761
早期公開論文
早期公開論文

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早期公開論文の54件中1~50を表示しています
  • 松野 隆幸, 西田 祐也, 米森 健太, 李 想, 向田 直樹, 加藤 直輝, Myo MYINT, 山田 大喜, Nwe Lwin KHI ...
    論文ID: 17-00242
    [早期公開] 公開日: 2018/01/19
    ジャーナル フリー 早期公開

    A variety of robots has been studied and developed for undersea exploration. One of the applications for undersea exploration is mining of undersea resources such as methane hydrate and rare metal by Autonomous Underwater Vehicle (AUV). To extend active duration time of the robot in the sea, a system through which the AUVs recharge autonomously batteries is a key technology. Our reseach group has confirmed in a pool environment the dual-eye visual servoing system made a pole attached to the vehicle dock into a hole. This experiment simulates situation where the vehicle approaches recharging station under deep sea. But previous studies were conducted with ROV (Remotely Operated Vehicle) that is controlled by remote computer instead of human operator. In those experiments, power cables affected performance of control accuracy. Therefore the performance of visual feedback with AUV named Tuna-Sand2 that is compeletely indepent from cables or wires and has a general structure of modernized AUV system, has been verified to confirm the practicability of dual-eye dockig system.

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  • 廣明 慶一, 渡辺 昌宏
    論文ID: 17-00416
    [早期公開] 公開日: 2018/01/19
    ジャーナル フリー 早期公開

    An instability mechanism of flutter generated on a rectangular flexible sheet in an axial fluid flow is investigated through the energy-transfer quantifications. The work done by unsteady fluid force acting on the fluttering sheet surface is calculated based on a three dimensional flutter analysis utilized the Doublet-point method and finite element method. Then the work done by fluid force is divided to three terms caused by fluid added mass, damping and stiffness by applying Roger's approximation, and influence of each term on stability is clarified. As a result, it is clarified that the work caused by fluid added stiffness is dominant for excitation of flutter. Lastly, the influence of the work caused by interaction of natural vibration modes of the sheet which are dominant for flutter on stability is investigated, and the instability mechanism of flutter is discussed.

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  • 東海林 一, 水谷 義弘, 葭田 貴子
    論文ID: 17-00452
    [早期公開] 公開日: 2018/01/19
    ジャーナル フリー 早期公開

    Generally in Japan, high skilled UT engineer performed examination and high reliability of examination results are achieved. However, it is not confirmed how high skill and actual probability of detection (POD). In the performance demonstration (PD) system in US, there are determined that the number of defect, minimum number of detection, number of unflawed area and allowable false detection, but it is not considered the defect size. In this study, based on the signal detection theory, the actual POD was estimated by the signal amplitude (defect size) and observed reflection position of field experience data. It was confirmed that the POD is decreased with a less than 3.2 mm depth. The estimated POD for each crack depth well matches the result of laboratory experience data. The probability of failure for piping system was calculated based on this estimated POD, it was lower than 10-7 in case of stress corrosion cracking (SCC) on low carbon stainless steel piping SCC, and it was lower than 10-3 in case of SCC on sensitized stainless steel 304. In order to keep the probability of failure is 10-3 or less, it is only necessary that the POD is 0.95 or greater for large crack as 3.2 mm depth or more. Based on these result, this paper proposed the acceptance criteria for qualification test as training graduation.

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  • 田勢 泰士, 齊藤 梓, 太田 崇文, 佐藤 慧, 高松 久一郎, 吉田 一也, 川上 勝, 古川 英光
    論文ID: 17-00459
    [早期公開] 公開日: 2018/01/19
    ジャーナル フリー 早期公開

    Our group has developed a 3D gel printer called "SWIM - ER" (Soft and Wet Industrial Material - Easy Realizer). Here we are aiming to improve the gel material used in the SWIM-ER system for problems related to free forming and mechanical strength. The composition of the high strength gel material with low viscosity and easy modeling was clarified by adjusting the concentration of the crosslinking agent of 1st gel against the problem that the viscosity of the material is too high and it was difficult to shape. We tried tear tests in addition to various evaluation tests, tensile tests, compression tests. We thought that we can estimate and evaluate dissipation and diffusion of fracture energy by microscopic observation of specimens after tear tests.

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  • 高瀬 徹, 小山 敦弘, 内田 武
    論文ID: 17-00489
    [早期公開] 公開日: 2018/01/19
    ジャーナル フリー 早期公開

    In order to design a rotating shaft, it is necessary to investigate the fatigue characteristics under the variable amplitude loading by using a rotating bending fatigue machine. However, the stress amplitude cannot be changed frequently in a commercial rotating bending fatigue machine. Therefore, the automatic loading apparatus was manufactured in order to perform the fatigue test under the repeated two-step variable amplitude loading by using the commercial rotating bending fatigue machine. In this apparatus, the load was changed by loading or unloading the weight using air pressure. The high stress amplitude and the low stress amplitude were alternately applied to the specimen in the rotating bending fatigue test under repeated two-step variable amplitude loading. Rotating bending fatigue tests were performed using heat-treated 0.45%C steel specimens. Before the fatigue tests, the performance test of the automatic loading apparatus was conducted and it was found that the apparatus was available for fatigue tests. Next, the fatigue tests under the repeated two-step variable amplitude loading were carried out based on the results in the Hi-Lo two-step loading fatigue test and then the cumulative fatigue was investigated. The total fatigue lives to failure of low stress amplitude under the repeated two-step variable amplitude loading are almost same as lives under the Hi-Lo two-step loading, but they have the longer lives as the low stress amplitudes decrease. Finally, the life prediction method for the specimens subjected to repeated two-step variable amplitude loading was proposed. The results estimated based on the proposed method were in good agreement with the experimental ones.

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  • 田中 椋也, 涌井 伸二
    論文ID: 17-00424
    [早期公開] 公開日: 2018/01/18
    ジャーナル フリー 早期公開

    This paper considers the implementation of a cascade type PIS compensator for the pneumatic anti-vibration apparatuses (AVA) control system. In precedence research the parallel type PIS compensator was used. This is composed of a PI and S compensators connected in parallel. However a PIS compensator is interpreted as a special case of what is used in repetitive control. In this case, a cascade connected compensators is used. According to this, the PIS compensator should be in series type. Also, parallel type PIS compensator generates swing of the output signal. Through above problems, cascade type PIS compensator is considered. However, the AVA control system with the compensator causes collision and steady-state deviation. In order to resolve these problems, we improve the structure of the compensator and its switching method. This experimental result shows that the normal operation of the AVA control system with cascade type PIS compensator. From the above, we show that the implementation of cascade type PIS compensator for the AVA control system.

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  • 金子 康智, 岸本 星太, 森 一石, 大山 宏治
    論文ID: 17-00447
    [早期公開] 公開日: 2018/01/18
    ジャーナル フリー 早期公開

    Although, in designing blades, it is assumed that all blades on a disk are identical (tuned system), the vibration characteristics of the blade is slightly different due to the manufacturing tolerance, the deviation of the material property, and so on (mistuned system). As a result, in the forced response of an actual bladed disk caused by the flow distortion, the responses of all the blades on a disk become different, and the response of a certain blade may become extremely large, due to the split of the duplicated natural frequencies, the distortion of the vibration modes, and so on. On the other hand, it is suggested by many researchers that the mistuning suppresses the blade flutter, because the complete travelling wave mode is not formed in a disk. In other words, the effect of the mistuning acts on the dangerous side for the forced vibration, while on the safety side for the blade flutter. In this study, the stability analysis and the frequency response analysis of mistuned bladed disks are carried out using the reduced model with high fidelity, in order to research the vibration characteristics of typical mistuned bladed disks. Based on the analysis results, an optimal design procedure of mistuned bladed disks considering both the forced response and the self-excited vibration is proposed.

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  • 松田 吉平, 田中 謙一郎, 今井 秀幸, 五井 龍彦, 佐藤 恭一, 田中 裕久
    論文ID: 17-00472
    [早期公開] 公開日: 2018/01/18
    ジャーナル フリー 早期公開

    The traction drive - integrated drive generator (T-IDG®) has been developed since 1999 to replace current hydrostatic transmission drive generators. The T-IDG® consists of a generator and a half-toroidal traction-drive continuously variable transmission (CVT), which maintains a constant output speed of 24,000 rpm. In terms of coping with recent trends of high-power electric drive aircraft (MEA) and the need for weight reduction, a high-speed traction-drive CVT is advantageous over current hydro-static drive transmissions. To control a speed ratio of the high-speed CVT accurately, it is essential to know the speed-changing response. In conventional study, the speed-changing response is approximately proportional to a rotational speed; however, in the high speed CVT, a minute deformation during the speed change affects its response. This paper describes the analysis and a developed theory of the speed-changing response of a toroidal CVT, with showing test results which verify the response of the high speed CVT, whose input speed is 20,000 rpm at maximum with a peripheral speed of traction contact of 70 m/s.

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  • 竹内 誠, 鈴木 伸治, 阿部 穣
    論文ID: 17-00269
    [早期公開] 公開日: 2018/01/17
    ジャーナル フリー 早期公開

    Low-temperature-difference indirect heating Stirling engine is the most suitable device for a small-scale wood biomass combined heat and power. To design this type of Stirling engine, conventional design method is not sufficient for optimizing working space temperature difference. Therefore, a new design method is developed. A ratio of working gas displacement to volume change is defined, which is found to be a simple function related to the temperature ratio of the ideal Stirling cycle. Through the preliminary study, it is found that the conventional alpha, beta and gamma Stirling engines are not suitable for practical low-temperature-difference engines. Finally, alpha-plus-type engine which is optimized for low temperature difference operation is proposed. The new engine is developed and the results of the operation test is demonstrated.

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  • 泉 政明, 尾田 京磨
    論文ID: 17-00317
    [早期公開] 公開日: 2018/01/17
    ジャーナル フリー 早期公開

    Mass transfers in porous electrodes of fuel cells affect the performance of the fuel cells. The aim of this study is to verify effectiveness of a measurement method of a hydrogen gas concentration in a fuel electrode of a solid oxide fuel cell (SOFC) to clarify the mass transfer mechanism. This technique was applied to a SOFC which was composed of 8 mol % Y2O3-ZrO2 (YSZ) electrolyte and Ni-YSZ fuel electrode. A sensor which was made of a platinum wire coated with zirconia and alumina was inserted into the fuel electrode to measure the oxygen partial pressure. The hydrogen gas concentration was determined from the oxygen partial pressure which was obtained from an electromotive force of the sensor using Nernst's equation. The hydrogen gas concentration decreased with increasing the current density up to 0.45 A/cm2 and also with increasing the operating temperature (1173 K to 1273 K) at the same current density. The measured values of the hydrogen gas concentration were proportional to the values calculated by three dimensional numerical simulation. These results indicated the measurement method had a potential for the measurement of hydrogen gas concentrations in fuel electrodes. Furthermore, the effective diffusivity of hydrogen gas in the fuel electrode could be obtained from the hydrogen gas concentration.

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  • 中山 万希志, 奥井 博己, 木村 尚人, 栗屋 効典
    論文ID: 17-00362
    [早期公開] 公開日: 2018/01/17
    ジャーナル フリー 早期公開

    In this paper, we discuss a modeling method and an altitude control system for a drone type UAV using the image information from the forward camera of the UAV. The model for the UAV dynamics is constructed based on the motion equation and the unknown velocity control logic which was made the internal organs in the drone system, and the parameters of the model are obtained by some experiments of the velocity constant control. The transfer function are expressed the 2 dimensional state space equation, and the optimal control method applied to the system include some limitation of the velocity control logic. This optimal control logic is realized as a PID control system. The P gain range of the PID controller is determined by the parameter of performance index of optimal control logic and the system keep optimal control feature in the range. By the experimental results, we confirmed that this system is stable and efficient.

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  • 北村 健三, 光石 暁彦, 鈴木 孝司
    論文ID: 17-00410
    [早期公開] 公開日: 2018/01/17
    ジャーナル フリー 早期公開

    The natural convective heat transfer from banks of heated horizontal cylinders to air was investigated experimentally. The experiments were mainly carried out with the in-line tube banks consisted of five stairs of ten-cylinder-row aligned horizontally. The whole cylinders in the bank were heated with identical heat flux and their diameter d, vertical and horizontal gaps Gh, Gv between cylinders were varied as d=8.4, 14.4 mm, Gh=10.6-30.6 mm and Gv=5.6-30.6 mm. The flows induced in the banks were first visualized with smoke and the Nusselt numbers of the whole cylinders in the banks were subsequently measured. The visual results depicted that the smokes issued from the upstream of the bank gather gradually toward the vertical centerline of the bank. With the gathering of the plumes, the Nusselt numbers of the cylinders placed near the center of the horizontal rows show marked reduction in the downstream direction. Their Nusselt numbers were rearranged with several parameters to obtain non-dimensional heat transfer correlations. It was found that the Nusselt numbers NuGv for the second to fifth stairs in the bank are correlated well with the parameter [RaGv*(Gv/d)(Gh/d)], while those for the first stair are predicted well with the parameter [RaGv*(Gv/d)2], where NuGv and RaGv* stand for the Nusselt and the modified Rayleigh numbers based on the vertical gaps Gv.

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  • 末永 陽介, 柳岡 英樹, 菊池 護, 佐々木 駿
    論文ID: 17-00444
    [早期公開] 公開日: 2018/01/17
    ジャーナル フリー 早期公開

    An experimental study investigated the frequency characteristics of a stretched cylindrical diffusion flame in response to sinusoidal air flow velocity oscillation. The flame has a convex curvature with respect to the air stream. The fuel was methane diluted with nitrogen, and oxidizer air. The flame was formed in the air stream side from the stagnation surface. The oscillation frequency f ranged from 10 Hz to 250 Hz. In order to clarify the influence of an oscillation amplitude A of the air flow velocity on the flame responses, three kinds of amplitude were chosen. The flame was photographed by the high speed video camera, and flame radius rf, flame thickness δ, and flame luminosity Lf were analyzed. The air flow velocity va at the nozzle outlet was measured by using particle image velocimetry. Though velocity gradient of the air flow ga responds quickly to the changing va regardless of f and A, the gradient of the fuel flow gf delays with increasing f and A. Here, ga correlates to the flame stretch effect, and gf impacts the fuel transportation. Response of rf to varying va also delays with increasing f and A. δ/rf, which relates to the flame curvature effect, responds complicated with the change in f and A. Oscillation amplitudes of Lf have maximum values with respect to f regardless of A. These maximum values are greater than those of a steady flame, over the same air velocity fluctuation ranges. This complex change in the Lf with respect to f is closely related to the phase difference in the respective time variations in δ/rf and gf, and the magnitude of these values.

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  • 篠木 俊雄, 藤本 泰貴, 神園 正章, 前田 毅, 片桐 康誌, 久住 真己, 谷川 博哉, 舟木 治郎, 平田 勝哉
    論文ID: 16-00252
    [早期公開] 公開日: 2018/01/16
    ジャーナル フリー 早期公開

    The authors develop a small and simple steam-reforming reactor in a home-use size for n-dodecane as a heavy-hydrocarbons fuel. Under the thermal condition controlled by electric heaters and a gas burner with a thermal diffuser, the authors measure the inside-temperature profile and the hydrogen molar fraction (concentration) CH2, together with the molar fractions CCH4, CCO and CCO2 of other main gas components such as CH4, CO and CO2, respectively. As a result, the authors successfully achieve suitable inside-temperature profiles. And, the authors experimentally reveal the effects of the liquid-hourly space velocity LHSV upon the molar fractions, in addition to the LHSV effect upon a conversion ratio XC12H26. Furthermore, the authors reveal the effects of the temperature T inside the reactor upon both the molar fractions and XC12H26, comparing with the chemical-equilibrium theory in a wide range of LHSV. The comparison with the chemical-equilibrium theory indicates that the temperature at the catalyst-layer-bed downstream end could be regarded as the reaction temperature.

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  • 長山 格
    論文ID: 16-00366
    [早期公開] 公開日: 2018/01/16
    ジャーナル フリー 早期公開

    An intelligent snatching detection system (ISDES) for autonomous detection of criminal incident by using machine learning approach is presented in this paper. Also, ESSM (Extended Snatching Situation Model) is presented to give an effective definition of the whole snatching situation including victim's behaviors. Rule-based decision making and machine intelligence are primary components of the proposed system to act without being explicitly programmed for data dispersion. Some motion characteristics are determined from video streams, also using the ESSM and machine intelligence, the system automatically classifies the situation of the video streams into criminal or non-criminal scenes. After constructing the system, we use test sequences that are continuous video streams of human behavior consisting of several actions in succession. We consider six types of scenarios for the experiments including victime's behaviors as the snatching incidents performed with motorcycle. The experimental results show that the system can effectively detect criminal scenes with an accuracy of 95.83 %.

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  • 鈴木 貴士, 佐藤 衛, 梅沢 修一, 横森 剛, 植田 利久
    論文ID: 17-00168
    [早期公開] 公開日: 2018/01/16
    ジャーナル フリー 早期公開

    Flame height variations of a laminar stagnating premixed flame with gas component transition between fuel mixture A (methane:92%, ethane:6.7%, propane:1.3%) and B(methane:84%, ethane:13.3%, propane:2.7%), and between A and C (methane:76%, ethane:20.0%, propane:4.0%) are discussed. The estimation of the flame speed and the flame temperature of fuel mixtures A, B and C by the Chemkin-Pro show almost the same values for all fuel mixtures. In experiments, the transition between A and B and between A and C were performed. The transition time changes from 1 s to 10 s, keeping flow velocity and equivalence ratio constant at 0.8 m/s and 0.7 respectively. The flame position was measured by using images taken by a high speed camera with 125 fps. Two transition patterns are examined, keeping the total flow rate of premixed mixture constant. One is the constant flow rate transition, which changes the gas component, keeping the fuel mixture flow rate constant. The other is the constant equivalence ratio transition, keeping the equivalence ratio constant. In the case of the constant flow rate transition, the equivalence ratio changes which results in the variation in the flame speed, the flame temperature and the flame height. It means that the combustion state changes with the transition. On the other hand, in the case of the constant equivalence ratio transition, the flame speed, the flame temperature and the flame height keep almost the same state, which means that the gas component can be changed, keeping the combustion state the same.

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  • 山本 悠貴, 洪 基源, 三目 直登, 山田 知典, 吉村 忍
    論文ID: 17-00451
    [早期公開] 公開日: 2018/01/16
    ジャーナル フリー 早期公開

    In mesh-based fluid-structure interaction (FSI) analysis, mesh moving techniques are essential for preventing mesh distortion and improving the robustness of FSI analysis. In our previous study, we have proposed a new mesh moving technique with minimum-height-based stiffening, which is more robust against the mesh distortion compared to existing techniques. Although this technique provides reasonable distribution of stiffness in space depending on minimum height of each mesh, there is a parameter that determines relationship between the minimum height and the stiffness. Optimal value of this parameter varies depending on problem. However, it is empirically determined in usual. In this study, we develop optimization approaches for the parameter both in space and time directions adopting three optimization methods: static optimization, global optimization and local optimization. Benchmark problems were analyzed for quantitative evaluation of these three approaches. The static optimization provides the best parameter in the minimum-height-based stiffening technique without optimization in time direction. The results with the global optimization contain the best in all results in this study. However, this approach requires unacceptable computational cost from a practical point of view. The local optimization has a good balance between computational cost and robustness since it can achieve comparable to or more robustness against the mesh distortion with much chaper cost compared with the static optimization. This approaches are expected to be applicable to FSI analyses, and improve their accuracy and stability.

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  • 上澤 伸一郎, 堀口 直樹, 柴田 光彦, 吉田 啓之
    論文ID: 17-00392
    [早期公開] 公開日: 2018/01/15
    ジャーナル フリー 早期公開

    The filtered venting system has the functions of preventing the overpressure breakage of a primary containment vessel of a reactor and reducing the release amount of the radioactive materials to the environment. One of the filtered venting systems is a Venturi scrubber to remove small particles of the radioactive materials. However, the physics of the two-phase flow in the Venturi scrubber has not been clarified. In this study, the experimental results of the water-vapor two-phase flow in a Venturi tube are reported. As the gas flow rate increased, the supply amount of scrubbing water decreased and eventually stopped because the pressure at the throat increased with increasing the gas density. This phenomenon was caused by the gas compressibility. By visualizing the two-phase flow in the Venturi tube, we cannot measure the spraying from the water supply port, which is considered to affect decontamination of the Venturi scrubber. However, it was confirmed that the water film on the wall at the diverging part of the Venturi tube, and the dispersed water droplets were formed intermittently from the water film. In addition, generation of the liquid at the divergent area was observed even though scrubbing water-supply stopped.

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  • 内堀 昭寛, 渡部 晃, 髙田 孝, 大島 宏之
    論文ID: 17-00394
    [早期公開] 公開日: 2018/01/15
    ジャーナル フリー 早期公開

    When pressurized water or vapor leaks from a failed heat transfer tube in a steam generator of sodium-cooled fast reactors, a high-velocity and high-temperature jet with sodium-water chemical reaction may cause wastage on the adjacent tubes. To evaluate the effect of the reacting jet to the adjacent tubes, a computational fluid dynamics code SERAPHIM, in which a compressible multicomponent multiphase flow with sodium-water chemical reaction is computed, has been developed. The multiphase flow under the tube failure accident is calculated by the multi-fluid model considering compressibility. The chemical reaction between liquid sodium and water vapor is considered under the assumption of an infinite reaction rate. The original SERAPHIM code is based on the finite difference method. In this study, unstructured mesh-based numerical method was developed and introduced into the SERAPHIM code to advance a numerical accuracy for a complex-shaped domain including multiple heat transfer tubes. Validity of the unstructured mesh-based SERAPHIM code was investigated through the analysis of an under-expanded jet experiment, which is a key phenomenon in the tube failure accident. The calculated pressure profile showed good agreement with the experimental data. Numerical analysis of water vapor discharging into liquid sodium was also performed. The calculated temperature field agreed with the existing experimental knowledge. It was demonstrated that the proposed numerical method could be applicable to evaluation of the sodium-water reaction phenomenon.

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  • 安永 健, 森崎 敬史, 池上 康之
    論文ID: 17-00398
    [早期公開] 公開日: 2018/01/15
    ジャーナル フリー 早期公開

    Thermal efficiency is commonly applied in the power plants for the purpose of evaluating heat engines. However, the maximization of the thermal efficiency does not lead the maximization of the available power output from ocean thermal energy conversion (OTEC), which converts the finite thermal energy stored between different temperature seawaters into work. The maximum work efficiency based on the theoretical maximum work from the ideal heat engine has been identified for evaluation; however, the implication in the available thermal energy has not yet been substantially identified. This paper theoretically reveals the available thermal energy from the ocean thermal gradient and the effective energy, which is known as the exergy, using the reference of the equilibrium temperature as the dead state. By employing the finite-time thermodynamics, the available energy and the exergy calculation methods for OTEC are obtained. For the evaluation of the systems, the normalized thermal efficiency is proposed instead of the conventional thermal efficiency and the exergy efficiency for OTEC is proposed as well. The results indicated that increases in the normalized thermal efficiency increase the power output from the OTEC system and the maximum normalized thermal efficiency conditions correspond to the maximum power output heat balance. They also showed the effectiveness of the proposed exergy for OTEC derived by entropy generation minimization.

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  • 岩本 浩祐, 塩見 謙介, 森下 信
    論文ID: 17-00359
    [早期公開] 公開日: 2018/01/12
    ジャーナル フリー 早期公開

    Mullins effect is the phenomenon of stress softening due to prior straining. Stress softening affects the response of facilities isolated by rubber bearings to strong earthquakes because it changes the stiffness of rubber bearings. The influence of the Mullins effect on seismic responses needs to be understood in detail in order to design facilities isolated by rubber bearings based on performance design. The stiffness of rubber isolators which is affected by stress softening, varies over time because stress softening changes depending on the number of repetitions of straining and the magnitude of the generated strain. The magnitude of strain generated in a facility before the principle seismic motion of an earthquake reaches the facility differs depending on whether the earthquake is subduction-zone earthquake or an active fault earthquake because the principle seismic motion of an active fault earthquake reaches the facility in a shorter time. This paper presents the results of a study to investigate the influence of stress softening caused by the Mullins effect and differences in the seismic response of a facility depending on the characteristics of earthquakes.

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  • 萩谷 功, 加藤 千幸, 山出 吉伸, 深谷 征史, 長原 孝英
    論文ID: 17-00363
    [早期公開] 公開日: 2018/01/12
    ジャーナル フリー 早期公開

    For designing a high-performance mixed-flow pump, control and suppression of performance-curve instability is crucial. For doing so, clarification of the essential flow physics that leads to the performance-curve instability is crucial in addition to an accurate prediction of the performance curve. We investigated internal flows of a mixed-flow pump, with performance-curve instability at round 60% of the designed flow rate, by using Large Eddy Simulation (LES). In the previous report, we clarified that drop of the Euler's head caused by stall near the tip of the impeller's blades is the major cause of the performance-curve instability. In the present report, we investigated in detail unsteady internal flows of individual blade passage near the head-drop point. As a result, we clarified the followings. (1) When the flow rate through a blade passage is low, the Euler's head is high for that particular passage, and this condition propagates in the direction of the impeller rotation for the whole impeller while the impeller makes approximately 20 revolutions. (2) Upstream flow of the stalled blade passage is deviated to the downward neighboring blade passage, resulting in increase in the load of the neighboring blade near its trailing edge. The neighboring blade passage will then be stalled. (3) When the flow rate in a stalled blade passage reaches the minimum, the passage starts to recover from stall while the pressure gradient in the streamwise direction will decrease.

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  • 田 宏志, 寇 ギョウ郡, 見浪 護
    論文ID: 17-00182
    [早期公開] 公開日: 2018/01/11
    ジャーナル フリー 早期公開

    Visual servoing towards moving target with hand-eye cameras fixed at a hand of a robot is inevitably affected by the hand's dynamical oscillations, therefore it is difficult to keep target's position always at the center of camera's view, because nonlinear dynamical effects of whole manipulator stand against tracking ability of the visual servoing. One possible solution to overcome this problem is that the visual servoing control of the hand and eye-vergence is separated independently, so that the camera can track the target to observe it at the center of camera images to enhance the tracking ability (trackability). In line with this tactics, the authors have developed an eye-vergence visual servoing control system to enhance the trackability. With several experiments, it has been shown that the trackability of the eye-vergence motion is superior to the one of hand-eye system since the eyes' motion can be quicker than the hand's motion.

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  • 島崎 航平, 姜 明俊, 高木 健, 石井 抱
    論文ID: 17-00469
    [早期公開] 公開日: 2018/01/11
    ジャーナル フリー 早期公開

    In this study, we propose a fast algorithm for vision-based vibration source tracking that can significantly reduce the computational complexity in pixel-level digital filters. The algorithm reduces the complexity by adjusting the sampling rate to twice the vibration frequency of the target object to be tracked using frame interpolation. The computational complexity and properties of the pixel-level digital filters for downsampled images are evaluated; the proposed algorithm can accelerate the pixel-level digital filters, while retaining the admissible filter property for vibration source tracking unlike the approach used previously in which the input images captured at a high frame rate were directly processed using pixel-level digital filters. The pixel-wise accuracy in vibration source tracking is demonstrated by several evaluation results of offline high-frame-rate videos, which displayed various flight scenarios of a multicopter with its propellers rotating at 90-100 Hz.

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  • 楊 蔚涛, 小林 重昭, 齋藤 栄
    論文ID: 17-00353
    [早期公開] 公開日: 2018/01/10
    ジャーナル フリー 早期公開

    Effect of grain boundary microstructure, such as the spatial distribution and the connectivity of grain boundaries with different character, on the process of fatigue crack propagation in SUS430 ferritic stainless steel was investigated using the technique combined in-situ observations of crack propagation with EBSD measurements. The ratio of intergranular fracture to the overall fracture path increased with decreasing stress intensity factor range. Particularly, the ratio of intergranular fracture reached about 60 %, when the stress intensity factor range was less than 40 MPa m1/2. Moreover, the larger deflection of crack propagation occurred by the cyclic deformation at the higher stress intensity factor range more than 50 MPa m1/2, depending on the grain boundary microstructure. The intergranular fatigue cracks mainly propagated along random boundaries, and the deflection of intergranular crack path occurred at grain boundary triple junctions, owing to the further propagation along random boundary ahead. Moreover, when the fatigue crack propagation along random boundaries was inhibited by a triple junction composed of low-∑ CSL boundaries, the branching of fatigue crack occurred at a triple junction behind and the crack subsequently propagated along another random boundary. The propagation of fatigue crack was inhibited for a while by crossing low-∑ CSL boundaries and triple junctions. The possible grain boundary microstructure for control of fatigue crack propagation in SUS430 stainless steel was discussed based on the observed results.

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  • 中村 眞実, 岡﨑 三郎, 松永 久生, 松岡 三郎
    論文ID: 17-00437
    [早期公開] 公開日: 2018/01/10
    ジャーナル フリー 早期公開

    In order to study the hydrogen embrittlement behavior of austenitic stainless steel weld metal, slow strain rate tensile (SSRT) tests and fatigue life tests were performed in high-pressure hydrogen gas. Tensile and fatigue life specimens, in which whole of the gauge section consists of weld metals, were machined out from a TIG welded round bar. The base metal of multi-pass welded bar was SUS316 (hi-Ni), and the filler metal was 317L. Two series of weld metals were tested; one was an as-welded metal having coarse columnar gain with dendrite and δ-ferrite, and the other was a post-welded solution-treated metal. The relative reduction of area, RRA, was 0.55 for 317L as-welded metal, and approximately 0.9 for SUS316 (hi-Ni) base metal and 317L post-welded solution-treated metal. The fracture surface of 317L as-welded metal included lamellar weld (LW) fracture surface, whereas those of SUS316 (hi-Ni) base metal and 317L post-welded solution-treated metal were entirely covered with dimples. Fractographic observation in combination with EDS manifested that δ-ferrite was responsible for the hydrogen-enhanced crack growth leading to the formation of LW, and therefore the post-welded solution-treated metal without δ-ferrite exhibited excellent resistance to hydrogen. Regardless of the heat treatment, the fatigue limit of 317L weld metal was not degraded in hydrogen gas as well as the austenitic stainless steel base metal.

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  • 山田 竜大, 谷口 大二郎, 來海 博央
    論文ID: 17-00442
    [早期公開] 公開日: 2018/01/10
    ジャーナル フリー 早期公開

    Micro-Raman spectroscopy is used to measure phases, stresses and strains in microstructures comprising semiconductor materials, such as Si. However, the two-dimensional Raman imaging techniques for directly observing phases and measuring stresses and strains in a large area are required. In this study, we develop a new micro-Raman spectroscope equipped with an integral field unit (IFU) for two-dimensional imaging. Two-dimensional Raman images are obtained without scanning laser spots and stages. In addition to the IFU, this instrument primarily comprises an illumination optical system. In the illumination optical system, a diffractive optical element is used to enlarge the area of the laser spot and transform the circular laser beam into a square beam. The IFU simultaneously collects two-dimensional Raman signals using a microlens array, 4 × 4 optical fiber bundle, two-dimensional imaging spectrometer, and highly sensitive two-dimensional charge-coupled device (CCD) detector. Subsequently, we conduct two-dimensional imaging of the Si phase and residual stress components of the (111)-oriented single-crystal Si wafer induced by Vickers indentation. The Raman spectra are measured under polarization conditions to decompose the triple degeneracy of Si, and the residual stress components around Vickers indentation are calculated from the relations between the Raman shift and applied strain.

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  • 齊藤 亜由子, 宮脇 和人, 木澤 悟, 小林 義和
    論文ID: 17-00488
    [早期公開] 公開日: 2018/01/09
    ジャーナル フリー 早期公開

    This paper describes the use of nine-axis motion sensors to evaluate knee joint angle estimation accuracy during walking. The nine-axis motion sensor comprises a three-axis gyro sensor, a three-axis acceleration sensor and a three-axis geomagnetic sensor. It can estimate joint angles during exercise by correcting the drift of the three-axis gyro sensor using information obtained from the other two sensors. Human movement results from the rotational motion of the respective joints, so that the proportion of the centrifugal acceleration and the tangential acceleration in the output of the acceleration sensor increases during exercise. Processing the centrifugal acceleration and tangential acceleration appropriately and ascertaining the degree of estimation error are important for improving the joint angle estimation accuracy. For this study, the authors produced a sensor fusion algorithm using an extended Kalman filter to correct the acceleration sensor output. The sensor fusion algorithm uses information obtained from the nine-axis motion sensors to estimate the knee joint angle by correcting the centrifugal acceleration and tangential acceleration. During the experiment, the 3D motion analysis system and two nine-axis motion sensors measured walking exercise. The knee joint angle was estimated using an extended Kalman filter with information obtained from the nine-axis motion sensors. We evaluated the system accuracy for knee joint angle estimation by comparing the nine-axis motion sensor results and the 3D motion analysis system results. This analytical method is anticipated for use in estimating motion in sports and healthcare applications.

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  • 山下 駿野, 倉林 大輔, 服部 佑哉
    論文ID: 17-00338
    [早期公開] 公開日: 2017/12/28
    ジャーナル フリー 早期公開

    In this paper, we proposed a system in which robot swarms autonomously divide or merge themselves according to phase gradients emerged by coupled oscillators. Due to the limitation of communication cost or ability, a large-scale swarm should be controlled in the distributed manner. Although the agents in the proposed system were equipped local communication system only, they successfully organized group formations, and divided or merged them. We employed phase gradients emerged by phase oscillators, which we could find similar phenomena in living slime molds. We implemented a phase oscillator on an agent, and proposed an algorithm to move along the gradients. By controlling phase gradients, we could make the swarms dividing or merging themselves in the self-organization manner. We provided formulations and analyses to guarantee those performances. Simulations and experiments were carried out in order to verify the performance of the proposed system.

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  • 高橋 護, 岩野 耕治, 酒井 康彦, 伊藤 靖仁
    論文ID: 17-00430
    [早期公開] 公開日: 2017/12/28
    ジャーナル フリー 早期公開

    Joint statistics between velocity gradient and fluctuating static pressure in a turbulent planar jet are experimentally investigated. The experimental data was acquired by simultaneous measurements of velocity gradient ( ∂u’2/∂x1 and ∂u’1/∂x2, where u’1, u’2, x1 and x2 are fluctuating stereamwise velocity, fluctuating cross-streamwise velocity, streamwise coordinate, and cross-streamwise coordinate, respectively) and fluctuating pressure p′ using two combined probes. One of the combined probe consists of an X-type hot-wire probe and a pressure probe and the other combined probe consists of two I-type hot-wire probes arranged in vertical direction and a pressure probe. In the time-series, it is shown that the events in which the instantaneous Reynolds stress, squared cross-stramwise velocity, and product of velocity gradient and pressure shows significantly large value (so-called “significant events”) occur intermittently with negative pressure fluctuation, this implies that the Reynolds stress transport phenomena are locally active with the large-scale vortex structures observed in a turbulent planar jet. It was also found that the standard deviation of (p’/ρ)(∂u’2/∂x1) conditioned by the negative pressure fluctuation is 21% larger than the unconditioned standard deviation. The cospectra show that the correlation (p’/ρ)(∂u’2/∂x1) greatly contributes the local isotropy of the flow field. On the other hand, we confirmed that ∂u’1/∂x2 is almost unrelated to the pressure fluctuation in the present turbulent planar jet. The results show that there is little contribution on the Reynolds stress transport by the correlation (p’/ρ)(∂u’1/∂x2).

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  • 立矢 宏, 伊勢 大成, 樋口 理宏, 藤城 慶治
    論文ID: 17-00435
    [早期公開] 公開日: 2017/12/28
    ジャーナル フリー 早期公開

    Previously, in order to measure friction coefficients of tire grounding surface in car slipping, a cantilever-type sensor that can detect the vertical load and friction force as well as the direction of the friction force simultaneously has been proposed. The sensing part, which contacts grounding surface, of the proposed sensor is pulled out of the tire tread through a hole. However, penetrating the hole through tire tread part has some problems: leakage of air from the tire, weakening of the rigidity etc. Therefore this study proposes a sensor that can be installed on the inner surface of a tire without penetrating hole through the tire tread by filling the detecting part of the sensor in the inner part of the tire tread. If the detecting part filled in the inner surface has sufficient airtight structure from the integral manufacturing, the durability of the sensor as well as retaining air pressure are expected. This study measured the deformation of the inner part of the tread through the detecting part under high-load at tire slipping state. Furthermore, relation between the measurement values and the force applied to the tire from grounding surface was clarified. As a result, the study confirmed that the proposed method can detect the friction coefficients between the tire and tire grounding surface.

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  • 小島 明寛, 奥井 学, 山田 泰之, 中村 太郎
    論文ID: 17-00299
    [早期公開] 公開日: 2017/12/27
    ジャーナル フリー 早期公開

    A pneumatic artificial muscle is a rubber actuator activated by air pressure. It is lightweight and has the high power density compared to other actuators such as motors and fluid powered cylinders. In addition, it can provide high compatibility with human since its flexibility. Authors have developed the Straight-fiber-type pneumatic artificial muscle which has high output and high contraction amount compared to the McKibben type artificial muscle that is widely used. However, the lifetime of the Straight-fiber-type pneumatic artificial muscle has not been considered so far. In this paper, effects of aspect ratio and materials on the lifetime of the artificial muscle are examined for prolonging the lifetime. Firstly, the desirable maximum stretch rate of the material is developed. Secondly, fatigue life is measured by reducing the elongation of the rubber material by changing the aspect ratio of length and inner diameter in the SF-ARM. Finally we measure the influence on the output characteristics by changing aspect ratio. The result shows relationship of the lifetime and the aspect ratio of the artificial muscle. We showed that the artificial muscle’s lifetime and contraction characteristics can be selected according to the application.

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  • 小川 亜樹, 安達 和彦
    論文ID: 17-00341
    [早期公開] 公開日: 2017/12/27
    ジャーナル フリー 早期公開

    This study aims to establish the fundamental theory of function of the practical inerters. Inerter is effective component for mechanical vibration system to control vibration frequency characteristics. Many studies related to inerter had been examined in the past. Although most of the previous studies are examined with ideal inerter which ignore mass and inertia of the devices themselve. We assume that the function of practical inerter can be regarded as the function of ideal inerter with two inertias connected to each terminal. We formulate four types of practical inerters: three types of torsional inerter constracted by planetary gear unit and one linear type inerter using rack and pinion gear mechanism. Re-arranging dynamic characteristics based on the assumption of the practical inerter function, it is confirmed that function of each practical inerter can be represented as the combination of two functions: one is ideal inerter function and the other is inertia-distribution function which is redistributed the inertia of the devices to each terminal. In addition, the inertia-distribution function could furthermore devide three subfunctions: first is inertia transfer, second is the directly connected inertia to the terminals, third is the indirectly connected inertia to the terminals. As the concluding remarks, fundamental theory of the practical inerter function is sucsessfully derived.

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  • 石原 国彦, 工藤 哲, 桝本 貴之, 森 正明
    論文ID: 17-00365
    [早期公開] 公開日: 2017/12/27
    ジャーナル フリー 早期公開

    Karman vortex shedding occurs when the gas passes through the duct with tube bank of the heat exchangers, such as gas heaters and boilers. Very high level sound in called “self-sustained tones” occurs due to the interference of the vortex and the sound field in the duct. In general, baffle plates are used to suppress the self-sustained tone. However, it is difficult to use them effectively, because insertion conditions have not been established. Then, perforated plates are installed in both sides of the duct to suppress the self-sustained tones. As a result, it was clarified that the perforated plate could suppress the self-sustained tone as expected. The perforated plates are generally used with a cavity to obtain the suppression effect effectively. However the perforated plates change the acoustic natural frequency of the sound field of the duct. In previous paper, this was not referred. This paper aims to clarify the role of the perforated plates when it changes the acoustic natural frequency of the duct. In this study, one dimensional duct will be used for simplicity and the relationship between the aperture ratio and the acoustic natural frequency will be obtained analytically and experimentally. As a result, it was clarified that the analytical results are in good agreement with the experimental ones and the plates with holes had a role of acoustic damping in calculation of the acoustic natural frequency of the one dimensional sound field like a duct with plates with holes.

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  • 矢田 浩基, 高屋 茂, 若井 隆純, 仲井 悟, 町田 秀夫
    論文ID: 17-00389
    [早期公開] 公開日: 2017/12/26
    ジャーナル フリー 早期公開

    In the in-service inspection of sodium cooled fast reactors, an examination by continuous leak monitoring will be applied for components constituting sodium boundaries. The continuous leak monitoring examinations are premises in a LBB (leak before break) being established. In previous LBB evaluation, the axial crack of the elbow flank has been evaluated, because in the piping system of the fast reactor with high thermal expansion, high stress is generated in the elbows flank. However, the LBB evaluations for circumferential cracks are important in the point of continuous leak monitoring in the in-service inspection. In this study, the load conditions in the LBB assessments for circumferential cracks were examined and LBB characteristics of class 1 pipes of the prototype fast breeder reactor "Monju" were evaluated as an example. Additionally, in order to research the relationship between pipe condition and LBB, many pipes were evaluated with actual conditions. As results, following conclusions were obtained. It was demonstrated that LBB characteristics are established at class 1 pipes in “primary heat transport system” and “cooling system for maintenance” of “Monju”. LBB characteristics are correlated with pipe diameter and thickness.

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  • 川原 顕磨呂, 高木 航, 西岡 大輝, 遠藤 将人, 佐田富 道雄
    論文ID: 17-00396
    [早期公開] 公開日: 2017/12/26
    ジャーナル フリー 早期公開

    This study investigates the effects of mixing vane (MV) attached to a grid spacer on pressure drop for air-water annular flows in a vertical circular pipe of 16 mm I.D. In order to know the effects of MV, grid spacers with or without MV were installed in the test pipe. Three types of grid spacers with MV which has four MVs inclined 20, 30 degree from the vertical flow axis (4-MV20, 4-MV30) and two MVs inclined 30 degree (2-MV30) were used. In addition, two liquid injection methods (wall and center jet injections) are adopted to control liquid droplet entrainment faction in gas core. In the experiment, pressure drop along the channel upstream and downstream from the spacer was measured with a pressure transducer. In the analysis, the correlation of the pressure drop across the spacer is newly developed based on the present data.

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  • 西村 瑞希, 小牧 晃洋, 山田 敏彦
    論文ID: 17-00399
    [早期公開] 公開日: 2017/12/26
    ジャーナル フリー 早期公開

    While the efforts to control global warming are being strengthened all over the world, expectations for CO2 Capture, Utilization and Storage (CCUS) technology for coal fired power plants are increasing. IHI has been working on development of oxyfuel-combustion technology since 1989 with the aim of easily capturing and storage CO2 emitted from coal fired power plants. For the demonstration of oxyfuel-combustion technology, IHI participated in the Callide Oxyfuel Project with collaboration between Australian and Japanese under the financial support of Australian, Queensland state and Japanese governments. In the project, the oxyfuel-combustion process was applied to the existing coal power plant in Queensland, Australia, and demonstration was carried out and successfully completed without any significant technical barrier to commercialization in March, 2015. In Oxyfuel-combustion, the coal-fired boiler is operated with an inlet O2 content of 27 vol% in order to achieve the same furnace heat transfer as in conventional air-firing. The first outcome of oxyfuel-combustion is a significant reduction in NOx production, typically 60% reduction, measured in mgNOx/MJcoal. The second outcome of oxyfuel-combustion is a reduction in the actual volumetric flow of flue gas, typically a 60% to 70% reduction in gas flow measured as m3/h, and a proportionate increase in the CO2 content of the flue gas from ~ 15 vol% (dry) in airfiring mode to 70 to 80 vol% (dry) in Oxyfuel mode. In addition, CO2 product from the Callide Oxyfuel Project was injected into the Paaratte formation in the Otway Basin (Victoria) to investigate the geochemical effects of CO2 (normal product) and CO2 with added impurities. The recent research and development about characteristics of roller mill and electrical precipitator using combustion test facilities for the flexibility of plant design and the current commercialization activities of oxyfuel power plant are introduced in this paper.

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  • 江口 隆夫, 松尾 武, 村谷 諒, 古賀 毅
    論文ID: 17-00270
    [早期公開] 公開日: 2017/12/21
    ジャーナル フリー 早期公開

    This research addresses an evaluation method of business value considering risk-hedging options from the first stage of the product development. A scenario planning method is introduced into the estimating method of the business value in order to identify uncertain factors, which affect to the business value. Generally, the scenario planning method has a weak point that it is difficult to apply its result into the project plan, because the specified factors are relatively qualitative. Proposed uncertainty analysis organizes the qualitative factors into four types of stochastic distributions. By combining the risk-hedge options and probabilistic distributions, a decision tree diagram, which contains the numerical estimated values about product development project, is calculated. The decision tree diagram describes project's EPV (Expected Present Value), so that the best combination of options is derived. The proposed method is applied to the i-Painter development project, which is automatic repairing robot of the buildings as an example. Two risks about future technological change in painting mechanics and flooding around factory are identified, calculated, and compared. The application result shows that the proposed method can surely help the development member to specify the economical external element change. In addition, the result indicates that the best business value is estimated and best risk hedge option can be calculated.

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  • 市原 順一
    論文ID: 17-00373
    [早期公開] 公開日: 2017/12/21
    ジャーナル フリー 早期公開

    The slider/disk spacing of magnetic disk drives has been reduced in order to increase the recording density. Especially, the thermal flying-height control technology, where the electromagnetic transducer is protruded into the slider/disk spacing by heating the slider partially, contributes to make the flying height less than 2nm. Because of the narrower gas bearing clearance, the bearing pressure rises up to several tens times of atmospheric pressure. This pressure rise causes the deformation of slider and disk surface. The slider and disk surface deformation causes the change of gas bearing clearance and consequently the change of air bearing pressure. The pressure change causes the flying attitude. The flying characteristics also may be different from that of expected at the design, where the effect of deformation is not included. It is important to estimate correct flying characteristics affected by the deformation to realize stable flying and accurate recording. We introduced iterative method for searching the flying attitude affected by the slider/disk deformation. We obtained the air bearing pressure by solving the molecular gas lubrication equation numerically. And the simple numerical method, which utilizes the elastic half-space assumption, was employed for calculating the deformation of pressurized disk surface. The finite element method was applied to analyze the slider deformation. And the effect of deformation on the slider attitude is evaluated.

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  • 川副 祥規, 網 健行, 梅川 尚嗣, 小澤 守
    論文ID: 17-00380
    [早期公開] 公開日: 2017/12/21
    ジャーナル フリー 早期公開

    Critical heat flux is one of the most important key parameters for various boiling systems, such as nuclear reactors and conventional boilers. Thus, many investigations have been reported, but most of these are concerned with the upward flow condition, and the phenomena under downward flow condition have not been fully understood. In this series of studies, the critical heat flux under the downward flow condition was classified into four mechanisms, i.e. dryout of falling liquid film, critical heat flux caused by the flooding, critical heat flux caused by the hydraulic instability and the liquid film dryout in annular flow regime. In addition, evaluation models of CHF were presented for each mechanism. Although these explanations showed the features of CHF under downward flow condition adequately, they were not suitable to explain the characteristics of CHF caused by the hydraulic instability. In this investigation, CHF of this region was formulated by two different models based on the comparison of the data in the experimental results obtained by using the tube with heated length of 200 mm and that of 400 mm. As a result, the model based on the Kelvin-Helmholtz instability was found to be suitable for relatively low mass flux condition. Under relatively high mass flux condition, the modified model of the departure from nucleate boiling (DNB) is proposed. These models show good agreement with the experimental results.

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  • 長沼 恒雄, 橋本 浩一
    論文ID: 17-00417
    [早期公開] 公開日: 2017/12/21
    ジャーナル フリー 早期公開

    This article suggests the machine operation mode can be estimated from sensors attached to the machine in the production line. An injection molding machine (IMM), which is widely operated in the plastics industry, was used in this research within an actual production line. Four strain sensors were attached to the IMM to measure the clamping force in each production cycle. Auto or semi-auto mode was estimated from the clamping force sequence. Auto mode is continuous production by the machine itself, while semi-auto mode involves intermittent human operation and includes such functions as machine start, machine finish, and trouble shooting. Approximately 340000 cycle data were obtained in 10-week production. The changing value was calculated by the binomial filter statistical technique, as well as the differencing of time series data from the clamping force in each cycle. And the relationship between changing value and operation mode is evaluated by the area under the curve (AUC) calculated from the receiver operating characteristic curve (ROC curve). As a result, we obtained that AUC value was 0.86 from 10-week production data, which means operation mode can be estimated from the changing value of clamping force in a high level. This estimating method has a low computational cost; therefore it is easy to install on a machine's board control system. We expect that this method will be used to detect the defective product, the machine malfunction or the mold failure.

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  • 吉川 穣, 西尾 悠, 伊澤 精一郎, 福西 祐
    論文ID: 17-00478
    [早期公開] 公開日: 2017/12/20
    ジャーナル フリー 早期公開

    Numerical simulations are carried out aimed at finding a key flow structure which leads to a laminar-turbulent transition of a boundary layer with streaky structures. In the preliminary computation, an array of cuboids is used to form streaky structures inside a boundary layer. Then, a disturbance is introduced into the boundary layer by ejecting a short-duration jet from a hole in the wall into a low-speed region in the streaky structures. Although the boundary layer returns to a laminar state when the jet velocity is set to 18% of the uniform flow velocity, it eventually turns into a turbulent state downstream in the 20% case. The differences are investigated in detail in terms of the vortical structures. As a result, only in the stronger jet case, a flat spanwise vortex is generated beside one leg of a hairpin vortex and it merges with the streamwise vortex nearby forming an inclined streamwise vortex. On the other hand, the flat spanwise vortex disappears without being connected to the streamwise vortex in the weaker jet case. The inclined streamwise vortex is stretched by the mean velocity gradient of the boundary layer growing into a strong vortex, and new vortex structures are generated around the inclined one, which leads to turbulence. Therefore, the results suggest that formation of the inclined vortex is the key to transition of the boundary layer.

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  • 生沼 駿, 中谷 祐二郎, 今井 潔, 高橋 武雄, 佐々木 隆
    論文ID: 17-00383
    [早期公開] 公開日: 2017/12/19
    ジャーナル フリー 早期公開

    700°C class A-USC (Advanced Ultra Super Critical) thermal power plant is one of the solutions to reduce carbon dioxide (CO2) emission. In order to meet the design requirement, which is capable to be operated under 700°C steam condition, the development of Ni-based superalloys is essential. Fundamental research and demonstration of mock-up plants have been driven by national project in Japan, US, Europe and China, to confirm the reliability of Ni-based superalloys. One issue of superalloys reported by others is the stress accelerated grain boundary oxidation (SAGBO), leading to the deterioration of creep rupture properties during service. We newly manufactured the test apparatus which enables to creep test under high temperature steam environment, and evaluated the grain boundary oxidation behavior of Ni-based rotor material, TOS1X-2, under various stresses and atmosphere. Microstructure observation after creep tested at 750°C for 2,500h, found that thin layer of Cr-rich and Al-rich oxides form at all stress and atmosphere condition. Detail studies revealed that the Al-rich oxide were formed at fine, recrystallized grain boundary, which is driven by initially induced strain by machining. The quantitative analysis of microstructure showed that steam atmosphere slightly accelerates the grain boundary oxidation. On the contrary, effect of applied stress on oxidation depth was not observed. The grain boundary oxidation observed in this study was very small, suggesting that TOS1X-2 exhibits good oxidation and creep rupture properties in 700°C A-USC operating condition.

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  • 池田 生馬
    論文ID: 17-00322
    [早期公開] 公開日: 2017/12/18
    ジャーナル フリー 早期公開

    Even in a state that the person is resting, the person vibrates with a small amplitude. This vibration is called human tremor. For example, when performing precise work such as watch assembly or surgical operation, the tremor will have an influence on the accuracy of work. In order to suppress the tremor, frequency spectrum analysis of the tremor is necessary. However, only dominant frequency of the tremor have been calculated in previous works. In this paper, human tremor model for frequency spectrum analysis is proposed. In the model, the tremor is regarded as forced vibration. Forearm is modeled as a rigid link, which is antagonistically driven by two Hill's muscle models. The stiffness of muscle model is considered as non-linear. This makes it possible to estimate the difference of frequency spectrum of the tremor occurs due to different angle of the elbow. Moreover, the force driving the forearm is generated from muscle by using leaky Integrate-and-Fire cell model. In a previous study, it was confirmed that neural cell had a refractory period, and there was randomness in the period. Therefore, in this study, the refractory period of the cell model is set to the normal distribution. Because the force is intermittently generated by the random period, the forearm is vibrated. The vibration spectrum obtained from the simulations and that obtained from the experiments quantitatively agreed.

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  • 松岡 三郎, 濱田 繁, 吉田 聡子, 飯島 高志, 松永 久生, 山辺 純一郎
    論文ID: 17-00385
    [早期公開] 公開日: 2017/12/15
    ジャーナル フリー 早期公開

    In order to investigate the suitable test methods for determining threshold of hydrogen-induced crack growth, KI,H, JIc, none-unloading JIc, constant-load and constant-displacement tests were conducted in 115 MPa hydrogen gas at room temperature, using SCM435 low alloy steels whose tensile strengths were between 824 and 1127 MPa. Constant-load and constant-displacement tests have been standardized by ASME KD-10 for determining KI,H in hydrogen gas. JIc test has been standardized by ASTM E1820 for determining fracture toughness JIc or KIc in air. Recently, JIc test was done in hydrogen gas to obtain KI,H. In this study, there were many cases when JIc tests were not conducted in hydrogen gas, because CT specimens broke before the first unloading. Then, none-unloading JIc test, where unloading processes were eliminated in JIc test, was employed in hydrogen gas. All four tests were done under small scale yielding in 115 MPa hydrogen gas. KI,H obtained by four tests was almost the same. KD-10 demands that constant-load and constant-displacement tests of ferritic steels such as SCM435 are done for 1000 hours. Contrary to this, none-unloading test at displacement rate of 2×10-3 mm/s was finished within one hour. It was concluded from these results that none-unloading JIc test was the best test for determining KI,H in 115 MPa hydrogen gas. On the other hand, JIc test was the only test for determining KIc in air, because KIc was obtained under large scale yielding.

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  • 于 豊銘, 岡部 洋二
    論文ID: 17-00406
    [早期公開] 公開日: 2017/12/15
    ジャーナル フリー 早期公開

    Because of the stable material property of optical fiber up to 1000℃, fiber-optic Bragg grating (FBG) sensor is considered as one of possible ultrasonic sensors used at ultrahigh temperature. However, disappearance of reflectivity of a normal FBG in the high temperature above 900℃ makes the ultrasonic detection impossible. In order to detect ultrasonic wave under high temperature environments, we conducted an anneal heat treatment to produce a regenerated fiber Bragg grating (RFBG) sensor. Because the RFBG has a stable reflectivity even at temperature of 1000℃, we detected the ultrasonic wave successfully at the temperature. Especially, because a π-phase-shifted FBG (PSFBG) was used as the seed grating, the RFBG sensor possessed very short effective gauge length that resulted in a broad bandwidth response to ultrasonic wave over 1 MHz. Hence, we believe that the ultrasonic RFBG sensors could be potentially applied for ultrasonic detection in non-destructive tests to evaluate microscopic damage in materials under extreme high-temperature environment.

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  • 奥田 昇也, 米澤 政昭
    論文ID: 17-00172
    [早期公開] 公開日: 2017/12/14
    ジャーナル フリー 早期公開

    This study describes a method to reliably search and determine design points required for constructing importance sampling probability density functions (p.d.f.s) in the method of estimating the structural failure probability based on multiple importance sampling simulation. In order to search out and determine all of design points without any omission, the initial points of Rackwitz Fiessler (RF) algorithm that performs the design point search are proposed to be set on limit state surfaces within the entire quadrants of the basic random variables space. First, from the standardized normal p.d.f., several samples, referred to as real samples, are generated in the specific quadrants. Using the newly proposed "inter-quadrant relational expression", the coordinates of the real sample points are converted to the coordinates of the sample points called pseudo samples in all the quadrants except those of the real sample points. In this way, real samples or pseudo samples are generated and determined in all quadrants. Next, the coordinates of intersection points of the limit state surface and straight lines extending from the origin and passing through respective real and pseudo sample points are determined. And the intersections determined on the limit state surfaces in all quadrants are proposed to adopt as initial points of RF algorithm. By executing RF algorithm from respective initial points determined, all of design points are searched out completely, and the importance sampling p.d.f.s are constructed by making use of the respective design points determined. Numerical examples for estimating the failure probability of structural systems having multivariable nonlinear limit state functions are shown based on multiple importance sampling simulation using all of the constructed importance sampling p.d.f.s and the proposed method shows accurate estimations of structural failure probabilities.

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  • 金 太成, 酒井 貴広, 星 雄大, 二川 秀史, 細井 厚志, 川田 宏之
    論文ID: 17-00313
    [早期公開] 公開日: 2017/12/14
    ジャーナル フリー 早期公開

    Carbon nanotube yarn, which is an aggregate form of carbon nanotubes (CNTs), is expected to be practically used as a lightweight wiring material. In recent years, CNT/metal composite yarn has been fabricated for making the CNT yarn highly conductive. While improving conductivity in the CNT/metal composite yarns, current capacity, which determines durable current value of the wiring material, has not reached practical value. In this study, composite material of untwisted CNT yarn and copper was fabricated by plating treatment for the purpose of creating a lightweight wiring with larger ampacity than metal wiring. In addition, CNT/copper composite yarns having different composite structures were fabricated and the relationships between the composite structure and electric characteristics were evaluated. One of the composite yarns had a two-layer structure in which copper was deposited on the surface of the CNT yarn, and the other had a structure in which copper precipitated to the inside of the CNT yarn. As a result of the plating treatment using a copper sulfate bath, current capacity of the composite yarn reached 6.87×108 A/m2 at the copper volume fraction of 28.9%, and the specific current capacity was 1.29 times larger than copper wire. From evaluation of the fracture mechanism, it was revealed that combustion of the CNTs and melting of the metal part were suppressed by combining the CNT yarn with copper, and it led to the large ampacity. In addition, it was possible to electroplate inside of the yarn by adding a dipping step to the plating process. In the case of the composite yarn plated the inside, an increase in resistance under large current was suppressed and further improvement of the current capacity was achieved.

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  • 山口 貴吏
    論文ID: 17-00327
    [早期公開] 公開日: 2017/12/14
    ジャーナル フリー 早期公開

    In this paper, we have proposed a simple buckling evaluation method for plate structures of which original shapes and boundary conditions do not change before buckling, and buckling modes of the plates are uniform along longitudinal directions of the plates. Buckling forces of the plates in the structures are derived from the product of the Euler buckling forces and buckling coefficients of the plates. For the establishment of a relationship between the buckling coefficient and support stiffness of plates elastically supported by adjoining plates, buckling analyses by FE models were executed under conditions of different support stiffness for the adjoining plates, and then an approximate function between the support stiffness and the buckling coefficient was derived. This function was applied to examples with another moment ratio, a plurality of adjoining plates and asymmetric adjoining plates, and the buckling coefficients predicted by the function. It was then found that the buckling coefficients obtained by the proposed method matched those of the buckling analysis results. Furthermore, this buckling evaluation method was applied to plate structures, and a buckling force of a buckling plate was compared with a buckling analysis result. It was found that the buckling force could be evaluated within a difference of 6.8 %.

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  • 淺田 隆文, 山﨑 大志
    論文ID: 16-00492
    [早期公開] 公開日: 2017/12/12
    ジャーナル フリー 早期公開

    Newly developed 3D scanning optical endoscopic probe consists of φ1.5mm quartz pipe and 2 micro motors that run inside and conduct helical 3D scanning. This research looks into the possibility of accurately measuring the inner wall of extremely small diameter object by combining 3D scanning endoscopic optical probe and OCT (optical coherence tomography). Conventionally, precision measurement of such extreme inner diameter size was not possible due to influence of what is called “fluctuation of light” and “mechanical run-out of the measuring instrument itself” in axial and radial direction. In the new method, the inner wall of quartz pipe is measured in advance by calibration work, and the inner wall of the object is measured based on the quartz pipe. Applying this method, we succeeded in measuring with standard variation 0.07μm(σ) repeatedly. This new method also features auto-correction of the incline angle between the optical probe and the measuring object by computing, which prevents setting error and variation.

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