Recently, Life Cycle Assessment (LCA) has attracted attention in the manufacturing field. Some consumer devices have been designed with consideration of LCA. However, there have been very few reports on consideration of LCA with machine tools. Using LCA, we attempt to estimate the environmental burden of a desktop-sized five-axis Computer Numerical Control (CNC) machine tool. We focus on the concept that small parts should be machined with small machine tools. A comparison of the manufacturing loop using a conventional machining center with that using a desktop-sized machine tool demonstrated that use of a smaller machine tool is an effective method to reduce the environmental burden in small part manufacturing.
When a train is running in a tunnel, a pressure wave is continuously radiated from both end portals to the outside. We herein call this a “tunnel continuous wave”. Though some characteristics of the tunnel continuous wave have been revealed from previous research, the relation between the tunnel continuous wave radiating to the outside and the pressure wave inside the tunnel has not yet been obtained. The pressure wave measured at a fixed point in the tunnel is the superposition of two kinds of waves (an incident wave and a reflected wave) propagating in the opposite directions. Therefore, to investigate the relation between the tunnel continuous wave and the pressure wave inside a tunnel, it is necessary to separate the incident wave and the reflected wave from the measured combined pressure wave. In this paper, we propose a method of separating the incident wave and the reflected wave from the pressure waves measured inside a tunnel. The validity of this method is confirmed by numerical and experimental investigation.
In this study, we focused on optimizing a part of the furnace and operating conditions of the fiber yielding system from fused coal ash to expand ash utilization for building materials; promotion of ash use is desirable because slag inhibits the elution of toxic heavy metals, such as Hg, Pb and As, to undetectable levels, making the fibers safe to use. In particular, the fiber materials from coal ash slag are expected to be used as thermal insulators and acoustic materials. We designed a coal ash fusing furnace which is suitable for the fiber manufacturing and recovery process. To manufacture fiber materials which are both safe and homogeneous, the slag viscosity had to be stabilized to approximately 1 Pa·s at the slag-tapping hole of the furnace. However, the slag temperature at 1 Pa·s was too high to measure. Thus, we estimated the slag temperature at 1 Pa·s using Riboud’s and Urbain’s expressions. To control the slag viscosity and temperature, CaCO3 addition to coal ash was effective. When the basicity (CaO/SiO2(wt%/wt%)) of the coal ash sample was 0.98, the fused slag temperature at 1 Pa·s was estimated as 1563 °C. Then, we verified that to yield 1 Pa·s fusing slag from 120 kg/h coal ash, the necessary fuel quantity of the coal ash fusing furnace was 40 kg/h coal and 4 m3N/h LPG.
In this study, we propose an experimental method for evaluating dipole sound on the basis of the vortex sound theory. By using time-resolved particle image velocimetry (PIV) in a wind tunnel test, we measured time series data of unsteady two-dimensional flow around a circular cylinder which is suitable for applying the vortex sound theory and validating our proposed methods. The sound pressure in the far field experimentally estimated from PIV measurements is validated by a correlation analysis with a measured sound pressure. Furthermore, we performed a correlation analysis between the source intensity defined as the integrand in the equation of the vortex sound theory and the measured sound pressure to determine the relationship between the estimated dipole sound and the measured flow field. The results show that the estimated sound pressure can detect the Aeolian tone due to Karman vortex shedding. Periodic fluctuation around the shear layer separation regions and the vortex formation region in the wake region causes the estimated dipole sound.
We studied the mechanism of drag reduction due to textured hydrophobic surfaces in Newtonian laminar flow through a rectangular channel. The test wall surfaces were fabricated with different fine groove patterns and groove area ratios, and were then coated with PTFE to produce hydrophobic surfaces. Drag reduction was estimated by pressure loss measurements in a 12 × 12 mm channel. Visualization of the gas-liquid interface was carried out using a 0.5 × 5 mm microchannel to investigate the mechanism of drag reduction. A series of experiments showed that the gas-liquid contact area ratio and the air layer thickness influence the drag reduction, the maximum drag reduction ratio is 3.7 %.
This study focuses on the starting performance of small Darrieus wind turbines. Numerical simulations of the starting torque acting on a stationary wind turbine were performed to determine the wing section and wing setting angle that optimize the starting performance. Three different wing types, NACA0018, NACA4418 with its camber facing outward, and NACA4418 with its camber facing inward, were used for the analysis. The following conclusions were obtained. (1) With the wing setting angle of 0 degrees, symmetric arrangement of NACA0018 airfoils generated the highest minimum starting torque among the three types of wings tested. (2) With NACA0018, the starting performance can be further improved by setting the wings at a 5-degree outward angle because of an increase in the minimum starting torque.
This paper presents an approach to modeling the hysteresis nonlinearity of pneumatic muscle actuators and to coping with undesirable hysteresis effects in controlling a manipulator consisting of pneumatic muscles by using a hysteresis model. The hysteresis model is constructed in the form of the Preisach model originally developed for magnetic materials and is used to describe hysteresis nonlinearity in the relationship between the contraction and internal pressure of pneumatic muscle. This model is also used for control of a parallel manipulator driven by three pneumatic muscles. The control system is based on contraction motion control system of each muscle that is composed of a contraction controller reinforced by an internal pressure controller and a feedforward controller that works to produce inputs in order to compensate for hysteresis behavior of the muscle. In addition, a component for switching the hysteresis compensator using a learning vector quantization neural network is attached to the system in order to overcome performance deterioration caused when the manipulator handles external objects. Experimental results show that incorporating the hysteresis compensator leads to an improvement in the control performance of the pneumatic muscle manipulator.
Although there are many studies on vibration reduction of a panel by making use of constrained viscoelastic materials, there is almost no research on vibration reduction for light weight paddle throughout the low to high frequency domains whose dynamic properties might be affected by the weight and rigidity of constrained viscoelastic damping materials. There is also little work on optimizing both parameters of constrained viscoelastic materials and light reinforced structural materials simultaneously. In this research, above-mentioned lightweight structure such as a solar paddle of a small satellite is of interest. For a lightweight structure like a solar paddle, the use of vibration control devices is not practical because of its cost and increase of mass, and then large modification of structure is not also practical. Furthermore, large response in high frequency domain is very critical for such structures from the viewpoint of fatigue. The objective of this research is to propose an optimum vibration control design method applicable throughout low to high frequency domains by considering parameters of the thickness, pasting regions for the constrained viscoelastic materials, and the position and cross section shape of stiffener simultaneously by making use of Response Surface Method (RSM) and Genetic Algorithm (GA). Through the design of a solar paddle of a small satellite, the effectiveness of the proposed method was demonstrated in comparison with other four methods including a conventional way.
The characteristics of multi-surface liquid motion in a rectangular tank are investigated. The rectangular tank is divided into two parts by a baffle, which is vertical to the bottom of the tank and does not reach the bottom. The cases that two liquid surfaces have different areas from each other are mainly interested. Boundary element method is applied to the Laplace equation with linearized boundary conditions. In order to confirm the validity of the calculation, the experiment using the model tank is conducted. A good agreement was found between the theoretical and experimental results. Effects caused by the position of the baffle, and the distance between the baffle and the bottom, upon the natural frequencies and corresponding mode shapes are discussed.
The porous material with continuous pore is useful for the sound absorbing material. In this research work, rice straw, rice husks, and buckwheat husks were dealt as a porous sound absorbing material that applied the biomass. About rice straw, geometrical condition of that was reproduced in the narrow tube of the simple structure, and the effect of absorbing sound of the tubule in the composite structure was verified. In the experiment, for the various thickness and the back air space were tested by using two microphone impedance tube, and the normal incidence sound absorption coefficient was measured. Moreover, the absorption coefficient was calculated from the acoustical constant obtained from the result of a measurement in a specific condition. And, these calculation values were compared with experiment values. As a result, it was shown to be able to estimate the absorption coefficient of the condition of the unmeasurement. As for rice straw, rice husks, and buckwheat husks, it has been understood it has a useful characteristic of absorbing sound. It leads to the fixation of the carbon, and even if the incineration processing is done, it is a carbon neutral.
The objective of this study was to clarify the mechanical body load during walking in water by the simulation, considering the fluid force acting on the lower extremities. First, the joint torque and force were analyzed by the simulation model of walking in water, which was developed by modifying the swimming human simulation model SWUM, and whose input data were obtained in the previous experiment. Second, the muscle force was analyzed by a two-dimensional musculoskeletal model for the lower extremities. The following findings were obtained from those analyses: The hip extensor muscles are employed more greatly during the stance phase of walking in water, compared to walking on land. The joint force in the compressing direction during walking in water is significantly lower than that of walking on land. From these results, it can be concluded that walking in water is suitable for rehabilitation. In addition, it was also found that the joint torque due to the fluid force component mainly acts in the swing phase. Therefore, the lower extremity muscles can be trained effectively by the use of the fluid force in the swing phase.
In this paper, the effect of magnetic field on fretting wear under gross slip was investigated in ranging number of cycles from 102 to 105 under the Hertz-type contact of steel ball to steel plate. The amount of fretting wear volume was evaluated by wear occurring on the surface of the steel plate with and without magnetic field. The experimental results show that the wear region spreads under the magnetic field and the worn volume is increased resulting from accumulation of the wear particles near contact tracks under the magnetic field. It is concluded that the wear particles trapped along the contact annulus increase the worn volume by abrasive and/or pile up action under magnetic field.
This paper presents a novel level set-based topology optimization method that incorporates the augmented Lagrangian method. In previously proposed level set-based topology optimization methods, dealing with multiple constraints has been problematic; nonetheless, this remains a typical requirement of real-world design problems. Herein, the augmented Lagrangian method is incorporated in a level set-based topology optimization method to enable the handling of multiple constrains. The level set function is discretized using finite elements and updated based on the design sensitivity of the augmented Lagrangian with respect to the discretized level set function. In this paper, the newly proposed method is applied to the minimum compliance problem and a compliant mechanism design problem. In the formulations of these problems, a perimeter constraint is imposed to overcome the ill-posedness of level set-based topology optimization. Some numerical examples that include multiple constraints are provided to confirm the validity of the proposed method, and we show that appropriate optimal structures are obtained.
To conventionally extend heat transfer area in shell-and-tube heat exchangers, a method is proposed where sheet materials with high thermal conductivities are stretched among tubes. The numerical simulations are carried out to predict the performance of heat exchanger with or without the sheets. As a result, it is found that thermal contact resistances between the sheet and tubes rather than thickness and thermal conductivity of the sheet influence overall heat transfer coefficient. In the experiments, the carbon fibers clothes (27 W m-1 K-1) are pass zigzag though the tubes whose pitch is 20 mm. The heat transfer rate between hot water flowing in the tube side and air in the shell side are measured. No substantial improvement of heat transfer is unfortunately observed experimentally due to contact thermal resistance. The method proposed in this study conclusively has a potential that the heat transfer rate improves no less than a few ten percents.
To mitigate global warming, a system that can dissolve huge amount of gaseous CO2 expelled from a fossil fuel-fired power plant into the ocean, which must be at the same time eco-friendly to the ocean environment, is indispensable. We propose a system of sequestrating such CO2 in the deep ocean water based on gas-lift effects, the so-called GLAD (Gas-Lift Advanced Dissolution) system. The primary system is an inverse-J (originally) pipeline set in the ocean at a depth of 200-3000 m. In the system, pumping powered by buoyancy of the dissolving CO2 bubbles is used to transport CO2-rich seawater to great depths. In the present paper, we outline the GLAD system and summarize its related fundamental studies for the purpose of designing a highly efficient and extremely reliable system.
The chondrocyte-agarose construct has been employed as an experimental model in the cartilage tissue engineering context. We studied the influence of L-Ascorbic acid (AsA) concentration in culture medium on mechanical property of regenerated cartilage. Cylindrical chondrocyte-agarose constructs with a diameter of 4 mm and a height of 2.5 mm were prepared as test specimens. Chondrocytes isolated from metacarpal-phalangeal joint of steers were seeded in 1 g/mL agarose gel to give an initial cell density of 1×107 cells/mL, and cultured in sterile culture medium within a humidified tissue culture incubator. We cultured by using levels of five AsA concentrations, 0.64, 2.2, 3.2 and 6.4 pmol/109cells and without AsA. Culture medium was exchanged every two days. After culture periods of 1, 8, 15 and 22 days, tangent modulus of the cultured constructs and glycosaminoglycan (GAG) biosynthesis were evaluated by the unconfined compression test and the dimethylmethylene blue (DMMB) assay, respectively. The structural organization of the elaborated tissue was also examined morphologically by the confocal laser scanning microscope (CLSM). Results indicated that the tangent modulus of the cultured constructs increased with increasing the AsA concentration in culture medium. In addition, the growth rate of the tangent modulus was proportional to the AsA concentration. The increased amount of AsA would contribute to the accelerated self-assembly of the collagen fiber network and resultant improvement in the mechanical property, since the reduction ability of AsA could enhance the procollagen expression in cultured chondrocytes.
Cavitation-induced vibration and erosion of pipes are potential damaging factors in piping systems. To prevent damage, it is necessary to develop the detection method for cavitation phenomena. In power plants, it is especially desirable to detect their occurrence from outside the piping during operation. In this paper, detection of cavitation phenomena was experimentally investigated using microphones placed outside the piping at positions upstream and downstream from an orifice. The following results were obtained: (1) According to the development of cavitation state, the microphone output varied, and the amplitude and number of the pulse-shaped signals increased. However, it might be difficult to distinguish them from background noises in an operating plant. (2) Microphone output was confirmed to be radiated sounds caused by vibration on the surface of the piping based on measurements of the time difference between accelerometer output and microphone output. (3) The results of the 1/3 octave band analysis revealed that noises due to cavitation increased in the high frequency region according to development of the cavitation state. In the developed cavitation state, high frequency noises downstream from the orifice were larger than those upstream. (4) The RMS (root mean square) ratio of the microphone output upstream and downstream from the orifice varied according to the development of the cavitation state, and increased by applying a high band pass filter. Therefore, from comparison of RMS values of the microphone output upstream and downstream from the orifice, it is possible to detect cavitation phenomena in piping systems of an operating plant.
A high emphasis is placed on exhaust gas disposal from diesel engines because of a growing concern about atmospheric pollution. Honeycomb-supported catalytic agents are commonly used for oxidation of NO into NO2, which is adopted to develop continuous regeneration-type DPF system. However, the measurement of NO and NO2 concentrations in the honeycomb is very difficult, because it is assembled with many millimeter-sized channels. Thus, it is necessary to investigate and understand the phenomenon in the honeycomb through a numerical simulation. We conducted a numerical study on NO oxidation by platinum catalyst in a channel using detailed elementary reaction kinetics for exhaust gas and platinum catalytic surface. Then, the details of NO oxidation on Pt surface in a channel, including species mass fraction in the gas, coverage on catalytic surface, and reaction rate of the elementary reaction, are obtained. In particular, the effects of the supported amount of catalyst as well as the composition and temperature of inflowing exhaust gas on NO oxidation have been examined; moreover, the catalytic reaction mechanism has been clarified.
Many examinations concerning the fatigue life reduction for structural materials of nuclear power plants in simulated LWR coolant have been performed, and the effects of several parameters on fatigue life reduction have been quantified in the time since the first paper on this subject was recognized in Japan. Based on these results, methods to evaluate fatigue damage for materials exposed to LWR coolant have been developed. The MITI Guidelines (2000) and the TENPES Guidelines (2002) were issued for evaluating environmental fatigue damage in operating plants. The Environmental Fatigue Evaluation Method (EFEM) for Nuclear Power Plants (JSME S NF1-2006) was established in the Codes for Nuclear Power Generation Facilities by the JSME by reviewing the equations for the environmental fatigue life correction factor, F en, and the techniques for evaluation based on the most up-to-date knowledge at the time. A revised version of the EFEM was drafted by incorporating updated knowledge and issued by the end of 2009. This paper outlines the revised JSME Codes and technical bases, and discusses the effects of several parameters on fatigue life reduction in such environments.
A new hybrid ventilation system for low energy buildings has been investigated theoretically using TRNSYS. The system is based on natural ventilation but utilizes a fan during hours when the natural driving forces are not sufficient. Heat from the exhaust air is recovered in an air-to-water heat exchanger. The heated water is pumped to the incoming ventilation air where it is heat exchanged to preheat the fresh air. Energy from solar collectors is used in combination with heat recovered from the sewage system to heat the ventilation air and to preheat the cold water for domestic use. Results from the TRNSYS simulations show that the bought annual auxiliary energy need for the new hybrid ventilation system is lower than for a conventional fan driven ventilation systems using air-to-air heat recovery units combined with an identical solar collector and sewage heat recovery unit. Since the new system is based on natural ventilation it is also more silent compared to standard mechanical ventilation systems.