A theoretical analysis for the shear horizontal (SH) wave in a thin plate with the material nonlinearity has been conducted by using a microscopic scalar model. In the present study, the effects of the material nonlinearity and dispersion of the wave are taken into account. Especially, the influence of the material nonlinearity of second order is also considered in addition to that of third order. A governing equation which describes the behaviors of the SH wave is derived from the microscopic scalar model. Since the governing equation is complicated, some mathematical techniques are applied in order to analyze the behaviors of the SH wave. As a result, it is shown that the SH wave which can propagate through the thin plate without dissipation exists theoretically. The factors which have the effects on the propagation of the SH wave are revealed clearly. Moreover, the conditions which make the SH wave exist without the dissipation are shown analytically.

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Input-output modelling, which is characterised as a flexible analytical tool, is intensively used in life cycle assessment to estimate the environmental impact of production and consumption. In this paper, the extended Leontief input-output model is used to examine SO₂ emissions in China in 2007. Since direct and indirect SO₂ emissions from each sector can be quantitatively calculated by this model, the results would help uncover the relationships between the SO₂ emission transactions of different sectors. A series of indicators, including SO₂ emission multiplier, intersectoral total SO₂ emission intensity, and total SO₂ emission discharge percentage, are also determined to obtain a full understanding of SO₂ emissions in China.

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The fuel cell is regarded as a highly efficient, low-pollution power generation system. In particular, Solid Oxide Fuel Cell (SOFC) has a high generation efficiency. However, a crucial issue in putting SOFC to practical use is the establishment of a technique for evaluating the deterioration. We previously developed a technique by which to measure the mechanical damage of SOFC using the Acoustic Emission (AE) method. In the present paper, we applied the kernel Self-Organizing Map (SOM), which is an extended neural network model, to produce a cluster map reflecting the similarity of AE events. The obtained map visualized the change in occurrence patterns of similar AE events, revealing four phases of damage progress. The methodology of the present study provides a common foundation for a comprehensive damage evaluation system and a damage monitoring system.

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The use of biogas by a cogeneration system (CGS) is a promising technology as an efficient method of energy utilization. Sewage treatment plants (STPs) are facilities that have been continuously producing biogas, and therefore the potential of application of a biogas-fuelled CGS in an STP is estimated to be very high. However, there have been few reports on efficient utilization of biogas by a CGS, especially in cold regions. Since ambient temperature in a cold region is low and varies greatly, heat demand in the STP is also great and varies greatly throughout the year. Thus, auxiliary components such as a boiler, heat pump and gas storage system are also required to cover the total heat demand throughout a year. In the present study, adopting an actual STP in a cold region and a micro gas turbine as the CGS prime mover, performance of a biogas-fuelled CGS was investigated. The performances of four possible arrangements of the CGS with different auxiliary components were compared to the performance of a conventional system. It was found that all CGS arrangements could cover the total heat demand by only using biogas produced in the facility. The CGS arrangements could reduce electrical power demand by 23∼31%, recover 74∼78% of the energy of biogas produced, and utilize almost 100% of the biogas. The CGS arrangements with a heat pump were more efficient than the CGS arrangements with a boiler. CGS arrangements that include a gas storage system will enable efficient utilization of biogas and recovered exhaust heat.

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In order to accurately calculate high-speed nonlinear transient phenomena of a large order rotor system such as rotor collision and rubbing with stator repeatedly due to blade loss, a very small incremental time step is required in numerical integration. But a small time step is known to become a cause of divergence or flutter type numerical instability when a direct integration such as Newmark-β method is applied in terms of physical coordinates. Normal mode method, which uses eigen modes instead of physical freedoms, is effective on this numerical stability, but the modes in the calculation are usually complex-modes and also need recalculation in accordance with varying rotational speed. Therefore, this method is inconvenient for an analysis of a rotor, especially speed varying system. This paper presents a new method using constraint real mode synthesis in which rotor modes are derived by neglecting gyroscopic moment as at 0 rpm and by fixing bearing connection interface freedoms to zero. This method is proved to be highly stable and also to have good accuracy and efficiency in the calculation.

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This paper examines the resonance characteristics of the wave power generation device which consists of pulley(s), wire(s), float(s), counterweight(s) and ratchet mechanism. The resonance analysis model introduces the relative displacement between the water level and the float's position into the dynamics model for the system in operation. The equations of natural frequency, ratio of wave frequency to natural frequency of the system, damping ratio and magnification ratio have been given. Further, the characteristics of average electric power output and maximum wire tension have been examined for wave periods near the natural period of the system. The relationship between natural period of the system and float dimensions, especially float's diameter to height ratio, has been examined. As an example, the annual average electric power output and energy conversion efficiency have been evaluated for the system with natural period near the dominant wave period when it operates off Kobe port where the annual variation of the wave period is small.

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In the present paper, the collapse behaviors of rectangular tubes subjected to pure bending are investigated using the finite element method. Such bending collapse has been investigated extensively. These studies have revealed the existence of two types of collapse. The first type is a collapse due to buckling at the compression flange, and the second type is a collapse due to plastic yielding at the flanges. However, another type of collapse may exist. For a rectangular tube in which the web is wider than the flange, collapse due to buckling may occur at the compression web. Furthermore, an approximate prediction method is proposed for estimating the maximum bending moment of rectangular tubes in which web buckling is also taken into account. The validity of this method is verified through comparison with the numerical results obtained by FEM under various conditions.

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Topology optimization has been successfully used in many industries, especially those engaged in the design and manufacturing of mechanical devices, but numerical problems are often encountered, such as grayscale representations of obtained composites. A type of structural optimization method using the level set theory for boundary expressions has been proposed, in which the outlines of target structures are implicitly represented using the level set function, and optimal configurations are obtained by updating this function based on the shape sensitivities. Level set-based methods typically have a drawback, however, in that topological changes that increase the number of holes in the material domain are not allowed. To overcome the above numerical and topological problems, this paper proposes a new topology optimization method incorporating level set boundary expressions based on the concept of the phase field method, which we apply to a minimum mean compliance problem. First, a structural optimization problem is formulated based on a boundary expression, using the level set function. Next, a time evolutionary equation for updating the level set function is formulated based on the concept of the phase field method, and the minimum mean compliance problem is formulated using a level set boundary expression. An optimization algorithm for the topology optimization incorporating the level set boundary expression based on the concept of the phase field method is then derived. Several examples are provided to confirm the usefulness of the proposed structural topology optimization method.

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A study on the environmental impact and fuel consumption of a long haul aircraft has been performed. Target of the study is to investigate the beneficial effect of refueling in long range flights, in terms of fuel consumption and CO2 emissions, while taking into account the adverse effect on flight duration. This has been achieved using the ‘Hermes’ aircraft performance model, developed at Cranfield University. In a further step, a parametric study has been performed in order to take into account non ideal conditions, where the refueling station is positioned further than mid-distance and extra range is required to be flown. Such data can be useful for scheduling real-life missions featuring refueling stops. The results show that the viability limit is affected by both type of the aircraft and payload, while a minimum range exists, under which the beneficial effect of refueling diminishes.

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We developed a mesh morphing technique that can be used to change the shape of existing analytical mesh models. We used it to generate a mesh model of a new shape by morphing the original mesh model. Our technique can be used for analysis during the early stages of design because it reduces the time required to generate analytical mesh models. Compared with conventional techniques, our technique adds and deletes features in the original mesh by using a Boolean technique and a mesh improvement technique. It can process the addition or deletion of a feature in a 100,000-element mesh model in about one minute. Moreover, it can generate high-quality meshes that ensure element stretch of over 0.1. We demonstrated the effectiveness of our technique by applying it to two engine block models.

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Experiment has been performed to clarify the structure of aerodynamic noise sources generated in a production vehicle. The details of noise sources were measured from the outside and inside of vehicle by applying noise source identification techniques. The noise sources show high level in the regions of bonnet head, front underbody, side window and rear window. Moreover, the noise sources are dominated by that from underbody in the low frequency, and side window in the high frequency, respectively. The velocity dependency of aerodynamic noise was analyzed based on Lighthill-Curle analogy. As a result, it is found that the noise sources around vehicle are mainly dipole sources.

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The mechanism of aerodynamic noise generated from front-pillar and door mirror of production automobile has been investigated by applying experiment and numerical simulation. In the simulation, the flow filed was firstly analyzed by Finite Differential Method (FDM) with 3rd-order upwind scheme, then Powell's acoustic analogy was applied to evaluate the acoustic source. Furthermore, the velocity fluctuation and acoustic source were clarified by the use of experiment. It is found that the interaction between vortices separated from front-pillar and door-mirror results in the instability of boundary layer, which induces the aerodynamic noise near side window. As a result, controlling the separation vortices from front-pillar and door-mirror is the key point to reduce the aerodynamic noise of automobile.

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Tapered seals are widely used to hold lubricating oil inside the clearance at the ends of fluid film bearings utilized in precise machines such as the spindle motors of HDD systems. This study is aimed at theoretically analyzing the mechanism responsible for leakage from the tapered seal when the sleeve is rotating. Three triggers that cause fluid to leak are found from the theoretical results on the meniscus of the interface (boundary surface of two kinds of fluids) which are regarding to surface tension cooperating with the results from computational fluid dynamics for velocities and pressure fields under axis-symmetric and steady-state conditions. The critical rotational speeds for these triggers to induce leakage are presented. We also report the relationship that the critical rotational speed is nearly inversely proportional to the projected area of the interface.

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Fundamental experiments on fluid leakage from tapered seals due to sleeve rotation were carried out. The apparatus was designed so that the surface tension, which generates a sealing function, acts effectively in terms of size and accuracy similar to its behavior in an actual device. The shapes of the interface (boundary surface of two kinds of fluids) at several rotational speeds were measured with an ultra-focus laser microscope, and the features of fluid leakage were observed with a high-speed camera. The experimental results of the positions of the bottoms of the interface coincided comparatively well with the theoretical ones. We also verified that the threshold speeds in the experiment on fluid leakage could broadly be estimated by using the theoretical ‘ultimate’ and ‘triggering’ critical rotational speeds of the sleeve.

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This paper describes the effects of the enclosure and its inlet on the performance of axial air-cooling fans installed in electronic equipment. The performance of an air-cooling fan is defined by its P - Q (pressure difference — flow rate) curve. Recent studies have reported that the P - Q curve of cooling fans depends on their operating environment. P - Q curves are normally used to define the performance of fans in the computational fluid dynamics (CFD) codes. Therefore the change of the P - Q curve may cause inaccurate CFD analyses to be performed in the thermal design of electronic equipment, including cooling fans. In this study, we measured the performance of test fans in an enclosure and explored the effects of the inlet size and shape while varying the speed of revolution of the fan. In particular, the static pressure difference between the front and rear of fans installed in a test enclosure was investigated. Our experiments clarified the effect of the enclosure on fan performance. The level of decrease of the maximum flow rate was found to be determined by the size of the inlet area, and was independent of the shape of the inlet and the revolution speed of the fan.

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The importance of the in-flow oscillation of a single cylinder in cross-flow has been highlighted since an accident in a FBR-type reactor. In-flow oscillations have also been observed in tube arrays. This report is an experimental study on this phenomenon using a maximum of nine cylinders in a water tunnel. Six patterns of cylinder array, one single cylinder, two & three cylinders in parallel and in tandem, and a nine cylinder bundle, are examined. The cylinders are constrained to move only in the in-flow direction. The cylinder motion is measured by strain gages and by a high-speed digital video camera. The results of these motions are compared with the visualized vortex motion. As main results, two excitation mechanisms, symmetric vortex shedding and alternate vortex shedding, are observed. A transition range is found between these two mechanisms where large amplitude vibrations are observed. An additional test has been done to determine the root cause of the large vibrations in the transition range.

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One of the most important goals on solar collector development is to increase the system's annual performance without increasing overproduction. The studied collector is formed by a compound parabolic reflector which decreases the collector optical efficiency during the summer period. Hence, it is possible to increase the collector area and thus, the annual solar fraction, without increasing the overproduction. Collector measurements were fed into a validated TRNSYS collector model which estimates the solar fraction of the concentrating system and also that of a traditional flat plate collector, both for domestic hot water production. The system design approach aims to maximise the collector area until an annual overproduction limit is reached. This is defined by a new deterioration factor that takes into account the hours and the collector temperature during stagnation periods. Then, the highest solar fraction achieved by both systems was determined. The results show that, at 50° tilt in Lund, Sweden, the concentrating system achieves 71% solar fraction using 17 m² of collector area compared to 66% solar fraction and 7 m² of a flat plate collector system. Thus, it is possible to install 2.4 times more collector area and achieve a higher solar fraction using the load adapted collector. However, the summer optical efficiency reduction was proven to be too abrupt. If the reflector geometry is properly design, the load adapted collector can be a competitive solution in the market if produced in an economical way.

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In present study, the effect of the ultrasound wave stimulation in acceleration of the osteocondutibity of bio-active pure titanium was investigated. Pure titanium (99.9% Ti) processed in chemical and heat treatments was used as a specimen, and soaked in simulated body fluid (SBF) under pulsed ultrasound wave for the planned time periods. The surface of samples was observed using scanning electron microscopy (SEM), X-ray diffraction, etc, to assess the state of hydroxyapatite formation.
SEM images showed that a richer and finer layer of calcium and phosphate compounds covered the titanium surface in the ultrasound wave group as compared with the non-ultrasound group. The measurements of mass of specimens also indicated the efficiency of ultrasound waves for hydroxyapatite formation.
These findings suggest that the nucleation and crystallization of apatite on bio-active material surfaces might be promoted by micro-moving and cavitation of low-intensity pulsed ultrasound waves. We propose that pulsed ultrasound stimulation has a great potential for further improvement of osteointegration and osteoconductivity for medical bio-active implants.

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This study has examined the influence of the addition of hydrogen to propane mixtures on its local burning velocity. Hydrogen added propane mixtures having nearly the same laminar burning velocity with different rates of addition of hydrogen δ_H and equivalence ratios Φ(0.8∼1.4) were prepared. A two-dimensional sequential laser tomography technique was used to obtain the temporal and statistical relationship between the flame shape and the flame displacement. The local flame displacement velocity S_F and curvature of turbulent flames were quantitatively measured as the key parameters on turbulent combustion. The Markstein number Ma was also obtained from outwardly propagating spherical laminar flames, in order to examine the effect of positive stretch on burning velocity. It became clear that the trends of the mean values of measured S_F with respect to δ_H and Φ gave good agreement with the turbulent burning velocity. The trends of Ma with respect to δ_H, Φ and fuel types could also explain qualitatively the local burning velocity and turbulent burning velocity.

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This paper presents the analytical method to evaluate the impact force and engine noise induced by piston slap considering the detailed piston profile and dynamic characteristics of the piston. This method was applied to examine the effect of the piston profile and piston pin offset on the piston slap impact force and its induced engine noise. Present numerical method showed that increasing the upper clearance of the piston skirt enlarged the higher frequency components of the piston impact force and engine noise and this was verified by the experimental results. The analysis revealed that piston movement at the vicinity of the combustion top dead center was governed by the friction moment around the piston pin and the additional piston pin offset moment induced by combustion pressure could cancel this friction moment and reduce the piston impact force if the piston pin was offset to the major thrust side. This analytical results was confirmed by the measured results of actual diesel engine.

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