Surge control of a centrifugal compression system by using a bouncing ball

The purpose of this study is to suppress the fluctuations of surge by a simple passive control method. A bouncing ball system with different weight of the balls was tested. As a result, the bouncing ball system suppressed mild surge without the deterioration of the performance characteristics, and moved the initiation point of surge toward the lower flow rate when the steel ball of 15mm outer diameter was used. The present system was effective to suppress the surge and to widen the stable operating range of a centrifugal compressor when the ball was chosen appropriately.     

A study on optimal motion of a biped locomotion machine

In this paper we propose a calculation method for the optimal trajectory of a biped locomotion machine which is based on inverse kinematics and inverse dynamics. First, the trajectory of the waist is expressed by a Fourier series, where the bases are selected appropriately so that the periodic boundary conditions are strictly satisfied. A biped locomotion machine establishes optimal walking by using kicking forces to the ground at the moment of switching legs. In order to include the effecs of the kicking forces, additional terms that indicate the impulsive forces at the moment of switching legs are included in the formulation. Then the angles of each joint are determined by inverse kinematics, and using inverse dynamics, the input torques of each joint are expressed in terms of Fourier coefficients. By defining the performance index as a quadratic form of the input torques, the motion planning problem is formulated as an optimization problem of the trajectory of the waist, whose paramaters are Fourier coefficients of the trajactory of the waist. Using the successive quadratic programming (SQP) method, the optimal trajectory of a biped locomotion machine is obtained. This work was presented, in part, at the Third International Symposium on Artificial Life and Robotics, Oita, Japan, January 19–21, 1998.     

Porphyromonas gingivalis Components/Secretions Synergistically Enhance Pneumonia Caused by Streptococcus pneumoniae in Mice

Streptococcus pneumoniae is an important causative organism of respiratory tract infections. Although periodontal bacteria have been shown to influence respiratory infections such as aspiration pneumonia, the synergistic effect of S. pneumoniae and Porphyromonas gingivalis, a periodontopathic bacterium, on pneumococcal infections is unclear. To investigate whether P. gingivalis accelerates pneumococcal infections, we tested the effects of inoculating P. gingivalis culture supernatant (PgSup) into S. pneumoniae-infected mice. Mice were intratracheally injected with S. pneumoniae and PgSup to induce pneumonia, and lung histopathological sections and the absolute number and frequency of neutrophils and macrophages in the lung were analyzed. Proinflammatory cytokine/chemokine expression was examined by qPCR and ELISA. Inflammatory cell infiltration was observed in S. pneumoniae-infected mice and S. pnemoniae and PgSup mixed-infected mice, and mixed-infected mice showed more pronounced inflammation in lung. The ratios of monocytes/macrophages and neutrophils were not significantly different between the lungs of S. pneumoniae-infected mice and those of mixed-infected mice. PgSup synergistically increased TNF-α expression/production and IL-17 production compared with S. pneumoniae infection alone. We demonstrated that PgSup enhanced inflammation in pneumonia caused by S. pneumoniae, suggesting that virulence factors produced by P. gingivalis are involved in the exacerbation of respiratory tract infections such as aspiration pneumonia.     

A Kinematic Analysis of Joint Synergy of the Lower Limb in Human Locomotion

This paper deals with the mode analysis of the kinematic structure of human locomotion. The authors investigated synergy mechanism of human locomotion from motion-captured data and EMG signal data. The authors extracted some common basic movements and residual modes, and analyzed the kinematical structures of limit cycle in joint angle space. The authors also implemented the numerical simulation analyses by using the motion captured data and EMG signal data to investigate the mechanical activities of human joints and to extract the mechanical structure of the limit cycle. The results show the joint synergy that is derived by the common basic modes, which expresses an inverted pendulum mode in support phase, and ballistic mode in swing phase with the kick-off motion in the most effective direction. This result can be guessed that the control strategy of human locomotion is simply based on the minimal control principle.     

Effect of Plasma Treatment on Titanium Surface on the Tissue Surrounding Implant Material

Early osseointegration is important to achieve initial stability after implant placement. We have previously reported that atmospheric-pressure plasma treatment confers superhydrophilicity to titanium. Herein, we examined the effects of titanium implant material, which was conferred superhydrophilicity by atmospheric-pressure plasma treatment, on the surrounding tissue in rat femur. Control and experimental groups included untreated screws and those irradiated with atmospheric-pressure plasma using piezobrush, respectively. The femurs of 8-week-old male Sprague-Dawley rats were used for in vivo experiments. Various data prepared from the Micro-CT analysis showed results showing that more new bone was formed in the test group than in the control group. Similar results were shown in histological analysis. Thus, titanium screw, treated with atmospheric-pressure plasma, could induce high hard tissue differentiation even at the in vivo level. This method may be useful to achieve initial stability after implant placement.     

Simultaneous Estimation and Modeling of Thermophysical Properties of Big-Eyed Tuna and Pacific Cod

The thermophysical properties (thermal conductivity, thermal diffusivity, and specific heat) of big-eyed tuna and pacific cod were measured at various temperatures (5–50°C) by the modified version of current probe method. The optimal prediction models for these thermophysical properties were determined. The random model was applied to predict the thermal conductivity of seafood in a wide range of temperature and it provided the accurate predictions for the samples. The thermal diffusivities of the samples could be predicted by Martens’s equation. An additive relationship exists between the specific heat of the sample, the composition, and the specific heat of each component.     

Gas permeability and side chain structure of poly(γ-benzyl L-glutamate)

Three structural modifications of poly(γ-benzyl L -glutamate) (PBLG), forms A, B, and C, were prepared by varying the casting solvents and casting temperature. From x-ray analysis, infrared absorption spectroscopy, differential scanning calorimetry, and viscoelastic measurements, it is concluded that form A of PBLG is characterized by intramolecular stacking between the benzene rings in the side chain, form B exhibits intermolecular stacking, and form C has no stacking. The transition which corresponds to the breakdown of stacking of form A at 135°C is irreversible, while that of form B at 110°C is reversible. The degree of stacking is larger for form A than for form B. These structural features of the side chain region reflect the permeation and sorption behavior of carbon dioxide. Breakdown of stacking between benzene rings causes an abrupt increase in permeability in both form A and form B, and the permeation behavior for form A is not reversible, as is suggested from the irreversibility of the transition. The larger the degree of stacking, the lower is the amount of sorption. Although stacking is considered to affect the sorption site (solubility) and molecular motion, its influence on solubility is more evident in the temperature range up to about 50°C.     

Effect of stress ratio on the enhancement of fatigue strength in high performance steel welded joints by ultrasonic impact treatment

In this study, we conducted fatigue tests under various stress ratios using cruciform welded joints to confirm the benefit of Ultrasonic Impact Treatment (UIT) for the fatigue strength of welded joints. The material used in the experiment is the JIS SBHS500 high performance steel for bridges. The fatigue life of the peened weld joint by UIT is significantly longer than that of as-welded joints, especially at a low stress ratio. We also estimated the fatigue life of these cruciform joints by crack growth analysis based on the crack opening and closure simulation using the modified strip-yielding model, accounting for the residual stress distribution created by welding or UIT. These estimation results demonstrate good agreement with experimental results obtained at various stress ratios.     

Theoretical study of surface interaction stresses considering one-dimensional material distributions in the in-plane direction based on the Lennard–Jones potential

In this work, the interaction stresses (i.e., pressures and shear stresses) between a half-space comprising a uniform material and a half-space comprising one-dimensional material distributions in the in-plane direction were theoretically derived. The interaction stress was derived from the Lennard–Jones potential as a vector for the (0, 0, 1) surface using two different material distribution patterns. The first pattern was a periodic distribution of materials (Pattern 1) and the second was a distribution of two materials with a single interface (Pattern 2). The interaction stresses for Pattern 1 were derived based on a Fourier series, while those for Pattern 2 were derived as elementary functions. The pressures possessed non-fluctuation terms and fluctuation terms, while the shear stresses possessed fluctuation terms only. The basic characteristics of these interaction stresses for parallel planes were quantitatively clarified by presenting the distributions and vector diagrams of the interaction stresses.

     

Study on paper-structured catalyst for direct internal reforming SOFC fueled by the mixture of CH4 and CO2

Inorganic fiber network including YSZ fiber which acts as catalyst support was created by the simple paper-making process, and novel Ni-loaded paper-structured catalysts (PSCs) with excellent catalytic activity for the dry reforming of methane were designed and developed. The PSCs exhibited high fuel conversion comparable to the conventional powdered catalysts with less than one-tenth catalyst weights. The significant advantages of the PSCs are their high mechanical flexibility and material workability. So far, a functionally-graded catalytic reaction field which leads to uniform temperature distribution during biogas reforming resulting in stable operation of planar SOFC was successfully developed by the PSC array based on the kinetic simulation model built in this research.