Effect of conformational changes and differences of proteins on frictional properties of poly(vinyl alcohol) hydrogel

In this study, albumin or γ-globulin, both of which are included in natural synovial fluid, was used as an additive into lubricants to investigate the ability to reduce the friction for poly(vinyl alcohol) hydrogel in mixed lubrication. It was found from a measurement in circular dichroism that albumin contains a large amount of α-helix structure and γ-globulin contains a large amount of β-sheet structure. The lubricant containing only albumin showed low friction compared to the lubricant containing only γ-globulin. The effect of protein boundary film was clarified by changing lubricant. Albumin kept the friction low after changing from γ-globulin used at initial rubbing, but γ-globulin increased the friction after changing from albumin at initial rubbing. From a sliding distance of 600 m, albumin showed lower friction but γ-globulin showed higher friction. Therefore, in the case of friction decreasing, γ-globulin forms a tight adsorbed layer and subsequently albumin forms a layer with low shearing strength. Hence, it is important to apply the adsorption layer of γ-globulin at the bottom and make a layered structure composed of albumin and γ-globulin to reduce both friction and wear.     

Development of Arm Equipped Single Wheel Rover: Effective Arm-Posture-Based Steering Method

We have been proposing a new planetary rover system named SMC Rover. This system consists of one main body and detachable units, which can work as child rovers, and also become driving units of the main body. Each detachable unit named Uni-Rover consists of a single manipulator mounted on a wheel. Prototype models of the Uni-Rover and the SMC Rover have been already developed. This paper describes a new method of trajectory modeling for the Uni-Rover using the relation between arm posture and turning radius. At first, an intuitively recognizable model which uses zero slip angle is introduced. However, because this intuitive model has some problems, a new solution which considers the loss of friction on the wheel and on the caster is also discussed. The validity of the presented method is verified by experiments with an actual mechanical model. Moreover, an effective steering method which considers the margin of the energy stability is introduced.Kazuhiro Motomura is a Ph.D candidate at the Tokyo Institute of Technology (Tokyo Tech). In 2001 he was admitted to skip the fourth grade of the bachelor course in the Department of Mechano-Aerospace engineering at Tokyo Tech to enterthe master course in the Department of Mechanical and Aerospace Engineering at the same Institute. He received the B.E. degree in National Institution for Academic Degrees an University Evaluation in 2002, and received the M.E. degree in the Department of Mechanical and Aerospace Engineering at Tokyo Tech in 2003. He has been a research fellow of the Japan Society for the Promotion of Science from 2004. He awarded the Incentive Award for the presentation in the 17th RSJ Annual Conference in 2001, and the Finalists for the Best Video Award in the IEEE International Conference on Robotics and Automation in 2003. His research interests include design of robotic mechanisms and control of mobile robots. He studies about the development of planetary rovers.Atsushi Kawakami awarded the chance to skip fourth gradein the bachelor course of Department of Mechano-Aerospace engineering in Tokyo Institute of Technology, and entered the master course in 1997. He received the M.E. and Dr. E. degrees in Department of Mechanical Engineering Science in Tokyo Institute of Technology in 1999 and 2003, respectively. From 2003, he is a post-doctoral researcher. His research interest is in design of robotic mechanisms. He studies about the development of planetary rover. He awarded the Incentive Award for the presentation in the 17th RSJ Annual Conference in 2001, and the Finalists for the Best Video Award in the IEEE International Conference on Robotics and Automation in 2003. He also acts as an organizer and lecturerin several hands on robots competitions that aim at the promotion and education for the beginners.Shigeo Hirose was born in Tokyo in 1947. He received the B. E. degree with first class honors in Mechanical Engineering from Yokohama National University in 1971, and the M. E. and Dr. E. degrees in Control Engineering from the Tokyo Institute of Technology in 1973 and 1976, respectively. From 1976 to 1979 he was a Research Associate, from 1979 to 1992 an Associate Professor and since 1992 he has been a Professor in the Department of Mechanical and Aerospace Engineering at the Tokyo Institute of Technology. He is the Fellow of both IEEE and Japanese Society of Mechanical Engineers. His research interest is in design of novel robotic mechanisms and its control. He awarded more than 30 prizes from academic societies; these include the first Pioneer in Robotics and Automation Award in 1999 and Best Conference Paper Award in 1995 both from IEEE Robotics & Automation Society. Prof. Hirose has published more than 200 academic papers as well as several books, including Snake Inspired Robots (Kogyo-chosakai Publishing Co. Ltd, 1987, in Japanese), Robotics (Shokabo Publishing Co. Ltd., 1987, in Japanese), and Biologically Inspired Robots (Oxford University Press,1993).     

Effect of sweep gas species on tritium release behavior from lithium titanate packed bed during 14 MeV neutron irradiation

In a fusion reactor, the prediction of tritium release behavior from breeder blanket is important to design the tritium recovery system, but the amount of tritium generated is necessary information to do that. Hence, tritium generation and recovery studies on lithium ceramics packed bed have been started by using fusion neutron source (FNS) in Japan Atomic Energy Agency (JAEA). Lithium titanate (Li₂TiO₃) was selected as tritium breeding material, and its packed bed was enclosed by the beryllium blocks, and was kept at certain temperature during fusion neutron irradiation. During irradiation, the packed bed was purged with the sweep gas continuously, and tritium released was trapped in each gas absorber selectively by chemical form. In this work, the effect of sweep gas species on tritium release behavior was investigated. In the case of sweep by helium with 1% of hydrogen, tritium in water form was released sensitively corresponding to the irradiation. This is due to existence of the water vapor in the sweep gas. On the other hand, in the case of sweep by helium without water vapor, tritium in gaseous form was released first, and release of tritium in water form was delayed from gaseous tritium and was gradually increased.     

THz-wave absorption by field-induced carriers in pentacene thin-film transistors for THz imaging sensors

Innovative sensing systems based on THz electromagnetic waves have been attracting a great deal of attention. Although many THz detectors have been developed over the years, it is currently difficult to manufacture low-cost THz sensing/imaging devices. In the present study, we propose to use organic field-effect transistors (OFETs) and small potential fluctuation against the carriers within them (N. Ohashi, H. Tomii, R. Matsubara, M. Sakai, K. Kudo, M. Nakamura, Appl. Phys. Lett. 91 (2007) 162105). We use THz time-domain spectroscopy for OFETs in which the carrier density in the pentacene active layer is modulated by the gate bias. We found evidence that the accumulated free holes in pentacene films can be excited by THz photons to overcome the surrounding barriers in the fluctuating potential. The Drude–Lorentz model could not account for the shape of the absorption spectra, which suggests that the holes are weakly restricted by the potential fluctuation. The integrated absorption intensity was proportional to the transfer characteristics of the OFETs. The present findings represent an important step toward developing a new class of THz-wave sensors.     

Current Pumping from Spin Dynamics

We show theoretically that charge and spin currents arise from spin dynamics in the presence of the spin–orbit interaction. The dominant calculation is the inverse spin Hall effect, namely the spin current pumped from precession of local spins is converted into the charge current by the spin–orbit interaction. The conversion mechanism is explained based on the conservation laws of charge and spin.     

Creep deformation properties of creep strength enhanced ferritic steels

Creep deformation properties of creep strength enhanced ferritic steels were investigated. Good linear relationships between creep strain vs. time and creep rate vs. time were observed within a transient stage in a double logarithmic plot. It was appropriately expressed by a power law rather than exponential law, logarithmic law and Blackburn’s equation. With decrease in stress, a magnitude of creep strain at the onset of accelerating creep stage decreased from about 2% in the short-term to less than 1% in the long-term. Life fraction of the time to specific strain of 1% creep strain and 1% total strain, to time to rupture tended to increase with decrease in stress. A time to 1% total strain, that is a parameter for design of high temperature components, was observed in the transient creep stage in the short-term regime, however, it shifted to the accelerating creep stage in the long-term regime. Difference in stress dependence of the minimum creep rate was observed in the high- and low-stress regimes with a boundary condition of 50% of 0.2% offset yield stress. Stress dependence of the minimum creep rate in the high stress regime was equivalent to a strain rate dependence of flow stress observed in tensile test, and a magnitude of stress exponent, n, in the high stress regime decreased with increase in temperature from 20 at 550°C to 10 at 700°C. On the other hand, n value in the low stress regime was about 5, and creep deformation in the low stress regime was considered to be controlled by dislocation climb.     

Application of magneto-optical sensors for fault location in an air-insulated substation bus

A new fault location system using optical current transducers (CTs) to detect faulted sections in the bus bars of directly grounded 275-kV substations has been developed. This system detects fault current by combining optical CTs with wound-type CTs. The new type of optical CT applies a bulk-type Faraday sensor to the combination of windings around a magnetic iron core and a solenoid coil. The optical CT was capable of current measuring over 50 kA. A current differential discriminator combining an optical CT and a wound-type CT verified the operational performance with 40-kA currents. The intended level of fault detection performance was obtained. Based on these results, a system is being made for actual application in 275-kV substations. © 1997 Scripta Technica, Inc. Electr Eng Jpn 119(2): 10–17, 1997     

Osteogenic activity of human periosteal sheets cultured on salmon collagen-coated ePTFE meshes

Our animal implantation studies have demonstrated that, after osteogenic processing, cultured human periosteal sheets form osteoid tissue ectopically without the aid of conventional scaffolding materials. To improve the osteogenic activity of these periosteal sheets, we have tested the effects of including a scaffold made of salmon collagen-coated ePTFE mesh. Periosteal sheets were produced with minimal manipulation without enzymatic digestion. Outgrown cells penetrated into the coated mesh fiber networks to form complex multicellular layers and increased expression of alkaline phosphatase activity in response to the osteoinduction. In vitro mineralization was notably enhanced in the original tissue segment regions, but numerous micro-mineral deposits were also formed on the coated-fiber networks. When implanted subcutaneously into nude mice, periosteal sheets efficiently form osteoid around the mineral deposits. These findings suggest that the intricate three-dimensional mesh composed of collagen-coated fibers substantially augmented the osteogenic activity of human periosteal sheets both in vitro and in vivo.     

Design and development of highly efficient transducer for ultrasonic wireless power transmission system

In this paper, a transducer that is suitable for the ultrasonic wireless power transmission system is discussed. The transducer is designed based on Mason's equivalent circuit theory, basically. The transducer was developed using design parameters optimized by multiphysics analysis. As a result, it is con?rmed that the transmission e?ciency is drastically improved to more than 50%. This result suggests that wireless power transmission by acoustic wave is feasible. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 184(3): 27–35, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22406     

Lagrangian method for deriving electrically dual power converters applicable to nonplanar circuit topologies

This paper proposes a novel method for deriving dual converters, namely deriving current‐source converters from voltage‐source counterparts, and vice versa. The conventional derivation method is based on the transformation of circuit topology, in which series connections are converted into parallel connections, and vice versa. However, this method cannot be directly applied to nonplanar circuits because they do not allow perfect topological transformation, although many of them are known to have duals. Lagrangian dynamics does not depend on the topological relation to transform a system into another equivalent system; therefore, it possibly avoids problems related to topological transformation and may provide a universal and systematic method that can be consistently applied to nonplanar circuits. This paper discusses the derivation of duals using Lagrangian dynamics. Along with the theory, this paper presents two examples of Lagrangian derivation of duals. One derives a dual of a planar circuit, to which the topological transformation is applicable. The other derives two duals of a nonplanar circuit. Consequently, these examples suggest that the proposed method is a prospective candidate for universal and systematic derivation of duals. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.