1.5 μm transmission experiment with distributed feedback laser

The paper reports an experiment which demonstrates the possibility of error-free transmission over 100 km without repeater, by using a single-mode fiber and a laser diode with distributed feedback emitting a single longitudinal mode at the wavelength 1.5 μm.     

The effectiveness of glass ionomer cement as a fiber post cementation system in endodontically treated teeth

This study compared the performance of a glass ionomer (GC Gold Label 1, GIC) as a fiber post cementation system for glass fiber posts with a self‐adhesive resin cement (Relyx U200, RUC) and a conventional resin cement system (Scotchbond Muli‐Purpose and Relyx ARC, RAC). Thirty endodontically treated canines were randomly divided in three groups (n = 10), according to the fiber post cementation system: (RAC)—Scotchbond Multi‐Purpose and Relyx X ARC; (RUC)—Relyx U200 and (GIC)—GC Gold Label 1 Luting & Lining. Rhodamine was incorporated into the cementation system prior to the fiber post cementation. After glass fiber post cementation, roots were incubated in artificial saliva for 6 months. After that, specimens from the cervical, middle, and apical thirds of the post space were prepared and analyzed using a push‐out bond strength test and confocal laser microscopy. ANOVA one way and Tukey tests showed that GIC and RUC demonstrated similar push‐out bond strength values, independently of the post space third (p > .05); however, values were greater than those shown by RAC (p < .05). For dentin penetrability, GIC and RUC also had similar results (p > 0.05) and lower than RAC (p < 0.05). Inside the root canal, the cementation system using glass ionomer cement (GC Gold Label 1 Luting & Lining) has similar push‐out bond strength to the self‐adhesive resin cement (Relyx U200) and these were higher than the conventional resin (Relyx ARC), despite its higher dentin penetrability.     

Simulation of kinetic analysis on terpolymerization of styrene/butyl methacrylate/methacrylic acid system

The simultaneous differential equations which connected the copolymerization kinetics of the component reaction in the multi-copolymerization system with the changing rate of the concentration of each monomer and radical, the concentration and the molecular weight of the polymer obtained are analysed in a number of ways. The distribution of the components and the degree of polymerization are also simulated. The styrene/butyl methacrylate/methacrylic acid terpolymerization system, using carbon tetrachloride as solvent and benzoyl peroxide as initiator, was chosen. The simulation model which satisfied the experimental values of the concentration of the multiple components in the system, the composition and molecular weight distribution and the number of chlorine atoms introduced into the copolymer ends is established. When the time interval changed, the effects on the distribution of the composition in copolymers and the distribution of the degree of polymerization were also calculated.     

Rotating fullerene chains in carbon nanopeapods

The rotation of fullerene chains in SWNT peapods is studied using low-voltage high resolution transmission electron microscopy. Anisotropic fullerene chain structures (i.e., C300) are formed in situ in carbon nanopeapods via electron beam induced coalescence of individual fullerenes (i.e., C60). A low electron accelerating voltage of 80 kV is used to prevent damage to the SWNT. The large asymmetric C300 fullerene structure exhibits translational motion inside the SWNT and unique corkscrew like rotation motion. Another asymmetric fullerene chain containing mixed fullerene species is prepared by fusing smaller C60 fullerenes to a larger Sc@C82 fullerene, and this also exhibits corkscrew rotational motion. Chains of Sc3C2@C80 in SWNT peapods adopt a zigzag packing structure, and the entire zigzag chain rotates inside the SWNT to induce structural modifications to the SWNT diameter and cross-sectional shape of the SWNT. The expansion and contraction of the diameter of the SWNT is measured as 17%, demonstrating nanoactuation behavior in carbon nanopeapods.     

Megasonic transducer drive utilizing MOSFET DC-to-RF inverter withoutput power of 600 W at 1 MHz

This paper describes MOSFET power inverter systems, each provided to drive a megasonic transducer with an output power of 600 W at a frequency of 1 MHz. Since the megasonic transducer is used as a resonant load with a series resistance of approximately 1 Ω, the impedance characteristic of the megasonic transducer used as an inverter load is analyzed and compared with measured data. A new method is developed to match the inverter output impedance to the load impedance of as low as 1 Ω at the resonant frequency using a high-performance output transformer which can feed RF power to the load at high efficiency. The output transformer having a primary-to-secondary winding ratio of 2 to 1 was used by the inverter to drive the megasonic transducer. Based on the analysis of the impedance characteristics of the load, two types of MOSFET dc-to-RF power inverters, a full-bridge version and a single-ended version, were designed and built. These power inverters were put into practical use in cleaners. The power conversion efficiency was greater than 80% for the full-bridge version at an output of approximately 600 W and 50% for the single-ended version at an output power of approximately 600 W. When the megasonic transducer was operated with an input power of 600 W. the operation was satisfactory     

Online tuning method of stator and rotor resistances in both motoring and regenerating operations for vector‐controlled induction machines

The vector control of induction motors is widely used. This method needs accurate motor parameter but the stator and rotor resistance vary due to motor temperature variation. If the value of resistance in the controller can be set up accurately at first, there must be a difference between the reference and real value of torque because of drift of the resistance. It is necessary to adapt the resistance value. The indirect field‐oriented control of an induction motor requires the value of rotor resistance only, but the direct field‐oriented control method with rotor flux observer requires the value of not only rotor resistance but also stator resistance in the controller. Consequently, it is necessary to adapt both stator resistance and rotor resistance. A parameter adaptation scheme has previously been proposed for the direct field‐oriented control method with rotor flux observer, but this method cannot be used when the motor is in regenerating operation. In this paper, a new stator and rotor resistance adaptation scheme is proposed, which can be applied when the motor is in regenerating operation. The usefulness of the proposed adaptation scheme is confirmed by simulation. © 2001 Scripta Technica, Electr Eng Jpn, 135(1): 56–64, 2001     

Interaction control between endohedral metallofullerene and metal substrate by introducing alkanethiol self-assembled monolayer

The interaction control between endohedral metallofullerenes and a metal substrate has been demonstrated by introducing hexanethiol, octanethiol, and decanethiol self-assembled monolayers (SAMs) as the interlayer. We observe the electric properties of terbium endohedral metallofullerenes (Tb@C82) on alkanethiol SAMs with different chain lengths by scanning tunneling microscopy (STM) and spectroscopy (STS). Based on the comparison of the high-resolution STM images of a Tb@C82 molecule on hexanethiol and octanethiol SAMs, the interaction between Tb@C82 and a hexanethiol SAM is found to be larger than that between Tb@C82 and an octanethiol SAM; this is because at 68 K, the rotational states of Tb@C82 terminate only on the hexanethiol SAM. Furthermore, we find that the tunneling current-voltage characteristics of Tb@C82 on the hexanethiol SAM show the rectifying effects that are also caused by the molecular energy level shifts of Tb@C82 molecules due to the large interaction.