Dielectric breakdown of new type polymerized polyethylene using asingle-site catalyst

We investigated the dielectric properties of a new type of polyethylene (PE) polymerized with a single-site catalyst. The new PE has much higher dielectric strength and volume resistivity than both conventional low-density PE and linear low-density PE. The increase in the density is considered to be responsible for the increase in dielectric strength. The type of the comonomer and melt flow rate (MFR) scarcely affect the dielectric properties     

Erbium-doped fiber amplifier for video distribution networks

The possibility of an application of Er-doped fiber amplifiers to AM-FDM (frequency division multiplexing) or FM-FDM video distribution networks is discussed. The measured noise and modulation distortion properties of ER-doped fiber amplifiers are good enough to meet even the severe quality standards set for trunk lines. A carrier-to-noise ratio (CNR) of 57 dB for an AM-FDM transmission was measured. A second-order harmonic distortion (HD2) of less than -56 dB was measured by the monotone method (modulation depth m=50%), and a cross modulation distortion (XM) of less than -63 dB was measured by the two-tone method (m=25%×channel). On the basis of these values, composite second-order distortion (CSO) and XM in a 40-channel transmission were estimated as less than -57 dB and -73 dB, respectively. Significant reduction of noise and modulation distortion is made possible by optimizing the length of Er-doped fiber amplifiers and using input- and output-port isolators     

Cationic ring-opening polymerization of 2-phenyl-1,2-oxaphospholane (deoxophostone)

Summary The ring-opening polymerization of deoxophostone 5, a five-membered cyclic phosphinite, has been studied. Some cationic initiators gave polymer whereas anionic and radical initiators as well as metal chloride (Lewis acid) catalysts did not yield polymer. The polymer consisted of a phosphine oxide repeating unit 6. The polymerization proceeded via the Arbuzov-type reaction. The reduction of polymer 6 with a HSiCl₃/Et₃N system gave polyphosphine 7.     

Copolymerization of methylmethacrylate on a ball-milled surface of coal at 77 K

The ball-milling of coal with methylmethacrylate monomer was carried out under vacuum at 77 K and at room temperature and in air. The e.s.r. and i.r. spectra of ball-milled material showed that a copolymer of coal and methylmethacrylate was formed on the surfaces of coal created by ball-mining. Oxygen is an inhibitor to this process.     

E.s.r. study of annealing and melting effects on the molecular motion of spin trapped chain-end radicals located on the polyethylene surface

E.s.r. spectra of chain-end spin labels on the surface of polyethylene powder were obtained for high and low density polyethylene samples at various stages of heat treatment process. The subsequent crystalline structures of the samples were examined with wide angle and small angle X-ray diffraction spectra. The effects of annealing on the motion of the labels were dependent on annealing temperature and the type of the samples. Higher temperature annealing decreased the rotational correlation times (τ_c) and their activation energy in high density polyethylene but did not affect those of low density polyethylene. Melting decreases the values of τ_c and ΔE for both high an low density polyethylene samples. The cause of these decreases were attributed to the changing of the sites of the chain-end labels. The motion of the labels appeared to be influenced by the local segmental motion of the polymer main chains.     

Feeder components and instrumentation for the JT-60SA magnet system

The modifying of the JT-60U magnet system to the superconducting coils is progressing as a satellite facility for ITER by both parties of Japanese government and European commission in the Broader Approach agreement. The magnet system requires current supplies of 25.7 kA for 18 TF coils and of 20 kA for 4 CS modules and 6 EF coils. The magnet system generates an average heat load of 3.2 kW at 4 K to the cryogenic system. The feeder components connected to the power supply provide current supply. The cooling pipes connected to the cryogenic system provide coolant supply. The instrumentation of the JT-60SA magnet system is used for its operation.     

A circulating current control scheme for multiple three‐level NPC inverter systems

In recent years, motor drive systems for steel rolling mills have been steadily increasing in capacity. In particular, the development of three‐level NPC (Neutral Point Clamped) inverters is now focusing on the replacement of cycloconverters. In order to satisfy such a requirement, in this paper a multiple three‐level NPC inverter system is proposed. The configuration consists of two three‐level NPC inverters with the same configuration connected in parallel by current limiting reactors. In this case, the circulating current flowing between the two three‐level NPC inverters must be controlled to prevent a decrease in the maximum output capacity. In particular, a new method for control of the circulating current is a major topic of discussion. The method is based on space voltage vector‐based PWM (Pulse Width Modulation) control for the three‐level NPC inverters and the circulating current is controlled by adjusting the output durations of the respective space voltage vectors. In this method the circulating current controller can be decoupled from the motor current controller. Therefore, it is possible to design the different controllers independently. In addition, the experimental results obtained using an induction motor show that the circulating current can be reduced to within 2% of the rated motor current when the motor current response exceeds 1000 rad/s. © 2001 Scripta Technica, Electr Eng Jpn, 136(2): 38–48, 2001     

Optimum Er3+-doped fiber amplifier design for optical AMvideo signal distribution systems

An investigation into the transmission characteristics of erbium-doped fiber amplifiers for use in optical AM frequency division multiplexing (FDM) video distribution systems is reported. The output signal power and noise characteristics of erbium-doped fibers were measured for different fiber lengths and different pump powers. The experimental results confirm that there exists an optimum amplifier design which gives the maximum distribution number when the pump power and the required video quality are given     

Microprocessor-Based Decoupled Control of Manipulator Using Modified Model-Following Method with Sliding Mode

A methodology of discontinuous feedback and continuous feedforward control is developed to achieve accurate decoupled tracking in a class of nonlinear, time varying systems in the presence of disturbances, parameter variations and nonlinear dynamic interactions. The method is based on an improved variable structure control with a sliding mode.