The influence of chain entanglement density on ultra-drawing behavior of ultra-high-molecular-weight polypropylene in the gel-casting method

The ultra-drawing behavior of ultra-high-molecular-weight polypropylene (UHMW-PP) in the gel-casting method has been investigated by using four kinds of gel-cast sheets prepared from four kinds of solutions of 1.0, 2.0, 4.0 and 6.0 wt.% of UHMW-PP. Consequently, it was found that the draw ratio during neck deformation (N.DR.) was related linearly to the inverse root of solution concentration of UHMW-PP. Since this phenomenon was similar to the relationship between the attained maximum draw ratio (λ_max) and the solution concentration, it was considered that N.DR. was related linearly to the inverse root of chain entanglement density. And, it was also found that λ_max could be defined by the maximum drawing stress (F) around yield point in the 2nd step drawing. On the other hand, no influence of solution concentration on the increasing behavior of strength and modulus with ultra-drawing was detected for the gel-cast sheet prepared from initial solution concentration of above 1 wt.%. The reason of this fact was inferred from the increase of the content of shishkebab structure in the gel-cast PE fiber from the high initial solution concentration.     

Stretched Polyaniline Films Doped by (±)‐10‐Camphorsulfonic Acid: Anisotropy and Improvement of Thermoelectric Properties

The stretched polyaniline films doped by (±)‐10‐camphorsulfonic acid exhibited significant anisotropy of the electrical and thermoelectric properties. The thermoelectric figure‐of‐merit (ZT) of the stretched films in the direction parallel to the stretching direction is much higher than that of the unstretched counterpart, and moreover, the ZT increased with increasing drawing ratio. According to the experimental results of X‐ray diffraction and UV‐Vis‐near IR spectroscopy the improvement of the ZT by the stretching process is revealed to be attributable to the increment of carrier mobility, which is proposed to be induced by the extended coil‐like conformation of polyaniline.     

A wave‐front‐time dependent corona model for transmission‐line surge calculations

For transmission‐line surge studies, the inclusion of corona discharge due to high voltage surges is important as well as the inclusion of frequency‐dependent effects. Because the charge‐voltage (q‐v) curve of a lightning surge is different from that of a switching surge, a corona model should reproduce different q‐v curves for different wave‐front times. The present paper proposes a wave‐front time dependent corona model which can express the dependence by a simple calculation procedure as accurately as a rigorous finite‐difference method which requires an enormous calculation time. The simplicity enhances the incorporation of the corona model into a line model, because a large number of models are to be inserted into the line model by discretization. The q‐v curves calculated by the proposed method agrees well with field tests. This paper also proposes an efficient method to deal with nonlinear corona branches in distributed‐parameter line model using the trapezoidal rule of integration and the predictor‐corrector method. © 1999 Scripta Technica, Electr Eng Jpn, 129(1): 29–38, 1999     

Physicochemical and Microbiological Changes Associated with Bakasang Processing—A Traditional Indonesian Fermented Fish Sauce

The production of ‘Bakasang’, an Indonesian fermented fish sauce, was replicated in the laboratory in order to study the physicochemical and microbiological changes associated with the process. Bakasang samples were produced by incubating mixtures of small sardine ( Engraulis japonicus ) at different concentrations of sodium chloride and glucose at 37°C for 40 days. Changes in pH, total soluble nitrogen, total free amino nitrogen, amino acid composition and total plate counts were observed. The isolation and identification of microflora were also performed. In general, the pH decreased throughout the incubation period, irrespective of NaCl and glucose concentrations. Increases in the amounts of total soluble nitrogen and total free amino nitrogen were noticed during the 40 days of fermentation. The amino acids, glutamic acid, alanine, isoleucine, and lysine were prominent at the end of the process. The total plate count increased during the first 10 days and then decreased gradually for both total microbial population and lactic acid bacteria population. Micrococcus , Streptococcus and Pediococcus spp were predominantly present during Bakasang fermentation.     

Hankel Singular Values and Vectors of a Class of Infinite-Dimensional Systems: Exact Hamiltonian Formulas for Control and Approximation Problems

This paper derives exact formulas for singular values and vectors of Hankel operators whose symbol is a product of a single-input single-output inner function and a multi-input multi-output rational function. This class of Hankel operators arises from the sensitivity minimization H ^∞ control problem with a rational weight function and the approximation problem of transfer functions having rational outer parts. It is shown that there is a Hamiltonian transcendental equation characterizing singular values which leads to a matrix function formula for singular vectors. Date received: May 12, 1998. Date revised: May 14, 1999.     

Switching surge overvoltages on the feeding system of a MAGLEV train

This paper investigates switching surge overvoltages due to a section switchgear between coils and a feeding cable, and surge overvoltages due to a ground fault in the feeding cable. The maximum overvoltage due to switchgear closing is about 25 kV on the coil and 15 kV on the cable sheath. The coil overvoltage becomes greater as a source voltage reaches its peak. The overvoltages due to switchgear breaking is dependent on the breaking current and they reach 115 kV on the coil and 15 kV on the cable sheath when the current is 50 A. The fault surge overvoltage is about 24 kV on the coil which is smaller than the switching overvoltage. On the other hand, the cable sheath overvoltage reaches 32 kV, which is the largest among various overvoltages investigated in this paper, and could result in sheath insulation breakdown. The coil overvoltage due to current breaking by a section switchgear may cause coil insulation breakdown when the breaking current is large. Both the coil and sheath overvoltages can be controlled to less than the insulation level by arresters. © 1998 Scripta Technica, Electr Eng Jpn, (4): 58–66, 1998     

A design of magnetic shielding for a superconducting magnetically levitated train

For EDS-type magnetically levitated trains, magnetic shielding of stray fields produced by superconducting magnets is an important task. We seek the “optimal” thickness distribution (configuration) of magnetic material, which is the lightest and keeps the magnetic field at tolerable levels in the vehicle. In many cases, trial-and-error methods have been adopted for this purpose. In this paper, we propose a new method for preliminary design of the magnetic shielding. In this method, we simplify the magnetic shielding problem, assuming infinite permeability of the magnetic material, and calculate the magnetic flux going into or out of the shield surface. In this case, we can design an optimal magnetic shield (distribution and configuration of the magnetic material) and know the minimum weight of the magnetic shielding. We finally present an example of the magnetic shielding designed by this method and investigate its characteristics in a magnetically levitated train. © 1998 Scripta Technica, Electr Eng Jpn, 124(1): 42–54, 1998