A generalized method of controlled voltage source-fed induction motor vector control using the observer theory

Vector control of induction motors is widely used for industrial applications. On-line parameter identification and speed sensorless control are being studied actively. A representative method for these problems is the application of an adaptive full-order observer. The rotor flux for vector control is estimated by a full-order observer and machine parameters, or the rotor speed is determined by an adaptive algorithm. In this paper, a new vector control scheme with parameter identification is proposed. This method is based on the adaptive full-order observer. However, the observed currents which are usually estimated in the voltage model are considered as command currents and the voltage model is used for the current controller. As a result, the proposed system is simpler than the conventional adaptive full-order observer system. Since the proposed system is composed of an induction motor model in a synchronously rotating reference frame, the well-known slip frequency control block is contained. The arrangement of the poles which are related to the torque transfer function is discussed. A linear model is derived taking into account the effects of the change of the stator and rotor resistances. The trajectories of poles and zeros of the torque transfer function are computed and discussed for various system parameters. Identification of stator and rotor resistances is confirmed by simulation using a nonlinear system model. The proposed idea is applied to a speed sensorless system; this system has a similar configuration to those of existing systems under some assumptions. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 119(4): 66–76, 1997     

Development of high voltage harmonic measuring instruments for distribution systems using optical voltage sensor and current sensor

Application of an optical measuring technique was attempted in order to develop harmonic voltage and current measuring instruments for distribution systems. To develop the harmonic voltage measuring system using a Bi₁₂GeO₂₀ crystal as a sensing Pockels cell for high‐voltage distribution lines, zinc oxide elements were adopted as a voltage divider. Also, an optical current sensor system was improved on the harmonic current measuring system using an R₃Fe₅O₁₂ film as a Faraday device. In practical three‐phase distribution systems, the developed high voltage harmonic measuring devices using the optical voltage sensor and current sensor were compared with conventional harmonic analyzers for low voltage. As a result, it was confirmed that the developed high voltage harmonic measuring devices had satisfactory characteristics for practical use. © 1999 Scripta Technica, Electr Eng Jpn, 128(4): 84–93, 1999     

Water Vapor Permeability of Poly(L‐lactide)/Poly(D‐lactide) Stereocomplexes

PLLA/PDLA blend films with only stereocomplex crystallites as a crystalline species together with pure PLLA and PDLA films with only homo‐crystallites as a crystalline species were prepared, and the effects of enantiomeric polymer blending, crystalline species, and crystallinity on the water vapor permeability were investigated. The WVT coefficient P of PLLA/PDLA blend films was 14–23% lower than that of pure PLLA and PDLA films in the crystallinity X_c range of 0–30%. Amorphous PLLA/PDLA blend films have a much lower P than pure PLLA and PDLA films. The dependence of P on X_c for blend films was stronger for X_c = 0–30% than for X_c = 30–100%. This dependence is discussed using the Nielsen model and the concept of “restricted” (or “restrained”) and “free” amorphous regions.

     

Engineering of alpha1-antitrypsin variants selective for subtilisin-like proprotein convertases PACE4 and PC6: importance of the P2' residue in stable complex formation of the serpin with proprotein convertase

Furin and PACE4, members of the subtilisin-like proprotein convertase (SPC) family, have been implicated in the metastatic progression of certain tumors in addition to the activation of viral coat proteins and bacterial toxins, indicating that these enzymes are potential targets for therapeutic agents. Alpha1-Antitrypsin Portland is an engineered alpha1-antitrypsin designed as a furin-specific inhibitor and has been used as a tool in the functional analysis of furin. In this work, we engineered rat alpha1-antitrypsin to create a PACE4-specific inhibitor. Substituting Arg-Arg-Arg-Arg for Ala-Val-Pro-Met(352) at P4-P1 and Ala for Leu(354) at P2' created a potent PACE4- and PC6-specific inhibitor. This variant (RRRRSA) formed an SDS- and heat-stable serpin/proteinase complex with PACE4 or PC6 and inhibited both enzyme activities. The RRRRSA variant was efficiently cleaved by furin without formation of the stable complex. This is the first report of a highly selective protein-based inhibitor of PACE4 and PC6. This inhibitor will be useful in delineating the roles of PACE4 and PC6 localized in the extracellular matrix.     

Morphological study on three kinds of two-dimensional spherulites of poly(butylene terephthalate) (PBT)

Three kinds of thin film specimens, each of which containing one of the three types of two-dimensional poly(butylene terephthalate) (PBT) spherulites (i: usual-positive type, ii: usual-negative type, and iii: unusual type), were prepared and studied mainly by transmission electron microscopy. It was confirmed that all these kinds of spherulites are made up of only the α-modification crystals, and the growth directions for usual-positive type, usual-negative type, and unusual type are the [010]^∗, ^∗, and ^∗ directions in the reciprocal lattice, respectively. Furthermore, the arrangement of unit cell in each type of the spherulites was determined. The relationships between the arrangements of unit cell and the types of each resulting spherulite are discussed.     

Blends of isotactic and atactic poly(lactide). I. Effects of mixing ratio of isomers on crystallization of blends from melt

Poly(L -lactide) (PLLA) and poly(DL -lactide) (PDLLA) blends were crystallized from the melt and their crystallization behaviors and morphologies were investigated using differential scanning calorimetry and polarizing microscopy. PLLA could crystallize from the melt in the presence of PDLLA when the PLLA content in the blend (X_PLLA) was higher than 0.2. Spherulites were formed when X_PLLA was between 0.6 and 1. The radius of the spherulites formed in the presence of PDLLA was larger than that of nonblended PLLA, probably because the coexisting PDLLA reduced the density of nuclei for the spherulites. Small crystallite assemblies were formed when X_PLLA was between 0.2 and 0.5, and grew spherically from the nuclei when X_PLLA was 0.5. Isotactic PLLA and atactic PDLLA seem to be miscible prior to crystallization, but PDLLA will be trapped between the lamellae of the spherulites or spherulitic assemblies during crystallization. PDLLA delayed the induction for crystallization of the blends. In spite of different morphology, the melting temperature and crystallinity of PLLA remained virtually constant when annealing was conducted for 600 min at X_PLLA between 0.5 and 1. © 1995 John Wiley & Sons, Inc.     

Self-assembly of nano-sized arrays on highly oriented thin films of poly(tetrafluoroethylene)

Self-assembly of nano-sized arrays by casting a dilute solution of a guest material on the friction-transferred poly(tetrafluoroethylene) (FT-PTFE) substrate was newly discovered. Long axis of the rod-like structures forming the arrays is aligned perpendicular to the chain direction of FT-PTFE, and accordingly, the arrays are highly anisotropic. This phenomenon was observed for aqueous or organic solutions of polymers or organic materials. Each rod-like structure forming the arrays is composed of small grains. The arrays in question are formed regardless to the crystallinity of the guest materials. The formation mechanism of the nano-sized arrays is still unclear. However, we guess that they are formed as a result of microscopic flow pattern at the edge of the solution film. The arrays in question may be a new type of dissipative structure.     

Nicotinic acid transport mediated by pH-dependent anion antiporter and proton cotransporter in rabbit intestinal brush-border membrane

In order to determine whether the vitamin nicotinic acid is absorbed via an anion antiporter, intestinal epithelial cell membrane transport mechanisms for nicotinic acid were characterized using isolated rabbit jejunal brush-border membrane vesicles. The uptake of nicotinic acid by the membrane vesicles showed an overshoot phenomenon in the presence of an outwardly directed bicarbonate gradient or an inwardly directed proton gradient and the uptakes were two times and six times greater, respectively, than that in the absence of any ion gradient. The bicarbonate-dependent initial uptake of nicotinic acid was increased at acidic pH, showing pH-dependent transport activity. An inhibitor of anion transport, 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid, specifically reduced bicarbonate-dependent transport of nicotinic acid. The initial uptakes of nicotinic acid via the anion antiporter and the proton cotransporter were specifically inhibited by monocarboxylic acids such as acetic acid, benzoic acid, D- and L-lactic acid, pravastatin and valproic acid, but not by di- or tricarboxylic acids, bile acids or amino acids. Nicotinic acid uptake activity was, furthermore, expressed in a Xenopus laevis oocyte system after injection of messenger RNA (mRNA) derived from rabbit intestinal epithelial cells. These observations demonstrate that nicotinic acid is absorbed by two independent active transport mechanisms from small intestine, i.e. a proton cotransporter and an anion antiporter. The pH-dependence observed in the intestinal absorption of nicotinic acid might, therefore, be ascribed partly to pH-sensitive and partly to carrier-mediated transport mechanisms in the brush-border membrane.