Output voltage control method of PWM-controlled cycloconverters with space vectors

A new output voltage control method for PWM-controlled cycloconverters with space vectors is proposed in this paper. Results are as follows:. (1) The classification and the systematic behavior of the space vectors of PWM-controlled cycloconverters are clarified through the analysis. (2) A new output voltage control method that makes excellent output voltage waveforms is proposed using the results of this analysis. (3) Feasibility of the proposed output voltage control method is confirmed by simulation. (4) Output voltage waveforms of the PWM-controlled cycloconverters are compared with those of the PWM-controlled inverters, using the performance index of variance of time-integral of higher harmonic components. Therefore, the proposed control method may reduce both acoustic noise and torque ripple of induction motors.     

Microstructure, thermal properties and hardness of the CeMO3 (M=Al,Ga) synthesized by arc-melting method

Synthesis of CeMO₃ (M=Al,Ga) was attempted by the arc-melting method. In the case of M=Al, the arc-melted sample consisted typically of three regions CeAlO₃, CeO₂ and eutectic, mainly Al₂O₃. A similar texture was also observed for the case of M=Ga. Both CeAlO₃ and CeGaO₃ are crystallized in a tetragonal system (space group:P4/mmm). Lattice parameters of the tetragonal cell for CeAlO₃ and CeGaO₃ are a=0.37669(9) nm, c=0.37967(7) nm and a=0.3873(1) nm, c=0.3880(1) nm, respectively. According to thermal analysis, decomposition of 2CeMO₃+1/2O₂→2CeO₂+M₂O₃ occurs for CeAlO₃ and CeGaO₃ at about 1275°C and 833°C, respectively. The TG curve shows that the onset-temperature of oxidation for CeAlO₃ is at 1170°C and for CeGaO₃ is at 720°C. After TG-DTA measurement, both compounds are completely decomposed to starting materials. The value of the micro-Vickers hardness for the CeAlO₃ and CeGaO₃ is 9.0 (±0.2) GPa and 7.2 (±0.4) GPa, respectively.     

Adsorption mechanism of a cationic surfactant on textiles in excess anionic surfactant solution

The present study was carried out to clarify the adsorption mechanism of a cationic surfactant (dihydrogenated tallow dimethyl ammonium chloride (DHTDMAC) onto various fibers in excess of anionic surfactant solutions. Actually, in such a solution, DHTDMAC becomes an anionic/cationic complex and comes into contact with fibers through the physical force of mechanical stirring. At that time, adsorption of the complex onto textile depends on the extent of the work of adhesion (WA). In fact, WA and amounts of DHTDMAC adsorbed onto fibers were correlated very closely. Furthermore, the difference of WA according to the complex is discussed. Two hypotheses are presented. One is based on differences arising from the hydrophobic character of the complex itself. The other is based on the manner in which the anionic surfactant and cationic surfactant are situated in the complex molecule. The WA of the complex is explained on the basis of these hypotheses.     

SiC coatings for first-wall candidate materials by R.F. sputtering

The r.f. sputtering technique was applied to form SiC coating films on first-wall candidate materials such as molybdenum, stainless steel and pyrolytic carbon at various temperatures. The coating films were examined by means of scanning electron microscopy, X-ray diffraction, Auger electron spectroscopy and roughness factor (RF) measurements. It was found that the coating films consisted of α-SiC and grew at relatively low temperatures, namely 300 °C, 600 °C and 800 °C on molybdenum, 304 stainless steel and pyrolytic carbon surfaces, respectively. The surfaces of α-SiC films grown above these temperatures were relatively smooth with small RFs in comparison with those prepared at lower temperatures. Lower temperature deposition gave rise to amorphous and rough coating films with considerably larger RFs.     

Reliability evaluation of a two-unit unrepairable system

As one of the redundancy techniques for an unrepairable system, we suppose an unrepairable two-unit standby redundant system in which each new component for replacement is supplied by an order. We analyze the stochastic behavior of our model applying a unique modification of Markov Renewal Processes. Further, we compare an unrepairable two-unit standby redundant system with an unrepairable one-unit system. Finally, we give numerical examples of the stochastic behavior for our model.     

Effect of (s)-(+)-ethyl-2-phenylbutanoate and poly(ethylene terephthalate) on the polymerization of propylene and 3-methyl-1-pentene over TiCl3-AlET3

Summary (s)-(+)-Ethyl-2-phenylbutanoate was synthesized and polymerizations of propylene and racemic 3-methyl-1-pentene were conducted over TiCl₃-AlEt₃ combined with the compound. The addition of the compound caused a significant increase in the isotacticity of polypropylene as well as a substantial decrease in the activity. However, stereoelective polymerization of racemic 3-methyl-1-pentene didn't take place at all. Propylene polymerization was also carried out over TiCl₃-AlEt₃ by using poly(ethylene terephthalate) in place of the compound. The results obtained have led to the conclusion that these additives act mainly as reagents to reduce the concentration of AlEt₃ by the formation of the complexes between AlEt₃ and these additives.