High-Speed Drive System with Ultrasonic MOSFET PWM Inverter and Single-Chip Microprocessor Control

The design of high-current high-voltage MOSFET inverters requires measures to reduce the switching losses of the flyback diodes. Saturable reactances have been used in the case of a 4.5-kVA MOSFET inverter to limit the di/dt during commutations. The switching overvoltages of the reactances are absorbed by one common clamping circuit per bridge leg. The drive control system and the space vector modulator for the generation of the PWM switching sequences are implemented in a single-chip microcomputer.     

Unvernetzte epoxid-amin-additionspolymere, 16. HPLC-analyse und 13C-NMR-spektroskopie von telechelen (diglycidylether-bisphenol A)-anilin-prepolymeren

Synthesis and properties of telechelic diglycidyletherbisphenol A (DGEBA)-aniline prepolymers with aminoalcohol endgroups are reported. The composition of the prepolymer mixtures obtained by addition polymerization was analyzed by means of HPLC using a LiChrosorb RP-18 column with water/acetonitrile gradient elution mode. The prepolymers represent a series of homologous oligo(aminodiols) 2 , n = (1), 2, 3, 4 ... which are separated into diastereomers. The average value n? depends on the molar ratio of the monomers and is varied between 1,0 and 14,0 resulting in M?_n (vapor pressure osmometry) 500–6000 g · mol^-1. C, H, N elemental analysis and ¹³C-NMR spectroscopy were used to estimate the chemical structure of the prepolymer mixtures.     

Final-state angular momentum distributions in charge transfer collisions at high energies

We investigate the influence of different terms of the Born series on the final-state angular momentum (l) distribution and the anisotropy of the captured electron. A variety of different l distributions depending on the projectile velocity v and the charge asymmetry Z_p/Z_T of the collision system can be found, revealing different underlying mechanisms for charge transfer. We compare the predictions of perturbation theories such as the first and second Born approximation, the continuum distorted wave (CDW) approximation and the post-collision interaction (PCI) model valid at high velocities with those of the “quasi-resonant over barrier” model of charge transfer valid at intermediate velocities.     

新型三辊组合式轧管机——3RCM的工艺特点

三辊组合式轧管机———3RCM是生产优质无缝钢管的新型机组,介绍了该机组的工艺特征、生产过程和工艺流程以及与传统轧管工艺的区别。该工艺优势在于只需配置两套机组就可构成无缝钢管的热轧生产线。经生产试验证明,这种工艺成熟,技术可靠。3RCM轧管机投资少、成本低,将使小型钢管厂具有一定的竞争优势。     

Counting curves and their projections

Some deterministic and probabilistic methods are presented for counting and estimating the number of points on curves over finite fields, and on their projections. The classical question of estimating the size of the image of a univariate polynomial is a special case. For curves given by sparse polynomials, the counting problem is #P-complete via probabilistic parsimonious Turing reductions.     

Mass Transport in the Presence of Internal Defect Reactions—Concept of Conservative Ensembles: II, Evaluation of Electrochemical Transport Measurements

It is shown that in the general case of a defective solid, where the ionic point defects can change their valence states, the evaluation formulas of well-known electrochemical techniques (such as concentration cell experiments, Wagner-Hebb method, chemical and electrochemical polarization and relaxation) have to be modified. The generalized relationships are derived.     

Einfluß des Verteilungsgrades der Carbide auf die Rekristallisation eines untereutektoiden Stahls C 22

Systematische Untersuchung der Rekristallisation in einem untereutektoiden Stahl C 22, in dem der Verteilungsgrad der Carbide in sehr weiten Grenzen verändert wird. Vergleich der Ergebnisse mit in früheren Arbeiten erörterten Prinzipien für Zweiphasensysteme, deren zweite Phase eine Ausscheidung ist. Aufstellung neuer Prinzipien, aufgrund deren eine optimale Wärmebehandlung des Stahls möglich ist. Thermomechanische Behandlung zur Herstellung eines breiten Bereichs von Dispersionsgefügen. Rekristallisationsglühung. Licht-, elektronenmikroskopische und röntgenographische Untersuchungen. Messung der mechanischen Eigenschaften.