Определение деформаций провода обмоток трансформатора собственным магнитным полем

Приводится рассмотрение продольных и поперечных деформаций проводника обмотки трансформатора, вызванных током короткого замыкания. Приводятся полезные соотношения, позволяющие оценить удлинения и сдвиг проводников в обмотке при известном токе. Приводится пример расчета распределения пондеромоторных сил для проводников обмотки трансформатора круглого и прямоугольного сечения

Метрологическое обеспечение измерения температуры в геологии при освоении Арктики

Micromachining of SiC with Nd:YAG laser radiation was performed in various processing gas atmospheres as a function of processing variables showing the influence of the heat and pressure load onto the precise geometric structures. Among effective material removal and reducing of debris in the surrounding of the generated structures the achievable surface roughness of microstructured ceramics are investigated, determining not only the dependence on overlap and fluence but also the influence of the properties of the processing gas atmosphere. 3d microstructures are produced by scanning and turning the focused laser beam onto the material surface. Structures < 100 mum and surface roughness < 1 mum require an overlap < 0.8 independent of the type of processing gas

Оценка нестационарной теплоотдачи при пленочной конденсации пара на вертикальной стенке

Получены расчетные зависимости коэффициента теплоотдачи, скорости движения и трансцендентное уравнение для толщины ламинарной пленки конденсата, справедливые для регулярного теплового режима

Fundamental investigations of micromachining by nano- and picosecond laser radiation

The removal processes of ceramics and metals were investigated using pico- and nanosecond laser radiation produced by diode-pumped Nd:YAG lasers. The laser radiation was focused to spot diameters smaller than 10 mu m, yielding power densities up to 5 X 10(exp 12) W/CM2 . The threshold fluence for removal and the removal depth per pulse were determined for 40 pico- and 10 nanosecond laser pulses using the fundamental wavelength, the second harmonic and the third harmonic laser radiation of the laser system. For 40 ps laser pulses pump and probe investigations were used to study the interaction of intense ultrashort laser beams with matter. By this technique ultrashort processes can be photographed with a time resolution determined by the pulse length of pump and probe pulses. The measurements allow a detailed characterization of the material removal including melting, vaporization and fast resolidification as well as the feedback of the surrounding atmosphere to the processed microstruc tures. The threshold fluences for material removal and the removal rates per pulse were determined for Si3N4, SiC and WC as a function of laser pulse length and laser wavelength. Using picosecond laser radiation microstructures were produced in different ceramics and metals demonstrating the suitability of short laser pulses for the production of microstructures with dimensions smaller than 10 mu m and for ultra-precise removal of thin layers