DC machines can be classified as self-excited, separately excited, permanent magnet (PM), and brushless. Self-excited machines can be further classified as shunt, series, and compound. Compound ...

Craftsmen in ancient China were using complex machines to work jewellery long before such devices are traditionally thought to have been invented. Dr Peter Lu claims spiral grooves on 2,550-year-old ...

Distinctive spiral patterns carved into a small jade ring show that China was using complex machines more than 2500 years ago, says a Harvard graduate student in physics. The ring was among the goods ...