Abstract: A DC reactor consisting of a coil formed of a superconducting material is provided. It is possible to reduce leakage reactance and to increase critical current by using a coil formed of a high temperature superconducting material and forming a first bobbin of the DC reactor as a toroid shape.

Abstract: Embodiments of a computer system and methods for changing operating systems (OSs) can perform a task switching into a different OS without checking a system reset or power off of the system. A method for changing the OS in a multi-OS system can include initializing, at the BIOS, a hardware and dividing an area on the main memory for a booting initiated by an instant-on key/signal; turning over a system control to the embedded OS after loading an embedded OS on a specific area of the divided main memory and booting the same, and operating an instant-on player (IOP). When the IOP is terminated by a user, forcibly loading the normal OS on the main memory. The normal OS can be loaded in a hidden state before termination of the IOP. Thus, a time to reach normal computer system operations from an instant-on-function can be reduced.