A hot water circuit supplies water to a plurality of rooms in a building from a central water source. The miniature spectrometer may further comprise a waveguide device, and the optical grating accommodation slot is positioned in a space defined by an opening of the waveguide device. Additionally disclosed is the use of the resulting hydrogels for production of aerogels. A computing node may be selected to execute the identified operation based on the expected completion times. One example method comprises, adjusting a brake torque applied to a deactivated rotating engine after an engine restart request, the brake torque applied to slow the engine to at least a predetermined threshold speed without stopping the engine, and engaging a starter to the still rotating engine to increase the engine speed and restart the engine. Thus, a given motor may be assembled to a variety of desired lengths by connecting the appropriate number of modular motor sections.