Abstract: A method for controlling an electric heater of a vehicular heating, ventilation, and air conditioning (HVAC) system includes turning on the electric heater; determining whether an ambient air temperature of a vehicle is higher than or equal to a threshold ambient air temperature, and a battery temperature is lower than or equal to a threshold battery temperature; determining whether battery efficiency is lower than or equal to threshold efficiency when the ambient air temperature of the vehicle is higher than or equal to the threshold ambient air temperature, and the battery temperature is lower than or equal to the threshold battery temperature; and turning off the electric heater when the battery efficiency is lower than or equal to the threshold efficiency, wherein the electric heater is configured to receive electric energy from the battery.

Abstract: Disclosed herein is a method of functionally coating a basalt fiber, including: coating a basalt fiber by passing the basalt fiber through an aqueous fluorine-based solution including 50˜60 wt % of polytetrafluoroethylene (PTFE), 2˜5 wt % of a nonionic surfactant and water at a passing speed of 1˜2 m/minute, the solution being maintained at a temperature of 20˜25° C.; drying the coated basalt fiber at a temperature of 80˜110° C.; heating the dried basalt fiber to a temperature of 180˜270° C.; and sintering the heated basalt fiber at a temperature of 360˜420° C. Further, disclosed herein is a method of functionally coating a basalt core yarn, including: preparing a basalt core yarn by winding a sub fiber around a basalt fiber, which is a main fiber, and then twisting the sub fiber and basalt fiber; coating the basalt core yarn by passing the prepared basalt core yarn through a coating solution including 35˜45 wt % of a phosphorus-based fire retardant, 50˜59.9 wt % of toluene, which is a solvent, and 0.