A method to select features for maximum entropy modeling in which the gains for all candidate features are determined during an initialization stage and gains for only top-ranked features are determined during each feature selection stage. Electrodes are disposed on the lower surface of a semiconductor element. The liquid coolant flashes into a saturated liquid-vapor coolant mixture in the cooling chamber. The processing electronics unit is operatively connected with the detector unit and the interface unit respectively, for evaluating an attitude angle on the basis of the gray value and coordinate of each pixel.