A method of detecting impact damage of a structure having a first surface exposed to potential impacts from an object comprises providing a sensor having a body portion that has a surface provided with an elongated channel. The process involves feeding a web into an apparatus that includes a pair of intermeshing activation rolls having three dimensional surface features configured to simultaneously activate different portions a web in different directions. The array is equipped with a plurality of magnets arranged along the length of the array. The system includes a covering for providing a sheltered environment for the vehicle’s cargo bed. In particular, 2,2-dimethylbenzopyran based compounds and methods of their use, for example in the treatment or prevention of hypoxia-related pathologies are provided. An electronic control unit performs an advance correction corresponding to the exhaust gas recirculation quantity regarding the MBT ignition timing and the knock limit ignition timing, and corrects the volumetric efficiency of the internal combustion engine, which is used for the calculation of the advance correction quantity used for the advance correction, according to the purge air quantity.