A system and method for simulating a circuit design using both an unknown Boolean state and a negative unknown Boolean state is provided. The first detection circuit detects the leading edge of the pulse waveform of an input signal. According to the component in FGD byproduct from thermal power plants and facilities, the amount for FGD byproduct from thermal power plants and facilities needed in the alkali soil to be ameliorated can be determined. A relevance score is determined for each of the suggested products based on relevance factors and social media influence factors, and recommended products are selected based on the relevance scores of the recommended products. A virtual electrode pair includes at least one virtual electrode contact. The L-shaped support bars may be flared outward and provided with a plate for mounting the step thereon.