Pecan "fruit of the walnut". They noted the particularly thin shell and acorn-like shape of the fruit, indicating they were indeed referring to pecans. The Spaniards took the pecan into Europe, Asia, and Africa beginning in the 16th century. In 1792, William Bartram reported in his botanical book, "Travels", a nut tree, "Juglans exalata" that some botanists today argue was the American pecan tree, but others argue was hickory, "Carya ovata". Pecan trees are native to the United States, and writing about the pecan tree goes back to the nation's founders. Thomas Jefferson planted pecan trees, "C. illinoinensis" (Illinois nuts), in
Two-sided Laplace transform notation for the two-sided transform; the formula_3 used here recalls "bilateral". The two-sided transform used by some authors is In pure mathematics the argument "t" can be any variable, and Laplace transforms are used to study how differential operators transform the function. In science and engineering applications, the argument "t" often represents time (in seconds), and the function "ƒ"("t") often represents a signal or waveform that varies with time. In these cases, the signals are transformed by filters, that work like a mathematical operator, but with a restriction. They have to be causal, which means that the output in a