Convex optimization of optimization problem is convex. "Standard form" is the usual and perhaps most intuitive form of describing a convex minimization problem. It consists of the following three parts: A convex minimization problem in standard form is thus written as In reality, this form of problem is exactly equivalent to a problem constrained by only equalities. You can rephrase the problem without equality constraints by replacing each equality constraint formula_52 with a pair of inequality constraints formula_64 and formula_65, and the previous analysis holds. This fact is why formula_53 being both convex and concave, i.e. both formula_53 and formula_68 are convex,
Compound refractive lens Compound refractive lens A Compound refractive lens (CRL) is a series of individual lenses arranged in a linear array in order to achieve focusing of X-rays in the energy range of 5-40 keV. They are an alternative to the KB mirror. For all materials the refractive index for X-rays is close to 1, hence a single conventional lens for X-rays has an extremely long focal length (for practical lens sizes). In addition, X-rays attenuate as they pass through a material so that conventional lenses for X-rays have long been considered impractical. The CRL gets its reasonably short focal length, on