This paper reviews recent progress in the application of Direct Methods to solve surface structures using surface X-ray or transmission electron diffraction data. The basic ideas of (crystallographic) Direct Methods are presented, as well as the additional problems posed by trying to apply them to surfaces and how they connect to the mathematical theory of projections. Surface crystallography n...

the democratic system is applied by three methods; by the representatives of people (indirect or representative democracy); by the people and their representative; and by the people themselves. in the constitution of the countries who accepted the national sovereignty doctrine the people's regime will be only applied by their representatives (like members of parliament, primeminister, the ...

This study presents a comparative survey of direct methods for solving Variational Problems. Thisproblems can be used to solve various differential equations in physics and chemistry like RateEquation for a chemical reaction. There are procedures that any type of a differential equation isconvertible to a variational problem. Therefore finding the solution of a differential equation isequivalen...