The economical criterion is accounted as the objective function to develop a computer program for designing lightning protection systems for substations by using masts and Matlab in this work. Masts are needed to be placed at desired locations; the program will then show mast heights whose sum is the smallest, i.e. satisfies the economical criterion. The program is helpful for engineers to quic...

A simple, clean, and environmentally benign three-component process for the synthesis of 2-amino-4Hchromenes using [mim]Cl, as an efficient catalyst under solvent-free conditions are described. A wide range of aromatic aldehydes easily undergoes condensations with 1-naphthol and malononitrile under solvent-free conditions to afford the desired products of good purity in excellent yields. Taking...

First-order logic (FOL) is undecidable — that is, no algorithm exists that can decide whether a formula of FOL is valid or not. However, there are various fragments of FOL that are known to be decidable. FO, the two-variable fragment of FOL, is one of such languages [1,2]. FO is a first-order language where formulas have maximally two variables, no function symbols, but possibly do have equalit...

This paper focusses on the description of reliable, safe and economical treatment of mine water from different types of mines and applications by advanced membrane systems. The applications include mine drainage water from underground mines, intrusion water in open pit mines and excess water from tailing storage facilities. The illustrated references confirm the existence of robust, reliable, a...

Several models have been proposed for scheduling the preventive maintenance (PM) of complex repairable systems in industry. These are often application-speci"c and some make unrealistic assumptions about stationarity of the process and quality of repairs. We investigate two principal types of general model, which have wider applicability. The "rst considers "xed PM intervals and is based on the...

In a recent work we showed that for a Hamiltonian system with constraints, the set of constraints can be investigated in first and second class constraint chains. We show here that using this ”chain by chain” method for an arbitrary system one can fix the gauges in the most economical and consistent way. We show that it is enough to assume some gauge fixing conditions conjugate to last elements...