The group of isometries Aut(Tn) of a rooted n-ary tree, and many of its subgroups with branching structure, have groups of automorphisms induced by conjugation in Aut(Tn). This fact has stimulated the computation of the group of automorphisms of such well-known examples as the group G studied by R. Grigorchuk, and the group Γ̈ studied by N. Gupta and the second author. In this paper, we pursue t...

We characterize those imaginary quadratic number fields, k, with 2-class group of type (2, 2, 2) and with the 2-rank of the class group of its Hilbert 2-class field equal to 2. We then compute the length of the 2-class field tower of k.

The notion of transducer integer sequences is considered through a series of examples (the chosen examples are related to the Tower of Hanoi problem on 3 pegs). By definition, transducer integer sequences are integer sequences produced, under a suitable interpretation, by finite transducers encoding rational tree morphisms (length and prefix preserving transformations of words that have only fi...

In a steam power plant, the temperature of the cooling water leaving the condenser for recyclingshould decrease. This is achieved in a cooling tower. The Heller cooling tower does not require waterfor operation, thus, it is a suitable system for use in thermal power plants throughout Iran. Wind is anenvironmental factor that unfavorably affects the performance of a cooling tower. Previous studi...

Design of a natural dry cooling tower has been accomplished in two sections: the design of heat exchangers and the numerical solution of flow through the tower. Heat exchanger (Heller type) has been simulated thermodynamically and then coupled with a computer program, which calculated the turbulent natural convection flow through the tower. The computer program developed for this purpose can be...

The present paper describes the designing of a thermally and economically optimum mechanical draft counter-flow wet cooling tower. The design model allows the use of a variety of packing materials in the cooling tower toward optimizing heat transfer. Once the optimum packing type is chosen, a compact cooling tower with low fan power consumption is modelled within the known design variables....

since the energy analysis considers the quantity of energy, it cannot show the performance of the cooling tower. therefore, in order to optimize the performance of the tower and also the process which the cooling tower is a part of it, it is necessary to analyze the energy and exergy of the tower simultaneously. in this paper, the energy and exergy of one of the cooling towers of khuzestan stee...

ghorban tower as an architectural monument is one of the outstanding resting- place of islamic era in hamadan city which has not been studied properly. previous studies on the tower concerning its architectural features or its historical background showed that the tower may be a place where a dignified religious man named khajeh hafez abol'ala hamadani berried inside in saljuk era and afte...

temperature restrictions on aqueous effluents dictate that streams with a temperature higher than the permitted level needed to pass through cooling systems to reduce the effluent temperature before discharge. in this study, by considering the grouping design rules based on pinch technology, an optimum design for a distributed effluent cooling system, has been developed. a counter-flow wet cool...

One of the most demanding current mega engineering projects on Earth is to build a space elevator for various space applications. The current trend in new inflatable structure applications lends itself to study for the preliminary engineering design analysis of the space tower. Today, to access outer space, conventional chemical rockets are the only method in use. This method is extremely ineff...