In a shell and tube heat exchanger, the failure of tube-to-tubesheet welds results in high-pressure water jet which erodes the refractory in front of the tubesheet. Finite element method was employed to simulate the welding process and post weld heat treatment (PWHT) to find the factors affecting the failure in tube-to-tubesheet weldments. Residual stresses in two different geometries of tube-t...

Heterogeneous Ziegler-Natta and homogeneous metallocene catalysts exhibit greatly different active sitenature in olefin polymerization. In our previous study, it was reported that MgCl2-supported titanocenecatalysts can generate both Ziegler-Natta-type and metallocene-type active sites according to the type of activators.The dual active site nature of the supported titanocene catalysts was furt...

heat stress is well recognized among the hazardous physical agents that might be present during work. this study aims to compare wbgt index at acclimated and unacclimated people to permissible threshold limit value and study the differences between physiological parameters at them. twenty one healthy men were participated in the study. all of the subjects were monitored in two different weather...

to find the effect of atriplex canescens on soil chemical properties, two adjacent areas, each with and area of 1 ha, were selected in hossein abad hapeshloo shahryar. in one area it was planted atriplex canescens in 2003 while the later one without atriplex canescens was considered as control area. to sample soil, random- systematic method was used along 3 transects with a length of 100 m. in ...

in this paper, the structural properties of c20 and c12b8 fullerene interacting with glycine based onthree active sites of glycine and one c atom or one b atom in c12b8 were analyzed through thedensity functional theory. it was found out that the binding of glycine to c12b8 generated a complex.our results were extremely relevant in order to identify the potential applications of functionalizedc...

Normally, the reporting of an evaluation study would commence with a detailed description of the project being evaluated in order to ensure there is a common understanding of the project and to provide an appropriate context for the remainder of the evaluation report. However, in this case, a comprehensive description of the project has already been provided in the preceding chapter. Furthermor...

The nonperturbative aspects of string theory are explored for noncritical string in two distinct formulations, loop equations and matrix models. The effects corresponding to the D-brane in these formulations are especially investigated in detail. It is shown that matrix models can universally yield a definite value of the chemical potential for an instanton while loop equations cannot. This imp...