this article analyses the push and pull factors that bring visitors to the iranian national parks. the study used a structured questionnaire to collect data on these factors and the socio-demographic profile of the visitors. survey conducted in boujagh national park, an area of 3177 hectares located in the north of the iran, produced 400 questionnaires. the factor analysis identified four push ...

An accurate frequency of the Helmholtz–Duffing oscillator is obtained by a sophisticated modification He’s formulation. The pull-down instability existing in symmetric breaking phenomenon newly discovered dynamic motion for oscillators with even nonlinearities. A criterion predicting asymmetrical amplitude and built measuring change. good matching performance between analytic results numerical ...

there are many techniques for reconstruction after total pharyngolaryngoesophagectomy. the use of a transposed stomach to restore gastrointestinal continuity, and this combined cervical and abdominal approach for pharyngolaryngoesophagectomy and gastric pull up has become one of the most popular. this retrospective study is a review of 50 consecutive iranian patients who underwent pharyngolaryn...

This paper investigates the parametric excitation of a micro-pipe conveying fluid suspended between two symmetric electrodes. Electrostatically actuated micro-pipes may become unstable when the exciting voltage is greater than the pull-in value. It is demonstrated that the parametric excitation of a micro-pipe by periodic (ac) voltages may have a stabilizing effect and permit an increase of the...

In the present work the pull-in voltage of a micro cracked cantilever beam subjected to nonlinear electrostatic pressure was studied. Two mathematical models were employed for modeling the problem: a lumped mass model and a classical beam model. The effect of crack in the lumped mass model is the reduction of the effective stiffness of the beam and in the beam model; the crack is modeled as a m...

The static pull-in instability of beam-type micro-electromechanical systems is theoretically investigated. Two engineering cases including cantilever and double cantilever micro-beam are considered. Considering the mid-plane stretching as the source of the nonlinearity in the beam behavior, a nonlinear size-dependent Euler-Bernoulli beam model is used based on a modified couple stress theory, c...

This article analyses the push and pull factors that bring visitors to the Iranian national parks. The study used a structured questionnaire to collect data on these factors and the socio-demographic profile of the visitors. Survey conducted in Boujagh National Park, an area of 3177 hectares located in the north of the Iran, produced 400 questionnaires. The factor analysis identified four push ...

This paper reports results from an investigation into the suction caissons failure mechanisms under vertical pull-out loads. An insight to the failure mechanisms of suction caissons paves the path for developing analytical solutions to their pull-out capacity. The numerical models of suction caissons have first been calibrated by and verified against several experimental data from other researc...

The effect of zinc phosphate (ZP) and zinc calcium phosphate (ZCP) coatings on the reinforcing mechanisms of smooth steel fiber in cementitious matrix have been studied. The results of pull out tests illustrated that by coating smooth steel fiber the pull-out load may be increased up to 100%. The effect of zinc phosphate coating on interface bonding was more than zinc-calcium phosphate coating....