Abstract An ultrashort H‐plane sheet beam traveling‐wave tube (SB‐TWT) coupler without transition structure is proposed. The adopts a new idea of directly coupling the microwave from slow‐wave circuit (SWC) and optimizes matching by introducing an asymmetric circular ridge on E‐plane coupled waveguide. As result, length SB‐TWT reduced more than 3λ to 1λ. At same time, tunnel area enlarged twice...

We compute the exact equation of state of circular strings in the (2+1) dimensional de Sitter (dS) and anti de Sitter (AdS) spacetimes, and analyze its properties for the different (oscillating, contracting and expanding) strings. The string equation of state has the perfect fluid form P = (γ − 1)E, with the pressure and energy expressed closely and completely in terms of elliptic functions, th...

This paper analyzes the measurement error, caused by the position of the current-carrying conductor, of a circular array of magnetic sensors for current measurement. The circular array of magnetic sensors is an effective approach for AC or DC non-contact measurement, as it is low-cost, light-weight, has a large linear range, wide bandwidth, and low noise. Especially, it has been claimed that su...

the construction of underground tunnel plays a more and more important role in the development of big cities. one of the most important problems caused by the construction of the tunnel is that underground excavation will cause large settlement of the ground and buildings. previous studied showed the difference between numerical and experimental results. in this study the case study of niyayesh...

Modern technology has been used to build tunnels in recent years by means of drilling machines (TBM) that were used for civil engineering work in large cities to reduce the harmful effects of spending on the surface of the earth significantly. To build the tunnel, numerical modeling was used on the basis of the finite element method to predict stress behavior during the tunnel construction proc...

Uncertainty is an essential property of rock mechanics and engineering, which great significance to excavation, design, control engineering. In this study, innovative framework the reliability-based design was developed for tunnel under uncertainty. The convergence-confinement method used characterize interaction mechanism between support structure surrounding mass. Artificial bee colony (ABC) ...