To achieve multi-GeV electron energies in the laser wakefield accelerator (LWFA) it is necessary to propagate an intense laser pulse long distances in plasma without disruption. A 3D envelope equation for a laser pulse in a tapered plasma channel is derived, which includes wakefields and relativistic and nonparaxial effects, such as finite pulse length and group velocity dispersion. It is shown...

The diverging and converging components of localized wave solutions are studied within the framework of both the Whittaker and Weyl plane wave expansions. The specific example of the splash pulse is considered because its evanescent components could be derived in an explicit closed form. It is shown that, in the Weyl picture, the evanescent fields associated with the diverging and converging co...

The Wenchuan earthquake of 12 May 2008 is the most destructive earthquake in China in the past 30 years in terms of property damage and human losses. In order to understand the earthquake process and the geo-morphological factors affecting the seismic hazard, we simulated the strong ground motion caused by the earthquake, incorporating three-dimensional (3D) earth structure, finite-fault ruptur...

In this work, we experimentally investigate several temporal and spectral methods to highlight extreme fluctuations which can develop during the Raman amplification of an ultrashort pulse train. Forward and backward pumping schemes are compared to dual pass configurations.

Dolph-Chebychev arrays are known to exhibit the best compromise between sidelobe level and directivity. However, they place a constraint on the null locations. Any attempt to impose nulls or get them deeper will impact the directivity/sidelobe level trade-off. In this work, null placement in Dolph-Chebychev arrays through element position perturbation is carried out based on Taguchi method whil...

This paper gives an analysis of operation of a self-phased array under conditions of multipath propagation (either reflections or jamming signals). A general method for the calculation of directivity of such an array has been proposed. Influence of reflections by way of the pilot signal channel as well as by way of the primary signal channel is taken into account. Some limitations of the approa...

A measurement system is presented that allows large aperture measurements with a high angular resolution and that is still compact and thus convenient for portable use. Theoretical considerations show that a cardioid microphone characteristic is desireable to achieve a low amplification of sensor noise throughout the audio frequency range. The directivity of real cardioid microphones, however, ...

In these research paper two designs such as rectangular microstrip antenna and concentric equilateral triangular microstrip antenna are presented. The resonant frequency of this antenna is 8 GHz suitable for wireless applications. The antenna is fed by microstrip feeding technique. Design of an antenna using ADS (Advanced Design System), based on MoM (Method of Moments) has been used to analyze...

A method for the joint localization and orientation estimation of a directional sound source using distributed microphones is presented. By modeling the signal attenuation due to the microphone directivity, the source directivity, and the source-microphone distance, a multi-dimensional search over all possible sound source locations and orientations is performed. This sound source scene reconst...

This paper increases directivity and gain of Small Planar Dipole Antenna (SPDA) by using Symmetrical Pyramidal Block (SPB) which operates in X band at 11 GHz. The SPB consists four sides; each of which is metamaterial with Epsilon Negative Medium (ENG) and Epsilon Near-Zero (ENZ). The results simulated using the High Frequency Structure Simulator (HFSS) show that the SPB is capable of enhancing...