A design problem of uniform linear antenna arrays for maximal side lobe level reduction with the constraint of a fixed beam width is dealt with. This problem is modelled as a simple optimization problem. The method of tabu search is used to determine an optimum a set of weights of antenna element that provide a radiation pattern with maximal side lobe level reduction with the constraint of a fi...

Several remedial measures like space diversity, frequency diversity, route diversity, increase in antenna height, antenna tilting, etc. have been tried by many workers to overcome the debilitating effect of multipath fading in fixed line-of-sight microwave and mobile communication links. Among these remedial measures, diversity techniques have been extensively studied in terms of improvement fa...

The origin of nonlinear dynamics traces back to the study of the dynamics of planets with the seminal work of Poincaré at the end of the nineteenth century: Les Méthodes Nouvelles de la Mécanique Céleste, Vols. 1-3 (Gauthier Villars, Paris, 1899). In his work he introduced a methodology fruitful for investigating the dynamical properties of complex systems, which led to the so-called "Poincaré ...

The Stanford Linear Accelerator has been running with polarized electrons both in the collider (SLC) mode and in the fixed target mode. The accelerator's polarized electron source is based on a thin, strained GaAs photocathode, which is held at a negative high voltage and illuminated by a Titanium Sapphire laser. The reliability of the source was better than 95% during the eight-month-long 1993...

We report an electronically switchable dielectric leaky wave antenna. The main beam angle can be electronically steered using p-i-n diodes. The diodes are used as switches to control the radiation from two sets of gratings with different periods, thereby switching the main beam angle. Beam steering is achieved at a single fixed frequency; no frequency sweeping is necessary. A microwave prototyp...

Indiana University has designed and finished construction of the Midwest Proton Radiotherapy Institute (MPRI) [1] consisting of one treatment room with two fixed horizontal beam lines and two treatment rooms with isocentric gantries. The first treatment room has been operating since February 2004, while the first Gantry treatment room has been in use treating patients since April 2007. The prot...

1 Abstract — It is shown that the limited-diffraction Bessel beam of order zero can be generated by a transducer with equal-area division of elements and with a fixed prefocus, i.e. conventional transducers used in medical imaging equipment. The element division implies that the scaling parameter must be chosen to contain the first lobe of the Bessel function in the first element. In addition t...

A 140 GHz high power gyrotron has recently been operated in a 14 T Bitter magnet to characterize emission as a function of magnetic field and beam current. The velocity ratio (or pitch angle) a = (v±.)/(v1 ) of the beam electrons is a critical parameter for high efficiency gyrotron operation and was measured using a capacitive probe located in the beam tunnel before the cavity. The observed vel...

A precise calibrating system for newly adopted beam position monitors (BPM) of upgraded injection system in NSRL phase II project is described. The fitting error of the electric field is presented. Using the calibrating system and the method which has a system error about ±15μm and the precision of 1μm, we have completed the calibration and checking of the quality to the developed equipment. Du...

The nonlinear electrostatic pull-in behaviour of MEMS Switches in micro-electromechanical systems (MEMS) is investigated in this article. We used the distributed model when the electrostatic pressure didn’t apply at the whole of the beam and applied only in the mid-part of the beam. In this part the electrostatic area is different from two other parts. The model uses Euler-Bernoulli beam theory...