Millimeter-wave (mmWave) communication has been considered as a promising communication system with large spectrum resource available. In mmWave communication systems, in order to overcome severe path-loss, beamforming technology is required to form narrow beam and generate high directional antenna gain. This will result in frequent beam handoff and severe link blockage, especially in mobile sc...

In this paper, we present a new algorithmic paradigm for cone-beam image reconstruction. The new class of algorithms, referred to as cone-beam reconstruction by moving frames, enables numerical implementation of exact cone-beam inversion using its intrinsic geometry. In particular, our algorithm allows a 3-D discrete approach to the differentiation-backprojection operator on the curved manifold...

Abstract We propose and analyze a scheme to generate enhanced narrow-band terahertz (THz) radiation through down-conversion of the frequency of optical lasers using laser-modulated electron beams. In the scheme the electron beam is first energy modulated by two lasers with wave numbers k1 and k2, respectively. After passing through a dispersion section, the energy modulation is converted to den...

Efficiently calculating accurate soft shadows cast by area light sources remains a difficult problem. Ray tracing based approaches are subject to noise or banding, and most other accurate methods either scale poorly with scene geometry or place restrictions on geometry and/or light source size and shape. Beam tracing is one solution which has historically been considered too slow and complicate...

In the paper, the geometrical parameters and energetics of the extremely narrow pseudo-nondiffracting beams with the spot size of several micrometers are examined. The main attention is focused on design, realization and testing of the set-up enabling conversion of the laser diode beam or the fiber mode to the narrow Bessel-Gauss beam whose spot can be continuously relocated across the plane pe...

PURPOSE The purpose is to evaluate effects of a new radiotherapy protocol, microbeam radiation therapy, on the artery wall. In previous studies on animal models, it was shown that capillaries recover well from hectogray doses of X-rays delivered in arrays of narrow (< or = 50 microm) beams with a minimum spacing of 200 microm. Here, short- and long-term effects of comparable microplanar beam co...

The application of directional antennas in wireless ad hoc networks brings numerous benefits, such as increased spatial reuse and mitigated interference. Most MAC protocols with directional antennas are based on the RTS/CTS mechanism which works well in wireless ad hoc networks using omni-directional antennas. However, RTS/CTS frames cannot mitigate the interference completely. Besides, they al...

analyzing the nonlinear vibration of beams is one of the important issues in structural engineering. according to this, an impressive analytical method which is called modified iteration perturbation method (mipm) is used to obtain the behavior and frequency of a cantilever beam with geometric nonlinear. this new method is combined by the mickens and iteration methods. moreover, this method don...