Search results for "Signal processing"
showing 10 items of 2451 documents
Double-pulse single-beam grazing-incidence pumping
2011
The paper reports on the optimization of a table-top nickel-like molybdenum transient collisionally excited soft x-ray laser (SXRL) at 18.9 nm, performed by double-pulse single beam grazing incidence pumping (DGRIP) [1]. This scheme allows for the first time the full control of the pump laser parameters including the pre-pulse duration, optimally generating the SXRL amplifier under grazing incidence. The single beam geometry of collinear double-pulse propagation guarantees the ideal overlap of the pre- and main pulse from shot to shot, resulting in a more efficient, highly stable SXRL output. SXRL energies up to 2.2 µJ are obtained with a total pump energy less than 1 J for several hours at…
Broadband microwave gas sensor: A coaxial design
2010
The method of gas detection by a broadband microwave gas sensor is presented in this article. The principle of this method is to use a sensitive material as substrate of a transmission coaxial line. The sensor represents an open line with an extreme surface in contact with gas. The interaction with the gas and the surface induces a dielectric variation of the substrate. From experimental results, the interaction between the sensitive material and each tested gas present a specific frequency spectrum of the reflection coefficient at the input of the line. The proposed method has the advantage of a compact size, wide bandwidth, simple structure, and capable with all sensitive materials. © 201…
Optical thermal filters for eXTP: manufacturing and characterization
2020
In order to ensure the effective detection of X-ray astronomical detectors by blocking ultraviolet, visible and infrared light, adding optical thermal filter in front of the load is an effective method. According to the scientific requirements of eXTP, optical thermal filters with aluminized polyimide (PI) film structure had been designed and tested in this paper, the results of mechanical tests including burst pressure, vibration and acoustic tests, also the transparent properties of optics in UV, Vis and IR lights are presented. The mechanical test results show that the filters for LAD and SFA can't pass the acoustic tests, causing the thickness of PI should be increased or a nickel mesh …
Chirped fibre Bragg gratings for phased-array antennas
1997
A variable delay line for phased-array antennas based on a chirped fibre Bragg grating is demonstrated. The time delay of a microwave modulating signal is modified by scanning in wavelength a chirped grating. In this initial experiment, time delay variations up to 556 ps have been achieved using a grating of 0.4 nm bandwidth and 6 cm length and modulating in the frequency range 390 MHz-5.20 GHz.
Time‐Domain Integration of Broadband Terahertz Pulses in a Tapered Two‐Wire Waveguide
2021
In this work, the time-domain integration of broadband terahertz (THz) pulses via a tapered two-wire waveguide (TTWWG) is reported. Such a guiding structure consists of two metallic wires separated by a variable air gap that shrinks down to a subwavelength size as the movement takes from the waveguide input to its output. It is shown that while an input THz pulse propagates toward the subwavelength output gap, it is reshaped into its first-order time integral waveform. In order to prove the TTWWG time integration functionality, the THz pulse is detected directly within the output gap of the waveguide, so as to prevent the outcoupling diffraction from altering the shape of the time-integrate…
Bayesian estimation of edge orientations in junctions
1999
Abstract Junctions, defined as those points of an image where two or more edges meet, play a significant role in many computer vision applications. Junction detection is a widely treated problem, and some detectors can provide even the directions of the edges that meet in a junction. The main objective of this paper is the precise estimation of such directions. It is supposed that the junction point has been previously found by some detector. Also, it is assumed that samples, possibly noisy, of orientations of the edges found in a circular window surrounding the point are available. A mixture of von Mises distributions is assumed for these data, and then a Bayesian methodology is applied to…
Data-Driven Pump Scheduling for Cost Minimization in Water Networks
2021
Pumps consume a significant amount of energy in a water distribution network (WDN). With the emergence of dynamic energy cost, the pump scheduling as per user demand is a computationally challenging task. Computing the decision variables of pump scheduling relies over mixed integer optimization (MIO) formulations. However, MIO formulations are NP-hard in general and solving such problems is inefficient in terms of computation time and memory. Moreover, the computational complexity of solving such MIO formulations increases exponentially with the size of the WDN. As an alternative, we propose a data-driven approach to estimate the decision variables of pump scheduling using deep neural netwo…
Explicit Recursive and Adaptive Filtering in Reproducing Kernel Hilbert Spaces
2014
This brief presents a methodology to develop recursive filters in reproducing kernel Hilbert spaces. Unlike previous approaches that exploit the kernel trick on filtered and then mapped samples, we explicitly define the model recursivity in the Hilbert space. For that, we exploit some properties of functional analysis and recursive computation of dot products without the need of preimaging or a training dataset. We illustrate the feasibility of the methodology in the particular case of the $\gamma$ -filter, which is an infinite impulse response filter with controlled stability and memory depth. Different algorithmic formulations emerge from the signal model. Experiments in chaotic and elect…
Partial joint processing with efficient backhauling using particle swarm optimization
2012
In cellular communication systems with frequency reuse factor of one, user terminals (UT) at the cell-edge are prone to intercell interference. Joint processing is one of the coordinated multipoint transmission techniques proposed to mitigate this interference. In the case of centralized joint processing, the channel state information fed back by the users need to be available at the central coordination node for precoding. The precoding weights (with the user data) need to be available at the corresponding base stations to serve the UTs. These increase the backhaul traffic. In this article, partial joint processing (PJP) is considered as a general framework that allows reducing the amount …
Functional A Posteriori Error Estimates for Time-Periodic Parabolic Optimal Control Problems
2015
This article is devoted to the a posteriori error analysis of multiharmonic finite element approximations to distributed optimal control problems with time-periodic state equations of parabolic type. We derive a posteriori estimates of the functional type, which are easily computable and provide guaranteed upper bounds for the state and co-state errors as well as for the cost functional. These theoretical results are confirmed by several numerical tests that show high efficiency of the a posteriori error bounds. peerReviewed