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1.
Haowei Zhang Junwei Xie Jiaang Ge Zhaojian Zhang Binfeng Zong 《European Journal of Operational Research》2019,272(3):868-878
A phased array radar (PAR) is used to detect new targets and update the information of those detected targets. Generally, a large number of tasks need to be performed by a single PAR in a finite time horizon. In order to utilize the limited time and the energy resources, it is necessary to provide an efficient task scheduling algorithm. However, the existing radar task scheduling algorithms can't be utilized to release the full potential of the PAR, because of those disadvantages such as full PAR task structure ignored, only good performance in one aspect considered and just heuristic or the meta-heuristic method utilized. Aiming at above issues, an optimization model for the PAR task scheduling and a hybrid adaptively genetic (HAGA) algorithm are proposed. The model considers the full PAR task structure and integrates multiple principles of task scheduling, so that multi-aspect performance can be guaranteed. The HAGA incorporates the improved GA to explore better solutions while using the heuristic task interleaving algorithm to utilize wait intervals to interleave subtasks and calculate fitness values of individuals in efficient manners. Furthermore, the efficiency and the effectiveness of the HAGA are both improved by adopting chaotic sequences for the population initialization, the elite reservation and the mixed ranking selection, as well as designing the adaptive crossover and the adaptive mutation operators. The simulation results demonstrate that the HAGA possesses merits of global exploration, faster convergence, and robustness compared with three state-of-art algorithms—adaptive GA, hybrid GA and highest priority and earliest deadline first heuristic (HPEDF) algorithm. 相似文献
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20 Hz~10 kHz光纤水听器相移灵敏度校准 总被引:3,自引:2,他引:1
利用相位生成载波解调技术精确测量光纤水听器的光相移量,在20 Hz~10 kHz频率范围实现了光纤水听器探头相移灵敏度的校准.20 Hz~1.25 kHz频段采用驻波管比较法进行校准,1.25 kHz~10 kHz频段采用自由场脉冲比较法进行校准.利用本文建立的校准系统,对TMD 35#光纤水听器的相移灵敏度进行校准,校准结果表明,两种方法测得的相移灵敏度具有很好的一致性,在1.25 kHz频率点的相移灵敏度值偏差为0.8 dB.不确定度分析表明,该校准系统的扩展不确定度(k=2)为0.9 dB. 相似文献
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Active cancellation stealth is a smart signal blanking method, that it has become an important developing direction on modern stealth technology. In order to further explore the active cancellation stealth technology, we are considering the detection and cancellation of receiving/transmitting antenna pattern is different. Put forward active cancellation system simulation structure diagram based on MATLAB/SIMULINK, where the phased array radar system as the modelling object, and established the active cancellation stealth system mathematical model based on digital radio frequency memory (DRFM) and the radar signal processing system of the coherent video simulation model, based on linear frequency modulation and radar coherent pulse signal simulation, verified the rationality and validity of the design, as the active cancellation stealth engineering technology laid the foundation. 相似文献
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A new technique for generating a continuous range of true time delay values is introduced. Heating optical fiber in order to change the effective index of the guided mode produces time delays. A 45-m section of single-mode silica fiber is demonstrated to produce a continuous range of time delay values from 0 to 211 ps over a temperature tuning range of 50°C (30–80°C). A thermal time delay factor is introduced and found to be 0.096 ps/m°C for Corning LEAF fiber. A 7.66-m section of multimode Lucina polymer fiber is demonstrated to produce a range of time delay values from 0 to 32 ps over a temperature tuning range of 30°C (30–60°C). The thermal time delay factor for this fiber is −0.1427 ps/m°C. 相似文献
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This paper presented development work of an in situ method for damage detection in thin-wall structures using embedded two-dimensional ultrasonic phased arrays. Piezoelectric wafer active sensors were used to generate and receive guided Lamb waves propagating in the plate-like structure. The development of a generic beamforming algorithm that does not require parallel ray assumption through using full wave propagation paths is described. A virtual beam steering method and device, the embedded ultrasonic structural radar, was implemented as a signal post-processing procedure. Several two-dimensional configurations were investigated and compared with beamforming simulation. Finally, rectangular shape arrays were developed for verifying the generic formulas and omnidirectionality. The rectangular arrays yield good directionality within the 360° full range and are able to detect damage anywhere in the entire plate. 相似文献
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In vivo diffusion tensor imaging (DTI) of rat cervical and thoracic spinal cord was performed using a three-element phased array coil at 7 T. The magnetic field was shimmed over the spinal cord in real time using an in-house developed automatic algorithm. Echo planar imaging (EPI)-based diffusion-weighted images (DWIs) were acquired with 21 gradient encoding directions. The DWIs were tensor encoded, and diffusion tensor metrics, fractional anisotropy (FA), mean diffusivity (MD), longitudinal diffusivity (λ0) and transverse diffusivity (λ) were determined for both white matter (WM) and gray matter (GM). The results on six normal rats indicated no significant differences in the diffusion tensor metrics between thoracic and cervical regions. However, the DTI-derived metrics in cervical spinal cord from our study are somewhat different from the published results in rats. The possible reasons for these differences are suggested. 相似文献
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Q. Md. Alfred T. Chakravarty G. Singh S. K. Sanyal 《International Journal of Infrared and Millimeter Waves》2007,28(10):881-887
In radar, planar phased array antenna plays vital role in electronic scanning in the azimuth and elevation direction to the
horizon. In most operations using planar phased array both the coordinates of azimuth and elevation, are steered electronically.
In this paper a conceptual schematic of a phased array antenna with programmable time delay units has been presented. It is
shown that by suitably exploiting the time delay matrix one can have electronic beam rotation around the target axis as required
in conical scan. Thus both the elevation and azimuth motors in conical scan system are replaced by electronic scanning. Heuristically,
we have selected eight consecutive points for beam rotation in a polygon shape and can also be extended almost circular shape
by increasing number of array elements and phase shifter (delays) in the delay matrix. The array requires dual control of
phase gradient and individual phase values. The whole array is controlled by micro-controller. This presents exciting possibilities
in radar operation. 相似文献
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N. Pathak G. K. Mahanti T. K. Sinha Mahapatra 《International Journal of Infrared and Millimeter Waves》2007,28(11):953-960
In this paper, we present a new method based on real-coded Genetic Algorithm (GA) with elitist model for optimal design of
a reconfigurable symmetrical dual-beam uniformly spaced linear isotropic antenna array with phase-only control of quantized
phase shifters. The problem is to find a common amplitude distribution that will generate a pencil beam with zero phases and
a flat-top beam with discrete phases of a six-bit discrete phase shifter, without or with pre-fixing the value of dynamic
range ratio (|I
max/I
min|) of excitation current amplitude distribution equal to or less than five. 相似文献
10.
Vossen M Teeuwisse W Reijnierse M Collins CM Smith NB Webb AG 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,208(2):291-297
We describe the design and testing of a quadrature transmit, eight-channel receive array RF coil configuration for the acquisition of images of the entire human spinal column at 7 T. Imaging parameters were selected to enable data acquisition in a clinically relevant scan time. Large field-of-view (FOV) scanning enabled sagittal imaging of the spine in two or three-stations, depending upon the height of the volunteer, with a total scan time of between 10 and 15 min. A total of 10 volunteers have been scanned, with results presented for the three subjects spanning the range of heights and weights, namely one female (1.6 m, 50 kg), one average male (1.8 m, 70 kg), and one large male (1.9 m, 100 kg). 相似文献