Dual-band bandstop filters using open-circuited stub-loaded resonators are presented. The first and second resonant frequencies of the opencircuited stub-loaded resonator can be flexibly controlled ...by tuning the length and position of the open-circuited stub. To illustrate the concept, a dual-band bandstop filter has been designed, fabricated and measured. The prototype of the dual-band bandstop filter achieved attenuation of 42 and 44 dB at 2.4 and 5.2 GHz. PUBLICATION ABSTRACT
Attenuation map or measurements based on local attenuation coefficient slope (ACS) in quantitative ultrasound (QUS) has shown potential for diagnosis of liver steatosis. In liver cancers, tissue ...abnormalities and tumors detected using ACS are also of interest to provide new image contrast to clinicians. Current phantom-based approaches have the limitation of assuming comparable speed of sound between the reference phantom and insonified tissues. Moreover, these methods present the inconvenience for operators to acquire data on phantoms as well as on patients. The main goal was to alleviate these drawbacks by proposing a methodology for constructing phantom-free regularized (PF-R) local ACS maps and investigate the performance in both homogeneous and heterogeneous media. The proposed method was tested on two tissue mimicking media with different ACS constructed as homogeneous phantoms, side-by-side and top-to-bottom phantoms, and inclusion phantoms with different attenuations. Moreover, an in-vivo proof-of-concept was performed on healthy, steatotic and cancerous human liver datasets. Modifications brought to previous works include: a) a linear interpolation of the power spectrum in log-scale; b) the relaxation of the underlying hypothesis on the diffraction factor; c) a generalization to nonhomogeneous local ACS; and d) an adaptive restriction of frequencies to a more reliable range than the usable frequency range. Regularization was formulated as a generalized LASSO, and a variant of the Bayesian Information Criterion (BIC) was applied to estimate the Lagrangian multiplier on the LASSO constraint. In addition, we evaluated the proposed algorithm when applying median filtering before and after regularization. Tests conducted showed that the PF-R yielded robust results in all tested conditions, suggesting potential for additional validation as a diagnosis method.
The SC EXCELL (Stratiform/Convective EXponential CELL) model, originally devised for the prediction of the complementary cumulative distribution function of rain attenuation (henceforth P(A)) on ...Earth-space radio links, is tested here in its ability to predict also the P(A) on terrestrial links. Thanks to its physical soundness in representing the rainfall environment, the proposed method does not require any calibration procedure on existing data, as is typically the case of most of the semi-empirical models proposed so far. When tested against the global DBSG3 database made available by the International Telecommunication Union - Radiocommunication Sector (ITU-R), the proposed model shows an improvement in the prediction accuracy with respect to the method currently recommended by the ITU-R. PUBLICATION ABSTRACT
This paper proposes a type of substrate integrated waveguide (SIW) 'corner cavity'. For each corner cavity, two transmission zeros (TZ) can be introduced and the location of either TZ can easily be ...controlled by adjusting suitable geometrical parameters. Using the corner cavities, a novel SIW filter with wide stopband characteristic is implemented. The central frequency of the filter is 20 GHz, and the first spurious appears at about 40 GHz, which is two times the central frequency. In addition, the measured stopband attenuation of the filter is better than 50 dB from 21.24 to 37.71 GHz.
This paper presents a new method to construct a decentralized nonlinear robust H super(infin) controller for a class of large-scale nonlinear uncertain systems. The admissible uncertainties and ...nonlinearities in the system satisfy integral quadratic constraints and global Lipschitz conditions, respectively. The decentralized controller, which is required to be stable, is capable of exploiting known nonlinearities and interconnections between subsystems without treating them as uncertainties. Instead, additional uncertainties are introduced because of the discrepancies between nondecentralized and decentralized nonlinear output feedback controllers. The H super(infin) control objective is to achieve an absolutely stable closed-loop system with a specified disturbance attenuation level. A solution to this control problem involves stabilizing solutions to algebraic Riccati equations parametrized by scaling constants corresponding to the uncertainties and nonlinearities. This formulation is nonconvex; hence, an evolutionary optimization method is applied to solve the control problem considered. Copyright copyright 2012 John Wiley & Sons, Ltd.
This study addresses the issue of robust H^sub ∞^ control for a class of uncertain Takagi-Sugeno fuzzy systems with distributed time delay and non-linear perturbations. By employing a new ...Lyapunov-Krasovskii functional together with linear matrix inequality (LMI) technique, a new set of delay-dependent conditions are derived to achieve the robust stabilisation of uncertain fuzzy systems for a prescribed disturbance attenuation level γ > 0. The state feedback H^sub ∞^ control law can be obtained by solving the corresponding LMIs. Further, some numerical examples are provided to demonstrate the effectiveness of the obtained results. The results reveal that the proposed theory significantly improve the allowable upper bounds of the delays over some existing results. PUBLICATION ABSTRACT
Ultrasound shear wave (SW) elastography has been widely studied and implemented on clinical systems to assess elasticity of living organs. Imaging of SW attenuation reflecting viscous properties of ...tissues has received less attention. A revisited frequency shift method (R-FS) is proposed to improve robustness of SW attenuation imaging. Performances are compared with the frequency-shift (FS) method that we originally proposed, and to the two-point frequency shift (2P-FS) and attenuation measuring ultrasound SW elastography (AMUSE) methods. In the proposed R-FS method, the shape parameter of the gamma distribution fitting SW spectra is assumed to vary with distance, in contrast to FS. Secondly, an adaptive random sample consensus (A-RANSAC) line fitting method is used to prevent outlier attenuation values in the presence of noise. Validation was made on ten simulated phantoms with two viscosities (0.5 and 2 Pa.s) and different noise levels (15 to -5 dB), two experimental homogeneous gel phantoms, and six in vivo liver acquisitions on awake ducks (including three normal and three fatty duck livers). According to conducted experiments, R-FS revealed mean reductions in coefficients of variation (CV) of 62.6% on simulations, 62.5% with phantoms, and 62.3% in vivo compared with FS. Corresponding reductions compared with 2P-FS were 45.4%, 77.1%, and 62.0%, respectively. Reductions in normalized root-mean-square errors for simulations were 63.9% and 48.7% with respect to FS and 2P-FS, respectively.
A user friendly online Photon Shielding and Dosimetry (PSD) software available at https://phy-x.net/PSD has been developed for calculation of parameters relevant to shielding and dosimetry. These ...parameters include linear and mass attenuation coefficients (LAC, MAC), half and tenth value layers (HVL, TVL), mean free path (MFP), effective atomic number and electron density (Zeff, Neff), effective conductivity (Ceff) energy absorption and exposure buildup factors (EABF, EBF). The software can generate data on shielding parameters in the continuous energy region (1 keV-100 GeV). Also, some well-known radioactive sources (22Na, 55Fe, 60Co, 109Cd, 131I, 133Ba, 137Cs, 152Eu and 241Am) along with their energies and some characteristic (K-shell) X-ray energies of Cu, Rb, Mo, Ag, Ba and Tb elements are available in the software and can be selected by the user. Thus, one can obtain the shielding parameters at photon energies available for the predefined energies. Moreover, another parameter relevant to shielding i.e. the fast neutron removal cross section (FNRCS) can be calculated for a compound or a mixture using this software. The software is freely available online after having registered to the Phy-X platform.
•A fast, accurate, practical and free software developed.•All X-ray and gamma shielding parameters are included.•Any element, compound or mixture can be analyzed.•Either mole fraction or weight fraction can be selected.•Calculations can be done for different materials at the same time.
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