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Cascaded Residual Dense Networks for Dynamic MR Imaging with Edge-Enhanced Loss Constraint
Ziwen Ke,Yanjie Zhu,Dong Liang 대한자기공명의과학회 2020 Investigative Magnetic Resonance Imaging Vol.24 No.4
Dynamic magnetic resonance (MR) imaging has generated great research interest, because it can provide both spatial and temporal information for clinical diagnosis. However, slow imaging speed or long scanning time is still a challenge for dynamic MR imaging. Most existing methods reconstruct dynamic MR images from incomplete k -space data under the guidance of compressed sensing (CS) or lowrank theory, which suffer from long iterative reconstruction time. Recently, deep learning has shown great potential in accelerating dynamic MR. Our previous work proposed a dynamic MR imaging method with both k-space and spatial prior knowledge integrated via multi-supervised network training. Nevertheless, there was still some smoothing needed in the reconstructed images at high acceleration. In this work, we propose cascaded residual dense networks for dynamic MR imaging with edge-enhanced loss constraint, dubbed cascaded residual dense networks (CRDN). Specifically, the cascaded residual dense networks fully exploit the hierarchical features from all the convolutional layers with both local and global feature fusion. We further use the higher-degree total variation loss function, which has the edge enhancement properties, for training the networks.
Jiang, Ziwen,Chen, Huanzhen 한국전산응용수학회 1998 Journal of applied mathematics & informatics Vol.5 No.1
Mixed finite element method is developed to approxi-mate the solution of the initial-boundary value problem for a strongly nonlinear second-order hyperbolic equation in divergence form. Exis-tence and uniqueness of the approximation are proved and optimal-order $L\infty$-in-time $L^2$-in-space a priori error estimates are derived for both the scalar and vector functions approximated by the method.
SECOND ORDER GENERALIZED DIFFERENCE METHODS OR ONE DIMENSIONAL PARABOLIC EQUATIONS
Jiang, Ziwen,Sun, Jian 한국전산응용수학회 1999 Journal of applied mathematics & informatics Vol.6 No.1
In this paper the second order semi-discrete and full dis-crete generalized difference schemes for one dimensional parabolic equa-tions are constructed and the optimal order $H^1$ , $L^2$ error estimates and superconvergence results in TEX>$H^1$</TEX> are obtained. The results in this paper perfect the theory of generalized difference methods.
Jiang, Ziwen 한국전산응용수학회 1999 Journal of applied mathematics & informatics Vol.6 No.1
In this paper we consider the second order generalized difference scheme for the two-point boundary value problem and ob-tain optimal order error estimates in $L^\infty$ and $W^{1,\infty}$ The results in this paper perfect the theory of the second order generalized difference method.
Seismic Coefficients and Earthquake Damage Predictions for a Space Truss with a Supporting Structure
Zailin Yang,Ziwen Wang,Yang Yong,Menghan Sun 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.4
Previous studies have shown that when the lower support structure is considered, the dynamic characteristics of grid structures change signifi cantly, and the stress distributions are also noticeably diff erent. Therefore, this paper discusses whether other simple and feasible structural seismic damage prediction methods could be proposed after accounting for the infl uence of the lower supporting structure. Considering diff erent site types and diff erent intensities, a time-history analysis was conducted using the mode decomposition response spectrum method for frequent 8- and 9-degree earthquake intensity. Then, the acceleration response spectra for diff erent sites experiencing 8- and 9-degree intensity of frequently occurring earthquakes specifi ed in the Code for Seismic Design of Buildings (GB50011-2010) were used to calculate and discuss the distribution law for the seismic internal forces of space truss structures. Based on the calculation conclusion, the design method and damage prediction method for a plate-like space truss structure under earthquake actions are discussed. Then, a new value of the seismic action coeffi cient was proposed in this paper, and the ground motion peaks for various types of earthquake damage for diff erent site types were obtained using the functional relationship.
Yanfei Qin,Ziwen Sun 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.7
By fully taking the effects of data injection attacks and nonlinear disturbances into consideration, based on dynamic asynchronous event-triggered approach, an observer asynchronous event-triggered robust H∞ adaptive switching method is proposed for the stability of ICPSs. On the one hand, an adaptive feedback controller is designed to resist the negative influence of data injection attacks in systems. On the other hand, a Luenberger state observer is designed to reconstruct a reliable estimate of the whole system state. Finally, the advantage of the presented approach is illustrated by some simulation results.
A characteristics-mixed finite element method for Burgers' equation
Huanzhen Chen,Ziwen Jiang 한국전산응용수학회 2004 Journal of applied mathematics & informatics Vol.15 No.-
In this paper, we propose a new mixed nite element method,called the characteristics-mixed method, for approximating the solution toBurgers’ equation. This method is based upon a space-time variationalform of Burgers’ equation. The hyperbolic part of the equation is approx-imated along the characteristics in time and the diusion part is approx-imated by a mixed nite element method of lowest order. The schemeis locally conservative since uid is transported along the approximatecharacteristics on the discrete level and the test function can be piece-wise constant. Our analysis show the new method approximate the scalarunknown and the vector ux optimally and simultaneously. We also showthis scheme has much smaller time-truncation errors than those of standardmethods. Numerical example is presented to show that the new scheme iseasily implemented, shocks and boundary layers are handled with almostno oscillations.One of the contributions of the paper is to show how the optimal errorestimates in L2(Ωare obtained which are much more dicult than inthe standard nite element methods. These results seem to be new in theliterature of nite element methods.
Elasticity Analysis of Hierarchical Road Network Performance Based on Modified Logit Models
Minghua Zeng,Ziwen Ling,Bing Zhang,Xiyan Huang 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.10
This paper investigates the impact of Variable Message Sign (VMS), stochasticity and hierarchy on the performance of a road network in the context of four typical Logit model types. These models are multinomial Logit (MNL), C-Logit (CL), Path Size Logit (PSL) and Cross-nested Logit (CNL). We quantify the road hierarchy and use the quantified hierarchy to calculate generalized path costs. Then, VMS information is quantified and integrated with the hierarchical property to calculate road “length. Furthermore, these calculation methods are applied to propose modified versions of the MNL, CL, PSL and CNL. Numerical calculations produce negative values of the dispersion elasticity and hierarchical elasticity of total travel time costs obtained from each Logit model. The results also show that the dispersion parameter, hierarchical structure and VMS information have significant and different impacts on the elasticity. The quantitative interactions among these factors, models and performance are practically useful for network design and management.
Farhad Aslani,Brian Uy,Ziwen Wang,Vipul Patel 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.22 No.5
While extensive efforts have been made in the past to develop finite element models (FEMs) for concrete-filled steel tubular columns (CFSTCs), these models may not be suitable to be used in some cases, especially in view of the utilisation of high strength steel and high strength concrete. A method is presented herein to predict the complete stress-strain curve of concrete subjected to tri-axial compressive stresses caused by axial load coupled with lateral pressure due to the confinement action in square and rectangular CFSTCs with normal and high strength materials. To evaluate the lateral pressure exerted on the concrete in square and rectangular shaped columns, an accurately developed FEM which incorporates the effects of initial local imperfections and residual stresses using the commercial program ABAQUS is adopted. Subsequently, an extensive parametric study is conducted herein to propose an empirical equation for the maximum average lateral pressure, which depends on the material and geometric properties of the columns. The analysis parameters include the concrete compressive strength (<i>f</i><i><sub>c</sub></i> = 20 - 110 N/mm<sup>2</sup>), steel yield strength (<i>f<sub>y</sub></i> = 220 - 850 N/mm<sup>2</sup>), width-to-thickness (<i>B/t</i>) ratios in the range of 15-52, as well as the length-to-width (<i>L/B</i>) ratios in the range of 2-4. The predictions of the behaviour, ultimate axial strengths, and failure modes are compared with the available experimental results to verify the accuracy of the models developed. Furthermore, a design model is proposed for short square and rectangular CFSTCs. Additionally, comparisons with the prediction of axial load capacity by using the proposed design model, Australian Standard and Eurocode 4 code provisions for box composite columns are carried out.