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Laplacian and bilateral weighted relative total variation sparse angle CT reconstruction

PHYSICA SCRIPTA 2024年第10期99卷 105212-105212页

作者： Du, Xiaoshuang Kong, Huihua Pan, Jinxiao Qi, Ziwen Li, Jiaxin North Univ China Sch Math Taiyuan 030051 Shanxi Peoples R China North Univ China Shanxi Key Lab Intelligent Detect Technol & Equipm Taiyuan 030051 Shanxi Peoples R China

Reconstruction of computed tomography (CT) images under sparse data conditions often leads to compromised quality, which can result in diagnostic inaccuracies. This study introduces a novel iterative reconstruction algorithm that combines a second-order differential Laplacian operator with a bilateral weighted relative total variation model to enhance the CT image quality from sparse datasets. The approach is designed to efficiently capture sharp edges and fine textures while reducing noise and maintaining critical edge features. Numerical simulations and preliminary clinical testing demonstrate that the algorithm significantly reduces streak artifacts and improves edge clarity, outperforming traditional methods in both qualitative and quantitative analyses. In summary, the developed iterative reconstruction algorithm substantially enhances the reconstruction quality of CT images with sparse data, showing significant advantages over conventional techniques, and promises to significantly improve the accuracy and reliability of clinical imaging diagnostics.

关键词： CT sparse reconstruction iterative optimisation algorithm Laplacian operator bilateral weighted relative total variation

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Physical layer security of interference aligned mixed RF/unified-FSO relaying network

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IET COMMUNICATIONS 2020年第14期14卷 2282-2293页

作者： Tubail, Deeb El-Absi, Mohammed Salhab, Anas Ikki, Salama Zummo, Salam Kaiser, Thomas Palestinian Technol Res Ctr Gaza Strip Palestine Duisburg Essen Univ Duisburg Germany King Fahd Univ Petr & Minerals Dhahran Saudi Arabia Lakehead Univ Thunder Bay ON Canada

In this study, the authors secure the mixed radio frequency/free space optical (FSO) relay-aided interference aligned system using a proposed physical layer security algorithm. This algorithm reduces the quality of the received signal at the eavesdropper through two procedures. First, it minimises the data transmission power from the legitimate users and the relays. Second, it jams the eavesdropper by broadcasting artificial noise from the users and the relays. Therefore, a joint optimisation problem is formulated to degrade the received signal at the eavesdropper from the users and the relays and to maximise the jamming artificial noise power, which is solved using an iterative optimisation algorithm beside a semi-definitive programming algorithm. Furthermore, the pre-coding and decoding matrices of the users and the relay are designed to enable the legitimate users to cancel the artificial noise, while the eavesdropper is disabled from distinguishing the artificial noise from the real streams. Moreover, the security performance of the proposed algorithm is analysed, and the impact of the FSO link's state on the security performance is studied. The extensive simulation results show the efficiency of the proposed algorithm and illustrate the role of the FSO link's state on the security performance.

关键词： radiofrequency interference free-space optical communication relay networks (telecommunication) telecommunication security jamming optimisation decoding precoding interference suppression mixed RF unified-FSO relaying network relay-aided interference aligned system physical layer security algorithm data transmission power joint optimisation problem jamming artificial noise power maximisation iterative optimisation algorithm semidefinitive programming algorithm pre-coding matrice decoding matrice artificial noise cancellation FSO link state security performance

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Max-min fair wireless energy transfer for multiple-input multiple-output wiretap channels

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IET COMMUNICATIONS 2016年第7期10卷 739-744页

作者： Wu, Wei Zhang, Xueqi Wang, Shaohang Wang, Baoyun Nanjing Univ Posts & Telecommun Coll Commun & Informat Nanjing 210003 Jiangsu Peoples R China

In this study, the authors study the max-min fairness for wireless energy transfer in a multiuser multiple-input multiple-output communication system with simultaneous wireless information and power transfer. In particular, they aim to maximise the minimum harvested energy among the multiple multi-antenna energy receivers while guaranteeing secure communication for multi-antenna information receiver. The dual use of artificial noise to facilitate both wireless energy transfer and secure communication is exploited in the authors' proposed problem. Both scenarios of perfect and imperfect channel state information (CSI) known at the transmitter are considered. For the perfect CSI case, the formulated max-min energy harvesting (MM-EH) problem is non-convex and intractable. To circumvent it, an iterative optimisation algorithm based on Taylor series expansion is proposed. Then, they turn their attention to the imperfect CSI case, where a max-min robust energy harvesting (MMR-EH) problem is considered. Though the MMR-EH problem is more complicated than the MM-EH problem, they reveal that the iterative optimisation method can be extended to the solution of the former, wherein the S-procedure is introduced. Simulation results show the efficiency of their proposed solutions in terms of energy harvesting.

关键词： inductive power transmission MIMO communication telecommunication security energy harvesting antenna arrays receiving antennas concave programming iterative methods multiuser channels wireless channels transmitting antennas max-min fair wireless energy transfer multiple-input multiple-output wiretap channels multiuser multiple-input multiple-output communication system simultaneous wireless information transfer simultaneous wireless power transfer multiple multiantenna energy receivers secure communication multiantenna information receiver perfect channel state information imperfect channel state information max-min robust energy harvesting problem nonconvex problem iterative optimisation algorithm Taylor series expansion MM-EH problem S-procedure

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Asynchronous algorithms for distributed optimisation and application to distributed regression with robustness to outliers

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IET CONTROL THEORY AND APPLICATIONS 2013年第17期7卷 2084-2089页

作者： Liu, Weikai Hua, Zeng Wuhan Inst Technol Sch Sci Wuhan 430073 Peoples R China

This study presents an asynchronous algorithm for distributed constrained optimisation problems in networks of agents. The iterative optimisation algorithm maintains a local estimate at each node and depends on local gradient or gradient-like updates in combination with a consensus policy, where an agent averages its own value with a current or outdated value of another. This asynchronous scheme does not require that agents exchange state information frequently, so it is more energy-efficient and more realistic than the synchronous one. Moreover, the proposed algorithm is fully distributed, that is, all agents only share data with their neighbours through local broadcasts. The proposed algorithm is applied to a distributed regression problem with robustness to outliers in sensor networks. Simulation results are provided to demonstrate the validity and superiority of the proposed scheme.

关键词： constraint handling gradient methods multi-agent systems multi-robot systems network theory (graphs) optimisation regression analysis asynchronous algorithm distributed regression problem outlier robustness distributed constrained optimisation problem iterative optimisation algorithm local gradient update gradient-like update consensus policy sensor network agent network

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Gaussian mixture image restoration based on maximum correntropy criterion

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ELECTRONICS LETTERS 2017年第11期53卷 717-718页

作者： Su, Zhenming Yang, Ling Zhu, Simiao Si, Ningbo Lv, Xin Lanzhou Univ Sch Informat Sci & Engn Lanzhou 730000 Peoples R China

Using Gaussian mixture model (GMM) as a patch prior has achieved great success in image restoration (IR). However, based on the derivations, the objective function of the conventional GMM-based IR methods can be expressed as the minimum of mean square error (MMSE) criterion based optimisation problem. As outliers may exist in the patch cluster obtained even within a spatially constrained window and MMSE is sensitive to outliers, using the MMSE criterion based strategy would lead to error results. A maximum correntropy criterion (MCC) based IR method with GMM as a patch prior is proposed. The proposed method can automatically identify outliers and assign weight for each patch within the k-nearest-neighbour patches with respect to each exemplar patch in the image and thus can robustly estimate the Gaussian parameters which results in more accurate estimation of the image patches. Finally, an effective iterative optimisation algorithm is designed to solve the proposed objective function under the MCC criterion. The experimental results for image inpainting demonstrate the capabilities of the proposed method.

关键词： maximum correntropy criterion MCC criterion Interpolation and function approximation (numerical analysis) minimum of mean square error criterion iterative optimisation algorithm optimisation image restoration maximum entropy methods Computer vision and image processing techniques Gaussian mixture model Other topics in statistics least mean squares methods Optical, image and video signal processing GMM iterative methods MMSE criterion optimisation techniques objective function image patches mixture models exemplar patch image inpainting k-nearest-neighbour patches patch cluster Gaussian processes

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Spaceborne SAR attitude steering method for smart imaging mode

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ELECTRONICS LETTERS 2017年第6期53卷 428-430页

作者： Yang, Wei Ma, Xiao-Cong Liu, Wei Chen, Jie Beihang Univ Sch Elect & Informat Engn Beijing 100191 Peoples R China Univ Sheffield Dept Elect & Elect Engn Sheffield S10 2TN S Yorkshire England

The current spaceborne synthetic aperture radar systems are operated to illuminate the scene along the satellite flying direction. However, in many cases, the interested areas are not parallel to the flying direction, so an innovative smart imaging mode is acquired, which can be employed for illuminating scene along a given direction. A novel three-axis attitude steering method is proposed for smart imaging mode. First, mathematical model of the attitude steering is built by considering the restrictive conditions of zero-Doppler centroid requirement and the position of interested area. Then, an iterative optimisation algorithm is designed to calculate the three-axis steering angles. Finally, experiment results using the satellite tool kit tool validate the proposed methods well, especially in the case of coastline imaging.

关键词： spaceborne radar synthetic aperture radar radar imaging stereo image processing iterative methods optimisation spaceborne SAR attitude steering method smart imaging mode spaceborne synthetic aperture radar system scene illumination satellite flying direction three-axis attitude steering method zero-Doppler centroid requirement iterative optimisation algorithm satellite tool kit coastline imaging

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Quantitative imaging of numerically realistic human head model using microwave tomography

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ELECTRONICS LETTERS 2014年第4期50卷 255-U175页

作者： Jalilvand, M. Wu, Chuanren Schmid, J. Zwick, T. KIT IHE Karlsruhe Germany KIT IBT Karlsruhe Germany

Microwave tomography (MWT) is exploited for the detection of haemorrhagic stroke by using a nonlinear iterative imaging algorithm. An anatomically realistic two-dimensional (2D) head model is simulated using a finite difference time-domain numerical solver. By using an iterative optimisation algorithm based on the Gauss–Newton approach, the head model with an artificially embedded stroke region modelled as blood is successfully reconstructed through a blind reconstruction procedure (i.e. no a priori information about the shape or the dielectric properties of the model is assumed). It is observed that beginning from a homogeneous guess similar to the background material, right after the first iteration the shapes of the layers are clearly distinguished and the values of the dielectric properties converge to the actual values after only 10 iterations.

关键词： Electrical activity in neurophysiological processes optimisation techniques nonlinear iterative imaging algorithm iterative optimisation algorithm Microwaves and other electromagnetic waves (medical uses) dielectric properties two-dimensional head model Biology and medical computing blood blind reconstruction procedure finite difference time-domain analysis Gauss-Newton approach Bioelectric signals biomedical imaging haemorrhagic stroke detection Numerical approximation and analysis image reconstruction iteration Patient diagnostic methods and instrumentation quantitative imaging brain microwave tomography Optical, image and video signal processing Interpolation and function approximation (numerical analysis) Computer vision and image processing techniques artificially embedded stroke region model iterative methods Other numerical methods medical image processing Microwaves and other electromagnetic waves (biomedical imaging/measurement) human head model neurophysiology FDTD numerical solver microwave imaging Microwave measurement techniques optimisation medical disorders bioelectric phenomena

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Accurate estimation of stitching error for high-resolution multi-sub-bands SAR system with image sharpness analysis

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ELECTRONICS LETTERS 2016年第23期52卷 1948-1950页

作者： Chen, Jie Wang, Kai Yang, Wei Collaborat Innovat Ctr Geospatial Technol Wuhan 430079 Peoples R China Beihang Univ Sch Elect & Informat Engn Beijing 100191 Peoples R China

Multi-sub-bands stitching technique is an effective method to achieve ultra-high range resolution in synthetic aperture radar (SAR) system. However, sub-bands stitching error results in artefacts in multi-sub-bands SAR images, e.g. defocused targets, higher sidelobes, which seriously degrade SAR image quality and cannot be mitigated by weighting function. A novel stitching error estimation method was presented. The stitching error is modelled by regarding phase error as function of range frequency, which will be estimated and compensated to reach the maximum image sharpness. First, amplitude balance is applied to single look complex SAR image in range frequency domain. Subsequently, based on image sharpness, an iterative optimisation algorithm is designed to estimate and compensate the stitching phase error. Finally, experimental results using both real RADARSAT-2 and airborne SAR dataset validate proposed method perform well in arbitrary scenes, and it outperforms the existing methods.

关键词： synthetic aperture radar radar imaging image resolution iterative methods optimisation novel stitching error estimation method high-resolution multi subbands SAR system image sharpness analysis multi subbands stitching technique ultra-high range resolution synthetic aperture radar system range frequency function amplitude balance iterative optimisation algorithm real RADARSAT-2 dataset airborne SAR dataset

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Service-dependent task offloading for multiuser mobile edge computing system

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ELECTRONICS LETTERS 2019年第15期55卷 839-+页

作者： Ni, Wanli Tian, Hui Lyu, Xinchen Fan, Shaoshuai Beijing Univ Posts & Telecommun State Key Lab Networking & Switching Technol Beijing 100876 Peoples R China

Mobile edge computing (MEC) has been deemed as one of the key technologies for pushing powerful computing ability to the radio access network. Different scenarios require different services, and tasks usually require computing in a specific runtime environment. However, few studies have taken this into consideration. To this end, the authors propose a novel model of service-dependent task offloading for the multiuser MEC system with resource constraints. Through determining which services should be deployed at the network edge and how many tasks should be offloaded, a revenue maximisation problem is constructed. Accordingly, they propose an iterative optimisation algorithm with high performance for the service deploying and task offloading problem. Finally, numerical simulations reveal that their proposed algorithm outperforms other schemes.

关键词： iterative methods radio access networks mobile computing optimisation multi-access systems service-dependent task offloading multiuser mobile edge computing system radio access network specific runtime environment multiuser MEC system network edge service deploying task offloading problem computing ability resource constraints revenue maximisation problem numerical simulations iterative optimisation algorithm

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Spatial coding in sonar imaging

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ELECTRONICS LETTERS 2017年第17期53卷 1222-1224页

作者： Wang, Jingxi Guo, Xin Ge, Feng-Xiang Arce, Gonzalo R. Beijing Normal Univ Beijing Peoples R China Huawei Technol Co Ltd Beijing Peoples R China Univ Delaware Newark DE 19716 USA

A practical deployment is presented for sonar imaging with fewer transmitters and receivers. Spatial coding via transmit beamforming is used for target detection and localisation. Transmit beamforming reduces the ambiguity in a model and improves imaging performance. To reconstruct the resultant underdetermined system of equations, a sparse signal reconstruction framework is used, and the inverse problem is solved by using an iterative optimisation algorithm. Deployment is optimised for better target detection and localisation performance. Successful sonar imaging reconstruction is guaranteed by the restricted isometry property with high probability. A numerical simulation shows that the proposed method can detect and localise targets efficiently, with better imaging results than those attained by conventional methods or the compressive sensing method without spatial coding.

关键词： sonar imaging image coding sonar detection object detection transmitters receivers array signal processing inverse problems iterative methods optimisation image reconstruction probability spatial coding transmitter receiver beamforming target detection target localisation sparse signal reconstruction framework inverse problem iterative optimisation algorithm sonar imaging reconstruction restricted isometry property probability numerical simulation compressive sensing method

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