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A New Method of Multi-Scale Geologic Modeling and Display

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Journal of Earth Science 2014年第3期25卷 537-543页

作者： Yongliang Bai Zhan liu Lanfa liu Roger Mason Binghu huang School of Geosciences China University of Petroleum Earth Sciences Faculty China University of Geosciences Wuhan

A new method of multi-scale modeling and display of geologic data is introduced to provide information with appropriate detail levels for different types of research. The multi-scale display mode employs a model extending existing 2D methods into 3D space. Geologic models with different scales are organized by segmenting data into orthogonal blocks. A flow diagram illustrates an octree method for upscaling between blocks with different scales. Upscaling data from the smallest unit cells takes into account their average size and the Burgers vector when there are mismatches. A geocellular model of the chengdao Reservoir of the Shengli Oilfield, china is taken as an illustrative case, showing that the methods proposed can construct a multi-scale geologic model correctly and display data from the multi-scale model effectively in 3D.

关键词： multi-scale geologic model block data organization topological relationship upscale geologic structure multi-scale display.

Study on periodic orbits around the dipole segment model for dumbbell-shaped asteroids

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Science china(Technological Sciences) 2018年第6期61卷 819-829页

作者： ZhANG YongLong ZENG XiangYuan liu XiangDong School of Automation Beijing Institute of Technology Beijing 100081 China

Equilibrium points and periodic orbits in irregular gravitational fields are significant for an understanding of dynamical behaviors around asteroids as well as deep space exploring missions. The dipole segment is a good alternative model to study qualitative dynamical properties near dumbbell-shaped asteroids. In this paper, the dipole segment model and its equilibrium points are simply introduced. The stability of the two triangular equilibrium points of the system is numerically examined. Next, periodic orbits are presented around the dipole segment model in two different cases, in which triangular equilibria are linearly stable and unstable,respectively. New types of periodic orbits are illustrated in detail, including their orbital shapes, periods and the Jacobi *** orbital stability, topological classification and bifurcations of these orbits are also analyzed with numerical continuations.

关键词： dipole segment model equilibrium points periodic orbits topological classification

Real-time online rescheduling for multiple agile satellites with emergent tasks

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Journal of Systems Engineering and Electronics 2021年第6期32卷 1407-1420页

作者： WEN Jun liu Xiaolu hE Lei college of Systems Engineering National University of Defense TechnologyChangsha 410073China

The emergent task is a kind of uncertain event that satellite systems often encounter in the application *** this paper,the multi-satellite distributed coordinating and scheduling problem considering emergent tasks is *** to the limitation of onboard computational resources and time,common online onboard rescheduling methods for such problems usually adopt simple greedy methods,sacrificing the solution quality to deliver timely *** better solve the problem,a new multi-satellite onboard scheduling and coordinating framework based on multi-solution integration is *** method uses high computational power on the ground and generates multiple solutions,changing the complex onboard rescheduling problem to a solution selection *** this method,it is possible that little time is used to generate a solution that is as good as the solutions on the *** further propose several multi-satellite coordination methods based on the multi-agent Markov decision process(MMDP)and mixed-integer programming(MIP).These methods enable the satellite to make independent decisions and produce high-quality *** with the traditional centralized scheduling method,the proposed distributed method reduces the cost of satellite communication and increases the response speed for emergent *** experiments show that the proposed multi-solution integration framework and the distributed coordinating strategies are efficient and effective for onboard scheduling considering emergent tasks.

关键词： agile satellite scheduling emergent task onboard rescheduling distributed coordinating multi-solution integration

Radar group target recognition based on hRRPs and weighted mean shift clustering

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Journal of Systems Engineering and Electronics 2020年第6期31卷 1152-1159页

作者： GUO Pengcheng liu Zheng WANG Jingjing National Laboratory of Radar Signal Processing Xidian UniversityXi’an 710071China Xi'an Electronic Engineering Research Institute Xi’an 710100China

When range high-resolution radar is applied to target recognition,it is quite possible for the high-resolution range profiles(hRRPs)of group targets in a beam to overlap,which reduces the target recognition performance of the *** this paper,we propose a group target recognition method based on a weighted mean shift(weighted-MS)clustering *** the training phase,subtarget features are extracted based on the template database,which is established through simulation or data acquisition,and the features are fed to the support vector machine(SVM)classifier to obtain the classifier *** the test phase,the weighted-MS algorithm is exploited to extract the hRRP of each ***,the features of the subtarget hRRP are extracted and used as input in the SVM classifier to be *** to the traditional group target recognition method,the proposed method has the advantages of requiring only a small amount of computation,setting parameters automatically,and having no requirement for target *** experimental results based on the measured data show that the method proposed in this paper has better recognition performance and is more robust against noise than other recognition methods.

关键词： clustering group target recognition high resolution range profile(hRRP) mean shift(MS)

Extraction Security of Sequential Aggregate Signatures

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chinese Journal of Electronics 2021年第5期30卷 885-894页

作者： ZhAI Jiaqi liu Jian chEN Lusheng School of Mathematical Sciences Nankai University School of cybersecurity College of Intelligence and ComputingTianjin University

Aggregate signature schemes enable anyone to compress many signatures into *** the unforgeability of aggregate signature,another property called aggregate extraction sometimes is *** sequential aggregate signature schemes,the aggregate signature is computed incrementally by the *** introduce extraction security in the sequential context which can be seen as an analogy of aggregate extraction introduced by Boneh et *** cRYPTO *** addition to the practical meaning,it also has benefits in the construction of hierarchical identity-based signatures as we will point *** study several well known aggregate signature schemes and prove some of them satisfy extraction security.

关键词： sequential context sequential aggregate signatures hierarchical identity-based signatures digital signatures aggregate extraction extraction security sequential aggregate signature schemes

Multi-time Scale Optimal Power Flow Strategy for Medium-voltage Dc Power Grid considering Different Operation Modes

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Journal of Modern Power Systems and clean Energy 2020年第1期8卷 46-54页

作者： Jianqiang liu Xiaoguang huang Zuyi Li School of Electrical Engineering Beijing Jiaotong UniversityBeijing 100044China Robert W.Galvin center for Electricity Innovation Illinois Institute of TechnologyChicago 60616USA

Direct current(Dc)power grids based on flexible high-voltage Dc technology have become a common solution of facilitating the large-scale integration of distributed energy resources(DERs)and the construction of advanced urban power *** this study,a typical topology analysis is performed for an advanced urban medium-voltage Dc(MVDc)distribution network with DERs,including wind,photovoltaic,and electrical energy storage ***,a multi-time scale optimal power flow(OPF)strategy is proposed for the MVDc network in different operation modes,including utility grid-connected and off-grid operation *** the utility grid-connected operation mode,the day-ahead optimization objective minimizes both the DER power curtailment and the network power *** addition,in the off-grid operation mode,the day-ahead optimization objective prioritizes the satisfaction of loads,and the DER power curtailment and the network power loss are minimized.A dynamic weighting method is employed to transform the multi-objective optimization problem into a quadratically constrained quadratic programming(QcQP)problem,which is solvable via standard *** intraday scheduling,the optimization objective gives priority to ensure minimum deviation between the actual and predicted values of the state of charge of the battery,and then seeks to minimize the DER power curtailment and the network power *** predictive control(MPc)is used to correct deviations according to the results of ultra short-term load ***,an improved particle swarm optimization(PSO)algorithm is applied for global intraday optimization,which effectively increases the convergence rate to obtain *** simulation results indicate that the proposed optimization strategy is effective and efficient.

关键词： Optimal power flow(OPF) medium-voltage direct current(MVDc) quadratically constrained quadratic programming(QcQP) model predictive control(MPc) particle swarm optimization(PSO)

An h-adaptive numerical manifold method for solid mechanics problems

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Science china(Technological Sciences) 2018年第6期61卷 923-933页

作者： YU changYi liu Feng XU Ying State Key Laboratory of hydraulic Engineering Simulation and Safety School of Civil Engineering Tianjin University Tianjin 300072 China State Key Laboratory of Geomechanies and Geoteehnical Engineering Institute of Rock andSoil Mechanics Chinese Academy of Sciences Wuhan 430071 China

The numerical manifold method(NMM) features its dual cover systems, namely the mathematical cover and physical cover,which provide a unified framework for mechanics problems involving continuum and discontinuum deformation. Uniform finite element meshes can be and are usually used to construct the mathematical cover. Though this strategy can handle different kinds of problems in a unified way, it is not economical for cases with steep deformation gradients or singularities. In this paper, using the recovery-based error estimator, an h-adaptive NMM on quadtree meshes is proposed to deal with such cases. The quadtree meshes serve as the mathematical meshes, on which the local refinement is carried out. When the quadtree meshes are refined,the corresponding mathematical cover, physical cover and manifold elements are updated accordingly. To handle the hanging nodes in the quadtree meshes, we resort to mean value coordinates. comparing to the refinement based on manifold elements,the proposed strategy guarantees consistent structured meshes throughout the adaptive process, thus retaining the unique feature of original NMM. In contrast with polygonal finite element method, an advantage of the proposed method is that the meshes do not need to conform to the crack face and material boundary, which means the adaptive NMM is very suitable for problems with complex geometric boundary. Several representative mechanics problems, including crack problems, are analyzed to investigate the effectiveness of the proposed method. It is demonstrated that the proposed adaptive NMM has higher accuracy and better performance comparing to uniform refinement strategy.

关键词： numerical manifold method (NMM) adaptive analysis quadtree meshes mean value coordinates cover refinement

Energy-efficient URLLc service provisioning in softwarization-based networks

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Science china(Information Sciences) 2021年第8期64卷 35-55页

作者： Mengjie liu Gang FENG Weihua ZhUANG National Key Laboratory on communications University of Electronic Science and Technology of China Department of Electrical and computer Engineering University of Waterloo

Software defined networking(SDN) and network function virtualization(NFV) as new technologies have shown great potential in improving the flexibility of resource management for network service provisioning. As traffic dynamics may cause violation of rigid service requirements, especially for ultrareliability and low-latency communication(URLLc) service, it is essential yet challenging to dynamically allocate an appropriate amount of resources(including computation, transmission, and energy) to network functions(NFs) in softwarization-based networks. Meanwhile, with the explosion of high resource-demanding applications, the energy efficiency of communication networks deserves significant attention. In this paper,we investigate the dynamic network function resource allocation(NFRA) problem with aim to minimize longterm energy consumption while guaranteeing the requirements of URLLc services in softwarization-based networks. To cater for efficient on-line NFRA decisions, we design a distributed dynamic NF resource allocation(DDRA) algorithm based on dynamic value iteration(DVI). The convergence of the DDRA algorithm is proved. We conduct simulation experiments based on real-world data traces for performance *** numerical results demonstrate that the proposed DDRA algorithm achieves around 25% and 20% energy consumption reduction when compared with two benchmark algorithms, respectively.

关键词： softwarization-based networks SDN/NFV URLLc energy efficiency dynamic resource allocation distributed value iteration

Improved coordinated control Approach for Evolved ccc-hVDc System to Enhance Mitigation Effect of commutation Failure

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Journal of Modern Power Systems and clean Energy 2021年第2期9卷 338-346页

作者： chunyi Guo Bo liu chengyong Zhao State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources(North china Electric Power University) BeijingChina

The evolved capacitor commutated converter(Eccc),embedded with anti-parallel thyristors based dual-directional full-bridge modules(APT-DFBMs),can effectively reduce commutation failure(cF)risks of line-commutated converter-based high voltage direct current(hVDc)and improve the dynamic responses of capacitor-commutated converterbased *** paper proposes an improved coordinated control strategy for Eccc with the following improvements:(1)under normal operation state,series-connected capacitors can accelerate the commutation process,thereby reducing the overlap angle and increasing the successful commutation margin;(2)under Ac fault conditions,the ability of Eccc to mitigate the cF issue no longer relies on the fast fault detection,since the capacitors inside the APT-DFBMs can consistently contribute to the commutation process and further reduce the cF probability;(3)the inserted capacitors can output certain amount of reactive power,increase the power factor,and reduce the required reactive power compensation ***,the proposed coordinated control approach is presented in detail,and the extra commutation voltage to mitigate the cFs provided by the proposed control approach and an existing approach is ***,the mechanism of the improved control approach to accelerate commutation process and improve the power factor is analyzed ***,the detailed electromagnetic transient(EMT)simulation in PScAD/EMTDc is conducted to validate the effectiveness of the proposed coordinated *** results show that the proposed approach can present a further substantial improvement for Eccc,especially enhancing the cF mitigation effect.

关键词： Evolved capacitor commutated converter(Eccc) coordinated control commutation failure power factor