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Performance Analysis and Flexible Control of a Novel Ball Double-screw Hydraulic Robot Knee Joint

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Journal of Bionic Engineering 2023年第5期20卷 2147-2163页

作者： Jie Shao Yongming Bian Meng Yang guangjun liu School of Mechanical Engineering Tongji UniversityShanghai201804China State Key Laboratory of Fluid Power and Mechatronic Systems Zhejiang UniversityHangzhou310027China Department of Control Science and Engineering Tongji UniversityShanghai201804China National Engineering Technology Research Center for Prefabrication Construction in Civil Engineering Tongji UniversityShanghai200092China

Focusing on the ball double-screw hydraulic knee joint as the research object,this paper analyzes the load driving performance of the hydraulic knee *** the posture data of the human body such as walking,squatting and landing buffer as initial learning objects,motion features are *** simplifying the trajectories of different motion actions into key feature control points and flexible trajectory fitting,the trajectory of joint actions is *** method can realize the adaptability of the hydraulic robot knee joint in different movements,and take the flexible action as the optimization goal under the condition of ensuring the movement performance,so as to reduce the damage to the knee joint caused by the foot impact in *** simulation model was built by Adams and Matlab to complete the performance analysis and motion optimization experiment of the knee *** simulation results show that the foot impact force of the experimental model decreases gradually through ***,the method is applied to the hydraulic joint experimental prototype to prove its load capacity and flexible motion control performance.

关键词： Bionic robot Ball double-screw hydraulic joint Robot knee joint Performance analysis Humanoid motion control Flexible control

Research on concrete structure defect repair based on three-dimensional printing

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Frontiers of Structural and Civil Engineering 2024年第5期18卷 731-742页

作者： Yang GU Wei LI Xupeng YAO guangjun liu School of Mechanical Engineering Tongji UniversityShanghai 201804China College of Civil Engineering Tongji UniversityShanghai 200092China Shanghai Engineering Research Center for Safety Intelligent Control of Building Machinery Shanghai 200032China

Quality assurance and maintenance play a crucial role in engineering construction,as they have a significant impact on project *** common issue in concrete structures is the presence of *** enhance the automation level of concrete defect repairs,this study proposes a computer vision-based robotic system,which is based on three-dimensional(3D)printing technology to repair *** system integrates multiple sensors such as light detection and ranging(LiDAR)and *** is utilized to model concrete pipelines and obtain geometric parameters regarding their ***,a convolutional neural network(CNN)is employed with a depth camera to locate defects in concrete ***,a method for coordinate transformation is presented to convert the obtained coordinates into executable ones for a robotic ***,the feasibility of this concrete defect repair method is validated through simulation and experiments.

关键词： concrete defect detection 3D printing deep learning point cloud data

Security Analysis and Improvement of a Tag Encoding Authentication Scheme for Network Coding

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Wuhan University Journal of Natural Sciences 2016年第5期21卷 394-398页

作者： liu guangjun School of Information Engineering Xi'an University

A tag encoding authentication scheme for network coding proposed by Wu et al was claimed to defend pollution attacks efficiently. However, we find that the scheme easily incurs multi-generation pollution attacks, where an adversary may be able to recover the main secret key of the source with high probability during multi-generation transmitting, and the scheme also cannot resist against inter-generation pollution attacks. Using a dynamic source secret key technology that the key can be updated with the change of generation identifier, an improved scheme is then presented, which can counteract these security defects without any efficiency compromise.

关键词： network coding pollution attack inter-generation pollution attack multi-generation pollution attack

Low-Complexity Secure Network Coding Against Wiretapping Using Intra/Inter-generation Coding

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China Communications 2015年第6期12卷 116-125页

作者： liu guangjun liu Binyue liu Ximeng LI Fang GUO Wangmei School of Information Engineering Xi'an University State Key Laboratory of Integrated Service Networks Xidian University

Existing solutions against wiretapping attacks for network coding either bring significant bandwidth overhead or incur a high computational *** order to reduce the security overhead of the existing solutions for securing network coding,a novel securing network coding paradigm is presented relying on two coding models:intra-generation coding and inter-generation *** basic idea to secure network coding using intra-generation coding is to limit the encryption operations for each generation,and then subject the scrambled and the remaining original source vectors to a linear *** method is then generalized seamlessly using inter-generation coding by further exploiting the algebraic structure of network *** show that the proposed schemes have properties of low-complexity security,little bandwidth consumption,and high efficiency in integrating with the existing security techniques effectively.

关键词： network coding security wiretap-ping attacks algebraic coding encryption

Matroidal Error Correction Networks and Linear Network Error Correction MDS Codes

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Wuhan University Journal of Natural Sciences 2013年第6期18卷 477-483页

作者： ZHOU Hang liu guangjun The State Key Laboratory of Integrated Services Networks Xidian University College of Science Engineering University of the Chinese People's Armed Police Force School of Mathematics and Computer Engineering Xi'an University of Arts and Science

In this paper, we further study the connections between linear network error correction codes and representable matroids. We extend the concept of matroidal network introduced by Dougherty et al. to a generalized case when errors occur in multi- ple channels. Importantly, we show the necessary and sufficient conditions on the existence of linear network error correction mul- ticast/broadcast/dispersion maximum distance separable （MDS） code on a matroidal error correction network.

关键词： network error correction code error pattern imagi-nary error channels extended network matroid

Security Analysis on a Remote Data Auditing Scheme for Distributed Storage Systems

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Wuhan University Journal of Natural Sciences 2020年第6期25卷 527-530页

作者： liu guangjun ZHANG Lining LI Xiangjun School of Information Engineering Xi’an UniversityXi'an 710065ShaanxiChina

Remote data auditing becomes critical to ensure the storage reliability in distributed cloud ***,Le et al proposed an efficient private data auditing scheme NC-Audit designed for regenerating codes,which claimed that NC-Audit can effectively realize privacy-preserving data auditing for distributed storage ***,our analysis shows that NC-Audit is not secure for that the adversarial cloud can forge some illegal blocks to cheat the auditor successfully with a high probability even without storing the user’s whole data,when the coding field is large enough.

关键词： data auditing regeneration code network coding distributed storage cloud computing

Efficient Schemes for Securing Network Coding Against Wiretapping

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Wuhan University Journal of Natural Sciences 2013年第4期18卷 355-362页

作者： liu guangjun ZHOU Hang State Key Laboratory of Integrated Service Networks Xidian University College of Science Engineering University of the Chinese People's Armed Police Force

Existing solutions for secure network coding either bring significant bandwidth overhead or incur a high computational complexity. For exploiting low-overhead mechanism for secure network coding against wiretapping, three efficient schemes are proposed for the applications with different security requirements. The basic idea behind this paper is first to encrypt a small part of source vectors and then subject the remaining original source vectors and the encrypted vectors to a special linear transformation. Also, a lightweight version of this scheme is then presented for resource-constrained networks. Moreover, an extensive scheme with enhanced security is also considered. All proposals are shown to have properties of lower security complexity and smaller bandwidth usage compared with the existing solutions. Also, the proposals can be easy to achieve flexible levels of security for various applications.

关键词： network coding security wiretapping pseudorandom function encryption

Connectivity of sparse vehicular ad hoc networks with channel randomness

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High Technology Letters 2010年第4期16卷 389-394页

作者：米振强 Yang Yang An Jianwei liu guangjun Department of Information Engineering University of Science and Technology Beijing Beijing 100083 P.R. China Department of Aerospace Engineering Ryerson University Toronto Canada M5A 2C9

In this paper, we investigate the connectivity of vehicular ad hoc networks in free-flow traffic situation with channel randonmess. In order to illustrate the realistic environment, we consider that vehicles are distributed in free-flow highway according to a Poisson point process, and signal propagation between connected vehicles is subjected to log-normal shadowing effects. We obtain the distribution of the space headway between successive vehicles and the distribution of signal coverage, which allows us to use the equivalent M/G/z~ queue theory to model the connectivity of VANETs in the form of average broadcast percolation distance and average number of connected nodes. Then, extensive simulation studies are conducted to evaluate the obtained results. The analytical model presented here is able to describe the impact of various system parameters, including traffic parameters and signal propagation parameters on the con- nectivity. We use our analytical results, along with the common signal propagation data, to understand impact of channel randomness on the connectivity of VANETs.

关键词： vehicular ad hoc networks (VANETs) queuing theory broadcast percolation distance log-normal shadowing connectivity

2-Level R-tree Index Based on Spatial Grids and Hilbert R-tree

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Geo-Spatial Information Science 2006年第2期9卷 135-141页

作者： GUO Jing liu guangjun DONG Xurong GUO Lei Beijing Institute of Command and Technology of Equipment 1 Jingjia Road Huairou District Beijing 101416 China

Multi-level spatial index techniques are always used in large spatial databases. After a general survey of R-tree relevant techniques, this paper presents a novel 2-level index structure, which is based on the schemas of spatial grids, Hilbert R-tree and common R-tree. This structure is named H2R-tree, and it is specifically suitable for the indexing highly skewed, distributed, and large spatial database. Algorithms and a sample are given subsequently.

关键词： spatial index GIS R-tree H2R-tree spatial index GIS R-tree H2R-tree