Effect of Initial Microstructure on the Hot Deformation Behavior and Microstructure Evolution of Aluminum Alloy AA2060

Chaoyang Li,Guangjie Huang,Lingfei Cao,Ruoxi Zhang,Yu Cao,Bin Liao,Lin Lin 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.7

The microstructure evolution and hot deformation behavior of a Li-containing aluminum alloy AA2060 with different initialmicrostructure (homogenized vs. pre-rolled) were studied by isothermal hot deformation. The tests were performed within awide range of deformation temperatures of 370–490 ℃ and strain rates of 0.01–10 s−1. Results show that the stress drop ratioof the pre-rolled specimen is higher than that of the homogenized one under the same deformation condition. Microstructurewere analyzed on the thermal processing maps in unstable and optimum processing domain, and a higher dynamic recrystallizationfraction can be observed in the pre-rolled specimen that has more substructures and smaller grains. Four typesof the dynamic recrystallization were observed and the mechanism for deformation softening was discussed in this work.

Elastostatic Stiffness Analysis of a 2PUR-PSR Overconstrained Parallel Mechanism

Chao Yang,Qiaohong Chen,Junhua Tong,Qinchuan Li 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.4

The elastostatic stiffness performance of a 2PUR-PSR (S: spherical joint; U: universal joint; R: revolute joint; P: prismatic pair) overconstrained parallel mechanism with two rotational and one translational (2R1T) degrees of freedom was studied based on screw theory and strain energy. First, the actuator and constraint wrenches of the mechanism were obtained based on screw theory. Second, by considering the space composite elastic deformation of the rod (including axial tension, and shear, torsional and bending deformation), compact limb stiffness matrixes were obtained in terms of strain energy and Castigliano’s second theorem. Finally, analytic expressions for the overall stiffness matrix of the mechanism and the amplitudes of the actuator and constrained wrenches were obtained based on the virtual-work principle and the balance equation for a moving platform. The relative error between results from the analytical model and the Workbench finite element model is approximately 1.3%, which validates the effectiveness of the proposed elastostatic stiffness model. Unlike traditional stiffness evaluation index, a regional stiffness index was proposed to measure the mechanism’s stiffness performance at various working heights. Using the index, it is possible to determine the optimum stiffness region of a moving platform with known external wrenches.

CacheSCDefender: VMM-based Comprehensive Framework against Cache-based Side-channel Attacks

( Chao Yang ),( Yunfei Guo ),( Hongchao Hu ),( Wenyan Liu ) 한국인터넷정보학회 2018 KSII Transactions on Internet and Information Syst Vol.12 No.12

Cache-based side-channel attacks have achieved more attention along with the development of cloud computing technologies. However, current host-based mitigation methods either provide bad compatibility with current cloud infrastructure, or turn out too application-specific. Besides, they are defending blindly without any knowledge of on-going attacks. In this work, we present CacheSCDefender, a framework that provides a (Virtual Machine Monitor) VMM-based comprehensive defense framework against all levels of cache attacks. In designing CacheSCDefender, we make three key contributions: (1) an attack-aware framework combining our novel dynamic remapping and traditional cache cleansing, which provides a comprehensive defense against all three cases of cache attacks that we identify in this paper; (2) a new defense method called dynamic remapping which is a developed version of random permutation and is able to deal with two cases of cache attacks; (3) formalization and quantification of security improvement and performance overhead of our defense, which can be applicable to other defense methods. We show that CacheSCDefender is practical for deployment in normal virtualized environment, while providing favorable security guarantee for virtual machines.

Arching Effect between the Pipes of a Pipe Umbrella Support Systemin a Shallow-Buried Tunnel

Chao Yang,Yanhua Chen,Da Huang,Lehua Wang 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.12

The pipe umbrella is one of the most commonly used prereinforcement techniques in tunnel construction. Current theoretical analyses of the pipe umbrella support mechanism are primarily based on the elastic foundation beam principle, whereby only a single pipe is concerned, and the interactions among pipes are ignored. In this study, a double-parameter elastic foundation beam theory-based model was established with consideration of the arching effect between two pipes. The model can simulate the support mechanism of the pipe umbrella system in shallow-buried tunnels. The support mechanisms of a pipe umbrella system installed in a rectangular tunnel and an arched tunnel were investigated. In the two cases, the arching effect and a single pipe were considered. The results indicate that the arching effect leads to larger pipe deflection and internal forces than considering a single pipe. The influences of the diameter of a single pipe, the distance between two pipes and the shear parameters of the surrounding rock on the pipe deflection and the arching effect are discussed. In addition, the proposed model was validated by the in situ monitoring results.

25th the Fall of Berlin Wall

Chao Yang 한국콘텐츠학회 2015 ICCC International Digital Design Invitation Exhib Vol.2015 No.5

Finite-time Synchronization of a Class of Coupled Memristor-based Recurrent Neural Networks: Static State Control and Dynamic Control Approach

Chao Yang,Yicheng Liu,Fangmin Li,Yangfan Li 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.1

This paper investigates the problem of the finite-time synchronization of a class of coupled memristorbased recurrent neural networks (MRNNs) with time delays. Based on the drive-response concept and differentialinclusions theory, several sufficient assumptions are given to ensure the finite-time synchronization of MRNNs. In order to realize the finite-time synchronization between the drive system and the response system, we designthree classes of novel control rules such as static state controller, static output controller, dynamic state controller. Using the theory of differential inclusion, a generalized finite-time convergence theorem and Lyapunov method, theconditions herein are easy to be verified. Moreover, the upper bounds of the settling time of synchronization areestimated and the designed dynamic state controllers have good anti-interference capacity. Finally, two numericalexamples are presented to illustrate the effectiveness and the validity of theoretical results.

Elastodynamic modeling of spatial parallel manipulators contain subclosed loops

Chao Yang,Yang Wang,Junbin Lou,Wei Ye,Fengli Huang 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.3

In this work, the delta parallel manipulator (PM) was considered as a case study to present a system elastodynamic modeling of spatial PMs contain subclosed loops. The mechanism consisted of major substructures including proximal, short, and distal links. Each link was divided into elements to establish the body-to-body and body-to-ground constraint equations. The global independent generalized displacement coordinates (IGDC) of the mechanism were extracted with the theory of multi-point constraint elements. Besides, the global IGDC and substructure synthesis approach was used to obtain the complete elastodynamic modeling of the mechanism without supplementing constraint equations. The resulting configuration-dependent elastodynamic modeling had fewer degrees of freedom, different from thousands used in finite element model (FEM). The natural frequencies could be predicted at any configuration of the mechanism, and were compared against the values of FEM to assess the correctness of the modeling. The proposed modeling could predict the distribution of natural frequencies of the mechanism in the workspace with computational efficiency. Therefore, it could be used as a numerical twin to simulate the elastodynamic performance of PMs in the pre-design stage.

Pattern-Oriented Agent-Based Simulation for Analyzing Family Strategies in Civil Service Examination in Imperial China

Chao YANG,Toru TAKAHASHI,Takashi YAMADA,Setsuya KURAHASHI,Isao ONO,Takao TERANO 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8

Pattern Oriented Modeling (POM) is an approach to bottom-up complex system analysis which was developed in ecology and for agent-based complex systems. This paper proposes a pattern-oriented agent-based simulation (POABS) approach to analyze agent-based complex system. We apply POABS to a history simulation domain to analyze a particular family line with more successful candidates in the civil service examination in imperial China. In order to decode family strategies along such an elite family line, we develop POABS to test relevant patterns observed in the real family system. Inverse simulation technique is applied to evaluate each simulated pattern through fitting the time-series of simulated profile data to real profile data with real-coded GA. Intensive experiments show a practical applicability of POABS in agent-based complex system.

Stress concentration factors test of reinforced concrete-filled tubular Y-joints under in-plane bending

Chao Yang,Jun-fen Yang,Mingzhou Su,Ming Lian 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.22 No.1

To study the stress concentration factors (SCFs) of concrete-filled tubular Y-joints subject to in-plane bending, experiments were used to investigate the hot spot stress distribution along the intersection between chord and brace. Three concrete-filled tubular chords forming Y-joints were tested with different reinforcing components, including doubler-plate, sleeve, and haunch-plate reinforcement. In addition, an unreinforced joint was also tested for comparison. Test results indicate that the three different forms of reinforcement effectively reduce the peak SCFs compared with the unreinforced joint. The current research suggests that the linear extrapolation method can be used for chords, whereas the quadratic extrapolation method must be used for braces. The SCF is effectively reduced and more evenly distributed when the value of the axial compression ratio in the chord is increased. Furthermore, the SCFs obtained from the test results were compared to predictions from some well-established SCF equations. Generally, the predictions from those equations are very consistent for braces, but very conservative for concretefilled chords.

Mapping QTLs for Tissue Culture Response in Soybean (Glycine max (L.) Merr.)

Chao Yang,Tuanjie Zhao,Deyue Yu,Junyi Gai 한국분자세포생물학회 2011 Molecules and cells Vol.32 No.4

Quantitative trait loci (QTLs) that control the tissue cul-ture response in soybean were detected by using 184 recombinant inbred lines (RILs) derived from two varieties: Kefeng No.1 and Nannong 1138-2. The molecular map consisting of 834 molecular markers using this population covered space 2307.83 cM of the genome throughout 24 linkage groups. The performance of tissue culture in soybean was evaluated by two indices: callus induction frequency (CIF) and somatic embryos initiation frequency (SEIF). They were expressed as the number of explants producing callus/ the number of total explants and the number of explants producing somatic embryos/ the number of total explants, respectively. The RIL lines showed continuous segregation for both indices. With the composite interval mapping (CIM) described in Windows QTL Cartographer Version 2.5, three quantitative trait loci (QTLs) were identified for the frequency of callus induction, on chromosomes B2 and D2, accounting for phenotypic variation from 5.84% to 16.60%; four QTLs on chromo-some G were detected for the frequency of somatic em-bryos initiation and explained the phenotypic variation from 7.79% to 14.16%. The information of new QTLs identified in the present study will contribute to genetic improvement of regeneration traits with marker-assisted selection (MAS) in soybean.