Effect of Asymmetric Rolling on the Microstructure, Mechanical Properties and Texture Evolution of Mg–8Li–3Al–1Y Alloy

Xiao Zhou,Ruirui Liu,Qiang Liu,Haitao Zhou 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.5

Asymmetric rolling was applied to dual phase Mg–8Li–3Al–1Y alloy with different speed ratio and rolling reduction. Withincreasing reduction at the same speed ratio the population of β-Li grains decreased with a feature of fibered grains alongthe rolling direction. As for different speed ratio under the same reduction, β-Li grains kept equiaxed, but α-Mg phase wasfirst elongated and fibered and then transited to equiaxed small grains. The enhanced yield strength and tensile strengthwere achieved with the increase of rolling reduction and speed ratio. In particular, when speed ratio reached to 1:1.3 underthe same rolling reduction (30%), the optimal mechanical properties were obtained. As for texture evolution, we found thebasal texture was obviously weakened and some new weak texture was formed after asymmetric rolling. Interestingly, it wasnoted that the texture on the side of slow roll is distinct from that on the side of the fast roll due to the different rolling speed.

Characterization of Microstructure and Mechanical Properties of Mg–8Li–3Al–1Y Alloy Subjected to Different Rolling Processes

Xiao Zhou,Qiang Liu,Ruirui Liu,Haitao Zhou 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.6

The mechanical properties and microstructure evolution of Mg–8Li–3Al–1Y alloy undergoing different rolling processeswere systematically investigated. X-ray diffraction, optical microscope, scanning electron microscopy, transmission electronmicroscopy as well as electron backscattered diffraction were used for tracking the microstructure evolution. Tensile testingwas employed to characterize the mechanical properties. After hot rolling, the MgLi2Alprecipitated in β-Li matrix due to thetransformation reaction: β-Li → β-Li + MgLi2Al + α-Mg. As for the alloy subjected to annealed hot rolling, β-Li phase wasclearly recrystallized while recrystallization rarely occurred in α-Mg phase. With regard to the microstructure undergoing coldrolling, plenty of dislocations and dislocation walls were easily observed. In addition, the microstructure of alloys subjectedto annealed cold rolling revealed the formation of new fresh α-Mg grains in β-Li phase due to the precipitation reaction. Themechanical properties and fracture modes of Mg–8Li–3Al–1Y alloys can be effectively tuned by different rolling processes.

Optimal Power Control in Cooperative Relay Networks Based on a Differential Game

Haitao Xu,Xianwei Zhou 한국전자통신연구원 2014 ETRI Journal Vol.36 No.2

In this paper, the optimal power control problem in acooperative relay network is investigated and a new powercontrol scheme is proposed based on a non-cooperativedifferential game. Optimal power allocated to each nodefor a relay is formulated using the Nash equilibrium in thispaper, considering both the throughput and energyefficiency together. It is proved that the non-cooperativedifferential game algorithm is applicable and the optimalpower level can be achieved.

Load Balancing Algorithm of Ultra-Dense Networks: a Stochastic Differential Game based Scheme

( Haitao Xu ),( Zhen He ),( Xianwei Zhou ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.7

Increasing traffic and bandwidth requirements bring challenges to the next generation wireless networks (5G). As one of the main technology in 5G networks, Ultra-Dense Network (UDN) can be used to improve network coverage. In this paper, a radio over fiber based model is proposed to solve the load balancing problem in ultra-dense network. Stochastic differential game is introduced for the load balancing algorithm, and optimal load allocated to each access point (RAP) are formulated as Nash Equilibrium. It is proved that the optimal load can be achieved and the stochastic differential game based scheme is applicable and acceptable. Numerical results are given to prove the effectiveness of the optimal algorithm.

Mechanical Behavior of 3D Woven Variable Thickness Composite Plate under Tensile Loading

Yu Zhou,Haitao Cui,Weidong Wen 한국섬유공학회 2022 Fibers and polymers Vol.23 No.3

As a directly net-shaped structure, 3D woven variable thickness composite plate is different from the constantthickness structure in terms of the changing weft yarn sizes and resulting various warp yarn direction. To investigate themechanical behavior of this structure, a finite element (FE) model was proposed in this paper on the basis of author’sprevious geometric model illustrating the characterized details. Mesh convergence was studied to determine the size ofelement in compromise of accuracy and efficiency. Linear displacement rather than periodic boundary conditions wereapplied due to the thickness change. For the validation of presented FE model, a sample variable thickness plate in 3D layerto layer weave style was tested under tensile load in warp direction whose thickness was changed in this direction by thechange of weft yarn size. The strain was monitored with the help of Digital Image Correlation (DIC) system. The resultsshowed that the predicted homogenized stiffness in warp direction decreased with the thickness increasing, in agreement withthe observation from experiments. The maximum error between the predicted stiffness and the measurements of typicalsegment (TS) in variable thickness region of the plate is 12.05 % while the minimum error is 0.7 %.

Developing a synergistic approach to engineering education: China’s national policies on university–industry educational collaboration

Tengteng Zhuang,Haitao Zhou 서울대학교 교육연구소 2023 Asia Pacific Education Review Vol.24 No.1

This article examines the intents and effects of China’s national policies to promote a synergistic approach to university–industry collaborative education. These policies set out to reduce the academia-industry disconnection for engineering education. Based on document analysis and interviews with various types of stakeholders, the study reveals that China has strived for a synergistic approach to education by strengthening the main-actor role of enterprises, framing a policy support system, incorporating external stakeholders in universities’ governance structures, and building a coordinated framework for a synergistic approach to education. These policies have enhanced enterprises’ motivation to participate in university education, deepened enterprises’ engagement with engineering education at course level, and created an educational innovation ecosystem. Some challenges remain such as the mismatch between course update and technological development, the mismatch between costs and return for faculty members, and difficulty in assessment of outcomes. Overwhelmingly, China has tried exploring a model conducive to the improvement of higher education quality, and the overlapping triple helix model, compared with the statist or laissez-faire patterns, has a more robust effect in galvanizing stakeholders towards their collective goal in the Chinese context.

An Intelligent MAC Protocol Selection Method based on Machine Learning in Wireless Sensor Networks

( Mu Qiao ),( Haitao Zhao ),( Shengchun Huang ),( Li Zhou ),( Shan Wang ) 한국인터넷정보학회 2018 KSII Transactions on Internet and Information Syst Vol.12 No.11

Wireless sensor network has been widely used in Internet of Things (IoT) applications to support large and dense networks. As sensor nodes are usually tiny and provided with limited hardware resources, the existing multiple access methods, which involve high computational complexity to preserve the protocol performance, is not available under such a scenario. In this paper, we propose an intelligent Medium Access Control (MAC) protocol selection scheme based on machine learning in wireless sensor networks. We jointly consider the impact of inherent behavior and external environments to deal with the application limitation problem of the single type MAC protocol. This scheme can benefit from the combination of the competitive protocols and non-competitive protocols, and help the network nodes to select the MAC protocol that best suits the current network condition. Extensive simulation results validate our work, and it also proven that the accuracy of the proposed MAC protocol selection strategy is higher than the existing work.

Response spectrum analysis considering non-classical damping in the base-isolated benchmark building

Huating Chen,Ping Tan,Haitao Ma,Fulin Zhou 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.64 No.4

An isolated building, composed of superstructure and isolation system which have very different damping properties, is typically non-classical damping system. This results in inapplicability of traditional response spectrum method for isolated buildings. A multidimensional response spectrum method based on complex mode superposition is herein introduced, which properly takes into account the non-classical damping feature in the structure and a new method is developed to estimate velocity spectra from the commonly used displacement or pseudo-acceleration spectra based on random vibration theory. The error of forced decoupling method, an approximated approach, is discussed in the viewpoint of energy transfer. From the baseisolated benchmark model, as a numerical example, application of the procedure is illustrated companying with comparison study of time-history method, forced decoupling method and the proposed method. The results show that the proposed method is valid, while forced decoupling approach can’t reflect the characteristics of isolated buildings and may lead to insecurity of structures.

Bacillus subtilis improves antioxidant capacity and optimizes inflammatory state in broilers

Yu Zhang,Junyan Zhou,Linbao Ji,Lian Zhang,Liying Zhao,Yubing Guo,Haitao Wei,Lin Lu Asian Australasian Association of Animal Productio 2024 Animal Bioscience Vol.37 No.6

Objective: Bacillus subtilis, a kind of probiotic with broad-spectrum antibacterial function, was commonly used in livestock and poultry production. Recent research suggested that Bacillus subtilis may have antioxidant properties and improve immune response. This study aimed to verify the probiotic function of Bacillus subtilis in the production of broiler chickens. Methods: A total of 324 (1-day-old) Arbor Acres broilers were selected and randomly divided into three groups: basal diet group (Ctr Group), basal diet + antibiotic growth promoter group (Ctr + AGP) and basal diet + 0.5% Bacillus subtilis preparation group (Ctr + Bac). The experiment lasted for 42 days. Muscle, serum and liver samples were collected at 42 days for determination. Results: The results showed that Bacillus subtilis could decrease malondialdehyde content in the serum and liver (p<0.05) and increase superoxide dismutase 1 mRNA expression (p<0.01) and total superoxide dismutase (p<0.05) in the liver. In addition, compared with AGP supplementation, Bacillus subtilis supplementation increased interleukin-10 (IL-10) and decreased tumor necrosis factor-α and IL-1β level in the serum (p<0.05). At 45 minutes after slaughter Ctr + Bac presented a higher a^* value of breast muscle than Ctr Group (p<0.05), while significant change in leg muscle was not identified. Moreover, there was no difference in weight, shear force, cooking loss and drip loss of breast and leg muscle between treatments. Conclusion: Our results demonstrate that Bacillus subtilis in diet can enhance antioxidant capacity and optimize immune response of broilers.

Numerical investigation of aerodynamic load on the impellers of centrifugal compressor with leakage flow

Jianchi Xin,Xiaofang Wang,Haitao Liu,Wang wei,Lusheng Zhou 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.2

Based on computational fluid dynamics (CFD) simulation, this study investigates the effect of leakage flow on the performance of centrifugal compressor, which helps to showcase the flow phenomenon considering the leakage flow and the aerodynamic load on the impellers. We consider four types of compressor models including the normal stage with hub and shroud leakages (SWT), the normal stage with hub leakage (SWH), the normal stage with shroud leakage (SWS), and the normal stage without leakages (SOT)). The results indicate that the leakage flow obviously affects the compressor performance, especially the flow field around the leading/trailing edge of the impeller. The aerodynamic load at the leading/trailing edge of the impeller was obtained for the models through unsteady simulation. The dominant frequency and the pulse amplitude obtained by Fast Fourier transforms revealed that the main frequencies of the aerodynamic load present different distributions under different leakage flows.