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Optimizing Light and Heavy Aromatic Ratios in Fluid Catalytic Cracking Slurry Oil for Mesophase Pitch with Wide-Area Optically Anisotropic Texture

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SSRN 2024年

作者： Liao, Gen Shi, Kui Ye, Chong Fan, Zhen Li, Tongqi Zhu, Shipeng He, Xubin Huang, Dong Han, Fei Liu, Hongbo Liu, Jinshui College of Materials Science and Engineering Hunan Province Key Laboratory for Advanced Carbon Materials and Applied Technology Hunan University Changsha410082 China Hunan Province Engineering Research Center for High Performance Pitch-based Carbon Materials Hunan Toyi Carbon Material Technology Co. Ltd. Changsha410000 China State Key Laboratory of Advanced Design and Manufacturing for vehicle Hunan University Changsha410082 China Key Laboratory of Advanced Functional Composite Materials Aerospace Research Institute of Materials and Processing Technology Beijing100076 China China Academy of Launch Vehicle Technology China

Aromatics are the preponderant component of fluid catalytic cracking (FCC) slurry oil, with notable differences in molecular structure between the light and heavy aromatics. The effect of these differences on the formation and optically anisotropic texture of mesophase remains elusive, impeding the preparation of high-quality mesophase pitch. This paper aims to regulate the ratio of light to heavy aromatics in the FCC slurry oil for optimizing the optically anisotropic texture of mesophase pitch. The results show that the heavy aromatics possess higher aromaticity, longer alkane side chains, larger molecular size and more reactive structures (methylene bridges, n-alkane structures) compared with the light aromatics. As an "accelerator", heavy aromatics can form mesophase quickly. Light aromatics not only served as a "diluent," but also assumed the function of a "lubricant", which facilitated the orderly arrangement of aromatic molecular lamellar. The system exhibits moderate reactivity that inhibits excessive condensation and modifies the structural orientation of pyrolysis products with the 2/5 ratio of light to heavy aromatics. Under these conditions, a high-quality mesophase pitch (d002=3.485 Å, Lc=19.832 Å) with wide-area optically anisotropic texture, suitable softening point (262°C) and short polymerization time (t=5.5 h) was obtained. This work provides theoretical support for the preparation of high-quality mesophase pitch by regulating the components of slurry oil. © 2024, The Authors. All rights reserved.

关键词： Aromatization

Flame Distortion and Backwards Heating Behaviors of Moving Fires: A Comparative Study

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SSRN 2023年

作者： Chen, Tao Zhou, Dan Lu, Zhaijun Meng, Shi Ministry of Education Hunan Changsha410075 China National & Local Joint Engineering Research Center of Safety Technology for Rail Vehicle Hunan Changsha410075 China Joint International Research Laboratory of Key Technology for Rail Traffic Safety Hunan Changsha410075 China

Moving fires have aroused attention in recent years, while the behavior of this special combustion phenomenon has not been fully investigated. In this paper, a 1:10 scale burning car was designed and established based on Froude similarity criterion, and a series of moving model experiments were performed. The discrepancy of flame morphological characteristics as well as heating behaviors between the stationary and moving fires were thoroughly compared. The results manifest that the distorted flame of moving fires is lengthened by 15.2%-45.7%, which cannot be predicted well by using current parameter models concerning stationary fire flames. Besides, the temperature upstream of the fire source is elevated sharply and the high-temperature zone is expanded substantially compared with stationary fires. Moreover, the heat flux induced by the flame of moving fires on the top surface of the burning car is dramatically enhanced. This paper represents a first step toward understanding the behavior of moving fires, which can provide a framework to deeply investigate the combustion mechanism of moving fires in the future. © 2023, The Authors. All rights reserved.

关键词： Fires

Mesh stiffness calculation and vibration analysis of the spur gear pair with tooth crack,considering the misalignment between the base and root circles

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International Journal of Mechanical System Dynamics 2021年第1期1卷 143-156页

作者： Jingyu Hou Shaopu Yang Qiang Li Yongqiang Liu Jiujian Wang School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijingChina State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversityShijiazhuangChina School of Mechanical Engineering Shijiazhuang Tiedao UniversityShijiazhuangChina State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan UniversityChangshaChina

An improved variable cross‐section cantilever beam model for evaluating the time‐varying mesh stiffness(TVMS)of the perfect gear tooth is developed in which the tooth number of driving gear is less than 42 and that of driven is more than *** TVMS obtained by the proposed method is compared with the result without considering the misalignment between the base circle and gear *** types of root crack models and changes inTVMS of 13‐crack levels are *** fault vibration characteristic of a single‐stage spur gear reducer with root crack is ana-lyzed and the correctness is qualitatively verified by the vibration signals of an experimental gearbox with crack or missing *** results presented in this paper are of great significance for a deep understanding of the possible causes of vibration and noise of gears and provide a theoretical foundation for the fault diagnosis of the gearbox.

关键词： backlash gear potential energy method time‐varying mesh stiffness(TVMS) tooth crack

Two-dimensional Rashba semiconductors and inversion-asymmetric topological insulators in monolayer Janus MAA'ZxZ'(4-x) family

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arXiv

arXiv 2024年

作者： Wei, Jinghui Tian, Qikun Xu, XinTing Qin, Guangzhao Zuo, Xu Qin, Zhenzhen Key Laboratory of Materials Physics Ministry of Education School of Physics Zhengzhou University Zhengzhou450001 China National Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle College of Mechanical and Vehicle Engineering Hunan University Changsha410082 China College of Electronic Information and Optical Engineering Nankai University Tianjin300350 China

The Rashba effect in Janus structures, accompanied by nontrivial topology, plays an important role in spintronics and even photovoltaic applications. Herein, through first-principles calculations, we systematically investigate the geometric stability and electronic structures of 135 kinds of Janus MAA'ZxZ'(4-x) family derived from two-dimensional MA2Z4 (M=Mg, Ga, Sr;A=Al, Ga;Z=S, Se, Te) monolayers, and design numerous Rashba semiconductors and inversion-asymmetric topological insulators. Specifically, there are a total of 26 Rashba semiconductors with isolated spin splitting bands contributed by Se/Te-pz orbitals at conduction band minimum, and their Rashba constant is closely related to the intrinsic electric field and spin-orbit coupling (SOC) strength. As the atomic number increases, the bandgap of Janus MAA'ZxZ'(4-x) continually decreases until it shrinks to a point where, when SOC is considered, band inversion occurs and it reopens with a nontrivial topology. In conjunction with band inversion, pz orbitals near the Fermi level can introduce double Rashba splitting featuring a distinctive hybrid spin texture, which can be further effectively adjusted through small biaxial strains and show a continuous evolution of topological to non-topological accompanied by different spin textures. This work provides new insights into Rashba and topology physics and further presents indispensable inversion asymmetry materials for the development of nonlinear optoelectronics. Copyright © 2024, The Authors. All rights reserved.

关键词： Topological insulators

Janus graphene: A two-dimensional half-auxetic carbon allotrope with a nonchemical Janus configuration

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Physical Review B 2024年第12期109卷 L121402-L121402页

作者： Linfeng Yu Jianhua Xu Chen Shen Hongbin Zhang Xiong Zheng Huimin Wang Zhenzhen Qin Guangzhao Qin State Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle College of Mechanical and Vehicle Engineering Hunan University Changsha 410082 People's Republic of China Institute of Materials Science Technical University of Darmstadt Darmstadt 64287 Germany Hunan Key Laboratory for Micro-Nano Energy Materials and Device and School of Physics and Optoelectronics Xiangtan University Xiangtan 411105 Hunan China School of Physics and Microelectronics Zhengzhou University Zhengzhou 450001 China Greater Bay Area Institute for Innovation Hunan University Guangzhou 511300 Guangdong Province People's Republic of China

We propose a nonchemical intrinsic Janus configuration and identify it in a pure sp2 hybridized carbon monolayer, termed Janus graphene. The spontaneous unilateral growth of carbon atoms drives the nonchemical Janus configuration in Janus graphene, which is totally different from the chemical effect in common Janus materials such as MoSSe. A structure-independent half-auxetic behavior is mapped in Janus graphene, that the structure maintains expansion whether stretched or compressed, which lies in the key role of the pz orbital. With the unique half-auxeticity that emerged in the nonchemical Janus configuration, Janus graphene enriches the functional carbon family as a promising candidate for micro/nanoelectronic device applications.

关键词： Crystal structure Poisson ratio 2-dimensional systems Graphene Janus particles Semiconductors First-principles calculations

Robust Enhanced Acoustic Sensing Via Gradient Phononic Crystals

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SSRN 2023年

作者： Chen, Tinggui Xia, Baizhan Yu, Dejie Bi, Chuanxing Institute of Sound and Vibration Research Hefei University of Technology Anhui Hefei230009 China State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle Engineering Hunan University Hunan Changsha410082 China

In this letter, a gradient phononic crystal (PC) structure is proposed for robust enhanced acoustic sensing. At first, the topologically protected edge states are introduced by breaking the space-inversion symmetry of the PC structure. Then, the topological edge mode dispersion curve and group velocity are demonstrated to be regulated by varying the structure parameters gradually and the edge states can be slowed down to zero group velocity and trapped at different positions. Consequently, topological acoustic rainbow trapping is formed. Furthermore, the robustness and enhancement properties are verified both numerically and experimentally. All the results indicate that the gradient PC structure is able to realize robust enhanced acoustic sensing. This work opens a new vista to improve the robustness of the PC-based enhanced acoustic sensing. © 2023, The Authors. All rights reserved.

关键词： Crystal structure

Constrained Probabilistic Pareto Dominance for Expensive Constrained Multiobjective Optimization Problems

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IEEE Transactions on Evolutionary Computation 2024年 1-1页

作者： Zhang, Zhiyao Wang, Yong Sun, Guangyong Pang, Tong Tang, Ke School of Automation Central South University Changsha China State Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle Hunan University Changsha China Guangdong Key Laboratory of Brain-Inspired Intelligent Computation Department of Computer Science and Engineering and the Research Institute of Trustworthy Autonomous Systems Southern University of Science and Technology Shenzhen China

This paper proposes a new parameterless constraint-handling technique, named constrained probabilistic Pareto dominance (CPPD), for expensive constrained multiobjective optimization problems (CMOPs). In CPPD, when comparing two solutions, in terms of each original objective, we design a new objective for each solution, which is the negative product of two probabilities calculated based on the predicted fitness mean values and the uncertainty information provided by Kriging models: 1) the probability that this solution satisfies all constraints, denoted as PoF, and 2) the probability that this solution is better than the other on the original objective, denoted as PoB. It is evident that for each solution, PoF and PoB indicate its feasibility and its optimality on the corresponding original objective, respectively. Then, Pareto dominance based on new objectives is executed. As a result, both competitive feasible solutions and promising infeasible solutions with good diversity can be preserved by CPPD. These two kinds of solutions can help the population to exploit the located feasible parts and to explore new feasible parts, respectively. Further, based on CPPD, we develop a Pareto-based Kriging-assisted constrained multiobjective evolutionary algorithm (called PEA) to deal with expensive CMOPs with two or three objectives. Finally, PEA is generalized to solve expensive constrained many-objective optimization problems, named PEA+. The effectiveness of CPPD, PEA, and PEA+ is verified by comprehensive experiments. IEEE

关键词： Evolutionary algorithms

safety Decision in Cyclist Injury-Based Motion Planning for Automated vehicles

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SSRN 2024年

作者： Yuan, Qiuqi Xiao, Zhi Zhu, Xiaoming Li, Jianyu Xiao, Peijie Xu, Shiwei School of Mechanical and Vehicle Engineering Hunan University Changsha410082 China State Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle Hunan University Changsha410082 China Suzhou Research Institute Hunan University Suzhou215144 China Shanghai Motor Vehicle Inspection Certification & Tech Innovation Center Co. Ltd. Shanghai201805 China

Automated vehicles (AVs) are expected to improve road traffic safety significantly. However, existing motion planning algorithms for AVs ignore the protection of vulnerable road users (VRUs) in corner cases (e.g., collisions are unavoidable). This work aims to reduce the severity of cyclist head injuries in the cases of an impending collision between AVs and two-wheelers by proposing a motion planning algorithm that combines injury prediction and optimization planning. First, we used the vehicle-two-wheeler simulated collision database to create a data mining-based prediction model for cyclist head injuries. Subsequently, a motion planning methodology that minimizes head injuries was proposed using this model. The proposed motion planning algorithm was tested under four typical cases. Simultaneously, we examined the effect of the initial speed of AV, the algorithm's starting position, and the algorithm's predictive-time domain on the algorithm's performance. The results demonstrate that the motion planning algorithm proposed in this study can considerably lower the severity of cyclist head injuries. The lower the initial speed of the AVs and the larger the predictive-time domain and the starting position of the algorithm, the greater the degree of reduction in the cyclist head injuries during the collision. It indicates that using the human injury prediction model based on data mining as the decision-making basis for the motion planning of AVs can significantly enhance road traffic safety. © 2024, The Authors. All rights reserved.

关键词： Bicycles

A Study of Lumbar Disc Injury under Typical Frontal Impact Load

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Journal of the Chinese Society of Mechanical Engineers, Transactions of the Chinese Institute of Engineers, Series C/Chung-Kuo Chi Hsueh Kung Ch'eng Hsuebo Pao 2021年第6期42卷 605-612页

作者： Xiao, Sen Qu, Zhi-Dong Yang, Ji-Kuang Huang, Jing Chen, Guang School of Mechanical Engineering Hebei University of Technology Tianjin300401 China Department of Applied Mechanics Chalmers University of Technology GothenburgSE-41296 Sweden State Key Laboratory of Advanced Design and Manufacture for Vehicle Body Hunan University Changsha410082 China

Although the number of seriously injured cases of frontal impact has been sharply decreased, the spine injury especially the lumber injury is still at a high level, thereby resulting in serious consequences. This paper is aimed to investigate the lumber injury mechanism in terms of the extension, compression, flexion and rotation loads during the frontal crash using the newly established lumbar model, especially to study the injury mechanism in the lumber disc on a microscale. A new detailed model for the lumbar was used, and the micro index of stress and strain was then investigated to analyze the injury mechanism of the lumber disc in the regulation frontal crash. The complex load can be divided into several representable load patterns. Four representative loads were used to reflect the loads in real accident. At last, the correlation of load types and the micro distribution was discussed to describe the injury mechanism. The results show that the disc will have the greatest stress when the loads applied on the sample. The strain in the disc is several times larger than that on the spine, which indicates the disc is the crucial part when considering the spine injury in the frontal crash. Each load poses its unique strain/stress response on the disc. The annulus fibrosus of the disc is dangerous under all loads, though the nucleus pulposus of the disc is safe during the impacts. Results in this study can provide a reference to the injury biomechanical study and the model can be spine used in the study of spine cord injury. © 2021, Chinese Mechanical engineering Society. All right reserved.

关键词： Lumber