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Boric Acid-Regulated Gelation and Ethanol-Assisted Preparation within Polybenzoxazine Aerogels Toward Excellent Flame Resistance, Alterable Wettability, and Effective Thermal Insulation

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SSRN 2023年

作者： Zhou, Jinlong Xiao, Yunyun Liu, Saihui Li, Zeyu Liu, Xinyi Zhang, Sizhao Li, Zhengquan International Institute for Innovation Jiangxi University of Science and Technology Jiangxi Nanchang330013 China Jiangxi Provincial Key Laboratory for Simulation and Modelling of Particulate Systems Jiangxi Nanchang330013 China School of Energy and Mechanics Jiangxi University of Science and Technology Jiangxi Nanchang330013 China

Polybenzoxazine aerogels have gained widespread attention in recent years, but the prevalent use of hazardous solvents in the preparation process has severely impeded their further development and promotion for practical applications. Herein, using ethanol as a solvent, a strategy of boric acid-induced microstructure regulation is proposed to construct boron-doped polybenzoxazine (BPBz) aerogels, which provides a feasible approach to overcome the above situation. The introduction of boric acid enhances the backbone strength by forming intermolecular bridging structures between PBz chains and allows the use of ambient pressure drying. The resulting BPBz aerogel demonstrates high stiffness (specific modulus up to 266.02 kN·m·kg−1), low bulk density (0.203 g·cm−3), and low thermal conductivity (0.043 W·m−1·K−1), exhibiting excellent fire resistance when exposed to a 1200 °C flame (the self-extinguishing interval less than 1 s). More interestingly, the aerogel demonstrates intrinsic and tunable wettability that correlates with the morphology. Combining the environmentally friendly preparation strategy and these advantages, BPBz aerogels hold promise for thermal management and fire protection applications in energy-saving construction and other harsh conditions. © 2023, The Authors. All rights reserved.

关键词： Boric acid

Lightweight and Covalent-Crosslinked Polybenzoxazine Aerogels for Fire Resistance and Thermal Insulation

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SSRN 2024年

作者： Li, Liangjun Zhou, Jinlong Xiao, Yunyun Zeyu, Li Liu, Saihui Zhang, Sizhao Feng, Jian Science and Technology on Advanced Ceramic Fibers and Composites Laboratory College of Aerospace Science and Technology National University of Defense Technology Changsha410073 China International Institute for Innovation Jiangxi University of Science and Technology Jiangxi Nanchang330013 China Jiangxi Provincial Key Laboratory for Simulation and Modelling of Particulate Systems Jiangxi Nanchang330013 China

The rapid advancement of modern industry and aerospace has imposed demands on thermal insulators to possess not only efficient isolation but also multifunctionality. Polybenzoxazine (PBz) aerogels with several advantages have garnered considerable research interests in recent years. Nevertheless, PBz aerogels acquired from ambient pressure drying still confront the challenge of exhibiting relatively high densities and thermal conductivities. Herein, to enrich the category and provide ideas for overcoming the above plight, hexamethylene diisocyanate (HDI) was chosen as an additive to achieve the chemical modification of the PBz aerogels. The chemical structure characterization shown that a successful reaction was occurred between the isocyanates and the hydroxyl groups, forming a urethane-bridged structure between two PBz molecular chains. In this paper, the effect of introducing HDI on the physical and thermal insulation properties of the aerogels was investigated. The HDI-modified PBz (PBz-HDI) aerogels demonstrated lower densities (0.237–0.256 g·cm−3) and thermal conductivities (0.0354−0.0370 W·m−1·K−1) in comparison with the pristine aerogel. In addition, despite an observed reduction in the residual char yields in the PBz-HDI groups, the introduction of HDI has been demonstrated to not impact their superior intrinsic flame retardancy. Given such commendable properties, PBz-HDI aerogel is expected to be a promising candidate for thermal insulation and fire resistance applications in various domains. © 2024, The Authors. All rights reserved.

关键词： Thermal insulation

Chaotic dynamics of granules-beam coupled vibration: Route and threshold

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arXiv

arXiv 2024年

作者： Li, Hang Li, Jian Fei, Hongzhu Hong, Guangyang Dong, Jinlu Yu, Aibing Key Laboratory of Structural Dynamics of Liaoning Province College of Sciences Northeastern University Shenyang110819 China ARC Research Hub for Computational Particle Technology Department of Chemical Engineering Monash University ClaytonVIC3800 Australia Centre for Simulation and Modelling of Particulate Systems Monash-Southeast University Joint Research Institute Suzhou China

Although granular materials are the second most processed in industry after water, the theoretical study of granules-structure interactions is not as advanced as that of fluid-structure interactions due to the lack of a unified view of the constitutive relation of granular materials. In the previous work [1], the theoretical model of granules-beam coupled vibration was developed and verified by experiments. However, it was also found that the system exhibits significant stiffness-softening Duffing characteristics even under micro-vibration, which implies that chaotic responses may be reached under certain conditions. To reveal the route and critical conditions for the system to enter chaos, in the present work, the chaotic dynamics of the system are studied. In qualitative analysis, Melnikov method is applied to analyze the instability behavior of the perturbed heteroclinic orbit of the system, thus the critical condition for the system to enter Smale horseshoe chaos, i.e., the Melnikov criterion, is obtained. The validity of the criterion is verified numerically. In experimental studies, the existence of chaotic responses and the route to chaos for granules-beam coupled vibrations is revealed. The experimental results suggest that the system response first experiences symmetry-breaking then undergoes a complete period-doubling cascade, and finally enters single-scroll chaos. In addition, although the Additional Dynamic Load (ADL) generated by granular media is highly complicated, a general and simple evolution pattern of the chaos threshold is found by parametric experiments, which is also supported by the Melnikov criterion. In short, the chaotic dynamics of granules-beam coupled vibration is revealed, which is a contribution to the engineering vibration aspect. On the theoretical side, an impressive result lies in that for the first time, the Melnikov criterion of such fractional-order systems is obtained in a global and closed form, which provides, respectively,

关键词： Granulation

Balancing Ventilation Performance and Energy Conservation: An Integrated Multi-Objective Optimization and Preference Decision-Making Model for Optimizing Impinging Jet Ventilation

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SSRN 2023年

作者： Dianyu, E. Tan, Cong Li, Jing Shi, Guangsi Liu, Yonggang Liu, Sida Yi, Lei Zhou, Zongyan Cui, Jiaxin Jiangxi Provincial Key Laboratory for Simulation and Modelling of Particulate Systems Jiangxi University of Science and Technology Nanchang330013 China International Institute for Innovation Jiangxi University of Science and Technology Nanchang330013 China ARC Research Hub for Computational Particle Technology Department of Chemical and Biological Engineering Monash University VIC3800 Australia

Balancing the requirements for thermal comfort (TC) and indoor air quality (IAQ) while minimizing energy consumption (EC) is a challenging trade-off problem in impinging jet ventilation (IJV), which has great potential for energy savings. Multi-criteria decision-making (MCDM) technology is a rapid and effective approach to address this issue in response to changing outdoor weather conditions. However, conflicting ventilation performances, such as TC (e.g. draught rate (DR), predictive mean vote (PMV)), IAQ (e.g. air change efficiency (ACE), local mean age of air (LMAA)) and EC, may present challenges in identifying optimal ventilation parameters. This study therefore proposes an integrated multi-objective optimization (MOO) and MCDM model to overcome this limitation. The former, which yields Pareto solutions, is to maintain ventilation performance indicators with good TC or IAQ standards within an acceptable range (e.g. -0.5 © 2023, The Authors. All rights reserved.

关键词： Energy conservation

Study on Effects of Operation Parameters on Ventilation Performances for a Floor-Standing Air Conditioner

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SSRN 2022年

作者： Dianyu, E. Tan, Cong Li, Jing Liu, Sida Zhou, Zongyan Cui, Jiaxin Yi, Lei Jiangxi Provincial Key Laboratory for Simulation and Modelling of Particulate Systems Jiangxi University of Science and Technology Nanchang330013 China International Institute for Innovation Jiangxi University of Science and Technology Nanchang330013 China ARC Research Hub for Computational Particle Technology Department of Chemical and Biological Engineering Monash University VIC3800 Australia

The floor-standing air conditioners (FSACs) have been widely used in civil and office buildings because of its advantages of high cooling/heating capacity and easy installation. The major challenge of FSACs is to meet the requirements of thermal comfort and indoor air quality (IAQ) while the operation energy consumption should be minimized. This study extensively examines the effects of some key operation parameters on the FSAC performance using validated computational fluid dynamics (CFD) method. The operation parameters include controllable supply vane angle, supply air velocity, supply air temperature, and uncontrollable outdoor weather condition. The main ventilation performance is assessed by indices such as predicted mean vote (PMV), predicted percent dissatisfied (PPD), draught rate (DR), local mean age of air (LMAA), and energy consumption (P system ). The relative importance of the operation parameters for each ventilation performance index is identified through evaluating the individual effects of the operation parameters on the ventilation performance. By comparing the individual effects and combined effects of the operation parameters on the ventilation performance, it is found that the variations of PMV, PPD, DR, LMAA and P system caused by the combined effects can be accounted by the corresponding most important operation parameters by 90.6%, 97.4%, 77.1%, 95.1% and 79.2%, respectively. Additionally, the outdoor weather conditions do not significantly affect DR, PPD and LMAA, but can shift PMV to uncomfortable levels. Finally, the constant-air-volume (CAV) system is recommended for FSACs during the steady stage and a simplified and optimized operation strategy is proposed. © 2022, The Authors. All rights reserved.

关键词： Sensitivity analysis

Balancing Ventilation Performance and Energy Conservation: An Integrated Multi-Objective Optimization and Preference Decision-Making Model for Optimizing Impinging Jet Ventilation

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SSRN 2023年

作者： Dianyu, E. Tan, Cong Li, Jing Shi, Guangsi Liu, Sida Yi, Lei Zhou, Zongyan Cui, Jiaxin Jiangxi Provincial Key Laboratory for Simulation and Modelling of Particulate Systems Jiangxi University of Science and Technology Nanchang330013 China International Institute for Innovation Jiangxi University of Science and Technology Nanchang330013 China ARC Research Hub for Computational Particle Technology Department of Chemical and Biological Engineering Monash University VIC3800 Australia

Balancing the requirements for thermal comfort (TC) and indoor air quality (IAQ) while minimizing energy consumption (EC) is a challenging trade-off problem in impinging jet ventilation (IJV), which has great potential for energy savings. Multi-criteria decision-making (MCDM) technology is a rapid and effective approach to address this issue in response to changing outdoor weather conditions. However, conflicting ventilation performances, such as TC (e.g. DR, PMV), IAQ (e.g. ACE, LMAA) and EC, may present challenges in identifying optimal ventilation parameters. This study therefore proposes an integrated multi-objective optimization (MOO) and MCDM model to overcome this limitation. The former, which yields Pareto solutions, is to maintain ventilation performance indicators with good TC or IAQ standards within an acceptable range (e.g. -0.5 © 2023, The Authors. All rights reserved.

关键词： Energy conservation

Balancing Ventilation Performance and Energy Conservation: An Integrated Multi-Objective Optimization and Preference Decision-Making Model for Optimizing Impinging Jet Ventilation

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SSRN 2023年

关键词： Energy conservation

Numerical Study of Percolation and Seepage Behaviors in Ion-Adsorption-Type Rare Earth Ore Leaching Process

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Mathematical Problems in Engineering 2023年第1期2023卷

作者： Dianyu, E. Su, Zhongfang Zeng, Jia Yang, Liuyimei Li, Jing Xu, Qiang Wang, Lin Cui, Jiaxin Jiangxi Provincial Key Laboratory for Simulation and Modelling of Particulate Systems Jiangxi University of Science and Technology Nanchang330013 China International Institute for Innovation Jiangxi University of Science and Technology Nanchang330013 China Ganjiang Innovation Academy Chinese Academy of Sciences Ganzhou341000 China ARC Research Hub for Computational Particle Technology Department of Chemical and Biological Engineering Monash University ClaytonVIC3800 Australia State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an710049 China Delft University of Technology Delft Netherlands

Ionic rare earth ore is a type of featured rare earth ore in China. Its mining process suffers from a long leaching cycle and considerable consumption of leaching agents. Improving mining efficiency requires a sound physical understanding of the leaching process. In this study, the CFD-based numerical model is used to analyze the physical process of leaching through porous media formed by particles. The simulation results indicate that a lower packing porosity and smaller particles packed granular porous medium result in much larger energy dissipation during seepage, and the energy dissipation increases with seepage velocity. It is found that when the seepage velocity increases to a certain high value, the energy dissipation exceeds the value predicted by Darcy's law, which is mainly caused by liquid turbulence. Additionally, the effect of particle shape is examined. The results show that the granular medium composed of prolate particles causes larger energy dissipation than oblate particles, and spherical particles play the least role. This phenomenon may result from the particle shape affecting the area of the frontal contact surface between particles and liquid. The results provide new insights into the fundamental understanding of percolation and seepage behaviors in the ion-adsorption-type rare earth ore leaching process. © 2023 E. Dianyu et al.

关键词： Energy dissipation

Numerical Investigation into the Impact of Oxy-Fuel Combustion on the Thermochemical State and Slab Heating Behaviour Inside a Metallurgical Heating Furnace

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SSRN 2024年

作者： Dianyu, E. Yang, Yifeng Weng, Lingyi Yang, Yingxin Liu, Yonggang Chen, Chao Cui, Jiaxin Liu, Lingling Jiangxi Provincial Key Laboratory for Simulation and Modelling of Particulate Systems Jiangxi University of Science and Technology Nanchang330013 China International Institute for Innovation Jiangxi University of Science and Technology Nanchang330013 China School of Energy and Mechanical Engineering Jiangxi University of Science and Technology Nanchang330013 China Faculty of Materials Metallurgy and Chemistry Jiangxi University of Science and Technology Ganzhou341000 China Xinyu Iron and Steel Group Co. Ltd Xinyu338001 China College of Materials Science and Engineering Taiyuan University of Technology Taiyuan030024 China State Key Laboratory of Vanadium Titanium Resources Comprehensive Utilization Chengdu610031 China Pangang Group Research Institute Co. Ltd. Chengdu610031 China Monash University Australia

Oxy-fuel combustion is a promising technology for the merits of energy-saving and NOx emission reduction and has been gradually promoted to the application of metallurgical heating furnaces. For the purpose of understanding and optimizing the heating process of the industrial furnace, with a particular focus on the effect of fuel types and oxy-fuel combustion, a comprehensive transient 3D CFD model was built for the simulation of the complicated in-furnace thermochemical states and the gas-solid heat transfer at multi-scales. It was observed that under constant calorific heat input conditions, the fuel composition appears to have little influence on the internal thermal state and the slab heating. Meanwhile, oxy-fuel combustion enhances the in-furnace heat radiation intensity, leading to higher average gas and thus higher slab temperatures. However, the in-furnace thermal distribution becomes uneven and the slab internal temperature difference increases. Under the prerequisite that the slab temperature leaving the furnace is between 1373-1573 K and the maximum internal temperature difference is less than 50 K/m, the production efficiency can be increased by 6.25% when oxy-fuel combustion is applied, with the corresponding slab residence time decreases from 7424s to 6960s. © 2024, The Authors. All rights reserved.

关键词： Optimization