JUSTC

2022-7 Contents

2022, 52(7): 1-2.

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Abstract:

2022-7 Abstract

2022, 52(7): 1-2.

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Abstract:

Multifunctional artificial nacre via biomimetic matrix-directed mineralization

Yu-Feng Meng, Bo Yang, Li-Bo Mao, Shu-Hong Yu

2022, 52(7): 1. doi: 10.52396/JUSTC-2022-0022

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Abstract:
Natural nacre, one of the most studied biological structural materials with delicate hierarchical structures and extraordinary performance, has inspired the design and fabrication of artificial structural ceramics with high fracture toughness. However, to meet the diverse requirements of different applications, future structural materials must be multifunctional with superior mechanical properties, such as strength, hardness, and toughness. Herein, based on the matrix-directed mineralization method for producing biomimetic structural materials, we introduce nanoparticles with different inherent functions into the platelets of artificial nacre via the co-mineralization of aragonite and the nanoparticles. Besides their enhanced mechanical properties, the obtained artificial nacre materials also exhibit different functions depending on the type of the nanoparticles. To extend the versatility of this strategy, the effects of nanoparticles of different sizes and zeta potentials on mineralization are also analyzed. This universal strategy can be applied to the fabrication of other types of functionalized biomimetic structural ceramics that have potential applications in various fields, such as biomedical science.

Simultaneous inference for a high-dimensional precision matrix

Wenjie Gao, Ruipeng Dong, Jie Wu

2022, 52(7): 2. doi: 10.52396/JUSTC-2022-0004

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Abstract:
Gaussian graphical models have been widely used for network data analysis. Although various methods exist for estimating the parameters, simultaneous inference is essential for graphical models. In this study, we propose a bootstrap procedure to conduct simultaneous inference for Gaussian graphical models. The simultaneous inference procedure is applied to large-scale graphical models and allows the dimension of the parameter vector of interest to exceed the sample size. We prove that the simultaneous test achieves a pre-set significance level asymptotically. Further simulation studies demonstrate the effectiveness of the proposed methods.

Enhancing the energy potential of food waste digestate via catalytic co-hydrothermal treatment: The pyrolysis and combustion performance of hydrochar

Xiefei Zhu, Zejun Luo

2022, 52(7): 3. doi: 10.52396/JUSTC-2022-0049

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Abstract:
Catalytic hydrothermal treatment is considered one of the most promising technologies for recovering energy from carbonaceous wastes. In so doing, it facilitates the realization of waste-to-energy and resource utilization efforts. In this study, hydrochar was prepared from food waste digestate and wood waste via catalytic co-hydrothermal treatment using potassium carbonate (K₂CO₃) and sodium carbonate (Na₂CO₃) as alkali catalysts. Based on the physicochemical properties of hydrochar, including proximate analysis, element distribution, high heating value (HHV), surface functional groups, and morphology, the gaseous products of pyrolysis and the combustion performance of hydrochar were further investigated using TG-FTIR-MS and TG-DSC, respectively. In addition, the hydrochar combustion kinetics and thermodynamics were probed. Specifically, the hydrochar obtained from Na₂CO₃ catalysis (HC-Na) demonstrated a higher heating value (26.85 MJ·kg⁻¹) with higher calcium retention, while the hydrochar obtained from K₂CO₃ catalysis (HC-K) had a greater number of functional groups and larger carbon content. Moreover, the pyrolysis gaseous products of hydrochar were rich in hydrocarbons. HC-K exhibited better comprehensive combustion performance with the activation energy (Ea) values of 79.32 kJ·mol⁻¹ and 67.91 kJ·mol⁻¹ using the Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose methods, respectively. These results provide a prospect for enhancing the comprehensive utilization of carbonaceous solid waste through catalytic co-hydrothermal treatment.

Comparison between homogeneous and separated flow models of isobutane flowing through adiabatic capillary tubes

Yonghui Shu, Peng Hu, Ibrahim Adnan, Lianghui Zhi, Qi Chen

2022, 52(7): 5. doi: 10.52396/JUSTC-2021-0130

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Abstract:
Capillary tubes have been widely used as expansion devices in small-scale refrigeration and heat-pump systems. However, adiabatic flow through a capillary tube is extremely complicated, despite its simple geometry. This work presents a comparative study on the homogenous flow model and separated flow model, which were used to simulate the flow of isobutene (R600a) through adiabatic capillary tubes. The influence of different combinations of friction factor and two-phase viscosity correlations, and the effect of metastable flow on the flow characteristics were investigated. The predicted mass flow rate was lower when the separated flow model was used. The separated flow model performed better in predicting a mass flow rate over 2 kg·h⁻¹. The Colebrook friction factor correlation combined with the Dukler or McAdams viscosity correlation yielded smaller deviations of 5.43%, 5.49% and 5.44%, 5.43% when ignoring and considering the metastable flow, respectively. Additionally, the homogenous flow model adopting the Bittle and Pate friction factor and Dukler viscosity correlations achieved the highest accuracy with a mass flow rate under 2 kg·h⁻¹. The mean error was 4.12% in the case without metastable flow, and 3.37% in the case with metastable flow.

Insights on cellulose hydrolysis in the porous structure of biomass particles using the lattice Boltzmann method

Haoyang Wei, Xiangqian Wei, Siwei Liu, Weitao Sun, Yunlong Tu, Chengguang Wang, Longlong Ma

2022, 52(7): 4. doi: 10.52396/JUSTC-2021-0268

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Abstract:
Lignocellulose biomass has been recognized as one of the most promising sources of low-cost and renewable biofuels, and its conversion into alternative fuels and valuable platform molecules has attracted widespread attention. The porous solid residue from lignocellulose biomass, which was pretreated by steam-stripping, is catalyzed by dilute sulfuric acid to form levulinic acid (LA). The process includes porous media diffusion, multicomponent reactive transport, liquid-solid interface reaction, and cellulose dissolution. Understanding the interactions between these complex physicochemical processes is the basis for optimizing the performance of the hydrolysis reaction. In this study, a porous reaction transport model based on the lattice Boltzmann method (LBM) was established to simulate the conversion of cellulose to LA which was catalyzed by dilute acid. The simulation results were compared with the existing experimental results to verify the accuracy of the model. The simulation results showed that temperature has a significant effect on hydrolysis and the highest carbon yield was obtained at 180 °C. Without considering the lignin reaction, the higher the sulfuric acid concentration, the better is the hydrolysis efficiency in the range of 4% – 8%. The influence of cellulose content and steam-stripping the residue porosity on the dissolution rate of cellulose was also evaluated. The average dissolution rate of cellulose is the highest within 75 min, when the porosity is 0.7 and the cellulose content is 50%.

Bundling strategies for platforms with an installed base

Jie Wu, Chenwei Zhou, Xiang Ji, Mingjun Li

2022, 52(7): 6. doi: 10.52396/JUSTC-2021-0257

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Abstract:
As an emerging platform, hardware/software platforms differ from traditional retail platforms because they require consumers to spend a certain amount of money accessing them. Therefore, an installation base is created. Considering the game console as an example, only consumers with an installation base can purchase a third-party game product on the platform. Otherwise, consumers will be unable to play games. It is generally believed that the existence of an installed base will benefit third-party content providers, and at the same time, it will not benefit platform manufacturers. Therefore, it can be observed that game platforms often bundle new consoles with third-party content, forcing consumers with installed bases to purchase a new console. Thus, building a model to study the impact of the installation based on the bundling strategy of the video game platform and to analyze the optimal pricing and profit under different bundling strategies is meaningful. Our study analyzed the impact of the installed base under different bundling strategies and found that the installed base dose not always have a positive impact on platform manufacturers. The study also analyzed the equilibrium of competing platform manufacturers and found that, under certain conditions, both the bundling-bundling strategy and the unbundling-unbundling strategy may exist as equilibrium.

2022 Vol. 52, No. 7

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