| 1. |
- Yang, Xigui, et al.
(author)
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Novel Superhard sp3 Carbon Allotrope from Cold-Compressed C70 Peapods
- 2017
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In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 118:24
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Journal article (peer-reviewed)abstract
- Design and synthesis of new carbon allotropes have always been important topics in condensed matter physics and materials science. Here we report a new carbon allotrope, formed from cold-compressed C70 peapods, which most likely can be identified with a fully sp3-bonded monoclinic structure, here named V carbon, predicted from our simulation. The simulated x-ray diffraction pattern, near K-edge spectroscopy, and phonon spectrum agree well with our experimental data. Theoretical calculations reveal that V carbon has a Vickers hardness of 90 GPa and a bulk modulus ∼400 GPa, which well explains the "ring crack" left on the diamond anvils by the transformed phase in our experiments. The V carbon is thermodynamically stable over a wide pressure range up to 100 GPa, suggesting that once V carbon forms, it is stable and can be recovered to ambient conditions. A transition pathway from peapod to V carbon has also been suggested. These findings suggest a new strategy for creating new sp3-hybridized carbon structures by using fullerene@nanotubes carbon precursor containing odd-numbered rings in the structures.
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| 2. |
- Yao, Mingguang, et al.
(author)
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Tailoring Building Blocks and Their Boundary Interactionfor the Creation of New, Potentially Superhard, Carbon Materials
- 2015
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In: Advanced Materials. - : John Wiley & Sons. - 0935-9648 .- 1521-4095. ; 27:26, s. 3962-3968
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Journal article (peer-reviewed)abstract
- A strategy for preparing hybrid carbon structures with amorphous carbon clusters as hard building blocks by compressing a series of predesigned two-component fullerides is presented. In such constructed structures the building blocks and their boundaries can be tuned by changing the starting components, providing a way for the creation of new hard/superhard materials with desirable properties.
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| 3. |
- Kristan, Matej, et al.
(author)
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The first visual object tracking segmentation VOTS2023 challenge results
- 2023
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In: 2023 IEEE/CVF International conference on computer vision workshops (ICCVW). - : Institute of Electrical and Electronics Engineers Inc.. - 9798350307443 - 9798350307450 ; , s. 1788-1810
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Conference paper (peer-reviewed)abstract
- The Visual Object Tracking Segmentation VOTS2023 challenge is the eleventh annual tracker benchmarking activity of the VOT initiative. This challenge is the first to merge short-term and long-term as well as single-target and multiple-target tracking with segmentation masks as the only target location specification. A new dataset was created; the ground truth has been withheld to prevent overfitting. New performance measures and evaluation protocols have been created along with a new toolkit and an evaluation server. Results of the presented 47 trackers indicate that modern tracking frameworks are well-suited to deal with convergence of short-term and long-term tracking and that multiple and single target tracking can be considered a single problem. A leaderboard, with participating trackers details, the source code, the datasets, and the evaluation kit are publicly available at the challenge website1
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| 4. |
- Xie, Shijie, et al.
(author)
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Numerical study on cracking behavior and fracture failure mechanism of fractured rocks under shear loading
- 2024
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In: Computational Particle Mechanics. - : Springer Nature. - 2196-4378 .- 2196-4386. ; 11:2, s. 903-920
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Journal article (peer-reviewed)abstract
- Pre-existing fractures in rock engineering significantly affect the entire structural stability. To deepen the understanding of the fracture mechanism of fractured rocks under shear loading, a numerical study based on the distinct element method was conducted to investigate the shear behaviors of rock fractures. A discrete element model with fractures of Barton's ten standard profiles was established, and shear simulations under different normal stresses and joint roughness coefficient (JRC) were carried out. The simulation results show that the shear stress–displacement curve can be divided into three stages: elastic loading stage, inelastic stage and stress drop stage. The shear strength, internal friction angle and cohesion increase with the increase of normal stress and JRC. These macroscopic mechanical characteristics are consistent with the results of previous experimental studies. Most of the microcracks generated during the shearing process are tensile microcracks, which are first formed at the steep position of the fracture profile line, and the proportion of shear microcracks is less than 10%. In addition, the contact force between particles is mainly compressive stress, which is greater in magnitude and density than tensile stress. As the shear proceeds, the displacement of the particles gradually changes from non-uniform distribution to uniform distribution.
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| 5. |
- Xie, Shijie, et al.
(author)
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Prediction of shear strength of rock fractures using support vector regression and grid search optimization
- 2023
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In: Materials Today Communications. - : ELSEVIER. - 2352-4928. ; 36
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Journal article (peer-reviewed)abstract
- The shear strength of rock fractures serves as a crucial control on the strength and deformation behavior of engineering rock masses. To reduce the uncertainties in the shear strength evaluation, a hybrid machine learning model (GS-SVR model) of the support vector regression (SVR) underpinned by the grid search optimization algorithm (GS) was proposed. It achieves the prediction of shear strength by generalization and deduction of a large amount of data on rock fracture parameters, which avoids the complex derivation of theoretical equations. For practical application, a dataset comprising more than 134 shear tests on various rocks was compiled to collect the relevant three-dimensional morphological and mechanical parameters for training and prediction. Three classical shear strength models and the original SVR model were introduced for further comparison. Finally, sensitivity analysis was carried out to explore the relative importance of input variables to the shear strength. The results showed that the GS-SVR model (correlation coefficient R2 = 0.984, root mean squared error RMSE=0.383) outperformed the original SVR model (R2 = 0.936, RMSE=0.568). Moreover, compared with three classical shear strength models, the prediction results of the GS-SVR model were also most consistent with the experimental results (with the lowest RMSE and the highest R2). This machine learning model enhanced by GS can be used as a reliable and accurate shear strength prediction tool to partially replace laboratory tests to save costs.
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| 6. |
- Zhou, Guoyi, et al.
(author)
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Climate and litter C/N ratio constrain soil organic carbon accumulation
- 2019
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In: National Science Review. - : Oxford University Press (OUP). - 2095-5138 .- 2053-714X. ; 6:4, s. 746-757
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Journal article (peer-reviewed)abstract
- Soil organic carbon (SOC) plays critical roles in stabilizing atmospheric CO2 concentration, but the mechanistic controls on the amount and distribution of SOC on global scales are not well understood. In turn, this has hampered the ability to model global C budgets and to find measures to mitigate climate change. Here, based on the data from a large field survey campaign with 2600 plots across China's forest ecosystems and a global collection of published data from forested land, we find that a low litter carbon-to-nitrogen ratio (C/N) and high wetness index (P/PET, precipitation-to-potential-evapotranspiration ratio) are the two factors that promote SOC accumulation, with only minor contributions of litter quantity and soil texture. The field survey data demonstrated that high plant diversity decreased litter C/N and thus indirectly promoted SOC accumulation by increasing the litter quality. We conclude that any changes in plant-community composition, plant-species richness and environmental factors that can reduce the litter C/N ratio, or climatic changes that increase wetness index, may promote SOC accumulation. The study provides a guideline for modeling the carbon cycle of various ecosystem scales and formulates the principle for land-based actions for mitigating the rising atmospheric CO2 concentration.
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| 7. |
- (Chris) Zhao, Yuxiang, et al.
(author)
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Factors that affect asker's pay intention in trilateral payment‐based social Q&A platforms : From a benefit and cost perspective
- 2020
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In: Journal of the Association for Information Science and Technology. - : Wiley. - 2330-1635 .- 2330-1643. ; 71:5, s. 516-528
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Journal article (peer-reviewed)abstract
- More and more social Q&A platforms are launching a new business model to monetize online knowledge. This monetizing process introduces a more complicated cost and benefit tradeoff to users, especially for askers' concerns. Much of the previous research was conducted in the context of free‐based Q&A platform, which hardly explains the triggers that motivate askers' pay intention. Based on the theories of social exchange and social capital, this study aims to identify and examine the antecedents of askers' pay intention from the perspective of benefit and cost. We empirically test our predictions based on survey data collected from 322 actual askers in a well‐known trilateral payment‐based social Q&A platform in China. The results by partial least squares (PLS) analysis indicate that besides noneconomic benefits including self‐enhancement, social support, and entertainment, financial factors such as cost and benefit have significant influences on the perceived value of using trilateral payment‐based Q&A platforms. More important, we further identify that the effect of financial benefit is moderated by perceived reciprocity belief, and the effect of perceived value is moderated by perceived trust in answerers. Our findings contribute to the previous literature by proposing a theoretical model that explains askers' behavioral intention, and the practical implications for payment‐based Q&A service providers and participants.
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| 8. |
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| 9. |
- Liu, Zhouying, et al.
(author)
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Exploring askers' switching from free to paid social Q&A services : A perspective on the push-pull-mooring framework
- 2021
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In: Information Processing & Management. - : Elsevier BV. - 0306-4573 .- 1873-5371. ; 58:1
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Journal article (peer-reviewed)abstract
- The purpose of this study is to explore the factors that prompt askers to switch from free to paid social question-and-answer (SQA) services. Prior studies have investigated users' motivations and participation in free and paid SQA services; however, little attention has been paid to askers' switching behavior. We empirically analyzed the content of qualitative interviews from 64 askers on a well-known SQA platform in China. Based on the push-pull-mooring framework, we identified and classified factors that influenced askers' to switch from free to paid Q&A services, using the critical incident technique, after which we calculated the entropy weights of the 16 subcategories before and after the switch, using the entropy weight method. The findings suggest that askers' switching behavior was influenced by push factors (i.e., dissatisfaction with the free SQA service), pull factors (i.e., satisfaction with the paid SQA service), and mooring factors (i.e., social factors, personal factors, situational factors). Moreover, the findings show that the effects of these factors vary significantly before and after a switch. Dissatisfaction with the quality of information from the free SQA service would influence users before a switch, whereas satisfaction with the quality of information from the paid SQA service would influence them after a switch. In terms of mooring factors, the effects of social and personal factors on askers' switching behavior, especially subjective norms and cognitive lock-in, turn out to be less significant after a switch, whereas the effect of trust is more significant. Besides, the effects of situational factors are more or less the same before and after a switch. To the best of our knowledge, this paper is one of the first attempts to explore factors that affect askers' switching behavior and to shed light on the managerial strategies of paid SQA services.
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| 10. |
- Xiong, Shaobing, et al.
(author)
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Direct Observation on p- to n-Type Transformation of Perovskite Surface Region during Defect Passivation Driving High Photovoltaic Efficiency
- 2021
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In: Joule. - : CELL PRESS. - 2542-4351. ; 5:2, s. 467-480
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Journal article (peer-reviewed)abstract
- Perovskite solar cells (PSCs) suffer from significant nonradiative recombination, limiting their power conversion efficiencies. Here, for the first time, we directly observe a complete transformation of perovskite MAPbI(3) surface region energetics from p- to n-type during defect passivation caused by natural additive capsaicin, attributed to the spontaneous formation of a p-n homojunction in perovskite active layer. We demonstrate that the p-n homojunction locates at similar to 100 nm below perovskite surface. The energetics transformation and defect passivation promote charge transport in bulk perovskite layer and at perovskite/PCBM interface, suppressing both defect-assisted recombination and interface carrier recombination. As a result, an efficiency of 21.88% and a fill factor of 83.81% with excellent device stability are achieved, both values are the highest records for polycrystalline MAPbI(3) based p-i-n PSCs reported to date. The proposed new concept of synergetic defect passivation and energetic modification via additive provides a huge potential for further improvement of PSC performance.
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