| 1. |
- Li, Nan, et al.
(författare)
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Study of the influence of the characteristics of loose residual coal on the spontaneous combustion of coal gob
- 2020
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Ingår i: Energy Science & Engineering. - : John Wiley & Sons. - 2050-0505. ; 8:3, s. 689-701
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Tidskriftsartikel (refereegranskat)abstract
- Mine fires are becoming a serious issue as the intensity of mining increases, especially in deep mines. Loose coal gob has a hidden ignition location and a high possibility of spontaneous combustion, which makes fire prevention difficult. Therefore, based on the theory of gas seepage and the characteristics of loose coal, a model of air leakage and spontaneous combustion in gob is established in this paper. Using working face #10414 in the Yangliu coal mine as an example, the relationship between the three spontaneous coal combustion (CSC) zones and the three stress zones is analyzed and verified by combining a FLAC3D simulation with field monitoring. In addition, the influence of advancing speed on the CSC is discussed, and suggestions for fire prevention are presented. The results show that the variation in the calorific value of the CSC with increasing degree of looseness of the residual coal in the gob forms an arch‐shape. There is a one‐to‐one relationship between the distribution of the three stress zones and the three CSC zones. In addition, as the advancing speed increases, the contact time between the loose coal body and the air decreases and the possibility of CSC decreases. This study provides a scientific basis for fire prevention and control in mines.
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| 2. |
- Bhalla, Aditya, et al.
(författare)
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Engineered Lignin in Poplar Biomass Facilitates Cu-Catalyzed Alkaline-Oxidative
- 2018
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 6:3, s. 2932-2941
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Tidskriftsartikel (refereegranskat)abstract
- Both untransformed poplar and genetically modified “zip-lignin” poplar, in which additional ester bonds were introduced into the lignin backbone, were subjected to mild alkaline and copper-catalyzed alkaline hydrogen peroxide (Cu-AHP) pretreatment. Our hypothesis was that the lignin in zip-lignin poplar would be removed more easily than lignin in untransformed poplar during this alkaline pretreatment, resulting in higher sugar yields following enzymatic hydrolysis. We observed improved glucose and xylose hydrolysis yields for zip-lignin poplar compared to untransformed poplar following both alkaline-only pretreatment (56% glucose yield for untransformed poplar compared to 67% for zip-lignin poplar) and Cu-AHP pretreatment (77% glucose yield for untransformed poplar compared to 85% for zip-lignin poplar). Compositional analysis, glycome profiling, and microscopy all supported the notion that the ester linkages increase delignification and improve sugar yields. Essentially no differences were noted in the molecular weight distributions of solubilized lignins between the zip-lignin poplar and the control line. Significantly, when zip-lignin poplar was utilized as the feedstock, hydrogen peroxide, catalyst, and enzyme loadings could all be substantially reduced while maintaining high sugar yields.
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| 3. |
- Gehrmann, Sebastian, et al.
(författare)
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GEMv2: Multilingual NLG Benchmarking in a Single Line of Code
- 2022
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Ingår i: Proceedings of the 2022 Conference on Empirical Methods in Natural Language Processing: System Demonstrations. - : Association for Computational Linguistics (ACL). ; , s. 266-281
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Konferensbidrag (refereegranskat)abstract
- Evaluations in machine learning rarely use the latest metrics, datasets, or human evaluation in favor of remaining compatible with prior work. The compatibility, often facilitated through leaderboards, thus leads to outdated but standardized evaluation practices. We pose that the standardization is taking place in the wrong spot. Evaluation infrastructure should enable researchers to use the latest methods and what should be standardized instead is how to incorporate these new evaluation advances.We introduce GEMv2, the new version of the Generation, Evaluation, and Metrics Benchmark which uses a modular infrastructure for dataset, model, and metric developers to benefit from each other’s work. GEMv2 supports 40 documented datasets in 51 languages, ongoing online evaluation for all datasets, and our interactive tools make it easier to add new datasets to the living benchmark.
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| 4. |
- Ji, Cheng, et al.
(författare)
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Crystallography of low Z material at ultrahigh pressure : Case study on solid hydrogen
- 2020
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Ingår i: Matter and Radiation at Extremes. - : American Institute of Physics (AIP). - 2468-2047 .- 2468-080X. ; 5:3
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Tidskriftsartikel (refereegranskat)abstract
- Diamond anvil cell techniques have been improved to allow access to the multimegabar ultrahigh-pressure region for exploring novel phenomena in condensed matter. However, the only way to determine crystal structures of materials above 100 GPa, namely, X-ray diffraction (XRD), especially for low Z materials, remains nontrivial in the ultrahigh-pressure region, even with the availability of brilliant synchrotron X-ray sources. In this work, we perform a systematic study, choosing hydrogen (the lowest X-ray scatterer) as the subject, to understand how to better perform XRD measurements of low Z materials at multimegabar pressures. The techniques that we have developed have been proved to be effective in measuring the crystal structure of solid hydrogen up to 254 GPa at room temperature [C. Ji et al., Nature 573, 558–562 (2019)]. We present our discoveries and experiences with regard to several aspects of this work, namely, diamond anvil selection, sample configuration for ultrahigh-pressure XRD studies, XRD diagnostics for low Z materials, and related issues in data interpretation and pressure calibration. We believe that these methods can be readily extended to other low Z materials and can pave the way for studying the crystal structure of hydrogen at higher pressures, eventually testing structural models of metallic hydrogen.
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| 5. |
- Tian, Jian-jun, et al.
(författare)
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Influence of heat treatment on fracture and magnetic properties of radially oriented Sm 2 Co 17 permanent magnets
- 2007
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Ingår i: Transactions of Nonferrous Metals Society of China. - 1003-6326 .- 2210-3384. ; 17:3, s. 491-495
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Tidskriftsartikel (refereegranskat)abstract
- The quenching, fracture and aging treatment of radially oriented Sm2Co17 ring magnets were investigated. The results indicate that the ring magnets have obvious anisotropy of thermal expansion, which easily leads to the splits of the magnets during quenching. The fracture is brittle cleavage fracture. The difference (δa) of the expansion coefficient reaches the maximum value at 800–850 °C. So, various quenching processes at different steps are adopted in order to reduce the splits. When the magnets are aged. 1:5 phase precipitates from the 2:17 matrix phase and forms a cellular microstructure with 2:17 phase. BHmax and 3Hc reach the maximum value 226 kJ/m3 and 2170 kA/m after being aged at 850 °C for 4 h and 8 h, respectively. The aging treatment at 850 °C has little influence on remanence(Br), which can always keep a high value (≥1.0 T). Through appropriate heat treatment, the ring magnets have uniform cellular microstructure and excellent magnetic properties: Br1.0T, 3Hc≥2 100 kA/m, BHmax≥220 kJ/m3.
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| 6. |
- Wei, Wei, et al.
(författare)
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Gradient-driven parking navigation using a continuous information potential field based on wireless sensor network
- 2017
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Ingår i: Information Sciences. - : Elsevier. - 0020-0255 .- 1872-6291. ; 408, s. 100-114
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Tidskriftsartikel (refereegranskat)abstract
- Wireless sensor networks can support building and transportation system automation in numerous ways. An emerging application is to guide drivers to promptly locate vacant parking spaces in large parking structures during peak hours. This paper proposes efficient parking navigation via a continuous information potential field and gradient ascent method. Our theoretical analysis proves the convergence of a proposed algorithm and efficient convergence during the first and second steps of the algorithm to effectively prevent parking navigation from a gridlock situation. The empirical study demonstrates that the proposed algorithm performs more efficiently than existing algorithms.
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