| 5101. |
- Wei, X., et al.
(författare)
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Assessing benefits in the flexibility of refined oil logistics from pipeline network integration reform : A case from South China
- 2022
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Ingår i: Chemical Engineering Science. - : Elsevier Ltd. - 0009-2509 .- 1873-4405. ; 253
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Tidskriftsartikel (refereegranskat)abstract
- The pipeline network integration reform enables unified management of pipelines from different entities. For refined oil logistics, this paper proposes a framework based on the MILP optimization model to quantify its flexibility. Considering the uncertainty, three disturbances occur in the logistics concurrently, and 10,000 simulations are performed to obtain the turnover cost. The ratio of pipeline transportation cost to the calculated average turnover cost is defined as the flexibility indicator. Taking China's largest refined oil pipeline network as an example, the results show that the flexibility rises 8.9% after the reform. The paper also quantifies the impact of the reform on logistics flexibility in South China, which is embodied in achieving lower freights and GHG emissions, lower impact by fluctuations, higher pipeline utilization, more efficient oil product turnover, and the avoiding of depot shortages when facing logistical disturbances. The underlying reasons for the results and 3E analysis are analyzed.
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| 5102. |
- Wei, Xiuyu, 1979, et al.
(författare)
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Corrosion Behavior of WC-Co-(Ni)-(Cr) Cemented Carbide in Neutral Solution
- 2020
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Ingår i: Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering. - 1002-185X. ; 49:1, s. 313-319
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Tidskriftsartikel (refereegranskat)abstract
- Three groups of WC-Co-(Ni)-(Cr) cemented carbides with different binder phase compositions were prepared by powder metallurgy using WC, Co, Ni and Cr3C2 powders as raw materials. The corrosion behavior of the three alloys in neutral solution was studied by polarization curve test and immersion experiment. The corrosion mechanism was discussed by means of scanning electron microscopy, energy spectrum analysis, X-ray photoelectron spectroscopy (XPS) and EBSD. The results show that in neutral solution the corrosion of WC-Co and WC-Co-Cr cemented carbides is mainly caused by the selective dissolution of Co and the corrosion products after immersion are mainly composed of Co(OH)2. The corrosion resistance of WC-Co cemented carbide in neutral solution can be improved by the addition of Cr, which may be related to the decrease in the content of hcp-Co in the binder phase by adding Cr. Adding Ni and Cr together can further improve the corrosion resistance of WC-Co cemented carbide in neutral solution. After immersion for 480 h in Na2SO4 solution, the WC-Co-Ni-Cr alloy sample is just corroded slightly.
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| 5103. |
- Wei, Xueqiong, et al.
(författare)
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Dataset of 1 km cropland cover from 1690 to 1999 in Scandinavia
- 2021
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Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3508 .- 1866-3516. ; 13:6, s. 3035-3056
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Tidskriftsartikel (refereegranskat)abstract
- Spatially explicit historical land cover datasets are essential not only for simulations of climate and environmental dynamics but also for projections of future land use, food security, climate, and biodiversity. However, widely used global datasets are developed for continental- to global-scale analysis and simulations. Their accuracy depends on the verification of more regional reconstruction results. This study collects cropland area data of each administrative unit (parish/municipality/county) in Scandinavia from multiple sources. The cropland area data are validated, calibrated, interpolated, and allocated into 1 km×1 km grid cells. Then, we develop a dataset with spatially explicit cropland area from 1690 to 1999. Results indicate that the cropland area increased from 1.82×106 ha to 6.71×106 ha from 1690 to 1950 and then decreased to 5.90×106 ha in 1999. Before 1810, cropland cover expanded in southern Scandinavia and remained stable in northern Scandinavia. From 1810 to 1910, northern Scandinavia experienced slight cropland expansion. The cropland area increased rapidly in the southern part of the study area before changing slightly. After 1950, the cropland areas began to decrease in most regions, especially in eastern Scandinavia. When comparing global datasets with this study, although the total Scandinavia cropland area is in agreement among SAGE (Center for Sustainability and the Global Environment), HYDE (History Database of the Global Environment ) 3.2, PJ (Pongratz Julia), and this study, the spatial patterns show considerable differences, except for in Denmark between HYDE 3.2 and this study. The dataset can be downloaded from https://doi.org/10.1594/PANGAEA.926591 (Wei et al., 2021).
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| 5104. |
- Wei, Xikun, et al.
(författare)
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Deep-learning-based harmonization and super-resolution of near-surface air temperature from CMIP6 models (1850–2100)
- 2023
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Ingår i: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 43:3, s. 1461-1479
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Tidskriftsartikel (refereegranskat)abstract
- Future global temperature change will have significant effects on society and ecosystems. Earth system models (ESM) are the primary tools to explore future climate change. However, ESMs have great uncertainty and often run at a coarse spatial resolution (usually about 2°). Accurate high-spatial-resolution temperature dataset are needed to improve our understanding of temperature variations and for many other applications. We apply Super resolution (SR) in computer vision using deep learning (DL) to merge 31 ESMs data. The proposed method performs data merging, bias-correction, and spatial downscaling simultaneously. The CRU TS (Climate Research Unit gridded Time Series) data is used as reference data in the model training process. To find a suitable DL method, we select five SR methodologies with different structures. We compare the performances of the methods based on mean square error (MSE), mean absolute error (MAE) and Pearson correlation coefficient (R). The best method is used to merge the projected monthly data (1850–1900), and monthly future scenarios data (2015–2100), at the high spatial resolution of 0.5°. Results show that the merged data have considerably improved performance compared with individual ESM data and their ensemble mean (EM), both spatially and temporally. The MAE shows significant improvement; the spatial distribution of the MAE widens along the latitudes in the Northern Hemisphere. The MAE of merged data is ranging from 0.60 to 1.50, the South American (SA) has the lowest error and the Europe has the highest error. The merged product has excellent performance when the observation data is smooth with few fluctuations in the time series. This work demonstrates the applicability and effectiveness of the DL methods in data merging, bias-correction and spatial downscaling when enough training data are available. Data can be accessed at https://doi.org/10.5281/zenodo.5746632.
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| 5105. |
- Wei, Xinshui, et al.
(författare)
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Delay-aware Rate Adjusting Scheme in Higher Speed Passive Optical Networks
- 2022
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Ingår i: Asia Communications and Photonics Conference, ACP. - 2162-108X. ; 2022-November, s. 1271-1274
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Konferensbidrag (refereegranskat)abstract
- Flexible rate is a new desirable operational feature of next-generation higher speed passive optical networks (e.g., ITU-50G PON). In this context, this paper proposes a delay-aware rate adjusting scheme, in which the line rate can be adjusted following the traffic load varying to save energy without degrading delay performance. Simulation results show that the proposed scheme has a similar performance with the benchmark in the aspect of energy saving, while the delay performance of time-sensitive services can be improved significantly, which can be up to 36%.
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| 5106. |
- Wei, Xikun, et al.
(författare)
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Evaluate Transformer model and Self-Attention mechanism in the Yangtze River basin runoff prediction
- 2023
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Ingår i: Journal of Hydrology: Regional Studies. - 2214-5818. ; 47
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Tidskriftsartikel (refereegranskat)abstract
- Study region: In the Yangtze River basin of China. Study focus: We applied a recently popular deep learning (DL) algorithm, Transformer (TSF), and two commonly used DL methods, Long-Short-Term Memory (LSTM) and Gated Recurrent Unit (GRU), to evaluate the performance of TSF in predicting runoff in the Yangtze River basin. We also add the main structure of TSF, Self-Attention (SA), to the LSTM and GRU models, namely LSTM-SA and GRU-SA, to investigate whether the inclusion of the SA mechanism can improve the prediction capability. Seven climatic observations (mean temperature, maximum temperature, precipitation, etc.) are the input data in our study. The whole dataset was divided into training, validation and test datasets. In addition, we investigated the relationship between model performance and input time steps. New hydrological insights for the region: Our experimental results show that the GRU has the best performance with the fewest parameters while the TSF has the worst performance due to the lack of sufficient data. GRU and the LSTM models are better than TSF for runoff prediction when the training samples are limited (such as the model parameters being ten times larger than the samples). Furthermore, the SA mechanism improves the prediction accuracy when added to the LSTM and the GRU structures. Different input time steps (5 d, 10 d, 15 d, 20 d, 25 d and 30 d) are used to train the DL models with different prediction lengths to understand their relationship with model performance, showing that an appropriate input time step can significantly improve the model performance.
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| 5107. |
- Wei, Xin-Feng, 1990-
(författare)
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Ageing behavior of plastics used in automotive fuel systems
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increase in service temperature and the use of biobased fuels, such as biodiesel, have raised concerns on the short/long-term performance of plastic components used in automotive fuel systems.In this work the ageing behavior of unreinforced and glass-fibre reinforced polyamide 12 (PA12), exposed to three different fuels (petroleum diesel, biodiesel, and a mixture of these (80/20)) at high temperature, was investigated. The interactions between the polymer and the fuel, and the associated polymer ageing mechanisms (fuel uptake, extraction of monomer and oligomers, annealing and oxidation), were found to be “generic” in the sense that they occurred, although to various extent, for all fuels. In the glass-fibre reinforced polyamides, the ageing occurred mainly in the polyamide matrix and not in the matrix-fibre interface. The semi-aromatic polyamide showed better performance when exposed to fuels than the aliphatic PA12. At a component level, multilayer polyamide-based pipes, with polyamide or fluoropolymer as inner layer, were aged under “in-vehicle” conditions where the pipes were exposed to fuel on the inside and to the air on the outside. All pipes stiffened during ageing but embrittlement occurred only for the pipes with polyamide being the inner layer. Compared to polyamide, the fluoropolymer inner layer showed significantly better barrier properties towards the fuel and no material was extracted into the fuel. The plasticizer loss from the PA12 outer layers into air was diffusion controlled and its diffusivity followed a linear Arrhenius behavior in the high temperature region. Relationships between plasticizer loss and the changes in mechanical properties were established.The polyamides experienced diffusion-limited oxidation when exposed to air and/or fuel, involving the formation of a thin oxidized surface layer which was responsible for a significant decrease in strain-at-break. The fracture behavior of PA 6 in air at high temperature, found to involve three distinct stages, were systematically studied and linked to underlying mechanisms responsible for the reduction in strain-at-break.
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| 5108. |
- Wei, Xin-Feng, et al.
(författare)
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Ageing properties and polymer/fuel interactions of polyamide 12 exposed to (bio)diesel at high temperature
- 2019
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Ingår i: npj Materials Degradation. - : Springer Science and Business Media LLC. - 2397-2106. ; :3
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Tidskriftsartikel (refereegranskat)abstract
- Biodiesel derived from oil crops and animal fats has been developed as a promising carbon-neutral alternative to petroleum fuels in the transport sector, but the compatibility between biodiesel/petroleum diesel and polymer components in the automotive fuel system has not been free from controversy. In this present study, the degradation of polyamide 12 (PA12), one of the most common polymers used in vehicle fuel systems, has been investigated after exposure to petroleum diesel, biodiesel and a mixture of these (20 vol.% of biodiesel/80 vol.% petroleum diesel). Fuel sorption kinetics, glass transition temperature data and mechanical properties all showed that the fuels plasticized the PA12. In addition, monomers and oligomers were extracted from PA12 by the fuels. The long-term exposure led to oxidation and an annealing-induced increase in crystallinity of the polymer. The plasticization, oxidation and annealing effects were combined with the tensile mechanical properties to assess the overall degree of ageing and degradation of the PA12 material. The fuel-polymer interactions and ageing mechanisms, demonstrated here at high temperature for PA12, are 'generic' in the sense that they are also expected to occur, to various degrees, with many other polymers and they indicate that care should be taken when choosing polymers in applications where they will be exposed to fuels at high temperature.
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| 5109. |
- Wei, Xin-Feng, et al.
(författare)
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Ageing properties of a polyoxymethylene copolymer exposed to (bio) diesel and hydrogenated vegetable oil (HVO) in demanding high temperature conditions
- 2021
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Ingår i: Polymer degradation and stability. - : Elsevier BV. - 0141-3910 .- 1873-2321. ; 185
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Tidskriftsartikel (refereegranskat)abstract
- The increasing use of renewable biofuels in the transportation sector has driven attention on the incompatibility issues between biofuels and the polymeric materials used in the vehicle fuel system. Here, the ageing effects on a polyoxymethylene copolymer exposed to four types of fuels; petroleum diesel, biodiesel, a commercial mixture of these, and hydrogenated vegetable oil (HVO) at demanding hightemperature conditions, were investigated and compared with its performance in air. The degree of material degradation during ageing was highest in the presence of the non-polar fuels (HVO/petroleum diesel). The samples aged in different fuels underwent the same increase in crystallinity due to annealing. Surface powdering was observed on the sample aged in the fuel mixture. The negative effects from a combination of plasticization and swelling, induced by the sorbed fuel, oxidation and surface cracks dominated the changes in mechanical properties, leading to reduced stiffness, strength and extensibility. The results indicate that care should be taken when choosing this polymer in contact with, especially, non-polar fuels at severe conditions.
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| 5110. |
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