5 results on '"Liu, Xuejun"'
Search Results
2. Surveillance-image-based outdoor air quality monitoring
- Author
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Wang, Xiaochu, Wang, Meizhen, Liu, Xuejun, Mao, Ying, Chen, Yang, and Dai, Songsong
- Published
- 2024
- Full Text
- View/download PDF
3. Atmospheric wet and dry phosphorus deposition in Lake Erhai, China.
- Author
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Shen, Qikun, Du, Xiaoyun, Kang, Jiahui, Li, Jiawei, Pan, Yuepeng, Liu, Xuejun, and Xu, Wen
- Subjects
ATMOSPHERIC deposition ,WATER quality ,LAKES ,PHOSPHORUS ,SPRING ,AUTUMN - Abstract
Lake Erhai is a potentially phosphorus (P)-limited lake and its water quality may have been affected by atmospheric P deposition. However, there have been few studies on atmospheric P deposition in this lake. In this study, we established five wet deposition monitoring sites and two dry deposition monitoring sites around Lake Erhai to quantify the wet and dry deposition of total phosphorus (TP), including dissolved inorganic phosphorus (DIP), dissolved organic phosphorus (DOP) and particulate phosphorus (PP) from July 2022 to June 2023. Wet deposition fluxes of P species were collected by automatic rainfall collection instrument, and dry deposition fluxes were estimated using airborne concentration measurements and inferential models. The results reveal that among the different P components, DOP had the highest contribution (50%) to wet TP deposition (average all sites 12.7 ± 0.7 mg P m
2 /yr), followed by PP (40%) and DIP (10%). Similarly, DOP (51%) was the major contributor to dry TP deposition (average two sites 2.4 ± 0.9 mg P m2 /yr), followed by DIP (35%) and PP (14%). Wet deposition dominated the annual total TP deposition (wet plus dry), accounting for approximately 83%. The key seasons for dry deposition were spring and autumn, which accounted for 64% of the annual total dry TP deposition. In comparison, wet deposition was significantly higher in the summer, accounting for 73% of the annual total wet TP deposition. The results of the potential source contribution function and concentration-weighted trajectories analysis indicate that local source emission and long-range transport from surrounding cities jointly exerted a substantial influence on aerosol P concentrations, particularly in the eastern and northwestern regions of the lake. These findings provide a comprehensive understanding of the different P components in atmospheric deposition, which is beneficial for developing effective strategies to manage the P cycle in Lake Erhai. [Display omitted] • Wet and dry fluxes of P were 12.7 and 2.4 mg P/m2 /yr in Lake Erhai, respectively. • DOP contributed 50% and 51% of total wet and dry P deposition fluxes, respectively. • Wet deposition peaked in summer, while dry deposition peaked in autumn or spring. • Total TDP deposition flux accounted for approximately 7% of the riverine TDP inputs. • Local emission sources and regional transport jointly affected P deposition. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
4. Exposure risk to rural Residents: Insights into particulate and gas phase pesticides in the Indoor-Outdoor nexus.
- Author
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Mu, Hongyu, Yang, Xiaomei, Wang, Kai, Osman, Rima, Xu, Wen, Liu, Xuejun, Ritsema, Coen J., and Geissen, Violette
- Subjects
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PESTICIDES , *RISK exposure , *AGRICULTURE , *OCCUPATIONAL exposure , *ENVIRONMENTAL sampling , *CARBENDAZIM - Abstract
[Display omitted] • Personal exposure to particulate and gaseous pesticides was characterized. • Particulate/gaseous distribution of pesticides was studied in indoor-outdoor nexus. • Two third of exposed pesticides mainly originated from non-occupational sources. • Over 43% of bystanders suffered the same exposure level as farmers. • Around 7% and 3% of local farmers and bystanders may suffer chronic health risk. Rural residents are exposed to both particulate and gaseous pesticides in the indoor-outdoor nexus in their daily routine. However, previous personal exposure assessment mostly focuses on single aspects of the exposure, such as indoor or gaseous exposure, leading to severe cognition bias to evaluate the exposure risks. In this study, residential dust and silicone wristbands (including stationary and personal wearing ones) were used to screen pesticides in different phases and unfold the hidden characteristics of personal exposure via indoor-outdoor nexus in intensive agricultural area. Mento-Carlo Simulation was performed to assess the probabilistic exposure risk by transforming adsorbed pesticides from wristbands into air concentration, which explores a new approach to integrate particulate (dust) and gaseous (silicone wristbands) pesticide exposures in indoor and outdoor environment. The results showed that particulate pesticides were more concentrated in indoor, whereas significantly higher concentrations were detected in stationary outdoor wristbands (p < 0.05). Carbendazim and chlorpyrifos were the most frequently detected pesticides in dust and stationary wristbands. Higher pesticide concentration was found in personal wristbands worn by farmers, with the maximum value of 2048 ng g−1 for difenoconazole. Based on the probabilistic risk assessment, around 7.1 % of farmers and 2.6 % of bystanders in local populations were potentially suffering from chronic health issues. One third of pesticide exposures originated mainly from occupational sources while the rest derived from remoting dissipation. Unexpectedly, 43 % of bystanders suffered the same levels of exposure as farmers under the co-existence of occupational and non-occupational exposures. Differed compositions of pesticides were found between environmental samples and personal pesticide exposure patterns, highlighting the need for holistic personal exposure measurements. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
5. An R-adaptive algorithm based on self-organizing maps for solving incompressible flows with high-order discontinuous Galerkin methods.
- Author
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An, Wei, Yu, Jian, Lyu, Hongqiang, and Liu, Xuejun
- Subjects
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SELF-organizing maps , *GALERKIN methods , *COMPUTATIONAL fluid dynamics , *FLOW coefficient , *VISCOUS flow , *INCOMPRESSIBLE flow - Abstract
Mesh quality is critical for the numerical accuracy of CFD (Computational Fluid Dynamics). Although various techniques have been developed to improve mesh applicability to complex flows, r-adaptive methods have received far too little attention. This paper introduces an r-adaptive algorithm based on the self-organizing maps (SOM) of Kohonen and applies it to unsteady CFD applications using the Discontinuous Galerkin (DG) method. Inspired by the properties of the DG method, the numerical discontinuity over the element interface is quantified as an adaptation indicator. The method requires only one adaptation, followed by solution projection onto the new mesh to save computational costs in unsteady cases. A significant advantage of this method is its higher efficiency without solving complex equations during the adaptation. The performance of the developed mesh adaptation algorithm is tested on the steady laminar viscous flow past a circular cylinder at R e = 40 and the unsteady laminar viscous flow past a circular cylinder at R e = 100 and two circular cylinders in a side-by-side arrangement at R e = 200. Significant improvements in flow contours and coefficients are obtained after adaptation. • The SOM method is adopted for unstructured mesh r-adaptation with the DG method. • The method avoids auxiliary mesh PDEs in traditional r-adaptation methods. • A one-time adaptation in unsteady cases saves computational costs. • The improvement of results in CFD applications validates method performance. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
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