分类： 农、林、牧、渔 >> 土壤学 提交时间： 2025-07-17 合作期刊: 《干旱区科学》
摘要： Intense evaporation in areas with loess-like sulfate saline soils has resulted in significant ecologicalchallenges that include water shortages and soil salinization. Investigating evaporation rate in loess-likesulfate saline soils under varying salt contents carries crucial implications for understanding regional waterloss processes, predicting soil salinization advancement, and formulating effective ecological managementstrategies. Therefore, this study sampled the loess-like sulfate saline soil that is widely distributed in westernChina as experimental materials and investigated the impact of different initial salt contents (0.00%, 0.50%,1.50%, 3.00%, and 5.00%) on the evaporation rate, water content, and temperature of soil. The resultsshowed that the evaporation rate decreased with increasing initial salt content. After a salt accumulationlayer formed on the soil surface, the water content of the surface soil fluctuated. An increase in the initialsalt content resulted in a corresponding increase in the surface temperature. Considering the evaporationcharacteristics of loess-like sulfate saline soil and the impact of an anomalous increase in surface soil watercontent on soil surface resistance, this study proposed a modified evaporation model on the basis ofFujimaki’s evaporation model of saline soil by introducing a correction coefficient β to modify the soilsurface resistance. A comparison of the calculated evaporation rates before and after the modification withthe measured evaporation rates revealed a significant improvement in the calculation accuracy of themodified model, indicating that the modified model is capable of more accurately simulating the evaporationrate of sulfate saline soil with different initial salt contents. This paper proposes an effective method forcalculating the evaporation rate of loess-like sulfate saline soils, providing a theoretical basis for evaporationresearch in saline soil.
分类： 核科学技术 >> 核探测技术与核电子学 提交时间： 2024-02-23
Zhao, Dong
Liang, Xuwen
Cai, Pingkun
Cheng, Wei
Jia, Wenbao
Hei, Daqian
Shan, Qing
Ling, Yongsheng
Shi, Chao
摘要： Time-encoded imaging is useful for identifying potential special nuclear materials and other radioactive sources at a distance. In this study, a large field-of-view time-encoded imager was developed for gamma-ray and neutron source hotspot imaging based on a depth-of-interaction (DOI) detector. The imager primarily consists of a DOI detector system and a rotary dual-layer cylindrical coded mask. An EJ276 plastic scintillator coupled with two SiPMs was designed as the DOI detector to increase the field of view and improve the imager performance. The difference in signal time at both ends and the log of the signal amplitude ratio were used to calculate the interaction position resolution. The position resolution of the DOI detector was calibrated using a collimated Cs-137 source, and the full width at half maximum of the reconstruction position of the Gaussian fitting curve was approximately 4.4 cm. The DOI detector can be arbitrarily divided into several units to independently reconstruct the source distribution images. The unit length was optimized via Am-Be source-location experiments. A multidetector filtering method is proposed for image denoising. This method can effectively reduce image noise caused by poor DOI detector position resolution. The vertical field of view of the imager was (-55°, 55°) when the detector was placed in the center of the coded mask. A DT neutron source at 20 m standoff could be located within 2400 s with an angular resolution of 3.5°.
分类： 天文学 >> 天文学 提交时间： 2024-10-08 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： We revisit the γ-ray emission above 300 MeV towards the massive star-forming region of Orion B by adopting 14 yr observations with the Fermi Large Area Telescope and utilizing the updated software tools. The extended γ-ray emission region around Orion B is resolved into two components (region I and region II). The γ-ray spectrum of region I agrees with the predicted γ-ray spectrum assuming the cosmic ray (CR) density is the same as that of Alpha Magnetic Spectrometer (AMS-02) measured locally. The γ-ray emissivity of region II appears to be deficit at low energy band (E < 3 GeV). Through modeling we find that CR densities exhibit a significant deficit below 20 GeV, which may be caused by a slow diffusion inside the dense region. This is probably caused by an increased magnetic field whose strength increases with the gas density.
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