| 1. |
- Wan, Cheng-Liang, et al.
(författare)
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基于玻璃毛细管的大气环境MeV质子微束的产生与测量 : [Production and measurement of MeV proton microbeams in atmospheric environment based on glass capillary]
- 2024
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Ingår i: Wuli xuebao. - 1000-3290. ; 73:10
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Tidskriftsartikel (refereegranskat)abstract
- 本文采用玻璃毛细管产生了大气环境中工作的2.5 MeV质子外束微束, 并对束斑直径及能量分布随玻璃毛细管与束流方向之间角度(倾角)变化进行测量. 测量结果表明, 在玻璃毛细管轴向与束流方向一致时(倾角为0°), 产生的微束中存在保持初始入射能量的直接穿透部分以及散射部分, 其中直接穿透的质子占比最大, 束斑直径也最大. 随着玻璃毛细管倾角的增大, 当其大于几何张角时, 束斑直径变小, 产生的微束全部为能量减小的散射部分, 直接穿透质子消失. 我们对质子在玻璃毛细管内传输时的内壁散射过程进行了模拟计算及离子轨迹分析, 发现大角度的散射部分决定了形成的外束微束斑外围轮廓, 而束斑中心区域由不与毛细管内壁产生任何作用的直接穿透离子构成, 其大小由玻璃毛细管出口直径以及几何容许张角决定. 采用玻璃毛细管产生的外束微束具有产生简单廉价, 微束区域定位简单的特点, 有望在辐射生物学、医学、材料等领域得到广泛应用.
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| 2. |
- Wang, Yan, et al.
(författare)
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Disaster effects of climate change and the associated scientific challenges
- 2024
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Ingår i: Chinese Science Bulletin. - 1001-6538. ; 69:2, s. 286-300
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Forskningsöversikt (refereegranskat)abstract
- Climate change can be observed in various spheres of the Earth's system, including atmosphere, lithosphere, hydrosphere, biosphere and cryosphere. The interactions among these spheres collectively impact the changes of the climate system. Natural disasters represent the most intense manifestation of the interactions among the Earth's spheres, and they have profound impacts on human society. In this study, we discuss the impact of climate change on natural disasters by examining the characteristics of climate change-induced hazards and the activity patterns of natural disasters. Furthermore, the response mechanisms of natural disasters to climate change are elaborated by exploring the formation and evolution of different types of natural disasters. Additionally, the future trends of disaster-pregnant environment under climate change are estimated, and the future trends of disaster risk are revealed by jointly considering the exposure and vulnerability. The main driving forces and formation conditions of natural disasters vary greatly among different geomorphic units, but they can generally be classified into three categories: Thermally driven disasters, gravitationally driven disasters, and hydrologically driven disasters. For example, heatwaves, tropical cyclones, tornadoes, and wildfires are common examples of thermally driven disasters which are forced by high temperatures or great thermal gradients. In addition, gravitationally driven disasters mainly occur in mountainous areas with significant differences in elevation, such as landslides, snow-ice avalanches and debris flows. The tsunamis caused by seabed movement are also gravity disasters. Furthermore, the disasters such as droughts, regional floods and sea-level rise are primarily driven by the changes in hydraulic conditions, and thus are classified as hydrologically driven disasters. In the context of enhanced climate change, the interactions among multiple spheres of the Earth's system are strengthened, causing the disaster-pregnant environment to evolve towards a more vulnerable state. Thus, the natural disasters present some new characteristics and trends, and the disaster risk shows a sharp increase. The interactions among different types of natural disasters have also become stronger, resulting in a significant rise in the risk of compound and cascading disaster. The differences in driving forces lead to significant variations in the disaster feedback to climate change among the varied geomorphic units. For example, the strengthened interaction between ocean and atmosphere leads to enhanced compound risk and destructive power of marine disasters. Besides, the intensification of water cycle contributes to increased spatial heterogeneity in drought and flood disasters, whose durations, intensities, and magnitudes show significant increasing trends. In addition, the high mountainous areas with altitude-dependent warming and the urban areas with significant heat island effects have obvious amplification effects in the responses to climate warming. This study advocates the goal of improving the accuracy and effectiveness of natural disaster prediction and early warning, and reducing the risk of climate change-related disasters. Five major scientific challenges of climate change-related disaster risk are proposed: (1) The mechanisms of climate change-driven interactions among Earth's spheres and the coupling of internal and external forces; (2) the spatio-temporal patterns of disaster development across different scales; (3) the perception of extreme event information and the data-driven risk identification; (4) the dynamics of disasters and the evolution of risk; (5) the disaster risk management and the resilient social development. By addressing the key issues in these five challenges through comprehensive and diversified approaches, we can deepen our scientific understanding on the Earth's system, adapt to global changes, and reduce disaster risks.
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| 3. |
- Xin, Yan-Bo, et al.
(författare)
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Research progress of hydrogen tunneling in two-dimensional materials
- 2017
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Ingår i: Wuli xuebao. - : CHINESE PHYSICAL SOC. - 1000-3290. ; 66:5
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Forskningsöversikt (refereegranskat)abstract
- One-atom-thick material such as graphene, graphene derivatives and graphene-like materials, usually has a dense network lattice structure and therefore dense distribution of electronic clouds in the atomic plane. This unique structure makes it have great significance in both basic research and practical applications. Studies have shown that molecules, atoms and ions are very difficult to permeate through these above-mentioned two-dimensional materials. Theoretical investigations demonstrate that even hydrogen, the smallest in atoms, is expected to take billions of years to penetrate through the dense electronic cloud of graphene. Therefore, it is generally considered that one-atom-thin materialis impermeable for hydrogen. However, recent experimental results have shown that the hydrogen atoms can tunnel through graphene and monolayer hexagonal boron nitride at room temperature. The existence of defects in one-atomthin material can also effectively reduce the barrier height of the hydrogen tunneling through graphene. Controversy exists about whether hydrogen particles such as atoms, ions or hydrogen molecules can tunnel through two-dimensional materials, and it has been one of the popular topics in the fields of two-dimensional materials. In this paper, the recent research progressof hydrogen tunneling through two-dimensional materials is reviewed. The characteristics of hydrogen isotopes tunneling through different two-dimensional materials are introduced. Barrier heights of hydrogen tunneling through different graphene and graphene-like materials are discussed and the difficulties in its transition are compared. Hydrogen cannot tunnel through the monolayer molybdenum disulfide, only a little small number of hydrogen atoms can tunnel hrough graphene and hexagonal boron nitride, while hydrogen is relatively easy to tunnel through silicene and phosphorene. The introduction of atomic defects or some oxygen-containing functional groups into the two-dimensional material is discussed, which can effectively reduce the barrier height of the hydrogen tunneling barrier. By adding the catalyst and adjusting the temperature and humidity of the tunneling environment, the hydrogen tunneling ability can be enhanced and the hydrogen particles tunneling through the two-dimensional material can be realized. Finally, the applications of hydrogen tunneling through two-dimensional materials in ion-separation membranes, fuel cells and hydrogen storage materials are summarized. The potential applications of hydrogen permeable functional thin film materials, lithium ion battery electrode materials and nano-channel ions in low energy transmission are prospected. The exact mechanism of hydrogen tunneling through two-dimensional material is yet to be unravelled. In order to promote these applications and to realize large-scale production and precision machining of these two-dimensional materials, an in-depth understanding of the fundamental questions of the hydrogen tunneling mechanism is needed. Further studies are needed to predict the tunneling process quantitatively and to understand the effects of catalyst and the influences of chemical environments.
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| 4. |
- Zhang, Fei-yan, et al.
(författare)
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Single-step purification of sIgA from bovine colostrums by anion-exchange chromatography
- 2011
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Ingår i: Science and Technology of Food Industry. - 1002-0306.
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Tidskriftsartikel (refereegranskat)abstract
- A fraction containing sIgA(sIgA-rich fraction)was prepared from bovine colostrum by anion exchange chromatography using alkali resin. The effect of changing buffer properties(pH and ionic strength)on purity of sIgA was studied. The best result was sIgA purity increasing from 16.31% in bovine colostrum solution to 91.24% in the eluting fraction with a recovery of 47% at the condition of pH 7.0,0.03mol/L sodium phosphate. These results suggested that the anion exchange chromatography using alkali resin was a potential process for sIgA purification from bovine colostrum.
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