排序方式： 共有10条查询结果，搜索用时 78 毫秒
1
1.
文章通过梳理在WOS（Web Of Science）核心数据集、谷歌学术、中国知网（CNKI）等平台筛选出的较高引用率、方法比较规范、与留守儿童主题相关性强的国内外文献159篇,从理论层面总结了儿童地理学研究的新转向：关注儿童与空间的关系,强调儿童在空间使用中的主体性,重视不同情境下儿童地理体验的差异性。并梳理了跨国迁移背景下留守儿童的3个研究主题：从空间视角探讨留守儿童的日常生活实践;从主体性出发探讨儿童在迁移链中的体验;在童年的差异性基础上讨论本土儿童的问题。同时从问题视角和积极视角分析了国内城乡迁移背景下留守儿童的研究主题,指出因现有研究范式中的经验主义和成人中心主义而存在的局限性。尝试勾勒出符合中国情境的留守儿童研究新范式,提出留守儿童的日常生活空间,留守儿童的能动性、异质性和多样性是国内留守儿童研究亟需关注的内容。呼吁学者采用历时和动态的研究设计,充分展现儿童如何理解、体验和应对复杂的流动背景下的日常生活。 相似文献
2.
3.
Wang Huan Chen Yudao He Lewei Jiang Yaping Xia Yuan Yang Pengfei 《Hydrogeology Journal》2022,30(1):151-161
Hydrogeology Journal - Enhanced bioremediation combined with in-situ chemical oxidation has the potential to remediate groundwater contaminated with organics. To explore the remediating effects of... 相似文献
4.
滩坝是隐蔽油气藏最重要的沉积储集层类型之一,已成为陆相断陷盆地油气勘探的重要领域。现代沉积滩坝的研究是深入认识滩坝沉积相的有效手段。环湖考察研究发现青海湖近岸滩坝类型多样,主要发育了废弃三角洲前缘处滩坝、三角洲侧缘处滩坝、湖岸线拐弯处滩坝、开阔滨浅湖处滩坝和冲积扇改造处滩坝5种类型。通过对各种类型滩坝剖面的详细分层及沉积物室内矿物组成分析等,发现不同类型滩坝砂体沉积特征存在很大差异。整体而言,青海湖近岸滩坝沉积物粒度较粗,黏土含量低,结构成熟度较高,沉积构造多见平行层理、交错层理和冲洗交错层理,垂向上表现出上粗下细的反韵律特征。同时,选取了青海湖南岸规模较大的坝相,分别对坝主体、坝间和坝侧缘进行详细的探槽剖面分析,得出坝主体单旋回厚度较坝间和坝侧缘大,沉积物粒度也相对较粗,黏土含量最低,分选性也最好,是发育为隐蔽油藏最有利的区域。 相似文献
5.
Li Shutong Li Shixiang Guo Ruiliang Zhou Xinping Wang Yang Chen Junlin Zhang Jiaqiang Hao Lewei Ma Xiaofeng Qiu Junli 《Natural Resources Research》2021,30(6):4379-4402
Natural Resources Research - Quantitative characterization of different occurrence states of soluble organic matter is the basis and key for shale oil resource evaluation and movable oil and... 相似文献
6.
针对姬原油田西部区块长6_1储层物性差、非均质性强、成岩作用较复杂的问题,文章通过铸体薄片、扫描电镜和物性资料分析手段,对其成岩作用和成岩相进行了研究。研究区以岩屑长石砂岩和长石岩屑砂岩为主,孔隙类型以残余原生粒间孔和次生溶蚀孔为主。主要的成岩作用有压实、胶结、溶蚀和交代作用。其中,压实作用和胶结作用是原生孔隙降低的主要原因,溶蚀作用形成的次生孔隙在一定程度上改善了储层物性。通过成岩作用、储层物性和沉积相综合研究,划分出了4种主要的成岩相:弱压实—强溶蚀相;中等溶蚀—硅质胶结—高岭石充填相;中等压实—弱溶蚀相和强压实—碳酸盐胶结相。最后结合储层常规测井特征对各成岩相在剖面上分布规律、组合模式进行分析表明,研究区长6_1储层在剖面上的岩相组合模式主要有侧向封堵式、同心环式和纵向互层式。 相似文献
7.
Yushu Zhang Hui Zhu Lewei Zhang Yihua He Zhonglei Gao Qinghua Zhou Chang Yang Fuliang Xiao 《Astrophysics and Space Science》2014,352(2):613-620
Using the STEERB (storm-time evolution of electron radiation belt) code, we simulate the evolution of radiation belt energetic electrons during geomagnetic storms in the case of low energy electron injection. The STEERB code is used to solve the three-dimensional Fokker–Planck diffusion equation which incorporates wave-particle interaction, Coulomb collisions and radial diffusion. Numerical simulations show that under the short time (～1 h) injection of low energy (0.1 MeV≤E k ≤0.2 MeV) fluxes of radiation belt energetic electrons can increase during the entire storm period. During the main and recovery phases, such injection efficiently enhances chorus-driven acceleration of radiation belt energetic electrons, allowing fluxes of energetic electrons by a factor of 1–2 orders higher than those in the absence of injection. The current results indicate that substorm-induced electron injection must be incorporated to investigate the evolution of radiation belt energetic electrons. 相似文献
8.
Zhonglei Gao Hui Zhu Lewei Zhang Qinghua Zhou Chang Yang Fuliang Xiao 《Astrophysics and Space Science》2014,351(2):427-434
Chorus waves have been suggested to be effective in acceleration of radiation belt electrons. Here we perform gyro-averaged test-particle simulations to calculate the bounce-averaged pitch angle and energy diffusion coefficients for parallel-propagating monochromatic chorus waves, and perform a comparison of test-particle (TP) model with quasi-linear (QL) theory to evaluate the influence of nonlinear processes. For small amplitude chorus waves, the diffusion coefficients of TP and QL models are in good agreement. As the wave amplitude reaches a threshold value, two nonlinear processes (phase trapping and phase bunching) start to occur, especially at large equatorial pitch angles. Phase trapping yields rapid increases in pitch angle and kinetic energy. In contrast, phase bunching causes overall decreases in pitch angle and kinetic energy. For the waves with amplitudes slightly above the threshold value, the average behavior is dominated by the phase trapping, and TP diffusion coefficients are larger than QL ones. As wave amplitude increases, TP diffusion coefficients become smaller than QL ones, indicating that phase trapping gradually reduces the dominance over phase bunching. 相似文献
9.
Chang Yang Lewei Zhang Yihua He Si Liu Qinghua Zhou 《Astrophysics and Space Science》2014,353(2):389-394
Using Cluster 4 satellite data, we examine activities of fast magnetosonic (MS) waves in the outer radiation belt near the location L=4.2 on 28 May 2005. We adopt a Gaussian distribution to fit the observed power spectral density of MS waves and find the fitting wave strength to be 245 pT. We then calculate the bounce-averaged diffusion coefficients and show that these diffusion coefficients are pronounced within a region of pitch angles about 25°–70°. By solving a 2D Fokker-Planck diffusion equation, we simulate the dynamic evolution of the electron phase space density (PSD), and demonstrate that significant increases in electron PSDs at energies of MeVs occur mainly within the aforementioned pitch-angle range over a time scale of several hours. The current results suggest that the interaction between MS waves and electrons could be an important mechanism of electron acceleration in the radiation belt. 相似文献
10.
渐新世花港组是东海陆架盆地西湖凹陷发育的最主要储层,基于普通薄片、铸体薄片、扫描电镜和荧光显微观察,结合同位素地球化学对东海陆架盆地西湖凹陷花港组砂岩储层的成岩作用、成岩序列及成岩流体演化进行了研究。结果表明,花港组砂岩储层目前处于中成岩阶段B期,主要经历了机械压实、绿泥石粘土摸、酸性及碱性溶蚀作用,石英次生加大,碳酸盐胶结和自生高岭石胶结等成岩作用。研究区发育有三期碳酸盐胶结物,早期菱铁矿胶结物,中期铁方解石和晚期铁白云石。根据碳酸盐胶结物的碳氧同位素特征分析认为早期碳酸盐胶结物是由过饱和的碱性湖水沉淀造成的,而晚期碳酸盐胶结物的形成与有机酸密切相关。研究区存在两类溶蚀作用,酸性溶蚀作用和碱性溶蚀作用,早期的酸性溶蚀作用主要是有机酸对长石、岩屑及早期碳酸盐胶结物的溶蚀,晚期的碱性溶蚀作用主要是发生于碱性环境下流体对石英及硅质胶结物的溶蚀。研究区发育有两期油气充注,早期发生于晚中新世,早期发生于晚中新世,早于中期碳酸盐胶结,晚于长石溶蚀和石英胶结充注,充注量较大,第四纪以来研究区发生了第二次充注,第二次充注发生于铁白云石胶结之后,此时储层已非常致密。 相似文献
1