submitted time 2024-04-03 Cooperative journals: 《农业图书情报学报》
Abstract： [Purpose/Significance] The introduction of national poverty alleviation policies and rural revitalization strategies has thrust the issue of education for left-behind children into the spotlight of scholarly attention. Education, far beyond serving as a mere instrument for personal growth and human capital accumulation for left-behind children, emerges as a pivotal measure in consolidating rural poverty alleviation endeavors and breaking the transmission of intergenerational poverty in China. It stands as a vital force propelling the future of rural revitalization. Yet, the existing literature on the education of left-behind children remains sporadic and dispersed. A more profound organizational effort, integrating, synthesizing, and evaluating this scattered literature, is imperative to establish a foundational framework for future research, fostering more cohesive and focused research endeavors. Presently, literature review studies primarily fall into three categories: qualitative review methods, meta-analysis, and bibliometric analysis methods employing tools like Citespace. This study sets out to achieve a systematic and comprehensive understanding of education-related issues for rural left-behind children through text mining methods grounded in topic models. [Method/Process] The advent of artificial intelligence and machine learning technologies has empowered the processing and analysis of vast amounts of textual data. Previous research, employing latent dirichlet allocation (LDA) topic models, successfully mined texts related to teacher team construction reform policies, internationalization in higher education literature, news reports, and online comments. In this study, a corpus was meticulously constructed using abstract texts extracted from 2037 journal articles published between 2002 and 2023. The structural topic model (STM) was chosen for topic modeling, overcoming the limitations associated with LDA, with a specific emphasis on exploring the diversity and dynamism of topics within the existing literature. [Results/Conclusions] The culmination of this research effort identified eight distinct research themes: psychological well-being, factors leading to left-behind children, macro-level coping strategies, types of guardianship, review studies, family education, media literacy, and micro-level coping strategies. By synergizing document metadata information, the study systematically unraveled the evolving trends of these topics over time, providing crucial insights into potential shifts in the focus of left-behind children's education research. It is essential to note that this study, while collecting abstracts instead of full texts, may not capture the entirety of information contained in complete research articles. Future research endeavors should explore left-behind children's education more comprehensively, leveraging full-text mining techniques for a more nuanced understanding of this critical subject.
Subjects: Geosciences >> Geography submitted time 2024-03-01 Cooperative journals: 《干旱区研究》
Abstract： Due to the interference from human activities and natural factors, the primary sierozem area in theNingxia desert steppe has gradually shrunk due to long-term desertification and formed island patches within thesurrounding aeolian soil. To reveal the spatiotemporal characteristics of soil moisture after sierozemdesertification, a comparative study was carried out between the large (200-300 m2), medium (approximately 100m2), and small (approximately 50 m2) sierozem patches and the surrounding aeolian soil in Wanjigou Village,Yanchi County, Ningxia, during the growing season (May to October from 2017 to 2019). The uniform rainfallpattern in 2017 led to the highest annual average soil moisture content. While the annual rainfall in 2018 wasslightly higher than that in 2017, it was concentrated in the spring, and there were almost no rainfall events in thesummer and autumn, resulting in a low soil moisture content throughout the year. The summer rainfall pattern in2019 resulted in the highest average soil moisture content during the summer period. The soil moisture content ofsierozem in the 0-100 cm soil layer first showed an increase and then a decrease with increases in soil depth andwas greatest in the 10-40 cm soil layer. The soil moisture content of the aeolian soil increased with soil depth,and the soil moisture content of the 0-20 cm soil layer was much lower than that of the 20-100 cm layer. Themoisture content of sierozem in the 0-20 cm soil layer was greater than that of the aeolian soil, while themoisture content of the sierozem in the 20-100 cm soil layer was significantly lower than that of the aeolian soil(except for small and medium-sized patches in 2018). There was no significant difference (P > 0.05) in the soilmoisture content of the sierozem between the different patch sizes, except that the soil moisture content of theaeolian soil surrounding the large-sized patches was significantly greater than that of the small and medium-sizedpatches (P < 0.05). The water storage of sierozem in the 0-100 cm soil layer was generally lower than that of theaeolian soil, and the variation range was smaller than that of the aeolian soil during the same period. When therainfall was <16 mm, the water in both soil types was in a consumption state. When the rainfall ranged from 16 to25 mm, the water storage capacity of the sierozem was greater than that of the aeolian soil, but when the rainfallwas >25 mm, the water storage capacity of the aeolian soil was greater than that of the sierozem. The soilmoisture content in the desert steppe was dominated by the rainfall, its distribution pattern, and soil type. Themoisture contents of the sierozem and aeolian soils differ in their profiles, as well as in response to rainfall.
Subjects: Library Science，Information Science >> Information Science submitted time 2023-04-01 Cooperative journals: 《图书情报工作》
Abstract： [Purpose/significance] This paper aims to analyze the impact of different discipline classification schemes on field normalization effects, and compare the field normalization effects of different field normalization methods in different discipline classification schemes. [Method/process] This study focused on two aspects: first, compared the effect of the mean method、median method and Z-score method under the Web of Science classification scheme; second, changed the different discipline classification schemes to test the sensitivity of the three field normalization methods under the Essential Science Indicators (ESI) and Organization for Economic Co-operation and Development (OECD) classification schemes. [Result/conclusion] The results show that the disciplinary classification scheme does not have a significant impact on field normalization effects, and the effects of field normalization methods under different discipline classification schemes remain basically unchanged. Judging from the CCDF distribution graph, the citation distribution after using the three field normalization methods is obviously closer than the original citation count, and the citation distribution of the three field normalization methods after changing the discipline classification scheme with different granularity is still roughly the same. When the top z% method is used to numerically test the field normalization effect, it is found that the effects of the three field normalization methods remain basically unchanged after changing the different discipline classification schemes, and show the following laws: When intercepting papers below 30% of the global top, the Z-score method is slightly different than the mean method, but both are better than the median method; 30%-40% stage, Z-score method shows obvious advantages; more than 40%, the median method is significantly better than the other two methods.
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology submitted time 2021-01-25 Cooperative journals: 《干旱区研究》
Abstract：在干旱地区通过人工灌木的引入治理沙化草地是一种广泛存在的生态治理措施。人工灌木可以通过其防风固沙作用，稳定地表环境，从而促进沙化草地的修复。柠条是荒漠草原常见的一种治沙用灌木，其引入多年后对沙化草地土壤修复的效果到底如何，依然缺乏区域性的总结分析。采用经典统计学与地统计学相结合的方法，通过对宁夏中部人工柠条林地和沙化草地的土壤颗粒含量以及灌丛和斑块尺度土壤黏粒的相对富集能力分析，探讨了柠条引入对沙化草地土壤颗粒组分的影响，以期为同类地区沙化土地的恢复提供决策参考。初步研究结果表明，人工柠条林和沙化草地间土壤颗粒含量差异均不显著。在灌丛尺度上，阴坡土壤黏粒的富集能力相对较强，平均富集率为0.11，最大值达到1.09，整体以正效应为主，尤其以研究区北部的阴坡最为显著，南部土壤黏粒的富集能力显著减弱；阳坡土壤黏粒的富集能力整体以负效应为主，平均富集率为-0.08；在斑块尺度上，土壤黏粒的富集能力整体显著低于灌丛尺度，阴坡仍以正效应为主，但富集率显著降低；阳坡仍以负效应为主，但负效应程度显著增强，平均富集率为-0.17。综上，柠条引入作为荒漠草原沙化草地治理的一个重要工程措施，其效果与土壤沙化本底情况有关，同时又受到微生境（坡向）的影响。就本研究区域而言，柠条引入后只是推动了土壤黏粒物质在局域尺度的空间再分配，并未导致黏粒物质总量的显著改善，甚至在一定程度上体现出灌丛入侵的负面效应，同时这种效应随草地本底沙化程度的增强而增强。
Subjects: Geosciences >> Other Disciplines of Geosciences submitted time 2019-09-11 Cooperative journals: 《干旱区研究》
Abstract：阐明斑块尺度上物种共存格局，对于深入认识荒漠草原破碎化草地生物多样性的维持机理具有重要意义。按斑块的土壤生境退化程度，选取短花针茅荒漠草原3类典型群落斑块为研究对象，对比分析不同斑块的物种构成、多样性及物种间的共存关系格局。结果表明：① 斑块A属单优种短花针茅（Stipa breviflora）群落；斑块B为短花针茅+草木樨状黄耆（Astragalus melilotoides）群落；斑块C为苦豆子（Sophora alopecuroides）+老瓜头（Cynanchum komarovii）+猪毛蒿（Artemisia scoparia）群落。② 群落结构中斑块A和斑块B多样性相近，均高于无短花针茅生长的斑块C。③ 基于零模型的分析结果显示，物种共存格局的复杂性和强度为：斑块A>斑块B>斑块C，且下降趋势明显，斑块A存在的16组显著物种对中有4组为显著竞争关系，而斑块C中的物种对减少到7组，且仅存在猪毛蒿与苦豆子组显著竞争物种对。结论：表明未沙化的土壤生境斑块是荒漠草原破碎化草地生物多样性维持的一个重要前提，土壤生境的退化显著降低了斑块内部群落组织的复杂性和物种间相互作用的强度，不利于群落的自我维持。
Subjects: Geosciences >> Other Disciplines of Geosciences submitted time 2019-09-10 Cooperative journals: 《干旱区研究》
Abstract：以荒漠草原人工中间锦鸡儿(Caragana intermedia)灌丛为对象，研究降雨量及降雨强度对两类形态灌丛（健康组和退化组）穿透雨、树干茎流和冠层截留的影响。结果表明：① 试验期间共观测到有效降雨33次，以中小降雨事件为主，总降雨量为251 mm，次平均降雨量和平均降雨强度分别为7.6 mm和1.14 mm·h-1，其中降雨量＜2 mm，降雨强度＜1 mm·h-1的降雨事件出现次数最多。② 健康组和退化组中间锦鸡儿平均穿透雨率、树干茎流率和冠层截留率分别为66.7%、8.5%、24.8%和75.4%、8.7%、16.0%，两类形态灌丛之间穿透雨和截留存在显著差异（P＜0.05）。③ 两类形态灌丛的穿透雨量、树干茎流量、截留量与降雨量成线性函数、对数函数和幂函数关系，且其穿透雨率、树干茎流率和截留率与降雨量、降雨强度之间成对数函数和幂函数关系。灌丛形态退化显著改变了冠层降雨再分配格局，冠层截留显著降低，穿透雨显著增加，潜在提高了降水对土壤水分的直接补充，一定程度上有利于人工中间锦鸡儿稳定性的维持。
Subjects: Geosciences >> Other Disciplines of Geosciences submitted time 2019-09-09 Cooperative journals: 《干旱区研究》
Abstract：为进一步认识荒漠草原带状人工中间锦鸡儿林（Caragana intermedia）植被稳定性维持的生态水文过程机制，通过对行生和散生中间锦鸡儿冠层穿透雨的对比研究，结果表明：① 两者对降水变化响应显著，但是差异不显著。散生和行生中间锦鸡儿穿透雨百分比变化范围分别为25.6%~96.5%（Cv=23%）和25.4%~96.1%（Cv=19%），穿透雨量均值分别为7.55 mm和7.40 mm。穿透雨量与降雨量、降雨历时、降雨强度都具有极显著的线性回归关系，但是穿透雨百分比与降水特征参数以幂函数关系为主。② 冠层下穿透雨分布存在明显的空间异质性。穿透雨百分比普遍随距灌丛基部距离的增大而线性增大。“旱区”集中出现在散生中间锦鸡儿灌木的基部，向外百分比逐步提高；行生中间锦鸡儿则出现了多个旱区和雨极镶嵌分布的情况。
Hits
Hits
Downloads
Comment