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1. chinaXiv:202109.00023 [pdf]

Spectrum Broadening due to Nonselective Linear Absorption

Zhang, Xingchu ; She, Weilong
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics

我们对纳灯近红外波段进行了发射光谱的中性吸收实验,并观察了纳灯发射光谱谱线宽度的变化。我们发现当光的强度因吸收变得很低时,这些发射光谱谱线会发生展宽现象,中性滤波片透过率越低,发射光谱的谱线展宽越明显。这是一种不同于已发现的、新的谱线展宽效应。

submitted time 2021-09-14 Hits6Downloads2 Comment 0

2. chinaXiv:202109.00022 [pdf]

乌鲁木齐市生态环境遥感评价及驱动因子分析

排日海·合力力
Subjects: Geosciences >> Geography

生态环境质量评估对于区域社会经济的可持续发展至关重要。以新疆乌鲁木齐市为研究区,通过对2000年、2010年和2019年3期Landsat系列数据进行预处理,利用主成分分析法构建遥感生态指数(Remote Sensing Eco?logical Index, RSEI),使用地理探测器中单因子分析和多因子交互作用分析法对RSEI的8个影响因子(人口密度、土地利用类型、海拔高度、经济密度、绿度、湿度、热度和干度)进行影响程度的定量探测,进而揭示出影响研究区生态环境质量的主导因素。结果表明:(1)2000年、2010年和2019年乌鲁木齐市RSEI均值分别为0.21、0.21、0.23呈增加趋势,研究期内乌鲁木齐市生态变好的面积大于变差的面积,说明乌鲁木齐市的生态环境质量处于转好的状态;(2)近20 a研究区8个影响因子中单因子热度指标对RSEI的空间分异特征解释力最强;(3)研究区生态环境的空间分布特征是多种影响因子共同交互作用的结果,在考虑多因子交互作用情景下人口密度,绿度指标和干度指标是区域生态环境质量状况的主要影响因素和关键驱动力。评价区域生态环境质量,了解生态环境状况及掌握其变化规律,不仅有利于促进区域经济可持续发展,而且对于城市生态文明建设具有重要的现实意义和参考价值。

submitted time 2021-09-14 From cooperative journals:《干旱区研究》 Hits2380Downloads23 Comment 0

3. chinaXiv:202109.00024 [pdf]

哈萨克斯坦首都努尔苏丹人工林健康评价

闫晋升
Subjects: Geosciences >> Geography

通过分析努尔苏丹不同人工林,筛选健康综合评价指标,建立健康综合评价模型,为努尔苏丹及其周边人工林提供健康综合评价理论基础。调查努尔苏丹25块人工林样地和2块天然林样地,选取林下植物Shannon-Wie?ner指数(X1)、Pielou指数(X2)、Simpson指数(X3)、林分空间综合结构综合指数(X4)、土壤有机质(X5)、全氮(X6)、全磷(X7)、pH(X8)、质量含水量(X9)、林木平均株高(X10)、平均胸径(X11)、平均枝下高(X12)、平均冠幅(X13)和林下更新(X14)共14个指标,采用因子分析、聚类分析、判别分析和逐步回归分析等多元统计分析法,对努尔苏丹人工林健康状况开展综合评价。通过因子分析将14个单项指标转换为4个相互独立的综合指标,其贡献率分别为30.482%、24.374%、19.711%和8.646%,代表了全部数据83.212%的信息量。结合因子得分系数矩阵与各因子权重得到健康综合得分值。对健康综合得分值进行聚类分析,将选择的样地划分为5类,优质健康(Ⅰ)、良好健康(Ⅱ)、一般健康(Ⅲ)、亚健康(Ⅳ)和不健康(Ⅴ)。使用判别分析验证聚类分析的效果,其自身验证与交叉验证的准确率分别为100%、85.185%。采取逐步回归分析建立努尔苏丹人工林健康评价最优数学模型,H= 0 + 0.293X13 +0.186X5 + 0.079X3 + 0.100X2 + 0.038X7(R2=0.987),筛选出5个判断人工林健康状况的指标,分别为平均冠幅、土壤有机质、Simpson指数、Pielou指数和土壤全磷。平均冠幅、土壤有机质、Simpson指数、Pielou指数和土壤全磷可作为判断努尔苏丹人工林健康状况的指标,可在相同条件下测定这5项指标,计算健康综合评价值并预测其健康状况。

submitted time 2021-09-14 From cooperative journals:《干旱区研究》 Hits11Downloads5 Comment 0

4. chinaXiv:202109.00025 [pdf]

基于VSD的近20 a 来浑善达克沙地生态脆弱性变化研究

陈臻琦
Subjects: Geosciences >> Geography

如何协调区域社会经济和人口、资源环境发展,已成为生态环境建设面临的紧迫任务,识别特定地区的脆弱性则是实现有效生态系统管理的前提。以京津风沙源——浑善达克沙地为研究区,采用“暴露-敏感-适应”(VSD)模型建立评价指标体系,结合Moran’s I 指数与主成分分析,对2000—2019年该沙地生态脆弱性进行评价和驱动机制分析。结果表明:浑善达克沙地生态脆弱性20 a间呈现增加的趋势;其生态脆弱性空间上呈集聚现象,表现为西部高-高聚集、东部低-低聚集的分布格局,且具有明显的空间相关性;生态脆弱性的时空分布的异质性是由不同程度的人类活动与气候因素的叠加效应造成的。该研究为浑善达克沙地的生态建设和生态恢复提供理论依据,并提出因地制宜的治理建议和措施。

submitted time 2021-09-14 From cooperative journals:《干旱区研究》 Hits9Downloads6 Comment 0

5. chinaXiv:202109.00026 [pdf]

巴尔喀什湖流域土地利用/覆被变化过程与趋势

刘婉如
Subjects: Geosciences >> Geography

巴尔喀什湖流域是跨越中国新疆(境内)和哈萨克斯坦(境外)的重要流域。利用1970s、2005年和2015年3期土地利用/土地覆被(Land Use and Land Cover, LULC)数据与马尔科夫模型等方法,分析1972年流域内最大的水利工程卡普恰盖水库建成和前苏联解体以来流域LULC变化过程和趋势,并对比流域境内外差异,为该地区土地资源管理及生态环境保护提供依据。结果表明:巴尔喀什湖流域LULC变化呈现出耕地和林地面积先减后增(总体增加)、水域和未利用地面积先增后减(总体减少)、草地和城乡建设用地面积持续增加的变化趋势。这表明后期LULC变化对整个研究期LULC变化影响更大。以上变化以双向转换为主,因此,整个研究期内全流域变化过程始终处于平衡状态。境内外LULC类型结构和变化过程均不相同,境内分配比境外均匀,单一类型和区域LULC变化趋势与状态指数均表明境内LULC类型变化过程比境外稳定,但由于境外面积占全流域86%,主导了全流域LULC类型结构和变化过程。全流域在研究期内始终处于平衡状态。

submitted time 2021-09-14 From cooperative journals:《干旱区研究》 Hits14Downloads8 Comment 0

6. chinaXiv:202109.00020 [pdf]

工作记忆训练诱发的神经可塑性——基于系列fMRI实验的脑区分布递减时空模型

党彩萍; 付彤; 刘昌; 伏云发; 李恩泽; 陈幸明; Jian ZHANG; 陈盛强; 张宾
Subjects: Psychology >> Cognitive Psychology

工作记忆训练(Working Memory Training, WMT)诱发神经可塑性,但其具体机制尚不明晰。为探讨WMT诱发正常人群大脑功能变化的时空特性,以“扩展的智力顶额整合理论”和“神经效率假说”为假设依据,采用逐层递进方法,对近20年来正常人群WMT的37篇fMRI文献进行梳理。首先,用叙述性综述、频数分析和卡方检验法比较脑区激活模式和功能连接在WMT前后发生的改变,发现大脑的5个联合区、7个宏观区和3个子区参与WMT。尤其,额上回、顶下小叶和扣带回这3个子区各自的减弱激活多于其增强激活,且这种差异分别具有统计学意义。其次,采用激活似然估计法对其中26篇进行元分析,发现WMT前后激活水平的差异具有统计学意义的子区有3个,即额中回(BA6和8)、额上回(BA6)和前扣带回(BA24和32)。再次,综合定性和定量分析结果,提出WMT脑区分布递减时空模型,并据此产生五个结果和讨论。然后,采用非参数检验进一步分析WMT效应可能的调节因素,发现WMT的任务类型和时间分别对脑区激活的影响具有统计学意义。接着,针对正常人群WMT诱发神经可塑性的时空特性,得出四个结论:第一,WMT可改变正常人群相应脑区的神经活动,表现为或减弱、或增强,但减弱更加突出,且更新和较短时间的WMT倾向于诱发较多减弱;第二,这些神经活动变化主要发生在额顶叶联合区,但也包括分别以颞叶、枕叶、扣带回及纹状体为主的联合区,在一定范围内体现了整脑功能联合;第三,额中回、额上回和前扣带回这3个子区的神经活动改变重点体现了WMT神经可塑性的空间特点,而额上回、顶下小叶和扣带回这3个子区重点体现了其时间特性;第四,“扩展的智力顶额整合理论”和“神经效率假说”分别支持了WMT脑区分布的空间和时间特性。最后,指出未来研究可能需要辨析额上回、顶下小叶和扣带回这三个子区体现的WMT效应、WMT导致脑区激活减弱或增强的综合性影响因素。

submitted time 2021-09-10 Hits2378Downloads318 Comment 0

7. chinaXiv:202109.00021 [pdf]

一种基于地球同步卫星光学遥感影像的运动船舶检测与跟踪方法

余伟
Subjects: Electronics and Communication Technology >> Information Processing

地球静止光学遥感卫星具有时间分辨率高、覆盖范围广等优点,可以大范围连续跟踪观察海上船舶目标。然而,地球同步卫星遥感影像中的船舶目标通常体积小、强度弱,易受云、岛等因素影响,给船舶目标的检测带来很大的困难。本文提出了一种从地球静止光学遥感图像中检测在海面上移动的船舶的新方法:首先,采用自适应非线性灰度拉伸(ANGS)方法对图像进行增强,以突出小而弱的船舶目标。其次,设计了一种多尺度双邻域差分对比度测量(MDDCM)方法来检测候选船舶目标的位置。然后,分析每个候选区域的形状特征以去除虚假的船舶目标。最后,联合概率数据关联(JPDA)方法用于多帧数据关联和跟踪。实验表明,该方法能够有效地检测和跟踪GF-4卫星光学遥感影像中的运动船舶目标,与其他经典方法相比,该方法具有更好的检测性能。

submitted time 2021-09-10 Hits1388Downloads263 Comment 0

8. chinaXiv:202107.00032 [pdf]

The Relationships among Structural Social Support, Functional Social Support, and Loneliness in Older Adults: Analysis of Regional Differences based on a Multigroup Structural Equation Model

Haifeng Li; Cong Wang
Subjects: Psychology >> Social Psychology

Objective: This study investigated the relationship between structural social support and loneliness and explored whether functional social support had an intermediate role therein. It also employed a multigroup structural equation model to compare mediation models among older adults living in cities, towns, and rural areas. Methods: Using a self-made demographics questionnaire, the structural-functional social support scale, and the 3-item UCLA loneliness scale, this study collected information from 1,325 older adults identified via convenience sampling. Results: The results showed that: (1) compared with older adults living in towns, older urban and rural adults had higher structural social support and experienced less loneliness, while older adults’ functional social support showed no difference among the three regions (2) An analysis of the models of regional differences indicated that functional social support served as a full mediator in the relationship between structural social support and loneliness in urban older adults, and a partial mediator for older adults living in towns and rural areas. Conclusion: The relationship between structural social support and loneliness is mediated by functional social support, and this mediation model varies between older adults in cities and towns/rural areas. This study helps us understand possible mechanisms through which structural social support impacts loneliness. It suggests that nursing strategies for older adults should be adjusted according to region and direct greater focus on the function (or quality) of the social support network and on older adults living in towns.

submitted time 2021-09-09 Hits3629Downloads350 Comment 0

9. chinaXiv:202109.00011 [pdf]

Effects of water and nitrogen on growth and relative competitive ability of introduced versus native C4 grass species in the semi-arid Loess Plateau of China

DING Wenli; XU Weizhou; GAO Zhijuan; XU Bingcheng
Subjects: Geosciences >> Geography

Switchgrass is an introduced C4 grass in the semi-arid Loess Plateau of China, but there is a lack of information to assess its ecological invasive risk. In this study, Old World bluestems (native C4 grass) and switchgrass were sowed at five mixture ratios (8:0, 6:2, 4:4, 2:6 and 0:8) under two soil water levels (80% field capacity (FC) and 40% FC) and two nitrogen (N) treatments (0 and 100 mg N/kg dry soil, termed N0-unfertilized and N1-fertilized treatments, respectively) in a pot experiment in 2012. Biomass, root morphological traits and relative competitive abilities of these two species were analyzed. Results showed that biomass of both species was significantly greater under 80% FC or N fertilization, and switchgrass had a relatively larger root: shoot ratio (RSR). Total root length (TRL) and root surface area (RSA) of switchgrass were significantly higher under 80% FC irrespective of N treatment, while those of Old World bluestems were only significantly higher under N fertilization. N had no significant effect on TRL and RSA of switchgrass, while RSA of Old World bluestems significantly increased under 80% FC and N fertilization. Under 40% FC and N0-unfertilized treatment, the aggressivity of Old World bluestems was larger than zero at 2:6 and 4:4 mixture ratios of two species, whereas it was close to zero at 6:2 mixture ratio. Root competitive ability of switchgrass significantly increased under 80% FC or N fertilization. The aggressivity of Old World bluestems was negative at 6:2 mixture ratio under 80% FC and N fertilization, while it was positive at 2:6 mixture ratio. Switchgrass may become more aggressive when N deposition or rainfall increases, while a proper mixture ratio with appropriate water and N management could help with grassland management in the semi-arid Loess Plateau.

submitted time 2021-09-08 From cooperative journals:《Journal of Arid Land》 Hits2450Downloads56 Comment 0

10. chinaXiv:202109.00012 [pdf]

Spatiotemporal variations of evapotranspiration and reference crop water requirement over 1957–2016 in Iran based on CRU TS gridded dataset

Brian COLLINS; Hadi RAMEZANI ETEDALI; Ameneh TAVAKOL; Abbas KAVIANI
Subjects: Geosciences >> Geography

Agriculture needs to produce more food to feed the growing population in the 21st century. It makes the reference crop water requirement (WREQ) a major challenge especially in regions with limited water and high water demand. Iran, with large climatic variability, is experiencing a serious water crisis due to limited water resources and inefficient agriculture. In order to overcome the issue of uneven distribution of weather stations, gridded Climatic Research Unit (CRU) data was applied to analyze the changes in potential evapotranspiration (PET), effective precipitation (EFFPRE) and WREQ. Validation of data using in situ observation showed an acceptable performance of CRU in Iran. Changes in PET, EFFPRE and WREQ were analyzed in two 30-a periods 1957–1986 and 1987–2016. Comparing two periods showed an increase in PET and WREQ in regions extended from the southwest to northeast and a decrease in the southeast, more significant in summer and spring. However, EFFPRE decreased in the southeast, northeast, and northwest, especially in winter and spring. Analysis of annual trends revealed an upward trend in PET (14.32 mm/decade) and WREQ (25.50 mm/decade), but a downward trend in EFFPRE (–11.8 mm/decade) over the second period. Changes in PET, EFFPRE and WREQ in winter have the impact on the annual trend. Among climate variables, WREQ showed a significant correlation (r=0.59) with minimum temperature. The increase in WREQ and decrease in EFFPRE would exacerbate the agricultural water crisis in Iran. With all changes in PET and WREQ, immediate actions are needed to address the challenges in agriculture and adapt to the changing climate.

submitted time 2021-09-08 From cooperative journals:《Journal of Arid Land》 Hits2571Downloads67 Comment 0

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