四川盆地西北部中二叠统栖霞组白云岩特征及成因探讨

白云岩特征及其形成机制的研究对白云岩化理论与白云岩储集层勘探具有重要意义。本文以四川盆地西北部中二叠统栖霞组白云岩为研究对象,通过野外剖面及岩心观察并采用铸体薄片、阴极发光、地球化学分析等方法对该段白云岩特征及成因进行研究。结果表明川西北地区栖霞组白云岩主要表现为块状晶粒白云岩、角砾状白云岩及斑状白云岩3种类型;碳同位素为正低值,氧同位素为负值,反映出其成岩过程中伴有早期淡水参与。结合工区构造沉积背景,对比以往经典白云岩化模式,发现四川盆地西北部中二叠统栖霞组白云岩化成因模式具有一定自身特点。通过对Folk “镁笼效应”理论进行延伸,认为栖霞组白云岩化模式在纵向上分为淡水渗流带、混合渗流带、混合潜流带及海水潜流带4个区带,其中混合渗流带和混合潜流带是白云岩发育的主要位置。在混合渗流带中,淡水与海水交替进入,未完全成岩的海洋沉积物质在成岩过程中受到淡水冲洗导致大量镁离子随淡水流入下部地层,而后又有海水携带镁离子进行补给,这为白云石形成提供了有利条件;混合潜流带内不断进入的混合流体携大量镁离子使得该带具有较高Mg/Ca值;而地幔上涌造成的地温升高克服了白云石形成的动力学屏障,有效促进了白云岩的形成。     

泥石流等级和灾度的定量计算

泥石流等级是描述一次泥石流规模大小的定量指标,泥石流灾度是描述一次泥石流造成社会损失大小的定量指标。这两个指标概念明确,简单易行,有利于使描述泥石流规模大小和灾情程度的术语逐步规范化、定量化和普及化。     

Can Plant Competition and Diversity Reduce the Growth and Survival of Exotic <Emphasis Type="Italic">Phragmites australis</Emphasis> Invading a Tidal Marsh?

The rapid proliferation of Phragmites australis in North America has challenged resource managers to curb its expansion and reduce the loss of functional tidal marsh. We investigated whether native plant competition could reduce the ability of Phragmites to invade a tidal marsh, and if plant diversity (species richness, evenness, and composition) altered the competitive outcome. Immature Phragmites shoots and four native halophytes were transplanted to small but dense field plots (~1,200 shoots m⁻²) comprising three community structure types (Phragmites alone, Phragmites + 1 native species, and Phragmites + 4 native species). Interspecific competition significantly reduced Phragmites aboveground biomass, shoot length production, density, and survival by approximately 60%. Additionally, plots planted with greater native diversity contained Phragmites with the lowest growth and survival, potentially indicating diversity-enhanced resource competition. Competition consistently reduced the growth of Phragmites even under favorable conditions: lack of strong tidal flooding stresses as well as elevated nutrient pools.     

Modeling of local ionospheric time varying characteristics based on singular value decomposition over low-latitude GPS stations

Singular Value Decomposition (SVD) model is implemented to recognize the Total Electron Content (TEC) time series of daily, temporal as well as seasonal characteristics throughout the 24th solar cycle period of the year 2015 in the study. The Vertical (vTEC) analysis has been carried out with Global Positioning System (GPS) data sets collected from five stations from India namely GNT, Guntur (16.44^° N, 80.62^° E), and IISC, Bangalore (12.97^° N, 77.59^° E), LCK2, Lucknow (26.76^° N, 80.88^° E), one station from Thailand namely AITB, Bangkok (14.07^° N, 100.61^° E), and one station from South Andaman Island namely PBR, Port Blair (11.43^° N, 92.43^° E), located in low latitude region. The first five singular value modes constitute about 98% of the total variance, which are linearly transformed from the observed TEC data sets. So it is viable to decrease the number of modeling parameters. The Fourier Series Analysis (FSA) is carried out to characterize the solar-cycle, annual and semi-annual dependences through modulating the first three singular values by the solar (F10.7) and geomagnetic (Ap) indices. The positive correlation coefficient (0.75) of daily averaged GPS–TEC with daily averaged F10.7 strongly supports the temporal variations of the ionospheric features depends on the solar activity. Further, the significance and reliability of the SVD model is evaluated by comparing it with GPS–TEC data and the standard global model (Standard Plasma-Spherical Ionospheric Model, SPIM and International Reference Ionosphere, IRI 2016).     

基于模糊综合评判的机械零件材料选择方法

针对在选择机械零件材料时采用传统方法所具有的主观性缺陷,本文结合设计实例,运用模糊数学理论,建立了零件材料选择的模糊综合评判的数学模型,能从多种可用材料中较客观、合理地确定出最适用的一种材料,从而提高了设计质量.     

New methods for calculating bare soil land surface temperature over mountainous terrain

Land surface temperature(LST) causes the phase change of water, links to the partitioning of surface water and energy budget, and becomes an important parameter to hydrology, meteorology, ecohydrology, and other researches in the high mountain cold regions. Unlike air temperature, which has common altitudinal lapse rates in the mountainous regions, the influence of terrain leads to complicated estimation for soil LST. This study presents two methods that use air temperature and solar position,to estimate bare LST with high temporal resolution over horizontal sites and mountainous terrain with a random slope azimuth. The data from three horizontal meteorological stations and fourteen LST observation fields with different aspects and slopes were used to test the proposed LST methods. The calculated and measured LST were compared in a range of statistical analysis, and the analysis showed that the average RMSE(root mean square error),MAD(mean absolute deviation), and R~2(correlation coefficient) for three horizontal sites were 5.09℃,3.66℃, 0.92, and 5.03℃, 3.52℃, 0.85 for the fourteen complex terrain sites. The proposed methods showed acceptable accuracy, provide a simple way to estimate LST, and will be helpful for simulating the water and energy cycles in alpine mountainous terrain.     

临汾台摆式倾斜仪平行观测的差异性特征及其观测布局建议

根据临汾地震台石英摆、垂直摆、宽带垂直摆3套摆式倾斜仪器的观测资料,对山西中南部几次中等地震进行分析,发现在地震前各仪器同测向曲线有一定的异常反映,但异常并非呈相关一致性变化,有的还表现出明显的差异性特征;在同一台址条件下,异常的差异性与仪器的工作周期、动态响应范围、记录频段等有关;河津地震前后宽带垂直摆倾斜仪记录到的连续阶跃扰动(错位掉格)可能是慢地震现象,由此说明了宽频段仪器的优越性及发展性;建议在形变台网观测中,同一台站应建立宽频或多种同类型的形变观测仪器,组成尽量具有低、中、高频段的全面观测系统,这可能对于扑捉近震的短临前兆异常有实效意义.     

中国雅丹地貌申报世界自然遗产的可行性研究

中国干旱区分布的大面积典型雅丹地貌具备申报世界自然遗产的条件,但是中国雅丹地貌的“申遗”工作长期以来被忽视。依据《世界遗产公约操作指南》中的相关标准,分析了中国雅丹地貌的世界自然遗产价值,论证了中国雅丹地貌申报世界自然遗产的条件,讨论了中国雅丹地貌申报世界自然遗产的重要意义,并建议有关部门尽快开展中国雅丹地貌“申遗”工作,使中国雅丹地貌尽早被世界遗产委员会列入《世界遗产名录》。     

Remote Sensing of Eupatorium Adenophorum Spreng Based on HJ-A Satellite Data

In the southwest of China, one of the greatest threats to local ecosystem is the area expansion of an invasive species, i.e., Eupatorium adenophorum Spreng (EAS). In this study, the remote-sensing technology was used to detect and map the spatial distribution of EAS in Guizhou Province, China. A series of vegetation indices, including normalized difference vegetation index (NDVI), simple ratio index (SRI) and atmospherically resistant vegetation index (ARVI), were used to identify EAS from HJ-A Chninese satellite data. According to the analysis results of fieldworks from March 21 to 22, 2009, it was found that the vegetation index of {1.9589 ≤ SRI ≤ 4.1095}∩{0.2359 ≤ ARVI ≤ 0.5193} was the optimal remote-sensing parameter for identifying EAS from HJ-A data. According to the spatial distribution of EAS estimated from HJ-A data, it was found that EAS was rather more in southwest of Guizhou Province than in northeast. EAS became sparse from southwest to northeast gradually, and the central Guizhou Province was the ecological corridor linking EAS in southwest to that in northeast. By comparison with validated data collected by the government of Guizhou Province, it was found that the uncertainty of remote-sensing method was 18.52%, 29.31%, 8.77% and 9.46% in grassland, forest, farmland and others respectively, and the mean uncertainty was 13.29%. Owing to the lower height of EAS than many plants in forest, the uncertainty of EAS was the greatest in forest than that in grassland, farmland and so on.