Monitoring of the urban sprawl using geoprocessing tools in the Shenzhen Municipality,China

Shenzhen, located in South China has experienced rapid urbanization over the past three decades. This paper focuses on the urban sprawl integrating remote sensing and geographic information systems (GIS). The overlay of the urban area maps for two adjacent study years was used to generate the sprawl categories map. The three main sprawl categories of infilling sprawl, edge-expansion sprawl and outlying sprawl were calculated and analyzed in regard to their distribution and change throughout different counties during the study years. The result showed that the urban area in the study region had increased dramatically from 19.55 km² in 1979 to 894.31 km² in 2005. The urban area centroids over the six study years transferred from southwest to northeast from 1979 to 2005. Among the study counties, the patterns of sprawl categories were markedly distinctive over different study periods. From 1979 to 2005, Shenzhen’s chief spread was outlying sprawl. Bao’an experienced the maximum sprawl within the three study counties. The findings show that studying urban sprawl can provide a method of monitoring urban area change, which, in turn, gives us a clearer perspective of urban sprawl patterns over a longer period of time. This would prove invaluable to those researchers such as land and urban planners.     

Shifting farming-pastoral ecotone in China under climate and land use changes

Meteorological records show a rise in temperature and decrease in precipitation in most parts of the farming-pastoral ecotone of Northern China over the last 50 years. During the last quarter of the 20th Century, the agrarian sector went through a series of reforms and changes in government policies on land use that have led to extensive changes in land cover. The objective of this study was to redefine the location and analyze the boundary variations under the effects of climate and land use changes in the farming-pastoral ecotone of Northern China. The results showed that the location of study area has been redefined as both a climatic ecotone from the perspective of suitability of precipitation and temperature for agricultural crops and vegetation growth, and also a land use ecotone based on the impacts of farmland restructuring by government policies on land use. In recent decades, the climatic boundary has moved southeast while the land use boundary has moved northwest, showing opposing directions of change. The extent of boundary changes in the northeast and northern sections are far greater than in the northwestern section of the farming-pastoral ecotone of Northern China.     

Age and geochemistry of Early Ordovician A-type granites in the Northeastern Songnen Block,NE China

Early Ordovician A-type granites in the northeastern (NE) Songnen Block NE China were studied to better understand the geodynamic settings in this region. This research presents new zircon U–Pb ages and whole-rock geochemical data for the Early Ordovician granites in the NE Songnen Block. Zircon U–Pb dating indicates that the granite in the Cuibei, Hongxing, and Meixi areas in the NE Songnen Block formed in the Early Ordovician with ages of 471–479 Ma. The granites show geochemical characteristics of high SiO₂ and K₂O compositions and low FeOT, MgO, CaO, and P₂O₅ compositions. They belong to a high K calc-alkaline series and display a weak peraluminous feature with A/CNK values of 0.98–1.14. The rocks have a ∑REE composition of 249.98–423.94 ppm, and are enriched in LREE with (La/Yb)_N values of 2.87–9.87, and display obvious Eu anomalies (δEu?=?0.01–0.29). Trace elements of the studied granites are characterized by enrichment in Rb, Th, U, Pb, Hf, and Sm, and depletion of Ba, Nb, Ta, and Sr. They display geochemical features of high Zr?+?Y?+?Nb?+?Ce values (324–795 ppm) and Ga/Al ratios consistent with A-type granites. Based on particular geochemical features, such as high Rb/Nb (7.98–24.19) and Y/Nb (1.07–3.43), the studied A-type granites can be further classified as an A2-type subgroup. This research indicates that the Early Ordovician A-type granites were formed by the partial melting of ancient crust in an extensional setting. Lower Sr/Y and (Ho/Yb)_N ratios indicate that plagioclase and amphibole are residual in the source, and garnet is absent, implying that the magma was generated at low levels of pressure. By contrast, the contemporaneous granites in the SE Xing’an Block suggest a subduction-related tectonic setting, and its adakitic property indicates a thickened continental crust. We suggest that the Paleo-Asian Ocean plate between the Xing’an and Songnen blocks subducted northward during the Early Ordovician. Meanwhile, the NE Songnen Block was exposed to a passive continental margin tectonic setting.     

Assemblage of strike-slip faults and tectonic extension and compression analysis: A case study of a Lower Permian commercial coal reservoir in China

The Qinshui Basin was an active residual basin in the Mesozoic and Cenozoic periods and is located inside the North China Plate. The Upper Paleozoic strata in the basin have been strongly deformed and have developed a large number of strike-slip faults. The Qinshui Basin has been influenced by compressive stress from the northeast direction since the Himalayan period, and the faults have a dextral strike-slip property. Under the action of such a stress field, the right-slip, right-order faults indicate an extension region, and the right-slip, left-order faults indicate a compression region. Based on this principle, the extension and the compression areas were divided. From northwest to southeast direction in the study area, two types of regions have interactive distribution characteristics. For the Fanzhuang block in the eastern part of the study area, the fault distribution has an ‘S-type’ trend from north to south, and the middle extension region is the ‘elbow’ or the ‘hinge zone’ of the ‘S-type’ area, which can also be called the ‘stress transition zone’. The tectonic stress field of the stress transition zone is complex, and tensile fractures are usually extremely developed with extension tectonics. Gas wells with higher capacity are mainly distributed in the extension zone, while the capacity of the gas wells in the compression area is usually lower. The study showed that the distribution of the gas well capacity is consistent with the tectonic extension and compression analysis, indicating that the tectonic analysis method in this study is reliable. The Upper Paleozoic coal measure strata in the Qinshui Basin represent a whole gas-bearing and stress-bearing system, the tectonic analysis method in this study is also applicable to other types of tight reservoirs for this set of depositional systems.     

China’s regional social vulnerability to geological disasters: evaluation and spatial characteristics analysis

The Andaman–Sumatra is one of the seismically active subduction zones and experienced three largest earthquakes in the recent past and rupturing more than 1,600-km-long portion of the plate boundary. The seismicity analysis of these large earthquakes source region (5°S–15°N latitude and 90°E–103°E longitude) has been carried out by several researchers and quantified the spatial and temporal variation of b-value which is a proxy to differential stress conditions and fractal dimension which is an indicator of material heterogeneity and strength. The results of all these studies clearly bring out the low b-value and low fractal dimension corresponding to locales were sizable magnitude earthquakes have occurred. Further locales of high stress regions are identified.     

The status of research on the development and characteristics of mass-flux-density profiles above wind-eroded sediments: a literature review

The mass-flux-density profile above wind-eroded sediments (MFDP) plays an important role in defining the characteristics and impacts of wind–sand flows, and, therefore, has great theoretical and practical significance. As a result, it has been extensively studied from the perspectives of geography, mechanics, physics, and engineering. This paper reviews the research work that has been conducted since Bagnold’s pioneering efforts, summarizes the research achievements, discusses the problems that have not yet been solved, and proposes future research directions. This field of research has progressed from field observations to theoretical analyses and numerical simulations, accompanied by increasing sophistication in the research, and the research scope includes land with mobile sands, wind-eroded farmland, gravel gobis, and degraded grasslands. Many mathematical functions have been proposed to describe MFDP, including exponential, power, modified exponential, modified power, and polynomial functions. This variation results from differences in the study conditions and in the parameters included in a given model and on differences between wind-tunnel experiments and field observations. However, there are the limitations of both wind tunnel experiments and theoretical derivations, and the key parameters of the profile lack a clear physical meaning, which limits the practical application of these functions. Future research must aim to solve these problems.     

山东田横岛海域长牡蛎性腺发育及生化成分周年变化

为了阐明青岛近海长牡蛎(Crassostrea gigas)性腺发育周期及生化成分周年变化,于2019年4月—2020年3月,对青岛田横岛海区长牡蛎的性腺发育周期、生化成分(糖原、脂肪、蛋白质)的周年变化与环境因子(温度、盐度、叶绿素a)关系进行研究。研究显示,调查区长牡蛎性腺发育周期分为两个阶段:休止期(10—12月)和配子发生期(1—9月)。少部分长牡蛎配子发生于温度较低的1月(5.4℃),随着温度升高配子逐渐发育成熟,在6月温度较高(20℃)和叶绿素a浓度较大(1.67μg·L^-1)情况下,配子进入排放期。在配子发生期间,随着配子的成熟,条件指数和卵径在5月达到最大值,在配子排放后降低。生化成分含量为:在冬末春初浮游植物繁殖期间糖原含量储存在长牡蛎各组织中,随着性腺发育,各组织的糖原含量逐渐下降,为配子发育提供能量,这表明贮藏在各组织的糖原是配子发生期间的主要能源物质;性腺-内脏团的脂肪和蛋白质含量随着卵径增加呈上升趋势,产卵后其含量显著下降,表明脂肪和蛋白质与配子发育密切相关。研究结果表明,田横岛海域长牡蛎配子的发育方式为保守种模式。     

不同数据源下毛乌素沙地风况及输沙势特征

风是干旱、半干旱区风蚀风积地貌发育的动力基础,我们通常使用风速资料探讨区域风况,但选取不同的风速资料研究同一区域风况时结果存在差异。以毛乌素沙地为例,分别选取中国气象数据网（CMDC）的日最大风速及风向与美国国家气候数据中心（NCDC）的日8个定时观测风速及风向,对比分析起沙风特征。结果表明：（1）毛乌素沙地平均起沙风速相差较小,但起沙风频率明显在CMDC数据源中较高;（2）毛乌素沙地年起沙风向均以WNW、W和NW为主,但年起沙风次风向、不同区域夏季和秋季起沙风次风向组成均在CMDC数据源中较复杂,且起沙风主次风向频率均在CMDC数据源中较高;（3）毛乌素沙地整体均属于低风能环境,中等风向变率,锐双峰或宽单峰风况,但以最大风速计算的年输沙势约是以定时观测风速计算结果的3.3倍。基于两套数据源定量对比分析毛乌素沙地风况及输沙势,这对区域风况研究是一种新的尝试,以期提高对不同数据源提供的风速差异的认识,为今后不同区域的起沙风分析提供一定的参考。     

黑龙江大兴安岭地区航磁异常特征及找矿效果

利用大兴安岭地区1∶5万高精度航磁资料,结合区域地质背景分析了该区航磁异常特征,依据地物化资料、已知矿(床)点的分布及成矿规律筛选出了一批航磁异常。在最新的高精度航磁图上,已知铁矿异常特征明显,经对比研究及综合查证发现了1处磁铁矿点及多处有色金属、贵金属矿点,在此基础上总结了查证经验,指明了今后采用航磁数据在区内的找矿方向。     

Development of a dynamic load direct shear apparatus for the study of permafrost

The dynamic parameters of permafrost are crucial to and directly affect the accuracy of engineering design and numerical simulation. This paper describes a new dynamic load direct shear apparatus that was developed to measure these parameters. The power systems and measurement and control systems of the device are described, as is a successful validation experiment. The results show that this dynamic load direct shearing device can accurately derive dynamic shear parameters within a certain range of frequencies and amplitudes of shear load.