AN EXPERIMENTAL STUDY ON TEMPORAL AND SPATIAL PROCESSES OF WANDERING-BRAIDED RIAVER CHANNEL EVOLUTION

1INTRODUCTIONErgodichypothesisisoneofthebasicconceptsofmoderngeomorphology.Itsuggeststhatundercertaincircumstancessamplinginspacecanbeequivalenttosamplingthroughtime;andthatspace-timetransformationsarepermissibleasaworkingtool.Thisisbasedontheassumptionthat,whenindividualmembersofapopulationoflandformsarechangingregularlythroughtime,thespatialfrequencyofoccurrenceofgiventypesoflandformsisinverselyproportionaltotheirrateofchange(Chorley,etal.,1985).TheconceptofthecycleofDavis'erosioninwhi…     

Crystal fractionation of granitic magma during its non-transport processes: A physics-based perspective

Granitic continental crust distinguishes the Earth from other planets in the Solar System. Consequently, for understanding terrestrial continent development, it is of great significance to investigate the formation and evolution of granite.Crystal fractionation is one of principal magma evolution mechanisms. Nevertheless, it is controversial whether crystal fractionation can effectively proceed in felsic magma systems because of the high viscosity and non-Newtonian behavior associated with granitic magmas. In this paper, we focus on the physical processes and evaluate the role of crystal fractionation in the evolution of granitic magmas during non-transport processes, i.e., in magma chambers and after emplacement. Based on physical calculations and analyses, we suggest that general mineral particles can settle only at tiny speed(~10~(-9)–10~(-7) m s~(-1))in a granitic magma body due to high viscosity of the magma; however, the cumulating can be interrupted with convection in magma chambers, and the components of magma chambers will tend to be homogeneous. Magma convection ceases once the magma chamber develops into a mush(crystallinity, F~40–50%). The interstitial melts can be extracted by hindered settling and compaction, accumulating gradually and forming a highly silicic melt layer. The high silica melts can further evolve into high-silica granite or high-silica rhyolite. At various crystallinities, multiple rejuvenation of the mush and the following magma intrusion may generate a granite complex with various components. While one special type of granites, represented by the South China lithium-and fluoride-rich granite, has lower viscosity and solidus relative to general granitic magmas, and may form vertical zonation in mineral-assemblage and composition through crystal fractionation. Similar fabrics in general intrusions that show various components on small lengthscales are not the result of gravitational settling. Rather, the flowage differentiation may play a key role. In general, granitic magma can undergo effective crystal fractionation; high-silica granite and volcanics with highly fractionated characteristics may be the products of crystal fractionation of felsic magmas, and many granitoids may be cumulates.     

基于多位点分子标记和线粒体基因组学中国蚌类(蚌目:蚌超科)物种分类与系统进化研究

中国是东亚蚌类（蚌目：蚌超科）物种分布中心,共记录有26属.然而,在世界蚌目框架下,中国仍缺乏一个完整科学的蚌类分类系统.本研究基于多位点分子标记（COI、16S、28S）和线粒体基因组学重构聚焦于蚌超科的蚌目系统发育关系,ML、BI和BEAST系统发育结果均支持蚌科5亚科分类系统,即（（（Ambleminae+Gonideinae）+Rectidentinae）+Unioninae）+Parreysiinae;珍珠蚌科2亚科分类系统,即（Gibbosulinae+Margaritiferinae）;中国蚌类隶属蚌科4亚科（Gonideinae,Rectidentinae,Unioninae,Parreysiinae）13族和珍珠蚌科两亚科（Gibbosulinae,Margaritiferinae）.基于化石标定的分子钟显示：蚌科物种分化时间为中三叠世（median=232.07 Ma）,其中雕刻蚌亚科（Parreysiinae）起源和物种分化时间早于其他亚科;矩形蚌亚科（Rectidentinae）物种分化时间最晚,为晚白垩世（median=94.72 Ma）;小方蚌亚科（Ambleminae）和隆脊蚌亚科（Gonideinae）最近共同祖先分化于晚侏罗纪世（median=144.69 Ma）,珍珠蚌科起源于晚石炭世（median=312.61 Ma）,物种分化于晚白垩世（median=91.59 Ma）,中国蚌科现生物种最早起源时间可追溯到白垩纪（中国尖嵴蚌（Acuticosta chinensis）,median=114.36 Ma）.蚌超科线粒体基因重排分析显示：蚌超科线粒体基因组有4种基因排列方式（GO）,珍珠蚌科独享一种（GO1）;蚌科中Unioninae和Ambleminae共享一种（GO2）;Gonideinae有2种基因排列方式（GO3和GO4）,其中室蚌（Chamberlainia hainesiana）独享一种（GO4）,其余物种共享一种（GO3）.以往作为高阶元分类的贝壳形态、钩介幼虫形态以及育儿囊类型,并不能作为蚌科属及以上阶元分类依据.本研究重构了世界蚌目聚焦于蚌超科的系统发育关系和进化历史,建立了中国蚌类分类系统,为今后该类群区系多样性研究及资源保护提供了分类依据.     

湖南省县域乡村反贫困绩效评价与空间分异特征

综合运用熵值法、地理探测器等方法,从基本生存绩效、自身发展绩效,县域扶贫绩效3个方面构建指标体系,对湖南省51个贫困县2017年反贫困绩效空间地域分异特征及其影响因素进行研究。结果表明：① 湖南省贫困农户一般能满足基本的生存需要;自身发展绩效水平得分较高的区域大多处于武陵源区、鹤城区等城市市区周围以及罗霄山片区,而雪峰山脉周围县市则普遍较低;县域扶贫绩效水平高的区域分布较为零散,大致位于各城区周围,而省城或西北的少数民族聚集区以及中南部绩效水平还有待提高。② 反贫困绩效总体上呈现出高、中、低3种绩效水平交替分布的空间特征,愈靠近武陵源区、鹤城区和长株潭地区的贫困县市,综合反贫困绩效水平愈高。③ 县域发展情况是影响湖南省反贫困绩效的决定性因素,农户条件与乡村状况是基础性因素,自然条件是重要因素,各因子间交互作用的影响远大于单因子,不存在独立作用的因素,体现出湖南省反贫困绩效影响因素的复杂性特征。     

广州市表层土壤磁学性质的空间插值方法比较

本文利用广州市范围内的350个表层土壤样品χ_lf、χ_ARM/SIRM、HIRM等14个磁学参数的测试结果,在对各磁学参数分别进行统计特征分析和正态性检验的基础上,对满足正态或近似正态分布的磁学参数进行趋势分析。利用确定性插值法（包括反距离权重法和径向基函数法）和地统计法（包括普通克里金法和泛克里金法）对14个磁学参数进行空间插值并根据交叉验证法（比较不同插值方法的交叉验证参数）的结果,比较地统计法和确定性插值法的预测误差,从而确定14个磁学参数的最优插值方法。结果表明：1）地统计法中,χ_ARM、χ_lf、χ_hf、S₁₀₀、S₃₀₀、S_-100、SIRM和HIRM的普通克里金法插值效果最好;SIRM/χ的泛克里金法插值效果最好;χ_ARM/SIRM和S_-300的普通克里金法（OK）和泛克里金法（UK）的插值效果接近。OK法作为最常用的地统计空间插值方法,在表土磁学参数上也相较于UK适用范围更广。2）确定性插值法中,χ_ARM、χ_lf、χ_hf、χ_fd（%）、χ_ARM/χ、χ_ARM/SIRM、HIRM的径向基函数法插值效果最优;S₁₀₀、S_-100、S_-300和SIRM的反距离权重法插值效果最优;反距离权重法和径向基函数法均可作为χ_fd、SIRM/χ、S₃₀₀的插值方法。3）综合比较地统计法和确定性插值法,发现χ_ARM、χ_lf、χ_hf、χ_fd、χ_fd（%）、χ_ARM/χ、χ_ARM/SIRM、S₃₀₀、HIRM的空间插值应采用径向基函数法;S₁₀₀、S_-100和S_-300的空间插值应选择反距离权重法;而SIRM/χ和SIRM空间插值建议分别采用泛克里金法和普通克里金法。     

从地理1到选择性必修1:联系基础上的进阶

地理1和选择性必修1课程内容要求之间的关系为联系基础上的进阶。整体联系体现在太阳辐射和地球自身特点共同作用下的自然带地域分异规律形成过程,是必修地理1和选择性必修1隐含的学科逻辑线索。这条内容线索也是理解“必修”二字的关键。在“必修”的基础上看“选择性”,地理1和选择性必修1内容要求之间的进阶,体现在内容构成上,从现象到规律、从单一要素到要素综合;在学习水平上,从“识记”、“领会”,提升到“领会”、“分析”水平。地理1和选择性必修1内容要求之间的联系与进阶,要求教师树立教学设计的整体意识,包括课程内容的结构化分析和教学目标的分层设计,从而在整体把握学科知识体系的基础上,有一条清晰的逐级递进、螺旋上升体现学习进阶过程的教学“路线图”。     

丹霞山长老峰国家重点保护野生植物丹霞梧桐数据采集与空间分布研究

使用固定翼无人机航测丹霞山核心区长老峰游览区（航测区面积4.25 km²）获得高精度影像数据638张,用Photoscan软件拼接正射影像地图及DEM数据生产。在ArcGIS10.5软件中将正射影像图批量分割成470幅图（长和宽为100 m×100 m,比例尺为1︰1 000）,在分割后的地图上目测识别并定位珍稀物种丹霞梧桐（Firmiana danxiaensis H. H. Hsue & H. S. Kiu）,共获取航测区内1 515株丹霞梧桐及其位置数据,构建地理数据库。利用ArcGIS10.5的空间分析模块,将DEM数据转换成坡度和坡向数据,叠加1 515株丹霞梧桐点位置数据与DEM数据、坡度和坡向数据后进行可视化定量分析。结果显示：航测区内有71.2%的丹霞梧桐（1078株）分布在海拔210±90 m的范围内。有68.3%（1033株）的丹霞梧桐分布在坡度>15°的丹霞崖壁地带,与实地观察的事实相吻合。虽然,在航测区长老峰的各个坡向上都可以实地观察丹霞梧桐的分布,但定量统计表明,在南东（295株）、南（276株）、南西（244株）3个坡向上分布相对集中,占总数的53.8%（815株）,这也与实地观察到的丹霞梧桐属于喜光照的向阳植物一致。小区域范围内珍稀物种的数据采集与空间分析,是珍稀物种保护的重要基础工作,还可以为较大区域范围内丹霞梧桐生态保护红线更准确的落地提供参考和依据。     

Negative differential resistance behaviour in N-doped crossed graphene nanoribbons

By using first-principles calculations and nonequilibrium Green's function technique, we study elastic transport properties of crossed graphene nanoribbons. The results show that the electronic transport properties of molecular junctions can be modulated by doped atoms. Negative differential resistance (NDR) behaviour can be observed in a certain bias region, when crossed graphene nanoribbons are doped with nitrogen atoms at the shoulder, but it cannot be observed for pristine crossed graphene nanoribbons at low biases. A mechanism for the negative differential resistance behaviour is suggested.     

Talc-beating serpentinized peridotites from the southern Mariana forearc： implications for aseismic character within subduction zones

The serpentinized peridotites overlying the subducted zones in the Izu-Bonin-Mariana (IBM) arc system have been interpret as the cause of the low-velocity layer identified beneath the IBM froearc, in turn few earthquakes occurred along the plate boundary. Chrysotile, which is a low temperature and highly hydrated phase of serpentine with low frictional strength, has been suggested as the low velocity material in the serpentinized peridotites, besides, brucite is inferred to be likely conducive to stable sliding. However, such idea encounters challenging in our serpentinized peridotites from the southern Mariana forearc, which absent both the above minerals. The presence of talc, which characterized by its weak, low-friction and inherently stable sliding behavior, provides new clue. Here we report the occurrence of talc in serpentinized peridotites collected from the landward trench slope of the southern Mariana forearc. We infer that talc is mainly forming as a result of the reaction of serpentine minerals with silica-saturated fluids released from the subducting slab, and talc also occurs as talc veins sometimes. Due to its unique physical properties, talc may therefore play a significant role in aseismic slip in the IBM subduction zone.

     

基于MapInfo平台的GIS应用集成开发

以可视化编程语言Visual C＋＋为例,详细介绍基于MapInfo地理信息系统平台的GIS应用集成开发方法,并介绍集成开发中所使用到的OLE调用、回调等主要技术。最后,给出了一个具体的应用实例。实践也证明地图集成开发是一种较为有效的GIS应用的开发模式。