A comparative study of natural and experimental nano-sized grinding grain textures in rocks

In three shallow-level fault systems in eastern China, nano-sized （30-100 nm） grinding grain textures are found in the thin-shelled theological layer representing frictional-viscous high strain field. The surface layer near slipping plane is composed of stacks of grinding grains with high sphericity and uniform nano-sized diameter, while the underlying layer appears as a mixture of irregular ones with diverse diameters. Rock deformation experiments indicate that the grinding grain texture is a common phenomenon in shearing fractures, suggesting a potential transition from sliding friction to rolling one during the rock deformation process. This transition is crucial for many tribological processes in geological fields.     

Dynamic control on grain-size distribution of terrigenous sediments in the western South China Sea: Implication for East Asian monsoon evolution

High-resolution oxygen isotope stratigraphy of Core MD05-2901, which is located off eastern Vietnam in the western South China Sea （SCS）, was established and indicated that the core spans a time period of the past 450 ka. Based on the bulk density, fractional porosity and lithogenic content of the sediments, terrigenous mass accumulation rate （TMAR） was obtained, which is 4.9-6.0 g cm^-2 ka^-1 on average during interglacial stages, higher than that during glacial stages, i.e. 1.9-5.0 g cm^-2 ka^-1, which is different from northern and southern SCS which show higher TMAR in glacial stages. By principle component analysis of grain size distribution of all the samples, two main control factors （F1 and F2） were obtained, which are responsible for about 80% variance of granularity. The contents of grain size population 1.26-2.66 μm% and 10.8-14.3 μm% which are sensible to F1 show high-frequency fluctuation, and correlate well with the summer insolation at 15^o N. They exhibit a distinct cyclicity with frequencies near 23 ka and 13 ka, in contrast to a strong frequency peak near 100 ka obtained in proxies 4.24-7.42 μm% and 30.1-43.7 μm% controlled mainly by F2. The sedimentary character of this part of the SCS was controlled by variations of input flux from two main source areas, namely the southwest and north SCS, which were transported by different circulations of surface current forced by East Asian summer monsoon and winter monsoon respectively. We believe that the East Asian summer monsoon has fluctuated with high frequency and been forced by changes in solar insolation in low latitude associated with precession and half precession, while ice-volume forcing is probably a primary factor in determining the strength and timing of the East Asian winter monsoon but with less important insolation forcing.     

Preparation of porous microstructures on NiTi alloy surface with femtosecond laser pulses

Porous microstructures on Nickel-Titanium （NiTi） alloy surfaces were prepared by linearly polarized femtosecond lasers with moving focal point at a certain speed. It was found that various novel micro- structures from feather-like ripples to cluster-like porous textures could be formed with increasing laser energy. Particularly, when the laser energy was 400 llJ, a periodic porous metal surface was gen- erated. Measurement of X-ray diffraction showed that the grains on the sample surface were refined through femtosecond laser ablation processes, but the crystal structures still kept their original states. Analysis by X-ray photoelectron spectroscopy revealed that Ni/l＂i on the sample surface was changed with an evident oxidization of titanium element under different laser energies. This investigation pro- vides a new approach to improve the biocompatibility of NiTi-based implant devices.     

Characteristics of paleoflood deposits archived in unit T0403 of Yuxi Site in the Three Gorges reservoir areas,China

Based on the detailed analyses,multi-proxies such as AMS 14 C dating,grain size,component and morphology of heavy minerals,micromorphology of zircon,magnetic susceptibility,Rb/Sr and Hg content are used to research the paleoflood sediments archived in the Yuxi Site.The research indicates that, since 7.6 kaBP,at least 16 times of paleoflood with water level above Wusong Elevation 147.024 m(a.s.l.) left deposits in the Neolithic layers of unit T0403 from the Yuxi Site.The results are induced from the following aspects:(1)The plaeoflood sediments take on great similarities with modern flood sediments in the Yuxi Site and Zhongba Site in probability cumulative curves which mainly show a pattern of 3 segments in fluvial pattern.(2)There is some resemblance between the heavy mineral components and the zircon shape characteristics of paleoflood deposits and those of modern flood deposits.(3) Magnetic susceptibility values(40.44―70.10SI)are lower than those of sediments from cultural layers (59.59―188.68SI).(4)Hg values(290.71―742.51 ng/g)are lower than those of sediments from cultural layers(344.16―10518.17 ng/g).(5)Rb/Sr values are higher than those of sediments from cultural layers, while those of the 4th,5th,6th,7th,8th cultural layers are high,which shows that they are inundated by paleoflood.The reason for many flood deposits existing is related to the site situated on the first terrace where the Yuxi River joins with the Yangtze River.As there are some similarities between the plaeoflood sediments and those of the Zhongba Site,it is feasible to confirm the existence of paleoflood sediments based on the above points.     

龙永煤田童子岩组地质——地球物理特征分析

本文就龙永煤田童子岩组地层的一般特征,各段及亚段在岩性、岩相、化石组合、岩石粒度趋势、含煤性、煤层灰成分、特别是地层的地球物理特征进行了分析,对各段及亚段的主要区别进行详细说明,有助于地质工作者清楚认识这些地层的特征,这对于解决复杂地质构造问题、进行岩煤层对比等有重要意义。     

反相微乳法制备BaAl12O19纳米颗粒及其形貌控制

采用反相微乳液法制备BaAl12O19纳米颗粒,并与常规沉淀法相比较.分析了反相乳液法制备过程中洗涤剂、煅烧温度、陈化时间对样品性能的影响.通过研究制备条件,改变溶液/油相比控制样品的形貌.溶液/油相比较小时,样品颗粒呈球形;溶液/油相比较高时,颗粒形貌呈棒状.研究表明,反相微乳法的煅烧温度低于常规沉淀法,且颗粒形貌可控.     

贵州省食物供需格局时空变化分析

为探究2000~2010年贵州省的食物供给时空变化,在分析各类食物产量变化趋势与耕地资源的基础上,采用营养物质转化公式及小康生活水平下营养需求标准,提取热量、蛋白质与脂肪关联数据,借助Arc GIS对贵州省及各区县的人口供养能力进行时空变化分析。研究得出:从整体来看,食物营养供给总量较为富余,营养物质供养人口能力:热量脂肪蛋白质,其中脂肪供给能力增长明显;从分县的数据来看,11年间三类营养物质县域自给自足数量增多,2010年热量、蛋白质与脂肪自给自足率分别达到91%、76%、81%;从分布上看,供应能力强的区域集中在遵义县及周边地区;研究期间内,旱地面积减少了14.79%,其中15°以上的坡耕地退耕显著,占减少总量的82%;水田面积变动不大,仅减少了0.8%。总体来看贵州省食物供给在全省和分县尺度下都存在时间与空间的不均衡。     

冷轧工艺对取向硅钢初次再结晶织构的影响

研究了取向硅钢制备过程中常见的两种冷轧工艺,主要研究了一阶段冷轧与两阶段冷轧+中间退火工艺对初次再结晶组织及织构的影响.结果表明:采用两阶段冷轧+中间退火工艺制备以Cu2S为主抑制剂的取向硅钢,其初次再结晶平均晶粒尺寸为181μm,高斯晶粒的体积分数为06%,迁移性强的重位点阵晶界(Σ5+Σ9)和高能晶界(20°~45°取向偏差角)所占比例分别为18%和504%.与一阶段冷轧工艺相比,其初次再结晶晶粒较细,且高斯晶核与特征晶界所占的比例较高,有利于高斯晶粒发生二次再结晶.     

施工阶段钢筋砼地下粮食筒仓仓壁受力分析

钢筋混凝土地下圆形粮食筒仓在施工过程中会出现只有仓底板和仓壁,而没有仓顶板的情况.利用有限单元法,分析了此种情况仓壁环向力、径向位移和竖向弯矩的大小以及分布情况.根据计算结果与使用阶段情况的对比,发现这种工况下仓壁拉应力峰值会增大,且最大压应力出现位置会向仓底移动,影响结构安全.实际工程设计时需要对结构认真复核.     

超重力场和稀土La变质对Al-14.5Si合金组织及硬度的影响

利用超重力场凝固技术和稀土La变质方法制备Al-14.5Si合金铸锭,研究了3000g超重力场下La含量对Al-14.5Si合金组织及硬度的影响。结果表明,3000g超重力场下凝固的Al-14.5Si合金铸锭主要分为边部和芯部两个区域。芯部占主要部分(14～16mm),在水平和垂直方向的组织都较为均匀,为超细共晶硅组织;边部厚度约为2～3mm,组织共晶硅较为粗大。水平方向上,铸锭显微硬度波动较大,中心区域最高;垂直方向上铸锭显微硬度波动较小。随着La含量的增加,共晶硅尺寸呈现先降低后增加的趋势,当La含量为0.6%时,晶粒细化程度最高,芯部共晶硅尺寸最小,平均直径约为0.25μm,平均长度约为0.37μm;芯部显微硬度随La含量增加呈先增加后降低的趋势,当La含量为0.4%时,铸锭芯部平均硬度最高可达HV91,相较普通重力场下未变质合金提升了48.2%。由此可见,超重力和稀土La变质对Al-14.5Si合金芯部共晶组织的细化及硬度的提升起到正协同作用。