Physical and mechanical properties and microstructures of submarine soils in the Yellow Sea

In recent years,the exploration of seabed has been intensified,but the submarine soils of silt and sand in the Yellow Sea area have not been well investigated so far.In this study,the physical and mechanical properties of silt and sand from the Yellow Sea were measured using a direct shear apparatus and their microstructures were observed using a scanning electron microscope.The test results suggest that the shear strength of silt and sand increases linearly with the increase of normal stress.Based on the direct shear test,the scanning electron microscope was used to observe the section surface of sand.It is observed that the section surface becomes rough,with many“V”‐shaped cracks.Many particles appear on the surface of the silt structure and tend to be disintegrated.The X‐ray diffraction experiment reveals that the sand and silt have different compositions.The shear strength of sand is slightly greater than that of silt under high stress,which is related to the shape of soil particles and the mineral composition.These results can be a reference for further study of other soils in the Yellow Sea;meanwhile,they can serve as soil parameters for the stability and durability analyses of offshore infrastructure construction.

幼儿数认知发展特点及其促进:平板电脑与面对面教学的比较

儿童早期数认知能力是其思维发展的重要指标,本研究首先探讨了176名3～5岁幼儿数认知能力的发展特点,然后在此基础上着重探究平板电脑教学与面对面教学对幼儿数认知能力发展的影响,结果发现:(1)3～5岁幼儿的数认知能力随年龄的增长不断提高,4岁幼儿的基数能力显著高于3岁幼儿;从4岁开始,幼儿的数数能力、符号数字知识能力、简单计算能力快速提高,4岁是幼儿数认知能力的发展加速期。(2)幼儿家庭社会经济地位是影响幼儿数认知能力发展的重要社会环境因素,其中父母职业与受教育水平和幼儿数学计算能力呈显著正相关。(3)平板电脑教学组和面对面教学组幼儿的数认知能力均显著提高,平板电脑教学组幼儿的数认知能力后测成绩在符号数字知识和计算上均显著高于面对面教学组,但面对面教学组幼儿的基数能力显著高于平板电脑教学组,这说明不同媒介对幼儿数认知能力发展的不同方面有不同的促进作用。采用平板电脑进行教学与日常学习活动对幼儿认知能力的提高有利有弊,幼儿主要养育者及教育者应采取科学方式引导幼儿合理使用平板电脑,以尽力发挥平板电脑促进幼儿思维水平提高的积极作用。

Human Plague Case Diagnosed in Ningxia Tracked to Animal Reservoirs—Inner Mongolia Autonomous Region,China,2021

Summary What is already known about this topic?There were a total of 4 and 3 human plague cases that occurred in the Inner Mongolia Autonomous Region in 2019 and 2020,respectively,with 1 and 2 deaths in 2019 and 2020 respectively,which indicated that plague still poses a significant threat to human health especially for farmers,shepherds,or residents living in native plague foci.What is added by this report?On August 14,2021,1 patient from the Otog Qi(County)in the Inner Mongolia sought treatment in Yinchuan City(the capital of Ningxia Hui Autonomous Region).

Phase separation and crystallization of La2O3 doped ZnO-B2O3-SiO2 glass

In order to investigate the effect of the La2O3 on the phase separation and crystallization of ZnO-B2O3-SiO2 glass, after the occurence of the phase separation and crystallization of glasses by heat treatment, the microstructure morphology and distribution of elements in different sample areas were characterized by the scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS);the non-isothermal crystallization kinetics of the glass samples was studied by using a differential scanning calorimeter(DSC) and the precipitated crystals of crystallized glass were determined by the X-ray diffraction(XRD). The results suggest that the phase separation and crystallization of 60ZnO-30 B2O3-10SiO2 glass occur at glass surface, and the incorporation of small amount(<4 mol%) of La2O3 significantly inhibits the glass phase separation and consequently improves the thermal stability of glass.Doping of La2O3 accelerates the glass crystallization at the elevated temperature(660 ℃), making the depth of crystal layer thicker and diffraction intensity in XRD patterns stronger. However, due to the precipitation of several crystals that occur simultaneously when La2O3 doping amount is 4 mol%, crystallization of the 60ZnO-30B2O3-10SiO2 glass is obviously depressed, the crystallization activation energy Ec and the relative crystallinity Xc of the glass reach the maximum and the minimum values, respectively.Although transition from one-dimensional growth of crystals to two-dimensional growth of crystals results from La2O3 addition, the one-dimensional growth of crystals remains dominant in crystallization process. This work can provide some useful information for preparing glass ceramics with nano-crystals precipitated in the glass surface.