Study on the creep permeability of mining-cracked N2 laterite as the key aquifuge for preserving water resources in Northwestern China

This research focused on the impact of mining on the permeability of key aquifuge （N2 laterite） that is widespread in the arid and semi-arid areas of northwestern China and is critical for preserving water resources. The impact of mining stress recovery on the permeability of cracked N2 laterite was assessed for parts of northwestern China that included the Jingle laterite and Baode laterite. The mineral compositions and swelling properties of the laterite at both locations were examined, and analytical results showed that the laterite contained abundant clay minerals. The Baode laterite exhibited higher expansibility than Jingle laterite. The triaxial creep permeability performance of laterite specimens with a prefabricated crack width of 1.0, 1.5, and 2.5 mm were tested. The results indicated that strain of cracked laterite all exhibited transient creep following each level of loading, and then unstable creep and stable creep. With the increase of loading, the transient creep deformation corresponding to each level of loading decreased, the unstable creep deformation produced by identical loading gradually and incrementally increased. The nonlinear power function equation was selected to fit creep grading curves which have high precision. The cracks within the laterite gradually closed with the stress recovery, and permeability gradually recovered. During the stress recovery, the narrower cracks exhibited a smaller change in permeability. However, for narrow cracks in mining soil, permeability recovered after mining stress when permeability was closer to initial permeability, and the Baode laterite showed greater recovery than that of the Jingle laterite.

酶-光偶联催化系统中分子-电子-质子传递过程与机制

酶-光偶联催化系统(EPCS)集成了半导体的光吸收能力和酶的高活性/特异性,可模拟自然界光合作用实现太阳能驱动的有用化学品合成.作为EPCS中的“能量货币”,辅因子(如NAD(P)+和NAD(P)H)参与了约80%的酶促氧化还原反应,且在酶-光间充当物质/能量交换的枢纽.然而,EPCS涉及光催化和酶催化反应,涉及分子、电子和质子传递过程,属于典型的复杂多相反应,导致其光-化学转化效率与理论值差距较大.本文从微观尺度对EPCS中分子-电子-质子传递过程进行了理解和剖析,系统介绍了自然界光合作用和EPCS中的“新三传”现象.此外,与传统化工领域通过强化宏观尺度上“三传”(即质量传递、热量传递和动量传递)提升单元操作过程效率的方法类似,本文总结并提出了通过协调优化“新三传”(即分子传递、电子传递和质子传递)来强化EPCS中物质-能量耦合关系,进而提升光-化学转化效率的新策略.其中,分子传递主要包括电子供体分子从反应液向催化剂传递以及辅因子分子在光催化模块和酶催化模块间穿梭;电子传递主要包括光生电子从其生成位点到光催化剂表面进而到电子媒介的传递;质子传递主要包括质子从溶液或催化剂表面向电子媒介的传递.期望通过“新三传”强化EPCS效率的理念,打破自然界光合作用的局限,实现温和条件下多种功能分子的高效合成,为人工光合与绿色生物制造领域提供新思路.

Detrimental phase evolution triggered by Ni in perovskite-type cathodes for CO2 electroreduction

Perovskite oxides are popular as cathode materials of solid oxide electrolysis cells, because of their good redox stability and high resistance to coke formation.Unexpectedly, a negative effect of Ni doping is found on Sr2Fe(1.5-x)NixMo(0.5)O(x = 0, 0.05, 0.1, 0.2) cathode for pure CO2 electroreduction at 800 ℃, although Ni is highly active for CO2 electroreduction.The CO2 electroreduction performance degrades with the increase of Ni doping amount.Various characterization techniques are used to disclose the negative effect.Ni doping decreases the perovskite stability under electroreduction conditions, Fe and Ni cations in the B-site are reduced to metal nanoparticles and SrCO3 forms on the surface of the perovskite.The phase instability results from the weaker Ni–O bond.Although the Fe-Ni nanoparticles are in favor of the CO2 electroreduction, too much SrCO3 and carbon deposition block the charge transfer and diffusion of oxygenous species on the cathode surface.

A method for predicting the water-flowing fractured zone height based on an improved key stratum theory

In the process of using the original key stratum theory to predict the height of a water-flowing fractured zone(WFZ),the influence of rock strata outside the calculation range on the rock strata within the calculation range as well as the fact that the shape of the overburden deformation area will change with the excavation length are ignored.In this paper,an improved key stratum theory(IKS theory)was proposed by fixing these two shortcomings.Then,a WFZ height prediction method based on IKS theory was established and applied.First,the range of overburden involved in the analysis was determined according to the tensile stress distribution range above the goaf.Second,the key stratum in the overburden involved in the analysis was identified through IKS theory.Finally,the tendency of the WFZ to develop upward was determined by judging whether or not the identified key stratum will break.The proposed method was applied and verified in a mining case study,and the reasons for the differences in the development patterns between the WFZs in coalfields in Northwest and East China were also fully explained by this method.

Preparation of natural brucite nanofibers by the dispersion method

The preparation of natural brucite nanofibers through dispersion by the wet process is described. The test results indicate that brucite fibers can be well dispersed by using sodium dioctyl sulfosuccinate （OT） as the dispersant at a dispersant/fiber mass ratio of 0.15：1, dispersing for 30 min at a water/solid mass ratio of 20：1. The prepared nanofibers were characterized with X-ray diffraction （XRD）, scanning electron microscope （SEM）, and transmission electron microscope （TEM）. It is shown that the prepared single brucite nanofiber is around 30 nm in diameter and the talus of the nonsingle brucite nanofibers is about 50-150 nm in diameter. Natural brucite mineral fibers were treated by the dispersion method to obtain nanomaterials. These fibers have significant advantages over artificial nanofibers both in yield and in cost.

3D视频在医学教育中应用的范围综述

目的3D视频在医学教育中的应用方兴未艾。本研究旨在综述3D视频在医学教育中的应用以及对课程活动的影响,为未来该领域的研究提供参考。方法遵循Arksey和O'malley的范围综述指南,采用系统检索策略检索9个英文文献数据库,仅纳人原始文献。2名作者根据纳人排除标准独立筛选了所有文献,并对最终纳入的原始研究文献进行了分析。结果共检索到1302篇文献,最终纳入了23篇。从文献中获得的3个主题包括:在医学教育中使用3D视频的优势,使用3D视频对学生学业成绩和能力的影响,以及学生关于医学教育中使用3D视频的体验。结论在医学教育中使用3D视频得到了广大学生和教育工作者的支持。然而,3D视频在医学教育中的应用效果仍存在争议。医学教育工作者应结合课程特点、学生学习情况和现有教育资源合理使用。

High‑Temperature Electrochemical Devices Based on Dense Ceramic Membranes for CO_(2) Conversion and Utilization

The adverse effects of global warming and climate change have driven the exploration of feasible routes for CO_(2) capture,storage,conversion and utilization.The processes related to CO_(2) conversion in high-temperature electrochemical devices(HTEDs)using dense ceramic membranes are particularly appealing due to the simultaneous realization of highly efficient CO_(2) conversion and value-added chemical production as well as the generation of electricity and storage of renewable energy in some cases.Currently,most studies are focused on the two processes,CO_(2) electrolysis and H2O/CO_(2) co-electrolysis in oxygen-conducting solid oxide electrolysis cell(O-SOEC)reactors.Less attention has been paid to other meaningful CO_(2)-conversion-related processes in HTEDs and systematic summary and analysis are currently not available.This review will fill the gap and classify the CO_(2)-conversion-related processes in HTEDs reported in recent years into four types accord-ing to the related reactions,including assisted CO_(2) reduction to CO,H2O and CO_(2) co-conversion,dry reforming of methane and CO_(2) hydrogenation.Firstly,an overview of the fundamentals of HTED processes is presented,and then the related mechanism and research progress of each type of reactions in different HTEDs are elucidated and concluded accordingly.The remaining major technical issues are also briefly introduced.Lastly,the main challenges and feasible solutions as well as the future prospects of HTEDs for CO_(2)-conversion-related processes are also discussed in this review.

Correction to:High‑Temperature Electrochemical Devices Based on Dense Ceramic Membranes for CO_(2) Conversion and Utilization

Correction to:Electrochemical Energy Reviews https://doi.org/10.1007/s41918-021-00099-2 The original version of this article unfortunately contained a mistake.The graphical abstract was missing.The original article has been corrected.

多相移光纤光栅滤波器的设计与制备

对多相移光纤光栅滤波器的光谱进行了理论仿真。理论结果证明:通过精确设计多相移光纤光栅的相移点数目、相移位置分布、耦合系数、长度等参数,可以获得窄带平顶滤波响应的光谱;而实际制备中引入的误差会导致滤波器光谱性能恶化。随后采用紫外辐照后处理的方式,制备了多相移光纤光栅滤波器,并对其光谱进行了测试。结果表明:当多相移光纤光栅滤波器带宽较宽时,实测光谱与理想仿真结果较为吻合;增大耦合系数以减小带宽时,滤波器的性能对工艺误差更敏感。最后对误差项进行了深入的分析与讨论,结果证明,采用较长的多相移光纤光栅可以有效地增大相移点位置和相移差的容限,减弱光致损耗对其性能的影响。

Wind tunnel simulation of wind erosion and dust emission processes,and the influences of soil texture

Dust emission caused by wind erosion of soil is an important surface process in arid and semi-arid regions.However,existing dust emission models pay insufficient attention to the impacts of aerodynamic entrainment of particles.In addition,studies of wind erosion processes do not adequately account for the dynamics of wind erosion rates and dust emission fluxes,or for the impact of soil texture on dust emission.Our wind tunnel simulations of wind erosion and dust emission showed that the soil texture,wind erosion duration,and shear velocity are major factors that affect the dynamics of wind erosion and dust emission.Because of the limited supply of surface sand and the change in surface erosion resistance caused by surface coarsening during erosion,the wind erosion rate and the flux of particles smaller than 10μm(PM_(10))caused by aerodynamic entrainment decreased rapidly with increasing erosion duration,which suggests that surface wind erosion and dust emission occur primarily during the initial stage of wind erosion.The PM_(10) emission efficiency decreased with increasing shear velocity following a power function,and finer textured sandy loam soils had greater PM_(10) emission efficiency than loamy sand soils.