电磁连铸对镁合金凝固和偏析的影响

对电磁连铸AZ31镁合金的宏观组织,以及溶质元素在铸锭截面上的分布规律进行了工业化(生产)规模的实验研究.结果表明:合适与匹配的连铸工艺和电磁场处理可使镁铸坯晶粒组织细化.在拉速8 cm/min和表观直流电流40 A的电磁场条件下,φ162 mm圆坯的AZ31镁合金宏观凝固组织细化为均匀的等轴晶组织.同时,铸坯中溶质元素的偏析明显改善.以Zn,Mn元素为例,其平均偏析度分别比普通连铸下降73%和67%.     

Simultaneous CO2 and H2O Activation via Integrated Cu Single Atom and N Vacancy Dual-Site for Enhanced CO Photo-Production

Photocatalytic conversion of CO₂ into fuels using pure water as the proton source is of immense potential in simultaneously addressing the climate-change crisis and realizing a carbon-neutral economy. Single-atom photocatalysts with tunable local atomic configurations and unique electronic properties have exhibited outstanding catalytic performance in the past decade. However, given their single-site features they are usually only amenable to activations involving single molecules. For CO₂ photoreduction entailing complex activation and dissociation process, designing multiple active sites on a photocatalyst for both CO₂ reduction and H₂O dissociation simultaneously is still a daunting challenge. Herein, it is precisely construct Cu single-atom centers and two-coordinated N vacancies as dual active sites on CN (Cu₁/N_2CV-CN). Experimental and theoretical results show that Cu single-atom centers promote CO₂ chemisorption and activation via accumulating photogenerated electrons, and the N_2CV sites enhance the dissociation of H₂O, thereby facilitating the conversion from COO* to COOH*. Benefiting from the dual-functional sites, the Cu₁/N_2CV-CN exhibits a high selectivity (98.50%) and decent CO production rate of 11.12 µmol g⁻¹ h⁻¹. An ingenious atomic-level design provides a platform for precisely integrating the modified catalyst with the deterministic identification of the electronic property during CO₂ photoreduction process.     

新疆乌恰康苏地区典型小流域生态景观及生态环境研究

新疆乌恰康苏地区是塔里木盆地西南缘重要的大型有色金属资源基地之一,本次通过康苏地区典型小流域生态景观及生态环境研究,将研究区划分为水源涵养功能区、荒漠化控制功能区、水土保持功能区、水域河流功能区、城镇功能区、农业功能区和资源基地功能区等7个生态功能区.在水土调查评价的基础上,确定资源基地敏感因素缓冲区范围750～100...     

液体火箭发动机U形环密封界面优化设计

U形密封环是液体火箭发动机常用的一种密封结构,其密封性能是决定发动机可靠性的关键因素。为研究U形环的密封机制,改善其整体结构的密封性能,构建U形环密封结构的有限元分析模型,分析常温预紧工况和低温工作工况下密封环的密封性能。结果表明：相对于常温（20 ℃）预紧工况,低温（-183 ℃）工作工况下U形环密封面的有效接触宽度和接触应力更大,但仍存在密封面接触不充分的问题。采用密封界面形貌的优化设计方法对U形环密封界面进行优化设计,优化后U形环密封面从平坦形貌变为非平坦的非线性形貌,低温工作工况下U形环密封面的有效接触宽度增加了138%,接触应力分布均匀程度提升了99%,密封面的有效接触宽度大幅增加,接触应力分布的均匀性大幅改善,整体结构的密封性能显著提升。     

HDPE/木粉改性复合材料的制备及其长效吸水性能研究

加入HDPE-g-MAH、CG-8831和KH-550制备HDPE/木粉改性复合材料。研究其长效吸水性,发现吸水率随时间延长先快速增加,浸水35 d后缓慢增至平衡,HDPE-g-MAH改性效果最好,其饱和吸水率仅为1.503%。利用Fick第二扩散定律拟合吸水动力学曲线,得扩散系数D的顺序:HDPE-g-MAH增容HDPE/木粉复合材料HDPE/木粉复合材料KH-550改性HDPE/木粉复合材料CG-8831改性HDPE/木粉复合材料。并证明该吸水过程符合Fick第二扩散定律,相关系数R2值达0.99以上。HDPE/木粉改性复合材料尺寸变化系数CDCWCT。     

PVP/PLA乳液静电纺丝成形及纤维毡亲水性能研究

利用乳液静电纺丝可制备一定复合结构的共混纤维,且可通过调控乳液的组成而实现聚合物溶液在低浓度下的静电纺丝成形。以聚乙烯基吡咯烷酮(PVP)水溶液为分散相,聚乳酸(PLA)氯仿溶液为基体相,制备不同水相比例的PVP/PLA乳液,研究了PVP/PLA乳液静电纺丝成形及其纤维毡的亲水性能。结果表明:乳液体系中PVP水相的加入可使PLA乳液在远低于其单独可纺溶液浓度下纺丝成形,所得纳米纤维随着PVP水相比例的提高而表现出纤维直径增加,并发生纤维集结成束,PVP大部分分布在复合纤维毡的表层,纤维毡呈现明显的透水性能;PVP的加入可有效改善PLA纳米纤维毡的亲水性能。     

西南天山西段有色金属资源基地生态资源环境评价

西南天山西段有色金属资源基地是中国重要有色资源基地之一,具有巨大的现有资源量及找矿潜力,同时面临着矿产资源开发利用与生态环境保护和寻求新的找矿方法促进资源基地发展的难题。本研究通过生态资源环境综合调查与评价,查明矿业开发对区域生态环境的影响,创建了生态-环境-资源-社会-经济五位一体的综合评价技术方法,建立了生态环境资源功能区划方案,划分了鼓励开发区、限制开发区及禁止开发区,优化了资源配置,促进绿色矿业发展和生态文明建设。     

电感耦合等离子体质谱法(ICP-MS)测定甜菜颗粒粕中的砷含量

利用微波消化－电感耦合等离子体质谱法（ＩＣＰ－ＭＳ）测定甜菜颗粒粕中砷含量。对添加０．５,２．０,４．０ｍｇ／ｋｇ砷的甜菜颗粒粕样品,回收率为６８．２％－７１．４％。变异系数（ＣＶ）为２．７％。方法检测低限为０．１μｇ／ｋｇ。本方法具有前处理简单、快速,检测限低等特点,可用于甜菜粕中砷的检测和监控。     

盖下坝水电站施工期温度应力及损伤仿真分析

结合盖下坝水电站工程实际情况,采用ANSYS软件及其二次开发技术,对该混凝土拱坝施工期的温度场和应力场进行全过程的三维仿真计算,得出施工期最高温度和最大温度应力.同时,利用损伤有限元程序对该大坝进行了损伤仿真计算,得出施工期重要时刻的损伤场.仿真结果表明,在合理的温控措施下,大坝施工期温度应力远小于设计容许值,损伤值也较小,施工期不会出现宏观裂缝.     

Fabrication of polypyrrole–glucose oxidase biosensor based on multilayered interdigitated ultramicroelectrode array with containing trenches

A miniature glucose biosensor has been developed based on electropolymerization of polypyrrole–glucose oxidase on a multilayered gold interdigitated ultramicroelectrode array with containing trenches. The basal band ultramicroelectrode with a functional width of 362 nm is fabricated using multilayered materials and conventional photolithographic techniques. The electrode surface is inside the containing trenches, the depth of which is larger than 1.5 μm. High quality electrodes with uniform geometries are characterized by microscopy and electrochemical techniques. The corrosion resistance is investigated on exposure to the normal saline, which indicates that the electrodes are adequate for acute experiments lasting a few hours. Fabricated by electropolymerization, the glucose oxidase/polypyrrole (GOx/PPy) biosensors can be used for detecting glucose concentration in the linear range of 0–10 mmol/L, with a sensitivity of 13.4 nA/(mmol L) and a correlation coefficient of 0.998, respectively.