科创中国

利用共沉淀法由Fe(NO3)3、Al(NO3)3、Zn(Ac)2和H2SO4制备了SO4^(2-)/Fe2O3/Al2O3/ZnO催化剂,并用于催化合成苯甲醛丙二醇缩醛,研究了醛醇摩尔比、催化剂用量、反应时间等因素对产品收率的影响.结果表明,在n(苯甲醛):n(丙二醇)=1:1.2,催化剂用量为反应物总质量的1%,反应时间50min的最佳条件下,苯甲醛丙二醇缩醛的收率可达97.6%.

Hydrostatic mechanical face seals for reactor coolant pumps are very important for the safety and reliability of pressurized-water reactor power plants.More accurate models on the operating mechanism of the seals are needed to help improve their performance.The thermal fluid–solid interaction(TFSI)mechanism of the hydrostatic seal is investigated in this study.Numerical models of the flow field and seal assembly are developed.Based on the mechanism for the continuity condition of the physical quantities at the fluid–solid interface,an on-line numerical TFSI model for the hydrostatic mechanical seal is proposed using an iterative coupling method.Dynamic mesh technology is adopted to adapt to the changing boundary shape.Experiments were performed on a test rig using a full-size test seal to obtain the leakage rate as a function of the differential pressure.The effectiveness and accuracy of the TFSI model were verified by comparing the simulation results and experimental data.Using the TFSI model,the behavior of the seal is presented,including mechanical and thermal deformation,and the temperature field.The influences of the rotating speed and differential pressure of the sealing device on the temperature field,which occur widely in the actual use of the seal,are studied.This research proposes an on-line and assembly-based TFSI model for hydrostatic mechanical face seals,and the model is validated by full-sized experiments.

The transient behavior of centrifugal pumps during transient operating periods,such as startup and stopping,has drawn more and more attention recently because of urgent needs in engineering.Up to now,almost all the existing studies on this behavior are limited to using water as working fluid.The study on the transient behavior related to solid-liquid two-phase flow has not been seen yet.In order to explore the transient characteristics of a high specific-speed centrifugal pump during startup period delivering the pure water and solid-liquid two-phase flow,the transient flows inside the pump are numerically simulated using the dynamic mesh method.The variable rotational speed and flow rate with time obtained from experiment are best fitted as the function of time,and are written into computational fluid dynamics(CFD)code-FLUENT by using a user defined function.The predicted heads are compared with experimental results when pumping pure water.The results show that the difference in the transient performance during startup period is very obvious between water and solid-liquid two-phase flow during the later stage of startup process.Moreover,the time for the solid-liquid two-phase flow to achieve a stable condition is longer than that for water.The solid-liquid two-phase flow results in a higher impeller shaft power,a larger dynamic reaction force,a more violent fluctuation in pressure and a reduced stable pressure rise comparing with water.The research may be useful to understanding on the transient behavior of a centrifugal pump under a solid-liquid two-phase flow during startup period.

利用同步辐射X射线荧光法(Synchrotron radiation X-ray fluorescence,SR-XRF)、离子色谱(Ion Chromatography,IC)、扫描电镜及其能谱分析(Scanning electron microscopy and X-ray energy dispersive microanalysis,SEM-EDX)、同步辐射微束X射线荧光法(Synchrotron radiation micro-beam X-ray fluorescence,μ-XRF)等手段研究上海某垃圾焚烧厂生活垃圾焚烧产物飞灰(Fly ash,FA)、炉渣(Bottom ash,BA)的元素浓度、离子组成、微观形貌、元素面分布,采用电感耦合等离子体质谱(Inductively Coupled Plasma Mass Spectrometry,ICP-MS)和X射线吸收精细结构谱(X-ray absorption near-edge structure,XANES)研究灰渣中Pb的同位素比值和化学种态.研究发现,飞灰中多数金属元素浓度高于炉渣中的,Pb、Cd明显富集于飞灰中,元素的富集因子显示Pb、Cd、Cu、Zn等呈极度污染状态.灰渣中水溶性成分主要为Ca、Na、K的氯化盐和硫酸盐,飞灰中离子浓度普遍高于炉渣中的.飞灰颗粒相对于炉渣颗粒粒径小、表面粗糙,更易于重金属的吸附.灰渣颗粒物的元素Pb、Zn、Cu、Cr、Fe、Mn等并不是均匀分布的,而是呈现局部明显富集.飞灰和炉渣Pb的来源相似,化学种态相似,主要为PbCl2、PbS和PbO.生活垃圾在焚烧过程中元素的迁移分布与元素本身的特性、焚烧环境相关,上海地区生活垃圾焚烧飞灰是危险废弃物,需稳定化处理后才能填埋,炉渣的资源化利用必需经过预处理.

采用高温固相反应法制备了Sr3-x-yAl2O6:xCe3+,yEu2+(x=0,y=0;x=0.04,y=0;x=0.04,y=0.02;x=0.04,y=0.04;x=0.04,y=0.06;x=0.04,y=0.08;x=0,y=0.04)荧光粉,研究其相组成与荧光特性,结果表明,样品具有单相Sr3Al2O6晶体结构.在360nm波长的紫外光激发下,Ce3+离子辐射出峰值在434nm附近的宽谱蓝光.通过能量传递作用,Eu2+离子辐射峰值为517nm左右的宽谱绿光.Ce3+和Eu2+的荧光组合获得了色坐标为(0.2611,0.3313)的近白光发射.样品的激发光谱分布在250~400nm的波长范围,这种荧光粉有望在紫外或近紫外激发的白光LED中获得应用.

将金精矿粉样品直接置于石英舟中,在高纯氧气氛中燃烧,释放出汞,与齐化管中的金形成金汞齐,于900℃热释放出汞蒸汽,用直接测汞仪法测定汞的含量.测定结果的相对标准偏差为0.28%~1.57%(n=6),方法检出限为1.0pg/kg,加标回收率为95.7%~117.4%.用该法对4种土壤标准样品进行了测定,测定结果与标准值相符.该方法适合于金精矿粉中微量汞的测定.

为了计算二极管抽运Nd∶ YAG晶体温度场及热形变场,建立了端面绝热、周边恒温的晶体热模型.基于Nd∶ YAG晶体导热系数及热形变系数与其温度的函数关系,应用Newton切线法对热传导方程进行求解,得到了变导热系数和变热形变系数矩形截面Nd∶YAG晶体端面抽运下的温度场和热形变场的一般表达式,同时计算了Nd∶ YAG晶体在不同抽运功率和抽运光斑半径下内部温度场和热形变场的分布变化.结果表明,使用钕离子质量分数为0.01、尺寸为3mm*3mm*8mm的Nd∶ YAG晶体,在功率为60W、光斑半径为450μm的抽运光照射下,变导热系数的Nd∶ YAG晶体端面最大温升为55.7℃,最大热形变量为2.85μm,而按传统将Nd∶ YAG晶体导热系数、热形变系数均视为定值时,晶体端面最大温升为43.4℃,端面最大热形变为2.84μm.

建立了蔬菜干制品中18种有机磷农药和拟除虫菊酯农药残留的在线凝胶渗透色谱一气相色谱/质谱(GPC-GC/MS)分析方法.样品以乙腈为提取剂超声波高速匀浆提取,提取液经ENVI.Carb固相萃取柱净化,除去样品中大部分的色素等干扰基质,再经在线GPC进一步净化除去大分子干扰物质,有效降低了样品基质带来的背景干扰.采用外标法定量,在质量浓度为0.02mg/kg,-0.5mg/kg有良好的线性关系,加标水平为0.4mg/kg时,18种农药的回收率基本都在80%-130%,相对标准偏差小于10%,检出限为0.001mg/kg-0.026mg/kg.经实验证明,该方法是一种快速,准确,灵敏度高的同时检测梅菜干中多种农药残留的检测方法.