Parameter fitting of constitutive model and FEM analysis of solder joint thermal cycle reliability for lead-free solder Sn-3.5Ag

The experimental tests of tensile for lead-free solder Sn-3.5Ag were performed for the general work temperatures range from 11 to 90 °C and strain rate range from 5×10⁻⁵ to 2×10⁻² s⁻¹, and its stress—strain curves were compared to those of solder Sn-37Pb. The parameters in Anand model for solder Sn-3.5Ag were fitted based on experimental data and nonlinear fitting method, and its validity was checked by means of experimental data. Furthermore, the Anand model was used in the FEM analysis to evaluate solder joint thermal cycle reliability. The results show that solder Sn-3.5Ag has a better creep resistance than solder Sn-37Pb. The maximum stress is located at the upper right corner of the outmost solder joint from the symmetric center, and thermal fatigue life is predicted to be 3.796×10⁴ cycles under the calculated conditions. Foundation item: Project(50376076) supported by the National Natural Science Foundation of China     

确定土壤背景值的Hazen概率法——以铜陵矿区Pb为例

本文选取已知土壤背景含量的铜陵矿区,基于Hazen概率曲线,探讨了土壤污染重金属元素Pb背景含量与污染叠加含量的区分方法.得到Pb元素的背景含量为28.5μg/g,与该区深层土壤样中Pb元素含量的平均值(34μg/g)比较接近.还得到了Pb元素污染叠加含量与背景含量的界线点51μg/g.基于Hazen概率曲线区分铜陵矿区土壤Pb元素背景含量与污染叠加含量的方法是有效的,有必要将该方法推广到土壤中其它重金属污染元素、其它地区作进一步研究.     

Non-polar nuclei in fungal microbial RNases

An application of a previously proposed method for the analysisof the non-polar structure of proteins is presented. A detailedanalysis of the composition and properties of non-polar nucleiand microclusters of fungal microbial ribonucleases has beenperformed on the basis of the 3-D structures of RNase T1 andrelated proteins. Three hydrophobic nuclei were found in thesestructures. It has been shown that all residues in non-polarnuclei have high homology ({small tilde}89%). Residues in thenuclei are practically fully buried in the interior of a molecule.Detailed analysis of non-polar nuclei properties shows thatthese nuclei determine the hydrophobic core of a protein andthe location and role of each residue in the non-polar interiorof proteins. In addition it was found that there are variableresidues not only on the surface of a protein but on the surfaceof the nuclei inside the protein and between the nuclei andthat there is a consistent region in all proteins, the hydrophobic-nuclei. An evaluation of the stability of non-polar nuclei,the conservation of their compositions and their positions inthe protein globule, allows one to assume that these three nucleiplay an important functional role in the stability and foldingof molecules of RNases and possibly can be considered as independentstructural elements of 3-D structures of these proteins.     

The surface morphologies of (Pb, Sr) TiO3 thin film fabricated on Si-buffered Pt/Ti/SiO2/Si substrate

(Pb, Sr)TiO3 (PST) thin film are fabricated by RF magnetron sputtering on Si-buffered Pt/Ti/SiO2/Si substrates with different buffer layer deposition time. Surface morphologies of the buffer layer indicate an improving surface roughness and larger grains with the prolongation of sputtering time. Deposition of PST thin films shows excellent surface fluctuation filling ability to improve the surface roughness of substrates. PST surface morphologies exhibit apparently different grain forms according to the preparation time durance of buffer layer.     

固体进样-石墨炉原子吸收法测定沙棘维生素P粉中铅含量

本研究采用直接固体进样-石墨炉原子吸收法（SS-GF AAS）测定沙棘维生素P粉中重金属铅的含量。通过对石墨炉工作程序的优化,同时采用基体改进剂技术,最终得到稳定而准确的结果,其结果与液体进样使用ICP-MS测量结果一致。本方法中RSD 2.29%-11.70%,回收率91.75%-114.05%,检出限0.0075ng。与湿法消解方法相比较,该方法无需样品前处理,具有简便、快速特点,同时可避免样品的稀释以及试剂的交叉污染带来的分析误差。     

基于单点观测的TSP与PM_（10）中铅的特性研究

以西安市东二环互助路立交附近地区为对象,采用连续提取法和原子吸收光谱法研究大气TSP和PM10浓度及铅的化学形态,并进行相关性分析和生物有效性分析.结果表明,观测点处TSP和PM10质量浓度和Pb元素均污染严重.TSP中Pb元素主要存在于碳酸盐结合态中,与扬尘有关;PM10中Pb元素主要分布在可交换态和残渣态中,主要与人类的生产生活及工业生产有关.生物有效性系数显示,Pb元素对人体健康有潜在的威胁,TSP中Pb元素的生物有效性高于PM10,且非采暖期高于采暖期.Pb元素在PM10中较TSP相对富集,且TSP与PM10中Pb元素有可能遵循相同的迁移转化规律并且有相同的来源.     

不同基体改进剂对粉状化妆品中铅含量测定的影响

本文研究了石墨炉原子吸收光谱法测定粉类化妆品中铅含量的方法。重点讨论了不同基体改进剂对样品铅测定结果的影响。结果表明,0．25％瞵酸二氢铵可有效改善和提高粉类化妆品铅含量测定的稳定性和灵敏度,RSD达到1．5％。     

氨基化磁性纳米粒子的制备及其对Pb2+吸附性能研究

采用改进的高温分解法制备单分散Fe3O4纳米粒子,以正硅酸乙酯为硅源在其表面包覆SiO2,以N-氨乙基-γ氨丙基三甲氧基硅烷为改性剂对复合粒子进行表面氨基化修饰,制备出氨基化磁性复合纳米粒子Fe3O4@SiO2—NH2。利用红外光谱(FT-IR)、透射电镜(TEM)、X射线衍射(XRD),振动样品磁强计(VSM)等手段对复合粒子进行了表征,并研究其作为吸附剂在不同条件下对Pb2+的吸附性能。表征结果显示,所制备的复合粒子具有核壳结构,粒径均匀大约在50nm,粒子表面拥有丰富的氨基功能基团;复合粒子饱和磁化强度为69.50A.m2/kg,具有超顺磁性。吸附实验表明所制备的氨基化磁性复合纳米粒子对Pb2+具有较大的吸附容量,是一种能够有效处理含铅废水的吸附材料。     

采用还原焙烧回收烟尘中的锌铅工艺研究

针对生产富锰渣过程中所产生的含锌铅烟尘回收困难的问题,提出还原焙烧挥发回收工艺。以国内三种含锌烟尘为原料,对焙烧温度、焙烧时间以及料层厚度等工艺参数进行了探讨和优化。结果表明：在含锌烟尘：还原煤：石灰=100：50：2．5,温度1200℃下还原焙烧90min后,挥发渣中的锌含量都小于0．5％,铅含量都小于0．1％,而锌和铅的挥发率分别超过97％和98％。实验证明,通过还原焙烧含锌锰烟尘可有效地回收原料中的锌和铅。     

Bioactive compound content,antioxidant activity,deoxynivalenol and heavy metal contamination of pearled wheat fractions

Wheat kernels are rich in antioxidant compounds, that are mainly present in the outer bran layers and which are removed during milling. Unfortunately, several contaminants, e.g., mycotoxins and heavy metals, are also concentrated in the external layers. Pearling of 3 wheat varieties gave five fractions (each 5% of the original grain weight), starting from the outer layer until the inner kernel, designated as 0–5%, 5–10%, 10–15%, 15–20%, 20–25%, respectively. The remaining 75% of the inner kernel was also collected. Dietary fibre, free phenolic acids and total antioxidant activity decreased progressively from the external to the internal layers. However, the 5–10% fraction was richer in β-glucan content than the external one (0–5%). Heavy metals were only found in the most external fraction. Deoxynivalenol contamination decreased from the external to the internal layers: 64% of total contamination of kernel was found in the 0–5% and 5–10% fractions. The 10–15% kernel fraction offered the best compromise between high nutritional value and low contamination risk.