不同方法对青海粮食产需水平的预测分析

本文运用灰色预测系统，三次指数平滑法和多元回归法，对在正常年景下２０００年，２００５年和２０１０年青海粮食产需水平进行预测，并对结果作出分析讨论。     

HDDR法制备高矫顽力NdFeB粘结磁体途径

通过HDDR法制备出内禀矫顽力达到15KOe的NdFeB各向同性粘结磁体，探讨了温度、时间、抽速等工艺参数时获取高矫顽力的作用，并对原始晶粒尺寸的影响作了初步研究。     

粮食中磺酰脲类除草剂的UPLC/MS/MS测定方法

建立了多类粮食作物中15种磺酰脲类除草剂的超高效液相色谱-串联质谱联用仪(UPLC/MS/MS)多离子监测(MRM)的多残留检测方法。样品经乙腈提取,乙腈饱和的正己烷液-液分配,石墨化碳氨基小柱净化,采用UPLC-MS/MS(ESI+)测定。方法中各种磺酰脲类除草剂在5～200μg/L浓度范围内线性良好,相关系数在0.9995～0.9999。在5～100μg/kg范围内,平均加标回收率在71.6%～115.3%之间,相对标准偏差不大于15%。各种药物的定量限(S/N≥10)均可达到5μg/kg。该方法可同时满足大豆、大米、玉米等多种粮食中磺酰脲类除草剂的检测需求。     

Ce0.8Nd0.2O1.9-La0.95Sr0.05Ga0.9Mg0.1O3-δ固体复合电解质的结构和电性能

采用溶胶-凝胶法分别制备La_0.95Sr_0.05Ga_0.9Mg_0.1O_3-δ (LSGM)和Ce_0.8Nd_0.2O_1.9 (NDC)电解质,并在NDC溶胶中加入0-15% (w,质量分数)的LSGM预烧粉体制得NDC-LSGM复合电解质,研究不同质量比复合电解质的结构和电性能. 采用X射线衍射(XRD)、场发射扫描电子显微镜(FE-SEM)和X能量色散谱仪(EDS)对样品进行结构表征,交流(AC)阻抗谱测试样品导电性能. 结果表明：NDC-LSGM复合体系主要由立方萤石结构相、钙钛矿结构相和杂质相组成;LSGM的添加可促进晶粒的生长,产生大量相界面,清除或降低SiO₂有害影响,明显提高晶界导电性;LSGM质量分数为10%的样品NL10 具有最高晶界电导率和总电导率,400 ℃时NL10 的晶界电导率σ_gb和总电导率σ_t分别为12.15×10^-4和3.49×10^-4 S·cm^-1,与NDC的σ_gb (1.41×10^-4 S·cm^-1)和σ_t (1.20×10^-4 S·cm^-1)相比分别提高了7.62和1.91倍,总电导率的提高主要归因于晶界电导率的影响.     

Sm, Pr掺杂CeO2和CeMoO15基固体电解质的结构与性能

采用溶胶凝胶法制备了Sm和Pr掺杂的CeO2和CeMoO15基固体电解质, 通过X射线衍射(XRD)、拉曼光谱(Raman)、场发射扫描电镜(FE-SEM)等手段对氧化物结构进行了分析, 用交流阻抗谱测试了其电性能, 并比较了不同基体及其掺杂体系的结构与电性能. 结果表明, Ce6MoO15基掺杂体系的导电性能高于CeO2基掺杂体系; 元素Mo的加入使Ce6MoO15基材料的晶粒尺寸增大, 晶界相成分减少, 材料的晶界电导率增加, 600 ℃以下材料导电性能明显提高; Pr的掺入减小了材料的晶粒尺寸, 提高了材料的晶界电导率.     

Atomistic simulations of elastic deformation and dislocation nucleation during nanoindentation

Nanoindentation experiments have shown that microstructural inhomogeneities across the surface of gold thin films lead to position-dependent nanoindentation behavior [Phys. Rev. B (2002), to be submitted]. The rationale for such behavior was based on the availability of dislocation sources at the grain boundary for initiating plasticity. In order to verify or refute this theory, a computational approach has been pursued. Here, a simulation study of the initial stages of indentation using the embedded atom method (EAM) is presented. First, the principles of the EAM are given, and a comparison is made between atomistic simulations and continuum models for elastic deformation. Then, the mechanism of dislocation nucleation in single crystalline gold is analyzed, and the effects of elastic anisotropy are considered. Finally, a systematic study of the indentation response in the proximity of a high angle, high sigma (low symmetry) grain boundary is presented; indentation behavior is simulated for varying indenter positions relative to the boundary. The results indicate that high angle grain boundaries are a ready source of dislocations in indentation-induced deformation.     

Pressure effect on grain boundary wetting at various temperatures

Bicrystals of Fe-6 at.% Si alloy containing <001> 5 tilt grain boundaries with a deposited zinc layer have been annealed at various hydrostatic pressure at four temperatures between 700° and 905°C. After the anneals the dihedral angle of the grain boundary groove formed at the site of the grain boundary intersection with the solid-melt interphase boundary has been measured. The transition from complete to incomplete wetting of the grain boundary by the zinc-rich melt (dewetting phase transition) has been found to occur as the pressure increased at all temperatures studied. The temperature dependence of the dewetting transition pressure p _w has been determined. That dependence has a minimum at a temperature of 790°C, which is close to the peritectic temperature in the Fe–Zn system (782°C). A thermodynamic analysis of the wetting phenomena in the two-component system, based on Becker's regular solution model for the surface tension of the interphase boundary, explains the minimum in the p _w (T) dependence.     

含He纳米钛膜的XRD研究

本文采用直流磁控溅射方法,在He／Ar混合气氛中,通过分别改变He／Ar流量比和沉积偏压制备不同He含量的钛膜。利用XRD(X-ray diffraction)对含He钛膜的微观结构和晶粒尺寸进行了研究。结果表明,在其它实验参数不变的情况下,当He／Ar流量比从1.0增加到25时,钛膜的平均晶粒尺寸从19.02nm减小到8.63nm。随着膜中He含量的增加,衍射峰宽化,晶粒细化,He的掺入有抑制纳米晶粒长大的趋势。而当沉积偏压从24V增加到151V时,其平均晶粒尺寸基本不变。He引入引起了（002）晶面衍射峰向小角度移动,晶格参数c增加,而a不变。     

复层籽晶制备单晶畴YBCO超导块材

本文介绍了沿c轴方向排布复层籽晶制备YBCO超导单畴的方法.该方法能够使123晶畴在不同深度进行生长.通过c轴方向籽晶的排布,研究了YBCO单畴中的(001)/(001)晶界.虽然由于压模中籽晶ab面的倾斜,造成部分(001)/(001)晶界出现大角晶界,使晶界上残余有液相,但仍有晶界连接良好、晶界上不存在残余液相和211粒子、错配角小于5°的(001)/(001)晶界的形成.对于制备有深度要求的单畴块材,复层籽晶法是一种有效的生长方法.在定向控制好籽晶方向的条件下,该方法可以提高超导单畴的生长深度.在77K,0.5T下,测试该样品磁悬浮力达到37N.     

Two types of diffusions at the cathode/electrolyte interface in IT-SOFCs

Analytical transmission electron microscopy, in particular with the combination of energy dispersive X-ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS), has been performed to investigate the microstructure and microchemistry of the interfacial region between the cathode (La_0.6Sr_0.4Co_0.8Fe_0.2O₃, LSCF) and the electrolyte (Gd-doped ceria, GDC). Two types of diffusions, mutual diffusion between cathode and electrolyte as well as the diffusion along grain boundaries, have been clarified. These diffusions suggest that the chemical stability of LSCF and GDC are not as good as previously reported. The results are more noteworthy if we take into consideration the fact that such interdiffusions occur even during the sintering process of cell preparation.