反应堆A0纯铝的点蚀模拟

测量A0纯铝在去离子水中的极化曲线用来模拟反应堆池壳的点蚀.研究表明A0纯铝在去离子水中很容易钝化.实验中用美国EG&G普林斯顿应用研究公司生产的273型恒电位/恒电流仪测量模拟孔电位,极化曲线表明模拟腐蚀坑处于钝化状态,即便是氧化膜破裂,腐蚀坑也发展得很慢.用pH计测量孔中pH的变化,并得到其工作曲线,此曲线表明带有氧化膜的点蚀坑坑内存在明显的酸化现象.并对A0铝池壳的服务寿命进行了估计.     

Electrochemical pitting behaviour of type 321 stainless steel in sulfide-containing chloride solutions

The pitting behaviour of type 321 stainless steel in sulfide-containing chloride aqueous environments was studied using cyclic potentiodynamic polarization. A well-established correlation between H₂S and Na₂S₂O₃ in the study of corrosion was applied, that is, H₂S was simulated by Na₂S₂O₃. The major factors affecting the pitting corrosion of type 321 stainless steel are the Cl^- concentration, solution pH and temperature. The results clearly indicate that both E_pit and E _pp decrease with increasing Cl^- concentration and temperature, while I _pass is more sensitive to temperature variation. E _pit decreased with decreasing pH in the range 2 < pH < 7.5. The surface morphology and chemistry of the corroded type 321 stainless steel resulting from anodic polarization in 0.01 M S₂O ₃ ^2- -containing Cl^- solution were analysed by XRD, SEM and EPMA. A higher concentration of sulfur was found in the pits, and the dark surface film was mainly composed of FeS and -Fe₂O₃. The results describe the pitting behaviour of type 321 stainless steel in sulfide-containing Cl^- aqueous environments.     

Pervaporation performance analysis and prediction—using a hybrid solution-diffusion and pore-flow model

A hybrid mathematic model for pervaporation is proposed which incorporates the concepts of solution-diffusion model and pore model. The model allows performance prediction as well as the establishment of the internal concentration and pressure profiles within the membrane. The model parameters specific to the particular membrane and mixture system are determined using liquid sorption and pervaporation experimental data. The model is experimentally examined using ethanol–water mixtures and poly(dimethyl siloxane)–poly(vinyldiene fluoride) (PDMS–PVDF) composite membranes. The characteristics of flux and separation factor predicted using the model are in fair agreement with the experimental data under various feed concentrations and downstream pressures for different membrane arrangements, including single-layer, reverse single-layer and double-layer PDMS–PVDF composite membranes. Internal profiles of pressure, concentration and component mole fraction can be established using the model. Concentration polarization phenomena for ethanol and water are located at membrane interfaces and vapor–liquid interfaces, respectively. Performances of several different membrane designs are compared using the model.     

金属－PTC陶瓷复合材料研究

研究低Ｔ＿ｃＰＴＣＲ复合材料的制备工艺，测试所制成样品的阻温特性。通过样品Ｘ射线定性相分析，探讨该复合材料所表现的ＮＴＣ阻温特性机理。     

高水头船闸一字闸门水动力特性数值模拟

针对某山区高水头船闸30 m淹没水深下一字闸门的水动力特性进行研究,借助FLUENT软件提供的Realizable k-ε紊流模型对门体启闭过程非恒定流场进行动态模拟,通过建立由二维平面混合网格纵向拉伸成的三维棱柱体网格,结合2.5D重构和弹性光顺动网格法,在降低网格数量、提高计算效率的同时,实现一字闸门启闭全过程三维流场模拟。引入VOF法对自由水面迭代求解,得到一字闸门启闭过程门前后水位差及动水阻力矩变化规律,将计算结果与模型试验进行比较,两者吻合较好。模拟计算发现:门底间隙对闸门运行整个阶段动水阻力矩均有影响,动水阻力矩峰值随门底间隙增大而变小。     

Kinetics of hydrogen evolution on submicron size Co, Ni, Pd and Co–Ni alloy powder electrodes by d.c. polarization and a.c. impedance studies

Submicron size Co, Ni and Co–Ni alloy powders have been synthesized by the polyol method using the corresponding metal malonates and Pd powder by reduction of PdO _x in methanol. The kinetics of the hydrogen evolution reaction (HER) in 6 M KOH electrolyte have been studied on electrodes made from the pressed powders. The d.c. polarization measurements have resulted in a value close to 120 mV decade^–1 for the Tafel slope, suggesting that the HER follows the Volmer–Heyrovsky mechanism. The values of exchange current density (i _o) are in the range 1–10 mA cm^–2 for electrodes fabricated in the study. The a.c. impedance spectra measured at several potentials in the HER region showed a single semicircle in the Nyquist plots. Exchange current density (i _o) and energy transfer coefficient () have been calculated by employing a nonlinear least square-fitting program.     

Self‐regulation during e‐learning: using behavioural evidence from navigation log files

The current paper examined the relationship between perceived characteristics of the learning environment in an e‐module in relation to test performance among a group of e‐learners. Using structural equation modelling, the relationship between these variables is further explored in terms of the proposed double mediation as outlined by Ning and Downing. These authors initially proposed that motivation and self‐regulation strategies are mediators between the perception of the learning environment and performance. In our replication and extension study, we substituted self‐reported self‐regulation with behavioural indicators of self‐regulation using navigation log files and focused on test‐taking rather than general motivation. We proposed that navigational patterns captured using log files can also help deduce self‐regulation in e‐modules and provide information in the absence of self‐reports. Path analyses provide partial support for our navigational hypotheses and the model. Implications of our results for the use of e‐module data and conclusions based on navigation are discussed.     

无铅阴极的相变致电子发射研究

研究了最新无铅阴极钛酸铋钠(Na1 2Bi1.2TiO3，NBT)基铁电陶瓷的电子发射性能和电子发射的机理。采用常规陶瓷工艺制备了发射阴极样品，并在阴极上施加高达15kV的激励脉冲，获得了20A／cm^2的最大发射电流密度。在施加激励电压的同时观察到3个发射电流脉冲峰值，该现象不同于其他的阴极。通过测试NBT基铁电陶瓷的相变性能，修正了得到公认的快极化反转致电子发射理论，提出相变致电子发射理论公式，合理解释了该新型无铅NBT基阴极的电子发射3个峰现象，说明了电子发射不仅可以由快极化反转产生，也可以由相变导致的极化变化产生。     

Admittance—Frequency Response in Zinc Oxide Varistor Ceramics

The lumped parameter/complex plane analysis technique revealed several contributions to the terminal admittance of the ZnO—Bi₂O₃ based varistor grain-boundary ac response. The terminal capacitance has been elucidated via the multiple trapping phenomena, a barrier layer polarization, and a resonance effect in the frequency range 10⁻²≤ f ≤ 10⁹ Hz. The characterization of the trapping relaxation behavior near ∼ 10⁵ Hz (∼ 10⁻⁶ s) provided a better understanding of a previously reported loss-peak. The possible nonuniformity in this trapping activity associated with its conductance term observed via the depression angle of a semicircular relaxation in the complex capacitance ( C *) plane has been postulated.     

基于单轴速率转台的角速度传感器标定方法

针对传统的标定方法标定成本高且对北向基准的要求严格等问题,提出了一种用单轴速率转台作为标定设备的光纤陀螺捷联航姿系统标定方法。对光纤陀螺组合的误差进行建模,将光纤陀螺捷联航姿系统安装于单轴速率转台上,使光纤陀螺捷联航姿系统的3个陀螺轴向分别朝下进行标定实验,由此标定出3只光纤陀螺的零偏、标度因数和安装失准角共12个误差参数。通过对标定精度进行分析,验证了该方法的可行性,其标定成本低且不需要北向基准,具有一定的工程应用价值。