Zr过渡层对Al膜微结构与性能的影响

为了增加高频声表面波器件用Al薄膜的功率承受力以及与基体的附着力，同时不增加薄膜在化学反应刻蚀中的难度。并精确地控制图形的尺寸。采用电子束蒸镀法研究了Zr过渡层和薄膜固化工艺对Al膜微结构、形貌、电性能及机械性能的影响。结果表明。适当厚度(5-30nm)的Zr过渡层增强了Al膜的(111)织构，增加了薄膜与LiNbO3基体的结合力，200℃固化后电阻率明显降低．拥有Zr过渡层的Al膜具有良好的工艺性能，通过反应离子刻蚀易获得精确的换能器图形．     

Vortex Motion and Quasiparticle Resistivity in MgB<Subscript>2</Subscript> at Microwave Frequencies

The electrical transport in superconductors at nonzero frequencies is affected by the normal and superfiuid fractions, as well as moving vortices, resulting in intricate expressions for the complex resistivity. In MgB₂, additional complications arise from the two-band nature of this material. We present an accurate study of microwave resistivity data measured in MgB₂ thin films by means of the Corbino disk broadband technique between 2 and 20 GHz. We show that a two-fluid model applies well in a relatively large region of the H–T phase diagram. Excellent agreement is found between the derived superfluid parameters (superfluid density, upper critical field) and theoretical predictions. In the same H–T region we isolate and discuss the vortex motion complex resistivity. To this end, we make use of the expressions given by the model by Coffey and Clem (CC). We show that the frequency dependence of the complex vortex resistivity recovers the CC model. However, the temperature and field dependence of the obtained parameters are at odds with the assumptions of the model. We discuss possible explanations of these oddities by considering collective pinning of vortices.     

Geophysical investigations of the Wairakei Field

Geophysical studies of the Wairakei sector of the Wairakei–Tauhara geothermal system started shortly after exploration drilling began in the early 1950s. These investigations have made a major contribution in defining the boundary of geothermal systems and understanding the changes that have occurred in the reservoir as a result of fluid production. The most successful tools have been electrical resistivity methods for delineating the field, while microgravity, heat loss and groundwater level monitoring surveys were useful to interpret production-induced changes. Seismic, gravity and magnetic surveys had only limited success.     

Three-dimensional electrical resistivity imaging of a gold heap

A case study is presented for an electrical resistivity geophysical survey, conducted on a gold leach pad of low-grade ore. The electrical resistivity method maps the spatial distribution of electrical resistivity, which is an intrinsic property of material that measures the resistance of electrical current flow through a medium. The property is influenced by moisture content, ionic strength of the porewater, and mineralization. The geophysical method was applied to the leach pad to discern patterns of high and low moisture from past infiltration into the heap. A total of 12 survey lines were run in parallel over an 8 ha portion of the pad. The results showed that the high electrical resistivity areas, which are likely related to low moisture, could be explained by the physics of unsaturated fluid flow or evapotranspiration. The low electrical resistivity areas were thought to be related to high moisture from preferential flow along highly permeable regions of the heap. Validation of electrical resistivity was accomplished by correlating co-located geophysical data and rock samples of moisture content and total gold concentration. On an individual point-by-point basis, the correlation between the two datasets was low, due to the mismatch in measurement scales of the two characterization methods. Averaged resistivity data within discrete bins of the independent variable (rock sample), however, produced high correlations and empirical models were developed from a linear regression of averaged behavior.     

Critical chloride content for reinforced concrete and its relationship to concrete resistivity

The critical chloride content for initiation of reinforcement corrosion is an essential element in service life design and modelling of concrete structures. The critical content is laden with questions regarding its definition, experimental assessment and practical aspects. It should be addressed by a statistical approach. The paper discusses such issues, presents experimental evidence and considers its relationship to the electrical resistivity of concrete. A low concrete resistivity can be theoretically argued to relate to a low critical chloride content. However, only part of the experimental data supports this. The resolution of available data does not allow distinction with regard to the critical content between cement types.     

Theoretical Issues in the Calculation of the Electrical Resistivity of Plasmas

We recall briefly how the Ziman theory of electrical conductivity, first proposed for solids and liquid metals, has been extended to the case of plasmas. The physical assumptions and parameters entering the formula are analyzed. A self-consistent model of electronic and ionic structure of plasmas is then described and applied to the calculation of the resistivity. Results obtained for aluminum are shown and compared to measurements done by Benage, along a thermo-dynamic path going from normal density at melting to 0.03 compression at 41 eV. The important differences between theory and experiment are discussed. The uncertainties inherent to the theory are emphasized, and physical effects not taken into account in the theory are discussed. Finally, the need for accurate measurements is emphasized.     

汽轮机转子钢时效老化作用研究

对30Cr1Mo1V汽轮机转子钢在630℃温度下，进行0h到1200h时间段内的时效老化试验，利用QJ57电阻电桥、维氏硬度计及光学显微镜对时效过程中电阻率、维氏硬度及组织变化规律进行了研究。     

数字相敏检波在随钻电阻率测井仪中的应用

本文设计了一种基于高性能DSP和FPGA控制的数字相敏检波系统。系统讨论了传统模拟相敏检波和新型数字相敏检波的原理特点、电路实现及实验数据分析。实验证明,该检波方法能有效利用测井信息,优化系统,为我国随钻测井仪器的研究提供新的方法和途径。     

Ti-doped copper nitride films deposited by cylindrical magnetron sputtering

Pure and Ti-doped copper nitride films were prepared by cylindrical magnetron sputtering on glass substrates at room temperature. The preferred orientation for copper nitride films changes from [1 1 1] for undoped film to [1 0 0] for Ti-doped films. The variation of surface morphology correlates to that of preferred orientation resulting from the variation of Ti-doped content. The electrical resistivity and optical band gap increases as the Ti-doped content increases.     

A practical method for calculating the corrosion rate of uniformly depassivated reinforcing bars in concrete

The quantification of active corrosion rate of steel in concrete structures through nondestructive methods is a crucial task for scheduling maintenance/repair operations and for achieving accurate service life predictions. Measuring the polarization resistance of corroding systems and using the Stern‐Geary equation to calculate the corrosion current density of active steel is a widely‐used method for this purpose. However, these measurements are greatly influenced by environmental factors; therefore, accurate monitoring of corrosion requires integrating the instantaneous corrosion rates over time. Although advanced numerical models are helpful in research settings, they remain to be computationally expensive and complex to be adopted by general engineering community. In this paper, a practical numerical model for predicting corrosion rate of uniformly depassivated steel in concrete is developed. The model is built on Stern's earlier work that an optimum anode‐to‐cathode ratio exists for which the corrosion current on the metal surface reaches a maximum value. The developed model, which represents the corrosion rate as a function of concrete resistivity and oxygen concentration, is validated using experimental data obtained from the literature.