Ductile/brittle grain-boundary fracture behaviour of L12-type intermetallic compounds

The fracture behaviour of grain boundaries in L1₂-type intermetallic compounds was investigated to explain recent experimental results reported by Takasugiet al. and Inoueet al. Inspection of these results revealed a simple rule; grain boundaries are ductile in Kurnakov compounds having an order-disorder transition below their melting point and a wide solid-solution field. On the other hand, grain boundaries are brittle in Berthollide compounds having no order-disorder transition below their melting point. The ductile grain-boundary behaviour in Kurnakov compounds is considered to be produced by disordered grain boundaries, intrinsically ductile and inherited when formed in disordered states.     

Three-Dimensional Green’s Functions for a Multilayered Half-Space in Displacement Potentials

To advance the mathematical and computational treatments of mixed boundary value problems involving multilayered media, a new derivation of the fundamental Green’s functions for the elastodynamic problem is presented. By virtue of a method of displacement potentials, it is shown that there is an elegant mathematical structure underlying this class of three-dimensional elastodynamic problems which warrant further attention. Constituted by proper algebraic factorizations, a set of generalized transmission-reflection matrices and internal source fields that are free of any numerically unstable exponential terms common in past solution formats are proposed for effective computations of the potential solution. To encompass both elastic and viscoelastic cases, point-load Green’s functions for stresses and displacements are generalized into complex-plane line-integral representations. An accompanying rigorous treatment of the singularity of the fundamental solution for arbitrary source-receiver locations via an asymptotic decomposition of the transmission-reflection matrices is also highlighted.     

Vertical dynamic interactions of poroelastic soils and embedded piles considering the effects of pile-soil radial deformations

The paper presents an analytical solution for the vertical dynamic interaction analysis of a poroelastic soil layer and an embedded pile with the consideration of pile-soil radial deformations. The soil is treated a three-dimensional porous continuum and described by the Boer’s poroelastic model, while the pile is treated as a two-dimensional rod with both radial and vertical deformations of which the equation of motion is derived by the Hamilton’s variational principle. Without the introduction of potential functions, first take the volumetric strain of soil skeleton and pore fluid pressure as intermediate variables to deal with the equations of motion for the soil and then use the separation of variables to solve the equations of motion for the soil and the pile. By imposing the boundary and continuity conditions of the pile-soil system, the dynamic impedance in frequency domain and the velocity response in time domain of the pile top are obtained. The present solution is then verified by comparing with the corresponding finite element model computation results and the existing solutions. The effects of the pile-soil parameters on the dynamic characteristic of the pile-soil system are also analyzed. Some significant conclusions are drawn, which can provide useful reference for related engineering practice.     

Electromigration-Induced Plastic Deformation in Cu Interconnects: Effects on Current Density Exponent, <Emphasis Type="Italic">n</Emphasis>, and Implications for EM Reliability Assessment

While Black’s equation for electromigration (EM) in interconnects with n = 1 is rigorously based on the principles of electrotransport, n > 1 is more commonly observed empirically. This deviation is usually attributed to Joule heating. An alternative explanation is suggested by the recent discovery of EM plasticity. To examine this possibility, we have retested samples that had been previously subjected to a predamaging phase of high temperature and current densities to determine whether the loss of median time to failure (MTF) is retained. We find that the predamaged samples exhibit MTFs that are permanently reduced, which is a characteristic of EM plasticity.     

Parameter optimization in the X-ray fluorescent analysis of coal

A method for express analysis of coal is proposed. In this method, the error in determining the calcium content is minimized by selecting the optimal parameters of the X-ray fluorescent method.     

Effect of different chemical treatments of surface on the height of Al-<Emphasis Type="Italic">p</Emphasis>-SiGe and Au-<Emphasis Type="Italic">n</Emphasis>-SiGe barriers

The effect of different chemical treatments on the properties of Au-n-SiGe and Al-p-SiGe Schottky barriers has been investigated. Etching under different conditions was used to prepare surfaces with different densities of surface states (D _ss). It is shown that the barrier height in the structures under study correlates with the D _ss value and germanium content in the Si_{1 − x} Ge _x alloy.     

Online Signal Injection Through a Bus-Referenced Current Transformer

An online signal injection approach based on a special current transformer is proposed as part of a solution for improving the test setup of transfer function diagnostics of transformers. However, the method is general and applicable to many types of substation equipment, such as circuit breakers and transmission lines. The system allows a high-power, high-frequency test signal to be injected directly on a high-voltage bus of an energized system. Due to the self-contained nature of the injector, no external power supplies or signal generators are needed and the design does not need to be ground-referenced. The system can thus be at the bus potential. In conjunction with wireless communication for control, no isolator bushings are required and the device can be constructed as a sleeve to be mounted around the busbar. This allows for economical retrofitting to existing installations. In this paper, the operational need for such an injection device is discussed, followed by the theory behind the proposed concept. Finally, a low-voltage, optically controlled, self-powered prototype is designed and demonstrated online to show the practical validity of the concept.