Fluid flow-assisted dielectrophoretic assembly of nanowires

The dielectrophoretic assembly of silicon carbide (SiC) nanowires in a microfluidic flow is shown to enhance the orientation and deposition yield of nanowires. The fluid flow delivers and orients the nanowires in the vicinity of a gap, and they are attracted and deposited by a dielectrophoretic force. Depending upon their lengths, the nanowires are selectively attracted to the gap because the dielectrophoretic force is largest when the lengths are comparable to the gap size. Precise control over the fluid flow and dielectrophoresis shows various interesting phenomena such as landing, shifting, and uniform spacing of nanowires during the assembly process. As a result, the precise control enables the selective positioning of nanowires only at the gap where the fluid direction is consistent with the electric field orientation.     

A biaxial test specimen for crack arrest studies

A biaxially loaded, single edge notched (SEN) fracture specimen, with mixed modes I and II loading, was used to study the crack arrest capability of a bonded and riveted tear strap without and with simulated multiple site damage (MSD). MSD was modeled by a 50-percent groove without which the running crack would inevitably kink due to K_II loading. A total of thirty-one 2024-T3 aluminum specimens with various crack and MSD configurations were tested. The fracture parameters associated with straight and curved crack paths were determined by using the experimenta results to drive a dynamic finite element model of the specimen in its generation mode. The crack kinking and extension criteria were verified by the excellent agreement between the prediction based on these fracture parameters and the measured crack kinking angles. Comparison between the test results generated by the biaxial stress specimens and by those generated by small- and full-scale pressurized fuselage rupture experiments showed that this specimen can be used to prescreen the effectiveness of tear straps and crack arrestors in an airplane fuselage.     

A Thurstonian view of the analytic hierarchy process

The application of deterministic decision models in situations characterized by noise and uncertainty is likely to produce results of questionable value. In this paper, some very simple probabilistic models are developed and substituted for the deterministic scales used in the Analytic Hierarchy Process (AHP). It is shown that the use of these probabilistic models can extend the domain of AHP to situations, such as consensual or group decision making, that possess significant amounts of uncertainty. In addition, explicit measures of the variation present in the evaluation of decision alternatives and attributes are obtained.