This letter describes the use of microlens projection photolithography (μLPL) for the fabrication of repetitive metallic micropatterns, and the application of these patterns as frequency-selective surfaces. Microlens projection photolithography uses an array of microlenses (diameter d=1–1000 micrometers) to project an array of images of an illuminated mask into photoresist. We converted these arrays into patterns in metals by electron beam evaporation and lift off. This technique can produce arrays over areas >10 cm2 with submicrometer feature sizes in a single exposure. We fabricated arrays of metallic micropatterns on substrates transparent to infrared radiation, and demonstrated that appropriate patterns acted as frequency-selective filters.
No abstract is provided for this article.
Indentation tests at scales on the order of one micron have shown that measured hardness increases significantly with decreasing indent size, a trend at odds with the size-independence implied by conventional plasticity theory. In this paper, strain gradient plasticity theory is used to model materials undergoing small-scale indentations. Finite element implementation of the theory as it pertains to indentation modeling is briefly reviewed. Results are presented for frictionless conical indentations. A strong effect of including strain gradients in the constitutive description is found with hardness increasing by a factor of two or more over the relevant range of behavior. The results are used to investigate the role of the two primary constitutive length parameters in the strain gradient theory. The study indicates that indentation may be the most effective test for measuring one of the length parameters.
No abstract is provided for this article.
This study was registered at controlled-trials.com (http://www.controlled-trials.com/ISRCTN35739639). International Standard Randomized Controlled Trial Number (ISRCTN): 35739639. Registration date: 5 October 2005.
Recent, detailed examinations of fault zones show that walls of faults are often bordered by materials that are different from each other and from the more uniform material farther away. In addition, they show that the ultracataclastic core of mature fault zones, where slip is concentrated, is less permeable to flow across it than the adjoining material of the damage zone. Inhomogeneous slip at the interface between materials with different poroelastic properties and permeabilities causes a change in pore pressure there. Because slip causes compression on one side of the fault wall and extension on the other, the pore pressure on the fault increases substantially when the compressed side is significantly more permeable and decreases when, instead, the extended side is more permeable. This change in pore pressure alters the effective normal stress on the slip plane in a way that is analogous to the normal stress alteration in sliding between elastically dissimilar solids. The magnitude of the effect due to induced pore pressure can be comparable to or larger than that induced by sliding between elastic solids with a dissimilarity of properties consistent with seismic observations. The induced pore pressure effect is increased by increasing contrast in permeability, but the normal stress alteration due to elastic contrast increases rapidly as the rupture velocity approaches the generalized Rayleigh velocity. Because the alteration in effective normal stress due to either effect can be positive or negative, depending on the contrast in properties, the two effects can augment or offset each other.
Abstract : Model 5365 is a 1/8.25th scale representation of the R/V Athena. This report documents both a new set of resistance, sinkage and trim, and longitudinal wave cut experiments as well as historical calm water resistance and sinkage and trim data which have been obtained on this model over the past few decades. The new resistance data were obtained in October and November of 2006 on Carriage 2 at the Naval Surface Warfare Center, Carderock, Division. In these experiments drag force was measured using both 6-component Kistler gages and a traditional block gage at the tow post location, as well as a Kistler gage located at the grasshopper bracket model attachment point. An in-situ calibration was also performed in order to verify loads at the tow post and grasshopper bracket location when a known load was applied to the system. Video and still digital cameras were also used to qualitatively characterize the wave field during the runs.
