Development of a double-tee flange connection using shape memory alloy rods

This study investigated the out-of-plane shear performance of a newly developed shape memory alloy (SMA) connector and a commonly used shear/alignment connector. The innovation lies in developing a durable and easily installed and maintained flange-to-flange connector between precast concrete double-tee members. The proposed connector consists of a superelastic SMA curved bolt inserted into a duct that is then cast into the precast concrete member. Two types of sealant materials were used: polyurethane elastomeric sealant and nonshrink cementitious grout. The shear/alignment and SMA connectors were tested under monotonic vertical shear. The tests were conducted on 4 ft × 4 ft × 4 in. (1.2 m × 1.2 m × 100 mm) slab specimens. The resulting capacities and associated damage were summarized. Higher stiffness and lower ductility were observed for the SMA connector with nonshrink grout compared with the shear/alignment connector with polyurethane elastomeric sealant. The average stiffnesses of the SMA and shear/alignment connector specimens were 116,681 lb/in. (20,434 kN/m) and 31,300 lb/in. (5481 kN/m), respectively. The ductility of the SMA connector was improved when using polyurethane elastomeric sealant; however, more tests should be done to confirm this behavior. The SMA rod was reused in several tests through reheating of the SMA element. The shear/alignment connector cannot be reused.

Evolution of Oceanic Near-Surface Stratification in Response to an Autumn Storm

Understanding the processes that control the evolution of the ocean surface boundary layer (OSBL) is a prerequisite for obtaining accurate simulations of air–sea fluxes of heat and trace gases. Observations of the rate of dissipation of turbulent kinetic energy (ε), temperature, salinity, current structure, and wave field over a period of 9.5 days in the northeast Atlantic during the Ocean Surface Mixing, Ocean Submesoscale Interaction Study (OSMOSIS) are presented. The focus of this study is a storm that passed over the observational area during this period. The profiles of ε in the OSBL are consistent with profiles from large-eddy simulation (LES) of Langmuir turbulence. In the transition layer (TL), at the base of the OSBL, ε was found to vary periodically at the local inertial frequency. A simple bulk model of the OSBL and a parameterization of shear driven turbulence in the TL are developed. The parameterization of ε is based on assumptions about the momentum balance of the OSBL and shear across the TL. The predicted rate of deepening, heat budget, and the inertial currents in the OSBL were in good agreement with the observations, as is the agreement between the observed value of ε and that predicted using the parameterization. A previous study reported spikes of elevated dissipation related to enhanced wind shear alignment at the base of the OSBL after this storm. The spikes in dissipation are not predicted by this new parameterization, implying that they are not an important source of dissipation during the storm.

Shear-solvo defect annihilation of diblock copolymer thin films over a large area

Achieving defect-free block copolymer (BCP) nanopatterns with a long-ranged orientation over a large area remains a persistent challenge, impeding the successful and widespread application of BCP self-assembly. Here, we demonstrate a new experimental strategy for defect annihilation while conserving structural order and enhancing uniformity of nanopatterns. Sequential shear alignment and solvent vapor annealing generate perfectly aligned nanopatterns with a low defect density over centimeter-scale areas, outperforming previous single or sequential combinations of annealing. The enhanced order quality and pattern uniformity were characterized in unprecedented detail via scattering analysis and incorporating new mathematical indices using elaborate image processing algorithms. In addition, using an advanced sampling method combined with a coarse-grained molecular simulation, we found that domain swelling is the driving force for enhanced defect annihilation. The superior quality of large-scale nanopatterns was further confirmed with diffraction and optical properties after metallized patterns, suggesting strong potential for application in optoelectrical devices.

Fabrication and 3D tomographic characterization of nanowire arrays and meshes with tunable dimensions from shear-aligned block copolymers

We demonstrate a scalable method to create metallic nanowire arrays and meshes over square-centimeter-areas with tunable sub-100 nm dimensions and geometries using the shear alignment of block copolymers.

Shear alignment and 2D charge transport of tilted smectic liquid crystalline phases – XRD and FET studies

In the tilted smectic phases of terthiophenes, shear alignment macroscopically aligns the tilt direction of the director leading to a substantial in-plane anisotropy of charge carrier mobility in organic field effect transistor (OFET) experiments.