A new fabrication method of low stress PECVD SiNx layers for biomedical applications

A new fabrication method to produce low residual stress PECVD SiN_x layers at high deposition rates was developed and their biomedical applications were reported in this paper. This new method employed up to 600 W high power to fabricate low stress SiN_x layers in high frequency (13.56 MHz). By adjusting the composition of reactant gases, the residual stress can be lowered to 4 MPa and high deposition rate up to 320 nm/min can be achieved. In addition, this paper also investigated the influence of other important parameter, such as pressure, power and gases flow rates. Moreover, by using this optimized process, an 11 μm thick low stress SiN_x layer was produced, which will be used to fabricate large window area for cell culture. Finally, a successful cell culture test involving cultivating mouse stem cells onto the porous membrane made of these low stress PECVD SiN_x layers indicated that these layers are biocompatible and are suitable for biomedical applications.     

Heating characteristics of western hemlock (Tsuga heterophylla) in a high frequency field

The research aimed to establish whether dielectric heating of wood at high frequency could be accomplished fast, without excessive temperature fluctuations and no wood degrade. The intention was to develop optimized dielectric heating schedules in order to effectively pasteurize green timbers and logs for export—an eco-friendly substitute to currently used toxic chemical method. Data analysis revealed that the electric field distribution within the specimen was a strong function of its dielectric properties. Specifically, homogeneous moisture contents generated constant electric field values while heterogeneous distributions generated sudden drops and raises of the electric field strength with heating uniformly dispersed due to a fast redistribution from hot to colder areas. Convection losses through air contact may reduce the average heating rate of the timber shell by about 50%.     

A flow‐aligning algorithm for convection‐dominated problems

This paper proposes and studies an algorithm for aligning a triangulation with a given convection field. Approximate solutions of convection‐dominated problems on flow‐aligned meshes typically have sharper internal layers, less over and undershooting and higher accuracy. The algorithm we present can be imported easily into any 2D finite element solver, does not change the number of meshpoints, and can improve solution quality quite dramatically. This improvement in solution quality on the flow‐aligned triangulation is illustrated for both the usual Galerkin method and the streamline‐diffusion method. Copyright © 1999 John Wiley & Sons, Ltd.     

Drying Related Strain Development in Restrained Wood

The objective of this study was to investigate elastic, viscoelastic, mechanosorptive, and plastic strains developed by the drying process in perpendicular-to-grain restrained western hemlock specimens. Drying tests were performed on small, clear wood specimens sawn in such a manner that either the tangential or the radial direction was parallel to their length, where stress driven deformation rates were determined using resistive transducers. Different mechanical restraint schemes were designed by using weights for partly and a load cell for totally restrained specimens. The difference from previous research done in this domain was the restraining technique, which allowed stress to be induced by the drying process, thus, wood was forced to lift the weight as it reached the fiber saturation point. Drying rates were determined gravimetrically on free specimens having similar wood structure. Experiments with free and restrained specimens were carried out simultaneously while drying at 40, 60, and 80°C, down to 17, 12, and 6% target moisture contents. Overall, the magnitude of restrained shrinkage was successfully quantified and separated in free, combined viscoelastic and mechanosorptive and plastic strains. In all these preliminary experiments the dimensional change started at high overall moisture contents, temperature and environmental conditions being key factors. The results can be used to assess the stress indirectly by studying the restrained strain together with moisture content value.     

ActiveSpaces: Exploring dynamic code deployment for extreme scale data processing

Managing the large volumes of data produced by emerging scientific and engineering simulations running on leadership‐class resources has become a critical challenge. The data have to be extracted off the computing nodes and transported to consumer nodes so that it can be processed, analyzed, visualized, archived, and so on. Several recent research efforts have addressed data‐related challenges at different levels. One attractive approach is to offload expensive input/output operations to a smaller set of dedicated computing nodes known as a staging area. However, even using this approach, the data still have to be moved from the staging area to consumer nodes for processing, which continues to be a bottleneck. In this paper, we investigate an alternate approach, namely moving the data‐processing code to the staging area instead of moving the data to the data‐processing code. Specifically, we describe the ActiveSpaces framework, which provides (1) programming support for defining the data‐processing routines to be downloaded to the staging area and (2) runtime mechanisms for transporting codes associated with these routines to the staging area, executing the routines on the nodes that are part of the staging area, and returning the results. We also present an experimental performance evaluation of ActiveSpaces using applications running on the Cray XT5 at Oak Ridge National Laboratory. Finally, we use a coupled fusion application workflow to explore the trade‐offs between transporting data and transporting the code required for data processing during coupling, and we characterize sweet spots for each option. Copyright © 2014 John Wiley & Sons, Ltd.