Something Old,Something New: Integrating Engineering Practice into the Teaching of Engineering Mechanics

This paper presents a multifaceted method for teaching engineering mechanics designed to satisfy the following set of desiderata: (1) integrate engineering practice into the teaching of engineering science; (2) address a wide set of learning styles; (3) provide opportunities for practice in group work and learning; (4) promote communication and synthesizing skills; (5) engage students in the teaching and learning process; (6) maintain traditional achievement levels with respect to traditional measures; (7) motivate students to continue their engineering studies; and (8) maintain reasonable resource demands. Consistent with this variety of objectives, the approach presented here is composed of a variety of ingredients. In addition to the standard homework problems and exams, these ingredients include design projects, group work, basic competency exams, computational environments for simulating and visualizing phenomena, multimedia instructional tools, hands-on experiences, and student presentations. This educational model is intended to be suitable for teaching engineering mechanics in general, but this paper focuses on a particular sophomore-level mechanics of materials course in which the method has been implemented, refined over several years of classroom use, and tested relative to traditional approaches. The paper describes the and techniques that together make up the method, followed by summaries of the results of evaluations that have been applied to the course.     

Monitoring children’s developmental progress using augmented toys and activity recognition

Previous research has established the connection between the way in which children interact with objects and the potential early identification of children with autism. Those findings motivate our own work to develop "smart toys," objects embedded with wireless sensors that are safe and enjoyable for very small children, that allow detailed interaction data to be easily recorded. These sensor-enabled toys provide opportunities for autism research by reducing the effort required to collect and analyze a child’s interactions with objects. In the future, such toys may be a useful part of clinical and in-home assessment tools. In this paper, we discuss the design of a collection of smart toys that can be used to automatically characterize the way in which a child is playing. We use statistical models to provide objective, quantitative measures of object play interactions. We also developed a tool to view rich forms of annotated play data for later analysis. We report the results of recognition experiments on more than fifty play sessions conducted with adults and children as well as discuss the opportunities for using this approach to support video annotation and other applications.     

Subcellular Localisation of a Quinoline-Containing Fluorescent Cyclometallated IrIII Complex in Plasmodium falciparum

A fluorescent analogue of a previously synthesised N,N-chelated Ir^III complex was prepared by coordination of the organic ligand to an extrinsic bis(2-phenylpyridine)iridium(III) fluorophore. This cyclometallated Ir^III complex in itself displays good, micromolar activity against the chloroquine-sensitive NF54 strain of Plasmodium falciparum. Live-cell confocal microscopy found negligible localisation of the fluorescent complex within the digestive vacuole of the parasite. This eliminated the haem detoxification pathway as a potential mechanism of action. Similarly, no localisation of the complex within the parasitic nucleus was found, thus suggesting that this complex probably does not interfere with the DNA replication process. A substantial saturation of fluorescence from the complex was found near phospholipid structures such as the plasma and nuclear membranes but not in neutral lipid bodies. This indicates that an association with these membranes, or organelles such as the endoplasmic reticulum or branched mitochondrion, could be essential to the efficacies of these types of antimalarial compounds.     

Processing,microstructure, and mechanical properties of hot-pressed ZrB2 ceramics with a complex Zr/Si/O-based additive

Densification behavior, microstructure, and mechanical properties of zirconium diboride (ZrB₂) ceramics modified with a complex Zr/Si/O-based additive were studied. ZrB₂ ceramics with 5–20 vol.% additions of Zr/Si/O-based additive were densified to >95% relative density at temperatures as low as 1400°C by hot-pressing. Improved densification behavior of ZrB₂ was observed with increasing additive content. The most effective additive amount for densification was 20 vol.%, hot-pressed at 1400°C (∼98% relative density). Microstructural analysis revealed up to 7 vol.% of residual second phases in the final ceramics. Improved densification behavior was attributed to ductility of the silicide phase, liquid phase formation at the hot-pressing temperatures, silicon wetting of ZrB₂ particles, and reactions of surface oxides. Room temperature strength ranged from 390 to 750 MPa and elastic modulus ranged from 440 to 490 GPa. Vickers hardness ranged from 15 to 16 GPa, and indentation fracture toughness was between 4.0 and 4.3 MPa·m^1/2. The most effective additive amount was 7.5 vol.%, which resulted in high relative density after hot-pressing at 1600°C and the best combination of mechanical properties.     

The distribution of grain boundary planes in polycrystals

During the last ten years, techniques have been developed to measure the distribution of grain boundaries in polycrystals as a function of both lattice misorientation and grain boundary plane orientation. This paper presents a brief overview of the techniques used for these measurements and the principle findings of studies implementing these techniques. The most significant findings are that grain boundary plane distributions are anisotropic, that they are scale invariant during normal grain growth, that the most common grain boundary planes are those with low surface energies, that the grain boundary populations are inversely correlated with the grain boundary energy, and that the coincident site lattice number is a poor predictor of the grain boundary energy and population.     

In-Plane Cracking Behavior and Ultimate Strength for 2D Woven and Braided Melt-Infiltrated SiC/SiC Composites Tensile Loaded in Off-Axis Fiber Directions

The tensile mechanical properties of ceramic matrix composites (CMC) in directions off the primary axes of the reinforcing fibers are important for the architectural design of CMC components that are subjected to multiaxial stress states. In this study, two-dimensional (2D)-woven melt-infiltrated (MI) SiC/SiC composite panels with balanced fiber content in the 0° and 90° directions were tensile loaded in-plane in the 0° direction and at 45° to this direction. In addition, a 2D triaxially braided MI SiC/SiC composite panel with a higher fiber content in the ±67° bias directions compared with the axial direction was tensile loaded perpendicular to the axial direction tows (i.e., 23° from the bias fibers). Stress–strain behavior, acoustic emission, and optical microscopy were used to quantify stress-dependent matrix cracking and ultimate strength in the panels. It was observed that both off-axis-loaded panels displayed higher composite onset stresses for through-thickness matrix cracking than the 2D-woven 0/90 panels loaded in the primary 0° direction. These improvements for off-axis cracking strength can in part be attributed to higher effective fiber fractions in the loading direction, which in turn reduces internal stresses on weak regions in the architecture, e.g., minicomposite tows oriented normal to the loading direction and/or critical flaws in the matrix for a given composite stress. Both off-axis-oriented panels also showed relatively good ultimate tensile strength when compared with other off-axis-oriented composites in the literature, both on an absolute strength basis as well as when normalized by the average fiber strength within the composites. Initial implications are discussed for constituent and architecture design to improve the directional cracking of SiC/SiC CMC components with MI matrices.