Interactive boundary element analysis for engineering design.

Structural design of mechanical components is an iterative process that involves multiple stress analysis runs; this can be time consuming and expensive. Significant improvements in the eciency of this process can be made by increasing the level of interactivity. One approach is through real-time re-analysis of models with continuously updating geometry. Three primary areas need to be considered to accelerate the re-solution of boundary element problems. These are re-meshing the model, updating the boundary element system of equations and re-solution of the system. Once the initial model has been constructed and solved, the user may apply geometric perturbations to parts of the model. The re-meshing algorithm must accommodate these changes in geometry whilst retaining as much of the existing mesh as possible. This allows the majority of the previous boundary element system of equations to be re-used for the new analysis. For this problem, a GMRES solver has been shown to provide the fastest convergence rate. Further time savings can be made by preconditioning the updated system with the LU decomposition of the original system. Using these techniques, near real-time analysis can be achieved for 3D simulations; for 2D models such real-time performance has already been demonstrated

Rapid re-meshing and re-solution of three-dimensional boundary element problems for interactive stress analysis

Structural design of mechanical components is an iterative process that involves multiple stress analysis runs; this can be time consuming and expensive. It is becoming increasingly possible to make significant improvements in the efficiency of this process by increasing the level of interactivity. One approach is through real-time re-analysis of models with continuously updating geometry. A key part of such a strategy is the ability to accommodate changes in geometry with minimal perturbation to an existing mesh. This work introduces a new re-meshing algorithm that can generate and update a boundary element mesh in real-time as a series of small changes are sequentially applied to the associated model. The algorithm is designed to make minimal updates to the mesh between each step whilst preserving a suitable mesh quality that retains accuracy in the stress results. This significantly reduces the number of terms that need to be updated in the system matrix, thereby reducing the time required to carry out a re-analysis of the model. A range of solvers are assessed to find the most efficient and robust method of re-solving the system. The GMRES algorithm, using complete approximate LU preconditioning, is found to provide the fastest convergence rate

Interactive three-dimensional boundary element stress analysis of components in aircraft structures

Computer aided design of mechanical components is an iterative process that often involves multiple stress analysis runs; this can be time consuming and expensive. Significant efficiency improvements can be made by increasing interactivity at the conceptual design stage. One approach is through real-time re-analysis of models with continuously updating geometry. Thus each run can benefit from an existing mesh and governing boundary element matrix that are similar to the updated geometry. For small problems, amenable to real-time analysis, re-integration accounts for the majority of the re-analysis time. This paper assesses how efficiency can be achieved during re-integration through both algorithmic and hardware based methods. For models with fewer than 10,000 degrees of freedom, the proposed algorithm performs up to five times faster than a standard integration scheme. An additional six times speed is achieved on eight cores over the serial implementation. By combining this work with previously addressed meshing and solution schemes, real-time re-analysis becomes a reality for small three-dimensional problems. Significant acceleration of larger systems is also achieved. This work demonstrates the viability of application in the aerospace industry where rapid validation of a range of similar models is an essential tool for optimising aircraft designs

First evidence of retained sexual capacity and survival in the pyrethroid resistant Sitobion avenae (F.) (Hemiptera: Aphididae) SA3 super-clone following exposure to a pyrethroid at current field-rate

peer-reviewedTeagasc PublicationThe grain aphid Sitobion avenae is a prolific pest of cereal crops worldwide, controlled effectively with pyrethroid insecticides. However, the classic knock down resistance (kdr) mutation, L1014F on the S. avenae sodium channel gene, has been identified as the cause of the recently observed heterozygous (kdr-SR) resistance in the SA3 grain aphid super-clone. Results indicate that the kdr-SR SA3 clone can survive pyrethroid exposure above twice the normal field rate, continuing to reproduce thereafter. Additionally, the SA3 clone was found to be capable of producing sexual oviparous morphs, able to lay eggs following pyrethroid exposure. This demonstrates that possession of the L1014F mutation does not preclude the capacity to produce sexual morphs. This makes the adoption of an effective resistance management strategy imperative, within a wider integrated pest management (IPM) approach to control grain aphid

Interactive Boundary Element Analysis for Engineering Design

Structural design of mechanical components is an iterative process that involves multiple stress analysis runs; this can be time consuming and expensive. Significant improvements in the eciency of this process can be made by increasing the level of interactivity. One approach is through real-time re-analysis of models with continuously updating geometry. Three primary areas need to be considered to accelerate the re-solution of boundary element problems. These are re-meshing the model, updating the boundary element system of equations and re-solution of the system. Once the initial model has been constructed and solved, the user may apply geometric perturbations to parts of the model. The re-meshing algorithm must accommodate these changes in geometry whilst retaining as much of the existing mesh as possible. This allows the majority of the previous boundary element system of equations to be re-used for the new analysis. For this problem, a GMRES solver has been shown to provide the fastest convergence rate. Further time savings can be made by preconditioning the updated system with the LU decomposition of the original system. Using these techniques, near real-time analysis can be achieved for 3D simulations; for 2D models such real-time performance has already been demonstrated

Engineering chiral light–matter interactions in a waveguide-coupled nanocavity

Spin-dependent, directional light–matter interactions form the basis of chiral quantum networks. In the solid state, quantum emitters commonly possess circularly polarized optical transitions with spin-dependent handedness. We demonstrate numerically that spin-dependent chiral coupling can be realized by embedding such an emitter in a waveguide-coupled nanocavity, which supports two near-degenerate, orthogonally polarized cavity modes. The chiral behavior arises due to direction-dependent interference between the cavity modes upon coupling to two single-mode output waveguides. Notably, an experimentally realistic cavity design simultaneously supports near-unity chiral contrast, efficient (>95%) cavity-waveguide coupling and enhanced light–matter interaction strength (Purcell factor FP > 70). In combination, these parameters enable the development of highly coherent spin–photon interfaces ready for integration into nanophotonic circuits

SosA inhibits cell division in Staphylococcus aureus in response to DNA damage.

Inhibition of cell division is critical for viability under DNA-damaging conditions. DNA damage induces the SOS response that in bacteria inhibits cell division while repairs are being made. In coccoids, such as the human pathogen, Staphylococcus aureus, this process remains poorly studied. Here, we identify SosA as the staphylococcal SOS-induced cell division inhibitor. Overproduction of SosA inhibits cell division, while sosA inactivation sensitizes cells to genotoxic stress. SosA is a small, predicted membrane protein with an extracellular C-terminal domain in which point mutation of residues that are conserved in staphylococci and major truncations abolished the inhibitory activity. In contrast, a minor truncation led to SosA accumulation and a strong cell division inhibitory activity, phenotypically similar to expression of wild-type SosA in a CtpA membrane protease mutant. This suggests that the extracellular C-terminus of SosA is required both for cell division inhibition and for turnover of the protein. Microscopy analysis revealed that SosA halts cell division and synchronizes the cell population at a point where division proteins such as FtsZ and EzrA are localized at midcell, and the septum formation is initiated but unable to progress to closure. Thus, our findings show that SosA is central in cell division regulation in staphylococci

Prospectus, March 7, 1990

https://spark.parkland.edu/prospectus_1990/1007/thumbnail.jp

Engineering strong chiral light-matter interactions in a waveguide-coupled nanocavity

Spin-dependent, directional light-matter interactions form the basis of chiral quantum networks. In the solid state, quantum emitters commonly possess circularly polarised optical transitions with spin-dependent handedness. We demonstrate theoretically that spin-dependent chiral coupling can be realised by embedding such an emitter in a waveguide-coupled nanocavity, which supports two near-degenerate, orthogonally-polarised cavity modes. The chiral behaviour arises due to direction-dependent interference between the cavity modes upon coupling to two single-mode output waveguides. Notably, an experimentally realistic cavity design simultaneously supports near-unity chiral contrast, efficient (β>0.95) waveguide coupling and enhanced light-matter interaction strength (Purcell factor FP>60). In combination, these parameters could enable the development of highly coherent spin-photon interfaces, and may even allow access to the chiral strong-coupling regime using integrated nano-photonic devices