Development of a Near Net Shape Processing Method for Rhenium Using Directed Light Fabrication

Directed Light Fabrication (DLF) is a direct metal deposition process that fuses gas delivered powder, in the focal zone of a high powered laser beam to form fully fused near net shaped components. The near net shape processing of rhenium and refractory metals is currently in development and may offer significant cost savings compared with conventional processing. A full y associative 3D design through manufacturing model is presented for the application of DLF for the fabrication of a near net shaped nozzle part. This study describes the ability to move from a parametric 3D model integrated into a manufacturing model, creating a control file which can run on the DLF machine to produce a near net shaped metal component. Examples of DLF deposited rheniurn and iridium show a continuously solidified microstructure in rod and tube shapes. Entrapped porosity indicates the required direction for continued process development. These results demonstrate a new methodology for fabricating complex near net shaped components using rhenium.     

Regulation of cardiac myocyte contractile function by inducible nitric oxide synthase (iNOS): mechanisms of contractile depression by nitric oxide

Inflammatory cytokines have been implicated in the reversible depression of cardiac contractile function accompanying local or systemic immune stimulation. Incubation of cardiac myocytes with soluble components in the supernatant from cultured rat lung macrophages activated with endotoxin decreases their contractile response to beta-adrenergic stimulation through the induction of iNOS and the subsequent production of nitric oxide by these cells. In the present study, we characterize the mechanisms underlying NO's attenuation of adrenergic responsiveness in cardiac myocytes. iNOS was induced in cultured ventricular myocytes from adult rats by incubation for 20 h with conditioned medium from lipopolysaccharide (LPS)-activated macrophages. iNOS induction did not induce any alteration in beta-adrenergic receptor density or affinity, Galphai protein abundance, or adenylyl cyclase activity in cultured myocytes. Myocyte exposure to activated macrophage-conditioned medium markedly attenuated the elevation of cAMP in response to isoproterenol (Iso, 2 nM). Induction of iNOS with the macrophage-conditioned medium also potentiated the Iso-induced increase in myocyte cGMP. This cGMP increase was totally abolished by NOS inhibitors. NOS inhibition also returned the attenuated cAMP response to 2 nM Iso to levels observed in control cells. Pre-incubation of the cells in isobutylmethylxanthine (IBMX), a phosphodiesterase inhibitor, also partly reversed the attenuation of cAMP increase with 2 nM Iso in cells expressing iNOS. Brief (15 min) exposure of myocytes to the NO donor, S-nitrosoacetylcysteine (SNAC, 100 micro M) which produced a three-fold increase in intracellular cGMP, also decreased by half the contractile response of cardiac myocytes to Iso (2 nM). We conclude that NO endogenously produced by iNOS decreases the intracellular levels of cAMP in response to beta-adrenergic stimulation in isolated cardiac myocytes, in part through a cGMP-mediated mechanism. This effect may participate in the NO-dependent depression of cardiac function following cytokine exposure.     

Effect of Dye Content on Point of Zero Charge of Anionic Lake Dyes

The pure dye content of FD&C yellow lake #5 and FD&C red lake #40 was found to be inversely related to the point of zero charge. The effect of the adsorbed anionic dye on the zeta potential of aqueous suspensions of FD&C yellow lake #5 at pH 5 was demonstrated.     

Statistical inference for general-order-statistics andnonhomogeneous-Poisson-process software reliability models

There are many software reliability models that are based on the times of occurrences of errors in the debugging of software. It is shown that it is possible to do asymptotic likelihood inference for software reliability models based on order statistics or nonhomogeneous Poisson processes, with asymptotic confidence levels for interval estimates of parameters. In particular, interval estimates from these models are obtained for the conditional failure rate of the software, given the data from the debugging process. The data can be grouped or ungrouped. For someone making a decision about when to market software, the conditional failure rate is an important parameter. The use of interval estimates is demonstrated for two data sets that have appeared in the literature     

Magnesium global development: Outcomes from the TMS 2007 annual meeting

The magnesium industry is experiencing dramatic growth, due in part to the demands of the automotive industry to improve fuel economy and emissions. As a result, the TMS annual magnesium symposium is one of the fastest-growing subject areas at TMS. In addition, TMS is recognized as the global light metals community’s preeminent forum for the presentation of magnesium science and technological issues. As a focal point of the 2007 TMS Annual Meeting in Orlando, Florida, the TMS Magnesium Committee held its first plenary session with expert representatives from around the world. In order to address the surge in magnesium technology in recent years, the TMS Magnesium Globalization plenary session included a variety of subjects that ranged from economic to technical.     

Duality of constrained Voronoi diagrams and Delaunay triangulations

We introduce theconstrained Voronoi diagram of a planar straight-line graph containingn vertices or sites where the line segments of the graph are regarded as obstacles, and show that an extended version of this diagram is the dual of theconstrained Delaunay triangulation. We briefly discussO(n logn) algorithms for constructing the extended constrained Voronoi diagram.This work was partially supported by a grant from the Natural Sciences and Engineering Research Council of Canada.     

Experimental investigation and numerical modelling of transient two-phase flow in a geysering geothermal well

Measurements of the periodic transient flow in a vertical geysering geothermal well are presented. The 70-m deep, 0.1-m internal diameter well taps a hot (about 87 °C) water aquifer rich in dissolved carbon dioxide. Transient pressures measured at various depths show the various flow regimes that develop in the borehole and demonstrate that the periodic flow is caused by the degassing of the water flowing up the well. A one-dimensional numerical model of the flow has been developed. The computed results exhibit the main characteristics of the test measurements. This agreement between model and measurements is considered to support both the numerical model and the conceptual model of the system deduced from the measurements.     

简化混合处理器应用开发 FPGA分担DSP功能降低构建成本

随着大规模现场可编程逻辑阵列(FPGA)的成本降低,加上面向软件的FPGA设计工具的发展,使得FPGA器件获得更多的使用,既能处理过去DSP处理器领域的功能,同时大大降低了专用ASIC方案的风险和前期成本.