Design and Implementation of Swirl Brakes for Enhanced Rotordynamic Stability in an Off-shore Centrifugal Compressor

Technical BriefsRotordynamic stability of gas compressors at high speeds and operating pressures is a significant technical challenge. Dynamic instability must be avoided for the sake of safe, reliable and continuous operation of turbomachinery. Experience and literature have shown that one of the main sources of instability is the swirl within the secondary leakage path in shrouded impellers, especially the swirl entering the shroud seals. The technical brief presents the design and implementation of swirl brakes for centrifugal compressors with Teeth-on-Rotor seal configurations for shrouded impellers. Discussion includes (a) aerodynamic design of swirl brakes with the help of Computational Fluid Dynamics (CFD), (b) sub-scale testing of the swirl brake design in an instrumented single-stage test rig to measure the inlet swirl ratio in a shrouded impeller, (c) full-scale prototype shop-testing and qualification, with and without the swirl brakes in a closedloop test facility, and (d) results of incorporating the swirl brakes at an off-shore compressor installation to improve rotordynamic stability

Design and Implementation of Swirl Brakes for Enhanced Rotordynamic Stability in an Off-shore Centrifugal Compressor

Technical BriefsRotordynamic stability of gas compressors at high speeds and operating pressures is a significant technical challenge. Dynamic instability must be avoided for the sake of safe, reliable and continuous operation of turbomachinery. Experience and literature have shown that one of the main sources of instability is the swirl within the secondary leakage path in shrouded impellers, especially the swirl entering the shroud seals. The technical brief presents the design and implementation of swirl brakes for centrifugal compressors with Teeth-on-Rotor seal configurations for shrouded impellers. Discussion includes (a) aerodynamic design of swirl brakes with the help of Computational Fluid Dynamics (CFD), (b) sub-scale testing of the swirl brake design in an instrumented single-stage test rig to measure the inlet swirl ratio in a shrouded impeller, (c) full-scale prototype shop-testing and qualification, with and without the swirl brakes in a closedloop test facility, and (d) results of incorporating the swirl brakes at an off-shore compressor installation to improve rotordynamic stability

Improving primary care management of asthma:do we know what really works?

Asthma imposes a substantial burden on individuals and societies. Patients with asthma need high-quality primary care management; however, evidence suggests the quality of this care can be highly variable. Here we identify and report factors contributing to high-quality management. Twelve primary care global asthma experts, representing nine countries, identified key factors. A literature review (past 10 years) was performed to validate or refute the expert viewpoint. Key driving factors identified were: policy, clinical guidelines, rewards for performance, practice organisation and workforce. Further analysis established the relevant factor components. Review evidence supported the validity of each driver; however, impact on patient outcomes was uncertain. Single interventions (e.g. healthcare practitioner education) showed little effect; interventions driven by national policy (e.g. incentive schemes and teamworking) were more effective. The panel's opinion, supported by literature review, concluded that multiple primary care interventions offer greater benefit than any single intervention in asthma management

Visual consumption, collective memory and the representation of war

Conceiving of the visual as a significant force in the production and dissemination of collective memory, we argue that a new genre of World War Two films has recently emerged that form part of a new discursive “regime of memory” about the war and those that fought and lived through it, constituting a commemoration as much about reflecting on the present as it is about remembering the past. First, we argue that these films seek to reaffirm a (particular conception of a) US national identity and military patriotism in the post–Cold War era by importing World War Two as the key meta‐narrative of America’s relationship to war in order to “correct” and help “erase” Vietnam’s more negative discursive rendering. Second, we argue that these films attempt to rewrite the history of World War Two by elevating and illuminating the role of the US at the expense of the Allies, further serving to reaffirm America’s position of political and military dominance in the current age, and third, that these films form part of a celebration of the generation that fought World War Two, which may accord them a position of nostalgic and sentimental greatness, as their collective spirit and notions of duty and service shine against the foil of what might frequently be seen as our own present moral ambivalence

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Ceph Day for Research and Non-profits

Compute Canada is the national platform for research computing in Canada. There are five high performance research computing sites across the country offering both traditional HPC and OpenStack cloud resources. This talk will give an overview of Ceph at the cloud sites and then focus on the specific implementation details of Ceph at, Arbutus. Hosted at the University of Victoria in British Columbia, Canada, Arbutus is the largest non-commercial research cloud in Canada. Ceph is integral to the success of our cloud deployments because of the versatility, price for performance and scalability. We started with a small 400TB Ceph install which has grown to a 5.3 PB installation, and in the near future are extending our offering to include CephFS and object storage

The OARS project final report

The principal aim of the Open Access Repository System (OARS) project was to enhance and consolidate the software platform on which Forced Migration Online (FMO) is built. This 18-month project, started in September 2009, aimed to replace the Digital Library and Journals sections of the FMO website with a new repository, built using open source technologies, that could eventually store and serve all types of content (e.g. documents, images, video, audio). This would make FMO technically easier to manage, as it would greatly improve the public and management interfaces to these sections, and reduce the software and hardware maintenance costs for FMO. The new repository would be globally interoperable with other open systems, including the University of Oxford’s institutional repository, the Oxford Research Archive (ORA)