Simulating a dual-recycled gravitational wave interferometer with realistically imperfect optics

We simulate the performance of a gravitational wave interferometer in the Dual Recycling (DR) configuration, as will be used for systems like Advanced-LIGO. Our grid-based simulation program models complex interferometric detectors with realistic optical deformations (e.g., fine-scale mirror surface roughness). Broadband and Tuned DR are modeled here; the results are also applied qualitatively to Resonant Sideband Extraction (RSE). Several beneficial properties anticipated for DR detectors are investigated: signal response tuning and narrowbanding, power loss reduction, and the reclamation of lost power as useful light for signal detection. It is shown that these benefits would be limited by large scattering losses in large (multi-kilometer) systems. Furthermore, losses may be resonantly enhanced (particularly for RSE), if the interferometer's modal resonance conditions are not well chosen. We therefore make two principal recommendations for DR/RSE interferometers: the DR/RSE cavity must be modally nondegenerate; and fabricated mirror surfaces and coatings must be as smooth as is practically feasible.Comment: 50 pages, 11 figure

CloVR: A virtual machine for automated and portable sequence analysis from the desktop using cloud computing

Next-generation sequencing technologies have decentralized sequence acquisition, increasing the demand for new bioinformatics tools that are easy to use, portable across multiple platforms, and scalable for high-throughput applications. Cloud computing platforms provide on-demand access to computing infrastructure over the Internet and can be used in combination with custom built virtual machines to distribute pre-packaged with pre-configured software. We describe the Cloud Virtual Resource, CloVR, a new desktop application for push-button automated sequence analysis that can utilize cloud computing resources. CloVR is implemented as a single portable virtual machine (VM) that provides several automated analysis pipelines for microbial genomics, including 16S, whole genome and metagenome sequence analysis. The CloVR VM runs on a personal computer, utilizes local computer resources and requires minimal installation, addressing key challenges in deploying bioinformatics workflows. In addition CloVR supports use of remote cloud computing resources to improve performance for large-scale sequence processing. In a case study, we demonstrate the use of CloVR to automatically process next-generation sequencing data on multiple cloud computing platforms. The CloVR VM and associated architecture lowers the barrier of entry for utilizing complex analysis protocols on both local single- and multi-core computers and cloud systems for high throughput data processing.https://doi.org/10.1186/1471-2105-12-35

Efficient Implementation of Sorting Algorithms on Asynchronous Distributed-Memory

The problem of merging two sequences of elements which are stored separately in two processing elements (PEs) occurs in the implementation of many existing sorting algorithms. We describe efficient algorithms for the merging problem on asynchronous distributed-memory machines. The algorithms reduce the cost of the merge operation and of communication, as well as partly solving the problem of load balancing. Experimental results on a Fujitsu AP1000 are reported

Low-cost Differential GPS for Field Robotics

In this paper we detail the design and implementation of a Differential GPS system that uses only low-cost, light-weight and widely available GPS modules. Such a system is desirable for modern field robotics in order to improve the performance of mapping, navigation, collision avoidance and other common tasks, especially on payload-constrained robots. The particular noise and error modes present in the low-cost system are investigated and algorithms introduced to minimise their effect. The system is demonstrated in the context of field robotics for stationary, ground-based and airbourne agents. It is found that the majority of the error due to the low cost components can be manipulated to be of a form easily mitigated for most robots. The system is shown to provide good results in the horizontal plane in open environments such as those typically used for outdoor experimental robotics while being one to two orders of magnitude cheaper than comparable commercial systems