47,552 research outputs found
Millimetre/submillimetre-wave emission line searches for high-redshift galaxies
The redshifted spectral line radiation emitted from both atomic
fine-structure and molecular rotational transitions in the interstellar medium
(ISM) of high-redshift galaxies can be detected in the centimetre, millimetre
and submillimetre wavebands. Here we predict the counts of galaxies detectable
in an array of molecular and atomic lines. This calculation requires a
reasonable knowledge of both the surface density of these galaxies on the sky,
and the physical conditions in their ISM. The surface density is constrained
using the results of submillimetre-wave continuum surveys. Follow-up OVRO
Millimeter Array observations of two of the galaxies detected in the dust
continuum have provided direct measurements of CO rotational line emission at
redshifts of 2.56 and 2.81. Based on these direct high-redshift observations
and on models of the ISM that are constrained by observations of low-redshift
ultraluminous infrared galaxies, we predict the surface density of
line-emitting galaxies as a function of line flux density and observing
frequency. We incorporate the sensitivities and mapping speeds of existing and
future millimetre/submillimetre-wave telescopes and spectrographs, and so
assess the prospects for blank-field surveys to detect this line emission from
gas-rich high-redshift galaxies.Comment: 13 pages, 12 figures, to appear in MNRAS. Final proof versio
SMIL State: an architecture and implementation for adaptive time-based web applications
In this paper we examine adaptive time-based web applications (or presentations). These are interactive presentations where time dictates which parts of the application are presented (providing the major structuring paradigm), and that require interactivity and other dynamic adaptation. We investigate the current technologies available to create such presentations and their shortcomings, and suggest a mechanism for addressing these shortcomings. This mechanism, SMIL State, can be used to add user-defined state to declarative time-based languages such as SMIL or SVG animation, thereby enabling the author to create control flows that are difficult to realize within the temporal containment model of the host languages. In addition, SMIL State can be used as a bridging mechanism between languages, enabling easy integration of external components into the web application. Finally, SMIL State enables richer expressions for content control. This paper defines SMIL State in terms of an introductory example, followed by a detailed specification of the State model. Next, the implementation of this model is discussed. We conclude with a set of potential use cases, including dynamic content adaptation and delayed insertion of custom content such as advertisements. © 2009 Springer Science+Business Media, LLC
An Architectural Framework for Collaboration of Heterogeneous Communication Devices Using WAP and Mobile Device Augmented(MDA)Gateway Integration
Within the last couple of years, the challenge of displaying collaborative multimedia
information has become very important with the large diversity of communication devices
such as Personal Computers, laptops, notebooks and handheld devices. The shared data
and information may be presented with different views depending on the communication
device used by a particular collaborator. The use of various web tools (HTML, WML etc)
offers some solutions to the problem but if the target application requires more complex
features such as rich multimedia data than is manageable using HTML or WML format,
something else need to be done. In this paper, we propose a framework that integrates WAP
and MDA Gateway to support collaboration among virtual teams and nomadic workers
using heterogeneous communication devices. We then discuss an approach for augmenting
mobile device small screen capabilities with surrounding large screen display device
GPU-based Real-time Triggering in the NA62 Experiment
Over the last few years the GPGPU (General-Purpose computing on Graphics
Processing Units) paradigm represented a remarkable development in the world of
computing. Computing for High-Energy Physics is no exception: several works
have demonstrated the effectiveness of the integration of GPU-based systems in
high level trigger of different experiments. On the other hand the use of GPUs
in the low level trigger systems, characterized by stringent real-time
constraints, such as tight time budget and high throughput, poses several
challenges. In this paper we focus on the low level trigger in the CERN NA62
experiment, investigating the use of real-time computing on GPUs in this
synchronous system. Our approach aimed at harvesting the GPU computing power to
build in real-time refined physics-related trigger primitives for the RICH
detector, as the the knowledge of Cerenkov rings parameters allows to build
stringent conditions for data selection at trigger level. Latencies of all
components of the trigger chain have been analyzed, pointing out that
networking is the most critical one. To keep the latency of data transfer task
under control, we devised NaNet, an FPGA-based PCIe Network Interface Card
(NIC) with GPUDirect capabilities. For the processing task, we developed
specific multiple ring trigger algorithms to leverage the parallel architecture
of GPUs and increase the processing throughput to keep up with the high event
rate. Results obtained during the first months of 2016 NA62 run are presented
and discussed
NaNet: a Low-Latency, Real-Time, Multi-Standard Network Interface Card with GPUDirect Features
While the GPGPU paradigm is widely recognized as an effective approach to
high performance computing, its adoption in low-latency, real-time systems is
still in its early stages.
Although GPUs typically show deterministic behaviour in terms of latency in
executing computational kernels as soon as data is available in their internal
memories, assessment of real-time features of a standard GPGPU system needs
careful characterization of all subsystems along data stream path.
The networking subsystem results in being the most critical one in terms of
absolute value and fluctuations of its response latency.
Our envisioned solution to this issue is NaNet, a FPGA-based PCIe Network
Interface Card (NIC) design featuring a configurable and extensible set of
network channels with direct access through GPUDirect to NVIDIA Fermi/Kepler
GPU memories.
NaNet design currently supports both standard - GbE (1000BASE-T) and 10GbE
(10Base-R) - and custom - 34~Gbps APElink and 2.5~Gbps deterministic latency
KM3link - channels, but its modularity allows for a straightforward inclusion
of other link technologies.
To avoid host OS intervention on data stream and remove a possible source of
jitter, the design includes a network/transport layer offload module with
cycle-accurate, upper-bound latency, supporting UDP, KM3link Time Division
Multiplexing and APElink protocols.
After NaNet architecture description and its latency/bandwidth
characterization for all supported links, two real world use cases will be
presented: the GPU-based low level trigger for the RICH detector in the NA62
experiment at CERN and the on-/off-shore data link for KM3 underwater neutrino
telescope
Every Cloud Has a Push Data Lining: Incorporating Cloud Services in a Context-Aware Application
We investigated context-awareness by utilising multiple sources of context in a mobile device setting. In our experiment we developed a system consisting of a mobile client, running on the Android platform, integrated with a cloud-based service. These components were integrated using pushmessaging technology.One of the key featureswas the automatic adaptation of smartphones in accordance with implicit user needs. The novelty of our approach consists in the use of multiple sources of context input to the system, which included the use of calendar data and web based user configuration tool, as well as that of an external, cloud-based, configuration file storing user interface preferences which, pushed at log-on time irrespective of access device, frees the user from having to manually configure its interface.The systemwas evaluated via two rounds of user evaluations (n = 50 users), the feedback of which was generally positive and demonstrated the viability of using cloud-based services to provide an enhanced context-aware user experience
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