26,450 research outputs found
Microjets in the penumbra of a sunspot
Penumbral Microjets (PMJs) are short-lived jets found in the penumbra of
sunspots, first observed in wide-band Ca H-line observations as localized
brightenings, and are thought to be caused by magnetic reconnection. Earlier
work on PMJs has been focused on smaller samples of by-eye selected events and
case studies. It is our goal to present an automated study of a large sample of
PMJs to place the basic statistics of PMJs on a sure footing and to study the
PMJ Ca II 8542 Angstrom spectral profile in detail. High spatial resolution and
spectrally well-sampled observations in the Ca II 8542 Angstrom line obtained
from the Swedish 1-m Solar Telescope (SST) are reduced by a Principle Component
Analysis and subsequently used in the automated detection of PMJs using the
simple learning algorithm k-Nearest Neighbour. PMJ detections were verified
with co-temporal Ca H-line observations. A total of 453 tracked PMJ events were
found, or 4253 PMJs detections tallied over all timeframes and a detection rate
of 21 events per timestep. From these, an average length, width and lifetime of
640 km, 210 km and 90 s were obtained. The average PMJ Ca II 8542 Angstrom line
profile is characterized by enhanced inner wings, often in the form of one or
two distinct peaks, and a brighter line core as compared to the quiet Sun
average. Average blue and red peak positions were determined at -10.4 km/s and
+10.2 km/s offsets from the Ca II 8542 Angstrom line core. We found several
clusters of PMJ hotspots within the sunspot penumbra, where PMJ events occur in
the same general area repeatedly over time. Our results indicate smaller
average PMJs sizes and longer lifetimes compared to previously published
values, but with statistics still in the same orders of magnitude. The
investigation and analysis of the PMJ line profiles strengthen the proposed
heating of PMJs to transition region temperatures.Comment: Figures 1, 2, 3, 4 and 11 exhibited artifacts in some pdf-readers,
and have been replotted with new graphical settings to remedy this. Apart
from slight changes in sizing and fonts, the figures are the same. The arXiv
abstract has had tex-syntax removed for better readabilit
Content vs. context for multimedia semantics: the case of SenseCam image structuring
Much of the current work on determining multimedia semantics from multimedia artifacts is based around using either context, or using content. When leveraged thoroughly these can independently provide content description which is used in building content-based applications. However, there are few cases where multimedia semantics are determined based on an integrated analysis of content and context. In this keynote talk we present one such example system in which we use an integrated combination of the two to automatically structure large collections of images taken by a SenseCam, a device from Microsoft Research which passively records a personâs daily activities. This paper describes the post-processing we perform on SenseCam images in order to present a structured, organised visualisation of the highlights of each of the wearerâs days
Multimedia search without visual analysis: the value of linguistic and contextual information
This paper addresses the focus of this special issue by analyzing the potential contribution of linguistic content and other non-image aspects to the processing of audiovisual data. It summarizes the various ways in which linguistic content analysis contributes to enhancing the semantic annotation of multimedia content, and, as a consequence, to improving the effectiveness of conceptual media access tools. A number of techniques are presented, including the time-alignment of textual resources, audio and speech processing, content reduction and reasoning tools, and the exploitation of surface features
A review of key planning and scheduling in the rail industry in Europe and UK
Planning and scheduling activities within the rail industry have benefited from developments in computer-based simulation and modelling techniques over the last 25 years. Increasingly, the use of computational intelligence in such tasks is featuring more heavily in research publications. This paper examines a number of common rail-based planning and scheduling activities and how they benefit from five broad technology approaches. Summary tables of papers are provided relating to rail planning and scheduling activities and to the use of expert and decision systems in the rail industry.EPSR
Development of Economic Water Usage Sensor and Cyber-Physical Systems Co-Simulation Platform for Home Energy Saving
In this thesis, two Cyber-Physical Systems (CPS) approaches were considered to reduce residential building energy consumption. First, a flow sensor was developed for residential gas and electric storage water heaters. The sensor utilizes unique temperature changes of tank inlet and outlet pipes upon water draw to provide occupant hot water usage. Post processing of measured pipe temperature data was able to detect water draw events. Conservation of energy was applied to heater pipes to determine relative internal water flow rate based on transient temperature measurements. Correlations between calculated flow and actual flow were significant at a 95% confidence level. Using this methodology, a CPS water heater controller can activate existing residential storage water heaters according to occupant hot water demand. The second CPS approach integrated an open-source building simulation tool, EnergyPlus, into a CPS simulation platform developed by the National Institute of Standards and Technology (NIST). The NIST platform utilizes the High Level Architecture (HLA) co-simulation protocol for logical timing control and data communication. By modifying existing EnergyPlus co-simulation capabilities, NISTâs open-source platform was able to execute an uninterrupted simulation between a residential house in EnergyPlus and an externally connected thermostat controller. The developed EnergyPlus wrapper for HLA co-simulation can allow active replacement of traditional real-time data collection for building CPS development. As such, occupant sensors and simple home CPS product can allow greater residential participation in energy saving practices, saving up to 33% on home energy consumption nationally
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