462 research outputs found

    Proceedings of the 2003 Winter Simulation Conference

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    In this paper we have applied an interval representation of time to represent and reason about activities, events, actions and situations relevant to the construction domain. The first part of the paper formally defines the situational simulation environment and develops a set of temporal axioms which can be used to 1) Express precedence constraints between time intervals and 2) Capture the causal relationships between actions and events. The second part of the paper looks at an agent reasoning mechanism used to perceive and predict actions and foresee future consequences of present actions within the simulation environment. Agent reasoning is based on awareness derived from a knowledge base of facts which captures the causal nature of events in the construction management domain

    Discovery of the Optical Transient of the Gamma Ray Burst 990308

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    The optical transient of the faint Gamma Ray Burst 990308 was detected by the QUEST camera on the Venezuelan 1-m Schmidt telescope starting 3.28 hours after the burst. Our photometry gives V=18.32±0.07V = 18.32 \pm 0.07, R=18.14±0.06R = 18.14 \pm 0.06, B=18.65±0.23B = 18.65 \pm 0.23, and R=18.22±0.05R = 18.22 \pm 0.05 for times ranging from 3.28 to 3.47 hours after the burst. The colors correspond to a spectral slope of close to fνν1/3f_{\nu} \propto \nu^{1/3}. Within the standard synchrotron fireball model, this requires that the external medium be less dense than 104cm310^{4} cm^{-3}, the electrons contain >20> 20% of the shock energy, and the magnetic field energy must be less than 24% of the energy in the electrons for normal interstellar or circumstellar densities. We also report upper limits of V>12.0V > 12.0 at 132 s (with LOTIS), V>13.4V > 13.4 from 132-1029s (with LOTIS), V>15.3V > 15.3 at 28.2 min (with Super-LOTIS), and a 8.5 GHz flux of <114μJy< 114 \mu Jy at 110 days (with the Very Large Array). WIYN 3.5-m and Keck 10-m telescopes reveal this location to be empty of any host galaxy to R>25.7R > 25.7 and K>23.3K > 23.3. The lack of a host galaxy likely implies that it is either substantially subluminous or more distant than a red shift of 1.2\sim 1.2.Comment: ApJ Lett submitted, 5 pages, 2 figures, no space for 12 coauthor

    A Large Area CCD Camera for the Schmidt Telescope at the Venezuelan National Astronomical Observatory

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    We have designed, constructed and put into operation a large area CCD camera that covers a large fraction of the image plane of the 1 meter Schmidt telescope at Llano del Hato in Venezuela. The camera consists of 16 CCD devices arranged in a 4 x 4 mosaic covering 2.3 degrees x 3.5 degrees of sky. The CCDs are 2048 x 2048 LORAL devices with 15 micron pixels. The camera is optimized for drift scan photometry and objective prism spectroscopy. The design considerations, construction features and performance parameters are described in the following article.Comment: 34 pages, 18 figures, accepted for publication in PAS

    Computerized cognitive training in attention-deficit/hyperactivity disorder (ADHD): a meta-analysis of randomized controlled trials with blinded and objective outcomes

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    This meta-analysis investigated the effects of computerized cognitive training (CCT) on clinical, neuropsychological and academic outcomes in individuals with attention-deficit/hyperactivity disorder (ADHD). The authors searched PubMed, Ovid, and Web of Science until 19th January 2022 for parallel-arm randomized controlled trials (RCTs) using CCT in individuals with ADHD. Random-effects meta-analyses pooled standardized mean differences (SMD) between CCT and comparator arms. RCT quality was assessed with the Cochrane Risk of Bias 2.0 tool (PROSPERO: CRD42021229279). Thirty-six RCTs were meta-analysed, 17 of which evaluated working memory training (WMT). Analysis of outcomes measured immediately post-treatment and judged to be “probably blinded” (PBLIND; trial n = 14) showed no effect on ADHD total (SMD = 0.12, 95%CI[−0.01 to −0.25]) or hyperactivity/impulsivity symptoms (SMD = 0.12, 95%[−0.03 to−0.28]). These findings remained when analyses were restricted to trials (n: 5–13) with children/adolescents, low medication exposure, semi-active controls, or WMT or multiple process training. There was a small improvement in inattention symptoms (SMD = 0.17, 95%CI[0.02–0.31]), which remained when trials were restricted to semi-active controls (SMD = 0.20, 95%CI[0.04–0.37]), and doubled in size when assessed in the intervention delivery setting (n = 5, SMD = 0.40, 95%CI[0.09–0.71]), suggesting a setting-specific effect. CCT improved WM (verbal: n = 15, SMD = 0.38, 95%CI[0.24–0.53]; visual-spatial: n = 9, SMD = 0.49, 95%CI[0.31–0.67]), but not other neuropsychological (e.g., attention, inhibition) or academic outcomes (e.g., reading, arithmetic; analysed n: 5–15). Longer-term improvement (at ~6-months) in verbal WM, reading comprehension, and ratings of executive functions were observed but relevant trials were limited in number (n: 5–7). There was no evidence that multi-process training was superior to working memory training. In sum, CCT led to shorter-term improvements in WM, with some evidence that verbal WM effects persisted in the longer-term. Clinical effects were limited to small, setting specific, short-term effects on inattention symptoms

    TNOs are Cool: A survey of the trans-Neptunian region V. Physical characterization of 18 Plutinos using Herschel PACS observations

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    We present Herschel PACS photometry of 18 Plutinos and determine sizes and albedos for these objects using thermal modeling. We analyze our results for correlations, draw conclusions on the Plutino size distribution, and compare to earlier results. Flux densities are derived from PACS mini scan-maps using specialized data reduction and photometry methods. In order to improve the quality of our results, we combine our PACS data with existing Spitzer MIPS data where possible, and refine existing absolute magnitudes for the targets. The physical characterization of our sample is done using a thermal model. Uncertainties of the physical parameters are derived using customized Monte Carlo methods. The correlation analysis is performed using a bootstrap Spearman rank analysis. We find the sizes of our Plutinos to range from 150 to 730 km and geometric albedos to vary between 0.04 and 0.28. The average albedo of the sample is 0.08 \pm 0.03, which is comparable to the mean albedo of Centaurs, Jupiter Family comets and other Trans-Neptunian Objects. We were able to calibrate the Plutino size scale for the first time and find the cumulative Plutino size distribution to be best fit using a cumulative power law with q = 2 at sizes ranging from 120-400 km and q = 3 at larger sizes. We revise the bulk density of 1999 TC36 and find a density of 0.64 (+0.15/-0.11) g cm-3. On the basis of a modified Spearman rank analysis technique our Plutino sample appears to be biased with respect to object size but unbiased with respect to albedo. Furthermore, we find biases based on geometrical aspects and color in our sample. There is qualitative evidence that icy Plutinos have higher albedos than the average of the sample.Comment: 18 pages, 8 figures, 8 tables, accepted for publication in A&
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