11,199 research outputs found

    A Survey of Agent-Based Modeling Practices (January 1998 to July 2008)

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    In the 1990s, Agent-Based Modeling (ABM) began gaining popularity and represents a departure from the more classical simulation approaches. This departure, its recent development and its increasing application by non-traditional simulation disciplines indicates the need to continuously assess the current state of ABM and identify opportunities for improvement. To begin to satisfy this need, we surveyed and collected data from 279 articles from 92 unique publication outlets in which the authors had constructed and analyzed an agent-based model. From this large data set we establish the current practice of ABM in terms of year of publication, field of study, simulation software used, purpose of the simulation, acceptable validation criteria, validation techniques and complete description of the simulation. Based on the current practice we discuss six improvements needed to advance ABM as an analysis tool. These improvements include the development of ABM specific tools that are independent of software, the development of ABM as an independent discipline with a common language that extends across domains, the establishment of expectations for ABM that match their intended purposes, the requirement of complete descriptions of the simulation so others can independently replicate the results, the requirement that all models be completely validated and the development and application of statistical and non-statistical validation techniques specifically for ABM.Agent-Based Modeling, Survey, Current Practices, Simulation Validation, Simulation Purpose

    Reader Polls Show Farmer Concerns

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    College editors and farm paper editors have the same basic concern. That is, communicating. To do this we have to know the audience

    Management of mental illness by the British Army

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    Background: The Ministry of Defence has its own hospital for soldiers requiring admission for mental health problems. Aims: To assess the efficiency of the army psychiatric hospital at restoring patients to full active duty. To assess whether a new military training and rehabilitation unit (MTRU) that emphasises military-skills training, improves outcome. Method: A 2-year, inception-cohort outcome study of hospital in-patients. A 12-month, case-matched, ā€˜before and afterā€™ outcome study compared MTRU patients with hospital in-patients. Results: I (hospital in-patients, n=309): at 2-year follow-up 67 (22%) were fully fit for active duty. Military psychiatrists' success rate at predicting recovery to active duty was 27%. 2: the odds of a soldier in the MTRU cohort (n=35) returning to active duty were 14 times greater than for the hospital cohort (n=35). The odds of remaining in the army while unfit for active duty were 20 times less for the MTRU than for the hospital cohort. Conclusions: The army hospital is inefficient at rehabilitation to active duty. The MTRU significantly increased the odds of returning to active duty and reduced the odds of remaining in the army while still unfit. These findings may be applicable to the emergency services

    GONG p-mode parameters through two solar cycles

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    We investigate the parameters of global solar p-mode oscillations, namely damping width Ī“\Gamma, amplitude AA, mean squared velocity āŸØv2āŸ©\langle v^2\rangle, energy EE, and energy supply rate dE/dt\mathrm{d}E/\mathrm{d} t, derived from two solar cycles' worth (1996 - 2018) of Global Oscillation Network Group (GONG) time series for harmonic degrees l=0āˆ’150l=0 - 150. We correct for the effect of fill factor, apparent solar radius, and spurious jumps in the mode amplitudes. We find that the amplitude of the activity related changes of Ī“\Gamma and AA depends on both frequency and harmonic degree of the modes, with the largest variations of Ī“\Gamma for modes with 2400ā€‰Ī¼Hzā‰¤Ī½ā‰¤3300ā€‰Ī¼Hz2400\,\mu\text{Hz}\le \nu \le 3300\,\mu\text{Hz} and 31ā‰¤lā‰¤6031\le l \le 60 with a min-to-max variation of 26.6Ā±0.3%26.6\pm0.3\% and of AA for modes with 2400ā€‰Ī¼Hzā‰¤Ī½ā‰¤3300ā€‰Ī¼Hz2400\,\mu\text{Hz}\le\nu\le 3300\,\mu\text{Hz} and 61ā‰¤lā‰¤10061\le l \le 100 with a min-to-max variation of 27.4Ā±0.4%27.4\pm0.4\%. The level of correlation between the solar radio flux F10.7F_{10.7} and mode parameters also depends on mode frequency and harmonic degree. As a function of mode frequency, the mode amplitudes are found to follow an asymmetric Voigt profile with Ī½max=3073.59Ā±0.18ā€‰Ī¼Hz\nu_{\text{max}}=3073.59\pm0.18\,\mu\text{Hz}. From the mode parameters, we calculate physical mode quantities and average them over specific mode frequency ranges. This way, we find that the mean squared velocities āŸØv2āŸ©\langle v^2\rangle and energies EE of p modes are anti-correlated with the level of activity, varying by 14.7Ā±0.3%14.7\pm0.3\% and 18.4Ā±0.3%18.4\pm0.3\%, respectively, and that the mode energy supply rates show no significant correlation with activity. With this study we expand previously published results on the temporal variation of solar p-mode parameters. Our results will be helpful to future studies of the excitation and damping of p modes, i.e., the interplay between convection, magnetic field, and resonant acoustic oscillations.Comment: Accepted for publication in Solar Physics. 33 pages, 16 figures, 5 table

    Preliminary Report on a Stratified Late Archaic-Woodland Era Rockshelter in Rogers County, Oklahoma

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    In northeastern Oklahoma, very little is known about the transition from the Late Archaic to the Woodland period (Wyckoff and Brooks, 1983: 55). To date, most of the archeological evidence documenting this time period has been derived from sites with mixed or otherwise uncertain components. In this report, we present a preliminary description of a small rockshelter, 34RO252, which has a Late Archaic deposit stratigraphically below a Woodland era cultural deposit. These two deposits are unmixed, discrete, and are physically separated by an apparently sterile clay soil horizon. It is anticipated that the stratified cultural deposits at this site will help characterize the transition from the Late Archaic to the Early Woodland period along the Verdigris River in northeast Oklahoma. This site was first reported in April 1994 by two men who had discovered partially exposed human skeletal remains located in the rear remnant of a rockshelter at Oologah Lake in Rogers County, Oklahoma. The two men illegally excavated the remains and removed them from the site. 1 The rockshelter where the remains originated was subsequently examined by the authors and additional skeletal material was identified, in situ, in an exposed soil profile. A series of three radiocarbon assays, described below, placed the cultural deposit and the human remains within the Late Archaic-Woodland period (circa 780 B.C. to A.O. 900).2 This site is provisionally classified as corresponding to a cultural sequence that includes the old Grove C described by Purrington and Vehik
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