43 research outputs found

    Subordinate Officers in Xenophon's Anabasis

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    This chapter focuses on Xenophon’s treatment of divisions within the command structure presented in the Anabasis, and in particular on three military positions that are briefly mentioned—the taxiarch, áœ‘Ï€ÎżÏƒÏ„Ïáœ±Ï„Î·ÎłÎżÏ‚, and áœ‘Ï€ÎżÎ»áœčÏ‡Î±ÎłÎżÏ‚. Arguing against the prescriptive military hierarchies proposed in earlier scholarship, it suggests that ‘taxiarch’ should be understood fluidly and that the appearance of both the áœ‘Ï€ÎżÏƒÏ„Ïáœ±Ï„Î·ÎłÎżÏ‚ and the áœ‘Ï€ÎżÎ»áœčÏ‡Î±ÎłÎżÏ‚ may be due to interpolation. The chapter also includes discussion of two types of comparative material: procedures for replacing dead, absent, or deposed generals at Athens and Sparta in the Classical period, and the lexical development of subordinate positions with the prefix áœ‘Ï€Îż-

    GOES-R Spacecraft Verification and Validation Compared with Flight Results

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    The Geostationary Operational Environmental Satellite, R-Series (GOES-R) represents a dramatic improvement in GEO (Geostationary Earth Orbit) weather observation capabilities over the previous generation. To provide these new capabilities, GOES-R incorporates a number of new technologies flying for the first time. As with any new spacecraft design, extensive ground testing was performed to validate the vehicle performance. In this paper, we present several successes and several lessons-learned from the GOES-R verification and validation (V&V) efforts. Included are the Dynamic Interaction Test (DIT) results for jitter assessment, and comparison to flight results. Also included are the effects of thermally-induced alignment perturbations, along with post-launch mitigations. Finally, we discuss unexpected GOES-17 gyro performance, which caused a Safe Mode entry shortly after launch. V&V mitigations are presented, which will be used for the next two GOES-R vehicles

    Guidance, Navigation, and Control Performance for the GOES-R Spacecraft

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    The Geostationary Operational Environmental Satellite-R Series (GOES-R) is the first of the next generation geostationary weather satellites. The series represents a dramatic increase in Earth observation capabilities, with 4 times the resolution, 5 times the observation rate, and 3 times the number of spectral bands. GOES-R also provides unprecedented availability, with less than 120 minutes per year of lost observation time. This paper presents the Guidance Navigation & Control (GN&C) requirements necessary to realize the ambitious pointing, knowledge, and Image Navigation and Registration (INR) objectives of GOES-R. Because the suite of instruments is sensitive to disturbances over a broad spectral range, a high fidelity simulation of the vehicle has been created with modal content over 500 Hz to assess the pointing stability requirements. Simulation results are presented showing acceleration, shock response spectra (SRS), and line of sight (LOS) responses for various disturbances from 0 Hz to 512 Hz. Simulation results demonstrate excellent performance relative to the pointing and pointing stability requirements, with LOS jitter for the isolated instrument platform of approximately 1 micro-rad. Attitude and attitude rate knowledge are provided directly to the instrument with an accuracy defined by the Integrated Rate Error (IRE) requirements. The data are used internally for motion compensation. The final piece of the INR performance is orbit knowledge, which GOES-R achieves with GPS navigation. Performance results are shown demonstrating compliance with the 50 to 75 m orbit position accuracy requirements. As presented in this paper, the GN&C performance supports the challenging mission objectives of GOES-R

    Guidance, Navigation, and Control Performance for the GOES-R Spacecraft

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    The Geostationary Operational Environmental Satellite-R Series (GOES-R) is the first of the next generation geostationary weather satellites, scheduled for delivery in late 2015 and launch in early 2016. Relative to the current generation of GOES satellites, GOES-R represents a dramatic increase in Earth and solar weather observation capabilities, with 4 times the resolution, 5 times the observation rate, and 3 times the number of spectral bands for Earth observations. GOES-R will also provide unprecedented availability, with less than 120 minutes per year of lost observation time. The Guidance Navigation & Control (GN&C) design requirements to achieve these expanded capabilities are extremely demanding. This paper first presents the pointing control, pointing stability, attitude knowledge, and orbit knowledge requirements necessary to realize the ambitious Image Navigation and Registration (INR) objectives of GOES-R. Because the GOES-R suite of instruments is sensitive to disturbances over a broad spectral range, a high fidelity simulation of the vehicle has been created with modal content over 500 Hz to assess the pointing stability requirements. Simulation results are presented showing acceleration, shock response spectrum (SRS), and line of sight responses for various disturbances from 0 Hz to 512 Hz. These disturbances include gimbal motion, reaction wheel disturbances, thruster firings for station keeping and momentum management, and internal instrument disturbances. Simulation results demonstrate excellent performance relative to the pointing and pointing stability requirements, with line of sight jitter of the isolated instrument platform of approximately 1 micro-rad. Low frequency motion of the isolated instrument platform is internally compensated within the primary instrument. Attitude knowledge and rate are provided directly to the instrument with an accuracy defined by the Integrated Rate Error (IRE) requirements. The allowable IRE ranges from 1 to 18.5 micro-rad, depending upon the time window of interest. The final piece of the INR performance is orbit knowledge. Extremely accurate orbital position is achieved by GPS navigation at Geosynchronous Earth Orbit (GEO). Performance results are shown demonstrating compliance with the 50 to 75 m orbit position accuracy requirements of GOES-R, including during station-keeping and momentum management maneuvers. As shown in this paper, the GN&C performance for the GOES-R series of spacecraft supports the challenging mission objectives of the next generation GEO Earth-observation satellites

    Induced pseudoscalar coupling of the proton weak interaction

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    The induced pseudoscalar coupling gpg_p is the least well known of the weak coupling constants of the proton's charged--current interaction. Its size is dictated by chiral symmetry arguments, and its measurement represents an important test of quantum chromodynamics at low energies. During the past decade a large body of new data relevant to the coupling gpg_p has been accumulated. This data includes measurements of radiative and non radiative muon capture on targets ranging from hydrogen and few--nucleon systems to complex nuclei. Herein the authors review the theoretical underpinnings of gpg_p, the experimental studies of gpg_p, and the procedures and uncertainties in extracting the coupling from data. Current puzzles are highlighted and future opportunities are discussed.Comment: 58 pages, Latex, Revtex4, prepared for Reviews of Modern Physic

    DeltaScan for the Assessment of Acute Encephalopathy and Delirium in ICU and non-ICU Patients, a Prospective Cross-Sectional Multicenter Validation Study

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    Objectives: To measure the diagnostic accuracy of DeltaScan: a portable real-time brain state monitor for identifying delirium, a manifestation of acute encephalopathy (AE) detectable by polymorphic delta activity (PDA) in single-channel electroencephalograms (EEGs). Design: Prospective cross-sectional study. Setting: Six Intensive Care Units (ICU's) and 17 non-ICU departments, including a psychiatric department across 10 Dutch hospitals. Participants: 494 patients, median age 75 (IQR:64-87), 53% male, 46% in ICUs, 29% delirious. Measurements: DeltaScan recorded 4-minute EEGs, using an algorithm to select the first 96 seconds of artifact-free data for PDA detection. This algorithm was trained and calibrated on two independent datasets. Methods: Initial validation of the algorithm for AE involved comparing its output with an expert EEG panel's visual inspection. The primary objective was to assess DeltaScan's accuracy in identifying delirium against a delirium expert panel's consensus. Results: DeltaScan had a 99% success rate, rejecting 6 of the 494 EEG's due to artifacts. Performance showed and an Area Under the Receiver Operating Characteristic Curve (AUC) of 0.86 (95% CI: 0.83-0.90) for AE (sensitivity: 0.75, 95%CI=0.68-0.81, specificity: 0.87 95%CI=0.83-0.91. The AUC was 0.71 for delirium (95%CI=0.66-0.75, sensitivity: 0.61 95%CI=0.52-0.69, specificity: 72, 95%CI=0.67-0.77). Our validation aim was an NPV for delirium above 0.80 which proved to be 0.82 (95%CI: 0.77-0.86). Among 84 non-delirious psychiatric patients, DeltaScan differentiated delirium from other disorders with a 94% (95%CI: 87-98%) specificity. Conclusions: DeltaScan can diagnose AE at bedside and shows a clear relationship with clinical delirium. Further research is required to explore its role in predicting delirium-related outcomes.</p

    DeltaScan for the Assessment of Acute Encephalopathy and Delirium in ICU and non-ICU Patients, a Prospective Cross-Sectional Multicenter Validation Study

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    OBJECTIVES: To measure the diagnostic accuracy of DeltaScan: a portable real-time brain state monitor for identifying delirium, a manifestation of acute encephalopathy (AE) detectable by polymorphic delta activity (PDA) in single-channel electroencephalograms (EEGs). DESIGN: Prospective cross-sectional study. SETTING: Six Intensive Care Units (ICU's) and 17 non-ICU departments, including a psychiatric department across 10 Dutch hospitals. PARTICIPANTS: 494 patients, median age 75 (IQR:64-87), 53% male, 46% in ICUs, 29% delirious. MEASUREMENTS: DeltaScan recorded 4-minute EEGs, using an algorithm to select the first 96 seconds of artifact-free data for PDA detection. This algorithm was trained and calibrated on two independent datasets. METHODS: Initial validation of the algorithm for AE involved comparing its output with an expert EEG panel's visual inspection. The primary objective was to assess DeltaScan's accuracy in identifying delirium against a delirium expert panel's consensus. RESULTS: DeltaScan had a 99% success rate, rejecting 6 of the 494 EEG's due to artifacts. Performance showed and an Area Under the Receiver Operating Characteristic Curve (AUC) of 0.86 (95% CI: 0.83-0.90) for AE (sensitivity: 0.75, 95%CI=0.68-0.81, specificity: 0.87 95%CI=0.83-0.91. The AUC was 0.71 for delirium (95%CI=0.66-0.75, sensitivity: 0.61 95%CI=0.52-0.69, specificity: 72, 95%CI=0.67-0.77). Our validation aim was an NPV for delirium above 0.80 which proved to be 0.82 (95%CI: 0.77-0.86). Among 84 non-delirious psychiatric patients, DeltaScan differentiated delirium from other disorders with a 94% (95%CI: 87-98%) specificity. CONCLUSIONS: DeltaScan can diagnose AE at bedside and shows a clear relationship with clinical delirium. Further research is required to explore its role in predicting delirium-related outcomes

    Thucydides, Sicily, and the Defeat of Athens

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    International audienceThis paper explores the reception of Thucydides’ account of the Athenian defeat in Sicily in 415–413 BC, with a particular focus on the relation between the Sicilian disaster and the final defeat of Athens in 404 BC. It starts with a brief exploration of the fame of Thucydides’ account. It then analyses the reception in later writers of a number of specific Thucydidean motifs: the idea that the Sicilian expedition is an emblem of Athens’ defeat; the use of Persian Wars intertexts; and the possibility that defeat could have been avoided. Finally, it argues that Thucydides’ own emplotment of the Sicilian expedition was destabilised by the transfer of motifs from his work to other wars involving Sicily.Cet article explore la rĂ©ception du rĂ©cit de Thucydide sur la dĂ©faite athĂ©nienne en Sicile en 415- 413 av. J.-C., en insistant sur la relation entre la catastrophe sicilienne et la dĂ©faite finale d’AthĂšnes en 404. Il commence par un bref aperçu de la renommĂ©e du rĂ©cit de Thucydide. Il analyse ensuite la rĂ©ception chez les Ă©crivains postĂ©rieurs d’un certain nombre de motifs thucydidĂ©ens spĂ©cifiques : l’idĂ©e que l’expĂ©dition de Sicile est un symbole de la dĂ©faite d’AthĂšnes, l’utilisation d’allusions littĂ©raires aux guerres mĂ©diques et l’idĂ©e que la dĂ©faite aurait pu ĂȘtre Ă©vitĂ©e. Enfin, il fait valoir que la structure du rĂ©cit de Thucydide sur l’expĂ©dition de Sicile a Ă©tĂ© perturbĂ©e par le transfert de motifs de son oeuvre Ă  d’autres guerres affectant la Sicile

    Thucydides, Sicily, and the Defeat of Athens

    No full text
    This paper explores the reception of Thucydides’ account of the Athenian defeat in Sicily in 415– 413 BC, with a particular focus on the relation between the Sicilian disaster and the final defeat of Athens in 404 BC. It starts with a brief exploration of the fame of Thucydides’ account. It then analyses the reception in later writers of a number of specific Thucydidean motifs : the idea that the Sicilian expedition is an emblem of Athens’ defeat ; the use of Persian Wars intertexts ; and the possibility that defeat could have been avoided. Finally, it argues that Thucydides’ own emplotment of the Sicilian expedition was destabilised by the transfer of motifs from his work to other wars involving Sicily.Cet article explore la rĂ©ception du rĂ©cit de Thucydide sur la dĂ©faite athĂ©nienne en Sicile en 415-413 av. J.-C., en insistant sur la relation entre la catastrophe sicilienne et la dĂ©faite finale d’AthĂšnes en 404. Il commence par un bref aperçu de la renommĂ©e du rĂ©cit de Thucydide. Il analyse ensuite la rĂ©ception chez les Ă©crivains postĂ©rieurs d’un certain nombre de motifs thucydidĂ©ens spĂ©cifiques : l’idĂ©e que l’expĂ©dition de Sicile est un symbole de la dĂ©faite d’AthĂšnes, l’utilisation d’allusions littĂ©raires aux guerres mĂ©diques et l’idĂ©e que la dĂ©faite aurait pu ĂȘtre Ă©vitĂ©e. Enfin, il fait valoir que la structure du rĂ©cit de Thucydide sur l’expĂ©dition de Sicile a Ă©tĂ© perturbĂ©e par le transfert de motifs de son oeuvre Ă  d’autres guerres affectant la Sicile.Rood Tim. Thucydides, Sicily, and the Defeat of Athens. In: KtĂšma : civilisations de l'Orient, de la GrĂšce et de Rome antiques, N°42, 2017. pp. 19-39
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