A Generic Framework for Criterion-Referenced Assessment of Undergraduate Essays

This paper presents a brief review of the relative merits of norm-referenced and criterion-referenced assessment of undergraduate students' written work. Acknowledging that there are both positive and negative aspects of criterion referencing, a generic framework for such assessment of undergraduate essays is presented. It comprises criteria and standards (organised by `dimensions of achievement', i.e. content, process, affect and skills), proficiency standards for English language and communication competence, and cartographic and graphic skills. Problems of implementation include the size and complexity of the framework and the need to interpret and clarify the criteria and standards for students

Propagating Disturbances in Coronal Loops: A Detailed Analysis of Propagation Speeds

Quasi-periodic disturbances have been observed in the outer solar atmosphere for many years now. Although first interpreted as upflows (Schrijver et al. (1999)), they have been widely regarded as slow magnetoacoustic waves, due to observed velocities and periods. However, recent observations have questioned this interpretation, as periodic disturbances in Doppler velocity, line width and profile asymmetry were found to be in phase with the intensity oscillations (De Pontieu et al. (2010),Tian1 et al. (2011))}, suggesting the disturbances could be quasi-periodic upflows. Here we conduct a detailed analysis of the velocities of these disturbances across several wavelengths using the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). We analysed 41 examples, including both sunspot and non sunspot regions of the Sun. We found that the velocities of propagating disturbances (PDs) located at sunspots are more likely to be temperature dependent, whereas the velocities of PDs at non sunspot locations do not show a clear temperature dependence. We also considered on what scale the underlying driver is affecting the properties of the PDs. Finally, we found that removing the contribution due to the cooler ions in the 193 A wavelength suggests that a substantial part of the 193 emission of sunspot PDs can be contributed to the cool component of 193\AA.Comment: 26 Papges, 15 Figure

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

An infrared sea surface temperature autonomous radiometer (ISAR) for deployment aboard Volunteer Observing Ships (VOS)

The infrared SST autonomous radiometer (ISAR) is a self-calibrating instrument capable of measuring in situ sea surface skin temperature (SSTskin) to an accuracy of 0.1 K. Extensive field deployments alongside two independent research radiometers measuring SSTskin using different spectral and geometric configurations show that, relatively, ISAR SSTskin has a zero bias ±0.14 K rms. The ISAR instrument has been developed for satellite SST validation and other scientific programs. The ISAR can be deployed continuously on voluntary observing ships (VOS) without any service requirement or operator intervention for periods of up to 3 months. Five ISAR instruments have been built and are in sustained use in the United States, China, and Europe. This paper describes the ISAR instrument including the special design features that enabled a single channel radiometer with a spectral bandpass of 9.6–11.5 ?m to be adapted for autonomous use. The entire instrument infrared optical path is calibrated by viewing two blackbody reference cavities at different temperatures to maintain high accuracy while tolerating moderate contamination of optical components by salt deposition. During bad weather, an innovative storm shutter, triggered by a sensitive optical rain gauge, automatically seals the instrument from the external environment. Data are presented that verify the instrument calibration and functionality in such situations. A watchdog timer and auto-reboot function support automatic data logging recovery in case of power outages typically encountered on ships. An RS485 external port allows supporting instruments that are not part of the core ISAR package (e.g., a solarimeter) to be logged using the ISAR system. All data are processed by the ISAR instrument and are relayed to a host computer via the RS232 serial link as (National Electronics Manufacturers Association) NEMA-style strings allowing easy integration into many commercial onboard scientific data logging systems. In case of a communications failure, data are stored on board using a CompactFlash card that can be retrieved when the instrument is serviced. The success of the design is demonstrated using results obtained over 21 months in the English Channel and Bay of Biscay as part of a campaign to validate SSTskin observations derived from the Environmental Satellite (Envisat) Advanced Along-Track Scanning Radiometer (AATSR).<br/

Towards Improved Validation of Satellite Sea Surface Skin Temperature Measurements for Climate Research.

Abstract not availableJRC.(SAI)-Space Application Institut

The thermal performance of fuel matrix material in a CO2 atmosphere

The thermal oxidation performance of a semi-graphitic fuel matrix-material has been compared to two grades of nuclear graphite between 600 C and 1200 C in flowing CO2. Fuel matrix material is used to produce compacts or pebbles containing TRISO coated particle fuel for High Temperature Reactors (HTRs). The A3-27 fuel matrix-material grade was compared to NBG-18 and Gilsocarbon nuclear graphite grades. At 1200 C temperatures A3-27 appears to be more reactive than NBG-18, but less so than Gilsocarbon. At 600 C the oxidation rate of A3-27 is comparable to that of NBG-18, but both are significantly higher than that of Gilsocarbon. It is concluded that the comparable thermal oxidation behaviour of graphite and fuel-matrix material suggests that operating temperatures in a CO2 cooled reactor fuelled with TRISO coated particle fuel would not need to be reduced below those considered acceptable for the use of nuclear graphite. © 2013 The Authors. Published by Elsevier B.V. All rights reserved

The Miami2001 Infrared Radiometer Calibration and Intercomparison. I - Laboratory Characterization of Blackbody Targets

The second calibration and intercomparison of infrared radiometers (Miami2001) was held at the University of Miami's Rosenstiel School of Marine and Atmospheric Science (RSMAS) during May-June 2001. The participants were from several groups involved with the validation of skin sea surface temperatures and land surface temperatures derived from the measurements of imaging radiometers on earth observation satellites. These satellite instruments include those currently on operational satellites and others that will be launched within two years following the workshop. There were two experimental campaigns carried out during the 1-week workshop: a set of measurements made by a variety of ship-based radiometers on board the Research Vessel F. G. Walton Smith in Gulf Stream waters off the eastern coast of Florida, and a set of laboratory measurements of typical external blackbodies used to calibrate these ship-based radiometers. This paper reports on the results obtained from the laboratory characterization on blackbody sources. A companion paper reports on the at-sea measurements. Five blackbody sources were intercompared by measurements of their brightness temperature using the National Institute of Standards and Technology (NIST) Thermal-infrared Transfer Radiometer (TXR). Four of these sources are used for calibration of sea surface temperature radiometers. The fifth was a NIST water bath blackbody used for calibration of the TXR. All blackbodies agreed to better than +/- 0.1 C at blackbody temperatures near the ambient room temperature. Some of the blackbodies had reduced effective emissivity relative to the NIST water bath blackbody, and hence they began to disagree at blackbody temperatures far enough away ( > 15 C) from the ambient room temperature. For these, relative effective emissivity values were determined so that corrections can be applied if they are used in conditions of nonlaboratory ambient temperatures