CLATHRATE HYDRATE FORMATION ENHANCES NEAR-CRITICAL AND SUPERCRITICAL SOLVENT EXTRACTION EQUILIBRIA

Pre-concentration of dilute aqueous solutions by hydrate formation can improve the effective distribution coefficient and selectivity of solvent extraction. Many solvents can serve simultaneously to promote solution concentration by hydrate formation and also to extract non-polar solutes from the resulting concentrated solution. This concept is illustrated for systems with supercritical ethylene and with near-critical liquid carbon dioxide, and its application to conventional solvents is discussed.     

15 years of processing and dissemination of SPOT-VEGETATION products

Throughout the VEGETATION programme, the Flemish Institute for Technological Research (VITO) uninterruptedly hosted the prime user segment of both VEGETATION 1 and VEGETATION 2 multispectral instruments on board the Satellite Pour l’Observation de la Terre 4 (SPOT 4) and SPOT 5 satellites. Operational since the launch of SPOT 4 in March 1998, and foreseen to continue at least until the end of the SPOT 5 mission (anticipated in spring 2014), this user segment comprises a processing facility (PF), actively receiving, processing, correcting, archiving, and distributing the VEGETATION data and derived added-value products. First and foremost, the VEGETATION programme has been serving the needs of operational users – both institutional and commercial – requesting data in near-real time. However, scientific and educational users too benefited significantly, in particular from VEGETATION’s unique time series of the Earth’s land cover, and more specifically the vegetation cover. Over the years, the centralized archive houses processed data covering the equivalent of 11,000 times the Earth’s surface, and delivered more than 50 terapixels to around 10.000 users. As such, VEGETATION’s mission is a prime example of what Europe wants to achieve through the Global Monitoring for Environment and Security (GMES) initiative: truly operational services providing reliable and up-to-date information.

This article describes the processing facility, the way the data and products are archived, the different dissemination channels as well as the data policy adopted and the users served. One of the recent evolutions, the development of an entirely new product distribution facility (PDF), implemented as part of the Project for On-Board Autonomy – Vegetation (PROBA-V) user segment is discussed.     

Heavy-fuel flame radiation in gas turbine combustors—exploratory results

With lower costs and greater availability, heavy fuel oil appears as an attractive alternative to the conventional gas oil used in industrial gas turbines. However, higher levels of radiation and smoke are expected, and this note reports on some preliminary tests made with a combustion chamber burning fuels of different carbon content, ranging from kerosine to a 25% blend of residual fuel oil in gas oil, at a chamber pressure of 10 atm^*. The combustion rig was equipped with a total-radiation pyrometer and black-body furnace capable of measurement at different axial stations along the spray-stabilized flame. The presence of the residual fuel oil in the gas oil was found to promote significant increases in the mean levels of radiation, emissivity and smoke density, with a modest increase in liner temperature.     

Microstructure and its relationship to deformation processes in amorphous polymer glasses

The microdeformation morphology of a number of vinyl polymers with bulky side chains (type I) and arylene polymers with flexible oxygen linkages (type II) was studied by electron microscopy. The polyarylenes crazed only near the glass transition while the polyvinyls exhibited a crazing regime that extended to liquid nitrogen temperatures. In addition significantly less plastic strain was localized in type II glass crazes relative to those in type I glasses. In compatible blends of polystyrene (PS) and 2,6-dimethyl poly(phenylene oxide) (2MPPO), ca. 30% 2MPPO was sufficient to induce a transition from type I to type II crazing behavior. Small amounts of PS suppressed the low-temperature 2MPPO β relaxation but enhanced the intermediate transition of 2MPPO at higher temperatures. Blending increased the conformational energy of the 2MPPO chain and improved interchain packing. The propensity for the polymer glass to form sharp shear bands at the expense of diffuse bands was increased by a decrease in the conformation energy of the polymer chain and an improvement in the glassy state packing.     

Intrinsic reactivity of gold nanoparticles: Classical, semi-empirical and DFT studies

Gold nanoparticles used in most experiments (1–10 nm) in gold catalysis show varying degrees of reactivity, with particles below 5 nm generally being more reactive. The origin of this activity is a subject of a number of model experiments and theoretical studies on either clusters of a few atoms in size or extended surfaces (smooth or stepped). In the work described here, a classical theory for the variation of the metal workfunction with cluster size, Extended Hückel Theory (EHT) calculations combined with DFT calculations, as well as a carbon monoxide (CO) chemisorption model are combined to develop a relationship between metal particle size and the particle's reactivity towards CO. For gold, it is shown that while the contribution of the d-band hybridization energy to the total CO chemisorption energy is unfavourable for bulk gold, this is not true for gold particles below 5–6 nm. That is, the d-band hybridization energy is negative for small gold particles. This is believed to be explanation of the onset of high reactivity for small gold particles.     

A high temperature apparatus for measurement of the Seebeck coefficient

A high temperature Seebeck coefficient measurement apparatus with various features to minimize typical sources of error is designed and built. Common sources of temperature and voltage measurement error are described and principles to overcome these are proposed. With these guiding principles, a high temperature Seebeck measurement apparatus with a uniaxial 4-point contact geometry is designed to operate from room temperature to over 1200 K. This instrument design is simple to operate, and suitable for bulk samples with a broad range of physical types and shapes.     

Wetland change mapping for the U.S. mid-Atlantic region using an outlier detection technique

Although the impacts of wetland loss are often felt at regional scales, effective planning and management require a comparative assessment of local needs, costs, and benefits. Satellite remote sensing can provide spatially explicit, synoptic land cover change information to support such an assessment. However, a common challenge in conventional remote sensing change detection is the difficulty of obtaining phenologically and radiometrically comparable data from the start and end of the time period of interest. An alternative approach is to use a prior land cover classification as a surrogate for historic satellite data and to examine the self-consistency of class spectral reflectances in recent imagery. We produced a 30-meter resolution wetland change probability map for the U.S. mid-Atlantic region by applying an outlier detection technique to a base classification provided by the National Wetlands Inventory (NWI). Outlier-resistant measures – the median and median absolute deviation – were used to represent spectral reflectance characteristics of wetland class populations, and formed the basis for the calculation of a pixel change likelihood index. The individual scene index values were merged into a consistent region-wide map and converted to pixel change probability using a logistic regression calibrated through interpretation of historic and recent aerial photography. The accuracy of a regional change/no-change map produced from the change probabilities was estimated at 89.6%, with a Kappa of 0.779. The change probabilities identify areas for closer inspection of change cause, impact, and mitigation potential. With additional work to resolve confusion resulting from natural spatial heterogeneity and variations in land use, automated updating of NWI maps and estimates of areal rates of wetland change may be possible. We also discuss extensions of the technique to address specific applications such as monitoring marsh degradation due to sea level rise and mapping of invasive species.     

Mediating Power: Distance Learning Interfaces, Classroom Epistemology, and the Gaze

Distance learning's interfaces—from corresponding through the postal service to the televised talking head—have traditionally been designed from the top down, supporting banking models of learning or, in writing instruction, current-traditional rhetoric pedagogies. Due to temporal and spatial constraints, these interface designs often support (or encourage) one-way communication from the instructor to the student. Students mostly interact with the instructor by asking questions or submitting work, and they tend to have little correspondence with other peers. These methods clearly privilege the instructor's knowledge and evaluation. Furthermore, these interface designs empower the instructor to gaze upon the students and assess them—often not as a corporeal body but as a corpus of texts. Thus, each interface adopted for distance learning sets up a power dynamic in which the capability to share the roles of creating knowledge is juxtaposed with the instructor's capability to normalize the students and reify their own authority through their gaze. In this article we examine the traditional classroom interface through the correspondence course interface, the simulated classroom interface, and the synchronous video interface to raise questions about the infrastructures of distance learning and their implications for student learning.     

On the estimation of adequate test set size using fault failure rates

Test set size in terms of the number of test cases is an important consideration when testing software systems. Using too few test cases might result in poor fault detection and using too many might be very expensive and suffer from redundancy. We define the failure rate of a program as the fraction of test cases in an available test pool that result in execution failure on that program. This paper investigates the relationship between failure rates and the number of test cases required to detect the faults. Our experiments based on 11 sets of C programs suggest that an accurate estimation of failure rates of potential fault(s) in a program can provide a reliable estimate of adequate test set size with respect to fault detection and should therefore be one of the factors kept in mind during test set construction. Furthermore, the model proposed herein is fairly robust to incorrect estimations in failure rates and can still provide good predictive quality. Experiments are also performed to observe the relationship between multiple faults present in the same program using the concept of a failure rate. When predicting the effectiveness against a program with multiple faults, results indicate that not knowing the number of faults in the program is not a significant concern, as the predictive quality is typically not affected adversely.