Shock reflection and surface effects in the shock tube

A thin-film resistance thermometer, mounted on the end-wall of a shock tube, is used to record surface temperatures and heat transfer rates following reflection of the primary shock wave. This information is combined with the results of theoretical investigations to produce simultaneous information about surface accommodation effects and gas thermal conductivities at high pressures and moderate temperatures

Is anaphoric resolution instruction more effective than existing instruction at improving the reading comprehension achievement of secondary students with poor reading comprehension?

This study examined the effect of teaching anaphoric resolution skills on the reading comprehension of Year 10 students with poor reading comprehension. Two direct teaching programmes, an anaphoric resolution programme (A.R.Programme) and a reading comprehension skills programme based on the Unit curriculum objectives of the Ministry of Education of Western Australia (U.C. Programme), were developed and taught to two groups of eleven Year 10 poor reading comprehenders. The two groups were pretested and posttested for anaphoric resolution skill and reading comprehension achievement, and the increases in mean scores were compared for significant differences using Analysis of Variance (ANOVA). The Anova results showed that the A.R. Programme was significantly more effective at increasing both anaphoric resolution skill and reading comprehension achievement. After consideration of limitations these results are tentatively accepted

A preliminary experimental investigation of the effect of surface catalytic efficiency on stagnation point heat transfer

Results of an experimental investigation to measure the difference between the heat transfer rate to a catalytic wall and to a non-catalytic wall are presented. Using thin film thermometer techniques, associated with an electrical analogue, direct measurement was made of the heat transfer rate to a chemically deposited platinum film and a vacuum evaporated silicon monoxide film. These films were formed near the stagnation point of a pyrex glass sphere and the experiments were done in the College of Aeronautics shock tube. The models were designed so that the heat transfer rates were measured under identical flow conditions. The results obtained indicate that the heat transfer rate to the platinum film is significantly higher than the heat transfer rate to the silicon monoxide film

Gap and Stand Dynamics of a Southern Appalachian Spruce-Fir Forest

Southern Appalachian spruce-fir forest dynamics were investigated by field studies and computer simulations. Mechanisms of old-growth stand dynamics were determined in a Great Smoky Mountains spruce-fir forest (elev. 1770-1830 m). The possible effects of anthropogenic disturbances on the mature forest were investigated with a gap model adapted to upper spruce-fir zone forests. An analysis of stand dynamics involved the study of population interactions in the context of gap phase dynamics. Tree population structure and dispersion were quantified. Regeneration requirements and canopy-understory interactions were determined. Canopy turnover was modeled using species-by-species gap phase tree replacement probabilities. Finally, a spatial gap model was developed to simulate compositional and structural dynamics of a forest stand The old-growth forest is comprised of stable, all-aged spruce and fir populations. Fir is more abundant than spruce, but spruce dominates the forest because of its relatively long life span and large size. Shade tolerant spruce and fir saplings, regenerated in advance, are highly successful invaders of canopy gaps created by tree fall. Fir captures a large proportion of gaps regardless of gap maker species. It is successful because of its high regeneration and growth rates. The canopy residence time of fir, however, is relatively short. Birch and other hardwoods are maintained by gap phase regeneration resulting in occasional gap capture. Simulated balsam woolly aphid infestation results in a spruce dominated forest. In the absence of fir, stand biomass recovery is slow and total stand density is reduced. A moderately severe spruce growth decline in the presence of an undisturbed fir population results in a fir-birch forest. In association with a fir population decline the effects of spruce growth stress are diminished. The contemporaneous decline of spruce and fir populations results in a hardwood dominated forest with low total stand biomass. The old-growth forest is close to equilibrium composition. As a consequence of small disturbance patch size, forest composition, biomass and structure are relatively constant over a small landscape area. This degree of equilibrium is unique among spruce-fir forests of eastern North America

On some aspects of the noise propagation from supersonic aircraft

The noise problem associated with an aircraft flying at supersonic speeds is shown to depend primarily on the shock wave pattern formed by the aircraft. The noise intensity received by a ground observer from a supersonic aircraft flying at high as well as low altitudes, is shown to be high although it is of a transient nature. Continues

Air Traffic Control Operating Modes and the Management of Complexity

This report describes research exploring the relationship between structure and cognitive complexity in Air Traffic Control (ATC). Current work on structure and cognitive processes in ATC is reviewed leading to an ATC process model. Based on observations of the performance of the ATC system it appears that air traffic controllers have the ability to manipulate structure and structure-based abstractions in order to regulate the complexity of an ATC situation. The management of complexity has been integrated into the Controller Process Model through a Complexity Manager. It is hypothesized that the Complexity Manager operates by commanding switches between operating modes. In order to explore whether these operating modes can be observed in a simple ATC task, an experiment was designed. Participants were given scenarios with varying traffic levels. Their commands and their performance have been collected and analyzed. The experimental results show participants appeared to use each of the hypothesized operating modes. The use of the structure in each mode was also as expected

Monotone Regression: A Simple and Fast O(n) PAVA Implementation

Efficient coding and improvements in the execution order of the up-and-down-blocks algorithm for monotone or isotonic regression leads to a significant increase in speed as well as a short and simple O(n) implementation. Algorithms that use monotone regression as a subroutine, e.g., unimodal or bivariate monotone regression, also benefit from the acceleration. A substantive comparison with and characterization of currently available implementations provides an extensive overview of up-and-down-blocks implementations for the pool-adjacent-violators algorithm for simple linear ordered monotone regression

Compression of tetrahedrally bonded SiO2 liquid and silicate liquid‐crystal density inversion

We have investigated the response to pressure of liquid SiO2 by performing a quantitatively realistic Monte Carlo simulation. The model liquid was restricted to at most four‐fold Si‐O coordination by the effective imposition of an infinite potential barrier to a fifth bond. We thus obtained an unambiguous comparison of the compression mechanisms of solid and liquid tetrahedral networks. In spite of this restriction, the density of the simulated liquid exceeds that of the corresponding models of quartz, coesite and cristobalite at high pressure. The efficient compression of the liquid results from a continuous restructuring of the network that leaves the mean Si‐Si distance virtually unchanged and does not require an increase in the coordination number. The restructuring is effected by local breaking and reconnecting of bonds, a mechanism that is not available to a perfect crystal

Visualising the structure of document search results: A comparison of graph theoretic approaches

This is the post-print of the article - Copyright @ 2010 Sage PublicationsPrevious work has shown that distance-similarity visualisation or ‘spatialisation’ can provide a potentially useful context in which to browse the results of a query search, enabling the user to adopt a simple local foraging or ‘cluster growing’ strategy to navigate through the retrieved document set. However, faithfully mapping feature-space models to visual space can be problematic owing to their inherent high dimensionality and non-linearity. Conventional linear approaches to dimension reduction tend to fail at this kind of task, sacrificing local structural in order to preserve a globally optimal mapping. In this paper the clustering performance of a recently proposed algorithm called isometric feature mapping (Isomap), which deals with non-linearity by transforming dissimilarities into geodesic distances, is compared to that of non-metric multidimensional scaling (MDS). Various graph pruning methods, for geodesic distance estimation, are also compared. Results show that Isomap is significantly better at preserving local structural detail than MDS, suggesting it is better suited to cluster growing and other semantic navigation tasks. Moreover, it is shown that applying a minimum-cost graph pruning criterion can provide a parameter-free alternative to the traditional K-neighbour method, resulting in spatial clustering that is equivalent to or better than that achieved using an optimal-K criterion

Diagnostic accuracy of chest radiograph interpretation by graduate radiographers in Uganda

Background. Radiographers are increasingly being called on to take on new roles, such as X-ray film interpretation in imaging departments. In Uganda, where this study was conducted, there are just >40 radiologists in a population of ~40 million. In many hospitals, especially in rural areas, clinicians often rely on radiographers to obtain an opinion to assist with proper patient  management. Therefore, Ugandan radiographers are being trained in basic radiographic interpretation to address the shortage of radiologists. Objective. To determine the diagnostic accuracy of graduate radiographers in interpreting chest radiographs. Methods. This was a cross-sectional retrospective study involving 57 graduate radiographers who were provided with 53 randomly selected chest radiographs to interpret. The validation of a radiographer’s interpretation of a radiograph was aided by the opinion of two senior radiologists. SPSS version 25 software (IBM Corp, USA) was used to analyse the findings and the radiographer’s performance was assessed using the receiver operating characteristic (ROC). The mean abnormality location sensitivity, overall radiographer sensitivity, specificity and false-positive rates were calculated. Results. The radiographers’ diagnostic accuracy was high. The abnormality location sensitivity was 88.7%, overall sensitivity 76.6%, specificity 79.7% and false-positive rate 20.1%. Conclusion. The study demonstrated that radiographers, if trained, can accurately report on chest radiographs to an acceptable  standard