3,938 research outputs found

    The design of efficient air pollution control strategies

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    This statement addresses gains in economic efficiency which could be obtained by removing barriers to advances in the technology and procedures commonly used for designing air pollution abatement strategies

    Hommage à Dali

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    An Objective Analysis Technique for Constructing Three-Dimensional Urban-Scale Wind Fields

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    An objective analysis procedure for generating mass-consistent, urban-scale three-dimensional wind fields is presented together with a comparison against existing techniques. The algorithm employs terrain following coordinates and variable vertical grid spacing. Initial estimates of the velocity field are developed by interpolating surface and upper level wind measurements. A local terrain adjustment technique, involving solution of the Poisson equation, is used to establish the horizontal components of the surface field. Vertical velocities are developed from successive solutions of the continuity equation followed by an iterative procedure which reduces anomalous divergence in the complete field. Major advantages of the procedure are that it is computationally efficient and allows boundary values to adjust in response to changes in the interior flow. The method has been successfully tested using field measurements and problems with known analytic solutions

    Post-Exposural Eye Movements and Lateral Differences in Tachistoscopic Recognition

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    Left-right differences in visual field accuracy obtained in studies of tachistoscopic recognition have been typically discussed in terms of a covert post exposure scanning process derived from the horizontal eye movements (EM) habitually used in reading. Further, some evidence exists that indicates the occurrence of EM concomitant with the recognition process. By monitoring EM during a representative recognition task, the present study attempted to establish the relation between overt EM elicited by the task, and response accuracy. Using a projection tachistoscope (duration 100 msec.), 8 female Ss were presented with a random trial series of 8-element letter, number, and symbol arrays exposed bilaterally, and 4 letter arrays exposed unilaterally. In a second trial series, bilateral and unilateral letter arrays were presented at a 1 sec. duration. A high resolution corneal reflection technique was used to detect the latency and direction of EM. The pattern of recognition accuracy for alphanumeric stimuli generally conformed to the results of previous investigations based on grouped data. Marked individual variation was noted in the present results, suggesting a source of variability worthy of analysis. Response accuracy obtained for symbol arrays was highly variable and demonstrated a lack of lateral disparity, indicating an unstructured encoding process for this material. The post exposure EM was established as a reliable phenomenon, identical in topography to the EM evoked with the stimulus present. However, the EM behaviour did not relate to recognition accuracy, a result that does not limit the use of reading EM as a model for the scanning process. Rather, the lack of relation does indicate that overt EM are not involved in that process. Further implications of the EM and recognition results for theory and future research are discussed in detail

    Temperature Dependence of the Retention of Organic Fines Using a Cationic Retention Aid

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    Stock of 50:50 bleached Kraft softwood and hardwood run through the Valley beater at 350 CSF with high fines content (25-30% fines from softwood and hardwood fractions run through a Wiley mill) was prepared and tested for fines fractionation, fines retention, and system surface charge at 10, 25, 40, and 55°C using a Dow Chemical cationic polymer of 1,000,000 molecular weight: SEPARAN CP-7. The Britt Dynamic Drainage Jar was used for fines fractionation and retention data and Halabisky\u27s Colloid Titration Technique for surface charge data. Cationic polymer loadings were taken at 0.25, 0.50, and 0.75 pounds of polymer per ton of paper produced (pulp present). Rotor or agitation speed for retention determinations was held constant at 1000 rpm. Surface charge reagents were not diluted (5X) as suggested by Halabisky. Fines fractionation decreased on rising temperature to show increased fines to fiber attraction. An increase in SEPARAN CP-7 loading increased fines retention though instabilities existed below room temperature. The optimum retention temperature was around 40°C then fell off from there while there was no point of diminishing returns on retention with loading. Because of strong polymer-temperature interactions, may unexpected charge decreases and charge inversions appeared upon cationic loading increases through data error was very high. Extensive temperature range; pH; polymer molecular weight, combination, and charge nature; stock alteration; filler; and agitation effects were suggested as important parameters to research in terms of temperature effects of fine and filler retention and surface charge

    Giant Electron-hole Charging Energy Asymmetry in Ultra-short Carbon Nanotubes

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    Making full usage of bipolar transport in single-wall carbon nanotube (SWCNT) transistors could permit the development of two-in-one quantum devices with ultra-short channels. We report on clean ∼\sim10 to 100 nm long suspended SWCNT transistors which display a large electron-hole transport asymmetry. The devices consist of naked SWCNT channels contacted with sections of SWCNT-under-annealed-gold. The annealed gold acts as an n-doping top gate which creates nm-sharp barriers at the junctions between the contacts and naked channel. These tunnel barriers define a single quantum dot (QD) whose charging energies to add an electron or a hole are vastly different (e−he-h charging energy asymmetry). We parameterize the e−he-h transport asymmetry by the ratio of the hole and electron charging energies ηe−h\eta_{e-h}. We show that this asymmetry is maximized for short channels and small band gap SWCNTs. In a small band gap SWCNT device, we demonstrate the fabrication of a two-in-one quantum device acting as a QD for holes, and a much longer quantum bus for electrons. In a 14 nm long channel, ηe−h\eta_{e-h} reaches up to 2.6 for a device with a band gap of 270 meV. This strong e−he-h transport asymmetry survives even at room temperature

    Semantic Integration Portal

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    The Semantic Integration Portal is a demonstration of the potential capabilities of Semantic Web applications in a knowledge-rich context. Source data is taken from different online terrorist incident aggregators and marked up according to ontologies specific to those domains. Unlike other semantic web techniques, which scrape the internet for raw data and then mark-up against a standard ontology, the approach here is to allow each data source to have its own domain-specific ontology. This allows the data producers the opportunity to mark up their data in their own way, producing RDF data according to their own ontologies without the need to conform to a standard. A variety of semantic integration techniques can then be applied to these ontologies, both automatic and interactive, allowing data from both sets to be viewed in a suitable application, in this case the mspace browser. Future iterations of the semantic integration portal aim to introduce more automated ontology-mapping techniques, aligning data from a variety of diverse sources with less need for human intervention
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