976,484 research outputs found

    Presenting Schur superalgebras

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    We provide a presentation of the Schur superalgebra and its quantum analogue which generalizes the work of Doty and Giaquinto for Schur algebras. Our results include a basis for these algebras and a presentation using weight idempotents in the spirit of Lusztig's modified quantum groups.Comment: 28 pages, to appear in the Pacific Journal of Mathematic

    A self-mobile skeleton in the presence of external loads

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    Multicore clusters provide cost-effective platforms for running CPU-intensive and data-intensive parallel applications. To effectively utilise these platforms, sharing their resources is needed amongst the applications rather than dedicated environments. When such computational platforms are shared, user applications must compete at runtime for the same resource so the demand is irregular and hence the load is changeable and unpredictable. This thesis explores a mechanism to exploit shared multicore clusters taking into account the external load. This mechanism seeks to reduce runtime by finding the best computing locations to serve the running computations. We propose a generic algorithmic data-parallel skeleton which is aware of its computations and the load state of the computing environment. This skeleton is structured using the Master/Worker pattern where the master and workers are distributed on the nodes of the cluster. This skeleton divides the problem into computations where all these computations are initiated by the master and coordinated by the distributed workers. Moreover, the skeleton has built-in mobility to implicitly move the parallel computations between two workers. This mobility is data mobility controlled by the application, the skeleton. This skeleton is not problem-specific and therefore it is able to execute different kinds of problems. Our experiments suggest that this skeleton is able to efficiently compensate for unpredictable load variations. We also propose a performance cost model that estimates the continuation time of the running computations locally and remotely. This model also takes the network delay, data size and the load state as inputs to estimate the transfer time of the potential movement. Our experiments demonstrate that this model takes accurate decisions based on estimates in different load patterns to reduce the total execution time. This model is problem-independent because it considers the progress of all current computations. Moreover, this model is based on measurements so it is not dependent on the programming language. Furthermore, this model takes into account the load state of the nodes on which the computation run. This state includes the characteristics of the nodes and hence this model is architecture-independent. Because the scheduling has direct impact on system performance, we support the skeleton with a cost-informed scheduler that uses a hybrid scheduling policy to improve the dynamicity and adaptivity of the skeleton. This scheduler has agents distributed over the participating workers to keep the load information up to date, trigger the estimations, and facilitate the mobility operations. On runtime, the skeleton co-schedules its computations over computational resources without interfering with the native operating system scheduler. We demonstrate that using a hybrid approach the system makes mobility decisions which lead to improved performance and scalability over large number of computational resources. Our experiments suggest that the adaptivity of our skeleton in shared environment improves the performance and reduces resource contention on nodes that are heavily loaded. Therefore, this adaptivity allows other applications to acquire more resources. Finally, our experiments show that the load scheduler has a low incurred overhead, not exceeding 0.6%, compared to the total execution time

    EXAMINING READING-RELATED TEACHER EDUCATION AMONG TEACHERS OF STUDENTS WITH LEARNING DISABILITIES IN SAUDI ARABIA

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    The purpose of this study was to examine the relationship between reading-related training (university courses and professional development beyond university training) and the implementation of reading instruction among teachers of students with LD in Saudi schools. A survey was sent to both male and female teachers of students with LD (N = 2158) in Saudi schools, asking them about their demographic information, reading-related courses, reading- related professional development activities, and their implementation of reading instruction in their classroom. A multiple regression analysis was conducted to examine the correlation between teachers’ reading-related training and their implementation of 17 reading practices for students with LD. The results indicated that teachers’ reading-related training was significantly related to their implementation of ten reading practices. The implications and recommendations for future research, policy, and practice are discussed

    Flow and Distribution of Water in Fractional Wettability Unsaturated Porous Media

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    In recent years, interest in fluid flow and transport in the unsaturated zone has gained more attention, due to growing concerns that the quality of the subsurface environment is adversely affected by agricultural, industrial, and municipal activities. The wettability properties (e.g., water repellency) of soil in the unsaturated zone play an important role in determining fluid movement and ultimate distributions. A number of studies have shown that preferential flow and spatially variable moisture content is likely to occur in water repellant soils. Development of appropriate constitutive relations for numerical modeling becomes even more difficult in systems that contain water repellant soils. First, flow through fractionally-wet systems often follows preferential flow paths. Preferential flow can result in fast and deep infiltration of water and may impact solute and colloid/virus transport and plant growth. Second, it is difficult to incorporate pore- and centimeter-scale processes that result in irregular water flow and distribution during and following drainage. The resulting small-scale heterogeneities may impact subsequent infiltration and evaporation/volatilization processes. In this research, mm- and cm-scale capillary pressure¡Vwater content experiments and computed x-ray microtomography (CMT) were used to obtain quantitative data describing drainage and the irreducible water distribution in fractionally-wet systems. The findings from this research showed that wettability and pore-size distribution affected the capillary pressure-water content relationship in uniform and well-graded sand. As expected, an increase in the fractional wettability caused a decrease in the air entry pressure for all the sands tested. As the fractionally wettability increased, the slope of the capillary pressure-water content became steeper for the uniform sands and shallower for the well-graded sand. Comparison of mm- and cm-scale drainage capillary pressure-water content experiments showed that columns designed for CMT experiments can be used for low values of fractional wettability (less than 25%). CMT was successfully used to image the heterogeneous distribution of water during and following drainage; water content values obtained from the images when combined with the corresponding capillary pressure head values matched the laboratory experimental data. Finally, CMT was shown to be a highly effective technique to quantitatively characterize ƒÝm-scale grain, pore, and fluid properties

    Private Supplementary Tutoring in Turkey Recent Evidence on Its Various Aspects

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    This paper first describes the educational system in Turkey and the two national examinations for advancing upper levels of schooling which give raise to the demand for private tutoring called “dersane” in Turkish. Second, the evolution of the Private tutoring Centers (PTC) are described and compared with the high schools in the country. Third, geographical distribution of the PTC, general high schools and the proportion of high school age population are compared over the provinces to give an idea about special equity issues. Other topics addressed include gender and PTC students, disruption of mainstream education, determinants of the demand for services of the PTCs, cost of PTCs and evidence on the effectiveness of PTCsPrivate Tutoring, Education, Demand for Education

    A model for characterising the collective dynamic behaviour of evolutionary algorithms

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    Exploration and exploitation are considered essential notions in evolutionary algorithms. However, a precise interpretation of what constitutes exploration or exploitation is clearly lacking and so are specific measures for characterising such notions. In this paper, we start addressing this issue by presenting new measures that can be used as indicators of the exploitation behaviour of an algorithm. These work by characterising the extent to which available information guides the search. More precisely, they quantify the dependency of a population's activity on the observed fitness values and genetic material, utilising an empirical model that uses a coarse-grained representation of population dynamics and records information about it. The model uses the k-means clustering algorithm to identify the population's "basins of activity". The exploitation behaviour is then captured by an entropy-based measure based on the model that quantifies the strength of the association between a population's activity distribution and the observed fitness landscape information. In experiments, we analysed the effects of the search operators and their parameter settings on the collective dynamic behaviour of populations. We also analysed the effect of using different problems on algorithm behaviours.We define a behavioural landscape for each problem to identify the appropriate behaviour to achieve good results and point out possible applications for the proposed model
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