953 resultados para Field Theories in Lower Dimensions
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We investigate the design of electronic dispersion compensation (EDC) using full optical-field reconstruction in 10Gbit/s on-off keyed transmission systems limited by optical signal-to-noise ratio (OSNR). By effectively suppressing the impairment due to low- frequency component amplification in phase reconstruction, properly designing the transmission system configuration to combat fiber nonlinearity, and successfully reducing the vulnerability to thermal noise, a 4.8dB OSNR margin can be achieved for 2160km single-mode fiber transmission without any optical dispersion compensation. We also investigate the performance sensitivity of the scheme to various system parameters, and propose a novel method to greatly enhance the tolerance to differential phase misalignment of the asymmetric Mach-Zehnder interferometer. This numerical study provides important design guidelines which will enable full optical-field EDC to become a cost-effective dispersion compensation solution for future transparent optical networks.
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Signal resolution in H NMR is limited primarily by multiplet structure. Recent advances in pure shift NMR, in which the effects of homonuclear couplings are suppressed, have allowed this limitation to be circumvented in 1D NMR, gaining almost an order of magnitude in spectral resolution. Here for the first time an experiment is demonstrated that suppresses multiplet structure in both domains of a homonuclear two-dimensional spectrum. The principle is demonstrated for the TOCSY experiment, generating a chemical shift correlation map in which a single peak is seen for each coupled relationship, but the principle is general and readily extensible to other homonuclear correlation experiments. Such spectra greatly simplify manual spectral analysis and should be well-suited to automated methods for structure elucidation. © 2010 American Chemical Society.
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For over 30. years information-processing approaches to leadership and more specifically Implicit Leadership Theories (ILTs) research has contributed a significant body of knowledge on leadership processes in applied settings. A new line of research on Implicit Followership Theories (IFTs) has re-ignited interest in information-processing and socio-cognitive approaches to leadership and followership. In this review, we focus on organizational research on ILTs and IFTs and highlight their practical utility for the exercise of leadership and followership in applied settings. We clarify common misperceptions regarding the implicit nature of ILTs and IFTs, review both direct and indirect measures, synthesize current and ongoing research on ILTs and IFTs in organizational settings, address issues related to different levels of analysis in the context of leadership and follower schemas and, finally, propose future avenues for organizational research. © 2013 Elsevier Inc.
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This survey is devoted to some fractional extensions of the incomplete lumped formulation, the lumped formulation and the formulation of Lauwerier of the temperature field problem in oil strata. The method of integral transforms is used to solve the corresponding boundary value problems for the fractional heat equation. By using Caputo’s differintegration operator and the Laplace transform, new integral forms of the solutions are obtained. In each of the different cases the integrands are expressed in terms of a convolution of two special functions of Wright’s type.
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We present a test for identifying clusters in high dimensional data based on the k-means algorithm when the null hypothesis is spherical normal. We show that projection techniques used for evaluating validity of clusters may be misleading for such data. In particular, we demonstrate that increasingly well-separated clusters are identified as the dimensionality increases, when no such clusters exist. Furthermore, in a case of true bimodality, increasing the dimensionality makes identifying the correct clusters more difficult. In addition to the original conservative test, we propose a practical test with the same asymptotic behavior that performs well for a moderate number of points and moderate dimensionality. ACM Computing Classification System (1998): I.5.3.
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2000 Mathematics Subject Classification: 35B40, 35L15.
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This study was conducted during the 1994-1995 academic year. Seven social work education programs in the state of Florida, all accredited by the Council on Social Work Education, participated in this study. Graduate and undergraduate social work students in child welfare field placements, and their field instructors, were surveyed during the Spring 1995 semester to assess their satisfaction with field placements in this area and the relationship of this satisfaction to employment interests and field placement recommendations.^ The majority of social work students responding to this survey were generally satisfied with several aspects of their field placements--the learning, field work program, field instructor, child welfare agency, and overall field experience. The field instructors were generally more satisfied than the students, but only statistically different from the students in the areas of satisfaction with the field work program and the child welfare agency. Multiple regression analysis revealed that learning assignment opportunities, field instructor relationship characteristics, placement preference, and pre-placement interview contributed to the prediction of student satisfaction.^ Student satisfaction in field placement was significantly related to the acceptance of employment, if offered, and the recommendation of the field placement to other students. Logistic regression analysis revealed that satisfaction with the child welfare agency was the greatest contributor to the prediction of acceptance of employment, and satisfaction with the field work program was the greatest contributor to the prediction of field placement recommendation. ^
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We tested the relative importance of top-down and bottom-up effects by experimentally evaluating the combined and separate effects of nutrient availability and grazer species composition on epiphyte communities and seagrass condition in Florida Bay. Although we succeeded in substantially enriching our experimental cylinders, as indicated by elevated nitrogen concentrations in epiphytes and seagrass leaves, we did not observe any major increases in epiphyte biomass or major loss of Thalassia testudinum by algal overgrowth. Additionally, we did not detect any strong grazer effects and found very few significant nutrient-grazer interactions. While this might suggest that there was no important differential response to nutrients by individual grazer species or by various combinations of grazers, our results were complicated by the lack of significant differences between control and grazer treatments, and as such, these results are best explained by the presence of unwanted amphipod grazers (mean = 471 ind. m–2) in the control cylinders. Our estimates of grazing rates and epiphyte productivities indicate that amphipods in the control cylinders could have lowered epiphyte biomass to the same level that the experimental grazers did, thus effectively transforming the control treatments into grazer treatments. If so, our experiments suggest that the effects of invertebrate grazing (and those of amphipods alone) were stronger than the effects of nutrient enrichment on epiphytic algae, and that it does not require a large density
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The purpose of this study was to find out the impact of field experience in hospitality education and whether such field experience and others such as semi-practicum, the cooperative, and the work study programs will not play an important role of a closer alliance between the academic and the hospitality industry. II. If it is justifiable to say that it is possible to provide field experience which will enhance the professionally oriented course work, while educators and employers strive to design curriculum that is needed to meet the educational and the industry demands and goals.
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This study was conducted during the 1994-1995 academic year. Seven social work education programs in the state of Florida, all accredited by the Council on Social Work Education, participated in this study. Graduate and undergraduate social work students in child welfare field placements, and their field instructors, were surveyed during the Spring 1995 semester to assess their satisfaction with field placements ii this area and the relationship of this satisfaction to employment interests and field placement recommendations. The majority of social work students responding to this survey were generally satisfied with several aspects of their field placements--the learning, field work program, field instructor, child welfare agency, and overall field experience. The field instructors were generally more satisfied than the students, but only statistically different from the students in the areas of satisfaction with the field work program and the child welfare agency. Multiple regression analysis revealed that learning assignment opportunities, field instructor relationship characteristics, placement preference, and pre-placement interview contributed to the prediction of student satisfaction. Student satisfaction in field placement was significantly related to the acceptance of employment, if offered, and the recommendation of the field placement to other students. Logistic regression analysis revealed that satisfaction with the child welfare agency was the greatest contributor to the prediction of acceptance of employment, and satisfaction with the field work program was the greatest contributor to the prediction of field placement recommendation.
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In this thesis, we consider N quantum particles coupled to collective thermal quantum environments. The coupling is energy conserving and scaled in the mean field way. There is no direct interaction between the particles, they only interact via the common reservoir. It is well known that an initially disentangled state of the N particles will remain disentangled at times in the limit N -> [infinity]. In this thesis, we evaluate the η-body reduced density matrix (tracing over the reservoirs and the N - η remaining particles). We identify the main disentangled part of the reduced density matrix and obtain the first order correction term in 1/N. We show that this correction term is entangled. We also estimate the speed of convergence of the reduced density matrix as N -> [infinity]. Our model is exactly solvable and it is not based on numerical approximation.
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Acknowledgement Construction and maintenance of the experiment system was funded by the state Special Fund for Agro-scientific Research in the Public Interest “Climate Change Impacts on Crop Production and Mitigation” under a grant number 200903003. This work was financially supported by Ministry of Science and Technology of China under a grant number 2012BAC19B01 and Department of Science and Technology of Jiangsu province under a grant number BK20150684. The international cooperation was funded by “111 project” (B12009) and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD). The contribution of Pete Smith was funded by the Chinese Ministry of Agriculture and the United Kingdom Department for Environment, Food and Rural Affairs (DEFRA) under UK-China Sustainable Agriculture Innovation Network (SAIN). The contribution of Timothy Filley was also funded by the state foreign expert agency under a project of Foreign High-end expert program. The authors thank Jiangsu Tianniang Agro-Technology Company Ltd. for the assistance in maintaining the experiment system.
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Review paper, to appear in the Springer Lecture Notes in Physics volume "Thermal transport in low dimensions: from statistical physics to nanoscale heat transfer" (S. Lepri ed.)
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Acknowledgements This work was funded by Natural Science Foundation of China under grant numbers of 41071337 and 40830528 and jointly by the Priority Academic Program Development of Jiangsu Higher Education Institutions, China.