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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
201

Innovation in impact assessment: a bibliometric review and a practical test. / Inovação em avaliação de impactos: revisão bibliométrica e teste prático.

Bruno Pontes Costanzo 01 September 2017 (has links)
A bibliometric study was carried out to identify the main innovations and shortcomings pointed out by scientific research on impact assessment (IA). Out of 1,547 articles published between 1990 and 2015 in two leading journals, IAPA and EIAR, 381 were reviewed for their contents related to new methodological approaches or proposals for improving practice. It was found that innovations and gaps are predominantly treated disregarding IA\'s theoretical basis. We suggest that IA core values shall always guide innovation. It is proposed that the theoretical boundaries of an IA System shall be previously stablished when discussing innovation. The information systematized through a bibliometric approach allowed to propose a framework that correlates IA theoretical foundations with innovation options in a vertical integration way. / Um estudo bibliométrico foi desenvolvido para identificar as principais inovações e lacunas apontadas pela pesquisa científica em avaliação de impactos (AI). Dos 1.547 artigos publicados entre 1990 e 2015 nos dois periódicos de maior relevância na área, o IAPA e o EIAR, 381 artigos tiveram seus conteúdos analisados em relação a novas abordagens metodológicas ou propostas para melhoria da prática. Verificou-se que as inovações e lacunas são tratadas predominantemente desconsiderando a base teórica de AI. Sugerimos que os valores fundamentais da avaliação de impactos devem sempre orientar a inovação. Propõe-se que as fronteiras teóricas de um Sistema AI sejam estabelecidas previamente ao se discutir a inovação. A informação sistematizada através de uma abordagem bibliométrica permitiu propor uma estrutura que correlaciona os fundamentos teóricos da avaliação de impactos com as opções de inovação.
202

Rapidly converging boundary integral equation solvers in computational electromagnetics / Solveurs à convergence rapide pour équations intégrales aux élément de frontière en électromagnétisme computationnel

Adrian, Simon 09 March 2018 (has links)
L'équation intégrale du champ électrique (EFIE) et l'équation intégrale du champ combiné (CFIE) souffrent d'un mauvais conditionnement à haute discrétisation et à bassefréquence : si la taille moyenne des arrêtes du maillage est réduite ou si la fréquence est diminuée le conditionnement du système se dégrade rapidement. Cela provoque le ralentissement ou la non convergence des solveurs itératifs. Cette dissertation présente de nouveaux paradigmes permettant l'obtention de solveurs à convergence rapide pour équations intégrales; pour prévenir la dégradation du conditionnement nous avançons l'état de l'art des techniques de préconditionnement dites de Calderon et de celles reposant sur l'utilisation des bases hiérarchiques. Pour traiter l'EFIE, nous introduisons une base hiérarchique pour maillages structurés et non-structurés dérivant des pré-ondelettes primaires et duales de Haar. De plus, nous introduisons un nouveau cadre permettant de préconditionner efficacement l'EFIE dans le cas d'objets à connexion multiples. L'applicabilité à la CFIE des préconditionneurs à bases hiérarchiques fait l'objet d'une étude aboutissant à la formalisation d'une technique de préconditionnement. Nous présentons aussi un préconditionneur multiplicatif de type Calderon (RF-CMP) qui permet l'obtention d'une matrice système Hermitienne, définie positive (HDP) et bien conditionnée, sans avoir recours, contrairement aux préconditionneurs existants, au raffinement du maillage ni à l'utilisation de fonction duales. Puisque la matrice est HPD, la méthode du gradient conjugué peut servir de solveur itératif avec une convergence garantie. / The electric field integral equation (EFIE) and the combined field integral equation(CFIE) suffer from the dense-discretization and the low-frequency breakdown: if the average edgelength of the mesh is reduced, or if the frequency is decreased, then the condition number of the system matrix grows. This leads to slowly or non-converging iterative solvers. This dissertation presents new paradigms for rapidly converging integral equation solvers: to overcome the illconditioning, we advance and extend the state of the art both in hierarchical basis and in Calderón preconditioning techniques. For the EFIE, we introduce a hierarchical basis for structured and unstructured meshes based on generalized primal and dual Haar prewavelets. Furthermore, a framework is introduced which renders the hierarchical basis able to efficiently precondition the EFIE in the case that the scatterer is multiply connected. The applicability of hierarchical basis preconditioners to the CFIE is analyzed and an efficient preconditioning scheme is derived. In addition, we present a refinement-free Calderón multiplicative preconditioner (RF-CMP) that yields a system matrix which is Hermitian, positive definite (HPD), and well-conditioned. Different from existing Calderón preconditioners, no dual basis functions and thus no refinement of the mesh is required. Since the matrix is HPD—in contrast to standard discretizations of the EFIE—we can apply the conjugate gradient (CG) method as iterative solver, which guarantees convergence. Eventually, the RF-CMP is extended to the CFIE.
203

Molecular Modeling of Dirhodium Complexes

Debrah, Duke A 01 December 2014 (has links)
Dirhodium complexes such as carboxylates and carboxylamidates are very efficient metal catalysts used in the synthesis of pharmaceuticals and agrochemicals. Recent experimental work has indicated that there are significant differences in the isomeric ratios obtained among the possible products when synthesizing these complexes. The relative stabilities of the Rh2(NPhCOCH3)4 tolunitrile complexes, Rh2(NPhCOCH3)4(NCC6H4CH3)2, were determined at the HF/LANL2DZ ECP, 6-31G and DFT/B3LYP/LANL2DZ ECP, 6-31G levels of theory using NWChem 6.3. The LANL2DZ ECP (effective core potential) basis set was used for the rhodium atoms and 6-31G basis set was used for all other atoms. Specifically, the o-tolunitrile, m-tolunitrile, and p-tolunitrile complexes of the 2,2-trans and the 4,0- isomers of Rh2(NPhCOCH3)4 were compared.
204

Computational Quantum Chemistry Studies of the Stabilities of Radical Intermediates Formed During the Oxidation of Melatonin

Warden, Constance E 01 December 2016 (has links)
Melatonin, a nontoxic natural antioxidant, is of interest as a possible spin trap for use in spectroscopic methods to observe and identify short-lived free radicals, which have been linked to oxidative stress that may result in serious health problems. However, the reaction mechanisms for the oxidation of melatonin to form the product N1-acetyl-N2-formyl-5-methoxykynuramine are still not well understood. Computational quantum chemistry studies have been done on four proposed reaction mechanisms, involving the following major intermediate structures: a dioxetane, an epoxide, a melatonin radical cation, and a spin radical adduct. Molecular geometries were optimized at the DFT/B3LYP/cc-pVTZ level of theory, and single point energies were extrapolated to the complete basis set limit at the Hartree-Fock and second-order Møller-Plesset perturbation levels of theory using the cc-pVXZ (X = D, T, Q) basis sets. The lowest energy pathway was found to be the single electron transfer pathway, involving the melatonin radical cation intermediate.
205

A REPRESENTATION THEOREM FOR MATERIAL TENSORS OF TEXTURED THIN SHEETS WITH WEAK PLANAR ANISOTROPY

Sang, Yucong 01 January 2018 (has links)
Herein we consider material tensors that pertain to thin sheets or thin films, which we model as two-dimensional objects. We assume that the thin sheet in question carries a crystallographic texture characterized by an orientation distribution function defined on the rotation group SO(3), which is almost transversely-isotropic about the sheet normal so that mechanical and physical properties of the thin sheet have weak planar-anisotropy. We present a procedure by which a special orthonormal basis can be determined in each tensor subspace invariant under the action of the orthogonal group O(2). We call members of such special bases irreducible basis tensors under O(2). For the class of thin sheets in question, we derive a representation formula in which each tensor in any given tensor subspace Z is written as the sum of a transversely-isotropic term and a linear combination of orthonormal irreducible basis tensors in Z, where the coefficients are given explicitly in terms of texture coefficients and undetermined material parameters. In addition to the general representation formula, we present also the specialized form for subspaces of tensor products of second-order symmetric tensors, a type commonly found in mechanics of materials.
206

The Geomorphic Basis of Colorado Squawfish Nursery Habitat in the Green River Near Ouray, Utah

Rakowski, Cynthia L. 01 May 1997 (has links)
Nursery habitat availability is considered a bottleneck to successful recruitment of Colorado squawfish (Ptychocheilus Lucius). Detailed geomorphic studies were conducted in a 1.5-km reach to examine channel response to flows and the geomorphic setting of nursery habitats during a 2-year period. Videography was used to extend relationships in the 1.5-km reach to a longer 10-km reach. Nursery habitat availability varied yearly with little persistence in location or geomorphic setting of individual habitats for the 2 years of this study. A small number of habitats provided most of the area of high-quality (i.e., deep) habitat, and most of the total area of habitat was formed by three geomorphic classes. Although the 1993 flood reduced the area of available habitat, area of deep habitat increased. The 1994 low-peak flood increased the area of habitat, but most habitats were shallow. The 1993 and 1994 multi-peaked habitat availability curves for the 1.5-km-reach bank-attached bar were the result of the superposition of curves from habitats in each geomorphic classification, and showed that the discharge that maximized habitat availability changed yearly. A complexity index was evaluated for the 10-km reach as surrogate for habitat availability. Total base-flow habitat availability was significantly correlated to the complexity index, but deep habitat availability was not. Measured channel topography was used as input to a flow and sediment transport model. Simulated hydrograph runs produced greater bank-attached bar aggradation and thalweg scour than steady flows, although some unrealistic patterns of scour occurred. New flow recommendations must include occasional high flows sufficient to rebuild channel topography. Flaming Gorge Dam releases should be used to augment the Yampa River flood peak, but not increase low flood-peak duration. The conceptual model for habitat availability developed here may be used to target the formation and availability of habitats. Base flow recommendations designed to maximize habitat availability should be evaluated annually. Winter flows should be reevaluated for their negative effects on habitat.
207

A Radial Basis Neural Network for the Analysis of Transportation Data

Aguilar, David P 04 November 2004 (has links)
This thesis describes the implementation of a Radial Basis Function (RBF) network to be used in predicting the effectiveness of various strategies for reducing the Vehicle Trip Rate (VTR) of a worksite. Three methods of learning were utilized in training the Gaussian hidden units of the network, those being a) output weight adjustment using the Delta rule b) adjustable reference vectors in conjunction with weight adjustment, and c) a combination of adjustable centers and adjustable sigma values for each RBF neuron with the Delta rule. The justification for utilizing each of the more advanced levels of training is provided using a series of tests and performance comparisons. The network architecture is then selected based upon a series of initial trials for an optimum number of hidden Radial Basis neurons. In a similar manner, the training time is determined after finding a maximum number of epochs during which there is a significant change in the SSE. The network was compared for effectiveness against each of the following methods of data analysis: force-entered regression, backward regression, forward regression, stepwise regression, and two types of back-propagation networks based upon the attributes discovered to be most predictive by these regression techniques. A comparison of the learning methods used on the Radial Basis network shows the third learning strategy to be the most efficient for training, yielding the lowest sum of squared errors (SSE) in the shortest number of training epochs. The result of comparing the RBF implementation against the other methods mentions shows the superiority of the Radial Basis method for predictive ability.
208

Förskollärarkårens professionaliseringssträvanden 1960 – 2005 ur ett fackligt perspektiv

Nyberg, Britt January 2008 (has links)
<p>The overall point of the study is to describe and understand the endeavours of the pre-school teachers’ trade union to establish professionalism within this field of work, from the end of the 1960s to 2005. In order to shed light on the subject the main questions asked and answered in this study were: How does the pre-school teachers’ trade union act on issues regarding the autonomy of the pre-school teaching profession? To what extent, and in what way, does the pre-school teachers’ trade union strengthen the pre-school teaching profession’s position by differentiating itself from, and/or allying itself with other professional groups? Which knowledge base is the pre-school teachers’ trade union trying to establish and how does the union act on issues concerning the pre-school teaching profession’s knowledge base? How can these endeavours be understood from a gender perspective? The study presents profession and gender theoretical perspectives. It is based on an analysis of trade-union and official documents concerning pre-school, such as government enquiries, general guidelines and formal instructions.</p><p>The analysis shows that state regulation of pre-school and its teachers has increased over the 45-year period in question. The result of this has been clearer directives but, at the same time, a loss of professional autonomy. The pre-school teachers’ trade unions’ endeavours to establish a professional monopoly through attempting to differentiate the profession by excluding people without a university degree, has been unsuccessful despite exclusion strategies aimed at nursery nurses. A clear effort can be seen to build an alliance with the teachers in compulsory schools. Aside from extending the pre-school teachers’ university training to 3.5 years, it is also evident that the move from care and developmental psychology to pedagogy and learning has been effected through the alliance with the compulsory school teachers. From a gender perspective, the context of pre-school teaching can be seen to have changed symbolically from one primarily intended to provide care and monitor children to a more pedagogical institution. Pre-school teachers have become teachers and children’s learning is emphasised more than their development. Overall this means that the pre-school teachers have a new identity and that pre-school teaching is no longer so clearly a woman’s job.</p>
209

Study of control actions reveals disturbance patterns for cross directional control of basis weight / Studier av styrutslag avslöjar störningsmönster hos tvärsprofilstyrningen av ytvikt

Broman, Patrik January 2004 (has links)
<p>The purpose of this thesis was to examine the demand for cross directional control of basis weight on a board machine. To analyse the demand, changes made by the control system are studied. The significant changes were expected to be present when a major event occurred on the machine. The events classified as major were changes in basis weight, of grade or of coating blade. Break of board and stoppage of the machine were also included. These events can be seen as large disturbances to the machine. </p><p>In order to identify the disturbances a methodology had to be developed. The methodology developed is to analyse the output from a model with the actuators of the control system as input and measurement of basis weight as output. The analysis of this output was done using the multivariate method of principal component analysis. </p><p>The data analysed in this thesis was collected on-line from a board machine operating within the Stora Enso group. Over a period of 3 months, a total of 47 sets of data were collected, each set representing 12-14 hours. The data analysis shows that the variations in the control system are greater than the variation in the measured basis weight. This is a strong indication that the control system is needed and in order to find disturbances in the cross directional profile it is not enough only to analyse the final product, the control signals also have to be analysed. </p><p>The large disturbances do not necessarily emerge from the major events as assumed. Other causes might havelarger impact to the process then first believed. </p><p>One of the major obstacles in trying to explain the variations is that the basis weight is controlled by using the centre layer of the board but measured on the final product. This leads to the fact that the errors seen by the measuring system can result from anything on the machine and be compensated by basis weight in the centre layer of the board.</p>
210

Real-Time Optimal Parametric Design of a Simple Infiltration-Evaporation Model Using the Assess-Predict-Optimize (APO) Strategy

Ali, S., Damodaran, Murali, Patera, Anthony T. 01 1900 (has links)
Optimal parametric design of a system must be able to respond quickly to short term needs as well as long term conditions. To this end, we present an Assess-Predict-Optimize (APO) strategy which allows for easy modification of a system’s characteristics and constraints, enabling quick design adaptation. There are three components to the APO strategy: Assess - extract necessary information from given data; Predict - predict future behavior of system; and Optimize – obtain optimal system configuration based on information from the other components. The APO strategy utilizes three key mathematical ingredients to yield real-time results which would certainly conform to given constraints: dimension reduction of the model, a posteriori error estimation, and optimization methods. The resulting formulation resembles a bilevel optimization problem with an inherent nonconvexity in the inner level. Using a simple infiltration-evaporation model to simulate an irrigation system, we demonstrate the APO strategy’s ability to yield real-time optimal results. The linearized model, described by a coercive elliptic partial differential equation, is discretized by the reduced-basis output bounds method. A primal-dual interior point method is then chosen to solve the resulting APO problem. / Singapore-MIT Alliance (SMA)

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