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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.
121

Developmental Trajectories of Physical Aggression and Nonaggressive Rule-Breaking among At-risk Males and Females during Late Childhood and Early Adolescence

Givens, Eugena 09 September 2014 (has links)
Criminological, psychological, and developmental researchers have relentlessly explored behavioral characteristics and juvenile justice outcomes in an effort to establish the most appropriate means of analyzing childhood and adolescent problem behaviors. Cross-discipline, empirical evidence and factor analytic research has consistently identified the presence of two predictive concepts, physical aggression and nonaggressive rule-breaking. Research pertaining to the risk factors and correlates of these two distinct substructures of offending align with theoretically postulated typologies of delinquency and offending as well as the frequently cited patterns of delinquency and offending within reviews of longitudinal research. Using longitudinal data from a sample of 756 at-risk, males and females during late childhood and early adolescence, the present research examined variations in latent trajectories of physical aggression and nonaggressive rule-breaking as well as empirically substantiated risk factors that may influence problem behaviors and juvenile justice involvement. The findings support a 4-class model for both physical aggression and nonaggressive rule-breaking as well as a relationship between supported risk factors and latent class membership. A comprehensive understanding of physical aggression and nonaggressive rule-breaking may provide the basis for targeted, problem-specific strategies aimed at early intervention.
122

Adolescents at risk of persistent antisocial behaviour and alcohol problems : The role of behaviour, personality and biological factors

Eklund, Jenny M. January 2005 (has links)
<p>Antisocial behaviour and alcohol problems are areas of great concern to society, not only associated with personal and emotional costs for the affected individuals and their victims, but also with major societal financial costs. What makes some individuals more likely than others to develop these kinds of problems? The general aim of this thesis was to explore the role of individual characteristics in the development of antisocial behaviour and alcohol problems. More specifically, the research focused on aspects of hyperactive behaviour, personality traits and biological vulnerability indicators in relation to self-reported norm breaking and violent behaviour, registered general criminality and violent offending in particular, and further, on risky alcohol use and drinking offences. The studies were based on both a prospective longitudinal project in which a group of adolescent male lawbreakers and controls were followed from the 1960s into the 1990s, and on more recently collected data on a representative group of Swedish male and female adolescents.</p><p>The results of the thesis supported that neuropsychological deficits, manifested in attention difficulties, and personality traits reflecting disinhibition and negative emotionality, influence the development of antisocial behaviour and risky alcohol use, which in turn increases the risk of subsequent alcohol problems. The findings indicated, furthermore, that these neuropsychological deficits may be associated with an underlying biological vulnerability to various forms of disinhibitory psychopathology. Although the thesis focuses on individual characteristics, the results also support the view that environmental risk factors such as the influence of family and peers and possible stress experiences, play an important role. It was emphasized that individual characteristics continuously interact with environmental conditions in shaping each individual’s developmental course. Results also revealed that adolescent females displaying violent behaviour and engaging in potentially harmful use of alcohol deviated more in personality traits than did the corresponding group of males. Further knowledge of the development of these problems in females is crucial, since most theories in this area have been developed primarily on male samples.</p>
123

Symmetry Breaking Ordering Constraints

Kiziltan, Zeynep January 2004 (has links)
<p>Many problems in business, industry, and academia can be modelled as constraint programs consisting of matrices of decision variables. Such “matrix models” often have symmetry. In particular, they often have row and column symmetry as the rows and columns can freely be permuted without affecting the satisfiability of assignments. Existing methods have difficulty in dealing with the super-exponential number of symmetries in a problem with row and column symmetry. We therefore propose some ordering constraints which can effectively break such symmetries. To use these constraints in practice, we develop some efficient linear time propagators. We demonstrate the effectiveness of these symmetry breaking ordering constraints on a wide range of problems. We also show how such ordering constraints can be used to deal with partial symmetries, as well as value symmetries.</p>
124

Numerical Simulation of Breaking Waves Using Level-Set Navier-Stokes Method

Dong, Qian 2010 May 1900 (has links)
In the present study, a fifth-order weighted essentially non-oscillatory (WENO) scheme was built for solving the surface-capturing level-set equation. Combined with the level-set equation, the three-dimensional Reynolds averaged Navier-Stokes (RANS) equations were employed for the prediction of nonlinear wave-interaction and wave-breaking phenomena over sloping beaches. In the level-set finite-analytic Navier-Stokes (FANS) method, the free surface is represented by the zero level-set function, and the flows are modeled as immiscible air-water two phase flows. The Navier-Stokes equations for air-water two phase flows are formulated in a moving curvilinear coordinate system and discretized by a 12-point finite-analytical scheme using the finite-analytic method on a multi-block over-set grid system. The Pressure Implicit with Splitting of Operators / Semi-Implicit Method for Pressure-Linked Equation Revised (PISO/SIMPLER) algorithm was used to determine the coupled velocity and pressure fields. The evolution of the level-set method was solved using the third-order total variation diminishing (TVD) Runge-Kutta method and fifth-order WENO scheme. The accuracy was confirmed by solving the Zalesak's problem. Two major subjects are discussed in the present study. First, to identify the WENO scheme as a more accurate scheme than the essentially non-oscillatory scheme (ENO), the characteristics of a nonlinear monochromatic wave were studied systematically and comparisons of wave profiles using the two schemes were conducted. To eliminate other factors that might produce wave profile fluctuation, different damping functions and grid densities were studied. To damp the reflection waves efficiently, we compared five damping functions. The free-surface elevation data collected from gauges distributed evenly in a numerical wave tank are analyzed to demonstrate the damping effect of the beach. Second, as a surface-tracking numerical method built on curvilinear coordinates, the level-set RANS model was tested for nonlinear bichromatic wave trains and breaking waves on a sloping beach with a complex free surface. As the wave breaks, the velocity of the fluid flow surface became more complex. Numerical modeling was performed to simulate the two-phase flow velocity and its corresponding surface and evolution when the wave passed over different sloping beaches. The breaking wave test showed that it is an efficient technique for accurately capturing the breaking wave free surface. To predict the breaking points, different wave heights and beach slopes are simulated. The results show that the dependency of wave shape and breaking characteristics to wave height and beach slope match the results provided by experiments.
125

Symmetry Breaking Ordering Constraints

Kiziltan, Zeynep January 2004 (has links)
Many problems in business, industry, and academia can be modelled as constraint programs consisting of matrices of decision variables. Such “matrix models” often have symmetry. In particular, they often have row and column symmetry as the rows and columns can freely be permuted without affecting the satisfiability of assignments. Existing methods have difficulty in dealing with the super-exponential number of symmetries in a problem with row and column symmetry. We therefore propose some ordering constraints which can effectively break such symmetries. To use these constraints in practice, we develop some efficient linear time propagators. We demonstrate the effectiveness of these symmetry breaking ordering constraints on a wide range of problems. We also show how such ordering constraints can be used to deal with partial symmetries, as well as value symmetries.
126

Adolescents at risk of persistent antisocial behaviour and alcohol problems : The role of behaviour, personality and biological factors

Eklund, Jenny M. January 2005 (has links)
Antisocial behaviour and alcohol problems are areas of great concern to society, not only associated with personal and emotional costs for the affected individuals and their victims, but also with major societal financial costs. What makes some individuals more likely than others to develop these kinds of problems? The general aim of this thesis was to explore the role of individual characteristics in the development of antisocial behaviour and alcohol problems. More specifically, the research focused on aspects of hyperactive behaviour, personality traits and biological vulnerability indicators in relation to self-reported norm breaking and violent behaviour, registered general criminality and violent offending in particular, and further, on risky alcohol use and drinking offences. The studies were based on both a prospective longitudinal project in which a group of adolescent male lawbreakers and controls were followed from the 1960s into the 1990s, and on more recently collected data on a representative group of Swedish male and female adolescents. The results of the thesis supported that neuropsychological deficits, manifested in attention difficulties, and personality traits reflecting disinhibition and negative emotionality, influence the development of antisocial behaviour and risky alcohol use, which in turn increases the risk of subsequent alcohol problems. The findings indicated, furthermore, that these neuropsychological deficits may be associated with an underlying biological vulnerability to various forms of disinhibitory psychopathology. Although the thesis focuses on individual characteristics, the results also support the view that environmental risk factors such as the influence of family and peers and possible stress experiences, play an important role. It was emphasized that individual characteristics continuously interact with environmental conditions in shaping each individual’s developmental course. Results also revealed that adolescent females displaying violent behaviour and engaging in potentially harmful use of alcohol deviated more in personality traits than did the corresponding group of males. Further knowledge of the development of these problems in females is crucial, since most theories in this area have been developed primarily on male samples.
127

Socrates in the Classroom : Rationales and Effects of Philosophizing with Children

Pihlgren, Ann S January 2008 (has links)
Socratic seminars have long been practiced internationally by educators and philosophers as a supplement to classroom teaching and coaching. However, the rationales and effects of this methodology including how these effects are achieved have not been thoroughly investigated or systematically analyzed. The first section of this study is a theoretical review of literature, investi-gating the pedagogical rationales for using a Socratic methodology. The second section is an analysis of sixteen seminars conducted over three years with children from five to sixteen years old. The students’ body language and group interaction were analyzed closely through a phenomenological approach. The analysis focused on how the seminar culture was taught and learned and whether the intended methodology made a difference. The literature review reveals that the various Socratic traditions describe a set of methodological steps to attain similar objectives. By using these steps, intellectual and dialogical habits of mind are expected to be internalized. The seminar analysis shows that the skilled participants shifted their interaction towards an “inquiring” dialogue over time, and that the distribution of rhetorical power changed to a more cooperative communication. The students’ learning proceeded through a series of stages, partly different from the anticipated ideal. The facilitator’s ability to handle rule breaking, and to create a safe environment for intellectual exploration, was significant. The findings show that intricate “silent” moves like gestures and glances helped maintain a productive and egalitarian seminar culture. The participants developed their thinking skills over time, evolving from relativism to critical examination.
128

Physical Simulation of an Embedded Surface Mesh Involving Deformation and Fracture

Clack, Billy 2012 May 1900 (has links)
Simulating virtual objects which can deform or break apart within their environments is now common in state-of-the-art virtual simulations such as video games or surgery simulations. Real-time performance requires a physical model which provides an approximation to the true solution for fast computations but at the same time provides enough believability of the simulation to the user. Recent research in object deformation and fracture has revolved around embedding portions of the simulation for graphical display inside a much simpler physical domain which is invisible to the user. Embedding complex geometry in a simpler domain allows for very complex effects to occur in a much more robust and computationally efficient manner. This thesis explores a novel method to efficiently embed a high-resolution surface mesh inside a coarse tetrahedral physical mesh for the purposes of interactive simulation and display. A technique to display interior regions as solid geometry without explicitly re-meshing the graphical mesh during fracture has been explored and developed. Keeping the graphical mesh static in memory during simulation allows the geometry to be off-loaded to the GPU while shaders can be utilized to only display portions of the geometry which are locally contained within the physical mesh. Recent advances in GPU technology have also been exploited in order to provide an increase in visual fidelity and help achieve the illusion that the virtual object itself is breaking apart in a physically plausible manner.
129

Nonlinear Interaction Between Ultrasonic Waves and Cracks and Interfaces

Poznic, Milan January 2008 (has links)
The subject of this thesis is the development of new ultrasound inspection techniques for detection of cracks that are smaller than the wavelength of the inspecting wave and the characterization of cracks in fluid-filled pipes as either surface-breaking or subsurface. The spectrum of the scattered field of a partially closed crack comprises harmonic components not expected to be found in the case of linear scatterers such as pores or inclusions. Paper A presents an experimental investigation into the linear reflection and generation of the 2nd harmonic component following the incidence of an ultrasonic wave onto a dry or water-confining interface formed by elasto-plastic steel-steel surfaces in contact. The results indicate that water has an unexpected effect on the reflection, at low interfacial pressures, suggesting that fluid mediated forces play a role not accounted for in current models. The level of the generation of the 2nd harmonic measured provides support for further development of the technique for detection of dry, partially closed cracks or fluid-filled, nearly open cracks. A theoretical model describing the nonlinear scattering of acoustic waves by surface-breaking cracks with faces in partial contact is presented in Paper B. Both linear and nonlinear response of the crack are shown to be the largest for a SV wave incident on the surface containing the crack at an angle just above the critical angle for longitudinal waves. A method which provides information on whether a fracture is surface-breaking or subsurface has been modelled and its optimal experimental set-up examined in Paper C. The main assumption of the model is that water carried by pressurized pipes infiltrates and fills a surface-breaking crack, while a subsurface crack is dry. The model simulates an inspection in which the modulation technique is employed and the surface hosting the crack is not accessible. A parameter, constructed with signals recorded in backscattering configuration during a modulation cycle, is examined and shown to provide a clear criterion to distinguish subsurface from surface-breaking cracks when a SV wave at 45 degree incidence is employed as a probe. Finally, in Paper D the modulation technique is experimentally tested on steel beams that host surface-breaking fatigue cracks. The method is shown to be a successful tool to distinguish a dry from a fluid-filled crack. Furthermore, it is revealed that the dynamics of the fluid needs to be accounted for in a more accurate simulation tool. / QC 20100906
130

Complex Plasmonic Nanostructures: Symmetry Breaking and Coupled Systems

January 2012 (has links)
Metallic nanostructures support resonant oscillations of their conduction band electrons called localized surface plasmon resonances. Plasmons couple efficiently to light and have enabled a new class of technology for the manipulation of light at the nanoscale. Nanostructures that support plasmon resonances have the potential for a wide range of applications such as enhanced optical spectroscopy techniques for chemical- and bio-sensing, cancer diagnosis and therapy, metamaterials, and energy harvesting. As the field of plasmonics has progressed, these applications have become more sophisticated, requiring increasingly complex nanostructures. For example, coupled nanostructures of two or more nanoparticles are used extensively in plasmon-enhanced spectroscopy techniques because they exhibit extremely large optical field enhancements. Asymmetric nanostructures, such as nanocups (metallic semishells), have been shown to support magnetic modes that could be used in metamaterials applications. This class of complex plasmonic nanostructures holds great potential for both the observation of new physical phenomena and practical applications. This thesis will focus on the fabrication and characterization of several examples of these complex nanostructures using darkfield spectroscopy. The plasmon modes of a dimer consisting of two nanoshells are investigated in both the separated and conductively overlapping regimes and are interpreted using the plasmon hybridization model. Next, coupled nanoclusters of seven particles arranged in a hexagonal pattern are studied. It is found that these nanoclusters support Fano resonances due to the coupling and interference of degenerate subradiant and superradiant plasmon modes. These structures are found to have an extremely high sensitivity to the local dielectric environment, making them attractive for biosensing applications. Variations on the nanocluster geometry are then explored, and it is observed that by adding more particles and varying their sizes, the lineshape of the Fano resonance can be precisely engineered. The underlying subradiant and superradiant modes are then analyzed using cathodoluminescence imaging and spectroscopy. Finally the plasmon modes of asymmetric nanostructures are measured. Nanoeggs (nanoshells with an offset core) and nanocups (metallic semishells) are fabricated by electron beam induced ablation, and their plasmon modes are measured. The plasmon modes of nanocups are studied in detail, and nanocups are found to support both electric and magnetic plasmons.

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