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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.
531

A cumulative effects approach to wetland mitigation

Nielsen, Jesse Lee 30 March 2010 (has links)
Wetlands are among the most ecologically productive lands in the world, but every year they continue to be lost due to increasing pressures from agriculture, industrial development, urbanization and the lack of effective mitigation to deal with such pressures. Despite environmental assessment processes, policies, and regulations to ensure the mitigation of affected wetlands, wetlands continue to experience a loss in areal extent, but more importantly, a functional net-loss. This is attributed, in large part, to the lack of incorporating cumulative effects principles into project-based wetland impact assessment and mitigation. The majority of activities that affect wetlands are either assessed at the screening level, where cumulative effects are rarely considered, or are deemed insignificant and do not trigger any formal environmental assessment process. As a result, the mitigation of cumulative effects on wetlands is often insufficient or completely lacking in development planning and decision-making. Part of the challenge is that there currently does not exist methodological guidance as to how to identify wetland cumulative effects and corresponding mitigation needs early in the project design process. This research presents a methodological framework and guidance for the integration of cumulative effects in decision-making for project-based, wetland impact mitigation. The framework provides a means for the early indication, assessment, and mitigation of the potential cumulative effects of project developments on the wetland environment, with the objective of ensuring a no-net-loss of wetland functions.
532

Demand for Higher Education : Interaction effects of parental income and parental education on the educational choice made by young individuals in Sweden

Bäckström, Peter January 2011 (has links)
No description available.
533

Effekten av massagebehanling vid hypertoni : en litteraturstudie

Johansson, Anna, Leopoldson, Carolina January 2012 (has links)
Aim: The aim is to create a review that examines different forms of massage therapy and their effects on hypertension. Method: Literature review of 10 scientific articles on the subject of massage and its effects on blood pressure. The literature searches were made with PubMed and Cinahl using the keywords "massage therapy", "effects" and "blood pressure". Results: The articles showed that massage had a positive effect in lowering blood pressure. This could be explained by greater extent of relaxation in the participants investigated and an increased activity of parasympaticus and reduced secretion of stress hormones. The articles do not agree on what form of massage therapy is most effective in lowering blood pressure and it is uncertain for how long the effect can remain. Conclusion: Massage is usually seen as a treatment without scientific basis. There is evidence that suggests that massage therapy is an effective treatment for lowering blood pressure. The articles show that different forms of massage effect blood pressure in various ways. However, a larger randomized controlled trial is needed to determine whether massage therapy can be used as a complement to medical treatment for hypertension and what form of massage is the most effective.
534

Identifying Relevant Variables for Understanding How School Facilities Affect Educational Outcomes

Bosch, Sheila Jones 07 January 2004 (has links)
Many school facilities in the United States are old, out-of-date, poorly maintained, and lack specific design elements that are likely to enhance teaching, learning, behavior, and other desirable outcomes. This study proposed that one reason why previous research regarding the effects of the physical school environment on educational outcomes has had little impact on the quality of schools is because there is a lack of knowledge about these relationships. A multi-method approach was used to solicit information from educators and researchers familiar with school facility effects literature to develop a set of research priorities to guide future research. In Phase I, a literature analysis provided important physical and outcome variables to seed brainstorming lists used in following phases of the research and provided the basis for a gap analysis to identify unavailable information. A concept mapping methodology was utilized in Phase II to solicit feedback from a group of seventeen experienced educators who were asked to brainstorm a list of measures of student, school, or school district success, sort their final list of more than 100 items into categories that made sense to them, and rate each item regarding how important it is to monitor or otherwise track. Using a Delphi method, a series of four questionnaires was given to a group of experienced researchers who developed a list of physical variables plausibly related to educational outcomes, rated the importance of those items, developed hypotheses that included top-rated physical variables and top-rated outcome variables (i.e., measures of success rated by educators), and then selected from those hypotheses several that became the basis of the recommended research priorities for the field. These research priorities propose investigations of the relationships between a set of physical variables (including the provision of team work stations and faculty collaborative spaces, well-designed circulation spaces, spaces for quiet reflection, adaptable seating, daylighting in classrooms, and overall maintenance and building quality) and a variety of educational outcomes (e.g., achievement, behavior, satisfaction, affective performance).
535

Analysis of topography induced flow variations along the Gao-Ping Submarine Canyon based on hydrographic observations

Gau, Ming-Shiung 29 April 2011 (has links)
This study investigates the hydrodynamic variations along the Gao-ping Submarine Canyon influence by the topography effects. The data used in this study were collected from two cruises of field observations using research vessel OR3. Instruments applied include sb-ADCP¡Bbm-ADCP¡Bmoored-ADCP¡BCTD and several vertical strings of temperature loggers. Parameters recorded include flow velocities, water temperature and tidal elevation. The analysis method is enlightenment by the case study in the Monterey Canyon of California. The results show that (1) the current speed in the lower layer is faster than that of upper layer, which is explained due to v-shape of topography and bottom-trapped effect of internal tide. This result is consistent with previous studies. (2) In flood tide, the currents flowed into the Canyon from deep water to shallower. The baroclinic kinetic energy decreased to 0.2 at the turning point of canyon axis at 230m water, whichwas caused mainly by bottom friction. On the other hand, the baroclinic kinetic energy increased to 0.47 at 250m water in ebb tide when there was less influence of bottom friction. (3) In comparison the effects of bottom slope and area of cross section of the canyon, the baroclinic kinetic energy dissipation was mainly occurred at up slope flow during the flood tide. The change of the canyon width had less influence. During the ebb, the baroclinic kinetic energy was mainly due to the change of canyon width in the region shallower then the 230m of the second turning of the canyon. (4) The loss of kinetic energy during flooding up slope current can be verified by the changes of water mass temperature. Cold bottom was raised to upper layer when there was large drop of kinetic energy. There was likely a conversion of kinetic energy to potential energy. No upwelled cold water detected during ebb current with increase of kinetic energy.
536

The chemical mechanisms of flavin-dependent amine oxidases and the plasticity of the two-his one-carboxylate facial triad in tyrosine hydroxylase

Ralph, Erik C. 15 May 2009 (has links)
Despite a number of kinetic and spectroscopic studies, the chemical mechanisms of amine oxidation by flavoenzymes remain widely debated. The mechanisms of by Nmethyltryptophan oxidase (MTOX) and tryptophan 2-monooxygenase (TMO) were probed using a combination of pH and primary deuterium, solvent, and 15N kinetic isotope effects. Slow substrates were chosen for these studies; MTOX was characterized with N-methylglycine and TMO was characterized with L-alanine. Primary deuterium kinetic isotope effects of 7.2 and 5.3 were observed for sarcosine oxidation by MTOX and for alanine oxidation by TMO, respectively, independent of the substrate concentration and pH. Monitoring the reduction of flavin spectroscopically revealed no intermediate flavin species with both enzyme-substrate systems. Furthermore, the magnitudes of the 15N kinetic isotope effects observed with both systems suggest that nitrogen rehybridization and C-H bond cleavage are concerted. These results are consistent with both enzymes utilizing a hydride transfer mechanism for amine oxidation. The role of the iron ligands of tyrosine hydroxylase (TyrH) was also investigated. TyrH contains one iron per monomer, which is held by three conserved amino acid residues, two histidines and a glutamate. As a probe of the plasticity of the metal binding site, each of the metal ligands in TyrH was substituted with glutamine, glutamate, or histidine. The resulting proteins were characterized for metal content, catalytic activity, and dopamine binding. The H336E and H336Q enzymes retain substantial catalytic activity. In contrast, the E376Q enzyme retains about 0.4% of the wild-type catalytic activity, and the E376H enzyme has no significant activity. The H331E enzyme oxidizes tetrahydropterin in a tyrosine-independent manner. The position of the charge-transfer absorbance band for the H336E and H336Q enzyme-inhibitor complexes is shifted relative to that of the wild-type enzyme, consistent with the change in the metal ligand. In contrast, the E376H and E376Q enzymes catalyze dopamine oxidation. These results provide a reference point for further structural studies of TyrH and the other aromatic amino acid hydroxylases, and for similar studies of other enzymes containing this ironbinding motif.
537

Effect of Corrosion on the Seismic Response of a Single-Bent, Reinforced Concrete Bridge

Harvat, Jessica 2009 May 1900 (has links)
The effect of corrosion on a single-bent, reinforced concrete (RC) bridge subject to seismic loading is the primary focus of this research. This work attempts to determine the effects of decreasing rebar diameter and concrete cover spalling on the strength and stiffness of the RC bridge. The application of these results to the field of historic preservation will also be explored. Through the use of static and dynamic analyses, this research shows that the effects of corrosion only have a slight influence on the seismic fragility of the RC bridge. The loss of three inches of concrete cover from the bridge column is shown to have a greater effect on the strength and stiffness of the bridge than decreasing the rebar diameter by 10%. The deformation capacity and demand both increase for bridges with reduced reinforcing steel and concrete cover; however, the capacity increases to a greater degree than the demand. The seismic fragility of the bridge based on deformation criteria is greatest for the pristine structure, and it decreases as the level of damage increases. Future work should include verifying the hysteretic behavior by accounting for reinforcement slip caused by a loss of bond.
538

Analysis of Topological Chaos in Ghost Rod Mixing at Finite Reynolds Numbers Using Spectral Methods

Rao, Pradeep C. 2009 December 1900 (has links)
The effect of finite Reynolds numbers on chaotic advection is investigated for two dimensional lid-driven cavity flows that exhibit topological chaos in the creeping flow regime. The emphasis in this endeavor is to study how the inertial effects present due to small, but non-zero, Reynolds number influence the efficacy of mixing. A spectral method code based on the Fourier-Chebyshev method for two-dimensional flows is developed to solve the Navier-Stokes and species transport equations. The high sensitivity to initial conditions and the exponentional growth of errors in chaotic flows necessitate an accurate solution of the flow variables, which is provided by the exponentially convergent spectral methods. Using the spectral coefficients of the basis functions as solved through the conservation equations, exponentially accurate values of velocity everywhere in the flow domain are obtained as required for the Lagrangian particle tracking. Techniques such as Poincare maps, the stirring index based on the box counting method, and the tracking of passive scalars in the flow are used to analyze the topological chaos and quantify the mixing efficiency.
539

Numerical Investigation of Interaction Between Hydraulic Fractures and Natural Fractures

Xue, Wenxu 2010 December 1900 (has links)
Hydraulic fracturing of a naturally-fractured reservoir is a challenge for industry, as fractures can have complex growth patterns when propagating in systems of natural fractures in the reservoir. Fracture propagation near a natural fracture (NF) considering interaction between a hydraulic fracture (HF) and a pre-existing NF, has been investigated comprehensively using a two dimensional Displacement Discontinuity Method (DDM) Model in this thesis. The rock is first considered as an elastic impermeable medium (with no leakoff), and then the effects of pore pressure change as a result of leakoff of fracturing fluid are considered. A uniform pressure fluid model and a Newtonian fluid flow model are used to calculate the fluid flow, fluid pressure and width distribution along the fracture. Joint elements are implemented to describe different NF contact modes (stick, slip, and open mode). The structural criterion is used for predicting the direction and mode of fracture propagation. The numerical model was used to first examine the mechanical response of the NF to predict potential reactivation of the NF and the resultant probable location for fracture re-initiation. Results demonstrate that: 1) Before the HF reaches a NF, the possibility of fracture re-initiation across the NF and with an offset is enhanced when the NF has weaker interfaces; 2) During the stage of fluid infiltration along the NF, a maximum tensile stress peak can be generated at the end of the opening zone along the NF ahead of the fluid front; 3) Poroelastic effects, arising from fluid diffusion into the rock deformation can induce closure and compressive stress at the center of the NF ahead of the HF tip before HF arrival. Upon coalescence when fluid flows along the NF, the poroelastic effects tend to reduce the value of the HF aperture and this decreases the tension peak and the possibility of fracture re-initiation with time. Next, HF trajectories near a NF were examined prior to coalesce with the NF using different joint, rock and fluid properties. Our analysis shows that: 1) Hydraulic fracture trajectories near a NF may bend and deviate from the direction of the maximum horizontal stress when using a joint model that includes initial joint deformation; 2) Hydraulic fractures propagating with higher injection rate or fracturing fluid of higher viscosity propagate longer distance when turning to the direction of maximum horizontal stress; 3) Fracture trajectories are less dependent on injection rate or fluid viscosity when using a joint model that includes initial joint deformation; whereas, they are more dominated by injection rate and fluid viscosity when using a joint model that excludes initial joint deformation.
540

Design of Antennas for Radio Frequency Identification and Analysis of Power Coupling Effects

Wang, Pai-Chieh 25 July 2005 (has links)
In this paper, we propose tag antennas and reader antennas, which are suitable for radio frequency identification system. Antennas operating in the ISM and the UHF bands are designed. The antenna dimensions are minimized by employing the meander-line technology. Adopting the concepts of Yagi-Uda antennas, We use parasites to increase the antenna gain and to create an end-fire radiation pattern. The fact that the design comes without a ground plane can achieve cost down of the antenna. Higher antenna gains allow a greater effective read-zone distance. Also, the directional radiation pattern eliminates the degradation of performance due to multi-path loss. The design of tag antennas shows good performances in terms of both cost and antenna characteristics for radio frequency identification systems. The reader antennas are designed. Etching a slit in a square patch can achieve the requirement of circular polarization. It can effectively reduce the polarization mismatch when the tags are point to different orientation. Therefore the reliability of system operation will be improved. The antenna performance is measured by the experiments. Moreover, it will be compared with the simulation. In the latter part of paper, the simulation of the power coupling will be carried out. According to the result of power coupling simulation, we analyze and discuss which factor will affect the reliability of the identification. Identification failure will be effectively avoided and a robust identification system can be built if the analyses are properly employed.

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