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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.
481

Density and What Matters: A Study of People's Attitudes Toward and Perceptions of Urban Density

Xu, Yining 18 March 2010 (has links)
As long as the population keeps growing and lands are desired, the research on how the city could be developed is needed. Higher density development, considered as the alternative for urban sprawl, is a new trend for future development. The barrier between advocacy of higher density environment and misconception of density asks for a descriptive and systematic interpretation for human perception of density. In response to this demand, this research aims to provide a description of the factors that influence people's perception of higher density environments. Also, it aims to identify people's important concerns while using outdoor environments. This study is based on data obtained from an online survey questionnaire that polled public attitudes toward density. The findings from the data indicate that the more important characteristics that people are concerned about the higher density environment are presence of nature, interaction opportunities, building identity and perceived safety. This study also points out that people's attitudes toward density vary based on certain factors. Those factors are age, occupation, place of residents and type of residents. This research could be used as a reference for future planning and design. Results of this study reflect participants' attitudes towards density. It initiates a discussion of future research and generates a frame work for future study for a larger population. / Master of Landscape Architecture
482

Evaluation of Current Decision Rules and Healthcare Professional Practices for Detecting Osteoporosis Risk in the Young Adult Population

Willig, Amanda Lynn 12 July 2004 (has links)
Osteoporosis is caused by a multitude of factors. An individual’s risk for experiencing a bone fracture as a senior citizen increases without early intervention. Healthcare professionals do not have access to validated survey tools to identify young adults in need of osteoporosis prevention education, although survey tools to identify postmenopausal women at high risk for low bone mass are available. The purposes of this study were to evaluate three of these survey tools for use in a younger population, and to determine if young adults with osteoporosis risk factors received bone health education from a health professional. Forty-two men and 41 women completed surveys and health questionnaires; responses were compared to bone mineral density (BMD) and content (BMC) measurements. Healthcare professionals discussed bone health with only 13% of participants. Chi-square analysis revealed that health professionals were not more likely to discuss osteoporosis with subjects based on age or gender. Participants with T-scores ≤ -1.0 were not more likely to receive bone health education. Area under the receiving operating characteristic (AUROC) curves analysis revealed that no survey tools were able to identify moderate-risk participants at T-scores ≤ -1.0, and AUROC curves for all surveys did not exceed 0.525 at this level. Two surveys detected participants at high risk for bone disease with identical AUROC curves of 0.821 at a T-score ≤ -2.0, and 0.813 at a T-score ≤ -2.5. The AUROC curves indicate that current tools designed for older women do not detect young adults with moderately low T-scores. / Master of Science
483

Changes in Bone Mineral Density and Biomarkers of Bone Turnover with Calcium Supplementation During Initial Military Cadet Exercise Training

Watson, Elizabeth M. 02 May 2001 (has links)
Osteoporosis is a condition involving decreased bone mineral density (BMD) and increased fragility of the skeletal system. Osteoporosis affects ~75 million individuals in the United States, Europe, and Japan. In the United States alone, hip fractures affect 500,000 individuals per year, and annual healthcare costs for osteoporotic fractures are approximately $14 billion. A high peak BMD can prevent or delay the onset of osteoporosis and its complications. Exercise and diet may affect peak BMD by as much as 20 to 40% each and have been identified as the two most important controllable factors determining BMD. The current study investigated the effect of a calcium, vitamin D, and vitamin K supplement combination during initial military cadet exercise training on: BMD, stress fracture occurrence, hormones associated with BMD, and biochemical markers of bone turnover. Significant changes in BMD, either between the supplemented group or the unsupplemented group or across time for both groups were not found. The majority of participants (n = 22) had unexpectedly high levels of physical activity prior to enrollment, and the initial military exercise training program included only moderate levels of activity. Therefore, the exercise stimulus to bone was likely insufficient to promote gains in BMD, regardless of the nutrient supplement status. Serum insulin-like growth factor-1 and osteocalcin significantly increased over time (p < 0.05 and p < 0.001, respectively), irrespective of treatment group. Significant decreases were found in dietary intake of calories (p < 0.01), carbohydrate (p < 0.05), protein (p < 0.0001), and fat (p < 0.01) over time. Decreases in reported dietary intake were likely due to less variety of foods eaten, and diminished compliance with food records. Significant differences were not found between groups or across time in dietary intakes of calcium, vitamin D, or vitamin K. Low dose supplementation with a calcium, vitamin D, vitamin K supplement during initial military training in young-adult cadets did not change BMD or alter stress fracture occurrence. / Master of Science
484

Nulling the motion aftereffect with dynamic random-dot stimuli: limitations and implications.

Keeble, David R.T., Castet, E., Verstraten, F. January 2002 (has links)
No / We used biased random-dot dynamic test stimuli to measure the strength of the motion aftereffect (MAE) to evaluate the usefulness of this technique as a measure of motion adaptation strength. The stimuli consisted of noise dots whose individual directions were random and of signal dots moving in a unique direction. All dots moved at the same speed. For each condition, the nulling percentage (percentage of signal dots needed to perceptually null the MAE) was scaled with respect to the coherence threshold (percentage needed to perceive the coherent motion of signal dots without prior adaptation). The increase of these scaled values with the density of dots in the test stimulus suggests that MAE strength is underestimated when measured with low densities. We show that previous reports of high nulling percentages at slow speeds do not reflect strong MAEs, but are actually due to spatio-temporal aliasing, which dramatically increases coherence thresholds. We further show that MAE strength at slow speed increases with eccentricity. These findings are consistent with the idea that using this dynamic test stimulus preferentially reveals the adaptation of a population of high-speed motion units whose activity is independent of adapted low-speed motion units.
485

The relationship between residential density and human activity

Mansour, Yasser Mohamed. January 1985 (has links)
Call number: LD2668 .T4 1985 M367 / Master of Architecture
486

TECHNIQUE FOR DETERMINING THE POWER FLUX DENSITY OF INTERFERING SIGNALS AT TELEMETRY RECEIVING STATIONS

Law, Eugene 10 1900 (has links)
ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada / This paper will present techniques for accurately measuring the power flux density (PFD) of interfering signals at telemetry receiving stations. The solar power flux density is measured daily by radio astronomers and will be used as a calibration signal. The electromagnetic spectrum is being used more intensely as time marches on so being familiar with interference measurement techniques is becoming more important because more interfering signals are present.
487

A study of the structural properties of SiC and GaN surfaces and theirinterfaces by first principle total energy calculation

Dai, Xianqi., 戴憲起. January 2003 (has links)
published_or_final_version / Physics / Doctoral / Doctor of Philosophy
488

Bergman kernel on toric Kahler manifolds

Pokorny, Florian Till January 2011 (has links)
Let (L,h) → (X,ω) be a compact toric polarized Kahler manifold of complex dimension n. For each k ε N, the fibre-wise Hermitian metric hk on Lk induces a natural inner product on the vector space C∞(X,Lk) of smooth global sections of Lk by integration with respect to the volume form ωn /n! . The orthogonal projection Pk : C∞(X,Lk) → H0(X,Lk) onto the space H0(X,Lk) of global holomorphic sections of Lk is represented by an integral kernel Bk which is called the Bergman kernel (with parameter k ε N). The restriction ρk : X → R of the norm of Bk to the diagonal in X × X is called the density function of Bk. On a dense subset of X, we describe a method for computing the coefficients of the asymptotic expansion of ρk as k → ∞ in this toric setting. We also provide a direct proof of a result which illuminates the off-diagonal decay behaviour of toric Bergman kernels. We fix a parameter l ε N and consider the projection Pl,k from C∞(X,Lk) onto those global holomorphic sections of Lk that vanish to order at least lk along some toric submanifold of X. There exists an associated toric partial Bergman kernel Bl,k giving rise to a toric partial density function ρl,k : X → R. For such toric partial density functions, we determine new asymptotic expansions over certain subsets of X as k → ∞. Euler-Maclaurin sums and Laplace’s method are utilized as important tools for this. We discuss the case of a polarization of CPn in detail and also investigate the non-compact Bargmann-Fock model with imposed vanishing at the origin. We then discuss the relationship between the slope inequality and the asymptotics of Bergman kernels with vanishing and study how a version of Song and Zelditch’s toric localization of sums result generalizes to arbitrary polarized Kahler manifolds. Finally, we construct families of induced metrics on blow-ups of polarized Kahler manifolds. We relate those metrics to partial density functions and study their properties for a specific blow-up of Cn and CPn in more detail.
489

Assessment of density functional methods for computing structures and energies of organic and bioorganic molecules

Cao, Jie January 2011 (has links)
The work in this thesis mainly focuses on the assessment of density functional methods for computing structures and energies of organic and bioorganic molecules. Previous studies found dramatic conformational and stability changes from B3LYP to MP2 geometry optimization for some Tyr-Gly conformers. Possible reasons could be large intramolecular basis set superposition errors (BSSEs) in the MP2 calculations and the lack of dispersion in the B3LYP calculations. The fragmentation method and three kinds of rotation methods were used to investigate intramolecular BSSE. It is concluded that the rotation method cannot be used to correct intramolecular BSSE along a rotation profile. Another methodology is to employ modern density functionals. We focused on M06-L with the Tyr-Gly conformer ‘book6’. Potential energy profiles were determined by computing the energy for geometries optimized at various fixed values of a distance that controls the degree of foldedness of the structure. M06-L manifested itself as a very promising method to investigate the potential energy surface of small peptides containing aromatic residues. To predict Tyr-Gly structures, 108 potential conformers were created with a Fortran program. The geometry optimizations were done using M06-L/6-31G(d) and M05-2X/6-31+G(d). Two schemes were employed and the most stable conformers were compared to the 20 stable conformers found by B3LYP. Both schemes found 10 conformers similar to one of the B3LYP stable conformers, as well as several newly found conformers. The study of a missing B3LYP stable conformer showed that the possible reason of missing conformers may be the lack in dispersion in B3LYP theory. To study the hydration effect, we studied the conformations of neutral and zwitterionic 3-fluoro-γ-aminobutyric acid (3F-GABA) in solution using different solvation models, mainly the explicit water molecule models. Zwitterionic forms of 3F-GABA are preferred in solution. M06-2X performs better in calculating transition energy profiles than MP2.
490

Development of a Borehole Log Signature for Oceanic Anoxic Events and Its Application to the Gulf of Mexico

Brewton, Asani 19 December 2008 (has links)
Oceanic anoxic events (OAEs) are periods in Earth's history when oceans were depleted in dissolved oxygen and characterized by deposition of organic-rich sediments. The Oceanic Drilling Program (ODP) has drilled through OAEs in a number of areas worldwide, collecting core and borehole log data. This project attempts to identify a characteristic signature from known ODP OAE sections using these data and to apply the signature to identify OAE intervals in Gulf of Mexico wells where cores are lacking. Additionally, pseudo density curves were generated from ODP logs and compared to bulk density logs to determine if the deviation between the two would aid identification of OAE intervals. A general, though not fool proof, signature of high gamma ray, uranium, neutron porosity and low density was seen in nearly all of the ODP holes. Using this signature 20 potential OAE intervals were identified in the Gulf of Mexico.

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