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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.
1

Retention behaviour of draftees and volunteers.

Gur, Kemalettin 12 1900 (has links)
Approved for public release; distribution is unlimited / Experts believe that draft would require a larger number of accessions, since draftees and draft-motivated volunteers are more likely to leave military service than volunteers at their first opportunity. This thesis presents evidence on this issue. We are able to compare retention behaviour and service lengths of draftees and volunteers in the same cohort by using data files consisting of enlistees during lottery draft years. / http://archive.org/details/retentionbehavio00gurk / Lieutenant, Junior Grade, Turkish Navy
2

Geometry of numbers, class group statistics and free path lengths

Holmin, Samuel January 2015 (has links)
This thesis contains four papers, where the first two are in the area of geometry of numbers, the third is about class group statistics and the fourth is about free path lengths. A general theme throughout the thesis is lattice points and convex bodies. In Paper A we give an asymptotic expression for the number of integer matrices with primitive row vectors and a given nonzero determinant, such that the Euclidean matrix norm is less than a given large number. We also investigate the density of matrices with primitive rows in the space of matrices with a given determinant, and determine its asymptotics for large determinants. In Paper B we prove a sharp bound for the remainder term of the number of lattice points inside a ball, when averaging over a compact set of (not necessarily unimodular) lattices, in dimensions two and three. We also prove that such a bound cannot hold if one averages over the space of all lattices. In Paper C, we give a conjectural asymptotic formula for the number of imaginary quadratic fields with class number h, for any odd h, and a conjectural asymptotic formula for the number of imaginary quadratic fields with class group isomorphic to G, for any finite abelian p-group G where p is an odd prime. In support of our conjectures we have computed these quantities, assuming the generalized Riemann hypothesis and with the aid of a supercomputer, for all odd h up to a million and all abelian p-groups of order up to a million, thus producing a large list of “missing class groups.” The numerical evidence matches quite well with our conjectures. In Paper D, we consider the distribution of free path lengths, or the distance between consecutive bounces of random particles in a rectangular box. If each particle travels a distance R, then, as R → ∞ the free path lengths coincides with the distribution of the length of the intersection of a random line with the box (for a natural ensemble of random lines) and we determine the mean value of the path lengths. Moreover, we give an explicit formula for the probability density function in dimension two and three. In dimension two we also consider a closely related model where each particle is allowed to bounce N times, as N → ∞, and give an explicit formula for its probability density function. / <p>QC 20151204</p>
3

An Experimental Study of Flame Lengths and Emissions of fully-Modulated Diffusion Flames

Usowicz, James E 02 May 2001 (has links)
A pulsed fuel injector system was used to study flame structure, flame length, and emissions of ethylene jet diffusion flames over a range of injection times and duty-cycles with a variable air co-flow. In all cases the jet was completely shut off between pulses (fully-modulated) for varying intervals, giving both widely-spaced, non-interacting puffs and interacting puffs. Imaging of the luminosity from the flame revealed distinct types of flame structure and length, depending on the duration of the fuel injection interval. Flame lengths for isolated puffs (small injection times) were up to 83% less than steady state flames with the same injection velocities. With the addition of co-flow flame lengths grew to a maximum of 30% longer than flames without any co-flow. A scaling argument is also developed to predict the amount of co-flow that gives a 15% increase in mean flame length. Interacting flames with a small co-flow and small injection times (injection time = 5.475 ms) experienced flame length increases of up to 212% for a change in injection duty-cycle from 0.1 to 0.5. For interacting flames with long injection times (on time = 119 ms), essentially no change in flame length was noticeable over the same range of duty-cycles. Emission measurements suggest partial quenching of the reaction in isolated puffs with low duty-cycles and injection times (injection times less than 5.475 ms) resulting in high CO and UHC concentrations and low NO and NOx concentrations. With an increase in duty-cycle, the puffs began to interact and CO and UHC concentrations decreased while NO and NOx concentrations increased. For flames with injection times greater than 5.475 ms emission concentrations seem to be reasonably constant, with a slight increase in NO and NOx concentrations as the duty-cycle increased. Also the duty-cycle experienced in the vicinity of the probe is estimated and used as a scaling factor for the emission measurements.
4

Continued Radicals and Cantor Sets

Clark, Thomas Tyler 01 May 2012 (has links)
We examine the formation of sets homeomorphic to the ternary Cantor set by continued radicals. We determine properties of bridges and gaps and calculate the thickness of the Cantor set. From this we apply information from continued fractions to continued radicals to obtain new results. We also consider the measure of several Cantor sets.
5

Temporal and spatial distribution of Chaetognaths in relation to environmental factors in Kaoping coastal waters, southwestern Taiwan

Wang, Shih-Hung 13 August 2003 (has links)
Abstract The species composition, abundance, body lengths and stages of chaetognaths in relation to environmental factors at nine stations in Kaoping coastal waters were investigated during June 2001 to March 2002. In the surface tows, 20 species of chaetognaths, belonging to 10 families and 4 orders, were found, with the mean abundance of 17753 ¡Ó14593 ind./ 100m3. The 4 most dominant species, Flaccisagitta enflata, Aidanosagitta crassa, Sagitta bipuncata and Ferosagitta ferox, comprised > 80% of total chaetognaths. Flaccisagitta enflata was the most common and abundant species and occupied 53% of total chaetognaths. In 100m oblique tows, 21 species of chaetognaths, belonging to 11 families and 4 orders were found, with the mean abundance of 23535 ¡Ó 18696 ind./ 100m3. The 4 most dominant species were Flaccisagitta enflata, Aidanosagitta regularis, Serratosagitta pacifica and Aidanosagitta crassa, and comprised 77% of total chaetognths. Pseudosagitta lyra was the species found only in the 100m oblique tows. The abundance of chaetognaths changed with seasons and had the highest abundance in summer and the lowest in late autumn. The relation between abundance of chaetognaths showed significantly negative relationship with salinity but not for temperature, and had larger variation when salinity > 32 o/oo. Multi-Dimensional Scaling (MDS) method was used to elucidate the variation of chaetognaths community among seasons and stations. The community structure of chaetognaths had somewhat difference among seasons, with higher similarity between August and November, but these two months showed apparently different from June and March. The variation of chaetognaths community among stations was different seasonally, with higher in August and lower in March and June. Furthermore, three species groups were distinguished and their distribution patterns were herein disscussed. The Stage¢¹of chaetognaths dominated in this study area and occupied > 70 % of total count, and the number decreased rapidly following the developmental stages. The most dominant species, Flaccisagitta enflata, was also dominated by stage¢¹throughout the year, implied it might breed in the whole year. The body length of chaetognaths increased apparently with increasing of developmental stages, but overlapped among stages due to the wider variation in each stage.
6

The effect of organic matter on greenhouse plants

Hartman, Elmer Louis January 1932 (has links)
No description available.
7

Sterically Crowded Copolymers Based on Functionalized Stilbenes

Li, Yi 02 May 2012 (has links)
The research in this dissertation is focused on the synthesis and characterization of sterically crowded, precisely charged polyelectrolytes based on substituted stilbene comonomers. New sterically crowded polyelectrolytes based on functionalized stilbenes with maleic anhydride or functionalized N-phenylmaleimides were prepared via a "protected" precursor polymer strategy. The polyelectrolyte precursors readily dissolved in organic solvents and were characterized by 1H NMR, SEC, TGA, and DSC. The polyelectrolytes were obtained via simple deprotection chemistries. The use of different combinations of the donor-acceptor comonomer pairs and the alternating copolymerization of these comonomers lead to precise control over charge density and placement of charged groups along the polymer backbone. Analogous styrenic copolymers, for direct comparison to the stilbene structures, were also prepared. Broad peaks in 1H NMR spectra were observed. There were no thermal transitions measured by DSC below the degradation temperature. A strong polyelectrolyte effect, for both stilbene and styrene copolymers, occurred in deionized water and was suppressed by adding NaCl to the polymer solution. These results are not consistent with "rigid" rod polyelectrolytes in which chain collapse in the presence of added salt and chain expansion on dilution should not be observed. In response to these observations persistence length measurements were conducted on the stilbene and styrene copolymers to assess directly the steric crowding effect of added phenyl groups in stilbene copolymers. Both SEC and SAXS measurements were used to obtain persistence lengths. The results from three different approaches, Bohdanecký, graphical and Sharp and Bloomfield Global, were in good agreement. The persistence lengths of stilbene containing copolymers range from 3 to 6 nm and the added phenyl groups increase the rigidity of the polymer chain by about 30-50%. This puts these polymers into a broadly defined "semi-rigid" category of polymers and is consistent with the solution polyelectrolyte effect observed. In dilute solution characterization of stilbene containing polyanions, a 2-step dissociation behavior was observed for the two adjacent carboxylic acids in maleic acid containing polyanions. Stilbene polyanion solutions showed high Rh values in deionized water as shown by DLS measurements and a decrease of Rh values followed by aggregation upon gradual addition of salt. Bimodal peaks were observed in SEC measurements with the copolymer of 4-methylstilbene and maleic anhydride. DLS measurements indicated interchain aggregation as the origin of the apparent high molecular weight fraction. The antiviral activity of the polyanion based on sodium 4-styrenesulfonate and N-(4-sodium sulfophenyl)maleimide was found to be ~50 times higher than the microbicide, sodium poly(styrene sulfonate). The early study of antiviral activities of carboxylated stilbene and styrene polyanions also showed promising results. The synthesis of methyl sulfonate ester-functionalized polyanion precursors was attempted because they can be characterized without the complications caused by directly using charged sulfonate groups. / Ph. D.
8

VISUALISING DATA FRAME FORMATS CONTAINING SUPER COMMUTATION AND VARIABLE WORD LENGTHS

Kitchen, Frank 10 1900 (has links)
International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Compiling a PCM data frame with super commutation poses problems of maintaining constant sample intervals for the parameters whilst keeping within channel bandwidth limitations. Add an extra requirement of using variable word lengths to optimise the use of available bit rate and the problem becomes more challenging. The available telemetry or tape recorder channel bandwidth rather than the capabilities of the data acquisition system normally govern the amount of data that can be acquired by the aircraft instrumentation system. The amount of data demanded usually expands to fill all available bandwidth and the bit rates are operated at the maximum for the particular channel. The use of variable word lengths can, in some circumstances, increase the utilisation of a channel bandwidth. In order to visualise if a particular requirement can be accommodated within a given data structure a method of sketching PCM data frames containing a wide mixture of sample rates using an intermediate matrix has been devised. The method is described in three stages. 1. Compiling a simple PCM frame. 2. Sketching the intermediate matrix to assist in visualising super commutation limits. 3. Mixing variable word lengths and super commutation in the same PCM format. The method is not guaranteed to be the most efficient but does give a relatively simple, non mathematical, way to visualise if the required sample rates can be accommodated in a given data structure. If the requirement will not fit into the data structure then the method allows the impact of the necessary changes to the structure to be rapidly assessed. The paper includes comments on the relevant characteristics needed in the aircraft data acquisition system. These include variable word lengths, frame lengths, incremental bit rates and coherency of multiple data bus word parameters
9

Analysis of Telomerase Activity and Telomere Lengths in Human Umbilical Cord Cell Populations During Ex Vivo Amplification of Hematopoietic Stem Cells

Chomal, Manish R 05 December 2002 (has links)
"Human umbilical cord blood (CB) hematopoietic stem cells (HSCs) have well established applications for cellular therapy. Current protocols for isolating HSCs from bone marrow or cord select for CD34 + cells, however some CD34 - populations have recently been shown to also contain strong HSC activity. Thus the positive selection of HSCs based on cell surface markers remains controversial. However, it is clear from the literature that differentiated hematopoietic cells (lineage positive, Lin + ), representing the vast majority (>90%) of most blood populations, contain no long-term reconstitution potential. Thus Viacell Inc. (Worcester, MA) expands and enriches its populations of cells containing HSCs by removing only those Lin + cells known not to contain HSCs. This is accomplished on two separation columns (post-sep-1, and post-sep-2) (separated by 7 days of cell growth) that contain a variety of antibodies to known differentiation surface markers. Although this process strongly enriches functional HCSs, these primitive cell populations remain biochemically uncharacterized. Because HSC populations containing long chromosomal telomeres and high telomerase activity (which helps maintain telomeres) have been shown to display the strongest long-term reconstitution potential, the purpose of this thesis was to investigate these two parameters in selected samples of Viacell’s ex vivo amplification procedure. Two specific hypotheses were tested: 1. the removal of Lin + cells will appear to increase the telomerase activity and telomere lengths in the remaining cell population, and 2. these two parameters will decrease upon hematopoietic cell differentiation and proliferation. Telomerase activity was assayed using a telomeric repeat amplication protocol (TRAP), and normalized relative to a cancer cell line positive control. Relative to fresh cord blood, telomerase activity was found to increase significantly in post-sep-1 (from 8.5 ± 1.5% to 76.2 ± 4.9%, p = 0.0001, n = 5) and post-sep-2 (8.5 ± 1.5% to 111.3 ± 4.9%, p = 0.0001, n = 5) fractions following the removal of Lin + cells. This increase was found to be highly reproducible, showing very low intra-cord and inter-cord variability. Telomere lengths were assayed using a telomere length assay (TLA). Relative to fresh cord blood, telomere lengths increased significantly in post-sep-1 (from 10 to 12 kb, n = 2) and post-sep- 2 (from 10 to 14 kb, p = 0.001, n = 2) fractions. These apparent increases likely result from the direct removal of cells low in telomerase activity with short telomeres since the Lin + cells from the post-sep-1 column were found to contain relatively low telomerase activity (32.1 ± 15%, p = 0.001, n = 2) and short telomeres (7.5 kb, p = 0.001), which supports our first hypothesis. Finally, we show that telomerase activity and telomere lengths decreased in Day-14 cells (expanded and differentiated 14 days) relative to post-sep-2 (from 111.8 ± 19.6% to 54 ± 21.2%, p = 0.001, n = 3 for the TRAP, and from 14 kb to 9 kb, p = 0.0001, n = 2 for the TLA). Those two parameters also decreased in pre-sep-3 cells (terminally differentiated by treatment with All Trans Retinoic Acid for 14 days) relative to post-sep-2 (from 111.3 ± 4.9% to 14.8 ± 1.7%, p = 0.0001, n = 6 for the TRAP, and from 14 kb to 7.5 kb, p = 0.001 for the TLA), supporting our second hypothesis. Telomerase activity was found to not directly correlate with CD34 + CD38 - content, supporting recent observations that a significant portion of HSCs reside outside this population."
10

"Percepção visual e háptica de comprimentos de linha apresentados em diferentes formas". / Visual and haptic perception of line lengths presented in different shapes.

Tosetto, Ana Paula 16 September 2005 (has links)
O presente estudo buscou investigar se participantes videntes apresentaram a mesma performance nos julgamentos de comprimentos de linha do que participantes videntes vendados, cujas estimativas foram realizadas através da percepção tato-cinestésica háptica). Além disso, buscou-se conhecer se esta relação é mantida nas três diferentes formas de comprimentos de linha apresentados: reta, em L e curva e na utilização de dois métodos psicofísicos diferentes: estimação de magnitude e estimação de categoria. A amostra foi constituída por 120 participantes com visão normal, de ambos os sexos, com idade entre 18 e 35 anos, divididos em dois grupos de acordo com a modalidade sensorial: vidente e não vidente (vidente vendado). Os experimentos consistiram em: 1. estimação de magnitude visual; 2. estimação de magnitude não-visual; 3. estimação de categoria visual e 4. estimação de categoria não-visual. Trinta participantes se submeteram a cada um destes experimentos, divididos em três grupos de 10, de acordo com a forma dos comprimentos. Análises estatísticas permitiram concluir que: 1) comprimentos de linha diferentes foram percebidos como diferentes em todos os grupos; 2) a forma dos comprimentos de linha não interferiu nos julgamentos dos participantes; 3) a modalidade sensorial não interferiu nos julgamentos de comprimentos de linha dos participantes e 4) a relação entre o comprimento físico e a estimativa foi mantida em ambos os métodos utilizados, estimação de magnitude e estimação de categoria. / The present study aimed to investigate if sighted participants presented the same performance in the judgements of length of line as blindfolded sighted participants, whose estimates were performed through the touch-cinestesic (haptic) perception. Besides, it aimed to know if this relation is kept in the three different shapes of line length presented: straight; L-shaped and curved and in the use of two different psychophysics methods: magnitude estimation and category estimation. The sample was composed by 120 participants with normal sight, of both sexes, aged between 18 and 35, divided into two groups according to the sensorial mode: sighted participants and blindfolded sighted participants. The experiments consisted in: 1. visual magnitude estimation; 2. non-visual magnitude estimation; 3. visual category estimation and 4. non-visual category estimation. Thirty participants were submitted to each of them, divided into three groups of ten, according to the shape of the lengths. Statistic analysis allowed to conclude that: 1) different line lengths were perceived different in all the groups; 2) the shape of the line lengths did not interfere in the judgements of the participants; 3) the sensorial mode did not interfere in the participants’ judgements of line lengths; 4) the relation between physical length and estimate was kept in the use of both methods: magnitude estimation and category estimation.

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