Дисертації: "PILE SIZE"

1

Seymour, Geoff, and Aregai Tecle. "Impact of Slash Pile Size and Burning on Ponderosa Pine Forest Soil Physical Characteristics." Arizona-Nevada Academy of Science, 2003. http://hdl.handle.net/10150/296601.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

2

Heavin, Joseph Carl. "Influence of Material Type, Aggregate Size, and Unconfined Compressive Strength on Water Jetting of CIDH Pile Anomalies." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/266.

Повний текст джерела

Анотація:

Water jetting as a means for removing anomalous materials from cast-in-drilled-hole (CIDH) piles was examined. The primary objective of this research was to establish empirical relationships between different jetting parameters and the removal of commonly occurring anomalous zone materials, including low-strength concrete, slurry mixed concrete, grout, and clay soil. Also investigated was the current standard-of-practice used by water jetting contractors within California. The testing specimens consisted of typical anomalous material with unconfined compressive strengths between 5 and 6,000 psi. The experimental work consisted of water blasting submerged specimens using rotary jets, nozzles, and pumping equipment typically used in construction practice. Two testing protocols were developed. The first testing protocol called for the nozzle to be held stationary and the second allowed the nozzle to be cycled up and down across the anomaly. During testing, material removal rates were measured as a function of jet pressure and standoff distance. Water blasted specimens were cut apart after testing to confirm erosion measurements and to permit inspection of the water blasted surfaces. Based on the results, erosion rates and the effectiveness of water jetting are primarily influenced by unconfined compressive strength, when using standard test equipment and jetting pressures. Further, aggregate size and material type in the anomalous material does not appear to influence both total erosion and erosion rate.

Стилі APA, Harvard, Vancouver, ISO та ін.

3

Tirado, Sandra M. "Effects Of Turning Frequency, Pile Size And Season On Physical, Chemical And Biological Properties During Composting Of Dairy Manure/Sawdust (Dm+S)." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1218133685.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

4

Gross, Donovan. "Mountain Pine Beetle Fecundity and Offspring Size Differ Among Lodgepole Pine and Whitebark Pine Hosts." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/34.

Повний текст джерела

Анотація:

Whitebark pine (Pinus albicaulis Engelmann) is a treeline species in the central Rocky Mountains. Its occupation of high elevations previously protected whitebark pine from long-term mountain pine beetle outbreaks. The mountain pine beetle, however, is currently reaching outbreaks of record magnitude in high-elevation whitebark pine. We used a factorial laboratory experiment to compare mountain pine beetle (Dendroctonus ponderosae Hopkins) life history characteristics between a typical host, lodgepole pine (Pinus contorta Engelmann), and whitebark pine. We tested the effects of natal host and brood host on beetle fecundity, offspring size, and brood sex-ratio. We reared mountain pine beetles from whitebark pine and from lodgepole pine, and infested half of them into their natal host and half into the other host. Fecundity was greater overall in lodgepole pine brood hosts. Among lodgepole brood hosts, beetles from whitebark pine had greater fecundity. Fecundity was also significantly related to phloem thickness, which was greater in lodgepole pine. Offspring were larger from whitebark brood hosts than from lodgepole, regardless of their parents’ natal host. Finally, sex-ratio was closer to 1:1 in lodgepole than in whitebark brood hosts. We conclude that host species affects life history of mountain pine beetle with consequences for individual beetle fitness.

Стилі APA, Harvard, Vancouver, ISO та ін.

5

Chauvin, Alan. "Contribution à l'optimisation globale pour le dimensionnement et la gestion d'énergie de véhicules hybrides électriques basée sur une approche combinatoire." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0101/document.

Повний текст джерела

Анотація:

L'hybridation des sources de puissance dans le domaine des applications embarquées s'est imposée comme une solution adéquate pour répondre aux législations environnementales et atteindre une meilleure efficacité énergétique. Toutefois, le choix dans le dimensionnement des composants et la stratégie de commande doivent répondre à un cahier des charges, souvent complexe et hétérogène, tout en limitant les coûts du système. La résolution de ce problème d'optimisation incluant de nombreuses variables peut s'avérer complexe à cause des non-linéarités présentes dans le problème formulé. Il faut donc disposer d'outils de résolution efficaces et capables de fournir une solution fiable. Dans cette thèse, nous proposons une méthode d'optimisation globale pour le dimensionnement et la commande optimale de véhicules hybrides basée sur l'optimisation combinatoire, et en particulier sur la programmation linéaire en nombres entiers (PLNE). A partir d'un problème d'optimisation non linéaire, le problème initial est reformulé en une multitude de sous-problèmes linéaires en nombres entiers sur lesquels un algorithme de Branch & Bound parallèle est exécuté. Afin de résoudre des problèmes de grande taille, un second algorithme basé sur le Branch & Cut est développé. Cette méthode est déployée pour l'étude d'un système d'alimentation hybride d'une mini-excavatrice électrique. Le problème d'optimisation, dans lequel des contraintes énergétiques et des contraintes de vieillissement sont implantées, est évalué suivant différents paramètres du cahier des charges. Enfin, cette approche est également appliquée pour l'optimisation de trajectoires d'un système multi-actionneur synchronisés
Hybridization of power sources for embedded applications becomes an interesting solution to respect environmental legislation and achieve a higher energy efficiency. However, the choice for components sizing and the energy management strategy need to meet specifications while reducing costs. To solve this optimization problems including several types of variables can be complex because of non linearities included in the formulated problem. Therefore the use of effective solving tools, able to provide a reliable solution, is required. In this thesis, a global optimization method is proposed for the design and the optimal control of hybrid vehicles based on combinatorial optimization, particularly on integer linear programming. From a non-linear optimization problem, the initial problem is reformulated into a multitude of integer linear sub-problems for which a parallel Branch & Bound algorithm is executed. In order to solve large-scale problems, a second algorithm based on the Branch & Cut is developed. This method is used for the study of a hybrid power supply system of a mini-excavator electric. The optimization problem, where energy constraints and aging constraints are implemented, is evaluated according to several parameters and specifications. Finally, this approach is also applied for the optimization of trajectories for a synchronized multi-actuators system

Стилі APA, Harvard, Vancouver, ISO та ін.

6

Adams, Thomas P. "Reconstructing Scotland's pine forests." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4730.

Повний текст джерела

Анотація:

The Caledonian pinewoods are a habitat of crucial environmental and cultural importance, and the sole home of many rare species. However, they have seen steady decline in recent centuries, through the establishment of hunting estates and forestry plantations. A recent trend in management is the attempted transformation of existing plantations (dense communities with a regular spatial structure and low variance in size and age) towards a state mimicking the perceived natural condition, which has a lower density, irregular spatial pattern, high variance in size and age. This presents a problem for traditional forestry practices, which were conceived primarily with “even-aged” plantation populations in mind. The shift towards management of an uneven-aged structure requires a more in-depth consideration of individual trees’ lifecycles and their effect upon long-term population dynamics. In recent years, great advances in computational and mathematical models for spatially interacting populations have been made. However, certain complications have prevented them from being utilised to their full potential for the purposes of forest management. Forest communities are not only spatially structured; the size of each tree plays a role in its ability to acquire resources for growth and survival. Existing models of population dynamics are discussed, and their extension to incorporate both size- and spatially- structured interactions is presented. The key aspects of populations’ structural development are studied. Data from both plantation and semi-natural Scots Pine stands in Scotland allow parameterisation of a stochastic individual-based model, which in turn provides insights into the behaviour of real populations, and the importance of spatial effects and heterogeneity in individuals. A partial differential equation (moment) approximation to the stochastic model is presented. While this is analytically intractable, numerical integration and heuristic analysis of the equations enable clearer identification of the drivers of population structure. Many results are concordant with existing models of both qualitative forest stand development and theoretical dynamics of spatially-structured populations, while others are specific to joint size-space structure. This deeper understanding of the population dynamics allows robust recommendations for diverse uneven-aged stand management objectives to be made. Approaches to accelerating the transformation of plantation stands towards a “natural” state (using two key operations: thinning – removal of trees, and planting) are investigated. Finally, approaches to so-called “continuous cover forestry” – the practice of maintaining a quasi-natural state while also obtaining economic value from a forest – are also considered. In both cases, the model’s simplicity enables clearer conclusions than would be possible using other approaches.

Стилі APA, Harvard, Vancouver, ISO та ін.

7

Amarasekera, Hiran S. "Juvenile wood formation in relation to crown size in Corsican pine." Thesis, Bangor University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278803.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

8

Hartt, Sarah L. "Monitoring a Pile-Supported Integral Abutment Bridge at a Site with Shallow Bedrock." Fogler Library, University of Maine, 2005. http://www.library.umaine.edu/theses/pdf/HarttSL2005.pdf.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

9

VanderSchaaf, Curtis Lee. "Modeling maximum size-density relationships of loblolly pine (Pinus taeda L.) plantations." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/29489.

Повний текст джерела

Анотація:

Self-thinning quantifies the reduction in tree numbers due to density-dependent mortality. Maximum size-density relationships (MSDRs) are a component of self-thinning that describe the maximum tree density per unit area obtainable for a given average tree size, often quadratic mean diameter (D). An MSDR species boundary line has been defined as a static upper limit of maximum tree density -- D relationships that applies to all stands of a certain species within a particular geographical area. MSDR dynamic thinning lines have been defined as the maximum tree density obtainable within an individual stand for a particular D which have been shown to vary relative to planting density. Results from this study show that differences in boundary levels of individual stands cause the MSDR species boundary line slope estimate to be sensitive to the range of planting densities within the model fitting dataset. Thus, a second MSDR species boundary line was defined whose slope is the average slope of all MSDR dynamic thinning lines. Mixed-models are presented as a statistical method to obtain an estimate of the population average MSDR dynamic thinning line slope. A common problem when modeling self-thinning is to determine what observations are within generally accepted stages of stand development. Segmented regression is presented as a statistical and less subjective method to determine what observations are within various stages of stand development. Estimates of D and trees per acre (N) where MSDR dynamic thinning lines begin and end on the logarithmic scale were used as response variables and predicted as a function of planting density. Predictions of MSDR dynamic thinning line beginning and ending D and N are used in an alternative MSDR dynamic thinning line slope estimation method. These models show that the maximum value of Reineke's Stand Density Index (SDI) varies relative to planting density. By relating planting density specific Zone of Imminent Competition Mortality boundaries to a MSDR species boundary line, self-thinning was found not to begin at a constant relative SDI. Thus, planting density specific Density Management Diagrams (DMD) showed that self-thinning began at 40 to 72% for planting densities of 605 and 2722 seedlings per acre, respectively.
Ph. D.

Стилі APA, Harvard, Vancouver, ISO та ін.

10

Needham, Ted Daniel. "Factors affecting loblolly pine growth following site preparation." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/71162.

Повний текст джерела

Анотація:

Site preparation is a required silvicultural practice for establishing loblolly pine plantations in the Piedmont physiographic region of the southeastern U.S.; however, relatively little is known about its effect on soil and site factors that influence growth and yield. In this study, the effect of seven different site preparation prescriptions on competing vegetation, tree nutrition, and the spatial distribution of planted seedlings was examined. Three treatments had a soil tillage component and differed with respect to the number of operations employed in removing residual trees and logging slash prior to discing. One treatment involved roller chopping and broadcast burning, one an application of the herbicide glyphosate followed by a broadcast-burn, one involved shearing all raking fogging-debris into windows, and one was no site preparation prior to planting. All treatments were applied to 12 sites in the South Carolina and Georgia Piedmont. After four years in the field, 756 trees within the site preparation treatment areas were randomly selected for analysis of foliar nutrients, soil nutrients, and competing vegetation. Herbaceous, woody shrub, and hardwood competition levels were not significantly different among site preparation treatment areas after four years. However, hardwood competition levels had increased at a faster rate during the last two growing seasons on chopped and disced areas than on the other areas. Hardwood competition became the predominant factor limiting pine basal diameter when 83% of the total basal area was in hardwoods or hardwood basal area levels exceeded 3.5 m²ha⁻¹. Potassium was identified as the most limiting nutrient 38% of the time, compared to 28% for phosphorus, 14 % for nitrogen, 7% for calcium, aiid 13% for magnesium. A significant linear relationship between soil and foliar nutrients confirmed these results. No treatment effect on nutrient deficiencies was evident. Foliar nutrient critical levels were derived using the Diagnosis and Recommendation Integrated System (DRIS) and were the same as those reported in the literature for nitrogen, phosphorous, and magnesium while potassium and calcium critical levels were determined to be twice as high as those reported (0.52% and 0.19%, respectively). The spatial distribution of seedlings at planting and after 2 years was determined. Spatial patterns varied from uniform to random as the degree of logging slash removal decreased. After two years, the spatial distribution shifted toward random and clustered. The degree of change was similar in all but the herbicide burn and untreated areas, which exhibited the greatest change and whose mortality tended to be clustered.
Ph. D.

Стилі APA, Harvard, Vancouver, ISO та ін.

11

Eren, Tuna. "Foam Chacrization Effects Of Bubble Size And Texture." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605373/index.pdf.

Повний текст джерела

Анотація:

Foam is one of the most frequently used multiphase fluids in underbalanced drilling operations because of its high carrying capacity of cuttings, compressibility property, formation fluid influx handling, etc. Foam rheology has been studied for many years. Researchers tried to explain foam behaviour by using conventional methods, i.e., determining rheological parameters of pre-defined rheological models like Power law, Bingham Plastic etc., as a function of gas ratio. However, it is known that bubble size and texture of the foam is also effective on foam behaviour. When foam is generated by using different foaming agents, even if the gas ratio is constant, different rheological parameters are observed. Therefore a more general foam characterization method that uses the bubble size and texture of foam is required. Improvements on image analysis, and computer technology allow monitoring the bubble size and texture of foam bubbles. A more comprehensive model of foam rheology definition in which the bubble size, and texture effects of the foam body is developed. Three different analysis methodologies are introduced
i) Generalized volume equalized approach, ii) Generalized volume equalized approach and image processing data, and iii) Image processing data only. The necessary information including the rheological information and image data is acquired from the experimental set-up developed for this study. It has been observed that, the pressure losses could be predicted as a function of bubble size, circularity and general rheological parameters, in &
#61617
20 % certainty limit. It is also observed that using only the image information is possible to characterize the foam in an accurate and fast manner.

Стилі APA, Harvard, Vancouver, ISO та ін.

12

Arirachakaran, Srihasak. "Two-phase slug flow splitting phenomenon at a regular horizontal side-arm tee /." Access abstract and link to full text, 1990. http://0-wwwlib.umi.com.library.utulsa.edu/dissertations/fullcit/9111868.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

13

Bustamante, Guillermo. "Influence of Pile Shape on Resistance to Lateral Loading." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/5630.

Повний текст джерела

Анотація:

The lateral resistance of pile foundations has typically been based on the resistance of circular pipe piles. In addition, most instrumented lateral load tests and cases history have involved circular piles. However, piles used in engineering practice may also be non-circular cross-section piles such as square and H piles. Some researchers have theorized that the lateral resistance of square piles will be higher than that of circular piles (Reese and Van Impe, 2001; Briaud et al, 1983; Smith, 1987) for various reasons, but there is not test data to support this claims. To provide basic comparative performance data, lateral load tests were performed on piles with circular, square and H sections. To facilitate comparisons, all the tests piles were approximately 12 inches in width or diameter and were made of steel. The square and circular pipe sections had comparable moments of inertia; however, the H pile was loaded about the weak axis, as is often the case of piles supporting integral abutments, and had a much lower moment of inertia. The granular fill around the pile was compacted to approximately 95% of the standard Proctor maximum density and would be typical of fill for a bridge abutment. Lateral load was applied with a free-head condition at a height of 1 ft above the ground surface. To define the load-deflection response, load was applied incrementally to produce deflection increments of about 0.25 inches up to a maximum deflection of about 3 inches. Although the square and pipe pile sections had nearly the same moment of inertia, the square pile provided lateral resistance that was 20 to 30% higher for a given deflection. The lateral resistance of the H pile was smaller than the other two pile shapes but higher than what it is expected based on the moment of inertia. Back analysis with the computer program LPILE indicates that the pile shape was influencing the lateral resistance. Increasing the effective width to account for the shape effect as suggested by Reese and Van Impe (2001) was insufficient to account for the increased resistance. To provide agreement with the measured response, p-multipliers of 1.2 and 1.35 were required for the square pile and H piles, respectively. The analyses suggest that the increased resistance for the square and H pile sections was a result of increases in both the side shear and normal stress components of resistance. Using the back-calculated p-multipliers provided very good agreement between the measured and computed load-deflection curves and the bending moment versus depth curves.

Стилі APA, Harvard, Vancouver, ISO та ін.

14

Avila, Olga B. "Survival equations for loblolly pine trees in cutover, site- prepared plantations." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-03122009-040658/.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

15

Matsson, Ingvar. "Studies of Nuclear Fuel Performance Using On-site Gamma-ray Spectroscopy and In-pile Measurements." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6912.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

16

Fahlman, Johan. "Size selective predation of pike on whitefish : The effects on resource polymorphism in Scandinavian whitefish populations." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-87582.

Повний текст джерела

Анотація:

The mechanisms behind speciation have been subject of debate for centuries. The presence of resource polymorphism has been discovered to play a significant part in this process, and has been proven to induce phenotypic and genetic divergence. Although resource polymorphism has been intensely studied during the last few decades, there is a gap of information as to why this can be observed in some systems but not in others. Recent studies of European whitefish (Coregonus lavaretus) in Scandinavian lakes have shown that predation, in this case by Northern pike (Esox lucius), could be the factor that induces resource polymorphism. European whitefish is known to diverge into several ecomorphs in Scandinavian lakes, but only in the presence of pike. Divergence is assumed to be caused by the size selectivity of pike, and the following niche separation and eventually reproductive isolation. In this study, pike prey selectivity was studied in the field through sample fishing using hooks baited with whitefish of different sizes. The hypothesis was that pike prefers smaller prey over larger and mainly hunts in the littoral zone. This should causes smaller whitefish ecomorphs to be prone to predation in the littoral and thus utilize refuge spawning grounds with low predation pressure. However, no pike were caught on whitefish spawning grounds, and fishing at two additional pike rich sites displayed a preference towards medium-sized whitefish (p < 0.05). This indicates a size selectivity, although further and improved studies would be required to answer the question of the pike’s role in resource polymorphism.

Стилі APA, Harvard, Vancouver, ISO та ін.

17

Eisenbies, Mark Hale. "Loblolly Pine and Soil-Site Responses to Harvesting Disturbance and Site Preparation at Stand Closure." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11203.

Повний текст джерела

Анотація:

Intensively managed forests of the Southern United States are among the most important sources of wood fiber and timber in this country. There is a great deal of concern that disturbances associated with trafficking by heavy machinery might diminish long-term soil-site productivity. However, determining the effect of harvesting disturbance and silvicultural treatments on the long-term productivity of pine plantations is difficult because, in addition to harvesting effects, growth distributions are affected by changes in climate, silviculture, and genetics. The primary objectives of this study were to determine (1) whether logging disturbances under operationally realistic circumstances affect soil quality, hydrologic function, and loblolly pine (Pinus taeda L.) productivity on wet pine flats, and (2) whether intensive forest management practices mitigate disturbance effects if they exist. Three 20-ha loblolly pine plantations located on wet pine flats in South Carolina were subjected to combinations of wet- and dry-weather harvesting and mechanical site preparations. Changes in soil-site productivity after five years were evaluated using a new rank method. The key advantage of the rank change method is that it is largely independent of the confounding factors (e.g. genetics, silvicultural practices, and climate) that affect comparisons of tree growth and soil quality between growth cycles. After five years, loblolly pine site indexes (base age 25) ranged between 13 and 33 m, and production ranged between 0.5 and 95 Mg ha-1. Soil bulk densities increased from 1.15 to as high as 1.44 g cm-3 after harvesting; by age 7 years it had decreased to approximately 1.25 g cm-3. At the sub-stand scale (0.008 ha), visually assessed soil physical and harvesting residue disturbances had little influence on relative changes in soil-site productivity after five years. Factors that specifically reflect site drainage were the most influential on changes in productivity. At the operational scale (3.3 ha), there were no differences between wet- and dry- harvested sites as long as bedding was applied as a site treatment. These results indicate that when standard site preparation is employed, fertile, wet pine flats such as these are resilient in that they recover from severe, but operationally realistic, harvesting disturbances.
Ph. D.

Стилі APA, Harvard, Vancouver, ISO та ін.

18

Rose, Nathan S. Loehr J. Erik. "Laboratory load tests of side shear for axially loaded piles." Diss., Columbia, Mo. : University of Missouri--Columbia, 2008. http://hdl.handle.net/10355/6286.

Повний текст джерела

Анотація:

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb. 19, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dr. J. Erik Loehr, Thesis Supervisor. Includes bibliographical references.

Стилі APA, Harvard, Vancouver, ISO та ін.

19

Futch, Jana. "Historical Archaeology of the Pine Level Site (8DE14), DeSoto County, Florida." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3745.

Повний текст джерела

Анотація:

In 1866 the seat of Manatee County was moved to Pine Level, a newly-formed town in the wilderness of south Florida. By the 1880s, it contained stores, boardinghouses, churches, and government buildings. In 1887, Pine Level became DeSoto County’s first seat. However, when it lost county seat status to Arcadia only 18 months later, in 1888, Pine Level rapidly declined in population and importance, and eventually died out. The investigations of the Pine Level site detailed in this thesis were carried out as a public archaeology project, involving the DeSoto County Historical Society, University of South Florida, and the Florida Public Archaeology Network West Central Region. As a public archaeology project, one central goal of this work was to involve the local community in the fieldwork and ongoing research. The efforts of community volunteers, along with graduate and undergraduate students, were critical to several phases of this project, which is presented in this thesis. The second goal of the project was to learn as much as possible about the little-studied site of Pine Level and its inhabitants, and to contextualize its founding, growth, and downfall within the development of the south Florida region. Specifically, one goal was to learn more about the people who moved to this rural town, including their ethnicity, social status, livelihoods, and political outlook. The second research question was discovering how Pine Level had been spatially organized, whether this layout had changed over time, and x what this spatial patterning could reveal about the town’s function within greater south Florida. Historical and archaeological research methods were used to try to answer these questions. Historical research into the Reconstruction era placed Pine Level in context within the tumultuous changes of this period. Study of primary documents revealed information about how the town was organized, and how several buildings at the site were probably constructed. Oral history interviews were also conducted with community members who had knowledge of Pine Level. Archaeological investigations at the site included a surface survey, artifact collection, shovel testing, and unit excavation. This work was focused on ground-truthing the information gathered during the historical research and oral histories. Last, analysis of the ceramic, glass, and metal artifacts at the site added to the interpretation of the social status of Pine Level’s citizens, contributed to an evaluation of the site’s spatial patterning, and underscored functional differences between certain areas of Pine Level. The research presented in this thesis shows that Pine Level was the creation of a Republican politician, and that it functioned as an enclave of Republican power during the Reconstruction era. During this time, Pine Level’s growth was sluggish, and it remained unpopular with many citizens in Manatee County. It consisted of a few government buildings in the center of the town, but little else. However, with the fall of the Manatee County Republicans in 1876, Pine Level suddenly began to prosper, adding many new landowners and businesses. A distinct business district developed, and areas of the town near the major roads garnered particularly high prices. Artifact analysis shows that the income level of these newcomers was probably modest, but that they had xi access to consumer goods from across the United States and as far away as England. The town’s prosperity was short-lived, though. As detailed in this thesis, once Pine Level lost county seat status, it immediately began to decline, and businesses quickly moved to Arcadia. The town continued on as a small community through at least the first decade of the twentieth century, but eventually became a nothing more than a spot on a map.

Стилі APA, Harvard, Vancouver, ISO та ін.

20

Simões, Mário da Silva Correia. "Développement d'électrocatalyseurs anodiques plurimétalliques nanostructurés pour une application en pile à combustible à membrane alcaline solide (SAMFC)." Poitiers, 2011. http://nuxeo.edel.univ-poitiers.fr/nuxeo/site/esupversions/b019adc2-f6df-4414-a842-7e161cb5227f.

Повний текст джерела

Анотація:

Les piles à combustible alcalines sont des alternatives aux PEMFC, permettant un plus large choix des catalyseurs et de combustibles, comme les petites molécules organiques et les borohydrures. L'activité et la sélectivité de nanocatalyseurs synthétisés par une méthode colloïdale ont été évaluées pour l'électrooxydation du glycérol et du borohydrure de sodium en milieu alcalin. La formulation des catalyseurs a été basée sur le palladium. Son interaction avec Au, Ni et Bi a été étudiée. Un catalyseur Pt/C a été également étudié ainsi que son interaction avec Bi. Concernant l'oxydation du glycérol, les catalyseurs PdAu/C sont plus actifs que les catalyseurs Au/C et Pd/C. Ce fait est expliqué par un effet synergétique entre les deux métaux qui forment des alliages ordonnés. Dans le cas des catalyseurs PdNi/C riches en Pd un mécanisme bi-fonctionnel semble plus probable pour expliquer l'augmentation d'activité. Les catalyseurs PdBi/C et PtBi/C sont les plus actifs. Les fonctions alcools primaires du glycérol sont oxydées préférentiellement sur les catalyseurs à base de Pd et Pt. La production de l'ion hydroxypyruvate a été détectée sur le catalyseur Au/C. Un mécanisme de l'oxydation de NaBH4 sur le Pd a été proposé, impliquant les réactions d'hydrolyse, d'oxydation de l'hydrogène et du borohydrure. Les catalyseurs Pd0,5Au0,5/C et Pd0,5Ni0,5/C ont une activité identique à celle du Pd/C. Le catalyseur Pt0,9Bi0,1/C est actif pour l'oxydation directe de NaBH4 à bas potentiels. L'oxydation du glycérol permet la cogénération d'électricité et de produits chimiques à haute valeur ajoutée, tandis que l'oxydation de NaBH4 permet d'atteindre de fortes densités d'énergie et de puissance
Solid Alkaline Membrane Fuel Cells are feasible alternatives to PEMFCs, allowing a wider choice of catalytic materials and fuels other than hydrogen, like small organic molecules and borohydrides. Several nanocatalysts were synthesized by a colloidal method and their activity and selectivity were studied toward the glycerol and NaBH4 electrooxidation in alkaline medium. Those catalysts are palladium based. Its interaction with Au, Ni and Bi were also evaluated. A Pt/C catalyst was also studied as well as its interaction with bismuth. PdAu/C catalysts presented a higher activity toward the glycerol electrooxidation than monometallic Au/C and Pd/C. This fact is explained by a synergetic effect between both metals that form ordered alloys. A bifunctional mechanism seems more appropriate to explain the increased activity of palladium rich PdNi/C catalysts. PdBi/C and PtBi/C are the most active catalysts for the glycerol oxidation due to adatom and bifunctional effects. The primary alcohol functions of the glycerol molecule are preferentially oxidized on Pd and Pt based catalysts. The production of hydroxypyruvate ion species was evidenced on Au/C catalyst. A mechanism was proposed for the NaBH4 oxidation on palladium, involving hydrolysis, hydrogen and borohydride oxidation steps. Pd0,5Au0,5/C and Pd0,5Ni0,5/C catalyst activities are similar to that of Pd/C. NaBH4 direct oxidation occurs on Pt0,9Bi0,1/C at low potentials without hydrogen evolution. Glycerol oxidation in alkaline fuel cell allows the cogeneration of electricity and high value added chemicals while NaBH4 oxidation allows for high energy and power density systems

Стилі APA, Harvard, Vancouver, ISO та ін.

21

Ferrandez, Anne-Claire. "Synthèse et caractérisation des nouvelles architectures catalytiques pour une application en pile à combustible du type PEMFC." Poitiers, 2011. http://nuxeo.edel.univ-poitiers.fr/nuxeo/site/esupversions/1cb2c4a4-6d5f-47d5-b0a0-5d40f245abd4.

Повний текст джерела

Анотація:

Cette thèse s'inscrit dans le contexte de développement de nouvelles couches catalytiques pour les piles à combustible du type PEMFC, basée sur la transposition de la phénoménologie du point triple à l'échelle moléculaire. Les travaux portent sur le greffage de polymères conducteurs protoniques à la surface de nanoparticules de platine afin d'obtenir des complexes catalytiques hybrides (organique/inorganique). Les matériaux ont été obtenus par deux méthodes de greffage du polystyrène sulfonate de sodium. La première méthode est la voie dite "grafting from". Elle consiste à polymériser le styrène sulfonate de sodium à partir de l'amorceur présent à la surface des nanoparticules de platine qui est greffé soit par "post greffage", soit par "greffage in situ". La seconde méthode appelée "grafting onto", quant à elle, consiste à synthétiser le polystyrène sulfonate de sodium en phase homogène puis de le condenser à la surface des nanoparticules de platine soit par "post greffage", soit par "greffage in situ" pendant les synthèses microémulsion "water in oil" et "instant method". La variation des paramètres de synthèse a permis de constituer une gamme de matériaux présentant une variété de densité de greffage à la surface des nanoparticules de platine. C'est sous la forme acide du polymère que s'opère la conduction protonique. Un traitement acide des matériaux a permis d'obtenir le polystyrène sulfonique (SO3H) à la surface des nanoparticules de platine. Les caractérisations électrochimiques réalisées dans deux milieux (support et oxydant) avec différentes électrodes de travail ont permis d'apporter de nombreuses informations sur la structure, l'activité et la sélectivité des complexes catalytiques hybrides
This thesis is within the scope of new catalytic layers development for proton exchange membrane fuel cell (PEMFC) based on the transposition of the phenomenology of the three-phase boundary at the molecular scale. The fieldwork concerns the working out of hybrid organic/inorganic catalyst by grafting proton conducting polymers (PSS). Both methods have been developed to introduce the polymer on the platinum nanoparticles. The first method consists of using the "grafting from" technique and controlled radical polymerization (Atom Transfer Radical Polymerization). The second grafting method used is the "grafting onto" technique. It consists first in synthesizing the polymer and second in grafting by reaction of the functions of the latter with platinum nanoparticles. Modifications of synthesis parameters allowed constituting a collection of objects showing a wide range of grafting density. Electrochemical characterizations have brought numerous information on the structure, activity and selectivity of hybrid catalytic complex

Стилі APA, Harvard, Vancouver, ISO та ін.

22

Korakaki, Evangelia. "The role of size and age in the physiological ecology of Scots pine and poplar trees." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/12105.

Повний текст джерела

Анотація:

The main objective of the present thesis is to investigate the mechanisms underlying the age- and size-related decline observed in growth efficiency and in relative above ground mass growth rates in both Scots pine and poplar (clonal) chronosequences. Hence, I compared differentially aged Scots pine stands and trees growing at the same site, in contrast to most previous studies, isolating leaf- from stand-level responses. In addition, I used poplar clonal material to compare growth and morphological parameters of genetically identical cuttings taken from young, middle-age and old plants belonging to four clones and I carried out investigations both in the field on the original donor trees (trees of identical meristematic ages and different sizes) and on rooted cuttings (identical meristematic ages and same size). Scots pine study: Our results partially supported the hydraulic limitation hypothesis, but at the same time suggested that additional factors were also involved in the decline in growth efficiency with age. Such factors may involve decreased soil nutrient availability, increased below-ground allocation and reduced turgor pressure in tall trees. Poplar study: The observed decline in growth and carbon uptake in poplar donor trees in the field was related to the increases in tree size, the increased path length and possibly the architectural complexity, or in some cases to decreased nutrient availability in the soil but not to cellular senescence per se.

Стилі APA, Harvard, Vancouver, ISO та ін.

23

Klinka, Karel, Qingli Wang, G. G. Wang, K. Dave Coates, and Christine Chourmouzis. "Predicting site index of Lodgepole pine and interior spruce in the sub-boreal spruce zone." Forest Sciences Department, University of British Columbia, 2001. http://hdl.handle.net/2429/684.

Повний текст джерела

Анотація:

Knowledge of ecological site characteristics and tree growth on different sites is fundamental for silvicultural decisionmaking and planning. With biogeoclimatic ecosystem classification in place in British Columbia, silvicultural management has been given an ecological foundation; however, relationships between growth and site quality have not yet been fully investigated. The purpose of this study was to determine how site conditions within the SBS zone affect the height growth of lodgepole pine (Pl) and interior spruce (Sx).

Стилі APA, Harvard, Vancouver, ISO та ін.

24

Schaefer, Chloe. "Pipe dream : why Utah's water managers continue to prioritize supply-side solutions." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99087.

Повний текст джерела

Анотація:

Thesis: M.C.P., Massachusetts Institute of Technology, Department of Urban Studies and Planning, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 51-59).
More than 150 years ago, the Mormon pioneers entered the Salt Lake Valley and immediately set to work digging irrigation ditches and canals to harness what water there was for their farms. Since then, Utah water managers have solved water supply problems by building large infrastructure projects. Today, Utah's population is growing rapidly, but the water supplies that enable its desert oases are not, and climate change is expected to make matters worse. This increasing tension between growing populations and dwindling water supplies is not unique to Utah. However, while other states in the region have implemented aggressive demand-side measures to conserve water, Utah's conservation efforts have been relatively minimal. Utah's history of water engineering, the cultural importance of agriculture, the precedent of federal funding for large water projects, and some of the cheapest water rates in the country make demand-side measures a tough sell for addressing water needs in Utah. However, supply-side projects are costly for taxpayers and for the environment, take decades to complete, and are based on unreliable forecasts of future water demand and uncertain water sources. It is time for Utahans to look past traditional supply-side solutions and embrace water conservation measures, requiring changes to the dominant water planning mindset. In order to do this, the state could take regulatory action, and both the state and LDS Church can act as water efficiency exemplars. It is also time for Utahans to become more involved in Utah's water planning and decide for themselves whether to continue attempting to conquer nature or to live within its bounds.
by Chloe Schaefer.
M.C.P.

Стилі APA, Harvard, Vancouver, ISO та ін.

25

Klinka, Karel, Gordon J. Kayahara, and Christine Chourmouzis. "Testing site index-site factor relationships for predicting lodgepole pine and interior spruce productivity in central British Columbia." Forest Sciences Department, University of British Columbia, 1998. http://hdl.handle.net/2429/767.

Повний текст джерела

Анотація:

Knowledge of the potential productivity of a tree species becomes especially important when timber production is the primary management objective. However, direct determination of potential productivity is often not possible. For example, in situations where the site is unstocked, stocked with trees unsuitable for productivity measurement, or stocked with species other than the one of interest. In these cases, an indirect estimate using known characteristics of the site itself is required. Such estimates were made using regression to model site index with indirect measures of site quality for lodgepole pine (Pinus contorta) and interior spruce (Picea engelmannii × P. glauca) in the Sub-Boreal Spruce (SBS) zone of central BC. We tested the utility of these productivity relationship models for predicting the site index of lodgepole pine and interior spruce (Kayahara et al. accepted for publication).

Стилі APA, Harvard, Vancouver, ISO та ін.

26

Saqib, Muhammad. "The use of laboratory and site tests data in the finite element modelling of offshore piles subjected to tensile loading." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.

Знайти повний текст джерела

Анотація:

The thesis investigate the response of pile foundations subjected to axial load, with application to offshore wind turbines supported by multi-pod steel jackets. Wind turbines are relatively light weight structures as compared to other offshore structures and this results on the foundation in high tensile loadings. For this reason, the thesis focus is the response of a open ended steel pile subjected to pull out. The study develops on the results of a large-scale testing campaign recently conducted at the Test Centre of Support Structures of the Universität Hannover. The model piles encompassed various lenghts, diameters and thicknesses. In the thesis, different design methods (ICP-05, UWA-05, NGI-05 and Fugro-05) have been used to back analyse the experimental results and were compared to each others. Results of site and laboratory tests on the soil used in the experiments were also used to identify the soil parameters required to implement finite element models of the tested piles. In particular, CPT tests and triaxial tests were considered and the parameters derived are the soil behavior type, the soil unit weight, the stiffness modulus, the relative density, the poissons ratio, and the peak friction angle. Finite element analyses were then run in the experimental boundary and loading conditions e the results were compared with experimental data. A good agreement was observed, particularly on the capacity. The advantage of using the finite element method is the possibility to gain an insight in the pile behaviour and describe the entire load-displacement curve, when compared to CPT based bearing capacity prediction. Good results were achieved using a simple constitutive model, improvement can be surely gained by implementing more sophisticate soil models.

Стилі APA, Harvard, Vancouver, ISO та ін.

27

Gray, Janet Bracey. "Rare vascular flora of the longleaf pine-wiregrass ecosystem temporal responses to fire frequency and population size /." NCSU, 2001. http://www.lib.ncsu.edu/theses/available/etd-20011129-090701.

Повний текст джерела

Анотація:

GRAY, JANET BRACEY. Rare vascular flora of the longleaf pine-wiregrass ecosystem: temporal responses to fire frequency and population size. (Under the direction of Dr. Thomas R. Wentworth) We examined factors likely to be important in the management of rare flora occurring in the longleaf pine-wiregrass ecosystem on Fort Bragg and Camp Mackall Military Reservations in North Carolina. Thirty-six rare plant species, comprising 1,268 records, were documented during the course of two inventories of rare flora conducted during the periods 1991-93 and 1998-99. There were 891 (70.3%) records of persistence, 258 (20.3%) records of extinction, and 119 (9.4%) records of colonization; extinctions exceeded colonizations by 139 records. We used analyses of contingency table frequencies and logistic regressions to test hypotheses about temporal responses of local populations of rare flora. We found statistically significant effects of fire frequency on the colonization and extinction of rare flora; extinctions declined and colonizations increased with increasing fire frequency. There were statistically significant effects of both area occupied and stem number on the persistence and extinction of rare flora; extinctions declined and persistences increased with increasing area occupied and stem number. Relative turnover of rare flora was correlated with mean fire frequency and mean stem number. Relative turnover increased with increasing fire frequency and declined with increasing population size. Our analyses indicate the importance of fire and population size for the conservation of rare flora in this landscape.

Стилі APA, Harvard, Vancouver, ISO та ін.

28

Cerchiaro, Michael Paul. "Loblolly Pine (Pinus taeda L.) Plantation Response to Mechanical Site Preparation in the South Carolina and Georgia Piedmont." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/31435.

Повний текст джерела

Анотація:

Site preparation is fundamental for establishing loblolly pine (Pinus taeda L.) plantations, but long-term sustainability of plantations established using mechanical treatments is in question because of concerns regarding soil tillage and the removal of harvest residue and soil organic matter. A study was installed in 1981 on 12 locations in northeastern Georgia and west-central South Carolina to evaluate pine plantation response to mechanical site preparation. Site preparation treatments induced gradients of organic matter manipulation and soil tillage. The treatments included: Control, Chop/Burn, Shear/Disc, Shear/V-Blade, Shear/Rake, and Shear/Rake/Pile. Research was conducted to address the following objectives: (i) compare rotation-age forest response to several intensive site preparation treatments used to establish pine plantations in the Piedmont of the southeastern United States; (ii) correlate growth response with the gradients of soil organic matter removal, soil tillage, and hardwood control; (iii) determine the influence of intensive management on the amount of carbon contained in pine plantations.

All site preparation treatments increased year-18 volume accumulation compared to the control treatment. Chop/Burn and Shear/Disc treatments, with pine volumes of 214 m3 ha-1 and 232 m3 ha-1, respectively, conserved harvest residue and out-performed the Shear/Rake treatment (191 m3 ha-1), which completely removed harvest residue. Treatments that included tillage provided growth benefits that lasted throughout the rotation even when tillage was accompanied by complete organic matter removal. Hardwood competition had the greatest influence on pine volume accumulation, explaining over 54% of the variation in pine growth at age 18. Treatments that included tillage most effectively controlled hardwood competition.

At year 18, site preparation treatments significantly affected soil organic matter (SOM) content; however, soil nitrogen, foliar nitrogen, bulk density, and macroporosity were not affected by site preparation. All treatments were equally deficient in foliar nitrogen. The Shear/Disc and Shear/Rake/Disc treatments had a significantly positive relationship between foliar nitrogen and pine volume. These treatments had lower hardwood basal areas (below 15%), indicating that once hardwoods were controlled, nitrogen became limiting to pine growth.

Using pre-harvest characterization data, carbon accumulation during old-field succession increased fourfold compared to agricultural sites on the nearby Calhoun Experimental Forest. Carbon accumulation on these old-field loblolly pine sites reached quasi-equilibrium after 40 years as shown by uncut reference stands. Site preparation significantly affected the amount of soil C in the upper 20 cm of the soil. Those site preparation treatments that removed harvest residue and accelerated SOM decomposition through tillage had the lowest soil carbon levels. The Shear/Rake/Disc treatment had 10% lower soil carbon content than the Control and Shear/V-Blade treatments.
Master of Science

Стилі APA, Harvard, Vancouver, ISO та ін.

29

Usmani, Shirin Mustaquim. "Wood treated with nano metal fluorides - relations between composition, size, and durability." Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://dx.doi.org/10.18452/22553.

Повний текст джерела

Анотація:

In dieser Arbeit werden die nanoskaligen Partikel von Magnesiumfluorid (MgF2) und Calciumfluorid (CaF2), die als Nano-Metallfluoride (NMFs) bekannt sind, auf ihr Potenzial zur Verbesserung der Beständigkeit von Holz-basierten Materialien untersucht. Ihre besondere Eigenschaft der geringen Wasserlöslichkeit ist Grundlage dafür, einen langanhaltenden Schutz des behandelten Holzes aufrechtzuerhalten, indem die Auslaugung von Fluorid reduziert wird. Die Partikelgröße der synthetisierten NMFs und ihre Verteilung in behandelten Holzproben wurde charakterisiert. Rasterelektronenemikroskopaufnahmen und der zugehörigen energiedispersiven Röntgenspektroskopie zeigen, dass Aggregate dieser Partikel eine homogene verteilung in der untersuchten Holzmatrix von behandelten Proben. Die Fluoridaggregate bilden eine Schutzschicht um die Zellwände und blockieren deren Hoftüpfel, dadurch ist der mögliche Fließweg für die Wasseraufnahme ins Holz eingeschränkt. Dies zeigt sich in erhöhter Hydrophobie des mit Nano-Metallfluorid (NMF)-behandelten Holzproben. Die biozide Wirkung der NMFs wurde gegen Braunfäulepilzen (Coniophora puteana und Rhodonia placenta), am Weißfäulepilz (Trametes versicolor) und den Termiten (Coptotermes formosanus) geprüft. Im Vergleich zu unbehandelten Proben weist das mit Fluorid behandelte Holz eine höhere Beständigkeit gegen Fäulnis und Termitenfraß auf. Obwohl alle NMF-Behandlungen den durch Fäulnis verursachten Masseverlust des Holzes reduzieren, zeigt nur eine kombinierte Behandlung mit MgF2 and CaF2 eine höhere Wirksamkeit gegen Fäulnis und Termitenfraß auf. Die Ergebnisse dieser Arbeit zeigen, dass NMFs robust genug sind für Anwendungen im Freien mit Bodenkontakt. Darüber hinaus stellen sie aufgrund ihrer sehr schlechten Wasserlöslichkeit ein geringeres Risiko für die menschliche Gesundheit und Umwelt dar. Die neuartigen Ergebnisse dieser Arbeit zeigen das Potenzial von NMFs, die Lebensdauer von Baumaterialien aus nicht haltbarem Holz zu erhöhen.
In this study, nanoscopic particles of magnesium fluoride (MgF2) and calcium fluoride (CaF2) also known as nano metal fluorides (NMFs), were evaluated for their potential to improve wood durability. Their distinct property of low-water solubility is proposed to maintain long-lasting protection of treated wood by reducing the leaching of fluoride. Analytical methods were used to characterize the synthesized NMFs and their distribution in treated wood specimens. In nano metal fluoride (NMF) treated specimens, aggregates of these particles are uniformly distributed in the wood matrix as confirmed with scanning electron microscopy images and their corresponding energy-dispersive X-ray spectroscopy maps. The fluoride aggregates form a protective layer around the tracheid walls and block the bordered pits, thus reducing the possible flow path for water absorption into wood. This is reflected in the increased hydrophobicity of NMF treated wood. The biocidal efficacy of NMFs was tested against brown-rot fungi (Coniophora puteana and Rhodonia placenta), white-rot fungus (Trametes versicolor), and termites (Coptotermes formosanus). Compared to untreated specimens, the NMF treated specimens have a higher resistance to decay caused by brown-rot fungi, white-rot fungus, and termites. Although all NMF treatments in wood reduce the mass loss caused by fungal decay and termite attack, only the combined treatment of MgF2 and CaF2 has efficacy against brown-rot fungi and white-rot fungus. Similarly, wood treated with the combined NMF formulation is the least susceptible to attack by C. formosanus. In this thesis, it was proven that NMFs are robust enough for above ground contact outdoor applications of wood in permanent wetness conditions. Also, they pose a low risk to human health and the environment because they are sparingly soluble. Overall, the novel results of this study show the potential of NMFs to increase the service life of building materials made from non-durable wood.

Стилі APA, Harvard, Vancouver, ISO та ін.

30

Houghton, Damon. "Minimum tree height sample sizes necessary for accurately estimating merchantable plot volume in Loblolly pine plantations." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-05022009-040541/.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

31

Menzer, Jeremy G. "Discovering Rock Features with Geophysical Exploration and Archaeological Testing at the Mississippian Pile Mound Site, Upper Cumberland Plateau, Tennessee." Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/etd/2509.

Повний текст джерела

Анотація:

The Pile Mound survey includes magnetometry paired with targeted ground-penetrating radar (GPR) and electromagnetic induction (EMI) surveys of the mound and testing of associated features over the ca. 6.5 ha site. The GPR survey discovered six rock features (five large rock features within the mound and one marking the outside of the mound). Knowledge of mounds in the Upper Cumberland Plateau (UCP) is lacking—the closest other studied sites are at the Corbin Site, Croley-Evans, Bell Site, and Beasley Mounds, approximately 75 – 100 km away. However, the most similar mound construction is found at Corbin and Cherokee sites, some 175 – 275 km away. In addition, the associated ceramic assemblage appears to reflect more similarity to the East Tennessee Valley rather than the Middle Cumberland region. These data provide a unique opportunity to better understand the Mississippian occupation in the UCP of Tennessee.

Стилі APA, Harvard, Vancouver, ISO та ін.

32

Yang, Sheng-I. "Estimation and Determination of Carrying Capacity in Loblolly Pine." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/80442.

Повний текст джерела

Анотація:

Stand carrying capacity is the maximum size of population for a species under given environmental conditions. Site resources limit the maximum volume or biomass that can be sustained in forest stands. This study was aimed at estimating and determining the carrying capacity in loblolly pine. Maximum stand basal area (BA) that can be sustained over a long period of time can be regarded as a measure of carrying capacity. To quantify and project stand BA carrying capacity, one approach is to use the estimate from a fitted cumulative BA-age equation; another approach is to obtain BA estimates implied by maximum size-density relationships (MSDRs), denoted implied maximum stand BA. The efficacy of three diameter-based MSDR measures: Reineke's self-thinning rule, competition-density rule and Nilson's sparsity index, were evaluated. Estimates from three MSDR measures were compared with estimates from the Chapman-Richards (C-R) equation fitted to the maximum stand BA observed on plots from spacing trials. The spacing trials, established in the two physiographic regions (Piedmont and Coastal Plain), and at two different scales (operational and miniature) were examined and compared, which provides a sound empirical basis for evaluating potential carrying capacity. Results showed that the stands with high initial planting density approached the stand BA carrying capacity sooner than the stands with lower initial planting density. The maximum stand BA associated with planting density developed similarly at the two scales. The potential carrying capacity in the two physiographic regions was significantly different. The value of implied maximum stand BA converted from three diameter-based MSDR measures was similar to the maximum stand BA curve obtained from the C-R equation. Nilson's sparsity index was the most stable and reliable estimate of stand BA carrying capacity. The flexibility of Nilson's sparsity index can illustrate the effect of physiographic regions on stand BA carrying capacity. Because some uncontrollable factors on long-term operational experiments can make estimates of stand BA carrying capacity unreliable for loblolly pine, it is suggested that the stand BA carrying capacity could be estimated from high initial planting density stands in a relatively short period of time so that the risk of damages and the costs of experiments could be reduced. For estimating carrying capacity, another attractive option is to choose a miniature scale trial (microcosm) because it shortens the experiment time and reduces costs greatly.
Master of Science

Стилі APA, Harvard, Vancouver, ISO та ін.

33

Neaves, Charles Mitchell III. "Long term effects of wet site timber harvesting and site preparation on soil properties and loblolly pine (Pinus taeda L.) productivity in the lower Atlantic Coastal Plain." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/77702.

Повний текст джерела

Анотація:

Short term studies have suggested that ground based timber harvesting on wet sites can alter soil properties and inhibit early survival and growth of seedlings. Persistence of such negative effects may translate to losses in forest productivity over a rotation. During the fall and winter of 1989, numerous salvage logging operations were conducted during high soil moisture conditions on wet pine flats in the lower coastal plain of South Carolina following Hurricane Hugo. A long-term experiment (split-plot within an unbalanced randomized complete block design) allowed assessment of long term effects of rutted and compacted primary skid trails and subsequent site preparation on soil properties and loblolly pine (Pinus taeda L.) productivity. The experiment had 12 blocks, four levels of site preparation as the whole plot factor (bedding, disking with bedding, disking, and no site preparation), and two levels of traffic as the subplot factor (primary skid trail, no obvious traffic). After 23 years, bedding and disking with bedding treatments effectively enhanced soil physical properties and stand productivity via promoting greater survival and stocking, but had little effect on the size of individual trees relative to disking and no site preparation treatments. Primary skid trails significantly reduced the size of individual trees, but had no appreciable long term effects on soil properties or stand productivity after 23 years. The study suggests that bedding is the most efficient practice to enhance soil properties, seedling survival, and stand productivity on wet sites. However, site preparation is not necessary for these soils and sites, if strictly intended to restore soil properties and stand productivity in primary skid trails. Reduction in individual tree sizes on primary skid trails emphasizes benefits in minimizing the spatial extent of disturbance.
Master of Science

Стилі APA, Harvard, Vancouver, ISO та ін.

34

Norris, Paul. "The behaviour of jacked concrete pipes during site installation." Thesis, University of Oxford, 1992. http://ora.ox.ac.uk/objects/uuid:7081bc8a-c149-4706-83f9-d041ce066819.

Повний текст джерела

Анотація:

While much money and effort has been spent by manufacturers and users of pipe jacking equipment to develop suitable techniques, this work appears to be the first to study the method at full scale, in a scientific research programme. It has involved monitoring a series of five pipe jacks during construction. In each case a heavily instrumented pipe was incorporated into the pipe string to measure pipe joint stresses, pipe and joint compressions and contact stresses between pipe and ground. Total jacking loads and movements of the pipe string were also measured and all results correlated with a detailed site log, full tunnel alignment surveys, and observed ground conditions. The success of the site monitoring has been highly dependent upon the development of a suitable instrumentation and data acquisition system in conjunction with appropriate site procedures for working in the restricted and physically demanding pipe jack environment without undue disruption to normal site operations. The build up of total jacking force is the result of highly complex soil-pipe interaction. The local interface stresses are essentially frictional in most ground conditions, and can be related to the shear strength of the ground. The problem is in determining the effective radial stresses which are affected by soil insitu stresses, stiffness and strength; groundwater conditions; rate of progress; pipeline misalignment and use of lubricants. Relations between pressure distributions at pipe joints and measured tunnel alignments are presented. That small angular deviations between successive pipes cause severe localisation of stresses on their ends is clearly demonstrated. Careful back analysis shows that the linear stress approach of the Concrete Pipe Association of Australia can adequately match the measured stresses and could be used by pipe manufacturers to provide design data on allowable jacking forces for pipes on the basis of pipe size, packer properties, concrete strength and angular alignment. It is also clear from the small pipe barrel stresses that improved packing materials would allow more of the potential strength of pipes to be achieved. Since relative angular than absolute deviations control transfer mechanisms between pipes, uncritical adherence to specifications based on absolute line and level is counter-productive.

Стилі APA, Harvard, Vancouver, ISO та ін.

35

Walsh, Patrick J. "The influence of site factors on the community structure of pine beauty moth predators." Thesis, University of Ulster, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281211.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

36

Walsh, Terese Ann Catherine. "Diameter/basal area increment equations for loblolly pine trees in cutover, site-prepared plantations." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/94489.

Повний текст джерела

Анотація:

The objective of this study was to develop diameter/basal area increment equations for loblolly pine trees in thinned and unthinned plantations on cutover, site-prepared areas. Results indicated that one set of coefficients was sufficient to estimate individual tree growth (for the three year period following thinning) on lightly thinned and heavily thinned plots. However, unthinned plots required a separate set of coefficients and therefore a separate equation to estimate growth. Diameter growth was adequately explained by some form of the following regressor variables: pine basal area, hardwood basal area, initial age, initial diameter, average height of the dominant and codominant trees, and crown ratio ( optional). Transforming the dependent variable from a function of diameter to a similar function of basal area had no apparent effect on the precision of the predicted results. Two alternative methods of predicting diameter growth were evaluated: (1) direct fitting of diameter growth, and (2) fitting a potential diameter growth equation and a modifier function. Even though the potential times modifier approach performed slightly better in terms of fitting the data, it provided unrealistic results at ages beyond the upper range of the data. After additional data are obtained at older ages, the potential times modifier approach may surpass the direct approach. However, at present, the direct diameter growth model was chosen as the final model form.
M.S.

Стилі APA, Harvard, Vancouver, ISO та ін.

37

Paganelli, David. "Nitrogen dynamics after site preparation in three loblolly pine plantations on the Virginia Piedmont." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/91052.

Повний текст джерела

Анотація:

Intensive site preparation practices and their effect on nitrogen cycling have been implicated as possible causes of productivity declines on forest sites in Australia and New Zealand. This study was initiated in order to determine the effects of site preparation intensity upon N distribution and availability in loblolly pine (Pinus taeda L.) plantations in Virginia. In the summer of 1982, three forest sites at the Reynolds Homestead Research Center on the Virginia Piedmont were clearcut. In the fall of the same year all three sites were prepared for planting using one of the following treatments: 1. shear, rake, disk (S,R,D) (3-passes); 2. shear-disk (S-D) (1-pass); and 3. chop, burn (C,B) (high intensity burn). During March of 1983, 1-0 genetically improved loblolly pine seedlings were planted on all sites. Pine biomass was greatest on the S,R,D area after three growing seasons. Total biomass and N content (NCONT) of native vegetation and forest floor were greatest in the S-D area. Total N in the upper 15 cm of mineral soil was also greatest in the S-D area. Total system N was highest in the S-D area and this treatment is more N-conservative than either of the more intensive treatments. During the third growing season potentially mineralizable N levels were highest on the two disked treatment areas, 157 and 144 kg N/ha for the s-o, and S,R,D areas, respectively. Pine foliar nutrient concentrations determined after the second and third growing seasons provided no evidence of existing or impending nutrient deficiencies. These results show that short-term pine nutrition and growth were not adversely affected by reductions of N capital on these sites. However, if wasteful practices, such as raking and burning with high intensity fires, are also used to establish subsequent stands on these same sites, cumulative losses of N could result in productivity declines.
M.S.

Стилі APA, Harvard, Vancouver, ISO та ін.

38

Lakel, William A. "Slash Mulching and Incorporation as Mechanical Site Preparation for Pine Plantation Establishment and Subsequent Effects on Soil Moisture and Site Hydrology." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/9874.

Повний текст джерела

Анотація:

Over one million hectares of pocosins and wet flats in the southeastern coastal plain are intensively managed for the production of loblolly pine (Pinus taeda) plantations. These management activities may have adverse effects on soil physical properties, site hydrology, and overall site productivity. Substantial quantities of wood residues are often left on these sites by timber harvesting operations, and it was hypothesized that the incorporation of this slash into the soil could improve the soil physical properties and site hydrology. One organic pocosin site and one mineral wet flat site were chosen post-harvest for treatment. The wet flat study was organized as an incomplete block design having four blocks and six treatments: (i) conventional bedding, (ii) strip surface mulching with bedding, (iii) strip surface mulching with tillage and bedding, (iv) broadcast mulch without bedding, (v) broadcast mulch with bedding, and (vi) flat planted control. The pocosin study was organized as a randomized complete block design with four blocks and four treatments. The treatments are identical to those of the wet flat site without the broadcast mulch treatments (iv and v). Soil physical property data was analyzed pre- and post-treatment, while post-treatment site hydrology and soil water chemistry data was analyzed periodically for one year. Seedling survival and height data were analyzed after one growing season. The treatments had little effect on soil physical properties, site hydrology, soil water nutrients, or seedling survival on the wet flat study site. Bedding in general significantly increased tree height growth, but mulching had no significant effects. The treatments had little effect on soil physical properties on the pocosin study site except for soil macroporosity, which was significantly increased by bedding. Site hydrology and soil water nutrients were not significantly affected by the treatments, but seedling survival and height growth were significantly increased by bedding. Mulching had no significant effects on any of the parameters studied.
Master of Science

Стилі APA, Harvard, Vancouver, ISO та ін.

39

Holstad, Ylva, and Sara Boström. ""Det kan vara byta p-piller lösning, det kan vara ingen lösning alls... ingenting är svart eller vitt där" : En fokusgruppstudie om barnmorskors handläggning och uppfattningar av p-piller och biverkningar." Thesis, Umeå universitet, Institutionen för omvårdnad, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-105285.

Повний текст джерела

Анотація:

Objective: To study midwives management, practice and reasoning regarding contraceptive counseling for women who are experiencing "mild" side effects of the pill Methods: Four focus groups, made up of three to five midwives per group, participated in focus group discussions. Qualitative design with the method “Think-Aloud” has been used to collect data and the material was analyzed using content analysis. Results: The study identified three categories, the first "How midwives practice regarding the side effects of the pill," shows that midwives have a systematic approach when meeting with women who are experiencing side effects of the pill. The next category "Using a holistic and professional approach for women" highlights that the midwives take women's side effects seriously and that midwives respect individual woman’s autonomy. Finally in the third category "Lack of evidence about side effects becomes a women's dilemma" here midwives describe varying ways of interpreting side effects as well as attitudes and socio-economic conditions in society that affect women's choice of contraception. Conclusion: The midwives express that side effects such as loss of libido, depression and weight gain are complex and often difficult to attribute solely to the pill. The midwives' work is characterized by a holistic approach. We see the benefits of sharing information in groups, therefor we suggest that midwives create mediums where they can learn from each other by sharing their valuable experience and knowledge.

Стилі APA, Harvard, Vancouver, ISO та ін.

40

Kelting, Daniel Ladd. "Timber Harvesting and Site Preparation Effects on Soil Quality for Loblolly Pine Growing on the Lower Coastal Plain of South Carolina." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/26842.

Повний текст джерела

Анотація:

The Lower Coastal Plain of the southeastern United States is a major wood producing region. The region is characterized by a combination of nearly-level topography, poorly-drained soils, and high rainfall, which results in a perched water table in some soils that inundates the surface several times each year. Harvesting timber under wet site conditions often results in extensive soil compaction, rutting, soil displacement, and waterlogging. Forest managers are concerned that these visually-displeasing soil disturbances may cause site damage and reduced productivity. These concerns were addressed in an operational-scale field experiment conducted in South Carolina. The objectives of this experiment were to determine: (i) if soil disturbance changes key soil properties and processes; (ii) if soil disturbance reduces loblolly pine productivity; and, (iii) if disturbance can be mitigated with site preparation practices? Three 20-ha, 20-yr-old loblolly pine (Pinus taeda L.) plantations were harvested under wet and dry conditions to create a broad gradient in soil disturbance. Within each harvested plantation, a subset of 3-ha plots were site prepared by either bedding, or mole-plowing plus bedding, then all sites were established as 3rd -rotation pine plantations. Prior to site preparation, each plot was classified and mapped using a 5 by 5 soil disturbance (none to churned) by organic debris (none to slash piles) classification matrix. Within each plot, data were collected on several soil physical, chemical, and biological properties over a 2-yr period following site preparation. Key soil properties were integrated into a Soil Quality Index (SQI) and compared to aboveground productivity of 2-yr-old loblolly pine trees growing on closely-spaced (30 by 30 cm) bioassay plots planted across the gradient of soil disturbance. The soil physical properties were used to determine the least limiting water range (LLWR), the range in soil water content within which root growth is not limited. Soil compaction and deep rutting reduced the LLWR. Retention of logging slash improved the LLWR for compacted and rutted soils. Site preparation improved the quality of the soil physical environment across all levels of soil disturbance. Soil disturbance had no effect on soil chemical or biological properties as evidenced by no change in soil pH, ECEC, base saturation, available P, or net N mineralization with disturbance. The base saturation exceeded 80 % on all sites, with Ca saturation controlling soil pH. The high base saturation buffered any redox-induced changes in soil chemistry that would have resulted from disturbance. The results showed that high fertility is an important mechanism for buffering the potentially-negative effects of soil disturbance on the soil nutritional environment. Site preparation changed soil chemical properties, but the changes were probably associated with tillage effects on organic matter and clay content, not redox processes. The SQI showed that surface soil compaction and deep rutting reduced soil quality, mainly by decreasing the LLWR and aeration depth. Site preparation mitigated the effects of most disturbances on soil quality, evidenced by similar aboveground biomass production among soil disturbance classes after bedding. A regression model was developed for predicting aboveground biomass production as a function of SQI. SQI explained 73 % of the variation in aboveground biomass production. The regression model showed that compression tracks and rutting decreased aboveground biomass production compared to undisturbed soils. The long-term effect of these disturbances on productivity will depend on natural soil recovery processes. However, these early results suggest that compaction and rutting should be minimized on similar sites, especially if sites will not be bedded before reforestation. The mole-plow / bedding treatment increased aboveground biomass production, indicating that this experimental treatment may be a viable practice for enhancing productivity.
Ph. D.

Стилі APA, Harvard, Vancouver, ISO та ін.

41

Moberg, Lennart. "Models of knot properties for Norway spruce and Scots pine /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5855-2.pdf.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

42

Butnor, John Robert. "Influence of site factors and vascular conductivity on the development of procerum root disease." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-11182008-063437/.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

43

Gailly, Frédéric. "Alimentation électrique d'un site isolé à partir d'un générateur photovoltaïque associé à un tandem électrolyseur/pile à combustible (batterie H2/O2)." Phd thesis, Toulouse, INPT, 2011. http://oatao.univ-toulouse.fr/11527/1/Gailly_Frederic.pdf.

Повний текст джерела

Анотація:

Les systèmes à énergies renouvelables couplés à un stockage hydrogène apportent des solutions nouvelles et innovantes à l'alimentation électrique des milieux peu ou non électrifiés. Le concept de batterie H2 qui équipe ce type de système est une forme de stockage originale qui apporte l'autonomie et l'indépendance électrique pour des longues durées (typiquement stockage saisonnier). Le fonctionnement de cette batterie H2 est le suivant : un électrolyseur produit des gaz (H2 et O2) avec les surplus d'énergie de la source renouvelable ; l'hydrogène, voire l'oxygène, est ensuite stocké dans des réservoirs pour être utilisé ultérieurement grâce à une pile à combustible lorsque la source renouvelable est insuffisante. Dans cette étude, nous nous intéresserons spécifiquement au couplage entre des générateurs photovoltaïques avec une batterie H2/O2 pour l'alimentation d'un site isolé sans interruption. Ces travaux de recherche s'inscrivent dans le projet ANR PEPITE (ANR-PanH 2007-2012) et ont été menés en partenariat avec HELION Hydrogen Power, le CEA Liten et l'Université de Corse. Le projet est également labellisé par les pôles de compétitivité CAPENERGIES et TENERRDIS. Tout d'abord, une réflexion générale s'appuyant sur les propriétés d'une batterie H2/O2 démontre la nécessité d'introduire une batterie (ici au plomb) pour garantir un fonctionnement instantané et sans interruption. Puis, une étude qualitative sur les architectures électriques possibles (bus de tension DC, AC…) a été menée pour s'achever sur une étude quantitative réalisée spécifiquement pour le projet PEPITE. Parallèlement à cela, différentes stratégies de gestions énergétiques ont été proposées afin d'utiliser les deux stockages dans les meilleures conditions, de limiter leur vieillissement ainsi que les pertes. Deux bancs d'essais à échelle réduite (un premier à bus DC et un second à bus AC) ont été réalisés au sein du laboratoire LAPLACE afin de valider les études et de préparer le prototype final qui sera testé sur le site de HELION Hydrogen Power au cours de l'été 2011.

Стилі APA, Harvard, Vancouver, ISO та ін.

44

Miller, Gabriel J. "Home range size, habitat associations and refuge use of the Florida pine snake, Pituophis melanoleucus mugitus, in southwest Georgia, U.S.A." [Gainesville, Fla.] : University of Florida, 2008. http://purl.fcla.edu/fcla/etd/UFE0023735.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

45

Story, Scott Joseph. "Nest-Site Selection and Nest Survival of Two Woodpecker Species in Ponderosa-Pine Dominated Forests." Thesis, Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/story/StoryS1207.pdf.

Повний текст джерела

Анотація:

Management of woodpecker populations requires knowledge of nesting habitat and vital rates in different forest conditions. We examined nest-site selection and nest survival for two woodpeckers, northern flicker (Colaptes auratus) and hairy woodpecker (Picoides villosus) at three locations in ponderosa-pine forests of the interior Columbia River Basin. Our goals were to: (1) characterize the range of habitat conditions available to nesting woodpeckers in our study area; (2) determine which habitat features best discriminated between nest and non-nest plots, and (3) establish which habitat features most influenced daily nest survival. Northern flickers and hairy woodpeckers were more likely to choose snags than live trees. Both species used larger diameter snags than those available at random. Nest snags tended to be in plots that had higher snag densities and lower live tree densities. For northern flickers, a model of constant daily survival received more support than any model containing habitat covariates. Daily nest survival from the best model for northern flickers was estimated to be 0.55 (95% CI: 0.46-0.64). Increasing live tree density and coarse woody debris volume were included in the most well supported model for hairy woodpeckers. Results from this study did not provide support for the "nest-quality" hypothesis. Nest survival for woodpeckers in this study was low, especially at the Idaho location; we hypothesize that this could be because of differences in predator abundance among the three locations. In ponderosa pine forests that have not been recently disturbed, we recommend maintaining clumps of snags, especially those that contain large snags. Further research is needed to understand the mechanisms that dictate woodpecker nest survival in ponderosa pine forests.

Стилі APA, Harvard, Vancouver, ISO та ін.

46

Herrmann, Andrew F. ""You Have Pipe Bombed our Community": Clashing Metaphors and the Closing of Social Network Site." Digital Commons @ East Tennessee State University, 2012. https://dc.etsu.edu/etsu-works/827.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

47

Klinka, Karel, Pavel Krestov, and Christine Chourmouzis. "Relationships between site index of major tree species in the ESSF zone and ecological measures of site quality." Forest Sciences Department, University of British Columbia, 1999. http://hdl.handle.net/2429/720.

Повний текст джерела

Анотація:

Knowledge of ecological characteristics of sites and growth of trees on different sites is fundamental for silvicultural decision-making and planning. With the biogeoclimatic ecosystem classification in place in British Columbia, silvicultural management has been given an ecological foundation; however, relationships between growth and site quality have not yet been fully investigated, particularly for high-elevation tree species and sites. One of the contributing factors for this situation is limited knowledge of forest productivity in the high-elevation Mountain Hemlock (MH) and Engelmann Spruce - Subalpine Fir (ESSF) biogeoclimatic zones. Consequently, the management and planning in the high-elevation forest is fraught with difficulties and uncertainties. Current harvest rates of old-growth forest stands and the method and distribution of cuttings in these zones suggest that there needs to be more recognition of the uppermost elevation limit for harvesting. Subalpine fir (Bl), Engelmann spruce (Se), and lodgepole pine (Pl) are important timber crop species in the interior high-elevation forest which is represented predominantly by the subalpine boreal ESSF zone. This zone extends from 49° to approximately 57° N latitude and from approximately 900 to 1,700 m in the north, from 1,200 to 2,100 m in central BC, and from 1,500 to 2,300 m in the south. In view of this relatively wide climatic and edaphic amplitude, a large variability in productivity is expected. The objective of this study was to quantify relationships between site index (height @ 50 yrs @ bh) of Bl, Se, and Pl, and three ecological determinants of site quality: climate, soil moisture, and soil nutrients. Quantitative relationships between site index and these measures provide predictive models for estimating site index. Additionally, we compared the site indices of the three study species to each other to examine their early height growth performance on the same sites.

Стилі APA, Harvard, Vancouver, ISO та ін.

48

Ilie, Valentina Alina. "Contribution à l'optimisation des AMEs et au développement des métrologies spécifiques pour les piles à combustible PEMFC et SAMFC." Poitiers, 2010. http://nuxeo.edel.univ-poitiers.fr/nuxeo/site/esupversions/b6c1771f-b6ea-470a-8e47-6083123f84ad.

Повний текст джерела

Анотація:

Cette thèse vise l'optimisation du processus de fabrication des AMEs par le pressage à chaud pour les PEMFC, l'optimisation des piles de type SAMFC et le développement de la métrologie spécifique pour la gestion de l'eau et de la chaleur dans le cœur des piles. Ces recherches ont été réalisées dans le cadre du projet « CHAMEAU » du programme PAN-H de l'ANR et du projet AMELI-0Pt du programme « Energies » du CNRS. Le premier objectif concerne la recherche des paramètres optimaux (température, pression, temps de pressage) de fabrication des AMEs par le pressage à chaud. Les résultats obtenus à travers la planification expérimentale annoncent la température comme le facteur le plus influent sur les performances électriques de la pile. Ces dernières augmentent avec la température sur la plage 100°C-115°C et diminuent brutalement après cette valeur critique. Deuxièmement, on s'intéresse sur le développement des piles SAMFC à combustible glycérol. Des travaux sur l'optimisation des conditions opératoires ont permis d'identifier les paramètres importants pour l'amélioration de performances des piles SAMFC et de mettre en place un protocole de test en pile. Des catalyseurs sans/ou avec peu de platine ont dévoilé une augmentation visible des performances électriques par rapport aux catalyseurs Pt/C. Des membranes plasma ont permis de tripler les performances électriques des piles SAMFCs. Troisièmement, on cible le développement d'une métrologie spécifique pour la mesure de la température à l'interface entre la membrane et la couche active. Des capteurs thermo-résistifs intégrés dans l’AME ont montré la possibilité et l'utilité de suivre en temps réel la température de la couche active
This thesis point to the optimization of the PEMFC MEAs made by hot pressing, the optimization of SAMFC working parameters and performances, and the development of specific metrologies for the water and heat management inside the AMEs core. This research is part of the “CHAMEAU” project and ANR PAN-H program and of the “AMELI-0Pt” project of CNRS “Energy” program. First objective concerns the search for the optimal parameters (temperature, pressure, and pressing time) of the MEAs manufacturing by hot pressing. The results obtained through designed experimental make known temperature as the most influential factor on the fuel cell electrical performances. The electrical power density increases with the temperature range 100°C-115°C and decreases sharply after. This critical value is seemed to be associated to the Nafion® glass temperature. Secondly, we focus on the development of the glycerol SAMFC fuel cells. Studies concerning the optimization of the operating conditions have identified the important parameters for improving the SAMFC performances and help to realize a test protocol. Catalysts less/free platinium have revealed a visible increase in electrical performance compared to the pure Pt/C catalysts and plasma membranes shown the possibility to triple the SAMFCs electrical performance. The third target, is the development of specific metrologies for the temperature measurements at the interface between the membrane and the active layer. MEA embedded thermo-resitive sensors have shown the feasibility and the utility of the real-time monitoring temperature of the active layer

Стилі APA, Harvard, Vancouver, ISO та ін.

49

Hook, Benjamin Austin. "Compression wood formation in Pinus strobus L. following ice storm damage in southwestern Virginia." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/42492.

Повний текст джерела

Анотація:

To evaluate the compression wood response in eastern white pine (Pinus strobus L.) following a severe ice storm in 1994, 47 trees were felled in 2007 and cross-sectional samples were collected at 0.5 (Â±0.2) m stem height. The disks were sanded and digitally scanned, and the cross-sectional area (mm2) of compression wood within each tree-ring was quantified using image analysis software. Topographic data (slope, aspect, and elevation) were also recorded for each P. strobus tree, along with a modified competition index. Wood anatomical features were also quantified in the three years before and after the storm along a tree diameter gradient. Although tree age was relatively constant in this stand, tree size was influenced by topographic position; larger trees grew in the valley while smaller trees were found growing in thin soils at the mid-slope position. When the cohort was about 25 years old, ice deposition caused a heterogeneous compression wood response which was highly related to tree size. In the thirteen years following the ice storm, the 6 â 9 cm (2007) diameter class formed significantly more compression wood area than any other, followed by the 10 â 13 cm (2007) diameter class. The tree diameter range that formed the most post-storm compression wood was 4 â 8 cm at the time of the storm, suggesting that this diameter range was most affected by 8.5 cm of ice loading in P. strobus. Trees > 18 cm in 1994 did not form any compression wood after the storm, but many experienced a growth release to fill canopy gaps. Topographic variables did not influence compression wood formation directly, but only one plot was sampled so these results are tenuous. However, topography did influence tree size which was the most important predictor in compression wood. There was no relationship between compression wood area and competition index. Due to compression wood formation after the ice storm, cell wall thickness and cell circularity were significantly higher in the 1994 tree-ring than in other rings examined (1991 â 1993, 1995, and 1996). Tracheid and lumen diameters were significantly smaller in compression wood cells (30.5 and 19.5 Î¼m, respectively) than in normal wood (36.8 and 28.4 Î¼m, respectively); opposite wood cells were intermediate in size (32.4 and 24.4 Î¼m, respectively). Due to small tracheid size, compression wood contained significantly more cells mm-1 (33) than normal wood (27), but no significant differences in cell wall area. Therefore, cumulative cell wall area occupied 47% of the cross-section in compression wood tissue on average, compared to 31% in normal wood. Dispersing tree weight across a greater surface area may help compression wood to prop up a bent tree, but reduced lumen area may also impact hydraulic conductivity in the stem.
Master of Science

Стилі APA, Harvard, Vancouver, ISO та ін.

50

Andersson, Tobias. "Analysis of 3D surface data for on-line determination of the size distribution of iron ore pellet piles on conveyor belt." Licentiate thesis, Luleå : Luleå University of Technology, 2007. http://epubl.luth.se/1402-1757/2007/48.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Дисертації з теми "PILE SIZE"

Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями