• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 60
  • 12
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 85
  • 51
  • 46
  • 31
  • 26
  • 25
  • 23
  • 23
  • 22
  • 19
  • 19
  • 19
  • 17
  • 17
  • 16
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Topographic influences on Kelvin-Helmholtz instability

Holt, Jason Tempest January 1995 (has links)
No description available.
2

Groundwater elevation estimation model in the sloping Ogallala aquifer

Mzava, Philip G. January 1900 (has links)
Master of Science / Department of Civil Engineering / David R. Steward / A one-dimensional model was developed to study the flow of groundwater in the sloping Ogallala Aquifer at a steady state during predevelopment condition. The sloping base was approximated using a stepping base model. GIS applications were applied during data collection and preparation, and later during interpretation of model results. Analytical and numerical methods were employed in the development of this model which was used to try to understand long-term water balance in the study region. The conservation of mass was achieved by balancing groundwater input, output, and storage; this led to understanding the interactions of groundwater and surface water in the predevelopment conditions. The study resulted in identification of where natural discharge from groundwater to surface water occurred, and the quantity of these flows was obtained. The Ogallala Aquifer is thick in the south western part of Kansas, this region had an average saturated thickness of 100m during predevelopment conditions. The model found that groundwater flowed at a discharge per width of approximately 17 m[superscript]2/d in this region. The aquifer thickness tends to gradually decrease from west to east and from south to north. The northern part had an average saturated thickness of 40m during predevelopment conditions; the model found that groundwater flowed at a discharge per width of approximately 3 m[superscript]2/d in this region. It was also found that groundwater leaves the Ogallala Aquifer on the eastern side with discharge per width between 0-3 m[superscript]2/d. The discharge from groundwater to surface water was summed over contributing areas to river basins. The discharge to streams necessary to satisfy long-term conservation of mass computed by the model showed that Cimarron River has total baseflow of about 5.5 m[superscript]3/s; this was found to be almost 100% of the total streamflow recorded during predevelopment conditions. The Arkansas River was found to have total baseflow of about 0.97 m[superscript]3/s, which is approximately 14.3% of the total streamflow recorded during predevelopment conditions. The Smoky Hill River was found to have total baseflow of about 1.7 m[superscript]3/s, which is approximately 73.9% of the total streamflow recorded during predevelopment conditions. The Solomon River was found to have total baseflow of about 0.95 m[superscript]3/s, which is approximately 41.1% of the total streamflow recorded during predevelopment conditions. The Saline River was found to have total baseflow of about 0.25 m[superscript]3/s, which is approximately 62.5% of the total streamflow recorded during predevelopment conditions. The Republican and Pawnee River was found to have total baseflow of about 0.38 m[superscript]3/s and 0.22 m[superscript]3/s, which is approximately 18.5% and 12.6% of the total streamflow in the predevelopment conditions respectively. The model was found to be always within -16 to +12 meters between observed values and the model results, with an average value of 0.15m and a root mean square error of 1.98m. Results from this study can be used to advance this study to the next level by making a transient model that could be used as a predictive tool for groundwater response to water use in the study region.
3

Soil Erosion Studies on Steep Slopes of Humid-Tropic Philippines

Presbitero, Alan Ludovice, n/a January 2003 (has links)
An in-situ water-induced soil erosion study of two years duration was conducted at a low slope of about 10%, and also on steep slopes of about 50%, 60% and 70% at the experimental site located at a soil and water research area contiguous to the Department of Agricultural Engineering and Applied Mathematics of the Visayas State College of Agriculture (ViSCA). ViSCA is located in the town of Baybay at the island of Leyte in humid tropical Philippines (latitude of 10 degrees 44' north and longitude of 124 degrees 48' east). The study has the following aims, namely: 1) to investigate the effect of local farming practices on soil erosion, particularly at steep slopes; 2) to study the hydrology and soil erosion processes in steep slope conditions in humid tropical climate; and 3) to apply and determine the limitations of a physical process-oriented sediment transport model for water-induced soil erosion model (Griffith University Erosion System Template, GUEST) to a very permeable soil under very high rainfall conditions. In the context of the steep slope experiments at ViSCA: a) across the slope planting of corn is equally effective in controlling soil loss as hedged farming alone or in combination with peanut intercrop; b) across the slope planting of corn in hedged runoff plots is as effective in controlling soil loss as when combined with peanut intercrop; c) farmer’s practice of planting a rowcrop like corn along the slope (providing ready-made downslope pathways for runoff water thus, encouraging flow-driven soil erosion) produces significant soil loss, often larger than from a bare runoff plot; d) hedgerows significantly reduced sediment concentration provided they remain intact; e) "failure" in hedgerows, often results in massive soil loss, being even greater than that in a comparable bare runoff plot. (Failure is manifested by runoff breaching the litter barrier at the base of the hedgerow in a localized position, leading to concentrated flow and extension of rills upslope from base of hedgerow) of hedged runoff plot (even though contour planted) and f) application of stubble in combination with across slope planting in hedged runoff plots (with or without a closely growing intercrop) provided both maximum surface cover (aerial and contact) and protection against soil loss in steep slopes. These conclusions are likely to apply to crops similar to corn, with an intercrop similar to peanut in morphology and root system. These conclusions might also be expected to apply to low slopes, though the effect of such protection might not be as pronounced as in steep slope runoff plots. Soil erosion mechanisms in steep slopes are dominated mainly by the runoff-driven processes of entrainment and re-entrainment. Average sediment concentration c and total soil loss M are shown to be functions of positive coefficient runoff related regressors and a parameter that measures rills formed and permanently imprinted on soil surface, and of negative coefficient regressors related to surface contact cover, at least for the steep slopes considered in this study. The relatively high streampower associated with overland flow on steep slopes suggests that overland flow dominates over rainfall impact as a source of soil sediment concentration. This was confirmed by the low value of the measured ratio of soil sediment concentration shed by net-rainfall detachment trays to that lost from the bare runoff plots. On the effect of surface contact cover on average sediment concentration c, the following findings were made, namely: a) surface contact cover of only about 20% to 30% is sufficient to reduce c to low levels, assuming the cover is well distributed; b) an "exponential-decay" form of relationship existed between surface contact cover and the average sediment concentration from the non-bare soil without normalizing with respect to sediment concentration from a reference bare soil runoff plot; and c) such nonlinear relationship is indicative of the dominating runoff processes of entrainment and re-entrainment compared to the linear form of relationships if rainfall –driven processes of detachment and re-detachment dominate. In runoff dominated soil erosion processes, surface contact cover (including both living and dead vegetative cover close enough to the soil surface to impede overland flow) is more significant in curtailing soil erosion than aerial surface cover. ...continued.
4

Surface-Wave Propagation on a Gentle Bottom with Lagrangian Form

Huang, Chi-Yang 01 August 2000 (has links)
¡@¡@The main purpose of this paper is to analyze the surface progressive gravity waves propagating on a gentle sloping beach in two dimension. Instead of using the method of Eulerian system by the previous investigators, we introduce the governing equations completely in the Lagrangian system directly. All the characteristics of the wave system is expressed by a suitable perturbation expansion in the bottom slope under linearizing the problem in wave amplitude, then all the governing equations are systematically expanded to order. The solution of the wave system is to be solved to second order , even to high order could also be obtained. Based on the obtained results, the velocity potential, pressure and motion of the fluid particle in the wave system in time and space is therefore presented, and we can see that the bottom slope is a main factor to screw the wave field to deform to break. Finally, the experimental result is cited to compare and verify.
5

Finite Difference Solution for Drainage of Heterogeneous Sloping Lands

Natur, Fahd Salih 01 January 1974 (has links)
The two-dimensional problem of tile drainage on sloping heterogeneous lands was considered. The land surface and the impermeable boundaries of the problem were of a general shape. The flow in both the saturated and unsaturated zones was considered and the system was treated as one composite system. The problem was solved by a finite difference numerical method using the successive over-relaxation iterative (SOR) method for the steady state case with no local recharge, and a combined Newton inner iteration and successive over-relaxation outer iteration for the transient state case with local recharge. Both the rising water table and the falling water table cases were simulated. A computer program was written in Fortrain IV language for this purpose, and a UNIVAC 1108 computer system was used. The results of two runs for a hypothetical problem and one run for a field testing problem are presented. The results were compared with some approximate mathematical solutions for the falling water table.
6

Evaluation agro-économique ex-ante de systèmes de culture en agriculture familiale : le cas de l’agriculture de conservation en zone tropicale humide de montagne (Nord Vietnam) / Ex-ante agronomic and economic assessment of cropping systems under smallholder farming : the case of conservation agriculture in mountainous humid tropics (Northern Vietnam)

Hauswirth, Damien 18 December 2013 (has links)
Le besoin d'une intensification accrue des systèmes agricoles rend nécessaire l'identification des contextes et options permettant à des modes de mise en valeur intensifs et durables de se développer. Cette question est cruciale dans des contextes de petite agriculture familiale et de pression élevée sur les ressources naturelles, dont les zones tropicales humides d'Asie constituent un exemple typique. Dans cette région, l'agriculture de conservation (AC) est considérée comme un moyen de parvenir à cet objectif. Dans ce contexte, notre travail avait pour objectif d'évaluer dans quelle mesure l'AC peut constituer une réponse efficace et adaptée aux contraintes et besoins de petits producteurs familiaux dans une région montagneuse caractérisée par une forte pression sur les ressources naturelles et un taux de pauvreté élevé. Nous avons d'abord effectué un diagnostic des facteurs critiques de durabilité associés à la diversité régionale des systèmes agricoles conventionnels incorporant une production de maïs sur pente. Nous avons développé une approche originale combinant différentes méthodes d'analyse multivariée et de classification. Cette approche nous a permis d'identifier des types de systèmes agricoles aux performances contrastées en termes d'atteinte d'objectifs de durabilité. Les caractéristiques territoriales à différentes échelles, de l'écorégion au village, ont été identifiées comme prévalant sur les caractéristiques biophysiques des parcelles et l'accès aux moyens de production à l'échelle de l'exploitation pour expliquer la diversité des systèmes de culture sur pentes. Nous avons ensuite exploré dans quelle mesure des données collectées sur des sites de démonstration en AC pouvaient être utilisées pour évaluer les performances de prototypes de systèmes de culture en AC. L'AC pratiquée à un niveau de fertilisation suffisant n'a pas eu d'impact négatif sur les rendements la première année après conversion. Elle a significativement amélioré productivité et efficacité agronomique la seconde année après conversion. Toutefois, cette amélioration des performances agronomiques n'était pas suffisante, aux conditions économiques actuelles, pour assurer une meilleure rentabilité économique que l'agriculture conventionnelle sur un horizon de deux ans, du fait de l'augmentation des coûts de production associée au passage à l'AC. Les perspectives scientifiques issues de ce travail comprennent (i) l'utilisation des données issues de dispositifs de démonstration dans une perspective de modélisation pour prendre en compte, dans l'évaluation des systèmes de culture, les processus à l'origine de leur performances en fonction des variations de contexte biophysique et économique et (ii) l'évaluation de la capacité de l'agriculture de conservation à tamponner la variabilité des performances des systèmes de culture. La principale implication pratique pour l'intensification durable de l'agriculture dans le contexte du Nord Vietnam est la prise en compte de la diversité des systèmes agricoles dans le prototypage et la diffusion de systèmes de culture innovants. Une nouvelle hypothèse est qu'il est nécessaire d'envisager la valorisation au moins partielle des plantes de couverture, une conversion par étapes et/ou des incitations permettant de compenser l'augmentation de coûts générée par le passage à l'agriculture de conservation pour que celle-ci devienne économiquement attractive pour de petits producteurs familiaux dans un horizon de deux années. / The global need for further agricultural intensification makes necessary to identify contexts and options for sustainable intensive land uses to develop. This question is crucial under contexts of smallholder farming and high pressure on natural resources, such as in Asian humid tropics. In this region conservation agriculture (CA) is considered a leeway towards sustainable intensification. Within this context, our work aimed at preliminary assess to which extent CA fits the needs and constraints of smallholder farmers in a mountainous region where the high level of pressure on natural resources adds-up to a high poverty rate.We implemented a diagnosis of sustainability gaps associated with the regional diversity of maize based agricultural systems on sloping land. We applied an original methodological approach combining diverse classification tools. We identified contrasted types of farming and cropping systems for management practices, performances and sustainability issues. The local diversity in maize cropping systems resulted from multi-scale interactions between territory-related factors, farm/farmer characteristics and field biophysical conditions. Territory-related factors were of prevailing importance over plot biophysical conditions and farm/farmer related characteristics to drive diversity of cropping systems.We subsequently investigated to which extent data collected at CA-demonstration sites can be used to assess performances of CA-based cropping system prototypes over a 2-year period. Within the context of our study, CA associated with sufficient fertilization levels did not depress yields the first year after conversion. The second year, CA significantly increased maize productivity and agronomic efficiency. Such improvement of agronomic performances was not sufficient to ensure better economic performances than conventional agriculture over two years, due to the increase in production costs associated with transition to CA.Main scientific perspectives from our work include (i) coupling CA-demonstrations with modeling to account in cropping system evaluation for processes driving their performances across variations in biophysical and economic conditions (ii) assessment of CA capacity to buffer variability in cropping system performances. Main implication for CA-based sustainable intensification in tropical humid highlands of Vietnam is the need to tailor technical proposals to the identified diversity of agricultural systems. To make conversion to CA worth for farmers within a period of two years, a major assumption is the requirement for cover plant valorisation, implementation of stepwise transition to CA, and/or tailoring incentives to support smallholder farmers in overcoming costs associated with conversion to CA.
7

Horský hotel s wellness centrem / Mountain hotel with wellness centre

Bartošová, Pavlína January 2019 (has links)
The diploma thesis contain complete solution for Mountain hotel with wellness center including project documentation. The building is situated near area of Beskydy Mountains. Building plot is located in village Kunčice pod Ondřejníkem. The hotel consists of three parts: Wellness center, restaurant facilities, accommodation with recreational areas. The building has 4 floors and is non-celluar. The roof in the first floor is solved by vegetation roof, followed up with metal sloping roof . Construction structure is made of Porotherm ceramic blocks.
8

Characterization of surface soil hydraulic properties in sloping landscapes

Waduwawatte Lekamalage, Bodhinayake 23 March 2004
Saturated and near-saturated surface soil hydraulic properties influence the partition of rainfall and snowmelt into infiltration and runoff. The goal of this study was to characterize near-saturated surface soil hydraulic properties and water-conducting porosity in sloping landscapes. The specific objectives included exploration of tension and double-ring infiltrometers for estimation of soil hydraulic properties in sloping landscapes, development of an improved method for determining water-conducting porosity, and the application of these methods in characterizing soil hydraulic properties and water-conducting porosity under three land use. Water infiltration from a double-ring infiltrometer and a tension infiltrometer at water pressures between -2.2 and -0.3 kPa was measured in a cultivated field with 0, 7, 15, and 20% slopes at Laura and under three land use (native grass, brome grass and cultivated) at St. Denis in Saskatchewan, Canada. Three-dimensional computer simulation studies were also performed for tension infiltrometer with various disc diameters, water pressures, and surface slopes. Steady infiltration rates and estimated field-saturated hydraulic conductivity (Kfs), hydraulic conductivity-water pressure relationship (K(h)), and inverse capillary length parameter were compared for different slopes and land use. These parameters were not significantly different (p<0.05) among slopes. For specific K(h) functions, a new analytical solution was developed and compared with existing methods for calculating water-conducting porosity. The new method reliably determined water-conducting porosity of surface soils and gave consistent results, regardless of the width of water pressure ranges. At the -0.3 kPa water pressure, hydraulic conductivity of grasslands was two to three times greater than the cultivated lands. Values of inverse capillary length parameter were about two times and values of Kfs about four times greater in grasslands than in cultivated fields. Water-conducting macroporosity of grasslands and cultivated fields were 0.04% and 0.01% of the total soil volume, respectively. Over 40% and 50% of the total water flux at -0.06 kPa water pressure was transmitted through macropores (pores > 1×10-3 m in diameter) of the cultivated land and the grasslands, respectively. Experimental and simulation results of this study indicated that both tension and double-ring infiltrometers are suitable for characterization of saturated and near-saturated surface soil hydraulic properties in landscapes up to 20% slope. The new method can be used to characterize water-conducting porosity from in situ tension and double-ring infiltrometers measurements more adequately and efficiently than the existing methods. Application of these methods for three land use indicated that land use modified surface soil hydraulic properties and consequently may alter the water balance of an area by affecting the partition between, and relative amount of infiltration and surface runoff.
9

Characterization of surface soil hydraulic properties in sloping landscapes

Waduwawatte Lekamalage, Bodhinayake 23 March 2004 (has links)
Saturated and near-saturated surface soil hydraulic properties influence the partition of rainfall and snowmelt into infiltration and runoff. The goal of this study was to characterize near-saturated surface soil hydraulic properties and water-conducting porosity in sloping landscapes. The specific objectives included exploration of tension and double-ring infiltrometers for estimation of soil hydraulic properties in sloping landscapes, development of an improved method for determining water-conducting porosity, and the application of these methods in characterizing soil hydraulic properties and water-conducting porosity under three land use. Water infiltration from a double-ring infiltrometer and a tension infiltrometer at water pressures between -2.2 and -0.3 kPa was measured in a cultivated field with 0, 7, 15, and 20% slopes at Laura and under three land use (native grass, brome grass and cultivated) at St. Denis in Saskatchewan, Canada. Three-dimensional computer simulation studies were also performed for tension infiltrometer with various disc diameters, water pressures, and surface slopes. Steady infiltration rates and estimated field-saturated hydraulic conductivity (Kfs), hydraulic conductivity-water pressure relationship (K(h)), and inverse capillary length parameter were compared for different slopes and land use. These parameters were not significantly different (p<0.05) among slopes. For specific K(h) functions, a new analytical solution was developed and compared with existing methods for calculating water-conducting porosity. The new method reliably determined water-conducting porosity of surface soils and gave consistent results, regardless of the width of water pressure ranges. At the -0.3 kPa water pressure, hydraulic conductivity of grasslands was two to three times greater than the cultivated lands. Values of inverse capillary length parameter were about two times and values of Kfs about four times greater in grasslands than in cultivated fields. Water-conducting macroporosity of grasslands and cultivated fields were 0.04% and 0.01% of the total soil volume, respectively. Over 40% and 50% of the total water flux at -0.06 kPa water pressure was transmitted through macropores (pores > 1×10-3 m in diameter) of the cultivated land and the grasslands, respectively. Experimental and simulation results of this study indicated that both tension and double-ring infiltrometers are suitable for characterization of saturated and near-saturated surface soil hydraulic properties in landscapes up to 20% slope. The new method can be used to characterize water-conducting porosity from in situ tension and double-ring infiltrometers measurements more adequately and efficiently than the existing methods. Application of these methods for three land use indicated that land use modified surface soil hydraulic properties and consequently may alter the water balance of an area by affecting the partition between, and relative amount of infiltration and surface runoff.
10

Improving high-frequency audibility for hearing-impaired listeners using a cochlear implant or frequency-compression aid

Simpson, Andrea Unknown Date (has links) (PDF)
Listeners with severe-sloping losses often don’t perceive high-frequency sound cues. Conventional amplification fails to provide these cues due to loudness discomfort experienced by the listener, and/or acoustic feedback. Alternative signal-processing solutions include shifting higher frequencies down to lower frequencies, or providing electrical stimulation via a speech processor. Three experiments were carried out on adult hearing-impaired listeners to determine the best way of providing high-frequency information: conventional amplification, frequency compression or cochlear implantation.

Page generated in 0.0411 seconds