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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Quantification of spray drift from aerial applications of pesticide

Caldwell, Daniel Morgan 02 April 2007 (has links)
With widespread use of pesticides in modern agriculture, the impacts of spray drift have become a topic of considerable interest. The drifting of sprays is a highly complex process influenced by many factors. Advances in aerial application technology and in our ability to measure drift, coupled with the adoption of new technologies for regulating pesticide application have necessitated further research in the pesticide application process. Experiments were conducted to quantify spray drift and describe its movement from aerial applications of pesticide. The effects of spray quality, atomizer type and ground cover were examined. Initial airborne drift amounts were greater than downwind deposits, thus not all of the drifting spray was deposited in the measuring area. Total off-target movement of spray was significantly greater for Fine compared to Coarse sprays. Rotary and hydraulic atomizers, both producing Fine sprays, produced statistically similar off-target movement of sprays. Similarly, no significant statistical differences in spray drift between applications to bare ground and applications to a headed barley crop canopy were not identified. Contrary to expectations, aerial application to bare ground seemed to result in less off-target movement than application to a crop canopy. The vertical spray cloud profiles were similar for all applications with the greatest amount of spray present at the height of release. Spray concentrations diminished from that height upward with diffusion and downward with deposition. The empirical data disagreed with the mechanistic model AgDISP which is currently used in the Canadian regulatory process. The model over-predicted drift deposition by a factor of two to five. Variability in spray deposit values could not be attributed to average differences in meteorological conditions at the time of application. Experiments with appropriate protocols for increased sensitivity may be required to more accurately report subtle differences in drift at distances greater than 200 m from the target area.
92

The effects of wind and topography to coastal current variations at daily to seasonal cycles

Chang, Chun-hsiang 10 September 2007 (has links)
The coastal current is influenced by coastline topography, its advection direction is parallel with coastline because different periodic of wind field function makes the ocean dynamics is more complicated in coastal. In order to treat the effects of topography and wind to coastal current variations, we make long time observation data about ocean and meteorology and analyze them near the harbor of HSinDa in Kaohsiung . This research use bottom Acoustic Doppler Current Profiler (bm-ADCP ) , Temperature and Pressure Logger(TP ) , anemometer and wind direction vane to observe flow field ,tidal and wind field in the locality. The collected data are analyzed through a variety of time series analysis technique , such as strain wave, harmonic analysis , Fast Fourior Transform (FFT) analysis that uses different frequency wave bands make an relevant analysis materials and then. The results show that (1) when sea-land breeze was weak, the main axial angle of diurnal tide ellipticity of the current was parallel with the coastline direction. Because the friction of sea flow affected; the ellipticity became smaller and assumed the reciprocal motion¡Fwhen sea-land breeze was stronger, diurnal tide ellipticity of the current was bigger, and main axial angle from coastline parallel changes to follow the sea-land breeze heading. It means sea-land breeze can affect the surface flow motion. (2)When a front passed in winter, it produces the current faced to the southeast along the coast. In the energy spectrum effect, the wind field and the flow field have the same peak of the period, the period was 4 days, 5.5 days, and 8 days, it means that the correlation of the flow field and wind field is good; this result is closed with the observes in land station. (3)In the period of southwest monsoon, there has coastal current toward northwest in the southwest of Taiwan straits. In the other period, the direction of current always moved toward southeast. The result of the low-frequency filter, the flow is smaller than tidal current and wind-drift current. It means that this sea area is affected by tide current and wind-drift current.
93

Faskompenseringsutredning vid ett pappers och massabruk

Sjödin, Joakim January 2015 (has links)
Sammanfattning Rapporten innehåller en utredning om, hur och på vilket sätt, det är möjligt att minska det reaktiva effektuttaget vid Metsä Boards fabrik i Husum. Detta är inget problem i normalfallet, men om någon av fabrikens tre turbiner på grund av till exempel service inte är i drift så kan det reaktiva effektuttaget bli för stort enligt avtal med elnätsägaren. Om elnätsägarens gräns överskrids måste en straffavgift betalas per varje överskridet kVAr, vilket Metsä vill undvika. Fokus för arbetet ligger på fabrikens papperbruk eftersom detta är problemområdet. Efter genomgång av enlinjescheman och olika mätutrustningar som finns belägna i fabriken inses att det är mest lämpligt att kompensera i anslutning till bestrykningsmaskinen (BM1). Bestrykaren är den enda linjen på pappersbruket som inte har faskompenseringsutrustning. För att hålla sig inom nätägarens gräns beräknades att faskompensering med en kapacitet på 15 MVAr räcker. Den kapaciteten täcker även upp för ett bortfall av den generator som producerar mest reaktiv effekt, generator G1. Men för att undvika eventuella problem med övertoner blir resultatet att en kompenseringsutrustning på totalt 16 MVAr med snedavstämda filter passar anläggningen bättre. Det finns planer att sätt massabruket i ö-drift och detta blir möjligt med den rekommenderade faskompenseringsutrustningen utan att överskrida den reaktiva effekt gränsen som är satt av nätägaren. / Abstract This report contains an investigation on, how and in what way, it´s possible to reduce the reactive effect (VAR) consumption at Metsä Board Mill in Husum. The VAR consumption is not a problem during normal operation, but if one of the mill´s three turbines for some reason falls out of operation the VAR consumption may exceed the agreement with the mill´s electricity distributor. If the agreed VAR consumption is exceeded, the mill has to pay a fee for each kVAr that exceeds the agreed consumption level. This is something that the mill wants to avoid because the turbines aren’t always operational due to the need of maintenance work. The largest VAR consumption is located at the paper mill, which is why the compensation measures are focused in this area. After studying the mill´s single-line diagram of the electrical distribution and different measuring equipment located in the mill, it becomes clear that the VAR compensation equipment is best fitted at the mill´s coating machine. The coating machine is the only production line in the paper mill that is missing VAR compensation equipment, that’s why the compensation measures are needed here. After calculations it’s clear that the needed VAR compensation capacity is 15 MVAr and should be placed in connection to the coating machine. This capacity is enough to compensate for a loss of the VAR generated from the turbine G1, which is assumed to produce 15 MVAr guaranteed. That compensation is enough to avoid exceeding the VAR consumption agreement with the electricity distributor. But to avoid problems with harmonics, 16 MVAr compensation equipment is recommended instead because it´s more suited for the job. Metsä has plans to put their pulp mill in insulated operation that separates the mill´s grid from the distribution grid. This becomes possible whit the recommended VAR compensation equipment to avoid over consumption of VAR from the electricity distributor.
94

Turbulent particle and thermal transport in magnetized plasmas

Fu, Xiangrong 22 October 2013 (has links)
The particle and thermal transport by low-frequency drift waves in magnetized plasmas are studied with theories and simulations. Universal in inhomogeneous plasmas, drift waves in Earth's ionosphere, the GAMMA-10 Tandem Mirror machine, the Columbia Linear Machine and C-Mod tokamak are studied in this thesis. The first investigations are E x B particle transport in the given electric and magnetic fields of the GAMMA-10 mirror machine at the University of Tsukuba in Japan. The results show that the formation of E [subscript r]-shear by local heating of electrons can reduced the radial particle loss. The turbulent impurity particle transport driven by various modes in the MIT tokamak Alcator C-Mod is studied by a quasilinear theory and compared to experimental measurement of Boron density profiles. A code is developed for solving eigensystems of drift wave turbulence equations for the multi-component fusion plasmas and calculating quasilinear particle fluxes. The calculations are much faster than nonlinear simulations and may be suitable for real-time analysis and feedback control of tokamak plasmas. The electron temperature gradient (ETG) mode is a candidate mechanism for anomalous electron thermal transport across various magnetic confinement geometries. This mode was produced in the Columbia Linear Machine (CLM) at Columbia University. Large scale simulations of the ETG mode in the CLM by a gyrokinetic code GTC are carried out on supercomputers at TACC and NERSC. The results show good agreement with experiments in the dominant mode number, wave frequencies and the radial structure. Some nonlinear properties are also analyzed using the code. / text
95

Concept drift learning and its application to adaptive information filtering

Widyantoro, Dwi Hendratmo 30 September 2004 (has links)
Tracking the evolution of user interests is a problem instance of concept drift learning. Keeping track of multiple interest categories is a natural phenomenon as well as an interesting tracking problem because interests can emerge and diminish at different time frames. The first part of this dissertation presents a Multiple Three-Descriptor Representation (MTDR) algorithm, a novel algorithm for learning concept drift especially built for tracking the dynamics of multiple target concepts in the information filtering domain. The learning process of the algorithm combines the long-term and short-term interest (concept) models in an attempt to benefit from the strength of both models. The MTDR algorithm improves over existing concept drift learning algorithms in the domain. Being able to track multiple target concepts with a few examples poses an even more important and challenging problem because casual users tend to be reluctant to provide the examples needed, and learning from a few labeled data is generally difficult. The second part presents a computational Framework for Extending Incomplete Labeled Data Stream (FEILDS). The system modularly extends the capability of an existing concept drift learner in dealing with incomplete labeled data stream. It expands the learner's original input stream with relevant unlabeled data; the process generates a new stream with improved learnability. FEILDS employs a concept formation system for organizing its input stream into a concept (cluster) hierarchy. The system uses the concept and cluster hierarchy to identify the instance's concept and unlabeled data relevant to a concept. It also adopts the persistence assumption in temporal reasoning for inferring the relevance of concepts. Empirical evaluation indicates that FEILDS is able to improve the performance of existing learners particularly when learning from a stream with a few labeled data. Lastly, a new concept formation algorithm, one of the key components in the FEILDS architecture, is presented. The main idea is to discover intrinsic hierarchical structures regardless of the class distribution and the shape of the input stream. Experimental evaluation shows that the algorithm is relatively robust to input ordering, consistently producing a hierarchy structure of high quality.
96

Multi-Body Vehicle Dynamics Modeling for Drift Analysis

Loh, Francis January 2013 (has links)
One area of vehicle handling performance that has been the focus of an OEM{'}s (Original Equipment Manufacturer) engineering effort is within the realm of vehicle straight-line performance. As the name implies, straight-line performance is determinant on the vehicle{'}s tendency to resist vehicle lateral drift when being driven straight. Vehicle lateral drift is a condition where the driver must apply a constant correctional torque to the steering wheel in order to maintain a straight line course. A full vehicle model was developed to simulate the influences of suspension parameters on vehicle drift. Adams 2010 was chosen as the multi-body dynamics (MBD) software for this research for its ability to develop a full vehicle high fidelity model without the need for physical test data. The model was created from standard Adams/Car suspension templates modified to accommodate the subject vehicle. The front suspension sub-assembly model was built upon the front MacPherson strut suspension template. Likewise, the rear suspension sub-assembly model was created from the rear multi-link suspension template. The tire model used in the full vehicle model was based on the Pacejka 2002 formulation. A model of a similar tire was generated using a custom spreadsheet based on the PAC2002, a slightly modified version of the Pacejka 2002 formulation found within Adams/Car. A virtual tire test rig and a 6/7-DoF model were created to understand and verify the behaviour of the generated tire models. The virtual tire test rig was used to compare the outputs of the PAC2002 tire model to the calculated values from a custom tire property spreadsheet. The 6/7-DoF model was used to test and verify the effect of the tire{’}s residual lateral forces. The full-vehicle model was verified using the parallel wheel travel and opposite wheel travel suspension analyses. The parallel wheel travel analysis was used to tease out binding issues within the designed travel of the suspension. The opposite wheel travel analysis was used similarly for anti-roll bar systems. Simulations based on the industry standard vehicle drift tests were run to understand the effect of certain vehicle suspension geometry on vehicle drift, namely the vehicle{’}s front and rear camber and toe angles. The full-vehicle model was also subjected to straight-line performance simulations with various road bank or crown angles. The results were compared with industry-standard vehicle drift test data gathered by the OEM on their own test track. The results indicate that the direction of vehicle pull matches with the OEM test data, but the magnitudes differ in both the positively and negatively banked road simulation results. It is likely that the difference in vehicle drift is due to the lack of steering data obtained for the full-vehicle model.
97

Determination of changes of surface height, 1957-1967, of the Gilman Glacier, North Ellesmere Island, Canada.

Arnold, K. C. (Keith C.) January 1968 (has links)
No description available.
98

Internal stress in a floating cover of sea ice

Wright, B. D. January 1974 (has links)
No description available.
99

Energy-drift correction of electron energy-loss spectra from prolonged data accumulation of low SNR signals

Muto, Shunsuke, Sasano, Yusuke 10 1900 (has links)
No description available.
100

The vegetation history of the Shirdley Hill Sand in south-west Lancashire

Baxter, Janet January 1983 (has links)
No description available.

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