• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 151
  • 60
  • 44
  • 28
  • 25
  • 6
  • 4
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 377
  • 55
  • 40
  • 37
  • 34
  • 31
  • 28
  • 26
  • 24
  • 24
  • 22
  • 21
  • 21
  • 21
  • 19
  • 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.
341

Vyhledávání objektů v obraze na základě předlohy / Image object detection using template

Novák, Pavel January 2014 (has links)
This Thesis is focused to Image Object Detection using Template. Main Benefit of this Work is a new Method for sympthoms extraction from Histogram of Oriented Gradients using set of Comparators. In this used Work Methods of Image comparing and Sympthoms extraction are described. Main Part is given to Histogram of Oriented Gradients Method. We came out from this Method. In this Work is used small training Data Set (100 pcs.) verified by X-Validation, followed by tests on real Sceneries. Achieved success Rate using X-Validation is 98%. for SVM Algorithm.
342

Detekce, lokalizace a rozpoznání dopravních značek / Detection, Localization and Recognition of Traffic Signs

Svoboda, Tomáš January 2011 (has links)
This master's thesis deals with the localization, detection and recognition of traffic signs. The possibilities of selection of areas with possible traffic signs occurrence are analysed. The properties of different kinds of features used for traffic signs recognition are described next. It focuses on the features based on histogram of oriented gradients. Some possible classifiers are discussed, in the first place the cascade of support vector machines, which are used in resulting system. A description of the system implementation and data sets for 5 types of traffic signs is part of this thesis. Many experiments were accomplished with created system. The results of the experiments are very good. New datasets were acquired from approximately 9 hours of processed video sequences. There are about 13 500 images in these datasets.
343

Modélisation et discrétisation des écoulements diphasiques en milieux poreux avec réseaux de fractures discrètes / Modelization and discretization of two-phase flows in porous media with discrete fracture networks

Groza, Mayya 10 November 2016 (has links)
Les travaux de cette thèse portent sur la modélisation et la discrétisation des écoulements diphasiques dans les milieux poreux fracturés. On se place dans le cadre des modèles dits dimensionnels hybrides couplant l'écoulement dans la matrice 3D à l'écoulement dans un réseau de fractures modélisées comme des surfaces 2D. La discrétisation s'appuie sur le cadre abstrait des schémas gradients. Dans cette étude nous présentons deux classes de schémas de types Gradient Schemes sur ces modèles en monophasique et en diphasique. Les objectifs sont motivés par l'application cible de la thèse qui concerne les procédés de récupération assistée de gaz par fracturation hydraulique dans les réservoirs de très faibles perméabilités / This thesis presents the work on modelling and discretisation of two-phase flows in the fractured porous media. These models couple the flow in the fractures represented as the surfaces of codimension one with the flow in the surrounding matrix. The discretisation is made in the framework of Gradient schemes which accounts for a large family of conforming and nonconforming discretizations. The test cases are motivated by the target application of the thesis concerning the gas recovery under the hydraulic fracturing process in low-permeability reservoirs
344

Geografická variabilita ve funkčních znacích ptáků Evropy / Geographical variation in functional traits of European birds

Kopsová, Lenka January 2011 (has links)
Each species has specific adaptations to its environment, and since environmental parameters reveal geographic trends, it is reasonable to expect the existence of geographic trends in species characteristics as well. The aim of this study has been to evaluate the effect of environmental conditions on geographic variability of functional traits of European birds. I have analysed the effect of temperature, precipitation, productivity, altitude and habitat type (forest, open habitats, bush, settlements, wetlands) on clutch size, number of clutches per breeding season, egg size, incubation length, age of maturity, body mass, wing, tail, bill and tarsus length. I have used data from the European breeding bird atlas, so that I have calculated mean values of all the traits for quadrats 50x50 km, and then related them to environmental characteristics using OLS and GLS. Clutch size increases with temperature, whereas the number of clutches decreases with it, indicating possible trade-off between clutch size and the number of clutches, whose result is determined by the length of breeding season. Egg size decreases with temperature, possibly due to higher survival of large eggs (and consequently juveniles) in cold regions. Incubation length increases with both temperature and environmental productivity,...
345

Explainable AI For Predictive Maintenance

Karlsson, Nellie, Bengtsson, My January 2022 (has links)
As the complexity of deep learning model increases, the transparency of the systems does the opposite. It may be hard to understand the predictions a deep learning model makes, but even harder to understand why these predictions are made. Using eXplainable AI (XAI), we can gain greater knowledge of how the model operates and how the input in which the model receives can change its predictions. In this thesis, we apply Integrated Gradients (IG), an XAI method primarily used on image data and on datasets containing tabular and time-series data. We also evaluate how the results of IG differ from various types of models and how the change of baseline can change the outcome. In these results, we observe that IG can be applied to both sequenced and nonsequenced data, with varying results. We can see that the gradient baseline does not affect the results of IG on models such as RNN, LSTM, and GRU, where the data contains time series, as much as it does for models like MLP with nonsequenced data. To confirm this, we also applied IG to SVM models, which gave the results that the choice of gradient baseline has a significant impact on the results of IG.
346

Active Structural Acoustic Control of Clamped and Ribbed Plates

Johnson, William Richard 12 December 2013 (has links) (PDF)
A control metric, the weighted sum of spatial gradients (WSSG), has been developed for use in active structural acoustic control (ASAC). Previous development of WSSG [1] showed that it was an effective control metric on simply supported plates, while being simpler to measure than other control metrics, such as volume velocity. The purpose of the current work is to demonstrate that the previous research can be generalized to plates with a wider variety of boundary conditions and on less ideal plates. Two classes of plates have been considered: clamped flat plates, and ribbed plates. On clamped flat plates an analytical model has been developed for use in WSSG that assumes the mode shapes are the product of clamped-clamped beam mode shapes. The boundary condition specific weights for use in WSSG have been derived from this formulation and provide a relatively uniform measurement field, as in the case of the simply supported plate. Using this control metric, control of radiated sound power has been simulated. The results show that WSSG provides comparable control to volume velocity on the clamped plate. Results also show, through random placement of the sensors on the plate, that similar control can be achieved regardless of sensor location. This demonstrates that WSSG is an effective control metric on a variety of boundary conditions. Ribbed plates were considered because of their wide use in aircraft and ships. In this case, a finite-element model of the plate has been used to obtain the displacement field on the plate under a variety of boundary conditions. Due to the discretized model involved, a numerical, as opposed to analytical, formulation for WSSG has been developed. Simulations using this model show that ASAC can be performed effectively on ribbed plates. In particular WSSG was found to perform comparable to or better than volume velocity on all boundary conditions examined. The sensor insensitivity property was found to hold within each section (divided by the ribs) of the plate, a slightly modified form of the flat plate insensitivity property where the plates have been shown to be relatively insensitive to sensor location over the entire surface of the plate. Improved control at natural frequencies can be achieved by applying a second control force. This confirms that ASAC is a viable option for the control of radiated sound power on non-ideal physical systems similar to ribbed plates.
347

The Origin of Certain Granitic Rocks Occurring In Glamorgan Township, Southeastern Ontario / Origin of Certain Granitic Rocks

Chesworth, Ward 05 1900 (has links)
<p> Glamorgan township in southeastern Ontario, is underlain by Precambrian rocks of the Grenville province. Prominent amongst these are migmatite, paragneiss, and granite gneiss, VJhich collectively form a series of rocks (the Glamorgan gneiss aeries). </p> <p> Field work revealed that this series is completely gradational from a geological aspect, and that the geological gradation is complemented by a geochemical gradation. <p> An explanation of these gradational relationships constitutes the main contribution of this study. The conclusions reached are that partial melting of paragneiss produced migmatite and a trondhjemitic melt, which later produced granitic (in the strict sense) derivatives. </p> <p> In developing the main conclusions, a number of subsidiary problems are discussed, chief of which are the possible metavolcanic or metasedimentary o'rigin of the paragneiss and the possible origin of so-called diorite as a differentiate of an alkaline gabbro. Metamorphism was concluded to be of Miyashiro's low pressure intermediate type. </p> <p> By the use of experimentally determined reactions and stability fields a metamorphic grid was devised, which led to the following upper limits of metamorphic conditions: 550 to 650°C and 3 to 6.5 kilobars total pre5sure. These estimates in turn lead to the following limiting geothermal gradients: 25 to 55°C per kilometre. </p> <p> The Glamorgan occurrence was found to share three characteristics with many other Precambrian terrains : 1. migmatisation and emplacement of granite accompanied high grade metamorphism; 2. an early sodium-rich granite was followed by a more potassic one; and 3. the more sodic granite is associated with a small amount of basic igneous rock. These three generalisations were used to formulate a possible model for deep crustal petrogenesis. </p> / Thesis / Doctor of Philosophy (PhD)
348

Social Gradients in Subjective Well-being during the COVID-19 Pandemic in Sweden

Johansson, Ida January 2024 (has links)
The COVID-19 pandemic prompted governments around the globe to employ various measures, such as social distancing and quarantine, to prevent its spread. The pandemic contributed to drastic changes in everyday life, through economic shocks, fear of the virus, morbidity, and mortality.  It was quickly suspected that stress, fear, and loneliness resulting from these factors, would have a negative impact on mental health. While previous research suggests an increase of clinical mental morbidity in Sweden during the pandemic, its impact on subjective well-being remains unexplored. The aim of this study is to broaden the understanding of public health during the pandemic by considering a self-reported measure of well-being. Using data from the latest Swedish Generations and Gender Survey (2021), this study sets out to answer two research questions. First, how are demographic characteristics associated with worsened subjective well-being? Secondly, given that foreign-born individuals were disproportionately affected by a range of COVID-19 related negative outcomes, this thesis asks whether foreign-born individuals were particularly affected by worsened subjective well-being. The questions are analysed through descriptive statistics and stepwise modeling using Linear Probability Models. Findings suggest that younger age and being female is associated with negative changes in subjective well-being, net of resources in terms of education, income and activity status, and family status. Foreign-born individuals were indeed particularly affected by worsened subjective well-being. This was partly mediated through their higher propensity of unemployment and on average lower income. By using a nationally representative sample and timely data, this thesis contributes to the understanding of COVID-19 related effects in Sweden. Furthermore, it sheds lights on the experiences of foreign-born individuals, a previously understudied group within the well-being literature.
349

Refractive Indices Of Liquid Crystals And Their Applications In Display And Photonic Devices

Li, Jun 01 January 2005 (has links)
Liquid crystals (LCs) are important materials for flat panel display and photonic devices. Most LC devices use electrical field-, magnetic field-, or temperature-induced refractive index change to modulate the incident light. Molecular constituents, wavelength, and temperature are the three primary factors determining the liquid crystal refractive indices: ne and no for the extraordinary and ordinary rays, respectively. In this dissertation, we derive several physical models for describing the wavelength and temperature effects on liquid crystal refractive indices, average refractive index, and birefringence. Based on these models, we develop some high temperature gradient refractive index LC mixtures for photonic applications, such as thermal tunable liquid crystal photonic crystal fibers and thermal solitons. Liquid crystal refractive indices decrease as the wavelength increase. Both ne and no saturate in the infrared region. Wavelength effect on LC refractive indices is important for the design of direct-view displays. In Chapter 2, we derive the extended Cauchy models for describing the wavelength effect on liquid crystal refractive indices in the visible and infrared spectral regions based on the three-band model. The three-coefficient Cauchy model could be used for describing the refractive indices of liquid crystals with low, medium, and high birefringence, whereas the two-coefficient Cauchy model is more suitable for low birefringence liquid crystals. The critical value of the birefringence is deltan~0.12. Temperature is another important factor affecting the LC refractive indices. The thermal effect originated from the lamp of projection display would affect the performance of the employed liquid crystal. In Chapter 3, we derive the four-parameter and three-parameter parabolic models for describing the temperature effect on the LC refractive indices based on Vuks model and Haller equation. We validate the empirical Haller equation quantitatively. We also validate that the average refractive index of liquid crystal decreases linearly as the temperature increases. Liquid crystals exhibit a large thermal nonlinearity which is attractive for new photonic applications using photonic crystal fibers. We derive the physical models for describing the temperature gradient of the LC refractive indices, ne and no, based on the four-parameter model. We find that LC exhibits a crossover temperature To at which dno/dT is equal to zero. The physical models of the temperature gradient indicate that ne, the extraordinary refractive index, always decreases as the temperature increases since dne/dT is always negative, whereas no, the ordinary refractive index, decreases as the temperature increases when the temperature is lower than the crossover temperature (dno/dT<0 when the temperature is lower than To) and increases as the temperature increases when the temperature is higher than the crossover temperature (dno/dT>0 when the temperature is higher than To ). Measurements of LC refractive indices play an important role for validating the physical models and the device design. Liquid crystal is anisotropic and the incident linearly polarized light encounters two different refractive indices when the polarization is parallel or perpendicular to the optic axis. The measurement is more complicated than that for an isotropic medium. In Chapter 4, we use a multi-wavelength Abbe refractometer to measure the LC refractive indices in the visible light region. We measured the LC refractive indices at six wavelengths, lamda=450, 486, 546, 589, 633 and 656 nm by changing the filters. We use a circulating constant temperature bath to control the temperature of the sample. The temperature range is from 10 to 55 oC. The refractive index data measured include five low-birefringence liquid crystals, MLC-9200-000, MLC-9200-100, MLC-6608 (delta_epsilon=-4.2), MLC-6241-000, and UCF-280 (delta_epsilon=-4); four middle-birefringence liquid crystals, 5CB, 5PCH, E7, E48 and BL003; four high-birefringence liquid crystals, BL006, BL038, E44 and UCF-35, and two liquid crystals with high dno/dT at room temperature, UCF-1 and UCF-2. The refractive indices of E7 at two infrared wavelengths lamda=1.55 and 10.6 um are measured by the wedged-cell refractometer method. The UV absorption spectra of several liquid crystals, MLC-9200-000, MLC-9200-100, MLC-6608 and TL-216 are measured, too. In section 6.5, we also measure the refractive index of cured optical films of NOA65 and NOA81 using the multi-wavelength Abbe refractometer. In Chapter 5, we use the experimental data measured in Chapter 4 to validate the physical models we derived, the extended three-coefficient and two-coefficient Cauchy models, the four-parameter and three-parameter parabolic models. For the first time, we validate the Vuks model using the experimental data of liquid crystals directly. We also validate the empirical Haller equation for the LC birefringence delta_n and the linear equation for the LC average refractive index . The study of the LC refractive indices explores several new photonic applications for liquid crystals such as high temperature gradient liquid crystals, high thermal tunable liquid crystal photonic crystal fibers, the laser induced 2D+1 thermal solitons in nematic crystals, determination for the infrared refractive indices of liquid crystals, comparative study for refractive index between liquid crystals and photopolymers for polymer dispersed liquid crystal (PDLC) applications, and so on. In Chapter 6, we introduce these applications one by one. First, we formulate two novel liquid crystals, UCF-1 and UCF-2, with high dno/dT at room temperature. The dno/dT of UCF-1 is about 4X higher than that of 5CB at room temperature. Second, we infiltrate UCF-1 into the micro holes around the silica core of a section of three-rod core PCF and set up a highly thermal tunable liquid crystal photonic crystal fiber. The guided mode has an effective area of 440 ƒÝm2 with an insertion loss of less than 0.5dB. The loss is mainly attributed to coupling losses between the index-guided section and the bandgap-guided section. The thermal tuning sensitivity of the spectral position of the bandgap was measured to be 27 nm/degree around room temperature, which is 4.6 times higher than that using the commercial E7 LC mixture operated at a temperature above 50 degree C. Third, the novel liquid crystals UCF-1 and UCF-2 are preferred to trigger the laser-induced thermal solitons in nematic liquid crystal confined in a capillary because of the high positive temperature gradient at room temperature. Fourth, we extrapolate the refractive index data measured at the visible light region to the near and far infrared region basing on the extended Cauchy model and four-parameter model. The extrapolation method is validated by the experimental data measured at the visible light and infrared light regions. Knowing the LC refractive indices at the infrared region is important for some photonic devices operated in this light region. Finally, we make a completely comparative study for refractive index between two photocurable polymers (NOA65 and NOA81) and two series of Merck liquid crystals, E-series (E44, E48, and E7) and BL-series (BL038, BL003 and BL006) in order to optimize the performance of polymer dispersed liquid crystals (PDLC). Among the LC materials we studied, BL038 and E48 are good candidates for making PDLC system incorporating NOA65. The BL038 PDLC cell shows a higher contrast ratio than the E48 cell because BL038 has a better matched ordinary refractive index, higher birefringence, and similar miscibility as compared to E48. Liquid crystals having a good miscibility with polymer, matched ordinary refractive index, and higher birefringence help to improve the PDLC contrast ratio for display applications. In Chapter 7, we give a general summary for the dissertation.
350

Prescribed Fire and Thinning Effects on Tree Growth and Carbon Sequestration in Mixed-Oak Forests, Ohio, U.S.A.

Anning, Alexander K. January 2013 (has links)
No description available.

Page generated in 0.0385 seconds