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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.
11

Spatial Operations in a GIS-Based Karst Feature Database

Gao, Yongli 01 May 2008 (has links)
This paper presents the spatial implementation of the karst feature database (KFD) of Minnesota in a GIS environment. ESRI's ArcInfo and ArcView GIS packages were used to analyze and manipulate the spatial operations of the KFD of Minnesota. Spatial operations were classified into three data manipulation categories: single layer operation, multiple layer operation, and other spatial transformation in the KFD. Most of the spatial operations discussed in this paper can be conducted using ArcInfo, ArcView, and ArcGIS. A set of strategies and rules were proposed and used to build the spatial operational module in the KFD to make the spatial operations more efficient and topographically correct.
12

On a Two Dimensional Inverse Scattering Problem for a Dielectric / Auf einer zweidimensionalen Inverse Scattering Problem für eine Dielektrische

Altundag, Ahmet 07 February 2012 (has links)
No description available.
13

Investigation of Electro-thermal and Thermoelectric Properties of Carbon Nanomaterials

Verma, Rekha January 2013 (has links) (PDF)
Due to the aggressive downscaling of the CMOS technology, power and current densities are increasing inside the chip. The limiting current conduction capacity(106 Acm−2)and thermal conductivity(201Wm−1K−1 for Al and 400 Wm−1K−1 for Cu) of the existing interconnects materials has given rise to different electro-thermal issues such a shot-spot formation, electromigration, etc. Exploration of new materials with high thermal conductivity and current conduction has thus attracted much attention for future integrated circuit technology. Among all the elemental materials, carbon nanomaterials (graphene and carbon nanotube) possess exceptionally high thermal (600-7000 Wm−1K−1) and current( ~108 -109 Acm−2)conduction properties at room temperature, which makes them potential candidate for interconnect materials. At the same time development of efficient energy harvesting techniques are also becoming important for future wireless autonomous devices. The excess heat generated at the hot-spot location could be used to drive an electronic circuit through a suitable thermoelectric generator. As the See beck coefficient of graphene is reported to be the highest among all elementary semiconductors, exploration of thermoelectric properties of graphene is very important. This thesis investigates the electrothermal and thermoelectric properties of metallic single walled carbon nanotube (SWCNT) and single layer graphene (SLG) for their possible applications in thermal management in next generation integrated circuits. A closed form analytical solution of Joule-heating equation in metallic SWCNTs is thus proposed by considering a temperature dependent lattice thermal conductivity (κ) on the basis of three-phonon Umklapp, mass-difference and boundary scattering phenomena. The solution of which gives the temperature profile over the SWCNT length and hence the location of hot-spot(created due to the self-heating inside the chip) can be predicted. This self-heating phenomenon is further extended to estimate the electromigration performance and mean-time-to-failure of metallic SWCNTs. It is shown that metallic SWCNTs are less prone to electromigration. To analyze the electro-thermal effects in a suspended SLG, a physics-based flexural phonon dominated thermal conductivity model is developed, which shows that κ follows a T1.5 and T−2 law at lower(<300 K) and higher temperature respectively in the absence of isotopes(C13 atoms). However in the presence of isotopic impurity, the behavior of κ sharply deviates from T−2 at higher temperatures. The proposed model of κ is found to be in excellent match with the available experimental data over a wide range of temperatures and can be utilized for an efficient electro-thermal analysis of encased/supported graphene. By considering the interaction of electron with in-plane and flexural phonons in a doped SLG sheet, a physics-based electrical conductance(σ) model of SLG under self-heating effect is also discussed that particularly exhibits the variation of electrical resistance with temperature at different current levels and matches well with the available experimental data. To investigate the thermoelectric performance of a SLG sheet, analytical models for See beck effect coefficient (SB) and specific heat (Cph) are developed, which are found to be in good agreement with the experimental data. Using those analytical models, it is predicted that one can achieve a thermoelectric figure of merit(ZT) of ~ 0.62 at room temperature by adding isotopic impurities(C13 atoms) in a degenerate SLG. Such prediction shows the immense potential of graphene in waste-heat recovery applications. Those models for σ, κ, SB and Cph are further used to determine the time evolution of temperature distribution along suspended SLG sheet through a transient analysis of Joule-heating equation under the Thomson effect. The proposed methodology can be extended to analyze the graphene heat-spreader theory and interconnects and graphene based thermoelectrics.
14

Multi-class recognition using pair-wise classifiers / Daugelio klasių atpažinimas naudojant klasifikatorius poroms

Kybartas, Rimantas 01 October 2010 (has links)
There are plenty of solutions for the task of multi-class recognition. Unfortunately, these solutions are not always unanimous. Most of them are based on empirical experiments while statistical data features consideration is often omitted. That’s why questions like when and which method should be used, what the reliability of any chosen method is for solving a multi-class recognition task arise. In this dissertation two-stage multi-class decision methods are analyzed. Pair-wise classifiers able to better exploit statistical data features are used in the first stage of such methods. In the second stage a particular fusion rule of the first stage results is used to fuse the first stage results in order to produce the final classification decision. Complexity issues of pair-wise classifiers, training data size and precision of method quality estimation are pointed out in the research. The precision of algorithm highly depends on the data and the number of experiments performed (data permutation, division into training and testing data). It is shown that the declared superiority of some known algorithms is not reliable due to low precision of estimation. A detailed comparison of well known multi-class classification methods is performed and a new pair-wise classifier fusion method based on similar method used in multi-class classifier fusion is presented. The recommendations for multi-class classification task designer are provided. Methods which allow reducing classification... [to full text] / Daugelio klasių atpažinimo uždaviniams spręsti yra sukurta aibė sprendimų ir ne visada vieningų rekomendacijų. Dauguma jų paremta empiriniais bandymais, retai atsižvelgiama į statistines duomenų savybes. Dėl to sprendžiant daugelio klasių klasifikavimo uždavinį kyla klausimų, kurį metodą ir kada geriausia naudoti, koks vieno ar kito metodo patikimumas. Disertacijoje nagrinėjami dviejų pakopų sprendimo priėmimo metodai, kai pirmame etape sudaromi klasifikatoriai poroms (angl. pair-wise), sugebantys geriau išnaudoti klasių tarpusavio statistines savybes, o kitame etape yra atliekamas klasifikatorių poroms rezultatų apjungimas. Tyrime ypatingas dėmesys yra skiriamas klasifikatorių poroms sudėtingumui, mokymo duomenų kiekiui bei algoritmų kokybės įvertinimo tikslumui. Tikslumas labai priklauso nuo duomenų bei atliktų eksperimentų kiekio (duomenų permaišymo klasėse, juos skirstant į mokymo ir testavimo). Parodyta, jog dėl žemo įvertinimo tikslumo kai kurių publikuotų algoritmų deklaruojamas pranašumas prieš žinomus algoritmus nėra patikimas. Darbe atliktas detalus žinomų metodų palyginimas bei pristatytas naujai sukurtas klasifikatorių poroms apjungimo algoritmas, kuris yra paremtas analogišku algoritmu daugelio klasių klasifikatorių rezultatų apjungimui. Pateiktos bendros rekomendacijos, kaip projektuotojui elgtis daugelio klasių atveju. Pasiūlyti metodai, leidžiantys sumažinti klasifikavimo klaidą atliekant klasifikatorių poroms apjungimo koregavimą, kad algoritmas nebūtų... [toliau žr. visą tekstą]
15

Daugelio klasių atpažinimas naudojant klasifikatorius poroms / Multi-class recognition using pair-wise classifiers

Kybartas, Rimantas 01 October 2010 (has links)
Daugelio klasių atpažinimo uždaviniams spręsti yra sukurta aibė sprendimų ir ne visada vieningų rekomendacijų. Dauguma jų paremta empiriniais bandymais, retai atsižvelgiama į statistines duomenų savybes. Dėl to sprendžiant daugelio klasių klasifikavimo uždavinį kyla klausimų, kurį metodą ir kada geriausia naudoti, koks vieno ar kito metodo patikimumas. Disertacijoje nagrinėjami dviejų pakopų sprendimo priėmimo metodai, kai pirmame etape sudaromi klasifikatoriai poroms (angl. pair-wise), sugebantys geriau išnaudoti klasių tarpusavio statistines savybes, o kitame etape yra atliekamas klasifikatorių poroms rezultatų apjungimas. Tyrime ypatingas dėmesys yra skiriamas klasifikatorių poroms sudėtingumui, mokymo duomenų kiekiui bei algoritmų kokybės įvertinimo tikslumui. Tikslumas labai priklauso nuo duomenų bei atliktų eksperimentų kiekio (duomenų permaišymo klasėse, juos skirstant į mokymo ir testavimo). Parodyta, jog dėl žemo įvertinimo tikslumo kai kurių publikuotų algoritmų deklaruojamas pranašumas prieš žinomus algoritmus nėra patikimas. Darbe atliktas detalus žinomų metodų palyginimas bei pristatytas naujai sukurtas klasifikatorių poroms apjungimo algoritmas, kuris yra paremtas analogišku algoritmu daugelio klasių klasifikatorių rezultatų apjungimui. Pateiktos bendros rekomendacijos, kaip projektuotojui elgtis daugelio klasių atveju. Pasiūlyti metodai, leidžiantys sumažinti klasifikavimo klaidą atliekant klasifikatorių poroms apjungimo koregavimą, kad algoritmas nebūtų... [toliau žr. visą tekstą] / There are plenty of solutions for the task of multi-class recognition. Unfortunately, these solutions are not always unanimous. Most of them are based on empirical experiments while statistical data features consideration is often omitted. That’s why questions like when and which method should be used, what the reliability of any chosen method is for solving a multi-class recognition task arise. In this dissertation two-stage multi-class decision methods are analyzed. Pair-wise classifiers able to better exploit statistical data features are used in the first stage of such methods. In the second stage a particular fusion rule of the first stage results is used to fuse the first stage results in order to produce the final classification decision. Complexity issues of pair-wise classifiers, training data size and precision of method quality estimation are pointed out in the research. The precision of algorithm highly depends on the data and the number of experiments performed (data permutation, division into training and testing data). It is shown that the declared superiority of some known algorithms is not reliable due to low precision of estimation. A detailed comparison of well known multi-class classification methods is performed and a new pair-wise classifier fusion method based on similar method used in multi-class classifier fusion is presented. The recommendations for multi-class classification task designer are provided. Methods which allow reducing classification... [to full text]
16

Comportement vibratoire de structures composites intégrant des éléments amortissants / Vibro-acoustocal behavior of composite structures with damping elements

Castel, Alexis 21 November 2013 (has links)
Ce travail traite de la modélisation de structures composites intégrant des éléments amortissants passifs. Un modèle de plaque "équivalent simple couche" générique utilisant des fonctions de description du cisaillement transverse est présenté. Plusieurs méthodes d'obtention de ces fonctions sont décrites, permettant de retrouver des modèles classiques ou issus de la littérature. Deux nouvelles méthodes d'obtention de ces fonctions sont aussi présentées.Plusieurs méthodes de discrétisation adaptées au modèle générique sont étudiées. La méthode de Navier permet de tester la qualité de chaque modèle associé à un jeu de fonctions de description du cisaillement transverse. La méthode de Rayleigh-Ritz permet l'étude du comportement vibratoire d'une plaque rectangulaire munie d'un ou plusieurs patchs viscocontraints. Plusieurs éléments finis issus de la littérature, adaptés au modèle, sont aussi présentés.À l'aide de la méthode de Navier, une étude numérique du comportement statique et dynamique de plusieurs configurations de plaques permet la comparaison des différents modèles présentés. La méthode de Rayleigh-Ritz est utilisée pour étudier le comportement vibratoire d'une plaque munie d'un patch viscocontraint. Une comparaison des résultats obtenus avec le modèle présenté et ceux issus de calculs éléments finis tridimensionnels permet de valider notre modèle. Une étude énergétique de la plaque patchée permet d'illustrer le comportement du patch. Enfin une méthode inverse d'identification des matériaux viscoélastiques, basées sur une combinaison du modèle décrit et d'un algorithme génétique, montre une application du modèle. / This work is on the subject of modelization of structures treated with passive damping elements. A generic "equivalent single layer" plate model using transverse shear warping functions is presented. Several methods to obtain these functions are described, allowing the implementation of classical models and others issued from the litterature. Two new methods for obtaining these functions are also presented.Several discretization methods adapted to the generic plate model are studied. Navier's procedure allows the testing of the quality of each model associated with a set of transverse shear warping functions. Rayleigh-Ritz method allows the study of the vibrational behavior of a rectangular plate treated with one or several constrained damping patches. Several finite elements issued from the literature are also presented.Using Navier's procedure, a numerical study of the static and dynamic behavior of several plate configurations allows the comparison of the different plate models. Rayleigh-Ritz method is used to study the vibrational response of a plate treated with a constrained damping patch. A comparison of the results with those obtained with three dimensional finite element calculations permits the model validation. An energetic study of the patched plate allow us to understand the constrainted damping patch behavior. Finally, an inverse method, allowing the identification of the properties of viscoelastic materials, based on a combination of the presented model and a genetic algorithm, shows a possible application of the model.
17

Mateřská škola / Kindergarten

Macháček, Pavel January 2013 (has links)
The subject of this project is a nursery school in Sokolnice. The building consists of four departments, facilities for personnel and kitchen. The building is designed as a two-storey cellarless building. It has concrete foundations. The external walls are designed from POROTHERM 425 T Profi bricks with internal insulation. The internal vertical construction is designed from POROTHERM bricks for thin-layer masonry. The supporting structure of roof is provided by slab method Spiroll. The entrance doors are made from aluminum sections, plastic windows. The building has single-layer flat roof with waterproofing coating.
18

Long Cavity Quantum Dot Laser Diode And Monolithic Passively Mode-locked Operation

Shavitranuruk, K 01 January 2010 (has links)
Advantage of the single QD active layer is its potential for very low threshold current density, which in turn can produce low internal optical loss. The low threshold current density and low internal loss thus enable a significant increase in laser diode cavity length. Because of the importance of the threshold current density in heatsinking, future technology of broad-area monolithic laser diodes can be implemented. The dissertation describes the development and the unique characteristics of single QD active layer laser with long cavity. The data are presented on single layer QD laser diodes that reach threshold current densities values of 11.7 A/cm2 in a p-up mounted 2 cm long cavity and as low as 10 A/cm2, with CW output power of 2 W in a p-down mounted 1.6 cm long cavity. The 8.8 A/cm2 in a p-down mounted 2 cm long cavity is reported. To our knowledge the value 8.8 A/cm2 is the lowest threshold current density ever reported for a room temperature laser diode. These single layer QD laser diodes reach an internal loss of ~0.25 cm-1, which is also the lowest ever reported for a room temperature laser diode. These unique characteristics of single layer QD and laser diode size are potentially promising for the monolithic mode-locked laser because of relatively high peak power with a low repetition rate that is on the order of a few GHz, which can be the novel device for external clocking in the optical interconnect applications. In this dissertation, the stable optical pulse train in a 40 µm wide stripe with a repetition rate of 3.75 GHz with 1.1 cm cavity length through the passive mode-locked onto the monolithic two-section device fabricated from this single layer QD laser is observed.
19

Remote Sensing of Soybean Canopy Cover, Color, and Visible Indicators of Moisture Stress Using Imagery from Unmanned Aircraft Systems

Anthony A Hearst (6620090) 10 June 2019 (has links)
Crop improvement is necessary for food security as the global population is expected to exceed 9 billion by 2050. Limitations in water resources and more frequent droughts and floods will make it increasingly difficult to manage agricultural resources and increase yields. Therefore, we must improve our ability to monitor agronomic research plots and use the information they provide to predict impacts of moisture stress on crop growth and yield. Towards this end, agronomists have used reductions in leaf expansion rates as a visible ‘plant-based’ indicator of moisture stress. Also, modeling researchers have developed crop models such as AquaCrop to enable quantification of the severity of moisture stress and its impacts on crop growth and yield. Finally, breeders are using Unmanned Aircraft Systems (UAS) in field-based High-Throughput Phenotyping (HTP) to quickly screen large numbers of small agronomic research plots for traits indicative of drought and flood tolerance. Here we investigate whether soybean canopy cover and color time series from high-resolution UAS ortho-images can be collected with enough spatial and temporal resolution to accurately quantify and differentiate agronomic research plots, pinpoint the timing of the onset of moisture stress, and constrain crop models such as AquaCrop to more accurately simulate the timing and severity of moisture stress as well as its impacts on crop growth and yield. We find that canopy cover time series derived from multilayer UAS image ortho-mosaics can reliably differentiate agronomic research plots and pinpoint the timing of reductions in soybean canopy expansion rates to within a couple of days. This information can be used to constrain the timing of the onset of moisture stress in AquaCrop resulting in a more realistic simulation of moisture stress and a lower likelihood of underestimating moisture stress and overestimating yield. These capabilities will help agronomists, crop modelers, and breeders more quickly develop varieties tolerant to moisture stress and achieve food security.
20

Daugiafazių elektromechaninių keitiklių tyrimas / Research of multi-phase electromechanical inverters

Ostanovkaitė, Aurelija 21 June 2013 (has links)
Tiriamajame darbe elektromagnetiniu požiūriu palyginamos viensluoksnė forminė trifazė ir to pačio tipo šešiafazė apvijos. Atlikta šių apvijų kuriamų sukamųjų magnetovarų harmonė analizė ir pagal gautus rezultatus apskaičiuoti elektromagnetinio efektyvumo koeficientai. Gauta, kad viensluoksnė forminė šešiafazė apvija turi geresnius elektromagnetinius parametrus. Šios šešiafazės apvijos efektyvumo koeficientas yra 8,7 % didesnis nei viensluoksnės forminės trifazės apvijos. Atliktas eksperimentinis tyrimas su 1,5 kW asinchroniniu varikliu su viensluoksne formine trifaze apvija ir su tuo pačiu pervyniotu varikliu su ta pačia šešiafaze apvija. Asinchroninio variklio su viensluoksne formine trifaze apvija ir to pačio pervynioto variklio su ta pačia šešiafaze apvija visi energiniai rodikliai apskaičiuoti atlikus tuščiosios veikos ir apkrovos bandymus. Atlikus asinchroninio variklio eksperimentinius bandymus prie nurodytosios apkrovos trifaziam ir šešiafaziam asinchroniniam varikliui, buvo gauti tokie skaičiavimo rezultatai: pervynioto šešiafazio variklio statoriaus apvijos fazinė srovė sumažėjo 25 %, imama iš tinklo galia sumažėjo 10 %, galios suminiai nuostoliai sumažėjo 38 %, galios faktorius padidėjo 4 %, naudingumo faktorius padidėjo beveik 15 %, sukimosi momentas padidėjo apie 5 %. Nustatyta, kad asinchroninis variklis su viensluoksne formine šešiafaze apvija turi geresnius energinius rodiklius nei asinchroninis variklis su to paties tipo trifaze apvija. / In this research electromagnetic properties of single-layer former three-phase winding and the same type six-phase winding are assessed and compared. Harmonic analyses of magnetomotive force was carried out on the rotary forces they generate and, according to final results, the electromagnetic efficiency coefficients were calculated. It was established that electromagnetic parameters of the single-layer former six-phase winding are better. The efficiency coefficient of the single-layer former six-phase winding is 8,7 % higher compared to the same three-phase winding. The experimental analysis of a three-phase asynchronous 1,5 kW motor with a single-layer three-phase winding and the same rewound motor with the same six-phase winding was performed. All energetic indicators of the asynchronous motor with a single-layer former three-phase winding and rewound motor the same six-phase winding were calculated after performing a no-load and load tests. Performing a load testing of the asynchronous motor for single-layer three-phase winding and the same six-phase winding it was established that the current of the stator winding of the rewound asynchronous motor with a single-layer six-phase winding decreased by 25 % at the indicated load, the power from the network decreased by 10 %. Moreover, the power loss decreased by 38 %, the power factor increased by 4 %, the efficiency factor increased almost by 15 %, and the torque increased by 5 %. It was established that the asynchronous... [to full text]

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