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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.
321

Kvantifikace turbulence pomocí ekvivalentního teplotního gradientu / Quantification of turbulence by the Equivalent Temperature Gradient

Kovaľová, Alžbeta January 2021 (has links)
The diploma thesis is focused on the optical beam propagating in the atmosphere in a wireless communication optical link. The first part of the work explains the atmospheric transmission media with turbulence and its effects on reliability of the optical system. The second part introduces methods for turbulence determination based on a statistical approach to turbulence quantification are introduced. In the third part, method of equivalent temperature gradient is described with the advantage of immediate turbulence evaluation. The output of this thesis is the model of turbulent environment formed by the optical elements. Analysis of turbulent properties and non-reciprocal nature of turbulent channel is processed by a 2D simulator based on the mentioned model and method of equivalent temperature gradient.
322

Synthèse et étude de récepteurs tritopiques de type bis-calix[6]tris-(thio)urée

Moerkerke, Steven 18 March 2016 (has links) (PDF)
Ce travail s’inscrit dans le cadre de la chimie supramoléculaire, domaine qui traite des systèmes comportant deux ou plusieurs entités moléculaires, organisées et maintenues ensemble par des interactions intermoléculaires non covalentes. Ces interactions sont très répandues dans les systèmes naturels et de nombreux récepteurs moléculaires synthétiques ont été développés afin d’améliorer la compréhension des différents processus de reconnaissance hôte-invité. Parmi ces récepteurs, les calix[6]arènes sont des candidats de choix car ils possèdent une cavité hydrophobe idéale pour l’inclusion de petites molécules organiques. De plus, de nombreuses méthodes de synthèse ont été mises au point pour les modifier chimiquement. Un certain nombre de travaux publiés dans la littérature ont porté sur la synthèse de récepteurs multitopiques à base de deux sous-unités calixaréniques reliées entre elles :les bis-calixarènes. L’objectif consiste à obtenir des tubes possédant des propriétés de complexation inédites. Parmi les composés préalablement étudiés au sein du Laboratoire de Chimie Organique, le bis-calix[6]tris-amide est le premier exemple de récepteur multitopique, car il permet l’inclusion d'un ammonium et de son contre-ion selon un processus de reconnaissance de paires d'ions associés, mais également l'inclusion d'un second ammonium pour obtenir des complexes cascade, dans un solvant apolaire (CDCl3). Cependant, ces propriétés de reconnaissance sont particulièrement limitées dans un solvant protique (CD3OD), restreignant de ce fait leur applicabilité.L’objectif de nos travaux a été de synthétiser et d’étudier les propriétés hôte-invité de nouveaux dérivés bis-calix[6]aréniques, modifiés à diverses positions, afin de moduler et renforcer les propriétés de reconnaissance, notamment en milieu protique. Pour ce faire, cinq nouveaux récepteurs ont été développés. Tout d’abord, le remplacement des trois liens amide par trois liens urée ou thiourée a permis d'améliorer la reconnaissance d’une grande variété de paires et triades d’ions organiques, grâce à un remarquable phénomène d’adaptation induite et avec une sélectivité importante pour les ammoniums linéaires associés à un anion dichargé. Les processus de complexation sont hautement coopératifs et sont en grande partie dirigés par l’interaction ionique. L'étude approfondie de ces récepteurs a permis de mieux comprendre le mode d'insertion des ammoniums qui s’insèrent très probablement dans les cavités en passant par les petits cols calixaréniques, le méthyle terminal en premier. Ces deux récepteurs sont également aptes à complexer des ammoniums quaternaires fonctionnalisés et des zwittérions de type bétaïne :l’ammonium est alors reconnu au sein d’une des deux cavités aromatiques tandis que le second groupe fonctionnel interagit avec le site tris-(thio)urée. La reconnaissance sélective de lipides de type phosphatidylcholine a également été mise en évidence. Il est très intéressant de noter que ces récepteurs constituent un très bel exemple de biomimétisme, avec un mode de reconnaissance très proche de celui des transporteurs naturels de ces molécules. D’autre part, le bis-calix[6]tris-thiourée peut également servir de détecteur capable de discriminer divers anions en présence d'un petit ammonium primaire dans le chloroforme.En présence de deux sites tris-urée sur chaque bras reliant les deux sous-unités calixaréniques, la formation de complexe quaternaire avec des bis-anions de type disulfate ou dicarboxylate a été observée tandis qu’en supprimant les groupes méthyle des petits cols calixaréniques via une réaction de déméthylation sélective, le bis-calixarène hexa-déméthylé possède une meilleure affinité pour les triades d’ions d’ammoniums secondaires et quaternaires, grâce à la plus grande flexibilité de ce récepteur par rapport à son équivalent hexa-méthylé. Enfin, l’introduction de bras fonctionnalisé sur le bis-calix[6]arène tris-urée a permis de former sélectivement des complexes quaternaires de type [1+1+1+1] en incluant deux ammoniums différents. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished
323

Kaskádní model silnoproudého vedení pro PLC / Cascade model of power lines for PLC

Dziura, Michal January 2012 (has links)
The thesis is dealing with data transmission over the electric network. It describes PLC technology, its properties, and elements used in this type of network. The important part of this thesis is discussion over the mathematical model of distribution network with two-port cascades. Transmission functions created according to mathematical model were compared with each other. Thesis was concluded with observation of the impact of interconnected parts on transmission function of designed branched conductor. Final results were processed by Matlab and compared with each other.
324

Entropicky řízené kaskádové hybridizační reakce pro detekci mikroRNA / Entropically driven cascade hybridization reactions for detection of microRNA

Runová, Alžbeta January 2020 (has links)
The emerging potential of miRNA molecules as diagnostic biomarkers calls for the development of a new quantification method. Current approaches usually require time-consuming and costly miRNA isolation for proper sample analysis. In this thesis, a new, isolation-free, oligonucleotide- modified gold nanoparticle (AuNP/DNA) system is proposed and designed for miRNA detection and quantification in living cells. This cascade, entropy-driven, and enzyme-free amplification system provides fluorescence signal upon selective interaction with the target miRNA. For this purpose, citrate-stabilized gold nanoparticles were synthesized, and their diameters were determined by dynamic light scattering and transmission electron microscopy. The AuNP/DNA conjugates were prepared following a recently published "freezing method". Their reaction kinetics with the target miRNA and selectivity to various miRNAs were compared with those of an analogous DNA system without AuNPs in a series of fluorescence measurements. Furthermore, stability experiments in glutathione environment were conducted, as well as DNA electrophoresis, demonstrating the mechanistic aspects of the reaction. The reaction yields and selectivity to target miRNA of 42.31 ± 2.91 nm AuNP/DNA constructs, containing approximately 25 DNA complexes per AuNP,...
325

Applications of a Mid-IR Quantum Cascade Laser in Gas Sensing Research

Sajid, Muhammad Bilal 05 1900 (has links)
Laser absorption based sensors are extensively used in a variety of gas sensing areas such as combustion, atmospheric research, human breath analysis, and high resolution infrared spectroscopy. Quantum cascade lasers have recently emerged as high resolution, high power laser sources operating in mid infrared region and can have wide tunability range. These devices provide an opportunity to access stronger fundamental and combination vibrational bands located in mid infrared region than previously accessible weaker overtone vibrational bands located in near infrared region. Spectroscopic region near 8 µm contains strong vibrational bands of methane, acetylene, hydrogen peroxide, water vapor and nitrous oxide. These molecules have important applications in a wide range of applications. This thesis presents studies pertaining to spectroscopy and combustion applications. Advancements in combustion research are imperative to achieve lower emissions and higher efficiency in practical combustion devices such as gas turbines and engines. Accurate chemical kinetic models are critical to achieve predictive models which contain several thousand reactions and hundreds of species. These models need highly reliable experimental data for validation and improvements. Shock tubes are ideal devices to obtain such information. A shock tube is a homogenous, nearly constant volume, constant pressure, adiabatic and 0-D reactor. In combination with laser absorption sensors, shock tubes can be used to measure reaction rates and species time histories of several intermediates and products formed during pyrolysis and oxidation of fuels. This work describes measurement of the decomposition rate of hydrogen peroxide which is an important intermediate species controlling reactivity of combustion system in the intermediate temperature range. Spectroscopic parameters (linestrengths, broadening coefficients and temperature dependent coefficients) are determined for various transitions of acetylene. Furthermore, methane and acetylene sensors are developed for shock tube applications. The application of these sensors (along with an ethylene sensor) has been demonstrated to measure these species during the pyrolysis of n-pentane and iso-pentane.
326

A Survey of the Development of Daubechies Scaling Functions

Age, Amber E 06 July 2010 (has links)
Wavelets are functions used to approximate data and can be traced back to several different areas, including seismic geology and quantum mechanics. Wavelets are applicable in many areas, including fingerprint and data compression, earthquake prediction, speech discrimination, and human vision. In this paper, we first give a brief history on the origins of wavelet theory. We will then discuss the work of Daubechies, whose construction of continuous, compactly supported scaling functions resulted in an explosion in the study of wavelets in the 1990's. These scaling functions allow for the construction of Daubechies' wavelets. Next, we shall use the algorithm to construct the Daubechies D4 scaling filters associated with the D4 scaling function. We then explore the Cascade Algorithm, which is a process that uses approximations to get possible representations for the D2N scaling function of Daubechies. Lastly, we will use the Cascade Algorithm to get a visual representation of the D4 scaling function.
327

Evoluce vnímání světla u strunatců / Evolution of light detection in chordates

Pergner, Jiří January 2018 (has links)
Light detection is one of the crucial abilities of all animals. The light cues are important e.g. for maintaining of circadian rhythms, regulation of spawning cycles, changes of pigmentation and arguably most importantly for vision. Most animals detect light by opsins, members of the G protein coupled receptors superfamily. Amphioxus belongs to earliest branching chordate clade, cephalochordates. Thanks to their phylogenetic position, physiology and morphology, cephalochordates became the most relevant model organism for understanding the evolutionary origins of vertebrate specific traits. Amphioxus evince various reactions to light throughout its development. In the presented thesis light detecting systems of amphioxus were studied thoroughly. More specifically characterization of the opsin gene repertoire of two amphioxus species Branchiostoma floridae and Branchiostoma lanceolatum and their comparison with opsins from other animals is presented. In addition, remarkable similarity on the gene expression level between one of amphioxus visual organs, so called frontal eye, and neurons and retinal pigmented epithelium in vertebrate retina was shown. These data confirm the long time ago proposed homology between amphioxus frontal eye and vertebrate lateral eyes. Taken together all the presented data...
328

Characterization of Cascade gearbox for wave energy converter / Karakterisering av kaskadväxel för vågenergiomvandlare

Ljungbäck, Jacob January 2015 (has links)
This Master Thesis, written in collaboration with CorPower Ocean, serves as the finalization of the author’s master degree education at KTH (Royal Institute of Technology) Stockholm. The purpose has been to characterize the Cascade gearbox which is used to convert vertical motion induced by waves to rotational motion which powers generators in the company’s future wave energy power plant. The purpose was also to suggest future improvements and shed light on any problems discovered. The method for characterizing the Cascade gearbox was to conduct physical measurements of the load sharing in the inherently overdetermined geometrical design. These data were then used to calibrate a static as well as a dynamic model also developed for this thesis. Focus has been on determining that the novel load sharing method is sufficient and that no gear takes more than the 2,5% overload during max load the gearbox is dimensioned for at any time. Also included in the thesis is an analysis of the tolerances effect on the performance of the Cascade gearbox. Results showed that the current design perform within the expected dimensioning limits. However some unexpected characteristics were discovered after analysis of the results. Because of deliberate geometric decisions half of the gears trail behind initially in one direction causing uneven load sharing and unwanted lateral forces on the rack. Also discovered was the importance of equal stiffness of the flex units, used to divide the load evenly between the gears, since the load sharing factor converges towards values directly proportional to the stiffness ratios in between them. As a conclusion it can be said that although the current design is sufficient, there is still room for improvements which could enhance life expectancy as well as load sharing performance of the Cascade gearbox. / Detta examensarbete utfört i samarbete med CorPower Ocean, är det slutgiltiga steget i författarens utbildning på masternivå på KTH (Kungliga Tekniska Högskolan) Stockholm. Syftet med arbetet är att karakterisera en kaskadväxellåda som används för att omvandla vertikal rörelse från vågor till rotation som driver generatorer i företagets framtida vågkraftverk samt att utifrån resultat föreslå möjliga förbättringar och belysa eventuella problem. Den metod som använts för att karakterisera kaskadväxellådan var att via fysiska mätningar, på den testrigg placerad på KTH (Kungliga Tekniska Högskolan) i Stockholm, erhålla data för lastfördelningen i den geometriskt överbestämda konstruktionen. Dessa data användes sedan för att kalibrera en statisk och en dynamisk modell som också utvecklades för det här projektet. Huvudfokus för arbetet har legat i att ta reda på om den konstruktion som används för att fördela lasten mellan kugghjulen fungerar tillfredställande samt att säkerställa att inget kugghjul tar mer än de 2,5% överlast vid fullast växellådan är dimensionerad för vid något tillfälle. Examensarbetet inkluderar även feltoleransers inverkan på lastfördelningen i kaskadväxeln. Resultaten visade att den nuvarande konstruktionen presterar inom de specificerade dimensioneringsintervallen. Några oväntade karaktärsdrag upptäckdes dock vid analys av resultaten. På grund av en avsiktlig geometrisk oregelbundenhet släpade hälften av kugghjulen efter åt ena hållet vilket i sin tur resulterade i en ojämn lastfördelning och oönskade sidokrafter på kuggracken. Flexenheterna som används för att fördela lasten likvärdigt mellan kugghjulen skilde sig åt i styvhet. Den inverkan spridningen av dessa har på lastfördelningen belystes också eftersom lastfördelningen konvergerar mot värden direkt proportionella mot styvhetsförhållandet mellan dem. Slutsatsen från examensarbetet är att den nuvarande konstruktionen, även om den fungerar tillfredställande, lämnar utrymme för förbättringar som potentiellt kan förbättra både livslängd och lastfördelningsprestanda.
329

Visual Vehicle Identification Using Modern Smart Glasses / Visuell fordonsidentifiering med moderna smarta glasögon

Malmgren, Andreas January 2015 (has links)
In recent years wearable devices have been advancing at a rapid pace and one of the largest growing segments is the smart glass segment. In this thesis the feasibility of today’s ARM-based smart glasses are evaluated for automatic license plate recognition (ALPR). The license plate is by far the most prominent visual feature to identify a spe- cific vehicle, and exists on both old and newly produced vehicles. This thesis propose an ALPR system based on a sequence of vertical edge detection, a cascade classifier, verti- cal and horizontal projection as well as a general purpose optical character recognition library. The study further concludes that the optimal input resolution for license plate detection using vertical edges is 640x360 pixels and that the license plate need to be at least 20 pixels high or the characters 15 pixels high in order to successfully segment the plate and recognize each character. The separate stages were successfully implemented into a complete ALPR system that achieved 79.5% success rate while processing roughly 3 frames per second when running on a pair of Google Glass. / Under de senaste åren har området wearables avancerat i snabb takt, och ett av de snabbast växande segmenten är smarta glaögon. I denna examensuppsats utvärderas lämpligheten av dagens ARM-baserade smarta glasögon med avseende på automatisk registreringsskyltigenkänning. Registreringsskylten är den i särklass mest framträdande visuella egenskapen som kan användas för att identifiera ett specifikt fordon, och den finns på både gamla och nyproducerade fordon. Detta examensarbete föreslår ett system för automatisk registreringsskyltigenkänning baserat på en följd av vertikal kantdetektering, en kaskad av boostade klassificerare, vertikal och horisontell projektion samt ett optiskt teckenigenkänningsbibliotek. Studien konstaterar vidare att den optimala upplösningen för registreringsskyltdetektion med hjälp av vertikala kanter på smarta glasögonär 640x360 pixlar och att registreringsskylten måste vara minst 20 pixlar hög eller tecknen 15 pixlar höga för att registreringsskylten framgångsrikt skall kunna segmenteras samt tecken identifieras. De separata stegen implementerades framgångsrikt till ett system för automatisk registreringsskyltigenkänning på ett par Google Glass och lyckades känna igen 79,5% av de testade registreringsskyltarna, med en hastighet av ungefär 3 bilder per sekund.
330

Concept Development of anElectromechanical Cylinder : With a Cascade Gear Unit / Konceptutveckling av elektromekanisk cylinder : med en kaskadväxelenhet

Bergqvist, Karl, Sevefjord, Linn January 2014 (has links)
A new invention has been developed by CorPower Ocean; a mechanical rack and pinion solution called a cascade gearbox. The primary function of the gearbox is transforming a linear motion into a rotational motion. The novelty is its unique properties; it is capable of combining heavy loads and high velocities, and at a high efficiency. CorPower Ocean is aiming at finding applications where the gearbox’s unique properties can be of use. If the gearbox is combined with a motor it forms an electromechanical actuator. Therefore, an investigation of applications using actuators has been targeted. More specifically, the master thesis assignment was to examine in which applications the transition of a cascade electromechanical actuator was technically viable. Research questions that derived was to answer if an implementation of an cascade electromechanical cylinder is technically feasible and if it implicates improved results regarding environmental related goals. The methodology executed to finalize the project included several stages. The first stage was the background study which consisted of reviewing trends and gathering technical data for case studies of targeted applications. The targeted applications were heavy lifting equipment and injection molding machines. With the help of CorPower software, gearbox dimensioning examples were drafted and could be evaluated from a size and weight perspective. To further evaluate potential applications, interviews were conducted with targeted equipment manufacturers. The selection of applications was completed by evaluating the interview responses and the drafted gearbox examples. Chosen applications were ultimately a nine tonnes forklift and an empty container handler, mainly due to good customer response, integration ability and potential of performance enhancement. An optimisation was performed to achieve a concept solution that satisfied customer needs such as low cost and a slim design. In order review the business cases in each application, energy savings and performance cases were conducted, benchmarking against the hydraulic solution. In the ECH case, the energy saved was 54% and the productivity increased with 9.6%. In the forklift case, the energy saved was 52% and the productivity increased with 1%. Both of applications have great potential of a transition from hydraulic cylinders to electromechanical cylinders in terms of implementation and technical feasibility. The final concept solutions exceeded the hydraulics in performance, retaining a slim and acceptable size and design. Furthermore, this sector of heavy lifting equipment had high potential for electrification which can contribute to reduced emissions and fuel savings. Keywords: electromechanical cylinders, concept development, cascade gearbox / En ny innovation har utvecklats av CorPower Ocean; en mekanisk rack och pinjonglösning kallad kaskadväxel. Dess primära funktion är att transformera en linjär rörelse till en roterande rörelse och vice versa. Nyhetsvärdet är växellådans unika prestanda; den kan hantera kombinationen av höga laster och höga hastigheter till en hög verkningsgrad. Nu önskar CorPower Ocean att hitta applikationer där kaskadväxelns unika prestanda kommer till användning. Om kaskadväxeln kombineras med en motor bildas en elektromekanisk aktuator, och därför har en utredning av applikationer som använder aktuatorer utsetts som en marknad att undersöka närmare. Mer specifikt var examensuppdraget att undersöka i vilka applikationer en sådan övergång skulle vara genomförbar ur ett tekniskt perspektiv. Forskningsfrågor som önskades besvaras var huruvida en sådan övergång är genomförbar ur ett tekniskt perspektiv och om en sådan implementation innebär förbättringar vad gäller miljörelaterade mål. Metodologin som användes för att slutföra projektet utgjordes av flera steg. Första steget var att genomföra en bakgrundsstudie om elektrifiering och produkttrender samt samla teknisk data på utsedda applikationer. De utsedda övergångsområdena var maskiner för tunga lyft samt plastformssprutningsmaskiner. Med CorPowers mjukvara kunde dimensioneringsexempel göras för kaskadväxellådor och utvärderas utifrån sin storlek och vikt. För en fortsatt utvärdering av applikationer genomfördes intervjuer med tillverkare av de utsedda applikationerna. Val av applikationer slutfördes genom att utvärdera svar från målkunder samt dimensioneringsexempel av växellådorna. De valda applikationerna blev slutligen en nio tons gaffeltruck och en tomcontainertruck. Valet baserades huvudsakligen på bra respons från kunder, bra integrationsmöjligheter samt potentiella prestandaförbättringar. Fokus låg på att byta ut lyftcylindrarna och bortse från övriga mindre cylindrar. Lösningarna optimerades för att matcha kundkrav så som kostnad och passform. Ett energibesparingscase utfördes för att jämföra kaskadlösningen med nuvarande hydrauliska lösning. I tomcontainertruckens fall sänktes energiförbrukningen med 54 % och produktiviteten ökade med 9.6%. I gaffeltruckens fall sjönk energiförbrukningen med 52 % och produktiviteten ökade med 1 %. Båda applikationerna uppvisade stor potential för ett byte från hydraulcylindrar till elektromekaniska cylindrar. De slutgiltiga koncepten överträffade hydraulikens prestanda medan de bibehöll en acceptabel storlek. Vidare fanns det en stor potential inom lyftindustrin att genom elektrifiering kunna minska utsläpp och bränsleförbrukning. Nyckelord: elektromekanisk cylinder, konceptutveckling, kaskadväxel

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