• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 213
  • 69
  • 42
  • 33
  • 23
  • 13
  • 4
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 449
  • 449
  • 89
  • 88
  • 67
  • 63
  • 63
  • 46
  • 43
  • 40
  • 35
  • 31
  • 30
  • 29
  • 28
  • 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

Návrh štíhlé výroby s využitím produktů ICT / Proposal Lean Manufacturing, with Products ICT

Janošec, Michal January 2017 (has links)
The diploma thesis focuses on the implementation of production management tools in the form of modern ICT technologies. The final solution, divided into software and hardware part, assists the company in applying the principles of lean manufacturing and the theory of constraints. The work includes a proposal that helps to increase enterprise productivity and eliminates excess inventory in the organization.
322

Développement d'algorithmes d'analyse spectrale en spectrométrie gamma embarquée / Embedded gamma spectrometry : new algorithms for spectral analysis

Martin-Burtart, Nicolas 06 December 2012 (has links)
Jusqu’au début des années 1980, la spectrométrie gamma aéroportée a avant tout été utilisée pour des applications géophysiques et ne concernait que la mesure des concentrations dans les sols des trois radionucléides naturels (K40, U238 et Th232). Durant les quinze dernières années, un grand nombre de dispositifs de mesures a été développé, la plupart après l’accident de Tchernobyl, pour intervenir en cas d’incidents nucléaires ou de surveillance de l’environnement. Les algorithmes développés ont suivi les différentes missions de ces systèmes. La plupart sont dédiés à l’extraction des signaux à moyenne et haute énergie, où les radionucléides naturels (K40, les chaînes U238 et Th232) et les produits de fission (Cs137 et Co60 principalement) sont présents. A plus basse énergie (< 400 keV), ces méthodes peuvent toujours être utilisées mais les particularités du fond de diffusion, très intense, les rendent peu précises. Cette zone énergétique est importante : les SNM émettent à ces énergies. Un algorithme, appelé 2-fenêtres (étendu à 3), a été développé permettant une extraction précise et tenant compte des conditions de vol. La surveillance du trafic de matières radioactives dans le cadre de la sécurité globale a fait son apparition depuis quelques années. Cette utilisation nécessite non plus des méthodes sensibles à un élément particulier mais des critères d’anomalie prenant en compte l’ensemble du spectre enregistré. Il faut être sensible à la fois aux radionucléides médicaux, industriels et nucléaires. Ce travail a permis d’identifier deux familles d’algorithmes permettant de telles utilisations. Enfin, les anomalies détectées doivent être identifiées. La liste des radionucléides nécessitant une surveillance particulière, recommandée par l’AIEA, contient une trentaine d’émetteurs. Un nouvel algorithme d’identification a été entièrement développé, permettant de s’appuyer sur plusieurs raies d’absorption par élément et de lever les conflits d’identification. / Airborne gamma spectrometry was first used for mining prospection. Three main families were looked for: K40, U238 and Th232. The Chernobyl accident acted as a trigger and for the last fifteen years, a lot of new systems have been developed for intervention in case of nuclear accident or environmental purposes. Depending on their uses, new algorithms were developed, mainly for medium or high energy signal extraction. These spectral regions are characteristics of natural emissions (K40, U238- and Th-232 decay chains) and fissions products (mainly Cs137 and Co60). Below 400 keV, where special nuclear materials emit, these methods can still be used but are greatly imprecise. A new algorithm called 2-windows (extended to 3), was developed. It allows an accurate extraction, taking the flight altitude into account to minimize false detection. Watching radioactive materials traffic appeared with homeland security policy a few years ago. This particular use of dedicated sensors require a new type of algorithms. Before, one algorithm was very efficient for a particular nuclide or spectral region. Now, we need algorithm able to detect an anomaly wherever it is and whatever it is : industrial, medical or SNM. This work identified two families of methods working under these circumstances. Finally, anomalies have to be identified. IAEA recommend to watch around 30 radionuclides. A brand new identification algorithm was developed, using several rays per element and avoiding identifications conflicts.
323

Topography-controlled alignment of DNA origami nanotubes on nanopatterned surfaces

Teshome, Bezuayehu, Facsko, Stefan, Keller, Adrian 02 December 2019 (has links)
The controlled positioning of DNA nanostructures on technologically relevant surfaces represents a major goal along the route toward the full-scale integration of DNA-based materials into nanoelectronic and sensor devices. Previous attempts to arrange DNA nanostructures into defined arrays mostly relied on top-down lithographic patterning techniques combined with chemical surface functionalization. Here we combine two bottom-up techniques for nanostructure fabrication, i.e., self-organized nanopattern formation and DNA origami self-assembly, in order to demonstrate the electrostatic self-alignment of DNA nanotubes on topographically patterned silicon surfaces. Self-organized nanoscale ripple patterns with periodicities ranging from 20 nm to 50 nm are fabricated by low-energy ion irradiation and serve as substrates for DNA origami adsorption. Electrostatic interactions with the charged surface oxide during adsorption direct the DNA origami nanotubes to the ripple valleys and align them parallel to the ripples. By optimizing the pattern dimensions and the Debye length of the adsorption buffer, we obtain an alignment yield of ~70%. Since this novel and versatile approach does not rely on any chemical functionalization of the surface or the DNA nanotubes, it can be applied to virtually any substrate material and any top-down or bottom-up nanopatterning technique. This technique thus may enable the wafer-scale fabrication of ordered arrays of functional DNA-based nanowires.
324

Resumovaná chirální poruchová teorie a studium Kl4 rozpadů / Resumovaná chirální poruchová teorie a studium Kl4 rozpadů

Motloch, Pavel January 2012 (has links)
The F and G formfactors of Kl4 decays are calculated to O(p4 ) in isospin limit in Resummed Chiral Perturbation Theory. Formulae for reparametrization of low-energy constants L1 - L3 in terms of physical observables are derived. They are used to obtain values of these low-energy constants from recent experimental data, theoretical error of the result is estimated and dependence on parameters X, Z of spontaneous symmetry breaking of SU(3) × SU(3) chiral symmetry and quark mass ratio r is investigated. Convergence of the formfactors in Resummed Chiral Perturbation Theory is discussed and it is suggested that inclusion of σ as an explicit degree of freedom into Chiral Perturbation Theory could significantly improve overall covergence of chiral series. 1
325

Advanced doping techniques and dehydrogenation properties of transition metal-doped LiAlH 4 for fuel cell systems

Fu, Jie 06 January 2015 (has links)
Hydrogen is an efficient, carbon-free and safe energy carrier. However, its compact and weight-efficient storage is an ongoing subject for research and development. Among the intensively investigated hydrogen storage materials, lithium aluminum hydride (LiAlH4) is an attractive candidate because of its high theoretical hydrogen density (volumetric: 96.7g H2/l material; gravimetric: 10.6 wt.%-H2) in combination with rather low decomposition temperatures (onset temperature <100°C after doping). Although the reversible dehydrogenation of LiAlH4 must be carried out with the help of organic solvent, LiAlH4 can serve as single-use hydrogen storage material for various special applications, for example, hydrogen fuel cell systems. This thesis deals with transition metal (TM)-doped LiAlH4 aiming at tailored dehydrogenation properties. The crystal structure and morphology of TM-doped LiAlH4 is characterized by XRD and SEM respectively. The positive effects of four dopants (NiCl2, TiCl3, ZrCl4 and TiCl4) on promoting the dehydrogenation kinetics of LiAlH4 are systematically studied by thermal analysis. Based on the state of each TM chloride (solid or liquid), three low-energy-input doping methods (1. ball-milling at low rotation speed; 2. manual grinding or magnetic stirring; 3. magnetic stirring in ethyl ether) are compared in order to prepare LiAlH4 with the maximum amount of hydrogen release in combination with fast dehydrogenation kinetics. The dehydrogenation properties of the TM-doped LiAlH4 powders are measured under isothermal conditions at 80°C at a H2 pressure of 1 bar, which is within the operating temperature range of proton exchange membrane (PEM) fuel cells, aiming at applications where the exhaust heat of the fuel cell is used to trigger the dehydrogenation of the hydrogen storage material. Furthermore, the mid-term dehydrogenation behavior of TM-doped LiAlH4 was monitored up to a few months in order to test its mid-term storability. In addition, the pelletization of TM-doped LiAlH4 is investigated aiming at a higher volumetric hydrogen storage capacity. The effects of compaction pressure, temperature and the H2 back-pressure on the dehydrogenation properties of TM-doped LiAlH4 pellets are systematically studied. Moreover, the volume change through dehydrogenation and the short-term storage of the TM-doped LiAlH4 pellets are discussed in view of practical applications for PEM fuel cell systems. / Wasserstoff ist ein effizienter, kohlenstofffreier und sicherer Energieträger. Jedoch die kompakte und gewichtseffiziente Speicherung ist ein permanentes Forschungs- und Entwicklungsthema. Unter den intensiv untersuchten Materialien für die Wasserstoffspeicherung ist aufgrund der hohen theoretischen Speicherdichte (volumetrisch: 96,7 g H2/L, gravimetrisch: 10.6 Gew.%-H2) in Kombination mit sehr niedrigen Zersetzungstemperaturen (Anfangstemperatur < 100°C nach Dotierung) Lithium Aluminiumhydrid (LiAlH4) ein vielversprechender Kandidat. Obwohl die reversible Dehydrierung von LiAlH4 mit Hilfe von organischen Lösungsmitteln durchgeführt werden muss, kann LiAlH4-Pulver als Einweg-Speichermaterial für verschiedene Anwendungen dienen, beispielsweise für Wasserstoff/Brennstoffzellensysteme. Diese Doktorarbeit beschäftigt sich mit LiAlH4 dotiert mit Übergangsmetall, mit dem Ziel maßgeschneiderte Dehydrierungseigenschaften zu erreichen. Die Kristallstruktur und die Morphologie der mit Übergangsmetallen dotierten LiAlH4-Pulver wurden mit Röntgenbeugung (XRD) und Rasterelektronenmikroskopie (REM) charakterisiert. Weiterhin wurde der positive Effekt der Dotanden auf die reaktionsfördernde Dehydrierung von LiAlH4 systematisch mit Hilfe thermoanalytischer Methoden untersucht. Für jedes Übergangsmetall, welches in Form von Übergangsmetallchloriden vorlag, wurden drei Dotierungsmethoden mit niedrigem Energieeintrag (Kugelmahlen mit geringer Rotations-geschwindigkeit, manuelles Schleifen/Magnetrühren, Magnetrühren mit Ethylether) verglichen, um LiAlH4-Pulver mit einer maximalen Wasserstofffreisetzungsmenge in Kombination mit einer schnellen Dehydrierungskinetik zu erzielen. Die Dehydrierung des dotierten LiAlH4-Pulvers wurde unter isothermen Bedingungen bei 80°C und einem H2-Druck von 1 bar gemessen, was im Bereich der Betriebstemperatur von PEM-Brennstoffzellen (Proton Exchange Membran) liegt. Dadurch sollen Anwendungen anvisiert werden, bei denen die entstehende Abwärme der Brennstoffzelle genutzt wird, um die Dehydrierung des Wasserstoffspeichermaterials auszulösen. Zudem wurde das Dehydrierungsverhalten des dotierten LiAlH4 bis zu einigen Monaten kontrolliert, um die mittelfristige Haltbarkeit zu testen. Weiterhin wurde die Pelletierung des mit Übergangsmetallen dotierten LiAlH4 mit dem Ziel untersucht, eine hohe volumetrische Speicherkapazität zu erreichen. Der Einfluss des Pressdrucks, der Dehydrierungstemperatur und des H2-Gegendrucks auf die Dehydrierungseigenschaften der mit Übergangsmetallen dotierten LiAlH4-Presslinge wurde systematisch analysiert. Außerdem wird die Volumenveränderung durch die Dehydrierung und die Kurzzeitspeicherung der mit Übergangsmetallen dotierten LiAlH4-Presslinge im Hinblick auf praktische Anwendungen unter Nutzung der Brennstoffzelle diskutiert.
326

Non-equilibrium structural Dynamics of incommensurate Charge-Density Waves / Diffractive Probing with a micron-scale ultrafast Electron Gun

Storeck, Gero 12 June 2020 (has links)
No description available.
327

Remise diabetu 2. typu u pacientů na různých dietních režimech / Remission of type 2 diabetes in patients on various dietary regimens

Kábelová, Adéla January 2020 (has links)
Type 2 diabetes mellitus (T2D) is a highly prevalent metabolic disorder linked with the development of specific complications and comorbidities that negatively affect life quality and greatly increase the risk of an early death. The main goal of T2D treatment, which in common clinical practice comprises lifestyle changes and pharmacotherapy, is to delay onset of these complications. Evidence from many recent studies shows the ability of some interventional methods to induce remission of T2D, meaning a major improvement or complete disappearance of T2D symptoms. Besides bariatric surgery procedures, some dietary regimens such as low-energy diet, low-carbohydrate diet and intermittent fasting, can also lead to T2D remission. Attributes of these dietary regimens, especially their effect in T2D treatment, is summarized in the theoretical part of this theses. The aim of the practical part of this thesis was to assess the effect of the dietary regimens mentioned above on morphometric and biochemical parameters associated with T2D by clinical and survey research. In most of the subjects with T2D, the individual dietary regimens, more precisely low-energy diet and low-carbohydrate diet, decreased body weight, where the weight loss induced by low-carbohydrate diet was caused by major decrease in the amount...
328

Exploring climate impacts of timber buildings : The effects from including non-traditional aspects in life cycle impact assessment

Peñaloza, Diego January 2015 (has links)
There is an urgency within the building sector to reduce its greenhouse gas emissions and mitigate climate change. An increased proportion of biobased building materials in construction is a potential measure to reduce these emissions. Life cycle assessment (LCA) has often been applied to compare the climate impact from biobased materials with that from e.g. mineral based materials, mostly favouring biobased materials. Contradicting results have however been reported due to differences in methodology, as there is not yet consensus regarding certain aspects. The aim of this thesis is to study the implications from non-traditional practices in climate impact assessment of timber buildings, and to discuss the shortcomings of current practices when assessing such products and comparing them with non-renewable alternatives. The traditional practices for climate impact assessment of biobased materials have been identified, and then applied to a case study of a building with different timber frame designs and an alternative building with a concrete frame. Then, non-traditional practices were explored by calculating climate impact results using alternative methods to handle certain methodological aspects, which have been found relevant for forest products in previous research such as the timing of emissions, biogenic emissions, carbon storage in the products, end-of-life substitution credits, soil carbon disturbances and change in albedo. These alternative practices and their implications were also studied for low-carbon buildings. The use of non-traditional practices can affect the climate impact assessment results of timber buildings, and to some extent the comparison with buildings with lower content of biobased building materials. This effect is especially evident for energy-efficient buildings. Current normal practices tend to account separately for forest-related carbon flows and aspects such as biogenic carbon emissions and sequestration or effects from carbon storage in the products, missing to capture the forest carbon cycle as a whole. Climate neutrality of wood-based construction materials seems like a valid assumption for studies which require methodological simplification, while other aspects such as end-of-life substitution credits, soil carbon disturbances or changes in albedo should be studied carefully due to their potentially high implications and the uncertainties around the methods used to account for them. If forest phenomena are to be included in LCA studies, a robust and complete model of the forest carbon cycle should be used. Another shortcoming is the lack of clear communication of the way some important aspects were handled. / <p>QC 20150310</p>
329

Samband mellan självrapporterad menstruationsdysfunktion och skador bland danska och svenska kvinnliga elitidrottare

Löfgren, Johan January 2022 (has links)
Bakgrund: Återhämtning och nutrition är viktiga aspekter för att minimera risken för skador hos idrottare. Ett för lågt energiintag kan leda till flera negativa fysiologiska effekter då kroppens energibehov inte tillgodoses. Hos kvinnor är menstruationsdysfunktion (MD) ett vanligt symptom på långvarig låg energitillgänglighet och hög förekomst har främst rapporterats hos kvinnliga idrottare inom viktkänsliga idrotter såsom uthållighetsidrott. Syfte: Syftet med denna studie var därför att beskriva skadebilden hos svenska och danska kvinnliga landslagsidrottare på seniornivå samt undersöka eventuella samband mellan förekomst av skador och menstruation. Metod: Alla danska och svenska kvinnliga landslagsidrottare blev kontaktade per mejl och tillfrågade om deltagande via online-enkät där frågor om skador det senaste året och menstruation ingick. Deltagare blev klassificerade att ha MD om de uppgav att de aldrig haft menstruation, ingen menstruation de senaste tre månaderna, menstruationscykler med längre intervall än 35 dagar eller &lt;9 menstruationscykler de senaste 12 månaderna. Alla deltagare blev klassificerade som antingen icke-viktkänsliga (t.ex. bollsport) eller viktkänslig idrottare (t.ex. uthålligsidrott). Resultat: Totalt svarade 634 (25%) idrottare på enkäten. Den rapporterade skadeprevalensen under de senaste 12 månaderna för samtliga inkluderade deltagare var 57%. 30% av deltagarna blev klassificerade att ha MD med en högre förekomst i viktkänsliga idrotter (39% vs 24%; P = &lt;0,001). Deltagare med MD rapporterade fler skador under de senaste 12 månaderna (P = 0,004) och hade en högre risk för skada (OR = 1,52; 95% CI = 1,06–2,19; P = 0,024) samt högre risk för att ha varit långvarigt skadad (&gt;22 dagar) (OR = 1,87; 95% CI = 1,23–2,55; P = 0,003) jämfört med deltagare med regelbunden menstruation. Deltagare från viktkänsliga idrotter hade en högre risk för skada (OR = 1,50; 95% CI = 1,02–2,21; P = 0,039) och högre risk för att ha varit långvarigt skadad (OR = 2,11; 95% CI = 1,38–3,24; P = &lt;0,001) jämfört med deltagare från icke-viktkänsliga idrotter. Konklusion: Resultaten indikerar att kvinnliga landslagsidrottare med självrapporterad MD har en ökad skaderisk, speciellt inom viktkänsliga idrotter som uthållighetsidrott. Menstruationsdysfunktion bör därför tas i beaktning då det har negativ inverkan på idrottares hälsa och prestation. Vidare finns det ett stort behov av mer kunskap för att implementera effektiva kön- och idrottsspecifika preventionsåtgärder. / Background: Recovery and nutrition are important aspects in order to minimize injury risk in athletes. Multiple negative physiological impairments have been recognized in athletes due to low energy intake. One common symptom of prolonged low energy availability in females is menstrual dysfunction (MD) and high prevalence has been reported mostly in female athletes in weight-sensitive sports like endurance sports. Aim: The aim of the present study was to describe injuries among Swedish and Danish female national team athletes and to investigate potential connections between injury prevalence and menstruation. Method: All Swedish and Danish national team athletes were invited via e-mail to complete an anonymous online survey, which held questions about injuries the past year and menstruation. Participants were classified with MD if they stated that they never had menstruation, no menstruation the last three months, menstruation cycles with longer intervals than 35 days or &lt;9 menstruation cycles the last 12 months. The participants were also divided in groups of non-weight sensitive athletes (e.g. ball game) or weight sensitive athletes (e.g. endurance sport). Results: A total of 634 (25%) athletes completed the survey. Among all participants an injury prevalence of 57% was observed and 30% were classified with MD. Higher prevalence of MD was reported in weight-sensitive sports (39% vs. 24%; P = &lt;0,001). Athletes with MD sustained more injuries (P = 0,004), reported higher risk of injury (OR = 1,52; 95% CI = 1,06–2,19; P = 0,024) and to be long-term injured (&gt;22 days) (OR = 1,87; 95% CI = 1,23–2,55; P = 0,003) compared to athletes with regular menstruation. In athletes from weight-sensitive sports a higher risk of injury was observed (OR = 1,50; 95% CI = 1,02–2,21; P = 0,039) and also to be long-term injured (OR = 2,11; 95% CI = 1,38–3,24; P = &lt;0,001) compared to athletes from non weight-sensitive sports. Conclusion: The result indicates that female national team athletes with self-reported MD have increased injury risk, especially in weight-sensitive sports like endurance sports. Menstrual dysfunction has a negative impact on both health and performance, and therefore athletes and coaches need to pay attention to menstrual function. More research is needed to implement effective sex and sport-specific preventive measures.
330

Accessibility Studies of Potentially Hazardous Asteroids from the Sun-Earth L2 Libration Point

GANESAN, GAUTHAM January 2020 (has links)
A newly proposed F-class mission by the European Space Agency (ESA) in 2019,Comet Interceptor, aims to dynamically intercept a New Solar System Objectsuch as a Dynamically New Comet (DNC). The Spacecraft will be placed in aperiodic (Halo) orbit around the Sun-Earth L2 Lagrangian point, waiting for furtherinstructions about the passage of a comet or an asteroid, which could well bereached within the stipulated mission constraints.A major part of the detection of these bodies will be owed to the Large SynopticSurvey Telescope (Currently under construction in Chile), which hopes to vastlyincrease the ability to discover a possible target using the catalogue of LongPeriod Comets and a set of its orbits. It is suggested that, in a mission length of&lt;5 years, discoveries and warnings are possible so that optimization of thetrajectory and characterisation of the object are done within the set windows.This thesis is aimed at facilitating a transfer to a Potentially Hazardous Asteroid(PHA), a subset of the Near-Earth Objects (NEO), as a secondary choice on theoff-chance that the discovered comet could not be reached from the L2 Librationpoint within the mission constraints.The first section of this thesis deals with the selection of a Potentially HazardousAsteroid for our mission from the larger database of the Near-Earth Objects,based on a measure of impact hazard called the Palermo Scale, while the secondsection of the thesis aims to obtain a suitable Halo orbit around L2 through ananalytical construction method. After a desired orbit is found, the invariantmanifolds around the Halo orbit are constructed and analysed in an attempt toreduce the ΔV, where from the spacecraft can intercept the Potentially Hazardous Asteroid through the trajectory demanding the least energy.

Page generated in 0.0639 seconds