Global ETD Search

281	Phase Field modeling of sigma phase transformation in duplex stainless steels : Using FiPy-Finite Volume PDE solver Bhogireddy, Venkata Sai Pavan Kumar January 2013 (has links) Duplex Stainless Steels (DSS) are used extensively in various industrial applications where the properties of both austenite and ferrite steels are required. Higher mechanical strength and superior corrosion resistance are the advantages of DSS. One of the main drawbacks for Duplex steels is precipitation of sigma phase and other intermetallic phases adversely affecting the mechanical strength and the corrosion behavior of the steels. The precipitation of these secondary phases and the associated brittleness can be due to improper heat treatment. The instability in the microstructure of Duplex stainless steels can be studied by understanding the phase transformations especially the ones involving sigma phase. To reduce the time and effort to be put in for experimental work, computational simulations are used to get an initial understanding on the phase transformations. The present thesis work is on the phase transformations involving sigma phase for Fe-Cr system and Fe-Cr-Ni system using theoretical approach in 1D and 2D geometries. A phase field model is implemented for the microstructural evolution in DSS in combination with thermodynamic data collected from the Thermo-Calc software. The Wheeler Boettinger McFadden (WBM) model is used for Gibbs energy interpolation of the system. FiPy- Finite volume PDE solver written in python is used to simulate the phase transformation conditions first in Fe-Cr system for ferrite-austenite and ferrite-sigma phase transformations. It is then repeated for Fe-Cr-Ni ternary system. In the present study a model was developed for deriving Gibbs energy expression for sigma phase based on the common tangent condition. This model can be used to describe composition constrained phases and stoichiometric phases using the WBM model in phase field modeling. Cogswell’s theory of using phase order variable instead of an interpolating polynomial in the expression for Gibbs energy of whole system is also tried. Phase field Duplex Stainless steels Sigma phase Other Materials Engineering Annan materialteknik Metallurgy and Metallic Materials Metallurgi och metalliska material
282	Darstellung und Verwendung von Nucleolipiden zur Lipophilisierung von Nucleinsäuren sowie deren Wechselwirkung und Duplex-Bildung an horizontalen Lipid-Bilayers und Phasengrenzen zur Entwicklung einer neuartigen RNA/DNA-Analytik / Synthesis and Application of Nucleolipids for the Lipophilization of Nucleic Acids and Their Interaction and Duplex Formation at Horizontal Lipid-Bilayers and Phase Boundaries for the Development of a Novel RNA/DNA Analytics Werz, Emma 17 February 2016 (has links) Ziel der vorgestellten Arbeit war die Synthese von Nucleolipiden zur Lipophilisierung von Oligonucleotiden sowie deren Untersuchung im Hinblick auf ihre Wechselwirkung und Duplex-Bildung an horizontalen Lipidmembranen und verschiedenen Phasengrenzen zur Entwicklung eines neuartigen Bio-Chips für die RNA/DNA-Analyse. Mit der Synthese N(3)-prenylierter und 2’,3’-O-ketalisierter Pyrimidinbasen Uridin und Methyluridin wurden Nucleolipid-Bausteine dargestellt, die auch als terminale Kopfgruppen eines Oligonucleotid-Dodecamers den lipophilen Charakter dieser Oligonucleotid-Sequenz erhöhten. Für den Einsatz solcher LONs (Lipo-Oligonucleotide) in einer vereinfachten RNA/DNA-Analytik wurde eine Vielzahl von Lipo-Oligonucleotiden mit diversen Nucleolipid-Kopfgruppen synthetisiert und auf ihr Einlagerungsverhalten in künstliche Lipid-Bilayer untersucht. Fluoreszenz-spektroskopische Untersuchungen zeigten, dass alle Lipo-Oligonucleotide in der Lage sind, sich in künstliche Lipid-Bilayer einzulagern. Abhängig von der Struktur, der Länge und der Anzahl der C-Atom-Ketten dieser lipophilen Anker-Bausteine wurden die Geschwindigkeit und die Festigkeit der Verankerung im Lipid-Bilayer beeinflusst. Des Weiteren wurde die Hybridisierung von LONs mit komplementären Oligomeren an Lipidmembranen untersucht. Es konnte gezeigt werden, dass die im Bilayer verankerten Lipo-Oligonucleotide mit komplementären Oligomeren DNA-Duplexe bilden. Die hybridisierte DNA wurde nicht nur über einen kovalent gebundenen Cy5-Fluorophor am Gegenstrang nachgewiesen, sondern auch über den DNA-Interkalator SYBR Green I (SG). Am Beispiel von zwei Lipo-Oligonucleotiden (LON 20 und 23), die sich schnell und fest in der Bilayermembran verankern, konnte eine spontane Akkumulation dieser LONs an CHCl3/H2O sowie H2O/n-Decan Grenzflächen direkt nach der Probenzugabe beobachtet werden. Diese und andere Ergebnisse stützen den Einsatz von Lipo-Oligonucleotiden als Ziel-Oligomere in einem neuartigen RNA/DNA-Nachweisverfahren an Phasengrenzen. Lipid-Bilayer FCS Lipo-Oligonucleotide Fluoreszenz lipophilisierte DNA Akkumulation Phasengrenzen Diffusionskoeffizient Nucleolipide SYBR Green I Lipophilie DNA-Duplex Diffusionszeit DNA-Interkalator Cy5 DNA-Duplex-Bildung DNA duplex formation Alkylierung 2`,3`-O-Ketale Farnesyl LONs lipid-bilayer FCS lipo-oligonucleotides fluorescence lipophilized DNA accumulation phase boundaries diffusion coefficient nucleolipids SYBR Green I lipophilicity DNA duplex diffusion time DNA intercalator Cy5 alkylation 2`,3`-O-ketals farnesyl LONs 35.78 - Lipide 42.12 - Biophysik 35.65 - Nukleinsäuren 35.66 - Terpene, Steroide, Alkaloide ddc:540 ddc:570
283	WEAR AND CORROSION RESISTANT TRIBOLOGICAL SURFACE TREATMENTS FOR TITANIUM ALLOYS: EVALUATION OF COMPLIMENTARY AND SUPPLEMENTARY DUPLEX TREATMENT PROCESSES Strahin, Brandon L. 24 June 2019 (has links) No description available. Mechanical Engineering Materials Science Metallurgy Chemical Engineering Titanium Duplex Surface Treatment Thermochemical PVD Tribology Corrosion Tribocorrosion Critical Load
284	Examination of inclusion size distributions in duplex stainless steel using electrolytic extraction Shoja Chaeikar, Siamak January 2010 (has links) Nowadays due to large demand for clean and defect-free steels, several techniques based on different characteristics of particles are applied to investigate the steel cleanness. Outokumpu Stainless AB in Avesta has performed extensive work in this field by applying several methods, which all of them have specific advantages and limitations. However, it is necessary to find an accurate technique to investigate real properties of inclusions in duplex stainless steels. For routine analytical methods, calibration and parameters adjustment can be followed by help of these investigation results. The aim of present work is to apply automated INCA-Feature method for controlling cleanness of LDX 6112 duplex stainless steels after electrolytic extractions (EE) as a reference method. Three methods of investigations, INCA-Feature on polished samples as two-dimensional and on film-filter as three-dimensional and EE as three-dimensional analyses, were compared. The results of comparison between running INCA-Feature on polished samples and film filters show an acceptable agreement which proves the possibility of performing EE on this steel grade and using INCA-Feature for investigating this as a fast method. These methods are compared statistically and quantitative results are reported in details. Inclusion SEM-INCA Electrolytic Extraction Duplex Stainless Steel Three dimensional Two dimensional Other Materials Engineering Annan materialteknik
285	Ultrasonography-based evaluation and simulation of the hemodynamic consequences of arterial stenoses Lamontagne, Brigitte C. January 2002 (has links) Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal. Ultrasonographie duplex Doppler Acrosyndrome vasculaire Ratio de vélocité Vitesse systolique maximale Gradient de pression Sténose Sténoses étagées Simulations In vitro
286	Performance of UE Relaying for 6G Networks Hermoso Díaz, Celia January 2023 (has links) Throughout the evolution of communication networks, users have consistently been demanding additional data and coverage. Future 6G networks seek to enable a seamless cyber-physical world through interconnected and integrated connectivity. Hereafter, to address these challenges and ensure the adaptability of future wireless networks, new technologies emerge. Relaying presents an attractive alternative, as it can be a cost-efficient deployment of highly dense networks, and it can enhance the performance of mobile networks in terms of both coverage and capacity. In addition, to meet the demanding Key Performance Indicators (KPI) of user experience, the relaying can be achieved via a User Equipment (UE) through UE-to-Network relaying as an alternative to conventional small-cell deployment of relay stations. The purpose of this project is to assess the impact of UE-based relaying policies. A comparative analysis is conducted, examining these schemes and a macro-only deployment. The study begins by conducting an analysis of the Third Generation Partnership Project (3GPP) urban macro scenario and then extends to include the real-world deployment scenario in London. Results have validated that UE relaying techniques help improve cell edge capacity and coverage compared to macro-only deployments. User throughput is enhanced up to three times in Downlink (DL) and twelve times in Uplink (UL) in the 3GPP urban macro deployment. While user throughput is improved up to ten times in DL and thirteen times in UL on the London map deployment. / Under utvecklingen av kommunikationsnätverk har användarna konsekvent efterfrågat ytterligare data och täckning. Framtida 6G-nätverk strävar efter att möjliggöra en sömlös cyber-fysisk värld genom sammanlänkad och integrerad anslutning. För att möta dessa utmaningar och säkerställa anpassningsbarheten hos framtida trådlösa nätverk framträder nya teknologier. Reläering utgör ett attraktivt alternativ eftersom det kan vara en kostnadseffektiv implementering av högt täta nätverk och signifikant förbättra prestandan hos mobila nätverk både vad gäller täckning och kapacitet. Dessutom kan reläeringen användas för att möta de utmanande behoven av användarupplevelse genom att användarutrustning (UE) används för reläeringen, vilket utgör ett alternativ till konventionell implementering av småceller för relästationer. Det primära fokuset för detta projekt är att bedöma påverkan av reläeringspolicyn baserad på UE. En jämförande analys genomförs där dessa metoder och enbart makroimplementering undersöks. Inledningsvis utförs studien i en urbant makroscen från Third Generation Partnership Project (3GPP), vilket utgör en grund för att utöka metodologin till en verklig implementeringsscen i London. Resultaten har visat att UE-reläeringstekniker bidrar till att förbättra kapaciteten och täckningen i cellens utkanter jämfört med enbart makroimplementering. Användarnas genomströmning ökar upp till tre gånger i nerlänken (DL) och tolv gånger i upplänken (UL) i 3GPP: s urbana makroimplementering. Samtidigt förbättras användarnas genomströmning upp till tio gånger (DL) och tretton gånger (UL) i Londonkartaimplementationen. Half duplex KPI multi-hop multi-path UE relay Elektroteknik och elektronik
287	Mechanism of Biocorrosion Caused by Biofilms and Its Mitigation Liu, Jialin January 2017 (has links) No description available. Biomedical Engineering Microbiology Biochemistry 2205-Cu duplex stainless steel Pseudomonas aeruginosa Desulfovibrio vulgaris Microbiologically influenced corrosion Biofilm Antimicrobial mechanism
288	Reverse Channel Training in Multiple Antenna Time Division Duplex Systems Bharath, B N January 2013 (has links) (PDF) Multiple-Input Multiple-Output (MIMO) communication using multiple antennas has received significant attention in recent years, both in the academia and industry, as they offer additional spatial dimensions for high-rate and reliable communication, without expending valuable bandwidth. However, exploiting these promised benefits of MIMO systems critically depends on fast and accurate acquisition of Channel State Information (CSI) at the Receiver (CSIR) and the Transmitter (CSIT). In Time Division Duplex (TDD) MIMO systems, where the forward channel and the reverse channel are the same, it is possible to exploit this reciprocity to reduce the overhead involved in acquiring CSI, both in terms of training duration and power. Further, many popular and efficient transmission schemes such as beam forming, spatial multiplexing over dominant channel modes, etc. do not require full CSI at the transmitter. In such cases, it is possible to reduce the Reverse Channel Training (RCT) overhead by only learning the part of the channel that is required for data transmission at the transmitter. In this thesis, we propose and analyze several novel channel-dependent RCT schemes for MIMO systems and analyze their performance in terms of (a) the mean-square error in the channel estimate, (b) lower bounds on the capacity, and (c) the diversity-multiplexing gain tradeoff. We show that the proposed training schemes offer significant performance improvement relative to conventional channel-agnostic RCT schemes. The main take-home messages from this thesis are as follows: • Exploiting CSI while designing the RCT sequence improves the performance. • The training sequence should be designed so as to convey only the part of the CSI required for data transmission by the transmitter. • Power-controlled RCT, when feasible, significantly outperforms fixed power RCT. Wireless Channel Model Mimo Systems - Reverse Channel Tranining Reverse Channel Training Reciprocal Multiple Antenna Systems Reverse Channel Training (RCT) TDD-SIMO Systems Multiple Antenna Systems Communication Engineering
289	A Study of EAF Austenitic and Duplex Stainless Steelmaking Slags Characteristics Mostafaee, Saman January 2010 (has links) <p>The high temperature microstructure of the solid phases within the electric arc furnace (EAF) slag has a large effect on the process features such as foamability of the slag, chromium recovery, consumption of the ferroalloys and the wear rate of the refractory. The knowledge of the microstructural and compositional evolution of the slag phases during the EAF process stages is necessary for a good slag praxis.</p><p>In <strong>supplement 1</strong>, an investigation of the typical characteristics of EAF slags in the production of the AISI 304L stainless steel was carried out. In addition, compositional and microstructural evolution of the slag during the different EAF process stages was also investigated. Computational thermodynamics was also used as a tool to predict the equilibrium phases in the top slag as well as the amount of these phases at the process temperatures. Furthermore, the influence of different parameters (MgO wt%, Cr<sub>2</sub>O<sub>3</sub> wt%, temperature and the top slag basicity) on the amount of the spinel phase in the slag was studied. In <strong>supplement 2</strong>, a novel study to characterize the electric arc furnace (EAF) slags in the production of duplex stainless steel at the process temperatures was performed. The investigation was focused on determining the microstructural and compositional evolution of the EAF slag during and at the end of the refining period.</p><p>Slag samples were collected from 14 heats of AISI 304L steel (2 slag samples per heat) and 7 heats of duplex steel (3 slags sample per heat). Simultaneously with each slag sampling, the temperature of the slag was measured. The selected slag samples were studied both using SEM-EDS and LOM. In some cases (<strong>supplement 2</strong>), X-ray diffraction (XRD) analyses were also performed on fine-powdered samples to confirm the existence of the observed phases.</p><p>It was observed that at the process temperature and at all process stages, the stainless steel EAF slag consists mainly of liquid oxides, magnesiochromite spinel particles and metallic droplets. Under normal operation and at the final stages of the EAF, 304L steelmaking slag contains 2-6 wt% magnesiochromite spinel crystals. It was also found that, within the compositional range of the slag samples, the only critical parameter affecting the amount of solid spinel particles in the slag is the chromium oxide content. Petrographical investigation of the EAF duplex stainless steelmaking showed that, before FeSi-addition, the slag samples contain large amounts of undissolved particles and the apparent viscosity of the slag is higher, relative to the subsequent stages. In this stage, the slag also includes solid stoichiometric calcium chromite. It was also found that, after FeSi-injection into the EAF and during the refining period, the composition and the basicity of the slag in the EAF duplex steelmaking and EAF stainless steelmaking are fairly similar. This indicates that, during the refining period, the basic condition for the utilization of an EAF foaming-slag praxis, in both austenitic and duplex stainless steel cases, is the same. Depending on the slag basicity, the slag may contain perovskite and/or dicalcium silicate too. More specifically, the duplex stainless steel slag samples with a higher basicity than 1.55 found to contain perovskite crystals.</p> EAF Slag Duplex steel 304L stainless steel Characterization Microstructural evolution Spinels Basicity Computational thermodynamics Slag foaming
290	Modeling, analysis, and optimization of multi-tier cellular networks Sakr, Ahmed 02 February 2017 (has links) Multi-tier cellular networks have led to a paradigm shift in the deployment of base stations (BSs) where macrocell BSs are overlaid with smaller and lower power BSs such as microcells, picocells, and femtocells. Stochastic geometry has been proven to be an effective tool to capture such heterogeneity and uncertainties in deployment of cellular BSs. In stochastic geometry, random spatial models are used to model multi-tier cellular networks where the locations of BSs is each tier is assumed to be drawn from a point process with the appropriate spatial density. This thesis proposes stochastic geometry-based approaches to analyze, model, and optimize multi-tier cellular networks under several setups and technologies. First, I propose a novel location-aware cross-tier cooperation scheme that aim at improving the performance of users with low signal-to-interference-plus-noise ratio (SINR). Second, I study the performance of cognitive device-to-device (D2D) communication in multi-channel downlink-uplink cellular network with energy harvesting. For the coexistence between cellular and D2D transmissions, I propose a spectrum access policy for cellular BSs to avoid using D2D channels when possible. Third, I investigate the feasibility of energy harvesting from ambient RF interference in multi-tier uplink cellular networks. For this setup, I capture randomness in the network topology and the battery dynamics. Fourth, I extend multi-tier uplink cellular networks to consider the case when users do not necessarily associate with the nearest BS (i.e., flexible cell association). Finally, I compare between different cell association criteria including coupled and decoupled cell association for uplink and downlink transmissions in multi-tier full-duplex cellular networks. For all network setups, I use stochastic geometry to derive simple and closed-form expressions to evaluate the performance in terms of several metrics, e.g., outage probability, mean rate, transmission probability, success probability, and load per BS. I also highlight main tradeoffs in different networks and provide guidelines to optimize different performance metrics by carefully tuning fundamental network design parameters. / February 2017 Multi-tier cellular networks Stochastic geometry Full-duplex communication Device-to-device communication Energy harvesting Location-aware cooperation Cognitive radio access

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