491 |
FUNCTIONALIZED MEMBRANES FOR ENVIRONMENTAL REMEDIATION AND SELECTIVE SEPARATIONXiao, Li 01 January 2014 (has links)
Membrane process including microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) have provided numerous successful applications ranging from drinking water purification, wastewater treatment, to material recovery. The addition of functional moiety in the membranes pores allows such membranes to be used in challenging areas including tunable separations, toxic metal capture, and catalysis. In this work, polyvinylidene fluoride (PVDF) MF membrane was functionalized with temperature responsive (poly(N-isopropylacrylamide), PNIPAAm) and pH responsive (polyacrylic acid, PAA) polymers. It’s revealed that the permeation of various molecules (water, salt and dextran) through the membrane can be thermally or pH controlled. The introduction of PAA as a polyelectrolyte offers an excellent platform for the immobilization of metal nanoparticles (NPs) applied for degradation of toxic chlorinated organics with significantly increased longevity and stability. The advantage of using temperature and pH responsive polymers/hydrogels also includes the high reactivity and effectiveness in dechlorination.
Further advancement on the PVDF functionalization involved the alkaline treatment to create partially defluorinated membrane (Def-PVDF) with conjugated double bounds allowing for the covalent attachment of different polymers. The PAA-Def-PVDF membrane shows pH responsive behavior on both the hydraulic permeability and solute retention. The sponge-like PVDF (SPVDF) membranes by phase inversion were developed through casting PVDF solution on polyester backing. The SPVDF membrane was demonstrated to have 4 times more surface area than commercial PVDF MF membrane, allowing for enhanced nanoparticles loading for chloro-organics degradation. The advanced functionalization method and process were also validated to be able to be scaled-up through the evaluation of full-scale functionalized membrane provided by Ultura Inc. California, USA.
Nanofiltration (NF) between UF and RO presents selectivity controlled by both steric and electrostatic repulsions, which are widely used to reject charged species, particularly multivalent ions. In this work, selective permeation of CaCl2 and high sucrose retention are obtained through the modification of nanofiltration membranes with lower charge compared to commercial nanofiltration membrane. The membrane module also shows high stability with constant water permeability in a long-term (two months) test. Extended Nernst-Planck equation were further used to evaluate the experimental results and it fits well.
|
492 |
VIABILITY OF A CONTROLLABLE CHAOTIC MICROMIXER THROUGH THE USE OF TITANIUM-NICKEL SHAPE MEMORY ALLOYLilly, David Ryan 01 January 2011 (has links)
Microfluidic devices have found applications in a number of areas, such as medical analysis, chemical synthesis, biological study, and drug delivery. Because of the small channel dimensions used in these systems, most microchannels exhibit laminar flow due to their low Reynold’s number, making mixing of fluids very challenging. Mixing at this size scale is diffusion-limited, so inducing chaotic flow patterns can increase the interface surface area between two fluids, thereby decreasing overall mixing time.
One method to create a chaotic flow within the channel is through the introduction of internal protrusions into the channel. In such an application protrusions that create a rotational flow within the channel are preferred due to their effectiveness in folding the two fluids over one another. The novel mixer outlined in this paper uses a Ti-Ni shape memory alloy for the creation of protrusions that can be turned controlled through material temperature. Controllability of the alloy allows users to turn the chaotic flow created by the protrusions off and on by varying the temperature of the mixer. This ability contributes to the idea of a continuous microfluidic system that can be turned on only when necessary as well as recycle unmixed fluids while turned off.
|
493 |
Explorations for Efficient Reversible Barrel Shifters and Their Mappings in QCA NanocomputingChen, Ke 01 January 2015 (has links)
This thesis is based on promising computing paradigm of reversible logic which generates unique outputs out of the inputs and. Reversible logic circuits maintain one-to-one mapping inside of the inputs and the outputs. Compared to the traditional irreversible computation, reversible logic circuit has the advantage that it successfully avoids the information loss during computations. Also, reversible logic is useful to design ultra-low-power nanocomputing circuits, circuits for quantum computing, and the nanocircuits that are testable in nature. Reversible computing circuits require the ancilla inputs and the garbage outputs. Ancilla input is the constant input in reversible circuits. Garbage output is the output for maintaining the reversibility of the reversible logic but is not any of the primary inputs nor a useful bit. An efficient reversible circuit will have the minimal number of garbage and ancilla bits.
Barrel shifter is one of main computing systems having applications in high speed digital signal processing, oating-point arithmetic, FPGA, and Center Processing Unit (CPU). It can operate the function of shifting or rotation for multiple bits in only one clock cycle. The goal of this thesis is to design barrel shifters based on the reversible computing that are optimized in terms of the number of ancilla and garbage bits. In order to achieve this goal, a new Super Conservative Reversible Logic Gate (SCRL gate) has been used. The SCRL gate has 1 control input depending on the value of which it can swap any two n-1 data inputs. We proved that the SCRL gate is superior to the existing conservative reversible Fredkin gate. This thesis develops 5 design methodologies for reversible barrel shifters using SCRL gates that are primarily optimized with the criteria of the number of ancilla and garbage bits. The five proposed methodologies consist of reversible right rotator, reversible logical right shifter, reversible arithmetic right shifter, reversible universal right shifter and reversible universal bidirectional shifter. The proposed reversible barrel shifter design is compared with the existing works in literature and have shown improvement ranging from 8.5% to 92% by the number of garbage and ancilla bits. The SCRL gate and design methodologies of reversible barrel shifter are mapped in Quantum Dot Cellular Automata (QCA) computing. It is illustrated that the SCRL-based designs of reversible barrel shifters have less QCA cost (cost in terms of number of inverters and majority voters) compared to the Fredkin gate- based designs of reversible barrel shifters.
|
494 |
Optimisation of semiconductor optical amplifiers for optical networksKelly, Anthony Edward January 2000 (has links)
No description available.
|
495 |
Caractérisation des process de fabrication microélectroniques pour l'éco-conception des futures technologiesBaudry, Ingwild 14 October 2013 (has links) (PDF)
L'industrie microélectronique est engagée depuis longtemps dans des mesures visant à réduire ses impacts sur l'environnement, et ce sur toutes les phases du cycle de vie de ses produits. Sur les sites de fabrication, la suite logique à la mise en place de système de traitement des pollutions est l'anticipation de ces dernières. L'éco-conception des technologies microélectroniques, c'est-à-dire l'intégration de paramètres environnementaux dans leur processus de développement, permet de répondre à cet objectif. Notre travail de recherche a pour but de caractériser environnementalement les procédés de fabrication microélectronique afin de proposer des outils et méthodes pour leurs concepteurs. Nous avons donc modélisé une technologie microélectronique, et associé des impacts environnementaux aux flux entrants et sortants. Cela nous a permis de proposer des indicateurs environnementaux destinés à la R&D et adaptés à un site de développement et de production microélectronique.
|
496 |
Electrocinétique tridimensionnelle de particules colloïdales en géométrie microfluidique et application à la manipulation de cellulesHonegger, Thibault 17 November 2011 (has links) (PDF)
Les propriétés électrocinétiques de cellules ou de complexes colloïde-cellule visant leur manipulation individuelle dans une puce microfluidique devrait permettre de proposer de nouveaux types d'application dans le domaine des laboratoires-sur-puce et de la recherche biomédicale. Les travaux présentés dans ce manuscrit visent à créer une nouvelle technologie de puce microfluidique permettant la manipulation électrocinétique tridimensionnelle sans contact de particules colloïdales. Cette technologie innovante associée à la réalisation de particules colloïdales multifonctionnelles (Janus) permet d'étudier et de contrôler les interactions d'un complexe colloïde-cellule. Une technologie originale de puce microfluidique tridimensionnelle transparente présentant des niveaux d'électrodes biplanaires est développée sans couche résiduelle classiquement présente dans les technologies de scellement microfluidique. Parallèlement, de nouveaux types de colloïdes anisotropes (Janus) et multifonctionnels (fluorescents, fonctionnalisés avec des protéines...) sont fabriqués en associant la synthèse colloïdale aux techniques de la microélectronique et à la fonctionnalisation de surface. La compréhension et l'exploitation des forces électrocinétiques créées par un champ électrique alternatif et non-uniforme sur la solution colloïdale confinée dans cette puce permettent de proposer une nouvelle méthode de détermination du facteur de Clausius-Mossotti. Ce facteur est un paramètre intrinsèque à la solution colloïdale qui régit la force diélectrophorétique. La détermination expérimentale de ce facteur, combinée à une analyse théorique pour les solutions colloïdales étudiées, définit les paramètres du champ électrique à appliquer (fréquence, tension) pour localiser, séparer ou manipuler en trois dimensions des particules micrométriques de tout type (particules nu, fonctionnalisées, disymétriques...). Le mélange de ces particules dans des milieux de culture cellulaire contenant des cellules de lignées humaines crée des complexes colloïde-cellule. En fonction du type cellulaire, ces complexes se caractérisent par une cellule ayant internalisé des colloïdes ou une cellule décoré par des colloïdes attachés sur sa membrane. Soumis à des forces électrocinétiques déterminées, ces complexes démontrent des réponses duales des particules et des cellules contrôlables indépendamment. En combinant l'ingénierie des particules colloïdales et la technologie microfluidique de manipulation électrocinétique sans contact, des forces locales peuvent être exercées sur les cellules par l'intermédiaire des particules.
|
497 |
Cobalt thin films produced by conventional and photo-assisted metal-organic chemical vapour depositionChioncel, Mariana F. January 2000 (has links)
No description available.
|
498 |
Fabrication and Characterization of Nanowires and Quantum Dots for Advanced Solar Cell ArchitecturesSadeghimakki, Bahareh January 2012 (has links)
The commercially available solar cells suffer from low conversion efficiency due to the thermalization and transmission losses arising from the mismatch between the band gap of the semiconductor materials and the solar spectrum. Advanced device architectures based on nanomaterial have been proposed and being successfully used to enhance the efficiency of the solar cells. Quantum dots (QDs) and nanowires (NWs) are the nanosclae structures that have been exploited for the development of the third generation solar cell devices and nanowire based solar cells, respectively. The optical and electrical properties of these materials can be tuned by their size and geometry; hence they have great potential for the production of highly efficient solar cell. Application of QDs and NWs with enhanced optoelectronic properties and development of low-cost fabrication processes render a new generation of economic highly efficient PV devices. The most significant contribution of this PhD study is the development of simple and cost effective methods for fabrication of nanowires and quantum dots for advanced solar cell architectures.
In advanced silicon nanowires (SiNWs) array cell, SiNWs have been widely synthesised by the well-known vapor-liquid-solid method. Electron beam lithography and deep reactive ion etching have also been employed for fabrication of SiNWs. Due to the high price and complexity of these methods, simple and cost effective approaches are needed for the fabrication of SiNWs. In another approach, to enhance the cell efficiency, organic dyes and polymers have been widely used as luminescent centers and host mediums in the luminescent down shifting (LDS) layers. However, due to the narrow absorption band of the dyes and degradation of the polymers by moisture and heat, these materials are not promising candidates to use as LDS. Highly efficient luminescent materials and transparent host materials with stable mechanical properties are demanded for luminescent down shifting applications. In this project, simple fabrication processes were developed to produce SiNWs and QDs for application in advanced cell architectures. The SiNWs array were successfully fabricated, characterized and deployed in new cell architectures with radial p-n junction geometry. The luminescence down shifting of layers containing QDs in oxide and glass mediums was verified. The silica coated quantum dots which are suitable for luminescence down shifting, were also fabricated and characterized for deployment in new design architectures.
Silicon nanowires were fabricated using two simplified methods. In the first approach, a maskless reactive ion etching process was developed to form upright ordered arrays of the SiNWs without relying on the complicated nano-scale lithography or masking methods. The fabricated structures were comprehensively characterized. Light trapping and photoluminescence properties of the medium were verified. In the second approach, combination of the nanosphere lithography and etching techniques were utilized for wire formation. This method provides a better control on the wire diameters and geometries in a very simple and cost effective way. The fabricated silicon nanowires were used for formation of the radial p-n junction array cells. The functionality of the new cell structures were confirmed through experimental and simulation results.
Quantum dots are promising candidates as luminescent centers due to their tunable optical properties. Oxide/glass matrices are also preferred as the host medium for QDs because of their robust mechanical properties and their compatibility with standard silicon processing technology. Besides, the oxide layers are transparent mediums with good passivation and anti-reflection coating properties. They can also be used to encapsulate the cell. In this work, ordered arrays of QDs were incorporated in an oxide layer to form a luminescent down shifting layer. This design benefits from the enhanced absorption of a periodic QD structure in a transparent oxide. The down shifting properties of the layer after deployment on a crystalline silicon solar cell were examined.
For this purpose, crystalline silicon solar cells were fabricated to use as test platform for down shifting. In order to examine the down-shifting effect, different approaches for formation of a luminescence down shifting layer were developed. The LDS layer consist of cadmium selenide- zinc sulfide (CdSe/ZnS) quantum dots in oxide and glass layers to act as luminescent centers and transparent host medium, respectively. The structural and optical properties of the fabricated layers were studied. The concept of spectral engineering was proved by the deployment of the layer on the solar cell.
To further benefit from the LDS technique, quantum efficiency of the QDs and optical properties of the layer must be improved. Demand for the high quantum efficiency material with desired geometry leaded us to synthesis quantum dots coated with a layer of grown oxide. As the luminescence quantum efficiency of the QDs is correlated to the surface defects, one advantage of having oxide on the outer shell of the QDs, is to passivate the surface non-radiative recombination centers and produce QDs with high luminescent quantum yield. In addition, nanoparticles with desired size can be obtained only by changing the thickness of the oxide shell. This method also simplifies the fabrication of QD arrays for luminescence down shifting application, since it is easier to form ordered arrays from larger particles. QD superlattices in an oxide medium can be fabricated on a large area by a simple spin-coating or dip coating methods. The photonic crystal properties of the proposed structure can greatly increase the absorption in the QDs layer and enhance the effect of down shifting.
|
499 |
Varactor-Based Tunable Planar Filters and Post-Fabrication Tuning of Microwave FiltersRezazadeh Sereshkeh, Alborz January 2012 (has links)
Post-fabrication tuning of filters is usually realized by adding number of elements for tuning the frequency and/or controlling the couplings between the resonators. The task of these tuning elements is to control resonators center frequency, inter-resonators coupling and input/output couplings. While the most common tool for the post-fabrication tuning is to use tuning screws and rods, it is not usually practical to tune a planar filter with these tools.
This thesis introduces a novel method for global post-fabrication tuning of microwave filters by designing and adding a passive distributed-element circuit in parallel to the detuned filter. The idea, which is demonstrated by experimental results, has several advantages over traditional techniques for filter tuning that use screws. The quality factor of resonator reduces significantly after adding the tuning screws while the proposed method does not affect the Q of resonators.
The most important advantage of the proposed compensator circuit is that it can be employed without knowing details of the detuned filters. Since the compensator circuit will be added in parallel to the detuned filter, it will not affect the elements of filter individually. So whether the filter is planar or cavity, the proposed circuit can be used for the tuning. The experimental results obtained demonstrate the validity of this method.
The dissertation also presents a novel concept for designing a center frequency and bandwidth tunable microstrip filter by using GaAs varactors. The proposed isolated coupling structure which is used in this filter makes the bandwidth tuning possible by reducing the loading effect of coupling elements on the resonators. The center frequency of this filter can be also tuned by using a different set of varactors connected to resonators. A 3-pole filter based on this concept has been designed and simulated. The concept can be expanded to higher order filters.
|
500 |
Reliability Analysis of Nanocrystal Embedded High-k Nonvolatile MemoriesYang, Chia-Han 01 December 2011 (has links)
The evolution of the MOSFET technology has been driven by the aggressive shrinkage of the device size to improve the device performance and to increase the circuit density. Currently, many research demonstrated that the continuous polycrystalline silicon film in the floating-gate dielectric could be replaced with nanocrystal (nc) embedded high-k thin film to minimize the charge loss due to the defective thin tunnel dielectric layer.
This research deals with both the statistical aspect of reliability and electrical aspect of reliability characterization as well. In this study, the Zr-doped HfO2 (ZrHfO) high-k MOS capacitors, which separately contain the nanocrystalline zinc oxide (nc-ZnO), silicon (nc-Si), Indium Tin Oxide (nc-ITO) and ruthenium (nc-Ru) are studied on their memory properties, charge transportation mechanism, ramp-relax test, accelerated life tests, failure rate estimation and thermal effect on the above reliability properties.
C-V hysteresis result show that the amount of charges trapped in nanocrystal embedded films is in the order of nc-ZnO>nc-Ru>nc-Si~nc-ITO, which might probably be influenced by the EOT of each sample. In addition, all the results show that the nc-ZnO embedded ZrHfO non-volatile memory capacitor has the best memory property and reliability. In this study, the optimal burn-in time for this kind of device has been also investigated with nonparametric Bayesian analysis. The results show the optimal burn-in period for nc-ZnO embedded high-k device is 5470s with the maximum one-year mission reliability.
|
Page generated in 0.1083 seconds