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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

Toward the Synthesis of Naphthalene-Bridged Bis-Triazole Bimetallic Complexes

Johnson, Sean M. 28 June 2017 (has links)
Bimetallic complexes are known to have unique electronic properties and are used in a variety of organic transformations as catalysts. The use of naphthalene-bridged bis- triazoles (NBT) for bimetallic complexes is unknown. NBTs have the unique property of being fluorescent stemming from a twisted intramolecular charge transfer. With the non- coplanar geometry and the distance between the 1,2,3-triazole rings, we hypothesized that 1,8-bis(4-phenyl-2H-1,2,3-triazol-2-yl)naphthalene (12) would be a suitable ligand to synthesize a bimetallic complex. The synthesis of 12 was optimized for large scale synthesis and was synthesized on a 78 mmol scale in 15% total yield. Metal complexation trials were conducted on 12 and several insoluble solids were observed.
12

Immobilised growth factors for scalable cell therapy manufacturing platforms

Worrallo, Matthew J. January 2018 (has links)
Regenerative medicine has the potential to establish or restore normal function in defective tissues and organs. The realisation of such therapies is restricted due to costs, lack of scalability and inefficient manufacturing process controls. A major contributor to cost is the use of expensive growth factors supplemented into media at high concentrations. In vivo, growth factors exist in soluble, immobilised and transmembrane forms, expressed in a spatiotemporal fashion within the stem cell niche. In comparison to soluble equivalents, immobilised growth factors exhibit increased potency, distinct functional activities, improved cell phenotypic control and act in synergy with other soluble and immobilised ligands. To date, most research into immobilised growth factors has been restricted to planar cell culture surfaces such as tissue culture plastics which have limited scalability. To address the scalability limitations, a novel growth factor immobilisation technology was developed using magnetic microparticles which can be scaled with respect to surface area to volume ratio in standard stirred tank bioreactors. Three clinically relevant growth factors, SCF, TPO and GM-CSF were immobilised and were shown to remain functionally active where surface concentration could be manipulated in a number of ways. Through a series of experiments, it was demonstrated that immobilised growth factors exhibited ~10-fold increase in potency compared with soluble equivalents and remain stable for up to 192 hours following recycling during multiple media passages. Immobilised growth factors were able to expand more cells over a longer period of time after transient exposure and finally, the immobilisation technique was successfully applied to the expansion of umbilical cord derived haematopoietic stem cells using immobilised SCF. The immobilisation method described here has the potential to significantly reduce media costs in large scale cell manufacturing processes.
13

SCALABLE LOW COMPLEXITY CODER FOR HIGH RESOLUTION AIRBORNE VIDEO

Lalgudi, Hariharan G., Marcellin, Michael W., Bilgin, Ali, Nadar, Mariappan S. 10 1900 (has links)
ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Real-time transmission of airborne images to a ground station is highly desirable in many telemetering applications. Such transmission is often through an error prone, time varying wireless channel, possibly under jamming conditions. Hence, a fast, efficient, scalable, and error resilient image compression scheme is vital to realize the full potential of airborne reconnaisance. JPEG2000, the current international standard for image compression, offers most of these features. However, the computational complexity of JPEG2000 limits its use in some applications. Thus, we present a scalable low complexity coder (SLCC) that possesses many desirable features of JPEG2000, yet having high throughput.
14

Realization and Lateral Stable Workspace Analysis of an Axially Symmetric Scalable Hexapod Robot

Qu, Long 12 September 2013 (has links)
"The maintenance and inspection of societal structures and equipment such as skyscrapers, bridges, and ship hulls are important to maintaining a safe lifestyle. Improper maintanance and delayed inspection can lead to catastrophic failure. In lieu of placing humans in potential harm, mobile robotic machining systems can be used to enable remote repair and maintenance within constrictive, hazardous, and inaccessible environments. Due to their intrinsic high mobility and 6-DOF control, hexapod walking robots are a salient solution to mobile machining. However, the static structure of traditional hexapod robots can be rather limiting when attempting to traverse over irregular terrain or manipulating objects. This research realizes a new scalable hexapod robot and analyzes the lateral stable workspace of the robot under different external loading conditions. The scalable design allows the robot to extend its legs which enhances the workspace and improves stability while manuevering through constrictive and irregular terrain. The design incorporates two additional prismatic joints into the legs of the traditional hexapod robot design providing a compact, rigid, and efficient design. The electronic printed circuit boards were designed and assembled in-house. A distributed control architecture was implemented to off-load low-level leg control to dedicated leg controllers. An analysis on the lateral stable workspace of the scalable hexapod robot under different external loading conditions is presented. A dynamic stable workspace criterion is derived. The stable workspace criterion provides a metric for comparing stable workspaces between hexapod robots with different configurations. Multiple simulations and physical experiments were conducted to demonstrate the advantages of a scalability in hexapod designs."
15

Scalable Fabrication of High Efficiency Hybrid Perovskite Solar Cells by Electrospray

Jiang, Yuanyuan 18 June 2019 (has links)
Perovskite solar cells have attracted much attention both in research and industrial domains. An unprecedented progress in development of hybrid perovskite solar cells (HPSCs) has been seen in past few years. The power conversion efficiencies of HPSCs has been improved from 3.8% to 24.2% in less than a decade, rivaling that of silicon solar cells which currently dominate the solar cell market. Hybrid perovskite materials have exceptional opto-electrical properties and can be processed using cost-effective solution-based methods. In contrast, fabrication of silicon solar cells requires high-vacuum, high-temperature, and energy intensive processes. The combination of excellent opto-electrical properties and cost-effective manufacturing makes hybrid perovskite a winning candidate for solar cells. As power conversion efficiencies of HPSCs improves beyond that of the established solar cell technology and their long-term stability increases, one of the crucial hurdles in the path to commercialization remaining to be adequately addressed is the cost-effective scalable fabrication. Spin-coating is the prevailing method for fabrication of HPSCs in laboratories. However, this technique is limited to small areas and results in excessive material waste. Two types of scalable manufacturing methods have been successfully demonstrated to fabricate HPSCs: (i) meniscus-assisted coating such as doctor-blade coating and slot-die coating; and (ii) dispersed deposition based on the coalescence of individual droplets, such as inkjet printing and spray coating. Electrospray printing belongs to the second category with advantages of high material utilization rate and patterning capability along with the scalability and roll-to-roll compatibility. In Chapter 3 of this dissertation, electrospray printing process is described for manufacturing of HPSCs in ambient conditions below 150 C. All three functional layers were printed using electrospray printing including perovskite layer, electron transport layer, and hole transport layer. Strategies for successful electrospray printing of HPSCs include formulation of the precursor inks with solvents of low vapor pressures, judicial choice of droplet flight time, and tailoring the wetting property of the substrate to suppress coffee ring effects. Implementation of these strategies leads to pin-hole free, low surface roughness, and uniform perovskite layer, hole transport layer and electron transport layer. The power conversion efficiency of the all electrospray printed device reached up to 15.0%, which is among the highest to date for fully printed HPSCs. The most efficient HPSCs rely on gold and organic hole-transport materials (HTMs) for achieving high performance. Gold is also chosen for its high stability. Unfortunately, the high price of gold and high-vacuum along with high-temperature processing requirements for gold film is not suitable for the large-scale fabrication of HPSCs. Carbon is a cheap alternative electrode material which is inert to hybrid perovskite layer. Due to the ambipolar transport property of hybrid perovskite, perovskite itself can act as a hole conductor, and the extra hole transport layer can be left out. Carbon films prepared by doctor-blade coating method have been reported as the top electrode in HPSCs. The efficiencies of these devices suffer from the poor interface between the doctor-blade coated carbon and the underlying perovskite layer. In Chapter 4, electrospray printing was applied for the fabrication of carbon films and by optimizing the working distance during electrospray printing, the interface between carbon and the underlying perovskite layer was greatly improved compared to the doctor-blade coated carbon film. The resulting HPSCs based on the electrospray printed carbon electrode achieved higher efficiency than that based on doctor-blade method and remarkably, this performance is close to that of gold based devices. In Chapter 5, preliminary results are provided on the laser annealing of hybrid perovskite films to further advance their scalable manufacturing. All layers of HPSCs require thermal annealing at temperature over 150 C for about half an hour or longer. The time-consuming conventional thermal annealing complicates the fabrication process and is not suitable for continuous production. High temperature over150 C is also not compatible with flexible substrates such as PET. Laser annealing is a promising method for overcoming these issues. It has several other advantages including compatibility with continuous roll-to-roll printing, minimal influence on non-radiated surrounding area, and rapid processing. Laser annealing can be integrated with the electrospray process to realize the continuous fabrication of hybrid perovskite film. Rapid laser annealing process with optimized power density and scanning pattern is demonstrated here for annealing perovskite films. The resulting hybrid perovskite film is highly-crystalline and pin-hole free, similar to that obtained from conventional thermal annealing. / Doctor of Philosophy / Hybrid perovskite solar cell (HPSC) is a promising low-cost and high efficiency photovoltaic technology. One of the big challenges for it to be commercially competitive is scalable fabrication method. This dissertation focuses on developing electrospray printing technology for HPSCs. This is a scalable method with high material usage rate that naturally lead to large scale fabrication of HPSCs. Electrospray printing parameter space was systematically studied and optimized to synthesize high-quality perovskite films and other functional layers including hole transport layer and electron transport layer. All electrospray printed high-efficiency perovskite solar cell devices were successfully demonstrated under the ambient condition and low temperature. Another achievement of this thesis is the electrospray printing of carbon film to replace the costly gold electrode in perovskite solar cells. Laser annealing technique is demonstrated for HPSCs, which is compatible with continuous fabrication and integrates easily with electrospray printing.
16

Image Compression Using Wavelet Based Scalable Modeling of Residual Image

Lin, Wan-Shan 14 July 2000 (has links)
This thesis is based on the modified JPEG encoding which uses a preprocessing called as Cubic Convolution Spline Interpolation to subsample the original image into lower resolution image, the subsampled image is encoded by JPEG. The modified JPEG can get very high compression ratio, it¡¦s quality is better than the JPEG file which has the same compressing ratio, but it still is not good enough. In this thesis we use the scalable wavelet encoding to encode the residual image, which is the difference between original and compression image. Due to the high compressing ratio and scalablity. We can attach the compressed residual image with modified JPEG compressed image to get the scalable compressed image whose compressing ratio can tun from 125 to 50 and always get better quality than optimal JPEG.
17

Design of a Power Scalable Capacitive MEMS Accelerometer Front End

Tse, Colin 19 March 2013 (has links)
This thesis presents the design, implementation and fabrication for a 0.13μm interface to a capacitive MEMS accelerometer. By varying the number of amplifier slices used in concurrence based on different full scale input ranges, the analog circuitry power scales as the input range scales. Due to the oversampling nature of typical accelerometer front ends, for a full-scale input increase of N times, the analog circuitry power reduces by N2 times. The front end has two signal amplification stages, with the first stage power scaled. The chip is 1.15mmx1.15mm and implemented in a 0.13μm CMOS process. The design was packaged with the MEMS accelerometer chip inside a 44 pin CQFP. Measured results show an output rms noise of 63μVrms in a 100Hz bandwidth. The total analog circuitry power scales very linearly with different full scale ranges. A novel simple offset removal network is also shown and confirmed via measurement results.
18

Design of a Power Scalable Capacitive MEMS Accelerometer Front End

Tse, Colin 19 March 2013 (has links)
This thesis presents the design, implementation and fabrication for a 0.13μm interface to a capacitive MEMS accelerometer. By varying the number of amplifier slices used in concurrence based on different full scale input ranges, the analog circuitry power scales as the input range scales. Due to the oversampling nature of typical accelerometer front ends, for a full-scale input increase of N times, the analog circuitry power reduces by N2 times. The front end has two signal amplification stages, with the first stage power scaled. The chip is 1.15mmx1.15mm and implemented in a 0.13μm CMOS process. The design was packaged with the MEMS accelerometer chip inside a 44 pin CQFP. Measured results show an output rms noise of 63μVrms in a 100Hz bandwidth. The total analog circuitry power scales very linearly with different full scale ranges. A novel simple offset removal network is also shown and confirmed via measurement results.
19

Precision-integrated scalable monitoring

Jain, Navendu 27 April 2015 (has links)
Scalable system monitoring is a fundamental abstraction for large-scale networked systems. The goal of this dissertation is to design and build a scalable monitoring middleware that provides system introspection for large distributed systems and that will facilitate the design, development, and deployment of distributed monitoring applications. This middleware will enable monitoring applications to flexibly control the tradeoff between result precision and communication cost and to improve result accuracy in the face of node failures, network delays, and system reconfigurations. We present PRISM (PRecision-Integrated Scalable Monitoring), a scalable monitoring middleware that provides a global aggregate view of large-scale networked systems and that can serve as a building block for a broad range of distributed monitoring applications by coordinating views of multiple vantage points across the network. To coordinate a global view for system introspection, PRISM faces two key challenges: (1) scalability to large systems and high data volumes and (2) safeguarding accuracy in the face of node and network failures. To address these challenges, we design, implement, and evaluate PRISM, a system that defines precision as a new unified abstraction to enable scalable monitoring. PRISM quantifies (im)precision along a three-dimensional vector: arithmetic imprecision (AI) and temporal imprecision (TI) balance precision against monitoring overhead for scalability while network imprecision (NI) addresses the challenge of providing consistency guarantees despite failures. Our prototype implementation of PRISM addresses the challenge of providing these metrics while scaling to a large number of nodes and attributes by (1) leveraging Distributed Hash Tables (DHTs) to create scalable aggregation trees, (2) self-tuning AI budgets across nodes in a principled, near-optimal manner to shift precision to where it is useful, (3) pipelining TI delays across tree levels to maximize batching of updates, and (4) applying dual-tree prefix aggregation which exploits symmetry in our DHT topology to drastically reduce the cost of the active probing needed to maintain NI. Through extensive simulations and experiments on four large-scale testbeds, we observe that PRISM provides a key substrate for scalable monitoring by (1) reducing monitoring load by up to two orders of magnitude compared to existing approaches, (2) providing a flexible framework to control the tradeoff between accuracy, bandwidth cost, and response latency, (3) characterizing and improving confidence in the accuracy of results in the face of system disruptions, and (4) improving the observed accuracy by up to an order of magnitude despite churn. We have built several monitoring applications on top of PRISM including a distributed heavy hitter detection service, a distributed monitoring service for Internet-scale systems, and a detection service for monitoring distributed-denial-of-service (DDoS) attacks at the source-side in distributed networked systems. Finally, we demonstrate how the unified precision abstraction enables new monitoring applications by presenting experiences from these applications. / text
20

Bio-inspired agent-based programming environment for pervasive platforms / Environnement de Programmation Orienté Agent et Bio-Inspiré pour Plateformes Pervasives

Brousse, Olivier 26 February 2010 (has links)
La tendance marquée de ces dernières années au niveau des systèmes informatiques est à l'Ubiquitous Computing. Ces plateformes pervasives ont des contraintes (environnementales et architecturales) qui leurs sont propre et influence la manière de les programmer. En se basant sur l'étude des réseaux de capteurs une approche orientée agents et bio-inspirée est proposée pour programmer les plateformes pervasives en assurant leur adaptabilité dans un environnement non maitrisé. La question se pose de savoir comment améliorer les performances de ce type de plateforme construites à partir de modules possédant peu de ressources de calcul. L'emploi de coprocesseurs parallèles est envisagé. L'utilisation de matériel spécifique à l'un ou l'autre des modules de la plateforme pose des problèmes de facilité de programmation. Une solution de programmation adaptée est proposée tirant partie de la portabilité de Java et de la flexibilité de l'environnement proposé précédemment. L'ensemble de ces deux contributions qui forme un environnement de programmation pour plateformes pervasives, a été testé sur la plateforme PERPLEXUS. / Ubiquitous Computing is the emerging trend in computing systems. These pervasives platforms have characteristic constraints (environmental and architectural). Such characteristics clearly impact the way pervasive platforms should be programmed. Base on Sensor Network programming experience an agent oriented and bio-inspired approach is proposed as a reliable programming framework for pervasive platforms. Nevertheless, how to improve performance of such platforms made of modules with small computing resources. The use of parallel coprocessors is then considered. Such distributed and locally hardware dependent programming does not ease platform programming. Taking advantage of Java's portability and of the proposed framework flexibility a coprocessor programming solution is proposed. These contributions are basic blocks of a pervasive platform programming environment that has been tested on the PERPLEXUS platform.

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