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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.
111

Enhancement of anaerobic biodegradation of petroleum hydrocarbons in contaminated groundwater: laboratory mesocosm studies

Fan, Xiaoying 06 1900 (has links)
This project was a part of a study to evaluate natural attenuation (NA) as a viable remedial option for petroleum hydrocarbon (PHC) contamination at upstream oil- and gas-contaminated sites in Alberta, Canada. Laboratory mesocosms were set up using groundwater and sediment materials collected from two PHC contaminated sites (Site 1 and Site 3) in Alberta to investigate the enhancement of anaerobic PHC biodegradation by amendment of terminal electraon acceptors (TEAs, nitrate or sulfate) and/or nutrients (ammonium and phosphate). Multiple lines of evidence, including the removal of benzene, toluene, ethylbenzene and xylenes (BTEX) and CCME F1 fraction hydrocarbons (C6 to C10), rapid depletion of TEAs, the production of biogenic gases, and detection of the metabolites verified that anaerobic PHC biodegradation was occurring in both laboratory mesocosm studies. Selective biodegradation of PHCs under different reducing conditions was observed. However, there was no conclusive evidence that one reducing condition will universally favor the biodegradation of specific PHCs. In both studies, nutrient amendment showed no enhancement effects. The calculated first-order biodegradation rates in Site 1 mesocosm study ranged from 0.0032 to 0.033 d-1 for benzene, 0 to 0.028 d-1 for ethylbenzene, 0.0021 to 0.036 d-1 for m-, p-xylenes, and 0.0006 to 0.0045 d-1 for F1-BEX (F1 hydrocarbons exclduding BEX) under the tested conditions. The laboratory first-order biodegradation rates of BEX were higher than the estimated field rates, indicating the potential of enhanced anaerobic biodegradation in situ. However, when comparing the TEA amended mesocosms with the unamended controls (in which iron reduction might be the predominant process), the enhancement effects were less apparent and inconsistent. The calculated first-order biodegradation rates in Site 3 mesocosm study ranged from 0 to 0.0009 d-1 for benzene, 0 to 0.011 d-1 for ethylbenzene, 0 to 0.0016 d-1 for m- and p-xylenes, and 0 to 0.15 d-1 for o-xylene. Sulfate amendment significantly stimulated biodegradation of all xylenes and CCME F1 hydrocarbons. However, there was no definitive evidence that nitrate or sulfate amendment could enhance benzene or ethylbenzene biodegradation. / Environmental Engineering
112

Learning Applications based on Semantic Web Technologies

Palmér, Matthias January 2012 (has links)
The interplay between learning and technology is a growing field that is often referred to as Technology Enhanced Learning (TEL). Within this context, learning applications are software components that are useful for learning purposes, such as textbook replacements, information gathering tools, communication and collaboration tools, knowledge modeling tools, rich lab environments that allows experiments etc. When developing learning applications, the choice of technology depends on many factors. For instance, who and how many the intended end-users are, if there are requirements to support in-application collaboration, platform restrictions, the expertise of the developers, requirements to inter-operate with other systems or applications etc. This thesis provides guidance on a how to develop learning applications based on Semantic Web technology. The focus on Semantic Web technology is due to its basic design that allows expression of knowledge at the web scale. It also allows keeping track of who said what, providing subjective expressions in parallel with more authoritative knowledge sources. The intended readers of this thesis include practitioners such as software architects and developers as well as researchers in TEL and other related fields. The empirical part of the this thesis is the experience from the design and development of two learning applications and two supporting frameworks. The first learning application is the web application Confolio/EntryScape which allows users to collect files and online material into personal and shared portfolios. The second learning application is the desktop application Conzilla, which provides a way to create and navigate a landscape of interconnected concepts. Based upon the experience of design and development as well as on more theoretical considerations outlined in this thesis, three major obstacles have been identified: The first obstacle is: lack of non-expert and user friendly solutions for presenting and editing Semantic Web data that is not hard-coded to use a specific vocabulary. The thesis presents five categories of tools that support editing and presentation of RDF. The thesis also discusses a concrete software solution together with a list of the most important features that have crystallized during six major iterations of development. The second obstacle is: lack of solutions that can handle both private and collaborative management of resources together with related Semantic Web data. The thesis presents five requirements for a reusable read/write RDF framework and a concrete software solution that fulfills these requirements. A list of features that have appeared during four major iterations of development is also presented. The third obstacle is: lack of recommendations for how to build learning applications based on Semantic Web technology. The thesis presents seven recommendations in terms of architectures, technologies, frameworks, and type of application to focus on. In addition, as part of the preparatory work to overcome the three obstacles, the thesis also presents a categorization of applications and a derivation of the relations between standards, technologies and application types. / <p>QC 20121105</p>
113

The effects of intrafraction motion on dose heterogeneity

Sidhu, Sabeena 11 April 2005
Intrafraction motion has long been suspected of causing inaccuracies in the resultant dose delivered to the patient. This study attempts to determine how breathing motion affects intact-breast cancer patients for three different treatment techniques commonly used in the clinic: physical wedge compensators (PWs), enhanced dynamic wedges (EDWs), and step-and-shoot intensity modulated radiation therapy (ssIMRT). Some of the effects of intrafraction motion can be eliminated with Gating Therapy. In this study, we have also investigated the efficiency of a Real-Time Position Management Gating System. In order to mimic patient breathing, equipment has been designed to simulate respiratory motion to a first order approximation. A breast phantom has also been designed to represent patient tissue and shape. Film was used as a dosimeter and static dosimetry data were used as a control for comparison. Three velocities of the breast phantom were studied, and Gating Therapy was introduced for each data set. Dose area histograms were calculated for a breast and lung planning target area (PTA), and Normalized Agreement Test (NAT) Indexes were calculated in reference to the static case. Our study shows that the results are dependent on the respiratory rate and the wedge angle and that deviation from the static case is highest if the collimator speed is of the same magnitude as the speed of the target. Generally, there is a large overdosage to the lung PTA and a large underdosage to the breast PTA. However, with the implementation of Gating Therapy, these dose discrepancies are dramatically reduced. The areas of high and low dose within the treatment field observed in this study can be related to other treatment sites affected by respiratory motion. Based on these results, we highly recommend using Gating Therapy for all treatments that may be affected by intrafraction organ motion.
114

Electrical and Optical Characterization of Nanoscale Materials for Electronics

Chang, Chi-Yuan 1980- 14 March 2013 (has links)
Due to a lack of fundamental knowledge about the role of molecular structures in molecular electronic devices, this research is focused on the development of instruments to understand the relation between device design and the electronic properties of electroactive components. The overall goal is to apply this insight to obtain a more efficient and reliable scheme and greater functional control over each component. This work developed a fabrication method for porphyrinoids on graphene-based field effect transistors (FETs), and a chemical sensing platform under an ambient environment by integrating a tip-enhanced Raman spectroscope (TERS), atomic force microscope (AFM), and electronic testing circuit. The study is divided into three aspects. The first is aimed at demonstrating fabrication processes of nanoscale FETs of graphene and porphyrinoid composites based entirely on scanning probe lithography (SPL). A nanoshaving mechanism was used to define patterns on octadecanethiol self-assembled monolayers on gold film evaporated on graphene flakes, followed by metal wet etching and/or oxygen plasma etching to develop patterns on Au films and graphene, respectively. The integrity and optoelectronic properties were examined to validate the processes. The second area of study focused on the development of the chemical sensing platform, enabling chemical changes to be monitored during charge transports under an ambient environment. The localized Raman enhancement was induced by exciting surface plasmon resonance in nanoscale silver enhancing probes made by thermal silver evaporation on sharp AFM tips. As the system was designed along an off-axis illumination/collection scheme, it was demonstrated that it was capable of observing molecular decomposition on opaque and conductive substrates induced by an electric bias. The third line of work proposed a novel TERS system and a probe preparation method. Silver nanowires mounted on AFM tips were used to locally enhance the Raman scattering. The observed Raman enhancement allows quick chemical analysis from a nanoscale region, and thus enables chemical mapping beyond the diffraction limit. Compared with other TERS geometries, the new optical design not only allows analysis on large or opaque samples, but also simplifies the design of the optical components and the alignment processes of the setup.
115

Enhanced sampling and applications in protein folding

Zhang, Cheng 24 July 2013 (has links)
We show that a single-copy tempering method is useful in protein-folding simulations of large scale and high accuracy (explicit solvent, atomic representation, and physics-based potential). The method uses a runtime estimate of the average potential energy from an integral identity to guide a random walk in the continuous temperature space. It was used for folding three mini-proteins, trpzip2 (PDB ID: 1LE1), trp-cage (1L2Y), and villin headpiece (1VII) within atomic accuracy. Further, using a modification of the method with a dihedral bias potential added on the roof temperature, we were able to fold four larger helical proteins: α3D (2A3D), α3W (1LQ7), Fap1-NRα (2KUB) and S-836 (2JUA). We also discuss how to optimally use simulation data through an integral identity. With the help of a general mean force formula, the identity makes better use of data collected in a molecular dynamics simulation and is more accurate and precise than the common histogram approach.
116

Voice-over-IP over Enhanced Uplink / Kapacitet för IP-telefoni i den förbättrade WCDMA-upplänken

Brännström, Nils January 2007 (has links)
The traditional voice service in mobile networks is an important service that mobile users expect high quality from. With the convergence of mobile networks towards an all-IP network, an IP-based speech service becomes important which is referred to as Voice-over-IP (VoIP). The traditional voice service is highly optimized and a VoIP service must therefore fulfil strict quality requirements to provide the same speech service quality. The air interface technology, WCDMA, which is used in third generation communication systems in Europe is constantly developed. An improved concept for the mobile-to-network transmission, called the Enhanced Uplink (EUL) provides for higher uplink capacity for packet data services. It also includes features that may provide a sufficient VoIP service quality in mobile networks, when considering the uplink transmission. The purpose of this thesis is to evaluate the VoIP capacity over EUL and identify crucial aspects of radio resource management in order to increase the capacity. This is done through dynamic system simulations, using a realistic VoIP traffic model. The VoIP capacity is also estimated by a derived theoretical framework.\newline It is shown by simulation results and theoretical estimations, that power control is a vital mechanism in order to increase the capacity. Simulation results indicate that a VoIP over EUL capacity of 65\% of the traditional voice service capacity may be reached. The results also indicate that to improve the capacity for larger cells, the allowed VoIP packet delay must be increased.
117

The effects of intrafraction motion on dose heterogeneity

Sidhu, Sabeena 11 April 2005 (has links)
Intrafraction motion has long been suspected of causing inaccuracies in the resultant dose delivered to the patient. This study attempts to determine how breathing motion affects intact-breast cancer patients for three different treatment techniques commonly used in the clinic: physical wedge compensators (PWs), enhanced dynamic wedges (EDWs), and step-and-shoot intensity modulated radiation therapy (ssIMRT). Some of the effects of intrafraction motion can be eliminated with Gating Therapy. In this study, we have also investigated the efficiency of a Real-Time Position Management Gating System. In order to mimic patient breathing, equipment has been designed to simulate respiratory motion to a first order approximation. A breast phantom has also been designed to represent patient tissue and shape. Film was used as a dosimeter and static dosimetry data were used as a control for comparison. Three velocities of the breast phantom were studied, and Gating Therapy was introduced for each data set. Dose area histograms were calculated for a breast and lung planning target area (PTA), and Normalized Agreement Test (NAT) Indexes were calculated in reference to the static case. Our study shows that the results are dependent on the respiratory rate and the wedge angle and that deviation from the static case is highest if the collimator speed is of the same magnitude as the speed of the target. Generally, there is a large overdosage to the lung PTA and a large underdosage to the breast PTA. However, with the implementation of Gating Therapy, these dose discrepancies are dramatically reduced. The areas of high and low dose within the treatment field observed in this study can be related to other treatment sites affected by respiratory motion. Based on these results, we highly recommend using Gating Therapy for all treatments that may be affected by intrafraction organ motion.
118

Acoustically Enhanced Boiling Heat Transfer

Douglas, Zachary W. 10 July 2007 (has links)
An acoustic field is used to increase the critical heat flux of a copper boiling heat transfer surface. The increase is a result of the acoustic effects on the vapor bubbles. Experiments are being performed to explore the effects of an acoustic field on vapor bubbles in the vicinity of a rigid heated wall. Work includes the construction of a novel heater used to produce a single vapor bubble of a prescribed size and at a prescribed location on a flat boiling surface for better study of an individual vapor bubble s reaction to the acoustic field. Work also includes application of the results from the single bubble heater to a calibrated copper heater used for quantifying the improvements in critical heat flux.
119

Multi-Factor Model and Enhanced Index Fund Performance Analysis in China

Lee, Cheng-ju 27 July 2010 (has links)
In recent years, the economic exchanges between China and Taiwan have become more frequent, hence the Chinese financial market is the main target that we should research and participate in actively. This study refers to Barra Multi-Factor Modeling process to construct a China Multi-Factor Model. We then apply MFM to establish a Shanghai Stock Exchange 50 enhanced index fund. The first objective of this study is to discover significant factors which can explain excess return of securities. The second is to identify significant factors to forecast stock returns and show the alpha effect in an Enhanced Index Fund via a new weight allocating model developed by this study. The result shows that the eight significant factors are Earning Quality, Efficiency, Growth, Momentum, Size, Trading Activity, Value, and Volatility. The performance of Enhanced Index Fund is better than that of the benchmark. Information ratio is 0.86, and turnover rate is 213%, which is acceptable.
120

Enhanced Index Fund Performance Analysis under Multi-Factor Alpha Model

Hsu, Yu-hsiang 28 July 2010 (has links)
The objective of this study is to build a complete process of quantitative stockselection model construction that combines a Multi-Factor Model and informationanalysis. Based on the quantitative stock selection model, we construct anenhanced index fund that uses the Taiwan 50 index as its benchmark. Stock prices change for a multitude of reasons, and these reasons may changeover time. In this study, we use a Multi-Factor Model and information analysis to find the relationship between stock price behavior and a factor‟s condition. Wecan use this relationship as a basis for stock selection. Moreover, the purpose of this study is to construct an enhanced index fund,hence we need to control the tracking error. We use an intuitive portfolio construction method, the original weight retention rate of the benchmark, to control tracking error. In addition, the turnover rate of a portfolio is also a significant problem as it may cause the profit of a portfolio to decreasesignificantly. In this study, we use the smoothing alpha score method to control the turnover rate of our portfolio.

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