Dissertations / Theses on the topic 'Source environments'
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Ma, Ling. "Acoustic environments as a source of context information." Thesis, University of East Anglia, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423507.
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Choi, Bumsuk. "Acoustic source localization in 3D complex urban environments." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/27739.
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The detection and localization of important acoustic events in a complex urban environment, such as gunfire and explosions, is critical to providing effective surveillance of military and civilian areas and installations. In a complex environment, obstacles such as terrain or buildings introduce multipath propagations, reflections, and diffractions which make source localization challenging. This dissertation focuses on the problem of source localization in three-dimensional (3D) realistic urban environments. Two different localization techniques are developed to solve this problem: a) Beamforming using a few microphone phased arrays in conjunction with a high fidelity model and b) Fingerprinting using many dispersed microphones in conjunction with a low fidelity model of the environment.
For an effective source localization technique using microphone phased arrays, several candidate beamformers are investigated using 2D and corresponding 3D numerical models. Among them, the most promising beamformers are chosen for further investigation using 3D large models. For realistic validation, localization error of the beamformers is analyzed for different levels of uncorrelated noise in the environment. Multiple-array processing is also considered to improve the overall localization performance. The sensitivity of the beamformers to uncertainties that cannot be easily accounted for (e.g. temperature gradient and unmodeled object) is then investigated. It is observed that evaluation in 3D models is critical to assess correctly the potential of the localization technique. The enhanced minimum variance distortionless response (EMVDR) is identified to be the only beamformer that has super-directivity property (i.e. accurate localization capability) and still robust to uncorrelated noise in the environment. It is
also demonstrated that the detrimental effect of uncertainties in the modeling of the environment can be alleviated by incoherent multiple arrays. For efficient source localization technique using dispersed microphones in the environment, acoustic fingerprinting in conjunction with a diffused-based energy model is developed as an alternative to the beamforming technique. This approach is much simpler requiring only microphones rather than arrays. Moreover, it does not require an accurate modeling of the acoustic environment. The approach is validated using the 3D large models. The relationship between the localization accuracy and the number of dispersed microphones is investigated. The effect of the accuracy of the model is also addressed. The results show a progressive improvement in the source localization capabilities as the number of microphones increases. Moreover, it is shown that the fingerprints do not need to be very accurate for successful localization if enough microphones are dispersed in the environment.Ph. D.
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Dale, Gregory E. "Electron accelerator-driven photoneutron source for clinical environments /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p3091914.
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Yang, Hui. "Methodologies for information source selection under distributed information environments." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060511.123303/index.html.
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Johansson, Anders M. "Acoustic sound source localisation and tracking : in indoor environments /." Karlskrona : Department of Signal Processing, Blekinge Institute of Technology, 2008. http://www.bth.se/fou/Forskinfo.nsf/allfirst2/beeb3e73884ff408c125744f00370a08?OpenDocument.
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Talantzis, Fotios. "Equalization and source separation techniques in acoustic reverberant environments." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428487.
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Johansson, Anders. "Acoustic Sound Source Localisation and Tracking : in Indoor Environments." Doctoral thesis, Blekinge Tekniska Högskola [bth.se], School of Engineering - Dept. of Signal Processing, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00401.
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With advances in micro-electronic complexity and fabrication, sophisticated algorithms for source localisation and tracking can now be deployed in cost sensitive appliances for both consumer and commercial markets. As a result, such algorithms are becoming ubiquitous elements of contemporary communication, robotics and surveillance systems. Two of the main requirements of acoustic localisation and tracking algorithms are robustness to acoustic disturbances (to maximise localisation accuracy), and low computational complexity (to minimise power-dissipation and cost of hardware components). The research presented in this thesis covers both advances in robustness and in computational complexity for acoustic source localisation and tracking algorithms. This thesis also presents advances in modelling of sound propagation in indoor environments; a key to the development and evaluation of acoustic localisation and tracking algorithms. As an advance in the field of tracking, this thesis also presents a new method for tracking human speakers in which the problem of the discontinuous nature of human speech is addressed using a new state-space filter based algorithm which incorporates a voice activity detector. The algorithm is shown to achieve superior tracking performance compared to traditional approaches. Furthermore, the algorithm is implemented in a real-time system using a method which yields a low computational complexity. Additionally, a new method is presented for optimising the parameters for the dynamics model used in a state-space filter. The method features an evolution strategy optimisation algorithm to identify the optimum dynamics’ model parameters. Results show that the algorithm is capable of real-time online identification of optimum parameters for different types of dynamics models without access to ground-truth data. Finally, two new localisation algorithms are developed and compared to older well established methods. In this context an analytic analysis of noise and room reverberation is conducted, considering its influence on the performance of localisation algorithms. The algorithms are implemented in a real-time system and are evaluated with respect to robustness and computational complexity. Results show that the new algorithms outperform their older counterparts, both with regards to computational complexity, and robustness to reverberation and background noise. The field of acoustic modelling is advanced in a new method for predicting the energy decay in impulse responses simulated using the image source method. The new method is applied to the problem of designing synthetic rooms with a defined reverberation time, and is compared to several well established methods for reverberation time prediction. This comparison reveals that the new method is the most accurate.
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O'Leary, Kevin C. "Source apportionment of volatile organic compounds in urban micro-environments." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0015/MQ48454.pdf.
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Hof, Christoph. "Optimization of source and receiver placement in multistatic sonar environments." Thesis, Monterey, California: Naval Postgraduate School, 2015. http://hdl.handle.net/10945/45875.
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Approved for public release; distribution is unlimitedIncluces supplemental materials.
The usage of non-collocated sources and receivers in multistatic sonar networks (MSNs) has emerged as a promising area of opportu-nity in sonar systems. This thesis addresses point coverage sensing problems in MSNs, where a number of points of interest (targets) must be monitored. For detection we assume cookie-cutter sensors and a two-dimensional homogenous environment. Based on cur-rent algorithms and the theory of detection discs, we develop the new preprocessing algorithm LOC-GEN-II to determine possible locations for sources given a set of targets and receivers. The high efficiency of this algorithm is based on the greedy-like approach it is built upon and allows a significant reduction of computing time compared to a recent algorithm from the literature. We also address the problem of optimally placing multiple sources and receivers for a given set of targets. Up to now, this problem was solved with the simplification of setting receivers randomly and placing only sources optimally.We develop LOC-GEN-II further into a two-step process of determining near optimal positions for receivers and sources successively. The procedure is implemented as a faster one-step solution and a slower iterative approach, which leads to better detection results. With this approach we show that the newly developed algorithms allow solution of multiple sensor placement problems in an acceptable time with significantly better detection results compared to the benchmark.
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Cheal, Chris. "Light source spectrum brightness and visual performance in pedestrian environments." Thesis, University of Sheffield, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443864.
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Khan, Muhammad Salman. "Informed algorithms for sound source separation in enclosed reverberant environments." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/13350.
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While humans can separate a sound of interest amidst a cacophony of contending sounds in an echoic environment, machine-based methods lag behind in solving this task. This thesis thus aims at improving performance of audio separation algorithms when they are informed i.e. have access to source location information. These locations are assumed to be known a priori in this work, for example by video processing. Initially, a multi-microphone array based method combined with binary time-frequency masking is proposed. A robust least squares frequency invariant data independent beamformer designed with the location information is utilized to estimate the sources. To further enhance the estimated sources, binary time-frequency masking based post-processing is used but cepstral domain smoothing is required to mitigate musical noise. To tackle the under-determined case and further improve separation performance at higher reverberation times, a two-microphone based method which is inspired by human auditory processing and generates soft time-frequency masks is described. In this approach interaural level difference, interaural phase difference and mixing vectors are probabilistically modeled in the time-frequency domain and the model parameters are learned through the expectation-maximization (EM) algorithm. A direction vector is estimated for each source, using the location information, which is used as the mean parameter of the mixing vector model. Soft time-frequency masks are used to reconstruct the sources. A spatial covariance model is then integrated into the probabilistic model framework that encodes the spatial characteristics of the enclosure and further improves the separation performance in challenging scenarios i.e. when sources are in close proximity and when the level of reverberation is high. Finally, new dereverberation based pre-processing is proposed based on the cascade of three dereverberation stages where each enhances the twomicrophone reverberant mixture. The dereverberation stages are based on amplitude spectral subtraction, where the late reverberation is estimated and suppressed. The combination of such dereverberation based pre-processing and use of soft mask separation yields the best separation performance. All methods are evaluated with real and synthetic mixtures formed for example from speech signals from the TIMIT database and measured room impulse responses.
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Bettadapura, Raghuprasad Shivatejas. "Echo Delay Estimation to Aid Source Localization in Noisy Environments." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/50517.
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Time-delay estimation (TDE) finds application in a variety of problems, be it locating
fractures or steering cameras towards the speaker in a multi-participant conference application. Underwater acoustic OFDM source localization is another important application of TDE. Existing underwater acoustic source localization techniques use a microphone array consisting of three or four sensors in order to effectively locate the source. Analog-to-digital (ADC) converters at these sensors call for a non-nominal investment in terms of circuitry and memory. A relatively inexpensive source localization algorithm is needed that works with the output of a single sensor. Since an inexpensive process for estimating the location of the source is desired, the ADC used at the sensor is capable only of a relatively low sampling rate. For a given delay, a low sampling rate leads to sub-sample interval delays, which the desired algorithm must be able to estimate. Prevailing TDE algorithms make some a priori assumptions about the nature of the received signal, such as Gaussianity, wide-sense stationarity, or periodicity. The desired algorithm must not be restrictive in so far as the nature of the transmitted signal is concerned.
A time-delay estimation algorithm based on the time-frequency ratio of mixtures (TFRM) method is proposed. The experimental set-up consists of two microphones/sensors placed at some distances from the source. The method accepts as input the received signal which consists of the sum of the signal received at the nearer sensor and the signal received at the farther sensor and noise. The TFRM algorithm works in the time-frequency domain and seeks to perform successive source cancellation in the received burst. The key to performing source cancellation is to estimate the ratio in which the sources combine and this ratio is estimated by means of taking a windowed mean of the ratio of the spectrograms of any two pulses in the received burst. The variance of the mean function helps identify single-source regions and regions in which the sources mix.
The performance of the TFRM algorithm is evaluated in the presence of noise and is compared against the Cramer-Rao lower bound. It is found that the variance of the estimates returned by the estimator diverge from the predictions of the Cramer-Rao inequality as the farther sensor is moved farther away. Conversely, the estimator becomes more reliable as the farther sensor is moved closer.
The time-delay estimates obtained from the TFRM algorithm are used for source localization. The problem of finding the source reduces to finding the locus of points such that the difference of its distances to the two sensors equals the time delay. By moving the pair of sensors to a different location, or having a second time delay sensor, an exact location for the source can be determined by finding the point of intersection of the two loci.
The TFRM method does not rely on a priori information about the signal. It is
applicable to OFDM sources as well as sinusoidal and chirp sources.Master of Science
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Mutuku, James. "An open source model for teaching environments incorporating wireless devices." Master's thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/6422.
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Word processed copy.Attempts have been made at bridging the digital divide in schools using desktop PC systems without much success. As a result many computer laboratories sit empty. There are many reasons for these failures. Often there are incompatibilities of software applications for the PC and its operating systems. In other cases non-existent infrastructure such as networking support for the operations. This paper describes a project aimed at achieving a more successful school educational environment by using students' mobile devices, desktop computer and open source applications. The project therefore, looks forward to a time when schools no longer have to purchase computers for their students but rather utilize mobile devices already owned by students. The paper presents results of an evaluation study on the interaction of students' moble devices with course material and teachers using open source applications in a teaching environment. The pilot project was undertaken by Schoolnet in Namibia. The result presented show that although there were constraints on such devices the educational benefits far outweight the physical limitations.
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Harris, Jack D. "Online source separation in reverberant environments exploiting known speaker locations." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/19627.
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This thesis concerns blind source separation techniques using second order statistics and higher order statistics for reverberant environments. A focus of the thesis is algorithmic simplicity with a view to the algorithms being implemented in their online forms. The main challenge of blind source separation applications is to handle reverberant acoustic environments; a further complication is changes in the acoustic environment such as when human speakers physically move. A novel time-domain method which utilises a pair of finite impulse response filters is proposed. The method of principle angles is defined which exploits a singular value decomposition for their design. The pair of filters are implemented within a generalised sidelobe canceller structure, thus the method can be considered as a beamforming method which cancels one source. An adaptive filtering stage is then employed to recover the remaining source, by exploiting the output of the beamforming stage as a noise reference. A common approach to blind source separation is to use methods that use higher order statistics such as independent component analysis. When dealing with realistic convolutive audio and speech mixtures, processing in the frequency domain at each frequency bin is required. As a result this introduces the permutation problem, inherent in independent component analysis, across the frequency bins. Independent vector analysis directly addresses this issue by modeling the dependencies between frequency bins, namely making use of a source vector prior. An alternative source prior for real-time (online) natural gradient independent vector analysis is proposed. A Student's t probability density function is known to be more suited for speech sources, due to its heavier tails, and is incorporated into a real-time version of natural gradient independent vector analysis. The final algorithm is realised as a real-time embedded application on a floating point Texas Instruments digital signal processor platform. Moving sources, along with reverberant environments, cause significant problems in realistic source separation systems as mixing filters become time variant. A method which employs the pair of cancellation filters, is proposed to cancel one source coupled with an online natural gradient independent vector analysis technique to improve average separation performance in the context of step-wise moving sources. This addresses `dips' in performance when sources move. Results show the average convergence time of the performance parameters is improved. Online methods introduced in thesis are tested using impulse responses measured in reverberant environments, demonstrating their robustness and are shown to perform better than established methods in a variety of situations.
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O'Leary, Kevin C. (Kevin Charles) Carleton University Dissertation Engineering Civil and Environmental. "Source apportionment of volatile organic compounds in urban micro-environments." Ottawa, 1999.
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Zhao, Yue. "Independent Component Analysis Enhancements for Source Separation in Immersive Audio Environments." UKnowledge, 2013. http://uknowledge.uky.edu/ece_etds/34.
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In immersive audio environments with distributed microphones, Independent Component Analysis (ICA) can be applied to uncover signals from a mixture of other signals and noise, such as in a cocktail party recording. ICA algorithms have been developed for instantaneous source mixtures and convolutional source mixtures. While ICA for instantaneous mixtures works when no delays exist between the signals in each mixture, distributed microphone recordings typically result various delays of the signals over the recorded channels. The convolutive ICA algorithm should account for delays; however, it requires many parameters to be set and often has stability issues. This thesis introduces the Channel Aligned FastICA (CAICA), which requires knowledge of the source distance to each microphone, but does not require knowledge of noise sources. Furthermore, the CAICA is combined with Time Frequency Masking (TFM), yielding even better SOI extraction even in low SNR environments. Simulations were conducted for ranking experiments tested the performance of three algorithms: Weighted Beamforming (WB), CAICA, CAICA with TFM. The Closest Microphone (CM) recording is used as a reference for all three. Statistical analyses on the results demonstrated superior performance for the CAICA with TFM. The algorithms were applied to experimental recordings to support the conclusions of the simulations. These techniques can be deployed in mobile platforms, used in surveillance for capturing human speech and potentially adapted to biomedical fields.
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Wilson, Kevin W. (Kevin William) 1977. "Estimating uncertainty models for speech source localization in real-world environments." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38227.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (p. 131-140).
This thesis develops improved solutions to the problems of audio source localization and speech source separation in real reverberant environments. For source localization, it develops a new time- and frequency-dependent weighting function for the generalized cross-correlation framework for time delay estimation. This weighting function is derived from the speech spectrogram as the result of a transformation designed to optimally predict localization cue accuracy. By structuring the problem in this way, we take advantage of the nonstationarity of speech in a way that is similar to the psychoacoustics of the precedence effect. For source separation, we use the same weighting function as part of a simple probabilistic generative model of localization cues. We combine this localization cue model with a mixture model of speech log-spectra and use this combined model to do speech source separation. For both source localization and source separation, we show significantly performance improvements over existing techniques on both real and simulated data in a range of acoustic environments.
by Kevin William Wilson.
Ph.D.
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Schofield, Andrew John. "Knowledge and resource sharing in free and open source software community environments." Thesis, University of Salford, 2010. http://usir.salford.ac.uk/26898/.
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This thesis describes a research study which investigated on-line communities based around Free and Open Source Software (FOSS) support and development. Specifically, the study examined how knowledge and resources are shared within these communities. Emphasis was placed on the issues of organisation and governance of these communities, collaboration, and the motivation of the participants involved. The research was carried out from an interpretive philosophical perspective and was therefore exploratory in nature, focusing on the perspectives of FOSS community participants. Following an in-depth literature review on the topics of FOSS and Knowledge Management, a multi-method approach was employed using three data collection techniques; an on-line questionnaire targeting participants in FOSS interest groups and communities, interviews with community participants and observation of two FOSS communities. The results of the research have revealed interesting findings relating to the social, managerial and technological mechanisms which facilitate knowledge transfer and creation in FOSS communities, and the important role that leadership styles, participant motivations, organisational structures and cultures, degrees of formality, relationships between participants and the use of information technology have to play in the success or failure of FOSS projects and communities. The research has shown that extremely strict or relaxed forms of leadership are likely to cause problems in a project and community, that a wide array of motivational factors drive participants, that many and varied forms of organisational structure and cultures exist, often influenced by leadership styles, that levels of formality in a community can have significant effects on knowledge sharing and collaboration, that social interaction acts as a foundation for FOSS activities but has little significance beyond that, and that to a certain extent, disagreements and arguments between participants and even project forking can be beneficial to a FOSS project and community. A generic finding was that FOSS communities vary considerably, based on the factors described above. This research therefore goes some way towards creating a generic model of FOSS communities and projects and specifies a number of 'recipes' for project and/or community success.
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Hummersone, Christopher. "A psychoacoustic engineering approach to machine sound source separation in reverberant environments." Thesis, University of Surrey, 2011. http://epubs.surrey.ac.uk/2923/.
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Reverberation continues to present a major problem for sound source separation algorithms, due to its corruption of many of the acoustical cues on which these algorithms rely. However, humans demonstrate a remarkable robustness to reverberation and many psychophysical and perceptual mechanisms are well documented. This thesis therefore considers the research question; can the reverberation-performance of existing psychoacoustic engineering approaches to machine source separation be improved. The precedence effect is a perceptual mechanism that aids our ability to localise sounds in reverberant environments. Despite this, relatively little work has been done on incorporating the precedence effect into automated sound source separation. Consequently, a study was conducted that compared several computational precedence models and their impact on the performance of a baseline separation algorithm. The algorithm included a precedence model, which was replaced with the other precedence models during the investigation. The models were tested using a novel metric in a range of reverberant rooms and with a range of other mixture parameters. The metric, termed Ideal Binary Mask Ratio, is shown to be robust to the effects of reverberation and facilitates meaningful and direct comparison between algorithms across different acoustic conditions. Large differences between the performances of the models were observed. The results showed that a separation algorithm incorporating a model based on interaural coherence produces the greatest performance gain over the baseline algorithm. The results from the study also indicated that it may be necessary to adapt the precedence model to the acoustic conditions in which the model is utilised. This effect is analogous to the perceptual Clifton effect, which is a dynamic component of the precedence effect that appears to adapt precedence to a given acoustic environment in order to maximise its effectiveness. However, no work has been carried out on adapting a precedence model to the acoustic conditions under test. Specifically, although the necessity for such a component has been suggested in the literature, neither its necessity nor benefit has been formally validated. Consequently, a further study was conducted in which parameters of each of the previously compared precedence models were varied in each room in order to identify if, and to what extent, the separation performance varied with these parameters. The results showed that the reverberation-performance of existing psychoacoustic engineering approaches to machine source separation can be improved and can yield significant gains in separation performance.
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Massoud, Mostafa. "Evaluation of an Adaptive AUTOSAR System in Context of Functional Safety Environments." Master's thesis, Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-230004.
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The rapidly evolving technologies in the automotive industry have been defining new challenges, setting new goals and consenting to more complex systems. This steered the AUTOSAR community toward the independent development of the AUTOSAR Adaptive Platform with the intention of addressing and serving the demands defined by the new technology drivers.
The use of an already existing software based on an open-source development - specifically GNU/Linux - was recognized as a matching candidate fulfilling the requirements defined by AUTOSAR Adaptive Platform as its operating system. However, this raises new challenges in addressing the safety aspect and the suitability of its implementation in safety-critical environments.
As safety standards do not explicitly handle the use of open-source software development, this thesis proposes a tailoring procedure that aims to match the requirements defined by ISO 26262 for a possible qualification of GNU/Linux. And while very little is known about the behavior specification of GNU/Linux to appropriate its use in safety-critical environments, the outlined methodology seeks to verify the specification requirements of GNU/Linux leveraging its claimed compliance to the POSIX standard.
In order to further use GNU/Linux with high pedigree of certainty in safety-critical applications, a software partitioning mechanism is implemented to provide control over the resource consumption of the operating system –specifically computation time and memory usage- between different criticality applications in order to achieve Freedom from Interference. The implementation demonstrates the ability to avoid interference concerning required resources of safety-critical applications.
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Collins, Christopher Michael. "Development of a Virtual Acoustic Showroom for Simulating Listening Environments and Audio Speakers." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/9965.
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Virtual acoustic techniques can be used to create virtual listening environments for multiple purposes. Using multi-speaker reproduction, a physical environment can take on the acoustical appearance of another environment. Implementation of this environment auralization could change the way customers evaluate speakers in a retail store.
The objective of this research is to develop a virtual acoustic showroom using a multi- speaker system. The two main components to the virtual acoustic showroom are simulating living environments using the image source method, and simulating speaker responses using inverse filtering. The image source method is used to simulate realistic living environments by filtering the environment impulse response by frequency-dependant absorption coefficients of typical building materials. Psychoacoustic tests show that listeners can match virtual acoustic cues with appropriate virtual visual cues. Inverse filtering is used to "replace" the frequency response function of one speaker with another, allowing a single set of speakers to represent any number of other speakers. Psychoacoustic tests show that listeners could not distinguish the difference between the original speaker and the reference speaker that was mimicking the original. The two components of this system are shown to be accurate both empirically and psychologically.Master of Science
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Ma, KeYang. "Hydrocarbon source and depositional environments in the central Papual Basin, Papua New Guinea /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18901.pdf.
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Tsay, Jason Tye. "Software Developers Using Signals in Transparent Environments." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/948.
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One of the main challenges that modern software developers face is the coordination of dependent agents such as software projects and other developers. Transparent development environments that make low-level software development activities visible hold much promise for assisting developers in making coordination decisions. However, the wealth of information that transparent environments provide is potentially overwhelming when developers are wading through information from potentially millions of developers and millions of software repositories when making decisions around tasks that require coordination with projects or other developers. Overcoming the risk of overload and better assisting developers in these environments requires a principled understanding of what exactly developers need to know about dependencies to make their decisions. My approach to a principled understanding of how developers use information in transparent environments is to model the process using signaling theory as a theoretical lens. Developers making key coordination decisions often must determine qualities about projects and other developers that are not directly observable. Developers infer these unobservable qualities through interpreting information in their environment as signals and use this judgment about the project or developer to inform their decision. In contrast to current software engineering literature which focuses on technical coordination between modules or within projects such as modularity or task assignment mechanisms, this work aims to understand how developers use signals to information coordination decisions with dependencies such as other projects or developers. Through this understanding of the signaling process, I can create improved signals that more accurately represent desired unobservable qualities. My dissertation work examines the qualities and signals that developers use to inform specific coordination tasks through a series of three empirical studies. The specific key coordination tasks studied are evaluating code contributions, discussing problems around contributions, and evaluating projects. My results suggest that when project managers evaluate code contributions, they prefer social signals over technical signals. When project managers discuss contributions, I found that they attend to political signals regarding influence from stakeholders to prioritize which problems need solutions. I found that developers evaluating projects tend to use signals that are related to how the core team works and the potential utility a project provides. In a fourth study, using signaling theory and findings from the qualities and signals that developers use to evaluate projects, I create and evaluate an improved signal called “supportiveness” for community support in projects. I compare this signal against the current signal that developers use, stars count, and find evidence suggesting that my designed signal is more robust and is a stronger indicator of support. The findings of these studies inform the design of tools and environments that assist developers in coordination tasks through suggestions of what signals to show and potentially improving existing signals. My thesis as a whole also suggests opportunities for exploring useful signals for other coordination tasks or even in different transparent environments.
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Valtierra, Robert Daniel. "Source location of narrow band signals in multipath environments, with application to marine mammals." Thesis, Boston University, 2013. https://hdl.handle.net/2144/11072.
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Thesis (Ph.D.)--Boston UniversityPassive acoustic localization has benefited from many major developments and has become an increasingly important focus point in marine mammal research. Several challenges still remain. This work seeks to address several of these challenges such as tracking the calling depths of baleen whales. In this work, data from an array of widely spaced Marine Acoustic Recording Units (MARUs) was used to achieve three dimensional localization by combining the methods Time Difference of Arrival (TDOA) and Direct-Reflected Time Difference of Anival (DRTD) along with a newly developed autocorrelation technique. TDOA was applied to data for two dimensional (latitude and longitude) localization and depth was resolved using DRTD. Previously, DRTD had been limited to pulsed broadband signals, such as sperm whale or dolphin echolocation, where individual direct and reflected signals are separated in time. Due to the length of typical baleen whale vocalizations, individual multipath signal arrivals can overlap making time differences of arrival difficult to resolve. This problem can be solved using an autocorrelation, which can extract reflection information from overlapping signals. To establish this technique, a derivation was made to model the autocorrelation of a direct signal and its overlapping reflection. The model was exploited to derive performance limits allowing for prediction of the minimum resolvable direct-reflected time difference for a known signal type. The dependence on signal parameters (sweep rate, call duration) was also investigated. The model was then verified using both recorded and simulated data from two analysis cases for North Atlantic right whales (NARWs, Eubalaena glacialis) and humpback whales (Megaptera noveaengliae). The newly developed autocorrelation technique was then combined with DRTD and tested using data from playback transmissions to localize an acoustic transducer at a known depth and location. The combined DRTD-autocorrelation methods enabled calling depth and range estimations of a vocalizing NARW and humpback whale in two separate cases. The DRTD-autocorrelation method was then combined with TDOA to create a three dimensional track of a NARW in the Stellwagen Bank National Marine Sanctuary. Results from these experiments illustrated the potential of the combined methods to successfully resolve baleen calling depths in three dimensions.
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Swartling, Mikael. "Direction of Arrival Estimation and Localization of Multiple Speech Sources in Enclosed Environments." Doctoral thesis, Blekinge Tekniska Högskola, Avdelningen för elektroteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00520.
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Speech communication is gaining in popularity in many different contexts as technology evolves. With the introduction of mobile electronic devices such as cell phones and laptops, and fixed electronic devices such as video and teleconferencing systems, more people are communicating which leads to an increasing demand for new services and better speech quality. Methods to enhance speech recorded by microphones often operate blindly without prior knowledge of the signals. With the addition of multiple microphones to allow for spatial filtering, many blind speech enhancement methods have to operate blindly also in the spatial domain. When attempting to improve the quality of spoken communication it is often necessary to be able to reliably determine the location of the speakers. A dedicated source localization method on top of the speech enhancement methods can assist the speech enhancement method by providing the spatial information about the sources. This thesis addresses the problem of speech-source localization, with a focus on the problem of localization in the presence of multiple concurrent speech sources. The primary work consists of methods to estimate the direction of arrival of multiple concurrent speech sources from an array of sensors and a method to correct the ambiguities when estimating the spatial locations of multiple speech sources from multiple arrays of sensors. The thesis also improves the well-known SRP-based methods with higher-order statistics, and presents an analysis of how the SRP-PHAT performs when the sensor array geometry is not fully calibrated. The thesis is concluded by two envelope-domain-based methods for tonal pattern detection and tonal disturbance detection and cancelation which can be useful to further increase the usability of the proposed localization methods. The main contribution of the thesis is a complete methodology to spatially locate multiple speech sources in enclosed environments. New methods and improvements to the combined solution are presented for the direction-of-arrival estimation, the location estimation and the location ambiguity correction, as well as a sensor array calibration sensitivity analysis.
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Hernandez, Tatiana X. "Rainfall-Runoff Modeling in Humid Shallow Water Table Environments." Scholar Commons, 2001. https://scholarcommons.usf.edu/etd/1537.
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Simulating the processes of rainfall and runoff are at the core of hydrologic modeling. Geomorphologic features, rainfall variability, soil types, and water table depths strongly influence hydrological process in Florida ecosystems. Topographic characteristics of the terrain define the stream paths and landscape. Alteration of these characteristics as a result of urban and/or agricultural developments, for example, can highly influence wetlands and river basin response. There are two predominant landforms in Florida: wetlands, where Variable Saturated Areas form near streams causing saturation excess runoff, and uplands where runoff is mainly generated by infiltration excess. The objective of this work is to analyze the impacts of geomorphologic and hydrologic characteristics on runoff mechanisms in humid environments such as Florida. In general, most research at the hillslope scale use hypothetical values of rainfall, sometimes non-realistic values, and single slope forms to explain the geomorphic and hydrologic process on Variable Saturated Areas. In this thesis, the complexity of hillslope processes on actual Florida topography is assessed by coupling a Digital Elevation Model with a two-dimensional variable saturated-unsaturated flow model called HYDRUS-2D. Actual rainfall records and soil parameters from the Characterization Data for Selected Florida Soils, Soil Survey were used to evaluate hydrologic impacts. A commercial software package, River Tools was used to display and extract topographic information from the Digital Elevation Models.
Results show that when inflitration excess runoff is dominant, infiltration and runoff are very sensitive to time resolution, especially for convective storms. When saturation excess occurs, runoff is not affected by rainfall intensity. However, saturated hydraulic conductivity, depth to the water table, slope and curvature highly influence the extent of Variable Saturated Areas. Results indicate runoff in shallow water table environments is produced mainly by subsurface storm runoff, running below the surface, except in hillslopes with concave curvature and mild slopes. Additionally, concave hillslopes generate more saturation excess runoff than straight and convex hillslopes.
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Geoghegan, Mark, and Robert Schumacher. "PERFORMANCE RESULTS USING DATA QUALITY ENCAPSULATION (DQE) AND BEST SOURCE SELECTION (BSS) IN AERONAUTICAL TELEMETRY ENVIRONMENTS." International Foundation for Telemetering, 2017. http://hdl.handle.net/10150/627011.
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Flight test telemetry environments can be particularly challenging due to RF shadowing, interference, multipath propagation, antenna pattern variations, and large operating ranges. In cases where the link quality is unacceptable, applying multiple receiving assets to a single test article can significantly improve the overall link reliability. The process of combining multiple received streams into a single consolidated stream is called Best Source Selection (BSS). Recent developments in BSS technology include a description of the maximum likelihood detection approach for combining multiple bit sources, and an efficient protocol for providing the real-time data quality metrics necessary for optimal BSS performance. This approach is being standardized and will be included in Appendix 2G of IRIG-106-17. This paper describes the application of this technology and presents performance results obtained during flight testing.
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Mitra, Raktim. "Collaborative learning in Open Source Software (OSS) communities: The dynamics and challenges in networked learning environments." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/43463.
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The proliferation of web based technologies has resulted in new forms of communities and organizations with enormous implications for design of learning and education. This thesis explores learning occurring within open source software (OSS) communities. OSS communities are a dominant form of organizing in software development with implications not only for innovative product development but also for the training of a large number of software developers. The central catalyst of learning within these communities is expert-novice interactions. These interactions between experts and novices or newcomers are critical for the growth and sustenance of a community and therefore it is imperative that experts are able to provide newcomers requisite advice and support as they traverse the community and develop software.
Although prior literature has demonstrated the significance of expert-novice interactions, there are two central issues that have not been examined. First, there is no examination of the role of external events on community interaction, particularly as it relates to experts and novices. Second, the exact nature of expert help, particularly, the quantity of help and whether it helps or hinders newcomer participation has not been studied. This thesis studies these two aspects of expert-novice interaction within OSS communities.
The data for this study comes from two OSS communities. The Java newcomer forum was studied as it provided a useful setting for examining external events given the recent changes in Javaâ s ownership. Furthermore, the forum has a rating system which classifies newcomers and experienced members allowing the analysis of expert-novice interactions. The second set of data comes from the MySQL newcomer forum which has also undergone organizational changes and allows for comparison with data from the Java forum. Data were collected by parsing information from the HTML pages and stored in a relational database.
To analyze the effect of external events, a natural experiment method was used whereby participation levels were studied around significant events that affected the community. To better understand the changes contextually, an extensive study of major news outlets was also undertaken. Findings from the external event study show significant changes in participation patterns, especially among newcomers in response to key external events. The study also revealed that the changes in participation of newcomers were observed even though other internal characteristics (help giving, expert participation) did not change indicating that external events have a strong bearing on community participation.
The effect of expert advice was studied using a logistic regression model to determine how specific participation patterns in discussion threads led to the final response to newcomers. This was supported by social network analysis to visually interpret the participation patterns of experienced members in two different scenarios, one in which the question was answered and the other where it was not. Findings show that higher number of responses from experienced members did not correlate with a response. Therefore, although expert help is essential, non-moderated or unguided help can lead to conflict among experts and inefficient feedback to newcomers.Master of Science
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Parikh, Devangi Nikunj. "Improving the quality of speech in noisy environments." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45889.
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In this thesis, we are interested in processing noisy speech signals that are meant to be heard by humans, and hence we approach the noise-suppression problem from a perceptual perspective. We develop a noise-suppression paradigm that is based on a model of the human auditory system, where we process signals in a way that is natural to the human ear. Under this paradigm, we transform an audio signal in to a perceptual domain, and processes the signal in this perceptual domain. This approach allows us to reduce the background noise and the audible artifacts that are seen in traditional noise-suppression algorithms, while preserving the quality of the processed speech. We develop a single- and dual-microphone algorithm based on this perceptual paradigm, and conduct subjecting tests to show that this approach outperforms traditional noise-suppression techniques. Moreover, we investigate the cause of audible artifacts that are generated as a result of suppressing the noise in noisy signals, and introduce constraints on the noise-suppression gain such that these artifacts are reduced.
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Riley, H. Bryan. "Matched-field source detection and localization in high noise environments a novel reduced-rank signal processing approach." Ohio : Ohio University, 1994. http://www.ohiolink.edu/etd/view.cgi?ohiou1173982711.
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Mahlstedt, Nicolaj [Verfasser], and Brian [Akademischer Betreuer] Horsfield. "Evaluating the late gas potential of source rocks stemming from different sedimentary environments / Nicolaj Mahlstedt. Betreuer: Brian Horsfield." Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2012. http://d-nb.info/102779825X/34.
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Masek, Caroline Humphrey. "Adapting the SCS method for estimating runoff in shallow water table environments." Scholar Commons, 2002. http://purl.fcla.edu/fcla/etd/SFE0000040.
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Jankaew, Kruawun. "Organic geochemistry of the Neogene sediments from the Pattani Basin, Gulf of Thailand, palaeodepositional environments and hydrocarbon source potential." Thesis, University of Aberdeen, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252117.
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The Neogene sediment from the Pattani Basin, Gulf of Thailand, were subjected to detailed organic geochemical study. The results suggest that the Neogene source rocks have potential for hydrocarbon generation (as shown by high TOC content). Sequences 2, 3 and part of Sequence 4 are mature and capable of producing hydrocarbons, while those from Sequence 5 are immature. The top of the oil window estimated from biomarker maturity parameters (i.e. CPI and homohopane ratios) is at approximately 6000 feet. SCI data also support this proposal. The biomarker composition and distributions of the bitumen extracts reflect the abundance of higher plant contributions with varying amount of bacterial input, in oxic to sub-oxic conditions during deposition of the sediments. A strong contribution of terrestrially derived organic matter (higher plants) is indicated by the bimodal distribution of n-alkanes, OEP distribution of the n-alkanes in the range C23-C33, high Pr/Ph ratios, low S%, the occurrence and abundance of several biological markers, including oleanenes, oleanane, bicadinanes, tricyclic terpanes, abnormally high C31 homohopane R epimer, and high C29 steranes. Abundant coals in Sequences 5 and 4 contain higher plant material, interpreted as deposited in deltaic swamp environments. Kerogen typing shows that vitrinite (Type III kerogen) is the dominant organic matter in the samples from the Pattani Basin, suggesting potential to generate gas and condensate. The other organic macerals found include cutinite and spore/pollen (Type II kerogen), amorphous (Type I/II/III kerogen) and inertinite (Type IV). In general, molecular and microscopic examination of the Neogene succession of the Pattani Basin suggests a fluvio-deltaic environment, with peat swamps in Sequence 5 and the upper part of Sequence 4. This interpretation is confirmed by pollen analysis data. The age diagnostic pollen found in a few samples from Sequence 5 suggest the time of deposition as Middle Miocene to Pliocene.
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Aspeslagh, Sofie. "An investigation into the perceptual adaptation to spatialised multi-source acoustic environments in normal-hearing and hearing-impaired listeners." Thesis, University of the West of Scotland, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.739195.
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Sideris, Nikolaos. "Spatial decision support in urban environments using machine learning, 3D geo-visualization and semantic integration of multi-source data." Thesis, Limoges, 2019. http://www.theses.fr/2019LIMO0083/document.
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La quantité et la disponibilité sans cesse croissantes de données urbaines dérivées de sources variées posent de nombreux problèmes, notamment la consolidation, la visualisation et les perspectives d’exploitation maximales des données susmentionnées. Un problème prééminent qui affecte l’urbanisme est le choix du lieu approprié pour accueillir une activité particulière (service social ou commercial commun) ou l’utilisation correcte d’un bâtiment existant ou d’un espace vide. Dans cette thèse, nous proposons une approche pour aborder les défis précédents rencontrés avec les techniques d’apprentissage automatique, le classifieur de forêts aléatoires comme méthode dominante dans un système qui combine et fusionne divers types de données provenant de sources différentes, et les code à l’aide d’un nouveau modèle sémantique. qui peut capturer et utiliser à la fois des informations géométriques de bas niveau et des informations sémantiques de niveau supérieur et les transmet ensuite au classifieur de forêts aléatoires. Les données sont également transmises à d'autres classificateurs et les résultats sont évalués pour confirmer la prévalence de la méthode proposée. Les données extraites proviennent d’une multitude de sources, par exemple: fournisseurs de données ouvertes et organisations publiques s’occupant de planification urbaine. Lors de leur récupération et de leur inspection à différents niveaux (importation, conversion, géospatiale, par exemple), ils sont convertis de manière appropriée pour respecter les règles du modèle sémantique et les spécifications techniques des sous-systèmes correspondants. Des calculs géométriques et géographiques sont effectués et des informations sémantiques sont extraites. Enfin, les informations des étapes précédentes, ainsi que les résultats des techniques d’apprentissage automatique et des méthodes multicritères, sont intégrés au système et visualisés dans un environnement Web frontal capable d’exécuter et de visualiser des requêtes spatiales, permettant ainsi la gestion de trois processus. objets géoréférencés dimensionnels, leur récupération, transformation et visualisation, en tant que système d'aide à la décisionThe constantly increasing amount and availability of urban data derived from varying sources leads to an assortment of challenges that include, among others, the consolidation, visualization, and maximal exploitation prospects of the aforementioned data. A preeminent problem affecting urban planning is the appropriate choice of location to host a particular activity (either commercial or common welfare service) or the correct use of an existing building or empty space. In this thesis we propose an approach to address the preceding challenges availed with machine learning techniques with the random forests classifier as its dominant method in a system that combines, blends and merges various types of data from different sources, encode them using a novel semantic model that can capture and utilize both low-level geometric information and higher level semantic information and subsequently feeds them to the random forests classifier. The data are also forwarded to alternative classifiers and the results are appraised to confirm the prevalence of the proposed method. The data retrieved stem from a multitude of sources, e.g. open data providers and public organizations dealing with urban planning. Upon their retrieval and inspection at various levels (e.g. import, conversion, geospatial) they are appropriately converted to comply with the rules of the semantic model and the technical specifications of the corresponding subsystems. Geometrical and geographical calculations are performed and semantic information is extracted. Finally, the information from individual earlier stages along with the results from the machine learning techniques and the multicriteria methods are integrated into the system and visualized in a front-end web based environment able to execute and visualize spatial queries, allow the management of three-dimensional georeferenced objects, their retrieval, transformation and visualization, as a decision support system
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Mello, Marcio Rocha. "Geochemical and molecular studies of the depositional environments of source rocks and their derived oils from the Brazilian marginal basins." Thesis, University of Bristol, 1988. http://hdl.handle.net/1983/a29755bf-1342-4601-8c5a-23849275f37c.
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A geochemical survey of Brazilian marginal basins using a wide selection of source rocks and oils, ranging from Lower Cretaceous to Tertiary in age, has been undertaken. The aims were to assess the palaeoenvironment of deposition of the source rocks, to correlate reservoired oils with their putative source rocks and to understand the effects of maturity on the composition and absolute concentrations of biological markers. The geochemical analyses included evaluation of organic ca~bon contents, Rock-Eval pyrolysis data, vitrinite reflectance measurements, determination of carbon isotope ratios, elemental and visual kerogen analysis, and molecular studies involving liquid and gas chromatography, qualitative and quantitative biological marker investigations using GC-MS, metastable GC-MS .and GC-MS/MS for saturated and aromatic hydrocarbons, and UV/vis spectrophotometry, probe MS and HPLC for metalloporphyrins. The metastable ion GC-MS data were evaluated using principal component analysis. Integration of the results with geological and paleontological data provides the recognition and differentiation of seven depositional regimes, namely lacustrine freshwater, lacustrine saline water, marine evaporitic, marine carbonate, marine deltaic with carbonate influence, open marine highly anoxic with a predominance of calcareous mUdstone lithology, and open marine anoxic, with predominance of siliciclastic lithology. The analyses of the oils reveal significant differences between groups which enable a correlation with putative source rocks laid down in five of the above depositional regimes: lacustrine freshwater; lacustrine saline water; marine evaporitic: marine carbonate and marine deltaic with carbonate influence. The quantitative approach used to determine the effect of thermal maturity on the composition and concentration of the biological markers shows that care must be taken in their use as maturity indicators, since source input and mineral matrix might play an important role. On the other hand, it also shows that the concentrations decrease considerably between the onset of petroleum generation and its peak. Thus, care must also be exercised when using biological marker concentration in palaeoenvironmental assessment The metalloporphyrins in a selection of organic rich sediments have also been examined. The results suggest that their distributions can be a useful auxiliary tool in the characterisation of depositional environments of petroleum source rocks. Finally, a combined geochemical and micropalaeontological study of Cenomanian to Maastrichtian pelitic sediments from the continental margin extends the occurrence of the recognised Cenomanian-Turonian and santonian "oceanic anoxic events". As an extension, the presence of such events in the Coniacian is reported. In contrast, the Campanian-Maastrichtian appears to be a time interval when deposition under oxygenated conditions produced sediments with low organic carbon contents and poor hydrocarbon source potential. In summary, biological marker characteristics of organicrich sediments can distinguish different types of depositional environments, assessment of from analysis allow oil-source rock correlations, and the the depositional environment of the source rocks only of the oils. Thus, this thesis provides a framework of biological marker characteristics which can be compared with samples from other parts of the world.
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Spaak, Gemma. "Molecular and isotopic perspectives on Australian petroleum systems: Hydrocarbon fluid correlations and source rock depositional environments in the Canning and Browse basins." Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/69412.
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This PhD study provides further insights into the petroleum systems of the Canning and Browse basins, Western Australia. Oil-oil correlations, oil-source correlations and palaeoenvironmental reconstructions of Paleozoic source rock intervals are performed. Non-conventional correlation tools such as quantitative diamondoid analysis and δ13C of individual aromatics were successfully applied for hydrocarbon correlation purposes. This work has implications for the petroleum industry but also provides a further understanding of the evolution of life during the Paleozoic.
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Hanus, Michael D. "The Impact of Source and Message Customization on Reactance: A Model for Customization Reducing Reactance to Persuasive Messages." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461235493.
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Burn, Laurie. "Isotopic and elemental tracers in ice and snow as indicators of source regions of aerosols and changing environmental conditions." Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/152.
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Pioneering studies of lead (Pb) concentrations in polar ice by Clair C. Patterson and co-workers (e.g. Murozumi et al., 1969; Boutron and Patterson, 1983, 1986) revealed important information on climatic changes dating many thousands of years in the past and the effect that humans have had on these pristine environments. Rosman and co-workers (e.g. Rosman et al., 1993, 1994a) extended this research utilising the isotopic composition of Pb preserved in the ice to identify the source regions of both natural and anthropogenic Pb transported to the polar regions, thereby adding significantly to the understanding of atmospheric transport mechanisms and the impact of continental anthropogenic activity on the pristine polar environments. This thesis extends this area of research by investigating seasonal and short-term variability in Pb, Ba and In concentrations and Pb isotopes through the accurate sectioning of decontaminated glacial ice cores at high spatial resolution. This improves our understanding of the processes impacting on the deep ice core records, which, in turn, expands the interpretation and application of these records.A new sample preparation technique, incorporating a mechanised circular saw blade arrangement into the lathe design, first described by Candelone et al. (1994), has been developed to sample glacial ice cores at high spatial resolution with minimal contamination. This technique was extensively tested using artificially made ice cores, prepared from ultra-pure water, to quantify and minimise the Pb, Ba and In contamination associated with the process. The residual contamination in each inner core slice from the procedure amounted to 0.2 ± 0.2 pg Pb with [superscript]206Pb/[superscript]207Pb, [superscript]208Pb/[superscript]207Pb and [superscript]206Pb/[superscript]204Pb ratios of 1.16 ± 0.12, 2.35 ± 0.16 and 15.3 ± 6.7 respectively, 1.5 ± 0.4 pg Ba and 0.6 ± 2.0 fg In. This technique was then utilised to obtain high resolution analyses of Pb, Ba and In concentrations, and Pb isotopes in ice core sections recovered from Law Dome, East Antarctica and from the East Rongbuk Glacier on the northern slope of Mount Everest in the Himalaya.Law Dome, East Antarctic Holocene ice cores provide strong evidence for the transport of anthropogenic Pb from Australia to the Law Dome environment during the late 19th century, with [superscript]206Pb/[superscript]207Pb and [superscript]208Pb/[superscript]207Pb ratios as low as 1.061 ± 0.001 and 2.339 ± 0.002 respectively, in close agreement with the Pb isotopic characteristics of Australian Broken Hill Pb ores. The onset of anthropogenic pollution of the Law Dome environment occurred in spring 1889 AD, associated with the onset of Pb ore smelting activities in Port Pirie, South Australia. Seasonal variability is most clearly seen in anthropogenic Pb and Ba (as a proxy for mineral dust) concentrations where peaks in concentrations generally occur in the autumn and spring periods, with consistently low concentrations during winter. Lead isotopic [superscript]206Pb/[superscript]207Pb ratios are inversely correlated with residual (anthropogenic + crustal) Pb concentrations with the lowest ratios occurring during periods of high Pb concentrations. The observed seasonal variability is associated with the annual cycle in position and strength of the Antarctic Circumpolar Trough, a region of low pressure situated off the coast of Antarctica, which moves closest to the Antarctic coast and increases in strength during the autumn and spring seasons. Concurrently, a strengthening of the Southern Ocean westerlies entrains and transports more atmospheric impurities from continental regions such as Australia. The low Pb concentrations and relatively more radiogenic [superscript]206Pb/[superscript]207Pb ratios that appear in the winter layers are indicators of aerosol inputs into the Law Dome environment from a well mixed Southern Hemisphere atmospheric background.Law Dome deep ice core sections, sampled at short-term resolution, show variability in all measured species over time indicating a general instability in temperature (as indicated by δ18O compositions) and environmental conditions (as indicated by elemental concentrations) prevailing during the periods of time integrated by the ice. Based on Pb isotopic [superscript]206Pb/[superscript]207Pb ratios, which reach values of 1.225 ± 0.004 and 1.230 ± 0.003 in glacial, and last glacial – Holocene transition ice respectively, noticeable volcanic Pb contributions are found to occur in both time periods, reaching as high as ~39% and ~46% respectively. These increases are associated with a decrease in mineral dust concentrations due to relatively warmer climatic conditions prevailing within the times integrated by the ice core sections. A link between temperature and environmental conditions in glacial ice is observed when changes in δ18O compositions (as a proxy for temperature) exceed 0.24‰. In contrast, there is no link between temperature and environmental conditions during the last glacial – Holocene transition period, demonstrating a complicated climatic and environmental state existing at Law Dome at this time that incorporates aspects of both cold and warm climates.The high spatial resolution sectioning of continental glacial ice cores recovered from the East Rongbuk Glacier on the northern slopes of Mount Everest, and dated to the 18th and 20th centuries, has similarly shown variability in all measured species over time. Elemental Pb, Ba and In concentrations are very well correlated in all ice core sections confirming the environment of the East Rongbuk Glacier, within the investigated time periods, to be strongly controlled by the input of mineral dust. Isotopic [superscript]206Pb/[superscript]207Pb ratios in 18th century ice range from 1.18 – 1.21 which are attributed to a natural mineral dust background devoid of any influences of anthropogenic [or volcanic] activity. During 18th century monsoon periods (when mineral dust concentrations are generally low), local Himalayan material plays an important role on crustal inputs into the sampling region, with some inputs of Indian derived material possibly sourced to the Indian Peninsula, and Trans-Himalayan belt/Lhasa block material sourced to locations slightly north of Mount Everest. During non-monsoon periods (when mineral dust concentrations are generally high), it is likely that mineral dust from regions in northern Africa and central Asia are impacting on the high altitude Himalaya, with some possible contributions from the arid regions in north-western India and local Himalayan material.Based on elemental (Pb/Ba) and Pb isotopic ratios, there is no indication ofanthropogenic [or volcanic] Pb contributions in the 20th century East RongbukGlacier ice core samples indicating that, prior to 1952 AD, the high altitude samplingsite was isolated from the effects of anthropogenic Pb pollution. Consequently, inthe 20th century, Pb transported to the East Rongbuk Glacier site is sourced tomineral dust. An increase in elemental concentrations is observed in 20th century ice,indicating increased mineral dust deposition relative to the 18th century.Concurrently, a marked change in the isotopic characteristics of 20th century ice coredata, relative to 18th century ice core data, is observed, with a clear segregation ofmonsoon and non-monsoon data and the transition of 20th century data to lessradiogenic values. This adjustment likely reflects environmental changes that haveoccurred from the 18th to the 20th centuries.
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Yuan, Jia [Verfasser], Ralf [Akademischer Betreuer] Riedel, and Zhaoju [Akademischer Betreuer] Yu. "SiHf(B)CN-based ultra-high temperature ceramic nanocomposites: Single-source precursor synthesis and behavior in hostile environments / Jia Yuan. Betreuer: Ralf Riedel ; Zhaoju Yu." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2015. http://d-nb.info/111191138X/34.
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Nangle, Edward J. "The effect of Trinexapac Ethyl and three Nitrogen sources on creeping bentgrass (Agrostis stolonifera) grown under three light environments." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1204660743.
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Brigatti, Junior Luiz Antonio. "A utilização de tecnologias digitais Open Source: uma contribuição ao estudo comparativo de ambientes virtuais na PUC-SP." Pontifícia Universidade Católica de São Paulo, 2010. https://tede2.pucsp.br/handle/handle/18257.
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Previous issue date: 2010-03-19Methods that allow the observation of users of virtual learning environments acting in the work place tend to become increasingly more necessary when the number of computer users and the inherent complexity of systems grow. Processes of continuous assessment carried out during the life cycle of Virtual Learning Environments (VLEs) seem to be required condition for users to reach good results. This research used information provided by professors to verify their usage process, and compare the use of the open source tools and the difficulties found in the virtual environments Moodle and TelEduc , both in use at PUC-SP. Thus, this dissertation argues that approaches in which VLEs are used by the faculty members of the School of Economics, Administration, Accounting and Actuary (FEA at PUC-SP) represent tools of effective gain in quality
À medida que cresce o número de usuários de computadores e a inerente complexidade dos sistemas, métodos para observar usuários de ambientes de aprendizagem virtuais em seu local de trabalho tendem a ser cada vez mais necessários. Processos de avaliação contínua, a serem executados durante o ciclo de vida dos ambientes virtuais de aprendizagem (AVAs), se apresentam como condição necessária a um bom resultado para seus usuários. Esta pesquisa buscou averiguar com usuários docentes o processo da utilização, além de comparar o uso das ferramentas open source e as dificuldades encontradas nos ambientes virtuais Moodle e Teleduc na PUC-SP. Assim, nessa dissertação argumenta-se que abordagens com a utilização de AVAs pelo corpo docente da Faculdade de Economia, Administração, Contabilidade e Atuária (FEA-PUC-SP), representam uma ferramenta de efetivo ganho de qualidade
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Hursky, Paul. "Using ambient noise and sources of opportunity to estimate environment parameters and improve matched field source detection and localization /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2001. http://wwwlib.umi.com/cr/ucsd/fullcit?p3000404.
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Hernandez, Unpingco Jose. "Environmental source tracking using one sensor /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1997. http://wwwlib.umi.com/cr/ucsd/fullcit?p9821366.
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Lee, Young Chang Kai-Hsiung. "Automated source code measurement environment for software quality." Auburn, Ala., 2007. http://repo.lib.auburn.edu/2007%20Fall%20Dissertations/Lee_Young_28.pdf.
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GUENA, ANA M. de O. "Avaliação ambiental de diferentes formas de geração de energia elétrica." reponame:Repositório Institucional do IPEN, 2007. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11501.
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IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Feshbach, Emma (Emma Elizabeth). "GroBot : an open-source model for controlled environment agriculture." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98965.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 50-51).
The growing demand for food challenges our current farming methods, motivating the search for new paradigms for agricultural production. In this work, the GroBot is presented as an open-source model for the fourth agricultural revolution. This indoor cultivation system was fabricated to provide a replicable supply of produce, using modular parts that are easily to machine, assemble, and manufacture. Off-the shelf, low cost components and publically available designs ensure accessibility for the average person, enabling peer-produced knowledge and community participation. Networked data and software will further support the GroBot system, building off past maker movements like the RepRap 3D printer and Linux operating system. The initial prototypes were optimized, evaluating the materials, structures, manufacturing, and assembly processes. A hardware assembly manual and parts list were created with the goal of mobilizing growers, farmers, and hackers to participate in iterative development and information sharing. Through its technological, biological, and social platform, the GroBot forms the foundation for the future of food at both the consumer and industrial scale.
by Emma Feshbach.
S.B.
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Harrington, Rebecca M. "The effects of faulting environment on the seismic source triggering, source parameter relationships, and energy considerations /." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1610470811&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Pope, Joanna Mary Haas Charles N. "Tracking the sources of fecal contamination in the Wissahickon Creek Watershed using Phenotypic and genotypic analytical methods /." Philadelphia, Pa. : Drexel University, 2009. http://hdl.handle.net/1860/3074.
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Puente, Isabel. "Sources of Coliphage to the Marine Environment." NSUWorks, 1991. http://nsuworks.nova.edu/occ_stuetd/361.
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Coliphages may be an alternative to bacterial indicators of sewage pollution in sea water. However, non-human sources of coliphage to the marine environment have not been investigated. A study was conducted in Southeastern Florida to determine how E. coli C (ATCC 13706) bacteriophages of non-human origin could interfere with the coliphage indicator system in the monitoring of human fecal pollution in sea water. Coliphages were detected, in variable numbers, in 12.5%, 80%, and 33.3% of human, seagull (Larus delawarensis), and pelican (Pelicanus occidentalis carolinensis) fecal samples, respectively, as well as in 100% of raw sewage samples. No coliphage was detected in feces of dolphin (Tursiops truncatus) and sea lion (Zalophus californianus). Single fecal samples of cormorant (Phalacrocorax auritus floridanus) and royal tern (Thalasseus maximus maximus) also contained coliphage. The coliphage content per gram of dry weight of raw sewage was significantly (α = 0.00007) higher than that of all the other fecal samples. Even though coliphage titers in the animal feces are lower than in raw sewage, in restricted geographical areas (i.e. marinas), non-human animal sources may still be important.
Three time series analyses were performed to investigate the inconsistent detection of coliphage in human feces. Coliphage was present in only 3 out of 7 fresh human stool samples. However, coliphages appeared after several days of aging of the samples in a dilution of sterile phosphate buffered water. It is hypothesized that lysogenic bacteria in human feces release coliphage through spontaneous induction and physico-chemical conditions outside the human intestine may trigger this induction.