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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.
281

Senior executives and the emergence of local responsibilities in large organisations : a complexity approach to potentially better results

Groot, Nol January 2010 (has links)
All executives strive for better results in their organisations. They are always dependent on others to achieve these results and this dependency is particularly evident in large organisations. This thesis is concerned with the ways in which these better results might be achieved and the role senior executives might play in this process. The traditional view is that senior executives design and control the way their organisations function and better results therefore depend upon getting the design and the controls ‘right’. My personal experience, supported by many authors, is that this view is often far from reality. In this thesis I therefore draw on an alternative view of how organisations function, namely, the theory of complex responsive processes, in order to explore how senior executives can be more effective given their very limited ability to design and control their organisations. From a complex responsive processes perspective (Stacey, Griffin and Shaw, 2000; Stacey, 2003a), an organisation is understood, by analogy with the complexity sciences, to be processes of self-organising interaction between agents. The abstract analogy from the complexity sciences is interpreted in the case of human interaction according to the thinking of the American pragmatist G. H. Mead (1934). Mead explains the simultaneous emergence of mind and society in terms of the social act in which one person gestures to another and in doing so calls forth a response from that other in ongoing conversational processes in which patterns of communication (meaning) emerge across the organisational population. Work in organisations is accomplished in these conversational processes. In their conscious, self-conscious and responsive interaction, human agents depend on each other; according to the process sociologist N. Elias (1978), this means that all human relating is simultaneously constraining and enabling. Elias defines power as these enabling constraints between people, so that power is an aspect of all human relating. According to Elias, values, norms and ideology are the basis of power. Human choice and intention influence the shifting of power balances in which conflict, as a normal aspect of human interaction, plays an important role. Power, ideology and identity are then seen as central aspects of organisations. 4 People only interact locally with a small proportion of the total population they are part of, and do so on the basis of their own local organising principles (communication, power and choice) rather than simply obeying centrally set rules. This can be understood as self-organisation. The global patterns of communicative interaction and power relations across the organisation emerge in these local interactions rather than following a specific plan, programme or blueprint. The global patterns are unpredictable and are not under the control of any member of the organisation. Global – that is, company-wide – results are thus not directly determined by global design or control, but emerge in this local interaction. This approach means re-thinking what is involved in leadership and the roles of senior executives. From this perspective, senior executives are paradoxically in control and not in control at the same time (Streatfield, 2001). In this thesis I draw on my own personal experience over the past three years as a senior executive in a large services and transport company to identify the role a senior executive can actively play in potentially achieving better results despite not being fully in control. I emphasise the active contribution of senior executives in many local interactions in which global company-wide results emerge. Through the manner in which they participate in, and inspire, the development of local conversational interaction, senior executives can actively encourage front-line staff to take local responsibility for contributing to global, company-wide improvement of results. During these local interactions a chain reaction of local responsibilities can emerge that can contribute to the improvement of global company-wide performance. It is the responsibility of senior executives to communicate clearly in the organisation about demands on performance and results by customers and stakeholders in the market, and to encourage the taking of local responsibility for them. From a complexity view, the impact of leaders on the organisation is not less but different, with potentially better results.
282

Automated calculation of one-loop processes within MadGolem

Wigmore, Ioan Tomos January 2013 (has links)
In the current LHC era, a vast number of models for BSM physics are being tested. For predictions accurate enough to match experimental errors, theoretical calculations have to go beyond LO estimates. However, calculating one-loop corrections in BSM models involves many new particles with specific model dependent properties. Therefore, they are done largely by hand, or in partially–automated ways. I present a fully automated tool for the calculation of generic massive one-loop Feynman diagrams with four external particles, implemented as a module within the fully automated MadGolem framework. With this one can compute the NLO–QCD corrections to generic BSM heavy resonance production processes, for example in the context of supersymmetric theories.
283

Unbonded post-tensioned concrete structures in fire

Gales, John Adam Brian January 2013 (has links)
To achieve thinner and longer floor slabs, rapid construction, and tight control of inservice deflections, modern concrete structures increasingly use high-strength, posttensioned prestressing steel as reinforcement. The resulting structures are called posttensioned (PT) concrete. Post-tensioned concrete slabs are widely believed to benefit from ‘inherent fire endurance.’ This belief is based largely on results from a series of standard fire tests performed on simply-supported specimens some five decades ago. Such tests are of debatable credibility; they do not capture the true structural behaviour of real buildings in real fires, nor do they reflect modern PT concrete construction materials or optimization methods. This thesis seeks to develop a more complete understanding of the structural and thermal response of modern prestressing steel and PT concrete slabs, particularly those with unbonded prestressing steel conditions, to high temperature, in an effort to steer current practice and future research towards the development of defensible, performance-based, safe fire designs. An exhaustive literature review of previous experimentation and real case studies of fire exposed PT concrete structures is presented to address whether current code guidance is adequate. Both bonded and unbonded prestressing steel configurations are considered, and research needs are identified. For unbonded prestressing steel in a localised fire, the review shows that the interaction between thermal relaxation and plastic deformation could result in tendon failure and loss of tensile reinforcement to the concrete, earlier than predicted by available design guidance. Since prestressing steel runs continuously in unbonded PT slabs, local damage to prestressing steel will affect the integrity of adjacent bays in a building. In the event that no bonded steel reinforcement is provided (as permitted by some design codes) a PT slab could lose tensile reinforcement across multiple bays; even those remote from fire. Using existing literature and design guidance, preliminary simplified modelling is presented to illustrate the stress-temperature-time interactions for stressed, unbonded prestressing steel under localised heating. This exercise showed that the observed behaviour cannot be rationally described by the existing design guidance. The high temperature mechanical properties of modern prestressing steel are subsequently considered in detail, both experimentally and analytically. Tests are presented on prestressing steel specimens under constant axial stress at high temperature using a high resolution digital image correlation (DIC) technique to accurately measure deformations. A novel, accurate analytical model of the stresstemperature- time dependent deformation of prestressing steel is developed and validated for both transient and steady-state conditions. Modern prestressing steel behaviour is then compared to its historical prestressing steel counterparts, showing significant differences at high temperature. Attention then turns to other structural actions of a real PT concrete structure (e.g. thermal bowing, restraint, concrete stiffness loss, continuity, spalling, slab splitting etc.) all of which also play inter-related roles influencing a PT slab’s response in fire. A series of three non-standard structural fire experiments on heavily instrumented, continuous, restrained PT concrete slabs under representative sustained service loads were conducted in an effort to better understand the response of PT concrete structures to localised heating. To the author’s knowledge this is the first time a continuous PT slab which includes axial, vertical and rotational restraint has been studied at high temperature, particularly under localised heating. The structural response of all three tests indicates a complex deflection trend in heating and in cooling which differs considerably from the response of a simply supported slab in a standard fire test. Deflection trends in the continuous slab tests were due to a combination of thermal expansion and plastic damage. The test data will enable future efforts to validate computational models which account for the requisite complexities. Overall, the research presented herein shows that some of the design guidance for modern PT concrete slabs is inadequate and should be updated. The high temperature deformation of prestressing steel under localised heating, as would be expected in a real fire, should be considered, since uniform heating of simplysupported elements is both unrealistic and unconservative with respect to tensile rupture of prestressing steel tendons. The most obvious impact of this finding would be to increase the minimum concrete covers required for unbonded PT construction, and to require adequate amounts of bonded steel reinforcement to allow load shedding to the bonded steel at high temperature in the event that the prestressing steel fails or is severely damaged by fire.
284

Cosmology from large-scale galaxy clustering and galaxy–galaxy lensing with Dark Energy Survey Science Verification data

Kwan, J., Sánchez, C., Clampitt, J., Blazek, J., Crocce, M., Jain, B., Zuntz, J., Amara, A., Becker, M. R., Bernstein, G. M., Bonnett, C., DeRose, J., Dodelson, S., Eifler, T. F., Gaztanaga, E., Giannantonio, T., Gruen, D., Hartley, W. G., Kacprzak, T., Kirk, D., Krause, E., MacCrann, N., Miquel, R., Park, Y., Ross, A. J., Rozo, E., Rykoff, E. S., Sheldon, E., Troxel, M. A., Wechsler, R. H., Abbott, T. M. C., Abdalla, F. B., Allam, S., Benoit-Lévy, A., Brooks, D., Burke, D. L., Rosell, A. Carnero, Carrasco Kind, M., Cunha, C. E., D'Andrea, C. B., da Costa, L. N., Desai, S., Diehl, H. T., Dietrich, J. P., Doel, P., Evrard, A. E., Fernandez, E., Finley, D. A., Flaugher, B., Fosalba, P., Frieman, J., Gerdes, D. W., Gruendl, R. A., Gutierrez, G., Honscheid, K., James, D. J., Jarvis, M., Kuehn, K., Lahav, O., Lima, M., Maia, M. A. G., Marshall, J. L., Martini, P., Melchior, P., Mohr, J. J., Nichol, R. C., Nord, B., Plazas, A. A., Reil, K., Romer, A. K., Roodman, A., Sanchez, E., Scarpine, V., Sevilla-Noarbe, I., Smith, R. C., Soares-Santos, M., Sobreira, F., Suchyta, E., Swanson, M. E. C., Tarle, G., Thomas, D., Vikram, V., Walker, A. R. 01 February 2017 (has links)
We present cosmological constraints from the Dark Energy Survey (DES) using a combined analysis of angular clustering of red galaxies and their cross-correlation with weak gravitational lensing of background galaxies. We use a 139 deg(2) contiguous patch of DES data from the Science Verification (SV) period of observations. Using large-scale measurements, we constrain the matter density of the Universe as Omega(m) = 0.31 +/- 0.09 and the clustering amplitude of the matter power spectrum as sigma(8) = 0.74 +/- 0.13 after marginalizing over seven nuisance parameters and three additional cosmological parameters. This translates into S-8 = sigma(8)(Omega(m)/0.3)(0.16) = 0.74 +/- 0.12 for our fiducial lens redshift bin at 0.35 < z < 0.5, while S-8 = 0.78 +/- 0.09 using two bins over the range 0.2 < z < 0.5. We study the robustness of the results under changes in the data vectors, modelling and systematics treatment, including photometric redshift and shear calibration uncertainties, and find consistency in the derived cosmological parameters. We show that our results are consistent with previous cosmological analyses from DES and other data sets and conclude with a joint analysis of DES angular clustering and galaxy-galaxy lensing with Planck Cosmic Microwave Background data, baryon accoustic oscillations and Supernova Type Ia measurements.
285

SCALE UP! : An exploration of the limitations of the printing screen, the fabric width and the circle as a shape

Nordenståhl, Caisa January 2017 (has links)
SCALE UP! is an exploration in hand-printed surface patterns in relation to scale. The aim is to make hand-printed large-scale surface patterns, by challenging the limitations of the printing screen, the fabric width and the circle as a shape; with the circle as a pattern and structure to visualise it, by colours and bleed-through. The project is based in an interest in working large-scale, in the area of screen printing. We often see printed full-width fabrics where the repeat fills the whole width. However, a possibility to take it one step further and not be limited by the width of the fabric or the size of the printing screen was seen. Why be satisfied with the size of a full-width pattern and see the printing screen as a frame to keep within? The striving to challenge the size of the printing screen and the fabric width were the basis of the project. The result is one piece ~4,2 x 4,8 m big consisting of six hand-printed cloths.
286

SOUL: the Single conjugated adaptive Optics Upgrade for LBT

Pinna, E., Esposito, S., Hinz, P., Agapito, G., Bonaglia, M., Puglisi, A., Xompero, M., Riccardi, A., Briguglio, R., Arcidiacono, C., Carbonaro, L., Fini, L., Montoya, M., Durney, O. 27 July 2016 (has links)
We present here SOUL: the Single conjugated adaptive Optics Upgrade for LBT. Soul will upgrade the wavefront sensors replacing the existing CCD detector with an EMCCD camera and the rest of the system in order to enable the closed loop operations at a faster cycle rate and with higher number of slopes. Thanks to reduced noise, higher number of pixel and framerate, we expect a gain (for a given SR) around 1.5-2 magnitudes at all wavelengths in the range 7.5 <mR <18. The correction at short wavelength will be greatly improved (SR>70% in I-band and 0.6asec seeing) and the sky coverage will be multiplied by a factor 5 at all galactic latitudes. Upgrading the SCAO systems at all the 4 focal stations, SOUL will provide these benefits in 2017 to the LBTI interferometer and in 2018 to the 2 LUCI NIR spectro-imagers. In the same year the SOUL correction will be exploited also by the new generation of LBT instruments: V-SHARK, SHARK-NIR and iLocater.
287

Constraining the mass–richness relationship of redMaPPer clusters with angular clustering

Baxter, Eric J., Rozo, Eduardo, Jain, Bhuvnesh, Rykoff, Eli, Wechsler, Risa H. 21 November 2016 (has links)
The potential of using cluster clustering for calibrating the mass-richness relation of galaxy clusters has been recognized theoretically for over a decade. Here, we demonstrate the feasibility of this technique to achieve high-precision mass calibration using redMaPPer clusters in the Sloan Digital Sky Survey North Galactic Cap. By including cross-correlations between several richness bins in our analysis, we significantly improve the statistical precision of our mass constraints. The amplitude of the mass-richness relation is constrained to 7 per cent statistical precision by our analysis. However, the error budget is systematics dominated, reaching a 19 per cent total error that is dominated by theoretical uncertainty in the bias-mass relation for dark matter haloes. We confirm the result from Miyatake et al. that the clustering amplitude of redMaPPer clusters depends on galaxy concentration as defined therein, and we provide additional evidence that this dependence cannot be sourced by mass dependences: some other effect must account for the observed variation in clustering amplitude with galaxy concentration. Assuming that the observed dependence of redMaPPer clustering on galaxy concentration is a form of assembly bias, we find that such effects introduce a systematic error on the amplitude of the mass-richness relation that is comparable to the error bar from statistical noise. The results presented here demonstrate the power of cluster clustering for mass calibration and cosmology provided the current theoretical systematics can be ameliorated.
288

Large scale manufacturing of WS2 nanomaterials and their application in polymer nanocomposites

Xu, Fang January 2013 (has links)
With size down to nanoscale, nanomaterials exhibit novel properties exceeding or differing significantly from their bulk counterparts. In particular, amongst a wide range of interesting new nanostructures, tungsten based nanomaterials have demonstrated super physical, chemical, electronical and mechanical properties in a diverse range of applications which has been comprehensively reviewed. However, challenges still remain high on the effective processes to scale up the manufacturing of such nanomaterials, with desired shape, size and quality. These tungsten based nanomaterials are thus become the research subject of this project, and the study on continuous manufacturing of specifically inorganic fullerene WS2 (IF-WS2) nanoparticles, and their potential exploration as fillers to polymer matrix to fabricate nanocomposites with improved mechanical properties are the main objectives of this research. After a thorough assessment of the extremely promising potentials of tungsten based nanostructures, and review of the current bottleneck for large quantity production of IF-WS2, a generic experimental methodology and techniques used for the investigations have been described in experimental methodology part. In the following chapters, this thesis demonstrates the following research works: A novel rotary furnace for continuous scaling up manufacturing of IF-WS2 nanoparticles has been designed, constructed, tested and refined in this work. The new furnace consists of several key components: a tube furnace, self-contained rotary system, dynamic seal system, modified new tube with baffle, and a continuous gas-blow feeding system. Test results show that the rotary reactor has improved the lab scale manufacturing of IF-WS2 from sub-gram to several tens of grams per batch without agglomeration, which makes this technique a promising alternative for the replacement of the existing tall fluidised tower processing in industrial level production. As an important precursor for IF-WS2 nanomaterials production, the synthesis of WOx nanoparticles by high temperature thermal decomposition of Ammonium Paratungstate (APT) has been investigated, and the parameters have been optimised (with Ar flow at 6 L/min at 1350°C ) for achieving desired sizes. Further studies on the creation of uniform and ultra-thin WOx nanowires were carried out using solvothermal technique. The solvent concentrations, reaction time and solvent types have been systematically investigated, and the resulting WOx nanowires from tungsten chloride precursor in mixed cyclohexanol and ethanol solvent exhibited a record high specific surface area of 275 m2/g. This is fundamentally significant for their applications in sensor and electro-chromic devices. Reverse patterned growth of WOx nanorods was realised for the first time on an Au-coated W foil by a simple W-water vapour reaction. The resulting nanorods of different diameters, lengths and patterns have been created by tuning the growth parameters. Further nitriding under NH3 atmosphere at elevated temperature, converted the WOx nanorods, as a template, to WOxNy nanorods. The WOxNy nanorods have been found to inherit the patterns on the substrate and kept the size and shape of WOx nanorods. An interesting morphology revolution for the conversion of WOx to WOxNy nanorods was observed, and a mechanism has been proposed accordingly to account for the growth. This result represents a simple, innovative and efficient process for the reverse-patterned growth of new nanomaterials. Further development of the rotary furnace has led to a unique new class of core-shell composite nanoparticles, carbon (C)-coated IF-WS2 hollow nanoparticles, by continuous chemical vapour deposition (CVD) production. The composite nanoparticles exhibited a uniform and adjustable C coating, with little or no agglomeration. Importantly, the thermal stability of the core-shell C-coated IF-WS2 against oxidation in air has been improved by about 70°C, compared to the pristine IF-WS2. This new material could find applications where thermal stability is critical. Exploration of 0-4 wt% IF-WS2 as reinforcement in nylon 12 matrix nanocomposites has been carried out for the first time, using a combination of ultrasonic dispersion and magnetic stirring technique to achieve excellent IF-WS2 dispersion in the matrix. Tensile and bending test results showed moderate improvements of 27% and 28% respectively, with a 2 wt% IF-WS2 addition, but a staggering 185% and 148% improvement in toughness for the addition of 0.25 and 0.5 wt% IF-WS2 samples, against pure nylon 12, suggesting that such composites are promising candidates for structural and ballistic fibre applications.
289

Graph Signal Processing: Structure and Scalability to Massive Data Sets

Deri, Joya A. 01 December 2016 (has links)
Large-scale networks are becoming more prevalent, with applications in healthcare systems, financial networks, social networks, and traffic systems. The detection of normal and abnormal behaviors (signals) in these systems presents a challenging problem. State-of-the-art approaches such as principal component analysis and graph signal processing address this problem using signal projections onto a space determined by an eigendecomposition or singular value decomposition. When a graph is directed, however, applying methods based on the graph Laplacian or singular value decomposition causes information from unidirectional edges to be lost. Here we present a novel formulation and graph signal processing framework that addresses this issue and that is well suited for application to extremely large, directed, sparse networks. In this thesis, we develop and demonstrate a graph Fourier transform for which the spectral components are the Jordan subspaces of the adjacency matrix. In addition to admitting a generalized Parseval’s identity, this transform yields graph equivalence classes that can simplify the computation of the graph Fourier transform over certain networks. Exploration of these equivalence classes provides the intuition for an inexact graph Fourier transform method that dramatically reduces computation time over real-world networks with nontrivial Jordan subspaces. We apply our inexact method to four years of New York City taxi trajectories (61 GB after preprocessing) over the NYC road network (6,400 nodes, 14,000 directed edges). We discuss optimization strategies that reduce the computation time of taxi trajectories from raw data by orders of magnitude: from 3,000 days to less than one day. Our method yields a fine-grained analysis that pinpoints the same locations as the original method while reducing computation time and decreasing energy dispersal among spectral components. This capability to rapidly reduce raw traffic data to meaningful features has important ramifications for city planning and emergency vehicle routing.
290

Detection of the kinematic Sunyaev–Zel'dovich effect with DES Year 1 and SPT

Soergel, B., Flender, S., Story, K. T., Bleem, L., Giannantonio, T., Efstathiou, G., Rykoff, E., Benson, B. A., Crawford, T., Dodelson, S., Habib, S., Heitmann, K., Holder, G., Jain, B., Rozo, E., Saro, A., Weller, J., Abdalla, F. B., Allam, S., Annis, J., Armstrong, R., Benoit-Lévy, A., Bernstein, G. M., Carlstrom, J. E., Carnero Rosell, A., Carrasco Kind, M., Castander, F. J., Chiu, I., Chown, R., Crocce, M., Cunha, C. E., D'Andrea, C. B., da Costa, L. N., de Haan, T., Desai, S., Diehl, H. T., Dietrich, J. P., Doel, P., Estrada, J., Evrard, A. E., Flaugher, B., Fosalba, P., Frieman, J., Gaztanaga, E., Gruen, D., Gruendl, R. A., Holzapfel, W. L., Honscheid, K., James, D. J., Keisler, R., Kuehn, K., Kuropatkin, N., Lahav, O., Lima, M., Marshall, J. L., McDonald, M., Melchior, P., Miller, C. J., Miquel, R., Nord, B., Ogando, R., Omori, Y., Plazas, A. A., Rapetti, D., Reichardt, C. L., Romer, A. K., Roodman, A., Saliwanchik, B. R., Sanchez, E., Schubnell, M., Sevilla-Noarbe, I., Sheldon, E., Smith, R. C., Soares-Santos, M., Sobreira, F., Stark, A., Suchyta, E., Swanson, M. E. C., Tarle, G., Thomas, D., Vieira, J. D., Walker, A. R., Whitehorn, N. 21 September 2016 (has links)
We detect the kinematic Sunyaev-Zel'dovich (kSZ) effect with a statistical significance of 4.2 sigma by combining a cluster catalogue derived from the first year data of the Dark Energy Survey with cosmic microwave background temperature maps from the South Pole Telescope Sunyaev-Zel'dovich Survey. This measurement is performed with a differential statistic that isolates the pairwise kSZ signal, providing the first detection of the large-scale, pairwise motion of clusters using redshifts derived from photometric data. By fitting the pairwise kSZ signal to a theoretical template, we measure the average central optical depth of the cluster sample, (tau) over bar (e) = (3.75 +/- 0.89) x 10(-3). We compare the extracted signal to realistic simulations and find good agreement with respect to the signal to noise, the constraint on (tau) over bar (e), and the corresponding gas fraction. High-precision measurements of the pairwise kSZ signal with future data will be able to place constraints on the baryonic physics of galaxy clusters, and could be used to probe gravity on scales greater than or similar to 100 Mpc.

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