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Technology-based SMEs and the geography of knowledge sourcing : a systematic review of empirical evidenceKlangboonkrong, Yiarayong 08 1900 (has links)
Knowledge access is crucial for firms, especially those with resource constraints facing the rapid change in technology. This systematic review attempts to provide an understanding on how technology-based small and medium-sized enterprises (SMEs) source external knowledge. With the extant literature pointing to the spatial characteristics as the central theme, I identify four generic conditional dimensions that shape the overall geographical pattern of knowledge sourcing. The industrial knowledge base, the market, the local conditions, and the institutional environment influence from whom and where firms source knowledge. The empirical evidence leads to my contention that the conditional dimensions presented are far from being straightforward. Points of caution that should be incorporated when interpreting general patterns are discussed. The main argument is that further understanding of the geography of knowledge sourcing may start from generic external factors but contextual sensitivity and analytical interpretations are invariably essential. Further research opportunities call for more understanding on a) the relationship between private firms and the institutional environment, b) how an individual firm builds and develops own network, and c) how relational asset and different types of knowledge interact.
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The Impact of Non-thermal Processes in the Intracluster Medium on Cosmological Cluster ObservablesBattaglia, Nicholas Ambrose 05 January 2012 (has links)
In this thesis we describe the generation and analysis of hydrodynamical simulations of galaxy clusters and their intracluster
medium (ICM), using large cosmological boxes to generate large samples, in conjunction with individual cluster computations. The
main focus is the exploration of the non-thermal processes in the ICM and the effect they have on the interpretation of observations used for cosmological constraints. We provide an introduction to the cosmological structure formation framework for our computations and an overview of the numerical simulations and
observations of galaxy clusters. We explore the cluster magnetic field observables through radio relics, extended entities in the ICM characterized by their of diffuse radio emission. We show that statistical quantities such as radio relic luminosity
functions and rotation measure power spectra are sensitive to magnetic field models. The spectral index of the radio relic emission
provides information on structure formation shocks, {\it e.g.}, on their Mach number. We develop a coarse grained stochastic model of active galaxy nucleus (AGN) feedback in clusters and show the impact of such inhomogeneous feedback on the thermal pressure profile. We explore variations in
the pressure profile as a function of cluster mass, redshift, and radius and provide a constrained fitting function for this profile. We measure the degree of the non-thermal pressure in the gas from
internal cluster bulk motions and show it has an impact on the slope and scatter of the Sunyaev-Zel'dovich (SZ) scaling relation. We also find that the gross shape of the ICM, as characterized by scaled moment of inertia tensors, affects the SZ scaling relation. We demonstrate that the shape and the amplitude of the SZ angular power spectrum is sensitive to AGN feedback, and this affects the cosmological parameters determined from high resolution ACT and SPT cosmic microwave background data. We compare analytic, semi-analytic, and simulation-based methods for calculating the SZ power spectrum, and characterize their
differences. All the methods must rely, one way or another, on high resolution large-scale hydrodynamical simulations with varying assumptions for modelling the gas of the sort presented here. We show how our results can be used to interpret the latest ACT and SPT power spectrum results. We provide an outlook for the future, describing follow-up work we are undertaking to further advance the theory of cluster science.
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Progress in globular cluster research : insights from NGC 6397 and Messier 4Davis, Saul 05 1900 (has links)
Globular clusters are extreme stellar populations. They have the highest stellar density, and host both the oldest and most metal-poor stellar populations in the Galaxy. Their densities make them excellent testbeds for stellar dynamics, while the properties of their stars allows us to test our understanding of old and metal-poor stellar evolution. This thesis is comprised of three projects studying the two nearest globular clusters, NGC 6397 and Messier 4. By examining high-quality HST photometry of NGC 6397, we have constrained the binary fraction in both the central regions, and beyond the half-light radius. We find a binary fraction of ~0.05 in the core and ~0.015 in the outskirts. In the context of recent N-body simulations by Hurley et al., we interpret the observed binary fraction in the outer field as the primordial binary fraction. This value is lower than typically assumed, and has implications for cluster dynamics and N-body modeling. We report the discovery that young white dwarfs are dynamically hotter than their progenitors. Using the same photometry as mentioned above, and archival HST photometry of Messier 4, we have found that young white dwarfs have an extended radial distribution, and therefore a higher velocity dispersion, compared with older white dwarfs and their progenitors. This implies the existence of a ``natal kick''. Implications for cluster dynamics and stellar evolution are discussed. Finally, we present the spectra of 23 white dwarfs in Messier 4 obtained with the Keck/LRIS and Gemini/GMOS spectrographs. We find that all white dwarfs are of type DA. Assuming the same DA/DB ratio as is observed in the field, the chance of finding no DBs in our sample due to statistical fluctuations is 0.006. This suggests DB formation is suppressed in the cluster environment. Furthermore, we constrain the mass of these white dwarfs by fitting models to the spectral lines. Our best estimate of the masses of the white dwarfs currently forming in Messier 4 is 0.51+/-0.02 M_sun.This extends the empirical constraint on the initial-final mass relation over the entire range of initial masses that could have formed white dwarfs in a Hubble time.
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Probing the Environmental Dependence of Star Formation in Satellite Galaxies using Orbital KinematicsOman, Kyle Andrew January 2013 (has links)
(Abridged) Physical processes regulating star formation in satellite galaxies represent an area of ongoing research, but the projected nature of observed coordinates makes separating different populations of satellites (with different processes at work) difficult. The present-day phase space coordinates of a satellite galaxy carry information about its orbital history, which can then be compared to its star formation history (SFH). This is expected to reveal both a trigger time and timescale for environmental quenching. Finally, this can be related back to the physical process(es) regulating star formation in high density environments.
We use merger trees from the MultiDark Run 1 N-body simulation to compile a catalogue of satellite orbits in cluster environments. We parameterize the orbital history by the time since crossing within 2.5 virial radii of the cluster centre and use our catalogue to estimate the probability density over a range of this parameter given a set of projected phase space coordinates. We show that different populations of satellite haloes occupy (semi-)distinct regions of (projected) phase space. We generalize this result by producing a probability distribution function (PDF) of possible infall times at every point in projected phase space.
We apply our method to determining the infall time PDFs of a large sample of observed cluster satellite candidates from the Sloan Digital Sky Survey. We use galaxy colour as a proxy for SFH and model the distribution of satellite galaxy colours as two gaussian populations. We derive a Markov chain Monte-Carlo method to obtain the colour distribution as a function of the time since infall into the cluster environment. Our implementation of this method is still being tuned, but we use a second simpler (but much cruder) method to obtain an estimate of the evolution of the colour distribution. Our results are suggestive of a quenching process that begins within perhaps ±1 Gyr of virial radius crossing and which slows after pericentric passage. We stress that results obtained with this second method come with important caveats.
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Galaxy Transformations in the Last 5 Billion YearsLu, Ting January 2010 (has links)
It has become clear that the global star formation rate in the Universe has been decreasing since at least z~1, and blue, star-forming galaxies are transformed into red, passive galaxies through one or more processes. The origin of this decline and transformation remains unclear. The role environment plays in all this is especially uncertain. Despite the observed domination of a passive population in the cores of clusters, in contrast to the more actively star-forming field population, whether or not, and how environment affects the properties of galaxies when they fall into clusters is an unsettled question. In this thesis, we look into these issues by examining both the passive and star-forming galaxies, from the cores out to the infall regions, in a large sample of clusters at 0.15<z<0.36 we detected from the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS).
We find that in the cores of clusters, the red-sequence galaxies are a mixture of two populations, indicated by the inflexion in their luminosity function. There is no strong evolution in the shape of the red-sequence between z~0.4 and z~0.2; however, from z~0.2 to today, there is a rapid increase in the number of faint galaxies on the red-sequence relative to the bright ones, suggesting a rapid quenching of the faint galaxies in cluster cores within the last few billion years.
At z~0.2, we find that the red fraction (star-forming fraction), at all stellar mass explored (9.0<log10(M*/M_solar)<11.5), shows no dependence on the distance from cluster centres, in the range 3<r<7Mpc; but within the inner 3 Mpc, we see a clear increase (decrease) in the red fraction (star-forming fraction). Also, for the lowest stellar mass galaxies, their red fraction has increased by a factor of 2 from z~0.3 to z~0.2 (over 1 Gyr), and yet we do not detect any difference between the star formation properties of the star-forming galaxies in clusters at all radii and that in the field. This suggests that for the low mass galaxies, it is likely that a mechanism that truncates star formation rapidly (within 1 Gyr) is at work. In the outskirts of the clusters, despite the low density contrast with the field, the red fraction is still higher than that in the field, suggesting that those galaxies have had their star formation quenched relative to the field population, supporting the pre-processing scenario.
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The Effect of Linkages on Science and Technology at Historically Black Colleges and UniversitiesBrice, Kathryn T. 22 November 2005 (has links)
Historically Black Colleges and Universities (HBCUs) face the 21st century with questions about change and adaptation to an increasingly science and technology oriented society. They face the challenge of finding a strategy by which they can utilize current resources and energy to maximize their science and technology development. Using a mixed methods research design, this study conducted an analysis of science and technology at HBCUs. The primary objective was to determine what theories (when implemented they are termed strategies) account for the development of science and technology at successful research oriented HBCUs. This was accomplished through a secondary objective to assess productivity outputs at HBCUs using various science and technology indices.
The results and findings can be summarized by stating that the selection of strategy is dependent on the maturity of the HBCUs science and technology program. An HBCU that is seeking to initiate a science and technology program should pursue a strategy of federal or state policy supportive of introductory efforts. HBCUs with established science and technology programs that are seeking growth strategies should look toward collaborations and partnerships for the purposes of forming networks and clusters. The formation of joint ventures, partnerships, and networks will further develop their science and technology programs. Leadership is a sustaining factor that enhances the effectiveness of both policy and linkages.
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The Evolution of Multi-Site Small Cracks under Fatigue LoadingCappelli, Marcus Domenic 04 April 2007 (has links)
This thesis focuses on the growth of cracks which are small in relation to the material microstructure especially the situation of clusters of small cracks grown from smooth surfaces, termed micro-multi-site cracking, as is frequently the case for components in service. A proper understanding of this regime of crack growth will allow for less conservative maintenance schedules as well as the application of more sensitive health monitoring systems which are currently under development.
To address the problem a significant experimental investigation of micro-multi-site cracking was conducted on 7075-T7351 aluminum alloy. Using the resulting data a micro-structurally based transition crack length is defined to determine the point which separates small and long crack growth. This definition is based upon the observed evolution of scatter in the growth rates of growing small cracks. It is shown that this scatter falls with growth until the transition point is reached where it assumes a constant value for the growth of long cracks.
It is then shown that the total population of cracks within the clusters can be considered as bi-modal. One distribution consists of primary cracks which can grow and ultimately cause specimen failure. The second distribution consists of secondary cracks, the growth of which ultimately arrests. Several methods for experimentally separating the two distributions have been developed. The first method relies upon the defined transition point between small and long crack behavior. A second method based upon the second derivative of the crack length versus cycle count data has also been developed. Since the secondary cracks cannot lead to failure their data must be discarded prior to any analysis. It is then shown that failure to do so will lead to erroneous non-conservative predictions of crack growth.
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The New Techniques in Henry Cowell's Piano Solo MusicTeng, Yu-ling 15 July 2010 (has links)
Henry Cowell (1897-1965), American composer in 20th century, is the first who proposed the concept of tone clusters and placed many new techniques in his piano music. Innovative music theories and unique thoughts were displayed in his compositions and critiques. For developing both new visual and audio effects of piano music, Cowell played tone clusters with arms, palms, and fists, and also played strings inside piano to give new gesture and timbre of piano.
This thesis is divided into three parts besides introduction and conclusion. The first part describes the origin and development of new piano techniques in the 20th century. The second part investigates Cowell¡¦s compositional career, compositional methods and thoughts for piano music. The third part analyzes ways of performing tone clusters and strings in Cowell¡¦s solo piano pieces with new techniques. Through analyzing these particular techniques, the compositional methods and uniqueness of Cowell¡¦s piano music could be understood. In the meanwhile, the performers will pay more attention to avoid performing injuries and damaging pianos.
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Living (Rose Bengal Stained) Benthic Foraminifera in Sediments off the Southwest TaiwanChiang, Ai-Ping 24 August 2004 (has links)
The objective for this study was to provide the insight into the link between benthic foraminiferal assemblages and the surrounding environment. Stained sediment samples were collected from the continental shelf and slope off the southwest Taiwan, including the Kao-ping Submarine Canyon. In addition to faunal census, total organic carbon (TOC), carbonate, and coarse fraction of the sediments were also measured. Nevertheless, the downcore record of the excess 210Pb from selected sites offers the constraint for stratigraphy time frame for discussion.
The benthic foraminiferal assemblages were analyzed by statistics. Clusters analysis shows that all species present in this study could be divided into two groupings. One is those distributed in outer shelf and the other is those found in the inner shelf of the southwest Taiwan. Different from previous studies, the spatial distribution of stained benthic foraminifera seems not to be related with TOC contents in the sediment and water depth. Both the diversity index and Eqitability show that sites inside of the canyon have lower values. The higher Living/Total ratios and lower dead tests at the head of Kao-ping Submarine Canyon than adjacent area might be the effect of migration. Furthermore, the species within the canyon are similar to the southern and northern continental shelf. These findings indicate that the spatial distribution of benthic forams within canyon might be the effect of transport, which could result from the complex interaction between tides and currents.
Augmented with the profiles of excess 210Pb, the temporal variation of benthic foraminifera was revealed. Generally there is a progressive decrease in the abundance of Ammonia sp.. It is possible that the diminishing trend was caused by the increase of anthropogenic activity for the last 30 years.
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Investigation into Temperature and Size Effects on Behaviors of Water NanoclustersYang, Sheng-Hui 03 August 2006 (has links)
Structure properties of water clusters are investigated in this study by means of molecular dynamics simulations. The oxygen density profile, dipole moment and hydrogen bond properties of water clusters are all examined. The temperature dependence and size dependence of the structure properties are also explored in the present study. Upon the molecular dynamics simulations, the flexible three-centered (F3C) water potential is used to model the inter- and intra-actions of the water molecule. It is found that as the temperature rises, the density of the oxygen and the average number of hydrogen bonds per water molecule will decrease. The effect of cluster size, however, is less significant on the structure properties.
The differences between the structural properties for the surface region and those for the interior region of the cluster are also investigated. It is found that as the temperature rises, the average number of hydrogen bonds per water molecule decreases, but the ratio of surface water molecules increases. After comparing the water densities in interior regions and the average number of hydrogen bonds in those regions, we find there is no apparent size effect on water molecules in the interior region, whereas the size of the water cluster has a significant influence on the behavior of water molecules at the surface region.
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