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Search Results: 1 - 10 of 3367 matches for " Dirk "
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New Candidate Massive Clusters from 2MASS  [PDF]
Dirk Froebrich
International Journal of Astronomy and Astrophysics (IJAA) , 2013, DOI: 10.4236/ijaa.2013.32018
Abstract:

Massive stars are important for the evolution of the interstellar medium. The detailed study of their properties (such as mass loss, rotation, magnetic fields) is enormously facilitated by samples of these objects in young massive galactic star clusters. Using 2MASS we have searched for so far unknown candidates of red supergiant clusters along the Galactic Plane. Utilising deep high resolution UKIDSS GPS and VISTA VVV data to study colour-magnitude diagrams, we uncover six new massive cluster candidates in the inner Galaxy. If spectroscopically confirmed as real clusters, two of them could be part of the Scutum-Complex. One cluster candidate has a number of potential red supergiant members comparable to RSGC1 and 3. Our investigation of UKIDSS data reveals for the first time the main sequence of the massive cluster RSGC2. The stars of the sequence show an increased projected density at the same position as the known red supergiants in the cluster and have E(J-K) = 1.6 mag. This either indicates an unusual extinction law along the line of sight or a much lower near infrared extinction to the cluster than previously estimated in the literature. We suggest that psf-photometry in UKIDSS images might be able to uncover the main sequence of other RSGC clusters.

Troodos: A Giant Serpentinite Diapir  [PDF]
Roelof Dirk Schuiling
International Journal of Geosciences (IJG) , 2011, DOI: 10.4236/ijg.2011.22010
Abstract: Troodos is a classical ophiolite complex. It is proposed that the serpentinized harzburgites that now form the top of the mountain and represent the originally lowest part of the ophiolite sequence rose as a diapir. This diapiric rise is caused by the pervasive serpentinization of a suboceanic harzburgite, due to rock-sea water interaction. The serpentinization caused a 44% expansion of the rocks. Contrary to salt diapirism, the driving force for this diapiric rise is not so much the difference in density, but the volume increase asscociated with the transformation of harzburgite into serpentinite. The overlying gabbros, sheeted dike complex and pillow lavas were pierced by this serpentinite diapir but barely deformed. Their interaction with sea water was li- mited to some pyroxenes in the gabbros being transformed to amphiboles, and epidotisation of some of the dikes in the sheeted dike complex. The location of steep faults in the Troodos massif is determined by the contrasting expansion behavior of different rock-types on both sides of the fault.
A Note on Secondary Buyouts-Creating Value or Recycling Capital  [PDF]
Jana KITZMANN, Dirk SCHIERECK
iBusiness (IB) , 2009, DOI: 10.4236/ib.2009.12015
Abstract: This paper analyzes whether secondary buyouts of private equity (PE) investors in general create value and therefore are a suitable alternative to exit strategies like trade sales and IPOs. Theoretically, two conflicting approaches might explain the use of secondary buyouts as an exit channel of private equity investors: the capital recycling effects and different potential sources of value creation. We present empirical tests of these approaches. The profitability of secondary buyouts is assessed by a comparison of exit multiples realized with secondary buyouts and trade sales. The results are not unequivocal, but overall we interpret our findings in a way that awards secondary buyouts a profitability that is not significantly different from trade sales. Therefore, we argue that secondary buyouts have the potential for adding value that arise from different sources like the reduction of agency costs or the functions of the financial investor. Secondary buyouts should thus not be seen as a second best alternative for recycling the PE investors’ capital in situations where alternative—and supposedly more attractive—exit channels are unavailable.
Increasing the Efficiency of Transboundary Water Management: A Regionalization Approach  [PDF]
Dirk Huchtemann, Manuel Frondel
Journal of Water Resource and Protection (JWARP) , 2010, DOI: 10.4236/jwarp.2010.26057
Abstract: In this paper, we develop a methodological approach to increase the efficiency of watershed management approaches that focuses on the reduction of diffuse water pollution. The basic idea is that the efficiency may be improved by identifying and constituting homogenous groups of contiguous administrative units of a watershed, which jointly implement water pollution reduction measures. Homogeneity means similarity of group members with respect to a set of local and environmental characteristics, such as the degree of pollution and abatement costs. We empirically apply our methodology to the watershed of the German river Ems and identify homogenous groups of contiguous administrative units using cluster analysis methods implemented in a Geographical Information System.
Melody Generator: A Device for Algorithmic Music Construction  [PDF]
Dirk-Jan Povel
Journal of Software Engineering and Applications (JSEA) , 2010, DOI: 10.4236/jsea.2010.37078
Abstract: This article describes the development of an application for generating tonal melodies. The goal of the project is to ascertain our current understanding of tonal music by means of algorithmic music generation. The method followed consists of four stages: 1) selection of music-theoretical insights, 2) translation of these insights into a set of principles, 3) conversion of the principles into a computational model having the form of an algorithm for music generation, 4) testing the “music” generated by the algorithm to evaluate the adequacy of the model. As an example, the method is implemented in Melody Generator, an algorithm for generating tonal melodies. The program has a structure suited for generating, displaying, playing and storing melodies, functions which are all accessible via a dedicated interface. The actual generation of melodies, is based in part on constraints imposed by the tonal context, i.e. by meter and key, the settings of which are controlled by means of parameters on the interface. For another part, it is based upon a set of construction principles including the notion of a hierarchical organization, and the idea that melodies consist of a skeleton that may be elaborated in various ways. After these aspects were implemented as specific sub-algorithms, the device produces simple but well-structured tonal melodies.
Use of Mineral Liberation Analysis (MLA) in the Characterization of Lithium-Bearing Micas  [PDF]
Dirk Sandmann, Jens Gutzmer
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2013, DOI: 10.4236/jmmce.2013.16043
Abstract: The capabilities and opportunities of the application of automated mineralogy for the characterization of lithium-bearing zinnwaldite-micas are critically assessed. Samples of a crushed greisen-type ore comprising mostly of quartz, topaz and zinnwaldite (Li-rich mica) were exposed to further comminution by cone crusher and high voltage pulse power fragmentation. Product properties were analyzed by using a Mineral Liberation Analyser (MLA) and the obtained mineralogical and mineral processing relevant parameters were carefully evaluated with special focus on the characteristics of zinnwaldite. The results illustrate that both samples contain a significant quantity of very fine particles that are products of comminution. The modal mineralogy in the different sieve fractions is characterized by the accumulation of minerals of low hardness in the finest fraction and the enrichment of topaz, having a high hardness, in the somewhat larger fractions. Based on the results of mineral association data for zinnwaldite, a displacement of the muscovite-quartz ratio, in comparison to the results of modal mineralogy, was observed by indicating good quartz-zinnwaldite boundary breakage and weak muscovite-zinnwaldite breakage. Liberation as well as mineral grade recovery curves indicate that fraction 1000 to +500 μm is most suitable for beneficiation. The results of this study demonstrate that SEM-based image analysis, such as MLA, can effectively be used to investigate and evaluate phyllosilicate minerals in a fast and precise way. It is shown that the results of MLA investigations, such as modal mineralogy, are in good agreement with other analytical methods such as quantitative X-ray powder diffraction.
Climate Change and CO2 Removal from the Atmosphere  [PDF]
Roelof Dirk Schuiling
Natural Science (NS) , 2014, DOI: 10.4236/ns.2014.69065
Abstract:

Several methods have been proposed in recent years to counteract climate change and ocean acidification by removing CO2 from the atmosphere (Carbon Dioxide Removal). The most versatile and widely applicable of these methods is enhanced weathering of olivine, which is capable of removing billions of tons of CO2 from the atmosphere at moderate cost compared to the high cost of Carbon Capture and Storage (CCS). Despite its disadvantages, CCS is still the favored solution of many governments. Many misunderstandings of the potential of enhanced weathering persist. This paper addresses some of these misunderstandings, mainly caused by models which ignore established facts.

Processes of Science and Art Modeled as a Holoflux of Information Using Toroidal Geometry  [PDF]
Dirk K. F. Meijer
Open Journal of Philosophy (OJPP) , 2018, DOI: 10.4236/ojpp.2018.84026
Abstract: An attempt is made to model the structure of science and art discovery processes in the light of currently defined ideas on the societal flow of knowledge and conservation of information, using the versatile physical concept of toroidal geometry. This should be seen as a heuristic model that is open for further development and evolution. The scientific process, has been often described as a iterative and/or recurrent process. Current models explain the generation of new knowledge on the basis of a number of sequential steps (activities) operating in a circular mode. This model intrinsically assumes this process to be congruent for all individual scientific efforts. Yet, such a model is obviously inadequate to fully describe the whole integral process of scientific discovery as an ongoing interactive process, performed in a cumulative fashion. This implies that any new cycle starts from a different perspective or, optimistically seen, is initiated from a higher level, in a spiral mode, that takes into account the ongoing rise of scientific perspectives. Also, any model that attempts to picture the scientific process, should include potential interactions of concepts or hypotheses, in the sense that concurrently developed concepts may (mutually) influence each other and even may be mixed or superposed or, alternatively, may even result in concept extinction. Science and art progression, both seen as an individual effort and as a historically-based flow of events, is inherently a non-linear or even sometimes a chaotic process, where quite suddenly arising visions can cast a very different light on main-stream scientific thought and/or seem to remove existing barriers in more traditional “habits of the mind”. In contrast to the rather gradual evolution of science, the history of art sometimes even shows complete rejection of preceding conceptualizations and styles. The dynamics of cognition and perception are fruitfully suggested by the rotational dynamics of a torus as a basis for its “self-reflexive” property. Also, the torus exhibits contraction/relaxation loops, in which the torus turns inside out in a vibrating mode, implying strange loop trajectories. This suggests that the toroidal geometry embodies a cognitive twist, relating the “inside” to “outside” of knowledge as with a Möbius strip, a phenomenon that can be seen as the basis for self-consciousness. The torus geometry may also be applied to the art process on the basis of personal
Lack of evidence for safe vaccination with the Muguga cocktail in Sudan
Dirk Geysen,Dirk Berkvens
Onderstepoort Journal of Veterinary Research , 2013,
Abstract: none
Consideration of Viscoelasticity in Time Step FEM-Based Restraint Analyses of Hardening Concrete  [PDF]
Dirk Schlicke, Nguyen Viet Tue
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.410A2002
Abstract:

Concrete structures may suffer considerable restraint stresses during their hardening period. This is caused by several deformation impacts, especially temperature field changings due to hydration heat and volume changes due to autogenous shrinkage. Mainly affected are massive concrete members, but also the application of new concrete types or the erection of outstanding constructions requires further investigations in this context. 3D-FEM analyses of hydration heat induced temperature development in combination with the well known shrinkage give sufficient results for the deformation impact. The according elastic restraint stresses can be determined with consideration of the concrete’s rising elastic modulus and the restraint degree of the system. But due to duration of the heat flow process, the height of restraint stresses is strongly dependent from the viscoelasticity of the concrete. The viscoelastic effects consist of many components constituted by changing material properties influencing themselves. In practice, different simplified approaches are available for considering this in calculations. Their implementation in time step analyses is not generally admitted and requires expertise. In contrast, present research develops material models needing specific input parameters for every use case. This contribution focuses on a practicable approach considering the superposition of the viscoelastic behaviour of every stress increment in time step FEM analysis. The differentiation between the pure viscoelastic material behaviour (as it is given in the codes for idealistic conditions like creep or relaxation) and the according viscoelastic system response (addicted to the systems variable restraint degree) allows the transfer of this model into practice. As one application example of this approach,

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