207 research outputs found
Investigation of the gap vortex street in densely packed tube arrays in axial flow using CFD and experiments
No full textAxial flow in tube bundles with small pitch-to-diameter ratio, a geometry encountered in nuclear reactor cores and heat exchangers, often displays periodic fluctuations. A significant velocity discrepancy between the inter-cylinder gap and subchannel center originates from the difference in through-flow area, feeding an instability. As it is associated with velocity-shear, it is similar to the Kelvin-Helmholtz type and the term 'gap instability' is adopted. A vortex street arises and structural vibration of the cylinders might develop due to the fluctuating pressure. Numerical simulations of this phenomenon were performed. The computational domain was constructed to match the most important geometrical features of an experimental setup. The bundle consists of 7 steel tubes in triangular array, placed in a hexagonal conduit. A flexible segment made of silicone is embedded in the central tube, with both extremes clamped to the steel parts of the cylinder. In the experiment, data of the fluctuating velocity was gathered using laser Doppler anemometry measurements. As first step, a completely rigid structure was considered. Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations were used to test if this particular geometry also triggers the gap vortex street, which was the case. The phenomenon clearly appears as oscillations of the velocity components. Subsequently, fluid-structure interaction (FSI) simulations, taking into account the flexible part, allowed to assess the effect of the fluctuating flow field on the structure. A comparison between one-way and two-way coupled simulations was made.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.RST/Reactor Physics and Nuclear Material
A comprehensive review on the long-term performance of stormwater biofiltration systems (SBS): Operational challenges and future directions
No full textStormwater biofiltration systems (SBS) are a popular technology for mitigating the negative effects of urbanization on the hydrological processes and water quality in urban areas. However, little is known about SBS's long-term performance in actual field conditions. The findings of a review of the scientific literature on the long-term performance of SBS are presented in this paper. The findings show that only a few studies have investigated the performance of SBS and its change over time, and that the results of laboratory and field experiments differed due to the presence of plants, regular maintenance, and some uncertain environmental factors. Based on the existing knowledge gaps in this field, the main challenges observed was the lack of long-term field data series, and the existing mathematical models are not able to accurately forecast the long-term performance of SBS. This could be owing to the difficulties in monitoring activities, the high costs involved and the unpredictability around the operational timeframe. Future study should concentrate on the implementation of simulation and modeling-based research in pilot and full-scale SBS, and the inclusion of new performance indicators should be considered as a priority.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Hydraulic Structures and Flood Ris
Discounted cash flow analysis: Assessor\u27s tool for single-property appraisal
No full textThe author discusses how financial calculators and computer programs make discounted cash flow analysis an easier tool to master
Dark image
No full textMotivacija za to magistrsko delo je bilo avtoričino iskanje
podobeprav določene podobe, izgubljene v najglobljih predelih
našega uma. Iskanje podobe, ki je nikoli nismo videli ali
doživelipodobe, ki je še nihče nikoli ni videl, ter ob tem
izzvati čutila in človeško naravo v danem trenutku.
Namen dela je iskati odgovore in si zastaviti vprašanja o tem,
kako zelo ljudje zaupajo svojim čutom, ter se spraševati o
njihovi zmožnosti, da spremenijo svoje vedenje in svoje rutine.
Opazovati, ali si za nekaj sekund drznejo ugasniti luč in s tem
pridobijo sposobnost, da vidijo na drugačen način. Ne preseneča
dejstvo, da se ljudje močno zanašajo na svoj vid, zaradi česar
preostala čutila postanejo nekako manj pomembna in zanesljiva.
To delo z naslovom "Temna podoba – podoba, ki smo jo izgubili v
temi", raziskuje moč podobe pri manipulaciji množice in vlogo
medijev pri nadzoru in pranju možganov pripadnikom nove
generacije.
V magistrskem delu avtorica najprej predstavi projekte "Kumra
1", "Kumra 2" in "Kaj vidiš v temi?" – poskuse, izvedene v prvem
in drugem letu raziskovanja, skozi katere predstavi analizo in
opazovanje svojih eksperimentov. Ti predstavljajo začetek
raziskovanja čutil v popolni temi, ki je nato pripeljalo do
"Sestavljanke", praktičnega dela te naloge, ki se sprašuje o
medijski manipulaciji z uporabo podobe.The motivation for this thesis was the author’s search for an
image, a particular image lost in the deepest parts of our mind,
searching for an image that we never saw or experienced before,
an image that no-one has ever seen, challenging the senses and
the human nature at a time.
The purpose of this thesis is to search for answers and to
question how much people trust their senses and to question
people’s ability to change their behavior and routines. To
measure people’s courage to turn off the light for a few seconds
and be able to see differently. It is no surprise that people
depend remarkably on their visual sense, which somehow made the
other senses less essential and less reliable. This thesis,
“Dark Image - The image we lost in the dark,” researches the
power of the image in manipulating masses and the role media
plays to control and brainwash the new generation with the least
effort spent.
In this thesis, the author first presents projects “KUMRA 1”,
“KUMRA 2” and “what does one see in the dark?” Experiments which
were made during the first year and second year of research and
through which the author presents her analysis and observation
of her experiments. It was the beginning of a sensual journey
exploring the senses in the deep dark. Which led to the master
thesis (practical) project Puzzle that questions the
manipulation of media using the image
Discontinuous modelling of strain localisation and failure
No full textThe computational simulation of failure in solids poses many challenges. A proper understanding of how structures respond under loading, both before and past the peak load, is important for safe and economical constructions. This requires numerical models for failure which are both faithful to the physical reality and mathematically well founded. A serious computational issue is that of objectivity with respect to the spatial discretisation of a problem. This requires that upon refinement of the spatial discretisation of a problem, a unique, physically meaningful result is approached. One approach to ensure objectivity with respect to spatial discretisation when simulating failure in solids is to allow displacement discontinuities in the solution. In this work, different techniques, of varying complexity, are developed to simulate displacement discontinuities which are independent of the spatial discretisation using finite elements. The different techniques are then critically evaluated. The first model examined involves adding only the effect of a displacement discontinuity to a finite element as an incompatible strain mode. This allows a traction–separation relationship to be applied at an interface and can be implemented simply in a standard finite element code. It is however shown that this type of model can be cast in an equivalent continuum format, a form which is known to be sensitive to the spatial discretisation. The second approach developed involves the addition of the Heaviside function to the underlying finite element interpolation basis. This method is based on the partition of unity concept, and allows the Heaviside function to be added locally to a finite element mesh to simulate a propagating displacement discontinuity. The approach is formulated for geometrically linear, geometrically nonlinear, quasi-static and dynamic problems. It is shown to be completely independent of the spatial discretisation. The partition of unity-based model is used also to simulate failure using a regularised strain softening model. When a critical level of inelastic deformation is reached, a displacement discontinuity is inserted. This model is better suited to modelling the entire failure process than a continuum or discontinuous model alone. Through numerical examples, it is shown that the inclusion of a displacement discontinuity during the failure process can lead to a different failure mode than for a continuum-only model
Zili is required for germ cell differentiation and meiosis in zebrafish.
No full textSmall RNAs exert an effect through diverse RNA interference pathways to transcriptionally or post-transcriptionally silence their targets. The Piwi-interacting RNAs (piRNAs) represent a germline-specific small RNA pathway where Piwi proteins themselves are thought to mediate piRNA biosynthesis. Here, we provide strong evidence for a piRNA amplification loop in zebrafish, in which Ziwi and Zili bind piRNAs of opposite polarity. Furthermore, we describe a function for Zili in transposon defense and germ cell differentiation, as well as a crucial function in meiosis, significantly extending the function of Piwi proteins beyond the control of transposable elements in vertebrates
The sense of a beginning : Bakhtinian dialogic criticism on 'the gospel' in Mark.
No full textContemporary literary approaches have caused paradigm shifts in Biblical Studies in the last two decades as it appears in a great deal of Markan studies using narrative, reader-response, deconstructive, feminist, and new historicist approaches. However, literary studies on the Gospel of Mark have not taken into account theoretical questions underlying those approaches. As a result biblical critics are driven by new trends without ever having a chance to examine the critical baggage of the approaches. Consequently, there is a gap of communication between the old and the new one. Therefore this thesis is an attempt to meet the need of enhancing the quality of critical endeavour in biblical studies. In the light of most recent competing critical theories of literature, the first contribution of this thesis is the methodological finding that Bakhtinian dialogic criticism contains the most profound philosophical and practical foundations for solving some crucial theoretical problems in contemporary literary theories. It is a critique to a Saussurian linguistic system of language which becomes the very foundation of modern and postmodern literary criticism. Bakhtinian literary theory shifts the foundation of literary criticism on linguistic signs into the creative activity of the socio-cultural production of human communication. The shift into socio-cultural reality of language communication makes the notion of 'genre' very important to unlock the problem of text and context in literary studies. Since the Gospel of Mark has fascinated most literary critics in Biblical Studies, the problem of 'genre' of this gospel is chosen as the focus of this study. Secondly, as no agreement is reached as to what 'genre' the Gospel of Mark belongs, this thesis makes its contribution to the discussion by locating the problem of 'genre' of Mark in the context of genre theories and argues that the Bakhtinian suggestion to find genre in the socio-cultural sphere by analysing artistic intercourse between narrative agents in Mark has freed the competing analysis from the unresolved problem between the kerygmatic (content oriented) approach and the analogical (form oriented) approach. To achieve finding 'genre' in the socio-cultural sphere, this thesis focuses on Bakhtinian analysis of the process of artistic intercourse between narrative agents. The narrative communicative interrelationships between narrative agents is constructed in this thesis as a 'stereophonic' Bakhtinian model of dialogic communication. This model is an original contribution of this thesis for revising the traditional two dimensional model of narrative communication. Based on this dialogical model of communication, a special role is given to the Bakhtinian 'author-creator' in the realization process of genre through the interaction of polyphonic voices. Through the interaction of voices of the author-artist and the hero we are led to discover a relatively stable type of portraying and controlling reality in Mark, known as the genre of Roman 'satire'. The closest literary affinity is Satyrica by Petronius. This narrative strategy of 'satire' in Mark has its root in the prophetic discourse of the Old Testament which is saturating the speech of the narrator, John the Immerser, the centurion, the people, and even Jesus. Finally, the whole search for Markan 'genre' culminates in the analysis of the realization of genre through the analysis of Bakhtinian chronotope. The reality of the genre of Mark is its social reality that is in its role as dpxrj/ 'beginning'. As the Gospel of Mark proclaims itself as 'a beginning', it defines its claim of socio-cultural 'authority' in early Christianity. It is this 'sense of beginning' which enables the narrating and the narrated world of Mark to interact dialogically
Analyzing a turbulent pipe flow via the one-point structure tensors: Vorticity crawlers and streak shadows
No full textAbstractEfforts to identify and visualize near-wall structures typically focus on the region y+≳5, where large-scale structures with significant turbulent kinetic energy content reside, such as the high-speed and low-speed streaks associated with sweep and ejection events. While it is true that the level of the turbulent kinetic energy drops to zero as one approaches the wall, the organization of near-wall turbulence does not end at y+≈5. Large-scale structures with significant streamwise extent and spatial organization exist even in the immediate proximity of the wall y+<5. These coherent structures have received less attention so far, but it would be both useful and enlightening to bring them to focus in order, on one hand, to understand them, but also to analyze their interaction with the energetic structures that reside at somewhat higher distances from the wall.We have recently developed a rigorous mathematical and computational framework that can be used for the calculation of the turbulence structure tensors in arbitrary flow configurations. In this work, we use this new framework to compute, for the first time, the structure tensors in a fully-developed turbulent pipe flow. We perform Direct Numerical Simulation (DNS) at Reynolds number Reb=5300, based on the bulk velocity and the pipe diameter. We demonstrate the diagnostic properties of the structure tensors, by analyzing the DNS results with a focus on the near-wall structure of the turbulence. We develop a new eduction technique, based on the instantaneous values of the structure tensors, for the identification of inactive structures (i.e. large-scale structures without significant turbulent kinetic energy). This leads to the visualization of “vorticity crawlers”
and “streak shadows”, large-scale structures with low energy content in the extreme vicinity of the wall. Furthermore, comparison with traditional eduction techniques (such as instantaneous iso-surfaces of turbulent kinetic energy) shows that the structure-based eduction method seamlessly captures the large-scale energetic structures further away from the wall. We then show that the one-point structure tensors reflect the morphology of the inactive structures in the extreme vicinity of the wall and that of the energy-containing large-scale structures further away from the wall. The emerging complete picture of large-scale structures helps explain the near-wall profiles of all the one-point structure tensors and is likely to have an impact in the further development of Structure-Based Models (SBMs) of turbulence
Explaining Abuse of the Disabled Child
No full textThis article discusses abuse of disabled children in terms of two competing theories for why it may occur. The evolutionary biology theory has been discussed in the legal literature as well as in biological and social science pieces. The author contrasts this theory with a novel one, mimetic desire, which may be less familiar in legal circles, but which, he believes, better explains the abuse of Attention Deficit Hyperactive Disorder children and offers more hope for preventing abuse without disrupting intact families. While the evolutionary biology explanations for child abuse may be helpful and important, more territory can be covered by Stanford professor Rene Girard\u27s mimetic cycling theory. In addition, this better fits the social capital literature in which, in Yoshihiro Francis Fukuyama\u27s work, for example, biology plays a helpful, though not completely satisfying, role. Social capital and mimetic theory in particular seem to do a more complete job of explanation. Links: Linking Servic
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