97 research outputs found
Aortoarteritis with tuberculosis
No full textAortoarteritis is an inflammatory condition of the aorta, which has been rarely reported due to tuberculous infection. We report two cases of children who had aortoarteritis along with tuberculosis (TB), of which one had collapse consolidation and the other had latent TB. Both patients were treated with anti-TB therapy and steroids
Text and the nation: mediating South Asian decolonization through postcolonial literature and posthuman knowledge
No full textThis work was accepted to the annual Graduate Research and Creative Works Symposium while the author was a graduate student at Rutgers University-Camden
Isogeometric Shell Discretizations for Flexible Multibody Dynamics
No full textThis work aims at including nonlinear elastic shell models in a multibody framework. We focus our attention to Kirchhoff-Love shells and explore the benefits of an isogeometric approach, the latest development in finite element methods, within a multibody system. Isogeometric analysis extends isoparametric finite elements to more general functions such as B-Splines and Non-Uniform Rational B-Splines (NURBS) and works on exact geometry representations even at the coarsest level of discretizations. Using NURBS as basis functions, high regularity requirements of the shell model, which are difficult to achieve with standard finite elements, are easily fulfilled. A particular advantage is the promise of simplifying the mesh generation step, and mesh refinement is easily performed by eliminating the need for communication with the geometry representation in a Computer-Aided Design (CAD) tool.
Quite often the domain consists of several patches where each patch is parametrized by means of NURBS, and these patches are then glued together by means of continuity conditions. Although the techniques known from domain decomposition can be carried over to this situation, the analysis of shell structures is substantially more involved as additional angle preservation constraints between the patches might arise. In this work, we address this issue in the stationary and transient case and make use of the analogy to constrained mechanical systems with joints and springs as interconnection elements. Starting point of our work is the bending strip method which is a penalty approach that adds extra stiffness to the interface between adjacent patches and which is found to lead to a so-called stiff mechanical system that might suffer from ill-conditioning and severe stepsize restrictions during time integration. As a remedy, an alternative formulation is developed that improves the condition number of the system and removes the penalty parameter dependence. Moreover, we study another alternative formulation with continuity constraints applied to triples of control points at the interface. The approach presented here to tackle stiff systems is quite general and can be applied to all penalty problems fulfilling some regularity requirements.
The numerical examples demonstrate an impressive convergence behavior of the isogeometric approach even for a coarse mesh, while offering substantial savings with respect to the number of degrees of freedom. We show a comparison between the different multipatch approaches and observe that the alternative formulations are well conditioned, independent of any penalty parameter and give the correct results. We also present a technique to couple the isogeometric shells with multibody systems using a pointwise interaction.Diese Arbeit zielt darauf ab, nicht-lineare elastische Schalenmodelle in ein Mehrkörpersystem zu integrieren. Wir konzentrieren unsere Aufmerksamkeit auf Kirchhoff-Love Schalen und untersuchen die Vorteile eines isogeometrischen Ansatzes, der die neueste Entwicklung unter den Finite-Elemente-Methoden darstellt, angewandt auf ein Mehrkörpersystem. Isogeometrische Analyse erweitert isoparametrische finite Elemente auf allgemeinere Funktionen wie B-Splines und Non-Uniform Rational B-Splines (NURBS) und arbeitet auf einer exakten Darstellung der Geometrie - sogar auf der gröbsten Diskretisierung. Wenn man NURBS als Basisfunktionen verwendet, werden die hohen Anforderungen an die Regularität des Schalenmodells, die bei Finiten Elementen schwer zu garantieren sind, einfach erfüllt. Ein besonderer Vorteil ist hierbei das Versprechen, dass die Netzgenerierung vereinfacht wird. Die Netzverfeinerung wird leicht dadurch ermöglicht, dass eine Kommunikation mit der Geometrie-Schnittstelle eines Computer-Aided Design (CAD)-Werkzeuges entfällt.
Häufig besteht das Gebiet aus mehreren Abschnitten, wobei jeder Abschnitt mit Hilfe von NURBS parametrisiert ist. Diese Flächenstücke werden dann durch Stetigkeitsbedingungen verklebt. Obwohl die Techniken, die aus der Gebietszerlegung bekannt sind, auch hier angewandt werden könnten, ist die Analyse von Schalenstrukturen wesentlich komplizierter, da zusätzliche Bedingungen zur Erhaltung der Winkel zwischen den Flächen auftreten können. In dieser Arbeit beschäftigen wir uns mit dieser Frage im stationären und transienten Fall und nutzen die Analogie zu mechanischen Systemen, die Gelenke und Federn als Verbindungselemente besitzen. Ausgangspunkt ist der bending strip-Ansatz, der künstlich als Strafterm eine steife Feder an der Grenzfläche zwischen zwei benachbarten Flächen einfügt und zu einem so genannten steifen mechanischen System führt. Solche Systeme führen im Allgemeinen zu schlechter Kondition und starken Schrittweitenbeschränkungen für das Zeitintegrationsverfahren. Als Abhilfe wird eine modifizierte Formulierung entwickelt, die die Konditionszahl des Systems verbessert und die Abhängigkeit von der Größe des Strafterms entfernt. Darüber hinaus untersuchen wir einen weiteren Ansatz, der mit Stetigkeitsbedingungen zwischen Kontrollpunkt-Tripeln an der Schnittstelle arbeitet. Das hier vorgestellte Vorgehen steife Systeme zu lösen ist sehr allgemein und kann auf alle Probleme mit Straftermen angewandt werden, die gewisse Anforderungen an ihre Regularität erfüllen.
Die numerischen Beispiele zeigen ein eindrucksvolles Konvergenzverhalten des Isogeometrische Ansatzes auch für grobe Gitter und bieten erhebliche Einsparungen in Bezug auf die Anzahl der Freiheitsgrade. Wir zeigen einen Vergleich zwischen den verschiedenen Mehr-Flächen-Ansätzen und beobachten, dass die alternativen Formulierungen gut konditioniert und unabhängig von der Größe des Strafterms sind und die korrekten Ergebnisse erzielen. Ebenfalls stellen wir ein Vorgehen vor, die Isogeometrischen Schalen durch punktweise Interaktion mit Mehrkörpersystemen zu koppeln
Gender and Public Spending on Education in Pakistan: A Case Study of Disaggregated Benefit Incidence
No full textIt is generally believed that education is one of the basic rights of every human being, irrespective of sex, age, creed, religion, etc. Moreover, the target of universal primary education cannot be achieved without female access to educational opportunities, which contains several external benefits. In addition, access to educational opportunities assumes prime importance for empowerment of women. However, inequalities in access to education between males and females can be found in many countries across the world including Pakistan. According to conventional wisdom, a combination of cultural, social, and economic factors are responsible for placing young girls and women at a serious disadvantage vis-a-vis access to school and the prospect of completing their education. This disadvantage can be altered through public policies including gender sensitive public spending on education. The above assertion about the role of public policy is based on the theory of public finance1, which demonstrates that public expenditure on education can affect the population in a number of ways, which has significant gender dimensions. For example, government spending on primary education is likely to generate more income for women than spending on universities, for the simple reason that there are relatively more women primary school teachers than women university lecturers. Moreover, these expenditures provide subsidized educational services, which is a form of “in kind transfers”. These “in-kind transfers” improve the current well-being of the recipients, and enhance their longer-run income-earning potential. They can be considered as both current and capital transfers to the recipients, and therefore can be termed as the “benefit incidence” of public spending. The main concern of this paper is to assess the gender dimension of the benefitincidence”. The tudy has two basic objectives. First and foremost, it aims to investigate which income group actually benefits from the government’s subsidized.
Stylization of shadows in ski-panorama maps: A case study on Atelier Novat
No full textPanorama maps can be defined as aerial-view paintings of geologically complex landscapes that are represented in a convenient manner to non-expert viewers. This thesis focuses on a specific variant of panorama maps known as "ski-panorama maps" or "piste-maps" drawn by the french landscape and panorama artist, Pierre Novat. These maps usually contain a multitude of visual cues that are specifically emphasized upon by the artist in order to improve viewer perception. Among these visual cues, cast-shadows play an important role in recognizing the shape, depth and height of the terrain. Therefore, the main goal of this thesis is to understand the use of shading based on the underlying rule-sets created by the artist, Pierre Novat. Through these rule-sets, we propose two contributions : a brief study of the artistic style of Atelier Novat along with a rendering framework for shadow stylization. This framework is mainly based on image-space filters, that takes a set of DEM (Digital Elevated Model) files as input and produces an image that resembles a ski-panorama map. The pipeline deals with the following components : a novel method for stylized shading - a set of methods for modifying structural properties of cast-shadows (according to artist-driven rulesets) and a hue transfer-function. As a final step, validation of the rendered images is empirically done by cross-referencing it with the specific panorama art-work and by taking feedback from the artist, Arthur Novat.Computer Scienc
Lattice Modelling of Moisture Transport in Uncracked and Cracked Concrete
No full textThe service life of concrete structures depend largely on the durability of concrete. The durability of concrete is influenced by mass transport mechanisms that can have severe deteriorating effects. Transport of water in concrete is of paramount importance as water can act as a carrier of ions such as chlorides which can corrode the reinforcement and reduce the service life of concrete structures. The main objective of this thesis is to study moisture transport through capillary absorption in concrete. Numerical simulation of moisture transport is performed through lattice elements with an irregular mesh configuration. New computational tools are developed and compared with the existing tools in terms of effectiveness to simulate moisture transport in homogeneous uncracked concrete. The existing numerical model uses approximate volume of transport elements to determine the volumetric capacity of elements. During discretization of the governing equation, the variation of diffusivity of the elements is approximated as a uniform mean distribution and an explicit time stepping scheme is implemented which has consequences on the flow equilibrium at each time step. In the proposed numerical model, exact volume of transport elements is considered and during the discretization of governing equations, exponential variation of diffusivity is considered along with an implicit time stepping scheme. Moisture transport is accurately simulated in uncracked homogeneous concrete even by using the existing model as validated through experimental results. Both the models are compared through error analysis by varying mesh size and time step. Moisture flow through different diffusivity coefficients is simulated using both the models and it is observed that the existing model suffers from oscillations in the saturation level during initial stages of flow due to inability of the existing model to maintain flow equilibrium at each time step. The proposed model on the other hand shows no such oscillations due to the flow equilibrium being maintained at each time step. Mesh size, magnitude of time step and diffusivity coefficient are shown to be the parameters limiting the effectiveness of either of the models. A single discrete crack is considered within the domain and its influence on moisture transport is observed. The nature of the crack is considered through two approaches. In the first approach, crack is considered as an additional porous phase in cement matrix and the entire volume occupied by the crack is considered to be a void. In the second approach, in addition to considering the porous nature of crack, moisture surface interaction between the water surface and crack walls is also considered. Horizontal moisture distribution around a planar crack is simulated using both the approaches which show similar results as in the experiment. The vertical moisture distribution is simulated within a wedge shaped crack and the results are compared with experimental observations. The first approach shows a slower rate of saturation of the crack as compared to the experiment. The second approach shows the vertical saturation of the crack similar to the experiment. A comparison between the Delaunay and Voronoi modelling techniques of moisture simulation in cracked domain is discussed. It is shown that the presence of a crack accelerates the moisture transport in concrete as it exposes additional surface of concrete from where water can penetrate in the material and also increases the diffusivity of the concrete material lying in the vicinity of the crack. Moisture transport is simulated in concrete considering its multi-phase nature. Concrete is considered to be composed of three phases i.e. cement paste, aggregates and ITZ around aggregates. Aggregates are considered to be impervious which do not allow the flow of moisture through them which slows down the flow in concrete. The ITZ around the aggregates have higher transport properties and accelerate the flow. A numerical framework is formulated in which spherical aggregates are projected on lattice elements which are assigned transport properties pertaining to the phase of concrete they represent. Moisture transport is simulated and compared with experimental results where an increase of volume fraction of aggregates leads to a decrease of cumulative saturation level. The influence of ITZ is observed on a local and global scale by varying the ITZ diffusivity coefficient. The moisture simulation is also modelled on a finer mesh to see the effect of mesh refinement. Finally, moisture transport is simulated in a numerical model that combines a planar crack along with heterogeneities and flow is observed at different time stages
Exploring demand response opportunities in energy communities: An agent-based modeling approach for attaining self-sufficiency in mixed energy communities in the Netherlands
No full textAmidst the discourse regarding the decentralization of urban energy systems, energy community has emerged as a solution for optimizing the electricity demand and distributed generation. Community energy projects also facilitate collaboration amongst local prosumers. An energy community is a collective of residential electricity consumers (or prosumers) and non-energy small and mediumsized enterprises (SMEs) formulating a social network involved in decentralized energy production. This study is focused on exploring demand response opportunities in community energy projects located in the Netherlands to reduce their dependence on the grid. Existing studies on community energy projects are primarily focused on residential members, and have little to no inclusion of nonresidential community members. However, recent studies regarding demand response in the energy community highlight the benefits of having a mixed configuration of residential and non-residential members. Introducing non-residential community members such as SMEs, offices, and schools with a complementary demand profile can help the community in attaining self-sufficiency through demand response. Formulating energy communities with a mixed configuration (i.e. including residential and non-residential community members) optimizes local electricity generation and consumption thus avoiding congestion in the distribution network....Engineering and Policy Analysi
Frequency control of deregulated power system using C19-BOA technique
No full textThis study presents the frequency control of hybrid deregulated power system. The power system is supplied with appropriate system non-linearity's for practicality. A resilient model predictive control based two degree of freedom proportional integral derivative controller is designed. The Covid-19 based optimization algorithm is applied for optimization purpose. The impact of solar and wind on system dynamics are also examined. Further, the capacitive energy storage is also incorporated to check its influence. The distribution companies' participation matrix changes with market fluctuations, so the matrix is varied to check its impact. Lastly, sensitivity assessment is performed to analyze the strength of proposed controller optimized gains achieved under nominal conditions
Towards a transaction cost approach to the essential facilities doctrine
No full textThis chapter makes an attempt to view the essential facilities doctrine (EFD) through transaction cost lens. Through narrating the evolution of the doctrine in the US (and subsequently in the EU), the authors have observed the divergent interests of the judiciary in the two regions. They have located the doctrine’s presence in Indian case laws, identified the problems therein (particularly in cases involving intellectual property) and have proposed that the doctrine’s construction in India should be guided by the EU model. To build this case, the authors have situated the doctrine in property-liability framework and invoked the concepts of transaction costs and bargaining power to guide their choices. The authors have concluded that societies characterised by a weak intellectual property regime (and hence high transaction costs) should adopt a more liberal approach towards EFD. They show that India is indeed, one such society
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