Simulation of unsteady rotational flow over propfan configuration

During the past decade, aircraft engine manufacturers and scientists at NASA have worked on extending the high propulsive efficiency of a classical propeller to higher cruise Mach numbers. The resulting configurations use highly swept twisted and very thin blades to delay the drag divergence Mach number. Unfortunately, these blades are also susceptible to aeroelastic instabilities. This was observed for some advanced propeller configurations in wind tunnel tests at NASA Lewis Research Center, where the blades fluttered at cruise speeds. To address this problem and to understand the flow phenomena and the solid fluid interaction involved, a research effort was initiated at Georgia Institute of Technology in 1986, under the support of the Structural Dynamics Branch of the NASA Lewis Research Center. The objectives of this study are: (1) the development of solution procedures and computer codes capable of predicting the aeroelastic characteristics of modern single and counter-rotation propellers; and (2) the use of these solution procedures to understand physical phenomena such as stall flutter, transonic flutter, and divergence

Novel black hole bound states and entropy

We solve for the spectrum of the Laplacian as a Hamiltonian on $\mathbb{R}^{2}-\mathbb{D}$ and in $\mathbb{R}^{3}-\mathbb{B}$. A self-adjointness analysis with $\partial\mathbb{D}$ and $\partial\mathbb{B}$ as the boundary for the two cases shows that a general class of boundary conditions for which the Hamiltonian operator is essentially self-adjoint are of the mixed (Robin) type. With this class of boundary conditions we obtain "bound state" solutions for the Schroedinger equation. Interestingly, these solutions are all localized near the boundary. We further show that the number of bound states is finite and is in fact proportional to the perimeter or area of the removed \emph{disc} or \emph{ball}. We then argue that similar considerations should hold for static black hole backgrounds with the horizon treated as the boundary.Comment: 13 pages, 3 figures, approximate formula for energy spectrum added at the end of section 2.1 along with additional minor changes to comply with the version accepted in PR

Fire Safety Analysis of a Railway Compartment using Computational Fluid Dynamics

Trains are considered to be the safest on-land transportation means for both passengers and cargo. Train accidents have been mainly disastrous, especially in case of fire, where the consequences are extensive loss of life and goods. The fire would generate smoke and heat which would spread quickly inside the railway compartments. Both heat and smoke are the primary reasons of casualties in a train. This study has been carried out to perform numerical analysis of fire characteristics in a railway compartment using commercial Computational Fluid Dynamics code ANSYS. Non-premixed combustion model has been used to simulate a fire scenario within a railway compartment, while Shear Stress Transport k-ω turbulence model has been used to accurately predict the hot air turbulence parameters within the compartment. The walls of the compartment have been modelled as no-slip stationary adiabatic walls, as is observed in real life conditions. Carbon dioxide concentration (CO2), temperature distribution and air flow velocity within the railway compartment has been monitored. It has been observed that the smoke above the fire source flows to both sides of the compartment. The highest temperature zone is located downstream the fire source, and gradually decreases with the increase in the distance from the fire source. It can be seen that CFD can be used as an effective tool in order to analyse the evolution of fire in railway compartments with reasonable accuracy. The paper also briefly discusses the topical reliability issues

Changes in the electronic structure and properties of graphene induced by molecular charge-transfer

Interaction with electron donor and acceptor molecules such as aniline and nitrobenzene brings about marked changes in the Raman spectrum and the electronic structure of graphene, prepared by the exfoliation of graphitic oxide.Comment: 13 pages, 4 figure

Economic Development: Is Social Capital Persistent?

URL des Documents de travail : http://centredeconomiesorbonne.univ-paris1.fr/documents-de-travail/Documents de travail du Centre d'Economie de la Sorbonne 2015.02 - ISSN : 1955-611XThis paper, on the one hand, goes a step closer to demonstrate the causality of social capital on economic performance. On the other hand, we confirm a continued role of social capital effects on economic performance in this paper by using a much larger sample, spanning three decades and increasing the scope of countries. This paper is unique in the sense that it contributes to revisiting questions of economic performance, social capital and institutions with a clearly better and updated dataset from the last 28 years building upon existing empirical evidence. We employ a longitudinal analysis (pooled unbalanced multiple cross-section datasets) with fixed effects in this study. Our sample includes both the World Values Survey and European Values Study dating back to the 1980s. Our results are twofold: Firstly, to confirm that trust has a significant positive effect on growth. And more importantly, they have a significant effect on growth for at least 5 years (for growth at 5, 7 and 10 years following a period of trust measure). Secondly, associational activities – another measure in the overarching definitions of social capital, along with institutions, inequality, and education are consistently significant determinants of trust

Concrescence in Primary Dentition: A Case Report

Concrescence is the connection of two or more teeth by root cementum alone after the tooth crown has been formed. The incidence of concrescent teeth is reported to be highest in the posterior maxilla. The presence of concrescent teeth may influence teeth extraction as well as periodontal, endodontic, orthodontic and even prosthodontic diagnosis and treatment planning. Unexpected complications arising from this condition may lead to legal complications. Therefore, consideration should be given to the possible occurrence, recognition, and implications of this anomaly in diagnosis and treatment planning. The purpose of this article is to report a case of teeth concrescence between upper primary incisors with grade II mobility as it was near exfoliation

Locked nucleic acid as a novel class of therapeutic agents

Locked Nucleic Acid (LNA) is a nucleic acid analogue with unprecedented binding affinity and excellent specificity toward complementary RNA and DNA oligonucleotides. The remarkable properties of LNA have led to applications within various gene silencing strategies both in vitro and in vivo. In the present review, we highlight the uses of LNA for regulation of gene expression with emphasis on RNA targeting

Locked nucleic acid oligonucleotides towards clinical applications

Nucleic acid–based therapeutic technologies (Figure 9.1) have significantly advanced in the past two decades toward the treatment of many diseases. The first such drug to enter clinic was vitravene®, an antisense oligonucleotide for the treatment of cytomegalovirus retinitis [1]. Later, research on aptamers led to the marketing of macugen®, an inhibitor of vascular endothelial growth factor (VEGF) for the treatment of age related macular degeneration (AMD) [2]. Nucleic acid–based therapeutic approaches mainly include antisense [3,4], ribozymes [4], small interfering RNA (siRNA) [4–6], microRNA (miRNA) [7–10] targeting and aptamers [11–15]. Oligonucleotides composed of naturally occurring DNA or RNA nucleotides pose some limitations because of their poor RNA binding affinity, low degree of nuclease resistance, and low bioavilability. To overcome these limitations, chemically modified nucleic acids have been introduced, among which locked nucleic acid (LNA) [16–20] proved to be unique and is now used extensively for various applications in chemical biology [21–23]