The build-up of coercive capacities

Do governments’ military build-ups foster the outbreak of intrastate violence? This article investigates the impact of governments’ arms imports on the onset of intrastate conflicts. There is scant empirical research on the role of the external acquisition of coercive technologies, and even fewer studies explore the respective causal mechanisms of their consequences. We argue that the existing literature has not adequately considered the potential simultaneity between conflict initiation and arms purchases. In contrast, our study explicitly takes into account that weapon inflows may not only causally induce conflicts but may themselves be caused by conflict anticipation. Following a review of applicable theoretical models to derive our empirical expectations, we offer two innovative approaches to surmount this serious endogeneity problem. First, we employ a simultaneous equations model that allows us to estimate the concurrent effects of both arms imports on conflict onsets and conflict onsets on imports. Second, we are the first to use an instrumental variable approach that uses the import of weapon types not suitable for intrastate conflict as instruments for weapon imports that are relevant for fighting in civil wars. Relying on arms transfer data provided by the Stockholm International Peace Research Institute for the period 1949-2013, we provide estimates for the effect of imports on civil war onset. Our empirical results clearly show that while arms imports are not a genuine cause of intrastate conflicts, they significantly increase the probability of an onset in countries where conditions are notoriously conducive to conflict. In such situations, arms are not an effective deterrent but rather spark conflict escalation

Détermination de l'impédance acoustique de matériaux absorbants en écoulement par méthode inverse et mesure LDV

La réduction des nuisances sonores est un enjeu permanent pour les acteurs de l aéronautique. L optimisation de la réduction de bruit apportée par les traitements acoustiques tapissant la nacelle des réacteurs turbofan passe par une caractérisation précise des matériaux employés dans l environnement aéroacoustique d utilisation, qui met en jeu un écoulement rasant de vitesse importante combiné à de forts niveaux sonores. L objectif de cette thèse est de développer une méthode inverse pour la détermination de l impédance acoustique de liners soumis à un écoulement rasant, basée sur des mesures non intrusives du champ de vitesse acoustique au-dessus du matériau par Vélocimétrie Laser Doppler (LDV). L impédance de liner est obtenue par minimisation de l écart entre le champ de vitesse acoustique mesuré et le champ simulé numériquement en résolvant les équations d Euler linéarisées bidimensionnelles harmoniques, discrétisées par un schéma Galerkin discontinu. Le gradient de la fonction objectif minimisée est calculé via la résolution, à chaque itération, des équations directes et adjointes. Une première étape de validation du solveur est effectuée sur des cas-tests académiques, puis sur des cas expérimentaux impliquant des mesures de pression acoustique en paroi rigide opposée au liner. Dans un second temps, la méthode est appliquée à des mesures de vitesse acoustique obtenues par LDV dans le banc B2A de l ONERA en l absence d écoulement. La dernière étape consiste à prendre en compte l effet d un écoulement rasant de profil cisaillé. Les impédances identifiées à partir de mesures LDV en présence d écoulement ont notamment permis de gagner en compréhension sur les phénomènes d absorption intervenant dans le banc B2A.While aircraft noise constraints become increasingly stringent, efficient duct treatment of turbofan engines requires an accurate knowledge of liner impedance with grazing flow at high acoustic levels. This thesis aims at developing an impedance eduction method in the presence of grazing flow. The inverse process is based on acoustic velocity fields acquired by Laser Doppler Velocimetry (LDV) above the liner. The liner acoustic impedance is obtained by minimization of the distance between the measured acoustic velocity field and the simulated one. Computations rely on the resolution of the 2D linearized Euler equations in the harmonic domain, spatially discretized by a discontinuous Galerkin scheme. The gradient of the objective function is achieved by the resolution, at each iteration on the liner impedance, of the direct and adjoint equations. The solver is first validated on academic test cases, then on experimental results of acoustic pressure measurements at the rigid wall opposite the liner. Secondly the method is applied to acoustic velocity measurements obtained by LDV above the liner without flow, in the ONERA B2A test bench. The last step consists in taking into account the effects of a sheared grazing flow. The impedances educed from LDV measurements in the presence of flow namely allowed to gain insight into the absorption phenomena occuring in the B2A test bench.TOULOUSE-INSA-Bib. electronique (315559905) / SudocSudocFranceF

ONERA-NASA Cooperative Effort on Liner Impedance Eduction

As part of a cooperation between ONERA and NASA, the liner impedance eduction methods developed by the two research centers are compared. The NASA technique relies on an objective function built on acoustic pressure measurements located on the wall opposite the test liner, and the propagation code solves the convected Helmholtz equation in uniform ow using a finite element method that implements a continuous Galerkin discretization. The ONERA method uses an objective function based either on wall acoustic pressure or on acoustic velocity acquired above the liner by Laser Doppler Anemometry, and the propagation code solves the linearized Euler equations by a discontinuous Galerkin discretization. Two acoustic liners are tested in both ONERA and NASA ow ducts and the measured data are treated with the corresponding impedance eduction method. The first liner is a wire mesh facesheet mounted onto a honeycomb core, designed to be linear with respect to incident sound pressure level and to grazing ow velocity. The second one is a conventional, nonlinear, perforate-over-honeycomb single layer liner. Configurations without and with ow are considered. For the nonlinear liner, the comparison of liner impedance educed by NASA and ONERA shows a sensitivity to the experimental conditions, namely to the nature of the source and to the sample width

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Identity, poverty, and electoral accountability in Africa’s democracies

Do voters in Africa’s new democracies hold leaders accountable for the results of their past actions? Are heads of state punished or rewarded in a fashion that credibly signals that stealing, poor policy choices, and bad leadership are not tolerated? Experts remain sceptical. While it is increasingly acknowledged that some African voters consider issues such as the national economy or the management of schools and roads, many scholars doubt that electoral reactions are strong enough to replace bad leaders and effectively incentivise good governance. This book presents the most comprehensive investigation of the matter so far. Based on a sanctioning model of electoral accountability, the study revolves around two critical conditions for effective accountability. Voters should (1) form unbiased performance perceptions and (2) act upon their judgements by re-electing successful leaders and voting against bad performers. The book combines two in-depth case studies of Ghana and Uganda and a comparison across 16 countries, drawing on altogether 59 nationally representative surveys. The case studies trace performance perceptions and voting intentions of relevant ethnic and partisan groups over a period of more than ten years, on and off campaign times. The comparative perspective verifies the generalizability of findings and sheds light on the distribution of accountability pressures across Africa. Important empirical and theoretical contributions accrue from the new perspectives. First, the country study of Ghana provides new persuasive evidence of effective accountability in Africa by demonstrating that all relevant ethnic and partisan constituencies contribute to the sanctioning signal, which creates strong incentives for leaders to pursue programmatic strategies to maximise the impact and the reach of developmental policies. Secondly, the work underlines the growing relevance of partisan identities in the region’s young systems. Partisanship is found to have a substantially stronger influence than ethnicity on performance perceptions and often overrides ethnic leanings. In some countries, most notably Ghana and Malawi, the study documents high levels of partisan polarization that cut across ethnic divisions. The observed patterns strongly indicate partisan-motivated reasoning and the emergence of affective partisan identities. By contrast, biases for coethnics are surprisingly rare across the 59 surveys. Only in three of 16 countries (Ghana, South Africa, and Malawi), ethnic identities have a robust and temporally stable influence on popular performance perceptions. Thirdly, the study highlights daily experiences of poverty as an often-overlooked source of information. I present robust evidence that people confronted with shortages in basic necessities tend to evaluate office holders critically, even if these are copartisans or coethnics. The finding indicates that personal exposure to poverty directly informs perceptions of government performance. Accordingly, poor people should not be underestimated as a critical force on election day; their judgements seem less prone to identity biases than those of citizens in relative economic security. Other informational indicators, including news consumption and political interest, show no bias-reducing effect. Last but not least, the comparative perspective illuminates the distribution of biases and the variation in the magnitude of performance voting across Africa. The results highlight that some conflicting findings in the literature are attributable to systematic cross-country differences. Performance voting is strongest in states with keenly contested elections. Interestingly, minor democratic deficits and low development show no adverse effect on electoral accountability within the 16-country sample

Evaluation of an adjoint-based liner impedance eduction technique

International audienceAcoustic liners placed in the aircraft nacelles play a key role in the reduction of turbofan noise. To determine their acoustic impedance, an " eduction method " with grazing flow is developed. It relies on the minimization of an objective function describing the distance between experimental data on one hand and numerical results obtained with 2-D Linearized Euler Equations on the other hand. The gradient of the objective function is calculated thanks to the adjoint equations rather than with finite differences, which gives more accurate results and makes easier a multi-parameter identification. The procedure is intended to be applied in a duct with non-intrusive acoustic velocity measurements obtained as close as possible to a sample liner by Laser Doppler Velocimetry (LDV), contrary to classical methods which use distant wall microphones. The eduction process is validated on results from literature and on LDV measurements performed at Onera, for different frequencies and flow configurations. Access to two-dimensional fields ensured by LDV allows to study the relevance of different objective functions and observation domains

The build-up of coercive capacities

Do governments’ military build-ups foster the outbreak of intrastate violence? This article investigates the impact of governments’ arms imports on the onset of intrastate conflicts. There is scant empirical research on the role of the external acquisition of coercive technologies, and even fewer studies explore the respective causal mechanisms of their consequences. We argue that the existing literature has not adequately considered the potential simultaneity between conflict initiation and arms purchases. In contrast, our study explicitly takes into account that weapon inflows may not only causally induce conflicts but may themselves be caused by conflict anticipation. Following a review of applicable theoretical models to derive our empirical expectations, we offer two innovative approaches to surmount this serious endogeneity problem. First, we employ a simultaneous equations model that allows us to estimate the concurrent effects of both arms imports on conflict onsets and conflict onsets on imports. Second, we are the first to use an instrumental variable approach that uses the import of weapon types not suitable for intrastate conflict as instruments for weapon imports that are relevant for fighting in civil wars. Relying on arms transfer data provided by the Stockholm International Peace Research Institute for the period 1949-2013, we provide estimates for the effect of imports on civil war onset. Our empirical results clearly show that while arms imports are not a genuine cause of intrastate conflicts, they significantly increase the probability of an onset in countries where conditions are notoriously conducive to conflict. In such situations, arms are not an effective deterrent but rather spark conflict escalation.ISSN:0022-3433ISSN:1460-357