Parallel Deferred Update Replication

Deferred update replication (DUR) is an established approach to implementing highly efficient and available storage. While the throughput of read-only transactions scales linearly with the number of deployed replicas in DUR, the throughput of update transactions experiences limited improvements as replicas are added. This paper presents Parallel Deferred Update Replication (P-DUR), a variation of classical DUR that scales both read-only and update transactions with the number of cores available in a replica. In addition to introducing the new approach, we describe its full implementation and compare its performance to classical DUR and to Berkeley DB, a well-known standalone database

Effects of rotation and sloping terrain on fronts of density current fronts

The initial stage of the adjustment of a gravity current to the effects of rotation with angular velocity f/2 is analysed using a short time analysis where Coriolis forces are initiated in an inviscid von Kármán–Benjamin gravity current front at tF=0. It is shown how, on a time-scale of order 1/f, as a result of ageostrophic dynamics, the slope and front speed UF are much reduced from their initial values, while the transverse anticyclonic velocity parallel to the front increases from zero to O(NH0), where N=g′/H0−−−−−√ is the buoyancy frequency, and g′=gΔρ/ρ0 is the reduced acceleration due to gravity. Here ρ0 is the density and Δρ and H0 are the density difference and initial height of the current. Extending the steady-state theory to account for the effect of the slope σ on the bottom boundary shows that, without rotation, UF has a maximum value for σ=\upi/6, while with rotation, UF tends to zero on any slope. For the asymptotic stage when ftF≫1, the theory of unsteady waves on the current is reviewed using nonlinear shallow-water equations and the van der Pol averaging method. Their motions naturally split into a ‘balanced’ component satisfying the Margules geostrophic relation and an equally large ‘unbalanced’ component, in which there is horizontal divergence and ageostrophic vorticity. The latter is responsible for nonlinear oscillations in the current on a time scale f−1, which have been observed in the atmosphere and field experiments. Their magnitude is mainly determined by the initial potential energy in relation to that of the current and is proportional to the ratio \it Bu−−−−−√=LR/R0, where LR=NH0/f is the Rossby deformation radius and R0 is the initial radius. The effect of slope friction also prevents the formation of a steady front. From the analysis it is concluded that a weak mean radial flow must be driven by the ageostrophic oscillations, preventing the mean front speed UF from halting sharply at ftF∼1. Depending on the initial value of LR/R0, physical arguments show that UF decreases slowly in proportion to (ftF)−1/2, i.e. UF/UF0=F(ftF,\it Bu). Thus the front only tends to the geostrophic asymptotic state of zero radial velocity very slowly (i.e. as ftF→∞) for finite values of LR/R0. However, as LR/R0→0, it reaches this state when ftF∼1. This analysis of the overall nonlinear behaviour of the gravity current is consistent with two two-dimensional non-hydrostatic (Navier–Stokes) and axisymmetric hydrostatic (shallow-water) Eulerian numerical simulations of the varying form of the rotating gravity current. When the effect of surface friction is considered, it is found that the mean movement of the front is significantly slowed. Furthermore, the oscillations with angular frequency f and the slow growth of the radius, when ftF≥1, are consistent with recent experiments

El Cambiante Perfil de las Ciencias Sociales: Continuidad y Renovación de la Sociología en el Siglo Veinte

La preeminencia de las discusiones teóricas y metodológicas en las Ciencias Sociales, hace difícil reconocer las tendencias de cambio más importantes en esas disciplinas. Para obviar esa dificultad, de acuerdo a las posturas historicistas de la Nueva Filosofía de la Ciencia, la práctica concreta de cada disciplina podría revisarse para encontrar en ella las transformaciones de mayor relevancia. Tomando como ilustración el caso de la Sociología durante el siglo veinte, es posible apreciar que esta ciencia social ha experimentado una significativa transformación en el perfil de su actividad investigadora. Los cultivadores de la disciplina en ese período pasaron desde la adhesión irrestricta a un modelo cientificista inspirado por las Ciencias Naturales a un enfoque dotado de mayor apertura hacia otros estilos de trabajo. Las nuevas definiciones acerca del objeto de la disciplina, de sus formas de elaboración teórica y estrategias metodológicas, de las relaciones con la aplicación del conocimiento, e incluso de los modos de comunicación de ese conocimiento, configuran un modelo emergente que está cambiando radicalmente el rostro de esta cienci

Historiographical perspectives about food in Ancient Greece

El estudio de la alimentación en el mundo antiguo ha sido uno de los aspectos que más han llamado la atención en la investigación moderna. No obstante, ante la elevada cantidad de trabajos que se han realizado, consideramos interesante ofrecer una perspectiva general del estado de la cuestión e indicar las principales tendencias y corrientes interpretativas acerca de la relación entre el individuo, el alimento y la sociedad del mundo griego.The study of food in the ancient world has been one of the most appealing aspects for the modern researchers. Nevertheless, the huge quantity of works related with this problematic has lead us to raise the question about the convenience of offering a general perspective about the main currents of study related with the relationship between the individual, the food and the ancient Greek society.España. Ministerio de Ciencia e Innovación HAR2010-1575

Javier García Liendo. El intelectual y la cultura de masas. Argumentos latinoamericanos en torno a Ángel Rama y José María Arguedas. West Lafayette: Purdue UP, 2017.

Review of Javier García Liendo. El intelectual y la cultura de masas. Argumentos latinoamericanos en torno a Ángel Rama y José María Arguedas. West Lafayette, Indiana: Purdue University Press, 2017

Sustainable Use of Soils and Water: The Role of Environmental Land Use Conflicts

This book on the sustainable use of soils and water addressed a variety of issues related to the utopian desire for environmental sustainability and the deviations from this scene observed in the real world. Competing interests for land are frequently a factor in land degradation, especially where the adopted land uses do not conform with the land capability (the natural use of soil). The concerns of researchers about these matters are presented in the articles comprising this Special Issue book. Various approaches were used to assess the (im)balance between economic profit and environmental conservation in various regions, in addition to potential routes to bring landscapes back to a sustainable status being disclosed

Experiments in identification and control of flexible-link manipulators

Interest in the study of flexible-link manipulators for space-based applications has risen strongly in recent years. Moreover, numerous experimental results have appeared for the various problems in the modeling, identification and control of such systems. Nevertheless, relatively little literature has appeared involving laboratory verification of tuning controllers for certain types of realistic flexible-link manipulators. Specifically flexible-link manipulators which are required to maintain endpoint accuracy while manipulating loads that are possibly unknown and varying as they undergo disturbance effects from the environment and workspace. Endpoint position control of flexible-link manipulators in these areas are discussed, with laboratory setups consisting of one and two-link manipulators