The motion of an axisymmetric body falling in a tube at moderate Reynolds numbers

This study concerns the rectilinear and periodic paths of an axisymmetric solid body (short-length cylinder and disk of diameter d and thickness h) falling in a vertical tube of diameter D. We investigated experimentally the influence of the confinement ratio (S=d/D<0.8) on the motion of the body, for different aspect ratios (χ=d/h=3, 6 and 10), Reynolds numbers (80<Re<320) and a density ratio between the fluid and the body close to unity. For a given body, the Reynolds number based on its mean vertical velocity is observed to decrease when S increases. The critical Reynolds number for the onset of the periodic motion decreases with S in the case of thin bodies (χ=10), whereas it appears unaffected by S for thicker bodies (χ=3 and 6). The characteristics of the periodic motion are also strongly modified by the confinement ratio. A thick body (χ=3) tends to go back to a rectilinear path when S increases, while a thin body (χ=10) displays oscillations of growing amplitude with S until it touches the tube (at about S=0.5). For a given aspect ratio, however, the amplitudes of the oscillations follow a unique curve for all S, which depends only on the relative distance of the Reynolds number to the threshold of path instability. In parallel, numerical simulations of the wake of a body held fixed in a uniform confined flow were carried out. The simulations allowed us to determine in this configuration the effect of the confinement ratio on the thresholds for wake instability (loss of axial symmetry at Rec₁ and loss of stationarity at Rec₂) and on the maximal velocity Vw in the recirculating region of the stationary axisymmetric wake. The evolution with χ and S of Vw at Rec₁ was used to define a Reynolds number Re*. Remarkably, for a freely moving body, Re* remains almost constant when S varies, regardless of the nature of the path

SRI analysis and asset management : independent or convergent ? : A field study on the French market

This article analyzes how the actual and expected future activities of French Socially Responsible Investment (SRI) analysts may reveal a convergence process between SRI decisions and traditional financial investment decisions, that is a form of "mainstreaming" of SRI processes, by asking the SRI analysts themselves how their work has evolved and how they perceive their positioning in the asset management sector. We present the results of a field survey on the composition and activities of French SRI analysts' teams of large institutional investors and asset managers in France in 2009. We show that the convergence towards the mainstream financial analysts seems to be clearly engaged. However, the SRI domain is still emerging and remains very fragmented leading to a wide heterogeneity of practices and positioning in the respective organizations. This is interpreted as a clear sign of a transition phase.Field survey ; French Asset Management industry ; Mainstreaming ; Socially Responsible Investments (SRI)

SRI Analysis and Asset Management: Independent or Convergent? A Field Study on the French Market

This article analyzes how the actual and expected future activities of French Socially Responsible Investment (SRI) analysts may reveal a convergence process between SRI decisions and traditional financial investment decisions, that is a form of “mainstreaming” of SRI processes, by asking the SRI analysts themselves how their work has evolved and how they perceive their positioning in the asset management sector. We present the results of a field survey on the composition and activities of French SRI analysts’ teams of large institutional investors and asset managers in France in 2009. We show that the convergence towards the mainstream financial analysts seems to be clearly engaged. However, the SRI domain is still emerging and remains very fragmented leading to a wide heterogeneity of practices and positioning in the respective organizations. This is interpreted as a clear sign of a transition phase.Field survey; French Asset; Management industry; Mainstreaming; Socially Responsible Investments (SRI)

Model Checking One-clock Priced Timed Automata

We consider the model of priced (a.k.a. weighted) timed automata, an extension of timed automata with cost information on both locations and transitions, and we study various model-checking problems for that model based on extensions of classical temporal logics with cost constraints on modalities. We prove that, under the assumption that the model has only one clock, model-checking this class of models against the logic WCTL, CTL with cost-constrained modalities, is PSPACE-complete (while it has been shown undecidable as soon as the model has three clocks). We also prove that model-checking WMTL, LTL with cost-constrained modalities, is decidable only if there is a single clock in the model and a single stopwatch cost variable (i.e., whose slopes lie in {0,1}).Comment: 28 page

Pure Nash Equilibria in Concurrent Deterministic Games

We study pure-strategy Nash equilibria in multi-player concurrent deterministic games, for a variety of preference relations. We provide a novel construction, called the suspect game, which transforms a multi-player concurrent game into a two-player turn-based game which turns Nash equilibria into winning strategies (for some objective that depends on the preference relations of the players in the original game). We use that transformation to design algorithms for computing Nash equilibria in finite games, which in most cases have optimal worst-case complexity, for large classes of preference relations. This includes the purely qualitative framework, where each player has a single omega-regular objective that she wants to satisfy, but also the larger class of semi-quantitative objectives, where each player has several omega-regular objectives equipped with a preorder (for instance, a player may want to satisfy all her objectives, or to maximise the number of objectives that she achieves.)Comment: 72 page

On Termination for Faulty Channel Machines

A channel machine consists of a finite controller together with several fifo channels; the controller can read messages from the head of a channel and write messages to the tail of a channel. In this paper, we focus on channel machines with insertion errors, i.e., machines in whose channels messages can spontaneously appear. Such devices have been previously introduced in the study of Metric Temporal Logic. We consider the termination problem: are all the computations of a given insertion channel machine finite? We show that this problem has non-elementary, yet primitive recursive complexity

Average-energy games

Two-player quantitative zero-sum games provide a natural framework to synthesize controllers with performance guarantees for reactive systems within an uncontrollable environment. Classical settings include mean-payoff games, where the objective is to optimize the long-run average gain per action, and energy games, where the system has to avoid running out of energy. We study average-energy games, where the goal is to optimize the long-run average of the accumulated energy. We show that this objective arises naturally in several applications, and that it yields interesting connections with previous concepts in the literature. We prove that deciding the winner in such games is in NP inter coNP and at least as hard as solving mean-payoff games, and we establish that memoryless strategies suffice to win. We also consider the case where the system has to minimize the average-energy while maintaining the accumulated energy within predefined bounds at all times: this corresponds to operating with a finite-capacity storage for energy. We give results for one-player and two-player games, and establish complexity bounds and memory requirements.Comment: In Proceedings GandALF 2015, arXiv:1509.0685

ECONOMIC RETURNS TO THE BOLL WEEVIL ERADICATION PROGRAM

The economic viability of the Boll Weevil Eradication program in Alabama, Florida, and Georgia is assessed based on a five-year survey of producers. Results indicate the program increases yield 100 pounds per acre. This implies a 19 percent internal rate of return for producers over a ten year period.Cotton, Pest management, Regional pest control, Crop Production/Industries,