Effect of the Coriolis Force on the Hydrodynamics of Colliding Wind Binaries

Using fully three-dimensional hydrodynamic simulations, we investigate the effect of the Coriolis force on the hydrodynamic and observable properties of colliding wind binary systems. To make the calculations tractable, we assume adiabatic, constant velocity winds. The neglect of radiative driving, gravitational deceleration, and cooling limit the application of our models to real systems. However, these assumptions allow us to isolate the effect of the Coriolis force, and by simplifying the calculations, allow us to use a higher resolution (up to 640^3) and to conduct a larger survey of parameter space. We study the dynamics of collidng winds with equal mass loss rates and velocities emanating from equal mass stars on circular orbits, with a range of values for the ratio of the wind to orbital velocity. We also study the dynamics of winds from stars on elliptical orbits and with unequal strength winds. Orbital motion of the stars sweeps the shocked wind gas into an Archimedean spiral, with asymmetric shock strengths and therefore unequal postshock temperatures and densities in the leading and trailing edges of the spiral. We observe the Kelvin-Helmholtz instability at the contact surface between the shocked winds in systems with orbital motion even when the winds are identical. The change in shock strengths caused by orbital motion increases the volume of X-ray emitting post-shock gas with T > 0.59 keV by 63% for a typical system as the ratio of wind velocity to orbital velocity decreases to V_w/V_o = 2.5. This causes increased free-free emission from systems with shorter orbital periods and an altered time-dependence of the wind attenuation. We comment on the importance of the effects of orbital motion on the observable properties of colliding wind binaries.Comment: 12 pages, 17 figures, accepted for publication in Ap

Using real options for an eco-friendly design of water distribution systems

Copyright © 2015 IWA Publishing. The definitive peer-reviewed and edited version of this article is published in Journal of Hydroinformatics volume 17 (1), pp. 20-35 (2015), DOI 10.2166/hydro.2014.122 and is available at www.iwapublishing.com.This paper presents a real options approach to handling uncertainties associated with the long-term planning of water distribution system development. Furthermore, carbon emissions associated with the installation and operation of water distribution networks are considered. These emissions are computed by taking an embodied energy approach to the different materials used in water networks. A simulated annealing heuristic is used to optimise a flexible eco-friendly design of water distribution systems for an extended life horizon. This time horizon is subdivided into different time intervals in which different possible decision paths can be followed. The proposed approach is applied to a case study and the results are presented according to a decision tree. Lastly, some comparisons and results are used to demonstrate the quality of the results of this approach.Programa Operacional Factores de Competitividade – COMPETEFCT – Fundação para a Ciência e Tecnologi

The Operation of Multiple Reservoir Systems

The purpose of this workshop was to discuss, compare and evaluate various methods of operating, and determining operating policies for multi-purpose, multiple reservoir systems. While total reservoir capacities are known, the allocation of various storage volume zones within the reservoirs to various purposes, such as water supply or flood control, may vary in time and be dependent on reservoir operating policy. In the guidelines for preparation of the papers included in this volume, it was stressed that discussion should cover reservoir operation for all possible hydrological situations, i.e., in periods of flood, normal flow, and drought conditions. The importance of procedures used to determine when an extreme situation (such as drought), begins and ends, was emphasized, especially with respect to possible changes in reservoir operation. The participants were requested to discuss how operating policies might differ, depending on whether the reservoirs are in series or are parallel. Also, they were requested to distinguish between operation of "large" over-year storage reservoirs and "small" within-year storage reservoirs. If short-term hydrological forecasting and real-time control models were to be used, the workshop discussion would consider how these could be used together with long-term operating policies. Some 30 participants from 13 countries presented 17 papers at the workshop, all of which are included in these proceedings. The first nine provide an overview of how multiple reservoir systems are operated in certain countries. The remaining papers report in more detail on diverse case studies and provide discussion of some specific issues related to the subject of the workshop

Loghub: A Large Collection of System Log Datasets towards Automated Log Analytics

Logs have been widely adopted in software system development and maintenance because of the rich system runtime information they contain. In recent years, the increase of software size and complexity leads to the rapid growth of the volume of logs. To handle these large volumes of logs efficiently and effectively, a line of research focuses on intelligent log analytics powered by AI (artificial intelligence) techniques. However, only a small fraction of these techniques have reached successful deployment in industry because of the lack of public log datasets and necessary benchmarking upon them. To fill this significant gap between academia and industry and also facilitate more research on AI-powered log analytics, we have collected and organized loghub, a large collection of log datasets. In particular, loghub provides 17 real-world log datasets collected from a wide range of systems, including distributed systems, supercomputers, operating systems, mobile systems, server applications, and standalone software. In this paper, we summarize the statistics of these datasets, introduce some practical log usage scenarios, and present a case study on anomaly detection to demonstrate how loghub facilitates the research and practice in this field. Up to the time of this paper writing, loghub datasets have been downloaded over 15,000 times by more than 380 organizations from both industry and academia.Comment: Dateset available at https://zenodo.org/record/322717

Biosensors to diagnose Chagas disease: A review

International audienceChagas disease (CD), which mostly affects underprivileged people, has turned into one 9 of Latin America's main public health problems. Prevention of the disease requires early diagnosis, 10 initiation of therapy, and regular blood monitoring of the infected individual. However, the majority 11 of the infections go undiagnosed because of general mild symptoms and lack of access to medical 12 care. Therefore, more affordable and accessible detection technologies capable of providing early 13 diagnosis and parasite load measurements in settings where CD is prevalent are needed to enable 14 enhanced intervention strategies. This review discusses currently available detection technologies 15 and emerging biosensing technologies for a future application to CD. Even if biosensing 16 technologies still require further research efforts to develop portable systems, we arrive to the 17 conclusion that biosensors could improve diagnosis and the patients' treatment follow-up, in terms 18 of rapidity, small sample volume, high integration, ease of use, real-time and low cost detection 19 compared to current conventional technologies. 2

Dynamic simulation of energy management control functions in VAV-HVAC systems

Energy Management Control Systems (EMCS) in buildings can help reduce the energy consumption while maintaining satisfactory occupant environment. The energy management control strategies have to be developed taking into consideration the thermal behavior of buildings and the thermal, operational characteristics of mechanical systems in buildings. In this thesis, improved EMC algorithms are developed and implemented in a variable air volume HVAC (VAV-HVAC) system. Firstly, HVAC system component dynamic models are developed. Then, several individual improved EMC functions (outdoor air economical cycle, programmed start time, programmed stop time, reset supply air temperature setpoint, occupied time control strategies) are developed and evaluated. Finally, real-time simulations are carried out, in which the results of implementing above improved EMC functions are compared with those of conventional EMC functions. This comparison reveals that the HVAC system with each independent improved function can save 7% to 12% energy. Simulation results also show that a VAV-HVAC system employing all EMC algorithms can save between 14% to 15% energy during summer and winter operation. An optimization methodology to compute optimal setpoints is proposed. These optimal setpoints were used as tracking signals to PI and adaptive control strategies developed in this thesis. The use of optimal setpoints resulted in 17% energy savings. A real-time supervisory EMC platform is developed in which the developed EMC algorithms are embedded. Simulation results showing the typical operation of a VAV-HVAC system under supervisory EMC system are presented

Gibbs entropy and irreversible thermodynamics

Recently a number of approaches has been developed to connect the microscopic dynamics of particle systems to the macroscopic properties of systems in nonequilibrium stationary states, via the theory of dynamical systems. This way a direct connection between dynamics and Irreversible Thermodynamics has been claimed to have been found. However, the main quantity used in these studies is a (coarse-grained) Gibbs entropy, which to us does not seem suitable, in its present form, to characterize nonequilibrium states. Various simplified models have also been devised to give explicit examples of how the coarse-grained approach may succeed in giving a full description of the Irreversible Thermodynamics. We analyze some of these models pointing out a number of difficulties which, in our opinion, need to be overcome in order to establish a physically relevant connection between these models and Irreversible Thermodynamics.Comment: 19 pages, 4 eps figures, LaTeX2