HPC Cloud for Scientific and Business Applications: Taxonomy, Vision, and Research Challenges

High Performance Computing (HPC) clouds are becoming an alternative to on-premise clusters for executing scientific applications and business analytics services. Most research efforts in HPC cloud aim to understand the cost-benefit of moving resource-intensive applications from on-premise environments to public cloud platforms. Industry trends show hybrid environments are the natural path to get the best of the on-premise and cloud resources---steady (and sensitive) workloads can run on on-premise resources and peak demand can leverage remote resources in a pay-as-you-go manner. Nevertheless, there are plenty of questions to be answered in HPC cloud, which range from how to extract the best performance of an unknown underlying platform to what services are essential to make its usage easier. Moreover, the discussion on the right pricing and contractual models to fit small and large users is relevant for the sustainability of HPC clouds. This paper brings a survey and taxonomy of efforts in HPC cloud and a vision on what we believe is ahead of us, including a set of research challenges that, once tackled, can help advance businesses and scientific discoveries. This becomes particularly relevant due to the fast increasing wave of new HPC applications coming from big data and artificial intelligence.Comment: 29 pages, 5 figures, Published in ACM Computing Surveys (CSUR

On fair cost facility location games with non-singleton players

In the fair cost facility location game, players control terminals and must open and connect each terminal to a facility, while paying connection costs and equally sharing the opening costs associated with the facilities it connects to. In most of the literature, it is assumed that each player control a single terminal. We explore a more general version of the game where each player may control multiple terminals. We prove that this game does not always possess pure Nash equilibria, and deciding whether an instance has equilibria is NP-Hard, even in metric instances. Furthermore, we present results regarding the efficiency of equilibria, showing that the price of stability of this game is equal to the price of anarchy, in both uncapacitated and capacitated settings

On the effectiveness of connection tolls in fair cost facility location games

We investigate the effectiveness of tolls to reduce the inefficiency of Nash equilibria in the classical fair cost facility location game. In this game, every terminal corresponds to a selfish player who wants to connect to some facility at minimum cost. The cost of a player is determined by the connection cost to the chosen facility plus an equal share of its opening cost. We are interested in the problem of imposing tolls on the connections to induce a socially optimal Nash equilibrium such that the total amount of tolls is minimized. It turns out that this problem is challenging to solve even for simple special cases. We provide polynomial-time algorithms for (i) instances with two facilities, and (ii) instances with a constant number of facilities arranged as a star. Our algorithm for (ii) exploits a relation between our tolling problem and a novel bipartite matching problem without crossings, which we prove to be NP-hard

Coastal aquifer hydrodynamics and salinity in response to the tide: case study in Lisbon, Portugal

The variability in dynamics and salinity of the coastal alluvial aquifer on which the city of Lisbon is located was evaluated. Such an evaluation was based on the analysis of level and groundwater electrical conductivity fluctuations depending on the tide in the Tagus River. The results obtained made it possible to recognize three sectors. First, a littoral sector where the variations in level and salinity are larger on the coast and decrease towards the innermost sections of the alluvial fan. Second, a sector close to the docks where there is greater dynamic and salinity variability than in the coastal sectors, as the excavations of the docks favour the tidal propagation towards the aquifer. And third, a sector located towards the apex of the alluvial fan associated with the dynamics of the stormwater channel. In this sector, the largest periodical water table fluctuations in the aquifer occur, since the freshwater that cannot drain towards the river enters the aquifer at high tide, causing a slight decrease in salinity content. On the basis of these results, conceptual models of hydrogeological behaviour were used to describe the spatial and temporal variations in the hydrodynamic and salinity characteristics of groundwater.Facultad de Ciencias Naturales y Muse

Background

Estimates of adherence to treatment of vivax malari

Permeability coefficients and vapor pressure determination for fragrance materials

Objective This study aims to correlate new experimental data relevant to the description of the combined evaporation/permeation process of a perfume applied onto the skin. Methods The vapor pressure data was measured by thermogravimetric analysis (TG‐DTA). The Antoine constants and the Clarke & Glew parameters were determined for the same set of fragrance molecules to describe its low vapor pressures at new temperature ranges. The permeability coefficient of a set of 14 fragrance molecules in ethanolic solution was determined by Franz diffusion cell experiments, using porcine skin. The samples were analyzed by gas chromatography with a flame ionization detector (GC/FID) and high‐performance liquid chromatography with UV visible detector (HPLC/UV). A QSAR model was proposed to correlate the experimental data. Results The Antoine constants were determined and presented low standard deviations. The Clarke & Glew physically significant parameters were obtained along with its statistical analysis. The fitting is good since the magnitude order is in accordance with the literature, associated with the low correlation between the estimated parameters and low standard deviations. The presented correlation, based on a mixture using only ethanol as solvent, showed better results than previous QSAR models with a standard relative deviation (σr) of 0.190, a standard error (SE) of 0.397, and a determination coefficient (R2) of 0.7786. Conclusion The dataset is still small compared to larger and more general QSAR models; however, it is much more specific as to the type of solvent and class of materials studied. This work represents an advance for the modeling of the perfume diffusion process since it specifies important properties that until then had been treated in a more general way.info:eu-repo/semantics/acceptedVersio

Enhanced oil recovery under laboratory conditions using biosurfactant-producing microorganisms

Oil recovery comprises a primary phase, which produces oil using the natural pressure drive of the reservoir, and a secondary phase, which includes the injection of water to improve the flow of oil to the wellhead [1,2]. While primary recovery produces 5-10% of the original oil in place, recovery efficiencies in the secondary stage vary from 10% to 40% [1]. Most of the unrecovered oil (up to two-thirds of the total oil reserves) is trapped in the reservoir pores by high capillary forces [2]. Microbial Enhanced Oil Recovery (MEOR) is a tertiary oil recovery process where microorganisms and their metabolites are used to retrieve unrecoverable oil from mature reservoirs. Stimulation of biosurfactant production by indigenous or injected microorganisms can reduce the capillary forces that retain the oil into the reservoir. In this work, a sand pack column model was designed to simulate the oil recovery operations in oil reservoirs and evaluate the mobilization of residual oil by microorganisms. Three Bacillus subtilis strains (309, 311 and 573), previously isolated from crude oil samples, were used in this study. They grow and produce extracellular biosurfactants at 40ºC under anaerobic conditions in medium supplemented with hydrocarbons. Biosurfactants produced by those isolates reduce the surface tension of water from 72 to 30 mN/m, exhibit emulsifying activity and are not affected by exposure to high temperatures (121ºC) which makes them good candidates for application in biosurfactant mediated MEOR. Acrylic columns (250 ml) packed with acid washed sand were first flooded with water, after that saturated with paraffin, and then washed with water to remove the excess of paraffin. Afterwards, the isolates were injected into the columns with the optimized medium and incubated at 40ºC. After 14 days, the columns were flooded with water and the additional oil recovery (AOR) was calculated as the percentage of paraffin recovered. AOR using B. subtilis 309, 311 and 573 was 35.0 ± 1.0 %, 23.5 ± 1.2 % and 19.8 ± 1.9 %, respectively. The results obtained suggest that stimulation of biosurfactant production by these strains in the oil reservoir can contribute to mobilize entrapped oi

Isolation and study of microorganisms from oil samples for application in Microbial Enhanced Oil Recovery

"Author's personal copy"Microbial Enhanced Oil Recovery (MEOR) is potentially useful to increment oil recovery from a reservoir beyond primary and secondary recovery operations using microorganisms and their metabolites. Stimulation of bacterial growth for biosurfactant production and degradation of heavy oil fractions by indigenous microorganisms can enhance the fluidity and reduce the capillary forces that retain the oil into the reservoir. MEOR offers major advantages over conventional EOR, namely low energy consumption and independence of the price of crude oil. In this work, the isolation and identification of microorganisms capable of producing biosurfactants and promote degradation of long-chain n-alkanes under conditions existent in oil reservoirs were addressed. Among the isolated microorganisms, five Bacillus strains were able to produce extracellular biosurfactants at 40 C under anaerobic conditions in medium supplemented with hydrocarbons. Three isolates were selected as the higher biosurfactant producers. The obtained biosurfactants reduced the surface tension of water from 72 to 30 mN/m, exhibited emulsifying activity and were not affected by exposure to high temperatures (121 C). These characteristics make them good candidates for use at conditions usually existing in oil reservoirs. Furthermore, it was here shown for the first time that Bacillus strains were able to degrade large alkyl chains and reduce the viscosity of hydrocarbon mixtures under anaerobic conditions. The results obtained show that the isolated microorganisms are promising candidates for the development of enhanced oil recovery processes.This work was supported by PARTEX OIL AND GAS. Jorge F. B. Pereira acknowledges the financial support from Fundacao para a Ciencia e a Tecnologia through doctoral research grant SFRH/BD/60228/2009

Liquid Mixtures Involving Hydrogenated and Fluorinated Chains: (p, ρ, T, x) Surface of (Ethanol + 2,2,2-Trifluoroethanol), Experimental and Simulation

The effect of mixing hydrogenated and fluorinated molecules that simultaneously interact through strong hydrogen bonding was investigated: (ethanol + 2,2,2-trifluoroethanol) binary mixtures were studied both experimentally and by computer simulation. This mixture displays a very complex behavior when compared with mixtures of hydrogenated alcohols and mixtures of alkanes and perfluoroalkanes. The excess volumes are large and positive (unlike those of mixtures of hydrogenated alchools), while the excess enthalpies are large and negative (contrasting with those of mixtures of alkanes and perfluoroalkanes). In this work, the liquid density of the mixtures was measured as a function of composition, at several temperatures from 278.15 to 353.15 K and from atmospheric pressure up to 70 MPa. The corresponding excess molar volumes, compressibilities, and expansivities were calculated over the whole (p, ρ, T, x) surface. In order to obtain molecular level insight, the behavior of the mixture was also studied by molecular dynamics simulation, using the OPLS-AA force field. The combined analysis of the experimental and simulation results indicates that the peculiar phase behavior of this system stems from a balance between the weak dispersion forces between the hydrogenated and fluorinated groups and a preferential hydrogen bond between ethanol and 2,2,2-trifluoroethanol. Additionally, it was observed that a 25% reduction of the F−H dispersive interaction in the simulations brings agreement between the experimental and simulated excess enthalpy but produces no effect in the excess volumes. This reveals that the main reason causing the volume increase in these systems is not entirely related to the weak dispersive interactions, as it is usually assumed, and should thus be connected to the repulsive part of the intermolecular potential