Towards a new ITU-T recommendation for subjective methods evaluating gaming QoE

This paper reports on activities in Study Group 12 of the International Telecommunication Union (ITU-T SG12) to define a new Recommendation on subjective evaluation methods for gaming Quality of Experience (QoE). It first resumes the structure and content of the current draft which has been proposed to ITU-T SG12 in September 2014 and then critically discusses potential gaming content and evaluation methods for inclusion into the upcoming Recommendation. The aim is to start a discussion amongst experts on potential evaluation methods and their limitations, before finalizing a Recommendation. Such a recommendation might in the end be applied by non -expert users, hence wrong decisions in the evaluation design could negatively affect gaming QoE throughout the evaluation

A confined-unconfined aquifer model for subglacial hydrology

Modeling the evolution of subglacial channels underneath ice sheets is an urgent need for ice sheet modellers, as channels affect sliding velocities and hence ice discharge. Owing to very limited observations of the subglacial hydraulic system, the development of physical models is quite restricted. Subglacial hydrology models are currently taking two different approaches: either modeling the development of a network of individual channels or modeling an equivalent porous layer where the channels are not resolved individually but modeled as a diffusive process, adjusted to reproduce the characteristic of an efficient system. Here, we use the latter approach, improving it by using a confined-unconfined aquifer model (CUAS), that allows the system to run dry in absence of sufficient water input. This ensures physical values for the water pressure. Channels are represented by adjusting the permeability and storage of the system according to projected locations of channels. The evolution of channel positions is governed by a reduced complexity model that computes channel growths according to simple rules (weighted random walks descending the hydraulic potential). As a proof of concept we present the results of the evolution of the hydrological system over time for a simple artificial glacier geometr

CO2-brine-mineral Interfacial Reactions Coupled with Fluid Phase Flow

AbstractDue to their widespread occurrence and large capacities, deep geological saline formations are regarded as an important storage option for anthropogenic CO2. Injection of supercritical CO2 into such a formation will result in a multi-phase flow porous media system. Both the CO2 and brine phase compositions are influenced by multiphase flow and mass transport processes as well as by interfacial reactions (gas dissolution, water vaporization, mineral dissolution and precipitation). For a model based assessment of CO2 storage, most simulation codes apply an operator-splitting approach to solve the coupled problem, where multi-phase flow and geochemical reactions are handled by separate routines sequentially. This approach relies on two approximations: (I) the dissolution of CO2 in the brine, which is usually quantified by the multiphase flow routine by using an equation of state approach, is treated as instantaneous, and (II) the amount of CO2 consumed during geochemical reactions quantified by the reaction routine is small compared to the amount dissolved, as during geochemical reactions CO2 is not resupplied from the CO2 phase by dissolution.To investigate these two approximations, the multiphase flow and multi-component reactive transport simulator OpenGeoSys was extended and now allows to simulate mineral-brine as well as the brine-CO2 interface reactions either kinetically controlled or by using an equilibrium approach, and to account for the presence of a CO2 phase during brine-mineral reactions. The code is used here to investigate a simple gas-liquid-solid phase (CO2-H2O- CaCO3) system controlled by fast reaction rates. Batch reaction calculations are performed for the multiphase system at various temperature and pressure conditions for different initial CO2 saturations. Two methods of approximating the equilibrium state of the system by an operator splitting approach are compared. The first method determines the gas-liquid and solid-liquid equilibria in separate subsequent steps. At reservoir conditions relevant for storage of CO2 (323K, 100bar) and for high CO2 saturations the error in predicted CO2 concentrations in the liquid phase reaches up to -2%. This error can be reduced to less than -0.5% by the second method, where a conjoint gas-liquid-solid equilibrium is accounted for in the reaction calculations. Accordingly, the latter approach should preferably be employed in multiphase flow reactive transport modeling based on operator splitting techniques

Large-scale Modelling of Subglacial Hydrology

Subglacial hydrology is a key component in ice sheet dynamics and controls the sliding of ice sheets. Modelling the integrated system between ice dynamics and subglacial hydrology is essential for understanding current changes in the system and projecting future evolution of ice sheets and their contribution to sea level rise. The recent acceleration of mass loss of the Greenland ice sheet can be largely attributed to dynamic thinning at the ice margin, where hydrologic processes play a significant role in the speed-up of outlet glaciers. Models of subglacial hydrology recently have progressed to incorporate multiple components of the drainage system and are able to represent observed seasonal evolution of an efficient drainage system during the melt season, but the application of models on a continental scale remains a challenge. This doctoral thesis analyzes different approaches to model the subglacial hydrology and its interaction with the ice flow in respect to their ability to be applied to large domains. Two different models are developed and analyzed. A balance flux model coupled to the ice dynamics model SICOPOLIS is used to study the effect of subglacial water on the Eurasian ice sheet, applied to the simulation of future sea level contribution of Greenland where it reveals that the effect of subglacial discharge on submarine melting is comparable to increased ocean warming. Additionally, this model is utilized in the study of subglacial lakes at Recovery Glacier, Antarctica. The second model is an equivalent aquifer model which describes the water flow in a porous layer adapted to exhibit the properties of the complex drainage system. The evolution of the system is achieved by locally adjusting the transmissivity. It is shown that this approach leads to realistic pressure and discharge distributions which compare well with more sophisticated models, while keeping computational costs low

COLLOIDAL NANOMATERIALS FOR LIFE SCIENCE APPLICATIONS - FABRICATION AND PHYSIOCHEMICAL STUDIES

Ph.DDOCTOR OF PHILOSOPH

Complex basal conditions influence flow at the onset of the Northeast Greenland Ice Stream

The onset and high upstream ice surface velocities of the North East Greenland Ice Stream (NEGIS) are not yet well reproducible in ice sheet models. A major uncertainty remains the understanding of basal sliding and a parameterization of basal conditions. In this study, we assess the slow-flowing part of the NEGIS in a systematic analysis of the basal conditions and investigate the increased ice flow. We analyze the spectral basal roughness in correlation with basal return power from an airborne radar survey with AWIs ultra-wideband radar system in 2018 and compare our results with current ice flow geometry and ice surface flow. We observe a roughness anisotropy where the ice stream widens, indicating a change from a smooth and soft bed to a harder bedrock as well as the evolution of elongated subglacial landforms. In addition, at the upstream part of the NEGIS we find a clear zoning of the bedrock return power, indicating an increased water content at the base of the ice stream. At the downstream part, we observe an increased bedrock return power throughout the entire width of the ice stream and outside its margins, indicating enhanced melting and the distribution of basal water beyond the shear zones