Автоматизация процесса выбора лекарственных препаратов на основе экспертных знаний

Материалы XX Междунар. науч.-техн. конф. студентов, аспирантов и молодых ученых, Гомель, 23–24 апр. 2020 г

Topographic, spectral and thermal inertia analysis of interior layered deposits in Iani Chaos, Mars

We present an analysis of Interior Layered Deposits (ILDs) in Iani Chaos using visible, infrared, hyperspectral and topographic datasets acquired by instruments aboard NASA’s Mars Global Surveyor, Mars Odyssey, Mars Reconnaissance Orbiter and ESA’s Mars Express spacecraft. We focus on four main regions where ILDs outcrop in Iani Chaos. Deposits span a ∼2 km range of elevations and exhibit moderate to high albedos, layering at sub-decameter scales, thermal inertias of 300–800 J m−2 K−1 s−1/2 and a range of surface textures. Thermal inertia calculations use slope and azimuth corrections from High Resolution Stereo Camera (HRSC) topography. Spectral features in hyperspectral data acquired by NASA’s Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) suggest that gypsum (CaSO4·2H2O) and kieserite (MgSO4·H2O) are present in most deposits. We report absorptions typically exhibited by alunite (KAl3(SO4)2(OH)6) and jarosite View the MathML sourceKFe33+(OH)6(SO4)2 as well as a number of features that may be attributable to a wide range of mono- and polyhydrated sulphates and hydroxyl-sulphates bearing a number of cations, including Mg2+, Fe2+, Fe3+ and Ca2+. Spectral features similar to those of ammonium sulphates may also be present. Analysis of a HiRISE stereo DEM shows planar layering in some ILDs, favouring a sedimentary deposition origin. Stratigraphic mapping of hydration and sulphate spectral features in flat ILDs in central Iani Chaos suggest that specific elevation intervals in the stratigraphic column were subject to different levels of hydration, perhaps during episodes of water table elevation. This is consistent with formation models for ILDs and hydrological modelling. Geomorphic characteristics of deposits in northern and southern Iani Chaos suggest their relatively recent exhumation and significant erosion by aeolian processes. We conclude that any formation theory for ILDs in Iani Chaos should support mechanisms for different hydration states at different stratigraphic elevations and subsequent significant aeolian erosion, burial and re-exposure

Resource Allocation in Operator-owned Content Delivery Systems

Live and on-demand video content have become the most important source of network traffic in mobile and fixed networks in recent years. In order to be able to efficiently deliver the increasing amount of video content, network operators have started to deploy caches and operator-owned CDNs. These solutions do not only reduce the amount of transit traffic of the operators but they may also improve the customers' quality of experience, through bringing the video content closer to customers. Nevertheless, their efficiency is determined by the algorithms and protocols used to allocate resources, both in terms of storage and bandwidth. The work in this thesis proposes and analyses algorithms for the allocation of these two resources for operator-owned content management systems. In the first part of the thesis we consider a cache maintained by a single network operator. We formulate the problem of content caching in a mobile backhaul as an integer program and we show that there exists an efficient centralized solution to the problem. Due to the prohibitive space complexity of the centralized algorithm, we propose two distributed approximations based on local information on the content demands. We then consider the problem of managing cache bandwidth so as to minimize the traffic cost of content delivery and we propose various approximations of the optimal stationary policy. We then consider the interaction among content management systems maintained by different network operators. First, we consider the problem of selfish replication on a graph as a model of network operators that use their caches to prefetch popular content, and try to leverage their peering agreements so as to minimize the traffic through their transit providers. We design efficient distributed algorithms that compute a stable content allocation through selfish myopic updates of content allocations at different network operators. We show that, if the cost function is neighbor-specific, network operators need bilateral payments to compute a stable content allocation that is individually rational. We then consider the problem of coordinated caching in a network of autonomous systems engaged in content-level peering. We investigate whether interacting operator-owned caches need explicit coordination in order to reach a stable content allocation efficiently. Beyond the theoretical contributions made to the analysis of player-specific graphical congestion games and their generalizations, the results in thesis provide guidelines for the design of protocols for standalone and for interconnected operator-owned content management systems.QC 20160107</p

Bandwidth and Storage Allocation for Operator-owned Content Management Systems

The demand for Internet-based visual content delivery has increased significantly in recent years, triggered mainly by the widespread use of Internet enabled smartphones and portable devices, and by the availability of super HD content.As a consequence, live and on-demand video content has become the most important source of network traffic in mobile and fixed networks alike.In order to be able to efficiently deliver the increasing amount of video traffic, network operators have started to deploy caches and operator-owned CDNs. These solutions do not only reduce the amount of transit traffic of the operators but they may also improve the customers' quality of experience, through bringing the video content closer to customers. Nevertheless, their efficiency is determined by the algorithms and protocols used to allocate resources, both in terms of storage and bandwidth. The work in this thesis addresses the allocation of these two resources for operator-owned content management systems. In the first part of the thesis we consider a cache maintained by a single network operator. We investigate how caching at a network operator affects the content distribution system as a whole, and consequently, the efficiency of content delivery. We propose a model of the decision process undertaken by a network operator that aims at optimizing the efficiency of a cache by actively managing its bandwidth. We design different algorithms that aim at approximating the optimal cache bandwidth allocation and we evaluate them through extensive simulations and experiments. We show that active cache bandwidth allocation can significantly increase traffic savings. We then consider the potential interaction among caches maintained by different network operators.We consider the problem of selfish replication on a graph as a modelof network operators that individually deploy replication systems, and try to leverage their peering agreements so as to minimize the traffic through their transit providers. We use game-theoretical tools to investigate the existence of stable and efficient allocations of content at the network operators. We show that selfish myopic updates of content allocations at different network operators lead the system to a stable state, and that the convergence speed depends on the underlying network topology. In addition, we show that interacting operator-owned caches can reach a stable content allocation without coordination, but coordination leads to more cost efficient content allocations.QC 20140401</p

Stable Content-peering of Autonomous Systems in a Content-centric Network

A future content-centric Internet would likely consistof autonomous systems (ASes) just like today’s Internet. It wouldthus be a network of interacting cache networks, each of themoptimized for local performance. To understand the influence ofinteractions between autonomous cache networks, in this paperwe consider ASes that maintain peering agreements with eachother for mutual benefit, and engage in content-level peering toleverage each others’ cache contents. We propose a model of theinteraction and the coordination between the caches managed bypeering ASes. We address whether stable and efficient contentlevel peering can be implemented without explicit coordinationbetween the neighboring ASes in order for the system to bestable. We show that content-level peering leads to stable cacheconfigurations, and that avoiding simultaneous updates by peeringISPs provides faster and more cost efficient convergence to a stableconfiguration. We validate our analytical results using simulationson the measured peering topology of more than 600 ASes.QC 20130731</p

Coordinated Selfish Distributed Caching for Peering Content-centric Networks

A future content-centric Internet would likely consist of autonomous systems (ASes) just like today’s Internet. It would thus be a network of interacting cache networks, each of them optimized for local performance. To understand the influence of interactions between autonomous cache networks, in this paper, we consider ASes that maintain peering agreements with each other for mutual benefit and engage in content-level peering to leverage each others’ cache contents. We propose a model of the interaction between the caches managed by peering ASes. We address whether stable and efficient content-level peering can be implemented without explicit coordination between the neighboring ASes. We show that content-level peering leads to stable cache configurations, both with and without coordination. However, peering Internet Service Providers (ISPs) that coordinate to avoid simultaneous updates converge to a stable configuration more efficiently. Furthermore, if the content popularity estimates are inaccurate, content-level peering is likely to lead to cost efficient cache allocations. We validate our analytical results using simulations on the measured peering topology of more than 600 ASes.QC 20190918</p

Selfish Content Replication on Graphs

Replication games are a model of the problem of content placement in computer and communication systems, when the participating nodes make their decisions such as to maximize their individual utilities. In this paper we consider replication games played over arbitrary social graphs; the social graph models limited interaction between the players due to, e.g., the network topology. We show that in replication games there is an equilibrium object placement for arbitrary social graphs. Nevertheless, if all nodes follow a myopic strategy to update their object placements then they might cycle arbitrarily long before reaching an equilibrium if the social graph is non-complete. We give sufficient conditions under which such cycles do not exist, and propose an efficient distributed algorithm to reach an equilibrium over a non-complete social graph.QC 2011111

A Game Theoretic Analysis of Selfish Content Replication on Graphs

Replication games are a model of the problem of content placement in computer and communication systems, when the participating nodes maketheir decisions such as to maximize their individualutilities. In this paper we consider replication gamesplayed over arbitrary social graphs; the social graphmodels limited interaction between the players due to,e.g., the network topology. We show that in replicationgames there is an equilibrium object placement forarbitrary social graphs. Nevertheless, if all nodes followa myopic strategy to update their object placementsthen they might cycle arbitrarily long before reachingan equilibrium if the social graph is non-complete. Wegive sufficient conditions under which such cycles do notexist, and propose an efficient distributed algorithm toreach an equilibrium over a non-complete social graph.QC 20130226</p