Oil scenarios for long-term business planning: Royal Dutch Shell and generative explanation, 1960-2010

Most executives know that overarching paints of plausible futures will profoundly affect the competitiveness and survival of their organisation. Initially from the perspective of Shell, this article discuses oil scenarios and their relevance for upstream investments. Scenarios are then incorporated into generative explanation and its principal instrument, namely agent-based computational laboratories, as the new standard of explanation of the past and the present and the new way to structure the uncertainties of the future. The key concept is that the future should not be regarded as ‘complicated’ but as ‘complex’, in that there are uncertainties about the driving forces that generate unanticipated futures, which cannot be explored analytically.oil scenarios; Shell; ACEGES; agent-based computational economics

Scheduling techniques to improve the worst-case execution time of real-time parallel applications on heterogeneous platforms

The key to providing high performance and energy-efficient execution for hard real-time applications is the time predictable and efficient usage of heterogeneous multiprocessors. However, schedulability analysis of parallel applications executed on unrelated heterogeneous multiprocessors is challenging and has not been investigated adequately by earlier works. The unrelated model is suitable to represent many of the multiprocessor platforms available today because a task (i.e., sequential code) may exhibit a different work-case-execution-time (WCET) on each type of processor on an unrelated heterogeneous multiprocessors platform. A parallel application can be realistically modeled as a directed acyclic graph (DAG), where the nodes are sequential tasks and the edges are dependencies among the tasks. This thesis considers a sporadic DAG model which is used broadly to analyze and verify the real-time requirements of parallel applications. A global work-conserving scheduler can efficiently utilize an unrelated platform by executing the tasks of a DAG on different processor types. However, it is challenging to compute an upper bound on the worst-case schedule length of the DAG, called makespan, which is used to verify whether the deadline of a DAG is met or not. There are two main challenges. First, because of the heterogeneity of the processors, the WCET for each task of the DAG depends on which processor the task is executing on during actual runtime. Second, timing anomalies are the main obstacle to compute the makespan even for the simpler case when all the processors are of the same type, i.e., homogeneous multiprocessors. To that end, this thesis addresses the following problem: How we can schedule multiple sporadic DAGs on unrelated multiprocessors such that all the DAGs meet their deadlines. Initially, the thesis focuses on homogeneous multiprocessors that is a special case of unrelated multiprocessors to understand and tackle the main challenge of timing anomalies. A novel timing-anomaly-free scheduler is proposed which can be used to compute the makespan of a DAG just by simulating the execution of the tasks based on this proposed scheduler. A set of representative task-based parallel OpenMP applications from the BOTS benchmark suite are modeled as DAGs to investigate the timing behavior of real-world applications. A simulation framework is developed to evaluate the proposed method. Furthermore, the thesis targets unrelated multiprocessors and proposes a global scheduler to execute the tasks of a single DAG to an unrelated multiprocessors platform. Based on the proposed scheduler, methods to compute the makespan of a single DAG are introduced. A set of representative parallel applications from the BOTS benchmark suite are modeled as DAGs that execute on unrelated multiprocessors. Furthermore, synthetic DAGs are generated to examine additional structures of parallel applications and various platform capabilities. A simulation framework that simulates the execution of the tasks of a DAG on an unrelated multiprocessor platform is introduced to assess the effectiveness of the proposed makespan computations. Finally, based on the makespan computation of a single DAG this thesis presents the design and schedulability analysis of global and federated scheduling of sporadic DAGs that execute on unrelated multiprocessors

Fluid evolution in Tertiary magmatic-hydrothermal ore systems at the Rhodope metallogenic province, NE Greece. A review

Characterization of various fluid parameters in magmatic-hydrothermal ore mineralizationsis potentially essential for interpretation of the conditions of formation and therefore formineral exploration. Fluid inclusions can provide a useful and promising tool in the researchof the ore forming processes in these systems. This review focuses on the nature,composition and origin of magmatic-hydrothermal ore forming fluids involved in the formationof representative Tertiary ore deposits at the Rhodope metallogenic province in NEGreece. These deposits are spatially related to Tertiary magmatism in NE Greece. Casestudies are presented here and include an intrusion-hosted sheeted vein system (Kavala), aAu-rich carbonate replacement and quartz-vein mineralization (Asimotrypes), mineralizedveins in Eptadendro-Rachi and Thasos island (Kapsalina and Panagia), porphyry Cu-Mo-Re-Au deposits in Pagoni Rachi and Maronia and epithermal Au-Ag mineralizations inPerama and Loutros. Hydrothermal fluids rich in CO2 together with elevated Au and Tecontent are common and occur at the Kavala intrusion hosted sheeted vein system, at theAsimotrypes Au-rich carbonate replacement mineralization and at the Panagia (Thasos)vein system. We classify all these ore mineralizations as intrusion-related gold systems(IRGS)v. Transport and precipitation of metals including Au and Te is favoured when CO2is present. Precipitation of the ore mineralization takes place due to the immiscibility of thecarbonic and the aqueous fluids which have a magmatic origin with the contribution ofmeteoric water. Cooling of magmatic hydrothermal fluids and dilution with meteoric wateris a common cause for ore mineral formation in the vein mineralizations of Eptadendro/Rachi and Kapsalina Thasos. At the Pagoni Rachi and Maronia porphyry deposits, boilingand the high proportion of the vapour phase are the most essential fluid processes whichaffected ore formation. The epithermal veins overprinting the Pagoni Rachi and the Maroniaporphyry systems and the HS-IS epithermal system in Perama Hill and the IS epithermalmineralization in Loutros are characterized by low to moderate temperatures and lowto moderate salinities. Cooling and dilution of the ore fluids are the main process for goldprecipitation. We conclude that the different fluid parameters and microthermometric dataindicate a variety of fluid origin conditions and sources which can affect the strategy forexploration and prospecting for gold, rare and critical metals

A note on the efficiency of position mechanisms with budget constraints

We study the social efficiency of several well-known mechanisms for the allocation of a set of available (advertising) positions to a set of competing budget-constrained users (advertisers). Specifically, we focus on the Generalized Second Price auction (GSP), the Vickrey–Clarke–Groves mechanism (VCG) and the Expressive Generalized First Price auction (EGFP). Using liquid welfare as our efficiency benchmark, we prove a tight bound of 2 on the liquid price of anarchy and stability of these mechanisms for pure Nash equilibria