Neutron and X-ray 3D and 4D imaging of fluid transport within natural and lab-deformed carbonate rocks

Carbonate reservoir rocks are characterised by complexities in their void space caused by various processes involved in deposition and diagenesis occurring through chemical dissolution, reprecipitation, dolomitization, fracturing etc. These complexities affect the transport properties of these rocks and hinder an accurate estimation, and therefore all ensuing simulation, of their hydraulic behaviour. This PhD aims to deepen understanding of the influence of core-scale complexities of the pore system of carbonate rocks on fluid transport properties and processes. For this purpose, the complementary capabilities of X-ray and Neutron imaging along with quantitative image analysis are employed to experimentally investigate the miscible and immiscible fluid transport processes within carbonate rocks. Different types of textural variations due to the depositional and mechanical deformational features within four types of carbonate rocks, Coquina limestone, Biolithite, Travertine and Oolitic limestone are first characterised by analysing X-ray micro-CT images acquired from dry samples. Then, a series of High Speed Neutron Tomographies (HSNT) are acquired during miscible and immiscible fluid flow experiments in the selected carbonate rock samples (38mm diameter core) to explore different fluid transport processes affected by the characterised core-scale features. Image analysis techniques are employed that allow the extraction of quantitative data of pore system properties and fluid transport from the captured X-ray micro-CT images and HSNTs. The analysis on X-ray micro CT images revealed the significant influence of features like fractures, lamina or layering, layering orientation and different types of textural variations on the pore network properties like porosity, permeability, pore connectivity and tortuosity. The fluid transport processes and properties including morphology of the flow patterns, fluid speed distribution, saturation/relative concentration distribution of fluid phases, capillary heterogeneity trapping and fracture-matrix flow were resolved using the combination of HSNT and quantitative image analysis. The results also provide important insight on miscible transport processes including irregularity in the advancing fluid front and longitudinal dispersion.James-Watt scholarshi

A review of source term estimation methods for atmospheric dispersion events using static or mobile sensors

Understanding atmospheric transport and dispersal events has an important role in a range of scenarios. Of particular importance is aiding in emergency response after an intentional or accidental chemical, biological or radiological (CBR) release. In the event of a CBR release, it is desirable to know the current and future spatial extent of the contaminant as well as its location in order to aid decision makers in emergency response. Many dispersion phenomena may be opaque or clear, thus monitoring them using visual methods will be difficult or impossible. In these scenarios, relevant concentration sensors are required to detect the substance where they can form a static network on the ground or be placed upon mobile platforms. This paper presents a review of techniques used to gain information about atmospheric dispersion events using static or mobile sensors. The review is concluded with a discussion on the current limitations of the state of the art and recommendations for future research.close

Performance Bounds and Suboptimal Policies for Multi-Class Queue

In this paper, we consider a general class of a queuing system with multiple job types and flexible service facility. We use a stochastic control policy to determine the performance loss in multi-class M/M/1 queue. The considered system is originally a Markov decision processes (MDP). The author showed how to compute performance bounds for the stochastic control policy of MDP with an average cost criteria. In practice, many authors used heuristic control policies due to some hardness in computing and running mathematically optimal policies. The authors found bounds on performance in order to an optimal policy where the goal of this job is to compute the difference of optimality and a specific policy. In other words, this study shows that, the optimal bounds of the average queue length for any non-idling policies can be found by a factor of service rates.В этой статье рассматривается общий класс системы массового обслуживания с несколькими типами заданий и гибкими возможностями обслуживания. Используется стохастическая стратегия управления для определения потери производительности в многоклассовой очереди M/M/1. Рассматриваемая система изначально представляет собой марковский процесс принятия решений. В работе показано, как рассчитать границы производительности для стратегии стохастического управления марковского процесса принятия решения с критериями средней стоимости. На практике многие исследователи использовали эвристические стратегии управления из-за некоторой сложности в вычислениях и использовании математически оптимальных стратегий. Цель данной работы заключается в расчете разницы между оптимальной и конкретной стратегий, а также в нахождении границы производительности для оптимальной стратегии. Другими словами, это исследование показывает, что оптимальные границы средней длины очереди для любых стратегий без простоя можно найти с помощью коэффициента скорости обслуживания

An inventory of UK mineral resources suitable for enhanced rock weathering

Enhanced Rock Weathering (ERW), a technology based on amending soils with crushed calcium- and magnesium-rich silicate minerals has substantial CO2 removal potential. Evaluation of the available resources of these minerals and current production capacity is crucial for early-stage deployment of this approach. A robust understanding of the potential limitations in exploiting these resources is also required to ensure the scalability of ERW. This paper provides a spatial inventory of basic silicate rock resources in the UK along with current production capacity and permitted reserves. We also integrate spatial data to assess the potential environmental and social impacts of current rock extraction. 68 active and 100 inactive quarries were identified within outcrops of basic silicate rocks which are mainly distributed in Northern Ireland and in the central belt of Scotland. 14.8 Mt yr−1 of basic silicate rock are estimated to be extracted from which up to 3.7 Mt yr−1 of basic silicate waste fines is estimated to be produced which may be available for ERW in the UK. 490 Mt of permitted reserves is associated with active and inactive queries. Spatial distribution of artificial alkaline minerals including Construction and Demolition Wastes (CDW) and legacy slags in the UK have also been included in the inventory. Transport distances are calculated between all resources and the UK's croplands where these materials may be applied for ERW. The relative appropriateness of the UK's croplands for CDR are also calculated based on their proximity to mineral resources and climate parameters controlling the rate of EW.</p

An inventory of UK mineral resources suitable for enhanced rock weathering

Enhanced Rock Weathering (ERW), a technology based on amending soils with crushed calcium- and magnesium-rich silicate minerals has substantial CO2 removal potential. Evaluation of the available resources of these minerals and current production capacity is crucial for early-stage deployment of this approach. A robust understanding of the potential limitations in exploiting these resources is also required to ensure the scalability of ERW. This paper provides a spatial inventory of basic silicate rock resources in the UK along with current production capacity and permitted reserves. We also integrate spatial data to assess the potential environmental and social impacts of current rock extraction. 68 active and 100 inactive quarries were identified within outcrops of basic silicate rocks which are mainly distributed in Northern Ireland and in the central belt of Scotland. 14.8 Mt yr−1 of basic silicate rock are estimated to be extracted from which up to 3.7 Mt yr−1 of basic silicate waste fines is estimated to be produced which may be available for ERW in the UK. 490 Mt of permitted reserves is associated with active and inactive queries. Spatial distribution of artificial alkaline minerals including Construction and Demolition Wastes (CDW) and legacy slags in the UK have also been included in the inventory. Transport distances are calculated between all resources and the UK's croplands where these materials may be applied for ERW. The relative appropriateness of the UK's croplands for CDR are also calculated based on their proximity to mineral resources and climate parameters controlling the rate of EW.</p

Fingerprinting sub-basin spatial sediment sources using different multivariate statistical techniques and the Modified MixSIR model

Information on the relative contributions of sediment from different sources is needed to target sediment control strategies to prevent excess sediment delivery to receptors like dam reservoirs. The overarching scientific objective of this study was therefore to apportion sub-basin spatial source contributions to the supply of fine sediment in an erodible mountainous basin in north-eastern Iran to inform management. The technical objective was to satisfy the scientific objective using a source fingerprinting procedure based on composite signatures selected by different statistical tests. Nine potential geochemical tracers were measured on 21 sediment samples collected to characterise the three sub-basin spatial sediment sources and seven sediment samples collected at the outlet of the main basin. The statistical analysis employed to select three different composite fingerprints for discriminating the sub-basin sediment sources comprised: (1) the Kruskal–Wallis H test (KW-H), (2) a combination of KW-H and discriminant function analysis (DFA), and (3) a combination of KW-H and principal components & classification analysis (PCCA). A Bayesian un-mixing model was used to ascribe sub-basin source contributions using the three composite fingerprints. Using KW-H, the respective relative contributions from subbasins 1, 2 and 3 were estimated as 45.6%, 3.8% and 50.6%, compared to 46.8%, 18.8% and 34.4% using KW-H and DFA, and 61%, 2.5% and 36.5% using KW-H and PCCA. Kolmogorov-Smirnov test pairwise comparisons of the distributions of predicted source proportions generated using different composite signatures confirmed statistically significant differences. The root mean square difference between the predicted source proportions based on different composite signatures was ~12%. This study therefore provides more evidence that source tracing studies should deploy a number of composite signatures selected using independent statistical tests to permit appraisal of the consistencies or otherwise in predicted source contributions based on the tracers used. The outputs of this preliminary study will be used to inform the spatial targeting of sediment mitigation. TESTING AMENDMENT

Resource Allocation in Cloud Computing Via Optimal Control to Queuing Systems

We consider resource allocation problem in the cloud computing. We use queuing model to model the process of entering into the cloud and to schedule and to serve incoming jobs. In this paper, the main problem is to allocate resources in the queuing systems as a general optimization problem for controlled Markov process with finite state space. For this purpose, we study a model of cloud computing where the arrival jobs follow a stochastic process. We reduce this problem to a routing problem. In the case of minimizing, cost is given as a mixture of an average queue length and number of lost jobs. We use dynamic programming approach. Finally, we obtain the explicit form of the optimal control by the Bellman equation.Рассматривается задача выделения ресурсов в облачных вычислениях. Мы используем модель очередей для моделирования процесса входа в облако, а также для планирования и обслуживания входящих заданий. Основной задачей, с которой мы сталкиваемся в данной статье, является задача распределения ресурсов в системах массового обслуживания как общая задача оптимизации для управляемого марковского процесса с конечным пространством состояний. Для этой цели мы изучаем модель облачных вычислений, в которой задания по прибытию следуют случайному процессу. Мы сводим эту задачу к задаче маршрутизации. В случае минимизации стоимость выражается через среднюю длину очереди и количество потерянных заданий. Мы используем подход динамического программирования и получаем явную форму оптимального управления по уравнению Беллмана