267 research outputs found

    Aqueous Solutions of Calcium Ions:  Hydration Numbers and the Effect of Temperature

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    p-wave phase shift and scattering length of 6^6Li

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    We have calculated the p-wave phase shifts and scattering length of 6^6Li. For this we solve the pp partial wave Schr\"odinger equation and analyze the validity of adopting the semiclassical solution to evaluate the constant factors in the solution. Unlike in the ss wave case, the semiclassical solution does not provide unique value of the constants. We suggest an approximate analytic solution, which provides reliable results in special cases. Further more, we also use the variable phase method to evaluate the phase shifts. The p-wave scattering lengths of 132^{132}Cs and 134^{134}Cs are calculated to validate the schemes followed. Based on our calculations, the value of the pp wave scattering length of 6^6Li is 45ao-45a_o.Comment: 10 figure

    Influence of test methodology and probe geometry on nanoscale fatigue mechanisms of diamond-like carbon thin film

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    The aim of this paper is to investigate the mechanism of nanoscale fatigue using nano-impact and multiple-loading cycle nanoindentation tests, and compare it to previously reported findings of nanoscale fatigue using integrated stiffness and depth sensing approach. Two different film loading mechanisms, loading history and indenter shapes are compared to comprehend the influence of test methodology on the nanoscale fatigue failure mechanisms of a DLC film. An amorphous 100 nm thick DLC film was deposited on a 500 μm silicon substrate using sputtering of graphite target in pure argon atmosphere. Nano-impact and multiple-load cycle indentations were performed in the load range of 100 μN to 1000 μN and 0.1 mN to 100 mN, respectively. Both test types were conducted using conical and Berkovich indenters. Results indicate that for the case of a conical indenter, the combination of nano-impact and multiple-loading cycle nanoindentation tests provides information on the life and failure mechanism of the DLC film, which is comparable to the previously reported findings using the integrated stiffness and depth sensing approach. However, the comparison of results is sensitive to the applied load, loading mechanism, test-type and probe geometry. The loading mechanism and load history are therefore critical which also lead to two different definitions of film failure. The choice of exact test methodology, load and probe geometry should therefore be dictated by the in-service tribological conditions, and where necessary both test methodologies can be used to provide better insights of failure mechanism. Molecular dynamics (MD) simulations of the elastic response of nanoindentation are reported, which indicate that the elastic modulus of the film measured using MD simulation was higher than that experimentally measured. This difference is attributed to the factors related to the presence of material defects, crystal structure, residual stress, indenter geometry and loading/unloading rate differences between the MD and experimental results

    Internet of Things and data mining: from applications to techniques and systems

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    The Internet of Things (IoT) is the result of the convergence of sensing, computing, and networking technologies, allowing devices of varying sizes and computational capabilities (things) to intercommunicate. This communication can be achieved locally enabling what is known as edge and fog computing, or through the well‐established Internet infrastructure, exploiting the computational resources in the cloud. The IoT paradigm enables a new breed of applications in various areas including health care, energy management and smart cities. This paper starts off with reviewing these applications and their potential benefits. Challenges facing the realization of such applications are then discussed. The sheer amount of data stemmed from devices forming the IoT requires new data mining systems and techniques that are discussed and categorized later in this paper. Finally, the paper is concluded with future research directions

    The vulnerability of the petroleum supply chain

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    Oil and its products are the main fuel of today's global society. It is therefore necessary to ensure the continuous, smooth and uninterrupted flow of oil to end users. The aim of this thesis is to examine and assess the ability of the petroleum supply chain to retain functionality when damaged in some way. The main causes of interruptions considered are random failures, such as natural disasters or accidental damages, malicious attacks and intentional disruptions. The research seeks a holistic assessment of oil supply chain vulnerability addressing such interruptions. A literature review is conducted on the topographic properties of networks and how network structure is related to reliability, vulnerability, robustness and criticality. The disruption causes and the various measures of vulnerability are also examined in order to identify the characteristics of critical failure scenarios. Literature review is further extended over the development, operations and management of the oil supply chain and the response measures in place for replacing and recovering lost throughput in case of a disruption. The methodology adopted consists of three optimization stages, namely shortest path finding, flow assignment and network interdiction. Shortest path finding is concerned with the topographic features of the oil supply chain and more specifically with the establishment of optimal origin-destination paths. The oil supply chain that is modelled as a multi-origin multi-destination spatial network making use of Djikstra's shortest path search algorithm. The second optimization stage regards the assignment of flow and the satisfaction of user demand. A minimum cost flow problem similar to the transportation problem is used for that purpose. The model is fitted to the oil context by adding a fleet capacity constraint and a deterministic fleet velocity factor. The latter optimization stage is conducted using a game theoretic interdiction model based on a two-player zero-sum game mixed strategy proposed by Bell (2000). The results obtained are both of methodological and practical nature. Vulnerability has been assessed for two different set-ups of the oil supply network aiming to capture different vulnerability aspects. The results highlight vulnerable network components and stress weak locations where infrastructure improvements can be made. Furthermore, policy weaknesses are identified.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
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