Optimal Emergency Shutdown Valve Configuration for Pressurised Pipelines

Pressurised pipelines are the primary mode of choice for transporting large quantities of hazardous fluids across the globe. The failure of such pipelines can lead to the release of significant amounts of flammable or toxic inventories, which may in turn present significant risks to life, environment and property. In order to mitigate such risks, various types of emergency shutdown valves (ESDVs), including Check Valves (CVs), Automatic Shut-off Valves (ASVs) and Remote Control Valves (RCVs), are installed along such pipelines as the front-line emergency mitigation tool. Accounting for the critically important ensuing in-pipe transient fluid flow, this thesis presents the development and application of a multi-objective optimisation study for selecting the ESDV type, number and spacing as well as its combinations and operational settings for striking a balance between the minimum valve capital cost against the efficacy in minimising and ultimately isolating outflow following pipeline failures. Two types of pipeline failures, including Full Bore Rupture (FBR) and puncture are considered. Ethylene and natural gas (typical flammable and explosive hydrocarbons) as well as Carbon Dioxide (CO2) are chosen as the transported fluids. CO2 is selected given its hazardous nature (an asphyxiant at > 7% v/v) and the extensive use of pressurised pipelines being proposed as the main method for transporting large quantities of captured CO2 for permanent geological storage as part of the Carbon Capture and Storage chain. The pipeline decompression model employed is based on the Homogeneous Equilibrium Mixture assumption, where the constituent fluid phases are assumed to be at both thermodynamic and mechanical equilibrium. The Peng-Robinson Equation of State along with relevant hydrodynamic and thermodynamic relations are employed to determine the required fluid thermophysical properties and phase equilibrium data. The impact of the valve closure on the in-pipe fluid flow dynamics is accounted for through the implementation of appropriate boundary conditions. The resulting system of conservation equations is solved numerically using the Method of Characteristics. The first part of the study focuses on the investigation of ESDV dynamic response and characteristics on the fluid behaviour following the accidental failure of a hypothetical nevertheless realistic ethylene pipeline. This is divided into two parts: in the first, the results based on the simulation of the pressure surges upon CV closure are presented for a wide practical range of ethylene pipeline operating pressures and temperatures. It is found that for high operating pressures (over 90 bar), pressure surges upon CV closure can lead to a large thrust or bending forces acting on the pipeline segments, potentially damaging the pipeline in the event of exceeding the maximum safe design operating pressure. In the second part, the impact of ASV and RCV activation pressure is assessed by determining the amount of escaped inventory prior to complete isolation in the event of pipeline FBR and different generic sizes of puncture failures. The results show that for FBR and relatively large puncture failures (> 50 % pipe i.d.), decreasing valve activation pressure results in an insignificant reduction in the total inventory loss prior to valve closure. In the case of small puncture diameter failures (less than 5 % pipe i.d.), ASV may not be self-activated given the relatively small pressure drop across the valve throughout the decompression process. The above is followed by the analysis of the efficacy of ESDVs using different inline valve combinations and spacings by performing two sets of investigations. The first includes the simulations of fluid flow behaviour upon valve closure using a hypothetical CO2 pipeline puncture decompression scenario. Different valve spacings and combinations of inline RCVs and CVs are investigated, and the results are presented and discussed in terms of the release pressure and temperature, the discharge mass flowrate and, more importantly, the total mass released, as a function of time during decompression. Next, based on the FBR failure of a high-pressure ethylene pipeline, the efficacy of CVs, RCVs and ASVs and their combinations for the emergency isolation is investigated by comparing the amount of escaped inventory prior to complete valve closure. Building on the above work, the study culminates in optimising inline ESDV configuration by developing a multi-objective optimisation method combined with Principal Component Analysis and applying it to a real, 1016 mm i.d., 150.2 km long natural gas transmission pipeline in China operating at 80 bar and 307.24 K. Starting with defining a set of 6 characteristic variables for ESDV settings, PCA is first employed in order to reduce the number of variables to 3, whilst retaining good agreement for the problem solution and emphasis on computational simplification. Next, a description of the optimisation problem is performed, detailing the objective functions used, including valve capital cost, and the various parameter realistic values assumed. The results of the multi-objective optimisation are presented using scatter plots providing a geometrical visualisation of the Pareto Front and Set. Such results serve as a highly informative tool in assisting pipeline operators in selecting the optimal inline ESDV configurations for pressurised pipelines

Spike timing reshapes robustness against attacks in spiking neural networks

The success of deep learning in the past decade is partially shrouded in the shadow of adversarial attacks. In contrast, the brain is far more robust at complex cognitive tasks. Utilizing the advantage that neurons in the brain communicate via spikes, spiking neural networks (SNNs) are emerging as a new type of neural network model, boosting the frontier of theoretical investigation and empirical application of artificial neural networks and deep learning. Neuroscience research proposes that the precise timing of neural spikes plays an important role in the information coding and sensory processing of the biological brain. However, the role of spike timing in SNNs is less considered and far from understood. Here we systematically explored the timing mechanism of spike coding in SNNs, focusing on the robustness of the system against various types of attacks. We found that SNNs can achieve higher robustness improvement using the coding principle of precise spike timing in neural encoding and decoding, facilitated by different learning rules. Our results suggest that the utility of spike timing coding in SNNs could improve the robustness against attacks, providing a new approach to reliable coding principles for developing next-generation brain-inspired deep learning

Effect of Narcissistic Personality on Entrepreneurial Intention Among College Students: Mediation Role of Entrepreneurial Self-Efficacy

Exploring the factors influencing entrepreneurial intention is crucial to entrepreneurial practice and education. For a comprehensive understanding of the influence of narcissistic personality on entrepreneurial intention, this study analyzed the relationship between narcissistic personality, entrepreneurial self-efficacy, and entrepreneurial intention in college students sampled from three higher vocational colleges in Beijing, China. A total of 252 valid questionnaires were collected. The results show that the narcissistic personality of the college students has a significant positive effect on entrepreneurial intention and entrepreneurial self-efficacy. Entrepreneurial self-efficacy of the college students has a significant positive effect on entrepreneurial intention and plays a partial mediation role in the relationship between narcissistic personality and entrepreneurial intention. Thus, the study results provide some reference for further improving entrepreneurial practice and education

Research progress in finite element analysis of ankle sprains

Ankle dislocation is the most common sports injury and is often associated with sports injuries. Among them, the tendon ligament causes damage to the posterior ankle ligament and the posterior ankle ligament. Important stabilizing structures, especially the anterior fibula ligament and the heelofibular ligament, play an important role in maintaining balance, and their injuries can lead to instability on the lateral side of the ankle. This seriously affects the function of the ankle. At the same time, it has a stabilizing effect on the lower joint, and its damage will also affect the function of the lower joint. [1-2] Foreign scientists have collected cases of acute fractures of the ankle joint, but only the central ligament rupture. Almost all injuries to the central tendon can cause a partial tear of the ligament. However, severe hallux valgus abuse can still lead to isolated damage to the triangular ligament. [3-4] Study surface emography and other techniques for basic ankle fracture studies to address the biomechanical and kinematic problems of ankle sprains. The biomechanics of ankle injuries will now be discussed in conjunction with the mechanisms of ankle injuries. To discuss the biomechanics and kinematics of ankle sprains