Dynamic Modeling and Extreme Tension Analysis of Mooring System for a Floating Offshore Wind Turbine

For offshore wind industry, exploiting the dynamic behaviors of mooring lines is of increasing importance in floating offshore wind turbine (FOWT) mooring system design. Currently, the design philosophy for structures and moorings is based on principles and practices adopted in offshore oil and gas, including mooring systems that are optimized for applications in deeper waters. However, the design of FOWT mooring systems is facing several challenges, including installation costs, the stability of light-weight minimalistic platforms, and shallow water depths (50-300m). The extreme tension in mooring lines of a light displacement platform in shallow water is dominated by snap loads. Hence the extreme tension values of the lines are one of the most important factors to consider for safe design of permanently FOWT mooring system. Thus, there is also a need for dynamic performance assessment of FOWT mooring systems using numerical modeling while considering the extreme events on the mooring lines. The overall goal of the study is to investigate the extreme dynamic tension of mooring systems of a FOWT and propose a long-term distribution model which could improve the current approach to design tension of a mooring line. This dissertation advances the current state-of-the-art with respect to mooring line design in the offshore wind industry by considering three interrelated issues. The first is to fundamentally understand the underlying physics of extreme dynamic tension of a mooring system. To reach the goal, the factors can influence the snap events on vertical hanging cable system are investigated. In this issue, the nonlinearity of bilinear cable stiffness, hydrodynamic drag force as well as the pretension of the cable are considered. Therefore, the present work finds that potential exists for snap type impact to affect the mooring system of the FOWT. Here, the DeepCWind semi-submersible floating wind system proposed by phase II of Offshore Code Comparison Collaboration Continuation (OC4) project, is selected for this study. There is a reasonably strong correlation between the tension spikes and wave motion, as well as the vertical motion of the fairlead. Third, to estimate the extreme mooring line tension due to snap loads, a composite Weibull distribution is proposed. The model is composed of two Weibull distributions with different characteristics on either side of a transition tension value, and whose parameters is estimated from test data. The proposed distribution model has a good fit to the measured tension data, particular in the extreme range. Moreover, the research addresses the simulation of long, time-dependent mooring tension sequences by coupled AQWA-OrcaFlex-FAST. A number of comparisons between numerical modeling predictions and test data are done and have good quality results validation. Therefore, the focus is shifted to a probabilistic examination of snap load frequency and magnitude both in experimental data and in the simulation. The CWD model of the numerical data is also compared with the CWD model of test data

Experimental Design and Construction for Critical Velocity Measurement in Spin-Orbit Coupled Bose-Einstein Condensates

Quantum simulation using ultra-cold atoms, such as Bose-Einstein Condensates (BECs), offers a very flexible and well controlled environment to simulate physics in different systems. For example, to simulate the effects of spin orbit coupling (SOC) on electrons in solid state systems, we can make a SOC BEC which mimics the behavior of SOC electrons. The goal of this project is to see how the superfluid property of BECs change in the presence of SOC. In particular, we plan to measure the critical velocity of an 87Rb BEC with and without SOC by stirring it with a laser. This laser needs to be blue-detuned for generating a repulsive potential as an obstacle. For this purpose, we build an external cavity diode laser (ECDL) at 776.47nm, which is blue-detuned to the D1 and D2 transition of 87Rb. To drive the ECDL, temperature and current controllers are designed and built. Since we need to focus the laser beam to the center of a BEC (about 20 by 55 micron), we set up a telescope to shrink the beam size to less than 10 micron. The optical design is accomplished by OSLO (optical system simulation software) with simulation results consistent with the Ray Transfer Matrix. To examine the superfluidity under different relative velocities, an acoustic-optic modulator will be used to move the beam against the BEC. At this point, the optical system is mostly finished. Our next step is to perform the critical velocity measurement of a BEC with and without SOC

Critical Care of Acute Heart Failure

Acute heart failure is a life-threatening medical condition. Improving acute heart failure care is important. Early diagnosis and evaluating the etiology are important in acute heart failure. Patients with suspected acute heart failure should have a diagnostic workup, and appropriate pharmacological and nonpharmacological management should be started promptly and in parallel. Diagnosis of acute heart failure should be based on history and symptoms. The physical examination typically presents with some combination of increased congestion and decreased peripheral perfusion, further confirmed by electrocardiogram, chest radiograph, biomarkers, and echocardiogram. The first step in the management of a patient is to address life-threatening issues. Patients with respiratory failure or cardiogenic shock should be treated soon. The next step is the identification of precipitants that needs urgent management. Evidence-based medication to reduce morbidity and mortality for patients with heart failure includes an angiotensin converting enzyme inhibitor, angiotensin receptor blocker, or angiotensin receptor-neprilysin inhibitor; a beta blocker; and a mineralocorticoid receptor antagonist. During an acute heart failure episode, management of these agents depends upon whether the patient has contraindications to therapy such as hemodynamic instability or acute kidney injury. Once the patient is stable, therapies are carefully initiated, reinitiated, or titrated with appropriate follow-up

Finding Related Publications: Extending the Set of Terms Used to Assess Article Similarity.

Recommendation of related articles is an important feature of the PubMed. The PubMed Related Citations (PRC) algorithm is the engine that enables this feature, and it leverages information on 22 million citations. We analyzed the performance of the PRC algorithm on 4584 annotated articles from the 2005 Text REtrieval Conference (TREC) Genomics Track data. Our analysis indicated that the PRC highest weighted term was not always consistent with the critical term that was most directly related to the topic of the article. We implemented term expansion and found that it was a promising and easy-to-implement approach to improve the performance of the PRC algorithm for the TREC 2005 Genomics data and for the TREC 2014 Clinical Decision Support Track data. For term expansion, we trained a Skip-gram model using the Word2Vec package. This extended PRC algorithm resulted in higher average precision for a large subset of articles. A combination of both algorithms may lead to improved performance in related article recommendations

Effects of System Characteristics on Adopting Web-Based Advanced Traveller Information System: Evidence from Taiwan

This study proposes a behavioural intention model that integrates information quality, response time, and system accessibility into the original technology acceptance model (TAM) to investigate whether system characteristics affect the adoption of Web-based advanced traveller information systems (ATIS). This study empirically tests the proposed model using data collected from an online survey of Web-based advanced traveller information system users. Con­firmatory factor analysis (CFA) was performed to examine the reliability and validity of the measurement model, and structural equation modelling (SEM) was used to evaluate the structural model. The results indicate that three system characteristics had indirect effects on the intention to use through perceived usefulness, perceived ease of use, and attitude toward using. Information quality was the most im­portant system characteristic factor, followed by response time and system accessibility. This study presents implica­tions for practitioners and researchers, and suggests direc­tions for future research.</p