LQR optimal control of two-rotor wind turbine mounted on spar-type floating platform

Interest is steadily growing for multi-rotor wind turbine concepts. This type of wind turbine offers a practical solution for scaling issues of large wind turbine components and for the reduction of costs associated with manufacturing, logistics, and maintenance. However, the literature lacks thorough knowledge of the dynamic performance of multi-rotor wind turbine concepts installed on floating platforms. Previous research studied the dynamic response of a two-rotor wind turbine concept mounted on a spar-type floating platform (2WT). Platform yaw motion is a significant dynamic factor directly caused by differential turbulence intensity experienced by the two hubs coupled with the distribution of thrust loads on the tower structure. Blade-pitch control analysis also showed how the 2WT yaw response is extremely sensitive to the control strategy employed. In this work, a linear quadratic regulator (LQR) is used to design an optimal controller for the 2WT prototype. Three LQR gain schedules corresponding to three operation regions are considered. An in-house tool for the dynamic analysis of multi-rotor floating wind turbines is used for linear state-space extraction and dynamic analysis. The control performance in different load conditions is assessed against the baseline OC3 proportional-integral (PI) control strategy and a PI-P control strategy in a previous article presented by the authors.acceptedVersio

Comparative dynamic analysis of two-rotor wind turbine on spar-type, semi-submersible, and tension-leg floating platforms

Multi-rotor floating offshore wind turbines have been recently proposed as an innovative technology to further reduce the cost of offshore wind energy. Even though examples of commercial prototypes are present, the literature lacks studies on the dynamic performance of such systems. This work presents a comparative analysis of a two-rotor wind turbine concept mounted on spar-type, semi-submersible, and tension-leg platforms. Their short-term performance is assessed by considering six different load cases considering directionally congruent turbulent wind profiles and irregular sea states. The analysis is carried out through an in-house fully-coupled code developed in Modelica. AeroDyn v15 within FAST v8 by NREL is coupled to the Modelica code to achieve blade-element momentum capabilities. Results indicate that platform yaw motion is an important dynamic mode of the systems, particularly for the spar configuration. Stiffer station-keeping lines and longer fairlead distance to the platform centerline reduce significantly yaw motion, as in the case of the semi-submersible and tension-leg configurations. Large tower base bending moment standard deviations and the associated concentration of energy at the platform heave and pitch motion frequencies indicate an increased risk for fatigue damage for the TLP configuration, especially at above-rated wind speeds. Moreover, large tendon loads can pose concerns in terms of fatigue and limit state performance. Large mean platform pitch angle and yaw standard deviation contribute to the reduction of electric power output quality. Extreme storm conditions greatly increase the response standard deviation, especially for the semi-submersible configuration.publishedVersio

COMPARATIVE LAW OF ISLAMIC INHERITANCE AND CIVIL LAW INHERITANCE (WEST)

Talking inheritance law can not be separated from some of the elements that are bound. The elements are as follows: 1) The Heir, heir is the person who died or people who give so-called legacy heir. Usually heir bestows both wealth and debt obligations or to other persons or heirs. 2) The heirs, heirs are those who inherit referred to as heir was given the legal right to receive the assets and liabilities or debts left by the testator. 3) Treasure heritage, heritage is everything that is given to the heir to the testator possessed, whether it be right or property such as houses, cars, and gold as well as liability for the debt. But, despite its importance, is often the subject of this heritage be problematic. Not surprisingly, many people who dropped the ropes brotherhood because of inheritance. The main problems are usually due to disagreements about equality and fairness. Indonesia has two Inheritance law, they are based on Islamic law (Faraidh) and Civil Law (Penal Code).

Prediction of long-term extreme response of two-rotor floating wind turbine concept using the modified environmental contour method

The modified environmental contour method (MECM) is assessed for the prediction of 50-year extreme response of a two-rotor floating wind turbine concept (2WT) deployed in two offshore sites in the northern North Sea (Norway 5) and the North Atlantic Ocean (Buoy Cabo Silleiro). The sites considered are in areas known for their floating wind development potential. The environmental contour method (ECM) is used to reduce the computational effort of full long-term analysis (FLTA) by only considering environmental conditions associated with a given return period. MECM is a modification of the ECM where additional environmental contours are included to account for discontinuous operation modes of dynamic structures. The results obtained in MECM are benchmarked against FLTA results and compared to ECM results. ECM leads to large underpredictions of responses governed by wind loads if compared to FLTA, as it is not capable of taking into account important operational modes of the 2WT. It is found that MECM, which includes the wind turbines cut-off contour, is able to reduce most response underpredictions within 15% difference compared to FLTA results. MECM may thus be considered as a sufficiently accurate and computationally efficient method for the long-term extreme analysis of 2WT concepts.publishedVersio

Una mirada internacional : marcos de relación y financiación entre gobiernos y ONG de desarrollo

Colabora en la publicación la AECIDBibliografía: p. 60-6

Novel phytoandrogens and lipidic augmenters from Eucommia ulmoides

BACKGROUND: Plants containing compounds such as the isoflavonoids, with female hormone-like effects that bind to human estrogen receptors, are known. But none has been previously shown to have corresponding male hormone-like effects that interact with the human androgen receptor. Here, we report that the tree bark (cortex) of the Gutta-Percha tree Eucommia ulmoides possesses bimodal phytoandrogenic and hormone potentiating effects by lipidic components. METHODS: The extracts of E. ulmoides were tested using in-vitro reporter gene bioassays and in-vivo animal studies. Key compounds responsible for the steroidogenic effects were isolated and identified using solid phase extraction (SPE), high performance liquid chromatography (HPLC), thin layer chromatography (TLC), gas chromatography-mass spectroscopy (GC-MS), electron spray ionisation-mass spectroscopy (ESI-MS) and nuclear magnetic resonance (NMR). RESULTS: The following bioactivities of E. ulmoides were found: (1) a phenomenal tripartite synergism exists between the sex steroid receptors (androgen and estrogen receptors), their cognate steroidal ligands and lipidic augmenters isolated from E. ulmoides, (2) phytoandrogenic activity of E. ulmoides was mediated by plant triterpenoids binding cognately to the androgen receptor (AR) ligand binding domain. CONCLUSION: In addition to well-known phytoestrogens, the existence of phytoandrogens is reported in this study. Furthermore, a form of tripartite synergism between sex steroid receptors, sex hormones and plant-derived lipids is described for the first time. This could have contrasting clinical applications for hypogonadal- and hyperlipidaemic-related disorders

Transport Properties of Doped t-J Ladders

Conductivity and Hall coefficient for various types of t-J ladders are calculated as a function of temperature and frequency by numerical diagonalization. A crossover from an incoherent to a coherent charge dynamics is found at a temperature T_{coh}. There exists another crossover at T_{PG} below which a pseudogap opens in the optical spectra, induced by the opening of a spin gap. In the absence of the spin gap, T_{coh} and the coherent weight are suppressed especially with increasing dimensionality. On the contrary, T_{coh} is strongly enhanced by the pseudogap formation below T_{PG}, where the coherent Drude weight decreases with increasing dimensionality. The Hall coefficient shows a strong crossover at T_{PG} below which it has large amplitude for small doping concentration.Comment: 4 pages, RevTeX, 5 PostScript figure

A Global Survey of Physicians Knowledge About Nonalcoholic Fatty Liver Disease

Background & Aims Despite rapidly increasing nonalcoholic fatty liver disease (NAFLD) prevalence, providers’ knowledge may be limited. We assessed NAFLD knowledge and associated factors among physicians of different specialties globally. Methods NAFLD knowledge surveys containing 54 and 59 questions covering 3 domains (epidemiology/pathogenesis, diagnostics, and treatment) were completed electronically by hepatologists, gastroenterologists (GEs), endocrinologists (ENDOs), and primary care physicians (PCPs) from 40 countries comprising 5 Global Burden of Disease super-regions. Over 24 months, 2202 surveys were completed (488 hepatologists, 758 GEs, 148 ENDOs, and 808 PCPs; 50% high-income Global Burden of Disease super-region, 27% from North Africa and Middle East, 12% Southeast Asia, and 5% South Asian and Latin America). Results Hepatologists saw the greatest number of NAFLD patients annually: median 150 (interquartile range, 60–300) vs 100 (interquartile range, 35–200) for GEs, 100 (interquartile range, 30–200) for ENDOs, and 10 (interquartile range, 4–50) for PCPs (all P < .0001). The primary sources of NAFLD knowledge acquisition for hepatologists were international conferences (33% vs 8%–26%) and practice guidelines for others (39%–44%). The Internet was the second most common source of NAFLD knowledge for PCPs (28%). NAFLD knowledge scores were higher for hepatologists than GEs: epidemiology, 62% vs 53%; diagnostics, 80% vs 73%; and treatment, 61% vs 58% (P < .0001), and ENDOs scores were higher than PCPs: epidemiology, 70% vs 60%; diagnostics, 71% vs 64%; and treatment, 79% vs 68% (P < .0001). Being a hepatologist or ENDO was associated with higher knowledge scores than a GE or PCP, respectively (P < .05). Higher NAFLD knowledge scores were associated independently with a greater number of NAFLD patients seen (P < .05). Conclusions Despite the growing burden of NAFLD, a significant knowledge gap remains for the identification, diagnosis, and management of NAFLD

Mutations in repeating structural motifs of tropomyosin cause gain of function in skeletal muscle myopathy patients

The congenital myopathies include a wide spectrum of clinically, histologically and genetically variable neuromuscular disorders many of which are caused by mutations in genes for sarcomeric proteins. Some congenital myopathy patients have a hypercontractile phenotype. Recent functional studies demonstrated that ACTA1 K326N and TPM2 ΔK7 mutations were associated with hypercontractility that could be explained by increased myofibrillar Ca(2+) sensitivity. A recent structure of the complex of actin and tropomyosin in the relaxed state showed that both these mutations are located in the actin–tropomyosin interface. Tropomyosin is an elongated molecule with a 7-fold repeated motif of around 40 amino acids corresponding to the 7 actin monomers it interacts with. Actin binds to tropomyosin electrostatically at two points, through Asp25 and through a cluster of amino acids that includes Lys326, mutated in the gain-of-function mutation. Asp25 interacts with tropomyosin K6, next to K7 that was mutated in the other gain-of-function mutation. We identified four tropomyosin motifs interacting with Asp25 (K6-K7, K48-K49, R90-R91 and R167-K168) and three E-E/D-K/R motifs interacting with Lys326 (E139, E181 and E218), and we predicted that the known skeletal myopathy mutations ΔK7, ΔK49, R91G, ΔE139, K168E and E181K would cause a gain of function. Tests by an in vitro motility assay confirmed that these mutations increased Ca(2+) sensitivity, while mutations not in these motifs (R167H, R244G) decreased Ca(2+) sensitivity. The work reported here explains the molecular mechanism for 6 out of 49 known disease-causing mutations in the TPM2 and TPM3 genes, derived from structural data of the actin–tropomyosin interface