Wind Turbine Controls for Farm and Offshore Operation

Development of advanced control techniques is a critical measure for reducing the cost of energy for wind power generation, in terms of both enhancing energy capture and reducing fatigue load. There are two remarkable trends for wind energy. First, more and more large wind farms are developed in order to reduce the unit-power cost in installation, operation, maintenance and transmission. Second, offshore wind energy has received significant attention when the scarcity of land resource has appeared to be a major bottleneck for next level of wind penetration, especially for Europe and Asia. This dissertation study investigates on several wind turbine control issues in the context of wind farm and offshore operation scenarios. Traditional wind farm control strategies emphasize the effect of the deficit of average wind speed, i.e. on how to guarantee the power quality from grid integration angle by the control of the electrical systems or maximize the energy capture of the whole wind farm by optimizing the setting points of rotor speed and blade pitch angle, based on the use of simple wake models, such as Jensen wake model. In this study, more complex wake models including detailed wind speed deficit distribution across the rotor plane and wake meandering are used for load reduction control of wind turbine. A periodic control scheme is adopted for individual pitch control including static wake interaction, while for the case with wake meandering considered, both a dual-mode model predictive control and a multiple model predictive control is applied to the corresponding individual pitch control problem, based on the use of the computationally efficient quadratic programming solver qpOASES. Simulation results validated the effectiveness of the proposed control schemes. Besides, as an innovative nearly model-free strategy, the nested-loop extremum seeking control (NLESC) scheme is designed to maximize energy capture of a wind farm under both steady and turbulent wind. The NLESC scheme is evaluated with a simple wind turbine array consisting of three cascaded variable-speed turbines using the SimWindFarm simulation platform. For each turbine, the torque gain is adjusted to vary/control the corresponding axial induction factor. Simulation under smooth and turbulent winds shows the effectiveness of the proposed scheme. Analysis shows that the optimal torque gain of each turbine in a cascade of turbines is invariant with wind speed if the wind direction does not change, which is supported by simulation results for smooth wind inputs. As changes of upstream turbine operation affects the downstream turbines with significant delays due to wind propagation, a cross-covariance based delay estimate is proposed as adaptive phase compensation between the dither and demodulation signals. Another subject of investigation in this research is the evaluation of an innovative scheme of actuation for stabilization of offshore floating wind turbines based on actively controlled aerodynamic vane actuators. For offshore floating wind turbines, underactuation has become a major issue and stabilization of tower/platform adds complexity to the control problem in addition to the general power/speed regulation and rotor load reduction controls. However, due to the design constraints and the significant power involved in the wind turbine structure, a unique challenge is presented to achieve low-cost, high-bandwidth and low power consumption design of actuation schemes. A recently proposed concept of vertical and horizontal vanes is evaluated to increase damping in roll motion and pitch motion, respectively. The simulation platform FAST has been modified including vertical and horizontal vane control. Simulation results validated the effectiveness of the proposed vertical and horizontal active vane actuators

Effect of tensor couplings in a relativistic Hartree approach for finite nuclei

The relativistic Hartree approach describing the bound states of both nucleons and anti-nucleons in finite nuclei has been extended to include tensor couplings for the $\omega$- and $\rho$-meson. After readjusting the parameters of the model to the properties of spherical nuclei, the effect of tensor-coupling terms rises the spin-orbit force by a factor of 2, while a large effective nucleon mass $m^{*}/M_{N} \approx 0.8$ sustains. The overall nucleon spectra of shell-model states are improved evidently. The predicted anti-nucleon spectra in the vacuum are deepened about 20 -- 30 MeV.Comment: 31 pages, 4 postscript figures include

Conditional Deletion of PDK1 in the Forebrain Causes Neuron Loss and Increased Apoptosis during Cortical Development

Decreased expression but increased activity of PDK1 has been observed in neurodegenerative disease. To study in vivo function of PDK1 in neuron survival during cortical development, we generate forebrain-specific PDK1 conditional knockout (cKO) mice. We demonstrate that PDK1 cKO mice display striking neuron loss and increased apoptosis. We report that PDK1 cKO mice exhibit deficits on several behavioral tasks. Moreover, PDK1 cKO mice show decreased activities for Akt and mTOR. These results highlight an essential role of endogenous PDK1 in the maintenance of neuronal survival during cortical development

Effects of Copper Oxide Nanoparticles on the Growth of Rice (Oryza Sativa L.) Seedlings and the Relevant Physiological Responses

Rice (Oryza sativa L.), a major staple food for billions of people, was assessed for its phytotoxicity of copper oxide nanoparticle (CuO NPs, size < 50 nm). Under hydroponic condition, seven days of exposure to 62.5, 125, and 250 mg/L CuO NPs significantly suppressed the growth rate of rice seedlings compared to both the control and the treatment of supernatant from 250 mg/L CuO NP suspensions. In addition, physiological indexes associated with antioxidants, including membrane damage and antioxidant enzyme activity, were also detected. Treatment with 250 mg/L CuO NPs significantly increased malondialdehyde (MDA) content and electrical conductivity of rice shoots by 83.4% and 67.0%, respectively. The activity of both catalase and superoxide dismutase decreased in rice leaves treated with CuO NPs at the concentration of 250 mg/L, while the activity of the superoxide dismutase significantly increased by 1.66 times in rice roots exposed to 125 mg/L CuO NPs. The chlorophyll, including chlorophyll a and chlorophyll b, and carotenoid content in rice leaves decreased with CuO NP exposure. Finally, to explain potential molecular mechanisms of chlorophyll variations, the expression of four related genes, namely, Magnesium chelatase D subunit, Chlorophyll synthase, Magnesium-protoporphyrin IX methyltransferase, and Chlorophyllide a oxygenase, were quantified by qRT-PCR. Overall, CuO NPs, especially at 250 mg/L concentration, could affect the growth and development of rice seedlings, probably through oxidative damage and disturbance of chlorophyll and carotenoid synthesis

The Function of the PRRSV–Host Interactions and Their Effects on Viral Replication and Propagation in Antiviral Strategies

Porcine reproductive and respiratory syndrome virus (PRRSV) affects the global swine industry and causes disastrous economic losses each year. The genome of PRRSV is an enveloped single-stranded positive-sense RNA of approximately 15 kb. The PRRSV replicates primarily in alveolar macrophages of pig lungs and lymphatic organs and causes reproductive problems in sows and respiratory symptoms in piglets. To date, studies on how PRRSV survives in the host, the host immune response against viral infections, and pathogenesis, have been reported. PRRSV vaccines have been developed, including inactive virus, modified live virus, attenuated live vaccine, DNA vaccine, and immune adjuvant vaccines. However, there are certain problems with the durability and effectiveness of the licensed vaccines. Moreover, the high variability and fast-evolving populations of this RNA virus challenge the design of PRRSV vaccines, and thus effective vaccines against PRRSV have not been developed successfully. As is well known, viruses interact with the host to escape the host’s immune response and then replicate and propagate in the host, which is the key to virus survival. Here, we review the complex network and the mechanism of PRRSV–host interactions in the processes of virus infection. It is critical to develop novel antiviral strategies against PRRSV by studying these host–virus interactions and structures to better understand the molecular mechanisms of PRRSV immune escape

Estimating the incubation period of hand, foot and mouth disease for children in different age groups

Abstract Hand, foot and mouth disease (HFMD) is a childhood disease causing large outbreaks frequently in Asia and occasionally in Europe and the US. The incubation period of HFMD was typically described as about 3–7 days but empirical evidence is lacking. In this study, we estimated the incubation period of HFMD from school outbreaks in Hong Kong, utilizing information on symptom onset and sick absence dates of students diagnosed with HFMD. A total of 99 HFMD cases from 12 schools were selected for analysis. We fitted parametric models accounting for interval censoring. Based on the best-fitted distributions, the estimated median incubation periods were 4.4 (95% CI 3.8–5.1) days, 4.7 (95% CI 4.5–5.1) days and 5.7 (95% CI 4.6–7.0) days for children in kindergartens, primary schools and secondary schools respectively. From the fitted distribution, the estimated incubation periods can be longer than 10 days for 8.8% and 23.2% of the HFMD cases in kindergarten and secondary schools respectively. Our results show that the incubation period of HFMD for secondary schools students can be longer than the ranges commonly described. An extended period of enhanced personal hygiene practice and disinfection of the environment may be needed to control outbreaks

Assessment of the Phytotoxicity of Metal Oxide Nanoparticles on Two Crop Plants, Maize (Zea mays L.) and Rice (Oryza sativa L.)

In this study, the phytotoxicity of seven metal oxide nanoparticles(NPs)—titanium dioxide (nTiO2), silicon dioxide (nSiO2), cerium dioxide (nCeO2), magnetite (nFe3O4), aluminum oxide (nAl2O3), zinc oxide (nZnO) and copper oxide (nCuO)—was assessed on two agriculturally significant crop plants (maize and rice). The results showed that seed germination was not affected by any of the seven metal oxide NPs. However, at the concentration of 2000 mg·L−1, the root elongation was significantly inhibited by nCuO (95.73% for maize and 97.28% for rice), nZnO (50.45% for maize and 66.75% for rice). On the contrary, minor phytotoxicity of nAl2O3 was only observed in maize, and no obvious toxic effects were found in the other four metal oxide NPs. By further study we found that the phytotoxic effects of nZnO, nAl2O3 and nCuO (25 to 2000 mg·L−1) were concentration dependent, and were not caused by the corresponding Cu2+, Zn2+ and Al3+ ions (0.11 mg·L−1, 1.27 mg·L−1 and 0.74 mg·L−1, respectively). Furthermore, ZnO NPs (<50 nm) showed greater toxicity than ZnO microparticles(MPs)(<5 μm) to root elongation of both maize and rice. Overall, this study provided valuable information for the application of engineered NPs in agriculture and the assessment of the potential environmental risks

Performance and mechanism of CO2 reduction by DBD-coupled mesoporous SiO2

In the process of CO2 reduction with dielectric barrier discharge (DBD)-coupled catalysis, the existing material presents unsatisfactory synergy, such as high cost, complicated preparation processes, and low conversion rates. An inexpensive and environmentally friendly mesoporous SiO2 with different morphologies by gel–sol method was synthesized and then introduced for synergistic conversion of CO2 with DBD. The physicochemical properties of the synthesized mesoporous SiO2 materials were analyzed using X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and Brunauer-Emmett-Teller method, indicated the prepared mesoporous materials manifested large specific surface areas, ordered pore channels and pore size, and good stability. The CO2 reduction performance, CO selectivity, and energy efficiency of DBD alone and DBD-coupled mesoporous SiO2 were investigated at different input powers. The SiO2 prepared with 1.05 g cetyltrimethylammonium bromide addition had the highest activity, in which the conversion of CO2, CO yield and energy efficiency were increased by 56.73, 68.41, and 122.31%, respectively, compared with DBD alone. The primary CO2 conversion mechanism of the mesoporous SiO2-coupled DBD was analyzed. It is shown that the suitable pore capacity structure, the large specific surface area, and the presence of filament discharge within the pore size of suitable mesoporous material can promote the decomposition of CO2 on its surface