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  • 1
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    A New Type Hi-Speed BLDC Control System Base on Indirect Current Control Strategy (2017)
    Institute of Physics (IOP)
    Details
    Publication Date: 2017-05-10
    Description: High speed BLDC has the characteristic as larger air gap smaller armature inductance, traditional PWM modulation will produce a great number of high frequency current harmonics which led problem like large torque ripple and serious motor heat. In the meantime traditional PWM modulation use the diode rectifier which cause harmonic pollution in electric power net. To solve the problem above, proposes a new motor controller topology. Using the IGBT device to replace the diode on frequency converter rectifier side, apply the power factor correction technology, reduce the pollution on the grid. Using busbar current modulation on the inverter, driving bridge-arm use 3-phase 6-state open as driving Mode, realize the control on a 10000r/min,10kw BLDC. The results of Simulation on matlab show the topological structure as proposed can effectively improve the network side power factor and reduce the motor armature winding harmonic and motor torque ripple.
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics (IOP)
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  • 2
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    Influence of blade angle distribution along leading edge on cavitation performance of a centrifugal pump (2015)
    Institute of Physics (IOP)
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    Publication Date: 2015-01-16
    Description: The influence of blade angle distribution along leading edge on cavitation performance of centrifugal pumps is analysed in the present paper. Three sets of blade angle distribution along leading edge for three blade inlet angles are chosen to design nine centrifugal pump impellers. The RNG k- ##IMG## [http://ej.iop.org/icons/Entities/epsilon.gif] {epsilon} turbulence model and the Zwart-Gerber-Belamri cavitation model are employed to simulate the cavitation flows in centrifugal pumps with different impellers and the same volute. The numerical results are compared with the experimental data, and the comparison proves that the numerical simulation can accurately predict the cavitation performance of centrifugal pumps. On the basis of the numerical simulations, the pump head variations with pump inlet pressure, and the flow details in centrifugal pump are revealed to demonstrate the influence of blade an...
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 3
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    Cavitation performance and flow characteristic in a centrifugal pump with inlet guide vanes (2015)
    Institute of Physics (IOP)
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    Publication Date: 2015-01-16
    Description: The influence of prewhirl regulation by inlet guide vanes (IGVs) on cavitation performance and flow characteristic in a centrifugal pump is investigated. At the impeller inlet, the streamlines are regulated by the IGVs, and the axial velocity distribution is also influenced by the IGVs. Due to the total pressure loss on the IGVs, the cavitation performance of the centrifugal pump degrades. The cavitation area in impeller with IGVs is larger than one without IGVs. The specify values of total pressure loss between the suction pipe inlet and impeller inlet for three cavitation conditions show that the IGVs will generate additional pressure loss, which is related to the IGVs angles and cavitation conditions.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 4
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    Numerical simulation of plunger valve of colliding energy dissipation in the condition of low backpressure and high pressure difference (2018)
    Institute of Physics (IOP)
    Details
    Publication Date: 2018-07-31
    Description: The plunger valve of colliding energy dissipation is one of the important parts in pipeline system. In the operation condition of low backpressure and high pressure difference, cavitation phenomenon is easy to come into being, which may result in noise and vibration and even lead to damage to valve. This article aims to decrease and even eliminate the cavitation phenomenon in plunger valve which may occur in this operation condition. Mathematical models including basic control equation, standard k-ε model, equation model of fluid, cavitation model and so on, are used to calculate flow field. Then, the physical model of plunger valve of colliding energy dissipation is built and numerical simulation study on valve’s inside flow is conducted in using software on the view of hydraulics. The physical model of plunger valve is built by using Pro/E, ICEM CFD and finally simulation is carried out by using Pumplinx software. Two calculations are performed in this study. One is calculatio...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 5
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    Numerical study on extracting energy efficiency by autorotation of elliptic cylinder from low velocity flow (2018)
    Institute of Physics (IOP)
    Details
    Publication Date: 2018-07-31
    Description: A new concept of power generator using autorotation of elliptic cylinder to extract energy from fluid is proposed in the present study. Numerical simulation studies Fluid-Structure Interaction of the fixed-axis autorotation of rigid elliptic cylinder using a coupled Computational Fluid Dynamics (CFD) – Rigid Body Dynamics (RBD) solver. This solver requires no solid mesh to setup FSI (Fluid Structure Interaction) simulation. Based on solving two-dimensional unsteady incompressible N-S equations and SST k - ω turbulent governing equations, the power generator of elliptic cylinder was investigated in different axis rations, eccentric distance ratios and Reynolds number conditions. Numerical results reveal that autorotation of elliptic cylinder can achieve energy extraction. With optimal parameters, the power generator can reach maximum energy extraction efficiency of 34%. The investigation results provided fundamental support for utilization of ocean current energy.
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 6
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    Activation of beta-catenin in dendritic cells regulates immunity versus tolerance in the intestine (2010)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2010-08-14
    Description: Dendritic cells (DCs) play a vital role in initiating robust immunity against pathogens as well as maintaining immunological tolerance to self antigens. However, the intracellular signaling networks that program DCs to become tolerogenic remain unknown. We report here that the Wnt-beta-catenin signaling in intestinal dendritic cells regulates the balance between inflammatory versus regulatory responses in the gut. beta-catenin in intestinal dendritic cells was required for the expression of anti-inflammatory mediators such as retinoic acid-metabolizing enzymes, interleukin-10, and transforming growth factor-beta, and the stimulation of regulatory T cell induction while suppressing inflammatory effector T cells. Furthermore, ablation of beta-catenin expression in DCs enhanced inflammatory responses and disease in a mouse model of inflammatory bowel disease. Thus, beta-catenin signaling programs DCs to a tolerogenic state, limiting the inflammatory response.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3732486/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3732486/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Manicassamy, Santhakumar -- Reizis, Boris -- Ravindran, Rajesh -- Nakaya, Helder -- Salazar-Gonzalez, Rosa Maria -- Wang, Yi-Chong -- Pulendran, Bali -- HHSN266 200700006C/PHS HHS/ -- N01 AI50019/AI/NIAID NIH HHS/ -- N01 AI50025/AI/NIAID NIH HHS/ -- R01 AI048638/AI/NIAID NIH HHS/ -- R01 AI056499/AI/NIAID NIH HHS/ -- R01 DK057665/DK/NIDDK NIH HHS/ -- R01DK057665,/DK/NIDDK NIH HHS/ -- R37 AI048638/AI/NIAID NIH HHS/ -- R37 DK057665/DK/NIDDK NIH HHS/ -- R37AI48638,/AI/NIAID NIH HHS/ -- U19 AI057266/AI/NIAID NIH HHS/ -- U19AI057266,/AI/NIAID NIH HHS/ -- U54 AI057157/AI/NIAID NIH HHS/ -- U54AI057157/AI/NIAID NIH HHS/ -- New York, N.Y. -- Science. 2010 Aug 13;329(5993):849-53. doi: 10.1126/science.1188510.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Emory Vaccine Center, and Yerkes National Primate Research Center, 954 Gatewood Road, Atlanta, GA 30329, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20705860" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cytokines/metabolism ; Dendritic Cells/*immunology/metabolism ; Gene Expression Profiling ; *Inflammation ; Inflammatory Bowel Diseases/*immunology ; Intestinal Mucosa/cytology/*immunology/metabolism ; Macrophages/immunology/metabolism ; Male ; Mice ; Mice, Inbred C57BL ; Mice, Transgenic ; Oligonucleotide Array Sequence Analysis ; *Self Tolerance ; Signal Transduction ; T-Lymphocytes, Helper-Inducer/cytology/*immunology ; T-Lymphocytes, Regulatory/*immunology ; Tretinoin/metabolism ; Wnt Proteins/metabolism ; beta Catenin/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
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    Simulating-optimizing coupled method for pumping well layout at a nitrate-polluted groundwater site (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-11-06
    Description: The unreasonable pumping scheme of the pump-treat technology can lead to high repair cost and poor performance in contaminated groundwater remediation. In order to improve the cost effectiveness of the technology, we took a heavily nitrate-polluted informal domestic waste landfill site in North China as an example, and optimized the pumping scheme using Visual MODFlOW software combined with genetic algorithm (GA) in MGO module. By designing the constant pumping rate scheme and phased pumping rate scheme, optimal layout of pumping wells were determined with the minimum total pumping capacity as the optimal target. The result showed that the two wells which located near the central axis and in the middle and lower reaches of the plume with a constant pumping rate of 13.2 m 3 /d and continuous pumping for 75 days was the optimal pumping solution in constant pumping rate scheme. While the pump schedule as Q 1 = 19.8 m 3 /d, Q 2 =...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 8
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    21st-century rise in anthropogenic nitrogen deposition on a remote coral reef (2017)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2017-05-19
    Description: With the rapid rise in pollution-associated nitrogen inputs to the western Pacific, it has been suggested that even the open ocean has been affected. In a coral core from Dongsha Atoll, a remote coral reef ecosystem, we observe a decline in the 15 N/ 14 N of coral skeleton–bound organic matter, which signals increased deposition of anthropogenic atmospheric N on the open ocean and its incorporation into plankton and, in turn, the atoll corals. The first clear change occurred just before 2000 CE, decades later than predicted by other work. The amplitude of change suggests that, by 2010, anthropogenic atmospheric N deposition represented 20 ± 5% of the annual N input to the surface ocean in this region, which appears to be at the lower end of other estimates.
    Keywords: Geochemistry, Geophysics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 9
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    Numerical investigation on pressure fluctuations in centrifugal compressor with different inlet guide vanes pre-whirl angles (2013)
    Institute of Physics (IOP)
    Details
    Publication Date: 2013-12-22
    Description: The pressure fluctuations in a centrifugal compressor with different inlet guide vanes (IGV) pre-whirl angles were investigated numerically, as well as the pre-stress model and static structural of blade. The natural frequency was evaluated by pre-stress model analysis. The results show that, the aero-dynamic pressure acting on blade surface is smaller than rotation pre-stress, which wouldn't result in large deformation of blade. The natural frequencies with rotation pre-stress are slightly higher than without rotation pre-stress. The leading mechanism of pressure fluctuations for normal conditions is the rotor-stator (IGVs) interaction, while is serious flow separations for conditions that are close to surge line. A few frequency components in spectra are close to natural frequency, which possibly result in resonant vibration if amplitude is large enough, which is dangerous for compressor working, and should be avoided.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 10
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    Forty years of reform and opening up: Chinas progress toward a sustainable path (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉After 40 years of reform and "opening up," China has made remarkable economic progress. Such economic prosperity, however, has been coupled with environmental degradation. We analyze diverse long-term data to determine whether China is experiencing a decoupling of economic growth and environmental impacts, and where China stands with respect to the Sustainable Development Goals (SDGs) in terms of reducing regional division, urban-rural gap, social inequality, and land-based impacts on oceans. The results highlight that China’s desire to achieve "ecological civilization" has resulted in a decoupling trend for major pollutants since 2015, while strong coupling remains with CO〈sub〉2〈/sub〉 emissions. Progress has been made in health care provision, poverty reduction, and gender equity in education, while income disparity continues between regions and with rural-urban populations. There is a considerable way to go toward achieving delivery of the SDGs; however, China’s progress toward economic prosperity and concomitant sustainability provides important insights for other countries.〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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