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  • 1
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    Numerical investigation for one bad-behaved flow in a Pelton turbine (2015)
    Institute of Physics (IOP)
    Details
    Publication Date: 2015-01-16
    Description: The gas-liquid two-phase flow in pelton turbines is very complicated, there are many kinds of bad-behaved flow in pelton turbines. In this paper, CFD numerical simulation for the pelton turbine was conducted using VOF two-phase model. One kind of bad-behaved flow caused by the two jets was captured, and the bad-behaved flow was analysed by torque on buckets. It can be concluded that the angle between the two jets and the value of ratio of runner diameter and jet diameter are important parameters for the bad-behaved flow. Furthermore, the reason why the efficiency of some multi-jet type turbines is very low can be well explained by the analysis of bad-behaved flow. Finally, some suggestions for improvement were also provided in present paper.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics (IOP)
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  • 2
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    Investigation on cavitation for hump characteristics of a pump turbine in pump mode (2015)
    Institute of Physics (IOP)
    Details
    Publication Date: 2015-01-16
    Description: In order to get the accurate hump characteristic curve of a pump turbine in pump mode, three dimensional steady simulations were carried out using SST k-ω turbulence model with cavitation model and without cavitation model under different operation condition points with 19 mm guide vanes opening. A refinement grids were generated to adapt the turbulence model. The results obtained with cavitation model show a better agreement with experiments. The detailed analysis was undertaken to find out the relationship between the cavitation and hump region. It is concluded that the hump characteristic is related with cavitation.
    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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    Critical population density triggers rapid formation of vast oceanic fish shoals (2009)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2009-03-28
    Description: Similarities in the behavior of diverse animal species that form large groups have motivated attempts to establish general principles governing animal group behavior. It has been difficult, however, to make quantitative measurements of the temporal and spatial behavior of extensive animal groups in the wild, such as bird flocks, fish shoals, and locust swarms. By quantifying the formation processes of vast oceanic fish shoals during spawning, we show that (i) a rapid transition from disordered to highly synchronized behavior occurs as population density reaches a critical value; (ii) organized group migration occurs after this transition; and (iii) small sets of leaders significantly influence the actions of much larger groups. Each of these findings confirms general theoretical predictions believed to apply in nature irrespective of animal species.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Makris, Nicholas C -- Ratilal, Purnima -- Jagannathan, Srinivasan -- Gong, Zheng -- Andrews, Mark -- Bertsatos, Ioannis -- Godo, Olav Rune -- Nero, Redwood W -- Jech, J Michael -- New York, N.Y. -- Science. 2009 Mar 27;323(5922):1734-7. doi: 10.1126/science.1169441.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA. makris@mit.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19325116" target="_blank"〉PubMed〈/a〉
    Keywords: Animal Migration ; Animals ; Atlantic Ocean ; *Behavior, Animal ; Ecosystem ; Fishes/*physiology ; Population Density ; Reproduction ; Spatial Behavior ; *Swimming ; Time Factors
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Two pairs of neurons in the central brain control Drosophila innate light preference (2010)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2010-10-23
    Description: Appropriate preferences for light or dark conditions can be crucial for an animal's survival. Innate light preferences are not static in some animals, including the fruit fly Drosophila melanogaster, which prefers darkness in the feeding larval stage but prefers light in adulthood. To elucidate the neural circuit underlying light preference, we examined the neurons involved in larval phototactic behavior by regulating neuronal functions. Modulating activity of two pairs of isomorphic neurons in the central brain switched the larval light preference between photophobic and photophilic. These neurons were found to be immediately downstream of pdf-expressing lateral neurons, which are innervated by larval photoreceptors. Our results revealed a neural mechanism that could enable the adjustment of animals' response strategies to environmental stimuli according to biological needs.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gong, Zhefeng -- Liu, Jiangqu -- Guo, Chao -- Zhou, Yanqiong -- Teng, Yan -- Liu, Li -- New York, N.Y. -- Science. 2010 Oct 22;330(6003):499-502. doi: 10.1126/science.1195993.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, People's Republic of China. zfgong@moon.ibp.ac.cn〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20966250" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Behavior, Animal/*radiation effects ; Brain/cytology/physiology ; Drosophila melanogaster/cytology/growth & development/*radiation effects ; Green Fluorescent Proteins ; Larva/physiology/radiation effects ; *Light ; Neural Pathways ; Neurons/*physiology
    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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  • 5
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    A histone acetyltransferase regulates active DNA demethylation in Arabidopsis (2012)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2012-06-16
    Description: Active DNA demethylation is an important part of epigenetic regulation in plants and animals. How active DNA demethylation is regulated and its relationship with histone modification patterns are unclear. Here, we report the discovery of IDM1, a regulator of DNA demethylation in Arabidopsis. IDM1 is required for preventing DNA hypermethylation of highly homologous multicopy genes and other repetitive sequences that are normally targeted for active DNA demethylation by Repressor of Silencing 1 and related 5-methylcytosine DNA glycosylases. IDM1 binds methylated DNA at chromatin sites lacking histone H3K4 di- or trimethylation and acetylates H3 to create a chromatin environment permissible for 5-methylcytosine DNA glycosylases to function. Our study reveals how some genes are indicated by multiple epigenetic marks for active DNA demethylation and protection from silencing.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3575687/" 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/PMC3575687/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Qian, Weiqiang -- Miki, Daisuke -- Zhang, Heng -- Liu, Yunhua -- Zhang, Xi -- Tang, Kai -- Kan, Yunchao -- La, Honggui -- Li, Xiaojie -- Li, Shaofang -- Zhu, Xiaohong -- Shi, Xiaobing -- Zhang, Kangling -- Pontes, Olga -- Chen, Xuemei -- Liu, Renyi -- Gong, Zhizhong -- Zhu, Jian-Kang -- R01 GM059138/GM/NIGMS NIH HHS/ -- R01 GM070795/GM/NIGMS NIH HHS/ -- R01GM059138/GM/NIGMS NIH HHS/ -- R01GM070795/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2012 Jun 15;336(6087):1445-8. doi: 10.1126/science.1219416.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Shanghai Center for Plant Stress Biology and Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, China.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22700931" target="_blank"〉PubMed〈/a〉
    Keywords: Acetylation ; Arabidopsis/*genetics/*metabolism ; Arabidopsis Proteins/chemistry/genetics/*metabolism ; Chromatin/metabolism ; DNA Glycosylases/metabolism ; *DNA Methylation ; DNA, Plant/*metabolism ; Gene Silencing ; Genes, Plant ; Histone Acetyltransferases/chemistry/genetics/*metabolism ; Histones/metabolism ; Methylation ; Mutation ; Nuclear Proteins/genetics/metabolism ; Protein Structure, Tertiary ; Transgenes
    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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  • 6
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    The application of PA/CF in stab resistance body armor (2017)
    Institute of Physics (IOP)
    Details
    Publication Date: 2017-07-07
    Description: Stab resistance body armor (SRBA) is an essential defensive equipment to protect human body against injuries from stabbing. The conventional SRBAs shared low wearing frequency since they are heavy and poor in flexibility. This paper designed a structured stab-resistance plate using the model of crocodile armor and manufactured using 3D printing technology-laser sintering (LS). CF(Carbon fiber) was applied to enhance the stab resistance properties of SRBA. The effects of the material and structure were analysed through the stab resistance property tests based on the national standard GA68-2008. It is found that the stab resistance property of flat plates sintered by PA powder and PA/CF are both weaker than that of the structured plate. The penetrating depth of PA/CF structured plate is significantly 2-mm-less than the pure PA structured plate. The SEM observations confirmed the conclusion that addition of the CF largely improved the plate stab resistance property. Moreover, using...
    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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  • 7
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    Research of fluid-induced pressure fluctuation due to impeller-volute interaction in a centrifugal pump (2013)
    Institute of Physics (IOP)
    Details
    Publication Date: 2013-12-22
    Description: The fluid pressure fluctuation generated by unsteady flow is a very important factor to induce vibration of the centrifugal pump. The relative movement between impeller and volute generates an unsteady interaction which affects not only the overall pump performance, but is also responsible for pressure fluctuations. Pressure fluctuations interact with the volute casing or even with the circuit and give rise to dynamic effects over the mechanical parts, which are one of the most important sources of vibration and hydraulic noise. To investigate the flow characteristic in the centrifugal pump, the unsteady flow is simulated by CFD methods in this paper. Unsteady flow characteristic in the centrifugal pump is obtained considering the impeller-volute interaction in the whole flow field. Based on the unsteady flow simulation, amplitude-frequency characteristics of the pressure fluctuation in the centrifugal pump are obtained through setting up monitoring point at the impeller outlet....
    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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  • 8
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    Optimization of testing system and experiment research for pump turbine model (2013)
    Institute of Physics (IOP)
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    Publication Date: 2013-12-22
    Description: The pump turbine is key component of Pump Storage Power Plants. Moreover, the model testing proves significant guidance on design of pump turbine. Since pump turbine model testing is different from turbine model resulting from four quadrant experiment, point acquisition for transient operation conditions and special data processing, the optimization is made for these technological difficulties. In order to obtain a higher efficiency, a higher precision and a high degree of automation, the system of data acquisition is designed, in which the PXI platform was adopted, and the virtual instrument software LabVIEW was employed. And this system was successfully applied for the testing platform of Harbin Institute of Large Electric Machinery which achieves functions of transient conditions acquisition, measurement for positive and negative flow and speed, data processing, generating report, analysis for pressure fluctuation and so on. Finally four quadrant experiment was carried out in...
    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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  • 9
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    Environmental impact analysis of mine tailing reservoir (2016)
    Institute of Physics (IOP)
    Details
    Publication Date: 2016-09-03
    Description: Under certain conditions landscape topography which utilizes mine tailing reservoir construction using is likely to increase lateral recharge source regions, resulting in dramatic changes to the local hydrological dynamic field and recharge of downstream areas initiated by runoff, excretion state, elevated groundwater depth, shallow groundwater, rainfall direct communication, and thinning of the vadose zone. Corrosive leaching of topsoil over many years of exposure to chemical fertilizers and pesticides may result in their dissolution into the groundwater system, which may lead to excessive amounts of many harmful chemicals, therby affecting the physical and mental health of human residents and increase environmental vulnerability and risk associated with the water and soil. According to field survey data from Yujiakan, Qian'an City, and Hebei provinces, this paper analyzes the hydrogeological environmental mechanisms of areas adjacent to mine tailing reservoirs and establishes ...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics (IOP)
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  • 10
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    Observation of prethermalization in long-range interacting spin chains (2017)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2017-08-26
    Description: Although statistical mechanics describes thermal equilibrium states, these states may or may not emerge dynamically for a subsystem of an isolated quantum many-body system. For instance, quantum systems that are near-integrable usually fail to thermalize in an experimentally realistic time scale, and instead relax to quasi-stationary prethermal states that can be described by statistical mechanics, when approximately conserved quantities are included in a generalized Gibbs ensemble (GGE). We experimentally study the relaxation dynamics of a chain of up to 22 spins evolving under a long-range transverse-field Ising Hamiltonian following a sudden quench. For sufficiently long-range interactions, the system relaxes to a new type of prethermal state that retains a strong memory of the initial conditions. However, the prethermal state in this case cannot be described by a standard GGE; it rather arises from an emergent double-well potential felt by the spin excitations. This result shows that prethermalization occurs in a broader context than previously thought, and reveals new challenges for a generic understanding of the thermalization of quantum systems, particularly in the presence of long-range interactions.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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