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  • 1
    Publication Date: 2014-12-11
    Description: During the start-up process, the strong instabilities happened at no load operation in a low head axial flow fixed-blade turbine, with strong pressure pulsation and vibration. The rated speed can not reach until guide vane opening to some extent, and stable operation could not be maintained under the rated speed at some head, which had a negative impact on the grid-connected operation of the unit. In order to find the reason of this phenomenon, the unsteady flow field of the whole flow passage at no load conditions was carried out to analyze the detailed fluid field characteristics including the pressure pulsation and force imposed on the runner under three typical heads. The main hydraulic cause of no load conditions instability was described. It is recommended that the power station should try to reduce the no-load running time and go into the high load operation as soon as possible when connected to grid at the rated head. Following the recommendations, the plant operation pr...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 2
    Publication Date: 2014-03-19
    Description: Chaohu Lake is one of the largest freshwater lakes in China, however, with the rapid expansion of Hefei, the water environment of Chaohu Lake shows significantly deterioration. In this paper, RapidEye and MODIS imagery were used to monitor the chlorophyll alpha (Chla) distribution in Chaohu Lake. After analyzing the correlation between in-situ measured Chla concentrations and each channel of RapidEye and MODIS imagery, the optimal band combination for the establishment of Chla concentration was determined. For RapidEye imagery, the red edge channel and near infrared channel are relatively more sensitive than other channels. The inversion model using the feature of (B5+B4)/(B2+B1) worked the best with the square value of correlation coefficient reaching up to 0.745. A similar procedure was applied to MODIS imagery. The experiments show that RapidEye with its red edge channel is an effective data source for water environment monitoring, it could provide high spatial resolution of ...
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    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 3
    Publication Date: 2018-07-31
    Description: With the strong demands on the further development of economy and energy, tidal energy, with own green and renewable advantages, has gained more and more attention, of which as the main application type, bulb tubular turbines have played an important role in the power exploitation. Characteristic of low head and large discharge, flow properties of a bulb turbine turn out to be more complicated, which seriously affects the actual operation performance of the station. To promote wide development of tidal energy, it is ritual to deeply dig into the performance of bulb turbine. In this paper, a bulb-type model turbine used for tidal energy is taken for example. By means of CFD method and model test, hydraulic specifications, like efficiency and cavitation properties, have been obtained and compared in case of different conditions. Through the contrast between numerical simulation and model test, a novel corrected method relative to the low-head tidal turbine is brought out for furth...
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    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 4
    Publication Date: 2017-02-14
    Description: Soil erosion is serious with rocky desertification areas appearing in mountainous Karst regions in southwest China due to a conspicuous contradiction between man and the land resource. Land use and land cover play significant roles in regional soil erosion by water. This paper aimed to quantify regional soil erosion and to explore relationships between soil erosion and land use/land cover in order to locate high risk areas requiring soil conservation. Based on GIS, the Revised Universal Soil Loss Equation (RUSLE) was employed for erosion assessment for a typical Karst region, Jinfo Mountain region in southwest China, using local parameters. Spatial distribution of topsoil erosion was analyzed and relationships between soil erosion and land use/land cover changes (LULC) were statistically explored and discussed for regional erosion control. The overall values were under 25 t.ha.a, with the medium erosion areas accounting for 12.7% and the intense and very intense erosion areas to...
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  • 5
    Publication Date: 2016-11-22
    Description: Leaf Chlorophyll content (Ct) indicates plant physiological status and can be detected by hyperspectral measurements. However, it is difficult to conclude that different genotypes of same species have the same relationship with the hyperspectral data. The aim of this paper was to test that whether the different genotypes of same species have the similar relationship with hyperspectral reflectance. First of all, spectral reflectance of populus simonii (Populus simonii Carr) and I-72 poplar (Popul us euramericana cv. ‘San Martino I-72/58’) were collected by spectrometric meter, and then extract chlorophyll index (CI) and other 11 types of vegetation indices from the hyperspectral reflectance data. At last, relationships between different vegetation indices and Ct of the two genotypes of poplar were compared. Results show that (1) the relationships between SPAD value and Ct are different in the low and high Ct level, we can choose proper vegetation index, REPIG, mSR705...
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  • 6
    Publication Date: 2017-03-11
    Description: Surface treatment is one of the most effective ways to elongate the service life of concrete. The surface treatment agents, including organic and inorganic types, have been intensively studied. In this paper, the silica-based hybrid nanocomposite, which take advantages of both organic and inorganic treatment agents, was synthesized and used for surface treatment of hardened cement-based material. The effectiveness of organic and inorganic hybrid nanocomposite was evaluated through investigations on the gas permeability of cement-based materials. The results showed that SiO 2 /PMHS hybrid nanocomposite can greatly decrease the gas transport properties of hardened cement-based materials and has a great potential for surface treatment of cementitious materials.
    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
    Publication Date: 2016-12-14
    Description: For the low-head hydropower station, the operating head is low, and the turbine intake channel is relatively short. The turbine internal flow behaviour can be influenced by fluid flows in the upstream reservoir easily, then it would influence the turbine hydraulic performance. Water flows in the upstream reservoir can be influenced by the Coriolis force by the Earth rotation, and it differs at the different Rossby number. In this paper, the Coriolis effect on the approach flows and the turbine performances are investigated numerically for the low-head units. Firstly, the Coriolis effect (under the different latitudes and the same characteristic length scale) on reservoir flows was predicted. Secondly, the prototype performance of a bulb-type turbine was simulated including the reservoir flow with the Coriolis effect, and then the effect on the turbine performance is be discussed. Results show that the flow field in the upstream reservoir at the low Rossby number, the ratio of in...
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  • 8
    Publication Date: 2013-12-22
    Description: At the same oscillation amplitude, Reynolds Number, mean angle of attack, the dynamic stall characteristics of the NREL S809 airfoil undergoing sinusoidal pitch oscillations of different oscillation frequencies were investigated with modified k - ω SST turbulence model of CFD solution for two-dimensional numerical simulation. The predicted lift, drag coefficients and moment coefficients were compared with the Ohio State University wind tunnel test results, which showed a good agreement. The birth, development and breaking off of eddies were analyzed through streamline distribution around airfoil and the influence of oscillation frequencies on dynamic stall characteristics was also described and analyzed in detail, which enrich the database of dynamic stall characteristics needed by the quantization of oscillation frequencies on dynamic characteristics and prove that sliding mesh method is reliable when dealing with dynamic stall problems.
    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
    Publication Date: 2018-09-20
    Description: After evaluating the studio acoustics environment quality and finding problems, related reforms about acoustic were performed, such as consulting the acoustic design code related studio, through testing on background noise, reverberation time, evenness of acoustic field and other acoustic indeces at the coalface, making antithesis and analysis. Catching the defects of studio acoustic design implied that: electronic equipment running lead to the background noise in the studio is too large; the interface material in the room sounds absorption is too little, bringing the reverberation time is too long; the wall sounds absorbing material and reflector position is unreasonable begets the lack of evenness of the acoustic field. According to the problems above, a theoretical analysis and calculation of the overall acoustic of the studio was conducted, finally advancing the reforms plan. The reformation plan consists of processing door and window insulate sounds, increasing the sounds a...
    Print ISSN: 1757-8981
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 10
    Publication Date: 2017-10-21
    Description: The intersection element is an important part of the helicopter subfloor structure. The numerical simulation model of the intersection element is established and the crush simulation is conducted. The simulation results agree well with the experiment results. In order to improve the buffering capacity and energy-absorbing capacity, the intersection element is redesigned. The skin and the floor in the intersection element are replaced with foldcore sandwich structures. The new intersection element is studied using the same simulation method as the typical intersection element. The analysis result shows that foldcore can improve the buffering capacity and the energy-absorbing capacity, and reduce the structure mass.
    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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