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  • 1
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    Prediction of pressure fluctuation of a hydraulic turbine at no-load condition (2015)
    Institute of Physics (IOP)
    Details
    Publication Date: 2015-01-16
    Description: In order to study characteristics of pressure fluctuation of a turbine during the starting period, a turbine with guide vanes device at no-load condition was investigated using RNG k- ##IMG## [http://ej.iop.org/icons/Entities/epsilon.gif] {epsilon} turbulence model. The inner flow distribution and pressure fluctuation characteristics were analyzed. Results show that the pressure fluctuations in the region between the runner and guide vanes are different around the runner inlet. The dominant frequency of pressure fluctuation in the vaneless space close to the casing outlet is the blade passing frequency, while the dominant frequency at the rest region is the twice of the blade passing frequency. The increase of amplitude of pressure fluctuation close to the casing outlet can be attribute to the large scale stall at suction side of the runner inlet.
    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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  • 2
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    Online module-level fault detection of PV arrays using an improved two-stage Hampel identifier (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-10-31
    Description: This paper presents a novel fault detection method for photovoltaic (PV) array using an improved two-stage Hampel identifier, which can quickly detect the occurrence of faults and locate them at PV module level. The fault detection method is implemented in a two-level wireless sensor network based distributed on-line monitoring system which is developed to monitor the voltage of each PV module and current of all parallel PV strings in real-time. The 1 st stage Hampel identifier detects and locates the faulty PV strings by comparing the instantaneous currents of different PV strings. The 2 nd stage Hampel identifier detects and locates the faulty PV modules by comparing the instantaneous voltages of different PV modules in the faulty strings. Experimental results show that the proposed method can successfully detect and locate faulty strings and modules in several faulty cases, including the line-line faults, the degradation faults, the partial shading faults ...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 3
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    Synthesis, curing of hydroxyl-terminated liquid fluoroelastomer: thermal, chemical resistant and mechanical properties (2017)
    Institute of Physics (IOP)
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    Publication Date: 2017-07-07
    Description: A novel hydroxyl-terminated liquid fluoroelastomer (HTLF) was synthesized; FT-IR, GPC and 1 H-NMR result show that HTLF was synthesized successfully. Then HTLF was cured with HDI trimer, the structure of cured product was characterized by FT-IR. Compared with traditional solid fluorine elastomer, Cured HTLF has higher char yield and faster thermal decomposition rate. It ascribed to the introduction of ring structure the cross-link structure formed in the curing process. The study of chemical resistant properties and tensile strength of cured fluoroelastomer film suggested that Cured HTLF was provided with similar mmechanical properties, chemical resistant property than solid fluorine elastomer.
    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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  • 4
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    High speed observation of HIFU-induced cavitation cloud near curved rigid boundaries (2015)
    Institute of Physics (IOP)
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    Publication Date: 2015-01-16
    Description: This paper focuses on the experimental study of the influence of surface curvature to the behaviour of HIFU-induced cavitation cloud. A Q-switched ruby pulse laser is used to induce cavitation nuclei in deionized water. A piezoelectric ultrasonic transducer (1.7 MHz) provides a focused ultrasound field to inspire the nucleus to cavitation cloud. A PZT probe type hydrophone is applied for measuring the HIFU sound field. It was observed that the motion of cavitation cloud located near the boundary is significantly influenced by the distance between cloud and boundary, as well as the curvature of the boundary. The curvature was defined by parameters λ and ξ . Convex boundary, concave boundary, and flat boundary correspond to ξ 1 and ξ = 1, respectively. Different behaviours of the cloud, including the migration of the cloud, the characteristics of oscillation, etc., were observed under different boundary curvatures by high-speed photog...
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 5
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    Assessment of land degradation using time series trend analysis of vegetation indictors in Otindag Sandy land (2014)
    Institute of Physics (IOP)
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    Publication Date: 2014-03-19
    Description: Land condition assessment is a basic prerequisite for finding the degradation of a territory, which might lead to desertification under climatic and human pressures. The temporal change in vegetation productivity is a key indicator of land degradation. In this paper, taking the Otindag Sandy Land as a case, the mean normalized difference vegetation index (NDVI_a), net primary production (NPP) and vegetation rain use efficiency (RUE) dynamic trends during 2001–2010 were analysed. The Mann-Kendall test and the Correlation Analysis method were used and their sensitivities to land degradation were evaluated. The results showed that the three vegetation indicators (NDVI_a, NPP and RUE) showed a downward trend with the two methods in the past 10 years and the land was degraded. For the analysis of the three vegetation indicators (NDVI_a, NPP and RUE), it indicated a decreasing trend in 62.57%, 74.16% and 88.56% of the study area according to the Mann-Kendall test and in 57.85%, 68.38%...
    Print ISSN: 1755-1307
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    Topics: Geography , Geosciences , Physics
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  • 6
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    The development status of construction equipment and technology in China (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-09-20
    Description: In recent years, with the continuous development of urbanization in China, construction equipment and technology in the field of building are developing rapidly. China has made much progress in this field, but there is also a gap in comparison. Rapid growth needs to follow the appropriate direction of development. In the future, China will further accelerate the speed of urban intensive construction, so it is of great significance to find a correct direction for the development of Chinese cities. Based on this purpose, this paper summarizes the current situation and rules of building equipment and technology in the view of the rapid development of modern architecture and related practical achievements. This article further analyses the building technology and equipment from the aspects of social culture, political economy, laws and regulations, and discipline development. The conclusion is that in the future development of buildings, the energy saving of construction equipment a...
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    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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    An online health monitoring system for photovoltaic arrays based on the B/S architecture (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-10-31
    Description: In order to improve the working efficiency of the photovoltaic (PV) array inspection system, the application of online monitoring systems for the PV arrays is quickly rising. In this paper, an online PV array monitoring combining with B/S architecture, Python language, and Flask framework is developed to monitor and diagnose the status of PV arrays which can display the data of the PV array and facilitate the staff to monitor the working status of PV array. When a fault occurs, the staff can also register the fault information on the website quickly. The developed system is composed of three parts: data acquisition, data transmission and PV online monitoring website. Firstly, the system uses the Raspberry Pi3 to collect the data when the PV array operates in maximum power point (MPP), and the acquired data is stored locally in the Raspberry Pi. And then, the data is uploaded to the PC side via the FileZilla server software and further transmitted to online monitoring website. Fi...
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    Topics: Geography , Geosciences , Physics
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  • 8
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    Fault diagnosis and classification for photovoltaic arrays based on principal component analysis and support vector machine (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-10-31
    Description: In order to dig out more typical features of photovoltaic (PV) with multitudinous characteristic parameters, and realize fault diagnosis and classification for PV arrays effectively. A method based on principal component analysis (PCA) has been proposed in this paper. At first, the data set of PV array is processed by PCA and then a transform matrix is produced. Second, the processed data will be classified by supporting vector machine (SVM). Finally, a classification model will be built. Two sets of data, collected from PV simulation system and actual PV array, are adopted to examine this method. The result shows that the method is able to recognize four kinds of states accurately (normal, open circuit, short circuit and partial shadow). Consequently, the fault of PV array can be diagnosed and classified.
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    Topics: Geography , Geosciences , Physics
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  • 9
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    Hot spots detection of solar cells based on visual saliency and nonsubsampled contourlet transform (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-10-31
    Description: Hot-spot effect is well-known in the practical application of solar cells. The faults of hot spots seriously affect the performance and service life of solar cells. In order to highlight the infrared and visible complementary information of hot spots and discover more details, this paper presents a novel method, which fuses an infrared image saliency map based on random rectangular regions of interest with visible image by NonSubsampled Contourlet Transform (NSCT). Firstly, the infrared hot spots image was detected by saliency map which is randomly sampled. Secondly, the infrared and visible image of the hot spots are transformed into high-frequency and low-frequency sub-bands by NSCT. Finally, absolute value maximization and saliency map guidance are used to fuse low-frequency and high-frequency sub-bands respectively. The experimental results demonstrate that, compared with a set of related fusion methods, the presented method can better highlight the hot spots and other abund...
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    Topics: Geography , Geosciences , Physics
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  • 10
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    SAGA-FCM-LSSVM model-based short-term power forecasting of photovoltaic power plants (2018)
    Institute of Physics (IOP)
    Details
    Publication Date: 2018-10-31
    Description: With the rapid development of social economy, vigorously developing solar energy has become a powerful means to solve energy and environmental problems. However, the instability of weather condition makes the output of PV power have strong randomness, fluctuations and intermittence. Thus accurate photovoltaic (PV) power forecast eliminates the negative impacts of the grid connection of PV power generation systems, which are very meaningful for effectively integrating the PV power systems into the grid. The paper presents a Simulate Anneal and Genetic Algorithm (SAGA), fuzzy c-means clustering (FCM) and least square support vector machine (LSSVM) (SAGA-FCM-LSSVM) model-based power short-term forecasting of PV power plants approach. The experimental effect of the proposed prediction method is verified by employing large datasets from the Desert Knowledge Australia Solar Center (DKASC) website. In this work, the FCM clustering algorithm is adopted to cluster the historical power da...
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    Topics: Geography , Geosciences , Physics
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