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  • 1
    Publication Date: 2015-06-12
    Description: In this study, a numerical model has been established by employing a commercial software; ProCAST, to simulate the variation/distribution of temperature and the subsequent microstructure of Bi2Te3 fabricated by zone-melting technique. Then an experiment is conducted to measure the temperature variation/distribution during the zone-melting process to validate the numerical system. Also, the effects of processing parameters on crystallization microstructure such as moving speed and temperature of heater are numerically evaluated. In the experiment, the Bi2Te3 powder are filled into a 30mm diameter quartz cylinder and the heater is set to 800?C with a moving speed 12.5 mm/hr. A thermocouple is inserted in the Bi2Te3 powder to measure the temperature variation/distribution of the zone-melting process. The temperature variation/distribution measured by experiment is compared to the results of numerical simulation. The results show that our model and the experiment are well matched. Th...
    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
    Publication Date: 2015-12-11
    Description: When SKH 51 high-speed steel was first cryogenically treated and then tempered at 540 °C, the surface hardness of the SKH 51 steel increased from HRC 64 to HRC 65. This result indicates the reduction of retained austenite as well as the secondary precipitation of tiny carbides. TEM analyses indicated that cryogenic treatment can induce high-density dislocations and stacking faults within the martensite matrix. In the subsequent tempering process, conducted at 540 °C, tiny secondary carbides precipitated nearby the existing dislocations and stacking faults, resulting in the hardening of SKH 51 high-speed steel. These secondary carbides mainly consisted of V-rich MC carbides and (Mo, W)-rich M 2 C carbides, which were identified by STEM/EDS techniques. After being cryogenically treated and then tempered at 590°C, both the surface hardness and wear resistance of SKH 51 high-speed steel were weakened below acceptable ranges. This result indicates the promotion of rapid decom...
    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
    Publication Date: 2012-01-13
    Description: The effect of a medium-density DC-current and its direction on the directional solidification microstructure and cooling behavior of Pb-80wt%Sn alloy were studied. Experimental results indicated that the microstructure was refined with DC compared to the one without. With the increase of DC density, the primary ( λ 1 ) and secondary ( λ 2 ) dendrite arm spacing of the primary phase decrease clearly. It is also found that not only the intensity of the DC current but also its direction affects the microstructure. The size of λ 1 and λ 2 , in samples treated with positive DC, decreases more clearly than in those with negative DC. The interface morphology in samples processed without and with DC is different when the current direction is changed. Finally, the mechanism of microstructure evolution is discussed.
    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
    Publication Date: 2014-09-25
    Description: As the amount of reactive nitrogen (N) generated and emitted increases the amount of N deposition and its contribution to eutrophication or harmful algal blooms in the coastal zones are becoming issues of environmental concern. To quantify N deposition in coastal seas of China we selected six typical coastal sites from North to South in 2011. Concentrations of NH 3 , HNO 3 , NO 2 , particulate NH 4 + (pNH 4 + ) and pNO 3 − ranged from 1.97– 4.88, 0.46 –1.22, 3.03 –7.09, 2.24 – 4.90 and 1.13–2.63 μ g N m −3 at Dalian (DL), Changdao (CD), Linshandao (LS), Fenghua (FH), Fuzhou (FZ), and Zhanjiang (ZJ) sites, respectively. Volume-weighted NO 3 − –N and NH 4 + –N concentrations in precipitation varied from 0.46 to 1.67 and 0.47 to 1.31 mg N L −1 at the six sites. Dry, wet and total deposition rates of N were 7.8–23.1, 14.2–25.2 and 22.0 ...
    Print ISSN: 1748-9318
    Electronic ISSN: 1748-9326
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering
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  • 5
    Publication Date: 2018-08-03
    Description: As the main body of the Liaohe River Delta, the Panjin Wetland plays a vital role in maintaining the ecological balance throughout the region. The analysis of the correlation between NDVI and meteorological factors was carried out on reed wetland by using the normalized differential vegetation index (NDVI) data of Panjin Reed Wetland from 2006 to 2015 and such meteorological data as ten-day average temperature, ten-day precipitation, ten-day sunshine duration, ten-day relative humidity and ten-day evaporation capacity. The results showed that the NDVI of Panjin Reed Wetland had no obvious year-to-year changes from 2006 to 2015 and showed a slight upward trend with small fluctuations. However, the NDVI of Panjin Reed Wetland had significant intra-annual changes and was depicted as a single-peaked curve in the crop growing season. The curve reached the peak value in early- and mid-July, which was highly consistent with the phenophase. The ten-day NDVI of reed wetland is most and p...
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 6
    Publication Date: 2018-11-09
    Description: Coarse aggregate settlement may occur during concrete pouring, which affects the ability to resist projectile attack. In order to study the anti-penetration performance of concrete, and obtain high penetration resistance concrete, mesoscale finite element model of different aggregate space distribution of concrete was established, the numerical simulation of long rod rigid projectile penetrating into different concrete was conducted. The results showed that aggregate settlement had great influence on target scabbing; aggregate size and settlement had limited influence on projectile residual velocity.
    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: 2018-10-31
    Description: For Double-Fed Induction Generator (DFIG) wind farm systems with Static Synchronous Compensator (STATCOM), by optimizing multiple proportional integral (PI) controllers parameters of DFIG and STATCOM, the performance of the wind power system is significantly improved and the voltage of point of common coupling (PCC) is quickly restored when a low voltage due to a grid fault. Chaos orthogonal particle swarm optimization is proposed to make the integral time absolute error (ITAE) of active power of DFIG, DC-link voltage of converter of DFIG and voltage of PCC minimum. The orthogonal method is used to get the range of parameters and identify the weight relations between different indicators. And then the chaos algorithm is used to initialize the algorithm. Finally, the particle swarm optimization (PSO) can effectively improve the efficiency of the optimization. Based on MATLAB/Simulink, the simulations of wind farm containing STATCOM incorporated into the infinite system under diff...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 8
    Publication Date: 2017-06-14
    Description: Base on Northeast China region, according to land surface reflectivity of FY3B/MERSI data from 2011-2015, the underlying surface index of lakes and reservoirs, the original spectrum, normalized difference water index during different periods, were obtained. The monthly change was analyzed as well. Meanwhile, combined with GIS data, the model of extracting area was built. Using the TM data, the method was verified. The results indicated that the spectral reflectance are in accordance with the characteristics of water, with high reflection area in blue and green bands, low reflection area in near-infrared band ( 〈 6%), and more obvious reflectance spectral characteristics corresponding to higher cleanliness of water. The method could make area extracting in large scale. The method has higher accuracy up to 90%, which provides a preliminary method for the application of domestic satellite data.
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 9
    Publication Date: 2017-07-22
    Description: Magnetic sensors used in Above Ground Markers (AGM) to measure the magnetic field signals are one of the main parts of AGM. By collecting the change of magnetic field parameter using magnetic sensors, AGM can record the precise time when MFL_PIG is passing by the AGM. In this paper, the magnetic sensors, such as induced coil and magneto-resistive sensor, are investigated in characteristics and performance of measurement. With advantages of low cost, high resolution and wide range of measurement, the induced coil is adopted in a novel AGM. The traction test, seal ability test and temperature test show that the AGM with induced coil as magnetic sensor works well under extreme condition and reacts to change the magnetic field with high sensibility.
    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
    Publication Date: 2018-03-24
    Description: In 2017, the document No.1 of the Central Committee of the CPC explicitly proposed the construction of modernization irrigation district, the large-scale of modernization irrigation district is an important link to achieve the modernization of water conservancy and realize the socialist modernization. In the new era this paper expounded the connotation and characteristic of modernization irrigation district, put forward “safe”,” Sound ",” advanced ",” efficient “and” green “modernization irrigation district, and established the evaluation system of 5 first level indexes and 23 second level indexes.The threshold value of the evaluation index of the modernization irrigation district in 2035 was discussed. Binary fuzzy comparative analysis was used to determine the weight of indexes, and the degree of modernization irrigation district was divided into four levels, which provide a reference for the evaluation of the modernization of large-scale irrigation district.
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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