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  • 1
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    CFD numerical simulation of Archimedes spiral inlet hydrocyclone (2013)
    Institute of Physics (IOP)
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    Publication Date: 2013-12-22
    Description: For traditional linear type inlet, hydrocyclone has an unstable inner field, high turbulence intensity and low separation efficiency, this paper proposes an inlet mode that uses an Archimedes spiral hydrocyclone. A Mixture liquid-solid multiphase flow model combined with the kinetic theory of granular flow was used to simulate the high concentration water-sand-air three-phase flow in a hydrocyclone. We analyzed the pressure field, velocity field and turbulent kinetic energy and compared with traditional linear type inlet hydrocyclone inner field. The results show that Archimedes spiral inlet hydrocyclone's pressure field is evenly distributed. The Archimedes spiral inlet hydrocyclone can guide and accelerate the mixture flow and produce small forced vortex and less short circuit flow. The particles easily go to the outer vortex and are separated. The Archimedes spiral inlet hydrocyclone has effectively improved the stability of inner flow field and separation efficiency.
    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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    Quantum chemical calculation of imidization mechanism of polyamic acid (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-02-03
    Description: In this paper, the imidization mechanism of polyamic acid to prepare polyimide has been studied by the density functional theory (DFT) method. Our results have shown that the imidization would proceed via two different reaction paths. The activation barrier via hydrogen transfer to closer carboxylate oxygen in the COOH is 220.35 kJ/mol while the activation barrier via hydrogen transfer to hydroxyl oxygen in the COOH is 220.70 kJ/mol. Both reaction paths would run in the actual thermal imidization process with closer high activation barriers. The high energy barrier interpreted the fact that additional energy or catalyst is usually needed during imidization. Moreover, the intrinsic imidization mechanism indicated is critical to further improve the imidization process.
    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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    Theoretical and experimental investigations on the dynamic and thermodynamic characteristics of the linear compressor for the pulse tube cryocooler (2015)
    Institute of Physics (IOP)
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    Publication Date: 2015-12-19
    Description: Theoretical and experimental investigations on the dynamic and thermodynamic characteristics of a linear compressor incorporating the thermodynamic characteristics of the inertance tube pulse tube cold finger have been made. Both the compressor and cold finger are assumed as a one-dimensional thermodynamic model. The governing equations of the thermodynamic characteristics of the working gas are summarized, and the effects of the cooling performance on the working gas in the compression space are discussed. Based on the analysis of the working gas, the governing equations of the dynamic and thermodynamic characteristics of the compressor are deduced, and then the principles of achieving the optimal performance of the compressor are discussed in detail. Systematic experimental investigations are conducted on a developed moving-coil linear compressor which drives a pulse tube cold finger, which indicate the general agreement with the simulated results, and thus verify the rationali...
    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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    Application of chaotic prediction model based on wavelet transform on water quality prediction (2016)
    Institute of Physics (IOP)
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    Publication Date: 2016-09-03
    Description: Dissolved oxygen (DO) is closely related to water self-purification capacity. In order to better forecast its concentration, the chaotic prediction model, based on the wavelet transform, is proposed and applied to a certain monitoring section of the Mentougou area of the Haihe River Basin. The result is compared with the simple application of the chaotic prediction model. The study indicates that the new model aligns better with the real data and has a higher accuracy. Therefore, it will provide significant decision support for water protection and water environment treatment.
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 5
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    Synthesis of Plate-like Zinc Oxide Particles by the Transcription of Precursor's Shape (2011)
    Institute of Physics (IOP)
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    Publication Date: 2011-06-28
    Description: Plate-like zinc contained precursors such as simonkoleite or basic sulphate were successfully synthesized by using equilmolar of Zn 2+ / hexamethylenetetramine (HMT) acted as precursors, ethylene glycol(EG) as dispersant and surfactant additive, respectively. The reaction solution was sealed in a glass bottle and heated at 95°C for 3h. The zinc contained precursors possessed layered structure and plate-like morphology were successfully synthesized by controlling the zinc ions concentration, reaction temperature, organic solvent additives, anion additives. It was found that plate-like simonkolleite transformed to plate-like ZnO after calcination in air at 400°C, while it transformed to rod-like ZnO under hydrothermal conditions above 140°C. The additive of ethylene glycol decreased the particle size and affected the particle size distribution. The conductivity of the pressured powders was improved by small amount of Ga and Al doping followed by H 2 reduction t...
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 6
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    Partial Averaged Navier-Stokes approach for cavitating flow (2015)
    Institute of Physics (IOP)
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    Publication Date: 2015-01-16
    Description: Partial Averaged Navier Stokes (PANS) is a numerical approach developed for studying practical engineering problems (e.g. cavitating flow inside hydroturbines) with a resonance cost and accuracy. One of the advantages of PANS is that it is suitable for any filter width, leading a bridging method from traditional Reynolds Averaged Navier-Stokes (RANS) to direct numerical simulations by choosing appropriate parameters. Comparing with RANS, the PANS model will inherit many physical nature from parent RANS but further resolve more scales of motion in great details, leading to PANS superior to RANS. As an important step for PANS approach, one need to identify appropriate physical filter-width control parameters e.g. ratios of unresolved-to-total kinetic energy and dissipation. In present paper, recent studies of cavitating flow based on PANS approach are introduced with a focus on the influences of filter-width control parameters on the simulation results.
    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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  • 7
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    Effect of inlet geometry on macrosegregation during the direct chill casting of 7050 alloy billets: experiments and computer modelling (2012)
    Institute of Physics (IOP)
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    Publication Date: 2012-07-04
    Description: Controlling macrosegregation is one of the major challenges in direct-chill (DC) casting of aluminium alloys. In this paper, the effect of the inlet geometry (which influences the melt distribution) on macrosegregation during the DC casting of 7050 alloy billets was studied experimentally and by using 2D computer modelling. The ALSIM model was used to determine the temperature and flow patterns during DC casting. The results from the computer simulations show that the sump profiles and flow patterns in the billet are strongly influenced by the melt flow distribution determined by the inlet geometry. These observations were correlated to the actual macrosegregation patterns found in the as-cast billets produced by having two different inlet geometries. The macrosegregation analysis presented here may assist in determining the critical parameters to consider for improving the casting of 7XXX aluminium alloys.
    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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  • 8
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    Analyzing phenological changes with remote sensing data in Central Asia (2014)
    Institute of Physics (IOP)
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    Publication Date: 2014-03-20
    Description: Based on NOAA/AVHRR NDVI biweekly time-series data, the start and end of the growing season of Central Asia from 1982 to 2006 were estimated. Trend analysis results indicate an earlier green-up and a later dormancy over the entire area during the study period. For seven main vegetation types, the largest advance of greenup onset (0.597 days/year) occurs in cropland and the longest delay of dormancy (1.109 days/year) in open shrubland. The smallest advance (0.164 days/year) occurs in evergreen needleleaf forest and delay (0.443 days/year) in crop/natural vegetation mosaic. These results imply enhanced vegetation activity in the Central Asia region over last decades.
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 9
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    Reaction hot-pressing and property-composition relationships of modified sialon – boron nitride hetero-modulus ceramics (2011)
    Institute of Physics (IOP)
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    Publication Date: 2011-09-22
    Description: Hetero-modulus ceramics (HMC) present the combination of a ceramic matrix with inclusions of a dispersed phase with considerably lower values of Young's modulus, resulting in a material with significantly advanced properties. Densified '-Si 6−x Al x O x N 8−x based HMC materials, with various volume contents of low-modulus α-BN phase and modifiers such as TiN or ZrO 2 in sialon matrix, were prepared by high-temperature reaction hot-pressing in nitrogen atmosphere. The pristine blend composition for reaction hot-pressing consisted of mixed fine powders of Si, Al, B, Ti nitrides and Al, Zr oxides. Statistical design of 2 5−2 fractional factorial and third-order simplex-grid types was used for the experimental studies to estimate the effects of some technological factors on the densification of hot-pressed products and the property-composition relationships of modified HMC materials.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 10
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    On the mechanism of the formation of primary intermetallics under ultrasonic melt treatment in an Al-Zr-Ti alloy (2012)
    Institute of Physics (IOP)
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    Publication Date: 2012-01-13
    Description: Ultrasonic melt treatment (UST) is known to induce grain refinement in aluminum alloys, especially when transition metals like Zr and Ti are present. The refinement of primary intermetallics (e.g. Al 3 Zr, Al 3 (Zr,Ti)) caused by UST may influence the subsequent solidification process when intermetallics act as nucleation sites. In this paper, an Al-Ti-Zr alloy is used to analyse the effect of different ultrasonic intensities on the formation of these primary intermetallics. The possible nucleation behaviour of Al 3 Zr particles during UST is also discussed and an edge to edge matching model is used to make a preliminary analysis of lattice mismatch between aluminum oxide and Al 3 Zr phase. The experimental results show that when UST is applied, the Al 3 (Zr,Ti) particles might nucleate on aluminum oxides and remain fine during solidification.
    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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