Applied Mechanics and Materials Vols. 80-81

Abstract: With calculation results comparison of different throttle nozzle diameter value, This article analyses the flow field with throttle nozzle diameter variety of 1.0mm, 2.0mm, 2.4mm, 2.6mm, 2.8mm, 4.0mm, while the other parameters take same value (such as the inlet pressure is 20mpa, the outlet pressure is 10MPa, the temperature is 333k, and the well depth is about 2000m). the results present the influence upon downhole choke flow field including pressure, velocity, temperature distribution. The pressure field composed by minimum on the axis shows the pressure dropping change at the throttle nozzle outlet. Velocity field gives the maximum value of velocity and Mach number, which determines the flow field is subsonic or supersonic flow. With hydrate formation conditions, temperature field formed by minimum on the axis gives the existing judgment of hydrate formation under a certain condition. With the throttle nozzle diameter increasing, the outlet flow maximum velocity increases, and the differential pressure before and after nozzle becomes larger, which means the pressure drop effect is better. The downhole choke design of throttle nozzle needs to consider the combination effects of pressure drop and temperature drop. These parameters provide reference for downhole choke structure design and operating performance improvement.

Abstract: A heterocyclic derivative of 3-(N-mono-n-butylaminomethyl) quinazolin-4-one was synthesized and its tribological behavior as an ashless additve without phosphorus and sulphur in liquid paraffin was evaluated using a four-ball tester. On the basis of the experimental results, the novel additive has been found to be quite effective as a potential additive in liquid paraffin. The nature of the film on the rubbed surface was investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).

Abstract: Fly ash Ceramsite, Artificial Biofilter Bed, Dry Umbrella Bamboo, Phosphorus Removal Abstract: High calcium fly ash ceramsite had tremendous surface area and porosity, the unit weight of fly ash adsorption column adsorption capacity of ceramsite was 0.032mg•g-1, which was higher than normal calcium fly ash ceramsite adsorption capacity. The fix adsorption column tests showed that the adsorption capacity got stable when the contact time was 3 hours and the saturation adsorption was got at the ninth hour. The result of subsequent tests showed that the phosphorus resolve would not occur if the adsorption condition doesn’t change. The pilot test with actual wastewater was done and the results showed that the PO43- concentrations of effluent were less than 0.2mg•L-1 and the removal rate reached 90%, dry umbrella bamboo was the most suitable aquatic plant. The artificial biological filter process monitoring showed that the phosphorus of the sewage was mainly removed in the front of artificial biological filter bed.

Abstract: To solve the fatigue damage location problem of helicopter moving component, a new approach for linear location of acoustic emission (AE) source based on least squares support vector machine for regression (LS-SVR) and niche genetic algorithm (NGA) was proposed. Several time domain parameters of AE signal were taken as the inputs, and the linear coordinates of the breakpoints as the output. The sharing function based niche genetic algorithm is used to select the LS-SVR parameters automatically. The results of pencil lead break location experiment on specimen of carbon fiber materials indicate that the proposed approach can implement linear location of AE source effectively, and has better performance on convergence rate and location accuracy than RBF and BP neural network.

Abstract: Recent research progresses of design technologies for functionally gradient ceramic materials (FGCMs) at home and abroad are reviewed. The determination and application of component distribution model, micromechanical model, materials properties, distribution exponent, layer number and thickness, and thermal stress simulation, etc. have been analyzed and investigated emphatically. Problems existed are discussed and future design perspective of functionally gradient ceramic materials are pointed out.

Abstract: In this thesis, a unidirectional solidification model of NH4Cl solution is developed. The dynamics processes of the unidirectional solidification, such as temperature distribution and the location of phase interface are simulated timely. Based on those result data, the heat and mass transfer characteristic is analyzed. And it is found that with the stirring of the liquid zone, the temperature gradient in the liquid zone is decreased from 194 K/m to 24 K/m, and the thickness of the mush zone is enlarged.

Abstract: Pipelines are used widely to convey fluids and gases in the petrochemical, water, and energy sectors. Vibration, noise and fatigue failure of pipelines are serious problems in many engineering situations, especially in ship and ocean engineering areas. In this paper, the acoustic propagation and attenuation characteristics of axisymmetrical eigenmodes in a cylindrical, elastic, fluid-filled pipe are investigated analytically. Pipe equations for n=0 axisymmetrical wave motion are derived, and analytical expressions of wavenumber are obtained for s=1 and s=2 wave, which correspond to a fluid dominated wave and an axial shell wave, respectively. The numerical results for wavenumber of pipe and fluid are obtained and discussed. It shows that the frequency dependent phase velocity of this mode depend strongly upon the shell thickness/radius ratio and the density of the contained fluid. It seems that this analysis method is simple and effective.

Abstract: The molecular dynamics tool usually employs a neighbor list that contains the particle pairs for which non-bonded forces would be calculated. Though accessing to the array of atoms’ position and force does not exhibit a cache friendly pattern on a computer during the nonbonded force calculation, the neighbor list could be referred as a directive for the memory access. Designing specific data prefetching policy according to the neighbour list which was generated before the calculation can reduce the latency of memory access and improve the molecular dynamics simulation process. In this paper, an optimization memory access method referred by particle neighbor list based on CBEA was proposed. The experimental result shows that the proposed method reduces the latency of memory access and improves performance of the molecular-dynamics-based chemical simulation greatly.

Abstract: VO₂(B) nanobelts have been successfully prepared in V₂O₅ and water mixed suspension assisted by polyvinyl alcohol (PVA) via a mild hydrothermal approach. The as-obtained VO₂ nanobelts are several hundred nanometers to several micrometers long, typically 100-300 nm wide and about 20-30 nm thick. It was found that PVA could not only act as the reducing reagent but also as the structure-directing reagent. Besides, the PVA-assisted solid-solution-solid (SSS) transformation mechanism was proposed to illuminate the possible formation mechanism of VO₂(B) nanobelts. Furthermore, the electrochemical properties of VO₂(B) nanobelts were studied and they exhibited a high initial discharge capacity of 268 mAh/g, indicating that VO₂(B) nanoblets are promising electrode materials in lithium battery.

Abstract: Effect of nitric acid and the burning time on the liquid combustion synthesis of spinel LiMn₂O₄ has been studied, using lithium nitrite and Manganese acetate as raw a material. The results show that the main phases are all LiMn₂O₄, which can be obtained at 400-600 oC. Before modified, the impurity is Mn₃O₄ or Mn₂O₃. After modified, the impurity is only Mn₃O4. The aggregation obviously reduced after adding nitric acid, it is indicated that the crystalline increased. With the increasing temperatures, the modified particle size was increased and the aggregation reduced. The initial discharge capacity and cycle stability improved at some extent too. Its first discharge capacity was 104.6, 112.8 and 117.7mAh/g synthesized at 400, 500, 600 oC, respectively, and the 30^th capacity retention rate were 84.89%, 80.67% and 73.24%.