Wyniki wyszukiwania - Biblioteka Nauki

1

Process improvement and kinetic study on copper leaching from low-grade cuprite ores

100%

Bai S. , Fu X. , Li C. , Wen S.

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tom Vol. 54, iss. 2

300--310

EN

Process improvement and kinetic study on copper leaching from low-grade cuprite ores in sulfuric acid solution are presented in this paper. Effects of major leaching parameters on copper leaching efficiency are determined. The results indicate that copper minerals in the raw ores are mainly cuprites. The reaction rate of this ore increases with an increase in temperature, reaction time, sulfuric acid concentrations and decrease in the particle size of ore. Leaching of about 92.5% of copper is achieved using 0.125-0.074 mm ore particle size at a reaction temperature of 353 K for 180 min reaction time with 150 g/dm3 sulfuric acid. The solid/liquid ratio was maintained constant at 1:15. Leaching kinetic indicates experimental data complies with shrinking core mode (SCM). It is found in the study that agitation rate is not an influential factor on leaching rate and that the dissolution rate is controlled by surface chemical reaction. The average activation energy of the process is determined to be 45.28 kJ mol-1, and the reaction order of H2SO4 is 0.8093.

2

Method of regularized sources for two-dimensional Stokes flow problems based on rational or exponential blobs

88%

Wen S. , Wang K. , Zahoor R. , Li M. , Šarler B.

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2015

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tom Vol. 22, no. 3

289--300

EN

The solution of Stokes flow problems with Dirichlet and Neumann boundary conditions is performed by a non-singular method of fundamental solutions (MFS) which does not require artificial boundary, i.e., source points of fundamental solution coincide with the collocation points on the boundary. The fundamental solution of the Stokes pressure and velocity is obtained from the analytical solution due to the action of the Dirac delta- type force. Instead of Dirac delta force, a non-singular function called blob, with a free parameter epsilon is employed, which is limited to Dirac delta function when epsilon is limited to zero. The analytical expressions for related Stokes flow pressure and velocity around such regularized sources have been derived for rational and exponential blobs in an ordered way. The solution of the problem is sought as a linear combination of the fields due to the regularized sources that coincide with the boundary and with their intensities chosen in such a way that the solution complies with the boundary conditions. A numerical example for two-dimensional (2D) driven cavity and a flow between parallel plates are chosen to assess the properties of the method. The results of the posed method of regularized sources (MRS have been compared with the results obtained by the fine-grid second-order classical finite difference method (FDM) and analytical solution. The results converge with finer discretisation; however, they depend on the value of epsilon. The method gives reasonably accurate results for the range of epsilon between 0.1 and 0.5 of the typical nodal distance on the boundary. Exponential blobs give slightly better results than the rational blobs; however, they require slightly more computing time. A robust and efficient strategy to find the optimal value of epsilon is needed in the perspective.

3

Effect of electron beam injection on boron redistribution in silicon and oxide layer

75%

Qin S. , Tan Y. , Li J. , Jiang D. , Wen S. , Shi S.

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2017

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tom Vol. 35, No. 1

14--17

EN

The behavior of boron redistribution in silicon with and without oxide layer after electron beam injection (EBI) was investigated. Special defect shapes were generated on the surface of bare and oxidized silicon wafers. Secondary ion mass spectrometer was used to measure the boron profile. The results showed that after long EBI time, boron tended to be induced from both sides of the transition region between the oxide layer and silicon. For the sample without oxide layer after EBI, boron tended to diffuse towards the surface and its concentration obviously reduced inside the silicon. The results of the study show the potential use of the process in removing boron impurity in silicon.

4

Analysis of chloramphenicol in drinking water using an evaporation preparative step and isotope dilution liquid chromatography–tandem mass spectrometry

63%

Li Y. , Liu X. , Zhang R. , ZomPa D. , Luo P. , Tang L. , Liu X. , Zhou Y. , Wen S.

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tom Vol. 30, no. 1

17--20

EN

A reliable isotope dilution method for the determination of chloramphenicol (CAP) in drinking water was developed by using an evaporation preparative step. Each sample was monitored by ultrahigh-pressure liquid chromatography (UHPLC) coupled to tandem mass spectrometry (MS/MS) using an electrospray ionization interface (ESI) in negative ion modes. Recoveries of spiked samples were in the range from 93.2% to 95.7% with intra-day relative standard deviation lower than 6.7% and inter-day relative standard deviation lower than 8.2%. Limit of quantification (LOD) was 0.002 ng/mL. The developed method was successfully applied to the analysis of CAP in drinking water of Shannan region of Tibet.