Time filter

Source Type

Jiaozuo, China

Braune R.,Do Fluoride Chemicals Co. | Zapfel G.,Johannes Kepler University
Computers and Operations Research

Machine-based decomposition of total weighted tardiness job shops is known to be considerably more complicated than in the makespan case, mainly due to the structure of the underlying graph model and thus the arising one-machine subproblems. In fact, the effectiveness of a shifting bottleneck approach crucially depends on the employed subproblem solver. Although a sophisticated exact algorithm exists, problem instances involving more than 30 jobs are still challenging. In this paper, new heuristic approaches to subproblems of this kind are devised which rely on advanced problem-specific concepts like local optimality and dominance principles. The proposed subproblem solvers are combined with an iterated local search method for re-optimizing already scheduled machines. Computational experiments show that the final enhanced shifting bottleneck algorithms are not only applicable to job shops involving up to 100 jobs and 20 machines, but also able to improve existing results for benchmark instances. © 2015 Elsevier Ltd. All rights reserved. Source

Wen S.,Yangzhou University | Zhu X.,Yangzhou University | Wu X.,Do Fluoride Chemicals Co. | Qin X.,Yangzhou University
Analytical Methods

A novel procedure is presented for the speciation of Cr(iii)/Cr(vi) involving directly suspended single droplet microextraction combined with electrothermal atomic absorption spectrometry. In this method, Cr(iii) can be extracted with 1-decanol at pH 6.0 due to the formation of a hydrophobic complex, Cr(iii)-8-hydroxyquinoline (8-HQ), whereas Cr(vi) remains in the aqueous solution. The Cr(vi) concentration was calculated by subtracting the concentration of Cr(iii) from the total chromium concentration after reducing Cr(vi) to Cr(iii) by addition of hydroxylamine hydrochloride. Different factors affecting the extraction of Cr(iii), such as pH, 8-HQ concentration, stirring rate, extraction temperature and time, and interfering ions, were schematically evaluated. Under the selected conditions, the limit of detection for Cr(iii) was 0.03 ng mL-1 with a relative standard deviation of 4.7% (C = 1.0 ng mL-1, n = 5). The calibration curve was highly linear for the Cr(iii) concentration range of 0.10-2.0 ng mL-1. The proposed method was validated against certified reference materials of environmental water (GSBZ50027-94, GBW(E)080642), and successfully applied in the speciation of chromium in well and tap water samples. © The Royal Society of Chemistry 2014. Source

Meng J.,Zhengzhou University | Cao Y.,Zhengzhou University | Zheng G.,Hong Kong Polytechnic University | Li J.,Do Fluoride Chemicals Co. | And 3 more authors.
Materials Research Bulletin

Aluminum substituted MCM-48 (Al-MCM-48) mesoporous molecular sieves was synthesized at mild temperature without using hydrothermal process. It was used for the first time to assemble the supported H3PW12O 40 (HPW) mesoporous materials with various HPW loadings. The mesoporous materials were characterized by various techniques and their catalytic activities in the green synthesis of benzoic acid were evaluated under organic solvent-free conditions. The characterizations showed that these mesoporous materials retained the cubic phase of MCM-48 and their textural parameters decreased with increasing loading of HPW. The catalytic results suggested that the supported material was an efficient catalyst for the oxidation of benzyl alcohol and benzaldehyde with 30% H2O 2. Furthermore, the sample with 35 wt% loading of 12-tungstophosphoric acid was found to show the highest activity for the oxidation of benzaldehyde under the reaction conditions. © 2014 Elsevier Ltd. All rights reserved. Source

Meng J.,Zhengzhou University | Suo Y.,Zhengzhou University | Li J.,Do Fluoride Chemicals Co. | Zheng G.,Hong Kong Polytechnic University | And 4 more authors.
Materials Letters

Three-dimensional nitrogen-doped graphene aerogel (N-GA) is facilely synthesized via a hydrothermal method combined with freeze drying. When it is used as an anode for lithium-ion battery, N-GA possesses larger surface area (SBET=379.1 m2 g-1), higher reversible capacity (535.3 mAh g-1 in the 100th cycle) and more stable cycling performance compared with those of pristine GA, which could result from the structural defects caused by the nitrogen doping. © 2015 Elsevier B.V. All rights reserved. Source

Suo Y.,Zhengzhou University | Zhao Q.-Q.,Zhengzhou University | Meng J.-K.,Zhengzhou University | Li J.,Do Fluoride Chemicals Co. | And 5 more authors.
Materials Letters

A novel facile strategy was developed to prepare the Fe3O4@graphene aerogel (Fe3O4@GA) composites. Fe3O4 nanoparticles were uniformly dispersed into the 3D network of graphene aerogel and the resultant hybrid composites contained meso- and macro-scale pores with high specific surface area (276.9 m2 g-1) and large pore volume (0.3230 cm3 g-1). The electrochemical performance revealed that the Fe3O4@GA anode exhibited high reversible capacity (~941.5 mAh g-1 at a current density of 100 mA g-1), stable cycling performance, and excellent rate capability. © 2016 Elsevier B.V. Source

Discover hidden collaborations